Morphogenetic response to activator treatment

Nonextraction treatment of Class II, Division 1 malocclusions

Nonextraction treatment of three different types of Class II, Division 1 malocclusions that focused on solving the imbalances of the dentofacial configuration have been presented. Diagnostic features encountered were anterior alveolar hyperplasia that required simultaneous maxillary incisor intrusion and retraction, severe mandibular crowding requiring functional alveolar arch development, and maxillary prognathism requiring distal movement of the maxilla and incisor retraction. Since many factors contribute to the makeup of various types of Class II, Division 1 malocclusions, orthodontic mechanics should address the specific needs of each patient.

Response to activator treatment in Class II malocclusions

A clinical study was designed to disclose the effects of activator treatment in the correction of Class II malocclusions. The rationale for the use of the activator appliance was based on the premise that correction of distocclusion can be achieved by inhibition of forward growth of the maxilla, inhibition of mesial migration of maxillary teeth, inhibition of maxillary alveolar height increase and extrusion of mandibular molars, increased growth of the mandible, anterior relocation of the glenoid fossa, mesial movement of mandibular teeth, and combinations of these effects. The appliance, as designed for this study, could potentially have an effect on all of these factors. Measurements were obtained from cephalometric head films obtained at 6-month intervals. Matched-pairs analyses of control versus treatment change after 6 months and after 1 year of treatment were done on 36 and 29 pairs, respectively. Pretreatment versus treatment changes were analyzed on 33 subjects by means of the spline regression analysis; posttreatment versus treatment changes were analyzed on 18 subjects by means of the Student Newman-Keuls multiple comparison test. The matched-pairs analyses of mean values demonstrated significant reduction in forward growth of the maxilla, uprighting of the maxillary incisors, reduced overjet, leveling of the mandibular occlusal plane, improved molar relationship, downward and forward relocation of the glenoid fossae, increased advancement of all mandibular structures, increased face profile angle, and increased lower face height. The two longitudinal analyses yielded similar findings, but some differences were noted. Because rather severe dental malocclusions were corrected, the slight average inhibition of maxillary growth and the anterior relocation of glenoid fossae alone could not account for the correction of the Class II dental arch relationship. It was therefore concluded that, in addition to the statistically significant changes, smaller changes occurred in several areas without being consistent enough or of a large enough magnitude to become statistically significant in the analyses of mean values. Comparison of group averages may mask treatment effects that significantly contribute to the correction of malocclusions in individual cases.

Skeletal and dental changes following functional regulator therapy on class II patients

Craniofacial growth in 100 patients treated with the functional regulator of Fränkel for about 24 months was compared with craniofacial growth seen in a matched group of untreated persons with Class II malocclusion. Both conventional and geometric cephalometric analyses were used to evaluate the skeletal and dental adaptations. This study shows several clear effects of treatment in either of two age ranges considered. The principal skeletal effect was advancement of the mandible along the direction of the facial axis. This advancement resulted in increases in mandibular length and in vertical facial dimensions. There was little effect of treatment upon maxillary skeletal structures with the exception of point A, which moved slightly posteriorly. Dentoalveolar adaptations due to treatment included a decrease in the normal forward movement of the upper molar and an increase in the normal vertical movement of the lower molar. There was a 2-mm posterior movement of the tip of the upper incisor but minimal anterior tipping of the lower incisor.

Activator headgear therapy

A method of treatment is described using an activator and cervical headgear simultaneously to correct malocclusions of the Class II, Division 1 type. The case reports of ten treated patients are used to demonstrate the effects of the application of this technique. Changes in the dentition and facial skeleton were analyzed and the significance of the different responses to the application of the same appliances assessed. The hypothesis proposing that a simultaneous application of both appliances may result in a number of desirable effects greater than that induced by each individual appliance is examined. The hypothetical basis for the application of this technique is partially substantiated by the clinical observations. Within a period of about 1 year, correction of the Class II molar occlusion to a Class I molar occlusion is obtained, with a simultaneous reduction of overbite and overjet. Skeletal changes were found to be variable and related to facial type and the rate of facial growth. Brachyfacial and mesofacial types responded most favorably to treatment. The most favorable effects were observed when there was a large quantitative mandibular growth and brachyfacial or mesofacial growth pattern. In dolichofacial types with a slow mandibular growth rate, mandibular rotation was found to be clockwise; cervical traction appears contraindicated, and a combination of activator with occipital medium to high pull is considered more appropriate.

