Dental Caries

OPERATIVE DENTISTRY Part 1: Dental Caries Dental Caries -infectious bacterial disease caused by cariogenic plaque formation on tooth that results in demineralization of enamel at pH 5.5 or less, sometimes requiring restorative tx or even extraction -for caries to occur, three things must be present at same time: 1) cariogenic bacteria 2) susceptible tooth surface 3) foodstuffs to support bacterial growth Specific Plaque Hypothesis -not all of bacterial species in oral cavity cause caries; only the bacteria that generate plaque formation resulting in caries are considered cariogenic (not all plaque is cariogenic) -ex. Viridans streptococci cause plaque but much less virulent for caries formation Streptococcus Mutans -nonmotile, gram+ bacteria that is cariogenic (primary causative agent of initial caries formation) -adheres to enamel through glucosyltransferase enzyme, which causes formation of extracellular polysaccharide that allows it to stick to smooth tooth surfaces -converts sucrose into fructans and glucans, which extrude from bacteria and stick to tooth -produces and tolerates acid (metabolizes sucrose to lactic acid) -thrives in sucrose-rich environment -produces bacteriocins, which kill off competing organisms Enamel Caries -ion transfer continuously occurs at plaque-enamel surface -initial decalcification occurs at subsurface -may be 1-2 years before enough decalcification occurs to cause surface integrity loss a) Incipient caries: caries that have not progressed farther than enamel and are reversible/able to remineralize b) Frank caries: caries that have progress just into DEJ and not reversible Zones of Carious Enamel 1) Surface zone: outermost zone which seems unaffected by caries 2) Body zone: largest zone which represents demineralizing phase 3) Dark zone: represents remineralization; named b/c it can’t transmit polarized light 4) Translucent zone: deepest zone; named b/c of its absent appearance under polarized light -represents advancing front of enamel lesion Dentinal Caries -once enamel decalcification occurs, the underlying dentin has already been affected by progression of the destruction -Lactobacillus organism becomes a primary agent for further destruction of the dentin -Lactobacillus produces lexan instead of dextran -dentin is less resistant to caries and can progress rapidly through proteolysis of dentin -dentin is less mineralized than enamel and has tubular structures allowing for spread of acid destruction -caries appears V-shaped w/ base at DEJ and apex toward pulp -necrotic dentin appears soft, wet, and mushy 1) Infected dentin: tubules infected w/ cariogenic bacteria and proteolytic activity causes degradation 2) Affected dentin: bacteria present but in smaller amounts; demineralization occurs but can be reversed if infected layer removed and environment favorable

Zones of Carious Dentin (from innermost to outermost) 1) Normal dentin: deepest area; no bacteria or byproducts present 2) Subtransparent dentin: demineralization from acidogenesis but no bacteria found in tubules -capable of remineralization 3) Transparent dentin: softer than normal and has further demineralization; no bacteria here --capable of remineralization 4) Turbid dentin: zone of first encountered bacterial invasion w/ tubules filled w/ bacteria; zone must be removed 5) Infected dentin: outermost zone; consists of decomposed dentin and many bacteria found in this zone and must be removed -zones 1-3 are capable of remineralization -zones 2 and 3 (subtransparent and transparent) termed affected dentin and zones 4 and 5 (turbid, infected) are termed infected dentin Tertiary/Reparative Dentin -produced by secondary odontoblasts in response to irritants -if insult is strong enough, it will kill odontoblasts and form dead tracts, which calcify to form sclerotic dentin -other types of dentin: 1) Primary dentin: dentin forming initial shape of tooth and deposited before completion of apical foramen 2) Secondary dentin: dentin formed after completion of apical foramen Other Bacteria Involved in Caries 1) Actinomyces viscus: most common cariogenic bacteria in root surface caries and smooth surface caries 2) Streptococcus sanguis: earliest bacteria in dental plaque 3) Other cariogenic bacteria: Actinomyces naeslundi, Veillonella, Streptococcus salivarious Cyclic Process of Caries -as plaque is exposed to sucrose, the plaque metabolism produces acid which when less than pH 5.5, causes demineralization of tooth structure -as sucrose or plaque is removed, ions from saliva (Na, K, Ca) cause remineralization to occur, which attempt to restore ionic component of tooth structure -when fluoride is present, it is picked up by tooth and forms fluoroapatite in enamel, which is even more resistant to future demineralization than normal enamel Hydrodynamic Theory of Pain from Caries -when tooth is subjected to insult, fluid movement through tubules increases and greater flow deforms the nerve endings in pulp leading to pain response -cold conductivity increases both volume and flow in tubules resulting in pain stimulus Saliva -saliva is a major block barring the cariogenic bacteria -protective mechanisms: 1) Bacterial clearance: large carbohydrate-protein molecules in saliva cause some bacteria to agglutinate and then be removed by swallowing 2) Buffering action: saliva contains urea and other buffers to help dilute plaque acid 3) Antimicrobial actions: a variety of proteins and Ab in saliva discourage/kill bacterial growth a) Lysozyme: destroys bacterial cell walls and causes membrane permeability b) Lactoferrin: actively binds iron, which is important for bacterial enzyme production and fxn (may also destroy S. mutans) c) Lactoperoxidase: inactivates bacterial enzymes d) Type A secretory immunoglobulin: Ab in saliva which fights S. mutans attacks 4) Remineralization: Ca, K, PO4, and F ions in saliva assist w/ remineralization of enamel -some salivary proteins promote remineralization (statherin, cystatin, histatin, proline)

Common Drugs Causing Xerostomia 1) Anticholinergics (atropine) 2) Diuretics (hydrochlorothiazide) 3) Local anesthetics 4) Antipsychotics 5) Beta blockers (atenolol) 6) Benzodiazepines (alprazolam) 7) Antihistamines Identification of High-Risk Caries Patients -no exact mechanism for determination, but some factors that predispose to caries: 1) high S. mutans count 5) large number of restorations 9) oral appliances 2) 2 or more active lesions 6) poor oral hygiene 10) deep pits/fissures 3) poor diet 7) suboptimal fluoride 11) exposed roots 4) low salivary flow 8) unusual tooth morphology 12) drug use Fluoride -is bactericidal and provides fluoride ion for remineralization -sources: 1) water fluoridation systems 4) varnishes 2) rinses 5) toothpaste 3) gels Prevention of Dental Caries 1) Decrease S. mutans activity and educate pt that repairing carious lesion doesn’t cure caries problem 2) Intense antimicrobial application on short-term basis 3) Fluoride 4) Saliva -alter salivary-reducing meds if possible -use saliva stimulants (gum, paraffin wax, saliva substitutes, diet high in protein and vegetables) 5) Decrease sucrose in diet (better to decrease FREQUENCY than QUANTITY) -single exposure to sucrose for caries-active mouth can result in pH reduction below 5.5 for sustained period of time b/c of rapid metabolism by S. mutans 6) Xylitol (natural sugar from birch trees that keeps sucrose from binding w/ S. mutans) -S. mutans can’t ferment xylitol 7) Enforce good oral hygiene (disrupts plaque formation) 8) Sealants (removes habitat for S. mutans) 9) Restorations Treatment of Carious Lesions 1) Restorations: when cavitated lesions present, they must be restored (Cavitated lesions > Restore) -use of antimicrobials must wait until after cavitated lesion is restored, or the antimicrobial will disrupt the normal flora and allow virulent organisms in protected, cavitated area to flourish on now-unprotected surfaces -restorations remove large nidi of infectious organisms as well as remove habitats for more bacterial adherence -restorations alone don’t cure caries problems, need better preventive strategies 2) Sealants -sealants should be applied simultaneously to at-risk molars and premolars as well as ditched restoration margins (etch enamel and microabrade amalgam) 3) Intense, short-term use of agents -Chlorhexidine -Fluoride varnishes 4) Xylitol products 5) Fluoride rinses (OTC) -use after Chlorhexidine is finished and use at difft. times than for brushing 2x/day 6) 3-month recalls after Chlorhexidine/fluoride varnish application

