Preparation of a uniform angle of walls is essential for making an ideal\nconvergence angle in fixed prosthodontics. We developed a de novo detachable\nangle-correction apparatus for dental handpiece drills that could help the ideal tooth\npreparation.\nMethods: We utilized a gyro sensor to measure the angular velocities to calculate\nthe slope of an object by integrating the values, acceleration sensor to calculate the\nslope of an object by measuring the acceleration relative to gravity, and Kalman filter\nalgorithm. Converting the angulation of the handpiece body to its drill part could be\nperformed by a specific matrix formulation set on two reference points (2° and 6°). A\nflexible printed circuit board was used to minimize the size of the device. For convergence\nangle investigation, 16 volunteers were divided randomly into two groups for\nperforming tooth preparation on a mandibular first molar resin tooth. All abutments\nwere scanned by a 3D scanner (D700®, 3Shape Co., Japan), the convergence angle\nand tooth axis deviation were analyzed by a CAD program (SolidWorks 2013®, Dassault\nSystems Co., USA) with statistical analysis by Wilcoxon signed-rank test.........
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