Principles of Tooth Reduction for Extra-Coronal Restorations PDF

Principles of tooth reduction of extra-coronal restorations REDUCTION OF SOUND TOOTH STRUCTURE BIOLOGIC PRINCIPLES: 1. Preservation of maximum amount of sound tooth structure. 2. Preservation of pulp vitality.  PREVENTION OF DAMAGE DURING TOOTH PREPARATION Adjacent Teeth So...

Principles of tooth reduction of extra-coronal restorations REDUCTION OF SOUND TOOTH STRUCTURE BIOLOGIC PRINCIPLES: 1. Preservation of maximum amount of sound tooth structure. 2. Preservation of pulp vitality.  PREVENTION OF DAMAGE DURING TOOTH PREPARATION Adjacent Teeth Soft Tissues (Cheek, lips, tongue and gingiva) Pulp CAUSES OF PULP INJURY Temperature (due to excessive pressure, higher speed, type, shape and condition of the cutting instrument) Coolant: Air/water spray Chemical Action (Dental materials and luting agents) Bacterial Action (Either left behind or gained access due to microleakage)  Protection of adjacent tooth The proximal enamel of the tooth being Matrix band can be placed around the adjacent prepared is used creating an enamel lip to tooth to protect it from the abrasive contact. avoid damage of the adjacent teeth during However, its not enough to be used alone as it opening of the proximal contact. might get perforated and lead to damage of the adjacent tooth Guidelines for Conservation of Tooth Structure: Use partial coverage rather than complete coverage restoration. CONSERVATION OF TOOTH STRUCTURE Supragingival finish line is always selected whenever possible. Avoid undue extension of the finish line subgigivally CONSERVATION OF TOOTH STRUCTURE Select the most conservative finish line that provides bulk for the intended restoration CONSERVATION OF TOOTH STRUCTURE An anatomically prepared occlusal surface results in adequate clearance without excessive tooth reduction Conservation of sound tooth structure The path of insertion should coincide with the long axis of the tooth, which for a mandibular molar is typically inclined 9 to 14 degrees lingually. Preparing such a tooth with a path of placement that is perpendicular to the occlusal plane of the mandibular arch is a common clinical error that results in additional unnecessary removal of tooth structure (cross-hatched area). CONSERVATION OF SOUND TOOTH STRUCTURE Orthodontic uprightening prior to reduction to achieve a more conservative preparation Preservation of pulp vitality Conserve as much tooth structure as possible. This will reduce the harmful pulpal effects of the various procedures and material used. Why? The thickness of the remaining dentin has been shown to be inversely proportional to the pulpal response. Preservation of pulp vitality The proper amount of tooth reduction is determined by: ▪ Axial reduction ▪ Occlusal reduction Axial reduction Removal of undercut area Alignment with path of insertion Resistance of restoration to deformation Material of restoration Tipping or tilting of the tooth Occlusal reduction Degree of occlusal wear The area of occlusal contact Overeruption of the opposing teeth Amount of occlusal reduction Uniform occlusal reduction in Only remove enough tooth tilted tooth would produce structure to provide necessary excessive occlusal clearance space for the restoration. and unnecessarily short mesial Notice that some of the original wall occlusal surface may not need to be cut at all. Correction of overerupted opposing tooth to establish balanced occlusion is necessary before we start constructing a fixed partial denture in the lower arch Correction of overeruption 1. Simple contouring of plunger cusp and topical application of fluoride. 2. Orthodontic intrusion. 3. Onlay or occlusal veneer. 4. Crowning of over-erupted tooth. 5. Endodontic treatment and crowning of over-erupted tooth. 6. Extraction. Removal of decay Removal of decay and cavity restoration Any caries left under the crown or bridge will lead to pulp involvement and periapical pathosis with subsequent failure of the restoration.