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At least 577 records · Page 32Linked to original sources
PubMed1996

Postoperative function after implant insertion in vascularized bone grafts in maxilla and mandible.

Between 1988 and 1992, 80 Brånemark-type implants were inserted in 18 patients during reconstruction of the mandible or maxilla with vascularized iliac crest or scapula grafts with or without additional soft tissue pedicles. In these procedures, nine vascularized bone grafts were combined with a primary insertion of 32 implants and a secondary insertion of 48 implants. Twelve patients are currently wearing the implant-borne dentures. From 32 implants inserted primarily, eight could not be used for prosthodontic rehabilitation because three were lost with a graft, three were left as sleepers, and two demonstrated a lack of osseointegration. None of the implants inserted secondarily in grafts were lost. Primary implant insertion should be performed only in close cooperation with the prosthodontist and in selected cases, for example, in free-end reconstruction of the mandible with a straight graft and where a limited number of implants is needed. Although restoration of masticatory function in patients with head and neck cancer can be achieved, compared with a healthy control group, functional impairments remain. Patients subjectively favor the nonreconstructed side of the mandible or maxilla for chewing. These findings can be correlated with a postoperative follow-up investigation using a miniature force transducer and the T-scan system.

Denture, Partial↗
PubMed1997

Migration of hydroxyapatite onlays into the mandible and nasal bone and local bone turnover in growing rabbits.

To determine the effects of local bone turnover on the migration of macroporous hydroxyapatite onlays in the nasal bone and mandibular ramus, we performed histomorphometric analyses of the underlying bone area in 41 New Zealand White rabbits from the age of 4 weeks. The hydroxyapatite implants were placed under the periosteum of the right nasal bone (a depository bone onto its periosteal surface and endosteal resorptive) and the mandibular ramus (resorptive onto its outer surface). The corresponding left sides were sham operated. Following fluorescence bone labeling, composite specimens of the hydroxyapatite block including both sides of the nasal bone and mandible were removed at 0 (n = 1), 3, 6, 9, 12, and 16 weeks postoperatively (n = 8, respectively) and processed to yield undecalcified sections. Bone-bone marrow interfaces in the entire area within 200 microns beneath the base of the hydroxyapatite and in the counter-area on the sham-operated side were measured under a light microscope. In all grafted specimens, the hydroxyapatite matrix was directly united with the underlying tissue by bone ingrowth. However, the sinking of the hydroxyapatite graft in the nasal bone was significant at 3 weeks postoperatively and gradually increased thereafter. In the mandible, the sinking became significant at 6 weeks. In the nasal bone, the bone area density beneath the graft showed a time-dependent decrease during the experimental period, but in the mandibular bone, the value was initially decreased at 3 weeks and then recovered to baseline level. In both bones, parameters of bone resorption, such as osteoclast number and osteoclast surface, were significantly increased from 3 weeks. While the parameters of bone formation, such as osteoblast surface and mineralizing surface, were significantly decreased from 3 weeks in the nasal bone, they were significantly increased in the mandible. Mineral apposition rate showed a significant decrease in both bones. Our data indicate that while the bone area density beneath the hydroxyapatite seemed to depend on bone formation, increased bone resorption would be more critical for the remodeling of underlying bony architecture in the migration of the hydroxyapatite graft.

Animals↗
PubMed1999

Reconstruction of the mandible with osseous free flaps: a 10-year experience with 150 consecutive patients.

Osseous free flaps have become the preferred method for reconstructing segmental mandibular defects. Of 457 head and neck free flaps, 150 osseous mandible reconstructions were performed over a 10-year period. This experience was retrospectively reviewed to establish an approach to osseous free flap mandible reconstruction. There were 94 male and 56 female patients (mean age, 50 years; range 3 to 79 years); 43 percent had hemimandibular defects, and the rest had central, lateral, or a combination defect. Donor sites included the fibula (90 percent), radius (4 percent), scapula (4 percent), and ilium (2 percent). Rigid fixation (up to five osteotomy sites) was used in 98 percent of patients. Aesthetic and functional results were evaluated a minimum of 6 months postoperatively. The free flap success rate was 100 percent, and bony union was achieved in 97 percent of the osteotomy sites. Osseointegrated dental implants were placed in 20 patients. A return to an unrestricted diet was achieved in 45 percent of patients; 45 percent returned to a soft diet, and 5 percent were on a liquid diet. Five percent of patients required enteral feeding to maintain weight. Speech was assessed as normal (36 percent), near normal (27 percent), intelligible (28 percent), or unintelligible (9 percent). Aesthetic outcome was judged as excellent (32 percent), good (27 percent), fair (27 percent), or poor (14 percent). This study demonstrates a very high success rate, with good-to-excellent functional and aesthetic results using osseous free flaps for primary mandible reconstruction. The fibula donor site should be the first choice for most cases, particularly those with anterior or large bony defects requiring multiple osteotomies. Use of alternative donor sites (i.e., radius and scapula) is best reserved for cases with large soft-tissue and minimal bone requirements. The ilium is recommended only when other options are unavailable. Thoughtful flap selection and design should supplant the need for multiple, simultaneous free flaps and vein grafting in most cases.