The effect of on the incisor teeth of activator treatment: a follow-up study

A follow-up study of the effect of activator treatment on the incisors is presented. Much of the effect of activator treatment is due to movement of the incisors. It has been claimed that the upper incisors become retroclined, however, a proclination of the lower incisors may also occur and this has been regarded by many as a contra-indication. This aspect has been studied in a material consisting of 40 Angle Class II:1 cases treated with the activator. Mean age at the start of treatment was 11 years and at the end of treatment 12.5 years. Incisor position and inclination were recorded on radiographs taken before and after treatment. The results indicate a significant improvement regarding upper incisor position and inclination whereas the lower incisors had moved forward 2.6 mm and proclined 1.6 degrees on average. A regression analysis suggested, however, that cases with proclined lower incisors prior to treatment underwent retroclination during treatment (p less than 0.001). Furthermore, 25 per cent of the patients studied showed retroclination of the lower incisors during activator treatment. It is thus concluded that proclined lower incisors is not necessarily a contra-indication for treatment using the activator.

Vertical control as an important ingredient in the treatment of severe sagittal discrepancies

The control of vertical development, in particular in the maxillary molar region, has often been suggested as a method of implementing sagittal change in treatment of Class II skeletal discrepancies. A group of twenty-eight Italian children in the early mixed-dentitional stage, with increased overjet and distal molar relationship, were treated orthodontically with a combination of a removable maxillary splint and high-pull extraoral traction. While only slight dorsal repositioning of the maxilla could be observed, an effective retardation of the vertical maxillary development was recorded, as well as a pronounced forward displacement of the mandibular symphysis. Distal movement of the maxillary dentition contributed likewise to the elimination of overjet observed clinically. The center of mandibular rotation was evaluated for each patient and displayed a pronounced variation illustrating different responses to the same type of appliance by different patients. The clinical implications of the above findings are discussed, and the necessity for constant appraisal of results during treatment is stressed.

Delayed bone grafting in the cleft maxilla and palate: a retrospective multidisciplinary analysis

The results of delayed bone-grafting procedures in a group of twenty-four cleft patients are reported. All patients benefitted from closure of their fistulas. The need for a prosthesis was eliminated in twelve patients, and eight of the remaining twelve patients required only a three-unit bridge. Residual movement of the premaxilla in two of the nine bilateral cases included in this study was detectable. The esthetic benefits were difficult to assess since sixteen of the patients simultaneously underwent lip and nasal revisions. In seventeen patients, the graft was placed prior to canine eruption, and in sixteen of these patients, the canine erupted passively into the arch. Not every patient with a cleft is a candidate for delayed bone grafting, but the procedure has been found to be beneficial in selected persons.

Facial growth during treatment with the function regulator appliance

Facial growth was examined in ten patients who had completed one year of treatment with the function regulator 2 (FR-2) as described by Fränkel. Cephalometric headfilms taken before and one year into treatment were superimposed on stable structures in the anterior cranial base, and the qualitative changes were analyzed. The results showed that facial growth in most patients was mainly in the vertical plane, but considerable individual variations were seen. The maxilla generally became more retrognathic during treatment and showed backward rotation and posterior displacement in some patients. Marked individual variations were seen in the mandible. No indications were found that the FR-2 promoted forward growth of the mandible as used in this study (no notching of teeth and less than 5 mm of mandibular advancement). The improvement in dental occlusion observed was primarily due to changes in the vertical relationship between the jaws.

