Search

The purpose of this research was to determine the reliability and validity of selected clinical judgments of malocclusion, including general evaluations of occlusal status and more specific aspects of dentofacial malrelations. Study casts of twenty-one adolescents planning orthodontic treatment and twenty-nine not planning treatment were examined and rated. The examiners were five dentists in an orthodontic specialty-training program. They completed ratings on six dimensions: (1) need for treatment, (2) degree of malocclusion, (3) potential for tissue loss, (4) negative effect on occlusal stability, (5) negative effect on dental-facial attractiveness, and (6) negative effect on masticatory function. Six weeks later the same five rates scored the fifty casts, using the standardized Treatment Priority Index (TPI). Three weeks later, or 9 weeks after the initial ratings, the casts were again rated on the two general dimensions: need for treatment and degree of malocclusion. Correlations among all the measures were examined. Inter-rater reliability was highest for the ratings of impact on dental-facial attractiveness (r = 0.88). The two general assessments also yielded relatively high rater reliabilities, and the second rating yielded stability coefficients of 0.84 for both of these ratings. Correlations with total TPI scores were 0.70 for the dental-facial attractiveness measure and 0.65 and 0.64, respectively, for assessments of need for treatment and degree of malocclusion. The data indicate that clinical evaluations of the severity of malocclusions are comparable to objective measures in terms of inter-rater reliability. Clinical evaluations are also relatively stable over time. Correlations with the TPI scores also provide evidence of the concurrent validity of clinical judgments.

Cephalometric analyses based on angular and linear measurements have obvious fallacies, which have been discussed in detail by Moyers and Bookstein. However, the clinical application of such an analysis by the orthodontic profession in treatment planning is widely accepted. Variations of angle ANB are commonly used to determine relative jaw relationships in most of the cephalometric evaluations. Several authors, including points A and B influences angle ANB, as does rotational growth of the upper and lower jaws. In addition, the authors point out that growth in a vertical direction (distance N to B) and an increase of the dental height (distance A to B) may contribute to changes in angle ANB. For a Class I relation (Wits = 0 mm), a mathematical formula has been developed which enables the authors to study the geometric influence of angle ANB caused by the following four effects: (1) rotation of the jaws and/or occlusal plane relative to the anterior cranial base; (2) anteroposterior position of N relative to point B, (3) vertical growth (distance N to B); (4) increase in dental height (distance A to B). It was observed that, contrary to the common belief that an ANB angle of 2 +/- 3.0 degrees is considered normal for a skeletal Class I relation, the calculated values of angle ANB will vary widely with changes in these four controlling factors under the same skeletal Class I conditions (Wits = 0 mm). Therefore, in a case under consideration, angle ANB must be corrected for these geometric effects in order to get a proper perspective of the skeletal discrepancy. This is facilitated by comparing the measured ANB angle with the corresponding ANB angle calculated by a formula for a Class I relationship. The corresponding calculated angle ANB can be taken from the tables which are based upon the formula using the same values for SNB, omega (angle between occlusal plane and anterior cranial base), b (which is distance N to B) and a (dental height measured as perpendicular distance A to occlusal plane plus perpendicular distance occlusal plane to B). The difference between actual and calculated angle ANB is a measurement of the severity of the skeletal discrepancy. This leads to a new definition of what denotes skeletal Class II and III relationships, since and angle ANB calculated for a skeletal Class I (Wits = 0 mm) can vary widely and can be either negative or positive.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

It is often claimed that occlusal variation ("malocclusion") is under strong genetic control. This study of a large age-standardized series of families (parents and offspring) shows that the genetic contribution to occlusal variation is quite low. On average, only about 10 percent of the variation in overjet, overbite, crowding, tooth rotations, and molar relationships results from nonenvironmental causes. In contrast, about 60 percent of the variation in measurements of arch size and shape is attributable to heredity.

A previous report describes the reliability and validity of a scale designed to assess perceptions of dental-facial attractiveness, independent of occlusal function. The purpose of the present study was to assess the consistency of judgments of dental-facial attractiveness (DFA) for sex and race differences in photographed children. Using a five-pont DFA scale, twelve college freshmen (three black females, three black males, three white females, three white males) rated ninety-six photographs of the mouths and jaws of 13- to 14-year-old children (twenty-four black females, twenty-four black males, twenty-four white females, twenty-four white males). No significant mean differences were found between the black and white photographed or between the female and male children photographed. However, means were significantly different for DFA judgments by race and sex of the raters. Black raters judged all photographs to be more attractive than did white raters, and female raters judged all photographs to be more attractive than did male raters. Correlational data are presented describing consistency of perception within rater groups and photographed groups of children.

