Mandibular Deficiency Research Articles

Mandibular augmentation.

Porous polyethylene implants are available that are designed to augment the mandibular ramus and body. They can be used to increase the bigonial distance in patients with normal mandibular anatomy who desire an increase in lower facial width. When used in combination with extended chin implants, they can camouflage the skeletal contour inadequacies associated with class II mandibular deficiency. The implants are placed through intraoral incisions and fixed with titanium screws. In a clinical experience with 11 patients over 6 years, this technique has proven to be safe and effective.

Controlled multiplanar distraction of the mandible. Part III: Laboratory studies of sagittal (anteroposterior) and horizontal (mediolateral) movements.

Distraction osteogenesis has proven to be an effective technique for the correction of mandibular deficiencies. However, problems have been encountered in achieving a final, idealized form of the mandible when using distraction devices capable of moving the bone segments in only one dimension (uniplanar). Specifically, occlusal irregularities and deficiencies in lower facial contour have been seen following uniplanar distraction. To address these problems, a distraction device capable of independent movements in three planes (multiplanar) was developed. Previously reported studies in a canine model have demonstrated that this device can successfully distract the mandible along both the sagittal axis (anteroposterior or z-axis) and the vertical axis (superoinferior or y-axis). This study examines the ability of the multiplanar device to distract along the sagittal and horizontal axes (mediolateral or x-axis). A total of 12 dogs were included in the study. All animals underwent unilateral or bilateral mandibular distraction using an external multiplanar device. After a latency period of 5 days, primary distraction along the anteroposterior axis at a rate of 1 mm/day for 10 days (10 mm total) was performed. During the following 10 days, along with an additional 11 mm to 20 mm of anteroposterior axis distraction, concomitant secondary distraction was performed along the horizontal (mediolateral) axis at a rate of 5 degrees/day (50 degrees total). Cephalometric radiographs were obtained preoperatively and at the conclusion of both anteroposterior and combined anteroposterior-mediolateral distraction. Computed tomography (CT) scans were obtained preoperatively and at the end of consolidation (28 days), after which all animals were sacrificed and the dry skulls examined. In all animals, distraction along the mediolateral or x-axis was found to change the anteroposterior projection of the mandible. Varus angulation of the device with respect to the midline of the mandible caused compression of the distracted segments and reduced the anteroposterior thrust of the mandible. In contrast, valgus positioning of the device, with respect to the midline of the mandible, created the opposite effect, increasing the distracted length in the anteroposterior direction. The bone (mandibular) segments being distracted assumed the orientation of the device only for valgus positioning of the device (producing a decrease in the bigonial distance). Conversely, there was no effect from the mediolateral angulation on the distracted segments during varus positioning of the device. A possible explanation for this finding may be a greater resistance to an increase in the bigonial distance (varus positioning of the device) posed by obstruction of lateral movement of the condyle. This stands in contrast to a decrease in the bigonial distance observed following valgus positioning of the device. These findings confirm the clinical impression that distraction along the anteroposterior or sagittal axis remains the critical or keystone therapeutic maneuver in distraction of the mandible. Mediolateral or horizontal axis distraction is best used only as a supplementary movement; in essence, it only affects the anteroposterior dimension with little impact on clinically relevant changes to the bigonial distance.

Free fat transplantation for facial tissue augmentation

For maxillary and mandibular deficiencies of a primarily aesthetic nature, restructuring the soft tissues of the face with one's own fatty tissue has the potential to be a great tool for maxillofacial surgeons. In this article, Savastano and his colleagues attempt to demonstrate the potential applicability of fat grafting to the maxillofacial region. Even though the basic theories they propose have a somewhat sound basis, the actual procedure described and the cases presented do not follow these theories. Furthermore, the limited analysis of the few patients' results and the lack of clear documentation concerning these results make it difficult to be enthusiastic about their approach.

Model surgery prediction for mandibular midline distraction osteogenesis

Mandibular midline distraction osteogenesis is available as a treatment option for the correction of mandibular transverse arch deficiency. A model surgery technique is presented here through a case report that will allow the surgeon to predict the amount of transverse expansion that can be gained by this procedure. Utilizing measurements from a three-dimensional stereolithography model, the mandibular cast is mounted on a semi-adjustable articulator. The maxillary model is mounted onto the articulator using an interocclusal record. Acrylic straps are fabricated that relate the condylar elements of the articulator to the right and left mandibular dental segments. The mandibular model is sectioned at the midline, the hemi-mandibular segments are rotated laterally until the desired midline expansion is achieved and the mandibular model is luted into its new position. The post-expansion relationship of the maxillary and mandibular arches can be visualized on the articulator and provide useful information to the surgeon and orthodontist.