Morphologic response to changes in neuromuscular patterns experimentally induced by altered modes of respiration

The present experiment was designed to test whether specific recordable changes in the neuromuscular system could be associated with specific alterations in soft- and hard-tissue morphology in the craniofacial region. The effect of experimentally induced neuromuscular changes on the craniofacial skeleton and dentition of eight rhesus monkeys was studied. The neuromuscular changes were triggered by complete nasal airway obstruction and the need for an oral airway. Alterations were also triggered 2 years later by removal of the obstruction and the return to nasal breathing. Changes in neuromuscular recruitment patterns resulted in changed function and posture of the mandible, tongue, and upper lip. There was considerable variation among the animals. Statistically significant morphologic effects of the induced changes were documented in several of the measured variables after the 2-year experimental period. The anterior face height increased more in the experimental animals than in the control animals; the occlusal and mandibular plane angles measured to the sella-nasion line increased; and anterior crossbites and malposition of teeth occurred. During the postexperimental period some of these changes were reversed. Alterations in soft-tissue morphology were also observed during both experimental periods. There was considerable variation in morphologic response among the animals. It was concluded that the marked individual variations in skeletal morphology and dentition resulting from the procedures were due to the variation in nature and degree of neuromuscular and soft-tissue adaptations in response to the altered function. The recorded neuromuscular recruitment patterns could not be directly related to specific changes in morphology.

A cephalometric analysis of skeletal and dental changes contributing to Class II correction in activator treatment

The purpose of this investigation was to evaluate cephalometrically the mechanism of anteroposterior occlusal changes in activator treatment. The analysis used made it possible to relate alterations in the occlusion to sagittal skeletal and dental changes in the maxilla and mandible. The sample consisted of thirty Class II, Division 1 malocclusion cases treated successfully with activators during an average time period of 32 months. Before- and after-treatment head films in centric occlusion were analyzed. The occlusal line (OL) and occlusal line perpendicular (OLp) through sella were used for reference. Linear measurements were performed parallel to OL. The following results were found: (1) The improvement in occlusal relationships in the molar and incisor segments was about equally a result of skeletal and dental changes. (2) Overjet correction averaging 5.0 mm was a result of 2.4 mm more mandibular growth than maxillary growth, a 2.5 mm distal movement of the maxillary incisors, and a 0.1 mm mesial movement of the mandibular incisors. (3) Class II molar correction averaging 5.1 mm was a result of 2.4 mm more mandibular growth than maxillary growth, a 0.4 mm distal movement of the maxillary molars, and a 2.3 mm mesial movement of the mandibular molars. (4) When the findings were compared with longitudinal records of persons with normal occlusion (Bolton standards), activator treatment seemed to inhibit maxillary growth, move the maxillary incisors and molars distally, and move the mandibular incisors and molars mesially. Mandibular growth appeared not to be affected by activator treatment.

Orthopedic coordination of dentofacial development in skeletal Class II malocclusion in conjunction with edgewise therapy. Part II

This second of two articles describes the effects of mandibular growth enhancement in a comprehensive orthopedic approach to the correction of skeletal Class II malocclusion. Clinical and experimental evidence gives support to the concept, and case histories show the clinical mode of use of the appliance system. An initial 10- to 12-month orthopedic phase is followed by a second phase of similar duration in which full edgewise therapy is used to establish a gnathologically ideal occlusion. As the essential corrections are achieved in the orthopedic phase, the second phase is much reduced in complexity and is generally confined to alignment and final detailing. This combined approach to skeletal Class II treatment offers the possibility of better harmony of dental and facial features, with continued stability through the period of facial growth.

