Hydroxyapatite (HAP) inserts minimize restoration contraction by constituting a major part of the restoration; however, their effect on the relaxation of tooth tissues has not been previously tested. Finite element analysis was employed to estimate stress and displacement when HAP inserts with a thickness of 1.7 mm or 4.7 mm and a diameter of 4.7 mm were used to substitute for dentin. The volumetric contraction of the composite during polymerization, simulated through steady-state heat transfer analysis, yielded a contraction rate of 3.7%. Descriptive statistics revealed that the incorporation of HAP inserts reduced the displacement of dentin, enamel, and restoration caused by contraction by 44.4% to 66.7%, while maximal stress was reduced by 8.1% to 52%. Subsequent loading on the occlusal tooth surface showed that displacement values decreased by 12.1% to 33.3%, while maximum von Mises stress in enamel decreased by 32.8% to 40.6% with the use of HAP inserts. Although the maximum stress values in dentin were not significantly decreased (3% to 8.8%), the stress located at the bottom of the cavity was notably reduced, particularly in deep cavities at root canal entrances. The use of HAP inserts in restorative dentistry provides benefits for the preservation of prepared teeth, especially in preventing irreparable vertical root fractures of endodontically treated teeth.

Background/Objectives: To evaluate the impact of dental laboratory material overlays on metal artifact reduction in multidetector computed tomography (MDCT) of the oral cavity across different CT protocols and reconstruction algorithms. Methods: An anthropomorphic mandible phantom was constructed using extracted human teeth, metal-ceramic restorations, and ballistic gelatin as a soft-tissue analog. Six dental materials (Elite HD+, Vonflex S Putty, Tropicalgin, MB Wax 1, Zetaplus, and COE-PAK) were tested as overlays. MDCT imaging was performed following low-dose and standard protocols with primary and O-MAR reconstructions, yielding 28 datasets. Two radiologists independently assessed artifact indices (AIs), overall image quality (OIQ), and spherical marker visibility (SMV), with excellent inter-observer agreement (ICC = 0.985). Results: Vonflex S Putty model consistently demonstrated the lowest AIs and highest OIQ scores, while maintaining stable performance across both protocols and reconstructions. Elite HD+ and Zetaplus also showed favorable results, while COE-PAK and MB Wax 1 frequently underperformed. Tropicalgin exhibited high AIs with primary reconstruction but improved markedly with O-MAR. SMV analysis confirmed Vonflex S Putty as the only material to consistently outperform the control under low-dose conditions. Conclusions: Silicone-based overlays, particularly Vonflex S Putty, are effective in reducing metal artifacts and improving image quality in MDCT. Overlay selection, combined with MAR algorithms such as O-MAR, represents a complementary strategy for optimizing diagnostic accuracy in patients with metallic restorations.