Kenneth E. Glover

Landmark identification error in posterior anterior cephalometrics.

This study was designed to quantify the intraexaminer and interexaminer reliability of 52 commonly used posterior anterior cephalometric landmarks. The horizontal and vertical identification errors were determined for a sample of 33 skulls and 25 patients. The results show that there is a considerable range in the magnitude of error with different horizontal and vertical values. Interexaminer landmark identification error was significantly larger than intraexaminer error for many landmarks. The identification error was different for the skull sample compared to the patient sample for a number of landmarks. The relevance of knowing the identification error for each landmark being considered in a particular application was discussed.

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.

The Effect of Vertical and Horizontal Head Positioning in Panoramic Radiography on Mesiodistal Tooth Angulations

The purposes of this study were to examine the effect of potentially common patient positioning errors in panoramic radiography on imaged mesiodistal tooth angulations and to compare these results with the imaged mesiodistal tooth angulations present at an idealized head position. A human skull served as the matrix into which a constructed typodont testing device was fixed according to anteroposterior and vertical cephalometric normals. The skull was then repeatedly imaged and repositioned five times at each of the following five head positions: ideal head position, 5 degrees right, 5 degrees left, 5 degrees up, and 5 degrees down. The images were scanned and digitized with custom software to determine the image mesiodistal tooth angulations. Results revealed that the majority of image angles from the five head positions were statistically significantly different than image angles from the idealized head position. Maxillary teeth were more sensitive to 5 degrees up/down head rotation, with 5 degrees up causing mesial projection and 5 degrees down causing distal projection of maxillary roots. Mandibular anterior teeth were more sensitive to 5 degrees right/left head rotation, with the projected mesiodistal angular difference between 5 degrees right and 5 degrees left rotation ranging from 4.0 degrees to 22.3 degrees. Maxillary teeth were relatively unaffected by 5 degrees right/left head rotation, and mandibular teeth were relatively unaffected by 5 degrees up/down head rotation. It was concluded that the clinical assessment of mesiodistal tooth angulation with panoramic radiography should be approached with extreme caution with an understanding of the inherent image distortions that can be further complicated by the potential for aberrant head positioning.

Effect of head orientation on posterior anterior cephalometric landmark identification

This study examined the effect of head rotation about the vertical and transverse axes on posterior anterior cephalometric landmarks. Radiographs were taken on 25 skulls, first in a normal position, then in four positions each rotated 5 degrees from normal. The identification errors of 52 bilateral and midline landmarks were determined in the horizontal and vertical dimensions. The landmark identification errors for each of the five orientations were compared and those landmarks affected by 5 degrees rotation were identified. Landmarks with significantly larger identification error in a rotated position were: nasal cavity, mandible/occiput, foramen rotundum and orbitale. Best fit vertical and horizontal reference lines were determined, and the effect of head rotation on the choice of best fit reference lines was assessed. Rotation about the transverse axis did not affect the relationship of landmarks to the best vertical or horizontal lines. Rotation about the vertical axis did not affect the relationship of landmarks to the best horizontal line but did affect their relationship to the best vertical line.

Correlations between condylar characteristics and facial morphology in Class II preadolescent patients

The aim of this retrospective study was to determine correlations between condylar characteristics measured from preorthodontic tomograms of preadolescents and their facial morphologic characteristics. The sample consisted of 136 patients displaying a Class II malocclusion, a vertical or horizontal skeletal growth tendency, and ranging in age between 10 years 0 months and 12 years 6 months for males and 9 years 0 months and 11 years 6 months for females. Two groups were established: the vertical group had 68 patients, 36 males and 32 females, (average pretreatment age, 11 years 0 months); the horizontal group also had 68 patients, 29 males and 39 females, their average pretreatment age was 10 years 9 months. The central cut of axially corrected lateral tomograms of the left and right temporomandibular joints for each group was randomized, blinded, and traced for condyle/fossa measurements including: anterior, superior and posterior joint space; condylar head and posterior condylar ramus inclination; condylar neck width; and condylar shape and condylar surface area. A logistic discriminant analysis with significance values set at p < 0.05 was used to determine the most reliable condylar characteristics to predict facial morphology. A cluster analysis was completed on the significant variables to form three clusters. Numeric ranges separating these clusters were then calculated. Chi-square tests measures of association were computed for significant variables and tested for associations between facial morphologic characteristics. Condylar head inclination and superior joint space proved to be significantly correlated to facial morphology (p values ranged from 0.010 to 0.018). Patients with vertical facial morphologic characteristics displayed decreased superior joint spaces and posteriorly angled condyles. Increased superior joint spaces and anteriorly angled condyles were significantly correlated to patients with a horizontal facial morphology. No significant correlations between the other condylar characteristics and facial morphology were determined.

