Maria J. Troulis

A protocol for management of temporomandibular joint ankylosis in children.

Temporomandibular joint (TMJ) ankylosis in children is a challenging problem. Surgical correction is technically difficult and the incidence of recurrence after treatment is high. The purpose of the present report is to describe the protocol currently used at the Massachusetts General Hospital for the management of TMJ ankylosis in children. It has been our observation that the most common cause of treatment failure is inadequate resection of the ankylotic mass and failure to achieve adequate passive maximal opening in the operating room. The 7-step protocol consists of 1) aggressive excision of the fibrous and/or bony ankylotic mass, 2) coronoidectomy on the affected side, 3) coronoidectomy on the contralateral side, if steps 1 and 2 do not result in a maximal incisal opening greater than 35 mm or to the point of dislocation of the unaffected TMJ, 4) lining of the TMJ with a temporalis myofascial flap or the native disc, if it can be salvaged, 5) reconstruction of the ramus condyle unit with either distraction osteogenesis or costochondral graft and rigid fixation, and 6) early mobilization of the jaw. If distraction osteogenesis is used to reconstruct the ramus condyle unit, mobilization begins the day of the operation. In patients who undergo costochondral graft reconstruction, mobilization begins after 10 days of maxillomandibular fixation. Finally (step 7), all patients receive aggressive physiotherapy. A case series of children with ankylosis treated using this protocol is presented.

Effects of latency and rate on bone formation in a porcine mandibular distraction model.

PURPOSE Long treatment protocols currently limit the application of distraction osteogenesis (DO). The purpose of this study was to develop a porcine model for DO and to define the effects of latency and distraction rate on bone formation. MATERIALS AND METHODS Distractors were placed through submandibular incisions. For analysis of latency, mandibular osteotomies were distracted after 0 (n = 3) or 4 (n = 2) days at a rate of 1 mm/d (7 days) with 14 days fixation. For analysis of rate, osteotomies were distracted at 1 mm (n = 4), 2 mm (n = 4), or 4 mm (n = 4) per day to produce a 12-mm gap with 24 days fixation. DO wounds were assessed in vivo with bimanual palpation to detect mobility across the gap. Harvested specimens were evaluated by gross appearance and bimanual palpation. Standardized radiographic techniques were used to estimate bone density. RESULTS During DO, animals showed normal activity. There were no infections, and no distractors were removed prematurely. Clinical and radiographic evaluation of the groups that underwent distraction after 0- or 4-day latency showed equivalent healing. In the comparison of distraction rates, stability was greatest in the group distracted at 1 mm/d. CONCLUSIONS A porcine model for mandibular DO has been developed in which mandibular lengthening was successfully performed without latency and at a rate of 1 mm/d. The relationships among latency, gap size, rate, and duration of fixation are poorly understood and can be defined with relevant animal models.

Three-Dimensional Computed Tomographic Airway Analysis of Patients With Obstructive Sleep Apnea Treated by Maxillomandibular Advancement

PURPOSE To evaluate changes in airway size and shape in patients with obstructive sleep apnea (OSA) after maxillomandibular advancement (MMA) and genial tubercle advancement (GTA). MATERIALS AND METHODS This was a retrospective cohort study, enrolling a sample of adults with polysomnography-confirmed OSA who underwent MMA + GTA. All subjects who had preoperative and postoperative 3-dimensional computed tomography (CT) scans to evaluate changes in airway size and shape after MMA + GTA were included. Preoperative and postoperative sleep- and breathing-related symptoms were recorded. Descriptive and bivariate statistics were computed. For all analyses, P < .05 was considered statistically significant. RESULTS During the study period, 13 patients underwent MMA + GTA, of whom 11 (84.6%) met the inclusion criteria. There were 9 men and 2 women with a mean age of 39 years. The mean body mass index was 26.3; mean respiratory disturbance index (RDI), 48.8; and mean lowest oxygen saturation, 80.5%. After MMA + GTA, there were significant increases in lateral and anteroposterior airway diameters (P < .01), volume (P = .02), surface area (P < .01), and cross-sectional areas at multiple sites (P < .04). Airway length decreased (P < .01) and airway shape (P = .04) became more uniform. The mean change in RDI was -60%. CONCLUSIONS Results of this preliminary study indicate that MMA + GTA appears to produce significant changes in airway size and shape that correlate with a decrease in RDI.

Age-related changes of the upper airway assessed by 3-dimensional computed tomography.

