Morphogenetic response to activator treatment

Condylar growth and glenoid fossa displacement during childhood and adolescence

This study evaluated age and gender differences in the growth of the mandibular condyle and displacement of the glenoid fossa. The results pertain to longitudinal samples of untreated French Canadians, including 118 children and 155 adolescents. Childhood and adolescent growth were described for girls aged between 6 and 10 years and 9 and 13 years, respectively, and for boys aged between 8 and 12 years and 11 and 15 years, respectively. Four-year growth changes of the cephalometric landmarks condylion and articulare were evaluated. Mandibular and cranial/cranial base structural superimpositions were used to assess condylar growth and fossa displacement, respectively. The results showed that the condyle grew between 0.8 and 1.3 mm posteriorly and between 9.0 and 10.7 mm superiorly over the 4-year periods; the articulare landmark showed significantly more posterior and less superior growth than the condylion landmark. Relative to the cranial base reference structures, the fossa was displaced between 1.8 and 2.1 mm posteriorly and between 1.0 and 1.8 mm inferiorly. The articulare showed significantly more inferior movement than the condylion. Boys showed significantly greater superior condylar growth during adolescence than during childhood. The glenoid fossa demonstrated greater posterior and inferior displacement during adolescence than during childhood.

An evaluation of two-phase treatment with the Herbst appliance and preadjusted edgewise therapy

The purpose of this study was to evaluate the skeletal and dentoalveolar changes occurring during two-phase orthodontic treatment. A cephalometric study of Class II correction was carried out in 40 subjects (20 females, 20 males) who had been treated with the acrylic-splint Herbst appliance immediately followed by a second phase of preadjusted edgewise therapy. The average age at the start of Herbst therapy was 12.5 +/- 0.8 years for females and 13.6 +/- 1.2 years for males. Descriptive cephalometric data were compared with the normative values derived from the University of Michigan Elementary and Secondary School Growth Study. Control values were generated for each of the 40 Herbst patients based on gender, initial age, and duration of treatment. The results of this study indicate that the Class II correction achieved during Phase I treatment with Herbst appliance was due mainly to an increase in mandibular length, as well as distal movement of the maxillary molars and mesial movement of the mandibular molars and incisors. The accelerated mandibular growth rate observed during Herbst therapy was followed by a diminished growth rate during the edgewise phase that was less than control values. The overall increase in mandibular length was slight (approximately 1 mm), but significantly greater than control data for the whole group and the male subgroup; however, it was not significantly different between the treatment group and control data in the female subgroup. There were no significant treatment effects on lower anterior facial height and the mandibular plane angle at the end of either phase of treatment. The skeletal changes contributed to 55% of the molar correction during the Herbst therapy, whereas at the end of the second phase of treatment, skeletal change accounted for 80%. Significant anteroposterior dentoalveolar rebound was seen during the edgewise phase.

The Goettingen "Pro-Stab" removable plate system. A retrospective cephalometric study of the effects of a new Class II treatment appliance

The new removable double-plate appliance has characteristics which provide for efficient treatment of Class II malocclusions: virtually unimpaired speaking and free breathing seem to support patient compliance. The sagittal activation is easy to change and the plates for the upper and the lower jaw can be worn separately or in combination, with and without the "Pro-Stab" rods even with different wearing hours (modular concept). Evaluation of lateral head films taken at the beginning and at the end of treatment (mean interval 1.45 years) of 40 patients provided information on therapy-induced changes, which were then compared with results of recent publications. The data obtained with the new system indicate similar results as with bite-jumping appliances and headgear-supported activators. Inhibition of the sagittal development of the upper jaw and retrusion of the upper incisor segment have been primarily responsible for the correction of Class II malocclusions. The effect as regards the sagittal position of the lower jaw has been moderate. In comparison with similar appliances, protrusion of the lower incisors was more pronounced when treated with the Goettingen Type I "Pro-Stab" removable plate system.

Orthopedics in orthodontics: Part I, Fiction or reality--a review of the literature

The purpose of this review is to investigate the orthopedic effect of functional appliances such as activators and Herbst appliances, and the orthopedic effect of extraoral traction appliances. A systematic review of mostly English-language orthodontic articles reporting treatment of Class II malocclusions with different orthopedic appliances was carried out. According to this review, only Herbst therapy was able to change mandibular growth to a clinically significant extent. In part II of this study, the long-term effect of these changes will be evaluated.

The inclined biteplane--a useful tool

A technique is described to help maintain overjet and overbite reduction achieved with a functional appliances, while waiting to proceed with definitive treatment or for use after a definitive course of fixed appliance therapy to help maintain the achieved result.

The use of a simple functional appliance as an adjunct to fixed appliance orthodontic treatment. Case reports

Three clinical case studies are presented to demonstrate the use of a simple functional appliance in orthodontic situations not covered by traditionally-accepted dental and skeletal indications. In each case, the appliance was used to reduce the severity of the malocclusion, before a routine fixed-appliance detailing phase.

Timing of hard palatal closure: a critical long-term analysis

The controversy about timing of cleft palate surgical procedures is focused on early palatoplasty for improved speech versus delayed hard palate repair for undisturbed facial growth. Timing and technique of palate repair are the most important influences on speech and facial growth, yet there is no consensus on the age or technique for surgery. The Oxford Cleft Palate Study was initiated to evaluate critically the long-term follow-up of 44 patients with early versus late closure of the hard palate. A multidisciplinary approach was used to determine the incidence of speech deficiencies, palatal fistulas, maxillofacial growth disturbances, and hearing abnormalities and to assess objectively the long-term effects of two different treatment modalities on the cleft palate patient. The 44 patients were selected randomly, interviewed, and examined by the multidisciplinary Oxford Cleft Palate Study team. The average age at follow-up in the early closure group was 17.0 years versus 18.2 years in the late closure group. There was a similar number of unilateral and bilateral clefts in both the early and late closure groups. The hard palate was closed in the early group at an average age of 10.8 months versus 48.6 months in the late closure group. All operative procedures in each group were performed by the same senior plastic surgery consultant. Both consultants have since retired and did not participate in the study. Each patient was evaluated by the same plastic surgeon, speech pathologist, orthodontist, and otologist. All examiners were blinded in that they were unaware of the type or timing of the surgical technique and had no prior knowledge of or access to the patient's medical records. Furthermore, none of the examiners participated in the initial care and surgery of these patients. Statistically significant greater speech deficiencies were noted with delayed hard palate closure, especially in articulation, nasal resonance, intelligibility, and substitution pattern assessment (overall intelligibility, p < 0.01). Likewise, the persistent palatal fistula rate in the late closure group was 35 percent in comparison with 5 percent for the early closure group (p <0.02). No significant differences in hearing or maxillofacial growth impairment were delineated in either group. Our data suggest that delaying hard palate closure results in significant speech impairment without a beneficial maxillofacial growth response.

