Mandibular advancement using an intra-oral osteogenic distraction technique: a report of three clinical cases

Treatment outcomes of archwise distraction osteogenesis in mandibular dentoalveolar retrognathia cases

The aim of this study was to describe the treatment of class II malocclusion by sagittal advancement of the alveolar bone in the symphyseal area using an intraoral archwise distractor device and to determine the effects of this method on the dentoalveolar complex. Fifteen patients (10 female, five male) aged 16-20 years with a class II division 2 malocclusion, characterized by mandibular dentoalveolar retrusion and a prominent chin, underwent archwise alveolar distraction in the anterior mandible. Lateral cephalometric radiographs were obtained before distraction (T0), after 6 weeks of consolidation (T1), and after debonding (T2). Linear and angular skeletal, dental, and soft tissue measurements were performed. Forty-seven parameters were measured for each of the 15 subjects on pre- and postoperative lateral cephalometric radiographs (T0, T1, and T2). The distraction protocol was successful in all patients. Skeletally, the mandible showed a clockwise rotation. B-point moved forward significantly (P<0.05). Overjet decreased significantly (P<0.001). The total profile angle was unaffected, and the improvement in the submental fold was highly significant (P<0.001). The intraoral archwise distraction force that is applied through brackets and archwires is sufficiently effective for alveolar advancement. This procedure is simple and effective in the treatment of specific adult patients with a class II division 2 malocclusion, characterized by a prominent chin and severe mandibular dentoalveolar retrusion.

A paralleling device and ethylene vinyl acetate baffles for use with mandibular distraction osteogenesis: technical note

A novel method for planning the placement of intra-oral lengthening devices using a paralleling device is described and illustrated with a case report. Simple radiographic measurements and study models are all that is required to construct a simple acrylic splint with guides, which allows accurate positioning of the distractors at surgery. The construction of ethylene vinyl acetate (EVA) baffles to prevent trauma to the labial mucosa from the intra-oral link arms is a technique that enhances patient comfort during distraction of the mandible. The case report demonstrates the application of the surgical planning technique and the use of EVA baffles for a patient with an overjet of 21.5 mm.

A preliminary study of hardness and modulus of elasticity in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy

Objectives: To investigate the quality of newly formed bone in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy (LLLT), based on hardness and modulus of elasticity values. The ideal moment for laser application (during the latency/activation period vs. during the bone consolidation period) was also evaluated. Computed tomography imaging was used to assess relapse as a result of early device removal. Study design: Extraoral distraction devices were placed in five sheep so as to achieve 1.5 cm of lengthened bone in 60 days. Distraction devices were removed 50, 40, and 33 days after surgery. Four animals were treated with LLLT, at different times, and one was used as control (no LLLT). Results: When applied during the bone consolidation period, LLLT caused an increase in hardness and modulus of elasticity values. On the other hand, animals irradiated with LLLT during the latency/activation period presented a delay in bone healing. A period of consolidation of 13 days (early device removal) was associated with relapse. Conclusions: Nanoindentation tests were able to detect slight abnormalities in bone metabolism and proved to be important tools for the assessment of bone quality following distraction osteogenesis. LLLT provided increased benefits when applied during the bone consolidation period, once it promoted an increase in hardness and modulus of elasticity values. According to our results, the bone consolidation period should be of at least 3 weeks, so as to prevent relapse.

Key words: Osteogenesis distraction, low-level laser therapy, elastic modulus, hardness tests.

EFFECTS OF AGING ON THE LATENCY PERIOD IN MANDIBULAR DISTRACTION OSTEOGENESIS: A COMPUTATIONAL MECHANOBIOLOGICAL ANALYSIS

Mandibular symphyseal distraction osteogenesis is a clinical procedure utilized in orthodontics for solving problems of dental overcrowding on the mandibular arch. A critical issue is to evaluate the optimal duration of the latency period between the osteotomy and the first aperture of distraction device. In fact, the latency period should change with the patient's age. To this end, a computational mechanobiological model has been developed in order to find optimal durations of latency period for young, adult, and elder patients. The model is implemented in a finite element framework simulating the process of tissue differentiation in the bone callus formed after osteotomy. The biophysical stimulus regulating the tissue differentiation process is hypothesized to be a function of the octahedral shear strain and interstitial fluid flow velocity. The resulting spatial distribution of stiffness properties in the callus region is analyzed in order to assess the risk of premature bone union of osteotomy edges. The three-dimensional (3D) finite element model (FEM) of human mandible is reconstructed from computed tomography (CT) scans and also includes a tooth-borne device. Under unilateral occlusion, the mandible is submitted to full mastication loading or to mastication forces reduced by 70%. The results show that optimal durations of the latency period for preventing premature bone union are about 5–6 days for the young patient, 7–8 days for the adult patient, and 9–10 days for the elder patient. These durations seem rather insensitive to the magnitude of mastication forces. Finally, distraction force values predicted by the present mechanobiological model are in good agreement with data reported in the literature.

Meta-analysis of mandibular distraction osteogenesis: clinical applications and functional outcomes

BACKGROUND

Mandibular distraction osteogenesis has been used effectively to treat syndromic craniofacial deformities. In recent years, its scope of application has widened to include treatment of airway obstruction in adults and children and nonsyndromic class II mandibular hypoplasia. So far, there has been no evidence-based review of mandibular distraction osteogenesis for mandibular lengthening.

METHODS

Two rounds of searches were performed by two independent assessors. The first-round PubMed search used the keywords "mandible" and "distraction osteogenesis." In the second-round search, the reference lists of the articles were retrieved. For both rounds, abstracts and then full articles were reviewed and selected on the basis of a set of inclusion and exclusion criteria.

RESULTS

The 178 retrieved articles yielded 1185 mandibular distraction osteogenesis patients: 539 received unilateral mandibular distraction osteogenesis and 646 received bilateral mandibular distraction osteogenesis. Mandibular distraction osteogenesis was reported to improve facial asymmetry and retrognathia (50.1 percent), correct the slanted lip commissure (24.7 percent), and improve or level the mandibular occlusal plane (11.1 percent) in unilateral asymmetry cases, whereas bilateral mandibular distraction osteogenesis was shown to be effective in preventing tracheostomies for 91.3 percent of neonates or infants with respiratory distress, and in relieving symptoms of obstructive sleep apnea for 97.0 percent of children and 100 percent of adult patients.

CONCLUSIONS

Mandibular distraction osteogenesis is effective in treating craniofacial deformities, but further clinical trials are required to assess the long-term stability and to compare the treatment with conventional treatment methods, especially in cases of obstructive sleep apnea or class II mandibular hypoplasia.