The effect of heavy orthopedic forces on the maxilla in the growing Saimiri sciureus (squirrel monkey)

Maxillary dento-skeletal outcomes after orthopedic forward (class III) and backward (class II) traction in growing subjects

BACKGROUND

This retrospective study investigated the treatment effects produced by two orthopedic appliances, an extraoral orthopedic traction on Stephenson plate (SP) in skeletal Class II malocclusion and Delaire Facial Mask (FM) in skeletal Class III malocclusion.

METHODS

FM Group comprised 25 patients (13 males; 12 females, mean age 9.3 years, CS 1-2) undergoing Delaire Facial Mask therapy (mean treatment duration 1.5 years ± 1.2, 700-800 gr per side). SP Group comprised 24 patients (9 males; 15 females, mean age 10.5 years ± 1.9, CS 1-3) treated with extraoral orthopedic traction on Stephenson plate (mean treatment duration 1.6 years ± 0.8, 700-900 gr per side). For all subjects lateral cephalograms before (T0) and after (T1) therapy were obtained and traced. Descriptive statistics, t-test and Shapiro-Wilks test were calculated for each variable.

RESULTS

A mesial movement of the maxillary bone of 2.4 mm in the FM group and a distal movement in the PS group (0.4 mm) was found. SNA° was reduced 1.4° after SP and increased 0.7° after FM. The overjet decreased by 4 mm after SP, while it grew after FM by 2.4 mm, as well as molars relationships (4.5 vs. 0.8 mm).

CONCLUSIONS

Facemask induced greater skeletal movements than extraoral traction on Stephenson plate. PS produced a limited downward movement of the whole maxilla together with notable incisors and molars back corrections. Based on our results, it could be speculated that orthopedic mesial traction of maxillary bone may result easier than the distal movement.

Dental and skeletal components of Class II open bite treatment with a modified Thurow appliance

INTRODUCTION

Due to the lack of studies that distinguish between dentoalveolar and basal changes caused by the Thurow appliance, this clinical study, carried out by the School of Dentistry--State University of São Paulo/Araraquara, aimed at assessing the dental and skeletal changes induced by modified Thurow appliance.

METHODS

The sample included an experimental group comprising 13 subjects aged between 7 and 10 years old, with Class II malocclusion and anterior open bite, and a control group comprising 22 subjects similar in age, sex and mandibular plane angle. Maxillary/mandibular, horizontal/vertical, dental/skeletal movements (ANS, PNS, U1, U6, Co, Go, Pog, L1, L6) were assessed, based on 14 landmarks, 8 angles (S-N-ANS, SNA, PPA, S-N-Pog, SNB, MPA, PP/MPA, ANB) and 3 linear measures (N-Me, ANS-Me, S-Go).

RESULTS

Treatment caused significantly greater angle decrease between the palatal and the mandibular plane on the experimental group, primarily due to an increase in the palatal plane angle. ANB, SNA and S-N-ANS angles significantly decreased more in patients from the experimental group. PNS was superiorly remodeled. Lower face height (ANS-Me) decreased in the experimental group and increased in the control group.

CONCLUSIONS

The modified Thurow appliance controlled vertical and horizontal displacements of the maxilla, rotated the maxilla and improved open bite malocclusion, decreasing lower facial height.

Combining traditional techniques to correct anterior open bite and posterior crossbite

The treatment of anterior open bite often requires the use of skeletal anchorage to prevent excessive eruption of the posterior teeth and consequent downward rotation of the mandible. However, this procedure might not always be accomplished. This article reports the successful treatment of an anterior open bite and a posterior crossbite in a young boy, combining traditional techniques and involving high-pull maxillary traction to help growth to correct the skeletal Class II malocclusion without skeletal anchorage. The vertical dentoalveolar contribution of maxillary growth was also favorable to close the bite, whereas cross-elastics corrected the axial inclination of the mandibular posterior teeth, eliminating the inverted posterior crossbite. The open bite was completely closed with edgewise appliances, which also achieved normal overjet, intercuspation, and incisor exposure on smiling. Traditional mechanics for the treatment of open bite and crossbite remain a useful alternative when patients do not accept skeletal anchorage.