Osseous Morphology and Spatial Relationships of the Temporomandibular Joint: Comparisons of Normal and Anterior Disc Positions

The objective of this study was to determine differences in spatial relationships and osseous morphology between temporomandibular joints with normal and anterior disc positions. Magnetic resonance imaging was employed to determine disc position in 335 temporomandibular joints in 175 subjects (106 female and 69 male) between the ages of 7.27 years and 20.0 years (mean age: 13.08 years). Twelve tomographic variables were measured from preorthodontic tomograms of the same individuals. Tomographic data were cross-referenced with MRI data for those with normal and full anterior disc displacement. Independent sample t-tests revealed significant differences for all measures of joint space, condylar position, and morphology of the articular eminence (P < .05) between joints with normal disc position and with full anterior disc displacement. This study indicated that measures of joint space and eminence morphology might provide diagnostic information for the assessment of joint status in the adolescent population.

Stability of maxilla downgrafting after rigid or wire fixation

PURPOSE This article compares the long-term outcomes of rigid internal fixation with wire fixation. PATIENTS AND METHODS In this retrospective study, nine cases of vertical midface augmentation in which rigid fixation was used were compared with 11 cases with wire fixation. One surgeon completed all cases for the rigid fixation group, and another surgeon completed the cases in the wire fixation group. RESULTS Follow-up was 16 +/- 11 months for the rigid fixation group and 20 +/- 12 months for the wire fixation group. Inferior movement at the anterior portion of the maxilla was 7.0 +/- 2.9 mm with rigid fixation and 4.5 +/- 3.6 mm with wire fixation (P < .05). Postsurgical superior movement (relapse) was 0.4 +/- 0.4 mm with rigid fixation and 2.4 +/- 2.4 mm with wire fixation (P < .01). Inferior movement at the posterior maxilla was 3.1 +/- 0.2 mm with rigid fixation and 2.8 +/- 2.3 mm with wire fixation. Postsurgical superior movement (relapse) was 0.8 +/- 0.4 mm with rigid fixation and 0.5 +/- 2.3 mm with wire fixation, which was not significantly different. CONCLUSION This comparison showed downgrafting of the maxilla using autogenous bone harvested from the iliac crest and rigid internal fixation to be a predictable and stable procedure.

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.

Shear/peel bond strength of repositioned ceramic brackets.

Improper orthodontic bracket position may necessitate bracket removal and rebonding to establish correct bracket position. This procedure is necessary to use efficient orthodontic mechanics. The purpose of the study was to investigate (1) the amount of bonding resin remaining on single crystal bracket bases following electrothermal debonding, and (2) the bond strength of rebonded single crystal ceramic brackets under different treatment conditions. The bases of debonded, single crystal ceramic brackets (n = 100) were inspected for resin, classified with an adaptation of the adhesive remnant index (ARI), and evenly assigned to four experimental groups (n = 25). Groups were (1) silane coupling agent, (2) heat plus silane coupling agent, (3) hydrofluoric acid plus silane coupling agent, and (4) heat plus hydrofluoric acid plus silane coupling agent. An additional group of brackets not previously bonded was used as the control (n = 25). The brackets were bonded to 125 fresh bovine teeth. A force was applied 1 mm from the bracket-resin interface by a testing machine. The force measured in this experiment was shear/peel and the ratio of shear to peel was 0.53. The AI index showed 79% of the brackets had no resin on their bases. The shear/peel bond strnegth was significantly greater for the control group than all other groups (P < 0.01). Treatment of electrothermally debonded ceramic brackets with silane or heat plus silane resulted in bond strength greater than 9 MPa. The use of hydrofluoric acid significantly reduced the bond strength below 2 MPa.

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.