Mandibular lengthening using preprogrammed intraoral tooth-borne distraction devices

Purpose: This report describes the application of an intraoral device for treatment of malocclusions characterized by mandibular deficiency and the surgical technique for its placement. Patients and Methods: In an office setting, 5 retrognathic patients underwent mandibular lengthening via distraction osteogenesis with an intraoral tooth-borne distraction device. Under local anesthesia and sedation, mandibular corticotomies, mobilization, and placement of the distractors were performed. Preoperative, intradistraction, and postoperative dental casts, photographs, and cephalometric radiographs were used to analyze the results. Results: In 3 of the 5 cases, distraction occurred along the planned vector. The remaining 2 cases showed opening rotations of the mandibular anterior segment along with the advancement. Conclusions: This study documents that the mandible and the dental arch can be lengthened successfully using this technique.

Early decannulation with bilateral mandibular distraction for tracheostomy-dependent patients.

Obstructive sleep apnea in the neonatal period may originate from a hypoplastic mandibular framework causing retroposition of the base of the tongue and an inadequate hypopharyngeal space. A tracheotomy in childhood is an effective treatment for obstructive sleep apnea, but it is associated with increased morbidity, management problems, and difficulties in social interaction. Tracheostomy-dependent pediatric patients who underwent mandibular distraction were reviewed to determine the effectiveness of this technique in achieving decannulation. A clinical review was completed to determine the status of the tracheostomy after external, unidirectional distraction in tracheostomy-dependent patients. Expansion of the mandibular framework was analyzed using traditional bony landmarks on predistraction and postdistraction lateral cephalograms. The area of the lower face was analyzed, and changes in the position of the hyoid bone were determined. Four patients with tracheostomies underwent an average of 21.3 mm and 20.8 mm of distraction on the left and right hemimandibles, respectively. The average age at the time of distraction was 2.7 years (range, 2.2 to 3.2 years). All patients underwent successful decannulation at an average of 3.8 months (range, 1.5 to 5.5 months) after completion of distraction. The area of the lower face increased 26.9 percent (range, 12.2 to 53.5 percent) after distraction, and the hyoid bone advanced an average of 14.5 mm (range, 8 to 25 mm). Bilateral mandibular distraction is an effective method of expanding the mandibular framework and concomitantly advancing the base of the tongue. The technique provides a tool for early intervention and decannulation in pediatric patients with indwelling tracheostomies secondary to mandibular deficiencies.

Controlled multiplanar distraction of the mandible, Part II: Laboratory studies of sagittal (anteroposterior) and vertical (superoinferior) movements.

The application of distraction osteogenesis in craniofacial surgery has significantly altered the treatment of congenital mandibular deficiencies. However, evaluation of results in both animal studies and clinical cases has revealed deficiencies, particularly in two areas. First, distraction using a uniplanar device in an anteroposterior direction can result in a persistent anterior open bite. Second, the lateralization of the distracted hemimandible was often limited, with insufficient incremental gain in the bigonial distance. To overcome these shortcomings, a multiplanar distraction device was developed and tested in the canine model. This report details canine studies addressing the first problem: combined anteroposterior or sagittal (z-axis) and superoinferior or vertical (y-axis) movements. Six dogs underwent bilateral mandibular distraction with an external (extraoral), multiplanar device and completed sagittal plus vertical distraction. Evaluation included clinical examination (facial form, jaw position, and occlusion), photography, cephalograms (posteroanterior, basilar, and lateral), three-dimensional computed tomography reconstructions, and examination of dry skulls. The dogs averaged 18.5 mm (range, 15-20 mm) of sagittal distraction and 41.0 degrees (range, 21-50 degrees) of vertical distraction. Marked anterior open bites were produced after vertical distraction secondary to premature contact of the maxillary and mandibular molars. Distraction in the vertical direction also had the additive effect of increasing the sagittal gains by approximately 5% to 10%. In conclusion, a multiplanar distraction device (with the potential for distraction in three planes) was effective in increasing mandibular anteroposterior thrust (sagittal distraction) and also in creating an anterior open bite (vertical or superoinferior distraction). Vertical distraction probably requires bilateral osteotomies to obtain optimal results. The preliminary gains in sagittal length are modified (reduced or increased) after distraction in a second plane (vertical and horizontal). Specifically, vertical distraction in the inferior direction (creating an open bite) also leads to isolated increases in the anteroposterior plane. Conversely, vertical distraction in the superior direction (closing an open bite), as seen in a human malocclusion, may lead to isolated decreases in the anteroposterior plane, but this question remains to be investigated in the laboratory.

