The efficacy of a tissue-engineered xenograft in conjunction with sodium hyaluronate carrier in maxillary sinus augmentation: a clinical study.

PepGen P-15 Putty comprises anorganic bovine bone matrix (ABM) coupled with a synthetic cell-binding peptide, suspended in a sodium hyaluronate carrier. The P-15 portion exhibits a similar structure and properties to the cell-binding region of type I collagen. This study was performed to evaluate ABM/P-15 putty as the sole graft in sinus augmentation. Ten patients for whom both a sinus augmentation and two implants were indicated in the posterior maxilla were enrolled. Bone cores were harvested at 8 and 16 weeks, followed by placement of one implant at 8 weeks and the second at 16 weeks. Twenty collected bone cores were evaluated histologically and by micro-computed tomography. Results showed a significant increase (P<0.05) in bone mineral density at 8 weeks (0.70±0.13g/cm(3)) and 16 weeks (0.97±0.08g/cm(3)) in the graft compared to native (control) bone (0.04±0.02g/cm(3)). There was no significant difference (P>0.05) in the percentage bone volume at the two time intervals (PBV 21.14±4.56 at 8 weeks and 26.33±5.60 at 16 weeks). The average increase in bone height at 16 weeks was 10.55±0.53mm. It is concluded that PepGen P-15 Putty is capable of conducting and accelerating new bone formation and can successfully support dental implants.

Agmatine attenuates silica-induced pulmonary fibrosis.

There is a large body of evidence that nitric oxide (NO) formation is implicated in mediating silica-induced pulmonary fibrosis. As a reactive free radical, NO may not only contribute to lung parenchymal tissue injury but also has the ability to combine with superoxide and form a highly reactive toxic species peroxynitrite that can induce extensive cellular toxicity in the lung tissues. This study aimed to explore the effect of agmatine, a known NO synthase inhibitor, on silica-induced pulmonary fibrosis in rats. Male Sprague Dawley rats were treated with agmatine for 60 days following a single intranasal instillation of silica suspension (50 mg in 0.1 ml saline/rat). The results revealed that agmatine attenuated silica-induced lung inflammation as it decreased the lung wet/dry weight ratio, protein concentration, and the accumulation of the inflammatory cells in the bronchoalveolar lavage fluid. Agmatine showed antifibrotic activity as it decreased total hydroxyproline content of the lung and reduced silica-mediated lung inflammation and fibrosis in lung histopathological specimen. In addition, agmatine significantly increased superoxide dismutase (p < 0.001) and reduced glutathione (p < 0.05) activities with significant decrease in the lung malondialdehyde (p < 0.001) content as compared to the silica group. Agmatine also reduced silica-induced overproduction of pulmonary nitrite/nitrate as well as tumor necrosis factor α. Collectively, these results demonstrate the protective effects of agmatine against the silica-induced lung fibrosis that may be attributed to its ability to counteract the NO production, lipid peroxidation, and regulate cytokine effects.

Effects of enamel matrix protein application on the viability, proliferation, and attachment of human periodontal ligament fibroblasts to diseased root surfaces in vitro.

OBJECTIVES: The purpose of this research was to examine the influence of enamel matrix proteins (EMP) on the viability, proliferation, and attachment of periodontal ligament fibroblasts (PDLF) to diseased root surfaces. MATERIALS AND METHODS: Primary cell cultures of PDFL were obtained from clinically healthy third molars or premolar teeth. Viability and proliferation rates were carried out over a 10-day period. A total of 80,000 cells were plated in 24-well plates followed by EMEM with 10% FBS (positive control) and EMEM plus EMP at 25, 50, 75, and 100 micro g/ml. Cells were harvested on days 1, 3, 5, 7, and 10 and viability was performed utilizing an MTS assay. PDLF proliferation rates were assessed by a CyQUANT GR dye assay. SEM analysis was used to examine the qualitative effects of cellular attachment to diseased root surfaces following EMP compared to nontreated controls. RESULTS: The results indicated that viability was negatively affected for higher doses over time while lower doses displayed viability effects similar to control. Proliferation, however, appeared to be ameliorated following exposure to EMP. The SEM analysis suggests that cellular attachment to diseased dentin was enhanced following EMP application. CONCLUSION: These in vitro studies support the concept that EMP may act as a suitable matrix for PDLF.

