Cephalometric and clinical examination data from a group of 62 subjects with documented structural and functional changes in the temporomandibular joint were compared with that of a group of 102 subjects from a normative sample. The purpose of the study was twofold: to provide a description of a sample of subjects with documented TMJ alterations and to make cephalometric comparisons between this sample and a sample of control subjects from the general population. Results indicated an increased proportion of subjects with "high plane" characteristics and a decreased proportion of subjects with "low plane" characteristics in the experimental sample, but little or no differences in dental and occlusal parameters were found. There were no differences in the proportions or characteristics of subjects in any Angle classification group. There was a tendency, based solely on descriptive statistics, for the group of experimental subjects with negative trauma histories to exhibit an increased proportion of "division 2" incisal relationships.

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.

A system that uses stereophotogrammetry to semi-automatically generate three-dimensional facial soft tissue surfaces is presented. The basis of the system is the stereometric technique of Direct Linear Transformation (DLT) which is utilized to eliminate the elaborate instrumentation of present day systems. Automatic digitizing using a scanning image analyzer will require no hand digitizing, and a lightweight headframe will provide orientation information for use in evaluating facial changes. The system is computer based to provide graphic images of the resulting data to ease understanding and to provide the beginnings of a large data base concerning human facial form.

Elastic bonds used for orthodontic tooth movement without benefit of attached mechanisms have been shown to migrate apically, causing severe periodontal damage and eventual tooth mobility and tooth loss. The literature indicates high mortality rates for such involved teeth. A case report is presented, illustrating initial successful retention of teeth following surgical removal of a displaced elastic band. Cooperation between oral surgeon, periodontist, and orthodontist, in conjunction with high standards of oral hygiene by the patient, may lead to successful retention of otherwise condemned teeth. It is also suggested that elastic band therapy be carefully supervised when used to move teeth without controlling attachment mechanisms.

Several procedures were identified as important adjuncts to successful orthognathic results. Among these were the use of laminagraphic X-rays to monitor condyle displacement, condyle resorption and fibrous union problems. Other aspects involve gnathological errors in splint and positioner design, misdiagnosis because of a lack of soft-tissue analysis, differential treatment planning in deciding if surgery is needed, and understanding surgical effects on proportionality of the nose and lip esthetics.

Sophisticated treatment planning for those individuals with severe dental and facial disproportions requires accurate prediction of posttreatment results. Preand posttreatment cephalometric X-rays for a group of twelve patients treated by a combined orthodontic-oral surgical approach were evaluated. The surgery was of either the standard mandibular subapical osteotomy or Kole type of procedure. Surgical repositioning of the anterior mandibular alveolus resulted in various changes in hard tissue and soft tissue profile. In summary, these changes were: 1. Decreased lower facial height. 2. More relaxed lip posture as revealed by an increased superior vermilion lip length and decreased inferior vermilion lip length. 3. Stomion moved inferior and posterior relative to the lower facial plane. 4. Superior labial sulcus became less concave. 5. Inferior labial sulcus became more concave. 6. Superior vermilion and inferior vermilion moved posterior relative to the lower facial plane. 7. Chin radius and lip-chin-throat angle decreased. 8. Overbite and overjet increased while Wits analysis decreased. 9. Facial contour angle was unchanged. Changes were similar for both standard subapical and Kole groups with the main difference being a greater reduction in facial height with the Kole group.

Growth of the orofacial region is quantitatively described by locating the center of mandibular rotation relative to the cranial base. The center of mandibular rotation is positioned by the ratio of vertical facial growth (AFH/PFH) and the direction of condylar growth. Appliance therapy is associated with changes in the means of both of these parameters. These changes reduce or stop favorable anterior mandibular rotation and redirect the mean condylar growth vector more posteriorly. When appliance therapy is stopped, these parameters return toward their resting values. The mean direction of the condylar growth vector became even more anteriorly directed after treatment than the pretreatment mean value. These data support the hypothesis that orthodontic appliances significantly alter the facial growth pattern and when they are stopped, the growth pattern tends to rebound to or beyond the pretreatment values.

S tudies using cephalograms employ a method of tracing skeletal structures on a radiograph exposed at one time point, tracing these structures again on a second radiograph exposed at a second time point, superimposing the two tracings on some central reference point, and connecting presumed identical landmarks with a straight line .6p 6 This technique produces a self-fulfilling conclusion that the face and jaws grow downward and forward from beneath the cranium in a linear, translatory fashion. This perspective has influenced orthodontists to expect that the dental occlusion will also be carried in a similar, straight-line, downward and forward manner. Interest in vertical facial growth lead BjSrk,lv * Bjiirk and Palling,s Bjork and Skieller,4 e)degaard,*l-I2 Schudy,13-15 and Isaacson and associatess-lo in recent years to focus more attention on nonlinear jaw growth or jaw rotation. Jaw rotation was not recognized by early workers using cephalograms because of surface remodeling bone changes masking rotational effects as they occurred. This phenomenon of bone remodeling in jaws during normal growth has been carefully documented by BjSrk and Skieller,4 using metallic implants, and Enlow and Hunter,s using histologic techniques. Tooth movement also masked changes in dissimilar jaw growth by compensatory movements at the periodontal regions causing the occlusion to remain apparently in nearly constant relations.4 A recent report focused on a mechanism whereby vertical condylar growth can be converted into changes in anteroposterior jaw relationslo This mechanism explains how vertical condylar growth can, under specific conditions, result in significant anteroposterior dental and profile changes. According to this report, the long-held and widely reported concept of linear downward and forward facial growth is the exception rather than the rule. This report noted that, in order for translatory mandibular growth to occur, vertical

