Induced leukemia and antineoplastic agent carmustine cause permanent changes in craniofacial growth of immature rats

OBJECTIVES

The purpose of the present study was to investigate the possible effects of untreated terminal leukemia on craniofacial growth (Study I), and also the effects of the antineoplastic agent carmustine on craniofacial growth in both leukemic and healthy rats (Study II).

MATERIAL

A total of 367 inbred Piebald variegated rats was used.

METHOD

Transmission of leukemic cells was carried out intraperitoneally at 30 days of age, and without treatment (Study I), the rats reached the terminal phase within 17 +/- 1 days. Rats with induced leukemia was cured with 10 mg/kg carmustine (BCNU) given on days 6 and 13 following cell transmission (Study II), the rats remaining in remission until they were killed at 100 days of age. Final weight was recorded and 12 craniofacial dimensions and tibial length were measured with a digital sliding caliper.

RESULTS

The results showed that the effect of untreated terminal rat leukemia (Study I) on craniofacial growth differed between the genders. Male rats showed clearly reduced dimensions of facial structures and also retarded general body growth, whereas females showed differences mainly in general body growth. The effect of cured leukemia (Study II) as such was minor, while BCNU had a strong and permanent reducing effect on both craniofacial and general body growth in both genders.

CONCLUSION

We suggest that the results in Study I came both from a direct effect of leukemia and an indirect effect of untreated terminal leukemia through malnutrition. The alkylating agent BCNU seemed to be the main cause of permanent craniofacial and general growth retardation in Study II.

[Pathomorphology of regenerative processes in mandibular fracture after sodium succinate treatment and laser magnetotherapy in an experimental setting]

Morphological reactions in tissue adjacent to mandibular angular fracture were studied in guinea pigs treated with sodium succinate and laser magnetotherapy. Due to succinate therapy the exudative component of inflammation was less expressed in comparison with the control, macrophagal reaction and neoangiogenesis were activated, the volume of damaged muscle tissue and the incidence of suppurations decreased. The number of osteoblasts increased and new bone structures acquired a lamellar pattern earlier than in the control. Sodium succinate therapy in combination with laser magnetotherapy had a more pronounced positive effect as regards activation of macrophagal reaction and neoangiogenesis and a decrease in the area of fibrosclerotic changes in the zone of damaged muscles, where newly formed myosymplasts differentiated into myotubes and even in muscle fibers. Suppuration of the wound was prevented. Bone tissue in the fracture zone formed without preliminary formation of cartilaginous tissue, which resulted in more rapid osteogenesis (lamellar bone growth in the fracture zone).

Effects of selenium on the structure of the mandible in experimental diabetics

In the treatment of diabetes-induced pathologies, beneficial results have been obtained with administration of antioxidants. Selenium is an antioxidant and essential trace element in living organisms. The aim of this study was to investigate the possible effects of selenium on the structural alterations of the mandible due to diabetes. In this study thirty-nine Wistar rats were used and a control, a selenium given control, a diabetic and a selenium given diabetes groups were formed. Experimental diabetes was induced by a single i.p. injection (50 mg/kg) of streptozotocin (STZ). The diabetic + selenium and the control + selenium groups were injected with a daily dose of 5 micro mol/kg/day sodium selenite (i.p.) for 4 weeks while the diabetic and the control groups were injected with distilled water. Mandibles of all the animals were excised and examined at the 5th week. High blood glucose level and low body weight in the diabetic group were not significantly affected by selenium administration. Furthermore, a negligible increase in blood glucose level was observed in the selenium given control group. Densitometric analysis revealed a significant reduction in bone density and presence of resorption in the diabetic and the selenium given control groups as compared to the selenium given diabetes and the control groups. In X-ray diffraction analysis, the reduction in peak intensity of the reflected light in both the diabetic and the selenium given control groups indicated a possible alteration in the crystallinity or a poor crystalline substance. Histological investigation showed that there was progressive resorption, trabecular and cortical irregularity and vascular proliferation in the diabetic and the selenium given control groups, whereas a more healthy appearance was detected in the selenium given diabetes group. The results of this study suggest the positive effects of selenium on diabetes-induced structural alterations in the mandible. However, the unexpected results in the selenium given control group necessitate further studies on the mechanism of selenium effects in organisms.

Anabolic effects of recombinant human parathyroid hormone (1 - 84) and synthetic human parathyroid hormone (1 - 34) on the mandibles of osteopenic ovariectomized rats with maxillary molar extraction

In rodent osteoporosis models such as ovariectomized (OVX) rats, intermittently administered human parathyroid hormone (hPTH) has an anabolic effect in vertebrae and long bones. In the present experiments, subcutaneously injected hPTH(1 - 34) or hPTH(1 - 84) dose- and time-dependently increased bone mineral density (BMD) as measured by dual energy X-ray absorptiometry in mandibles, L2 to L4 vertebrae and femurs of such rats. The highest dose (15.9 nmol/kg, s. c.) of either peptide given four times weekly for 10 weeks completely reversed the effects of overiectomy on BMD. Significant elevation in lumbar BMD after 10 weeks was observed with hPTH(1 - 34) or hPTH(1 - 84) at 1.1 nmol/kg, whereas hPTH(1 - 34) at 1.1 and 4.2 nmol/kg significantly increased BMD of the whole bone and the metaphysis of the femur and the diaphysis of the bone, respectively. In contrast, significant effects of hPTH(1 - 84) administration on BMD increase in the femur were observed at 4.2 and 15.9 nmol/kg in the whole bone and the metaphysis, and in the diaphysis, respectively. Maxillary molar extraction left mandibular BMD in rats with intact ovaries unchanged, but significantly decreased mandibular BMD in OVX rats. Administration of hPTH(1 - 84) for 10 weeks in OVX rats without or with extraction significantly increased BMD in the mandibular molar region at doses of 15.9 and 4.2 nmol/kg, respectively, indicating that efficacy was increased by extraction. A significant BMD increase in the molar region in OVX rats with extraction occurred at only 1.1 nmol/kg of hPTH(1 - 34) and 4.2 nmol/kg of hPTH(1 - 84). Also, BMD of the ramus region was increased by administration of both peptides to a lesser extent than that of the molar region in these rats. Thus, intermittent administration of hPTH, especially hPTH(1 - 34), has an anabolic effect on bone, particularly alveolar bone. Such treatment may increase alveolar bone mass in postmenopausal women with osteoporosis.

The effect of growth hormone therapy on mandibular and cranial base development in children treated with total body irradiation

The aim of the present investigation was to study craniomandibular development during growth hormone (GH) therapy in nine girls and one boy, aged between 7.3 and 16 years, who exhibited pronounced growth reduction after total body irradiation (TBI) and bone marrow transplantation (BMT). Age- and sex-matched healthy children with normal dentofacial development constituted the control material. The investigation data were based on measurements made on lateral skull radiographs taken at the start and, on average, 6 months after cessation of GH treatment. The control group comprised similar longitudinal cephalographic records. The results showed that GH therapy in patients who exhibited growth retardation after TBI and BMT had only a minor effect on cranial base dimensions, probably due to the fact that the development of this area is completed at a relatively early age. The effect of GH treatment on mandibular growth was very obvious. The dimensional increase of the mandibular variables in the patients was equivalent to, or in some cases even exceeded, that of the controls. In relation to basion, the mandibular condyles were displaced in a backward/upward direction in the patient group. Displacement in the opposite direction was recorded in the controls. It seems likely that the development seen in the patients is a reflection of a normalization of the condyle-fossa relationship made possible by enhanced condylar growth. This change should be advantageous for the function of the craniomandibular complex.

[Evaluating angiogenesis and osteogenesis modified by vascular endothelial growth factor (VEGF)]

PURPOSE

This intention of this study was to investigate the influence of controlled release of vascular endothelial growth factor (VEGF) on angiogenesis and osteogenesis in a mandibular defect model.

METHODS

A total of 56 rabbits were operated and bicortical holes were placed in the mandible. The defects were filled with collagen type I implants, collagen implants complexed with 0.8-microgram VEGF165, or left without any filling. After 3, 7, 14, and 28 days specimens were taken and histologic, histomorphometric, and immunohistologic analyses were carried out concerning density of vessels, total surface of vessels, bone surface, and bone density.