A bioengineered implant for a predetermined bone cellular response to loading forces. A literature review and case report.

The presence of fibrous tissue has long been known to decrease the long-term survival of a root-form implant. Excessive loads on an osseointegrated implant may result in mobility of the supporting device, and excessive loads may also fracture an implant component or body. Although several conditions may cause crestal bone loss, one of these may be prosthetic overload. Excessive loads on the bone cause strain conditions to increase. These microstrains on the bone may affect the bone remodeling rate in a direct relationship. When strain conditions to the interfacial bone are in the mild overload zone, an increased bone remodeling response occurs, which results in a reactive woven bone formation that is less mineralized and weaker. Greater stresses may cause the interfacial strain to reach the pathologic overload zone and may cause microfracture of the bone, fibrous tissue formation, and/or bone resorption. Recent reports suggest that the bone remodeling rate next to an implant may be used to evaluate biomechanical conditions and their influence on the implant-to-bone interface. These include a number of factors, such as loading conditions, implant body surface conditions, and implant design. For a given load condition, the implant design is one of the primary factors that determine the resultant strain at the interface. A predetermined goal was established to bioengineer a dental implant to load the bone at the interface in a predetermined stress strain relationship, in order to maintain lamellar bone at the interface. A case report is presented of 2 bioengineered implants loaded for 1 year, which demonstrates that the bone was primarily lamellar in structure, the bone turnover rate was less than 5 microns/day, and was the same as the bone away from the interface. These findings corroborate those observed in a prior animal study reported with the same implant design. Although the number of implants evaluated in those 2 reports is few, they support a predetermined histological outcome.

The effects of rhBMP-2 on human osteosarcoma cells and human gingival fibroblasts in vitro.

Certain cells of the periodontium are necessary for the regeneration of tissues that are destroyed as a result of periodontal disease. There has been debate regarding which cells are the primary participants in periodontal regeneration. It is a well-known fact that osteoblasts are essential in new bone formation, but controversy surrounds the role that gingival fibroblasts may play in the regeneration of the hard tissues of the periodontium. If gingival fibroblasts could contribute to the regeneration of these tissues, they might provide an additional source of progenitor cells. The bone morphogenetic proteins are potent stimulators of cell differentiation and have been shown to induce new bone formation in many experimental models. This project investigated the ability of recombinant human bone morphogenetic protein-2 (rhBMP-2) to (1) enhance the production of markers of osteoblastlike cells (osteocalcin and mineralization in culture) in human osteosarcoma cells (MG63) and to (2) induce the expression of an osteoblast phenotype in cultured human gingival fibroblasts (HGFs). MG63 cells and pooled HGFs were exposed to varying concentrations of rhBMP-2 for 24, 48, and 72 hours after 9 days in culture, and osteocalcin levels were measured by enzyme immunosorbent assay in the cell supernatants. In addition, the cells were exposed to rhBMP-2 for 72 hours after 18 days in culture, and mineralization was determined by the Von Kossa stain. The rhBMP-2 had an inhibitory effect on both osteocalcin production and mineralization (p < 0.05) in MG63 cells compared with untreated controls. In addition, increasing doses of rhBMP-2 inhibited both osteocalcin and mineralization in HGF cells. These results suggest that HGFs can express an osteoblastic phenotype when exposed to rhBMP-2; however, rhBMP-2 has inhibitory effects at higher rhBMP-2 doses in both cell types and may, in fact, be inhibitory to MG63 cells.

Ultrastructural characterization of the rabbit mandibular condyle following experimental induction of anterior disk displacement.