Orthodontic and orthopedic effects of Activator, Activator-HG combination, and Bass appliances: a comparative study

The orthodontic and orthopedic effects of the Activator, Activator-Headgear Combination (ACHG) and the Bass appliance systems were compared by analyzing the cephalometric records of 64 subjects, who were treated for skeletal Class II malocclusion, with both conventional and Pancherz's methods. Differences between observations on the different occasions (starting and ending values) were tested with Wilcoxon's matched pairs rank test. Kruskal-Wallis nonparametric analysis of variance was carried out in different situations among all three groups. If a level of significance less than 0.05 was observed, Scheffè's method of multiple comparisons was used to determine differences among groups. The results of this study showed that greater improvement in sagittal skeletal relationship (ANB angle) was obtained in both Bass and ACHG groups than in the Activator group. The differences between the groups were most pronounced for dental variables. The Bass appliance was found to be more effective in the control of the unwanted side effects (proclination of lower incisors, retroclination of upper incisors). Unfavorable labial tipping of the lower incisors was also prevented with the ACHG appliance.

Associations between changes in selected facial dimensions and the outcome of orthodontic treatment

The purpose of this study was to determine, in children with Class II, Division I malocclusion who were treated with functional appliances, the strength of the associations between the changes over 18 months in selected facial dimensions and the success of orthodontic treatment as determined by the weighted Peer Assessment Rating (PAR). Forty-two children, between 10 and 13 years of age (mean age 11.6 years), were randomly assigned to either an untreated group (control) or a group treated with either a Fränkel function regulator or Harvold activator (treatment). The outcome of treatment was assessed on study models and the craniofacial changes were measured on lateral cephalometric radiographs. Correlation coefficients were then calculated between the differences in the cephalometric variables over 18 months and the differences in the PAR scores. In the treatment group, the effects of normal growth were held constant by partial correlation. The partial used was the change in both stature and weight. Significant positive partial correlations were found between the increases in total anterior face height, posterior face height, S-Pg, and treatment success. Significant negative partial correlations were found between downward movement of the maxilla and mandibular body and lower anterior face height and treatment success. It is postulated that these associations occurred mainly in response to the bite opening by the appliances. Treatment success was also significantly associated with maxillary restriction, an increase in the SNB angle and a reduction in the ANB angle. Changes in B point due to proclination of the mandibular incisors were considered to be responsible for the two latter significant associations. Although mandibular length increased significantly in the treatment group, as compared with the control group, it was not significantly associated with treatment success.

Maxillary and cranial base changes during treatment with functional appliances

The purpose of this prospective study was to investigate the maxillary and the cranial base changes after treatment with the Harvold activator and the Fränkel function regulator appliances. Forty-two children, who are 10 to 13 years old, with Class II, Division 1 malocclusions were matched in triads according to age and sex and randomly assigned to either the control, Harvold activator, or Fränkel function regulator group. Lateral cephalometric radiographs were taken at the start of the study and 18 months later. Both appliances reduced the overjet by tipping the maxillary incisors palatally and, as a consequence, the length of the maxillary arch was reduced. The appliances had no effect on either the horizontal or vertical position of the maxillary molars. Small, but statistically significant, changes in the cranial base angle in the Fränkel function regulator group were attributed to relatively large changes at basion in several children, influencing the results because of the small size of the sample. The appliances had no effect on the position of the maxilla.

Three-dimensional diagnosis and management of Class II malocclusion in the mixed dentition

Class II malocclusion is a commonly observed problem, occurring in about one third of the United States population. The numerous treatment approaches that have been advocated to treat this malocclusion presumably produce differing treatment effects within the skeletal, dentoalveolar, and soft tissue components of the face. In the first section of this article, the three-dimensional components of Class II malocclusion are described, with transverse maxillary discrepancy, mandibular skeletal retrusion, and increased lower anterior facial height observed as common findings in a mixed dentition sample of Class II subjects. Second, the literature concerning two seemingly diverse treatment methods (extraoral traction and functional jaw orthopedics) is reviewed in detail. Last, cephalometric data are presented from a retrospective clinical study and is used to evaluate the treatment effects produced by cervical traction and the FR-2 appliance of Fränkel in comparison with an untreated sample of mixed dentition Class II patients. The results of this study indicated that although both skeletal and dentoalveolar components of Class II, Division 1 malocclusion were altered in the Class I direction by either a facebow or a Fränkel appliance, these two appliance systems accomplished the correction in dramatically differing ways. Cervical traction affected the skeletal and dentoalveolar components of the maxilla and mandible, whereas the FR-2 appliance had less of an effect on maxillary and dentoalveolar components and a greater effect on mandibular length. Thus, these two treatment modalities produce decidedly different treatment effects in patients with Class II malocclusions.

