Anteroposterior skeletal and dental changes after early Class II treatment with bionators and headgear

The transfer of occlusal forces through the maxillary molars: a finite element study

The morphology of the skeleton is known to reflect functional demand. A change in the intramaxillary position of molars can be expected to influence the transfer of occlusal forces to the facial skeleton. A finite element analysis allows us to simulate the displacement of a molar in relation to the well-defined morphology of the maxilla. Three 3-dimensional unilateral models of a maxilla from a skull with skeletal Class I and neutral molar relationships were produced based on CT-scan data. The maxillary first molar was localized so that the contour of the mesial root continued into the infrazygomatic crest. When the molar was loaded with occlusal forces, the stresses were transferred predominantly through the infrazygomatic crest. This changed when mesial and distal displacements of the molars were simulated. In the model with mesial molar displacement, a larger part of the bite forces were transferred through the anterior part of the maxilla, resulting in the buccal bone being loaded in compression. In the model with distal molar displacement, the posterior part of the maxilla was deformed through compression; this resulted in higher compensatory tensile stresses in the anterior part of the maxilla and at the zygomatic arch. This distribution of the occlusal forces might contribute to the posterior rotation often described as the orthopedic effect of extraoral traction.

Activator versus cervical headgear: superimpositional cephalometric comparison

Clinical trials comparing activator and headgear treatment have shown comparable effectiveness in the total result achieved, but the mechanism of correction is still uncertain. Most studies have used conventional cephalometric methods to evaluate treatment effects, and this might be a factor for the inconclusive results. The aim of this retrospective investigation was to compare the effects of activator and cervical headgear treatment with a superimpositional cephalometric method that could discern between vertical and horizontal effects as well as skeletal, dental, and rotational treatment results. The sample consisted of 2 groups of Class II Division 1 patients, treated without extraction by the same clinician (22 patients were treated with a modified activator-type functional appliance, and 30 patients were treated with a combination of cervical headgear and fixed edgewise appliances). Lateral cephalometric radiographs taken at the beginning of treatment and after Class II molar correction were evaluated conventionally and with a superimpositional method. Regarding the conventional cephalometric measurements, the only difference in the anteroposterior dimension between the 2 treatment modalities was the significantly reduced SNA angle in the headgear group. Both appliances appeared to produce minimal changes in FMA and GoGn-SN angles, and there were no statistically significant differences between the treatment groups. Regional superimpositions showed differences in the movement of molars: the maxillary molar was found to move more posteriorly and inferiorly in the headgear group. Conversely, the mandibular molar was found to move toward the occlusal plane more in the activator group. Assessment of mandibular skeletal changes showed that the mandible moved anteriorly by approximately 1 mm more in the activator than in the headgear group. The overall effect of the 2 appliances was found to be clinically comparable. However, the individual components of change showed differences characteristic of each appliance.

Clinical trials in orthodontics I: demographic details of clinical trials published in three orthodontic journals between 1989 and 1998

AIM

To test the hypothesis that there is insufficient evidence available, from clinical trials, to allow evidence-based decisions to be made on the effectiveness of orthodontic treatment.

OBJECTIVES

To identify reports of orthodontic clinical trials and assess their demographic characteristics.

DESIGN

A retrospective, observational study.

SETTING

The American Journal of Orthodontics and Dentofacial Orthopedics, British Journal of Orthodontics, and European Journal Orthodontics.

DATA SOURCE

Clinical trials published between 1989 and 1998.

METHOD

A hand-search was performed to identify all clinical trials. The journal and year of publication, research method, interventions, and sample size of the trials reported were recorded.

RESULTS

One-hundred-and-fifty-five trial reports were identified of which 56 (36.1%) were published from 1989 to 1993 and 99 (69%) from 1994 to 1998. Ninety-nine (69%) reports were published in the AJO-DO, 18 (11.6%) in the BJO and 38 (24.5%) in the EJO. Eighty-five (54.8%) were reports of randomized controlled trials and 70 (45.2%) of controlled clinical trials. The interventions most frequently assessed were bonding materials (21.9%), growth modification treatments (21.3%), and oral hygiene procedures (9.0%). The median sample size was 32 (IQR 19.5, 50).

