Relationship between gap size of composite restoration and secondary caries

Objectives: Today, dental composite restoration is becoming more popular than traditional materials such as amalgam due to improved aesthetics, tooth-sparing preparation, lack of corrosion and etc. However, the inherent polymerization shrinkage of composites can produce gap formation at tooth-restoration interface. This gap formation may develop into secondary caries. The objective of this review was to evaluate influence of gap size between tooth-composite interface in developing secondary carious lesion.
Methods: Articles identified through an electronic search on MEDLINE®/PubMed which were limited January 2000 to May 2015. The keywords “gap size” and “secondary caries” were carried out and reviewed as per objectives. Only the articles that used composite material for experiment were included.
Results: The search yielded 5 publications which were either in vitro or in situ studies. The tooth-resin composite specimens or occlusal splint containing human dentin samples were used. Each study contains sample size of either 10 or 14 per group with different gap size in range of 0 μm to 1,025 μm. Majority of studies concluded that gap size is not relevant in developing secondary decay as long as caries risk is low and only in absence of fluoride release. When caries risk is high, even a gap size of 68 μm may allow to develop secondary caries. However, there was consensus that large enamel gap size ranging from 100 um -500um could lead to the development of dentin wall lesion at the tooth – resin composite interface
Conclusions: Our literature review concluded that wider the gap between tooth and composite restoration material will more likely develop secondary caries unless caries risk is low, absence of fluoride use. There is no consensus on exact threshold of gap size to develop possible decay. Therefore, further studies will be needed in future.