Treatment of proximal caries lesions by tunnel restorations

The "tunnel technique" may be used as an alternative to the "conventional" class II preparation for the treatment of proximal dentin caries. The purpose of this article was to summarize and discuss the available information concerning the tunnel technique and the clinical success of tunnel restorations.

Information from original scientific full papers or reviews listed in PubMed (search term: tunnel preparation or tunnel restoration) were included in the review. Papers dealing with endodontic or periodontal topics and case reports were not taken into consideration. Clinical studies were included when at least 20 restorations could be followed-up for at least 24 months. In vivo- and in vitro-studies were excluded when the number of restorations under observation or the decision criteria were not clearly defined. Insufficient data about tunnel restorations in the primary dentition do not allow for analysis.

Both effectiveness of caries removal and marginal ridge strength are reduced in tunnel restorations compared to conventional class II. Glass-ionomer tunnel restorations exhibit an annual failure rate of 7-10%. Therefore, the main reasons for clinical failure are marginal ridge fracture, recurrent caries and progression of demineralization. However, clinical studies indicate that composite but not glass-ionomer tunnel restorations might be a promising alternative.

Tunnel restorations filled with glass-ionomer cements exhibit technical deficiencies and a limited life-span compared to conventional class II composite or amalgam restorations and could not be recommended as an alternative preparation for proximal carious lesions. Promising clinical results of composite tunnel restorations need to be confirmed by long-term studies.