The decision to extract: Part 1--Interclinician agreement

As part of an ongoing prospective clinical trial of conventional orthodontic treatment, the decision making patterns of a representative group of orthodontic clinicians were examined. Data were available for 148 subjects (100 adolescents and 48 adults) who had presented at the University of California San Francisco Graduate Orthodontic Clinic requesting treatment for correction of a Class I or Class II malocclusion. The records for each subject were evaluated independently by each of five members of the clinical faculty, making available a total of 740 independent patient evaluations. With regard to the primary decision as to whether extraction or nonextraction treatment was to be preferred, agreement among clinicians was higher than had been anticipated. In almost two thirds of the cases, the decisions of all five clinicians were in agreement as to whether extraction or nonextraction was the preferred treatment modality. (This figure included 59 cases of complete agreement for extraction therapy (40%) and 38 cases of complete agreement for nonextraction therapy (26%)). In only 51 cases (34%), did the reviewing clinicians disagree as to whether extraction or nonextraction was the preferred modality of treatment. The clinicians were also asked to indicate their opinions as to whether orthognathic surgery was likely to be a part of the ultimate treatment course for each individual subject. Nine percent of the 740 patient evaluations contained a clinician judgement that surgery would be a probable or definite component of the orthodontic treatment plan. For 29% of the adult subjects (14 cases) and 23% of the adolescent subjects (23 cases), one or more of the five examining clinicians believed that adjunctive surgical intervention would probably or definitely be appropriate. These high values were unexpected, particularly because the sample had been prescreened by a single clinician to exclude subjects who might require orthognathic surgery. Clinician agreement of Angle classification was also evaluated. Disagreements were observed in 14 adult subjects (29%) and 27 adolescent subjects (27%). Little association was observed between clinician agreement on Angle classification and clinician agreement on whether or not to extract.

[The dental and skeletal effects of the jumping-the-bite plate and high-pull headgear combination. A clinical study of treated patients]

While planning treatment of the 30 patients with a dental and skeletal class II anomaly on which this study is based, the primary treatment goals were correction of the dental and skeletal structures and attenuation of vertical growth by means of influencing the maxillary skeletal structures and the resultant mandibular reaction. The desired treatment results were achieved in all patients. Even so, however, the effects on individual patients in respect to skeletal influences were markedly different. It was especially helpful that during therapy simultaneously with exerting influence on the maxillary base plane, the influencing of the occlusal plane occurred in the same direction. Through the additional application of high-pull headgear, maxillary growth was clearly restrained and the inclination of the maxillary base plane inhibited. Even difficult skeletal discrepancies, sagittal as well as vertical, can be treated with the bite-jump appliance in combination with a high-pull headgear. This also makes it possible to achieve protrusive repositioning of the mandible in patients with a pronounced vertical growth pattern without causing on open bite. In retrospective the patients' treatment plans proved to be completely appropriate, however, the fact should not be overlooked that changing the occlusal plane is essential for the realization of a positive therapeutic result.

[Skeletal and dental changes during the use of the bite-jumping plate. A cephalometric comparison with an untreated Class-II group]

In this study 95 patients with a malocclusion type Angle class II were treated with a bite jumping appliance and the results achieved were compared with untreated class II patients. A clear improvement in the skeletal and dental relationships was observed. Significant changes were achieved yearly in the following: 1. the angle SNA was reduced (0.82 degrees), 2. the angle SNB was increased (0.57 degrees), 3. the angle ANB was reduced (1.39 degrees). All 3 of these variables are significant. Other skeletal variables, most notably the incline of the maxilla to the line NS, were not influenced nor was the relation of posterior facial height to anterior facial height. The mandibular incisors did not exhibit increased protrusion relative to the mandibular plane. Only the angle of the mandibular incisor to NB was changed by the total protrusion of the mandible. The maxillary incisors in these cases manifested obvious lingual tipping. For this reason the orthodontist must weigh carefully on an individual patient basis, whether the use of adjunctive torque springs is required and necessary.

The burden of proof: a critical review of orthodontic claims made by some general practitioners

The increased demand for orthodontic treatment in the developed countries has led to a recent proliferation of "motel courses" that are specifically designed for general practitioners. Most of the techniques presented are only those that have long been available for selection by discerning orthodontists. However, when they are applied exclusively and indiscriminately by inexperienced clinicians, this may result in either prolonged, unnecessary treatment or failure through instability. Therefore some of the claims that are made will be examined and discussed with a review of the literature.

Orthodontic forces exerted by activators with varying construction bite heights

The present study was conducted to investigate the nature of forces induced with activators by measuring strains, electromyogram (EMG) and electroencephalogram (EEG) during a 2-hour sleep period. Fifteen adolescent patients with Class II and Class III malocclusions, (30 subjects) were used. Four types of activators were made for each patient with construction bites taken at incisal edge clearances of 2, 4, 6, and 8 mm vertically. The magnitude of forces generated by passive tension of soft tissues increased significantly (p < 0.01) from approximately 80 to 160 gf in the Class II group and from approximately 130 to 200 gf in the Class III group with varying construction bite heights from 2 to 8 mm. Higher construction bites also significantly changed (p < 0.01) the direction of forces by passive tension from vertical to posterior and from vertical to anterior in relation to the reference plane in the Class II and Class III groups, respectively. Duration of forces generated by passive tension was most significantly longer than that of active contraction of the jaw closing muscles, irrespective of the construction bite heights. It is concluded that passive tension, derived from viscoelasticity of soft tissues, plays a more important role in inducing changes that phasic stretch reflex during jaw orthopedic therapy with activators.

A growth control approach to Class II, Division 1 cases during puberty involving the simultaneous application of maxillary growth restriction and mandibular forward induction

A simple method that used headgear and a functional appliance simultaneously was used for the correction of Class II, Division 1 cases with severe denture base discrepancy. The treatment restricted the forward growth of the maxilla and advanced the mandible. The functional appliance, referred to as the mandibular growth advancer (MGA), advances the mandible progressively with a splint, with the objective of remodeling the condyle and the glenoid fossa in the temporomandibular joint. Functional adaptation was achieved as the muscles that are attached to the mandible adjusted to new positions. In the two cases that illustrate this method, the ANB angle decreased and the Ar-B distance increased over a short period to four and six times the mean Japanese growth rate, respectively. After the correction of the denture-base discrepancy, a multibracket fixed appliance was used for dental alignment, and good skeletal, occlusal relationships and profiles were obtained. Treatment of severe denture-base discrepancy in this manner may reduce the skeletal abnormality, decrease the number of extraction cases, and shorten the subsequent multibracket treatment time. And it may reduce the iatrogenic side effects caused by prolonged mechanotherapy with a fixed appliance.

