Intrapulpal temperature changes during the cementation of ceramic veneers

www.nature.com/scientificreports OPEN Intrapulpal temperature changes during the cementation of ceramic veneers Edina Lempel1*, Dóra Kincses1, Donát Szebeni1, Dóra Jordáki1, Bálint Viktor Lovász2 & József Szalma2 Adhesive cementation of ceramic veneers may increase pulpal temperature (PT) due to the combined effect of heat generated by the curing unit and the exothermic reaction of the luting agent (LA). PT increase may induce pulpal damage. The aim was to determine the PT rise during the luting of ceramic veneers (CV) of different thicknesses with light- or dual-curing (LC, DC) adhesive cements as well as pre-heated restorative resin-based composites (PH-RBC). For this a thermocouple sensor was positioned in the pulp chamber of a prepared maxillary central incisor. LC, DC adhesive cements and PH-RBCs heated to 55 °C were used for the luting of CVs of 0.3, 0.5, 0.7, and 1.0 mm thicknesses. The exothermic reaction of LAs added significantly to the thermal effect of the curing unit. PT change ranged between 8.12 and 14.4 °C with the investigated combinations of LAs and ceramic thicknesses (p ≤ 0.01). The increase was inversely proportional to the increasing CV thicknesses. The highest rise (p ≤ 0.01) was seen with the polymerization of PH-RBCs. Temperature changes were predominantly influenced by the composition of the LA, which was followed by CV thickness. Ceramic laminate veneers are widely used as esthetic restorations for the correction of unfavorable tooth appearance. The design of the preparation, tissue removal, as well as the thickness of the restoration is dependent on the specific indication for the ceramic veneer. Their proportionality is not unequivocal1. Although conventional tooth preparation for laminate veneers can be considered a reliable technique, minimally invasive or even ‘prepless’ veneers are regarded as additional methods applicable for tooth p reparation2. The clinical success and durability of a porcelain veneer is greatly influenced by the strength of the adhesion formed between the interfaces of the three different components; the porcelain veneer, luting agent and tooth surface3. A close apposition of the enamel and the porcelain surfaces has a synergistic effect on the overall bond strength of the enamel/luting agent/porcelain c omplex4. This complex is characterized by a higher bond strength compared to the sum of the individual attachments between the enamel/luting agent and luting agent/porcelain4. In order to provide this ultimate linkage, adhesive resin cements are typically used for the cementation of ceramic veneers. This also improves the fracture resistance of the inherently brittle c eramics5. Their good esthetic and mechanical properties as well as low solubility in the oral environment can further improve the quality of these restorations3,6,7. Within the group of adhesive cements, light-curing resin cements are generally preferred due to their longer working time and superior color s tability8. Since the porcelain veneer absorbs between 40 and 50% of the emitted light, their thickness is the primary factor in determining light transmittance available for polymerization9. In case of a porcelain with a thickness of more than 0.7 mm, light-cured resin composites do not reach their maximum hardness10. In such cases, the use of dual-cured adhesive resin cements is advised. Failures associated with these adhesive resin cements are disintegration in marginal integrity and discoloration1,11. The use of pre-heated restorative resin-based composites (RBC) as luting agents was first described in 198712. Their application is enjoying increasing popularity in today’s clinical practice. Given their reduced viscosity, allowing for thin film thickness, good adaptation and the benefits of high filler content the use of pre-heated RBCs as luting agents has been extensively assessed by clinical studies and laboratory investigations13–18. The increased filler load improves mechanical- and bond strength, thereby improving fracture r esistance15,19. In comparison to resin cements, pre-heated RBCs are also less expensive as well as offer a greater range of shades. Additionally, they decrease polymerization shrinkage and stress generation in the exposed cement layer at the bonded interface which imparts greater resistance to intraoral d egradation16. Aside from these benefits however, 1 Department of Restorative Dentistry and Periodontology, University of Pécs Medical School, Dischka Gy. Street 5, Pécs 7621, Hungary. 2Department of Oral and Maxillofacial Surgery, University of Pécs Medical School, Dischka Gy. Street 5, Pécs 7621, Hungary. *email: Scientific Reports | (2022) 12:12919 | https://doi.org/10.1038/s41598-022-17285-x 1 Vol.:(0123456789) www.nature.com/scientificreports/ Material (code) Shade Manufacturer Classification Resin system Filler Filler loading 38 vol% 64 wt% Variolink Esthetic LC (VE_LC) Light Ivoclar Vivadent, Schaan, Liechtenstein Light-curing adhesive resin cement UDMA, 1,10-DDMA 0.04–0.2 μm ytterbium trifluoride and spheroid mixed oxide Variolink Esthetic DC (VE_DC) Light Ivoclar Vivadent, Schaan, Liechtenstein Dual-curing adhesive resin cement UDMA, 1,10-DDMA 0.04–0.2 μm ytterbium trifluoride and spheroid mixed oxide 38 vol% 64 wt% Estelite Sigma Quick (EQ_55 °C) A1 E Tokuyama Dental, Tokyo, Japan Conventional submicron RBCpre-heated to 55 °C BisGMA, TEGDMA 0.1–0.3 μm monodispersing spherical silica-zirconia filler; prepolymerized filler of silica-zirconia and copolymer 71 vol% 82 wt% Filtek One Bulk Fill Restorative (FOB_55 °C) A1 3M ESPE, St. Paul, MN, USA Microhybrid bulk-fill RBC pre-heated to 55 °C AFM, UDMA, AUDMA, 1,12-DDMA 20 nm silica, 4–11 nm zirconia, cluster Zr-silica, 0.1 µm 58.5 vol% 76.5 wt% ytterbium-trifluoride Table 1.  Materials, manufacturers, classification and composition of the investigated adhesive resin cements and pre-heated resin-based composites. RBC resin-based composite, E enamel, BisGMA bisphenol-A diglycidil ether dimethacrylate, AFM addition fragmentation monomer, UDMA urethane dimethacrylate, AUDMA aromatic urethane dimethacrylate, 1,10-DDMA 1,10-dodecane dimethacrylate, 1,12-DDMA 1,12-dodecane dimethacrylate, LC light-cure, DC dual-cure, vol.% volumetric , wt% weight %. pre-heated RBCs were also found to negatively influence the adaptation of fixed dental prostheses as reported by a recent systematic review20. Regardless of the luting agent used, a high degree of conversion (DC) is key to achieving the previously described benefits through different thicknesses of ceramic veneers21,22. Although, the use of a high-irradiance curing unit or longer exposure duration can improve DC, these processes also involve thermal reactions which could potentially be hazardous to the dental p ulp23,24. The temperature rise during the curing of resin-based dental materials is attributed to both the energy absorbed during irradiation with light-curing units and (...truncated)