Effect of Different Surfaces of Implant Custom Abutments in Various Heights and Total Occlusal Convergences on Retention of Cement-retained Crowns.

摘要

Statement of the problem: The retentive strength of implant cement-retained crown can be influenced by many factors such as abutment form, surface and type of luting agent. Different methods of modifying abutment surface have been proposed to increase crown retention; however, no experimental data with custom abutments are yet available.;Purpose of the study: This study compared the effect of 3 different surfaces (polished, air-abraded, grooved) of implant custom abutments on retention of single crowns luted with polycarboxylate cement. This study particularly investigated the influence of abutment surface modifications on crown retention when heights and/or total occlusal convergences (TOC) of custom abutments were inadequate.;Materials and Methods: Twelve implant/abutment assemblies were used. Twelve wide titanium implant replicas were embedded in acrylic resin blocks. Titanium custom-abutments were digitally scanned, designed, and manufactured with milling machine using CAD/CAM technology. Four different combinations of height(mm) and TOC(°) were considered for abutment designs; Group A (6 mm + 8°), Group B (3 mm + 8°), Group C (6 mm + 16°), and Group D (3 mm + 16°), with width constant at 9 mm. Three different surfaces of abutments (polished, air-abraded, grooved) were proposed as sub-groups. A polished surface (conventionally machined and polished) represented the first sub-group. Second sub-group was composed of air-abraded surface (air-abraded with 50microm aluminum oxide particles). The third sub-group featured grooved surface (micro-circumferential grooves with depth of 0.10 mm and width of 0.20 mm). Custom abutments were tightened at 30 N cm clamping force onto implant replicas. Copings were cast with Chrome-Cobalt alloy using lost wax technique. Intaglio surfaces of copings were air-abraded with 150microm aluminum oxide. A polycarboxylate cement (IP Temp Cement) was used to cement the copings. Sample assemblies were stored in 100% humidity at 37°C for 24 hours before testing. Uniaxial tensile load was applied to separate the copings from their assemblies. Peak load-to-dislodgement for all samples was recorded. The same testing was performed eight times for each sample as suggested from the pilot study. 3-way ANOVA was used to test for a significant difference among the variables tested and 1-way ANOVA was utilized between the sub-groups, followed by the Tukey Honestly Significant Difference test (&agr; = .05).;Results: All tested variables displayed statistical differences. In all main groups, the air-abraded sub-group was statistically significantly different when compared to rest of the sub-groups (polished and grooved). The grooved sub-group was statistically significant within group (A) when compared to the polished group.;Conclusion: Within the limitations of this study, it is suggested that airborne-particle abrasion of custom abutment surface is an effective mean to increase the retention of cement-retained crowns regardless of abutment heights and TOC. The retention of implant cement-retained crowns did not benefit from the studied design of micro-circumferential grooves when abutment heights and/or TOC were inadequate.