Previous studies in our laboratory have shown that surgical induction of anterior disk displacement (ADD) in the rabbit craniomandibular joint (CMJ) leads to cellular and extracellular alterations consistent with osteoarthritis. Similar findings were also reported in human ADD as well as osteoarthritis of other joints. The purpose of this study was to further characterize these histopathological findings at the ultrastructural level. The right joint of 15 rabbits was exposed surgically and all discal attachments were severed except for the posterior attachment. The disk was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control. Ten additional joints were used as nonoperated controls. Mandibular condyles were excised 2 weeks following surgery and processed for transmission electron microscopy. Experimental condyles showed neovascularization, fibrillation and vacuolation of the extracellular matrix and an increase in the number of apoptotic cells compared to controls. In addition, chondrocytes in osteoarthritic cartilage showed an increase in the amounts of rough endoplasmic reticulum and Golgi complex suggesting an increase in protein synthesis. The presence of thick collagen fibers in osteoarthritic cartilage supports our previous immunohistochemical results of the presence of type I collagen instead of normally existing type II collagen. It was concluded that surgical induction of ADD in the rabbit CMJ leads to ultrastructural changes in the mandibular condylar cartilage consistent with degenerative alterations known to occur in osteoarthritis.

Distribution of plasma-membrane Ca2+ pump in mandibular condyles from growing and adult rabbits.

Chondrocytes may control the mineralization of the extracellular matrix of condylar cartilage by several mechanisms including the release of microvesicles involved in the initial nucleation, the creation or modification of the local matrix to help propagate or restrict mineralization, and the regulation of the ionic environment at the calcifying foci within the matrix. The plasma membrane Ca2+-Mg2+ ATPase (Ca2+ pump) is known to play a part in the vectorial efflux of calcium in a variety of cells including chondrocytes. The purpose here was to study the distribution of Ca2+-pump protein in mandibular condyles from growing and adult rabbits, and compare the expression of that protein in progressively differentiating chondrocytes whose final stage is associated with a mineralized extracellular matrix. Ca2+-pump antigen was identified immunohistochemically in six growing and six adult rabbit mandibular condyles with a Ca2+ pump-specific monoclonal antibody. The presence of Ca2+-pump antigen was established in hypertrophic chondrocytes, and in osteoblasts and osteoclasts of subchondral bone. Slot-blot analysis of nitrocellulose-immobilized chondrocyte homogenates showed that the amount of Ca2+ pump in growing cartilage was more than twice that in adult cartilage (p < 0.05). The demonstration of Ca2+-pump antigen in the hypertrophic chondrocytes of growing rabbit condyles is consistent with a role for the plasma-membrane Ca2+ pump in the calcification of mandibular condylar cartilage.

Human periodontal ligament fibroblast response to PDGF-BB and IGF-1 application on tetracycline HCI conditioned root surfaces.

The purpose of this study was to investigate the effect of 2 growth factors, platelet-derived growth factor-BB (PDGF-BB) and insulin-like growth factor-1 (IGF-1), alone or in combination, on the adherence of human periodontal ligament fibroblast (PDL) to tetracycline HCl (TTC) conditioned and nonconditioned periodontally involved root surfaces. There were 80 root dentine chips from 80 patients, ranging from 35 to 70 years of age, each with one periodontally involved tooth requiring extraction. A root dentine chip was obtained from the subgingival surface opposite to the periodontal pocket of each extracted tooth. The dentine chips were randomly distributed into one of 8 groups. In group 1, PDL fibroblasts were cultured and allowed to attach on the dentine surface. In group 2, PDL fibroblasts were cultured on a PDGF-BB pre-treated dentine surface and in group 3, they were cultured on a IGF-1 pre-treated dentine surface. In group 4, PDL fibroblasts were cultured on a dentine surface pretreated with a combination of PDGF-BB and IGF-1. In group 5, PDL fibroblasts were cultured and allowed to attach on the TTC conditioned dentine surfaces. In groups 6 and 7, surface of dentine chips were conditioned with TTC and then were treated with PDGF-BB or IGF-1 respectively, followed by placement of PDL fibroblast and cultured. In group 8, dentine surfaces were conditioned with TTC and then pre-treated with a combination of PDGF-BB and IGF-1 before the fibroblasts were cultured. After 24 h of incubation, the media was removed and samples were fixed and processed for SEM at magnifications of x34, x750, x2000. Photographing and evaluation of samples was performed at x750 in which fibroblast adherence was measured by counting cells within a standard test area. The results of the non-TTC conditioned root surfaces demonstrated a significant increase in fibroblasts adherence in the PDGF-BB and combination PDGF-BB/IGF-I treatment groups (groups 2, 4) when compared to the control (group 1) as well as the TTC control (group 5). The combination of PDGF-BB/IGF-1 (group 4) did not significantly improve the adhesion of cells compared to PDGF-BB alone (group 2), but did significantly improve adhesion when compared to IGF-1 alone (group 3). There were no significant differences in cell morphology between the growth factor groups (groups 2, 3, 4) and control (group 1). In general, the cells demonstrated a flat, stellate-shaped morphology. The results of the TTC conditioned root surfaces, showed a statistically significant increase of cellular adherence in the PDGF-BB group (group 6) when compared to the TTC control (group 5), similar to the non-TTC group (group 2). However, the morphology of the cells in groups 5, 6, 7, and 8 demonstrated generally a rounded or oval shape with only an occasional cell exhibiting a flat form. In the experimental system of this study, the inclusion of PDGF-BB on the surface of dentine chips increased the number of adhering PDL cells, and the addition of TTC conditioning had little effect except to change the morphology of adhering cells.

