Evaluating the accuracy of three-dimensional reconstruction of the intercuspal position for dentition casts aided by a mechanical appliance

目的 自主研发牙列模型咬合关系三维重建辅助装置并定量评价其精度,为临床应用提供参考.方法 三维设计并数控加工由上下颌体、上下磁性底座与支撑杆构成的辅助装置,单底座前壁、左右侧壁各均匀排布3个直径为3 mm的半球形突起(上下底座共18个,将上下底座对应的半球形突起组成球心对,共9对).用高精度三坐标测量系统测量各半球形突起球心点,获得球心点测量数据;将处于牙尖交错位的1副标准牙列石膏模型固定于上下底座.用牙颌模型三维扫描仪获取单颌模型及底座整体的三维数据,在软件中拟合各半球形突起球心点,也即球心点扫描拟合数据.以上下底座前壁、左右侧壁中央共3对球心点为对齐参考点,将球心点扫描拟合数据对齐于球心点测量数据,完成牙列模型牙尖交错位的三维重建.测量剩余6对球心点对间距离在冠状向(X)、矢状向(Y)及垂直向(Z)的分量长度,以球心点扫描拟合数据为实验组,球心点测量数据为对照组.计算两组差值,进行组间配对t检验.结果 对照组球心点对间距离在冠状向、矢状向和垂直向的分量长度分别为(2.30±0.18)、(4.00±0.13)、(80.46±0.18) mm,实验组分别为(2.35±0.13)、(3.98±0.15)、(80.47±0.15) mm,差值分别为(-0.05±0.10)、(0.02±0.06)、(0.01±0.05) mm;两组各方向分量长度的差异均无统计学意义(P＞0.05).结论 本项研究研发的辅助装置可通过上颌和下颌模型两次扫描完成咬合关系三维重建,可与各种常见模型扫描系统配合使用.Objective To develop a aided mechanical appliance for rapid reconstruction of three-dimensional(3D) relationship of dentition model after scanning and evaluation of its accuracy.Methods The appliance was designed by forward engineering software and fabricated by a high precision computer numerical control(CNC) system.It contained upper and lower body,magnetic pedestal and three pillars.Nine 3 mm diameter hemispheres were distributed equally on the axial surface of each pedestal.Faro Edge 1.8m was used to directly obtain center of each hemisphere(contact method),defined as known center.A pair of die-stone standard dentition model were fixed in intercuspal position and then fixed on the magnetic pedestals with low expansion ratio plaster.Activity 880 dental scanner was used to scan casts after the plaster was completely set.In Geomagic 2012,the centers of each hemisphere were fitted and defined as scanning centers.Scanning centers were aligned to known centers by reference point system to finish the 3D reconstruction of the intercuspal occlusion for the dentition casts.An observation coordinate system was interactively established.The straight-line distances in the X(coronal),Y(saggital),and Z(vertical) between the remaining 6 pairs of center points derived from contact method and fitting method were measured respectively and analyzed using a paired t-test.Results The differences of the straight-line distances of the remaining 6 pairs of center points between the two methods were X:(-0.05±0.10) mm,Y:(0.02±0.06) mm,and Z:(0.01 ± 0.05) mm.The results of paired t-test showed no significant differences(P＞0.05).Conclusions The mechanical appliance can help to reconstruct 3D jaw relation by scanning single upper and lower dentition model with usual commercial available dental cast scanning system.National Natural Science Foundation of China(81271181)国家自然科学基金PubMed中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)8501-5045