Mandibular changes during functional appliance treatment

The purpose of this prospective trial was to determine the changes in position and size of the mandible in children treated with either the Fränkel function regulator or Harvold activator. Forty-two 10- to 13-year-old children with Class II, Division 1 malocclusions were matched in triads according to age and sex and randomly assigned to either control, Fränkel function regulator, or Harvold activator groups. There were no statistically significant differences between the groups at the beginning of the study. After 18 months, significant increases in gonial angle and articulare-pogonion length in the Harvold group were attributed to a change in the location of articulare because the condyles were positioned downward and forward at the end of treatment. The main effects of both appliances were to allow vertical development of the mandibular molars and increase the height of the face. The Harvold appliance also proclined the lower incisors and increased mandibular arch length. We could find no evidence to support the view that either appliance was capable of altering the size of the mandible.

Magnetic activator device II (MAD II) for correction of Class II, division 1 malocclusions

A magnetically active, two-piece (upper and lower), functional orthopedic appliance has been developed, magnetic activator device (MAD) for the correction of Class II malocclusions. The magnetic forces are used to give freedom of mandibular movement and to allow for continuous functioning of the orofacial muscles when the appliance is worn. Samarium cobalt (Sm2Co17) magnets are incorporated on the buccal aspects of the upper and lower appliances. Magnetic forces ranging from 150 to 600 gm per side have been used on patients, and it seems that the skeletal versus dental response depends on the intensity of the magnetic force used. A force of 300 gm, when the magnets are in contact, on each side has been found to be an appropriate value in patients age 7 to 12 years. The use of this less bulky design rather than a traditional orthopedic appliance, along with the freedom of function it permits, has enabled patients to wear the appliance nearly 24 hours in most cases.

A tensor analysis to evaluate the effect of high-pull headgear on Class II malocclusions

The inaccuracies inherent in cephalometric analysis of treatment effects are well known. The objective of this article is to present a more reliable research tool in the analysis of cephalometric data. Bookstein introduced a dilation function by means of a homogeneous deformation tensor as a method of describing changes in cephalometric data. His article gave an analytic description of the deformation tensor that permits the rapid and highly accurate calculation of it on a desktop computer. The first part of this article describes the underlying ideas and mathematics. The second part uses the tensor analysis to analyze the cephalometric results of a group of patients treated with high-pull activator (HPA) to demonstrate the application of this research tool. Eight patients with Class II skeletal open bite malocclusions in the mixed dentition were treated with HPA. A control sample consisting of eight untreated children with Class II who were obtained from The Ohio State University Growth Study was used as a comparison group. Lateral cephalograms taken before and at the completion of treatment were traced, digitized, and analyzed with the conventional method and tensor analysis. The results showed that HPA had little or no effect on maxillary skeletal structures. However, reduction in growth rate was found with the skeletal triangle S-N-A, indicating a posterior tipping and torquing of the maxillary incisors. The treatment also induced additional deformation on the mandible in a downward and slightly forward direction. Together with the results from the conventional cephalometric analysis, HPA seemed to provide the vertical and rotational control of the maxilla during orthopedic Class II treatment by inhibiting the downward and forward eruptive path of the upper posterior teeth. The newly designed computer software permits rapid analysis of cephalometric data with the tensor analysis on a desktop computer. This tool may be useful in analyzing growth changes for research data.

Mandibular remodeling measured on cephalograms. 1. Osseous changes relative to superimposition on metallic implants

We report the results of a study aimed at quantifying remodeling of mandibular surfaces in a sample of growing children who represent those usually treated by orthodontists in the mixed and early adult dentition. The sample, 31 patients with metallic implants of the Björk-type, was monitored at annual intervals between 8 1/2 and 15 1/2 years of age. (Maxillary remodeling changes for the sample have been reported earlier.) The present article reports findings concerning changes at condyle, gonion, menton, pogonion, and point B as identified on lateral cephalograms. Data are reported in the Frankfort plane frame of reference with the cephalograms from different time points superimposed on the metallic implants. Mean displacement at condyle was larger than that at any other landmark and was similar in magnitude and direction to the observations of Björk when the difference in orientation of the vertical axis in the two studies is taken into account. The mean displacement of gonion was in an upward and backward direction at an angle of approximately 45 degrees to the Frankfort plane. Mean displacements at menton and pogonion were in a downward and backward direction but were very small. Mean displacement at point B was somewhat greater than that of menton and gonion, oriented in an upward and backward direction. Individual variation for most of the parameters measured was sufficiently large to warrant the inference that caution should be used when mean values are applied to the analysis of individual cases.

Cephalometric changes during treatment with the open bite bionator

Lateral cephalometric radiographs of 39 patients who were treated with an open bite bionator, also known as a "bionator to close the bite," were obtained from six private orthodontic practices. Comparisons of pretreatment cephalometric values with published standards indicate that clinicians do not generally use this appliance for patients who have marked excessive anterior vertical dimension. Rather, the cases appear to be Class II with mild anterior open bites or with some indication of open bite tendency, such as a steep mandibular plane angle. Changes in cephalometric values during treatment with the appliance were compared with normal growth standards. Patients exhibited a reduction in facial convexity and overjet, reduced eruption of maxillary molars, and less of an increase in facial height than expected. The appliance appears to be effective for Class II correction in patients who require control or improvement of moderately excessive vertical dimension.