CONCLUSION

There is sufficient evidence available from clinical trials to warrant doing systematic reviews of orthodontic clinical trials to aid decision-making.

Fränkel appliance therapy and the temporomandibular disc: a prospective magnetic resonance imaging study

This prospective clinical study assessed the effect of the Fränkel Functional Regulator-II (FR-II) treatment on the position and shape of the articular disc of the temporomandibular joint. The sample included magnetic resonance images of 112 temporomandibular joints taken initially (T1) and after 18 +/- 1 months (T2). The subjects were 56 white Brazilian children who were beginning their pubertal growth spurt. They had Class II Division 1 malocclusions and were selected from 800 children in neighborhood schools. They were randomly dichotomized into either the treated group (treated with the FR-II for 18 months) or the control group (not treated during the observation period). Our findings showed a low prevalence (3.57%) of disc displacement in the 112 temporomandibular joints. Mandibular propulsion with the FR-II had no unfavorable effect on the temporomandibular joints of the treated group; 100% of the patients kept an upper and interposed disc position (closed and open mouth, respectively) at T1 and T2. The control group had 7.1% partial anterior medial disc displacement, both at T1 and T2. Regarding disc morphology, the control group showed biconcave-shaped discs in 82.1% of the joints, statistically similar to the treated group (89.3%) at the beginning of the observation period. At T2, the articular disc morphology of the control group was unchanged, but that of the treated group was significantly more normal (P =.016), progressing from nonbiconcave at T1 (10.7%) to biconcave at T2 (100%). Our results showed that disc displacement is not a complication of functional appliance therapy; in fact, such treatment might help some children with incipient temporomandibular disorders.

Comparative study of the Fränkel (FR-2) and bionator appliances in the treatment of Class II malocclusion

The purpose of this investigation was to compare the dentoalveolar and skeletal cephalometric changes produced by the Fränkel (FR-2) and bionator appliances in persons with Class II malocclusion. Lateral cephalograms were available for 66 patients of both sexes, who were divided into 3 groups of 22. The control group included untreated Class II children, with an initial mean age of 8 years 7 months; they were followed without treatment for 13 months. The FR-2 appliance group had an initial mean age of 9 years; those children were treated for a mean period of 17 months. The bionator group initially had a mean age of 10 years 8 months; on average, they were treated for 16 months. The results demonstrated no significant changes in maxillary growth during the evaluation period. Both appliances showed statistically significant increases in mandibular growth and mandibular protrusion, with greater increases in patients treated in the bionator group. Both experimental groups showed an improvement in the maxillomandibular relationship. There were no significant changes in growth direction, while the bionator group had a greater increase in posterior facial height. Both appliances produced similar labial tipping and protrusion of the lower incisors, lingual inclination, retrusion of the upper incisors, and a significant increase in mandibular posterior dentoalveolar height. The major treatment effects of bionator and FR-2 appliances were dentoalveolar, with a smaller, but significant, skeletal effect.

A 3-dimensional analysis of molar movement during headgear treatment

Superimposition of serial cephalograms provides a limited description of tooth movement that could be complemented by data obtained from serial dental casts. The aim of this study was to develop a mathematical method for superimposing 3-dimensional data obtained from selected landmarks on longitudinally collected dental casts to describe maxillary first molar movement during headgear treatment. The material consisted of dental casts taken bimonthly from 36 children whose Class II Division 1 malocclusion was treated with straight-pull headgear during a 24-month period. Control data were collected from initial and final models of 38 subjects with a similar malocclusion who were not treated during a 24-month observation period. Spatial data from each subject's initial model were oriented similarly in an anatomically derived coordinate system, and a best-fit superimposition of palatal rugae landmarks from subsequent models allowed the measurement of molar movement. On average, headgear treatment resulted in distal movement of the molars, and the fitted net difference between treated and control subjects was 3.00 mm (SE, 0.37 mm; P < .001). Also, the headgear caused significantly more molar extrusion (0.56 mm; SE, 0.20 mm; P < .006) and buccal expansion (0.58 mm; SE, 0.17 mm; P < .001) on average than in the control group. Poor reliability of the method for measuring molar rotations indicated that they could not be determined accurately. Longitudinal description of molar movement for each subject revealed great individual variability in the amount and pattern of tooth movement. Several reasons could account for the wide range of individual variation and warrant exploration.

