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PubMed2003

Mandible bone loss in osteoporosis rats.

Change in the mandible during the development of osteoporosis has not been studied extensively. Thus, the present study was undertaken to clarify the target loci in the mandible during the development of experimental osteoporosis in aged female rats. Experimental osteoporosis was studied in 76 Wistar strain female rats, 35 weeks old, by means of ovariectomy and dietary calcium deficiency. The rats were divided into the following three groups: (1) group 1, unoperated basal control (Basal), maintained on a diet containing 1.0% calcium; (2) group 2, sham-operated (Sham), maintained on a diet containing 0.01% calcium; and (3) group 3, ovariecomized (OVX), maintained on a diet containing 0.01% calcium. Fifteen rats of each group, except the basal rats (10 and 6 rats), were killed at 3 and 6 months following ovariectomy, respectively. The mandible was extracted, cleaned, and then subjected to bone mineral content (BMC) and bone mineral density (BMD) analyses using a peripheral quantitative computed tomography (pQCT) bone scanner. Each mandible was scanned from the mesial margin of the first molar to distal margin of the second molar. The results showed that dietary calcium deficiency and ovariectomy caused significant decreases of trabecular and cortical BMCs and BMDs in Sham and OVX rats compared with Basal rats. Decreases due to dietary calcium deficiency were greater than those caused by ovariectomy. However, significant age-related changes were not observed in BMC and BMD in Sham and OVX rats for 3-6 months. In addition, the cortical and trabecular BMCs and BMDs obtained were found to relate to location in the mandible for each group.

Animals↗
PubMed2002

[Experimental study on the biomechanical stability of different internal fixators for use in the mandible].

BACKGROUND: Comparative studies of different forms of osteosynthesis require that biomechanical and biological criteria be observed. The conditions in experimental studies should be as close as possible to the in vivo situation. The aim of our study was to develop a fracture model that would allow determination of the micromovements in the gap tissue following different forms of internal fixation in fractured human mandibles. METHODS: Micromovements in the gap tissue of five human mandibles treated with different osteosynthetic systems (DCP, EDCP, Miniplates, 3-D systems) following osteotomy or fracture in the region of the corpus and median region were investigated by means of strain gauges. By fitting the human mandibles in plaster according to a method of our own it was possible to create fractures at predictable and comparable localizations. RESULTS: Our investigations show that the micromovements in the gap tissue of osteotomied and fractured mandibles are different and not dependent on the form of osteosynthesis applied. Physiological micromovements in the gap tissue were found under strain for all osteosynthetic systems used in fractured and congruently reset mandibles. DISCUSSION: Our fracture and osteosynthesis model allows the quantitative determination of micromovements in the gap tissue and shows the importance of ideal realignment, which has a decisive influence on micromovements in the gap tissue.

Biomechanical Phenomena↗
PubMed2005

[Autologous rib graft for restoration of continuity defects of the mandible].

BACKGROUND: Reconstruction of mandibular defects following tumor resection in infants is a particular challenge. Although autologous rib grafts have no relevance nowadays for restoration of mandibular bone defects following ablative tumor surgery due to limited bone stock and the availability of other donor areas, they are a useful surgical alternative following tumor surgery in infants. PATIENTS AND METHOD: We here report on the 5- and 10-year follow-up of two children who were diagnosed with benign tumors of the mandible with osseous destruction at the age of 4 and 6 months, respectively. Histological diagnoses were melanotic neuroectodermal tumor and hemangioendothelioma of the mandible. Following continuity resection of the mandible lateral mandibular bone defects were restored using autologous rib grafts. Yearly clinical and radiological follow-up visits in both children were performed to assess growth of the facial skeleton as well as mandibular growth. RESULT: Cephalometric measurements on panorex films as well as 3D CT scans revealed slight vertical growth excess and transversal growth inhibition of the reconstructed mandible in comparison with the non-operated side. DISCUSSION: Although further growth of rib grafts is difficult to predict and occlusal disharmony may occur due to physiologic maxillary growth and growth of the unaffected mandible, we believe that autologous rib grafts can be ideally used for restoration of mandibular continuity defects in newborns. Clinical follow-up visits on a yearly basis and orthodontic controls are useful for early orthodontic treatment of growth deficits. Further corrective surgery with bone augmentation or osseous distraction is required following completion of growth of the facial skeleton.

