Reliability of bolton teeth ratio in dual pour alginate impression with plaster and digital models

Aim: The purpose of this study was to compare the values of Bolton ratio for plaster dental casts versus software -based dental models made from a dual pour alginate impression. Materials and Methods: Maxillary and mandibular alginate impressions were made for a sample of thirty-six patients with permanent dentitions from first molar to first molar. Impressions were poured in plaster allowed to set for 8-10 minutes. Casts were removed after cleaning second plaster poured. Thus without damaging dual pour procedure were performed. For digital casts, obtained plaster casts were Scanned and imported into software to perform digital cast’s analysis. Measurements of mesiodistal tooth width were made using digital calipers or Nemoceph software. Overall and anterior Bolton analyses were performed for all models. Measurements were repeated no less than two weeks later. Results were statistically analyzed for correlation coefficients and student t –test was performed. Results: Correlations showed very high intrarater reliability for measurements made on both plaster and digital casts. Boltons ratio has shown statistically significance differences between plaster and digital casts in mesiodistal measurements of both maxillary and mandibular arches. Values of mean difference between plaster and digital casts were 0.68 mm in the maxillary arch and 1.35 mm in the mandibular arch. Value of mean difference between plaster and plaster and between digital and second pour were negligible. Conclusions: This study concludes that first pour plaster casts and second pour plaster casts has negligible differences, similarly between digital casts thus it is significant that both casts can be used for multiple uses depending up on clinician experience. Introduction Orthodontic treatment outcome has remained a challenging task for orthodontist to acquire safe, efficient, stable and predictable as per patient’s desire. Comprehensive treatment outcome depends upon accurate dimensional relationship between the maxillary and mandibular teeth to assure proper interdigitation, overbite and overjet establishment. Establishing accurate inter digitation, overjet, and overbite implicate amount and location of a tooth size discrepancy in pretreatment, as interarch tooth size discrepancies necessitate either removal or addition of tooth structure to open or close spaces in the opposing arches. Several studies have been reported that inter digitation of dental arches are under the influences of tooth size variation (C.W. Neff et al 1949), established anterior proportionality index and tooth size discrepancy index were failed to accept. Wayne A Bolton succeeded to explain and developed formula to anterior ratio (77.2), and overall ratio (91.3) on study models. W.A. Bolton in 1958 developed Bolton index, most significantly used, considered as seventh key of occlusion, and describes interarch discrepancies in tooth sizes. A sum of 55 persons study models with perfect occlusion was taken for the study to generate overall and anterior ratio. Application of Bolton analysis was that it provides information during orthodontic treatment, helps in evaluations pertaining to clinically relevant treatment planning decisions. The study models were fabricated with traditional dental plasters in orthodontic practice. However, the introduction of computer-based study models with analyzing computer software in all three dimensions has given birth to digital study models. Several studies have been reported in comparison with conventional plaster the digital study models were found to dimensionally stable for representations and for analysis. Few studies done(Tomassetti, et al., 2001 ,Garino, F. and Garino, JB, 2002 ,Whetten et al., 2006; Zilberman et al., 2003, Santoro et al., 2003, Quimby et al., 2004, Costalos et al., 2005 Rheude et al., 2005, Mayers et al., 2005, Stevens et al., 2006; Mullen et al., 2007, Okunami et al., 2007, Leifert et al., 2009). With aim to determine statistical, dimensional and analytical difference in conventional and digital study models. However, most of these studies were concluded reporting insignificant difference was seen between conventional and digital study models. Very rare studies have been done with multiple pours of alginate impression in respect to its impact on dimensional accuracy of digital study models and its implication on statistical and clinical applications. Aim of this paper is to compare value obtained by Bolton analysis from conventional study models against computer-based renderings (digital models) from dual Siddharth Sonwane et al. Reliability of bolton teeth ratio in dual pour alginate impression with plaster. Indian Journal of Orthodontics and Dentofacial Research, July-September 2016;2(3):115-118 116 pour of alginate impression and to determine its statistical difference. Material and Method The sample, in this study there were sum of 36 undergraduate students studying in Mansarovar Dental College, Kolar Road, Bhopal were included (13 male and 23 female) between the age group of 18-28 years. Sample selection was done after screening of 643 students. The following are the selection inclusive criteria  Full erupted all permanent teeth excluding the third molars on both side of arch.  No history of orthodontic treatment/ orthodontic extraction/ stripping.  Teeth showing normal developmental morphology