Adolescent↗
PubMed2002

The effects of magnitude and frequency of distraction forces on tissue regeneration in distraction osteogenesis of the mandible.

Callus distraction has become an accepted treatment procedure to lengthen hypoplastic mandibles in humans. For this purpose, extraoral and intraoral devices have been applied successfully. The effects of the distraction vector, distractor stability, and rate and frequency of callus distraction on the regenerating tissues have been examined in various studies. In an experimental animal trial on pigs (n = 12), a newly developed microhydraulic osteodistractor was tested. The animals were evenly assigned to two groups to perform a continuous and noncontinuous osteodistraction of the mandible. Initially, the forces necessary to distract the pig mandibles were recorded from a noncontinuous distraction procedure; the results were then used to perform continuous bone distraction. Besides testing the new distractor, the study proved that in continuous osteodistraction, intramembranous bone regeneration occurred, whereas in noncontinuous osteodistraction the bone regeneration process followed a chondroid ossification. In continuous osteodistraction, the bone regeneration proceeded at a higher speed with the lower distraction forces compared with noncontinuous distraction, thereby reducing the consolidation period. Clinical and microscopical results are presented.

Animals↗
PubMed1993

The edentulous mandible opposing maxillary natural teeth: treatment considerations utilizing implant overdentures.

The restoration of the edentulous mandible opposing all or part of the maxillary natural dentition with implant overdentures is described. There are many situations in which the maxillary teeth opposing an edentulous mandible can and should be retained. Mandibular implant overdentures can be utilized as long as health considerations, morphologic features of the resorbed mandible, and maxillomandibular jaw relationships are satisfactory.

Alveolar Bone Loss↗
PubMed2003

Osteotomy to treat malocclusion following reconstruction of the mandible with the free fibula flap.

Malocclusion may result after free fibula flap reconstruction of the mandible, because of inadequate positioning of the temporomandibular joint, inaccurate contouring of the reconstruction plate, or subsequent fracture of a miniplate. Factors that alter the vascularity of the transplanted fibula may also result in a delayed presentation of malocclusion. Seven cases are presented, in which primary surgical treatment consisted of segmental mandibulectomy and reconstruction with a free fibula osteoseptocutaneous flap. Fixation was achieved with a reconstruction plate in five cases and a miniplate in two cases. Malocclusion was corrected with an osteotomy performed at the junction of the fibula and the native mandible. The new osteotomy sites were fixed with miniplates and maintained with intermaxillary fixation. Complete bony union was achieved at the osteotomy sites. The correction of malocclusion was successful in all cases, and all patients have resumed a normal diet. This report demonstrates that osteotomy and realignment of the mandible are effective for the secondary correction of malocclusion after mandibular reconstruction with the free fibula osteoseptocutaneous flap.

Adult↗
PubMed2005

Three-dimensional finite element analysis of the mandible and temporomandibular joint on simulated occlusal forces before and after vertical ramus elongation by distraction osteogenesis.

Distraction osteogenesis has recently become a mainstay for treatment of mandibular hypoplasia. Thorough knowledge about changes in the temporomandibular joint (TMJ) and the surrounding parts of the mandible and the skull after mandibular distraction is still lacking. The purpose of the current study was to investigate the stress distribution in the mandible and the TMJ before and after skeletal correction by intraoral unilateral vertical mandibular ramus distraction, using a finite element (FE) model. The FE models were 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 mandible and TMJ before and after skeletal correction by 15 mm of vertical distraction of the mandibular ramus was analyzed quantitatively and compared during centric occlusion. Before the distraction osteogenesis treatment, the condyles, articular discs, and glenoid fossa regions are loaded with a different stress pattern. The affected right condyle, disc, and fossa are loaded diffusely and externally in comparison with the anterior and with centralized loading on the normal left side. After unilateral mandibular distraction osteogenesis, the load became more centric and symmetrical. The results suggest that correction of the mandibular deformity by distraction osteogenesis tends to normalize the stress patterns in the TMJ.

