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PubMed1998

Functional results of dental restoration with osseointegrated implants after mandible reconstruction.

We reviewed the cases of 20 cancer patients (mean age 47.4 years) in whom osseointegrated implants were used for dental restoration after mandibular reconstruction between January of 1988 and December of 1994. Seventy-one implants were placed into bone flaps (n = 60) or native mandible (n = 11), an average of 3.55 per patient (range, 2 to 5). Successful integration occurred in 91.5 percent (65 of 71); there were five early failures and one late failure, with no significant difference between the number lost in microvascular flaps (5 of 60) and native mandible (1 of 11) (as determined by Fisher's exact test). Functional evaluation included assessments of diet, speech, and cosmesis. Based on our review, we concluded that (1) implants enhance dental restoration in selected patients, and (2) microvascular bone flaps, including the fibula and iliac crest, are well suited for dental implant restoration.

Adult↗
PubMed2002

Effect of distraction osteogenesis of the mandible on upper airway volume and resistance in children with micrognathia.

Children with craniofacial anomalies often have compromise of the upper airway, a condition with potential for morbidity and mortality. In children with microretrognathia, the diminutive size and retruded position of the mandible reduces the size of the oropharynx, thereby predisposing to glossoptosis and airway obstruction. Although several authors have reported successful use of mandibular distraction osteogenesis to alleviate this type of upper airway obstruction, the physiologic relationship between changes in mandibular shape, size, and position and upper airway dynamics remains undefined. The purpose of this study was to develop methodologies to quantitatively evaluate upper airway dynamics in children with micrognathia both before and after mandibular distraction osteogenesis. The patient population consisted of four children with micrognathia who had successfully undergone upper airway stabilization by bilateral mandibular distraction osteogenesis. The data used were digitally archived computed tomographic scan data from high-resolution, thin-slice head computed tomographic scans obtained before and after mandibular distraction. Upper airway evaluation was performed in two ways: static and dynamic. Static analysis consisted of computer quantification of predistraction and postdistraction mandibular and upper airway volumes using Analyze imaging software. Dynamic analysis consisted of fabrication of rigid stereolithographic hollow cast models of the upper airway produced from computed tomographic scan data. Models were used for characterization of upper airway resistance and flow patterns as related to respiration. After distraction osteogenesis, mandibular total volume increased 32, 32, 18, and 25 percent (mean, 27 percent) and upper airway volume increased by 20, 31, 23, and 71 percent (mean, 37 percent). A significant decrease in flow resistance, both inspiratory and expiratory, was observed in the patient with the greatest upper airway volume increase (71 percent) after distraction. After distraction, the inspiratory resistance was diminished by 51 percent and the expiratory resistance diminished by 85 percent. However, the three patients with more modest upper airway volume increases of 20 to 31 percent demonstrated no statistically significant change in flow resistance after distraction. Results of this study support the conclusion that distraction osteogenesis of the micrognathic mandible increases the volume of the upper airway, roughly paralleling the increase in mandibular volume. In the biomechanical airway model studied, upper airway volume expansion has been shown to be able to decrease the flow resistance over the length of the airway, presumably secondary to an increase in the average cross-sectional area. The artificial rigidity of the stereolithographic "airway" compared with the elasticity of the human upper airway may account for the insensitivity of this model to smaller but clinically significant airway changes.

Airway Resistance↗
PubMed2001

Treatment of a microvascular reconstructed mandible using an implant-supported fixed partial denture: case report.

Oral rehabilitation of patients with mandibular discontinuity defects is a problem that faces both the oral surgeon and the restorative dentist. Advances in microvascular surgery can provide the mandible with vital bone grafts. Often, reconstruction of the bony defect alone does not guarantee an adequate foundation for successful conventional prosthetic rehabilitation. Osseointegrated implants placed in the microvascularized grafted bone offer an opportunity for improved function and patient satisfaction. This case report describes the use of an implant-supported bridge in a vascularized fibular bone graft to reconstruct a traumatic partially resected mandible.

Adult↗
PubMed2006

Reintegration success of osseotite implants after intentional countertorque liberation in the endentulous human mandible.

