The relationship between root-crown ratio of first molar's teeth with trauma from occlusion

Root-crown ratio is an important feature in the prognosis of teeth. The unbalanced root-crown ratio can be a factor of trauma from occlusion, which diagnosed subjectively through the radiographic examination. This study was conducted to confirm the subjective assessment into objective assessment. The aim of this study was to determine the clinical root-crown ratio of first molar which cause trauma from occlusion. Measurement root-crown ratio using method of Lind and its modifications to measure the decrease in alveolar bone height. The mean of clinical root-crown ratio for maxillary first molar is 0.814±0.308, and for mandibular first molar is 0.741±0.295. There are four categories of clinical root-crown ratio based on ROC curve test, which are: ratio > 1.51=good; 1-≤1.50= pretty good; 0.51-0.99= poor; ≤0.50= very bad. Significant result of the correlation between clinical root-crown ratio with: gingival recession (rs:-0.221 on mesial, -0.266 on buccal and -0.179 on lingual/palatal); loss of attachment (rs:-0.340 on mesial, -0.427 on buccal, -0.295 on distal and -0.382 on lingual/palatal); tooth mobility (rs:-0.358) and the thickening of lamina dura (-0.252). There is a relationship between clinical root-crown ratio of maxillary and mandibular first molar with trauma from occlusion that aggravated periodontitis.