RESULTS

The number of vessels was increased in all groups up to 14 days, followed by physiologic regression in the control groups, whereas the study group showed persistently high numbers. The density of regenerated bone was significantly higher in the study group.

CONCLUSION

The activation of angiogenesis using VEGF165 leads to more intensive angiogenesis and bone regeneration.

YY1 activates Msx2 gene independent of bone morphogenetic protein signaling

Msx2 is a homeobox gene expressed in multiple embryonic tissues which functions as a key mediator of numerous developmental processes. YY1 is a bi-functional zinc finger protein that serves as a repressor or activator to a variety of promoters. The role of YY1 during embryogenesis remains unknown. In this study, we report that Msx2 is regulated by YY1 through protein-DNA interactions. During embryogenesis, the expression pattern of YY1 was observed to overlap in part with that of Msx2. Most notably, during first branchial arch and limb development, both YY1 and Msx2 were highly expressed, and their patterns were complementary. To test the hypothesis that YY1 regulates Msx2 gene expression, P19 embryonal cells were used in a number of expression and binding assays. We discovered that, in these cells, YY1 activated endogenous Msx2 gene expression as well as Msx2 promoter-luciferase fusion gene activity. These biological activities were dependent on both the DNA binding and activation domains of YY1. In addition, YY1 bound specifically to three YY1 binding sites on the proximal promoter of Msx2 that accounted for this transactivation. Mutations introduced to these sites reduced the level of YY1 transactivation. As bone morphogenetic protein type 4 (BMP4) regulates Msx2 expression in embryonic tissues and in P19 cells, we further tested whether YY1 is the mediator of this BMP4 activity. BMP4 did not induce the expression of YY1 in early mouse mandibular explants, nor in P19 cells, suggesting that YY1 is not a required mediator of the BMP4 pathway in these tissues at this developmental stage. Taken together, these findings suggest that YY1 functions as an activator for the Msx2 gene, and that this regulation, which is independent of the BMP4 pathway, may be required during early mouse craniofacial and limb morphogenesis.

Effect of calcium supplementation on bone dynamics of the maxilla, mandible and proximal tibia in experimental osteoporosis

The effect of calcium supplementation on the bone dynamics in the hard palate of the molar region (maxilla), mandible and proximal tibia in experimental osteoporotic rats was examined. Ninety ovariectomized (OVX) and 45 sham-OVX Wistar female rats were used in this study. All the rats received surgical operation at 6 weeks of age. Ovariectomized rats were fed on a low calcium diet (0.02%) for 12 weeks post-operation, and then randomly divided into the two following groups. One group was fed on high calcium diet (2.30%) (OVX-HCa) and the other group was remained on the low calcium diet (OVX-LCa). Sham-OVX rats were fed on regular calcium diet (1.15%) during the experimental period (Sham-OVX). Histomorphological analysis was carried out from 12 to 32 weeks post-operation. On undecalcified thin section, bone volume, eroded surface, osteoid surface and bone formation rate were calculated for cortical bone of the maxilla, and for cancellous bone of the mandible and proximal tibia. In the OVX-LCa group, compared with the Sham-OVX group, decrease of the bone volume and increase of the bone resorption and formation parameters were detected throughout the observation periods. In the OVX-HCa group, compared with the OVX-LCa group, increase of the bone volume and temporarily increased parameters of bone formation at 1 week after feeding on high calcium diet were observed in the maxilla, but these changes were not observed in the mandible and proximal tibia. Moreover, the bone resorption and formation parameters in the maxilla, mandible and proximal tibia in the OVX-HCa group became equivalent to the Sham-OVX levels with the passage of time.

Effects of oestrogen deficiency on osteoclastogenesis in the rat periodontium

This study was designed to investigate quantitative changes in osteoclast generation in rat periodontium following ovariectomy. Wistar rats, aged 9 weeks, were subjected to either ovariectomy (OVX) or sham surgery. Osmotic pumps were implanted in 24 rats and either 17beta-oestradiol or vehicle solution were infused continuously. The rats were assigned to one of the following groups: (1) OVX+vehicle; (2) sham+vehicle; or (3) OVX+ 17beta-oestradiol. On the days 7 and 14 after surgery, four rats in each group were killed. Mandibles were demineralized and embedded in paraffin. Frontal sections of alveolar bone in the region of the first molar were cut for enzyme histochemistry and immunohistochemistry. On day 7, there was no significant difference in the number of tartrate-resistant acid phosphatase (TRAP)-positive cells located on bone surfaces in either group. However, the number of TRAP-positive mononuclear cells that were separated from the bone surface was significantly higher in group 1 than in groups 2 and 3. On the day 14, the number of TRAP-positive cells in group 1, which were attached to the bone surface, was significantly higher than had been apparent on day 7. There were also significant increases in the number of nuclei of TRAP-positive cells attached to the bone in group 1 compared with groups 2 and 3 on day 14. These findings demonstrate that oestrogen deficiency induces of osteoclastogenesis in the rat periodontium and that quantitative changes in osteoclastogenesis could be prevented by E2 infusion.

[The experimental study of Sr-HAP on reconstructing mandibular bone defect]

OBJECTIVE

Different ration of Sr-HAP was implanted in animals to study the bioreactions in order to prepare for the clinical applications in future.

METHODS

24 rabbits were divided into 3 groups for study. Bone defect of 6 mm x 12 mm x 4 mm was made at the mandibular angle of rabbits and Sr-HAP of different proportion (10%, 5%, 0%) was applied to reform the defect. One group of animals were killed at 1 month, 3 months, 6 months to evaluate the biologic capacity with anatomy, histology, SEM, tetracycline fluorescent marker, ECT and ration histology.

RESULTS

Sr-HAP had hardly been rejected by hosts, and in early period after operation the new bone in the Sr-HAP was found with great quantities as the degradation of Sr-HAP much more than that in the pure HA, and the difference of bone quantity can be shown in statistics.

CONCLUSIONS

1. Sr-HAP has a better biocompatibility, biodegradation than pure HA and a excellent osteoinductivity. The existence of Sr-HAP improves the total new bone quantity and the interface of bone, also prolongs the period of new bone increasing. 2. Sr-HAP has a good biodegradation and suitable speed of biodegradating, so the reconstruction effect with Sr-HAP is fairly satisfactory.

Platelet-derived growth factor/insulin-like growth factor-1 combination and bone regeneration around implants placed into extraction sockets: a histometric study in dogs

This study evaluated, by histometric analysis, the wound healing process of bone around implants placed into extraction sockets with or without the concurrent application of a combination of platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF-1). Mandibular premolars were removed, and 32 implants were inserted in eight dogs. Before insertion, two implants received a single application of 5 micrograms/mL of PDGF and IGF-1 delivered in 0.10 mL of 4% methylcellulose gel or 0.10 mL of 4% methylcellulose gel only as a control. To label regenerated bone, a 2% calcein green solution was administered by intramuscular injection at 0, 7, 15, 30, 45, 60, and 75 days after implant insertion. Three, 8, and 12 weeks after implant insertion, undecalcified sections were obtained, and the degree of bone contact with the implant surface, the bone area, and the intensity of bone labeling were measured into the limits of the threads of the implant. Greater extension of bone/implant contact (paired t test, P < .05) was observed in test (22.4% +/- 13.7%) than in control (17.2% +/- 13.6%) implants at 3 weeks. One-way ANOVA revealed a higher intensity of bone labeling (P < .05) at 3 weeks than at 12 weeks (127.8 +/- 42.59 and 56.7 +/- 26.34, gray scale values) for test implants. Within the limits of the present study, it was concluded that the combination of PDGF/IGF-I actively took part in the initial phase of bone repair.

