In Vitro Dentin Bond Durability of Additively Manufactured Hybrid Composite Restorations Luted with Preheated Composite: A Comparative Analysis of Fourth- and Sixth-Generation Adhesives

ORIGINAL ARTICLE
Timur V. Melkumyan, Kakhramon E. Shomurodov, Ibrokhimjon M. Azimov, Zurab S. Khabadze, Maria K. Makeeva, Roman A. Meremkulov, Surayo Sh. Sheralieva, Diyorakhon A. Inoyatova, Shakhnoza K. Musoshaykhova, Nuriddin Kh. Kamilov, et al.

 
For citation: Melkumyan TV, Shomurodov KE, Azimov IM, Khabadze ZS, Makeeva MK, Meremkulov RA, Sheralieva SSh, Inoyatova DA, Musoshaykhova ShK, Kamilov NKh, Shakirov ShM, Mukhamedov AA, Seeberger GK, Sakuk BY, Dadamova AD. In Vitro Dentin Bond Durability of Additively Manufactured Hybrid Composite Restorations Luted with Preheated Composite: A Comparative Analysis of Fourth- and Sixth-Generation Adhesives. International Journal of Biomedicine. 2026;16(2):242-247. doi:10.21103/Article16(2)_OA14
 
Originally published June 5, 2026

Abstract: 

Background: The purpose of this in vitro study was to evaluate and compare the shear bond strength (SBS) and failure mode kinetics of indirect 3D-printed ceramic-reinforced hybrid composite restorations to human tooth dentin using fourth-generation etch-and-rinse and sixth-generation self-etch adhesive systems under a co-curing protocol with a preheated universal composite resin luting material.
Methods and Results: Sound human third molars (N=156) were prepared to expose flat mid-dentin surfaces. Simulated indirect restorations were additively manufactured as composite cylinders (VarseoSmile TriniQ, BEGO) using a Formlabs Form 4B 3D printer. Samples were randomly divided into two experimental groups based on the adhesive system used: Group 1 (n=78, OptiBond FL, fourth generation) and Group 2 (n=78, Clearfil SE Bond 2, sixth generation). Preheated universal composite resin (Filtek Z350, 55°C) was used for luting under a co-curing sequence. Each group was subdivided (n=39) into a baseline subgroup (immediate testing) and a thermocycling subgroup (10,000 cycles, 5°C/55°C). SBS trials were performed at a crosshead speed of 1 mm/min, and debonded surfaces were evaluated under 40× magnification to classify failure modes. Statistical analysis was performed using SciPy 1.11. For continuous data with a normal distribution, inter-group comparisons were performed using Student’s t-test. Categorical variables were analyzed using the chi-square test. A P-value <0.05 was considered statistically significant.
At baseline, OptiBond FL (20.7 ± 4.6 MPa) and Clearfil SE Bond 2 (20.6 ± 4.2 MPa) demonstrated equivalent immediate bond strengths (P > 0.05) and identical mixed failure profiles. Thermocycling significantly degraded dentin bond integrity across all cohorts (P=0.000). However, post-aging evaluation revealed that Clearfil SE Bond 2 (16.8 ± 4.4 MPa) had a significantly higher remaining SBS than OptiBond FL (14.4 ± 4.7 MPa), P = 0.023. Microscopic analysis confirmed a complete absence of cohesive failures. Following thermal aging, the OptiBond FL interface underwent an acute intra-group shift toward true adhesive failures (84.6%), whereas Clearfil SE Bond 2 maintained high structural stability with a lower adhesive failure rate (61.5%), P= 0.022.
Conclusion. While both adhesive strategies exhibit equivalent immediate performance during preheated composite co-curing, the null hypothesis must be rejected after artificial aging. The sixth-generation 10-MDP-containing self-etch system provides superior hydrolytic stability and interfacial durability compared to the fourth-generation system. Clinically, a two-step self-etch protocol provides a more predictable, chemically driven interface for the long-term cementation of contemporary additively manufactured restorations.

Keywords: 
3D-printed composite • preheated resin composite • 10-MDP • shear bond strength • failure mode
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Received April 10, 2026.
Accepted May 31, 2026.
© 2026 The Author(s). International Journal of Biomedicine is published by IMRDC.
This is an open access article under the CC BY-NC-ND 4.0 license.