Peri-implant strain analysis: An in vitro comparison between screw- and cement-retained posterior base metal restorations.
TL;DR
Retention modality appears to influence peri-implant strain development in mesiodistal and occlusogingival dimensions for 3-unit single crown and splinted crown designs.
Abstract
Background
Research is required to characterize peri-implant strain distribution associated with different restorative designs.
Objectives
This in vitro qualitative photoelastic stress analysis aimed to compare the influence of retention modality (screw-retained or cement-retained) on strain development around implants supporting different 3-unit posterior restorative designs. MATERIAL AND
Methods
Six prosthetic restorative designs were evaluated according to retention modality and prosthetic configuration: 3 single crowns, cement-retained and screw-retained (SC-c and SC-s, respectively); 3 splinted crowns (SP-c and SP-s); and simple 3-unit bridges (SB-c and SB-s). All prosthetic units were morphologically identical. A photoelastic resin block incorporating 3 implants was mounted on a loading device that applied vertical loads of 200 N simultaneously at 3 identical loading points on each restoration to simulate chewing, occlusal clenching and deglutition. Fringe lines were photographically recorded and qualitatively analyzed after placement of the restorations and during loading.
Results
Screw-retained restoration with splinted crowns (SP-s) was the only design to exhibit strain in the unloaded state following placement, representing preload strain. Loading-induced strains were observed in SC-c and SC-s, with lower strain levels for SC-c than for SC-s, and in SP-c and SP-s, with lower strain levels for SP-c than for SP-s. Both configurations also exhibited crestal strains. The simple bridge (SB) designs revealed purely axial strains, with no crestal strains, regardless of retention modality.
Conclusions
Retention modality appears to influence peri-implant strain development in mesiodistal and occlusogingival dimensions for 3-unit single crown and splinted crown designs. Screw-retained 3-unit splinted prostheses may generate preload strains around the unloaded implant supporting the restoration. Simple 3-unit bridge designs demonstrated the most favorable strain pattern, regardless of the retention modality.