Part 2: Clinical Exam Clinical Exam for Caries 1) Visual changes in tooth surface texture or color 5) DIAGNOdent 2) Tactile sensation w/ explorer 6) DIFOTI (digital imaging fiberoptic transillum.) 3) Radiographs 7) Quantitative light-induced fluorescence (QLF) 4) Transillumination 8) Electronic caries monitor -no single test is completely accurate, so can’t rely solely on one test Caries Indicating Solution -colored dye in organic base adheres to denatured collagen, which distinguishes btw infected and affected dentin Occlusal Pits and Fissures -caries is most prevalent in faulty pits and fissures on occlusal surfaces where developmental lobes have failed to coalesce -occlusal grooves/fossae are smooth, valleys indicating region of complete coalescence of developmental grooves (not susceptible to caries normally b/c not prone to plaque formation) -occlusal fissures and pits are deep, tight crevices in enamel where lobes fail to coalesce -use of an explorer in diagnosing caries is strongly discouraged b/c injudicious use of explorer may actually cause fracture of surface enamel that was weakened by carious destruction beneath it -occlusal surface should be examined visually and radiographically -visual exam done by drying tooth and using illumination to look for chalkiness, brown-gray coloration or softening/cavitation in fissure/pit -radiographic diagnosis made by BW radiographs, looking for radiolucency beneath enamel surface at DEJ (narrow at enamel surface and spreads wide at DEJ (inverted V) -actual lesion much larger than clinically presentable -lesion progresses parallel to enamel rods -carious pits and fissures also occur on occlusal 2/3 of facial and lingual surfaces of posterior teeth and on lingual surface of max. incisors -pit/fissure caries mostly caused by Strep. Sanguis and other Strep species -prevented by fissurotomy or sealants Cusp Tip Caries -pre-carious or carious pits are occasionally found on cusp tips -these are result of developmental enamel defects Proximal Surface Caries -form of smooth surface caries located btw teeth -diagnosed radiographically most often, but may be detected visually w/ tooth separation or fiberoptic transillumination -starts wide at surface and converges toward DEJ (V-shape) -DEJ provides least resistance to caries and allows repaid spread once reached -proximal caries in anterior teeth may also be detected by explorer probing -located just gingival to IP contact -progresses much slower than pit/fissure caries Brown Spots -brown spots on intact, hard proximal surfaces adjacent to and gingival to contact area often seen in older pts who have low caries activity -are result of extrinsic staining during earlier caries demineralizing episodes that were remineralized -spots are no longer carious and usually more resistant to caries, so restorative tx not indicated

Smooth Surface Caries on Facial/Lingual Surfaces -mostly in gingival areas that are less accessible for cleaning -earliest evidence is incipient caries which shows as white spot that is visually difft. from adjacent translucent enamel and disappears when wetted (drying will cause it to reappear) -should promote remineralization of these incipient lesions -enamel hypocalcification does not disappear when wet -presence of several facial/lingual smooth surface lesions indicated high caries rate, so should always check facial/lingual areas of posterior teeth b/c these areas are at even more risk -advanced smooth surface caries will feel soft to explorer penetration and discolored (white to dark brown) -w/ slowly progressing caries, darkening occurs due to demineralization-remineralization cycle, resulting in hardened, arrested lesion -restoration not indicated, except for esthetics -dentin in an arrested lesion is termed eburnated or sclerotic Root Surface Caries (Senile Caries) -early on, root caries appears as well-defined discolored area adjacent to gingival margin near CEJ -softer than adjacent tissue and spreads laterally around CEJ -thin cementum layer provides little resistance to attack and results in rapid progression (progresses more rapidly than enamel and dentin caries) -progresses more laterally along surface than in depth -pathway of initial demineralization is along Sharpey’s fibers -no clinical criteria universally accepted for diagnosing root caries, it is agreed though that softened tooth structure compared to surrounding structure is characteristic -active root caries detected by softening and cavitation -may be detected radiographically, but careful clinical exam is crucial b/c root caries and cervical burnout are similar in appearance -vertical BW best for diagnosing root caries -appears as cupped-out/crater-shaped radiolucency just below CEJ -often occurs in elderly due to gingival recession (xerostomia and lack of hygiene play role also) -cementum is rougher than enamel and more likely to acquire plaque -often remineralize due to shallow nature -often asymptomatic and difficult to restore -best restored w/ glass ionomer Other Forms of Caries 1) Residual caries: infected tooth structure remaining after attempted removal in a complete cavity prep 2) Recurrent caries (secondary caries): decay that remains in completed cavity or forms around existing restoration -radiolucent bases/liners may be mistaken for recurrent decay on radiograph 3) Rampant caries (acute caries): rapidly progressing wide-spread caries; usually acute onset and painful -assoc. w/ poor hygiene, drug use, radiation, high sugar diet, xerostomia 4) Arrested caries (chronic caries): lesions that have remineralized -hard, black, and asymptomatic -should be completely removed if found in enamel or close to DEJ

Clinical Exam of Amalgam Restorations -involves visual observation, tactile sense w/ explorer, dental floss, radiographs, and knowledge of probabilities that given tooth or restoration is at risk for further breakdown -problems that can arise w/ amalgam restorations include: 1) Amalgam “blues”: discolored enamel resulting from leaching of corrosion products of amalgam into dentinal tubules or from color of underlying amalgam seen through thin, translucent enamel (unsupported) -does not indicate failing restoration/caries and no re-tx needed, unless for esthetics 2) Proximal overhangs: diagnosed visually, tactilely, and radiographically 3) Marginal gap/ditching: shallow ditching of amalgam margin less than 0.5mm usually not reason for retxt b/c it looks worse than it really is -eventual seal-sealing property of amalgam allows restoration to survive as long as it can be cleaned -if ditch is too deep to be cleaned or jeopardizes restoration/tooth structure, it should be replaced 4) Voids: accessible small voids in areas where enamel is thick may be corrected by recontouring or repairing w/ small restoration 5) Fracture lines: detected by clinical exam 6) Line indicating interface btw abutted restorations: acceptable and better than a small intervening strip of enamel 7) Improper anatomic contours: amalgams should mimic normal anatomic contours of teeth -restorations that impinge on soft tissue, have inadequate embrasure form, bad contact, or prevent use of floss should be replaced or recontoured 8) Marginal ridge incompatibility: marginal ridge of amalgam should be compatible w/ adjacent marginal ridge of tooth or restoration -should both be at about same level and display correct occlusal embrasure for passage of food to facial/lingual surfaces and proper contact area -if ridges aren’t compatible, have poor tissue health, food impaction, or can’t floss, should be replaced or recontoured 9) Improper proximal contacts: there should be closed and proper contact btw restoration and adjacent tooth -checked w/ floss or through illumination and mirror inspection (must be dry!) 10) Recurrent caries: detected visually, tactilely, and radiographically 11) Inadequate occlusal contacts: can cause improper occlusal fxning, and tooth movement Part 3: Treatment Planning Treatment Plan Sequencing 1) Urgent/Emergency phase 2) Disease control phase 3) Re-evaluation phase 4) Definitive phase 5) Maintenance phase Restoration of Incipient Lesions -incipient lesions are contained entirely within enamel and haven’t yet spread to dentin -two options to treat: 1) Targeted remineralization and monitoring: first and preferred approach for incipient lesions -incipient lesions do not progress rapidly -changing oral environment combined w/ fluoride varnish and home fluoride can remineralize these lesions 2) Restorative txt: last resort for incipient lesions -be as conservative as possible Criteria for Restoring 1) Poor oral hygiene 2) Low frequency of routine dental care 3) Hx of caries or numerous restorations 4) Cavitation or defect present

5) Lesion extends to DEJ 6) High degree of caries susceptibility 7) Patient age 8) Esthetic txt

Treatment of Abrasion, Erosion, and Attrition -areas of significant attrition that are worn into dentin and are sensitive or annoying should be restored -before cast restorations are used, a complete occlusal analysis and in-depth interview w/ pt regarding etiology should be done to reduce contributing factors -biteguard therapy should be considered also -abrasion or erosion should be considered for restoration if: 1) area is carious 2) defect s deep enough to compromise structural integrity of tooth 3) intolerable sensitivity exists and is unresponsive to desensitizing measures 4) defect contributes to perio problem 5) area to be involved in RPD 6) depth of defect close to pulp 7) pt wants esthetic improvement Treatment of Root Surface Caries -must use caution to only correct active root carious lesions, not areas that are arrested (discolored, but hard to explorer) Treatment of Root Surface Sensitivity -theory for cause of sensitivity is hydrodynamic theory which states the pain results from indirect innervation caused by dentinal fluid movement in tubules that stimulates mechanoreceptors near predentin -cause of fluid shift includes temp. change, air drying, and osmotic pressure -any tx that can reduce fluid shifts by occluding tubules may help reduce sensitivity -dentin hypersensitivity is problem in pts following perio surgery that exposes root surface -tx used to provide relief include topical fluoride, fluoride rinses, oxalate solutions, dentin bonding agents, sealants, iontophoresis, and desensitizing toothpastes -dentin bonding agents work best -when these methods don’t provide relief, restorative tx is indicated Indications for Indirect Tooth-Colored Restorations -may be indicated for class I and II restorations due to esthetics, strength, and other bonding benefits -b/c of potential for bonded restorations to strengthen remaining tooth structure, indirect restorations may be indicated for conservative restoration of weakened posterior teeth in esthetic areas -indirect tooth-colored restorations include: 1) Processed composite: have better wear resistance over direct composites -used mainly in conservative class I and II restorations in low-moderate stress areas 2) Feldspathic porcelain: used for inlays and onlays for class I and II restorations b/c highly esthetic -suffer from high incidence of fracture, especially under heavy occlusal forces -porcelain can also wear opposing tooth structure 3) Cast ceramic: inlays and onlays for class I and II preps have great marginal fit, low abrasion to opposing tooth structure, and superior strength compared to processed composite or Feldspathic -are excellent esthetic alternative to cast metal restorations 4) Computer-generated (CAD/CAM): better physical characteristics than processed composite, are also more expensive due to expense of equipment needed -advantage is they are fabricated chairside, so only one appt needed -do have high strength, low abrasiveness, and highly esthetic Part 4: Hand Instruments Hand Instrument Materials -hand instruments are made from two materials: carbon steel and stainless steel -some made w/ carbide inserts to provide more durable cutting edges (is more brittle though) -carbon steel is harder than stainless steel but will corrode easier -stainless steel will lose its keen edge quicker than carbon steel