Implant site assessment using panoramic cross-sectional tomographic imaging.

OBJECTIVES: The purpose of this study was to evaluate the ability of two different panoramic imaging systems to produce cross-sectional images with accurate vertical dimensions of the posterior mandible. STUDY DESIGN: Three partially edentulous human cadaver mandibles were used for this study. On each mandible, three potential implant sites were arbitrarily identified in an area between the mental foramen and the ascending ramus. Each site was imaged using two different panoramic machines. Using each image, the mandible's outline, cortical thickness, and position of the mandibular canal were traced on clear acetate film. The mandibles were then sectioned at each site to serve as a gold standard. The cadaver sections and tracings (corrected for magnification) were measured, recording the overall mandibular height, distance from the crest of the ridge to the superior aspect of the mandibular canal, and the thickness of the cortical bone at the most inferior aspect of the mandible. RESULTS: There were no significant differences between either of the system's image measures and the gold standard when considering the distance between the crest and the mandibular canal. Differences were noted between the systems measures and the gold standard in the assessment of the cortical bone thickness and the overall mandibular height. CONCLUSIONS: Both imaging systems can be useful for vertical measurements of a potential implant site in the posterior mandible.

Regional differences of dura osteoinduction: squamous dura induces osteogenesis, sutural dura induces chondrogenesis and osteogenesis.

Dura plays an important role in calvarial morphogenesis. However, precisely what that role is remains unclear. We present here in vivo evidence that dura without other central nervous system components induces both chondrogenesis and osteogenesis. The mechanism is, at least in part, by proximate tissue interaction. The objectives of this experiment were to answer the following: (1) Can dura actually induce osteogenesis without the influence of the underlying brain? (2) What are the requirements of this dura-induced heterotopic osteogenesis? (3) What are the differences between dura underlying sutures and dura underlying the squamous portions of the cranial bones? Dura underlying the metopic, sagittal, and lambdoidal sutures and dura underlying the flat portions of frontal and parietal bones were obtained from neonatal Lewis rats and transplanted into the posterior thoraces of adult Lewis recipients. In group I, dura underlying the metopic, sagittal, and lambdoidal sutures (n = 20) and dura underlying the flat portions of frontal and parietal bones (n = 20) were transplanted individually into separate epitheliomesenchymal pockets. Group II animals had dura underlying the metopic, sagittal, and lambdoidal sutures (n = 10) and dura underlying the flat portions of frontal and parietal bones (n = 10) transplanted individually into surgically created mesenchymal pockets by placing the dura grafts between panniculus carnosus and latissimus dorsi muscles. The animals were sacrificed at 2-week intervals. Light microscopy, special histochemical analysis, immunohistochemistry, and electron microscopy were performed. Bone formation was seen in 15 of the 18 animals (83 percent) in group I. No bone or cartilage formation was seen in group II. Chondrogenesis was seen in 4 animals receiving dura underlying the metopic, sagittal, and lambdoidal sutures in group I. Cellular hyperproliferation was seen at 2 weeks when dura was transplanted close to the hair follicles. These cells had a high nucleus-to-cytoplasm ratio and were positive for transforming growth factor beta. This hyperproliferation was followed by production and accumulation of Alcian blue-positive extracellular matrix that resisted digestion by hyaluronidase. Cellularly active cartilage was seen at 6 weeks. There was no chondrogenesis in animals receiving dura underlying the flat portions of frontal and parietal bones in group I. Electron microscopy demonstrated the presence of proteoglycan-like ground substance and type II collagen in the inner layer of sutural dura and the predominance of dense type I collagen in the squamous dura and the external layer of the sutural dura. The important findings of this experiment are that (1) heterotopically transplanted neonatal dura can induce osteogenesis, (2) this heterotopic osteoinduction by dura requires epitheliomesenchymal interaction, and (3) separating dura into sutural dura and squamous dura, chondrogenesis occasionally occurred in addition to osteogenesis with the former, while only membranous ossification occurred with the latter, indicating intrinsic differences within the dura mater. This dural heterogeneity is supported by direct ultrastructural data.

