Allen R. Firestone

The Accuracy and Reliability of Measurements Made on Computer-Based Digital Models

For reasons of convenience and economy, orthodontists who routinely use and maintain pre- and posttreatment plaster casts are beginning to use computer-based digital models. The purpose of this study was to determine the accuracy (validity), reproducibility (reliability), efficacy, and effectiveness of measurements made on computer-based models. A plastic model occlusion ie, dentoform, served as a gold standard to evaluate the systematic errors associated with producing either plaster or computer-based models. Accuracy, reproducibility, efficacy, and effectiveness were tested by comparing the measurements of the computer-based models with the measurements of the plaster models--(1) accuracy: one examiner measuring 10 models made from a dentoform, twice; (2) reproducibility and efficacy: two examiners measuring 50 models made from patients, twice; and (3) effectiveness: 10 examiners measuring 10 models made from patients, twice. Reproducibility (reliability) was tested by using the intraclass correlation coefficient. Repeated measures of analysis of variance for multiple repeated measurements and Students t-test were used to test for validity. Only measurements of maxillary and mandibular space available made on computer-based models differed from the measurements made on the dentoform gold standard. There was significantly greater variance for measurements made from computer-based models. Reproducibility was high for measurements made on both computer-based and plaster models. In conclusion, measurements made from computer-based models appear to be generally as accurate and reliable as measurements made from plaster models. Efficacy and effectiveness were similar to those of plaster models. Therefore, computer-based models appear to be a clinically acceptable alternative to conventional plaster models.

Smile esthetics from the layperson’s perspective

INTRODUCTION Computer-based smile esthetic surveys based on slider technology allow more precise control of variables and the possibility of obtaining continuous data. Variations in the perception of smiles from different facial perspectives have not been resolved. The objective of this study was to quantify the ideal and the range of acceptable values for smile variables judged by laypersons from a full-face perspective for comparison with lower-face data. METHODS Mirrored and symmetric male and female full faces previously determined by peers to be of average attractiveness were used. Ninety-six laypersons judged these smile variables: smile arc, buccal corridor fill, maxillary gingival display, maxillary midline to face, maxillary to mandibular midline discrepancy, overbite, central incisor gingival margin discrepancy, maxillary anterior gingival height discrepancy, incisal edge discrepancy, and cant. The judges manipulated the variables using adjustable image technology that allowed the variable to morph and appear continuous on a computer monitor. Medians for each smile variable were compiled, and the Fleiss-Cohen weighted kappa statistic was calculated to measure reliability. Multiple randomization tests with adjusted P values were used to compare these data with those for lower-face views. RESULTS Reliability ranged from 0.25 for ideal overbite to 0.60 for upper midline to face, except for upper and lower buccal corridor limits, which each had a kappa value near 0. There were no statistically significant differences between the ratings of male and female raters. The following variables showed statistically and clinically significant differences (>1 mm) when compared with the lower-face view: ideal smile arc, ideal buccal corridor, maximum gingival display, upper to lower midline, and occlusal cant. Although the smile arc values differed because of model lip curvature variations, the principle of tracking the curve of the lower lip was confirmed. For the full-face view, the raters preferred less maximum gingival display, less buccal corridor, more upper to lower midline discrepancy, and less cant of the occlusal plane. CONCLUSIONS Reliability was fair to moderate with the exception of the buccal corridor limits. Most variables showed no clinically meaningful differences from the lower-face view. The acceptable range was quite large for most variables. Detailed knowledge of the ideal values of the various variables is important and can be incorporated into orthodontic treatment to produce an optimal esthetic smile.

Validity of the Index of Complexity, Outcome, and Need (ICON) in determining orthodontic treatment need.

Occlusal indices are used to determine eligibility for orthodontic treatment in several publicly funded programs. The Index of Complexity, Outcome, and Need (ICON), based on the perception of 97 orthodontists from 9 countries, has been proposed as a multipurpose occlusal index. The aim of this study was to investigate the validity of the ICON as an index of orthodontic treatment need compared with the perception of need as determined by a panel of US orthodontists. One hundred seventy study casts, representing a full spectrum of malocclusion types and severity, were scored for orthodontic treatment need by an examiner calibrated in the ICON. The results were compared with the decisions of an expert panel of 15 orthodontic specialists from the central Ohio area. The simple kappa statistic (0.81) indicated very high agreement of the index with the decisions of the expert panel. The sensitivity (94%), specificity (85%), positive predictive value (92%), negative predictive value (90%), and overall accuracy of the ICON (91%) also confirmed good agreement with the orthodontic specialists. The panel found that 64% of the casts required orthodontic treatment; the ICON scores indicated that 65% of the cases needed treatment. There was agreement between the expert panel and the index in 155 of the 170 cases. These results support the use of the ICON as a validated index of orthodontic treatment need.

Smile esthetics from patients' perspectives for faces of varying attractiveness.

