Making three-dimensional Monson's sphere using virtual dental models.
OBJECTIVE
The Monson's sphere and curve of Wilson can be used as reference for prosthetic reconstructions or orthodontic treatments. This study aimed to generate and measure the three-dimensional (3-D) Monson's sphere and curve of Wilson using virtual dental models and custom software.


METHODS
Mandibular dental casts from 79 young adults of Korean descent were scanned and rendered as virtual dental models using a 3-D digitizing scanner. 26 landmarks were digitized on the virtual dental models using a custom made software program. The Monson's sphere was estimated by fitting a sphere to the cusp tips using a least-squares method. Two curves of Wilson were generated by finding the intersecting circle between the Monson's sphere and two vertical planes orthogonal to a virtual occlusal plane. Non-parametric Mann-Whitney and Kruskal-Wallis tests were performed to test for difference between sex and in cusp number within tooth position.


RESULTS
The mean radius of Monson's sphere was 110.89 ± 25.75 mm. There were significant differences between males and females in all measurements taken (p<0.01), within 16.87-17.27 mm. Furthermore, morphological variation derived from variability in cusp number in the second premolar and second molar were not found to influence occlusal curvature (p>0.05).


CONCLUSIONS
This study describes a best-fit algorithm for generating 3-D Monson's sphere using occlusal curves quantified from virtual dental models. The radius of Monson's sphere in Korean subjects was greater than the original four-inch value suggested by Monson.


CONCLUSIONS
The Monson's sphere and curve of Wilson can be used as a reference for prosthetic reconstruction and orthodontic treatment. The data found in this study may be applied to improve dental treatment results.
Department of Oral Anatomy, Dental Research Institute and School of Dentistry, Seoul National University, 28-22 Yunkeun-Dong, Chongro-Ku, Seoul 110-749, Republic of Korea.
Shin-Eun
SE
Nam
Young-Seok
YS
Park
WooCheol
W
Lee
Sug-Joon
SJ
Ahn
Seung-Pyo
SP
Lee
D000328:Adult; D000465:Algorithms; D059925:Anatomic Landmarks; D044466:Asian People / Q000208:ethnology; D002508:Cephalometry; D003198:Computer Simulation; D003724:Dental Arch / Q000033:anatomy & histology*; D003766:Dental Occlusion; D061827:Dimensional Measurement Accuracy; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D016018:Least-Squares Analysis; D008297:Male; D003765:Models, Dental; D056910:Republic of Korea; D012737:Sex Factors; D012984:Software; D018709:Statistics, Nonparametric; D019228:Tooth Crown / Q000033:anatomy & histology; D055815:Young Adult