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CAD/CAM - international magazine of digital dentistry

How do we prevent too much flexing in these teeth and prevent cracking? Some have won- dered whether a bonded inlay restoration would strengthen the tooth and prevent cuspal fracture. Astudyofbondedinlayrestorationsunderstatic load testing in maxillary premolars with large MOD preparations concluded that bonding ceramic or composite will not strengthen the tooth.3 A bonded resin or ceramic inlay will not prevent cuspal de- formation and fracture. However, bonded ceramic onlays have been shown to be an effective answer in restoring posterior teeth.4,5 Bakeman and Kois (2009) stated that all por- celain, adhesively retained restorations offered the possibility of limited or no removal of tooth struc- ture on the axial wall, while covering the cusps. The result is a tooth with more remaining original structure, less flexure under force and thus less risk of permanent deformation and fracture. It is important to preserve as much enamel as possible, as failure rates of adhesively retained restorations increase the more the tooth prepara- tion involves the dentin.6 In addition, the size of the remaining enamel ring after occlusal reduction is animportantdeterminantbetweenanadhesivelyor cohesively retained approach in tooth preparation. Increased occlusal reduction, or occlusal reduc- tion on a worn tooth, results in a preparation with 14 I I CE article _ biomechanical principles Fig. 9a_Measuring remaining enamel ring after occlusal reduction #4. Fig. 9b_Measuring remaining enamelringafterocclusalreduction#3. Fig. 9c_Occlusal reduction lateral view. Figs. 10–12_Breaking contacts and removing remainder of existing filling. Fig. 13_Blending occlusal and interproximal #4. Figs. 14a & b_Blending occlusal and interproximal #3. Figs. 15a & b_Final preparations occlusal views. Fig. 15c_Final preparations lateral view. CAD/CAM 1_2015 Fig. 10 Fig. 11 Fig. 9a Fig. 9b Fig. 12 Fig. 9c Fig. 15a Fig. 15b Fig. 15c Fig. 13 Fig. 14a Fig. 14b CAD0115_12-21_Young 02.03.15 12:38 Seite 3 CAD0115_12-21_Young 02.03.1512:38 Seite 3

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