Predictors for Class II treatment duration.

BACKGROUND: The purpose of this study was to identify clinical factors that predict treatment length for patients with Class II malocclusions. METHODS: A sample of 237 active retention patients representing 3 observational groups (Angle Class I nonextraction, and Class II Division 1 extraction and nonextraction), based on specific selection criteria, was obtained from 3 private offices. From the patient records, data were collected in these categories: (1) patient information, (2) model information, (3) pretreatment cephalogram information, and (4) treatment information. Two regression analyses were completed, with total treatment time as the dependent variable for both models. RESULTS: The first regression analysis (Class I and Class II patients) indicated significant predictors for the patient, model, and cephalometric variables. These predictors included age, pretreatment overjet, and pretreatment ANB angle. The second regression analysis (Class II treatment variables) identified the following factors as significantly associated with treatment length: (1) type of Class II appliance, (2) number of months of Class II appliance wear, (3) number of months of interarch elastic wear, (4) maxillary expansion, (5) number of debonds, and (6) average time (weeks) between appointments. CONCLUSIONS: Six variables explained 56.7% of the variation in Class II treatment length. Further research is required to help explain more of the variance associated with treatment duration.

An evaluation and comparison of orthodontic bracket bond strengths achieved with self-etching primer.

The bonding of orthodontic brackets to enamel is a multistep process. To simplify bonding and decrease chair time, Transbond Plus Self-Etching Primer (3M Unitek, Monrovia, Calif) has been introduced; the primer combines the etching, rinsing, and priming steps. This in vitro study evaluated the shear bond strengths and interoperator variability of self-etching primer, as compared with conventional phosphoric acid etching with 2 common orthodontic resins. A total of 214 teeth were bonded, according to the following protocols: group A: self-etching primer plus Transbond XT light-cured resin (3M Unitek); group B: 35% phosphoric acid (15 seconds) plus Transbond XT resin; and group C: 37% phosphoric acid (15 seconds) plus Enlight bonding resin (Ormco, Glendora, Calif). Significantly higher bond strengths were seen in group B than in group A (P =.004) and group C (P =.002). The mean shear bond strengths of group A were not significantly different from those of group C (P =.99). When 3 orthodontists bonded a total of 60 premolars using the protocols of groups A and B, significant differences in shear bond strengths and strength ranking were found. The mean values they obtained using the self-etching primer were not significantly different, but significant differences in mean values were found between operators when the phosphoric acid-etching technique was used.

Job satisfaction among Canadian orthodontists.

Job satisfaction has been well researched for many professions, including general dentistry. The job satisfaction of orthodontists has not been adequately studied. The aims of this study were to describe job satisfaction among orthodontists and to determine characteristics associated with job satisfaction in the profession. A self-administered, anonymous survey was mailed to Canadian orthodontists. It included a modified version of the Dentist Satisfaction Survey, an overall occupational stress score, and items addressing various characteristics of the respondents. Of 654 mailed surveys, 335 were returned, for a response rate of 51.2%. Most orthodontists (79.3%) were classified as satisfied according to the overall job satisfaction scale of the Dentist Satisfaction Survey; however, some (2.5%) were classified as dissatisfied. The facets of orthodontics with the highest degree of satisfaction were patient relations (93%), delivery of care (86%), respect (84%), professional relations (80%), and staff (76%). The most dissatisfaction was associated with personal time (26%) and practice management (15%). Stepwise multiple regression analysis resulted in a model including overall occupational stress, membership in the Canadian Association of Orthodontists, total number of staff, and age to account for 27.1% of the variation in the overall job satisfaction scale. Based on accountable sources of variance, the overall job satisfaction scale seems to be more affected by other variables than the characteristics evaluated by this survey.

Assessment of facial asymmetries from posteroanterior cephalograms: validity of reference lines.

The goal of this study was to determine the ability of various horizontal and vertical reference lines to provide measurements of dentofacial asymmetries from posteroanterior (PA) cephalograms. Ten horizontal and 15 vertical reference lines, including best-fit lines and lines most commonly used in PA analysis, were tested. A model of a dry skull was devised to create 30 asymmetric positions of the maxillomandibular complex. The true transverse and vertical asymmetries were calculated based on measurements of changes in the position of 24 dental and skeletal landmarks. A PA cephalogram was obtained for each asymmetric position. The horizontal and vertical reference lines were constructed on each PA cephalogram, and measurements of transverse and vertical asymmetries were obtained relative to the individual reference lines. Linear regression analyses were used to compare the actual asymmetries with those measured cephalometrically, relative to the individual reference lines. The adjusted R(2) values for all 10 horizontal lines indicated excellent agreement between the true asymmetries and the measured vertical asymmetries. Ten vertical lines accurately represented transverse asymmetry. Vertical lines constructed between 2 midline points, with 1 point located on the lower part of the skull, were not valid. The best-fit line and all lines constructed as perpendiculars through midpoints between pairs of orbital landmarks showed excellent validity. Crista galli-anterior nasal spine and nasion-anterior nasal spine had the lowest validity and should not be used in cephalometric analysis of asymmetries. The position of anterior nasal spine will be altered in facial asymmetry involving the maxilla.

A comparison of dynamic and static testing of latex and nonlatex orthodontic elastics.

