FUNDAMENTALS OF OCCLUSION Fun dament als of Fix ed Prosthodontics-Shillingburgh (Pp 11-23)
DR. MOHAMMAD AL AMRI
IMPORTANCE OF OCCLUSION
• The lo ng -term su cc ess of a rest or ati on is depend ent up on main tenanc e of oc cl us a harmony. • Fabr ic ate a resto rati on th at w il l n ot cr eate iatr og eni c o cc lu sal di sease.
GOALS OF RESTORATIVE TREATMENT us al c on s i nng podefl st eri orivt eeth • To th atcrsteate abi lioc zeclinst ead oftact cr eati ect e co nt act s t hat m ay d est abl ize th e mand ib ul ar position.
• The occ lus ion of a resto ratio n s hou ld be made in h armo ny w ith the opt imu m co ndy lar positi on – CENTRIC RELATION.
CENTRIC RELATION
An anteriorly, superiorly bra ced p osi tio n alon g t he art ic ul ar eminence of t he gl eno id f os sa, wi th t he arti cul ar di sc int erpo sed betwee n t he con dy le and eminence.
CENTRIC RELATION
• This p osi tio n of t he con dyl es in t he gl eno id fo ss ae has been di sc us sed and debated fo r many years . • It is us ed i n dent is tr y as a repe atabl e reference pos it ion for mou nti ng c asts .
CENTRIC RELATION • Many meth od s u sed t o g ui de th e mand ib le in to an i deal position. ept s of ccentri ent ri c re lati on iinnvvo ollv ved • Earl ier co connccept ed the most poste rior condyl ar po sitio sitionn in in tthe he fossa. coarmo nd yl et,was formo rc efu y manipu mami nidm pu lated • The th e re rearm osst, up perm ossttlland os t in to the uppe mid mos pos iti on ccalle alle d t he RUM positi on using tthe he chi n gui dance te chn iqu e.
PHYSIOLOGICAL POSITION • The mor e rece nt co nc ept descr ib es a phy sio log ica l posit ion re gardi ng the mus cul osk eletal relatio nsh ip of the structures. • It is not a for ced po sit ion , but is g entl y gu id ed b y t he op erato r u si ng th e bi lateral metho d o r b y allo win g t he natur al m usc le act io n t o p lace th e co nd yl e in a physio logica lly unstra ine d po sition .
MANDIBULAR MOVEMENT
Mand ib ul ar mo vement can be br ok en do wn int o a seri es of mot ion th at oc cu r aro un d th ree di ff erent axes
MANDIBULAR MOVEMENT
Varivement ou s m and ibcom ul ar po sed mo s are of motion occurring con cur rentl y abou t on e axi s or mo re.
MANDIBULAR MOVEMENT • The up a nd d own mot ion of t he mandibl e is a combi nation of two move ments.
• A pure hinge movement occurs as a re sul t o f t he con dyl es rotating in the lowe r com part ment o f th e TMJ wi thi n a 10-13 degr ee arc whi ch cr eates a 20-25 mm separati on of the a nterior teeth .
MANDIBULAR MOVEMENT
There is also som e gli din g (tr ansl ati on) mo vement in th e upp er com part ment duri ng ma xim um mouth ope ning
MANDIBULAR MOVEMENT (Protrusive) • slid When mand es th fo erwa rd s ib o le th at th e maxil lary a nd mandi bul ar anterior teeth are in end -to -end relatio nsh ip, it is i n a protrusive position . • Ideall y t he ant eri or segme nt of th e mandi bl e tr avel a path gu id ed b y t he co nt act s betwee n t he anterior teeth, wi th compl ete disoc clusi on of t he pos teri or tee th.
MANDIBULAR MOVEMENT (Lateral excur sio n) • Mandi bul ar mov ement to one side will place it in work ing sid e and t he oth er s ide will be the nonworki ng s ide . • In t his typ e of mov ement , the con dyl e on t he NW sid e wi ll arc for ward and medially. • The con dyl e on t he wor kin g side will shi ft laterall y and slightly p oste riorly.
