INTRAORAL BONDING OF 4-META MMA-TBB RESIN TO VITAL HUMAN DENTIN/

Purpose: To investigate and compare the in vivo and in vitro tensile b ond strengths of a 4-META/MMA-TBB adhesive resin (Superbond C&B, C&B-M etabond) to human dentin. Materials and Methods: Caries-free teeth pre sent on patients and scheduled for extraction for orthodontic reasons were used. Flat dentin surfaces were prepared and a 4-META/MMA-TBB res in applied. After 10 minutes, the teeth were extracted. Extracted cari es-free teeth were also used and treated similarly. Tensile bond stren gth was evaluated and all specimens were sectioned immediately after b ond testing, after polishing the debonded area or after treating the s urfaces with HCl acid. Results: Data were analyzed statistically, and no significant differences could be determined between third molars an d first premolars, and in vivo and in vitro specimens. Further, tensil e stress fractured specimens were examined under scanning and transmis sion electron microscopy. Widths (+/-5 mu m) of hybrid layers and impr egnation of adhesive monomers into 10-3 solution demineralized vital h uman dentin substrates were essentially similar to those observed in e xtracted samples. The adhesive resin penetrated tubules to form resin tags, unimpeded by intra-tubular fluid under physiologic pressure in i ntra-orally prepared specimens. A hybrid layer formed on resin tags to seal against microleakage and pulpal attack by bacteria and their by- products. An acid-resistant hybrid layer was also observed in enamel. Finally, hydroxyapatite crystals that were encapsulated by polymerized 4-META/MMA-TBB resin was observed at the bases of resin-reinforced hy brid layers in the human dentin substrates. This observation is consis tent with earlier findings and appears to be essential in maintaining durable dentin bonds.