Porous polysulfone coated with platelet-derived growth factor-BB stimulates proliferation of human periodontal ligament fibroblasts.

The purpose of this study was to investigate if the treatment of porous polysulfone (PPSF) with various concentrations of platelet-derived growth factor-BB (PDGF-BB) would stimulate the proliferation of the adherent human periodontal ligament fibroblasts (HPDLF) in culture. Sterilized PPSF cylinders were immersed in an Eagle's minimum essential medium supplemented with 0.5% fetal bovine serum and 1% penicillin/streptomycin containing either 0, 10, 20, or 50 ng/ml of PDGF-BB for 24 hours. After 24 hours, the PPSF cylinders were removed and allowed to dry then placed in culture plates for each time point. Pooled HPDLF (8 x 10(4)) and 3H-thymidine in medium were pipetted into each well to cover the treated and control PPSF cylinders and plates were then incubated. At 1, 4, and 10 days the PPSF cylinders were removed and macromolecular precipitation was performed. Incorporation of 3H-thymidine was measured and a 2-way ANOVA with repeated measures was performed. In addition, determination of binding and release was performed using I125-PDGF-BB treated PPSF at 0, 2, 12, and 24 hours, and at 4 and 10 days. Results showed that the effects on HPDLF were significant for dose (P = 0.0012; F = 5.74) and time (P = 0.0001; F = 40.83). At 4 days, the percent increases above the control for the doses 10, 20, and 50 ng/ml were 192%, 310%, and 162% respectively. In conclusion, our findings suggest that treating PPSF with PDGF-BB results in a significant increase in the proliferation of HPDLF cells adherent to PPSF.

Histochemical and immunohistochemical studies of the effects of experimental anterior disc displacement on sulfated glycosaminoglycans, hyaluronic acid, and link protein of the rabbit craniomandibular joint.

PURPOSE: The purpose of this study was to determine the effects of surgically induced anterior disc displacement (ADD) on sulfated glycosaminoglycans (GAGs) such as keratan sulfate (KS), chondroitin-4-sulfate (C4S), and chondroitin-6-sulfate (C6S), hyaluronic acid (HA), and link protein (LP) of the rabbit craniomandibular joint (CMJ) using histochemical and immunohistochemical techniques. MATERIALS AND METHODS: The right joint of 20 rabbits was exposed surgically, and all discal attachments were severed except for the posterior attachment. The disc was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control. Ten additional joints were used as nonoperated controls. Deeply anesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) after surgery. Discs, bilaminar zones, condyles, and articular eminences were excised. Condyles and articular eminences were decalcified in ethylenediaminetetraacetic acid (EDTA). All tissues were sectioned at 10 microns in a cryostat. Sections were incubated with alcian blue and monoclonal antibodies directed against KS, C4S, C6S, HA, or LP. After incubation in the appropriate fluorescein isothiocyanate (FITC)-labeled secondary antibodies, tissue sections were studied under the fluorescence microscope. RESULTS: The results showed a reduction in alcian blue staining and KS, C4S, C6S, HA, and LP immunostaining in the disc and articular surfaces at 2 weeks after induction of ADD. This reduction was followed by an increase in their immunostaining at 6 weeks. Also, there was a progressive increase in alcian blue staining, and KS, C4S, C6S, and HA immunostaining in the bilaminar zone at 2 and 6 weeks. CONCLUSION: It was concluded that surgical induction of ADD in the rabbit CMJ leads to alterations in KS, C4S, C6S, HA, and LP content, consistent with similar changes accompanying osteoarthritis of other synovial joints.