BENNETT MOVEMENT • Dur ing late ral excu rsi on, th e bodil y shi ft of the mandib le in t he direction of the work ing sid e was firs t descr ibed by BENNETT.
• The ang le for med in th e ho ri zon tal pl ane be tw een th e path e NW con dyl e way (the of math ndi bul ar translation) a nd the sagittal pl ane is c all ed t he BENNETT ANGLE.
OBJECTIVES OF RESTORATIVE DENTISTRY
• One of t he ob ject iv es of rest or ati ve denti str y i s t o p lace teeth in harmo ny wi th th e TMJ. • When t eeth are not in harm on y w it h t he joints and with mandibular movement, an INTERFERENCE is s aid t o exis t.
OCCLUSAL INTERFERENCES Int erf erenc es are und esi rabl e occ lu sal co nt act tha t m ay p rod uce ma ndi bul ar d evia tio n d uri ng clo sur e to ma xim um in tercu spa tio n or m ay hin der s moo th passa ge to a nd fro m t he inte rcuspa l posit ion.
There are fou r ty pes of oc cl us al in terf erenc es: 1. Cent ri c 3. Non wo rk in g 2. Wor ki ng
4. Pro tr us iv e.
OPTIMUM OCCLUSION 1. In cl osu re, the condy le is i n th e mos t supe roa nte rior posit ion in the gle noid fo ss a. The po st eri or t eeth are in s ol id and coslntigh acttls,y and th econt ant eri or teetheven a re in lig hter act. 2. Occl usal for ces are in lon g axe s o f teeth 3. In lateral excu rsi on, wor kin g-sid e co nt act s (pr efera bl y on t he canin es) di so cc lu de or sepa rate th e NW teeth instantly 4. In pro tr usi ve excu ion ,cclud th e anterior teeth contacts wi llrsdiso e the pos teri or tee th. 5. In an upr igh t pos iti on, the pos terio r teeth con tact mor e heavil y t han ant eri or t eeth .
ORGANIZATION OF OCCLUSION There a re th ree recog ni zed co nc ept s that de scr ibe the manner in w hic h teeth sh ould and sho uld n ot co nta ct in the vario us fu nct ion al and excu rsi ve posit ions of t he mandib le: 1.
Bil ateral b alanced occ lus ion .
2.
Unil nced o ccl usi on (grouateral p funbala ctio n).
3.
Mutually pr ote cte d o cclu sion (canin e pro tected occ lu sio n).
BILATERAL BALANCED OCCLUSION • It is a prosth odont ic co nce pt wh ich di ct ates t hat a ma xi mu m n um ber o f t eeth should conta ct in all e xcurs ive positi ons o f th e mandi bl e. • Part ic ul arl y u sefu l i n c om pl ete dent ur e construction. • Dif fi cu lt ty pe of a rr ang ement to ach ieve. e fr ic ti ondu al w o f t eeth • Exc mul ess tip leivcon tacts rinear g excu rsi vedu e to movements.
UNILATERAL BALANCED OCCLUSION • Commonl y known as group functi on. • All teeth on the working side to be in contact dur ing lateral excu rsi on. • Teeth o n th e no nw or ki ng s id e are co nt ou red to be fr ee of co nt act . • Teeth o n th e wo rk in g si de di st ri bu tes th e occ lus al loa d favor ably . • Absence of contact on the nonworking side pr event s te eth f ro m be in g su bj ect ed to destr uct ive , obliq uely dir ecte d for ces.
MUTUALLY PROTECTED OCCLUSION • Also known as canine prote cte d occlu sion. • The ant eri or teeth bear all th e lo ad and th e po st eri or teeth are di so cc lu ded i n any e xcu rsi ve pos iti on of th e mandi bl e.
• In th e in terc us pal po si ti on , th e po st eri or t eeth c on tact and relieve th e ant eri or teeth.
ARTICULATORS
Pp-25-32
ARTICULATOR
• An articulator is a mech ani cal devi ce th at si mu lates th e mo vement s of th e mandible.
ARTICULATOR • Pri nc ip le emp lo yed in the use of arti cul ator is th e mechanic al repl ic ati on o f th e path of m ov ement o f th e po st eri or dete rm in ant sthe TMJ. • The in st ru ment i s th en us ed in t he fabr ic ati on of denta l resto ratio ns th at are in harmon y wit h th ose move ments .
