The Versatility of Universal Resin Cements: Selective Adhesive Luting

Objectives: To exploit the versatility of universal resin cements (URCs) when used for combined adhesive/self-adhesive luting procedures on enamel and coronal dentin.
Methods: Enamel and dentin surfaces were embedded in acrylic resin, leaving one of the surfaces untouched and available for testing. Two URCs (Panavia SA Cement Universal, PAN, Kuraray Noritake and RelyX^TM Universal, RXU, 3M ESPE) and their pertinent universal adhesive systems (Quick Bond Universal and Scotchbond Universal Plus, respectively) were employed to lute composite cylinders. The following groups were formed, according to the luting procedures (n=15; total N=105): 1. URCs used in the self-adhesive mode (SA); 2. URCs applied after universal adhesive application (100%ADH); 3. The universal adhesives were applied to only 50% of the bonding area before cement application (50%ADH). Considering the drawbacks of enamel etching, two additional adhesive groups were considered on this tooth substrate after etching with H₃PO₄ (ETCH) for 30s (4. ETCH+50%ADH and 5. ETCH+100%ADH, respectively). After 24h, the micro-shear bond strength (µSBS) test was performed (UltraTester, Ultradent) and fractures evaluated. Data were statistically analyzed (p<0.05).
Results: The cement and the application mode influenced the bond strength (p<0.05). No differences existed between the tested URCs when used in the SA mode, both on enamel and dentin (p>0.05). The following differences were obtained in dentin both for PAN and RXU (P<0.05): 100%ADH>50%ADH>SA. On enamel, the statistical analysis revealed that (P<0.05): RXU/100%ADH=RXU/ETCH+100%ADH>RXU/50%ADH=RXU/ETCH+50%ADH>RXU/SA; PAN/100%ADH=PAN/ETCH+100%ADH>PAN/ETCH+50%ADH>PAN/50%ADH>PAN/SA. Mixed failures were predominant in all groups.
Conclusions: The selective adhesive luting technique with URCs could converge the benefits of self-adhesive and adhesive cementation. It could be proposed a reliable technique to be adopted to overcome uncertain clinical situations where it is not possible to turn to completely adhesive cementation, such as unretentive abutments or subgingival margins that do not allow to place rubber dam naturally requiring a self-adhesive approach.