Impact of the timing of indomethacin treatment in a model of synchronized bone remodelling in rats

Prostaglandins (PGs) promote both bone resorption and formation in vitro and in vivo. In a synchronised model of bone remodelling, indomethacin, an inhibitor of PG synthesis, given from the start of the sequence, transiently impaired bone resorption. In this study we further explored the involvement of PGs in this model by treating rats with indomethacin (7.5 mg x kg(-1) x day(-1)) for 6 days from the peak of resorption (day 4 after activation in this model) or during reversal (day 6 after activation). In rats treated from day 4, the resorption surface (Oc.S/BS) and the number of osteoclasts (N.Oc/BPm) were higher on day 10 (+69 %, P < 0.01, and +60 %, P < 0.02 compared with controls, respectively); no effect on cell resorptive activity was observed. The bone formation surface (OS/BS) was reduced (-50 %, P < 0.01). The inactive surface (In/BS) was not modified. In rats treated from day 6, the Oc.S/BS was also higher than in controls (P < 0.02), as was the N.Oc/BPm (P < 0.05). Osteoclast activity appeared to be increased, as the osteoclast-bone interface was larger (P < 0.02), but the mean lacuna area was reduced (-23 %, P < 0.05). Bone formation was also strongly affected: the OS/BS was decreased (-66 %, P < 0.01), as was the osteoid seam thickness (-24 %, P < 0.05). The In/BS was increased 1.5-fold (P < 0.05). These data indicate that PGs intervene at various stages of this remodelling sequence, as both resorption and formation were affected by indomethacin. Although resorption resumed in the two treatment groups despite treatment continuation, the timing of treatment was clearly important. Only inhibition of PG synthesis at the peak of resorption delayed all phases of the remodelling sequence. In contrast, inhibition during the reversal phase prevented activation of a significant part of the bone surface usually involved at this stage of remodelling; this treatment schedule reduced the resorptive capacity of the system, and depressed osteoblast activity.

Formation of the sphenomandibular ligament by Meckel's cartilage in the mouse: possible involvement of epidermal growth factor as revealed by studies in vivo and in vitro

In mammals, the midportion of the soft tissue of Meckel's cartilage at the degenerating stage forms a ligament known as the sphenomandibular ligament. To clarify the mechanism of formation of this ligament by Meckel's cartilage in mouse, we examined the effects of epidermal growth factor (EGF) on the chondrocytes in terms of the proliferation and differentiation of cells and calcification of the matrix in vivo and in vitro. The effects of EGF were examined by immunohistochemical staining, with EGF-soaked beads, by electron microscopy, and by general histochemical analysis of proteoglycans and calcification. Analysis of labeling with bromodeoxyuridine (BrdU) and the rate of cell growth revealed that EGF enhanced DNA synthesis and the proliferation of Meckel's chondrocytes. Histological findings in organ culture and in cell culture, with and without the application of EGF-soaked beads, revealed that EGF inhibited the differentiation of cells to chondrocytes and induced phenotypic changes in fibroblastic cells. The inhibition of alkaline phosphatase activity that resulted from exposure to EGF was accompanied by prolonged calcification of the matrix. Whole-mount staining revealed that subcutaneous injection of EGF enhanced the disappearance of Meckel's cartilage. Our results suggest a possible mechanism whereby the midportion of Meckel's cartilage remains uncalcified and is rapidly transformed into the sphenomandibular ligament.

Patterns of integrin expression in a human mandibular explant model of osteoblast differentiation

Cell-matrix interaction is crucial in regulating osteoblast differentiation and function. These interactions are themselves regulated, at least in part, by integrins. Although there are some data from mammalian models, few studies have compared integrin expression at different stages of the osteoblast lineage. Here, primary human mandibular osteoblast cultures were grown in the presence of epidermal growth factor (EGF), giving a proliferative, less differentiated phenotype, or of vitamin D(3) and hydrocortisone (D+Hc), giving a more differentiated phenotype. These cultures were compared with those of cells prepared in the absence of EGF or D+Hc by fluorescence-activated cell sorter using a panel of monoclonal antibodies to specific integrin heterodimers. To provide in vivo correlation, the same panel of antibodies was used to stain fresh-frozen, undemineralised sections of human mandibular bone. Under baseline conditions the alpha(3), alpha(5), alpha(v), alpha(v)beta(3), beta(3) and beta(1) integrin subunits were expressed strongly by the cells, with low-level expression of the alpha(1), alpha(2) and alpha(4) subunits. In the presence of EGF there was increased alpha(2) expression. With D+Hc, alpha(3) and alpha(5) expression was elevated. Immunohistochemical analysis demonstrated alpha(2), alpha(3), alpha(5), alpha(v)beta(3), beta(1) and beta(3) subunits in cells of the osteoblast lineage; alpha(2) staining was restricted to cells close to the bone surface whilst alpha(v)beta(3) and beta(3) were most frequently localised in the osteocytes. The results provide evidence that cells at successive stages of the osteoblast lineage show different patterns of integrin expression. These integrins may be important in cell-matrix interactions leading to osteoblast differentiation.

The effect of calcitonin on osseous healing in guinea pig mandible

Calcitonin (CT) is reported to be an effective medication for the treatment of inflammatory root resorption and to be capable of stimulating osteoblast proliferation in cell culture studies. In this study the effect of CT on the healing of osseous defects was evaluated in the mandibles of guinea pigs. After raising tissue flaps two experimental cavities were created on both sides of the corpus mandible of 33 guinea pigs. CT was applied into cavities either in hydroxypropyl methycellulose (HPMC) gel or gelatin as carrier. HPMC and gelatin alone and an empty cavity were also examined as control groups. Histopathological examinations under light microscopy were performed on weeks 1, 3, and 6. At week 1 in CT+gelatin and CT+HPMC groups, prominent osteoblastic activity was observed when compared with control groups. At week 3 the presence of woven bone in the experimental cavity areas reflected the increased osteoblastic activity in all groups. At the end of week 6 woven bone was gradually replaced by osteogenic tissue undergoing remodelization with Haversian systems in all groups. It is suggested that the osseous healing of the experimental cavity was enhanced by CT application in early stages (i.e. at week 1). However there was no significant difference of osteogenic activity between the control and CT-treated groups at the end of weeks 3 and 6.

Effect on bone healing of bone morphogenetic protein placed in combination with endosseous implants: a pilot study in beagle dogs

Although dental implants have become an effective treatment modality for the replacement of missing teeth, their predictability relies on successful osseointegration during the healing period. The purpose of this pilot study was to evaluate the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on early bone formation within the perforations of dental implants in beagle dogs. Histologic sections were evaluated for the extent of new bone formation within a 1-mm diameter of through-and-through perforations. Data indicated that significantly more bone formation occurred with rhBMP-2-treated sites within the implant perforation (P < 0.01) compared to sites treated with the vehicle alone. This pilot study indicates that rhBMP-2 increases the rate and extent of bone formation in combination with dental implants.

Anesthetic efficacy of infiltrations in mandibular anterior teeth

The purpose of this prospective, randomized, double-blind study was to measure the degree of anesthesia obtained with a labial infiltration of either 2% lidocaine with 1:50,000 or 2% lidocaine with 1:100,000 epinephrine in mandibular anterior teeth. Another objective was to measure the degree of anesthesia obtained with a lingual infiltration of 2% lidocaine with 1:100,000 epinephrine in mandibular anterior teeth. Through use of a repeated-measures design, 40 subjects randomly received a labial infiltration at the lateral incisor apex of either 1.8 mL of 2% lidocaine with 1:100,000 epinephrine or 1.8 mL of 2% lidocaine with 1:50,000 epinephrine at 2 separate appointments. An additional 40 subjects received a lingual infiltration at the lateral incisor apex of 1.8 mL of 2% lidocaine with 1:100,000 epinephrine. The mandibular anterior teeth were blindly pulp tested at 4-minute cycles for 60 minutes postinjection. No response from the subject to the maximum output (80 reading) of the pulp tester was used as the criterion for pulpal anesthesia. Anesthesia was considered successful when 2 consecutive 80 readings were obtained. For the 3 infiltrations, success rates for the lateral incisor ranged from 43 to 50%. Adjacent teeth had success rates of 27 to 63%. There was no significant difference (P > 0.05) in success between the labial infiltration of 2% lidocaine with 1:100,000 epinephrine and 2% lidocaine with 1:50,000 epinephrine or the lingual infiltration of 2% lidocaine with 1:100,000 epinephrine when compared with the labial infiltration of 2% lidocaine with 1:100,000 epinephrine. Duration of pulpal anesthesia declined steadily for all solutions over the 60 minutes. In conclusion, the success rate of 43-50% and declining duration of pulpal anesthesia over an hour indicates that a labial infiltration of 1.8 mL of either 2% lidocaine with 1:100,000 epinephrine or 1: 50,000 epinephrine or a lingual infiltration of 2% lidocaine with 1:100,000 epinephrine over the lateral incisor apex cannot be recommended clinically to provide profound pulpal anesthesia.