Arthritis, Juvenile↗
PubMed2005

Masticatory function in patients with an extremely resorbed mandible restored with mandibular implant-retained overdentures: comparison of three types of treatment protocols.

The objective of the present study was to analyse the effects of implant supported overdentures on masticatory function in patients with an extremely resorbed mandible, and to compare the masticatory function in these patients using three differing types of implant treatment protocols. The mandibular overdentures were retained by a transmandibular implant, by four endosseous implants following augmentation of the mandible, and by four short endosseous implants, respectively. Sixty patients (50 women, 10 men, mean age 59.4 years) were randomly allocated to one of the three treatment groups. Masticatory function was assessed before and after treatment using a questionnaire, a masticatory performance test, and a structured interview. The patient-based masticatory function improved significantly. Concerning these parameters there were no significant differences between the three groups before and after treatment. A significant difference existed between the three groups for the laboratory-assessed masticatory function before treatment, but after treatment this difference was no longer significant. From this study it can be concluded that patients with an extremely resorbed mandible and functional complaints of their lower denture report significant improvement in masticatory function after implant-overdenture treatment. Differences in masticatory function between the three studied modalities were not significant after treatment.

Aged↗
PubMed1987

Marginal resection of the mandible in treatment of cancer of the floor of the mouth.

In a series of 253 excisions of cancer of the floor of the mouth, 57 marginal resections of the mandible retaining mandibular continuity were performed. Tumour recurred at the primary site in six of the 47 patients available for review at three years; three within the mandible itself. Three patients died with uncontrolled primary disease, but the other three survived after additional surgery and/or radiation therapy. Although this recurrence rate might appear high, the outcome of the total series is comparable with other reported series. The results do not finally demonstrate that marginal resection can be used freely, but the low morbidity and good functional results make the technique attractive. Further prospective study is needed to refine the indications for both conservation and ablation of the mandible.

Adult↗
PubMed2006

Implant survival in mandibles of irradiated oral cancer patients.

OBJECTIVE: The aim of this study was to analyze long-term implant survival in the mandible after radiotherapy and radical surgery in oral cancer patients. STUDY DESIGN: Between 1990 and 2003, 71 patients (15 females, 56 males; average age 57.8 years, range 16-84.1 years) were treated with dental implants after radiochemotherapy and ablative surgery of oral cancer. Radiation therapy was delivered in daily fractions of 2 Gy given on 25 days (total dose of 50 Gy). Oral defects were reconstructed microsurgically with jejunal, iliac crest or radial forearm grafts. Thereafter 316 dental implants were placed in the non-irradiated residual bone (84; 27%), irradiated residual bone (154; 49%) or grafted bone (78; 25%) at various intervals (mean interval 1.41 (+/- 1.01) years, range 0.34-6.35 years). RESULTS: The mean follow-up time after implant insertion was 5.42 (+/- 3.21) years (range 0.3-13.61 years). The overall 2-, 3-, 5-, and 8-year survival rates of all implants were 95%, 94%, 91% and 75%. Forty-four implants were lost in 21 patients during the observation period. Irradiation of the mandibular bone showed significantly (P = 0.0028) lower implant survival compared with non-irradiated mandibular bone. The 8-year survival rate in the non-irradiated residual bone (two loss), irradiated residual bone (29 loss) or grafted bone (13 loss) were 95%, 72% and 54%, respectively. Time of implantation after irradiation showed no statistically significant influence. Implant brand, length or diameter or the incidence of resective surgery on the mandible and gender of patients had no statistically significant influence on implant survival. CONCLUSION: Radiation therapy with 50 Gy was significantly related to shorter implant survival in mandibular bone. Survival was lowest in grafted bone. Time of implant placement had no statistically significant influence on survival under the conditions of this study. Although implant survival is lower in irradiated mandibles, implants significantly facilitate prosthodontic treatment and enhance outcome of oral rehabilitation in cancer patients.

Adolescent↗
PubMed2006

Vertical distraction osteogenesis in the human mandible: a prospective morphometric study.