Effectiveness of early treatment of Class II malocclusion

The purpose of this study was to examine and report the effectiveness of early treatment with the headgear/biteplate and the bionator in patients with Class II malocclusion regardless of the mechanism of correction and to compare early-treatment results with changes over a similar time period in an observation group. The role of factors such as compliance was examined to determine their contribution to effective treatment. The experimental design was a prospective, longitudinal, randomized controlled trial. At the end of the early-treatment period, all 3 groups differed significantly (overall, P = .001) in percentage of treatment goal achieved, with median values of 83% for the bionator group, 100% for the headgear group, and 14% for the observation group. In both treated and observation subjects, the percentages of goal achieved varied by initial molar class severity (treated, P =.0205; observation, P = .0040) and race (treated, P = .0314; observation, P = .0416). Significant correlations in the treated subjects were identified between percentage of goal achieved and bone age (13 bones) (r = 0.16; P = .037), bone age (20 bones) (r = 0.16; P = .043), compliance (r = 0.26; P = .0005), and initial overjet (r = -0.26; P = .0095). Significant correlations were not detected in the observation group. Sex, treatment group, age, mandibular plane angle, pretreatment, and retention did not significantly affect percentage of goal achieved among the treated and the observation subjects. Correlation between normalized compliance scores and percentage of goal achieved was high for both bionator (r = 0.50) and headgear subjects (r = 0.49) at the end of treatment. Multivariate analysis suggested that headgear may be superior to bionator/biteplane in achieving a Class II correction during early treatment.

Changes in mandibular position and upper airway dimension by wearing cervical headgear during sleep

We previously reported that the wearing of cervical headgear induced forward displacement of the mandible in awake subjects. However, it was unclear whether such mandibular displacement also occurred during sleep. The purpose of this study was to examine changes in mandibular position and oropharyngeal structures that were induced by the wearing of cervical headgear during sleep. Ten healthy adults (7 male and 3 female) who gave their informed consent were included in this study. A pair of lateral cephalograms was taken with the patient in the supine position with and without cervical headgear at end-expiration during stage 1 to 2 non-rapid-eye-movement sleep. The Wilcoxon signed-rank test was used for a statistical analysis. The amount of jaw opening was significantly decreased by the wearing of the cervical headgear (P <.05), although no significant anteroposterior mandibular displacement was induced. The sagittal dimension of the upper airway was significantly reduced (P <.05); however, no significant changes were observed in the vertical length of the upper airway. Although the hyoid bone and the third cervical vertebra moved significantly forward by the wearing of the cervical headgear (P <.05), the relationship among the mandibular symphysis, the hyoid bone, and the third cervical vertebra did not change. These results suggest that cervical headgear significantly reduced the sagittal dimension of the upper airway during sleep, although there was no significant anteroposterior displacement of the mandible.

Comparison of 2 modifications of the twin-block appliance in matched Class II samples

The purpose of this study was to compare the skeletal and dental changes contributing to Class II correction with 2 modifications of the Twin-block appliance: Twin-block appliances that use a labial bow (TB1) and Twin-block appliances that incorporate high-pull headgear and torquing spurs on the maxillary central incisors (TB2). After pretreatment equivalence was established, a total of 36 consecutively treated patients with the TB1 modification were compared with 27 patients treated with the TB2 modification. Both samples were treated in the same hospital department and the same technician made all the appliances. The cephalostat, digitizing package, and statistical methods were common to both groups. The results demonstrated that the addition of headgear to the appliance resulted in effective vertical and sagittal control of the maxillary complex and thus maximized the Class II skeletal correction in the TB2 sample. Use of the torquing springs resulted in less retroclination of the maxillary incisors in the TB2 sample when compared with the TB1 sample; however, this difference did not reach the level of statistical significance.

