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Approximal fillings increase the caries risk

Placing a Class II composite restoration makes it five times more likely to require a restoration in the sound adjacent surface in the near future.

This is the result from a follow-up study of the findings presented in the NIOM Newsletter 10/2015. In that study, certain risk factors for caries development on approximal surfaces in contact with newly placed Class II composite restorations were identified. It was shown that during a five-year observation period, caries in dentin developed in a substantial amount of the surfaces in contact with restorations (Fig. 1). However, due to the study design it was not possible to prove that the contact surfaces actually were at higher risk of developing caries than other surfaces. To elucidate this, a sub-sample of patients from the original study, with sound surfaces adjacent to newly placed approximal posterior restorations in permanent premolars and molars, were selected for the new study. To achieve a split-mouth control site, only patients with an intact contralateral pair of teeth in the opposite quadrant in the same jaw without clinically or radiographically detectable caries were selected (n = 193). For example, for patients with a mesial composite restoration in an upper right molar and sound surface distally on the upper right premolar, both the mesial surface of the upper left molar and the distal surface of the upper left premolar had to be sound
in order to meet the inclusion criteria (Fig. 2).

On average, the 193 patients were followed for 4.8 years. Follow-up observations revealed that only 41% of the surfaces adjacent to composite restorations remained sound, compared with 67% of the control surfaces (p < 0.001). Restorations were placed during the observation period in 17% of adjacent surfaces, compared with 3% of the control surfaces (p<0.001)(Fig. 3). Sound tooth surfaces in contact with restorations are in fact at higher risk of developing caries than other surfaces. Thus, placing approximal composite restorations seems to enhance the need for future operative treatment. This must be regarded as an important adverse effect of the treatment.

Clinical significance
Operative treatment of unrestored approximal surfaces should be as conservative and cautious as possible in respect to the neighbouring surface. Interproximal surfaces in contact with a composite restored surface may require intensified preventive regimes, as well as close monitoring and follow-up.

More reading:
1. Skudutyte-Rysstad R, Tveit AB, Espelid I, Kopperud SE. Posterior composites and new caries on adjacent surfaces - any association? Longitudinal study with a split-mouth design. BMC Oral Health 2016;16:11.
2. Kopperud SE, Espelid I, Tveit AB, Skudutyte-Rysstad R. Risk factors for caries development on tooth surfaces adjacent to newly placed Class II composites – a pragmatic, practice based study. Journal of Dentistry. 2015;43:1323–1329.

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