Orthodontists' views of justification for cost of orthognathic surgery

The authors present an interesting article recognizing that health professionals, orthodontists, do influence patients’ decisions about treatment. With a survey instrument, the orthodontists are asked how the costs of surgery would influence their opinions/recommendations for patients with problems of increasing severity. Responses were grouped by orthodontists’ time after completing training, a proxy for experience. It is gratifying to see that at least 75% of respondents believed that a combined orthodontic/surgical approach was desirable for patients with “severe functional compromise” and at least 70% for “severe aesthetic compromise.” This opinion was not so pervasive in the past; some patients were treated with orthodontic camouflage, resulting in worse jaw function/aesthetics than before treatment. It is not clear from the article how well the distinction between the moderate and severe categories was presented to the orthodontists surveyed. A lack of clarity could account for the differences in response. It would be interesting also to know whether all of the orthodontists surveyed treated combined orthodontic/surgical cases. In the United States, some orthodontists seem to treat more complicated cases, which often include surgery; others never manage a case with combined treatment. In the most ideal circumstance, patients should be offered choices in their treatment, with options presented objectively. To present alternatives to patients, we are challenged to rely less on clinical judgment and more on data from well-conducted clinical studies that focus on outcomes from both clinical parameters and the patient’s perspective.’ It seems strange that we know more about clinical outcomes of patients treated with combined orthodontics/surgery than with orthodontics alone, but we do need additional clinical outcome data, particularly regarding jaw function.2 Most patients are satisfied after combined orthodontic/ surgical treatment, but we must learn more about how patients decide on a complicated plan of treatment and what will influence their perception of a good outcome. For example, the sequence and method of presenting a video image of the anticipated result to a patient can affect expectations after surgery. If the video is shown very close to the planned surgical procedure, anxiety is heightened.3 To offer patients the best information and advice to enable them to differentiate among the available options, guidelines based on clinical data and patients’ perception of the process of treatment would be helpful. Guidelines available for treating patients with severe mandibular deficiency are a step in that direction.* In the United States, no relationship exists between funding available for orthognathic surgery and the patient’s presenting problems. Perhaps this follows from a dual training system in which physicians learn almost nothing about oral health problems yet are called on to make judgments regarding treatment, and an economic climate in which reducing expenditures takes priority over benefit to individual patients. A more rational process is likely to emerge because some patients do have severe dentofacial problems, and their situation can be improved with combined orthodontic/surgical treatment. As added data on outcomes of the process of complex treatment become available, decision-making tools, such as utility analysis and clinical guidelines, can be applied to make funding decisions more objective and rational.

The value of long-term follow-up of mandibular advancement surgery in patients with a low to normal mandibular plane angle

The objective of this study was to evaluate retrospectively the stability of mandibular advancement via bilateral sagittal split osteotomies. Two fixation methods were compared: intermaxillary fixation (IMF) and rigid internal fixation (RIF). The hypothesis was that, in patients with a low to normal mandibular plane angle (MPA) in retrognathia, the bilateral sagittal split osteotomy (BSSO) to advance the mandible is a predictable and stable procedure and that no significant changes occur after 1 year. Twelve patients with mandibular deficiency with a low to normal MPA (mean 24.7 degrees, range 20.3 degrees-30.7 degrees) underwent BSSO with IMF. The follow-up period was at least 5 years (mean 6.3, range 5-9.1 years). Cephalometric analysis using a commercial software package was performed on radiographs that were taken immediately preoperatively (T0), within 6 weeks postoperatively (T1), 1 year postoperatively (T2), and at least 5 years postoperatively (T3). The average advancement at B point was 4.7 mm (range: 3-7 mm). The assessment of B point in regard to relapse showed no significant change. One patient showed a relapse due to condylar resorption. Forty-five consecutive patients were treated with RIF. Radiographs were taken preoperatively (T0), 6 weeks postoperatively (T1), and 1 year postoperatively (T2). This group had a mean MPA of 26.2 degrees, range 10 degrees-32 degrees. The average B-point advancement was 4.4 mm (range 1-10 mm). No patient showed a clinically significant relapse at T2.

Condylar resorption after bicortical screw fixation of mandibular advancement.