Osteogenesis in the glenoid fossa in response to mandibular advancement

The purpose of this study was to identify the temporal sequence of cellular changes in the glenoid fossa and to quantify the amount of bone formation in response to mandibular advancement. One hundred 35-day-old female Sprague-Dawley rats were randomly divided into 5 experimental groups (15 rats each) and 5 control groups (5 rats each). In the experimental groups, functional appliances were used to create continuous forward mandibular advancement. The rats were killed after 3, 7, 14, 21, and 30 days. Sections were cut through the glenoid fossa in the parasagittal plane and stained with periodic acid and Schiff's reagent for evaluation of bone formation and with hematoxylin and eosin for observation of cellular response. The results showed that, in the control rats, bone formation was initially higher in the posterior and middle regions than in the anterior region then decreased over time in all regions. In the experimental group, bone formation significantly increased from day 7 to day 30 compared with control rats. Day 21 marked the highest levels of bone formation in the middle (+184%) and posterior regions (+300%). Mandibular protrusion resulted in the osteoprogenitor cells being oriented in the direction of the pull of the posterior fibers of the disc and also resulted in a considerable increase in bone formation in the glenoid fossa.

Current concepts on functional appliances and mandibular growth stimulation

The mode of action of functional appliances, particularly in relation to stimulating mandibular growth, is a controversial subject. Many of the reports concerning growth effects of functional appliances have been characterized by poor methodology. In assessing functional appliances, results from prospective randomized clinical trials should be given prominence. On the basis of available evidence, it cannot be concluded that functional appliances are effective in stimulating and increasing mandibular growth in the long term. Although favourable growth changes have been reported following phase 1 therapy, they are generally not substantial and long term stability appears to be poor.

Effect of wearing cervical headgear on tongue pressure

The purpose of this study was to examine whether wearing cervical headgear affected tongue pressure on the lingual surface of mandibular incisors, with particular attention to suprahyoid muscle activity. Tongue pressure was recorded using a miniature pressure sensor without cervical headgear and with two cervical headgears with traction forces of 500 and 1200 g, respectively. Electromyographic activity of suprahyoid muscles and respiratory-related movement were recorded simultaneously. Wearing cervical headgear significantly affected tongue pressure and suprahyoid muscle activity in the short-term. A significant increase in tongue pressure was observed in association with an increase in traction force from 500 to 1200 g, whereas no significant difference in suprahyoid muscles activity was seen between these force levels. These results suggest that wearing cervical headgear increases tongue pressure on the lingual surface of mandibular incisors, and this increase in tongue pressure may result from changes in the electromyographic activity of suprahyoid muscles to maintain adequate pharyngeal patency.

Early orthodontic treatment: what are the imperatives?

BACKGROUND

Then authors provide a critical review of the issues involved in determining the appropriate timing of orthodontic treatment. Both single- and two-phase treatments are discussed and guidelines are offered to assist in formulating treatment plans.

OVERVIEW

In providing orthodontic care for pediatric patients, clinicians often question whether to begin treatment early--during the primary or early-transitional dentition--or wait until all or most of the permanent teeth are present. The authors review the most current literature (from 1991 to 1999), including several recently completed and ongoing randomized clinical trials, to critically evaluate the effectiveness of each approach.

PRACTICAL IMPLICATIONS

The controversy surrounding early vs. late orthodontic treatment is often confusing to the dental community. This article reviews both sides of the issue for orthodontic treatment of Class II and III malocclusions, as well as for the management of Class I crowding and problems in the transverse dimension. Early orthodontic treatment is effective and desirable in specific situations. However, the evidence is equally compelling that such an approach is not indicated in many cases for which later, single-phase treatment is more effective. Therefore, clinicians must decide, on a case-by-case basis, when to provide orthodontic treatment. For many patients, delaying treatment until later in their dental and skeletal development may be advisable.