Vertical distraction osteogenesis has received considerable interest as a way to augment bone prior to implant placement. However, very little is known regarding the appropriate distraction protocols in the human mandible. In this study, we evaluate the effect of the distraction rate and the duration of neutrofixation on bone formation and closure of the gap in the human mandible. Vertical distraction was performed in the atrophic mandible of 16 edentulous patients, aged 62+/-6 years. The bone was distracted for approximately 10 mm at a rate of either 0.5 or 1 mm/day. Bone biopsies were taken after 7-20 weeks of neutrofixation. Histological analysis demonstrated newly formed bone in the distraction gap in all biopsies. The bone was predominantly of the woven type. After 10 weeks of neutrofixation, the gap was bridged by new bone in two out of three intact samples in the 0.5 mm/day group, but not in two intact samples of the 1 mm/day group. Histomorphometry revealed longer bone trabeculae (P=0.02) and a somewhat increased bone volume in the area where new bone formation started (P=0.07) in the group of patients having the 0.5 mm/day of distraction rate than in the 1 mm/day group. We conclude that in elderly patients, a distraction rate of 0.5 mm/day results in faster osteogenesis in the distraction gap than a rate of 1 mm/day. A minimum of 10 weeks of neutrofixation seems to be needed to close a 10 mm gap after cessation of distraction.

Aged↗
PubMed2006

Formation of new bone during vertical distraction osteogenesis of the human mandible is related to the presence of blood vessels.

We examined the effect of distraction rate on blood vessel growth in intramembraneous ossification after vertical distraction osteogenesis in the human mandible. Six edentulous patients (aged 60+/-9 years) with a severely atrophic mandible underwent bone augmentation with distraction osteogenesis. Two distraction rates (0.5 and 1 mm/day) were compared and for each group three patients were analyzed. Vascular histomorphometry was carried out in two different areas in the distraction gap: (1) in the first and (2) in the second 1 mm area from the osteotomy line, representing the oldest and younger new-bone area, respectively. Correlation analysis was performed between blood vessel parameters and the amount of new bone formed during distraction. Histological analysis demonstrated the presence of blood vessels throughout the soft connective tissue in the distraction gap. The volume density of blood vessels between the two investigated areas was significantly lower in the 1 mm/day groups, suggesting a delay in angiogenesis in this group of patients. A positive correlation between blood vessel volume and bone volume density was found in the younger new-bone area but not in the oldest new-bone area. This correlation was due to a higher number of blood vessels rather than to a larger size of the blood vessels. Our data suggest that the lower blood vessel density found in the patients with 1 mm/day distraction rate may be related to disruption of angiogenesis in the soft connective tissue of the gap or to a less optimal mechanical stimulation of cells involved in angiogenesis. This probably results in the slower rate of osteogenesis seen at the 1 mm/day distraction rate compared with the 0.5 mm/day distraction rate. The data support the concept that a positive relationship exists between the density of blood vessels and the formation of bone. For distraction of the human mandible in elderly patients, a distraction rate of 0.5 mm/day seems beneficial.

Age Factors↗
PubMed1977

Variations in structure within the trabecular bone of the mandible.

A study of the intramandibular variations in bone mass, coarseness of the bone trabeculae and bone activity between incisor, premolar, and molar regions has been carried out, as well as estimation of possible differences in these variations between groups of mandibles with different dentition. The material consisted of 24 autopsy specimens of half mandibles from normal subjects. Microradiograms of ground sections from incisor, premolar, and molar regions were used. Quantitation of bone mass was done by an electronic point-counting system. The analysis indicates that (1) the variations in bone mass within same region are marked, (2) trabecular bone is denser and more delicately woven in the incisor region than in either premolar or molar regions, where mass of bone is the same, although there is probably more delicately woven trabecular bone in molar region, (3) bone activity lies on the same level all over in trabecular bone within the mandibular body and (4) the variations of these factors seem to be independent of state of dentition in the single mandible.

Bicuspid↗
PubMed1979

Comparative bone morphometric analysis of mandibles and iliac crests.

A comparative analysis of bone mass in the mandible and the iliac crest has been carried out in autopsy specimens from 30 subjects aged 23-84 years. Microradiograms of standardized 100-micrometer-thick sections of the undemineralized plastic embedded material from the two locations were used for quantitation. The following measurements were carried out by electronic point-counting: 1) the percentage of cortical bone mass in the subperiosteal and subendosteal layers, 2) mean cortical width, and 3) the percentage of trabecular bone mass in the iliac crest. Positive correlations were found in the expressions of bone mass within the mandible; the values were significantly higher in the 200-micrometer-thick subperiosteal layer than in the remaining part of the mandibular cortex. Only a poor or no correlation was found in the expressions of bone mass from the two sites. The investigation, therefore, shows that bone mass and cortical width in the mandible cannot be predicted from a biopsy from the iliac crest. This finding may partly be due to different age-dependent functional changes of the two bones.

Adult↗
PubMed1985

Dual-photon absorptiometry of mandibles: in vitro test of a new method.

