An assessment of interocclusal space in a dentate Nigerian population

To determine the average interocclusal space values in a dentate Nigerian population,and to examine the effect of gender, age and different molar relationships on the values obtained.

Three hundred and fifty one subjects mainly of Yoruba extraction with ages ranging from 16 to 78 years were involved in the study. They included 165 males and 186 females. Inclusion criteria in the study included the presence of a stable posterior occlusion with all first molars present and the absence of moderate to deep wear facets suggestive of parafunction. Subject's occlusal dimensions were measured with a calliper at rest and in occlusion. Interocclusal distances were determined by subtracting the occlusal vertical dimension from the rest vertical dimension. The Angles molar relationship was then recorded for each subject.

The average freeway space was 2.93 mm with a standard deviation of 1.38; with the females having marginally higher values. The mean values according to age groups were 15-25 years: 3.15 mm, 26-35 years: 2.68 mm, 36-45 years: 2.66 mm, 46-55 years: 3.2 2mm, 56-65 years: 2.74 mm and 66 years and over: 3.10mm.Class Imolar relationship predominated in the sample with 312 patients (88.9%).Nineteen patients (5.4%) had Class II and 20 patients (5.7%) had Class III.Mean freeway space values for Class I, Class II and Class III were: 2.84 mm, 3.88 mm and 3.37 mm respectively. The difference in values was statistically significant.

The average interocclusal space amongst the population assessed was 2.93 mm; a value which is similar to that previously reported for Nigerians. Marginally higher values were observed in females while the 26-35 and 36-45 year old groups had lower values than the other age groups. Angle's Class II and III subjects had higher values when compared to class I subjects and was statistically significant. A multi-centre study is recommended to assess possible ethnic variations in these values.