Effects on the maxilla and cranial base caused by cervical headgear: a longitudinal study

Objectives: The aim of this study is to test the possible orthopedic effects of cervical headgear on the cranial base and maxilla. Study design: a sample consisting of 79 subjects with skeletal class II malocclusion was divided into two groups. The experimental group was made up of 41 patients all treated with cervical headgear. The control group included a total of 38 non-treated patients. Each one of these groups was then subdivided according to age into one of three groups: prepubescent, pubescent or post-pubescent. Cephalometric parameters were compared in both groups in order to measure the cranial base angle and the vertical and sagittal position of the maxilla. Additionally, cephalometric superimpositions taken at the beginning and end of the study were compared. Results: results revealed significant differences in the cranial base angle and in the SNA angle (p<0.05). However, no differences were observed in the variables that measure the maxillomandibular relationship. While no changes were noted in the palatal plane slope, a flattening of the cranial base was found caused by the cervical headgear, in addition to a retrusion of point A that does not mean there was a reduction in the maxillomandibular relationship. Conclusions: cervical headgear treatment induces cephalometric flattening of the cranial base and a decrease of the SNA angle.

Key words:Orthodontics, cervical headgear, class II treatment, cephalometry, superimposition.

Molar distalization with a pendulum appliance K-loop combination

SUMMARY

The aim of this study was to evaluate the dentoalveolar effects of a pendulum appliance supported buccally by a K-loop, and to compare these with a cervical headgear (CHG) group. The records of 30 patients with skeletal Class I and dental Class II malocclusions were divided in to two groups: Patients in group 1 (seven females and eight males; mean age, 15.0 +/- 3.4 years) were treated with a pendulum appliance supported with a K-loop buccally, while in group 2 (10 females and 5 males; mean age, 14.2 +/- 2.9 years), the patients were treated with CHG. Standardized lateral cephalograms and study models were taken at the beginning of treatment (T0) and at the end of distal molar movement (T1). T0-T1 changes within the groups were analysed with a paired t-test, and between the groups with a t-test. The mean amount of distalization was 4.53 +/- 1.46 mm in group 1 and 2.23 +/- 1.68 mm in group 2. The mean amount of distal tipping for group 1 was 5.13 +/- 4.90 degrees; the mean amount of mesial tipping for group 2 was 0.80 +/- 2.27 degrees. Intrusion and mesiobuccal rotation of the maxillary molars were achieved in both groups. In group 1, the amount of labial protrusion and tipping of the maxillary incisors was not statistically significant. In group 2, palatoversion and retrusion of the maxillary incisors was statistically significant (P < 0.01 and P < 0.001, respectively). The two major disadvantages of intraoral appliances, which are distal tipping of molars and loss of anchorage at the anterior teeth, were significantly decreased with the use of a pendulum appliance K-loop combination.

Remodeling the dentofacial skeleton: the biological basis of orthodontics and dentofacial orthopedics

Orthodontic tooth movement is dependent upon the remodeling of the periodontal ligament and alveolar bone by mechanical means. Facial sutures are also fibrous articulations, and by remodeling these joints, one can alter the positional relationships of the bones of the facial skeleton. As might be expected from the structure and mobility of the temporomandibular joint (TMJ), this articulation is more resistant to mechanical deformation, and whether functional mandibular displacement can alter the growth of the condyle remains controversial. Clinical investigations of the effects of the Andresen activator and its variants on dentofacial growth suggest that the changes are essentially dento-alveolar. However, with the popularity of active functional appliances, such as the Herbst and twin-block based on 'jumping the bite', attention has focused on how they achieve dentofacial change. Animal experimentation enables informed decisions to be made regarding the effects of orthodontic treatment on the facial skeleton at the tissue, cellular, and molecular levels. Both rat and monkey models have been widely used, and the following conclusions can be drawn from such experimentation: (1) Facial sutures readily respond to changes in their mechanical environment; (2) anterior mandibular displacement in rat models does not increase the mitotic activity of cells within the condyle to be of clinical significance, and (3) mandibular displacement in non-human primates initiates remodeling activity within the TMJ and can alter condylar growth direction. This last conclusion may have clinical utility, particularly in an actively growing child.

