Facial size reduction and facial retraction are key features that distinguish modern humans from archaic Homo. In order to more fully understand the emergence of modern human craniofacial form, it is necessary to understand the underlying evolutionary basis for these defining characteristics. Although it is well established that the cranial base exerts considerable influence on the evolutionary and ontogenetic development of facial form, less emphasis has been placed on developmental factors intrinsic to the facial skeleton proper. The present analysis was designed to assess anteroposterior facial reduction in a pig model and to examine the potential role that this dynamic has played in the evolution of modern human facial form. Ten female sibship cohorts, each consisting of three individuals, were allocated to one of three groups. In the experimental group (n = 10), microplates were affixed bilaterally across the zygomaticomaxillary and frontonasomaxillary sutures at 2 months of age. The sham group (n = 10) received only screw implantation and the controls (n = 10) underwent no surgery. Following 4 months of post-surgical growth, we assessed variation in facial form using linear measurements and principal components analysis of Procrustes scaled landmarks. There were no differences between the control and sham groups; however, the experimental group exhibited a highly significant reduction in facial projection and overall size. These changes were associated with significant differences in the infraorbital region of the experimental group including the presence of an infraorbital depression and an inferiorly and coronally oriented infraorbital plane in contrast to a flat, superiorly and sagittally infraorbital plane in the control and sham groups. These altered configurations are markedly similar to important additional facial features that differentiate modern humans from archaic Homo, and suggest that facial length restriction via rigid plate fixation is a potentially useful model to assess the developmental factors that underlie changing patterns in craniofacial form associated with the emergence of modern humans.

Objectives: The objectives of this work were to: (1) establish methodology for pretreating osteoblast-like cells in vitro with dexamethasone to cause glucocorticoid-induced osteoporosis, (2) perform quantitative and qualitative assessments of cellular attachment of osteoporosis-like osteoblasts when grown on implant surfaces of differing roughness, (3) and explore the hypothesis that dexamethasone-treated osteoblasts have altered cell attachment properties by focal adhesion disassembly and decreased tyrosine phosphorylation of the focal adhesion tyrosine kinase. Methods: Osteoblasts were cultured with dexamethasone (10−7 and 10−6 M) for up to 4 days of incubation to induce osteoporosis-like conditions. Cellular attachment assays demonstrated the effect of dexamethasone treatments on cellular attachment properties of osteoblasts. Qualitative data were obtained utilizing immunofluorescent microscopy and Western blotting. Focal adhesion kinase (FAK) immunoprecipitation and tyrosine-phosphorylation Western blots were obtained from dexamethasone-treated human embryonic palatal mesenchymal- 1486 osteoblast cultures supplemented with ascorbate and β-glycerol phosphate medium. Results: Cellular attachment was significantly greater (P < 0.05) with non-dexamethasone-treated osteoblasts (92%) as compared todexamethasone-treated osteoblasts after 1 (72%), 2 (63%), and 4 days (53%) of exposure. Dexamethasone-treated osteoblasts were viable and capable of proliferation, suggesting that the reduction of cellular attachment may be related to these cell adhesion processes. Immunofluorescent microscopy of both dexamethasone-treated osteoblasts and non-dexamethasone-treated osteoblasts failed to show any relative difference in the disassembly of focal adhesions and actin filaments. Extended dexamethasone treatment periods (up to 3 weeks) showed changes in the levels of FAK and FAK-phosphotyrosine in human embryonic palatal mesenchymal-1486 osteoblasts. Conclusions: The protocol used in this study demonstrated a glucocorticoid-induced osteoporosis-like suppression of osteoblasts. FAK disassembly was not a significant factor in short period; however, FAK protein levels and phosphotyrosine signaling on FAK were affected after 1-week exposure to dexamethasone. Phosphorylated FAK was not associated with the rise in the level of FAK, further indicating the possibility of FAK involvement in reduced cell attachment.

