A theoretical and clinical investigation into the taper achieved on crown and inlay preparations

Abstract

The minimum angles of taper that can in theory be formed to various preparations were established for representative dental preparations and operating distances. These values were compared with the taper of dental preparations formed both under laboratory conditions and in clinical practice, the latter by measurement of taper on the dies of clinically successful crowns and inlays. A possible explanation for the discrepancy noted between recommended degrees of taper and the tapers produced under clinical conditions was considered to be due to the requirement by a dental surgeon to avoid forming undercuts to the line of withdrawal of a cast intracoronal or extracoronal retainer.

Dimensional Measurement for Dentistry

“…The comparisons of these data demonstrate that dental students in the Trinidad dental school have produced tapers that are comparable to dental students in many other dental schools around the world (Noonan & Goldfogel, 1991;Sato et al, 1998;Patel et al, 2005;Ayad et al, 2005;Mack, 1980). The dental students in the metrology study not only achieved mean tapers comparable to other students but also to dentists in a US study (Nordlander et al, 1988).…”

“…Although dimensional measurements have been widely applied in dental research, for some of the measurements, such as taper angle measurement, a consensus has been demonstrated (Noonan & Goldfogel, 1991;Sato et al, 1998;Patel et al, 2005;Ayad et al, 2005;Mack, 1980;Rafeek et al, 2006Rafeek et al, , 2010. In other areas, such as tooth wear measurements (Zhou and Zheng, 2008;Pintado MR et al, 2000;Mitchell and Chadwick, 1998) this has not been the case.…”

“…Several studies conducted using these traditional methodologies investigating tapers achieved by dental students have found mean tapers ranging from 11° -27° (Noonan & Goldfogel, 1991;Robinson & Lee, 2001;Smith et al, 1999;Mack, 1980;Ohm & Silness, 1978;Sato et al, 1998;Patel et al, 2005;Ayad et al, 2005) while studies on specialists and general dental practitioners and have found mean tapers in the range 14° -20° (Patel et al, 2005;Nordlander et al, 1988;Kent et al, 1988;Eames et al, 1978). Even though higher than ideal tapers are found in some studies, tapers of up to 20° have been shown to be clinically acceptable with only a few crowns that were reported to have loosened and lost retention or dislodged (Ohm & Silness,1978;Sato et al, 1998).…”

Crowns and other extra-coronal restorations:Preparations for full veneer crowns

“…[14][15][16][17][18] These studies showed mean values of about 20 o with a considerable variability around the mean. Furthermore, greater tapers were achieved on mandibular molars than on maxillary incisors 19 possibly because of differences in tooth shape and problems with access.…”

In vitro Evaluation of the Accuracy of Seating Cast Metal Fixed Partial Denture on the Abutment Teeth with Varying Degree of Convergence Angle

“…Further, according to Woosley and Matich [25] proximal grooves are effective partially to increase the resistance of single crown; and also, Reisbick and Shillinburg state that proximal grooves did not improve retention of single crowns [26]. According to Mack, unless special intraoral jigs are used, it is not possible to prepare teeth with a taper less than 12 0 [27].…”