Bone Transplantation↗
PubMed2005

[On the indications for and morbidity of segmental resection of the mandible for squamous cell carcinoma in the lower oral cavity].

BACKGROUND: Segmental resection of the mandibula in oral cancer surgery leads to both functional and aesthetic problems. The decision to preserve or resect the mandible depends on the vicinity of the lesion to the bone. Consequently, based on the rules of safety margins to all planes that are recommended for soft tissues, each lesion that is closer than 10 mm to the mandible needs resection of the bone. PATIENTS AND METHODS: To establish data-based treatment modalities, a retrospective study was initiated and the results from all preoperative staging investigations of 152 patients with intraoral squamous cell carcinoma who underwent continuity or marginal resection of the mandible were evaluated. The histological outcome of the resected bone was compared to the staging results. Functional rehabilitation and long-term follow-up including survival rates were evaluated. The study reports on typical complications following segmental resection such as fracture of the reconstruction plate and demonstrates experiences with secondary microsurgical reconstructive surgery. RESULTS: Mainly in cases of stage T1 and T2 carcinomas which are closer than 10 mm to the bone and clinically do not show any infiltration to the mandible, a marginal resection seems to be adequate. The decision about the extension of mandibular resection can be based on intraoperative cross sectional investigation of the periosteum. The survival rate of patients with intraoral carcinomas close to the mandible who underwent marginal mandibulectomy seems to be the same as in cases of continuity resection. A more conservative management of mandibular resection seems to be adequate and a data-based concept to standardize therapy of mandibular resection is presented.

Aged↗
PubMed2006

Vibrational analysis of mandible trauma: experimental and numerical approaches.

The aim of this study was to evaluate the effectiveness of vibrational assessment of the mandible fracture patterns. Measurement of natural frequencies and associated vibrational mode shapes was performed to determine the relationship between the dynamic behavior of the human mandible and incidence of mandibular fractures using both in vitro modal testing and finite element analysis. Our results show that the natural frequencies of the human mandible in dry and wet conditions are 567 Hz and 501 Hz, respectively. The first vibrational mode of human mandible is a bending vibration with nodes located at the mandibular body where bone fracture is less likely to occur. By contrast, high vibration amplitudes were identified in the symphysis/parasymphysis and subcondyle regions where bone fractures tend occur. These findings indicate that the vibrational characteristics of the mandible are potential parameters for assessment of the mechanisms of injury.

Finite Element Analysis↗
PubMed1984

Is the mandible intrinsically different in Apert and Crouzon syndromes?

Relative mandibular prognathism is an observed finding in Apert and Crouzon syndromes. This imbalance in the facial profile is generally attributed to the diminished growth of the maxilla, thereby increasing the disparity between maxilla and mandible with increasing age. What is not known is whether the mandible is, indeed, normal. Previous work by Kreiborg with Crouzon syndrome led to the conclusion that the mandible, although somewhat smaller, grew in a "normal" pattern. Our own observations, which used a greater variety of mandibular measurements on patients with both Apert and Crouzon syndromes, corroborated Kreiborg 's conclusions but go further to suggest a syndrome-specific mandibular malformation. Ramal height was found equal to the norm and sometimes greater. Mandibular body length was significantly shorter, thereby producing a distinctly different ramus/body length ratio, particularly in older patients. These findings become significant in the planning of reconstructive procedures. They also raise the question as to whether the shape of the mandible is genetic in origin or is an adaptation to the increasing derangements of the cranial base, maxilla, and occlusion observed with maturation in these patients. The possibility of interactive genetic and environmental factors affecting growth of the mandible emerges from the data.

Acrocephalosyndactylia↗
PubMed1983

Labelled-calcium release from rat mandibles exposed to prostaglandins in vitro.