Instrument Categories 1) Cutting: excavators, chisels, margin trimmers 2) Noncutting: condensers, mirrors, explorers, probes Instrument Design -most hand instrument have 3 parts: 1) Handle: part operator holds 2) Shank: connects handle to blade 3) Blade: working end of instrument -noncutting instruments have a nib instead of a blade -the end of the nib (working surface) is call the face Cutting Instrument Formulas 1) First number: width of blade in tenths of mm 2) Second number: primary cutting edge angle (always exceeds 50) -if edge is perpendicular to blade, this number omitted, resulting in 3 number formula 3) Third number (2nd number of 3-number code): blade length in mm 4) Fourth number (3rd number in 3-number code): blade angle (always 50 or less) Classification of Hand Instruments 1) Order: describes purpose of instrument 2) Suborder: describes position and technique 3) Class: describes form and shape (chisel or hatchet) 4) Subclass: describes angle of shank (straight, mono, bin, triple angles) Cutting Instrument Applications 1) Excavators: used for removal of caries and refinement of prep 2) Chisels: used for cutting enamel Excavators -four subdivisions: 1) Hatchets: has cutting edge of blade in same plane as long axis of handle -is bi-beveled -used primarily on anterior teeth for preparing retentive areas and sharpening internal line angles 2) Hoes: has cutting edge of blade perpendicular to axis of handle -used for planing tooth prep walls and forming line angles -commonly used in class III and V preps for gold 3) Angle-formers: is a mono-angle instrument w/ cutting edge at angle other than 90 degrees to blade -used primarily for sharpening line angles and creating retentive features in dentin -can also be used to place bevel in enamel margins -like a combo of chisel and gingival margin trimmer 4) Spoons: blades are slightly curved and cutting edges are circular (discoid) or claw-like (cleoid) -used for removing caries and carving amalgam and wax patterns Chisels 1) Straight chisel: cutting edge perpendicular to axis of handle and has bevel on only one side -force used is mainly straight thrust -used to plane/cleave enamel 2) Enamel hatchet: used for cutting and planing enamel surfaces 3) Gingival margin trimmer: designed to produce a proper bevel on gingival margins of proximo-occlusal preps and bevels on axiopulpal line angle in class II preps -blade is curved and cutting edge at angle other than perpendicular to axis of blade

Other Cutting Instruments 1) Knives (finishing knives, amalgam knives, gold knives): have thin, knife-like blade used to trim excess restorative material on gingival, facial, or lingual margins on proximal or class V preps 2) Files: also used to trim excess material, particularly at gingival margins 3) Discoid-Cleoid: used mainly to carve occlusal anatomy in unset amalgam -may be used to trim or burnish inlay-onlay margins -working ends larger than spoon excavator Using Hand Instruments -modified pen grasp has greatest intricacy of touch and is most common -palm and thumb grasp is most powerful grasp Part 5: Power Cutting Instruments Rotary Speed Ranges -rotational speed of power instruments measured in revolutions per minute (rpm) -3 speeds: 1) Low/Slow speed: < 12,000 rpm 2) Medium speed: 12,000 to 200,000 rpm 3) High speed: > 200,000 rpm -crucial factor is velocity at which edges of cutting instrument pass across surface being cut, which is proportional to: 1) rotational speed 2) diameter of instrument (large instruments have higher surface speeds) Laser Equipment -primarily used for soft tissue applications or hard tissue modifications -not used generally for tooth preparation b/c it is difficult to get a defined margin Carbide Dental Burs -rotary cutting burs that have bladed cutting heads -greater number of cutting blades, less efficient but smoother surface will result (polishing burs) -lesser number of cutting blades, more efficient but rougher surface will be (fissure burs) -includes burs for finishing metal restorations and surgical removal of bone, as well as tooth preps -there are also steel burs, which are used for finishing procedures Parts of Bur 1) Shank: part that fits into handpiece -straight, latch-type, and friction-grip 2) Neck: intermediate portion that connect head and shank -transmits rotational and translational forces to head 3) Head: working part of bur Sides of Bur Blade 1) Rake face: surface of blade which makes contact w/ tooth surface and daces in direction of bur rotation 2) Clearance face: surface of blade that faces away from direction of bur rotation Angles of Bur Blade 1) Rake angle: angle btw line connecting edge of blade to axis of bur and rake face -most impt part of bur blade -carbide burs for cutting tooth/amalgam have negative rake angle -burs used to cut acrylic/soft materials have positive rake angle 2) Edge angle: angle formed btw rake face and clearance face 3) Clearance angle: angle formed btw clearance face and tangent to path of rotation -eliminates friction (higher clearance angle, less friction) Round Burs -used for initial entry into tooth, preparation extension, preparing retentive features, and caries removal

Inverted Cone Bur (#34) -rapidly tapered cone wider at apex and tapers toward neck of bur -good for preparing undercuts into preparations Pear-Shaped Bur (#330) -more slightly tapered bur widest at apex and tapers toward neck of bur -end of bur is either continuously rounded or flat w/ rounded corners -used especially in Class I preps for gold foil as well as amalgam preps Straight Fissure Bur (#56) -elongated cylinder used for amalgam preps Tapered Fissure Bur (#169) -slightly tapered bur w/ narrowest part at apex and widest part at neck of bur -used for preps for indirect restorations that can’t have undercuts Diamond Abrasive Instruments -involves abrasive cutting instead of blade cutting -based on small, angular particles of a hard substance held in a matrix of softer material -cutting occurs at a large number of points where individual hard particles protrude from the matrix rather than along a continuous blade edge -diamond burs consist of a metal blank, the powdered diamond abrasive, and a metallic bonding material that holds diamond powder onto the blank Diamond Particle Factors -performance depends on size, spacing, uniformity, exposure, and bonding of diamond particles -increased pressure causes particles to dig into surface more deeply, leaving deeper scratches and removing more tooth structure -particles size categorized as coarse, medium, fine, and very fine, which corresponds to standard sieve sizes which separate diamond particles -larger particles means number of particles is decreased, so more force is applied to each particle -diamond finishing burs use even finer diamonds to produce smooth surfaces for final polishing Cutting Mechanisms -requirements for effective cutting include handpiece, air-water spray for cooling, high operating speed (>200,000 rpm), light pressure, and bur -carbide burs are better for end-cutting, produce lower heat, and have more blade edges per diameter -used for punch cuts to enter tooth structure, intracoronal tooth prep, amalgam removal, small preps, and secondary retentive features -diamond instruments have greater hardness and very high cutting effectiveness -more effective than burs for both intracoronal and extracoronal tooth preps, beveling enamel margins, and enameloplasty Hazards with Cutting Instruments 1) Pulpal precautions: cutting instruments can harm pulp by mechanical vibration, heat generation, dessication and loss of dentinal tubule fluid, and transection of odontoblastic processes -as thickness of dentin decreases, pulpal insult increases 2) Soft-tissue precautions: should isolate operating field from soft tissue by rubber dam, suction/assistant, cotton roll, mirror, etc. 3) Eye precautions: wear glasses w/ eye shields (dentist more likely to have eye injury than assistant) -if eye is injured, it should be covered w/ gauze until medical attention received 4) Ear precautions: high-pitch from high speed handpiece may cause hearing loss 5) Inhalation precautions: aerosols of tooth structure, restoration debris, microorganisms, etc. should be avoided by using intraoral evacuation when cutting -rubber dams can prevent inhalation by patient, but operators should use face masks (filter out bacteria and fine particulate matter, but not mercury or monomer vapors from restorations)

Part 6: Tooth Preparation Emphasis on Conserving Tooth Structure in Tooth Preps 1) Supragingival margins 2) Minimal pulpal depth 3) Minimal B-L width 4) Rounded internal line angles Principles of Tooth Preparation 1) All prepped walls and internal line angles should be placed in dentin that is free of infection, hard, and can’t be flaked away 2) Prepped cavity should be extended to include all decay and provide convenience for restoring and finishing 3) Enough depth and width should be prepped to prevent fracture of tooth and restoration a) about 1/5 distance btw buccal and lingual cusps b) at least 0.5mm into dentin c) pulpal floor should be flat and parallel to occlusal surface -should ideally be at least 2mm of dentin btw amalgam and pulpal floor -pulpal floor should be tilted lingually in mand 1st PM due to high buccal pulp horn d) line angles should be rounded and defined (sharp line angles increase risk of fracture) Cavity Classification by Number of Surfaces Involved 1) Simple cavity: lesion confined to one surface 2) Compound cavity: lesion involves two surfaces 3) Complex cavity: lesion involves three or more surfaces G.V. Black Cavity Classification 1) Class I: involves pit/fissure caries -occlusal surface of posterior teeth and lingual surface of anterior teeth -mesial/distal walls should diverge occlusally; buccal/lingual walls parallel -if width of marginal ridge less than 1.6mm, should be converted to class II -difficult to see radiographically 2) Class II: involves proximal surfaces on posterior teeth -occlusal outline at proximal segment dictated by position of proximal contact and extent of caries -proximal walls are divergent occluso-gingivally -gingival floor should parallel the enamel rods 3) Class III: on proximal surfaces of anterior teeth that don’t include incisal angle -for esthetic reasons, unsupported enamel may be left intact -composite is preferred material (distal of canine may be restored in amalgam) 4) Class IV: cavities of proximal surfaces of anterior teeth that involve incisal angle 5) Class V: cervical caries in gingival 1/3 of buccal or lingual surfaces -dictated by extent of caries -mesial and distal walls parallel enamel rods -occlusal wall is longer than cervical/gingival wall in ideal preps, giving trapezoidal shape 6) Class VI: on incisal edges of anterior teeth or on occlusal cusp heights of posterior teeth Initial Tooth Preparation 1) Outline form 2) Resistance form