Surgical versus orthodontic correction for Class II patients: age and severity in treatment planning and treatment outcome

Treatment options for Class II malocclusion include orthognathic surgery. Treatment choices are particularly difficult for young patients because of the uncertainty regarding future growth. Surgical treatment has generally been considered necessary for older patients with more severe Class II problems. The treatment records of more than 500 patients with Class II malocclusion were reviewed. Patients were grouped according to their initial treatment plan (surgery or orthodontics) and treatment outcome (overjet [OJ] reduced to < 4 mm or not). Discriminant function analyses using data from the patient's pretreatment cephalogram were used to determine whether age, in combination with malocclusion severity, could predict the choice of treatment, and whether a simple set of pretreatment variables could predict the success or failure of OJ reduction. The derived equations were tested in a similar group of growing Class II children. Although the data showed clinicians use patient's age in determining treatment choice, age did not seem to be associated with treatment outcome. The majority of the variability that determined the success or failure of OJ reduction was not explained by patient's age or malocclusion severity. These findings suggest other factors, including psychosocial variables, need to be explored if we are to gain a better understanding of why treatments succeed or fail.

Orthodontists' perceptions of the impact of phase 1 treatment for Class II malocclusion on phase 2 needs

The most appropriate timing for the treatment of Class II malocclusions is controversial. Some clinicians advocate starting a first phase in the mixed dentition, followed by a phase 2 in the permanent dentition. Others see no clear advantage to that approach and recommend that the entire treatment be done in the late mixed or early permanent dentition. This study examines how orthodontists, blinded to treatment approach, perceive the impact of phase 1 treatment on phase 2 needs. The sample consisted of 242 Class II subjects, aged 10 to 15, who had completed phase 1 or observation in a randomized clinical trial (RCT). For each subject, video orthodontic records, a questionnaire, a fact sheet, and a cephalometric tracing were sent to five randomly selected reviewing orthodontists blinded to subject group and study purpose. Reviewing orthodontists were asked to assess treatment need, general approach, need for extractions, priority, difficulty, and determinants. Orthodontists agreed highly on treatment need (95%) and moderately on treatment approach (84%) and extraction need (80%). They did not perceive differences in need, approach, or extractions between treated and control groups. Treated subjects were judged as less difficult (p = 0.0001) and to have a lower treatment priority (p = 0.0001) than controls. In ranking problems that affect treatment decisions, the orthodontists ranked dental Class II (p = 0.005) and skeletal relationships (p = 0.004) more highly in control than in treated patients. These data indicate that orthodontists do not perceive phase 1 treatment for Class II as preventing the need for a second phase or as offering any particular advantage with respect to preventing the need for extractions or other skeletal treatments in that second phase. They do view early Class II treatment as an effective means of reducing the difficulty of and priority for phase 2.

Some comments on clinical studies in orthodontics and their applications to orthodontic treatment

This article indicates the origins and background of the current series of National Institute of Dental and Craniofacial Research-funded, university-based clinical studies of orthodontic treatment. It suggests that future studies should be less focused on refining our estimates of mean changes during treatment and concentrate research on the systematic analysis of individual differences among patients' responses to treatment, and study how skilled clinicians make in-course corrections in response to unexpected changes in treatment conditions. Finally, some suggestions are made concerning optimization of decision making in the presence of uncertainty.

