J. F. Camilla Tulloch

Benefit of early Class II treatment: Progress report of a two-phase randomized clinical trial

Preadolescent children with overjet greater than 7 mm were randomly assigned to observation only, headgear (combination), or functional appliance (modified bionator) and were monitored for 15 months. Of the 166 patients who completed this first phase of the trial, 147 continued to a second phase of treatment. The data from the first 107 patients to complete phase 2 are available and form the basis of this progress report. During phase 1, on average there was no change in the jaw relationship of untreated children, but 5% showed considerable improvement and 15% demonstrated worsening. Both early-treatment groups had a significant average reduction in ANB angle, more by change in maxillary dimensions in the headgear group and mandibular growth in the functional appliance group. There were wide variations in response, however, with only 75% of the treated children showing favorable skeletal response. Failure to respond favorably could not be explained by lack of cooperation alone. The preliminary results from phase 2 show that, on average, time in fixed appliances was shorter for children who underwent early treatment, but the total treatment time was considerably longer if the early phase of treatment was included. Only small differences were noted in anteroposterior jaw position between the groups at the completion of treatment, and the changes in dental occlusion, judged on the basis of Peer Assessment Rating scores, were similar between groups. Neither the severity of the initial problem nor the duration of treatment was correlated with the occlusal result. The number of patients who required extraction of permanent teeth was greater in the early functional appliance group than in the headgear or control group. The option of orthognathic surgery was presented more often in the cases of children who did not undergo early treatment, but surgery was accepted or was still being considered almost as frequently in the previous headgear group as in the controls, less often in the patients previously treated with functional appliances.

The effect of early intervention on skeletal pattern in Class II malocclusion: A randomized clinical trial

Early treatment for Class II malocclusion is frequently undertaken with the objective of correcting skeletal disproportion by altering the growth pattern. Because the majority of previous studies of growth modification for Class II malocclusion have been based on retrospective record reviews, the efficacy of such an approach has not been well established. In this controlled clinical trial, patients in the mixed dentition with overjet > or = 7 mm were randomly assigned to either early treatment with headgear, or modified bionator, or to observation. All patients were observed for 15 months with no other appliances used during this phase of the trial. The three groups, who were equivalent initially, experienced statistically significant differences (p < 0.01) in skeletal change. There was considerable variation in the pattern of change within all three groups, with about 80% of the treated children responding favorably. Although patients in both early treatment groups had approximately the same reduction in Class II severity, as reflected by change in the ANB angle, the mechanism of this change was different. The headgear group showed restricted forward movement of the maxilla, and the functional appliance group showed a greater increase in mandibular length. The permanence of these skeletal changes and their impact on the subsequent treatment remains to be evaluated.

Influences on the outcome of early treatment for Class II malocclusion

In the first phase of a randomized clinical trial of early versus late Class II treatment, statistically significant differences were observed between the treatment and observation groups. However, there were wide variations in response. The change in jaw relationship (categorized as the annualized reduction in ANB angle) was favorable or highly favorable in 76% of the headgear, 83% of the functional appliance, and 31% of control (observation only) groups. The patients initial skeletal severity, age/maturity at the outset of treatment, growth pattern, and cooperation with treatment were examined as possible influences on early growth modification treatment. Correlations between the annualized change in the ANB angle and any of the possible influences were close to zero and not statistically significant. We conclude that there is little to be gained from precisely timing early treatment to specific age/maturity markers and that a favorable reduction in Class II skeletal problems can occur for patients in a broad range of skeletal severity and growth patterns. Cooperation, measured as the number of hours of reported wear, or the clinical assessment of compliance, explained little of the variation in treatment response. The wide variation in growth seen in the untreated patients highlights the importance of well-controlled studies if clinicians are to improve their ability to select children with the greatest chances of a favorable treatment response.

External apical root resorption in Class II malocclusion: a retrospective review of 1- versus 2-phase treatment.

External apical root resorption (EARR) is an imperfectly understood problem of orthodontic treatment. The records of 138 children with Class II malocclusion (overjet > 7 mm) participating in a randomized clinical trial of early orthodontic treatment were reviewed. The patients were treated in either 1 phase with fixed appliances only (n = 49) or 2 phases with headgear (n = 49) or bionator (n = 40) followed by fixed appliances. The 3 groups were similar in age, sex, and malocclusion severity at enrollment. The records examined included anamnestic data, clinical examination records, panoramic radiographs before and after fixed appliance therapy, and posttreatment periapical radiographs. All radiographs were reviewed and scored independently by 2 examiners for maxillary incisor root development, morphology, and EARR. Of the 532 incisors scored, 11% of central and 14% of lateral incisors demonstrated moderate to severe (>2 mm) EARR. The proportion of incisors with moderate to severe EARR was slightly greater in the 1-phase treatment group. There was no difference in the incidence of EARR between teeth that had had trauma and those that had not, and there was only a slight increase in frequency of root resorption in teeth with unusual root morphology. Significant associations exist among EARR, the magnitude of overjet reduction, and the time spent wearing fixed appliances. However, not all incisors in a child respond in the same way, so other variables must play a role in determining the root response to orthodontic forces.

