Fixed Prosthodontics Crowns and bridges lec 1 18.02.09 It is the art and science of restoring damaged teeth with 1) cast metal, 2)metal-ceramic or 3)all ceramic restoration and replacing missing teeth with fixed prostheses(cemented or screwed-in). Cemented means using cement : conventional cement, Glass Inomer cement, RMGI or Resin cement. But it has to be luted , cemented or screwed-in, this is why we call it fixed, the patient can not remove it and sometimes the dentist can not remove it. So it is fixed because it has been screwed to the structure underneath it either by screws or cements. Restoration in this field could be the finest service (you can give excellent service to the patient if your work is excellent) or could be the worst disservice (if you are bad), usually fixed prosthodontics lead us to irreversible outcome if goes bad. The scope of this field can range from the restoration of a single tooth to the rehabilitation of the entire occlusion. Which means, the patient may complaine of a bad broken tooth and you need to restore it with a crown which is a fixed prosthodontic and he might come to your clinic with no teeth and you need to rehabilitate him with fixed prosthodontics which could include implants. So it is a wide range of treatment from single tooth to rehabilitation of the entire occlusion. The restoration of single teeth (which they are there but damaged) could be: 1- Intra-coronal: means within the confines of the tooth(within the anatomy of the tooth), it is like a filling but it is not, because it is cemented or screwed-in {this is Page | 1
the deference between Intra-coronal fixed prosthodontics and Intra-coronal conventional operative 2- Extra-coronal: it’s a works(amalgam,composite,GI)}. restoration that covers the outer surfaces of the tooth(cover part of the tooth or all the tooth). Both Intra-coronal and Extracoronal are fixed because they are looted to the tooth structure.
Crown: one of the most common
Extra-coronal restoration.
It is an artificial replacement that replace missing tooth structure (if it is replacing missing tooth then it is bridge or fixed partial denture)by surrounding part of the tooth( we call it partial crown) but if surrounding the whole tooth (it’s called complete or full crown) with a material as 1)cast metal, 2) ceramics or 3)combination of both. Advanced material could be used. **Partial Crowns: surround one surface or more but they don’t surround the whole tooth structure. **Complete/Full Crowns: surround the whole tooth structure. The crown could be made of ceramic or metal or combination of them or other material. From design point of view, they are either Partial Crown or Complete Crown. From material point of view, 1)they could be cast (cast restoration is the restoration where you need to fabricate a mold usually out of wax and this will be replaced later on with molten material which could be metal or ceramics ) 2) they could be only ceramics, or 3)combination metal and the top of that a ceramic layer. The picture below explain what we mean by partial crown which covers mesial, distal and the palatal surfaces, but the labial surface is off.
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This picture below is complete crown which surround the whole surfaces of the tooth, if you look there, you can notice that the palatal surface is metal and the labial surface is ceramic, this is combination of metal and ceramic, it could be metal by it self or ceramic by it self or combination of both.
For Intra-coronal restoration it is unlikely to be a combination, it is either metal or ceramic or other material, it can not be combination for certain consideration which will be explained later on.
Inlays and onlays :
are intra-coronal restoration (within the confined of the tooth) artificial replacement that restore missing tooth structure. The former( which is inlays) restore mild to moderate lesions while the latter restores more extensive lesions with occlusal coverage. If you have Intra-coronal restoration and it covers part of the occlusal surface like the picture below:
Here we have MOD that covers the palatal cusp, this is called Onlay. And Onlay in dentistry means “cover the top”, for that reason called Onlay. The other type is the Inlay which restores mild to moderate lesions without occlusal coverage. Page | 3
These Inlays or Onlays could be made out of metal or ceramic or other materials and unlikely to have two layers metal and ceramic, so unlikely to have combination of these materials.
This is Inlay, but it could be Onlay if we cover the mesiobuccal cusp. So the point is covering the occlusal surface: if it is covered so it is Onlay but if not it is Inlay. The difference between the Inlays and the operative work of class II is: usually the lesions are bigger, difficult to create a contact point or proper contour, so you can not reproduce it with amalgam or composite then you have to think about something that could be build up properly with the contour and the contact area, and that can be done only in the lab, if you need it to be fabricated in the lab you have to take an impression and have a wax up mold then replace it with metal, so the only difference is that in the conventional operative work you do the filling inside the clinic, but in the Inlay you do it in the lab, and the reason is that you can not reform the tooth structure properly using the conventional plastic material like amalgam, composite, and GI. You need something with impression, so you give the chance for the technician to build it up as properly as he can, because he is working in a model not in the patient mouth. **Not every class II is going to be an Inlay, because class II could be done easily and properly within a certain range of tooth destruction within the patient mouth but if the destruction is big enough and you can not restore the function and form(because the lesion is too extensive) then you need to think about the Inlay. If you can not restore with the Inlay so you have Page | 4
to think about some thing more which is the Onlay, if you can not, then you go for a crown. So we start with a filling then we go to fixed prosthodontics branch. Note: by the end of the lecture you have to know what we mean by fixed, Intra-coronal, Extra-coronal, Inlay, Onlay, Crown, Bridge. Another restoration used in fixed prosthodontic is called laminate veneers, laminate means very thin, veneer means cover. Laminate veneers usually made of ceramic so we call them all ceramic laminate veneers or facial veneers. These facial veneers are extra-coronal restorations because they cover part of the tooth, used mainly to improve the aesthetics of anterior teeth using a thin layer of ceramic bonded to the facial surface of a tooth which otherwise sound. For example: a lady came to your clinic complaining of microdontic teeth(small teeth) and you need to build them up, you can build them up in you clinic with composite but it is better to build them up with ceramic, but to build them up with ceramic you need to have an impression, than send it to the lab and fabricate veneers to restore the aesthetics. Usually these teeth are sound, there is no caries, no fractures, and the problem is in the way they look like, for example: stain, space, crowded, so you can improve them by using laminate veneers.