This study evaluated long-term condylar resorption after mandibular advancements stabilized with bicortical screws. One hundred mandibular deficiency patients who underwent bilateral sagittal split osteotomies (BSSO) fixed with three bicortical screws per side, and who were followed for a minimum of 1 year with complete radiographic records, were evaluated. Preoperative panoramic radiographs were traced and superimposed as a best fit over long-term panoramic radiographs. Cephalometric tracings were available on all patients preoperatively, immediately after surgery, 6 to 8 weeks after surgery, and at long term after surgery. These tracings were used to show the amount of the initial advancement and any changes that occurred between 6 to 8 weeks and long term in those patients who exhibited 10% or greater changes in their condylar height. Preoperative temporomandibular joint signs and symptoms were recorded on all patients before surgery and at 6 months after surgery. There were 10 patients who had 10% or greater vertical change in their condyles; all changes were unilateral. Large advancement (P > .009) and preoperative temporomandibular joint symptoms (P > .01) statistically correlated with long-term postoperative condylar resorption. There was not a direct correlation between the amount of vertical change in the condyle and the amount of relapse. There was an improvement in temporomandibular joint symptoms for the group as a whole and in the group with condylar resorption. Patients with large advancements and preoperative temporomandibular joint symptoms appear to be at risk for condylar resorption. These results are similar to those from other studies in which rigid fixation or miniplates were used for cases of mandibular advancement.

Mandibular widening by intraoral distraction osteogenesis

Transverse mandibular deficiency with crowding of the mandibular anterior teeth is frequently present in patients with Class I and II malocclusions. The hallmarks of treatment by compensating orthodontics, functional appliances or orthopaedic devices are instability, compromised periodontium and compromised facial aesthetics. A new surgical technique has been developed to widen the mandible. The method is based upon gradual osteodistraction following vertical interdental symphyseal osteotomy. Ten patients with transverse mandibular deficiency and significant dental crowding were treated by symphyseal distraction and subsequent non-extraction decompensating orthodontic treatment. Either an intraoral tooth-borne Hyrax appliance or a new custom-made bone-borne osteodistractor was used to gradually widen the mandible. The surgical procedures were accomplished under local anaesthesia and intravenous sedation in an ambulatory surgical setting using an individualized distraction protocol. The appliances were activated 7 days after symphyseal osteotomies, once each day at a rate of 1 mm per day and stabilized for 30–60 days after distraction. After the segments were distracted, non-extraction orthodontic alignment of the mandibular anterior teeth was accomplished. The symphyseal distraction gaps were bridged by new bony regenerate. Distraction osteogenesis provided an efficient surgical alternative to orthognathic surgery for widening the mandible and treatment of transverse mandibular deficiency without extraction of teeth.

Mandibular distraction osteogenesis. Preliminary results of an animal study with a dentally fixed distraction device.

Lengthening of the human mandible by distraction osteogenesis has become an accepted treatment for correction of severe mandibular disto-basal discrepancies in recent years. This usually entails the deployment of extra-orally located distraction devices. This type of device often causes conspicuous scarring. To avoid this scarring, an intra-oral device is to be developed. In the present animal study, 2 "Troll" mini-pigs and 2 "Yucatan" micro-pigs were fitted with a new solely dentally fixed orthodontic device for mandibular distraction osteogenesis. Following bilateral osteotomy in the dentigerous area of the mandibular body and a latent period of 2 to 7 days, the apparatus was activated 1 mm per day. Within a period of 9 days, a mandibular lengthening of 9 mm was reached. This situation was retained using the distraction device for 6 weeks. After removal of the apparatus, there followed another 6-week period of consolidation. During the experiment, the callus and bone formation and potential dental and periodontal reactions were radiologically examined and underwent histological examination at the end of the experiment. Twelve weeks after the mandibular lengthening, the osteogenesis in the distraction areas was complete. No destructive processes were recognizable, either at the roots or at the periodontium of the teeth near the osteotomy gap. Lengthening of the mandibular body using distraction osteogenesis with the help of a solely dentally fixed distraction device is thus feasible and can, in the future, become the appropriate treatment in the correction of severe mandibular deficiency.