The periodontal health of a group of ninety-six patients who had received comprehensive fixed-appliance orthodontic treatment during adolescence between 12 and 35 years previously was evaluated. Comparisons were made with a group of 103 adults who were similar with regard to race, sex, age, socioeconomic status, dental awareness, and oral hygiene status but had malocclusions that had not been orthodontically treated. There were no statistically significant differences in the general prevalence of periodontal disease between the two groups. However, more detailed analysis revealed that the orthodontic group had a greater prevalence of mild to moderate periodontal disease in the maxillary posterior and mandibular anterior regions of the mouth, as compared to the control group. The results suggested that orthodontic treatment in adolescence is not a major factor in determining the long-term periodontal health status. No significant amount of either damage or benefit to the periodontal structures could be directly attributed to orthodontic therapy. Conversely, the lack of orthodontic therapy in adolescence does not appear to influence subsequent development or nondevelopment of periodontal disease in adults.

The authors discuss the influence of mandibular displacement in intercuspal position (ICP) on orthodontic planning and treatment. The correct therapeutic position in orthodontics should be assessed on the basis of clinical and radiographic parameters. Posteroanterior cephalograms can be of great diagnostic value; deviation from the norm of some measurements is highly indicative of a mandibular displacement in ICP. A repositioning occlusal splint is then constructed in the therapeutic position before the definitive orthodontic treatment is started; the splint should lead to improvement of the clinical and cephalometric data.

1. Four arch length prediction equations (Nance, Johnston-Tanaka, Moyers, and Hixon-Oldfather) were compared by examining pretreatment casts, pretreatment intraoral radiographs, and posttreatment casts of forty-one patients of mixed-dentition age. 2. A comparison of correlation coefficients and slopes of the predicted arch length versus the actual arch lengths revealed that the Hixon-Oldfather method conformed closest to the ideal. 3. No combination of the four methods produced a more accurate equation than the single most accurate method. 4. Neither the sex of the patient nor the type of occlusion affected the prediction accuracy of any of the four equations. 5. All methods tend to overpredict the arch length size by 1 to 3 mm., with the exception of the Hixon-Oldfather equation, which underpredicted by approximately 0.5 mm. 6. An analysis of the intrainvestigator error showed a very low standard error of estimate for individual tooth measurements and for the prediction values. 7. A variance analysis showed that most of the variation was due to arch length (85%), a slight amount was due to the prediction method (8%), and 6% of the variation was due to the rater. 8. A low correlation was found between space available versus actual discrepancy and space available versus actual arch length. 9. High correlation coefficients were found for the predicted arch lengths when compared with the actual arch lengths. As expected, the correlation coefficients for the predicted widths of only the canines and premolars compared with the actual widths were not quite as high.

A quantitative method of assessing mandibular anterior irregularity is proposed. The technique involves measurement directly from the mandibular cast with a caliper (calibrated to at least tenths of a millimeter) held parallel to the occlusal plane. The linear displacement of the adjacent anatomic contact points of the mandibular incisors is determined, the sum of the five measurements representing the Irregularity Index value of the case. Reliability and validity of the method were tested, with favorable results. At the University of Washington, several clinical studies have been and are continuing to be performed, using this technique as one of several methods of assessing pretreatment status and posttreatment change. It is hoped that this article will aid the reader in understanding the rationale and utility of a simple quantitative tool which could be used in malocclusion assessment.

Cephalometric tracings of twenty-seven untreated adult Caucasians, selected on a clinical impression of reduced lower facial height were studied and compared with tracings of nine untreated adult Caucasians with increased lower facial height. Various linear and angular measurements for both groups were analyzed and compared. As has been previously described for the SFS, the LFS group can be subdivided into at least two subtypes. Subtype I is characterized by a long ramus, increased OP-PP, an increased SN:MP-angle, and excessive lower anterior facial height. These persons manifest the most typical clinical characteristics of the long face syndrome and have excessively long faces. In Subtype II, however, extreme backward and downward rotation of the mandible, combined with a short or extremely short ramus, is associated with an increase in lower anterior facial height. The increase in posterior maxillary height was not striking in this subtype. It was demonstrated that many of the characteristics of the LFS group and the SFS group can be explained by clockwise or counterclockwise rotation of the mandible "in concert" with the hyoid, tongue, pharynx, and cervical spine. The LFS group was characterized by a clockwise rotation of the mandible "in concert" with the hyoid, tongue, pharynx, and cervical spine. The mandible of the SFS group rotated similarly, but in the opposite counterclockwise direction. The vital need to maintain patency of the upper airway at the level of the base of the tongue may account for rotation in the LFS.