Aberrant mandibular growth: theoretical implications

There is a multiplicity and variety of studies investigating mandibular growth. The exact role of the mandibular condyle in influencing mandibular growth is still a point of conflict. This study was conducted with six subjects who had different condylar defects. The cranium and the skeletal profile, as well as the position of the maxilla and the mandible, were investigated. In all cases, the mandible showed a tendency toward posterior rotation. The total mandibular length was reduced with deficient corpus length and ramus height. The influence of the integrity of the condylar head and its normal articulation in the temporal fossa on mandibular growth were emphasized.

The effect of functional appliances on the skeletal pattern

The findings of some 26 papers covering the results of Andresen and Fränkel appliances, as analysed from cephalometric radiographs, are reviewed. These findings show a high degree of consistency. They have been combined to produce larger samples, and compared with a control group produced from reports of untreated Class II division 1 individuals, with consequent gains in statistical significance. Generally, there is no appreciable holding back of maxillary advancement in either group (although a slight relative reduction in the angle SNA). There is a slight mean increase in mandibular growth, mainly in a vertical direction. This seems similar to that reported by several authors in conventional appliances. There is a wide variation in response.

The nature of Class II relapse after Herbst appliance treatment: a cephalometric long-term investigation

The purpose of this investigation was to assess the number of, and the interrelation between, skeletal and dental components that contribute to Class II relapse after Herbst treatment. A comparison was made between 15 relapse and 14 stable cases at least 5 years after treatment. Lateral cephalograms taken before and immediately after Herbst treatment, as well as 6 months and 5 to 10 years after treatment, were analyzed. The results revealed that relapse in the overjet and sagittal molar relationship resulted mainly from posttreatment maxillary and mandibular dental changes. In particular, the maxillary incisors and molars moved significantly (p less than 0.05) to a more anterior position in the relapse group than in the stable group. The interrelation between maxillary and mandibular posttreatment growth was favorable and did not contribute to the occlusal relapse. It is hypothesized that the main causes of the Class II relapse in patients treated with the Herbst appliance were a persisting lip-tongue dysfunction habit and an unstable cuspal interdigitation after treatment.

Skeletal, dental, and functional effects of headgear-activator therapy on Class II malocclusion in Japanese: a clinical case report

Ten orthodontic patients in whom a headgear-activator appliance was used in the first phase of treatment for Class II malocclusion were clinically evaluated. All patients had abnormal perioral muscle function at the initial examination. Myofunctional methods were used before and during active treatment. Pretreatment and posttreatment cephalometric tracings were evaluated to examine the effect of the appliance on dental, skeletal, and soft tissue structures. Five of the 10 cases illustrated distal movement of the lower first molar, a phenomenon not mentioned previously in the literature. Growth stimulation of the mandible was also observed in this patient sample, with some subjects demonstrating above-average mandibular growth when compared with a control group of normal subjects. Abnormal oral function was eliminated, and all patients had clinically acceptable results at the end of the treatment period. The headgear-activator appliance can be considered an effective tool for the control of vertical growth problems in growing mixed-dentition patients.

The effect of bite-opening appliances on mandibular rotational growth and remodeling in the rhesus monkey (Macaca mulatta)

Previous experimental studies that have used a bite-block cemented to the maxillary dental arch have shown that the direction of growth of the maxillary complex is redirected in a superior and anterior direction for approximately 12 weeks but reassumes a normal inferior and anterior direction after that time. The purposes of this study were (1) to examine the effect of increased vertical dimension and altered mandibular posture on growth of the mandible and (2) to determine whether or not an alteration in chronic mandibular position alters mandibular intramatrix rotation. Eleven Macaca mulatta monkeys wore 15 mm vertical bite-opening appliances for 24 or 48 weeks. Nine untreated animals were used as controls. All animals received tantalum bone implants to facilitate cephalometric analysis. Serial lateral radiographs of the mandible were traced and superimposed on bone implants for each animal to determine overall changes in mandibular shape (gonial angle) and the location of bone remodeling. During normal growth, the gonial angle closed an average of 0.1 degrees over a 48-week period. In the experimental animals, the gonial angle opened 6.4 degrees (p less than 0.005) as a result of remodeling during the period that mandibular posture was altered. Once normal mandibular posture was restored, this process was reversed; the gonial angle once again became more acute over time, and remodeling along the body and ramus of the mandible was similar to that observed in control animals. These results suggest that mandibular growth and remodeling can be influenced by altered mandibular vertical posture.

Effect of functional appliances on jaw muscle activity

The electromyographic (EMG) activity of masticatory muscles was monitored longitudinally with chronically implanted EMG electrodes to determine whether functional appliances produce a change in postural EMG activity of the muscles. Preappliance and postappliance EMG levels in four experimentals that had been fitted with functional appliances were compared against the background of EMG levels in controls without appliances. The insertion of two types of functional appliance to induce mandibular protrusion was associated with a decrease in postural EMG activity of the superior and inferior heads of the lateral pterygoid, superficial masseter, and anterior digastric muscles; the decrease in the first three muscles was statistically significant. This decreased postural EMG activity persisted for approximately 6 weeks, with a gradual return toward preappliance levels during a subsequent 6-week period of observation. Progressive mandibular advancement of 1.5 to 2 mm every 10 to 15 days did not prevent the decrease in postural EMG activity.

Dental and skeletal contributions to occlusal correction in patients treated with the high-pull headgear-activator combination

The purpose of this study was to examine dental and skeletal changes in patients treated with the high-pull headgear-activator combination. A group of 40 consecutively treated subjects with a Class II molar relationship and a minimum of 5 mm overjet was used for this study. The results showed that Class II correction often was achieved by distal repositioning of the maxillary teeth (mean, 0.07 mm) and mesial repositioning of the mandibular teeth (mean, 3.3 mm) with a wide range of variation. Correlation of maxillary molar repositioning with total interarch occlusal change showed a positive relationship; however, a weak correlation suggested that other variables were contributing factors, in addition to distal upper molar positioning. The change in mandibular molar position compared with the movement of pogonion strongly suggests that forward growth of the mandible is important to the correction of the Class II malocclusion. When total molar repositioning in the upper jaw was correlated with total molar repositioning in the lower jaw, a strong inverse correlation was found, indicating that upper molar movement parallels lower molar movement.