The purposes of this study were to establish normative data for airway size and shape and to evaluate differences associated with age and sex using 3-dimensional (3-D) imaging. Patients being evaluated by computed tomography (CT) for pathologic conditions not related to the airway were included. Using 3-D Slicer (Harvard Surgical Planning Laboratory, Brigham and Womens Hospital, Boston, MA), a software program, digital 3-D CT reconstructions were made and parameters of airway size analyzed: volume (VOL), surface area (SA), length (L), mean cross-sectional area (mean CSA), minimum retropalatal (RP), minimum retroglossal (RG), minimum cross-sectional area (min CSA), and lateral (LAT) and anteroposterior (AP) retroglossal airway dimensions. Evaluation of airway shape included LAT/AP and RP/RG ratios, uniformity (U), and sphericity, a measure of compactness (&PSgr;). Children were stratified by stage of dentition: primary, 0 to 5 years; mixed, 6 to 11 years; permanent, 12 to 16 years; and adults, older than 16 years. Differences in airway parameters by age and sex were analyzed. Forty-six CT scans (31 males) were evaluated. Adults had larger (VOL, SA, L, mean CSA, and LAT), more elliptical (increased LAT/AP, P = 0.01), less uniform (U, P = 0.02), and less compact (decreased &PSgr;, P = 0.001) airways than children. Among children, those in the permanent dentition demonstrated greater VOL (P < 0.01), SA (P < 0.01), L (P < 0.01), and mean CSA (P < 0.01) than those in the primary dentition. There were no gender differences in airway parameters. Understanding differences in 3-D airway size and morphology by age may serve as a basis for evaluation of patients with obstructive sleep apnea and may help to predict and to evaluate outcomes of treatment.

Three-Dimensional Computed Tomographic Analysis of Airway Anatomy in Patients With Obstructive Sleep Apnea

PURPOSE To identify abnormalities in airway size and shape that correlate with the presence and severity of obstructive sleep apnea (OSA). MATERIALS AND METHODS This was a retrospective case series of patients undergoing treatment of OSA who had preoperative computed tomographic (CT) scans of the upper airway available. Patients who had undergone CT scanning for nonairway pathologic features during the same period served as the controls. Digital 3D-CT reconstructions were made and 12 parameters of airway size and 4 of shape were analyzed. The posterior airway space, middle airway space, and hyoid to mandibular plane distance were measured on the lateral cephalograms of the patients with OSA. Bivariate analysis was used to identify the factors associated with the presence and severity of OSA as measured by the respiratory disturbance index (RDI). Multiple regression analysis identified the factors that correlated with the RDI. RESULTS Of the 44 patients with OSA, 15 (10 men and 5 women) had pre- and postoperative CT scans available. In addition, 17 patients (11 men and 6 women) were used as controls. The airway length was significantly increased in the patients with OSA (P < .01). On bivariate analysis, the length, lateral/retroglossal anteroposterior dimension ratio and genial tubercle to hyoid bone distance were associated with the RDI (P < .03). On multiple regression analysis, length (P < .01) had a positive correlation and the lateral/retroglossal anteroposterior dimension ratio (P = .04) an inverse correlation with the RDI. CONCLUSIONS The results of this study indicate that the presence of OSA is associated with an increase in airway length. Airways that were more elliptical in shape and mediolaterally oriented (greater lateral/retroglossal anteroposterior dimension ratio) had a decreased tendency toward obstruction.

Reconstructing Mandibular Defects Using Autologous Tissue-Engineered Tooth and Bone Constructs

PURPOSE Current strategies for jaw reconstruction require multiple operations to replace bone and teeth. To improve on these methods, we investigated simultaneous mandibular and tooth reconstruction, using a Yucatan minipig model. MATERIALS AND METHODS Tooth and bone constructs were prepared from third molar tooth tissue and iliac-crest bone marrow-derived osteoblasts isolated from, and implanted back into, the same pig as an autologous reconstruction. Implants were harvested after 12 and 20 weeks and evaluated by x-ray, ultrahigh-resolution volume computed tomographic (VCT), histological, and immunohistochemical analyses. RESULTS Small tooth structures were identified, and consisted of organized dentin, enamel, pulp, and periodontal ligament tissues, surrounded by new bone. No dental tissues formed in implants without tooth-bud cells, and bone regeneration was observed to a limited extent. Immunohistochemical analyses using tooth-specific and bone-specific antibodies confirmed the identity of regenerated tissues. CONCLUSIONS This pilot study supports the feasibility of tissue-engineering approaches for coordinated autologous tooth and mandible reconstruction, and provides a basis for future improvement of this technique for eventual clinical use in humans.

Tissue engineered hybrid tooth–bone constructs

Proper rehabilitation of craniofacial defects is challenging because of the complexity of the anatomy and the component tissue types. The ability to simultaneously coordinate the regeneration of multiple tissues would make reconstruction more efficient and might reduce morbidity and improve outcomes. The craniofacial complex is unique because of the presence of teeth, in addition to skin, bone, cartilage, muscle, vascular, and neural tissues since teeth naturally grow in coordination with the craniofacial skeleton, our group developed an autologous, tooth-bone hybrid model to facilitate repair of mandibular defects in the Yucatan minipig. The hybrid tooth-bone construct was prepared by combining tooth bud cell-seeded scaffolds with autologous iliac crest bone marrow derived stem cell-seeded scaffolds, which were transplanted back into surgically created mandibular defects in the same minipig. The constructs were harvested after 12 and 20 weeks of growth. The resulting bone/tooth constructs were evaluated by X-ray, ultra high-resolution volume computed tomography (VCT), histological, immunohistochemical analyses, and transmission electron microscopy (TEM). The observed formation of small tooth-like structures consisting of organized dentin, enamel, pulp, cementum, periodontal ligament, and surrounded by regenerated alveolar bone, suggests the feasibility for regeneration of teeth and associated alveolar bone, in a single procedure. This model provides an accessible method for future clinical applications in humans.

