Prediction of mandibular growth rotation

Apertognathia (open bite) and its surgical management

The etiology, diagnosis, and management of apertognathia are reviewed. 2 apertognathia cases treated with LeFort I osteotomy and adjunctive procedures are presented.

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.

Angular distortion in the orthopantomogram

The orthopantomogram is in popular use in orthodontic diagnosis and monitoring treatment progress. Being a laminographic-type radiograph, its image suffers from a variable degree of linear distortion and this has limited its use as a research tool. A wire-mesh frame shaped to represent the curvature of the dentition in the jaws, with lead shots representing the long axes of the teeth as well as certain skeletal landmarks, was used to investigate the accuracy of projection of its structures on to the X-ray film of the orthopantomograph. Angular parameters were used to identify and assess both the magnitude and distribution of angular distortion of the radiographic image. The canine--premolar region of both arches expressed the greatest amount of angular distortion and variability. The third molar regions, together with the landmarks projected at a lower level on the radiograph, were the least variable. The applications and implications of the findings are discussed.

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.

Roentgen stereometry with the aid of metallic implants in hemifacial microsomia

Displacement of the mandible and the maxilla with growth in relationship to the frontal bone was recorded in eleven children with hemifacial microsomia, aged 3 to 14 years at the initial examination. The goals were to assess the efficiency of the method for accurate recording of articular growth and to obtain information on facial development in each of these children. Correction of the skeletal asymmetry was not attempted during observation periods of from 707 to 1,484 days. In continued observations three of the children were treated with functional appliances. Roentgen stereometry with the aid of metallic implants proved to be an efficient method for highly accurate recordings of articular facial growth in relationship to the frontal bone. Displacement of the jaws was asymmetrical in all of the examined children as determined in the frontal and transverse planes of the head. In about 50 percent of the children the degree of asymmetry increased in one plane while it decreased in the other plane. No correlation was found between the extent of the mandibular deformity, as seen on orthopantomograms, and the displacements of the mandible. Generally, the displacement of the maxillary bones corresponded with the displacement of the mandible. Articular growth of the jaws was redirected toward a more favorable pattern in two of the children during the time they used a functional appliance. In the third child the use of a functional appliance had no such effect.

A clinician looks at facial growth

George Northcroft, whom this Lecture seeks to honour, was, in his day, one of the leading dentists of this country and was internationally renowned. He founded the British Society for the Study of Orthodontics, and was its second President. Perhaps his most lasting contribution was one of his few publications, his contribution to the volume of Dental Board lectures which were published under the title The Growth of the Jaws, Normal and Abnormal, in Health and Disease. He clearly understood the importance to the practising orthodontist of a knowledge of facial growth, a belief which I share. The purpose of this paper is therefore to attempt to summarize and comment upon present knowledge and belief on this subject.

Hereditary factors in the craniofacial morphology of Angle's Class II and Class III malocclusions

We attempted to assess the role of heredity in the development of Angle's Class II and Class III malocclusions by comparing craniofacial morphologic differences between parents with Class II offspring and those with Class III offspring and by analyzing the parent-offspring correlations within each Class II and Class III malocclusion group. Lateral and frontal roentgenographic cephalograms were obtained for ninety-six patients with Class II malocclusion, 104 patients with Class III malocclusion, and their respective parents. Mean cephalometric profile diagrams were superimposed between the two groups of parents as well as between their offspring. Within the two groups, the parent-offspring correlation coefficients were computed for nineteen variables connecting cephalometric landmarks. The differences in the craniofacial complex were evident in the two groups of parents as well as in their offspring. High correlation coefficient values were seen between parents and their offspring in the Class II and Class III groups. Thus, there appears to be a strong familial tendency in the development of Class II and Class III malocclusions. We conclude that the hereditary pattern must be taken into consideration in the diagnosis and treatment of patients with these classes of malocclusion.