A new method for non-invasive in vivo measurement of changes in bone mineral content (BMC) of mandibles, comprising two-dimensional dual-photon absorptiometry (GT45), has been developed and tested in vitro on mandibular specimens. The analysis showed that: 1) in vitro precision and accuracy of the methods are high, 2) effect of fat and soft tissue on photon attenuation is slight when scanning jaws and forearm bones, 3) BMC in units (U/cm2) in standard area, comprising mandibular base and body in left molar region, is representative for BMC in total mandibular base and body, 4) cortical bone constitutes the main part of measured BMC in mandibles, and 5) BMC of molar region is highly correlated to cortical bone mass in mm3/mm2 subperiosteal surface of standard locality anterior to and below mental foramen, measured by histomorphometry. GT45 seems suitable for in vivo estimation of BMC changes in edentulous jaws and in mandibular base and body of dentate mandibles in longitudinal and cross-sectional studies. The radiation dose is negligible.

Adipose Tissue↗
PubMed1993

Trabecular bone mineral density of mandible and alveolar height in postmenopausal women.

Mineral density of the trabecular bone of the mandible was determined by single-energy QCT (quantitative computed tomography) for 74 totally or nearly edentulous menopausal women. These results were compared with the bone mineral densities (BMD) of their lumbar area (L2-L4) and femoral collum, measured by dual-energy x-ray transmission, Lunar DPX. The remaining height of the residual ridge at the symphysis of the mandible was measured on computed tomography (CT) lateral projection view, and an index of the residual ridge status was introduced. To determine whether general osteoporosis status affects the remaining height of the residual ridges, we compared these values with all results for bone mineral density. The BMD of the lumbar area and that of the femoral collum correlated well with each other, but the BMD of the trabecular bone of the mandible did not correlate with either of the other two BMD measurements. Measurements of residual ridge height did not correlate with any BMD values. The effect of possible bone loss earlier in life is no longer apparent in mandibular height or trabecular BMD over 20 yr after tooth extractions.

Absorptiometry, Photon↗
PubMed1996

Long-term bone mass evaluation of mandible and lumbar spine in a group of women receiving hormone replacement therapy.

The overall aim of this study was to examine the relationship between bone mass of the jaw and the axial skeleton. Sixty-nine subjects (age at entry: 32-64), who underwent hormone replacement therapy during the study period, participated. Bone mass of the lumbar spine was determined using dual photon absorptiometry. The jaw-bone of the posterior region of the mandible was evaluated by means of standardized long-cone radiography using individual bite-blocks. A densitometric wedge in the film holder provided a reference to quantify bone mass. From both measurements, it appeared that the bone mass of the mandible and the lumbar spine showed a moderate relationship. The present results also confirmed that estrogen replacement therapy had a positive effect on the bone mass of the mandible and the lumbar spine. Different estrogen regimens resulted in different increases in bone mass during the observation period, which was on average 5 yr.

Absorptiometry, Photon↗
PubMed2002

Early loading of four or five Astra Tech fixtures with a fixed cross-arch restoration in the mandible.

BACKGROUND: A change in implant placement has emerged recently from two-stage to one-stage surgery and to earlier and even immediate loading of the fixtures. PURPOSE: The aim of this study was to verify whether four or five fixtures installed in the edentulous mandible were suitable for early loading with a cross-arch fixed restoration. MATERIALS AND METHODS: In 25 consecutively treated patients (28-88 yr), four or five Astra Tech fixtures (Mölndal, Sweden) were installed in edentulous mandibles. During the same surgical procedure, the abutments were connected. An impression was taken immediately after surgery. All patients received a fixed prosthetic rehabilitation of 10 to 12 teeth made of a cast metal framework and acrylic teeth/gingiva within a month. The fixtures were followed up clinically and radiographically for 7 to 24 months. Bone level was measured from the most coronal point of the vertical part of the fixture to the most apical bone level mesially or distally. RESULTS: No fixtures were lost during follow-up. No postoperative complications occurred. Radiographic analysis showed a mean bone level of 0.6 mm after 7 to 12 months. Fixtures followed up from 13 to 18 and 19 to 24 months showed a mean bone level of 0.7 mm. Around two fixtures, the bone level was found at the first implant thread. All other fixtures showed the bone level somewhere along the vertical unthreaded part of the fixture. CONCLUSIONS: Early loading within 1 month of four or five Astra Tech fixtures in the edentulous mandible is a predictable procedure for a follow-up period of 6 to 24 months.

Adult↗