3) Retention form

4) Convenience form

Outline Form -Def: Extension of the prep walls to sound tooth structure in all directions except pulpally. -shape or form of cavity on surface of tooth -margins placed in areas of lessened caries susceptibility (extension for prevention) -all undermined enamel must be removed -extension to sound, finishable tooth structure at initial depth of 0.2 to 0.75 mm into dentin 1) Principles: a) place margins where finishable b) remove unsupported, weakened tooth structure c) include all faults 2) Dictated by: caries, old material, defect size, occlusion, marginal configuration, and adjacent tooth contour 3) Features: a) Preserve cuspal strength d) Connect two close preps (within 0.5mm) b) Preserve marginal ridge strength e) Restrict depth to 0.2-0.75mm into dentin c) Keep B-L width narrow f) Use enameloplasty 4) Pit and fissure preps: extend to all of the fissure that is not eliminated by enameloplasty 5) Smooth surface preparations a) extend until no friable enamel remains b) don’t stop margins on cusp heights or ridge crests c) extend gingival margin/floor to get 0.5mm clearance d) extend facial and lingual proximal walls to clearance 6) For class V preps, outline is governed only by extent of lesion, except pulpally 7) Enameloplasty: removal of defect by recontouring enamel when defect is no deeper than ¼ thickness of enamel -when defect is greater than 1/3 thickness of enamel, the wall must be extended Resistance Form -prevention of tooth OR restoration fracture from occlusal forces along long axis of tooth 1) Factors: a) occlusal contacts b) amount of remaining tooth structure c) type of restorative material 2) Features: a) flat floors (pulpal and gingival) e) remove weakened tooth structure b) box shape f) cap cusps if needed c) preserve marginal ridges g) round internal line angles d) preserve cuspal strength h) adequate thickness of material Preserving Marginal Ridges -mesial and distal walls in class I prep should be divergent to prevent undermining of marginal ridges -for premolars, distance from margin of prep to proximal surface should be at least 1.6mm -for molars, distance from margin of prep to proximal surface should be at least 2mm Rule for Cusp Capping 1) If extension from a primary groove toward the cusp tip is no more than half the distance, no cusp capping needed 2) If extension is ½ to 2/3 of the distance, consider cusp capping 3) If extension is more than 2/3 the distance, usually cap the cusp Retention Form -prevention of dislodgement of restoration -preparation should have some undercuts for retention, or other retentive features if can’t use undercuts -should have sufficient height to have bulk of material Convenience Form -alterations made to prep to improve access and visibility for preparing and restoring the cavity

-aids operator in preparing, placing, and finishing restoration Final Tooth Preparations 1) Remove remaining caries 2) Secondary resistance/retention forms 3) Finishing external walls Removal of Remaining Caries -initial prep may remove all of caries, but additional removal may be needed -if have deep excavation and questionable dentin near pulp, can use indirect pulp cap (leave dentin, CaOH, GI base, restoration) Pulp Exposure 1) Indirect pulp cap indicated if: a) small exposure (<1mm) b) asymptomatic tooth c) isolated area d) hemorrhage controlled -indirect pulp capping should be reopened in 3-4 months to check status and remove remaining decay 2) Endo txt indicated if: a) Exposure large (>1mm) b) symptomatic tooth c) area contaminated (saliva, debris) d) purulent exudate Pulp Protection 1) Sealers: seal dentinal tubules -is desirable for ALL restorations 2) Liners: used when cavity prep is within 0.5mm from pulp -ex. CaOH (stimulates formation of reparative dentin) a) placed in 0.5mm thickness b) Provides minimal thermal and mechanical protection c) provides some chemical protection 3) Bases: provide bulk for thermal and mechanical protection (need approximately 2mm bulk between pulp and metallic restorative material) -glass ionomer is typical base choice -other bases are zinc phosphate and polycarboxylate cement Secondary Resistance and Retention Features 1) Mechanical/Preparation Features a) retentive locks, grooves, coves (mainly for metallic restorations) b) groove extensions c) skirts (for cast restorations) d) beveled enamel margins (cast and composite restorations) e) pins, slots, steps, amalgam pins (mainly for amalgams) 2) Surface treatment of prepared walls a) Enamel wall: etching for bonded restorations b) Dentin wall: etching and priming for bonded restorations 3) Cement (for cast restorations)

Finishing of External Walls -establishing the design and smoothness of cavosurface margin 1) Objectives: a) get best seal btw tooth and restoration b) have smooth junction btw tooth and restoration c) maximum strength for tooth and restoration 2) Features a) bevels b) butt joints 3) Considerations a) direction of enamel rods b) support of enamel rods c) type of material d) location of margin e) degree of smoothness required Tooth Preparation Features: Amalgam vs Composite Amalgam Includes adjacent suspicious Outline form areas Pulpal depth uniform 1.5mm Axial depth uniform .2-.5mm inside DEJ Cavosurface margin 90 degree amalgam margin Bevels only gingival Texture of prepped walls smooth Cutting Instrument burs Primary retention form convergence occlusally Secondary grooves, slots, locks, pins, retention form bonding Resistance flat floors, rounded angles, form box-shaped floors Base need 2mm btw pulp and indications amalgam Liner indications CaOH Sealer used when not bonding

Composite Does not include adjacent suspicious areas remove fault (not usually uniform) remove fault (not usually uniform) 90 or greater degrees included for esthetic and seal rough diamonds none needed (bonded) bonding similar for large preps; no special form for small restorations not needed CaOH sealed by bonding system

Part 7: Moisture Control Goals of Isolation 1) Moisture control 2) Retraction and access 3) Harm prevention 4) Local Anesthesia Rubber Dam -isolates working field, prevents moisture and contamination, retracts soft tissue, and saves time 1) Advantages a) increased access and visibility d) protects pt and operator g) impr. mater. properties b) isolates area e) retracts soft tissue c) keeps area dry f) preserves and protects materials 2) Disadvantages a) some pts object c) partially erupted teeth e) time consuming b) some situations don’t work d) extremely malpositioned teeth f) asthma -alternatives to rubber dam for moisture control include cotton roll isolation and cellulose wafers (dry angle) Five Fxns of Rubber Dam 1) Retracts soft tissue 2) Provides clean, dry field 3) Protects pt and dentist 4) Provides for maximum physical properties of materials 5) Can save time for multiple preps Problems w/ Rubber Dam 1) Wrinkling of rubber dam btw teeth: holes punched too far apart 2) Papillae protrude from beneath dam: holes punched too close together Clamping -for clamp to be stable, all four points of jaws of clamp must contact tooth gingival to HOC -points of clamp must not extend beyond line angles to prevent impinging on papillae and interference w/ wedge Rubber Dam Frames 1) Young’s frame: most popular; U-shaped metal frame 2) Woodbury’s frame: provides most retraction of soft tissues Part 8: Liners, Bases, and Cements Liners -the only use of liner is to effect a pulpal response to lay down reparative dentin as used for direct or near pulpal exposure -traditional liner used is CaOH -glass ionomer liners may be used in conjunction w/ composite restorations as stress breaker in class I composites and on root surface of class II composite -should have thickness of 5 microns -should differentiate btw liners and varnishes 1) Liners: suspensions of CaOH in water (DyCal); may contain fluoride -liners are thicker than varnishes 2) Varnishes: solution liners of resin in liquid (Copalite) -varnishes shouldn’t be used under composites b/c disrupt monomer -varnishes under amalgam serve to reduce microleakage and seals tubules -do not act as thermal barriers