Superimpositional assessment of treatment-associated changes in the temporomandibular joint and the mandibular symphysis

This article analyzes differences in the measured displacement of the condyle and of progonion when different vectors of force are delivered to the maxilla in the course of non-full-banded, Phase 1, mixed-dentition treatment for the correction of Class II malocclusion. The 238-case sample is identical to that for which changes in other parameters of facial form have been reported previously. Relative to superimposition on anterior cranial base and measured in a Frankfort-plane-determined coordinate system, we have attempted to identify and quantitate (1) the displacement of each structure which results from local remodeling and (2) the displacement of each structure which occurs as a secondary consequence of changes in other regions of the skull. We have also attempted to isolate treatment effects from those attributable to spontaneous growth and development. At the condyle, we note that in all three treatment groups and in the control group there is a small but real downward and backward displacement of the glenoid fossa. This change is not treatment induced but, rather, is associated with spontaneous growth and development. (See Fig. 5.) Some interesting differences in pattern of "growth at the condyle" were noted between samples. In the intraoral (modified activator) sample, there were small but statistically significant increases in growth rate as compared to the untreated group of Class II controls. To our surprise, similar statistically significant increases over the growth rate of the control group were noted in the cervical sample. (See Table III, variables 17 and 18.) Small but statistically significant differences between treatments were also noted in the patterns of change at pogonion. As compared to the untreated control group, the rate of total displacement in the modified activator group was significantly greater in the forward direction, while the rate of total displacement in the cervical group was significantly greater in the downward direction. There were no statistically significant differences in the rate of total displacement of pogonion between the high-pull sample and the control sample. (See Table IV, variables 21 and 22.

Orthopedic coordination of dentofacial development in skeletal Class II malocclusion in conjunction with edgewise therapy. Part I

The skeletal Class II malocclusion may be considered to develop as a failure of the coordinating process to maintain harmonious relationships within the developing dentofacial apparatus. If the skeletal elements are too far apart for adaptation to occur and/or if there are functional abnormalities of the orofacial musculature which inhibit coordination from taking place, a malocclusion will result. An orthopedic technique and appliance system has been developed with the intention of improving those factors responsible for the development and perpetuation of the skeletal Class II malocclusion in a primary stage of treatment. This is accomplished by means of restraint and redirection of forward maxillary growth and an increase in the velocity of mandibular growth. Concurrently, adverse soft-tissue influences are eliminated or ameliorated. Edgewise appliance therapy is subsequently carried out for the final correction. The subject is considered in two articles. This first article describes the effects of the restraint of maxillary growth on craniofacial development and the dental changes produced by a maxillary removable splint with extraoral traction and shows how they can be used clinically for correction of the skeletal Class II malocclusion. The experimental and clinical evidence supporting this approach is considered, and case histories show the clinical use of the maxillary splint. This form of maxillary therapy for the skeletal Class II malocclusion has limitations, and it is desirable for it to be incorporated into a comprehensive orthopedic system.

Orthopedic effects with "conventional" fixed orthodontic appliances: a preliminary report

This retrospective study involved sixty previously treated patients between the ages of 9 and 14 years, all of whom initially had Class II dental malocclusions. The primary purpose of the investigation was to determine whether orthodontic treatment with a specific round-wire edgewise technique (no extraoral forces) was simply producing dentoalveolar manipulations or was actually affecting measurable skeletal or orthopedic alterations in the craniofacial system. The mean linear changes before and after orthodontic treatment in the maxilla (Ar-ANS), mandible (Ar-PGN), and lower facial height (ANS-MN) were statistically compared with an untreated control group (the Burlington Growth Study). The study sample was analyzed selectively according to sex and also according to the angulation of the mandibular base to the anterior cranial base (the SNMP angle). Apparently, from the observations in this study, the particular edgewise technique employed for the orthodontic treatment of the sixty sample patients did statistically affect more than merely dentoalveolar alterations. The normal forward growth of the maxilla appeared to be hindered, the lower facial height was significantly increased (usually without an appreciable increase in the SNMP angle), and the mean increased growth of the mandible was also statistically significant. Admittedly not its primary purpose, this preliminary report appeared to at least indirectly compare, if not the actual treatment modalities, at least the treatment results between a specific fixed orthodontic appliance and certain removable "functional" appliances.