Distraction osteogenesis of the porcine mandible: histomorphometric evaluation of bone.

Distraction osteogenesis is a technique for skeletal lengthening that exploits the body’s innate capacity for bone formation in response to tension forces on the repair callus. The authors developed a distraction osteogenesis model with a semiburied device in the Yucatan minipig mandible because of similarities between human and porcine mandibular anatomy, temporomandibular function, chewing patterns, and bone turnover rates. The purpose of this study was to measure histomorphometric bone fill after different latency periods, rates of distraction, and duration of neutral fixation in the minipig mandible. In addition, the relationship between histomorphometric bone fill and clinical stability was investigated. Mandibular osteotomies in 20 female Yucatan minipigs weighing 25 to 30 kg were distracted with modified semiburied distraction devices. Variables included 0-day or 4-day latency; 1-mm, 2-mm, or 4-mm daily distraction rates; gap size of 7 or 12 mm; and evaluation after neutral fixation for various lengths of time. Specimens were fixed in 2% paraformaldehyde, pH 7.4, before being embedded in methylmethacrylate. Sections were prepared from the region just below the inferior alveolar canal. The area of new bone formation within the gap was measured and expressed as a percentage of the total area of the distraction gap. Bone fill ranged from 0 to 100 percent. A pilot study with 7-mm advancements showed similar bone fill with 0-day or 4-day latency, but with poor reproducibility. Mandibles that were distracted to 12 mm at 1 mm per day exhibited nearly complete bone fill, either with 0-day latency (average, 93 percent) or 4-day latency (average, 100 percent). Mandibles that had been distracted for 3 days at 4 mm per day showed moderate osteogenesis and clinical stability with increasing time of neutral fixation. Bone fill was significantly correlated with clinical stability (Spearman r = 0.801, p = 0.001). Histological examination showed exuberant periosteal osteogenesis in distracted mandibles, even in those that showed poor bone fill and clinical stability. Thus, the periosteum appears to be a major source of new bone formation. These results show that osteogenesis was nearly complete with 1 mm per day and 0-day or 4-day latency. These results are consistent with the authors’ previously reported clinical and radiographic observations that a latency period is not necessary for successful healing of the mandibular distraction osteogenesis wound.

Interventional Sialoendoscopy: Early Clinical Results

PURPOSE Sialoendoscopy is a novel minimally invasive technique to explore the salivary duct system and to treat obstructive salivary disease. This article describes the early clinical experience with endoscopic salivary duct exploration and sialolithectomy in 2 medical centers. PATIENTS AND METHODS This is a retrospective case series of 94 patients, with submandibular (n = 77) or parotid (n = 17) sialadenitis secondary to sialolithiasis, strictures, or mucous plugs. Patients underwent sialoendoscopy at Baptist Hospital, Miami (n = 52) or at Massachusetts General Hospital, Boston (n = 42). Dilatation of the duct through the natural orifice was accomplished with salivary dilators. Three endoscope systems with diameters from 1.1 to 2.3 mm were used. Using a basket, grasper, lithotripsy, laser, or a combination of these, stones were fragmented or removed endoscopically. Strictures were dilated and mucous plugs removed. All cases were carried out under general anesthesia. RESULTS Salivary duct navigation was accomplished in 91/94 patients. In 3 cases, duct dilatation was not possible due to scarring. Symptomatic relief was achieved in 81/91 patients (89.4%). Strictures and mucous plugs were visualized and managed in 18/18 patients. Sialoliths were visualized in 73 patients and stone fragmentation or retrieval was accomplished in 84.93% (62/73) of cases. Complications included 2 patients with temporary lingual nerve paresthesia and 1 patient with excess extravasation of irrigation fluid. CONCLUSION The results of this study indicate that interventional sialoendoscopy is an effective, minimally invasive alternative treatment for obstructive salivary gland disease.

Simultaneous maxillary and mandibular distraction osteogenesis with a semiburied device

Distraction osteogenesis is a technique utilizing natural healing mechanisms to generate new bone; it is commonly used to lengthen the hypoplastic mandible. Distraction of the maxilla and mandible as a unit is an obvious extension of the technique. We describe the application of a semiburied distractor to simultaneously lengthen the mandible and maxilla and level a canted occlusal plane in three cases. The indications for bimaxillary distraction are reviewed, including its advantages, disadvantages and limitations.