Posttreatment occlusion following orthognathic surgery is often different from that predicted in the treatment plan. Differences between intended and actual occlusion may be treatment-induced occlusal errors caused by mismatches between the centers of rotation of the mandible and of the articulated models. Discrepancies in the position of the articulator center of rotation (relative to the position of the center of rotation of the patient's mandible) influence the magnitude of occlusal errors. A computer model was developed to quantify these errors. As the center of rotation of the articulated models becomes more divergent from the patient's center of rotation, the magnitude of the occlusal errors increases. This magnitude increases most rapidly along the line that is perpendicular to the line joining the patient's center of rotation and a preselected mandibular landmark (incisor tip or molar cusp, for instance). For small changes in vertical dimension, clinically insignificant errors result, independent of the degree of mismatch between the centers of rotation. Clinical implications of these findings are discussed.

1. Most open-bites are deficient in growth of the upper face and in growth of the posterior face. However, some varieties have adequate posterior face height. A compensatory increase in lower anterior face height occurs in both types. 2. The ratio of upper anterior face height to lower anterior face height (UAFH/LAFH) is suggested as an aid in determining the prognosis for the orthodontic correction of anterior open-bite. 3. The treatments of eight patients were presented to illustrate this concept. The results were critically analyzed. 4. The validity of this index can be determined only after prolonged use by many orthodontists.

Several reports have suggested that orthognathic surgery may influence speech patterns. The purpose of this study was to examine the formant frequency changes of speech following orthognathic surgery in patients whose speech was considered perceptually normal preoperatively and postoperatively. Speech samples were obtained from five patients (three patients with Class II, Division 1 malocclusions and two patients with Class III malocclusions). Significant second-formant frequency shifts were found for the vowel 'e' (as in 'seat'); however, only minor second-formant frequency variations were found for the vowels 'a' (as in 'sat') and 'u' (as in 'suit'). The pattern of formant frequencies before and after surgical treatment suggested that the speakers adjusted their articulation to accommodate the orthognathic surgery. Overall, the data from this study indicate that speech patterns may be reorganized after orthognathic surgery even though speech remains perceptually "normal."

Lateral cephalograms of sixty patients with open bite and sixty untreated subjects who were determined clinically to have Class I normal occlusions were studied. The following six values were recorded: (1) ratio of posterior to anterior face height, (2) ratio of upper to lower face height, (3) Sn GoGn angle, (4) gonial angle, (5) SN-PP angle, and (6) PP-GoGn angle. Results were compared with previous studies. The constancy of the ratios and angles with age was tested and an attempt was made to separate the open-bite sample into skeletal and dentoalveolar groups. Results were generally consistent with those reported previously, except for the Sn PP angle, which was not significantly different from the normal group. In the open-bite sample the study showed a decrease in the ratio of PFH/AFH, a decrease in the ratio of UFH/LFH, and an increase in the other angles measured. Upon further division of the sample into mixed- and permanent-dentition groups, it was found that the angles and ratios remained relatively constant with age. An attempt to divide the open-bite sample into skeletal and dentoalveolar groups resulted in more extreme values for all the measurements made. The difficulty in differentiating between the two groups and the variability of dentoskeletal patterns in open bite is discussed.

In general orthopedics the relationship between postural behavior and skeletal deformities has long been recognized. The primary therapeutic problem in functional orthopedics is to overcome functional disorders. In this article the applicability of this functional concept to orofacial orthopedics is discussed on the basis of a longitudinal study of skeletal open bite. A comparison of a series of lateral cephalograms of thirty patients with skeletal open bite who were treated with functional regulators developed by Fränkel and those of eleven untreated open bite cases suggests that some dentofacial deformities in the skeletal open bite cases can be corrected to the average norms. In addition, as a result of overcoming the poor postural pattern of the orofacial musculature and re-establishment of a competent lip seal, a considerable change in the soft-tissue profile occurred.

In order to identify associations between the orientation of the superficial masseter and temporalis muscles and dentoskeletal morphology in a sample of fifty-five children with various malocclusions, eight muscle-orientation variables (relative to the occlusal plane) and twenty-three dentoskeletal variables were evaluated from lateral head films. The thirty-one measurements were reduced to six muscle-orientation and sixteen dentoskeletal variables by a principal component analysis. Three canonical correlations were identified between the muscle orientation and dentoskeletal variable groups at the 0.05 level of significance and canonical loadings were determined for each set of variables. The first canonical correlation (r1 = 0.931) represents a growth-related correlation factor between the masticatory muscle insertion positions relative to the occlusal plane and the dimensional and positional changes of craniofacial structures during growth. The second canonical correlation (r2 = 0.846) may account for an operational artifact in the geometric measurement process, and the third canonical correlation (r3 = 0.813) suggests an association between superficial masseter muscle orientation relative to the occlusal plane and mandibular form. This report confirms the usefulness of multivariate statistical methods to extract latent associations between muscle orientation and craniofacial morphology; the results obtained suggest a contribution from the geometric orientation of the masticatory muscles to the development and maintenance of the dentoskeletal system.

