To explore the effects of different pretreatment agents on primary tooth dentin bonding durability.

Forty-two retained primary molars were selected, 24 of which were cut along the mesial and distal directions; thus, 48 samples were obtained for shear bond strength tests, and the other 18 teeth were used for nanoleakage tests. According to different pretreatments, both experimental samples were divided randomly into three groups (Group A: distilled water pretreatment group; Group B: 2% chlorhexidine pretreatment group; Group C: 10 mg/mL resveratrol pretreatment group). The test specimens were prepared, the shear bond strength was tested, and interfacial nanoleakage evaluation and scanning electron microscope observation were performed to evaluate the effects of different pretreatment agents on the bonding interface immediately and after aging for one hour with 10% sodium hypochlorite aqueous solution.

The immediate shear bond strength results showed that there was no significant difference among the three test groups. After aging, the shear bond strength of Group C was significantly higher than that of Group A and Group B (P<0.05). After aging, the shear bond strength of Group A was significantly lower than the immediate shear bond strength (P<0.05), whereas there was no significant difference in shear bond strength before and after aging in Group B and Group C (P>0.05). For Group C, there was no significant difference in interfacial nanoleakage before and after aging. In addition, among the three groups, Group C had the lowest interfacial nanoleakage (P<0.05).

Both chlorhexidine and resveratrol pretreatment can improve the adhesion durability of deciduous dentin, but the effects of resveratrol are better than those of chlorhexidine.

To evaluate the impact of ultra-high-molecular-weight polyethylene (UHMWPE)-Ribbond fibers, when combined with different restorative materials, on fracture resistance and marginal adaptation of isolated primary molar defects, to provide a reference for clinical practice.

This study was approved by the Ethics Review Committee. A total of 72 extracted primary molars with complete crowns were collected, and 66 primary molars were randomly assigned as experimental groups for the fracture resistance and microleakage tests. The molars were divided into six groups (n = 11) based on the type of restorative materials and the application of Ribbond fibers: Group A1, 3M Filtek Z250 + Ribbond; Group A2, 3M Filtek Z250; Group B1, Beautifil Ⅱ LS + Ribbond; Group B2, Beautifil Ⅱ LS; Group C1, 3M Filtek Bulk Fill + Ribbond; and Group C2, 3M Filtek Bulk Fill. Groups A1, B1 and C1 received the fiber-reinforcing technique, whereas Groups A2, B2 and C2 received the direct restorative technique; the remainings were in Group D (blank control group), which did not receive treatment for the fracture resistance test. The fracture resistance test was divided into six experimental groups and one blank control group (n = 6). Primary molar teeth in each experimental group were prepared with Class Ⅱ cavities and filled. The fracture load of all samples was detected, and the fracture mode was analyzed after thermal cycling. The microleakage test was divided into six experimental groups, with five in each group. Class Ⅰ cavities with a diameter of 3 mm and depth of 2.5 mm were prepared within the mesial and distal marginal ridges on the occlusal surface and filled for primary molars in each group. Marginal microleakage was assessed after thermal cycling.

The fracture resistance test results showed that the fracture resistance in groups that received the fiber-reinforcing technique was greater than that in groups that received the direct restorative technique: Group A1>Group A2, Group B1>Group B2, Group C1>Group C2 (P<0.05). The application of Ribbond fibers increased fracture resistance to all tested restorative materials by 37.08% to 39.34%. The proportion of tooth frac-ture decreased significantly in groups A1, C1 compared with A2, C2, with a significant increase in the occurrence rate of “Repairable” (P<0.05). The fracture resistance in Group A1 was significantly greater than that in Group B1 and Group C1 (P<0.05). The marginal microleakage test results showed that the microleakage depth in groups that received the fiber-reinforcing technique was smaller than that in groups that received the direct restorative technique: Group A1<Group A2, Group B1<Group B2, Group C1<Group C2 (P<0.05). The microleakage depth in groups that received the fiber-reinforcing technique decreased by 53.90% to 66.96% compared to that in groups that received the direct restorative technique. The microleakage depth in Group B1 was significantly less than that in Group A1 and Group C1.

The application of Ribbond fibers combined with various restorative materials could enhance fracture resistance and diminish the microleakage depth to improve marginal adaptation.