Skeletal changes during the treatment of Class II/I malocclusions

Three groups of Class II/I patients were compared where treatment was carried out using Begg, Andresen and removable appliance techniques. Skeletal growth, as assessed by the dimensions S-Me, N-Me, ALFH and Me-Ar did not show any difference between the groups. All three groups showed an apparent improvement in skeletal pattern during treatment.

The MARS appliance. Report of a case

Inconsistent wearing of functional appliances, intermaxillary Class II elastics, and headgear during the treatment of Class II malocclusions is a common concern of many orthodontists. The MARS (Mandibular Advancing Repositioning Splint) is a functional device designed to overcome many such cooperation deficiencies. The MARS appliance is a fixed functional device which is attached to the arch wires of a multibanded orthodontic appliance. It is composed of a piston and cylinder which attach to the lower canine and the upper molar region of the dental arch wires on each side of the jaw. It forces the patient to maintain the mandible in a protruded position 24 hours a day and yet allows full and complete opening and closing as well as lateral excursive movement. The design, method of attaching, and adjustment of the appliance during treatment are discussed, and the results achieved in a single case are described. The results being achieved in the pilot study so far are encouraging and are being pursued further.

Surgical-orthodontic treatment planning for simultaneous mobilization of the maxilla and mandible in the correction of dentofacial deformities

Simultaneous mobilization of the maxilla and mandible is indicated for the optimal correction of specific dentofacial deformities, as discussed in the preceding publication. Because of the added complexity of this type of surgical-orthodontic treatment, it is important to determine the absolute need for surgery and to construct a detailed blueprint of the specific changes to take place at the time of surgical intervention as well as those to be made by the orthodontist prior to initiation of any treatment. The intent of this article is to describe a technique of treatment planning which includes cephalometric prediction tracings, model surgery, determination of orthodontic-surgical sequencing, splint construction, and specific sequencing of surgery. When followed, these guidelines will enable the surgeon and the orthodontist to accurately determine the need for simultaneous mobilization of both the maxilla and the mandible and provide more predictable and stable results when it is performed.

Anterior mandibular displacement and condylar growth. An experimental study in the rat

Anterior displacement of the mandible was produced in twenty-eight 1-month-old female rats by two methods: (1) cast-gold splints cemented to the maxillary incisor teeth and (2) a removable stainless steel mesh appliance worn 6 hours each day, during which time the animals were sedated. The controls were littermates without appliances and in the mesh group were also sedated. Animals in the splint group were killed after 24 hours, 1 week, and 1 month; those in the mesh group were killed after 24 hours and after 1 week. the condyles were removed and cultured for 24 hours in medium containing 3H-thymidine. One condyle from each animal was processed for routine histologic and autoradiographic study. The other was digested in phosphate-buffered saline containing RNA-ase and pronase, and the specific activity of 3H-thymidine incorporation expressed as dpm/microgramDNA. Anterior mandibular displacement produced by both methods failed to result in a significant increase in the incorporation of 3H-thymidine into explant DNA. In the 7-day mesh experiment, however, there was a significant increase in the DNA content of the condylar explants from the displacement group, suggesting an increase in the cell population. This finding should be treated with caution because of the small numbers of animals involved, but it indicates an important area for further study. Changes in the distribution of labeled cells within the proliferative zone (PZ) were also observed autoradiographically in the mesh group, but there was little to suggest that mandibular displacement was accompanied by a significant increase in cell division within the PZ. Remodeling changes affecting both the articular tissue and the subchondral bone were a characteristic feature of the 1-month bit plane group.