PURPOSE: Implants that rotate during abutment screw tightening may not necessarily constitute implant failure. This prospective study was designed to determine to what degree integrated implants could gain a state of reintegration after intentional countertorque to liberation from the bone. MATERIALS AND METHODS: There were 11 patients with fully edentulous mandibles restored with 2 "clinical" implants (3.75 x 10 mm) placed in the canine sites and an additional nonused "test" implant (3.75 x 10 mm) placed at the symphysis of the anterior mandible. At second-stage surgery, the test implant was countertorqued (T1) using a torque-metering wrench until it detached from the bone. The implant was returned to its original position and allowed to heal for a period until a second countertorque test (T2) was performed. In group A, patients (n = 5) received the countertorque T1 at 3 months and T2 at 5 months. In group B (n = 6) T1 was at 1.5 months, and T2 was at 3.5 months. After completion of T2, the group A test implants were removed with a 5-mm trephine for histologic examination. RESULTS: For both groups, peak forces, all higher than 37.4 Ncm at T1, indicate that all implants were integrated. At T2, torque values were higher than T1 values for most of the test implants. The clinical implants were restored with "patrix" abutments and an overdenture. Histology staining showed distinction between old and new bone, which formed during the remodeling process. DISCUSSION: The increase in peak forces needed to detach implants at T2 may be explained by bone-to-bone healing or the additional bone contact promoted by bleeding that occurred during the T1 procedure. CONCLUSION: The results suggest that all implants were reintegrated after being intentionally countertorqued to liberation and resumed healing in the original osteotomy position.

Aged↗
PubMed2005

Osteoradionecrosis of the mandible.

PURPOSE OF REVIEW: Osteoradionecrosis of the mandible is a serious complication of radiation therapy to the head and neck. Given the increased use of radiation therapy and combined chemotherapy-radiation therapy regimens in treatment of head and neck malignancies, it is anticipated that osteoradionecrosis will continue to be an important clinical problem. Recently, new concepts have been introduced regarding the pathogenesis of osteoradionecrosis, and these ideas help outline new guidelines for treatment. RECENT FINDINGS: Current literature focuses on the probability of a fibroatrophic mechanism for the development of osteoradionecrosis, rather than the traditional vascular insufficiency mechanism. Because of the evolution of this new idea, as well as a double-blinded, placebo-controlled study finding no benefit from the use of hyperbaric oxygen for advanced osteoradionecrosis of the mandible, new treatment considerations have emerged. Ongoing research is also being conducted to clarify the role of osteoclasts in the pathogenesis of osteoradionecrosis. Restoration of blood supply or vascularized tissue to the affected area continues to be of primary importance in the resolution of osteoradionecrosis. SUMMARY: It is clear that the cause and pathogenesis of osteoradionecrosis are far more complex than originally believed. Current and future research on this multifaceted topic will focus on the cellular basis of this condition, because as it is elucidated, more effective medical treatment regimens will become evident.

Disease Progression↗
PubMed2003

Volumetric change of the medial pterygoid following distraction osteogenesis of the mandible: an example of the associated soft-tissue changes.

Mandibular distraction osteogenesis lengthens not only the affected skeleton but also the associated muscles of mastication. The purpose of this study was to determine medial pterygoid volume before and after distraction by using computed tomography. Using computed tomographic scans, the volume of the medial pterygoid muscle was determined before and after mandibular distraction in six pediatric patients. In four unilateral distraction patients (average age, 65 months), the average increase of the medial pterygoid muscle on the distracted side of the mandible was 29 percent, and on the contralateral nondistracted side, 10 percent. The average increase in medial pterygoid muscle volume in two bilateral distraction patients (each aged 8 months) was 75 percent. Results of this study demonstrate that distraction osteogenesis of the human mandible not only lengthens deficient bone, but it also increases the volume of the attached musculature.

Child↗
PubMed2004

Mandibular angle reduction versus mandible reduction.

The terms "mandibular angle reduction" and "reduction angleplasty" refer to operations to reduce the width of the lower face and change a square face to an oval one. Because the terms emphasize the word angle, however, they imply that the operations apply to the mandibular angle. The most frequent complaint after these operations is that the change in the lateral appearance is clear but that the change in the frontal appearance is not noticeable. Such a result is related to the fact that bone resection is performed mainly in the mandibular angle area and is focused particularly on resection of the posterior projection through curved ostectomy. That is, because operations limited to the mandibular angle area cannot properly satisfy patients' requirements, the operation must be applied to a larger area. Therefore, it seems reasonable to change the terms "mandibular angle reduction" and "reduction angleplasty" to "mandible reduction" and "reduction mandibuloplasty." In addition, the most important technique in the operation is the resection of the outer cortex of the mandible. In particular, the corticectomy technique using a reciprocating saw is quite safe and effective for the maximum resection of lateral flaring within a very short time.

