Clinical tooth preparations and associated measuring methods: A systematic review

Survival rate of lithium disilicate restorations at 4 years: A retrospective study

“…A recent review of clinical tooth preparation 18 reported that the most important parameters for tooth preparation have changed and concluded that these parameters are rarely met. Clinical studies critically examining the causes of restoration failure are lacking, which can limit the prediction of outcomes.…”

Convergence Angles of Clinical Tooth Preparations for Metal Ceramic Restorations Among Dental Students and General Practitioners

“…This is different from "taper", which is the angle between one axial wall of the preparation and the long axis of the prepared tooth (2). A recent review has shown that TOC was the most important preparation parameter (3). Other less important factors than TOC include height of preparations of the abutment and margin designs and angles.3 However, there is no agreement in the literature concerning the recommended values of TOC.…”

Marginal and Internal Fit of CAD/CAM Crowns Fabricated Over Reverse Tapered Preparations

“…In fact, the reported frequency of undercuts in prepared teeth ranged from 30.7% (experienced general dental practitioners, in vivo) to 59.1% (final year students, in vitro) when attempting to achieve low TOC values. Therefore, more realistic TOC values are reported to be within the 10° to 22° range with no apparent correlation to the operator's level of education or experience …”

“…In this regard, the total occlusal convergence (TOC) angle of a prepared tooth plays an important role in the retention (g/mm²) of dental restorations in a hyperbolic relationship, 1 with parallel axial walls providing maximum values, and highly converging walls providing the least; however, achieving parallel walls or optimal TOC angles (<10°) is a clinically challenging task, prone to preparation undercuts. [2][3][4] In fact, the reported frequency of undercuts in prepared teeth ranged from 30.7% (experienced general dental practitioners, in vivo) 4 to 59.1% (final year students, in vitro) 3 when attempting to achieve low TOC values. Therefore, more realistic TOC values are reported to be within the 10°to 22°range 2 with no apparent correlation to the operator's level of education or experience.…”