All what we talked about before is restoration of damaged teeth. Now we will deal with other branch of fixed prosthodontics which is replacing missing teeth.
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Bridge(fixed partial denture):
Bridge is the British name, and fixed partial denture is an American name. A bridge partial denture that is cemented or otherwise securely retained ( it is retained either by cement or something else) to natural teeth, tooth roots and/or dental implant. The structure which support this bridge is called abutment that furnish the primary support for the prosthesis.
H
Here we have a missing lower 6, this lower 6 will be replaced by H(artificial tooth), this is called pontic, this pontic is connected to the adjacent teeth by small area called connectors, these connectors are connected to a natural teeth via an extra-coronal restoration (which is usually a crown)which is called retainer, the retainer is usually a crown if it is for a single tooth, but for a bridge we call it retainer. So we have retainer, connector, pontic, connector then another retainer. The tooth it self or the root (could be a root, tooth, implant) is called abutment. The abutments are the teeth which furnish the support for the bridge. The retainer is usually extra-coronal restoration( usually a crown) but we don’t call it crown in case of bridge, we call it retainer, because it retains the bridge in. The retainers should have a common path of insertion, we have one retainer on 2 nd premoler and one on 2 nd molar, if they don’t have a common path of insertion then you can not seat them on the abutments. The abutments should be parallel. In fixed prosthodontics we should have one way of insertion(parallelism).
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Do I need a retainer all the time?!! No, not every abutment will be used as a retainer and we will take that in the lecture of designing a bridge.
If we have teeth that are not parallel to each other(originally they should be parallel to each other), and we should have one way of insertion so we have to cut more tooth structure from one tooth than the other(usually more from the mal aligned tooth) so the bridge work is more destructive than crown work. The saddle is the area where the tooth has been missed, so the missing tooth area called the saddle. The last thing you need to understand is the Unit. Every bit of the bridge is called a unit. Pontic is a unit, retainer is a unit.. so this bridge is a three units bridge or a three units fixed partial denture.
Reachi Reaching ng a Diagn Di agnosi osis s: Your patient came to your clinic complaining of certain things, in any part of dentistry, crown and bridge is as any other dental special, you have chief complaint, history, examination, special investigations, diagnosis and prognosis. Chief complaint: patient comes with broken tooth, missing premolar or what ever. History: routine history of chief complaint for example when the pain starts, Medical history, Dental history. Examination: extra oral examination, intra oral examination
Intra-oral examination: *You have routine oral examination. *Periodontal assessment: this is very essential in fixed prosthodontic and include gingivae and periodontium, there is something called CPITN. Not for every patient you need to do full periodontal charting, is it true?!! You have to do full periodontal charting, Gingival Index, pocket depth, plaque Index for your perio patient. So there should be an easy way to Page | 7
assess the periodontal status of the patient without loosing a bit of time in your clinic. CPINT stands for Community Periodontal Index of Treatment Need. When your patient come to the clinic you can have something called WHO periodontal probe, it is a simple probe with spherical ended tip diameter 0.5 mm and the color band extending from 3.5 to 5.5 mm, we use this and walk through the whole dentition quite rapidly, when you start using it, you will not take more than few minutes, and you will score the teeth, but not for every tooth, you will score a areas, you will divide your teeth into 6 areas : lower left posterior, lower anterior, lower right posterior, upper left posterior, upper anterior, and upper right posterior. You have 6 areas, You will walk through the highest score for each area will be recorded, according to certain Index. When you record the whole areas, there is a Gide lines where you need to refer this patient, you need to treat this patient, you skip the perio stuff so this is just for your restorative work, we don’t use it for perio clinic, we use it for prostho, cons, surgery, you can use this just to have an idea about periodontal status of your patient . This is epidemiological tooth, uses just to have an idea, screen your patient, have an idea, we don’t want to fabricate a bridge for a patient who needs later on extraction of the tooth, so this is very essential,(the doctor will ask us about it). *Dental charting: fillings, caries, etc.
