Recently, a method of forming a slot in the prosthesis lingual has been introduced to solve the occlusal and aesthetic disadvantages of screw-retained prosthesis in the manufacture of implant-fixed prosthesis and to ensure retrievability in cement retained prostheses. The purpose of this study is to investigate the effect of the internal gap on the removal of the prosthesis in the preparation of cement-retained implant prostheses with lingual slots.

Titanium abutment and internal gap of the zirconia prosthesis to be attached to the upper part were set to 30, 35, and 50 µm, respectively. Three for each type total 15 were produced for each type. The zirconia prosthesis formed a retrievable cement-type slot with a space of 1 mm at the location where the titanium abutment meets the shelf area. Autocatalytic resin cement was used for bonding of abutment and zirconia prosthesis, and the maximum removal stress value was measured in units of Ncm by using the customized equipment of the cemented specimen. The Kruskal-Wallis test was used to compare the three groups by statistical analysis (α = .05), modified by post hoc test the Mann-Whitney U-test and the Bonferroni correction method were used to compare the two methods (α = .017).

There was no statistically significant difference in removal stress between the 30 µm group and the 35 µm group in the internal gap (P = .032), and there was a significant difference between the 30 µm group and the 50 µm group, between the 35 µm group and the 50 µm group (P < .017).

Thus, the internal gap of computer-aided design affected the retention between the zirconia prosthesis and the titanium abutment. (J Korean Acad Prosthodont 2018;56:206-11)