Adult↗
PubMed2007

Microvascular reconstruction of the pediatric mandible.

BACKGROUND: Free tissue transfer for adult mandibular reconstruction is a well-established technique; however, there are few reports of pediatric microvascular lower jaw reconstruction. METHODS: This retrospective study was undertaken to review the range of indications, choices, safety, and efficacy of pediatric free tissue transfer to the lower jaw. All patients underwent a parascapular, scapular, or fibula free tissue transfer. Flap choice was based on preoperative clinical examination, radiographic findings, need for linear or multiplanar mandibular reconstruction, need for dental restoration, severity of soft-tissue deficit, and peroneal artery anatomy. RESULTS: Over a 10-year period (1989 to 1999), we performed eight free tissue transfers to reconstruct the mandibles of seven children, aged 6 to 17 years. Indications included radiation-induced hypoplasia (n = 1), postsurgical resection of fibrous dysplasia (n = 1), hemifacial microsomia (n = 3), Robin sequence with severe micrognathia (n = 1), and osteomyelitis (n = 1). The authors transferred four parascapular osseocutaneous, two scapular osseocutaneous, one fibular osseocutaneous, and one fibular osseous flap to reconstruct five ramus, four condyle, and two subtotal mandibular defects. All bony defects were successfully bridged and all osseous flaps successfully integrated. Postoperatively, mandibular symmetry and Angle class I occlusion were restored in all patients throughout the 10.5-year follow-up period (range, 9 to 14 years). Two patients received osseointegrated dental implants. Our only complication was the partial loss of a skin paddle. CONCLUSION: Microvascular reconstruction of the pediatric mandible, in selected patients, is a safe, reliable procedure that provides the bone stock and soft tissue necessary to restore normal maxillomandibular growth and dental rehabilitation.

Adolescent↗
PubMed2005

Three-dimensional finite element analysis of the mandible and temporomandibular joint during vertical ramus elongation by distraction osteogenesis.

Distraction osteogenesis has been accepted as an alternative treatment modality for hypoplastic mandibles. Knowledge about the changes occurring in the temporomandibular joint region during mandibular distraction osteogenesis is, however, limited and controversial. Stress distribution in the temporomandibular joint region during unilateral vertical mandibular ramus distraction was studied using a finite element model. The finite element model was based on computed tomography scans and magnetic resonance imaging scans of a patient with unilateral hypoplasia of the right mandibular ramus caused by juvenile idiopathic arthritis. The character of stress distribution in the temporomandibular joint and mandible was analyzed quantitatively at different intervals of the vertical mandibular ramus elongation. During the distraction phase, the condyles, articular disks, and glenoid fossa regions were loaded with a differentiated stress pattern. The affected right condyle, disk, and fossa were submitted to increasing loads with increasing elongation compared with the contralateral temporomandibular joint. Loading on the unaffected left side shifted posteriorly and slightly laterally, because the left condyle was the center of rotation. The loading of the temporomandibular joint regions was low during the active distraction phase, although local areas were subjected to elevated peak stresses.

Arthritis, Juvenile↗
PubMed2004

Recruitment of osteoclasts in the mandible of osteopetrotic (op/op) mice.

Osteoclasts in osteopetrotic (op/op) mice are substantially reduced by the absence of functional activities of macrophage colony-stimulating factor (M-CSF). However, it is known that osteoclasts appear in op/op skeletal bones with aging, although the molecular mechanism for this is unknown. In order to investigate osteoclastic recruitment in the jaw bones of op/op mice, osteoclastic distribution was analysed for 2 yr after birth by histochemistry for tartrate-resistant acid phosphatase activity and immunohistochemistry for cathepsin K. Osteoclasts in op/op mandibular bones decreased rapidly in number after birth and disappeared by 3 d, although there was no difference in the osteoclastic distribution between op/op and normal littermates at birth. At 2 wk, osteoclasts began to reappear around op/op tooth germs, where no apparent connective tissue layer intervened between tooth germs and bone trabeculae. They increased in number and were scattered over the mandible, reaching a maximum at 8 wk, when periodontal ligament-like structures were recognizable around incisor germs. Osteoclasts then again decreased gradually, and after 62 wk few osteoclasts were seen in op/op mandibular bones, whose marrow space disappeared. These findings suggest that osteoclasts are recruited in an M-CSF-independent manner in op/op mandibles, especially in areas around tooth germs.

Acid Phosphatase↗
PubMed1988

Tooth support in the human mandible.