INTRODUCTION Delivering an attractive smile is a key element in orthodontic patient satisfaction. Smile characteristics can be affected by the facial context. The purpose of this study was to investigate smile esthetics related to facial attractiveness and sex of the model. METHODS Attractive, average, and unattractive model faces (2 of each; 3 male, 3 female) determined by peer ratings were combined with 10 smile variables (buccal corridor, smile arc, maxillary gingival discrepancy, gingival display, incisal-edge discrepancy, cant, overbite, central-incisor gingival margin discrepancy, and maxillary midline to face, and maxillary midline to mandibular midline). Each smile characteristic was altered digitally and presented with slider technology to allow a continuous range of choices. Raters chose the ideal and the limits of acceptability. The variables were divided into 6 separate surveys and rated 96 times. Reliability was assessed by answering each question twice. RESULTS Individual smile variable reliability ranged from fair to excellent, except for the buccal corridor. Clinically significant values were defined as greater than 1.0 mm with statistical significance (P <0.05). Rater sex did not make a difference. Clinical significance was found for smile arc, gingival display, and maxillary midline to face. For females, accentuated smile arcs were preferred for the unattractive and attractive models compared with the average models. The opposite was found for male models. More gingival display was preferred for the attractive and unattractive male and female models compared with the average models. Attractive models were allowed less midline deviation. CONCLUSIONS Facial attractiveness and model sex impacted smile variables with a facial context, except for occlusal cant. These smile characteristics with a facial context should be considered when diagnosing and planning treatment for an orthodontic patient.

Air-rotor stripping and enamel demineralization in vitro

This investigation sought to evaluate the effects of air-rotor stripping on the susceptibility of human enamel to demineralization using an in vitro caries model. Crowns of extracted premolar teeth were abraded (0.5 mm) on one proximal surface by air-rotor stripping. The teeth were placed in a demineralizing gel and removed at various intervals up to 336 hours. Lesion depth and mineral content on the abraded and intact surfaces was measured with contact microradiography and computerized image analysis (double window technique). For each time interval measured, lesion depth was greater (p < 0.05) on the abraded surfaces and mineral density was significantly less (p < 0.05). In a second experiment, the effect of fluoride supplements (dentifrice or topical gel) were examined on abraded and intact enamel surfaces that were exposed to the acid gel for 192 hours. The data showed that fluoride treatments significantly reduced lesion penetration on intact and abraded surfaces compared with a no fluoride group. Lesion depth on the abraded, fluoride treated surfaces was significantly greater (p < 0.05) than on the intact untreated surfaces. No significant differences (p < 0.05) were apparent between the fluoride treatment groups with respect to lesion depth and mineral density within the lesion. These results suggest that air-rotor stripping significantly increases the susceptibility of proximal enamel surfaces to demineralization. As a result, the clinician should use caution in the application of this technique until the long-term effects on caries susceptibility have been determined.

Treatment results in dental school orthodontic patients in 1983 and 1993

The effect of incremental changes in materials and techniques on orthodontic treatment outcomes is difficult to evaluate objectively. Treatment results for two groups of patients whose treatments were completed approximately 10 years apart were evaluated using the peer assessment rating (PAR) index and the index of orthodontic treatment need (IOTN) using the Wilcoxon matched-pairs signed-rank test. Patients in the later group who had been treated by postgraduate students primarily (using fixed appliances) had significantly lower IOTN and PAR scores at the end of treatment and showed a significantly greater reduction in the PAR score than a similar group of patients in the earlier group. There were no significant differences in treatment results between patients in the early and late groups who were treated with removable appliances. Differences in treatment results were most likely the result of changes in materials and techniques that had occurred in the 10 intervening years.

Orthodontic appliance preferences of children and adolescents

INTRODUCTION Although attractiveness and acceptability of orthodontic appliances have been rated by adults for themselves and for adolescents, children and adolescents have not provided any substantial data. The objective of this study was to evaluate preferences and acceptability of orthodontic appliances in children and adolescents. METHODS Images of orthodontic appliances previously captured and standardized were selected and incorporated into a computer-based survey. Additional images of shaped brackets and colored elastomeric ties, as well as discolored clear elastomeric ties, were captured and incorporated onto existing survey images with Photoshop (Adobe, San Jose, Calif). The survey displayed 12 orthodontic appliance variations to 139 children in 3 age groups: 9 to 11 years (n = 45), 12 to 14 years (n = 49), and 15 to 17 years (n = 45). The subjects rated each image for attractiveness and acceptability. All images were displayed and rated twice to assess rater reliability. RESULTS Overall reliability ratings were r = 0.74 for attractiveness and k = 0.66 for acceptability. There were significant differences in bracket attractiveness and acceptability in each age group. The highest-rated appliances were clear aligners, twin brackets with colored ties, and shaped brackets with and without colored ties. Colored elastomeric ties improved attractiveness significantly over brackets without colored ties for children in the 12-to-14 year group. There was a tendency for older subjects to rate clear orthodontic appliances higher than did younger subjects. Ceramic brackets with discolored ties tended to be rated lower than ceramic brackets with new ties and scored lowest in acceptability and attractiveness in all age groups. Girls rated shaped brackets significantly higher than did boys. CONCLUSIONS Childrens preferences for orthodontic appliances differ by age and sex. Child and adolescent preferences differ from adult preferences.