*Occlusal examination: in fixed prosthodontics occlusal examination will be essential. In occlusal examination there are: 1. Initial tooth contact: which include ICP (Inter-Cuspal Position), RCP(Retroted Contact Position), and slide between them. All these you need to examine them. Page | 8
2. General alignment: you look for crowding ,rotation , spacing, supra-eruption, overjet , overbite, saddles, tilting and drifting. 3.Lateral and protrusive movements: type of guidance and interferences. You record the whole stuff before fabrication your prosthesis.
Speci Spe cial al Inve Investi stigat gatio ions ns: Special Investigations are extremely important for fixed prosthodontics, nobody ask any of us in prosthodontic stuff in the clinic to see the patient before considering what the special Investigations you need. You have to tell the doctor what the special investigations you need for your patient before he come and look at the patient. The special Investigations include: 1.Vitality testing: you can not fabricate any fixed prosthesis without checking the vitality, this is starting from Intra-coronal, Extra-coronal, Crowns, Bridges. The teeth should be checked for the vitality using thermal, electrical or whatever. This test is essential (should be done for every single tooth which will be involved in the fixed prosthodontics) together with percussion for the involved tooth/teeth in fixed prosthodontics. Percussion we use it to check crack, fracture. 2.radiographic assessment: it is a must, you have to have your periapical radiographs for the tooth/teeth involved in your prosthesis. This is to assess caries, periodontal bone, pulp, root number and form, or any pathology. You can not ask the doctor to come to your unit before having your vitality test done and your X-rays asked for, but you have to get X-rays for the tooth involved in your procedure. 3.Diagnostic casts: it is a must in fixed prosthodontics specially in bridge cases.(MCQ)[diagnostic cast possibly requested for a crown, for Extra crown restoration, mostly for bridge cases, all are true]. They must have an accurate Page | 9
reproduction of the arches. They should be mounted on a semiadjustable articulator( because they simulate tooth movements and oral movements better than average value articulator). We need fixed prosthodontics to be more accurate than removable because whatever your accuracy in removable your bases are mobile, you have mucosa, but in fixed prosthodontics you have rigid bases which are teeth, so you need accurate reproduction of the movements (of your oral movements). Diagnostic cast is used for : a.Occlusal assessment: you check the occlusion inside the patient mouth, see drifting, rotation and all what we said before and you can see some of these using your diagnostic cast. b.Diagnostic wax-up c.Fabrication of provisional restorations
Here you use see your diagnostic cast to fabricate a provisional restoration, which is in this case acrylic partial denture. The doctor’s plannig later on to use implant . Right pic is where you can see a diagnostic wax-up, patient comes to your clinic and he needs veneers to improve his aesthetics, you can not make the veneers immediately in one step, you need a step in between called diagnostic wax-up where the technician build the wax to his best quality regarding the form and shape of the teeth. With this wax-up you can ask the patient are you happy to go through this procedure and end up with the look like this?! This is one of the benefits of using wax-up. The other thing you can use it for temporary restoration, how do we use it? We have to make a crown and you want to fabricate the temporary Page | 10
restoration( the best temporary restorations are those which based to have the shape and form of final restoration) we can do a matrix or a night guard. Diagnostic wax-up could show to the patient the outcome, could be used for temporary restoration, or the same diagnostic cast could be used for temporary restorations or provisional. 4.Shade selection: this is could be done at this stage or could be done in the treatment plan stage. But you have to make it before starting drilling the teeth. The shade is the color of the tooth, and you have to choose it before commencing your treatment, so you will keep the shade of the original teeth better than if you prepare it. Diagnosis
Your diagnosis could be dental caries, gingivitis, tooth fracture, missing teeth. You have diagnosed your patient, he could need endo, surgery, prostho, operative. You reach the diagnosis for every tooth. After that you jump to prognosis. Prognosis
If you diagnosed a tooth with dental caries and mobility (lets say a grade III mobility), then what is your prognosis? Could need extraction, could be restored, you need to tell the patient about the prognosis which is the likely course of a disease and this depend on: a.General factors: age, general disease.. b.Local factors: occlusal load, impactions, mobility.. imagine that you have a grade III mobility for a 75 years old patient, you have two options, either you to fire it out or to refer him to a periodontal treatment for a couple of years to stabilize it. Defiantly considering the age you will get it out, so general factors and local factors will determined the prognosis for each tooth. If you decided what is your diagnosis and prognosis you will end up with a treatment plan, this treatment plan for every tooth and for the whole dentition. Page | 11
Done by: Shahd Qeadan..
Imp. Note: Exam will be on 18.4.09 11:00-12:00 10H1+10H2
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