One-hundred Class II direct
resin composite inlays and 34 direct
resin composite restorations were placed in 40 patients. The restorations were evaluated clinically, according to modified USPHS criteria, annually over a 11-year period.
RESULTS: Of the 96
inlays/
onlays and 33 direct restorations evaluated at 11 years, 17. 7% in the
inlay/onlay group and 27.3% in the direct restorations group were assessed as unacceptable. The differences in longevity were not statistically significant. The main reasons for failure for the
inlays/
onlays and direct restorations were fracture (8.3 and 12. 1%, respectively),
occlusal wear in contact areas (4.2 and 6.1%, respectively) and secondary caries (4.2 and 9.1%, respectively). Eight of the non-acceptable
inlays/
onlays and five of the direct restorations were replaced, while the other ones were repaired with
resin composite. Unacceptable wear was observed in occlusal contact areas of six restorations, in patients who were severe bruxers. For the other restorations
occlusal wear was not found to be a clinical problem and no difference was observed between the
inlays/
onlays and direct composite restorations. The marginal adaptation of the
inlays/
onlays was still good at the end of the study. Ditching was only observed in a few
inlays. A higher failure rate was observed in molar teeth than in premolar teeth.
CONCLUSIONS: Good durability was observed for the direct
resin composite inlay/onlay technique. Excellent marginal adaptation and low frequency of secondary caries in patients with high caries risk were shown. No apparent improvement of mechanical properties was obtained by the secondary heat treatment of the
inlays. Also, the difference in failure rate between the
resin composite direct technique and the
inlay technique was not large, indicating that the more time-consuming and expensive
inlay technique may not be justified. The direct
inlay/onlay technique is recommended to be used in Class II cavities of high caries risk patients with cervical marginal placed in dentin.