Bases -additional bulk from base affords mechanical and thermal protection (low thermal conductivity) to pulp under metal (amalgam/gold) restorations -termed base when 2mm or thicker which fxn to replace missing dentin structure 1) Glass ionomer: has been recommended as base to overly any CaOH liner -protects liner from amalgam condensation or dissolution of liner from etchant application for composite -used for posterior composites, porcelain/composite inlays or onlays, and amalgam -considered near ideal base b/c adheres to tooth structure, snap set when light-cured, anticariogenic (fluoride-releasing), and can bond to composite 2) Zinc phosphate/zinc polycarboxylate: used under gold restorations -must use varnish before zinc phosphate application 3) Secondary bases: zinc phosphate cement over CaOH base over pulp exposure (direct pulp cap) Thermal Insulation Capacity of Base Dependent On: 1) Thickness of base 2) Thermal conductivity of base 3) Density of base Base Use w/ Amalgam Restorations 1) Shallow excavations: if 2+mm dentin remains after prep, only sealer needed (Gluma Desensitizer or Copalite) 2) Moderately deep excavations: if btw .5 and 2mm of dentin remains, GI base can be placed to build total thickness from pulp to 2mm then sealer 3) Deep excavation: if less than 0.5mm or small pulp exposure encountered, place CaOH liner and 2mm GI base then sealer Base Use w/ Composite Restorations 1) Shallow excavations: if 2+mm dentin remains, no varnish, liner or base needed (GI cement may be placed) 2) Moderately deep excavations: if btw 0.5mm-2mm dentin remains, GI base can be placed to fill 3) Deep excavations: if <0.5mm or small pulp exposure encountered, CaOH placed, then GI base Base Use w/ Indirect Inlay/Onlay Restorations 1) Shallow to moderately deep excavations: if at least 0.5mm of dentin remains, no liner or base needed 2) Deep excavations: if less than 0.5mm or small pulp exposure occurs, place CaOH only Cements -should have thickness of 15-25 microns 1) Glass ionomer: most common cement; used mostly for final cementation of crowns/bridges -fluoride releasing (anticariogenic), micromechanical and chemical bonds, nonirritating -water-based -contain fluoroalumina-silica glass powder and polyacrylic acid solution -least solubility after setting 2) Zinc polycarboxylate: zinc oxide powder and polyacrylic acid solution -used for final cementation of crowns/bridges -nonirritating but not as strong as other cements -water-based -most solubility after setting -first cement developed to chemically bond to tooth structure 3) Zinc phosphate: water-based cement for final cementation of cast crowns/bridges (not popular) -highly acidic (pH 4.2) and can cause pulpal damage so need varnish underneath to protect pulp -zinc oxide powder and orthophosphoric acid liquid -must be mixed on cold glass slab to increase working time by retarding exothermic rxn -shrinks slightly on setting

-superior strength compared other cements 4) Zinc oxide eugenol (ZOE): oil-based cement w/ sedative effect on pulp -can’t use w/ composite b/c eugenol inhibits polymerization -also can’t be used in direct pulp caps b/c irritates pulp when in direct contact -can be used as temporary cement (low strength) -zinc oxide, resin, zinc acetate, accelerator, and eugenol liquid -has pH of around 7, which makes it one of least irritating cements Interim Restorations -cements mixed to a thicker consistency can be used as temporary fillings -ZOE is most common (IRM) and protects pulp, reduces pulp inflamm., and maintains tooth structure -should be mixed in under 1 minute Part 9: Properties of Restorative Materials Ultimate Strength -defined as point on stress-strain curve at which fracture occurs -3 variables: 1) Compressive strength: stress required to fracture a material when forces applied opposite and towards each other (pressing) -enamel=amalgam>dentin=composite 2) Tensile strength: forces applied opposite and away from each other (pulling) -dentin>amalgam>composite>enamel 3) Shear strength: forces applied opposite and toward each other but at difft. positions (sliding) Dimensional Change -is the percent of expansion or contraction of a material -when thermal expansion of tooth does not equal that of restoration, the differing expansions result in leakage of fluids btw the two -percolation refers to intermittent inlet and outlet of fluid leakage and can result in marginal decay -coefficient of thermal expansion: measures per unit length expansion if a material is heated by 1 degree C -composite>amalgam>gold=tooth Thermal Conductivity -quantity of heat transferred per second across an area and length when temp. difference is 1 degree C/cm -gold>amalgam>composite=tooth Stress -force per unit area -stress=force/area -the smaller the area the force is applied, the greater stress experienced -a small area of contact on restoration has more stress than broad area of contact Strain -change in deformation per unit length of material subjected to stress -rubber has greater deformation (strain) than gold Elastic Modulus -measure of stiffness/rigidity of material -higher elastic modulus=more rigid material -elastic limit: greatest stress an object can be subjected to in which it can return to its original dimension once force is removed -material loaded beyond elastic limit results in both elastic and plastic deformation -gold>enamel>amalgam>composite>dentin

Proportionate Limit -stress at which material no longer fxns as elastic (greatest stress that can be produced before permt. deformation exists) -greatest stress produced such that stress is directly proportional to strain -yield strength: arbitrary stress point immediately higher than proportionate limit and defines point at which permt. deformation begins -gold>enamel>amalgam>composite>dentin -brittleness is measure of material’s likeliness to fracture at its proportional limit -brittle material has high compressive strength and low tensile strength Coefficient of Thermal Expansion -measure of tendency of material to change shape when subjected to temp. change -possible break in marginal seal of restoration becomes imminent when there is marked difference in CTE btw tooth and restoration -one of consequences of thermal expansion and contraction is percolation which is cyclic ingress/egress of fluids at restoration margins -possibility of recurrent decay increases w/ increased percolation -ranks of CTE: tooth
-mercury content should be less than 55% -reacts to produce difft. amalgam phases (initiates rxn w/ alloy) -amt of mercury remaining in set amalgam related to how much of mercury-rich matrix left in amalgam after condensation -key is to minimize amt of matrix forming during rxn -by condensing amalgam, mercury-rich matrix will come to surface and be removed when carving -mercury vapor most likely occurs during condensation, so high-speed suction should be used Types of Amalgam 1) Low copper: inferior properties; 6% or less copper; spherical particles 2) High copper: high copper alloys have 10-30% Cu by weight a) Spherical: has greater leakage and postop sensitivity (less mercury) -spherical amalgams high in copper have best tensile and compressive strength b) Lathe-cut: irregular (higher mercury) c) Admixed: combo of spherical and lathe-cut (easier to carve but need more condensation force) -copper adds strength by eliminating y2 phase -smaller particle size results in increased compressive strength and decreased setting expansion Properties of Amalgam -linear coefficient of thermal expansion (LCTE) is greater than tooth structure -compressive strength of high copper amalgam is similar to tooth structure -amalgam has 10x more compressive strength than tensile strength -weak condensation results in voids, causing weaker amalgam -amalgam is brittle and have low edge strength -creep is the gradual dimensional change resulting from constant stress -high copper amalgams have no clinically relevant creep or flow b/c y2 phase eliminated -over/undertriturating increase creep -increasing condensation pressure decreases creep -amalgam is a high thermal conductor and poor thermal insulator -amalgam should not contract or expand after setting -tarnishing and corrosion result from chemical rxns btw amalgam and oral environment a) tarnish: results in discoloration at amalgam surface -discoloration most likely a sulfide b) corrosion: results in destruction of restoration as it occurs deeper in body of amalgam -smoother, polished amalgams have decreased corrosion and tarnish -marginal leakage decreases w/ time due to increased corrosion byproducts (tin sulfide) -discolored, corroded superficial layer on amalgam surface is the sulfide Delayed Expansion of Amalgam -due to: 1) Insufficient trituration and condensation 2) Contamination by moisture during condensation (principle cause of failures) -moisture contamination greatly reduces compressive strength Trituration -process of mixing the alloy w/ mercury in amalgamator (coats alloy particles w/ mercury) a) Undertriturated: dull ,crumbly, decreased strength, increased creep b) Overtriturated: wet, runny, very decreased strength, increased creep, increased corrosion -overtriturated better than undertriturated c) Properly triturated: shiny, smooth, homogenous -Ag and Sn react to form silver alloy, which reacts w/ Hg to form dental amalgam -longer trituration time decreases setting expansion

Amalgamation -reaction of silver alloy w/ mercury: -Ag3Sn (y) + Hg  Ag3Sn (y) + Ag3Hg4 (y1) + Sn3Hg (y2) -y is strongest phase, y1 is second strongest, and y2 is weakest/most corrosive phase -strongest phase has no mercury b/c mercury decreases strength -adding Cu eliminates weak y2 phase -good condensation and carving can minimize amount of mercury-rich amalgam Advantages and Disadvantages of Amalgam 1) Advantages a) strength e) proven history of use b) wear resistance f) lower fees c) easy to use g) long term clinical longevity d) less technique sensitive 2) Disadvantages a) not esthetic b) conductivity c) tooth prep more demanding and less conservative Concerns for Amalgam 1) Mercury content and disposal 2) Removal of tooth structure 3) Esthetics

4) Unless bonded, no bonding benefits 5) Recurrent caries 6) Marginal leakage until corrosion occurs (several months)

Mercury Controversy -lack of scientific evidence that amalgam poses health risks to humans except for rare allergic rxns -efforts underway to reduce environmental mercury to which ppl are exposed to lessen exposure -there is no evidence ensuring that alternative materials pose lesser hazard -true allergies to amalgam rarely have been reported (1 in 100 million ppl) Amalgam Uses 1) Nonesthetic cervical lesions 2) Large class I and II restorations where heavy occlusion will be on the material 3) Class I and II restorations where isolation problems exist 4) Temporary/caries control restorations 5) Foundations 6) Patient sensitivity to other materials 7) Cost is factor 8) Inability to do a good composite Requirements for Successful Amalgam Restorations 1) High copper material 2) 90 degree cavosurface margins 3) Adequate thickness of amalgam (1-2mm) 4) Mechanical retention form 5) Sealing of tubules 6) Good condensation (including laterally)

