Determination of marginal permeability of restorations in the cervical region using a universal adhesive system: a randomized controlled open-label laboratory study

BACKGROUND: The occurrence of microleakage in the gingival margins of restorations using composite materials is a frequently observed phenomenon, raising the question about the ability of adhesive systems to hybridize dentin in this area. In the gingival margin of the restoration, microleakage is higher compared to the occlusal margin, as the thickness of the enamel decreases significantly in relation to the cementoenamel junction. Furthermore, the enamel on the gingival wall of a Class V cavity is thinner than in the occlusal zone. AIM: To evaluate marginal permeability at the tooth–restoration interface in the cervical region using a universal adhesive system compared with a 5th-generation adhesive system after thermocycling in vitro. METHODS: Marginal permeability at the tooth–restoration interface in the cervical region was determined: the experimental group (group 1) used the universal adhesive system Tokuyama Universal Bond II (Tokuyama Dental, Japan); the control group (group 2) used the 5th-generation adhesive system OptiBond Solo Plus (Kerr, USA) on extracted tooth samples. The laboratory study included sample preparation; thermocycling, staining, and sectioning of samples; photomicrography; and assessment of the degree of microleakage of restorations by independent experts. Statistical analysis was performed using SPSS Statistics. Teeth extracted for periodontal indications without carious lesions or large fillings were used to prepare the samples. The tests were conducted in accordance with GOST R 56924-2016 (Russian State Standard “Dentistry. Polymeric restorative materials”). RESULTS: In group 1 (universal adhesive), there was no microleakage on the occlusal wall of the cavity in the enamel area. The experts’ score assessment did not reveal any statistically significant differences (p 0.017). When assessing microleakage on the gingival wall in samples from group 1, statistically significant differences were found between the assessments of experts 1, 2, and 3 (p 0.017). In group 2 (5th-generation adhesive), when scoring microleakage on the occlusal wall, statistically significant differences were observed between experts 2 and 3 (p 0.017). When assessing microleakage on the gingival wall, the differences between the assessments of experts 1 and 3 were also statistically significant (p 0.017). CONCLUSION: In both groups, no permeability (0 [0; 1] at p 0.017) was found through the enamel wall. In the dentin/cement area during cervical restorations, a statistically significant difference in microleakage was observed between the universal adhesive group (2 [0; 3]) and the 5th-generation adhesive group (2 [1; 3] at p 0.017).