Guidelines for Class II Amalgam Cavity Preparation Accepted Accepted Accepted Unaccepted Guidelines 9 10 7.5 8.5 6.5 7 Below 6 – – – Follow central/ Slight deviation Significant Does not follow Occlusal Bu/Li grooves from grooves deviation from grooves Extensions precisely grooves Outline Smooth curve Slight sharp Markedly sharp Lack of a curve Slightly <; > ¼ Greater than 1/3 Width ¼ intercuspal 1/3 intercuspal intercuspal intercuspal Smooth, regular 90° Slight roughness; Significant Beveled margins Margins to unprepared tooth small areas where roughness structure margins not 90° Smooth, slight Slight roughness Rough; wall not Divergent Bu; Li convergence B; L properly aligned walls walls Walls Slightly divergent M, D Rounded line Some sharp internal Most internal line All internal line Line angles; axio-pulpal line angles; angles are sharp angles sharp Angles line angle rounded line angle still rounded Preparation 2.5mm from >2.5mm, <2.5mm >3.0mm; <2.0mm >3.5mm; <1.5mm Depth external walls Bu gingival contact Contact broken Tooth still in contact Bu; Li; gingival broken by line of slightly more than with adjacent tooth contact broken by Proximal explorer; Li contact line of explorer Bu; over 1mm Extensions broken by no more gingival than 1mm Follows curvature to Gingival floor Does not follow Gingival floor Proximal tooth; gingival floor slightly greater/less curvature of tooth greater than 2mm Box Form 1mm wide; proper than 1mm wide wide box form
Guidelines for Class II Amalgam Cavity Preparation Guidelines Accepted 9 – 10 Accepted 7.5 – 8.5 Accepted 6.5 – 7 Unaccepted Below 6 Occlusal Extensions Follow central/ Bu/Li grooves precisely Slight deviation from grooves Significant deviation from grooves Does not follow grooves Outline Smooth curve Slight sharp Markedly sharp Lack of a curve Width ¼ intercuspal Slightly <; > ¼ intercuspal 1/3 intercuspal Greater than 1/3 intercuspal Margins Smooth, regular 90° to unprepared tooth structure Slight roughness; small areas where margins not 90° Significant roughness Beveled margins Walls Smooth, slight convergence B; L walls Slightly divergent M, D Slight roughness Rough; wall not properly aligned Divergent Bu; Li walls Line Angles Rounded line angles; axio-pulpal line angle rounded Some sharp internal line angles; line angle still rounded Most internal line angles are sharp All internal line angles sharp Preparation Depth 2.5mm from external walls >2.5mm, <2.5mm >3.0mm; <2.0mm >3.5mm; <1.5mm Proximal Extensions Bu gingival contact broken by line of explorer; Li contact broken by no more than 1mm Contact broken slightly more than line of explorer Bu; gingival Tooth still in contact with adjacent tooth Bu; Li; gingival contact broken by over 1mm Proximal Box Form Follows curvature to tooth; gingival floor 1mm wide; proper box form Gingival floor slightly greater/less than 1mm wide Does not follow curvature of tooth Gingival floor greater than 2mm wide