The role of cervical headgear and lower utility arch in the control of the vertical dimension

INTRODUCTION

This study was carried out to evaluate the treatment changes in skeletal and dental parameters in growing patients.

METHODS

The sample consisted of 24 subjects with Class II Division 1 malocclusion. Half of the patients were treated with cervical headgear alone (group C, n = 12), and the other half received a combination of cervical headgear and lower utility arch (group CU, n = 12). The treatment groups were compared with a matched untreated control group (n = 12). The mean ages of the subjects at the beginning of the study were 8.85 +/- 1.19 years in group C, 9.23 +/- 0.76 years in group CU, and 8.62 +/- 0.78 years in the control group. The cervical headgear was used with an expanded inner bow and a 15 degrees to 20 degrees upward bend of the longer outer bow, worn 12 to 14 hours a day, with a force of 450 to 500 g per side. The lower utility arch was designed as described in the bioprogressive technique. Treatment changes were assessed on lateral cephalometric radiographs.

RESULTS

The cervical headgear produced Class II correction through maxillary orthopedic and orthodontic changes. Anterior face height increased more in the treatment groups than in the control group. The treatment groups also displayed statistically significant increases in ramus height. Due to these effects, mandibular plane orientation stayed relatively unchanged. There was no opening rotation of the mandible in the treatment groups. The lower utility arch produced intrusion and lingual tipping of the mandibular incisors and distal tipping without extrusion of the mandibular molars. The treatment groups showed significant anterior descents of the palatal plane. Maxillary molar total extrusion produced by cervical headgear treatment was an average of no more than 1 mm as compared with the control group. The utility arch did not appear to influence mandibular rotational response.

Modified Thurow appliance: a clinical alternative for correcting skeletal open bite

Open bite malocclusion is frequently discussed in orthodontics; diagnosis, treatment, and retention can be difficult because this malocclusion has numerous correlated etiological factors. The earlier this malocclusion is corrected, the better the prognosis will be, especially when the problem is skeletal. This article presents a patient with skeletal open bite who was treated in the mixed dentition with an orthodontic appliance that included an acrylic occlusal splint and an expansion screw, based on the original Thurow appliance, to guide the vertical force against the posterior teeth and the alveolar process.

Effects of cervical headgear and edgewise appliances on growing patients

Maxillary basal bone, dentoalveolar, and dental changes in Class II Division 1 patients treated to normal occlusion by using cervical headgear and edgewise appliances were retrospectively evaluated. A sample of 45 treated patients was compared with a group of 30 untreated patients. Subjects were drawn from the Department of Orthodontics, Araraquara School of Dentistry, Brazil, and ranged in age from 7.5 to 13.5 years. The groups were matched based on age, gender, and malocclusion. Roughly 87% of the treated group had a mesocephalic or brachicephalic pattern, and 13% had a dolicocephalic pattern. Cervical headgear was used until a Class I dental relationship was achieved. Our results demonstrated that the malocclusions were probably corrected by maintaining the maxillary first molars in position during maxillary growth. Maxillary basal bone changes (excluding dentoalveolar changes) did not differ significantly between the treated and the untreated groups. Molar extrusion after the use of cervical headgear was not supported by our data, and this must be considered in the treatment plan of patients who present similar facial types.

[A holographic study to demonstrate the initial displacements of a macerated human skull under the influence of the orthodontic force from headgear with traction in different directions]

The phenomena of maxillary displacement and the subsequent growth modifications which result from the application of orthopedic headgear traction are very complex and not yet completely understood. The aim of this study was to investigate with the help of holographic interferometry the influence of the headgear's differing traction directions on the initial bone displacement in the maxillary complex. 560 g high, straight, and low pull headgear traction exerted above, through, and below the center of resistance of the upper first permanent molars was simulated on a macerated human skull and skeletal changes were recorded by laser holography as they occurred. On the basis of the frontal and lateral holograms thus obtained, the initial displacement of the maxilla, zygoma, and zygomatic arch in both horizontal and vertical planes was evaluated. Substantial displacements in various parts of the studied structures, displacements such as bending, relative deformation, rotation, and translation, were detected, and, further, the direction of this complex displacement often deviated from the direction of the influencing force. The results obtained by this study indicate that the initial 3-dimensional skeletal displacements brought about by the headgear are very complex. The clinical implication is that they do not always correspond with the direction intended by the force applied.