An immunohistochemical study of collagen types III, VI and IX in rabbit craniomandibular joint tissues following surgical induction of anterior disk displacement.

The purpose of this study was to determine the effect of surgical induction of anterior disk displacement (ADD) on type-III, VI and IX collagens of the rabbit craniomandibular joint (CMJ) tissues using an immunohistochemical technique. The right joint was exposed surgically, all discal attachments were severed except for the posterior discal attachment (bilaminar zone). The disk was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control. Ten additional joints were used as non-operated controls. Deeply anesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) following surgery. The articular disk, bilaminar zone, mandibular condyle and articular eminence were excised. The last two were decalcified in EDTA. All tissues were then sectioned at 10 microns in a cryostat. Sections were incubated with monoclonal antibodies directed against type-III, VI or IX collagens. Following incubation in the appropriate FITC-labelled secondary antibodies, all sections were studied under the fluorescence microscope. The results showed a reduction in immunostaining for type-VI and IX collagens in the condylar cartilage, disk and articular eminence at 2 weeks, followed by an increase in their immunostaining at 6 weeks and the appearance of a de novo type-III collagen in the condylar cartilage and the articular eminence. It is concluded that surgical induction of ADD in the rabbit CMJ leads to alterations in its type-III, VI and IX collagens.

In situ hybridization and monoclonal antibody analysis of plasma membrane Ca-pump mRNA and protein in submandibular glands of rabbit, rat and man.

The degree of supersaturation of saliva with calcium (Ca) is related to the mineral phase of enamel in erupted teeth, the incidence of caries, and the formation of calculus. The mechanisms for regulating salivary Ca concentration are therefore of relevance to dentistry. Sections of rabbit, rat and human submandibular gland (SMG) were processed for immuno-histochemistry with a specific anti-plasma membrane Ca-pump antibody, 5F10. Western blots confirm that the molecular weight of the proteins identified by our antibody (135 kDa) is consistent with an appropriate molecular weight for PMCA antigen (135-150 kDa). Tissue sections were also processed for in situ hybridization to study the distribution of the PMCA mRNA isoforms. In mammals, the PMCA1 gene is reported to code for a PMCA protein with a role in maintaining the intracellular Ca levels in both epithelial and non-epithelial cells. Other genes including the PMCA2 and PMCA4 genes may code for PMCA proteins specific to Ca transporting tissues. Our studies demonstrate cytoplasmic labeling of PMCA mRNA with hPMCA-1 and hPMCA-4 specific cDNA probes in humans, and rPMCA-1 and rPMCA-2 specific oligonucleotide probes in rats. Labeling of PMCA protein and all mRNA isoforms was found in the cytoplasm of the interlobular and intralobular ducts (except for intercalated ducts). The demonstrated presence of PMCA in SMGs of rabbit, rat, and man, may suggest a role for PMCA in the regulation of intracellular Ca and in a mechanism for regulating and maintaining the high concentration of Ca in salvia.

An immunohistochemical study of the effects of surgical induction of anterior disc displacement in the rabbit craniomandibular joint on type I and type II collagens.

