Engaging vs. Non-Engaging Abutments: An In Vitro Study Evaluating Changes in Microgap and Screw Morphology

Area of Science:

• Dental Implantology
• Biomaterials Science
• Prosthodontics

Background:

• Microgaps in dental implants can harbor bacteria, potentially leading to peri-implantitis.
• Abutment design, specifically engaging (E) versus non-engaging (NE), may influence microgap formation and screw stability.

Purpose of the Study:

• To compare microgap size between E and NE abutments in single units and fixed partial dentures (FPDs).
• To evaluate screw morphology changes after cyclic loading (CL) in E and NE abutment configurations.
• To assess the influence of prosthetic design on microgap and screw integrity.

Main Methods:

• Thirty-six implants were divided into four groups: single units with E abutments, single units with NE abutments, three-unit FPDs with hemi-engaging abutments, and three-unit FPDs with two NE abutments.
• Microgap size was measured using a stereomicroscope.
• Screw morphology was qualitatively assessed using scanning electron microscopy (SEM) before and after cyclic loading (1.0 × 10^6 cycles) under axial and lateral (30°) forces.

Main Results:

• No significant differences in microgap size were observed between E and NE abutment groups, nor between different prosthetic designs.
• Cyclic loading did not significantly alter microgap sizes in any group.
• SEM revealed screw damage after CL, but the pattern of damage was similar between E and NE abutments.

Conclusions:

• Engaging and non-engaging abutments exhibit comparable microgap sizes in both single-unit and FPD configurations.
• Prosthetic design does not significantly impact microgap size.
• Screw morphology changes after cyclic loading are similar for both engaging and non-engaging abutments, indicating no distinct advantage of one over the other in terms of screw integrity under these conditions.