No abstract

The aims of this paper are to give a brief history of the tunnel restoration, to describe and illustrate one way of making this restoration and to review the clinical trials of the procedure carried out to date.

A clinical study was carried out to assess relationship between the presence of approximal cavitation, the radiographic depth of the lesion, the site–specific gingival index and the level of infection of the dentine. Adult patients assessed as needing operative treatment and presenting with approximal lesions visible in the outer third of dentine on bite–wing radiographs were included in the study. Direct lesion depth measurements were recorded from the radiographs and the site–specific gingival index adjacent to the lesion was noted. The presence or absence of a cavity was recorded on an impression following tooth separation. During operative treatment samples of dentine were taken on entry to the lesions to ascertain the level of infection of the dentine. Visual evaluation of 54 successfully recorded impressions revealed that 85% were cavitated. Cavitated lesions were found to have higher site–specific gingival index scores compared to non–cavitated lesions (p = 0.03). The probability of cavitation was greater for lesions >0.5 mm from the enamel–dentine junction on bite–wing radiographs (p<0.01). The level of infection of the dentine was significantly higher for cavitated lesions than for non–cavitated lesions (p = 0.02). However, the non–cavitated lesions were still infected.

A randomized controlled clinical study was set up to assess caries removal following tunnel preparation (test group) and class II cavity preparation (control group). Sixty approximal lesions in adult posterior teeth, visible in the outer third of dentine on bite–wing radiographs, were referred for operative treatment. Initial dentine samples were taken on entry to the lesions in both groups. Following cavity preparation dentine samples were taken from beneath the marginal ridge in the tunnel group and at the cervical floor in both groups. Microbiological analysis was carried out to establish the level of infection of the dentine. The bacterial counts were high on entry to the lesions with a median log₁₀ (CFU + 1) per sample of 3.07 (±1.24). Following cavity preparation bacterial counts at the cervical floor were significantly reduced in both amalgam and tunnel groups (p<0.00001). In the tunnel group, however, slightly increased bacterial counts were found beneath the marginal ridge compared to the cervical floor (p<0.01).