The right craniomandibular joint (CMJ) was exposed surgically and all the discal attachments severed except for the posterior one. The disc was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control; 10 other joints were used as non-operated controls. Deeply anaesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) after the induction of the anterior disc displacement (ADD). The articular disc, bilaminar zone, mandibular condyle and articular eminence were excised. The condyles and the articular eminences were demineralized in EDTA. All tissues were then sectioned at 10 microns in a cryostat. Sections were incubated with polyclonal antibodies directed against type I or type II collagens. Following incubation in the appropriate fluorescein isothiocyanate-labelled secondary antibodies, these specimens were studied under the fluorescence microscope. At 2 weeks there was a reduction in type II collagen immunostaining; some areas of the experimental condylar cartilage showed a switch from type II to type I collagen. However, at 6 weeks there was an increase in type II collagen immunostaining and a decrease in type I compared to the 2-week group. It is concluded that surgical induction of ADD in the rabbit CMJ leads to alteration in the condylar cartilage collagen phenotype similar to that reported for osteoarthritic cartilage of other synovial joints.

Enlargement of the rabbit mandibular condyle after experimental induction of anterior disc displacement: a histomorphometric study.

PURPOSE: Clinical and autopsy studies have shown that patients with temporomandibular joint dysfunction are more likely to have enlargement and deformity of the condyle and subsequently occlusal disharmony. However, it is not known what causes this enlargement. This study was designed to test the hypothesis that surgical induction of anterior disc displacement (ADD) in the rabbit craniomandibular joint (CMJ) could lead to enlargement and deformity of the condyle. MATERIALS AND METHODS: The right CMJ was exposed surgically, and the discal attachments were severed except for the posterior discal attachment (bilaminar zone). Then, the disc was repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control. CMJ tissues then were removed after fixation at 24 hours (5 rabbits), 1 week (10 rabbits), 2 weeks (10 rabbits), or 6 weeks (10 rabbits), processed, and stained with hematoxylineosin. Histomorphometric assessment was used to evaluate changes in condylar volume, and thickness of the fibrous, reserve cell, and condylar cartilage layers. RESULTS: The results showed a progressive enlargement of the condylar volume in all experimental joints compared with controls (P < .01). The enlargement was attributable to a significant increase in the cartilage thickness and surface area of the nonarticulating portion of the condyle in the 1-week group (P < .01). In the 2- and 6-week groups, there were significant, progressive increases in cartilage thickness and surface area of the articulating portion of the condyle (P < .01). In all animals, increased cartilage thickness was associated with a decrease in the thickness of the fibrous and the reserve cell layers (P < .01). CONCLUSION: It is concluded that surgical induction of ADD in the rabbit CMJ causes enlargement of the condyle, which is in part caused by hyperplasia of the condylar cartilage.

Alteration in fibronectin of the rabbit craniomandibular joint tissues following surgical induction of anterior disk displacement: immunohistochemical study.

The purpose of this study was to determine the effect of surgical induction of anterior disk displacement (ADD) on fibronectin amount and distribution in the rabbit craniomandibular joint (CMJ) tissues using an immunohistochemical technique. The right CMJ was exposed surgically, and all discal attachments were severed except for the posterior attachment. The disk was then repositioned anteriorly and sutured to the zygomatic arch. The left CMJ served as a sham-operated control. Ten additional joints were used as nonoperated controls. Deeply anesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) following surgery. Disks, bilaminar zones, condyles and articular eminences were excised. Condyles and articular eminences were decalcified in EDTA. All tissues were sectioned at 10 microns in a cryostat. Sections were incubated with monoclonal antibodies directed against fibronectin. Following incubation in the appropriate FITC-labeled secondary antibodies, tissue sections were studied under the fluorescence microscope. The results showed that at 2 weeks following induction of ADD, there was a reduction in fibronectin immunostaining in the condyle, articular eminence and articular disk. Depletion of fibronectin in these tissues was followed by restoration of its immunostaining at 6 weeks. Also, there was a progressive increase in fibronectin immunostaining in the bilaminar zone at 2 and 6 weeks. It was concluded that surgical induction of ADD in rabbit CMJ leads to alteration in the amount and distribution of fibronectin.

Changes in the innervation of rabbit craniomandibular joint tissues associated with experimental induction of anterior disk displacement: histochemical and immunohistochemical studies.

