Co-curing adhesives with composite resins can simplify restorative procedures and reduce film thickness, but attenuation of light and polymerization shrinkage stress often lead to compromised bond strengths. While preheating composite material improves its flowability and degree of conversion, rapid thermal dissipation during clinical handling remains a significant limitation. This study aimed to investigate the synergistic effect of simultaneous preheating and co-curing techniques on dentin bond strength, utilizing both total-etch (5th-generation) and self-etch (7th-generation) adhesive systems.

Methods: Eighty human teeth specimens with exposed flat dentin surfaces were divided into two main experimental groups depending on the adhesive system used: 5th-generation total-etch (OptiBond Solo Plus; Kerr) and 7th-generation self-etch (Bond Force II; Tokuyama). Each group was further subdivided into two subgroups (n = 30) based on the curing protocol: conventional sequential polymerization versus simultaneous co-polymerization with a composite resin (Herculite XRV; Kerr) that was preheated (40–43 °C) directly on the tooth surface using a specialized metal heating device. Shear bond strength (SBS) was measured using an UltraTester testing machine at a crosshead speed of 1 mm/min. Data were recorded in pounds and converted to megapascals (MPa), followed by statistical analysis using Student’s t-test (p < 0.05).

Results: Co-polymerization of the preheated composite with the 5th-generation adhesive system significantly decreased the SBS to dentin by 1.3-fold compared to conventional sequential polymerization (p < 0.05). Conversely, co-polymerization of the preheated composite with the 7th-generation self-etch adhesive resulted in a significant 1.2-fold increase in SBS (p < 0.05). Under the co-polymerization protocol, no statistically significant differences were observed between the two adhesive types.

Conclusions: The impact of combining preheating and co-curing protocols is strictly dependent on the adhesive system generation. Direct in situ heating of a composite resin over a self-etch adhesive significantly enhances its bonding performance, likely due to enhanced chemical interaction between monomers and tooth hydroxyapatite, whereas it impairs the performance of total-etch systems.

Shear bond strength, preheated composite, co-curing, self-etch adhesive, total-etch adhesive, ; dentin bonding

Vukelja J, Klarić Sever E, Sever I, Jukić Krmek S, Tarle Z. Effect of Conventional Adhesive Application or Co-Curing Technique on Dentin Bond Strength. Materials (Basel). 2021 Dec 12;14(24):7664. doi: 10.3390/ma14247664. PMID: 34947259; PMCID: PMC8709259.

Heboyan A, Vardanyan A, Karobari MI, Marya A, Avagyan T, Tebyaniyan H, Mustafa M, Rokaya D, Avetisyan A. Dental Luting Cements: An Updated Comprehensive Review. Molecules. 2023 Feb 8;28(4):1619. doi: 10.3390/molecules28041619. PMID: 36838607; PMCID: PMC9961919.

Eliasson, S. T., & Dahl, J. E. Effect of curing and silanizing on composite repair bond strength using an improved micro-tensile test method. Acta BiomaterialiaOdontologica Scandinavica. 2017 3(1), 21–29. https://doi.org/10.1080/23337931.2017.1301211

Sung-Ae SON1, Jae-Hoon KIM2, Deog-Gyu SEO3, Jeong-Kil PARK1. Effect of dentin surface conditions and curing mode of resin cement on the dentin bond strength. Dental Materials Journal. 2024 43(3), 1-8. doi:10.4012/dmj.2023-287

Poubel DLDN, da Silva RC, Ribeiro APD, Garcia FCP. Effect of preheating on the viscosity of composite resins. J Conserv Dent Endod. 2024 Apr;27(4):360-365. doi: 10.4103/JCDE.JCDE_75_23. Epub 2024 Apr 5. PMID: 38779215; PMCID: PMC11108411.

Falacho RI, Melo EA, Marques JA, Ramos JC, Guerra F, Blatz MB. Clinical in-situ evaluation of the effect of rubber dam isolation on bond strength to enamel. J EsthetRestor Dent. 2023;35(1):48-55. doi:10.1111/jerd.12979

Holanda DB, França FM, do Amaral FL, Flório FM, Basting RT. Influence of preheating the bonding agent of a conventional three-step adhesive system and the light activated resin cement on dentin bond strength. J Conserv Dent. 2013 Nov;16(6):536-9. doi: 10.4103/0972-0707.120965. PMID: 24347889; PMCID: PMC3842723.

Loguercio AD, Salvalaggio D, Piva AE, Klein-Júnior CA, AccorinteMde L, Meier MM, Grande RH, Reis A. Adhesive temperature: effects on adhesive properties and resin-dentin bond strength. Oper Dent. 2011 May-Jun;36(3):293-303. doi: 10.2341/10-218L. PMID: 21851256.

Daronch M, Rueggeberg FA, De Goes MF. Monomer conversion of pre-heated composite. Journal of Dental Research. 2005;84(7):663–667. doi:10.1177/154405910508400716.