In-vivo Method of Measuring Bone Loss Using CBCT and Mimics

Objective: To develop a new method of measuring residual ridge reduction of edentulous mandible underneath implant-retained overdenture opposing maxillary complete denture by cone-beam computerized tomography (CBCT) scanner and Mimics program. Materials and Methods: The CBCT (Planmeca Promax 3D, Helsinki, Finland) images were acquired prior to the treatment and after one year period of wearing implant-retained overdenture. The three-dimensional models of the mandible were generated based on these CBCT images using Mimics program (Materialise NV, Leuven, Belgium). The models were superimposed to identify the areas of bone resorption and to measure the reduction in the residual ridge height. In developing this method, four patients' data were used. They were 2 males age 63 & 64 and 2 females age 52 and 64 years old. All came from the same ethnic group and have been edentulous for more than 10 years. Results: Areas of residual ridge undergoing the most reduction were on the outer buccal aspect of the ridge in the molar regions. The reduction could be easily measured by the difference in height of contour of the superimposed models. The average bone loss measured after a year was in the range of 0.31 to 0.55 mm. The area of bone loss identified in this study is in agreement with previous findings but the amount is much smaller and within a narrow range compared to larger variation of 0.4 – 1.5 mm reported using different methods. Conclusion: This new method allows to precisely identifying and quantifying the areas of residual ridge undergoing resorption a year after wearing implant-retained overdenture in an in vivo fashion. It can be of clear clinical potential for developing a routine of resorption examination and monitoring. Acknowledgement: This study was funded by Ministry of Science, Technology and Innovation of Malaysia (e-science 02-01-01-SF0170) and the Australian-Malaysian Institute