The purpose of this study was to determine the effects of repeated stretching (cyclic testing) and static testing on the force decay properties of two different types of orthodontic elastics from a single supplier. Samples of American Orthodontics' 0.25 inch, 4.5 oz (6.35 mm, 127.5 g) latex and nonlatex elastics were used and a sample size of 12 elastics per group was tested. Static testing involved stretching the elastics to three times marketed internal diameter (19.05 mm) and measuring force levels at intervals over 24 hours. Cyclic testing used the same initial extension but cycled the elastics an additional 24.7 mm to simulate extension with maximal opening in the mouth. Both types of elastic had similar initial forces that were statistically below the marketed force (122 and 118 g for latex and nonlatex elastics, respectively) at three times marketed internal diameter. Cyclic testing caused significantly more force loss and this difference occurred primarily within the first 30 minutes. For statically tested elastics the percentage of initial force remaining at 4, 8, and 24 hours was 87%, 85%, 83%, and 83%, 78%, 69% for latex and nonlatex elastics, respectively. For cyclically tested elastics the percentage of initial force remaining at 4, 8, and 24 hours was 77%, 76%, 75%, and 65%, 63%, 53% for latex and nonlatex elastics, respectively.

Occupational stress among Canadian orthodontists.

The occupational stress associated with many professions, including general dentistry, has been well researched. An anonymous, self-administered, mail-out survey was distributed to Canadian orthodontists. The survey included 67 potential stressors, an overall occupational stress score, an overall job satisfaction scale, and items addressing various characteristics of the respondents. The response rate was 51.2% (335/654). Pronounced differences were found between the respondents in the evaluation of potential stressors and the overall occupational stress score. The category of stressors with the highest mean severity of stress scores was time-related stressors. The stressors with high mean severity scores and high mean frequency scores were as follows: falling behind schedule, trying to keep to a schedule, constant time pressures, patients with broken appliances, and motivating patients with poor OH and/or decalcification. Stepwise multiple regression determined a model, involving overall job satisfaction, age, participation in a study group, hours worked per week, part-time academics, days of continuing education per year, and participation in stress management, to account for 35.9% of the variation in overall occupational stress scores. The results indicate the importance of time-management skills in reducing occupational stress, but other factors seem to have more effect on reported occupational stress than do the characteristics addressed by this survey.

Orthodontic treatment outcome in a First Nations population in Alberta, Canada: a comparative study.

The primary objective of this study was to determine whether there was a significant difference in the degree of improvement after orthodontic treatment between a sample of First Nations orthodontic patients and a control sample of non-First Nations orthodontic patients. The secondary objective was to determine whether there was a difference in the severity of malocclusions being treated in a sample of the First Nations patients compared with a control sample of the non-First Nations patients. Several factors that might affect treatment outcome, such as missed appointments, treatment duration, oral hygiene, extractions, dental classification, and geographic location, were also studied. A sample of 60 First Nations patients and a control group of 60 non-First Nations patients between the 11 and 18 years of age who had been treated with full fixed orthodontic appliances were evaluated. The weighted peer assessment rating (PAR) index was applied to pretreatment and posttreatment study models to address the study's main objectives. The results showed that the First Nations group had greater PAR scores pretreatment than did the controls, and their weighted PAR scores improved more with treatment. Posttreatment PAR scores were similar between the 2 groups. In addition to First Nations status, only extractions and geographic location affected PAR improvement scores.

Tomographic assessment of temporomandibular joint osseous articular surface contour and spatial relationships associated with disc displacement and disc length.

The objective of this retrospective study was to determine whether associations exist between osseous temporomandibular joint (TMJ) characteristics and TMJ internal derangement (disc position and deformation) in an adolescent population. Magnetic resonance imaging (MRI) was used to quantitatively determine disc position and length in 335 TMJs in 175 subjects (106 female and 69 male) between the ages of 7.27 and 20.0 years (mean age, 13.08 years). Nine tomographic variables were measured from pretreatment tomograms. Tomographic data were cross-referenced with MRI data. Male and female samples were evaluated separately. Stepwise linear regression identified associations between disc displacement and reduced superior joint space, increased posterior joint space, increased anterior joint space, and reduced articular eminence convexity (male R(2) value, 0.41; female R(2) value, 0.38). Associations between reduced disc length and condylar position and eminence flattening were weaker (male R(2) value, 0.16; female R(2) value, 0.32). This study demonstrates that TMJ internal derangement is associated with functional osseous adaptation within the joint.

The accuracy of 4 panoramic units in the projection of mesiodistal tooth angulations.

The purpose of this study was to compare the mesiodistal tooth angulations determined with a typodont/skull testing device with the images of mesiodistal tooth angulations from 4 contemporary panoramic units (OP 100, Cranex 3+, Orthophos, PM 2002 EC). A typodont testing device was constructed, and the true mesiodistal tooth angulations relative to an orthodontic archwire were determined with a 3-dimensional coordinate-measuring machine and custom-designed software. A human skull served as the matrix into which the typodont was fixed for imaging. The skull was repeatedly imaged and repositioned 5 times for each panoramic unit. The images were scanned and digitized with custom software to determine the image mesiodistal angulations. Results revealed that the majority of image angles from the 4 panoramic units were statistically significantly different from the true angle measurements. However, definite trends were noted among the panoramic units. For the maxillary teeth, the images projected the anterior roots more mesially and the posterior roots more distally, creating the appearance of exaggerated root divergence between the canine and the first premolar. For the mandibular teeth, the images projected almost all roots more mesially than they really were, with the canine and the first premolar the most severely affected. The largest angular difference for adjacent teeth occurred between the mandibular lateral incisor and the canine, with relative root parallelism projected as root convergence. It was concluded that the clinical assessment of mesiodistal tooth angulation with panoramic radiography should be approached with extreme caution and with an understanding of the inherent image distortions.