Thirty-six patients with orthodontically treated mandibular prognathism were recalled for cephalometric and clinical evaluation. A comparison group of 32 non-Class III patients was similarly examined. Analysis of variables associated with the anterior dentition and documentationtion of labial gingival recession and tooth mobility led to the following conclusions concerning the role of dental compensations in the orthodontic treatment of mandibular prognathism. 1. Vertical and horizontal dental compensations were quantitated in the dentition of the study group (pretreatment to postretention). 2. Increased labial gingival recession and increased tooth mobility in functional jaw positions were present in anterior maxillary and mandibular teeth of the study group relative to the comparison group. 3. Proper diagnosis and the establishment of realistic treatment objectives by clinician and patient are necessary to avoid undesirable sequelae and/or undesirable facial esthetics in the treatment of mandibular prognathism.

A Bolton analysis of seventy-eight cases of Angle Class III malocclusion, twenty-six cases of Angle Class I malocclusion, and twenty-six cases of Angle Class II malocclusion was recorded. Frequency of excess mandibular tooth structure, magnitude of the excess, over-all ratios, and anterior segment ratios were computed and analyzed. Two clinical cases were presented to show the advantage of tooth-size harmony in mandibular prognathism. Analysis of the data as presented above suggests the following conclusions: 1. The frequency of mandibular tooth-size excess (over-all ratio) in this sample was greater in cases of mandibular prognathism than in Angle Class I and Angle Class II cases. 2. In those cases with mandibular tooth-size excess, there was a suggestion that the magnitude of the excess was greater in cases of mandibular prognathism than in Angle Class I and Angle Class II cases. 3. A tooth-size discrepancy analysis should be included as one part of the diagnostic records for mandibular prognathism.

No Abstract Available. Read at the January, 1975 meeting of the Midwestern Component of the Angle Society.

1. Tooth movement relative to the alveolar bone can be precisely described only by superimposing on fixed points in the bone. Implants are the best known way today. Over short-term studies laminagraphy and the use of bony trabeculations are also useful. Remodeling occurs extensively on bony surfaces, making them too labile for use as stable landmarks. To project small amounts of tooth movement based on the use of such methods is so questionable as to represent little better than a guess or a clinical impression. 2. Growth can be separated into vertical and anteroposterior vectors with respect to the dentition. Since the occlusion is the concern, orientation of vertical and anteroposterior vectors to the occlusal plane is a reasonable baseline. The vertical and anteroposterior dental changes may not show a linear relationship in the anterior and posterior parts of the mouth when jaw rotations are occurring. 3. Growth can be disproportionate in either the vertical and/or the anteroposteroir plane of space. If the vertical increments of the anterior face differ from the vertical increments at the posterior face, mandibular rotations occur. This growth is accompanied by dental compensations that tend to mask the rotation. Therefore, open bite and deep bite are frequently skeletal growth problems. 4. Disproportional forward growth of the maxilla or mandible in an anteroposterior direction can lead to Class II or III relations. The growth that leads to Class II or Class III is accompanied by dental migrations that tend to mask this disproportionate growth. Orthodontic treatment of growth disproportionalities usually represents attempts to make the teeth further compensate. If surgical options are elected, the dental compensations should be removed prior to surgery in order to achieve a full surgical correction. 5. The teeth tend to move and grow in the opposite direction of the growth disproportionality. The teeth tend to mask the disproportionality. Thus, in an open bite, the incisors tend to move vertically further than in deep bites. Vertical imbalances may be more difficult to mask. Backward rotation of the mandible requires more vertical movement at the incisor than at the molar just to maintain vertical incisor relationships.

A 45-year-old woman presented with an anterior open-bite complaining chiefly of her unpleasant smile esthetics and masticatory and speech problems. Treatment included speech therapy initiated immediately after bonding. Lingual spurs were positioned on the mandibular incisors in order to help tongue rehabilitation. During the working phase, temporary anchorage devices (TADs) were used at the mandibular anterior segment to intrude the lower left premolars. A splint was used to ensure retention in the upper and lower arches; an enveloppe linguale nocturne (ELN) was provided. Non-surgical open-bite treatment could offer a valid alternative to orthognanthic surgery when cephalometric evaluation shows no vertical growth pattern; patient compliance is essential to prevent relapse.

Pont’s index is an average measurement for a group, and although it can be applied to all group members, it must not be applied to the individual. Participants in the study (Navajo males and females, and dental students) had ideal occlusions with crowding or spacing of less than 1 mm. The measurements of the interarch widths of the maxillary premolars and first molars were compared with those calculated with use of Pont’s index. Differences between the measurements ranged from −12.5 to +9.8 mm for premolar widths, and from −15.1 to +14.7 mm for the molar widths. In most participants, the observed measurements were less than the calculated ones. Differences were found between arch forms in males and females with similar Pont indexes.