BORDER MOVEMENT • The out er l im it of all exc ur si ve mo vement s made by th e mandi bl e – BORDER MOVEMENT. • All functional movements are co nf in ed t o t he th ree di mens io nal env elo pe of movement.
BORDER MOVEMENT • Lim ite d by the ligaments • Hig hl y repe atable • Usefu l in sett in g th e vario a dju ani stmcal ents on th us e mech fo ss ae of an articulator
ARTICULATOR Articulators vary widely in the accu racy wit h whi ch the y re pro duc e th e mo vement s o f t he mandible Classification: 1 . Non -adj us tabl e 2 . Semi-adjustable 3 . Ful ly -adj us tabl e
NON-ADJUSTABLE ARTICULATOR • Usually a sma ll i nst ru ment. • Capable of o nl y a hin ge movement. • Dis tanc e betw een t he tee th and t he axis of r otation o n the sma ll i nstr ume nt i s shor ter th an it is i n the skull with the re sult ant loss of a ccur acy.
SEMI-ADJUSTABLE A RTICULTOR • Large siz e all ow s c lo se appro xima tion of the anatom ic di st anc e betwee n the a xis of r otation and t he teeth • The ra diu s of mov ement prod uce d o n t he arti cula tor will reprod uce the tooth clo sur e arc w ith rela tiv e accuracy.
SEMI-ADJUSTABLE ARTICULATOR • Semi-adjustable arti ator repro the cul directio n andduc endes point b ut not t he im medi ate tra ck of som e con dyl ar movements.
• Int erc on dy lar d is tanc e are no t t ot all y adjustable.
FULLY-ADJUSTABLE ARTICULATOR • Most accu rate ins tr ument. • Desi gn ed to r epr od uc e th e ent ire chara ct er o f b or der movement. • Intercon dyl ar di stance is com plete ly adju stable .
FULLY-ADJUSTABLE ARTICULATO • It i s expensi ve and time-consuming. • Demand s hi gh d egr ee of skill. • Primarily use d for ext ens iv e tr eatm ent , requir ing the recons truc tion of the entir e occlu sion
USES OF ARTICULATORS • Diagn os is : acc ur ate relatio n ofwd viagno casts allo isu alsti c exami nati on of th e oppo sin g ja w and too th r elatio n.
ati on • Fabr restoicratio n sofuch as crowns, FPD, RPD and c om pl ete dentu re.
ARCON AND NON-ARCON ARTICULATORS • There are tw o b asi c d esi gn s u sed i n t he fabri cati on of a rt icu lator s: • ARCON • NON-ARCON
ARCON ARTICULATOR • Con dy lar e leme nt s are pl aced in t he lo wer me mb er and th e mechanic al f os sae in th e up per m emb er o f t he arti cul ator sim ula tin g th e human TMJ; e.g. : WHIP-MIX ARTICULATOR
WHIP-MIX ARTICULATOR • Semi -adj us table arc on art ic ul ato r
WHIP-MIX ARTICULATOR
There are two versions: 1. Old versi on - st raigh t condyl ar housing with adj us tabl e in terc on dy lar wi dt h and b enn ett a ng le
WHIP-MIX ARTICULATOR
2. condyl New v ers io n- cu rvwith ed ar housing int erco ndy lar widt h fixe d at medi um .. Adjustable immediate sid e shi ft
WHIP-MIX ARTICULATOR
WHIP-MIX ARTICULATOR
WHIP-MIX ARTICULATOR
THE TOOTH-TRANSVERSE HORIZONTAL AXIS RELATIONSHIP
• To achi eve the hi gh est degr ee of acc ur acy fr om an art ic ul ato r, the ca st s mounte d on it sh ould be clo sin g arou nd a n axis o f ro tati on t hat is as cl os e as po ss ib le to t he tr ans vers e ho ri zon tal (hi ng e) axi s of th e pati ent ’s mand ib le.