Alterations in the periodontium after ovariectomy in rats: the effects of a Japanese herbal medicine, Chujo-to

Ovariectomy-induced changes on the periodontium (gingiva, alveolar bone, and periodontal ligament) in rats and the preventive effects of a Japanese herbal medicine, Chujo-to, were studied for a period of 49 days. The rats were divided into five groups: sham-operated (sham), ovariectomized (OVX), OVX given Chujo-to, OVX given 17beta-oestradiol, and OVX given the vehicle for 17beta-oestradiol, respectively. After the test period, the bone mineral content (BMC) of the mandibular condyle in OVX rats was similar to those in both sham rats and the OVX rats treated with either Chujo-to or 17beta-oestradiol. However, the scanning electron microscopic (SEM) analyses revealed that the periodontal ligament of the OVX rats and the OVX rats treated with Chujo-to became more coarse than that of the sham rats or the rats treated with 17beta-oestradiol. The surface of the alveolar bone in the OVX rats appeared to contain numerous small granules, which were not present in the sham rats and the rats treated with either Chujo-to or 17beta-oestradiol. These results suggest that ovariectomy caused alterations in the peridontium, but Chujo-to had a preventive effect on the surface architecture of the alveolar bones.

[Effect of bFGF on regeneration of distracted mandibles after radiation]

The potential of distraction osteogenesis in mandibular reconstruction has been limited by its questionable efficacy in previously irradiated bone. The possible osteogenetic effect of recombinant human basic fibroblast growth factor (bFGF) on lengthening of irradiated mandibles was investigated in beagle dogs. We studied nine adult dogs which underwent a full course of external beam radiation therapy (60 Gy/30 fractions). Six months after completion of radiotherapy, the molars were extracted bilaterally followed by bone lengthening of the mandible using an intraoral device. On postoperative day 3 and 7 we injected 10 micrograms bFGF into the osteotomy site of each right hemimandible. The left sides were used as controls. The time course in ossification of the distracted area was evaluated at 2, 4, and 6 weeks after completion of bone lengthening. The radiographs of the newly formed bone tissue were measured by digital image analysis. Corresponding to the radiographic findings, the histological examination of the removed jaws showed an earlier and more intensive bone formation in the treated side after 2, 4, and 6 weeks compared to the control side. We conclude that bFGF promotes the ossification of distracted mandibles after radiation therapy in dogs.

Mandibular bone formation rates in aged ovariectomized rats treated with anti-resorptive agents alone and in combination with intermittent parathyroid hormone

Anti-resorptive agents--including estrogen (E), calcitonin (CT), and bisphosphonates--are established in the treatment of osteoporosis. Intermittent administration of parathyroid hormone (PTH) stimulates bone formation and is a possible therapeutic agent for the restoration of bone mass. The purpose was to determine the effects of the anti-resorptive agents alone and in combination with intermittent PTH on bone formation in the mandible and a long bone in the aged ovariectomized (Ovx) rat. Female rats were ovariectomized or sham-operated. One year later, groups of Ovx rats were treated with E, CT, or the bisphosphonate, Risedronate (NE). Additional groups of Ovx rats were treated with each of these agents in combination with human PTH for 10 weeks. Estrogen treatment suppressed most indices of bone formation in the humerus and mandible, while NE decreased some indices of formation at the endocortical and endosteal surfaces of the mandible and humerus. Increased double-labeled surface and mineral apposition rates were observed only on the mandibular endosteal surfaces following CT treatment. When the anti-resorptive agents were combined with intermittent PTH, most indices of bone formation at all skeletal sites were substantially greater than those of the untreated Ovx controls as well as the E-, CT-, and NE-treated groups, respectively. These results provide additional evidence that established and emerging therapies for osteoporosis affect osseous tissues in the oral cavity, and this may influence the progression of diseases and/or aging changes at this site.

Effects of cancer therapy on dental and maxillofacial development in children: report of case

Malignant lymphoma is one of the most common hematological diseases of children. The prognosis is fairly good with multimodal cancer therapy. We reported a boy with Burkitt's lymphoma in the nasal cavity who received chemotherapy and irradiation of the head and neck area at four years of age. During seven years of follow-up, we studied the developmental effects of cancer therapy, including general growth, maxillofacial bones, and dentition. Compared with boys of matching age, the development of his entire body and maxillofacial bones was delayed. In the irradiated areas, the roots of teeth were short or poorly developed and the root apices showed premature closure. After the patient was in remission from the tumor in his early childhood, the long-term effects of cancer therapy on dental and maxillofacial development are worth our further evaluation and follow-up.

Reaction of bony tissue to implanted silver glass ionomer and a reinforced zinc oxide-eugenol cement

OBJECTIVE

To evaluate the tissue responses to implants of Ketac Silver and Super EBA cement in the guinea pig mandible.

STUDY DESIGN

Sixteen guinea pigs were used for 2 experimental periods of 4 and 12 weeks. Both materials were placed in Teflon applicators and implanted into surgically prepared sites in the mandible. A histologic examination for reaction to the material occurred after the animals were killed and processed.

RESULTS

After 4 weeks, minimal inflammatory reactions were observed in Ketac Silver implants, whereas the Super EBA implants showed minimal to moderate inflammation. Localized foreign body reaction was present in areas of fragmented small particles of Ketac Silver. At 12-weeks observation, no inflammatory reactions were present around either material. Direct bone contact was observed in 1 Ketac Silver implant.

CONCLUSIONS

Ketac Silver and Super EBA cement elicited mild reactions under the conditions of this model. From a biologic point of view, these 2 materials may offer equal utility in endodontic surgery.

Increased in vivo levels of neurotransmitters to trigeminal motoneurons: effects on craniofacial bone and TMJ

The results of chronic, in vivo delivery of excitatory and inhibitory neurotransmitter substances upon the craniofacial skeleton are of ongoing interest to clinician and basic scientist alike. Our purpose was to document and compare the effects of biodegradable glycine, glutamate, and thyrotropin-releasing hormone (TRH) microspheres upon the craniofacial skeleton and TMJ of actively growing rats. Glycine, glutamate, TRH, and blank microspheres were stereotactically implanted in proximity to motoneurons within the trigeminal motor nucleus in order to test the following null hypotheses: (1) neurotransmitter microspheres implanted near trigeminal motoneurons of growing rats have no significant effect on the craniofacial skeleton and temporomandibular joints of implanted animals, and (2) there are no significant differences between the relative effects of glutamate, TRH (excitatory to trigeminal motoneurons), and glycine (inhibitory to trigeminal motoneurons) implants upon the craniofacial skeleton and temporomandibular joint. Fifty male Sprague-Dawley rats underwent stereotactic neurosurgery at 35 days; five rats each were killed at 14 and 21 days postoperative for data collection and comparison between glycine-, glutamate-, TRH-, blank-microsphere, and sham-surgery rats. Glycine rats had significantly (P < or = 0.05, 0. 01) smaller implant-side cranial dimensions and mandibular condyles, all glycine rats showed increased gracility of implant-side bones, and deviation of their facial skeleton away from the implant-side; this was in contrast to the generally larger implant-side bony structures in both glutamate and TRH rats. The two null hypotheses were both rejected. Due to their inhibitory and excitatory effects upon trigeminal motoneurons, masticatory muscles, and their neuromuscular generation of biomechanical forces that affect bone, the neurotransmitter substances glycine, glutamate, and TRH appear to play an important role in the growth and development of the mammalian craniofacial skeleton and TMJ.