Prepared surfaces of anterior portions of dentate human mandibles were serially ground in steps of 0.2 mm and the anatomical features traced. The information was stored in a computer and then reassembled and plotted in colour. The percentage porosity of the bone, together with the width of the periodontal space was calculated. The cortical plates of the mandible appear to provide the major boney support for the anterior teeth, trabecular bone only being present in scant amounts in the periapical areas. The apparently random arrangement of trabeculae does not support the commonly accepted picture of trabeculae aligned to resist the functional loads transmitted by the periodontal ligament.

Bone Marrow↗
PubMed2005

Repair of mandible defect with tissue engineering bone in rabbits.

BACKGROUND: The aim of the present study was to investigate the effect of tissue engineering bone composed of bone marrow-derived osteoblasts and demineralized bone in repairing mandible defect. METHODS: Bone marrow-derived osteoblasts of 20 rabbits were cultured and seeded into scaffold of allogeneic demineralized bone to construct tissue engineering bone graft in vitro, which was used to repair the 10 x 5-mm bone defect made in the same rabbit mandible edge. Implant of demineralized bone alone was as the control. Rabbits were killed according to the schedule: five after 2 weeks, five after 4 weeks, five after 8 weeks, five after 12 weeks, and the implants were harvested for gross, radiographic, and histological observation. RESULTS: New bone formation at the margin region of defect and osteogenesis at the centre were observed in the implant of tissue engineering bone, and the bone formation pattern included osteogenesis, osteoconduction, and osteoinduction. In the implant of demineralized bone alone, the major bone formation pattern was 'creeping substitute'. CONCLUSIONS: The tissue engineering bone graft constructed by autogenous bone marrow-derived osteoblasts and allogeneic demineralized bone was better than demineralized bone alone in bone formation capability, which might be an ideal graft for bone defect repair.

Animals↗
PubMed2006

Inconsistency of the maxilla and mandible in the Minatogawa Man No. 1 hominid fossil evaluated from dental occlusion.

The Minatogawa man hominid fossils are human fossils from Japan and the oldest from the Late Pleistocene period. Of the Minatogawa skeletal remains, Minatogawa Man No. 1 is best preserved and is accompanied by the mandible. When the maxillary and mandibular dentitions of Minatogawa Man No. 1 were occluded, the dentitions did not align with one another. The attrition pattern of the maxillary teeth was of an inclined type, which tilted from the buccal to lingual side, whereas that of the mandibular dentition was of a horizontal type. Moreover, both left maxillary and mandibular third molars exhibited attrition on the distal portion of the occlusal surface. The occlusal surfaces did not complement each other in the range of mandibular movement without temporomandibular joint dislocation and the curve of Spee produced by the left maxillary and mandibular occlusal planes did not match. These findings suggest that the maxilla and mandible of Minatogawa Man No. 1 are, in fact, from different individuals.

Dental Occlusion↗
PubMed2007

Sexual dimorphism in the subadult mandible: quantification using geometric morphometrics.

There have been numerous attempts, with varying degrees of success, to differentiate males from females on the basis of the immature skeleton. We investigate here whether the mandible can discriminate immature individuals by sex; the techniques we apply are from the field of geometric morphometrics. The application of these methods in forensic anthropology is still relatively new; thus, an important aspect of this research is that it demonstrates potential applications in this discipline. The sample comprises 96 known age and sex subadult individuals; the three-dimensional coordinates of 38 landmarks are analyzed using the shape analysis software morphologika. Multivariate regressions indicated no significant sexual dimorphism in the subadult sample; this result is supported by poor cross-validated classification accuracy (59%). Our results suggest that the subadult mandible is not dimorphic (to the extent that dimorphism is not evident within the sample we studied); thus, sex determination using previously described criteria is likely to yield poor results.

Adolescent↗
PubMed2004

Three-dimensional morphometric analysis of human cadaver bone: microstructural data from maxilla and mandible.