Skeletal profile changes related to two patterns of activator effects

A longitudinal cephalometric study was carried out on twelve boys and thirteen girls who initially exhibited Class II, Division 1 malocclusion and who were treated exclusively with activators. Twenty-four boys and fifteen girls, corresponding with the experimental subjects with respect to initial age and observation period, were selected as controls. The aim of the investigation was to examine cephalometric profile changes associated with two patterns of effects of activator treatment detected previously. The findings demonstrate that the two types of reaction bring about similar corrections of both apical base discrepancy and dental Class II relationship but clearly differ in their effects on the skeletal profile. Whereas the first type of reaction results in an improvement in mandibular retrognathism, a marked rotation of the occlusal plane, and good vertical control of the upper and lower dental arches, the second type is distinguished by a significant reduction of maxillary prognathism, downward and backward rotation of the mandible, and forward tipping of the lower incisors. Additional evidence presented further suggests that the two patterns of effects are due to differences in the construction bites of the appliances. According to this hypothesis, a great interocclusal height of an activator would lead to the first and a low construction bite to the second type of reaction.

The interplay between sagittal and vertical growth factors. An implant study of activator treatment

Changes in sagittal jaw relationship are dependent on an interplay between a series of basal and dentoalveolar changes in both sagittal and vertical planes. The present article uses the implant method to examine and discuss this interrelationship as well as condylar growth and, in addition, comments on the relative value of accepted methods of expressing sagittal jaw relationship. The interplay between vertical and horizontal dentoalveolar, sutural, and condylar changes occurring relative to the occlusal plane in nineteen patients treated by means of activator was studied quantitatively by means of the implant method. Changes in the sagittal jaw relationship were evaluated by means of the change in ANB angle and utilizing the "Witts appraisal" with a modified occlusal plane construction. Change in sagittal jaw relationship was studied by means of a correlation analysis and shown to be largely dependent on the spatial development of the mandible; the latter was positively correlated to vertical condylar development and maxillary horizontal development but negatively correlated to increase in vertical sutural and dentoalveolar parameters. Vertical condylar development was also demonstrated to influence the rotational pattern of mandibular development. The clinical importance of controlling vertical development, sutural as well as dentoalveolar, in the treatment of sagittal discrepancies was stressed through the findings of the present study.

Dento-facial orthopaedics in the correction of class II malocclusion

An orthopaedic appliance system has been developed with the specific therapeutic intention of removing those factors responsible for the initiation or maintenance of the skeletal Class II malocclusion. This is accomplished by means of restraint and redirection of forward maxillary growth and induction of mandibular growth. Concurrently, adverse soft tissue influences are eliminated or ameliorated. Clinical and experimental evidence gives support to this concept and case histories show that clinical mode of use of the appliance system. An initial 10--12 month orthopaedic phase is followed by a second phase of similar duration, utilizing full Edgewise therapy to perfect the occlusion. The second phase is much reduced in complexity and is generally confined to alignment and final detailing as the essential corrections have been achieved in the orthopaedic phase. It is considered that this combined approach to Skeletal II treatment is more physiologic than conventional treatment and results in a better harmony of dental and facial features.

Morphologic changes in the sagittal dimension using the Fränkel appliance

Interceptive orthodontic treatment of four patients with the Fränkel appliance is presented. The Fränkel appliance is but one of many appliances available using the principle of functional jaw orthopedics. However, the Fränkel appliance seems to offer a broad range of potential corrections and appears worthy of consideration for early treatment by any orthodontist. The cases presented show various combinations of condylar growth, maxillary retraction, and dentoalveolar changes in the correction of Class II, Division I malocclusions with varying degrees of mandibular retrognathia. In all patients facial improvement was noted. Lateral expansion was also noted and offers another possibility in orthodontic treatment. It appears that the Fränkel appliance may be capable of taking advantage of three types of orthopedic correction: condylar growth, maxillary retraction, and lateral expansion. The possibilities of these changes occurring on a routine clinical level are discussed, and further studies of the Fränkel appliance are encouraged. It seems that, regardless of the orthodontist's choice of bands or bonds, the Fränkel appliance could be incorporated into any practice and offer potential orthopedic and/or orthodontic benefits for interceptive orthodontic treatment.