Proliferation of periodontal squamous epithelium in mink fed 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

The maxilla and mandible from 2 adult female mink fed 5.0 ppb 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for 6 mo were grossly unremarkable, but histologically had nests of squamous epithelium within the periodontal ligament. There was osteolysis of the adjacent alveolar bone.

[Man with cherubism]

Cherubism was diagnosed in a male when he was 6 years old. Cherubism is a benign, bilateral, painless lesion. It is commonly located in the mandible but in a minority of patients also in the maxilla. Cherubism is a familial condition with an autosomal dominant pattern of inheritance. At least one member of the family of the patient described had cherubism. The disease becomes manifest during early childhood and progresses until puberty when it spontaneously regresses. In the majority of patients no treatment is required. However, in the patient presented surgical procedures and odontological corrections were necessary. Due to a flare-up of the disease at the age of 22 years, the patient was treated with calcitonin for 1 year followed by bisphosphonates. During these treatments the disease symptoms diminished.

Effect of intermittent administration of human parathyroid hormone (1-34) on the mandibular condyle of ovariectomized rats

Intermittent administration of human parathyroid hormone (1-34) (PTH) increases bone mass in lumbar vertebrae and long bones of osteoporotic experimental animals. However, whether PTH has the same effect on jaw bones remains unclear. This study determined the effect of intermittent administration of PTH on rat mandibular condyle affected by estrogen deficiency. Fifty 6-month-old rats were either sham operated or ovariectomized, then divided into five groups depending on surgical procedure and hormone administration: sham + vehicle (SV), OVX + vehicle (OV), OVX + PTH 6 micrograms/kg once per week (OP6-1), OVX + PTH 60 micrograms/kg once per week (OP60-1), and OVX + PTH 20 micrograms/kg three times per week (OP20-3). PTH or vehicle was injected intermittently for 6 months in 5 rats of each group either immediately after surgery in a preventive administration experiment, or injected starting 6 months after surgery in a therapeutic administration experiment. The mandibles were excised, and bone morphometry was performed using confocal laser scanning microscopy and soft X-ray images. In both experiments, the bone volume of the OV groups was significantly lower than that of the SV group (P < 0.01); also, depending on dose and frequency, the bone volume of the OP group was higher than that of the OV group, particularly in the OP20-3 group. The value of mineralized surface of the OP groups was significantly higher than that of the OV group (P < 0.01), whereas the value of eroded surface of the OP groups was not significantly higher than that of the OV group. This study indicates that preventive and therapeutic intermittent administration of PTH in ovariectomized rats increase the bone formation in rat mandibular condyle without accelerating bone resorptive activity. This anabolic effect was best induced by the injection mode of 20 micrograms/kg three times per week.

[Focal morphological changes in the bone tissue of the mandible and tibia of rabbits under the influence of different metal inclusions]

Morphological changes in bone tissue were studied in an experimental model with electrochemical polarization of the bone, which was achieved by applying electrodes (anode made of silver-palladium alloy SPS-250 and cathode of copper-aluminum alloy manufactured as orthodontic ligature wire) on the mandibular periosteum and tibial bone of rabbits. Macroscopic changes were as follows: osseous tissue hypertrophy at the zone of cathode polarization with a corresponding increase in the area of transverse section of the mandible and atrophy of the bone under the anode, all this causing pronounced asymmetry of the jaw bones. Microscopic changes in the bone were adequate to the macroscopic and characterized by sharp activation of its apposition (under cathode) and resorption (under anode).

Enhancement by hepatocyte growth factor of bone and cartilage formation during embryonic mouse mandibular development in vitro

To elucidate the possible roles of hepatocyte growth factor (HGF) in the early development of mouse mandible, HGF was applied to an organ-culture system with chemically defined media. Mandibular arches microdissected from mouse embryos at the 10th day of gestation were cultured for 10 days with or without HGF, HGF plus HGF-receptor (c-met) antisense oligodeoxyribonucleotide, or HGF plus c-met sense oligodeoxyribonucleotide in the media. The cultured mandibles were then analysed, histologically in serial paraffin sections. In the absence of HGF, the tooth organs of bud stage, Meckel's cartilage and the tongue were formed, whereas only a slight amount of bone tissue was formed in the cultured mandible. The expression of intrinsic HGF and c-met in the cultured mandibles was confirmed by reverse transcriptase-polymerase chain reaction. Furthermore, immunohistochemistry demonstrated that both HGF and c-met were localized in areas of the mesenchymal tissue forming bone and cartilage. With HGF in the medium, the volume of both bone and cartilage increased significantly and dose-dependently. HGF also increased the rate of proliferation of osteogenic cells and chondrocytes. Addition of c-met antisense oligodeoxyribonucleotide partially inhibited the HGF-induced enhancement of bone and cartilage formation, whereas addition of c-met sense oligodeoxyribonucleotide had no effect. These results revealed that exogenous HGF enhances bone and cartilage morphogenesis in the cultured mandibles, suggesting physiological roles for intrinsic HGF in the early development of mouse mandible.

Convergence of the BMP and EGF signaling pathways on Smad1 in the regulation of chondrogenesis

Bone morphogenetic protein 4 (BMP4) induces, whereas epidermal growth factor (EGF) inhibits chondrogenesis. We hypothesize that BMP4 and EGF mediated intracellular signals are both coupled in the regulation of Meckel's cartilage development. Two chondrogenic experimental model systems were employed to test the hypothesis: (1) an ex vivo, serum-free, organ culture system for mouse embryonic mandibular processes, and (2) a micromass culture system for chicken embryonic mandibular processes. Chondrogenesis was assayed by alcian blue staining and expression of Sox9 and type II collagen. Exogenous EGF inhibited and BMP4 induced ectopic cartilage in a dose-dependent manner. When BMP4- and EGF-soaked beads were implanted in juxtaposition within embryonic day 10 mouse mandibular processes, the incidence and amount of ectopic cartilage, and Sox9 and type II collagen expression induced by BMP4, were significantly reduced as the concentration of EGF was increased. Similarly, in chicken serum-free micromass cultures, expression of a constitutively active BMP receptor type IB by replication competent avian retrovirus system promoted the rate and extent of chondrogenesis; however, exogenous EGF attenuated this effect. In micromass cultures, BMP signaling resulted in nuclear translocation and accumulation of the signaling molecule Smad1, whereas the addition of EGF inhibited this event. Our results suggest that BMP4 and EGF function antagonistically, yet are coupled in the regulation of initial chondrogenesis. Smad1 serves as a point of convergence for the integration of two different growth factor signaling pathways during chondrogenesis.

Bone regeneration by recombinant human bone morphogenetic protein-2 in rat mandibular defects. An experimental model of defect filling

BACKGROUND

Bone defects and irregularities are major problems for dental implant and periodontal therapies.

METHODS

We investigated whether the application of recombinant human bone morphogenetic protein-2 (rhBMP-2) induces bone formation in through-and-through bone defects in the rat mandible. A round through-and-through bone defect (5 mm in diameter) was created in the angle of the mandible on both sides of the jaw using a steel round bur in each of 8 Long-Evans rats. In the experimental group, polylactic acid-polyglycolic acid copolymer/gelatin sponge (PGS) containing rhBMP-2 (6 microg/60 microl) was inserted in the bone defect. In the control group, the same carrier without rhBMP-2 was applied in the bone defect on the opposite side. Four weeks after application, the rats were sacrificed. Step serial sections stained with hematoxylin and eosin at intervals of 200 microm were prepared in a bucco-lingual direction. The size of the bone defects and new bone formation were evaluated histometrically.

RESULTS

In all cases in the experimental group, a large quantity of newly formed bone was observed. The bone defects were completely filled with new bone in 4 of 8 rats in the experimental group. In the control group, small amounts of new bone formation were observed along the border of the original mandibular bone. Histometrical analysis revealed that the amount of new bone was significantly larger in the rhBMP-2 treated sites than in the control sites (P <0.0001; paired t-test).

