Rubber Dam Application (lower) Rubber Dam Application (upper) Cutting on Plastic Teeth H Shaped Preparation Cutting on Plastic Teeth Shaped Preparation I Guidelines for Class I Amalgam Cavity Preparation Accepted Accepted Accepted Unaccepted Guidelines 9 10 7.5 8.5 6.5 7 Below 6 – – – Follow central /Bu Slight deviation Deviation from Does not follow Occlusal /Li grooves from grooves grooves grooves Extensions precisely 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 Margins to unprepared tooth small areas where Beveled margins roughness structure margins not 90
Rubber Dam Application (lower) Rubber Dam Application (upper) Cutting on Plastic Teeth H Shaped Preparation Cutting on Plastic Teeth I Shaped Preparation Guidelines for Class I 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 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