Correlations between orofacial muscle activity and craniofacial morphology in a sample of control and anterior open-bite subjects

In order to investigate the correlations between genioglossus, masseter, and orbicularis oris muscle activity and craniofacial morphology, an electromyographic and cephalometric analysis was undertaken on a series of twenty-four human subjects. The activity from the muscles was recorded during voluntary opening movements of the mandible monitored by an electronic transducer. A computer-based method was devised to calculate the threshold incisor-separation position corresponding to a 20 percent increase in base line muscle activity for each of the muscles. In addition, twenty-seven anatmoic points were digitized from lateral head films, and a computer-based cephalometric analysis was completed for each subject. A number of significant correlations were found between the threshold muscle values and the thirty-one linear and angular morphologic variables. Low threshold values for the genioglossus muscle were correlated with negative overbites, undererupted maxillary and mandibular incisors, and low total face heights. Low threshold values for the masseter muscle were also associated with low overbite measurements. In contrast, orbicularis oris muscle thresholds did not appear to be correlated with any of the craniofacial variables measured. This interdependence of tongue and jaw muscle activity and facial morphology suggests a contribution of the musculature to the development and/or maintenance of the dentition.

The dentomaxillary complex and overjet correction in Class II, division 1 malocclusion: objectives of skeletal and alveolar remodeling

In recent years it has become apparent that there are limitations to the amount of tooth movement that can be accomplished by alveolar remodeling. Retraction of the maxillary incisor teeth should therefore be avoided during overjet correction if penetration of the palatal alveolar cortex is a probability. Since the Class II, Division 1 phenotype is characterized by abnormalities in both dentoalveolar process and maxillomandibular reactions, trying to compensate for the skeletal discrepancy through alveolar remodeling alone does not have logic on its side. Indeed, treatment philosophies based entirely on a concept of alveolar remodeling cannot be justified on biologic grounds. The most reliable method of avoiding destruction of the palatal alveolar cortex during overjet correction is by means of headgear mechanics designed to produce clinically significant skeletal remodeling. This holds as a general principle, even where extractions are an essential part of the treatment program. Furthermore, because the facial skeleton responds to mechanical deformation more readily in the growing person, the policy adopted by many orthodontists of deferring treatment until the permanent teeth have erupted has little to recommend it.

The functional compensation: an interceptive procedure in the mixed dentition

Functional compensation, like the morphologic one which accompanies it, is to be encountered naturally in each system or organ. It facilitates the performance of the required activities in spite of the defectiveness of one or more of their biocomponents. If the pathologic forms of compensation or simply their perturbing effects are noticed early enough, deleterious and irreversible effects on growth and development of the orofacial zone may be avoided. Instead of simply supervising dental evolution or limiting intervention to early procedures (extractions) until the time for corrective treatment, we propose functional interception. Inducing a therapeutic compensation by removable appliances, this therapy aims to modify the equilibrium of displaying forces and to favor a more physiologic alveolar and sutural growth. The proposed appliances are able to intervene in the postural and dynamic position of the mobile organs in the oral cavity. They compensate their action; that is, they correct, complete, or replace it. The bimaxillary appliance is called bioactivator "biprax". Based simultaneously on the principles of the activator and bionator, it exploits a normal display of the two praxisms-speech and deglutition. Being worn day and night, it is able to guide efficiently the evolution of dental, alveolar, and even basal relationships. Its interceptive use does not interfere in any way with the onset of a corrective treatment in the adult dentition.