Oral Health-Related Quality of Life in Children with Orofacial Clefts

Objectives To determine the impact of orofacial clefts on the oral health–related quality of life of affected children and whether the oral health–related quality of life of children with orofacial clefts differs among different age groups. To assess whether the responses of children with orofacial clefts differ from the caregivers’ perceptions of their childs oral health–related quality of life and compare with data from a control group. Design Cross-sectional study. Patients/Setting A total of 75 subjects with cleft lip and/or cleft palate (mean age, 13.0 years) from the Nationwide Childrens Hospital Craniofacial Anomalies Clinic, as well as their caregivers, and 75 control subjects (mean age, 13.9 years). Main Outcome Measure Self-reported oral health–related quality of life measured with the Child Oral Health Impact Profile, a reliable and valid questionnaire designed for use with children and teenagers. Results Children with orofacial clefts had statistically significant lower quality of life scores than control subjects had for overall oral health–related quality of life, Functional Well-being, and Social Emotional Well-being. There was a statistically significant difference in the interaction of age group and Social-Emotional Well-being between children with orofacial clefts and control children. No statistically significant differences were found between the responses of children with orofacial clefts and their caregivers’ reports. Conclusions Presence of an orofacial cleft significantly decreases overall oral health–related quality of life, Functional Well-being, and Social-Emotional Well-being in children and adolescents. The negative impact of orofacial clefts on Social-Emotional Well-being is greater in 15- to 18-year-olds than in younger age groups. Children with orofacial clefts and their caregivers had very similar evaluations of the childs oral health–related quality of life.

Factors associated with orthodontists’ assessment of difficulty

The difficulty of achieving an ideal or normal occlusion might lie in the pretreatment occlusion, patient-associated factors, and the treatment. The purpose of this study was to identify factors that were related to the treating orthodontists posttreatment categorization of a case as difficult or easy. Ten orthodontists each identified 10 easy cases and 10 difficult cases that they had treated. The initial malocclusion was measured with the peer assessment rating (PAR) index and the index of orthodontic treatment need (IOTN). Patient and treatment information was obtained from the treatment records. Statistical analysis with parametric or nonparametric testing was performed. Difficult cases had greater severity and need before treatment and greater residual malocclusion and need after treatment. Difficult cases had more chart entries for problems with hygiene and compliance. They were more likely to have had extractions and changes in treatment plan. Difficult cases also required more appointments and a longer treatment duration. Three logistic regression models were developed based on malocclusion severity, patient characteristics, and treatment characteristics. The models support a correlation between greater pretreatment malocclusion severity, 1-phase treatment, and the designation as a difficult case. This study supports a model in which malocclusion severity and factors associated with the patient and the treatment contribute to an orthodontists categorization of a case as easy or difficult.

Comparison of micro-CT and cone beam CT-based assessments for relative difference of grey level distribution in a human mandible

OBJECTIVES The purpose of this study was to examine the ability of CT to assess the relative difference of degree of bone mineralization (grey level) parameters in a human mandible. METHODS Ten mandibular sections from cadavers (81.5 ± 12.1 years) were scanned using micro-CT with 27.2 μm voxel size and cone beam CT (CBCT) with 200 μm, 300 μm, and 400 μm voxel sizes. In addition, 15 clinical CBCT images from young patients (mean age 18.9 ± 3.3 years) were identified. After segmentation of bone voxels, alveolar bone and basal cortical bone regions were digitally isolated. A histogram of grey level, which is equivalent to degree of bone mineralization, was obtained from each region of the CT images. Mean, standard deviation (SD), coefficient of variation (COV), fifth percentile low (Low(5)) and high (High(5)) of alveolar bone and basal cortical bone regions were obtained. Percentage differences of grey level parameters between alveolar and basal cortical bones were computed. RESULTS The alveolar bone region had significantly lower Mean, Low(5) and High(5) values but significantly higher SD and COV than the basal cortical bone region for all CT images (p < 0.05). All parameters were significantly lower for the old cadaver group than for the young patient group (p < 0.05). CONCLUSIONS CBCT and micro-CT provide comparable results in the assessment of relative difference in grey level distribution between alveolar and basal cortical bone regions in the human mandible. The percentage difference relative to an internal reference (basal cortical bone) can be a reliable method when assessing the degree of bone mineralization using CBCT images for both cross-sectional and longitudinal comparisons.