Distraction osteogenesis for correction of transverse mandibular deficiency: A preliminary report

Purpose: This article reviews the early results with distraction osteogenesis to correct transverse width deficiencies in the mandible. Patients and Methods: Nine patients with congenital/developmental maxillofacial skeletal deformities had distraction osteogenesis performed. All patients had study casts and cephalometric and dental radiographs obtained before and after surgery. Eight of the nine patients also had simultaneous surgical assisted-rapid palatal expansion (SA-RPE). The other patient had nonsurgical RPE. Results: Successful completion of the planned mandibular symphyseal distraction was achieved in eight of nine patients. Four of the nine experienced failure of the distraction appliance because of stripping of the distraction tram. Three of them underwent reoperation. The mean expansion achieved in the anterior mandible measured at the canines was 3.9 mm. Conclusions: These preliminary results suggest that distraction osteogenesis is a viable option to correct transverse discrepancies of the mandible.

Surgical Maxillofacial Treatment of Obstructive Sleep Apnea

Obstructive sleep apnea is the most common sleep-related breathing disorder, with a surprisingly high prevalence. The treatment of choice is nasal continuous positive airway pressure (CPAP) ventilation during sleep, which has to be applied throughout the patient's whole life. Because of various underlying pathomechanisms in patients with certain craniofacial disorders--narrow posterior airway space and maxillary-mandibular deficiency--surgical therapy by craniofacial osteotomies seems possible. A series of 38 consecutive patients were treated by 10-mm maxillomandibular advancement by retromolar sagittal split osteotomy and Le Fort I osteotomy, respectively. Obstructive sleep apnea syndrome was improved considerably in all patients; there was no significant difference compared to the results under nasal CPAP. In 37 of 38 patients, the postoperative apnea-hypopnea index was reduced clearly to under 10 per hour, oxygen saturation rose, and sleep quality improved. This was achieved by maxillomandibular advancement of 10 mm without secondary refinements in all but 2 patients. In one patient, the apnea-hypopnea index could only be reduced to 20 per hour, probably because of insufficient maxillary advancement. These results indicate that successful surgical treatment is possible in a high percentage of selected patients with certain craniofacial characteristics. In addition to cardiorespiratory polysomnography, there should be routine cephalometric evaluation of all patients. Maxillomandibular advancement should be offered as an alternative therapy to all patients with maxillary and/or mandibular deficiency or dolichofacial type in combination with narrow posterior airway space.

The value of long-term follow-up of mandibular advancement surgery in patients with a low to normal mandibular plane angle

The objective of this study was to evaluate retrospectively the stability of mandibular advancement via bilateral sagittal split osteotomies. Two fixation methods were compared: intermaxillary fixation (IMF) and rigid internal fixation (RIF). The hypothesis was that, in patients with a low to normal mandibular plane angle (MPA) in retrognathia, the bilateral sagittal split osteotomy (BSSO) to advance the mandible is a predictable and stable procedure and that no significant changes occur after 1 year. Twelve patients with mandibular deficiency with a low to normal MPA (mean 24.7°, range 20.3°–30.7°) underwent BSSO with IMF. The follow-up period was at least 5 years (mean 6.3, range 5–9.1 years). Cephalometric analysis using a commercial software package was performed on radiographs that were taken immediately preoperatively (TO), within 6 weeks postoperatively (T1), 1 year post-operatively (T2), and at least 5 years postoperatively (T3). The average advancement at B point was 4.7 mm (range: 3–7 mm). The assessment of B point in regard to relapse showed no significant change. One patient showed a relapse due to condylar resorption. Forty-five consecutive patients were treated with RIF. Radiographs were taken preoperatively (T0), 6 weeks post-operatively (T1), and 1 year post-operatively (T2). This group had a mean MPA of 26.2°, range 10°–32°. The average B-point advancement was 4.4 mm (range 1–10 mm). No patient showed a clinically significant relapse at T2.

Craniofacial abnormalities in obstructive sleep apnoea: implications for treatment.

Obstructive sleep apnoea (OSA) is a common disorder, and is characterized by repetitive closure of the upper airway during sleep. Upper airway narrowing and sleep-induced loss of muscle tone are important factors in the development of OSA. Over the last decade there has been a growing recognition that craniofacial abnormalities occur commonly in OSA patients. The more commonly identified abnormalities include mandibular deficiency, an inferiorly placed hyoid bone relative to the mandibular plane, a narrowed posterior air space, a greater flexion of the cranial base, and elongation of the soft palate. It is thought that these abnormalities result in upper airway narrowing, thereby predisposing to OSA. When the well established role of obesity in the development of OSA is taken into account, a model of OSA emerges in which the degree of craniofacial abnormalities determines the extent of obesity required to produce OSA in a given individual. The recognition of the role of craniofacial abnormalities in the development of OSA has led to a number of treatment strategies aimed at correcting or improving craniofacial structure, thereby preventing upper airway collapse during sleep. These treatments include dental appliances, and various maxillofacial surgical procedures. An improved understanding of the evolution of OSA from childhood to adulthood, in relation to facial development, may lead to a preventative strategy for this disorder.

