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At least 505 records · Page 28Linked to original sources
PubMed1997

Long-term evaluation of bone mass in free fibula flap mandible reconstruction.

BACKGROUND: Vascularized fibula transfer has become a preferred method of mandibular restoration after oncologic surgical ablation. In order to elucidate the long-term effect on fibular mass after mandibular reconstruction, change in fibular height was utilized as an indirect measure of change in bone mass over time. Other potentially influential factors in long-term bone mass preservation were evaluated; these included site of reconstruction (central, body, ramus), patient age, length of follow-up, adjuvant radiotherapy, and the delayed placement of osseointegrated dental implants. METHODS: A retrospective analysis of patients undergoing free fibula mandible reconstruction for oncologic surgical defects between 1987 and 1993 was performed. Postoperative panorex examinations were used to evaluate fibular height and bony union after osteotomy. Fixation hardware was used as a reference to eliminate magnification as a possible source of error in measurement. Only patients with at least 24 months follow-up were included in this study. RESULTS: There were 27 patients (15 males and 12 females) with a mean age of 43 years (range 14 to 65) included in this study. Mandibular defects were anterior (16) and lateral (11). There were between two and five segmental osteotomies per patient (excluding the ends of the graft). Thirty percent of patients had delayed placement of osseointegrated dental implants. Initial panorex examinations were taken between 1 and 9 months (mean 2) postoperatively. Follow-up panorex examinations were taken 24 to 104 months (mean 54) postoperatively. The bony union rate after osteotomy was 93%. Comparative measurements of fibular height revealed that central segments underwent a mean decrease in height by 4% (range 0% to 22%); body segments decreased in height by 7% (range 0% to 33%); ramus segments decreased in height by 5% (range 0% to 15%). In each anatomic segment, fibular height varied by 10% or less when compared with respect to patient age, length of follow-up, adjuvant radiation therapy, and the presence of osseointegrated dental implants. CONCLUSIONS: We conclude that the retention of fibula height seen in this study indicates that fibula bone mass is preserved after free flap mandible reconstruction. Furthermore, these findings are not affected by the site of reconstruction, patient age, length of follow-up, adjuvant radiation therapy, or presence of osseointegrated dental implants. This study further supports the efficacy of vascularized fibula grafts for mandible reconstruction.

Adult↗
PubMed2000

Elevation of histidine decarboxylase activity in the mandible of mice by Prevotella intermedia lipopolysaccharide and its augmentation by an aminobisphosphonate.

Lipopolysaccharide (LPS) produced by Gram-negative bacteria is an important cause of inflammation. Aminobisphosphonates are potent inhibitors of bone resorption but have inflammatory side-effects. Here, the effects of LPS from Prevotella intermedia (a prevalent Gram-negative bacterium both in periodontitis and endodontal infections) and alendronate (an aminobisphosphonate) on the activity of the histamine-forming enzyme, histidine decarboxylase (HDC), were examined in mouse mandible. Intravenous injection of P. intermedia LPS increased HDC activity in the mandible, maximal activity being induced within 3-6 h of the injection. The elevation of HDC activity was dependent on the dose of LPS, 10 microg/kg (0.25 microg/mouse) producing a significant elevation in enzyme activity. Intraperitoneal injection of alendronate (40 micromol/kg) also produced an increase in HDC activity. Moreover, the elevation of HDC activity induced by P. intermedia LPS was markedly augmented in mice given alendronate 3 days before the LPS injection. These results (i) suggest that P. intermedia LPS may stimulate the synthesis of histamine in the mandible and that the newly formed histamine may make at least some contribution to the development of inflammation (apical periodontitis and/or osteomyelitis); (ii) should encourage the clinical testing of antihistaminergic agents against inflammation; and (iii) confirm that care needs to be taken when administering aminobisphosphonates to patients.

Alendronate↗
PubMed2001

Differential expression of myosin heavy-chain mRNA in muscles of mastication during functional advancement of the mandible in pigs.