Superimposition of 3-dimensional cone-beam computed tomography models of growing patients

INTRODUCTION The objective of this study was to evaluate a new method for superimposition of 3-dimensional (3D) models of growing subjects. METHODS Cone-beam computed tomography scans were taken before and after Class III malocclusion orthopedic treatment with miniplates. Three observers independently constructed 18 3D virtual surface models from cone-beam computed tomography scans of 3 patients. Separate 3D models were constructed for soft-tissue, cranial base, maxillary, and mandibular surfaces. The anterior cranial fossa was used to register the 3D models of before and after treatment (about 1 year of follow-up). RESULTS Three-dimensional overlays of superimposed models and 3D color-coded displacement maps allowed visual and quantitative assessment of growth and treatment changes. The range of interobserver errors for each anatomic region was 0.4 mm for the zygomatic process of maxilla, chin, condyles, posterior border of the rami, and lower border of the mandible, and 0.5 mm for the anterior maxilla soft-tissue upper lip. CONCLUSIONS Our results suggest that this method is a valid and reproducible assessment of treatment outcomes for growing subjects. This technique can be used to identify maxillary and mandibular positional changes and bone remodeling relative to the anterior cranial fossa.

Three-dimensional analysis of maxillary protraction with intermaxillary elastics to miniplates.

INTRODUCTION Early Class III treatment with reverse-pull headgear generally results in maxillary skeletal protraction but is frequently also accompanied by unfavorable dentoalveolar effects. An alternative treatment with intermaxillary elastics from a temporary anchorage device might permit equivalent favorable skeletal changes without the unwanted dentoalveolar effects. METHODS Six consecutive patients (3 boys, 3 girls; ages, 10-13 years 3 months) with Class III occlusion and maxillary deficiency were treated by using intermaxillary elastics to titanium miniplates. Cone-beam computed tomography scans taken before and after treatment were used to create 3-dimensional volumetric models that were superimposed on nongrowing structures in the anterior cranial base to determine anatomic changes during treatment. RESULTS The effect of the intermaxillary elastic forces was throughout the nasomaxillary structures. All 6 patients showed improvements in the skeletal relationship, primarily through maxillary advancement with little effect on the dentoalveolar units or change in mandibular position. CONCLUSIONS The use of intermaxillary forces applied to temporary anchorage devices appears to be a promising treatment method.

Evaluation of the Costs and Relative Effectiveness of Alternative Strategies for the Removal of Mandibular Third Molars

Decision analysis is used to compare the cost and disability of alternative treatment strategies for asymptomatic mandibular third molars. The analysis shows that extracting only those third molars that remain impacted and become pathologically involved is always associated with less expected cost and disability than prophylactic removal of asymptomatic wisdom teeth.

Analysis of moment/force ratios in the mechanics of tooth movement.

Orthodontic tooth movement is analyzed by means of the center of rotation model and the concept of moment/force ratios. Several equivalent force systems are considered at both the bracket and the center of resistance of the tooth. When moment/force ratios are evaluated at the bracket, the laws of physics appear to be suspended: inconsistencies occurring as single forces applied at different points claim equivalent results and pure translational movements purport to be nonzero moment/force ratios. These paradoxes can be reconciled only if the moment/force ratios are analyzed at the center of resistance of the tooth. Here, all of the moments applied to the tooth by the force system are included in the analysis. Only when the force system is evaluated around the center of resistance of the tooth is the concept of moment/force ratios consistently correct.

The application of decision analysis to evaluate the need for extraction of asymptomatic third molars

A theoretical model using a decision tree is used to compare three alternative strategies: extract all third molars prior to complete root formation; extract only those third molars that become impacted; and extract only those impacted third molars that develop some associated pathology. The model used to determine the expected value of these alternative strategies depends on the probability of eruption, the type of impaction, and likelihood of developing preoperative pathology. The decision tree can be used to identify a preferred strategy either for an individual patient or for a policy recommendation under a variety of clinical conditions.

The randomized clinical trial as a powerful means for understanding treatment efficacy.

The comparison of technologies, ie, alternative ways to accomplish the same aim, is inherently difficult. In orthodontics, technology covers a wide spectrum of areas: variations in treatment approach, appliances, wires, diagnostic procedures, and patient management techniques. Clinical trial methodology has been developed to minimize the effect of bias and to provide more objective answers to questions of comparative efficacy and benefits of particular treatments or procedures. The randomized controlled clinical trial (RCT) is now generally considered the strongest research design for the comparison of treatments. This report reviews four issues that should be addressed in planning an RCT: defining the study cohort, selecting the treatment allocation technique, estimating sample size, and performing the trial.