Principles of Tooth Preparation 1) Initial stage a) place tooth prep extension into sound tooth structure at marginal areas (not pulpally or axially) b) extend depth pulpally and axially to uniform dimension c) provide an initial form that retains amalgam d) establish tooth prep margins in form that results in 90 degree amalgam margin once amalgam is inserted 2) Final stage -removes any remaining defect (caries/old restoration) and incorporates any additional prep features (slots, pins, etc.) to achieve retention and resistance form Initial Tooth Prep Depth -all initial depths of tooth prep for amalgam relate to DEJ, except in two instances: a) When occlusal enamel has been significantly worn thinner b) When prep extends onto root surface 1) Initial depth pulpally will be 0.2mm inside DEJ or 1.5mm as measured from depth of central groove, whichever results in greatest thickness of amalgam 2) Initial depth of axial wall will be 0.2mm inside DEJ where retention locks are used -deeper extension allows placement of retention locks without undermining marginal enamel -axial depths on root surface should be 0.75-1mm deep to provide room for retentive grooves and bulk of amalgam Outline Form for Amalgam -all walls meet surface of tooth at 90 degree angle -when making prep extensions, every effort should be made to preserve strength of cusps and marginal ridges -when possible, outline form should be extended around cusps and avoid undermining dentin support of marginal ridge enamel -when viewed from occlusal, the facial and lingual proximal box cavosurface margins of class II prep should be 90 degrees -facial and lingual proximal box walls should extend just into facial and lingual embrasures -provides adequate access for performing preparation, easier placement of matrix, and easier condensation and carving of amalgam Cavosurface Margin for Amalgam -if either enamel or amalgam has marginal angles less than 90 degrees, they are subject to fracture Primary Retention Form -retention form preparations lock/retain restorative material in the tooth -for composites, micromechanical bonding provides most of retention -for both bonded and nonbonded amalgams, the amalgam must be mechanically locked inside tooth -amalgam retention provided by: 1) Mechanical locking of amalgam into surface irregularities of prepped tooth 2) Preparation of vertical facial and lingual walls that converge occlusally -inverted cone bur (245) provides correct wall shape for retention 3) Locks, grooves, coves, slots, pins, steps, amalgampins (all of these type are actually secondary retention form) -retentive grooves can be placed in axiobuccal and axiolingual line angles in prox. boxes

Amalgampins -retention on pin increases as diameter of pin increases -largest pin that can be safely placed should be selected -one pin per missing axial line angle should be used -optimal placement is at line angles/corners of tooth where root mass is greatest and risk of perforation is lowest -pins should not be bent, but if necessary use a bending tool (not hand instrument) -placed to increase retention of large restorations, but weaken restoration overall -placed at least 0.5mm inside DEJ and 1.5mm from cavosurface margin -should extend 2mm into dentin and restorative material -coating pins w/ adhesion promoters improves fracture resistance of core materials -types of pins: 1) Cemented -serrated pins that are cemented into pinholes larger than diameter of pin 2) Friction-lock -tapped into pinholes smaller than diameter of pin -not to be used in RCT teeth 3) Self-threading (most retentive) -comes in self-limiting drill of optimal 2mm depth and self-shearing pins -most common type used -disadvantages: create stresses that craze tooth structure, increase microleakage, can cause pulpal problems Primary Resistance Form -helps restoration and tooth resist fracture from occlusal forces a) resistance form features that prevent tooth from fracturing include: 1) Maintaining as much unprepped tooth structure as possible (cusps and marginal ridges) 2) Pulpal and gingival walls/floors prepared perpendicular to occlusal forces 3) Rounded internal prep angles 4) Removing unsupported/weakened tooth structure 5) Placing pins into tooth (secondary resistance form) 6) Beveling gingival floor to prevent fracture of unsupported enamel in this area -only done if in enamel, not if gingival floor in cementum -not required in primary teeth b/c enamel rods extend occlusally in gingiva third b) resistance form features that prevent amalgam from fracturing include: 1) Adequate thickness of amalgam (1.5-2mm in occlusal contact areas; 0.75mm in axial areas) 2) Marginal amalgam angle of 90 degrees of more 3) Box-like prep form to provide uniform amalgam thickness 4) Rounded axiopulpal line angles in class II preps Convenience Form -features that make procedure easier or area more accessible -includes extension of outline form so marginal form can be established, caries better accessed, matrix band placement, or amalgam to be inserted, carved, and finished Secondary Resistance and Retention Form -if it is determined that insufficient resistance/retention form exists, additional procedures can be placed -many features that enhance retention form also enhance resistance form -includes grooves, slots, locks, coves, pins, amalgampins -usually, the larger the tooth prep, the more need for secondary resistance/retention form

Matrix Band 1) Objectives a) provide proper contact b) provide proper contour c) confine restorative material d) reduce amount of excess material 2) Placement principles a) must be easy to place and remove b) must extend below gingival margin and above marginal ridge height by at least 1mm c) must resist deformation during amalgam condensation -most difficult tooth to adapt matrix band to is mesial surface of max. 1st PM due to developmental depression -diagonal slot on Tofflemire always placed toward gingiva to facilitate easy separation of Tofflemire from matrix band in occlusal direction Wedges 1) Depress gingiva apically 2) Cause minimal separation 3) Minimize oozing of fluids through rubber dam -inserted through facial or lingual embrasure, whichever is larger -wedging action must provide enough separation to compensate for thickness of matrix band Condensing the Amalgam -lateral condensation very important in proximal box to ensure confluence of amalgam with margins -spherical amalgam is more easily condensed that admixed (lathe-cut) amalgam -smaller amalgam condenser are to be used first to allow amalgam to be properly condensed into internal line angles and secondary retention features -smaller the condenser point, the greater pressure exerted on amalgam -once amalgam is placed to slight excess w/ condensers, a pre-carve burnish should be done w/ acorn/eggshaped burnisher to finalize condensation and remove excess amalgam Carving the Amalgam -nonbonded amalgams are easier to carve than bonded amalgams due to excess adhesive resin which accumulates at margins -care must be taken to prevent breaking out huge chunks of amalgam when carving bonded amalgam 1) Occlusal areas: discoid-cleoid used to carve occlusal areas a) Rounded discoid part used first on unprepared enamel surface and pulled parallel to margin to remove excess amalgam from margin b) Cleoid part used next to carve in groove and pit anatomy c) Discoid portion used again to smooth out anatomic form d) for large class II amalgams, initial carving of marginal ridges and occlusal embrasure areas can be done w/ explorer tip pulled along inside of matrix band e) embrasure and marginal ridge form should be as identical as possible to adjacent tooth f) having definite and rounded occlusal anatomy helps provide spillways for escape of food from occlusal table 2) Facial/lingual areas: Hollenbeck carver useful in these areas, or base of amalgam knife (34/35 scaler) -contour of cervical areas of facial/lingual should be convex and follow tooth structure 3) Proximal embrasure areas: amalgam knife/scaler useful for contouring proximal embrasures -proximal contact can be checked w/ floss (carefully) or reflecting light through contact Finishing the Amalgam -occlusal contacts should be checked w/ articulating paper and adjusted as needed -lightly moistened cotton pellet can be used to smooth and polish amalgam

Polishing Amalgam Restorations -should wait at least 24 hrs to polish amalgam to make sure it is completely set -should use wet abrasive powder in paste form to prevent overheating past 60 C/140 F (danger point) -3 reasons to polish amalgams: 1) reduce marginal discrepancies and make more hygienic 2) reduce marginal breakdown 3) prevent tarnishing and improve appearance Repairing an Amalgam Restoration -if part of amalgam fractures during insertion, the defective portion can be reprepped as a small restoration w/ a new mix of amalgam condensed directly into defect and will adhere to amalgam already present Class V Amalgam Form -outline form should be deformed trapezoid (kidney-bean) and is determined by location and size of caries -retention form provided by retentive grooves placed at gingivoaxial and incisoaxial line angles -mesial and distal walls should never extend past transitional line angles -occlusal and gingival walls should be gently curved arcs as determined by contour of free gingival margin -two arcs should be as parallel to each other as possible -occlusal arc is usually longer of two -mesial, distal, gingival, and incisal walls should all diverge outward Common Problems of Amalgam Restorations 1) Postop sensitivity: caused by lack of adequate condensation or proper dentinal sealing 2) Marginal voids: caused by inadequate condensation or material pulling away from tooth during carving 3) Marginal ridge fracture: caused by not rounding axiopulpal line angle, leaving ridge too high, incorrect embrasure form, improper matrix removal, and overzealous carving 4) Amalgam scrap and mercury collection disposal Controversial Topics in Amalgam 1) Amalgam safety: amalgam is a safe material and US Public Health Service has reported its safety -proper handling of amalgam and its disposal are important 2) Spherical vs admixed amalgam: spherical amalgam has advantages in providing higher earlier strength and permitting use of less pressure -admixed amalgam permits easier proximal contact development b/c of higher condensation forces 3) Bonded amalgam restorations: bonded amalgams are no longer recommended, but if used, should be limited to larger restorations and still have secondary retentive features 4) Proximal retention locks: should only be used for larger amalgam restorations b/c correct placement if difficult Part 11: Dental Bonding Advantages of Bonding to Tooth Structure 1) Less microleakage 6) More conservative tooth preps 2) Less marginal staining 7) Improved retention 3) Less recurrent decay 8) Reinforcement of remaining tooth structure 4) Less pulp sensitivity 9) More conservative txt of root surface lesions 5) Reduced sensitivity in cervical erosion/abrasion Uses of Adhesive Techniques 1) Change shape and color of anterior teeth 2) Restore class I-VI lesions 3) Improve retention for metal or PFM crowns 4) Bonding ceramic restorations 5) Bonding indirect composites 6) Sealing pits and fissures