Developing outcome measures in orthodontics that reflect patient and provider values

During the past decade, emphasis in orthodontics has been directed toward the development of outcome measures from both the patient and clinician perspectives. New methodological standards of rigor have been introduced into research design to eliminate bias and test well-defined questions. Sample size calculations and established exclusion and inclusion criteria define sample populations and the ability to statistically accept or reject hypothesis-driven clinical studies. Although advances in our understanding of evidence-based medicine and dentistry from the provider perspective have been productive, the emerging value placed on patient perspective has not been as forthcoming. The emphasis placed on patient-oriented clinical research has resulted in new constructs of surveys and questionnaires in which the items are derived and tested from the patient's point of view. Because orthodontics is a condition without the natural history of a disease process for which no intervention has predictable consequences, new strategies have been developed to estimate need and demand for orthodontic treatment. Studies to measure seekers and nonseekers of orthodontic treatment are reported, as well as sex and cross-cultural issues in the use of established process and outcome measures. The design of clinical studies is discussed in the context of future directions for clinical research, and the usefulness of the information generated will directly relate to providing patients with the necessary information to make decisions and hence knowledgeably give informed consent for treatment interventions.

Early treatment outcome assessed by the Peer Assessment Rating index

In this study, the Peer Assessment Rating (PAR) index was used to objectively evaluate early treatment outcomes. Pretreatment and posttreatment casts of 103 consecutively treated patients were analyzed. The mean chronological, skeletal, and dental ages were 9. 82, 9.76, and 9.32 years, respectively. Calibrated examiners scored all models using the PAR ruler. PAR scores were weighed by means of a validation exercise. Cronbach alpha reliability analysis was used to establish the consistency of the subjective rating among 10 orthodontists of the severity of malocclusion. Pearson's correlation coefficient was used to assess the association among the orthodontists and the total PAR scores. Multiple regression analysis was used to determined the optimum weight of the PAR scores. Pretreatment and posttreatment differences were evaluated with t tests. The association between PAR scores and classification of malocclusions and treatment categories was assessed by means of multivariate analysis of variance (MANOVA). A reduction in the PAR index was observed for the mean raw and weighted scores, from 15.82 to 8.82 and from 5.28 to 3.73, respectively (P <.001). Twenty percent of the sample greatly improved the PAR index, by a 70% reduction.3 Forty-eight percent improved scores by at least a 30% reduction.4 The remaining 32% did not reduce scores by at least 30%. Subjects with both Class I and Class II malocclusions reduced their scores similarly. There was no statistically significant association between reduction of PAR scores and treatment modalities.

Orthodontic treatment timing: a survey of orthodontists

There has been much debate with respect to the ideal time to initiate orthodontic treatment. Recent clinical trials have tested the effects of early orthodontic treatment. The purpose of this study was to understand orthodontists' perspectives on the best time to initiate treatment, factors that preclude early treatment, and experiences with compliance or adherence problems among their younger patients. Questionnaires were distributed to 335 practicing orthodontists throughout the United States. Respondents were first asked to indicate the best stage to initiate orthodontic treatment for 41 different types of occlusal deviations. They were then asked what conditions might preclude early orthodontic treatment. After one reminder, 137 questionnaires (41%) were returned. The sample consisted of practitioners with 3 to 52 years of experience and represented 46 different orthodontic training programs; 19% were female. The majority (92%) were in private practice. Among the 41 conditions listed, orthodontists would most likely treat 21 in the early mixed dentition, especially anterior crossbites (> 76%); 13 in the late mixed dentition, especially deepbite (> 60%) and mandibular inadequacy (> 59%); and 4 in either stage. Only two conditions would be treated in later stages (maxillary midline diastema, 43%; and congenitally missing teeth,39%). One third would postpone treating mandibular prognathism until adulthood. Patient variables that precluded treatment were behavior (98%) and compliance (96%) problems. Finances (76%) and family disruptions (57%) were less important deterrents to treatment. Orthodontists' experience with Phase I treatment influenced their decisions (p < 0.01). Orthodontists who have been in practice longer were more likely to treat temporomandibular joint sounds (p < 0.003) and deviations in opening (p < 0.002) than less experienced orthodontists; the latter were more likely to refer such patients to temporomandibular disorder specialists. These findings suggest that early orthodontic intervention is the norm, but practice characteristics affect treatment timing.