Pulpal reaction and microorganisms under Clearfil Composite Resin in deep cavities with acid etched dentin.

Experimental buccal cavities were prepared on 31 pairs of contralateral human premolars. Both cavities were acid etched with 40% phosphoric acid for 15 seconds. The layer of etched enamel was removed from one of the cavities (test) in order to create conditions for microbial invasion to the presumed gap between the resin and dentin. Both cavities were filled with Clearfil Composite Resin after the application of Clearfil Bonding Agent. In the control cavity, the outer portion of the filling was removed and replaced with IRM cement in order to prevent microbial invasion. The teeth were extracted after 1 to 11 weeks. The presence of bacteria and pulpal reactions were studied using routine histological techniques. In several cases the inner resin surface analogous to the cavity floor was studied in the SEM. Bacterial growth was present on the dentinal walls as well as in some of the dentinal tubules in 24 of the 31 test cavities. The underlying pulpal areas showed signs of inflammation. Bacterial growth and pulpal inflammation were absent in 17 control cavities in spite of pulpal lesion or near lesion in 5 of the cavities. In 9 control cavities bacteria and pulpal inflammation were present. This suggests bacterial contamination and/or microbial invasion in spite of the IRM filling. The results show that Clearfil Bonding Agent in combination with Clearfil Composite Resin do not bind sufficiently to etched dentin in cavities to prevent the generation of a gap between the filling and dentinal wall. As a result infection can be established. The results also support the authors' earlier findings that neither acid etching of dentin for 15 seconds nor the chemical properties of resin materials have any especially injurious effect on the pulp, even in deep cavities.