FACEBOW • Transf ers th e relatio nsh ip of the maxil lary teeth ,th e transverse ho ri zon tal axi s and a th ir d refe rence point from patie nt’ s skt he ull to t he art ic ul ati ng device.
FACEBOW
• An instrument that reco rd s th e sp ati al relatio nsh ip and i s use d f or the att ach ment of th e maxi ll ary c ast t o th e articulator.
FACEBOW
There are tw o t yp es: 1 . Arbitrary
2 . Kinematic
ARBITRARY FACEBOW • A facebow that employs an app ro xi mate lo cati on of th e hi ng e axi s b ased on anatom ic avera ge.
• There are nu mero us techn iqu es u sed f or arbi tra ril y loc atin g the hi ng e axi s t o s erv e as a set o f po st eri or referenc e poi nts for the facebow .
QUICK MOUNT FACEBOW • Used wit h Whi p Mix Articulator. • Cali per- st yl e facebow . • Desi gn ed to be se lf centering s o lit tle tim e is w asted in cente rin g the bite fork and adjus ting indi vidual sid e arms .
QUICK MOUNT FACEBOW
r referenc • Pos po interio ts - Ext ern al e Auditory Meatus.
• Anterior reference po in t - Nasi on
QUICK MOUNT FACEBOW • Moun tin g maxil lary cast- H or izont al Con dy lar G ui dance set at “ FB” positi on or 30 degr ees • Upp er m emb er o f th e art ic ul ato r sho uld r est on the tr ans vers e bar o f th e face bo w.
KINEMATIC FACEBOW
• Uti lizes th e tr ue hi ng e axi s
PANTOGRAHIC RECORDING • It capt ur es all th e cha ract eri sti cs of the mandi bul ar bor der move ments from its retrud ed pos iti on t o its most forw ard a nd mos t l ateral po sit ion
PANTOGRAPHIC RECORDING
• The tracin g can be uti liz ed to its ful lest adv ant age when u si ng th e fu ll y adj us tabl e articulator
MAXILLARY CUSTOM TRAY
MAXILLARY CUSTOM TRAY
STOPS CUSPS ON • OCCLUSAL NON FUNCTIONAL
• MINIMUM OF THREE STOPPERS
MANDIBULAR CUSTOM TRAY
CUSTOM TRAYS
ANTERIOR DETERMINANT OF OCCLUSION Fundamentals of Fixed Prosthodontics Shillingburg, et al 1997, 3rd edition, pages 22,23 & 54, 55.
DR. MOHAMMAD AL AMRI
Hanau’s Quint By modifying the following five factors, a scheme of occlusion can be developed that will suit a particular patient best. 1. Condylar guidance 2. Incisal guidance 3. Occlusal plane orientation 4. Compensating curves 5. Height of the Cusp Except for the condylar guidance, all other factors can be modified during the fabrication of a prosthesis and the anterior guidance plays a predominant role.
Condylar Guidance Vs Incisal / Anterior Guidance
Anterior Guidance • The influence of contacting surfaces of anterior teeth on mandibular movements. • The influence of contacting surfaces of the guide pin and anterior guide table on articulator movements. • The fabrication of a relationship of the anterior teeth preventing the posterior tooth contact in all eccentric mandibular movements.
Protrusive Incisal Path
The of the incisal edges of track the mandibular teeth from maximum intercuspation to edge-to-edge occlusion.
Protrusive Incisal Path Angle
The angle formed by the protrusive incisal path and the horizontal reference plane is the and protrusive inclination. ranges from 50 – 70 degrees is oftenincisal 5-10ºpath steeper than theItsagittal condylar guidance.
Incisal Guide Angle The angle formed by the horizontal plane of occlusion and a line in the sagittal plane between the incisal edges of maxillary & mandibular central incisors when the teeth are in maximum intercuspation.
The angle formed in the sagittal plane between the horizontal plane and the slope of the incisal guide table.
Importance of Anterior Guidance
Opening and closing of the mandible is simply a rotation of the condyles in the articular fossae.
Importance of Anterior Guidance
As anterior guidance is normally steeper than the condylar downwards guidance, the anterior teeth guide the mandible during protrusive or lateral movement and ..
