A new optical method to evaluate three-dimensional volume changes of alveolar contours:: a methodological in vitro study

Objectives: The aim of this study was to evaluate the reproducibility and the accuracy of volumetric measurements of specimens imitating localized alveolar ridge defects using an optical three-dimensional (3D) system. Material and methods: Eight pairs of specimens (five with a cuboid and three with a geometrically complex form) were used for the measurements. Each of them imitated a pre-operative ridge defect and a corresponding surgically corrected post-operative situation. The true volume differences between two corresponding specimens were either assessed by a mechanical 3D coordinate measuring machine or by computer calculation (controls). For the test measurements, an optical 3D system with a newly developed software for volume measurements was utilized. The volumes of the specimen pairs were captured and the data digitized. The volume differences between the simulated pre- and post-operative situations were calculated by subtracting the two values obtained. The accuracy of the optical 3D system was assessed comparing the test and the control values. The difference between these values described the systematic error of the test method. The reproducibility was evaluated by calculating the coefficients of variation of repeated test volume measurements. Descriptive statistics were applied. Results: The accuracy of the optical 3D system was very high with differences between test and control measurements never exceeding 1.5%. The systematic error of the test measurements was consistently below 2.5 mm(3). The reproducibility of the measurements showed very low coefficients of variation ranging from 0.05% to 0.5%, indicating excellent reproducibility. Conclusions: The tested optical 3D system showed excellent accuracy and high reproducibility for measuring volume differences between specimens imitating localized alveolar ridge defects before and after augmentation procedures.