Bone resorptive effects of prostaglandins (PGs) in cultured mandibular bone tissue of rat fetus prelabelled with 45Ca were examined in comparison with those in radius-ulna. PGE1 (3 X 10(-6)-10(-4) M) and PGE2 (3 X 10(-8)-10(-4) M) could significantly stimulate the release of 45Ca from mandible with a peak effect at 3 X 10(-6) M. The effects of PGEs were more marked in mandible than in radius-ulna. Salmon calcitonin (SCT) inhibited the stimulating effect of PGE2. PGF 2 alpha did not cause the significant increase of 45Ca-release. Parathyroid hormone (PTH) at concentrations of 0.01-1.0 IU/ml dose-dependently stimulated 45Ca-release and the effects were greater in mandible than in radius-ulna. Dibutyryl cyclic (DBc)-AMP stimulated the release of 45Ca in mandible with a sharp peak effect at 5 X 10(-4) M. The results indicate that mandible is more susceptible to these bone resorptive agents than radius-ulna.

Alprostadil↗
PubMed1994

Sex-related differences in the bone mineral density of atrophic mandibles.

The bone mineral content in a standardized site was measured in 25 edentulous mandibles with dual-photon absorptiometry. The results of the bone mineral content examinations demonstrated a significant difference between the sexes. With advancing age of the subjects, the values measured in the men's mandibles tended to increase slightly, whereas those in the women's mandibles tended to decrease. As a functional adaptation to preserve the stability of the male atrophic mandible, the amount of inner cortical bone is increased. Explanations for this observation are discussed. That the mandibles of men and women change differently with increasing age should be considered in routine examinations, because osteoporosis may be regarded as a cofactor of residual ridge resorption in women.

Age Factors↗
PubMed1976

The retrognathic mandible--surgical correction.

The preceding case reports demonstrate the excellent results available to the patient with a retrognathic mandible. Etiology, adverse effects, and the modalities used in evaluation of the underdeveloped mandible have been discussed. The age at which surgical intervention is undertaken needs additional input by clinicians. Several surgical procedures have been and are employed to advance the mandible. The C osteotomy is recommended since the final result has been excellent and consistent. The surgeon has constant surgical control and vision. The advanced portion of the mandible can be firmly held by intraosseous wires. There is minimak disturbance of muscle position and the inferior alveolar nerve. We have not encountered unusual loss of blood, immediate postoperative problems with the airway, infection, or unfavorable relapse. A postoperative regimen that has been found rewarding is discussed. We have come to the conclusion that most patients can tolerate lengthy surgical procedures with few adverse side effects. Our colleagues in anesthesia and nursing provide superb operative and postoperative care. When the preoperative work-up indicates that more than one procedure is indicated, we recommend that the total surgical treatment plan be carried through at one operation, although occasionally this approach may be contraindicated. We should strive for perfection and can fall short of this goal when a patient will not return for additional surgical procedures which could have been accomplished during the first operation. Although good results have been experienced with both the C osteotomy and the sagittal split osteotomy, we believe that the C osteotomy is a superior procedure. However, this does not imply that the sagittal split osteotomy should not be a part of the armamentarium of the oral surgeon. In conclusion, the C osteotomy, the sagittal split osteotomy, genioplasty, and additional procedures--such as a mandibular alveolar osteotomy to intrude supraerupted teeth--when indicated, can provide very favorable results in cases of retrognathia or micrognathia of the mandible.

Adolescent↗
PubMed2006

Mechanical behavior of an osteotomized mandible with distraction orthodontic devices.

This work analyzes the mechanical behavior of a human mandible when distraction orthodontic devices are used for correcting problems of dental overcrowding and/or arch shrinkage. The mandible 3D model is reconstructed from CT scan data and meshed into finite elements. The distractor is also modeled. FEM analysis included geometric non-linearity. Displacement field of healthy and osteotomized mandibles are compared. Progressive expansion of the distractor and effects of mastication are also analyzed. Finally, we compare two distraction protocols PROT1 and PROT2 where device is, respectively, expanded by 0.6 or 1.2mm/day. The global displacement is 6mm according to clinical recommendations. It came out that mastication forces generate displacements compatible with bone remodeling. However, parasitic rotations of the mandible arms due to mastication may counteract arch expansion induced by the device. Stress concentrations occurred where the device is fixed: stress peaks stay however below yield limit. Finally, PROT2 reduced by about 10% stresses in mandible and reproduces better than PROT1 the displacement field imposed by the device.