The use of the activator to achieve molar correction and accelerate lower premolar extraction space closure

A case is reported in which a modified activator has been used to correct a post-normal molar occlusion following removal of all four first premolars in a Class I (incisor) malocclusion

Intra- and interexaminer variability in head posture recorded by dental auxiliaries

Determination of the natural head position is essential in the esthetic assessment of the facial profile and could be of value in prediction of facial developmental trends. Recording of head posture has previously been performed in university clinics under experimental conditions. The purpose of the present study was to examine the reliability of a method that dental auxiliaries could use for routine recording of the natural head posture in children in an orthodontic clinic. The material comprised thirty orthodontic patients 6 to 15 years of age and recorded on two occasions 1 to 35 days apart. The auxiliary staff consisted of three different operators. The duplicate cephalometric head films were analyzed separately for the groups of patients recorded by each of the three operators. The data were also divided into one group recorded by the same operator and another group recorded by different operators at the first and the second occasions. No systematic difference between the first and the second recordings was found for the patients examined by each of the three operators or for the groups examined by the same or by different operators. The error of the method for the whole group was 2.3 degrees for the position of the head in relation to the true vertical (NSL/VER), 3.1 degrees for the cervical inclination (OPT/HOR), and 3.4 degrees for the craniocervical angulation (NSL/OPT). The method was found to yield sufficient reproducibility and is suggested to be of clinical value in the study of head posture in relation to orthodontic treatment.

Molar occlusion and mandibular rotation: a longitudinal study

The human dentition undergoes a process of complex development. Growth of the skeleton, morphology and function of the soft tissues (muscles in particular and airway), space considerations, and other factors influence the development of the dentition. The present study considered two of the factors involved: molar relationship in the sagittal plane and mandibular rotation. Forty-two persons from the Burlington sample were studied to determine whether changes in molar relation between the mean of ages 7 to 12 years were correlated with the rotational growth pattern of the mandible. The sample was divided into forward rotators (FR) and backward rotators (BR), based on the changes in the SN-corpus axis angle over time. The statistically significant difference of 4.04 degrees in change of the SN-CA angle over time, between the FRs and BRs, indicates that this method of characterizing the two different types of growers is useful. It is interesting to note, however, that the FRs and BRs, on an average, initially had the same SN-corpus axis angles. The molar relationship was determined on the basis of the cusp-fossa relationship in the sagittal plane. In the twenty-eight forward rotators and fourteen backward rotators the molar relationship did not change in a predictable fashion. Statistically significant correlations were not found between molar occlusion and growth direction patterns. Also, the SN-corpus-axis angle, at a single point in time, is not a good predictor of whether an individual is going to exhibit a forward or backward mandibular rotational growth pattern. The change in molar occlusion during the process of growth and development is a multifactorial phenomenon and cannot be predicted on the basis of the direction of mandibular growth rotation between the ages of 7 and 12 years.

Condylar development and mandibular rotation and displacement during activator treatment. An implant study

An analysis of the effects of activator treatment on the spatial development of the mandible over 11 months was performed via the metal implant method for a group of nineteen patients. A series of centers of rotation were derived, the position and effect of which are described and related to observed changes in basal and dentoalveolar structures and the development of the mandibular condyle. A posteriorly directed condylar development, in conjunction with an anterior rotational pattern, was found to be optimal if a basal Class II malocclusion is to be treated by means of a forward developmental displacement of the mandible.

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.

Deliberate surgical control of mandibular growth. I. A biomechanical theory

Basic descriptive principles governing mandibular growth have been discussed. These principles were applied to evaluate growth changes after mandibular advancement surgery in 15 patients with idiopathic mandibular retrognathism. Subsequent mandibular growth proceeded in a downward and backward direction in all cases. This pattern of growth is not seen normally in patients with a low or median mandibular plane angle type of facial morphology. Since the functional biomechanical vector of force in the condylar-ascending mandibular ramus complex was changed surgically, it is postulated that this affected the subsequent pattern of mandibular relocation. A hypothesis for the specific manner in which surgical alteration of the basic biomechanics of mandibular function can deliberately affect subsequent mandibular growth direction is presented. Case reports are used to illustrate these effects. Further animal and clinical studies are currently underway to better elucidate the hypothesis put forth herein.

Mandibular rotation and Class III malocclusion

The purpose of this investigation was to examine Class III cases with reverse overjet and low maxillo-mandibular planes angle, before, during and following treatment. Several methods, including Björk's structural method, are used to assess any rotation occurring and the effects of such rotation on vertical facial dimension and antero-posterior jaw relationship. From these observations comments are made on the possible existence of overclosure in these cases.