This article investigates the relationship of skeletal facial pattern and soft-tissue nasal form. The case sample comprises 123 white female subjects, aged 11.0 to 20.6 years, with no histories of pathology, trauma, surgical intervention, or orthodontic treatment. Measurements were made from cephalometric radiographs, posteroanterior radiographs, and the physioprint photographs. Skeletal classifications were based on the relationship of the maxilla to the mandible; the three classifications were straight profile, retrusive chin profile, and prognathic profile. Pearson product--moment correlation coefficients were used to test intercorrelations of all quantitative variables (including age) with each other. Correlations were highly significant for age, the three profile measurements, and two of the frontal measurements. Hence, noses and skeletal structures showed, as expected, increases with age. Also, profile measurements were highly significantly correlated; larger noses were larger in all profile dimensions. A stepwise discriminant analysis was used to study nonquantitative categories of nasal shape (straight, convex, and concave). This analysis indicated that more than 86% of patients in the sample of 123 demonstrated a correlation of nasal shapes with specific skeletal groupings. Patients with straight profiles tended to have straight noses; convex profiles accompanied convex nasal shapes; and concave profiles were found with concave nasal shapes. The clinical significance of this research is to emphasize the importance of total facial harmony (especially nasal shape) during orthodontic diagnosis and treatment planning.

A total of thirty-six Japanese adult subjects (consisting of eighteen men and eighteen women) with normal occlusion and harmonious facial features were subjected to cephalographic examination for the purpose of studying their soft tissues. Out of this group, twenty were selected and compared with twenty Class II, Division 1 and twenty Class III patients for the purpose of establishing an appropriate diagnostic guide for the Tweed triangle. These are our conclusions: 1. The Z angle of the Japanese subjects with normal occlusion was 69.70 degrees for the men and 71.75 degrees for the women. There is no significant difference between the sexes. 2. Although there are no significant differences between the sexes for the integumental and total chins, there is slight sexual difference for the upper lip measurement. 3. As compared to the subjects with normal occlusion, there is a significant difference for the Z angle of Class II, Division 1 and Class III patients. 4. In this study, the measurements of the Tweed triangle were FMA 27.28 degrees, IMPA 95.50 degrees, and FMIA 57.22 degrees. On the basis of this study and the reports of other Japanese investigators, we would like to suggest an FMIA of 57 degrees as being the most suitable basis for the diagnosis of Japanese patients, but this should be modified according to the FMA value.

The integration of the diagnostic and treatment skills of both the orthodontist and the maxillofacial surgeon has become a standard procedure in the treatment of severe dentofacial dysplasias. Orthognathic surgery, surgery without prior tooth movement, is being replaced by an interdisciplinary approach as the treatment of choice. When a proper tooth-to-denture-base relationship is obtained, an ideal maxillomandibular relationship can be achieved surgically. The quadrilateral analysis enables the practitioner to obtain an individualized skeletal, dental, and soft-tissue assessment of each patient requiring treatment. It determines the direction and extent of the skeletal dysplasia in millimeter measurements and allows the clinician to outline the appropriate surgical orthodontic procedures. The quadrilateral analysis indicates that in a balanced facial pattern a 1:1 ratio exists between the maxillary bony base length (Max.Lth.) and the mandibular bony base length (Mand.Lth.); also that the average of the anterior lower facial height (ALFH) and the posterior lower facial height (PLFH) equals these bony base lengths. Simply stated, the Max.Lth. = Mand.Lth. = (formula; see text) An accurate diagnosis locates the area and quantifies the magnitude of skeletal dysplasia. Then the correct placement of a dentition within the denture bases and the appropriate surgery in the area of dysplasia can produce an individualized, balanced facial pattern.

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.

The long-term stability of orthodontic treatment was evaluated in a group of ninety-six former patients who were treated between 12 and 35 years previously. Dental relationships were recorded on study models taken prior to orthodontic treatment, at the end of active treatment, and at long-term follow-up. A malocclusion score was developed for this study, and the over-all static occlusal relationships were categorized by defining an ideal range for eleven variables. Ninety of the ninety-six cases were within the ideal range at the end of treatment. Most of the cases showed an improvement of their malocclusions in the long-term stage. However, of the ninety-six subjects, sixty-nine (72 percent) had at least one variable outside our ideal range in the long-term follow-up. A moderately increased overjet and overbite was responsible in most instances for the result being outside the ideal range in the long term. The long-term result as compared to the original malocclusion exhibited increased overbite in 16 percent of the cases, increased mandibular anterior crowding in 9 percent of the cases, and increased overjet in 5 percent of the cases. The range of ideal, considering only the variables used in this study, will to some extent vary with the eye of the beholder. Therefore, the results of this study need to be interpreted accordingly. It is suggested that orthodontists be well aware of long-term changes in dental relationships many years after treatment and take this into account when advising patients as to the potential benefits of orthodontic treatment.

