Treatment strategies for midline discrepancies

Objective:To develop a mathematical model that simulates whether or not to extract teeth in optimizing orthodontic treatment outcome and to formulate the morphologic traits sensitive to optimizing the tooth-extraction/nonextraction decisions. Materials and Methods: A total of 188 conventional orthodontic records of patients with good treatment outcomes were collected, and dentofacial morphologic traits, along with their degrees of influence in the optimized model, were determined. Results: The rate of coincidence between the recommendations given by the optimized model and the actual treatments performed was found to be 90.4%. The major morphologic traits and their corresponding influences in improving the simulation accuracy of the model were the incisor overjet (3.0) and the size of the basal arch relative to the sum of the mesiodistal crown diameters of the upper dentition (2.4) and the lower dentition (2.0). The remaining 22 morphologic-trait variables were also found to be indispensable in achieving robust simulation readings. Conclusion: A mathematical model that simulates whether or not to extract teeth in optimizing orthodontic treatment outcomes with a success rate of 90.4% at its prediction performance was developed. This model has 25 morphologic traits with four major categories (sagittal dentoskeletal and soft tissue relationship, vertical dentoskeletal relationship, transverse dental relationship, and intra-arch conditions) that affected the accuracy in determining optimal tooth extractions/nonextractions. (Angle Orthod. 2009;79:885-891.)

Section: Discussionsupporting

confidence: 87%

Computational Formulation of Orthodontic Tooth-Extraction Decisions

Takada

Yagi

Horiguchi

2009

“…Buccal corridor minimization is a critical smile feature, 4,6,[8][9][10] excessive gingival display does not appear to be well tolerated by raters, 4 and maxillary midline deviations can upset the balance of an otherwise esthetic smile. 8,9 Kokich et al 4 found an occlusal cant was detrimental to smile esthetics. 4 In addition, the location, shape, and contour of the gingiva in the maxillary anterior region also affects smile esthetics.…”

Section: Introductionmentioning

confidence: 99%

Esthetics and smile characteristics evaluated by laypersons

McLeod

Fields²,

Hechter³

et al. 2011

116

Objective: To collect data regarding Canadian laypersons' perceptions of smile esthetics and compare these data to US data in order to evaluate cultural differences. Materials and Methods: Using Adobe Photoshop 7, a digital image of a posed smile of a sexually ambiguous lower face was prepared so that hard and soft tissue could be manipulated to alter buccal corridor (BC), gingival display (GD), occlusal cant (OC), maxillary midline to face discrepancy (MMFD), and lateral central gingival discrepancy (LCGD). Adult Canadian laypersons (n 5 103) completed an interactive computer-based survey of 29 randomized images to compare smile preferences for these variables. The custom survey was developed to display fluid, continuously appearing modifiable smile variables using MATLAB R2008 for presentation. These data were compared with previously published data for US laypersons. Statistical inference was determined using Wilcoxon rank sum tests. Results: Canadian laypersons were more sensitive in detecting deviations from ideal and had a narrower range of acceptability thresholds for BC, GD, OC, MMFD, and LCGD. Ideal esthetic values were significantly different only for BC.Conclusions: It appears that cultural differences do exist related to smile characteristics. Clinically significant differences in the preference of the smile characteristics were found between Canadian and US laypersons. Canadian laypersons, on average, were more discriminating to deviations from ideal and had a narrower range of acceptability. (Angle Orthod. 2011;81:198-205.)

“…1 However, a mild degree of facial asymmetry commonly occurs in individuals 2 and is barely recognized by the general public. In certain cases, modification of the maxillary midline to achieve perfect frontal symmetry may require complex procedures, 3 increased treatment time, and substantial cost, although its benefits to the patient are uncertain.…”

Section: Introductionmentioning

confidence: 99%

Young People's Esthetic Perception of Dental Midline Deviation

Zhang¹,

Xiao²,

Li³

et al. 2010

Objective: To test the hypothesis that young people's esthetic perception of dentition midline deviation or the threshold below which they find the deviation ''acceptable'' depends on the gender and face type of the person with the deviation and the gender of the evaluator. Materials and Methods: Facial images of six young subjects with three different face types were captured, and their dentition midlines were altered digitally. The images were evaluated by young people with no dental training. Statistical analysis was carried out to determine the threshold for acceptable dentition midline deviation and factors influencing perception. Results: The mean value for the threshold below which a deviation was judged ''acceptable'' was 2.403 mm (95% confidence interval, 2.315-2.491). The preferences of evaluators did not significantly depend on the direction of the deviation. Both male and female evaluators were significantly less tolerant of deviation in female subjects than in male subjects. However, female evaluators were significantly more tolerant of midline deviations in male subjects than were male evaluators. In addition, the same degree of deviation was most noticeable in male subjects with a tapered face type and least noticeable in female subjects with a square face type. Conclusions: The gender and face type of an individual with dentition midline deviation and the gender of the evaluator do affect young people's esthetic perception of a dentition midline deviation and the threshold below which they find the deviation ''acceptable. '' (Angle Orthod. 2010;80:515-520.)