Dental and orthopedic effects of high-pull headgear in treatment of Class II, division 1 malocclusion

In the present study a prospective cephalometric investigation was undertaken to examine the skeletal and dental effects of the high-pull extraoral appliance, when the resultant force was directed through the level of trifurcation of the maxillary molars. Twelve adolescent patients with Class II, Division 1 malocclusions were selected for the study. Each patient wore the headgear for a 6-month period, an average of 12 hours a day. A group of untreated adolescent patients with Class II, Division 1 malocclusions who were in a similar age range, as well as skeletal and dental characteristics were chosen as controls. Lateral cephalometric films were taken before and after the 6-month treatment period, and before and after the observation period in the control group of patients. Our data indicate that by directing the force of the headgear approximately through the center of resistance of the maxillary molars, it is possible to accomplish simultaneously a substantial distal movement of the molars (2.6 +/- 0.6 mm), as well as significant intrusion (0.54 +/- 0.54 mm). In addition, our results demonstrate that the applied force of 500 gm was sufficient to initiate maxillary orthopedic changes in the treated patients. These changes include relative restriction of horizontal and vertical maxillary growth, as well as distal movement (mean: 0.8 mm) of the maxillary anterior border in the treatment group relative to an untreated control group. Such orthopedic changes have been previously described only in association with much higher force levels.

Three-dimensional model of the human craniofacial skeleton: method and preliminary results using finite element analysis

The purpose of this study was to develop a three-dimensional finite element model of the craniofacial skeleton using a dry human skull. The model consisted of 2918 nodes and 1776 solid elements, and was used to investigate the biomechanical effect of a distally directed orthopaedic force on the craniofacial complex. The force was applied at the level of the maxillary first molar. The results indicated that in response to the force system applied: the nasomaxillary complex displaces in a backward and downward direction and rotates in clockwise sense; the nasomaxillary complex, including the zygomatic bone, experiences high stress levels in comparison with those at the remaining bones; the stress distribution in the maxillary basal bone area is relatively uniform; and the stress distribution across the opposing surface of the bony margins of the sutures is non-uniform.

Holographic and cephalometric study of the relationship between craniofacial morphology and the initial reactions to high-pull headgear traction

Eight macerated human child skulls with a dental age of approximately 9.5 years (mixed dentition) were consecutively subjected to an experimental standardized high-pull headgear traction system attached to the maxilla at the first permanent molar area via an immovable acrylic resin splint covering all teeth. This system produced tensile forces from 0.5 to 3.5 N (1 N = 0.10 kg) per side. Laser holography was used to measure displacements in a three-dimensional coordinate system. Displacements varied in direction. In addition, conventional cephalometric analysis of standardized lateral roentgen cephalograms was performed. Displacements and cephalometric data were then compared. Results indicate that the direction of initial displacements of bones of the facial skeleton bears a definite relationship to the morphology of the individual skull. In skulls with high divergency values (large angles, sella-nasion-occlusal plane, sella-nasion-mandibular plane), displacements are in a backward and posterior downward direction; in skulls with a small sella-nasion-occlusal plane angle, backward displacements occur in a direction almost parallel to the occlusal plane.