[The modification of growth with the jumping-the-bite plate compared to other functional orthodontic appliances]

The bite-jumping-appliance BJA is a special functional appliance which affects the upper jaw comparably to activator headgear combinations (SNA angle). Concerning its influence on the lower jaw (SNB angle) the BJA can be compared with the Teuscher activator and the Klammt activator. The change in the inclination of the upper jaw (ANS-PNS to nasion-sella) proved to be negligible because the vector of the force passed through the center of resistance of the upper jaw. The extend of the dental influence was the largest with the activator, the smallest with the Fränkel II appliance. The inclination of the lower incisors (1 to gonion-menton) was hardly affected. The upper incisors were retruded however not be the same extend as with the Teuscher activator which even has torque springs (to avoid the retrusion). The treatment of all the patients ended in all cases excepting those that were treated with an activator in a nearly ideal IIW angle. Our findings encourage us to say that the BJA is an appliance with a far better working mechanism than the working mechanism of other functional appliances.

A cephalometric study to compare the effects of cervical traction and Andresen therapy in the treatment of class II division 1 malocclusion. Part 2--Dentoalveolar changes

Absolute distal movement of upper first molars together with distal tipping, but no significant extrusion, occurred with cervical traction. Distal movement of the maxillary first molars was more stable in the group where maxillary 2nd molars had been extracted. With Andresen treatment a restraining effect took place on the upper molars, while mesial movement of the lower first molars contributed to correction of the molar relationship.

Mandibular response to orthodontic treatment with the Bionator appliance

A group of 20 subjects who underwent successful Bionator treatment was compared with 20 subjects who were treated less successfully with the same appliance. Both groups had similar advancements in their bite registrations, as well as similar treatment times and growth-prediction parameters. Success was judged not on the final occlusion (all patients were treated to a Class I molar relationship) but on the posttreatment position of skeletal pogonion. The successful group experienced 3.5 mm or more of advancement in skeletal pogonion, whereas the less successful group had less than 3 mm of advancement of this point. The two groups were comparable in all features except, as may be expected, total mandibular growth, which was greater in the group with the larger anterior pogonion advancement. The results of this study suggest that persons who have small mandibles (as determined by comparison with published growth standards) may benefit more from functional appliance therapy than patients with normal-sized mandibles. The subjects with delayed growth may experience more mandibular development than those with average growth during treatment under the favorable growth environment created by functional appliance therapy.

A cephalometric study to compare the effects of cervical traction and Andresen therapy in the treatment of Class II division 1 malocclusion. Part 1--Skeletal changes

Lateral cephalometric radiographs at the beginning of treatment, end of active treatment, and post-treatment of 30 Andresen and 40 cervical traction patients were analysed, and compared with those of a control group of 22 untreated cases. The cervical traction group was divided into a non-extraction group and an extraction of maxillary second molars group. A clinically significant reduction of ANB was achieved, mainly by mandibular changes in the Andresen group and by maxillary changes in the cervical traction groups. Cervical traction was associated with a small distal positioning and anterior downward tipping of the maxilla during treatment. A more favourable sagittal position of the mandible was achieved in the Andresen group compared to the cervical traction groups, particularly the non-extraction group, where a greater transient backward rotation of the mandible occurred during treatment. A significant, but clinically small increase in mandibular body length occurred in Andresen patients compared to the control. However, in both treatment groups this was due to an increase in growth of the vertical ramus. The lower face heights, both anterior and posterior, increased in all groups, with the anterior upper face height also increasing in the cervical traction group.

Effects of a fixed magnetic appliance on the dentofacial complex

The purpose of the study was to design and evaluate the effects of a fixed magnetic appliance that hinged the mandible open and exerted an intrusive force on the teeth. Ten patients between the ages of 8 years and 10 years 6 months, with Class II, Division 1 malocclusion associated with mandibular retrusion and increased lower facial height, were treated with this appliance. The length of treatment was 4 months, after which the appliance was removed and the patients were followed up for 4 months. Ten children with similar age, sex, and dentofacial characteristics acted as controls and did not receive any appliance therapy. Changes in morphology of the dentofacial complex were evaluated by use of lateral cephalograms and study models. In addition temporomandibular joint and muscle functions were assessed. During treatment mandibular length increased 3.2 mm, angle of facial convexity decreased 2.8 degrees, the upper and lower teeth intruded an average of 1.5 mm each, and the mandibular plane angle decreased 1.3 degrees. In the follow-up period, some rebound eruption was noted; however, all other changes were stable.

Functional orthopedic magnetic appliance (FOMA) II--modus operandi

A new functional appliance (FA) to correct Class II dentoskeletal malocclusions is introduced. The functional orthopedic magnetic appliance (FOMA) II uses upper and lower attracting magnetic means (Nd2Fe14B) to constrain the lower jaw in an advanced sagittal posture. In vitro, a special gauge transducer measured the magnetic attractive path and forces. In vivo, 13 prepubertal female Macaca fascicularis monkeys received facial implants and were treated for 4 months with the following appliances: conventional FA (four subjects), FOMA II (five subjects), a combined FOMA II + FA (two subjects), and sham (control) appliance (two subjects). The in vitro results showed the following: vertico-sagitally displaced upper and lower magnets attracted ultimately along an oblique line with a terminal horizonal slide to become fully superimposed; the functional performance improved when the magnetic interface acted as a magnetic inclined plane; and the magnetic force was able to guide and constrain the mandible toward the constructive protrusive closure position (CPCP) (1.2 mm, F = 570 gm) from levels below the habitual rest position (3 mm, F = 219 gm) and the electromyographic (EMG) relaxed position (8.5 mm, F = 45 gm). The in vivo results demonstrated the following: functional performance increased in FOMA II (22%) and in the combined FOMA II + FA (28%) over the conventional FA; mandibular length increased significantly in the treated animals (means = 2.83 +/- 0.70 mm) over the control animals (means = 0.43 +/- 0.08 mm); incisor proclination was lower in magnetic appliances (means = 4.57 +/- 1.76 degrees) than in the conventional FA (means = 8.75 +/- 1.85 degrees); mandibular elongation and condylar posterior inclination resulted from posterosuperior endochondral growth (increased cell proliferation and/or hyperplasia of functional chondroblasts) and by bony remodeling of the condylar neck (apposition posterior border, resorption anterior border), respectively; virtually no anterior displacement of the postglenoid spine (means = 0.19 +/- 0.68 mm) nor the articular eminence (means = 0.36 +/- 0.69 mm) was found. Increased lower posterior alveolar height (means = 1.71 +/- 0.82 mm) is a major impediment in the correction of excessive lower anterior facial height. The results of the study highly recommend the exploration of the clinical application of the FOMA II.

