Tightness of dental contact points in spaced and non-spaced permanent dentitions

One of the characteristics of normal occlusion is tight dental contact poin ts (CPs). However, the magnitude and distribution of the tightness of a den tal contact point (TDCP) in non-spaced versus spaced dentitions are unknown , as well as the mechanism controlling this arrangement. Two hypotheses wer e examined: the compression theory, i.e. the teeth touch each other in a co mpressive state; and the resistance theory, i.e. size and number of roots d etermine TDCP values, for the study, 60 subjects (27 men, 33 women), mean a ge 25 +/- 4.3 years, with a complete permanent dentition and no missing tee th were divided into spaced (n = 22) and non-spaced dentitions (n = 38). Fo r each CP, four repeated measurements of peak strain were performed with a one-month interval. No significant differences were found between repeated measurements. All CP s demonstrated a continuous decreased TDCP in the postero-anterior directio n. Consequently, in non-spaced dentitions TDCPs between molars were 100 per cent higher than incisors. The five anterior CPs of each jaw demonstrated similar TDCP values. Maxillary TDCPs versus mandibular antagonists were not significant. Mandibular TDCPs were significantly higher in men than in wom en (14 per cent). Anterior TDCPs were less in spaced than in non-spaced den titions (55 per cent), Posterior TDCPs were also lower in spaced dentitions , however, to a lesser extent (25 per cent). With the exception of TDCPnon- spaced > TDCPspaced, which is partially explained by the compression theory , most of the findings support the resistance theory regulating TDCP charac teristics of the permanent dentition.