Intensive treatment of severe Class II malocclusions with a headgear-Herbst appliance in the early mixed dentition

In the correction of large sagittal discrepancies in the relationship between the maxilla and the mandible, the orthopedic effect of treatment is often of small magnitude when compared with the dentoalveolar changes. A group of patients with severe Class II malocclusions were treated to assess the effects of a therapeutic approach which specifically took into consideration important factors such as type of anchorage, amount of force, age at start of treatment, and intensity of treatment to obtain the maximal orthopedic improvement. A special headgear-Herbst appliance was designed and short intensive treatment, lasting 5 months, was performed in the very early mixed dentition. Comparison with an untreated control group revealed the dramatic effects of treatment. The overall average change in the sagittal relationship between the maxillary and mandibular teeth was 7.5 mm after active treatment. The posteriorly directed effect on the maxilla of 3.1 mm was due to a combination of distal movement of the dentoalveolar arch and of posterior translation of the basal portion of the maxilla. The anteriorly directed effect upon the mandible of 4.4 mm was due mostly to anterior movement of the basal part of that bone, with a small part resulting from labial movement of the lower incisors. This appeared to be the result of a stimulation of growth of the mandibular condyles, a change in mandibular morphology, and an anteroinferior change in position of the condyles with a possible anterior translation of the glenoid fossa. After a 10-month posttreatment period during which an activator was used during the initial 6 months, a new comparison between the treated group and the control group was made. Growth continued to the same extent in the treated group as in the control group. However, a tendency toward relapse in overjet of 2.3 mm was observed, leading to some modifications in the treatment approach in recently started cases. A short period of interceptive orthopedic treatment in the very early mixed dentition may be indicated to correct skeletal deviations and establish a normal relationship between the maxilla and the mandible. Treatment could then be followed by a period without appliance wear until final dentoalveolar adjustments, if necessary, are made in the permanent dentition.

Maxillary traction splint: a cephalometric evaluation

Orthodontists are particularly interested in knowing exactly what skeletal and dental changes are produced by headgear. With headgear and fixed appliances, part of the observed change is due to the headgear, part to the fixed appliances, and part to growth. Since the maxillary traction splint moves the teeth en masse, the dentoskeletal changes are due primarily to the headgear force. Selective mandibular dental changes can be produced by adjusting the mandibular occlusal contacts against the splint. In this study forty-seven patients with maxillary dentoalveolar protrusions and Class II, Division 1 malocclusions were treated with orthopedic headgear that attached to a full-coverage maxillary occlusal splint. Fifty-two patients were selected as a control for evaluation of growth changes versus treatment changes. Lateral cephalograms were taken before and after treatment, and the sagittal skeletal and dental changes were evaluated and quantified. The results of the investigation revealed (1) the establishment of a Class I posterior occlusion, (2) a significant overjet reduction, averaging 4.24 mm, (3) inhibition of vertical development of the maxilla and slight intrusion of the maxillary dentition, (4) overbite reduction by leveling of the mandibular dentition, (5) no indication that mandibular growth is accelerated, and (6) no significant increase in the mandibular plane angle. The maxillary traction splint is an effective means of correcting maxillary dentoalveolar protrusion in growing patients prior to fixed appliance therapy. The second phase of treatment with fixed appliances is necessary for individual tooth positioning and for detailing the occlusion.

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.

Primate models in surgical orthodontics

Between 1969 and 1980, 22 studies using nonhuman primates for experimental research in surgical orthodontics were published in the American Journal of Orthodontics, Angle Orthodontist, Journal of Oral Surgery, or International Journal of Oral Surgery. The most common species used was the rhesus monkey, Macaca mulatta. As laboratory animals, monkeys are relatively expensive and difficult to obtain. These problems have limited the design of experimental studies. Sample sizes are often too small for statistical analysis, control groups are small or omitted, and it has frequently been necessary to pool animals of different ages and sexes. These compromises might be appropriate if monkeys are the best available experimental model for humans, but there is little evidence that this is the case. Monkeys do not fill the usual role of good experimental models, which is to simplify a complex system. The monkeys used for craniofacial surgery have normal craniofacial function and morphology for their species, unlike human clinical patients. Cephalometric radiographs and skull measurements taken on monkeys of the five most common experimental species indicate that all experimental animals are much more prognathic than humans, and sex differences in prognathism are small. However, because many species have a large sex difference in canine size, females are a better experimental model than males for some questions. Considering recent federal legislative interest in animal research and the decreasing financial support for research, it is essential that the choice of experimental animals be justifiable and cost-effective. It would be worthwhile to consider alternatives to primates as the species of choice for experimental research in surgical orthodontics.