Cephalometric diagnosis and surgical-orthodontic correction of apertognathia

Nineteen postadolescent white woman with uncorrected Class I molar and/or canine occlusion were compared cephalometrically to thirteen postadolescent white women with skeletal apertognathia that was later corrected by a combination of surgical procedures, the common denominator being maxillary posterior superior repositioning. The cephalometric tracings were compared statistically by evaluating the study group preoperatively, immediately postoperatively, and at a long-term follow-up appointment. The results indicate that there is a statistical difference in certain important measurements between normal persons and preoperative apertognathic patients with the deformity identified in the dentoalveolar complex of the maxilla. Posterior maxillary superior repositioning tends to correct this skeletal deformity, with postoperative measurements approaching the normal values. The correction proved to be stable over a mean follow-up period of 19 months (range, 7 to 30 months).

Computer-aided head film analysis: the University of California San Francisco method

Computer technology is already assuming an important role in the management of orthodontic practices. The next 10 years are likely to see expansion in computer usage into the areas of diagnosis, treatment planning, and treatment-record keeping. In the areas of diagnosis and treatment planning, one of the first problems to be attacked will be the automation of head film analysis. The problems of constructing computer-aided systems for this purpose are considered herein in the light of the authors' 10 years of experience in developing a similar system for research purposes. The need for building in methods for automatic detection and correction of gross errors is discussed and the authors' method for doing so is presented. The construction of a rudimentary machine-readable data base for research and clinical purposes is described.

The dentoalveolar compensatory mechanism: background and clinical implications

The present paper aims to survey the background and clinical implications of the dento-alveolar compensatory mechanism by which the teeth and alveolar arches are adapted to the varying jaw relationships. The background, a large individual variability in the growth pattern of the jaws, is presented in some detail. The operation of the system is described, and possible underlying factors outlined. The relation to the development of malocclusion is analysed, and some consequences for the interpretation of cephalometric analysis systems and for orthodontic treatment planning are discussed.

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.

Growth influence on tubal function

The influence of growth on tubal function was studied in 26 children by means of tubal function tests in a pressure chamber and by geometric analysis of lateral cephalograms. Good tubal function coincided with mesoor brachycephalic skeletons, poor tubal function with dolichocephalic morphologic patterns. According to our results, tubal function seems to be strongly influenced by the growth processes of the skull.

The current status of facial growth prediction: a review

Facial growth has an important bearing on orthodontic treatment and on its stability. However, despite much research in this field, the prediction of facial growth is subject to considerable inaccuracies. The best that can be done is to base treatment on the existing facial pattern with an allowance for average growth according to age and sex. In view of the uncertainty of prediction, treatment planning should be based on facial and dental relationships that change least with growth.

Landmark identification accuracy in xeroradiographic cephalometry

Identification accuracy of fourteen cephalometric landmarks was compared between xeroradiographic cephalograms and conventional cephalograms. Four landmarks--point A, upper incisor tip, infradentale, and menton--were more accurately determined on the xeroradiograph, while two landmarks--point B and condylion--were more accurately determined on the conventional cephalogram. Although not conclusively demonstrated in this study, the xeroradiograph does appear to offer more clarity and detail than the conventional cephalogram. Further investigation of this new diagnostic medium will be necessary before its true significance to dentistry can be evaluated.

Effects of cervical anchorage during and after treatment: an implant study

Two groups of ten patients with postnormal molar relation, identical as regards facial morphology and dental stage, were treated for 8 months with cervical traction of the Kloehn type. The extraoral arch of the headgear was tilted upward in relation to the occlusal plane in one group and downward in the other. The local tooth movements were measured and related to metal implants inserted in the jaws. The movement of the implants in relation to the anterior cranial base expressed the amount and direction of the sutural and condylar growth. It was shown that a normal molar relationship was established in the shortest time with a downward tilt of the extraoral bow. A pronounced distal tipping of the molars was observed in these patients. The growth direction of the maxilla during cervical treatment was downward and backward and the mandible rotated posteriorly. The children were observed again 7 to 8 years after treatment, and it appeared that the influence of the headgear on the growth pattern of the facial skeleton was reversible, as a pronounced anterior direction of growth of the maxilla as well as of the mandible was observed in all but two subjects.

A remarkable spontaneous occlusal change

A case is described in which an overjet reduced spontaneously from 9 mm to 5 mm without orthodontic treatment.