At the present time, periodontists have no evidence to indicate that orthodontic treatment in the child will either enhance or detract from the periodontal health of the patient or that it will increase or decrease the longevity of the teeth. Many periodontists believe that much orthodontic treatment is undertaken on an esthetic or empirical basis. Proper emphasis on plaque control procedures prior to initial banding, altered and reinforced during the entire period of orthodontic treatment, may well minimize the inflammatory lesion often found during therapy. Gingival, periodontal, and mucogingival problems should be treated as soon as they are diagnosed. Limiting our orthodontic objectives in adult patients because of the possibility of inducing supporting alveolar bone loss and other problems that did not previously exist may be a worthwhile compromise. Orthodontic movement in periodontally healthy adults, and especially in those with periodontally involved teeth, constitutes a problem distinct from routine orthodontics. When periodontal disease has already produced significant destruction of supporting tissue and secondary occlusal trauma is a complicating factor, orthodontic treatment may possibly serve as another mode of treatment to reestablish the correct occlusal plane and alter bony deformities. Various methods can be used to try and place teeth into better bone. One should make certain that teeth are being moved into a greater volume of bone. The bite plane is of great value in allowing continuous eruption of the teeth and their supporting structures and in eliminating additional trauma by enabling the teeth to move into their correct cusp-fossa relationships unimpeded by the inclined planes of the opposing teeth. Since little is known about the interrelationships between orthodontic treatment and periodontal health and disease, there is still a great deal to learn. In spite of this lack of knowledge, the general practitioners and the various specialists of dentistry, each seeking a rationale for his preventive and therapeutic procedures, subject the patient to treatment based on concepts of the occlusion which have yet to be corroborated. In addition to the need for research in this field, a common language between the periodontist and the orthodontist must be established to eliminate the existing communications barrier. Once basic principles can be determined, elucidated, and applied correctly, the movement of teeth in periodontal cases will be limited only by the imagination of the operator.

Assessment at least 10 years postretention of sixty-five cases previously treated in the permanent-dentition stage with first-premolar extractions, traditional edgewise mechanics, and retention revealed considerable variation among patients. The long-term response to mandibular anterior alignment was unpredictable; no variables, such as degree of initial crowding, age, sex, Angle classification, etc., were useful in establishing a prognosis. Typically, arch width and length decreased after retention, regardless of treatment expansion or constriction. Two thirds of the patients had unsatisfactory lower anterior alignment after retention. Cases that were minimally crowded before treatment usually became more crowded, while initially severe crowding cases usually moderated.

In a sample of children with dual bite and symptoms in the masticatory system, the activity of the anterior temporal and masseter muscles was studied electromyographically during clench and light tapping in the posterior occlusal contact position and centric occlusion and in protrusive bite on the incisors. The findings indicated that the optimal muscle function during maximal clench and tapping with displayed in the posterior occlusal contact position, which in the present subjects was situated, on the average, 0.5 to 1 mm. anterior to the centric jaw relation. It should therefore be recommended that, in orthodontic treatment of children with dual bite, the intercuspal position (centric occlusion) should be established in the posterior occlusal relationship. This is in accordance with the opinion of several authors who have emphasized the use of the retruded contact position (the centric jaw relation) as key reference position in orthodontic treatment and occlusal rehabilitation. These authors have further emphasized the importance of stable occlusal contacts in centric relation, centric occlusion, and the various jaw excursions in obtaining and maintaining a harmonious function between the dentition, the temporomandibular joints, and the neuromuscular system.

Forty-two cases of Class II, Division 2 malocclusions were selected on the basis of Strang's first six steps. There were nineteen male and twenty-three female patients in the study. The average age was 12.5 years. These cases were compared with the normal sample of the Alabama Analysis. The Class II, Division 2 sample was compared to a sample of fifty-seven Class II, Division 1 cases. Means, standard deviations, and analyses of covariance, adjusted for age and sex, were derived. Illustrations show, numerically and graphically, the similarities and differences between Class II, Division 2 malocclusions and normal occlusions. Fig. 4 shows the comparison between the Class II, Division 1 and the Class II, Division 2 typical profiles.

