The effect of numbers and locations of retentive holes placed on master casts on reducing the polymerization distortion of the maxillary complete denture.

Polymerization shrinkage is one of the disadvantages ofpolymethyl methacrylate resulting in distortion of resin denture bases. The aim of this study is to analyze the effect of numbers and locations of retentive holes on reducing polymerization distortion. Forty eight master casts were assigned as: control group (A); one anchoring hole (B); three anchoring holes (C); five anchoring holes (D).The gap distances between the denture bases and casts were measured. The data were analyzed with one-way analysis of variance (ANOVA) followed by the Post-Hoc LSD test. Mechanical anchorage reduced the gap distances in lateral and mid-palate significantly; and this decrease was affected by numbers and locations of anchoring holes significantly.