Treatment of class II malocclusions by jumping the bite with the Herbst appliance. A cephalometric investigation

The purpose of this study was to investigate the effect of continuous bite jumping with the Herbst appliance on the occlusion and craniofacial growth. The material consisted of twenty growing boys with Class II, Division 1 malocclusion. Ten of the boys were treated with the Herbst appliance for 6 months. The other ten boys served as a control group. Dental casts, profile roentgenograms, and TMJ radiographs were analyzed before and after 6 months of examination. The following treatment results were found: 1. Normal occlusal conditions occurred in all patients. 2. Maxillary growth may have been inhibited or redirected. The SNA angle was reduced slightly. 3. Mandibular growth was greater than average. The SNB angle increased. 4. Mandibular length increased, probably because of condylar growth stimulation. 5. Lower facial height increased. The mandibular plane angle, however, remained unchanged. 6. The convexity of the soft- and hard-tissue profile was somewhat reduced.

Morphologic evidence of muscle influence on dental arch width

Tests on hypotheses to explain changes in arch width during correction of distoclusion with the activator appliance used in this study showed that statistically significant increases occurred in both maxillary and mandibular arch widths during treatment. The increase was substantially larger in the maxilla than in the mandible. The arch width showed no statistically significant decrease after completion of treatment. The activator designed for this study affected orofacial muscle balance. The findings suggest that there were changes in the influence of tongue and cheek muscles on the maxilla. Available experimental as well as clinical data support the assumption that the tongue had taken a higher and more anterior position in the palatal area and that the tension of the cheek muscles was reduced relative to the posterior part of the maxillary dental arch.

The use of muscle forces by simple orthodontic appliances

Orthodontic appliances of simple construction have been described. They are valuable in intercepting the deforming action of perioral muscle function or malfunction. The same muscles that have the deforming potential may be enlisted to correct dental malocclusions. Early interception often prevents a problem of considerably greater magnitude at a later date.

A growth-related concept for skeletal class II treatment

The use of a combined activator--high-pull headgear appliance for treatment of Class II, Division 1 malocclusion is presented as a preliminary report. The activator itself is equipped with a palatal bar, lower lip pads, and torque-control auxiliaries for the upper incisors. The face-bow is mounted directly on the activator, and the extraoral force vector is equivalent to that of an anterior high-pull vector. During bite registration the veritcal displacement of the mandible is restricted to a minimum, and the anterior displacement should not exceed 6 mm. On the basis of current knowledge of the growth of the bony facial structures, treatment objectives and a specific approach for skeletal Class II correction are defined. Following these objectives, the therapy aims at correcting the malocclusion without diverting the anterior landmarks of the bony face from their specific lines of growth. This is brought about by the corresponding mechanics of the activator-headgear combination. The corrective effect of this appliance may be assumed to be the result of several different factors. The maxillary dentition is restrained in a posterior cranial direction, and an inhibitory effect on the maxilla counter to its line of development is attained. The mandibular dentition is influenced in an anterior downward direction by means of the bite registration, and the occlusion is unlocked during treatment. Any transfer of distally directed headgear forces from the maxilla to the mandible is prevented. Temporary stimulation of condylar growth, possibly combined with temporary posterior deflection of condylar growth, may also be induced. In this way it is possible to take maximum advantage of condylar growth in the sagittal dimension. Thus, not only is the malocclusion corrected but, at the same time, decisive profile improvement is achieved by anterior development of the mandible. From the experience gained so far with a Class II, Division 1 sample undergoing treatment with the activator-headgear combination, it would appear that skeletal control of the direction of facial growth during treatment is possible. A quantitative report on this group of approximately forty patients, some of whom are still receiving treatment, is in preparation.

The effects of orthodontic treatment on the skeletal pattern

This paper reviews the principal scientific investigations into the effect of orthodontic treatment on the skeletal pattern. Both animal experiments and human studies are considered, covering attempts to move the upper jaw posteriorly by extra-oral forces and to move the mandible anteriorly, by functional appliances, or posteriorly, by use of a chin cap. It is concluded that if such changes occur, they are small in amount and prolong the treatment time unduly.

The activator

The Harvold activator is described and its effects are explained.