Importance of Anterior Guidance
(during protrusive movement) .. produces dis-occlusion or separation of the posterior teeth.
Importance of Anterior Guidance (during lateral movement)
Importance of Anterior Guidance Anterior guidance is linked to the combination of hor izont al & vert ical ov erlap of the a nterior teeth
and can affect the occlusal surface morphology of the posterior teeth.
Inter-relationship between Vertical & Horizontal Overlap of the Anterior teeth
Anterior guidance can be made steeper by either increasing the vertical overlap (overbite) ‘A-B’, or by reducing the horizontal overlap (over jet) ‘C-A’ of the anterior teeth. Anterior guidance can be made shallow by either decreasing the overbite ‘B-A’ or increasing the over jet ‘A-C’ of the anterior teeth.
Condylar Guidance & Posterior tooth Morphology (without considering the role of A.G.)
Shallow guidance normally requires shallowcondylar cusp angle or short cusp height and steeper condylar guidance requires steep cusp angle or longer cusp height.
Condylar side-shift & Posterior tooth Morphology (without considering the role of A.G.)
‘side shift +’
‘No side shift’
Similarly, in the presence of an immediate lateral side shift during lateral movement (Bennett’s movement) the cusp height and cusp angle should be shallow.
Influence of Anterior Guidance on Posterior tooth Morphology
Influence of A.G. on Posterior tooth Morphology (Effect of Overbite)
Greater overbite produces
Less overbite - less
more disocclusion hence permits longer cusp height
disocclusion - shorter Cusp height
Influence of A.G. on Posterior tooth Morphology (Effect of Over jet)
Greater over jet necessitates short cusp height
Less over jet needs long cusp height
Influence of A.G. on Posterior tooth Morphology Summarizing, greater anterior guidance allows posterior teeth to have longer cusp height & smaller anterior guidance allows posterior teeth to have shorter cusp height.
Fabrication of Custom Incisal Guide Table “Preservation of the Anterior Guidance of the Natural Teeth for its Reproduction in the Fixed Prosthesis”
To preserve and then to reproduce the anterior guidance provided by the natural teeth in the waxed up crowns, custom incisal guide table should be fabricated.
Steps in the Fabrication of Custom Anterior Guide Table 1. The mounted casts should study be examined on the articulator to assess the anterior guidance and to remove any nonworking side interference so that the articulator moves freely.
Steps in the Fabrication of Custom Anterior Guide Table
2. Ifremaining the anterior guidance provided by the teeth is inadequate, restore it to an optimal form with inlay wax, or denture tooth on the cast.
Steps in the Fabrication of Custom Anterior Guide Table
3. Raise the incisal pin (round end down) so that it will miss the plastic incisal table by at least 1mm during all movements.
Steps in the Fabrication of Custom Anterior Guide Table
4. Place one or two drops of auto-polymerizing acrylic resin monomer on the plastic incisal table.
Steps in the Fabrication of Custom Anterior Guide Table
5. Mix one half scoop of self curing acrylic resin polymer with monomer and place amount on the plastic table.a small As the resin develops more body, additional material is added until there is 6mm or ¼ inch of resin on the plastic table.
Steps in the Fabrication of Custom Anterior Guide Table
6. Lubricate the round end of the incisal pin and the functioning of the anterior teeth withsurfaces petrolatum jelly. Close the articulator in centric occlusion so that the incisal guide pin penetrates into the soft resin.
Steps in the Fabrication of Custom Anterior Guide Table
7.mandibular Move the articulator repeatedly through all movements (protrusive and both laterals)
Steps in the Fabrication of Custom Anterior Guide Table
The tip of the incisal pin molds the resin to conform to all the movements of the articulator. These movements should be repeated until the resin has polymerized.
Steps in the Fabrication of Custom Anterior Guide Table
8. Trim off the excess acrylic resin with a bur after it has polymerized completely.
Steps in the Fabrication of Custom Anterior Guide Table
The tip of the incisal pin has acted as a stylus in forming the registration of the anterior guidance. It will now be possible to duplicate the influence of the anterior teeth on the movement of the casts, even though the anterior teeth are now prepared and the incisal edges shortened.
SILICONE PUTTY