BackgroundRetention is an essential factor in the sustainability of the prosthesis, especially for short abutment. Despite, the availability of several auxiliary applications, achieving a clinically good retention for cast crowns in prepared short teeth remains a major challenge for the practicing dentist.ObjectivesThis study tests a new method for applying frustum-shaped grooves on short prepared abutments and compares them with traditional setting grooves.MethodsForty-eight copper machine-milled short dies with 3.5 mm length and 12o conversion with a chamfer finish line of 0.7 mm were prepared to mimic short prepared molars and distributed into 4 groups. A control group with two opposing setting grooves and two groups with dual opposing frustums, one of which was prepared to receive two integrated metal protrusions inside the casting that fit the frustums. Frustums were prepared with Komet bur No. 807 with dimensions 0.9 mm at the base and 0.7 mm at the occlusal surface. A direct wax-up was carried out on all dies and all castings were cemented with zinc phosphate cement. A pull-off test was applied until separation. Data were analysed to compare the correlation of the four groups using one-way ANOVA and Bonferroni test (p ≤ 0.05).ResultsThe mean retentive values in Newton were as follows: the control group, 457.80; the setting grooves group, 461.07; the frustum group, 597.59; and the frustum group with the two metal protrusions, 919.80. The retention was increased by 65% in frustum group and doubled in frustum group with the metal protrusions.ConclusionsThe results showed a statistical significance in retention in the frustum groups with and without metal protrusion over the retention of the control and the setting grooves groups.

Restoring the abutment with composite under the crown has long been considered a quick and ideal solution, but over time many researchers have been advised to avoid this procedure. As the concept of occlusal has undergone radical changes based on clinical reality. The existence of a large number of "prestigious" books and international publications founded some axioms have become a false intellectual heritage, because they do not reflect the clinical reality. Methods: Some illustrative schemata and opinions expressed in the book were studied, and criticism was built on clinical experience and researchers' publications. Results: The concept of muscular memory, occlusal memory or position memory does not exist. There are no grounds for the use of centric relationship which is preferred being replaced with the centric occlusion. Abutment's restoration under the crown with composite is a denied procedure from a healthy view. Relying on illustrative diagrams to present unproved ideas is unscientific, and the bending of nickel-chromium bridges is irrational. Significance: There is no justification for emphasizing some of the ideas contained in the book that are not clinically valid for the dentist practitioner, where these are recommended to be reconsidered.