Biomechanical Phenomena↗
PubMed2006

A biomechanical comparison of 2 techniques for reconstructing atrophic edentulous mandible fractures.

OBJECTIVES: The purpose of this investigation was to evaluate and compare the biomechanical behavior of 2 techniques for the reconstruction of atrophic edentulous mandible fractures. MATERIALS AND METHODS: Thirty polyurethane atrophic edentulous mandible replicas (Sawbones, Vashon Island, WA) were used in this investigation (10 controls, 10 replicas of 2 different fixation techniques). The first reconstruction technique was a traditional titanium locking reconstruction plate affixed to the lateral border (buccal surface) of the mandible. The second reconstruction technique used the same type of plate, but placed it on the inferior border of the mandible. Both constructs were subjected to vertical loading at the symphysis and torsional loading at the body regions of the mandible replicas by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. Mechanical deformation data within a 0-900 N range were recorded. Maximum load, displacement at maximum load, and stiffness were determined. Means and standard deviations were derived and compared for statistical significance using a Fisher's Protected Least Significant Differences Test with a confidence level of 95% (P < .05). Second- and third-order polynomial best-fit curves were also created for each group to further evaluate the mechanical behavior. RESULTS: For symphysis loading, statistically significant differences were noted between the control group and both of the plating techniques for displacement at maximum load. However, no differences were noted between the experimental groups for displacement at maximum load, stiffness, or maximum load. For body loading, statistically significant differences were noted between the control group and the inferior border plating group for displacement at maximum load. However, no differences were noted between the experimental groups for displacement at maximum load, stiffness, or maximum load. CONCLUSION: During this bench top investigation, there were no significant differences noted in mechanical behavior between the 2 specific experimental groups for any of the conditions measured. When placed in the context of functional parameters, both of the plating techniques met or exceeded the requirements for loading.

Alveolar Bone Loss↗
PubMed2006

Standard of care for the edentulous mandible: a systematic review.

STATEMENT OF PROBLEM: Implant therapies have increased the range of prosthodontic options for the treatment of edentulism. Considering both dentist- and patient-mediated outcomes, a universal treatment intervention for the treatment of the edentulous mandible has not been demonstrated. PURPOSE: The purpose of this study was to test the null hypothesis that there is no single standard of care for the edentulous mandible as defined by a specific treatment modality. MATERIAL AND METHODS: A review of the literature was undertaken seeking evidence of a superior intervention for the treatment of the edentulous mandible. A search of the English language peer-reviewed literature was completed using Medline and Google Scholar for the period from 1995 to 2005, focusing on evidence-based research. This was supplemented with a hand search of selected dental journals and textbooks. Longitudinal retrospective studies, longitudinal prospective studies, longitudinal experimental clinical studies, nonrandomized controlled studies, and randomized controlled clinical trials were included for review using a general linear hierarchical classification of studies. Articles that did not focus exclusively on treatment interventions for mandibular edentulism or on the effects of such therapies on the patient were excluded from further evaluation. The search period included articles that were published before the criteria for evidence-based literature were established, but this was not necessarily used to exclude an article. The last search was conducted on September 25, 2005. RESULTS: The literature demonstrates that the functional demands of edentulous patients are highly variable and that patient treatment responses are individual, vary significantly, and are influenced by psychosocial forces. The literature further demonstrates that patient acceptance of specific treatment modalities is modified by social and cultural influences, financial means, and adaptive capacity. Additionally, patient acceptance of a particular treatment modality is influenced by the educational background, knowledge, and experience of the dental health care provider, as well as by a host of other socioeconomic, regional, cultural, age, and gender influences. CONCLUSIONS: Within the limits of this review, there is no evidence for a single, universally superior treatment modality for the edentulous mandible. Better designed, long-term studies are required to further explore differences in patient acceptance to each treatment intervention for the edentulous mandible.