The effect of the amount of protrusion built into the bionator on condylar growth and displacement: a clinical study

To evaluate the treatment effects of a variable degree of forward posturing of the mandible incorporated into the Bionator, a study was undertaken on 14 patients with Class II, Division 1 malocclusion, treated for 1 year with a Bionator, maintaining the mandible in an edge-to-edge incisal position (Be group). This group was compared with a matched group of patients treated with the Bionator in whom the mandible was maintained in a "functional maxipropulsion" (Bmax group). Both groups were subdivided further according to sex for selected parameters. Twenty-nine measurements on cephalometric x-ray films taken before and after 1 year of treatment were statistically analyzed. According to this study, "edge-to-edge" protrusion is superior to "functional maxipropulsion" in increasing ramal height. The difference in increase in corpus length after treatment (greater in boys than in girls) was sex related rather than dependent on appliance characteristics. When studying the effect of functional appliances, it is suggested that a patient group be subdivided by sex. After treatment a repositioning of the condyle was found in a more downward and possibly slightly forward direction relative to sella point (S) in both groups. A relocation of the condyle should be considered as another treatment effect of functional appliances. The more important lowering of the condyle found in the Bmax group may partly explain the significant increase in SNB, the 1.6-fold larger decrease in overbite, and the highly significant increase in anterior lower facial height in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional appliances: a review

The purpose of this review was to evaluate the scientific studies that describe the effects of functional appliances on the dentofacial structures in the treatment of Class II malocclusions. The review is limited to two appliances: the activator and the functional regulator.

Treatment effects of the Herbst appliance

The purpose of this study was to examine the results of treatment with a modified Herbst appliance. The pretreatment and posttreatment cephalometric and dental cast records of 32 consecutively treated Class II, Division 1 cases were evaluated. Results showed that the skeletal Class II correction was achieved by an average 1.5 mm of greater than normal forward mandibular growth in conjunction with a minimal "headgear" effect inhibiting maxillary growth. Dental Class II correction was achieved by significant amounts of distal bodily movement and tipping of the maxillary first molars combined with bodily forward movement of the mandibular first molars. Significant increases were seen in maxillary arch length and maxillary intercanine and intermolar widths, while the mandibular arch demonstrated few changes. Slight forward movement of the mandibular incisors was noted with no significant change occurring in the maxillary incisors.

The effects of three methods of orthodontic appliance therapy on some commonly used cephalometric angular variables

This investigation was undertaken to study the effects of the Andresen activator functional appliance therapy, Begg therapy, and cervically directed extraoral forces upon several commonly used cephalometric angular variables, with particular reference to the relationship between the maxillary plane (palatal plane) and anterior cranial base as represented by SN line. The material consisted of 107 cases taken from the files of patients who had attended the Orthodontic Department, Eastman Dental Hospital, London. Ninety of the cases had received orthodontic treatment. For each case pretreatment, posttreatment, and postretention radiographs were traced and angular measurements made by means of a Lysta-Dent digitizer linked to an on-line computer. Descriptive statistics and one-sample and two-sample Student's t tests were performed. None of the treatment methods under investigation had a clinically significant effect upon the maxillary plane. An increase in the inclination of the mandibular plane was a feature of Begg and headgear therapies but not of Andresen therapy. Any increase observed was of a temporary nature. While no change in SNA occurred with Andresen therapy, Begg and headgear therapies produced a permanent reduction in the variable. A small reduction was also produced in SNB by Begg and headgear therapies. The behavior of SNB following Andresen therapy was not significantly different from that in the group of untreated subjects. Each appliance method produced a permanent reduction in ANB; however, a similar reduction was also demonstrated in the control group.

Biochemical and autoradiographical evidence that anterior mandibular displacement in the young growing rat does not stimulate cell proliferation or matrix formation at the mandibular condyle

A removable bite plate was used to induce forward mandibular displacement in four-week-old rats for 10 h/day for 1, 3, 7, 11 and 14 days. The animals were killed and the condylar explants pulsed in vitro for 6 h with either [3H]-thymidine or [3H]-proline or 35SO(2-)4. The specific activity of radio-isotope incorporation was expressed as dis/min per microgram DNA, dis/min per mg protein and dis/min per microgram sulphated glycosaminoglycans (GAG). [3H]-thymidine autoradiography was also used in a 14-day experiment to establish a radioactive index (labelled cells per 1000 cells counted) for the anterior, middle and posterior regions of the condyle. There was no significant alteration in either cell proliferation (dis/min per microgram DNA and radioactive index) or matrix formation (dis/min per mg protein and dis/min per microgram GAG) at any point in the time scale.

The influence of functional appliance therapy on glenoid fossa remodeling

This study investigates the remodeling changes in the condyle and glenoid fossa following a period of progressively activated and continuously maintained mandibular advancement using the Herbst appliance. Progressive mandibular advancement was achieved by adding stops to the telescopic arms of the appliance, with the total activation reaching 7.0 to 10.0 mm, dependent upon the length of the treatment phase. This mandibular advancement produced extensive remodeling and anterior relocation of the glenoid fossa, which contributed to anterior mandibular positioning and altered jaw relationships.

