Marginal gap formation and fracture strength of indirect inlay restorations cemented with preheated resin composites: an in vitro study

Title (English)

Marginal gap formation and fracture strength of indirect inlay restorations cemented with preheated resin composites: an in vitro study

Thong tin bai bao / Article info

• Tac gia / Authors: Engin Işık, Evrim Eligüzeloğlu Dalkılıç
• Tap chi / Journal: BMC Oral Health
• Ngay xuat ban / Published: 2026-08-01
• DOI: 10.1186/s12903-026-09466-1
• Nguon / Source: OpenAlex

Abstract (English)

Abstract Background Optimal marginal adaptation and adequate fracture strength are critical for the long-term clinical success of indirect posterior restorations. Preheated resin composites have been proposed as alternative luting agents; however, their effects on marginal integrity and mechanical performance of inlays remain unclear. This in vitro study aimed to evaluate gap formation and fracture strength of indirect inlay restorations cemented with preheated resin composites compared with a conventional resin cement. Methods Forty human mandibular molar teeth were divided into four groups ( n = 10/group). Group 1 used a conventional dual-cure resin cement. Group 2 used a preheated resin composite. Group 3 used a preheated bulk-fill resin composite. Group 4 served as the intact tooth control group and received no cavity preparation or restoration. Standardized Class II MOD inlay preparations were performed, with the mesial proximal box floor located in enamel and the distal box floor located in dentin. Indirect restorations were fabricated from resin nano-ceramic blocks via computer-aided design and computer-aided manufacturing (CAD-CAM). All teeth underwent thermal cycling and chewing simulation. Marginal gap formation was analyzed using micro-computed tomography (micro-CT). Fracture strength was assessed using a universal testing machine, and fracture modes were classified. Data were analyzed using the Shapiro–Wilk test and Levene’s test, followed by one-way ANOVA and repeated measures ANOVA with Bonferroni correction and Tukey’s post hoc test, and the Fisher–Freeman–Halton test. Results Enamel margin gap volumes were significantly higher in the preheated bulk-fill composite group compared with the conventional resin cement group ( p = 0.012), while no significant differences were observed at dentin margins ( p = 0.182). All restored groups exhibited significantly lower fracture strength values compared to the intact teeth group ( p = 0.003). Fracture mode distribution showed a tendency toward more repairable fractures in the preheated bulk-fill composite group and more irreparable fractures in the conventional resin cement group. Conclusions Preheated resin composites showed comparable performance to conventional resin cement in terms of marginal adaptation and fracture strength. However, their performance appears to be material-dependent. Therefore, preheated resin composites may be considered as potential alternative luting materials for indirect restorations within the limitations of this study. Clinical relevance Preheated resin-based composites are increasingly considered as alternative luting agents for indirect restorations. Understanding their influence on marginal adaptation and mechanical performance may assist clinicians in selecting appropriate cementation strategies for indirect inlay restorations.

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