Relationship of Mandibular Ramus Dimensions to Lower Third Molar Impaction

Abstract

Objectives The aim of this study was to investigate the mandibular ramus features that could contribute to the etiology of mandibular third molar impaction. Materials and Methods Two hundred and forty subjects were divided into two groups: impacted group: 115 subjects presented with an impacted mandibular third molar, and control group: 125 subjects with the normal mandibular third molar eruption. Digital panoramic radiographs were used, and four angular and twelve linear measurements were done. Comparisons between groups were done using Student's t-test. Pearson correlation and linear regression tests were used to assess the degree of relationship between retromolar space and mandibular measurements. Results Control group showed significant greater measurements in most of the variables, whereas the impacted group showed significant larger gonial angle and larger inclination of lower posterior teeth than the control group. Significant correlations were found between retromolar space and coronoid height, ramal heights, ramus notch depths, the inclination of lower posterior teeth, and retromolar space/3M width ratio in both groups. Conclusion The present study found that the configuration of the mandibular ramus appears to be discrete in many aspects in the erupted other than impacted lower third molars subjects, which might be a possible cause for the impaction.

Sex-related variation in the dimensions of the mandibular ramus and its relationship with lower third molar impaction

“…Some reports have found a more acute gonial angle in the impacted group than in the normal group, 17 something which was not found in our groups. Our findings are consistent with those obtained by Al-Gunaid et al., 11 who failed to identify any association between the magnitude of the gonial angle and third molar impaction. However, this does not support the results of Behbehani et al., 2 who reported that a small mandibular plane and gonial angle are correlated with an increased chance of third molar impaction.…”

“…This outcome is supported by Al-Gunaid et al. 11 who attributed the result to the smaller angle between the condyle and coronoid process and longer ramus heights in the control group than those in the impacted group (this results in less backward and forward slope of the posterior and anterior margins of the ramus in the control group). Subsequently, this suggests that the sigmoid notch depth in the control group is more likely to be more in-depth.…”

“…Al-Gunaid et al. 11 reported a significant but imperceptible correlation between retromolar space and ramus heights. The authors concluded that ‘these parameters could be a relevant indicator for predicting the eruption or impaction of third molars’.…”

“…Al-Gunaid et al. 11 attributed this difference to ‘the failure of remodelling of the anterior and posterior surfaces of the ramus, as well as the more backward and forward slope of the anterior and posterior borders of the ramus presented by the significantly smaller angle between the condyle and coronoid process in the impacted group’.…”

“…Using panoramic images, Al-Gunaid et al. 11 focused on the correlation between third molar impaction and ramus dimensions. In terms of the latter, they reported significant differences between subjects with mandibular third molar impaction and those with normally erupted molars.…”