Surgical and orthodontic treatment of retrognathia aims to improve orofacial function by adaptation and training of muscle capacity, which is connected with a change in muscle fibre-type proportions. The aim here was to analyse the proportion of myosin-heavy chain (MyHC) gene expression in type I (slow twitch/ST) and type IIb (fast twitch/FT) fibres during sagittal advancement of the mandible by reverse transcriptase-polymerase chain reaction (RT-PCR). The experiments were carried out on 10-week-old pigs (six test animals, six controls) over a 28-day period. Six pigs were fitted with acrylic bite blocks for sagittal advancement of the mandible. Tissue was taken from seven different regions of the masseter, temporal, medial pterygoid, and geniohyoid muscles. The 84 samples were used for histological fibre differentiation with ATPase staining and for isolation of total RNA. To measure the two MyHC isoforms, RT-PCR (in a single tube reaction with MyHC I, MyHC IIb, and GAPDH primers) was used. A significant increase was registered in the percentage of ST fibres and in mRNA from MyHC I in the anterior region of the masseter and in the posterior region of the temporal muscle of the treated animals. The proportion of ST fibres to FT fibres was increased by up to 12% after functional advancement of the mandible. The histological findings corresponded with the data for fibre mRNA generated by RT-PCR.

Acrylic Resins↗
PubMed1982

Mechanisms of early skeletal release following surgical advancement of the mandible.

Despite recent innovative technical and biological advances, surgical advancement of the mandible does not demonstrate uniform skeletal stability. In fact, the results of recent investigations have shown that considerable skeletal relapse occurs quite early in the post-surgical period. This article reviews current literature to implicate the factors primarily responsible for early skeletal relapse following surgical advancement of the mandible via the modified sagittal split ramus osteotomy. Three specific mechanisms which commonly predispose this orthognathic procedure to skeletal relapse are delineated. Prolonged skeletal stabilisation with control of the proximal segment of the mandible is advocated to insure predictably stable results.

Humans↗
PubMed2003

Clinical bone densitometric evaluation of the mandible in removable denture wearers dependent on the morphology of the mandibular cortex.

STATEMENT OF PROBLEM: Wide normal variations have been found in the structure and density of the human skeleton, as well as of the mandible. PURPOSE: The objective of this study was to determine whether the mandibular bone mineral density is correlated with the classification of the structure of the inferior cortex on panoramic radiographs in complete and removable partial denture wearers. MATERIALS AND METHODS: The mandibular cortical index of 136 randomly selected complete and removable partial denture wearers was evaluated via panoramic radiographs. The criteria for the mandibular cortical index were as follow: category 1, sharp endosteal margin of the inferior cortex; category 2, semilunar defects; and category 3, thick cortical residues on endosteal margin. Forty male patients (mean age 72.7; range 56 to 84 years) and 96 female patients (mean age 69.7; range 48 to 86 years) participated. With a copper stepwedge and DenEx 2001 computer program, the mandibular bone mineral density was investigated densitometrically on dental panoramic radiographs. Four experienced observers and 6 general dental practitioners made the observations on all panoramic radiographs. All bone mineral density values were expressed in equivalents of the actual stepwedge thickness. An independent t test (alpha =.05) was used. RESULTS: The severity of changes in the mandibular cortex was significantly related to all measured mandibular bone mineral density values (t test: P<.01). Mandibular cortical index category 3 had significantly lower bone mineral density values in all measured regions of interest. Interobserver and intraobserver agreement in mandibular cortical index assessment was excellent. CONCLUSION: Patients having lower bone mineral density values in the mandible have much more porous cortical layer of the inferior border of the mandible.

Absorptiometry, Photon↗
PubMed1997

Clinical application of short hydroxylapatite-coated dental implants to the posterior mandible: a five-year survival study.

STATEMENT OF PROBLEM: The surgical and restorative procedures at the posterior region of the maxilla and the mandible present a complex task in the treatment of partially edentulous patients. PURPOSE: The purpose of this study was to investigate the applicability of short hydroxylapatite-coated dental implants to the posterior mandible of partially edentulous patients. MATERIAL AND METHODS: Eight and 11 mm implants were evaluated as to their cumulative survival rate, clinical status (plaque index, gingival index, probing depth), and marginal bone loss over a 5-year period. RESULTS AND CONCLUSIONS: The verified overall cumulative survival rate was 94% for implants and 91% for prostheses. These results suggest predictable success for the application of short implants to the posterior mandible.

Alloys↗
PubMed1992

Anatomical relationship of the mandibular canal to its surrounding structures in mature mandibles.