CONCLUSIONS

These results indicate that the rhBMP-2/PGS system induced effective bone regeneration on mandibular defects in rats. This procedure may be suitable as an experimental model for bone regeneration using various growth factors and effective for alveolar ridge augmentation followed by dental implant surgery.

The effect of fibrin stabilizing factor (F.XIII) on healing of bone defects in normal and uncontrolled diabetic rats

This study was undertaken to examine the effect of fibrin stabilizing factor (F.XIII) on healing of bone defects in normal and uncontrolled diabetic rats. Eighty rats were divided into two groups: group I (diabetic) and group II (non-diabetic) (40 rats each). Diabetes was induced in group I using streptozotocin. Both groups were divided into two subgroups, control and experimental (20 rats each). Bone defect was created in the mandible. Rats in the experimental subgroups were injected with F.XIII, while those of the control groups were injected with saline (F.XIII solvent). Animals were killed at varying intervals and tissue sections stained with hematoxyline and eosin and Van-Gieson stains were examined. Differences in collagen deposition and bone formation were compared in both control and experimental groups. Collagen deposition was evident and appeared more oriented in diabetic rats treated with F.XIII, and signs of bone deposition started in the experimental group earlier than in the control group. On the other hand, F.XIII did not significantly affect healing in non-diabetic rats. It is concluded from these results that F.XIII may enhance early stages of bone healing in uncontrolled diabetic rats.

[Polylactic acid combined with recombinant human bone morphogenetic protein and basic fibroblast growth factor to repair the mandibular defects in rabbits]

OBJECTIVE

To study the effect of basic fibroblast growth factor(bFGF) on bone formation induced by recombinant human bone morphogenetic protein-2(rhBMP-2) in repair of mandibular defects in rabbits.

METHODS

56 adult domestic rabbits were classified into five groups. The mandiblar three-wall defects(1.5 cm x 0.5 cm, full thick) were created in right sides. The defects were implanted with various grafts: PLA/rhBMP-2/bFGF, PLA/rhBMP-2, PLA/bFGF, PLA and no implant as control group. At 2, 4 and 8 weeks after operation, the effectivenesses of defect repaire were observed by histological and roentgenographic analysis.

RESULTS

The composite consisting of three materials stimulated more bone formation than of two materials, and the latter was more than single PLA(at 4 weeks postoperation, P < 0.05). All experimental groups, which had one or two growth factors, were significantly higher compared with control group in every stage of postimplantation.

CONCLUSION

PLA has good biocompatibility, absorbability and osteoconductibility, rhBMP-2 and bFGF are cooperated in bone healing process, and PLA/rhBMP-2/bFGF is a promising bone substitute in clinical uses.

Epidermal growth factor receptor function is necessary for normal craniofacial development and palate closure

Craniofacial malformations are among the most frequent congenital birth defects in humans; cleft palate, that is inadequate fusion of the palatal shelves, occurs with an annual incidence of 1 in 700 to 1 in 1,000 live births among individuals of European descent. The secondary palate arises as bilateral outgrowths from the maxillary processes, and its formation depends on the coordinated development of craniofacial structures including the Meckel's cartilage and the mandible. Cleft lip and palate syndromes in humans are associated with polymorphisms in the gene (TGFA) encoding transforming growth factor-alpha (TGF-alpha), an epidermal growth factor receptor (EGFR) ligand made by most epithelia. Here we have characterized craniofacial development in Egfr-deficient (Egfr-/-) mice. Newborn Egfr-/- mice have facial mediolateral defects including narrow, elongated snouts, underdeveloped lower jaw and a high incidence of cleft palate. Palatal shelf explants from Egfr-/- mice fused, but frequently had residual epithelium in the midline. In addition, morphogenesis of Meckel's cartilage was deficient in cultured mandibular processes from Egfr-/- embryos. The secretion of matrix metalloproteinases (MMPs) was diminished in Egfr-/- explants, consistent with the ability of EGF to increase MMP secretion and with the decreased MMP expression caused by inhibition of Egfr signalling in wild-type explants. Accordingly, inactivation of MMPs in wild-type explants phenocopied the defective morphology of Meckel's cartilage seen in Egfr-/- explants. Our results indicate that EGFR signalling is necessary for normal craniofacial development and that its role is mediated in part by its downstream targets, the MMPs, and may explain the genetic correlation of human cleft palate with polymorphisms in TGFA.

[The optimization of the reparative processes in a mandibular bone wound in patients with chronic alcoholism]

A total of 148 chronic alcoholics with mandibular fractures were treated. Hydroxyapol and colapol were inserted in bone wounds for improving the reparative osteogenesis. Clinical, immunological, and echo-osteometric data demonstrated the efficacy of both preparations, which promoted bone repair and reduced the incidence of pyoinflammatory complications.

In vivo model for the experimental manipulation of calcified tissues: a surgical approach for accessing the odontogenic organ and associated tissues of the rat incisor

The tooth organ is extensively used in developmental biology to investigate organogenesis and cell differentiation. It also represents an advantageous system for the study of the various cellular and extracellular matrix events that regulate the formation of both collagenous and noncollagenous calcified tissues. This article describes an in vivo surgical approach to access and experimentally manipulate the tooth organ and supporting tissues of the rat incisor. By use of a dental drill, a "window" was created through the alveolar bone on the buccal aspect of the hemimandible at the apical end of the incisor. It is at this site that epithelial and mesenchymal precursors are situated and undergo cellular differentiation to give rise to cells of the odontogenic organ. Active bone remodeling is also observed in this area to accommodate posterior growth of the tooth. An osmotic minipump connected to the bony window through an outlet catheter was used for controlled and continuous administration of experimental agents over a predetermined period of time. To validate the model, vinblastine sulfate, fetuingold, and dinitrophenylated albumin were thus infused. The animals were then sacrificed and the hemimandibles were processed for histological and immunocytochemical analyses. The effects of the drug and the presence of tracers were restricted to the treated hemimandible and were found in the enamel organ and pulp, as well as in the tooth supporting tissues. Cellular changes typically associated with the administration of vinblastine were obtained, and tracers were localized both in the extracellular milieu and within the endosomal/lysosomal elements of cells. These results suggest that this new surgical approach could serve as an advantageous in vivo model in which various chemical agents, therapeutic drugs, molecular probes are locally administered to study the molecular events that regulate calcified tissue formation.

Surface modification of A12O3 bioceramic by NH2+ ion implantation

Ion implantation technique was applied to graft the -NH2 amidogen radicals onto the surface of Al2O3 bioceramic. Fourier transform infrared spectroscopy (FTIR) was used to confirm the presence of the implanted radicals on the Al2O3 ceramic surface. It was found that the amount of grafted amidogen radicals was proportional to the dosage of NH2+ ions used during the ion implantation. Furthermore, when implantation energy of 100 keV was used, maximum amount of -NH2 radicals would be grafted on the Al2O3 ceramic surface. The biocompatibility of the implanted Al2O3 ceramic was also investigated, and the results indicate that the implanted surface has better biocompatibility with animal bone tissue than the plain ceramic surface.

[Experimental study of osseointegrated dental implants placed into fresh extraction sockets in dogs]

OBJECTIVE

To investigate the better way in treating bone defects around implants.

METHODS

12 mongrel dogs, pure titanium implants were immediately inserted in the mesial roots of the second, third and fourth mandibular premolar sockets. The defects around implants were separately filled with demineralized freeze-dried bone allograft (DFDBA), demineralized freeze-dried allocancellous in combination with bBMP (bBMP compound bone) and nothing.

RESULTS

Histologic observation showed that bone defects around implants were substituted by new bone in DFDBA group at 12 weeks and in bBMP compound bone group at 8 weeks, and also the osseointegration were obtained between implants and bone, but bone defects were only filled about 3/5 in no graft group at 12 weeks.

CONCLUSION

Immediate implants could obtain good osseointegration if the defects around implants were treated properly and the right technique was used, and also the use of bBMP compound bone could promote obviously bone formation in defects around implants.