1. The AAO Handicapping Malocclusion Assessment Record (HMAR) was tabulated using 100 before-treatment records and dental casts of patients presenting with permanent dentition. 2. The 100-patient sample exhibited scores ranging from 52 points to 11 points. A cut-off point was established at 30 points. This divided the sample into two groups of fifty patients each. This hypothetic situation accepted for treatment those with the fifty highest scores and did not accept those fifty with the lowest scores. 3. The accepted group had 70 per cent skeletal malrelationships (Class II and Class III), while the nonaccepted group presented with 32 per cent skeletal discrepancies. 4. Maxillary incisor interarch deviations were found in 48 per cent of the accepted group but in only 12 per cent of the group not accepted. 5. Mandibular incisor interarch deviation (overbite) occurred in 6 per cent of the nonaccepted group and in 54 per cent of the accepted group of patients. 6. Four patients who required rapid palatal expansion and one who had undergone a mandibular resection were in the nonaccepted group. It was shown that if these patients were examined clinically using the Supplementary Oral Assessment Record, 19 their dentofacial deviations would merit 16 additional points and all five would be promoted to the accepted group.

This investigation was undertaken to examine the extent to which tooth size and jaw size each contribute to dental crowding. Two groups of dental casts were selected on the basis of dental crowding. One group, consisting of 50 pairs of dental casts (18 males and 32 females), exhibited gross dental crowding. A second group, consisting of 54 pairs of dental casts (24 males and 30 females), exhibited little or no crowding. Means and standard deviations of the following parameters were used to compare the two groups: individual and collective mesiodistal tooth diameters, dental arch perimeters, and buccal and lingual dental arch widths. Statistically, the crowded and noncrowded groups could not be distinguished from each other on the basis of mesiodistal tooth diameters. However, significant differences were observed between the dental arch dimensions of the two groups. The crowded group was found to have smaller dental arch dimensions than the noncrowded group. The results of this study suggest that consideration be given to those treatment techniques which increase dental arch length rather than reduce tooth mass.

The purpose of the study was to determine the nature and occurrence of bimaxillary protrusion in seventy-five students of the Faculty of Dentistry, University of Chiangmai, Thailand. The average age of the subjects was 22 years. Growth and development of facial dimensions were in a relatively stable configuration. Procedures included an evaluation of cephalographs, models, and photographs and an analysis of habits. A Steiner's analysis revealed the significance of the interincisal relationship for bimaxillary protrusion. In all cases the interincisal angle was below 124 degrees. In comparison with cases having an interincisal angle above 124 degrees, there was an increase in problems such as mouth breathing and tongue and lip habits, as well as a relative increase in tongue volume. Results of the study indicate that the etiology of bimaxillary protrusion is complex, involving environmental factors, soft-tissue function, volume, and habit.

The forming of arch wires is time consuming and often relies more on artistic interpolation than on scientific method, thus making the basis of orthodontic practice less precise. For years, various methods of designing arch wires have been tried and have been found inadequate. A new approach is advocated. Based on two decades of orthodontic practice and research, it elucidates a segment concept of arch pattern design, using three common reference measurements of the mandibular arch: canine width, molar width, and the sum of the mesiodistal diameters of the six mandibular anterior teeth. Normative data accumulated from 555 dental patients standardize basic measurements and variants. These data permit development of a finite number of arch patterns, adaptable to virtually all patients. A pattern, once selected, may be used as is or individualized to a specific arch form if necessary. Use of the segment concept might permit a much higher degree of clinical efficacy than that obtained with other methods of arch-wire construction.

Previous research into the origins of lower incisor crowding have not yet established the part played by skeletal morphology in its development. Longitudinal cephalometric records of twelve cases with spaced lower teeth were compared with those of twelve moderately crowded cases and twelve severely crowded cases. Significant differences were found between the three groups. These suggested that crowded cases are more likely to have larger Frankfort--mandibular and occlusal plane angles and shorter posterior face height and mandibular body. Both lower incisors and mandibular symphysis were found to be less protrusive in the crowded cases. During the period of study, from 8 years to 14 years, mandibular prognathism increased more in the spaced cases, although labial inclination of lower incisors increased less in these subjects.

Orthodontic extraction frequency describes the percentage of an orthodontic patient population experiencing extractions of one or more permanent teeth, excluding third molars. It is a useful statistical measure of the many variables associated with the extraction-nonextraction decision. For a study sample of 537 North American white orthodontic patients, the frequency of tooth extraction was determined as 42.1 percent. This is compared with a range of 6.5 percent to 83.5 percent reported in the world dental literature. Factors responsible for the enormous differences in orthodontic extraction frequency are explored. The study of extraction frequency offers a simple, valuable aid for the clinician to understand better the nature of his patient population, his treatment methods, and his rationalizations.

A new technique for accurately measuring tooth-to-arch-length discrepancies according to the ideal arch form is discussed. The armamentarium for making these measurements is explained, and the technique is demonstrated. Clearly, this is an important part of orthodontic diagnosis, and there is a need for greater accuracy than that which techniques of the past have made possible.