A lack of agreement exists in the literature regarding the anatomical relationship of the mandibular canal to its surrounding structures such as the root apices. The purpose of this investigation was to study the spatial relationship of the mandibular canal to the posterior teeth in dried human mandibles. Twenty-two mature dried mandibles were sectioned through the root apices of the first and second premolars and molars. Second premolars and second molars had the closest distances to the canal with a mean of 4.7 mm and 3.7 mm, respectively. With a mean of 6.9 mm, the apices of the mesial roots of the first molars were farthest from the canal. The canal pathway in mature mandibles followed in S-shaped curve in 31% of the cases. In 41% of the cases it was located lingual (19%), buccal (17%), or directly inferior (5%) to the apices of the posterior teeth. In 28% of the cases the canal could not be identified clearly in the second premolar and first molar regions. In a typical S-shaped configuration the canal was located buccal to the distal root of the second molar, crossed to the lingual below the second molar mesial root, ran lingual to the first molar, and crossed back to the buccal apical to the apex of the second premolar. Based on our results it appears that the mandibular second premolar and second molar are the most likely teeth to be involved in accidental damage to the mandibular canal during root canal therapy.

Bicuspid↗
PubMed2000

Effect of unilateral superior cervical ganglionectomy on bone mineral content and density of rat's mandible.

To assess the effect of a local sympathectomy on bone metabolism, the effect of a unilateral superior cervical ganglionectomy (Gx) on growth and bone mineral content and density of the ipsi- and contralateral mandibles was examined in female rats. A significant increase in the hemi-mandibular bone ipsilateral to Gx was found as compared to the contralateral, sham-operated side 30 days, but not 15 days, after surgery. Bone mineral content of the hemi-mandibular bones was significantly lower in the side ipsilateral to Gx in the group of rats killed on the 30th day after surgery. Since no difference in areas between innervated and denervated hemi-mandibles was found, bone mineral density was also significantly lower in the hemi-mandible ipsilateral to Gx. The results further support that a regional sympathectomy causes qualitative alterations in bone modeling and remodeling, leading to bone resorption.

Animals↗
PubMed1996

Distraction osteogenesis in the mandible with a motor-driven plate: a preliminary animal study.

Distraction osteogenesis is an established method for lengthening of the mandible and for reconstruction of bony defects. We report on our first experience with a motor-driven 2.7 mm plate which was fixed at the lingual surface of the body of the mandible in Göttingen minipigs following osteotomy of the mandible. The power supply and the timer module were inserted subcutaneously in a neck pocket. A maximum distraction of 13 mm was observed. Further research is necessary before clinical application of a comparable system.

Animals↗
PubMed1996

Clinical features and management of ameloblastoma of the mandible in children and adolescents.

Thirty cases of ameloblastoma of the mandible in children and adolescents were reviewed. During the period of evaluation, 206 patients with ameloblastoma in the craniofacial region were seen of which 14.6% were in children (under 18 years). The tumour was more prevalent in male (1.5:1). Enucleation with curettage of the surrounding bones appears adequate for unicystic lesions. Multicystic lesions were managed by radical resection of the mandible with or without immediate reconstruction of defect with bone graft or by resection of the lesion with the dentoalveolar structure and preservation of the lower border of the mandible. Uninvolved periosteum should be preserved because of its osteogenic potential.

Adolescent↗
PubMed1997

Surgical treatment of fractures of the edentulous mandible.

PURPOSE: This retrospective study presents treatment alternatives for fractures of the edentulous mandible. METHODS: A chart review of 34 patients with fractures of the edentulous mandible was performed. Patients were followed with clinical and radiographic examinations. RESULTS: Five different treatment groups were used, ranging from closed treatment to bone graft augmentation and immediate placement of dental implants. Twenty-five patients showed good bony union. Frequent complications were encountered, including pseudarthrosis, fractured plates, and persistent dysesthesia. Augmentation was more stable when implants were placed simultaneously. CONCLUSION: Treatment needs to be based on the type and location of the fracture and the degree of atrophy. Augmentation in combination with implants appears to be a good treatment for fractures of the edentulous mandible.

Adult↗
PubMed1997

A comparison of segmental and marginal bony resection for oral squamous cell carcinoma involving the mandible.

