Impact of Preparation Design on Marginal Adaptation and Fracture Resistance of Overlay Restorations

Ebnali, Ola Khaled; Salem, Mohammed Talaat; Abo-El Farag, Shaimaa Ahmed

doi:10.21608/acdj.2025.405579.1040

Impact of Preparation Design on Marginal Adaptation and Fracture Resistance of Overlay Restorations

Document Type : Original Article

Authors

¹ Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt

² Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University, Egypt

³ Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University, Mansoura National University (MNU), Egypt

10.21608/acdj.2025.405579.1040

Abstract

Objective: To assess the impact of different preparation designs on marginal adaptation (MA) and fracture resistance (FR) of indirect overlay restorations for maxillary premolars fabricated using two types of hybrid ceramics.
Materials and Methods: 48 sound human maxillary first premolars with homogenous dimensions were divided into three equal groups (16 each) based on the overlay preparation design; Group (1): 16 teeth with conventional design, Group (2): 16 teeth with shoulder palatal design, and Group (3): 16 teeth with circumferential shoulder design. Based on the hybrid ceramic material utilized for overlay fabrication, each group was subdivided into 2 subgroups (8 each); Subgroup (V): 8 teeth restored using Vita Enamic and Subgroup (C): 8 teeth restored using Cerasmart 270. Marginal adaptation testing was made before overlays cementation using a stereomicroscope. After cementation and thermal cycling aging, marginal adaptation was tested again followed by fracture resistance testing. The statistical significance of results was set at p ≤ 0.05.
Results: The marginal gap values decreased for the five groups after overlays cementation. Cerasmart overlays using shoulder palatal design recorded the highest value before (36.33 µm) and after (27.81 µm) cementation. Comparing fracture resistance between all tested groups, significant difference was found (p=0.002). Vita Enamic overlays using conventional design recorded the lowest value of fracture resistance (609.565 N), while Cerasmart overlays using circumferential shoulder design recorded the highest value (1458.796 N).
Conclusions: The preparation design and the restorative material significantly influence both the MA and the FR of hybrid ceramic overlay restorations for maxillary premolars.

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