In order to overcome the reportedly undesirable side effects of using multilooped arch wires in initial stages of Begg mechanotherapy, a clinical study was conducted in which treatment procedure was modified for the mandibular arch in one group of patients, who received nonlooped or plain mandibular arch wires. This group was closely matched with respect to age, sex, severity of malocclusion, and particularly the amount of anterior mandibular crowding with a group of patients who received multilooped arch wires designed very closely according to the classically prescribed methods. Comparison of the two groups by means of cephalometric measurements of the mandibular incisors at the end of Stage I of treatment demonstrated that the IMPA increased significantly more (p = 0.01) in the multilooped arch wire group. The over-all treatment time was not significantly different in the two groups, although it took longer to resolve the anterior mandibular crowding when plain wires were used. On the basis of this study, it would appear that the use of plain rather than multilooped arch wires in the mandibular arch deserves a favorable consideration in early Begg therapy.

The dental models of seventy-seven orthodontically treated patients were evaluated to determine the contribution of lower incisor tooth dimensions to their alignment many years after treatment. Tooth dimensions included the maximum mesiodistal (MD) and faciolingual (FL) dimensions and the shape ratio represented by MD/FL. Incisor alignment was assessed by means of Little's irregularity index, and all measurements were recorded to the nearest 0.1 mm with modified dial calipers. Multiple regression analysis revealed that the total contribution of all these lower incisor dimensions accounted for only 7.4% of the variability in their alignment, which was not statistically significant. A similar lack of association between lower incisor tooth dimensions and their alignment was found in a sample of eighty-six adults with untreated malocclusions. It therefore appears that the size and shape of the lower incisors do not significantly contribute to their alignment many years after orthodontic treatment.

Class II, Division 2 malocclusions show several common characteristics. One of the features is the presence of a deep overbite ("deckbiss"), which can be the result of an excessive eruption of the maxillary central incisors. This study tested the theory that the deep overbite, together with the apparent entrapment of the mandible, may be partly due to the bending of the maxillary central incisors or the presence of the Collum angle. In a comparison between the group of patients with Class II. Division 2 malocclusions and the control group, it was determined that the former group exhibited significantly larger Collum angles than the latter group (p < 0.005). It is suggested that in describing the maxillary incisor angulation in this type of malocclusion, the long axis of the crown, rather than the long axis of the tooth connecting the incisal edge to the apex, be used as a measure of their position.

A vertical analysis involving ten linear measurements was developed to localize skeletal and dentoalveolar dysplasias. The measurements are of biologic relevance, reflecting the amount of growth harmony or disharmony to the examination and record-taking time. The vertical dimensional analysis uses the age- and sex-related University of Michigan mean values for comparative data for each measurement. Ratios were computed for a five-unit proportional analysis. Both analyses were applied to assess the vertical problems of three female patients. The analyses detected specific areas of dysplasia for each patient.

Fifty subjects with amelogenesis imperfecta were investigated clinically and with cephalometric radiography in order to determine the prevalence and nature of the anterior open-bite, which has been reported in association with these enamel defects. Anterior open-bite occurred in 24 percent of the subjects and was always associated with a severe discrepancy in the vertical relationship of the jaws. This vertical dysgnathia also occurred in a further 20 percent who did not have anterior open-bite. It is suggested that the frequent association of anterior open-bite and amelogenesis imperfecta is caused by a genetically determined anomaly of craniofacial development, rather than by local factors influencing alveolar growth.

Control of the transverse dimension through surgical techniques now available for use by the orthodontist is a valuable treatment consideration for orthodontic therapy in the nongrowing patient. In this article, proper diagnosis of relative and absolute transverse maxillary deficiency or excess is stressed as being imperative prior to completion of definitive orthodontic and/or surgical treatment planning. Therapeutic alternatives designed to facilitate correction of transverse discrepancies concomitant with treatment objectives in the sagittal and vertical dimensions are discussed and illustrated with case reports.

Aberrant functional patterns of the masticatory musculature have been alleged as a factor influencing the morphogenesis of mandibular dysplasias. These include such expressions as the hyperdivergent skeletal open bite and its counterpart, the hypodivergent skeletal deep bite. A lack of anatomic data dealing with the actual musculoskeletal orientations of these types has resulted in speculative reports on divergent anatomy and its purported effects. In this study anatomic dissections of a hyperdivergent and a hypodivergent human cadaver illustrated that skeletally dysmorphic types possess different spatial orientations of the masticatory adductors in relation to dentofacial structures. A two-dimensional analysis of static equilibrium using computer-aided modeling demonstrated that these two types produce biomechanically distinct modes of muscle action. Temporalis activity must be 40% higher in the hyperdivergent model as compared with its counterpart to produce a biting force of 500 N (112 lb). The data suggest a rationale for the weak biting forces previously reported in long-faced persons when compared with horizontally developed subjects. The direction of condylar reaction force was also found to vary from a vertical orientation in the hyperdivergent model to oblique in the hypodivergent model. "Physis-like" behavior of the condyle, which can orient axially toward loading forces, may present an explanation for the reported differences in the direction of condylar growth in dysmorphic persons. A finite element analysis pictured distinct regions of deformation and compression in a novel perspective to help evaluate the currency of accepted hypotheses of stress-induced osteogenesis. The data support previous work reporting a latent geometric interdependency existing between muscle orientation and mandibular morphology.