PURPOSE: This study reviews the accuracy of preopertive diagnosis of mandibular invasion by oral squamous cell carcinoma and assesses the role of marginal resection of the mandible in its treatment. PATIENTS AND METHODS: A retrospective study of a 5-year cohort of 46 patients who underwent mandibular resection for previously untreated oral squamous cell carcinoma was done. Data evaluated included age; sex; site and stage of cancer; preoperative clinical, panoramic, and computed tomography (CT) evaluations; and histologic findings on the resection specimen. The type of mandibular resection (segmental vs marginal) and treatment outcome also were compared. RESULTS: Clinical examination, panoramic radiographs, and CT scans were 78.5% to 82.6% accurate in diagnosing mandibular invasion by squamous carcinoma. Clinical examination and panoramic radiographs are more sensitive than CT scans (86.6% vs 53%), but CT scans were more specific (92.5% vs 80%). The mandible was involved in 65% of patients with segmental resection and 7.6% of patients who had a marginal resection. Nineteen percent of the patients in the marginal resection group died of their oral cancer, two of five patients with local recurrence. Ten percent of patients in the segmental resection group died of oral cancer; no local recurrences were seen. CONCLUSION: There is no completely accurate method of diagnosing bony invasion of the mandible by oral squamous cell carcinoma. A combination of clinical examination, plain radiographs, and computed tomography (CT) scans may improve the diagnosis. Marginal resection is best reserved for cancers close to the bone with no invasion, minimal cortical invasion, or with early "arrosive" invasion. It is best in the symphysis region. Careful case selection will allow a favorable oncologic outcome with preservation of the mandibular contour.

Adult↗
PubMed1998

Experimental reconstruction of the mandible using polylactic acid tubes and basic fibroblast growth factor in alloplastic scaffolds.

PURPOSE: This study evaluated the use of a mitogenic growth factor in combination with barrier membranes and porous alloplastic scaffolds for the repair of segmental defects of the mandible. MATERIALS AND METHODS: Fifteen Göttingen minipigs were used for the study. In five animals, mandibular defects of 2 cm were created on both sides of the mandible and bridged by a system of polylactic acid (PLA) tubes and pyrolized bovine bone. On one side of the mandible, the alloplastic scaffolds were loaded with 115 microg recombinant human basic fibroblast growth factor (rhbFGF). In five other animals, defects 4 cm in length were created bilaterally, similarly bridged, and loaded with 230 microg of rhFGF. In five control animals, bilateral 2-cm defects were created that were left empty on one side and bridged with an empty PLA tube on the other. Mitogenic efficacy of the growth factor was assessed on fibroblast cultures by di-methyl-thiazol-2-tetrazolium-bromide assay before implantation. RESULTS: After 5 months, there was negligible bone regeneration in the control defects, regardless of whether they had been left completely empty or bridged by empty PLA tubes. The 2-cm defects showed bridging in 8 of 10 tubes, with complete consolidation by bone ingrowth in four defects. The 4-cm defects showed bony union in six cases, with complete bone fill in two tubes, and four defects incompletely filled. The bFGF had no appreciable effect with regard to velocity, quantity, and three-dimensional structure of bone formation, neither in the short nor in the long defects despite clear in vitro efficacy. CONCLUSION: Repair of segmental defects using bioresorbable membranes appears to be possible. However, a single-dose application of bFGF is apparently ineffective, possibly because of rapid dilution.

Animals↗
PubMed1999

Mechanical properties of trabecular bone in the human mandible: implications for dental implant treatment planning and surgical placement.

PURPOSE: This study sought to establish the relationships between bone density, elastic modulus, and ultimate compressive strength of trabecular bone in the human mandible, and to determine the influence that the cortical plates have on these values. MATERIALS AND METHODS: Nine fresh-frozen human mandibles between the ages of 56 and 90 years were cut into anterior (incisors and canine), middle (premolars), and distal (molars) sections. Seventy-six cylindrical trabecular bone specimens with bone marrow in situ were then prepared and tested in compression in the vertical direction. These tests were performed at a constant strain rate of 0.01 s(-1) with and without the presence of the cortical plates. RESULT: The density of mandibular trabecular specimens with bone marrow in situ ranged from 0.85 to 1.53 g/cm3, with a mean value of 1.14 g/cm3 (SD = 0.15). With the cortical plates present, the elastic modulus ranged from 24.9 to 240.0 megapascals (MPa), with a mean value of 96.2 MPa (standard deviation (SD) = 40.6). Without the cortical plates present, the elastic modulus ranged from 3.5 to 125.6 MPa, with a mean value of 56.0 MPa (SD = 29.6). The ultimate compressive strength of the trabecular bone ranged from 0.22 to 10.44 MPa, with a mean value of 3.9 MPa (SD = 2.7). CONCLUSION: This study indicates that the trabecular bone in the human mandible possesses significantly higher density, elastic modulus, and ultimate compressive strength in the anterior region than in either the middle or distal regions. The absence of cortical plates decreases the bone elastic modulus. These findings quantitatively confirm the need for clinical awareness in altering implant treatment plans and/or design in relation to bone density and the presence of the cortical plates.

