OBJECTIVES: Being a secondary outcome in a multicenter randomized controlled trial, the present analysis focused on interdental spacing in the shortened dental arch (SDA). The aim was to evaluate changes in interdental spacing in dependence of two different treatments after an observation period of up to 5 years.

MATERIAL AND METHODS: Patients were either treated with a partial removable dental prosthesis (PRDP) for molar replacement (PRDP group) or according to the SDA concept aiming at a premolar occlusion (SDA group) in a randomized manner. Interdental spacing in the anterior region was measured with gauges and categorized as "0" (<0.1 mm), "1" (<0.5 mm), "2" (0.5-1 mm), and "3" (>1 mm). The statistical analysis was performed with analysis of variance models followed by linear contrast.

RESULTS: Ninety-one patients (SDA n = 41, PRDP n = 50) were included. Changes of interdental spacing were detected in 70.7 % of all cases. A significant difference between the mean score changes was found in the mandible comparing the PRDP group and the SDA group. The respective mean score changes from baseline to 5 years were 0.23 (SD 0.49) for the PRDP group and 0.02 (SD 0.30) for the SDA group (p = 0.023).

CONCLUSIONS: Major interdental spacing could be observed in neither of the groups. The SDA concept resulted in a slightly better outcome.

CLINICAL RELEVANCE: When deciding whether to replace missing molars, the present results give further support to the SDA concept.