We have previously reported that surgical induction of anterior disk displacement (ADD) in a rabbit craniomandibular joint (CMJ) leads to histopathological changes consistent with osteoarthritis. This paper reports the changes that were noted in the innervation of rabbit CMJ tissues following surgical induction of ADD. The right joint of 30 rabbits was exposed surgically and the discal attachments were severed except for the posterior discal attachment (bilaminar zone). The disk was then displaced anteriorly and sutured to the zygomatic arch. The left joints was used as sham-operated control. CMJ tissues were then removed after fixation and processed for histochemical localization of nerve fibers using the silver impregnation technique and immunohistochemical localization of neurofilaments using monoclonal antibodies. The results showed an absence of nerve fibers in the control and experimental disks and their presence in the control and experimental bilaminar zones. The bilaminar zone adhesions to the experimental condyles were also innervated. The spread of nerve fibers into the pathological fibrous adhesions surrounding the arthritic condyles in this animal model of ADD may indicate a possible mechanism of nociception in this disease.

Histopathological changes in rabbit craniomandibular joint associated with experimentally induced anterior disk displacement (ADD).

Several studies have shown that anterior disk displacement (ADD) of human temporomandibular joint (TMJ) can lead to cellular and extracellular alterations in the disk proper, bilaminar zone (BZ), condyle, articular eminence and synovial membrane. Due to lack of an animal model for this disease, it is not known whether the mechanical displacement of the disk could lead to the observed histopathological changes. The purpose of this experiment was to investigate the histopathological changes that occur in the rabbit craniomandibular joint (CMJ) following surgical induction of ADD. The right CMJ was exposed surgically and the discal attachments were severed except for the BZ attachments. Then the disk was displaced anteriorly and sutured to the zygomatic arch. The left joint served as surgical control. The CMJs were removed after 24 h, 1 week, 2 weeks or 6 weeks and stained with H&E or modified Masson stain. The results showed neovascularization, cell clustering and fibrillation of the displaced disk. The BZ showed marked fibrosis. The condyle showed subchondral hemorrhage and fibrosis followed by osteoarthritic changes in the articular cartilage. The articular eminence showed chondrocytic clustering and an increase in the amount of chondroid bone. Synovial membrane exhibited marked hyperplasia. We concluded that surgical induction of ADD in the rabbit CMJ leads to cellular and extracellular alterations in the disk proper, BZ, condyle, articular eminence and synovial membrane similar to those described previously in human ADD. It appears that the mechanical trauma resulting from ADD could lead to a cascade of reparative and degenerative changes of the affected joints similar to those described for osteoarthritis.

Structural and functional changes of cementum surface following exposure to a modified Nd:YAG laser.

A modified Nd:YAG laser was evaluated for its effect on root cementum topography and fibroblastic attachment. Fifteen extracted human teeth were curetted, sectioned, and divided into 60 areas representing 4 groups. Group I were non-lased controls, while groups II, III, and IV were lased with the same power (4 watts, 1 second), but at 3 different laser-target distances (1, 3, and 5 mm), thus delivering 3 different energy levels. Following lasing, 20 areas (5 per group) were examined under SEM for detection of any structural changes. Human gingival fibroblasts were cultured on both experimental and control samples of the remaining 40 areas. Photomicrographs at x 500 were obtained and the number of attached fibroblasts were counted. Results showed that lased cemental surfaces exhibited changes in surface topography which ranged from what appeared to be an apparent fusion of the surface of the covering smear layer (lowest energy level), to cracking and fissuring of the lased surface (highest energy level). When fibroblasts were cultured on the specimens, the results demonstrated the presence of a monolayer of cells on the control surfaces and on the surfaces lased with the lowest energy level (5 mm distance). Specimens lased at the mid-energy level (3 mm) showed decreased numbers of attached cells, but not significantly different from the controls. On the other hand lasing the cementum surface at the highest energy level (1 mm distance) caused a significant decrease in the number of the attached cells as compared to the controls.(ABSTRACT TRUNCATED AT 250 WORDS)