Three-dimensional Evaluation Of The Relationship Between Dental And Basal Arch Forms

Objective1. This study aims to investigate the relationship between the dental and basal arch forms of patients in normal occlusion using three-dimensional virtual models.2. Find the veracity and boundedness of the Andrews Molar Ruler.3. Find the relationship between the dental and basal arch forms in different skeletal patterns.4. To evaluate the distances between the mandibular permanent teeth and the alveolar process in Jinan with normal occlusion.Subject46mandibular dental casts, aged21to28, were selected. We used15mandibular casts from uⅡntreated subjects who had permanent dentition and in normal occlusion to build Model. We selected31patients whose mandibular has little crowding as Model Ⅰ.The subjects have received CRM to measure skeletal-facial type. Two stainless steel balls were glued to the buccal aspect of each tooth on the casts. One is simulating the FA point,the other is simulating the WALA ridge, adjacent to the FA point. Then the casts were examined by3D scanning. The Pearson correlation coefficients between the intercanine and intermolar widths at the FA and WALA points were determined. Finally, measure the distances between the FA and WALA points using the Andrews Molar Ruler. Compared the difference between the two methods.Results1. The results showed a progressive increase of these distances from the canine region to the posterior region (molars), from0.14to3.42mm.2. A highly significant correlation was found both between the FA and WALA intermolar widths (r=0.794) and the intercanine widths (r=0.923).3. The FA and WALA curves are individual and the values describing the same teeth are scattered.4. The result is high consistency between using Andrews Molar Ruler method and Three-dimension measurement. The measurement can be used to measure the distance between the FA and WALA point in posterior region.5. A moderate correlation was observed between the∠ANB and the intercanine width at the WALA points;Also a moderate correlation was observed between the∠ANB and the distance between the FA point and the WALA point of the incisors of the mandible.6. The mean value of the distance between the FA points and the WALA ridge from central incisor to second permanent molar in our samples are-1.53±0.92mm,-0.97±1.1lmm,0.65±0.90mm,1.17±0.64mm,2.13±0.93mm,3.12±0.72mm,3.55±0.54mm。Conclusion1.Both FA and WALA point-derived arch forms were individual and therefore could not be defined by a generalized shape.2.WALA points proved to be a useful representation of the apical base and helpful in the predetermination of an individualized dental arch form.