Clinical evaluation of internal axial wall divergence in inlays and casting post-and-core fabrication

Background/purposeIn the fabrication of casting post and core or inlay the line angle of the cavity floor can be seen even when the internal axial walls are parallel or slightly convergent. It is conceivable that more sighted distance will be required for internal axial walls evaluation compared with external axial walls evaluation. The aim of the study is to derive a practical and convenient method and data for the evaluation of the divergent angle of internal axial walls.Materials and methodsThrough a scientific analysis, this study derived a practical and convenient method and data for the evaluation of the divergent angle of internal axial walls. The sighted distance between occlusal line angle and the cavity floor line angle at 30-cm distance was calculated by an established formula and expressed in 6°, 12°, and 18° of internal axial walls divergent angle respectively.ResultsTables 1–3 show the value of sighted distance with cavities of 6°, 12°, and 18° tapering. Based on the data, if more divergent angle is prepared; more sighted distance will be observed.ConclusionCompared with the teeth preparation of external axial wall in a single crown, the sighted distance at 30-cm distance in the internal axial wall is 1.5 × wider. More sighted distances are required to prevent undesired undercuts.