9) Bond conservative tooth-replacement restorations 10) Repair existing restorations 11) Provide foundation for crowns/onlays 12) Desensitize exposed root surfaces 13) Impregnate dentin to decrease risk of caries 14) Bond fragments of anterior teeth

7) Bonding ortho brackets 15) Bond prefabricated and cast posts 8) Bonding perio splints 16) Reinforce remaining enamel/dentin after preps Enamel vs Dentin Bonding 1) Enamel bonding: 30-40% phosphoric acid a) 15 second etch is sufficient b) fast, reliable, predictable, and strong c) microleakage virtually nonexistent d) resists polymerization shrinkage forces of composite 2) Dentin bonding: penetration of adhesive monomers into collagen fibers left by acid etching a) slower, less reliable, and less predictable b) may have microleakage c) similar or higher bond strengths than enamel d) may not resist polymerization shrinkage forces of composite Factors Affecting Ability to Bond to Dentin 1) Microstructural features of dentin a) Dentin composition: much less mineral, more organic (type I collagen), and more water than enamel (enamel is 90% mineral hydroxyapatite) b) Dentin tubules: peritubular, intratubular, and intertubular channels -tubules run from pulp to DEJ and contain odontoblastic extensions and fluid -tubules are much larger and numerous near pulp than DEJ -fluid movement inside tubules is dictated by pulpal pressure c) Dentin sclerosis: aging dentin, dentin below caries, or dentin exposed to oral fluids have increased mineral content and is more resistant to acid-etching and therefore penetration of dentin adhesive is limited d) Smear layer: debris left of surface after cutting -consists of hydroxyapatite and altered, denatured collages -fills orifices of dentin tubules, decreasing dentin permeability -etching removes smear layer, resulting in greater fluid flow onto dentin surface which can interfere w/ adhesion e) Linear coefficient of thermal expansion: dentin has LCTE 4x less than composite material 2) Tooth factors a) Attrition: normal tooth wear b) Abrasion: mechanical wear due to abnormal forces (toothbrushing) c) Erosion: wear due to chemical presence d) Abfraction: biomechanical loading causes loss of tooth structure in cervical region -occlusal forces cause tooth to bend, making microfractures in thin cervical enamel 3) Material factors: composites shrink as they polymerize, creating high stresses 4) Preparation factors: preps w/ multiple walls have limited stress relief opportunity for composite, so the high C-factor (configuration factor) may result in internal bond disruption and marginal gaps -C-factor determined by ratio of bonded:unbonded surfaces within a tooth prep -high C-factor may indicate increased risk for postop sensitivity Dentin Bonding Systems 1) Total etch (enamel and dentin etched) 2) Self-etching primer systems (SEP)

Total Etch Bonding System -etches enamel and dentin w/ acid simultaneously -two types: multi-bottle systems and one-bottle systems 1) Multi-bottle systems: etchant, primer, and adhesive separate (gold standard) -tooth structure is etched w/ acid to open microspaces in enamel/dentin which cleans debris from surface and increases surface area for bonding (etched enamel is chalky, dentin is normal) -etched dentin exposes a layer of collagen, and primer raises the collagen so adhesive can flow btw collagen and interlocks w/ it to form hybrid layer -most bond strength is from formation of hybrid layer (mix of dentin and resin) -this seals dentin to decrease post-op sensitivity -dentin has good bond strength (as good as or better than enamel bonding) 2) One-bottle systems: primer and adhesive are combined, but etchant is separate -most require wet bonding -bonding mechanism is also through hybrid layer -bond strengths not as high as multi-bottle systems but very close -is very technique sensitive and usually not performed any faster than multi-bottle systems Steps in Multi-Bottle System 1) Etch dentin and enamel w/ 34% phosphoric acid -etches enamel, removes smear layer, opens dentin tubules, demineralizes dentin, and etches out mineral (hydroxyapatite) but leaves collagen fibrils 2) Rinse etchant (must leave wet or rewet w/ AquaPrep or GLUMA Desensitizer) 3) Add primer (HEMA/BPDM) -HEMA: hydroxyethyl methacrylate; BPDM: biphenyl dimethacrylate -primer is resin monomer wetting agent which is bifunctional a) wets dentin (increases surface tension) b) bonds to overlying resin -primer also acts as a solvent to penetrate through remnant smear layer into intertubular dentin to fill in spaces left by dissolved hydroxyapatite crystals 4) Add adhesive/bonding agent (Bis-GMA) -Bis-GMA: bisphenol A glycidyl methacrylate -penetrates primed intertubular dentin and dentin tubules to provide polymerized surface layer than bonds primer and composite Steps in One-Bottle System 1) Etch for 10 seconds 2) Rinse well and leave moist 3) Apply 2-3 layers of primer/adhesive combo, thin w/ air spray, then light cure 4) Place composite Self-Etching Primer (SEP) Bonding Systems -etchant and primer combined or etchant, primer, adhesive all combined -objective is to remove operator variables (rinsing and drying) -do not completely remove smear layer (why they have less post-op sensitivity) -need to be refrigerated (have reactive components) -must use carbide burs for preps, not diamonds b/c diamonds leave much thicker smear layer -don’t etch enamel as well as phosphoric acid -two types: 1) One-step (all-in-one): risky to use -doesn’t remove smear layer -not as good bond to dentin 2) Two-step (self-etch primer, then use bonding adhesive) -requires multiple coats (~5) -doesn’t remove smear layer -no rinsing needed

-doesn’t bond well to uncut enamel, so must roughen enamel surface -low post-op sensitivity Advantages/Disadvantages of Self-Etching Systems 1) Advantages a) Easy to use b) Eliminates variables w/ wet bonding c) Depth of etch is self-limiting d) Sensitivity is reduced 2) Disadvantages a) Bond strengths to enamel and dentin lower b) Some don’t adequately etch uncut enamel c) Bond strengths to autocuring composites are poor d) Clinical performance not proven e) Bond durability questionable Technique Suggestions for Bonding Agents 1) Use microbrushes to apply primer/adhesive 2) Place bonding agent in small well to minimize evaporation, and replace cap quickly 3) Have good isolation 4) Roughen sclerotic dentin to increase surface area and remove some of the sclerotic dentin 5) Bevel or roughen to etch enamel 6) Must have dentin moist (or rewet) for total-etch systems 7) Apply and dry primer adequately or may have gross leakage and post-op sensitivity (dry w/ air syringe) -too much primer is better than too little Longevity of Resin to Dentin Bonds -there is a loss of bond strength over time -possibly due to hydrolysis of either adhesive resin or collagen fibers -all-in-one (one-step) types show the worst results -bond durability is much greater when peripheral margin is all in enamel Part 12: Composite Restorations Composition of Composites -three phases: 1) Resin matrix: bis-GMA or UEDMA (sometimes TEGDMA is used) 2) Filler particles a) fine (0.5-3 um): crystalline silica, lithium aluminum silicate, glass b) microfine (0.04 um): colloidal silica c) microhybrid: both fine and microfine particles -as filler particle content increases, physical, chemical, and mechanical properties improve 3) Coupling agent: silane -added materials: 1) Initiators: benzoyl peroxide, diketone, camphoroquinone 2) Accelerators: organic amines 3) Pigments: inorganic pigments provide various composite shades

Types of Composites 1) Unfilled resins -esthetic and smooth -discolor over time -low wear resistance, low compressive and tensile strength (softest of all restorative materials) -percolated (expand and contract from temp. change) -show greatest extent of marginal leakage from temp. change -unfilled resins have lowest thermal conductivity and diffusivity 2) Silicate cements -fluoride releasing -biodegraded over time 3) Conventional composites -have glass filler -improved physical properties -have some roughness 4) Microfill composites -have very small glass filler (0.04um) -reduced physical properties compared to conventional composites -LCTE, water absorption, surface texture, elastic modulus, solubility, strength -very smooth and excellent wear resistance -develops smoothest finish 5) Hybrid composites (composite resin/resin-based composite) -combined small and very small glass filler -good physical properties, smooth, and good wear resistance (optimum mechanical properties) 6) Flowable composites -lower filler content -higher polymerization shrinkage -used for cervical lesions, small restorations, pedo lesions, and sealants 7) Packable composites -increased viscosity and high filler volume -no documented benefits -used in class I and II restorations 8) Nanofill composites -extremely small filler particles (can incorporate higher filler content) -very good future potential 9) Core buildup composites -can be self-cure or dual cure Important Properties of Composites 1) Coefficient of thermal expansion -high CTE causes percolation, recurrent caries, and stain -increased resin matrix leads to increased thermal expansion -composites have higher thermal expansion than amalgam and tooth structure 2) Water absorption -high water absorption causes deterioration of material 3) Polymerization shrinkage -all composites shrink w/ polymerization -less resin matrix causes less shrinkage (microhybid less shrinkage than microfills) -curing composite in thin layers leads to less shrinkage 4) Wear resistance 5) Surface texture -smaller filler size leads to smoother surface 6) Strength -microhybrids have increased compressive strength and flexural strength compared to microfills

