A Study On The Algorithm Of Digital Dental Model Repairing

With the progress and the cooperation of computer aided design, computer aided manufacture, graphics digital collection technology and virtual reality, computer technology has increasingly penetration in medical field of teaching, scientific research and clinical application. People now can get the digital dental model very conveniently with the development and popularization of measurement technology, and this plays an impartment role in the dental clinical diagnosis and treatment. Holes may be exist in the model due to the incomplete measurement data caused by caries on the tooth, the damage of gypsum teeth model or shading of fixtures in the process of measurement. The repair techniques of digital dental model will be discussed in this paper.The acquisition of the digital dental model and the three dimensional reconstruction is the precondition of teeth repair. In this paper, the three dimensional reconstruction is made from the origin CT image of the lower head using the interactive medical image control system Mimics, and further processing has been done to get the surface data of three dimensional dental model and the triangular mesh model for teeth using in the experiment in this paper.An improved method of dental hole filling is presented, the hole boundary detection algorithm is studied and a detection algorithm based on the point is improved to make the result hole borders ordered. On dental mesh hole filling, this paper use the method of grid growth and the minimal angle principle, new triangle meshes are increased acceding to the setting role from the front side of the hole and this updates the hole boundary. Repeat this process until the hole area covered by the produced triangle meshes. A brief method by adding a new decision condition is given by the paper to solve the problem of the unqualified meshes such as getting too focus on one side of hole or too small new triangle meshes that lead to the shapes fail to meet the demand. The result of this method meets the basic requirements both in the quality and shape of meshes.This paper also presents a method of fixing the dental model with fitting and surface features. The adjustment is made to the added points by recalculate acceding to the surface feature, including density characteristics and curvature information. A scale attribute is set to border and new vertices to mark the density of the grid nearby; the density information of original triangle meshes is transferred to the internal grid by it in the process of grid growth, and makes the patch grid have the similar density with the grid around. The position of new points are calculated again acceding to the curvature of vertex of the grid around and this makes the new triangle meshes fit the shape of the missing area properly. The better quality repair meshes can be got without a subsequent optimization. Finally, multi NURBS surface is used to fit the fixed dental mesh, the continues surface of teeth is get for further geomantic process.