Temporomandibular joint symptoms in an orthognathic surgery population

The records of 317 consecutive patients who underwent orthognathic surgery in the Division of Maxillo-Facial Surgery of the General Hospital St. John, Bruges, Belgium, between 1.10.90 and 1.10.92 were evaluated for pre- and postoperative temporomandibular joint (TMJ) symptoms. Only 143 patients, with a normal/low angle mandibular deficiency deformity, treated by mandibular advancement, and 53 high angle absolute mandibular retrognathism patients having bimaxillary operations, were selected. Fewer TMJ symptoms were found postoperatively, than preoperatively in the total group (17.8% vs 26.5% p = 0.025, Mc Nemar). In the normal/low angle group, there was a decrease in TMJ symptoms after surgery from 30.0% to 14.6% (p = 0.0001, Mc Nemar). In the high angle group, however, more TMJ symptoms are seen postoperatively 26.4% versus 16.8% (p = 0.228, Mc Nemar). Possible hypothetical explanations are given.

Orthognathic surgery versus orthodontic camouflage in the treatment of mandibular deficiency

Surgical correction of Class II malocclusions, when associated with mandibular deficiency, often has improved results with combined orthodontic and surgical correction compared with orthodontic treatment alone. Strong consideration of surgical correction of mandibular deficiency should be based on the following questions: 1. 1) Do the patient's goals for treatment place a high priority on improvement in facial esthetics? As a corollary, even patients who are not particularly concerned with facial esthetics, but who may have a worsening in facial appearance as a result of orthodontic camouflage, should be considered for surgical correction. This may include patients with lack of upper lip support, an obtuse nasolabial angle, a large nose, and a long lower face height, all of which may become more apparent as a result of orthodontic camouflage treatment. 2. 2) Are the orthodontic movements required in excess of the envelope of discrepancy so that adequate orthodontic correction may not be achieved? 3. 3) Could orthodontic-surgical treatment result in a significant decrease in treatment time? An example would be when surgical treatment in combination with orthodontics could be accomplished without extraction, whereas orthodontic treatment alone would require extraction and space closure. 4. 4) Is there adequate patient compliance? Would orthodontic treatment alone be as ineffective without adequate patient cooperation? 5. 5) Are the risks of surgery within acceptable levels? Are the benefits of surgical treatment, as previously described, obvious?

Orthodontic camouflage versus orthognathic surgery in the treatment of mandibular deficiency

Clearly, there are postpubertal patients with Class II malocclusions for whom orthognathic surgery combined with orthodontics is the "best" option, but epidemiologic information suggests they are a relatively small percentage of the potential patient pool. The majority of patients fall into either an orthodontic treatment group or a borderline category. Many of these can be treated successfully with orthodontic camouflage. Research has shown psychosocial factors play a major role in determining the patient's selection of a treatment option. This emphasizes the need for careful attention to global psychologic factors, with special emphasis on patient concerns regarding body image. Morphometric criteria have been offered describing appropriate candidates for orthodontic camouflage. These are supported by a combination of research and clinical experience. Patients who do not fit these criteria should not automatically be considered candidates for surgery. Psychosocial research suggests a percentage of these individuals place less importance on facial change and are content to improve dental esthetics and function to the degree possible. To assist in the decision-making process, patients should be given the best information available regarding potential outcome. Currently this may involve treatment simulation using a combination of computer images and dental models. Caution has been suggested, given the variability associated with predicting soft tissue change. There are additional legal concerns regarding the implied guarantee of treatment outcome. Correspondingly, the influence of this technology must be kept in perspective. Recent research on the decision-making process found computer imaging to be an important factor in only 24% of the patients studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Planning Mandibular Distraction: Preliminary Report

Normal lengths of the vertical ramus, body, and angle of the mandible at different ages are presented. Before mandibular distraction is embarked on, the extent of the deficiency of the mandible is assessed. The length of the vertical ramus and body are measured on cephalometric radiographs or three-dimensional computed tomography (3D CT) scans. Deficiency of the length of the mandible is calculated. The position of the pin placement angle (from the horizontal ramus) is calculated by means of the following formula: 180 degrees minus mandibular angle times vertical ramus deficiency divided by total deficiency. Placing the pins correctly will result in correction of the vertical ramus and body deficiency of the mandible and the excessively obtuse angle of the mandible will become more acute.