Recombinant human bone morphogenetic protein-2 stimulation of bone formation around endosseous dental implants

BACKGROUND

Successful endosseous implant placement requires that the implant be stable in alveolar bone. In certain cases, the implant can be stabilized in native bone but some part of the implant is not covered by bone tissue. This often occurs during placement of implants into extraction sites or in areas where bone resorption has occurred and the ridge width is not sufficient to completely surround the implant. In those cases, the clinician usually employs a procedure to encourage bone formation. These procedures typically include a bone graft and/or membrane therapy. Recent advances have led to the isolation, cloning, and production of recombinant human proteins that stimulate bone formation. One of these bone morphogenetic proteins (rhBMP-2) has been extensively studied in animal models and is currently being tested in human clinical trials.

METHODS

In this study, rhBMP-2 was tested using a collagen sponge carrier to stimulate bone formation in defects in the canine mandible around endosseous dental implants. Six animals had a total of 48 implants placed. rhBMP-2 with the collagen carrier was implanted around 24 of these, the remainder having only the collagen carrier placed. Half the sites were covered with a nonresorbable expanded polytetrafluoroethylene membrane. Histologic analysis was performed after 4 and 12 weeks. The area of new bone formed, percentage of bone-to-implant contact in the defect area, and percentage fill of the defect was calculated.

RESULTS

The addition of rhBMP-2 resulted in significantly greater amounts of new bone area and percentage of bone-to-implant contact and with more percentage fill after 4 and 12 weeks of healing. The area of new bone formed was reduced after 4 weeks when a membrane was present but after 12 weeks, there was no significant difference between membrane and non-membrane treated sites. In some specimens, new bone was found coronal to the membranes, with rhBMP-2-treated sites having greater amounts than non-rhBMP-2-treated sites.

CONCLUSIONS

These data demonstrate that a bone differentiation factor significantly stimulates bone formation in peri-implant bone defects in the canine mandible. In addition, bone-to-implant contact was significantly enhanced along the rough implant surface. Membrane-treated sites had less new bone formation after 4 weeks of healing but were similar to non-membrane sites after 12 weeks. These results demonstrate that rhBMP-2 can be used to stimulate bone growth both around and onto the surface of endosseous dental implants placed in sites with extended peri-implant osseous defects.

Use of alendronate in peri-implant defect regeneration

BACKGROUND

Previous studies have demonstrated an increase in bone mass and density with use of systemic alendronate sodium. This agent acts as an inhibitor of osteoclast activity, and is thought to result in more net osteoblastic activity. The objective of this study was to determine the effects of locally applied alendronate sodium on guided bone regeneration around dental implants.

METHODS

Six adult mongrel dogs were divided into 2 groups: one group received alendronate-coated dental implants, and the other group served as control. Two types of dental implants were used in each dog: hydroxyapatite (HA)-coated and titanium machine-polished (TMP), for a total of 4 groups. Dental implants were placed immediately after extraction of the right and left second, third, and fourth mandibular premolars; a resorbable collagen membrane was secured over the implants and defects; and the flaps were closed primarily. Fluorescent labels were administered intravenously on days 0, 6, 12, and 22 to measure bone formation rate. Dogs were sacrificed on day 28. The specimens were sectioned and mounted, and bone formation rate was recorded with a computerized microscopic digitizer. Specimens were stained with Stevenel's blue and van Gieson's picric fuchsin. Bone-to-implant contact was recorded with a computerized microscopic digitizer.

RESULTS

The results indicated a significant effect of locally applied alendronate (P < 0.0001) with both types of implants (HA and TMP), as well as the HA coating (P< 0.02) on increased bone formation rate. Additionally, alendronate had a significant effect on bone-to-implant contact, with an increase in the TMP model (P < 0.0001) and a decrease in the HA model (P < 0.0001 ). HA coating also had a significant effect on increasing bone-to-implant contact (P < 0.04).

CONCLUSIONS

The results indicate that alendronate increases early bone formation rate around dental implants. Additionally, the local application as described resulted in greater bone-to-implant contact with TMP implants.

The effect of onlay Medpor implants on mandibular growth in young rabbits: an experimental study

Medpor implants were placed on the periosteum of the mandible in infant rabbits to study their effects on growth. Three months later radiological and histopathological studies were performed in situ and after removal of the mandible. The authors demonstrate that implants did not affect normal development of the mandible; however, there was a decrease in bone thickness and a mononuclear cell reaction was caused where the implant came in contact with the bone.

Effects of cyclosporin A on alveolar bone: an experimental study in the rat

BACKGROUND

There have been several investigations on the role of cyclosporin A (CSA) in gingival hyperplasia in both animals and humans. However, less attention has been given to the drug's effect on alveolar bone. This study used light microscopy to histologically and histometrically evaluate the effects of CSA on alveolar bone in the rat.

METHODS

Sixty, 6-week-old Sprague-Dawley rats were separated into test and control groups. Animals in the test group received CSA in mineral oil (30 mg/kg body weight) daily by gastric feeding over the 6-week study. Control animals received only mineral oil. Ten animals from each group were sacrificed at weeks 2, 4, and 6. After histologic processing, the labial crest of the alveolar bone in the anterior mandible was evaluated by light microscopy.

RESULTS

A distinct pattern of increased osteoclasia and reduced bone formation was observed in the CSA-exposed animals compared to the controls. Increased osteoclasia was observed in periodontal sites and decreased bone formation was observed in symphyseal sites.

CONCLUSIONS

The results suggest that CSA has distinct effects on alveolar bone.

Comparative study of intramuscular and intraskeletal osteogenesis by recombinant human bone morphogenetic protein-2

OBJECTIVE

The purpose of this study was to compare the osteoinducing activity of recombinant human bone morphogenetic protein-2 (rhBMP-2) at intramuscular and intraskeletal sites in rats.

STUDY DESIGN

Five tg of rhBMP-2 was implanted into the right calf muscle of each of 20 rats and into a hole (4 mm in diameter, 1.5 mm in depth) that was made in the mandibular body of each of 20 other rats, with atelopeptide type I collagen as a carrier. The alkaline phosphatase activity and calcium content were quantitatively analyzed 1, 3, 7, and 21 days after the implantation of rhBMP-2 into either mandibular bone (in the intraskeletal group) or calf muscle (in the intramuscular group). The new bone formation was evaluated histologically 21 days after implantation.

RESULTS

On days 1 and 3, the alkaline phosphatase activity and calcium content in the intraskeletal group showed no significant differences from those in the intramuscular group. On the 7th and 21st days after implantation, however, the alkaline phosphatase activity and calcium content in the intraskeletal group were significantly higher than those in the intramuscular group. Histometry of the microscopic views showed that the mean trabecular area was 0.87 mm2 in the intramuscular group and 2.66 mm2 in the intraskeletal group.

CONCLUSIONS

These results suggest that the new bone formation stimulated by rhBMP-2 in the intraskeletal group was greater than in the intramuscular group.

Effect of biphosphonates on abnormal mandibular growth of rats intoxicated with uranium

Intoxication with uranium induces severe alterations in kidneys and in acute intoxications inhibits bone formation and bone growth. Administered at high doses, uranium leads to death, an event that can be prevented by the administration of ethane-1-hydroxy-1,1 biphosphonate (EHBP), which would presumably exert its effect via its chelating properties. Based on this information, the aim of the present study was to determine the best therapeutic method for treatment using biphosphonates to prevent mandibular growth alterations in animals that survive uranyl nitrate poisoning. Seven groups of Wistar rats weighing 14 g were used as follows: I, untreated control; II, one intraperitoneal injection (IPI) of 2 mg Kg(-1) of body weight of uranyl nitrate (238U). In groups III to VII animals were intoxicated as in Group II and in addition were given a single injection of 10 mg Kg(-1) of ethane-1-hydroxy-1, 1-biphosphonate (EHBP), or 3-amine-1, 1-hydroxypropylene-1, 1 biphosphonate (APD) as follows; Group III, IPI of EHBP given immediately after poisoning (0 h); IV, IPI of EHBP given at 24 h; V, subcutaneous injection (SCI) of EHBP at 0 h; VI, SCI of EHBP at 48 h; VII SCI of APD at 0 h. Survivors were killed on the sixtieth day. Body weight increase, survival rate, and biometric parameters of mandibular growth (Eratalay's method) were studied. Student's "t" test was used for statistical analysis. On day 60 there was only one survivor in Group II and none in Group IV. All animals in the other groups survived. Mandibular growth parameters showed the worst results in Group VII and the best in Group V for which no difference with the controls was observed. These results show that a single subcutaneous injection of EHBP given immediately after uranium poisoning, apart from preventing death, is capable of preventing undesirable alterations in mandibular growth.