There must be a change in our approach to orthodontic diagnosis, especially in those cases involving skeletal dysplasias. The orthodontic practice of today requires a more in-depth diagnostic approach before a realistic treatment plan can be developed. An understanding of the problem that exists is emerging as the essential ingredient before appliance therapy can begin. Diagnosis should dictate the direction of treatment for both the orthodontist and the surgeon. A cephalometric analysis should be able not only to detect but to locate the area of the skeletal dysplasia. Surgery, if at all possible, should be performed where the problem exists. In many cases, it becomes rather confusing to determine whether or not surgical orthodontic treatment is indicated, because most of the cephalometric measurements that are used do not reveal whether a skeletal problem exists, its location, or its magnitude. We believe that current cephalometric analyses do not completely recognize the extent of the dysplasia or where it is located within the jaws. Because of this, surgery is performed by repositioning bones to mask the defect rather than to restore a normal balance between the bones of the face. The only recourse the surgeon has is to achieve an acceptable facial profile by relying on cephalometric norms or to make the necessary correction on what appears visually to be an acceptable profile. The quadrilateral analysis offers an individualized cephalometric diagnosis on patients with or without skeletal dysplasias. We believe that it is a reliable and accurate method of assessing whether orthodontic treatment, surgical treatment, or a combination of both is required to achieve a satisfactory result.

Orthodontists usually assume that genetic factors are of major significance to the development of malocclusion. Studies of twin similarities have lent support to this concept. Use of the twin model to estimate genetic variance, however, involves the assumptions that there are no mean or total variance inequalities between monozygotic and dizygotic twins. The environmental (including biologic) differences between monozygotic and dizygotic twin development may therefore constitute a source of bias. Genetic variance and heritability were estimated for a series of arch and occlusal traits in sixty twins using recently developed methods that are unbiased by variance heterogeneity between zygosities. Heterogeneity was demonstrated for twenty of the forty traits, suggesting considerable amounts of hidden environmental determinance. Tooth-displacement means differed between monozygotes and dizygotes, indicating bias in that trait's genetic variance analysis. Significant heritability could not be demonstrated for overbite, overjet, buccal segment relation, total tooth displacement, and occlusal discrepancies in arch shape. Arch size, individual tooth displacement scores, and cross-bite show significant genetic variance, averaging only about 36 percent of the total variance of these traits.

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).

This paper describes a method of cephalometric analysis which is currently used by the author in the evaluation and treatment planning of orthodontic and orthognathic surgery patients. In the analysis of a single film, the positions of the maxilla and mandible are related to cranial structures and to each other. Criteria for evaluation of the anteroposterior and vertical positions of the upper and lower incisors are provided, as is the documentation of the standards for each of the measures. In addition, the analysis of serial films is considered and a step-by-step outline of the cephalometric procedure is presented.

In the study of a sample of eighty 9- to 13-year-old subjects with Class I malocclusions, it was found that a clear relationship exists between the SNA and NSAr angles, which vary according to an inverse ratio. Their combined value, called the CV value, is often constant, near 204.5 degrees. The same holds true when the NSAr angle is larger or smaller than average, which suggests the hypothesis that when dealing with a sagittal malocclusion one should consider the CV value rather than a single angle.

Two patients with severe skeletal anterior open-bite have been presented. Treatment of these patients was accomplished mainly by mandibular repositioning (Case 1 by orthodontic means and Case 2 by a combination of surgery and orthodontics) and by an orthodontic change in the mandibular occlusal plane. A review and a discussion of the cause of this deformity were presented.

The effect of treatment with an oral screen was studied in sixteen children with incompetent lips who were compared with a control group of sixteen children who also had incompetent lips. The period of observation was 1 year. The treatment brought about retroclination of proclined maxillary incisors with a resulting decrease in overjet, in the diastema between the incisors, and in arch length. The mandibular incisors proclined somewhat. No change in general intermaxillary relation or in arch width was observed with the treatment. Neither lip morphology nor the electromyographically recorded function of the lips was affected by the treatment. The maximum force that the lips could exert to resist an external force was increased substantially by the treatment. Whether this is of value for the stability of the orthodontic treatment result is not known.