-increased fillers causes increased hardness and wear -bond btw composite and etched tooth is primarily mechanical Methods of Polymerization/Activation 1) Autocured/Chemical cured: must mix together, which can cause disturbance of polymerization -uses organic peroxide initiator (benzoyl peroxide) and tertiary amine activator -have less control of insertion time -may have increased porosity and discoloration due to chemical makeup of materials 2) Light-cured: requires light source (expensive); most common -composite polymerized by blue light (470 nm) -a diketone absorbs light and amine activator initiates polymerization by supplying free radicals -have indefinite insertion time, less porosity, and less finishing required -types of curing lights: tungsten/halogen and LED (light emitting diode)more promising -visible light curing systems now used (UV-light curing systems no longer used) Important Points in Light Curing Composites 1) Hold light as close to resin as possible (within 2mm) 2) Cure composite in 1.5-2mm increments 3) With darker resin shades, cure longer Uses of Composites 1) Class I-V restorations 2) Sealants 3) Hypocalcified areas 4) Partial and full veneers 5) Anatomic additions 6) Resin-bonded bridges

7) Luting agent/cement 8) Diastema closure 9) Foundation/core 10) Temporary material 11) Bonded amalgams

Advantages and Disadvantages of Composite 1) Advantages a) Esthetic e) Less mechanical retention form needed b) Insulation f) Strengthening of remaining tooth structure c) Bonds to tooth structure g) Minimal to no microleakage resulting in decreased staining, d) Conserves tooth structure recurrent decay, or post-op sensitivity 2) Disadvantages a) Wear b) Technique sensitive c) Polymerization shrinkage d) C-factor may cause sensitivity Restorative Technique for Composite 1) Remove faults/decay 2) Remove areas of most weakened tooth structure -no need for mechanical retention unless there is no enamel (root surface) or very large restoration 3) Protect pulp if necessary 4) Prepare enamel (bevel) -0.5mm wide at 45 degree angle w/ coarse diamond (increases surface area for increased retention) 5) Etch, prime, and bond 6) Insert and cure composite 7) Contour and polish composite Preliminary Considerations 1) Make sure there isn’t heavy occlusion on area being restored w/ composite 2) Clean tooth w/ pumice if no prep is being done 3) Select shade BEFORE teeth are dried 4) Make sure you achieve good isolation

Different Types of Composite Preparations 1) Conventional prep a) Remove decay b) Bevel enamel c) In non-enamel areas, use 90 degree margins and mechanical retention 2) Beveled conventional prep (replacement preparations) a) Maintain preparation form of restoration b) Bevel enamel (may need to place retention on root1/4 round bur used to make cove) 3) Modified preparation a) Fault/caries dictates outline form (only remove caries) b) Bevel enamel New/Controversial Approaches 1) Box only preps for class II 2) Tunnel prep (not recommended) -make tunnel from occlusal surface down and extends over to proximal lesion in class II 3) Sandwich technique Class V Composite Prep -resembles class V amalgam prep except internal line angles are much more rounded -also has cavosurface bevel of 0.2-0.5mm wide to prevent microleakage Glass Ionomers -fluoro-aluminosilicate glass powder and liquid solution of polymers of acrylic acid -high fluoride releasing -used in class V restorations and low stress-bearing areas in high risk pts due to low strength and low wear resistance -low solubility and high opacity -come in both light-cured and self-cured forms -light-cured preferred b/c of extended working time and improved physical properties -do not polish as well as composites Compomers -composites modified w/ polyacid groups -used in low stress areas (class V) b/c less wear resistant than normal composite -release fluoride Sealants -need micro-mechanical retention, so surface should be cleaned w/ pumice and water, isolated, acid-etched and then sealant placed -sealants are weaker than composites -strength sacrificed to make it flow into pits/fissures -sealants best retained on max. and mand. PM, but max. and mand 1st molars benefit most from sealants -low-viscosity sealants wet acid-etched tooth surface best -caries protection is 100% in pits and fissures that remain completely sealed -most common reason for failure is salivary contamination -sealants should be placed right after tooth fully erupts Components of Sealants 1) Monomer: Bis-GMA -may be diluted with TEGDMA to reduce viscosity 2) Initiator: benzoyl peroxide (self-cure) or diketone (light-cure) 3) Accelerator: amine 4) Opaque filler: titanium oxide

Other Composite Stuff -light will only cure 2-3mm depth increments of composite -cure each increment for 40 seconds from each angle Part 13: Gold Inlay/Onlay Restorations Advantages 1) Good track record 2) Good fit 3) Excellent method to restore occlusal relationship 4) Structurally sound material (gold will not corrode) Disadvantages 1) Not esthetic 2) Complicated tooth preps 3) Complicated marginal finishing 4) Need adequate lab support 5) High cost Indications 1) Large occlusal surface needs 2) Tooth contour needs 3) Fractures 4) Splinting 5) Bracing for endo treated teeth 6) Bridge retainers 7) Partial retainers Concepts of Tooth Preparations 1) Must have draw w/ divergence to external surface of 2-5 degrees -the longer the wall, the greater amt of draw needed -increased draw causes decreased retention -increased wall height gives more retention -more parallel=more retention 2) Beveled finish lines -gives good marginal fit/adaptation of gold to tooth that can be burnished -can bend a 30-50 degree gold margin -<30 degrees may be too thin and break ->50 degrees may be too thick and not bend 3) Pulp protection often needed -if use liners or bases, must be captured in impression 4) Must have good impression to fabricate restoration Aspects of Gold Inlay/Onlay Tooth Preparation 1) Occlusal bevel: 0.5mm width at 40 degree gold margin 2) Groove extension bevel: also 0.5mm wide w/ 40 degree gold margin 3) Cusp counterbevel: 0.5-1mm wide w/ 30 degree gold margin (for nonesthetic capped cusps) 4) Stubbed margin: 0.25-0.5mm wide and perpendicular to long axis of crown (for esthetic capped cusps) 5) Secondary flare: extends facial and lingual proximal margin into facial/lingual embrasure (40 degree margin) 6) Collar: beveled shoulder design around a capped cusp -provides bracing 7) Skirt: extends casting around line angle to increase retention and resistance form -margin is 0.5mm chamfer 8) Gingival bevel: 0.5-1mm wide

-must blend all bevels into each other Part 14: Fluoride Fluoride and Sealants -if topical fluoride and sealants both to be used, sealant should be placed before fluoride application Determining Mg of Fluoride -sodium fluoride or sodium monofluorophosphate contains about 1mg F- per gram toothpaste -so in 8.2 oz tube, must convert oz to grams -1 oz=28.35 g -8.2 x 28.35=232 grams -232 grams toothpaste=232mg FFluoride Toxicity -average adult lethal dose is4-5 grams -death likely in child who ingests more than 15mg F-/kg weight -minimum lethal dose (Probable Toxic Dose) is 5 mgF-/kg -most fluoride absorbed in small intestine and excreted through kidneys pH of Fluorides Toothpastes 1) 1.23% Acidulated phosphate fluoride: 3-3.5 (acidic) -most common in-office fluoride txt -contraindicated in porcelain, composites, and implants 2) 2% Sodium fluoride: 9.2 (basic) -most common OTC fluoride (0.05% NaF) 3) 8% Stannous fluoride: 2.1-2.3 (acidic) -bitter metallic taste, can burn mucosa, and can stain teeth Part 15: Miscellaneous Zones in Four-Handed Dentistry -in relation to pt’s head being at 12 o’clock position 1) Operator zone: from 8-11 o’clock 2) Assistant zone: from 2-5 o’clock 3) Transfer zone: from 5-8 o’clock 4) Static zone: from 11-2 o’clock Embrasure Spaces 1) Buccal/facial 2) Lingual -larger than facial 3) Occlusal/incisal 4) Cervical/gingival Functions of Embrasures 1) Make spillway for food 2) Make teeth self-cleansing 3) Protect gingival tissue from trauma Functions of Proximal Contact Area 1) Support neighboring teeth (stabilizes dental arch) 2) Prevent food particles from entering interproximal area 3) Protect periodontium 4) Form embrasures

Parts of Flame 1) Mixing zone: cool and colorless zone -air and gas are mixed 2) Combustion zone: greenish-blue zone where partial combustion occurs 3) Reducing zone: dim blue tip -is hottest area in flame and only part that should be used to heat alloys 4) Oxidizing zone: where final combustion btw gas and air takes place