Clinical Trials as Topic↗
PubMed2006

Biomechanical effects of fixed partial denture therapy on strain patterns of the mandible.

STATEMENT OF PROBLEM: The mandibular posterior 3-unit fixed partial denture (FPD) is a conventional prosthodontic therapy and presumably has an effect on the direction and magnitude of occlusal forces and, thus, on the biomechanical environment of the mandible, which may in turn affect bone structure. However, the impact of FPD therapy on mandibular biomechanics is unknown. PURPOSE: The purpose of this study was to test the hypothesis that 3-unit FPD therapy alters strain patterns in the mandible during loading. MATERIAL AND METHODS: Four human cadaver mandibles missing first molars were bilaterally fixed and artificially loaded on each tooth individually. Surface cortical bone strains were measured with multiple strain gauges during loading of up to 250 N. Next, 3-unit FPDs with a chamfer finish line were fabricated using Type IV gold alloy. Strain measurements were conducted in the same manner to assess differences in strain patterns before and after therapy. Paired-sample tests for metric and angular data were used to assess difference in strain pattern before and after therapies (alpha=.05). RESULTS: When loading was applied on the teeth not involved in FPD therapy, no differences were found before and after FPD placement. When the posterior retainers were loaded, the strain distribution differed (P=.01); on the buccal cortices, strain levels increased posteriorly but decreased significantly anteriorly. However, these differences were less than 100 muepsilon, and the overall deformation pattern of the mandible after the FPD therapy was similar to that before FPD therapy. Strain distributions when the pontic was loaded were similar to those when the posterior retainer was loaded. CONCLUSION: Three-unit FPD therapy did not alter the overall deformation pattern of the mandible during loading.

Analysis of Variance↗
PubMed2001

Effects of ovariectomy and/or dietary calcium deficiency on bone dynamics in the rat hard palate, mandible and proximal tibia.

The effects of ovariectomy and/or dietary calcium deficiency on bone dynamics were examined by comparing the histomorphometric changes in these bones. Five groups of rats were studied, (1) unoperated basal controls; (2) sham-operated, fed on a normal-calcium diet; (3) ovariectomized, fed on a normal-calcium diet; (4) sham-operated, fed on a calcium-deficient diet; (5) ovariectomized, fed on a calcium-deficient diet. The basal controls were killed at 6 weeks of age, and the remaining groups were killed at 18 weeks of age. The hard palate, mandible and proximal tibia were processed undemineralized for quantitative bone histomorphometry. Bone volume, eroded surface, osteoid surface and bone-formation ratio were calculated. A significant age-related increase in bone volume and a significant decrease in bone formation were observed in the hard palate and mandible, whereas no significant age-related increase in bone volume could be found in the tibia. In the hard palate, ovariectomy neither inhibited age-related increases in bone volume nor affected bone dynamics, while both the combined ovariectomy and dietary calcium deficiency and dietary calcium deficiency alone led to bone loss and increased bone turnover. In contrast, in the mandible and proximal tibia, ovariectomy alone as well as dietary calcium deficiency led to bone loss and increased bone turnover. Ovariectomy, therefore, produced no significant changes in the hard palate, but affected bone dynamics in the mandible and tibia. However, dietary calcium deficiency induced bone loss and increased bone turnover in the hard palate, mandible and proximal tibia, independently of ovariectomy.

Analysis of Variance↗
PubMed2003

Micromechanics/structure relationships in the human mandible.

