Preload evaluation of 2 implant-supported fixed partial denture abutment designs

Area of Science:

• Biomaterials Science
• Dental Implantology
• Mechanical Engineering

Background:

• Hemi-engaging abutment designs are proposed to enhance implant-to-abutment interface stability for fixed partial dentures.
• Controversy exists regarding the clinical benefit of hemi-engaging designs, necessitating mechanical testing of screw preload.
• Investigating screw preload differences between hemi-engaging and non-engaging abutments is crucial for understanding implant stability.

Purpose of the Study:

• To determine if significant differences in screw preload exist between hemi-engaging and non-engaging abutment designs in fixed partial dentures.
• To evaluate screw preload values before and after cyclic loading in vitro.
• To compare the mechanical performance of different abutment designs under simulated clinical stress.

Main Methods:

• Twenty-four conical connection implants were used to fabricate three-unit fixed partial dentures with either hemi-engaging (experimental) or non-engaging (control) abutment designs.
• Screw torque values (initial and final preload) were measured using a digital screw torque meter before and after cyclic loading (axial and lateral).
• Statistical analysis, including Mann-Whitney U tests, was performed to compare preload differences between the groups and loading types.

Main Results:

• No significant difference in reverse torque difference was found between axial and lateral cyclic loading (P=.773).
• The mean reverse torque difference was -0.65 ±1.95 Ncm for the hemi-engaging group and -2.5 ±5.44 Ncm for the non-engaging group, with no significant difference (P=.340).
• No significant difference was observed in preload loss between the non-engaging screws of the hemi-engaging design and the non-engaging screws of the control group (P=.355).

Conclusions:

• Screw preload stability is comparable between hemi-engaging and fully non-engaging abutment designs in three-unit fixed partial dentures supported by conical connection implants.
• Cyclic loading did not reveal significant differences in screw preload retention between the tested abutment designs.
• The findings suggest that both designs offer similar mechanical performance regarding screw preload under simulated clinical conditions.