A 3D-reconstruction measurement for cuspal inclination of the cracked molars

Objectives: To study a 3D-reconstruction measurement for cuspal inclination and cuspal incline angle and evaluate cuspal anotomy in pristine molars of the cracked tooth syndrome (CTS ). Methods: In this study a case-control study was conducted (14 cracked-molar dies enrolled clinically as an experiment group and 22 normal-molar dies as a control group ). All dies were scanned by spiral CT scan every 1mm frontally and images of DICOM format were immediately imported into Efilm1.8.3 software for 3D-reconstruction by using its multi-planar reformatting (MPR) technique. The image containing the mesiobuccal and mesiolingual cuspal tips was selected from mesiodistal serial layers of each die for measuring its mesiobuccal and mesiolingual cuspal inclination and cuspal incline angle. The data were subjected to the independent test (alpha=.05) in SPSS 12.0. Results: The mean value±standard deviation for mesiobuccal cuspal inclination and mesiolingual one in the experiment group were 45.07°±5.03°, 38.29°±5.40°respectively, and those in the control group were 36.05°±4.41°, 29.00°±3.74°. Both showed statistically significant difference(P<0.01). But the mean value ±standard deviation for cuspal incline angle in the experiment group was 97.21°±9.35° , while that in the control group was 114.55°±7.37°, which also showed statistical significance. Conclusions: The mean value of mediobuccal cuspal inclination in the experiment group was bigger than that in the control group, so was the mean value of mediolingual one . While the mean value of cuspal incline angle in the experiment group was smaller than that in the control group. Cuspal inclination was one of the important anatomical factors in the etiology of CTS in molars .The bigger the inclination and the smaller cuspal incline angle , the more likely the presence of CTS.