The mechanical behavior of bone is a critical factor in the attainment and maintenance of osseointegration. Current procedures and classifications in assessing bone quality have limitations. Micro-computed tomography (microCT) is a new method to image and quantify bone with very high resolution. This study was aimed to analyze cadaveric maxillary and mandibular trabecular bone with 3-D morphometric data acquired through microCT and correlate with conventional bone assessment methods. Moderately resorbed edentulous maxilla and mandible from a human cadaver were scanned in the conventional CT unit with opaque markers indicating specific anterior and posterior sites. These sites were then sectioned and standard periapical radiographs were obtained. Bone cores were harvested from the sectioned sites and scanned in the microCT unit. Bone density values based on the Hounsfield scale ranged from 51 to 529 in the mandible and 186 to 389 in the maxilla, anterior sites being higher in both. Periapical images did not yield distinct differences. 3-D morphometric analysis in microCT produced a range of values with anterior specimens being favorable: bone volume density (0.12-0.291), trabecular thickness (0.12-0.16 mm), trabecular separation (0.46-0.82 mm), trabecular number (1.08-2.071/mm) and structural model index (0.29-1.27). General agreement between bone density and microCT indices was noted; however, subtle differences have to be studied with larger samples. This preliminary study suggests that the understanding of mechanical competence of trabecular bone might reveal further information about the prognosis of implant therapy, advancements in implant design, surgical techniques and grafting.

Aged↗
PubMed2004

Vertical distraction osteogenesis of the mandible applied to an iliac crest graft: report of a case.

OBJECTIVES: This clinical case represents a particular application of vertical distraction osteogenesis of the mandible. The surgical technique was applied to an iliac crest bone graft previously positioned on an anterior mandibular defect with the aim to restore the vertical height after a partial resorption in a trauma patient. CASE REPORT: Distraction osteogenesis was applied because it was necessary to restore the mandibular height in a young male patient who presented with a post-trauma anterior mandibular bony deficiency. Because of the irregularity of the mandibular surface and the depth of the defect, the patient first underwent an iliac crest bone grafting that, after 3 months, showed partial resorption. Vertical distraction osteogenesis was performed on the grafted mandible in order to obtain a satisfactory bony height of the mandibular ridge. Then the patient was successfully rehabilitated by means of an implant-supported prosthesis. CONCLUSION: Vertical distraction osteogenesis appears to be a versatile surgical procedure, which can be applied as a secondary treatment in patients presenting with mandibular trauma sequelae.

Adult↗
PubMed2004

Area moments of inertia as a measure of the mandible stiffness of the implant patient.

It was hypothesized that the bending stiffness of the mandible is an important biomechanical parameter in implant dentistry. It was shown how this bending stiffness can be estimated by means of the principal area moments of inertia of the cortical and cancellous cross-sections as obtained by computed tomography, some image processing and subsequent calculation. It was found that the contribution of the cancellous bone to the bending stiffness is normally insignificant and that the principal area moments of inertia of the cortical cross-section show large variations, depending on the degree of resorption. It was furthermore found that the variations in the principal area moments of inertia of the cortical cross-section in one and the same potential implant patient were minor. Finally, in a three-dimensional finite element study, it was found that the peak bone stresses adjacent to implants, resulting from a standardized load at the distal end of an implant-supported bridge, were inversely related to the magnitude of the principal area moment of inertia about the horizontal axis of the cortical cross-section. It was concluded that the principal area moments of inertia of the cortical cross-section and the angulation of the principal axes of inertia might be useful as a quantitative characterization of the mandible stiffness in clinical research and perhaps also in clinical practice.

Bite Force↗
PubMed2004

Study on the necessity for cross-section imaging of the posterior mandible for treatment planning of standard cases in implant dentistry.

OBJECTIVE: To investigate whether cross-section imaging influences the planning and therapy of standard implant cases in the posterior mandible. MATERIAL AND METHODS: In a prospective study conducted over 16 months, the planned treatment (standard implant therapy without bone augmentation procedures in the premolar and molar regions of the mandible) was compared with the postoperative result in 50 randomly selected patients. Clinical examinations and panoramic radiographs were performed pre- and postoperatively, whereas cross-sectional tomography was performed only preoperatively. RESULTS: The vertical magnification factor in the panoramic radiographs was very constant pre- and postoperatively with 1 : 1.27 and in the spiral tomograms with 1 : 1.52. In 11 of 77 implant sites, the mandibular canal could not be evaluated in the spiral tomograms. The additional information from cross-sectional spiral tomography did not influence the original planning in 74 of 77 (96.1%) implant sites. Based on the postoperative panoramic radiograph, the average distance from the tip of the implants to the mandibular canal was 3.04+/-2.06 mm. In two cases (2.6%), transient postoperative altered tactile sensation of the mental nerve was found. CONCLUSION: The information from preoperative cross-sectional spiral tomography has minor impact on treatment planning in standard implant cases in mandibular premolar and molar regions. The clinical examination provides sufficient information for selecting implant diameter and the panoramic radiograph provides sufficient information for implant length selection.

Bicuspid↗