Postural response of the head to bite opening in adult males

The postural position of the head is a resultant of muscular interactions and reactions, influenced by gravity and functional demands. In order to investigate possible postural adaptation of the head to an altered functional status, a standard degree of jaw opening was produced by mechanical means in the mouths of thirty young males. There was an extension of the head associated with the jaw separation. In the majority of cases, a recovery to approximately the original posture resulted within 1 hour after removal of the bite-opening device.

Morphogenetic classification of malocclusion as a basis for growth prediction and treatment planning

This study has shown that the different groups, defined as morphogenetically homogeneous show homogeneity in several aspects. The individuals constituting a given group exhibit a peculiar pattern of craniofacial morphology, they grow alike and they seem to respond alike to a given type of treatment. Within the general frame defined by the group the occlusion seems to play an important role in the future development of the face. In this way the classification presented here is the first in the procedure leading to growth prediction and treatment planning. This classification also permits an analysis of the rotational pattern of the face and consequently allows one to pinpoint the 'failure' in facial growth more accurately. This should allow treatment to be more reliably matched to the growth pattern of the individual.

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.

The initial effects of orthopedic forces: a study of alterations in the craniofacial complex of a macerated human skull owing to high-pull headgear traction

The initial reaction of components of the craniofacial skeleton of a macerated human skull was studied after high-pull headgear traction. The applied forces were increased step by step from 0.5 N to 3.25 N per side (1N = 100 grams). Laser holography was used for measuring displacements in three dimensions in seventeen indicator points on the skull. These points were located near sutures or on the outer surface of individual bones. The skull was observed from the right frontal and from the left lateral side. Results indicate that displacements range from 0 micrometer to 17.0 micrometers, depending on force magnitude and on the location of the observed point. Individual components of the craniofacial skeleton were mostly displaced in a horizontal backward direction when the skull was viewed from the frontal aspect. Various compression and shearing patterns were observed in the craniofacial sutures, apparently depending on their spatial locations and intersutural surface morphology.

Biomechanical approaches to the study of alterations of facial morphology

An analysis of past experimental and clinical studies on orthopedic changes of craniofacial bones is presented. The theoretical aspects and technical improvements necessary for relating biomechanical principles to attain the desired alterations in craniofacial morphology are discussed. A critical evaluation of the past measurements and histologic techniques is also presented. Suggestions are given for directions to future research methodology which can offer reliable results.

Distal displacement of the maxilla and the upper first molar

Data from a sample of 198 Class II cases treated with various appliances which deliver distally directed forces to the maxilla were examined to determine the frequency of absolute distal displacement of the upper first molar and of the maxilla. Analysis revealed that such distal displacement is possible and that it is, in fact, a frequent finding following treatment. Long-range stability of distal displacement was not assessed.

The maxillary orthopedic splint

Craniomaxillary orthopedic correction of the skeletal imbalance of Class II malocclusions is often the desired method of treatment in these cases. The ability to apply a "pure" orthopedic force to the maxillary complex has so far eluded research efforts. However, the use of a maxillary splint with a high-pull extraoral traction assembly has been shown to be most effective in reducing Class II skeletal dysplasias through a combination of dentoalveolar and basal bone changes. Force delivery to the maxillary complex in Class II skeletal jaw disharmonies is through the teeth. The philosophy behind the use of the maxillary splint is that if the force delivered to the upper jaw involved the use of all the upper teeth (and hard palate) rather than only the maxillary first molars, as in conventional extraoral orthodontic therapy, the effect on the jaws would be more orthopedic than orthodontic in nature. The advantages of the use of the maxillary splint in the younger patient with a severe Class II malocclusion are that it reduces the vulnerability of the maxillary incisors to accidental fracture, while concomitantly reducing the Class II dysplasia, thereby effectively shortening the later-stage multiband corrective time and procedures. Further advantages of the maxillary splint described are ease of construction and clinical application, which makes it an attractive appliance for use in dental clinics or institutions in which patient volume, infrequent visits, and ecomomic factors are major considerations. This preliminary report on the philosophy of treatment procedure and description of the appliance design is to be followed by a further cephalometric and clinical evaluation of results achieved with its use.

