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الكلية كلية طب الاسنان
القسم ترميم ومعالجة الاسنان
المرحلة 4
أستاذ المادة احمد غانم مهدي الهلال
4/18/2011 8:34:50 AM
Direct and indirect posterior composite restoration
Composite resin has been suggested as possible replacement of dental amalgam with shorter half life (6-11 years for amalgam and 5-6 years for composite).
Advantage of posterior composite:
1. Bondable restoration so it requires more conservative tooth preparation.
2. Esthetically superior over metallic restoration.
Direct composite restoration:
This applied directly into the prepared cavity; in general it has low wear resistance compared with amalgam, the wear increases as we travel posteriorly and with increasing biting force and increasing the size of restoration.
Disadvantage of direct posterior composite:
1. Low wear resistance.
2. Polymerization shrinkage that result in less marginal adaptation.
3. Difficult to get proper proximal contour.
4. Microleakage and secondary caries at tooth restoration interface.
5. Highly technique sensitive (you must keep the area dry at all steps).
6. Expensive compared with amalgam.
In order to decrease some of these disadvantages, the manufacturers develops a new type called (packable or condensable posterior composite restoration) which consist of resin and ceramic components. Also there is improved distribution of filler sizes with decreased inter particles distance. So we get increase in wear resistance and decrease polymerization shrinkage but the microleakage is still higher than amalgam.
The adverse effect of this packable composite on the pulp is not related to the material itself but is duo to ingress of bacteria as a result of microleakage.
The microleakage and polymerization shrinkage can be minimized by:
1. Layering or incremental placement technique (each layer not exceeding 2mm thickness).
2. Using a ceramic inserts filler.
3. Using soft start light source for polymerization.
Indication of direct posterior composite:
It’s indicated in all classes cavity preparation but the cavity should have the following criteria to increase the half life of the restoration:
1. The cavity should not involve the cusps whenever possible.
2. Cavity width less than one third of intercuspal distance.
3. Cavity without functional contacts to decrease wear.
4. As a core for crown restoration.
Cavity preparation:
The principle of the cavity for posterior composite similar to these used for amalgam restoration but a more conservative tooth preparation in both extension and depth because the composite bond better to enamel than dentin, thus there is no need to extend the cavity to the dentin unless there is caries.
Caries is removed and obtain a convenient form to get access to the prepared cavity, in class II; the proximal box should result in the cavosurface margin at right angle to the enamel surface buccally and lingually.
Filling procedure:
Proper isolation with rubber dam is very important, in class II application of wedge before filling and immediately after rubber dam application is very important to get tighter composite contact with the adjacent tooth, then proper clear band is applied, liner application (the best is glass ionomer cement), total etching for 15 second with 37 % phosphoric acid, then wash and gently air dried.
The bonding agent is placed with a brush then the composite material is applied, in class II or deep class I the composite material should be applied in increments or layers and each layer should not be more than 2 mm thickness, the first layer should be placed in the box with condensation against the matrix band and cavity walls, followed by light application in all directions labially, lingually, and occlusally, then the rest of the cavity is filled with composite followed by light application in all directions, then the restoration is finished and polished.
Indirect composite restoration:
This type was introduced to overcome the disadvantages of direct composite restoration. The restoration are fabricated outside the patient mouth on a cast by technician, this composite is dense and well cured by using a device that cure the composite under pressure, vacuum, inert gas, intense light, heat or combination of these methods.
Advantages:
1. Easy fabrication and adjacement.
2. Proper esthetic.
3. Superior marginal adaptation.
4. Proper contour and contacts.
5. More wear resistant.
Indication:
1. Maximum wear resistance is desired.
2. Cavities in a location with biting forces.
Cavity preparation:
The cavity should be prepared without any undercuts and adequate thickness for the final restoration is important to prevent fracture of the restoration during handling, the isthmus is preferred to be one third of the intercuspal distance.
Filling procedure:
After finishing the cavity, an impression is taken and poured to get a cast, then the indirect restoration will be built on the cast by special machine with a xenon light to provide intense light and heat for composite curing, then the cured composite adjusted and finished. Then the restoration is cemented into the prepared cavity using resin cement which will compensate for polymerization shrinkage.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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