OBJECTIVES: A clear understanding of the relationship between the micromechanical properties and orientation of the osteons within the mandible is important to understand mandibular function, fracture repair, treatment of temporo-mandibular joint disorders, the materials and organization of dental implants. The objective of this research was to obtain the micromechanical properties of human mandibular cortical bone as a function of orientation from TMJ to TMJ. METHODS: A mandible obtained from a deceased 66 year-old female free of bone disease was used. The mandible was embedded in polymethylmethacrylate. The micromechanical properties analysis was obtained using the UH3 scanning acoustic microscope (SAM; Olympus Co., Tokyo, Japan). The coordinates system is defined such that the inferior border of mandibular is positioned on the x-y plane. x is along the anterior-posterior direction, y is in the horizontal direction and z is in superior-inferior direction. RESULTS: The osteonal orientations were almost parallel to the x axis and eventually branched into two directions towards the coronoid process and condylar head. The SAM revealed that almost the whole area of the mandible body was found to be transversely isotropic in the plane perpendicular to the x axis. In the parallel and oblique directions, all data were transversely isotropic with respect to the x axis. Data of the perpendicular osteons were transversely isotropic with respect to the z axis. SIGNIFICANCE: Having actual micromechanical properties as a function of orientation in the mandible could provide base line data for: fracture repair; choice of bone replacement materials.

Aged↗
PubMed2000

Intraoral distraction osteogenesis in the baboon mandible using a tooth and bone-anchored appliance.

PURPOSE: The purpose of this study was to determine the feasibility of using an intraoral, bone and tooth-anchored appliance to distract baboon mandibles using the principles of distraction osteogenesis (DO). MATERIALS AND METHODS: Seven juvenile baboons were used in this study. Mandibular corticotomies were made in the ramus of the mandible unilaterally (n = 5) or bilaterally (n = 2), and a "pin-in-tube" (PIT) distraction appliance was applied. The device was secured to the mandibular ramus posterior to the cortical cut with a bicortical screw and anteriorly to an occlusal splint. The appliance was activated an average of 0.86 mm/d (0.5 to 1.3 mm/d) for an average of 12.4 days (10 to 14 days). Predistraction and postdistraction measurements were made between metallic markers placed in the distraction area, in the dental midline, and of the overjet and overbite. RESULTS: Bone healing was complete in all mandibles. The average mandibular lengthening measured between the metallic markers was 7.9 mm. The mandibular midlines showed an average of 4.25 mm of lateral movement in the unilaterally distracted mandibles. There were no infections. CONCLUSIONS: The results of this study indicate that an intraoral bone and tooth-anchored distraction appliance is an effective method to produce lengthening in the mandible by distraction osteogenesis.

Animals↗
PubMed1991

The effect of electrical stimulation on bone formation around hydroxyapatite implants placed on the rabbit mandible.

Nonresorbable, nonporous, particulate hydroxyapatite (HA) was implanted on the mandible in rabbits and stimulated electrically, 4 hours per day, during the first postoperative week. Stimulated and control implant sites were recovered 8 weeks postoperatively and examined histologically. The HA migrated into the mandible in the electrically treated specimens, and was routinely found in intimate association with preexisting mandibular bone. In the controls, the HA remained superior to the mandibular surface. In further studies (without electrical stimulation) in which the implant site was recovered 26 weeks postoperatively, HA was observed in the mandible; some HA particles migrated completely through the mandible and were found in the adjacent soft tissue. It was concluded that, under the conditions studied, electrical stimulation does not promote bone growth into HA, but rather produces the opposite result--it promotes more rapid movement of HA particles into the mandibular bone. The HA particle migration into the mandible observed (longer postoperative times) in the absence of electrical stimulation suggests that migration is a general property of HA particles when placed over bone under muscle.

Animals↗
PubMed2001

2,3,7,8-tetrachlorodibenzo-p-dioxin affects size and shape, but not asymmetry, of mandibles in mice.

Fluctuating asymmetry (FA), the random differences between the left and right sides of a bilaterally symmetrical character, is often purported to be a sensitive measure of developmental instability particularly in populations exposed to environmental stressors. As the level of developmental instability increases, often too does the level of FA. In this study we tested the hypothesis that exposure of pregnant mice to low doses of 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) would increase the level of FA in the mandibles of their offspring. We used ten landmark coordinates around the mandible to create a single size variable (centroid size) and 20 Procrustes shape variables. These were used to test for effects of dioxin on mandible size and shape and their asymmetries. We found no detectable effect of TCDD on levels of FA in either size or shape of the mandible, but TCDD did produce a significant decrease in mandible size, and a significant effect on the overall shape.

Abnormalities, Drug-Induced↗