Adolescent↗
PubMed1999

Experimental computer-assisted alloplastic sandwich augmentation of the atrophic mandible.

PURPOSE: This study evaluated the effectiveness of a technique that combined computer-aided surgery with alloplastic augmentation and implant-borne prosthodontic rehabilitation of the atrophic mandible. MATERIALS AND METHODS: Computed tomographic (CT) data from an atrophic cadaver mandible were transferred to a computer-aided design (CAD) system that prepared an anterior sandwich osteotomy. The cranial segment was moved upward and backward to provide an ideal alveolar relationship, and the geometry of the intermediate space was used to design a titanium implant. Furthermore, a surgical template was derived for the osteotomies, and insertion of dental implants was planned to stabilize both the transposed bone and the intermediate implant on the bony base. An identical implant for augmentation was also fabricated from poly-D,L-lactide in a mold as a possible resorbable carrier for osteoinductive proteins. RESULTS: The experimental surgery was successfully performed with maximum precision on the dried mandible. The fabrication of an implant made out of poly-D,L-lactide for the same purpose was also possible. CONCLUSIONS: This preliminary experiment showed that it is possible to use CAD/computer-aided manufacturing (CAM) technology to prepare a prefabricated template and a corresponding titanium implant for mandibular augmentation with a high degree of exactness. Dental implants could be planned and integrated in this procedure as well. The fabrication of a mold using this method also provided the opportunity to give a complex shape to possible carriers of osteoinductive substances.

Alveolar Bone Loss↗
PubMed1980

Rhabdomyosarcoma: report of a case with involvement of the angle of the mandible.

The most common signs of a malignancy in the region of the head and neck are evidence of a mass or symptoms arising from it. In this report a patient is described with rhabdomyosarcoma of the mandible. An incidental x-ray taken some 3 months prior to the onset of clinical symptoms showed no evidence of bone involvement of the mandible. The onset of bone destruction of the angle and ascending ramus of the mandible as seen on a subsequent x-ray can be placed somewhere in this period of time.

Child↗
PubMed1984

Studies on protracted tissue reactions and repair after circulatory and skeletal damage to the rat mandible.

The effect of circulatory and skeletal damage to the distal part of the mandible was studied on young growing rats after interruption of the inferior alveolar artery. The central part of the mandible including the incisor was most vulnerable to circulatory trauma. Maximal damage was seen when the inferior alveolar artery was interrupted combined with bilateral reflection of the mandibular periosteum. The damage produced then was a necrosis of the incisor pulp, odontoblasts and enamel organ and extensive resorption of the centrally-located compact bone. When both sides of the mucoperiosteum remained intact, damage to the main vessels of the mandible did not produce total necrosis of the incisor pulp. Reparative events with production of a fibrous connective tissue of the pulp and osteodentin production were seen. After resorption of sequestered bone was finished, this was replaced by a cell-rich type of bone which also replaced the alveola of those animals which had had their incisors excised. Hypercementosis was seen in the molars after 1 year. No respiratory activity in the incisor pulps was seen after the circulatory damage.

Animals↗
PubMed1978

Correction of jaw deformities involving simultaneous osteotomy of the mandible and maxilla.

A one-stage surgical correction of gnathic deformities involving both jaws is described. It permits both the establishment of a normal occlusion and correct alignment of the occlusal plane to the skull. The osteotomy commences with the mandible. Its new position is oriented to the (as yet) untouched maxilla with the aid of an intermediate occlusal splint produced as a result of cephalometric evaluation and cast model surgery. The mandible is secured at its osteotomy sites by bone screws, in the correct final position. The maxilla is then oriented to the mandible, now correctly positioned with the aid of a second, preformed occlusal splint again produced on the basis of cast model surgery. Following intermaxillary fixation and internal wire suspension the splint is left in place until bony consolidation has taken place. External fixation is not required. The procedure enables the cephalometrically established measurements for the movements of both jaws to be easily reproduced with a high degree of accuracy. The technique is described in detail and discussed on the basis of clinical examples.

Cephalometry↗