Concepts on functional appliances' mode of action

Several working hypotheses have been conceived to explain the mode of action of various functional appliances. A review of the different concepts is presented and these concepts are tested by means of data from basic scientific research. Furthermore, a general concept is postulated that could unite the working principles of several functional appliances. Finally, the clinical relevance of scientific research in this area is evaluated.

An evaluation of combination second molar extraction and functional appliance therapy

The purpose of this study was to examine the results of a treatment regimen involving the extraction of four second molars followed by a combination of sagittal, Bionator, and fixed appliance therapy. The pretreatment and posttreatment cephalometric and dental cast records of 30 consecutively treated Class II, Division 1 cases were evaluated. Results showed that the Class II skeletal correction was achieved by a "headgear" effect inhibiting maxillary growth in conjunction with normal forward mandibular growth. No significant distal bodily movement or tipping of either maxillary or mandibular first molars was found. Significant increases were seen in maxillary arch length, maxillary intercanine and intermolar width, and mandibular intermolar width as a result of treatment. Maxillary third molar position tended to improve following second molar extraction; mandibular third molar changes were more variable.

A study in human subjects using a new device designed to mimic the protrusive functional appliances used previously in monkeys

A new appliance is described that mimics in function the protrusive jaw-positioning devices used previously in monkeys. The appliance consists of maxillary and mandibular posterior biteplates separated by a sharp vertical interface perpendicular to the occlusal plane. Function of the appliance was evaluated in 35 consecutively treated patients and compared against matched controls. The patients, who ranged in age from 9 to 14 years, accepted the appliance readily and wore it 24 hours each day, even while eating. Although cephalometrics was the primary assessment tool, tomograms and/or transcranial x-ray films and models were also obtained. The rate of mandibular length increase, measured from articulare, was comparable to or better than that found in monkeys using similar devices. The dentoalveolar effects were also similar to those found in monkeys, including anterior migration of the mandibular dentition and posterior movement of the maxillary dentition. The mandibular molars moved forward 4.8 mm of which 73% was determined to have come from increased anterior movement of the mandible. Subtracting normal growth, the net mandibular length increase was 2.2 mm during the 9.4-month average treatment interval.

Cephalometric landmark identification within the petrous temporal region

The literature is reviewed regarding the errors associated with relocating cephalometric petrous temporal landmarks. An experimental cranial fixation device, to be used with cephalostat ear rods that subsequently 'hinge away', is presented. Twenty-five consecutive cephalograms taken by this method (Group B) are compared with another two groups of 25 radiographs. The second group (Group A) constitutes those taken with perspex ear rods in situ, whilst the third group (Group C) constitutes those with wooden ear rods. The variance ratios demonstrate that the error in relocating most of the petrous temporal landmarks is significantly greater in Group B, when compared to either Group A or C. In comparing these latter two groups, the variance in Group A is greater for all these landmarks, significantly so for condylion and porion. Some possible factors contributing to these findings are discussed. It would seem that wooden ear rods produce less error in the relocation of the petrous temporal landmarks; that the absence of ear rods produces greater error; and that the presence of perspex ear rods increases the error in the relocation of anatomical porion.

Mandibular molar displacement secondary to the use of forces to retract the maxilla

Using previously described computer-aided techniques, we have been able to characterize quantitatively the displacements of the lower first molar associated with the use of several different therapeutic modalities that are conventionally employed to retract the maxilla in the treatment of Class II malocclusion. The total displacement of the molar has been partitioned into two components associated respectively with displacement of the entire mandible and with local interosseous migration (dental compensation) of the molar within the mandible. A further attempt has been made to partition treatment-associated effects from nontreatment-associated effects. While considerable variability in effect was observed within each sample on a case-by-case basis, some important normative trends did emerge. Contrary to our expectations, it was found that in each of the treatment groups, the mean local intraosseous rotational effect (Table IIB.2) was of greater magnitude than the mean effect of mandibular rotation (Table IIB.1). The character of the intraosseous rotation differed significantly (P less than 0.05) between the control group and each of the treatment groups. In the control group, a mean mesial crown tipping (that is, "proclination") was noted. In each of the treatment groups, a mean distal crown tipping ("uprighting") was noted. In both the cervical and intraoral groups, the lower molar tended to displace mesially more than in the control or high-pull groups. This mesial displacement derived from the mesial displacement of the mandible (Table IIC.3), rather than from displacement of the tooth within the bone (Table IIC.4). In both the high-pull and the intraoral groups, the lower molar erupted within the mandible significantly more than in the control and cervical groups (Table IIC.6). The statistically significant supereruption/extrusion of the upper molar in the cervical group (Table IIC.2) was not accompanied by an associated inhibition of the eruption of the lower first molar (Table IIC.6). In general, it seems reasonable to infer that the growth-related displacement of the mandible influenced the final position of the lower first molar more profoundly than did the treatment-associated displacement of the upper molar.

Cephalometric changes associated with treatment using the activator, the Fränkel appliance, and the fixed appliance

Treatment with the activator, the Fränkel appliance, and the edgewise appliance was compared in three separate groups; each group consisted of twenty-five nonextraction cases of Class II, Division 1 malocclusion. Hard- and soft-tissue profile changes caused by growth and treatment were assessed by means of pretreatment and posttreatment lateral cephalograms. Anterior movement of A point was 1.6 mm more in the activator group than in the fixed-appliance group. The most anterior point on the maxillary incisor moved 1.5 mm more distally in the fixed-appliance sample than in the functional groups. Among the three groups, the activator sample showed the most anterior movement of the mandible (2.3 mm); the fixed group showed the least (0.6 mm). The fixed-appliance group showed more posterior rotation of the mandible than the activator group. However, relative to cranial base, the movement of the mandibular symphysis was not statistically different in the three groups. There were little differences among the treatment groups with regard to changes in the soft-tissue profile. In clinical terms, there was a remarkable similarity in the changes that occurred in the three treatment groups.