[Osteoporosis]

Osteoporosis is an increasing major skeletal disease leading to disability. It is important to define this disease precisely, because the start is without any symptom in many cases. Causal factors are reviewed as also recognisable risk factors in early stage. The available recent literature and own studies did not show relationship between tooth loss, bone loss of the mandible, periodontitis and osteoporosis. However, corticosteroids diminish mandibular bone mass. Assessment to bone mineral density is a major diagnostic test for osteoporosis prediction. Recent findings in prevention and treatment of osteoporosis are reviewed extensively. The positive results of oestrogen replacement therapy on the oral bone loss and tooth loss from some large observational American studies are interesting.

Normalization of periodontal tissues in osteopetrotic mib mutant rats, treated with CSF-1

The osteopetrotic mib mutation in rats causes defects in the skeletal bone tissue in young animals. These defects, i.e. slow bone remodelling, changes in both crystallinity and mineral content, are transient and undergo normalization, even without any treatment in 6-wk-old animals. Treatment with CSF-1 (colony stimulating factor-1) accelerates the normalization process in skeletal bones. The periodontal tissues around the apices of incisors show abnormalities caused by the slow remodelling process of the mandible bone tissue, the deficiency of osteoclasts and their abnormal morphology, as well as the disorganization of periodontal ligament fibres. In contrast to the skeletal tissues, these abnormalities would not undergo spontaneous normalization. Under treatment with colony stimulating factor 1 (CSF-1), the primitive bone trabeculae of mandible are resorbed and the normalization of the number of osteoclasts and their cytology occurs. The organization of the periodontal ligament fibres is partially restored, resembling the histological structure of the normal one.

Growth factors and bone regeneration. Implications of barrier membranes

Insufficient or absence of bone healing is a frequent problem within all surgical fields. This often necessitates treatment by autogenous bone grafting. Recently, two new techniques to promote bone healing were introduced, the osteopromotive membrane technique, and local delivery of growth-stimulatory factors, both with a high rate of success in preclinical experiments. The aims of the present series of investigations were to further develop the membrane barrier technique, both by itself as well as in combination with local delivery of growth factors, in animal experiments. During membrane-promoted bone formation, the membrane porosity was found to be of importance for the initial rate of bone formation as well as for the performance of the material in the tissue. In contrast, the final amount of bone was not affected. In a well-known bone healing model, the 5 mm in diameter 'critical size defect' at the rat mandibular ramus, the efficacy of rhBMP-2, rhTGF-beta 1 and rhFGF-2 to promote bone regeneration alone and in combination with barrier membranes was evaluated. Under both conditions, rhBMP-2 was found to be an efficient promoter of bone healing. rhFGF-2 had some stimulatory effect both with and without barrier membranes, whereas rhTGF-beta 1 was found to have a minor stimulatory effect by itself, but in combination with barrier membranes it was inhibitory. These observations were interpreted as being the result of an effect of the growth factors at different levels of the osteoblastic lineage; rhBMP-2 being an inducer of osteoblastic cells from stem cells, whereas rhTGF-beta 1 may primarily act on already committed cells. In contrast, rhFGF-2 may have stimulatory effect at different levels of the lineage. Based on the positive results obtained by the combination of rhBMP-2 and barrier membranes in the rat mandible, this combination was then applied to (i) rabbit radius defects; and (ii) a rat calvarial osteoneogenesis model. In the long bone model, membranes by themselves were insufficient to promote bone healing, but the combination resulted in complete regeneration. In the osteoneogenesis model, the combination of barrier membranes and rhBMP-2 resulted in a 100% increase in the final amount of achievable bone. In the last study, rhFGF-2 (no barrier membranes) was shown to enhance revitalization of autoclaved autogenous bone grafts, a procedure clinically used in craniofacial reconstruction mainly after tumor surgery. The combined use of rhBMP-2 and barrier membranes has great potential to be a useful treatment for improving bone healing and might be an alternative to bone grafting.

Effects of irradiation and methyl-triazene on craniofacial development in mouse embryos: a semiautomated morphometric analysis

OBJECTIVE

The purpose of the present study was a 2D-semiautomated morphometric analysis of craniofacial growth in nuclear magnetic resonance imaged (NMRI) mouse embryos.

METHODS

The NMRI mouse embryos were exposed in utero to either a single dose of 2 Gy X-irradiation on day 9 of gestation (113 embryos) or to 1.5 mg methyl-triazene administered orally to their pregnant mothers on gestational day 10.5 (124 embryos). An additional group of 108 embryos was used as controls. Digitized pictures of embryos from gestational days 14 to 17 were taken in lateral right view using a video system. Landmarks were located and digitized for computerized analysis of growth changes in relation to developmental stages of the face.

RESULTS

The results revealed that the snout of control embryos lengthens during the developmental period considered. The snout of embryos previously submitted to methyl-triazene displayed micrognathia, and all treated fetuses exhibited macroscopic signs of microcephaly with a reduced mandible. The snouts of irradiated embryos appeared shortened at the 14-day stage and continued to shorten as development proceeded. A shortening of the midface was detected macroscopically in 83% of the cases.

CONCLUSION

The results of this morphometric analysis enabled us to trace the developmental progression of the induced dysmorphosis and to assess the differences compared with normal development.

Tissue reaction to implanted root-end filling materials in the tibia and mandible of guinea pigs

The purpose of this study was to examine the tissue reaction to implanted mineral trioxide aggregate (MTA), amalgam, Intermediate Restorative Material, and Super-EBA in the tibias and mandibles of guinea pigs. After anesthetizing 20 guinea pigs, raising tissue flaps, and preparing bony cavities, the test materials were placed in Teflon cups and implanted in the tibias and 10 days later in the mandibles. The animals were euthanized 80 days later and the tissues prepared for histological examination. The presence of inflammation, predominant cell type, and thickness of fibrous connective tissue adjacent to each implant were recorded. The tissue reaction to MTA implantation was the most favorable observed at both sites; as in every specimen, it was free of inflammation (p < 0.01). In the tibia, MTA was the material most often observed with direct bone apposition. Based on these results, MTA seems to be a biocompatible material.

Opposite effects of recombinant human transforming growth factor-beta 1 on bone regeneration in vivo: effects of exclusion of periosteal cells by microporous membrane

The efficacy of local delivery of recombinant human transforming growth factor-beta 1 (rhTGF-beta 1) to promote bone regeneration, with or without cellular contribution from the periosteum, was evaluated in transosseous defects. Implantation of rhTGF-beta 1 into 5 mm in diameter "critical size defects" in the rat mandible resulted in a dose-dependent (0.1-20 micrograms/defect) bone bridging at both 12 and 24 days, independent of the type of delivery system [3% methyl cellulose gel, porous CaCO3 particles, or poly(lactide-co-glycolide) beads]. The bridging, however, never exceeded 24% at 12 days or 34% after 24 days. In contrast, when access of cells from the periosteum to the defect was prevented by means of microporous expanded polytetrafluoroethylene barrier membranes (GORE-TEX membrane), rhTGF-beta 1 caused a dose-dependent inhibition of bone regeneration. The bioactivity of the growth factor was confirmed by implantation of 5 or 10 micrograms rhTGF-beta 1 in 12 mm in diameter bicortical defects in rabbit calvaria, which resulted in complete bone healing within 28 days, whereas control defects displayed a bridging of 40%-50%. The findings support the concept, based on in vitro experiments by others, that TGF-beta 1 primarily has a proliferative effect on cells already committed to the osteoblastic lineage, but also imply that TGF-beta 1 may be inhibitory to induction of osteogenic cells in vivo.