Implantation of cranial base metallic markers in nonhuman primates

Cranial base metallic markers are useful in growth and developmental research on the nonhuman primate model. Metallic implants aid in superimposing serial cephalometric roentgenograms in the study of craniofacial changes. They also enable measurement of linear and angular changes in the cranial base. The design of a special implant gun is described in detail. A suggested technique for placement of tantalum markers in the cranial base of nonhuman primates is discussed.

Research on control of craniofacial morphogenesis: an NIDR State-of-the-Art Workshop

To assess the wide clinical ramifications of control of craniofacial morphogenesis, a State-of-the-Art Workshop was conducted by the National Institute of Dental Research at the initiative of Richard L. Christiansen, Chief of the Craniofacial Anomalies Program. In conjunction with the authors listed above, the format for the workshop was developed and participants were selected. The workshop was designed to provide an in-depth review of present knowledge and to identify future goals and directions for research on guiding, altering, and thus controlling growth and development of the cranofacial skeleton. The agenda for discussion ranged from molecular biology to clinical arts such as orthopedics and surgery. It was evident during the workshop that the mechanisms and procedures for controlling craniofacial morphogenesis must be derived from many biologic, physical, and clinical fields of knowledge. It is hoped that there will evolve an interdisciplinary clinical art which is aimed at preventing and correcting craniofacial deformities. Substantial biologic information has already been accumulated on the craniofacial skeleton. The clinical art of correcting malocclusion through mechanical forces is now applicable to the entire skull. The outstanding technical accomplishments of radical surgery in the correction of congenital craniofacial anomalies show that the needed surgical skills are now available. When these resources are combined, an area of knowledge and a clinical discipline which might be called "orthocephalics" is already identifiable. The workshop was held at the National Institutes of Health in Bethesda, Maryland, on Feb. 12 and 13, 1974. The ideas exchanged were integrated and summarized by the planning committee to produce this report.

Maxillary rotation during human growth: annual variation and correlations with mandibular rotation. A metal implant study

For a longitudinal study of the maxillary rotation, based on lateral headplates, a material of 22 patients with metallic implants in both jaws has been used. It has been established that the degree of maxillary rotation shows variations in direction and in intensity each year. It is smaller, in absolute value, than the degree of mandibular rotation. Due to the fact the direction of the maxillary and mandibular rotations are not always the same, it appears that the interaction between the maxillary and mandibular rotations plays an important role in the vertical and sagittal relationships of both jaws.

The effects of orthopedic forces on the craniofacial complex utilizing cervical and headgear appliances

1. A three-dimensional anatomic model of a human skull was produced with birefringent materials for photoelastic analysis. By means of photoelastic techniques during application of high-pull and cervical extraoral traction, stresses were visualized within the model. 2. Extraoral anchorage affected the position of the maxillary molar and its resulting alveolar development. Cervical headgear had a much greater tipping effect on the maxillary molar than did the high-pull headgear. Both appliances examined could produce stresses which may be transmitted to distant eraniofacial sutures. As opposed to high-pull traction, cervical pull in general stressed more areas and to a much greater degree. 4. The pterygoid plates of the sphenoid bone, the zygomatic arches, the junction of the maxilla with the lacrimal bone and the ethmoid, and the maxillary teeth were affected by both types of headgear. 5. Only cervical traction produced stresses at the frontal process of the maxilla and the Zygomaticofrontal suture. 6. There were two findings which had not been previously reported: First, cervical traction tended to open the palate in the posterior region. Second, high-pull traction produced compressive stresses at the junction of the right and left maxillae inferior to the anterior nasal spine.

Cephalometric roentgenography for nonhuman primates utilizing a surgically implanted head positioner

Cephalometric roentgenography in nonhuman primates requires more precise head positioning than that afforded by commonly used ear rod techniques. A standard cephalometric headholder was therefore modified and a technique was developed to implant an attachment that permit precise positioning of the head in all three planes of spce. This method has been used in 36 animals, and at 35 months postsurgery the implants have remained stable and tissue compatiblity is generally excellent. Roentgenograms obtained with this technique offer a high degree of accuracy in documenting growth changes and response to orthodontic treatment.