INTRODUCTION:Conventional orthodontic treatment of vertical or anterior maxillary excess by growth modification can be problematic in children because of the high levels of patient compliance required. The purpose of this preliminary study was to investigate the use of rigid skeletal fixation to modify facial bone growth without compliance.METHODS:Three 30-day old female pigs from the same litter were included in phase I. Pediatric miniplates were rigidly fixated with monocortical screws in the experimental pig to bridge the zygomaticomaxillary suture and both the frontonasal and nasomaxillary sutures, bilaterally. In the sham experimental pig, the same surgical protocol was followed, but miniplates were omitted (ie, screw placement only). In the control pig, surgery was not performed. All 3 pigs were housed and fed a normal diet under identical conditions postoperatively for 63 days; then they were killed, their right hemi-skulls were prepared for and underwent 3-dimensional coordinate landmark analysis, and en-bloc specimens from the zygomaticomaxillary, frontonasal, and nasomaxillary sutures of the left hemi-skulls underwent histologic analysis. Two 50-day-old female pigs from the same litter were used in phase II. The same experimental protocol was followed as before for the experimental pig and the sham experimental pig. Both pigs were fed a normal diet for 105 days; then they were killed, and their skulls were prepared for and underwent 3-dimensional coordinate landmark analysis.RESULTS:Rigid plating restricted zygomaticolacrimal suture length, maxillary bone length, nasal bone length, midfacial breadth, and frontal bone length by an average of -14% to -15% (range, -4% to -36%). No growth differences were noted between the animals in maxillary height, mid-premaxillary length, bregma-lambda length, palatal lengths, or mandibular length. Also, plating the sutures produced a clear depressed concavity in the infraorbital region, altered the alignment of the infraorbital plane lateral to the concavity, inhibited the anterior migration of the maxillary tuberosity, and resulted in raised folding on the bony surface adjacent to the zygomaticomaxillary suture.CONCLUSIONS:Rigidly fixating frontonasomaxillary and zygomaticomaxillary sutures inhibits growth of facial bones and might provide a means of restricting excess growth without having to rely on patient compliance. In addition, these altered growth patterns in the plated pig model produced similar and potentially homologous infraorbital features shared by living humans in comparison with ancestral fossil forms.

PURPOSE:Usage of dental implants has become common for the treatment of edentulous patients, but concerns exist over the use of implants in patients where orofacial bone loss occurs. In the present study, the osseointegration of implants in rabbits under osteoporosis-like (OP-like) conditions simulating several clinically relevant conditions is reported.MATERIALS AND METHODS:Forty rabbits were divided into 4 groups of 10. Three groups of animals received daily intramuscular injections of glucocorticoids (7.5 mg/kg) for 8 weeks to induce OP-like conditions either before, simultaneous to, or after implant placement.RESULTS:The injections of glucocorticoids resulted in cortical thinning, irregular trabecular patterns, and impaired extracellular (ECM) matrix formation and mineralization. Although interfacial strength (8.5 +/- 1.3 MPa for the control group; 9.3 +/- 4.0 to 10.1 +/- 4.0 MPa for the experimental groups) was apparently not affected in this limited sample cohort (n = 3 per group), statistically significant decreases (P < .05) in implant-bone contact were observed in animals with OP-like conditions (49% +/- 10% for the control group; 24% +/- 16% to 42% +/- 16% for the experimental groups).DISCUSSION:Histologic features characteristic of OP-like conditions were observed in each experimental group. ECM expression also appeared to be altered and compromised in all animals with OP-like conditions, which may affect long-term biomechanical stability of the implants.CONCLUSION:OP-like conditions affect the osseointegration characteristics of implants, but long-term biomechanical stability under forces of mastication is unknown as yet.

The competitive growth patterns of osteoblasts and fibroblasts can determine if healthy bone or pathologic scar tissue is formed at a wound site. Cell interactions with various alloplastic biomaterials used for tissue-engineering applications is complex. Defined synthetic mediums are valuable for studying ionic and cell receptor–specific interactions. The objectives of this study were to determine if fibroblasts and osteoblasts differentially attached to HEMA and PEG hydrogels copolymerized with positive, negative, or neutral charge densities, or when grafted with specific integrin receptor RGD adhesion ligand. Cytoskeletal phenotypes were assessed with immunofluorescent microscopy and cell attachment assays. Osteoblast cell attachment to both HEMA and PEG hydrogels was significantly higher (P<0.01) as compared to fibroblast cells. Positively charged HEMA and PEG hydrogels supported the greatest cell attachment, followed by RGD grafted, negative, and neutral charge densities, respectively. Each of these conditions elicited nearly a two-fold increase in osteoblast cell attachment, as compared to fibroblasts. Cell attachment to serum-coated coverslips was used as the control. Immunofluorescent analysis showed that both cell types attached and spread better on the positively charged hydrogels. However, fibroblasts demonstrated less spreading as compared to osteoblasts. In conclusion, differences in hydrophilic properties differentially affect osteoblast and fibroblast cell attachment and spreading.

The objective of this study was to explore the hypothesis that osteoporotic-like (OP) conditions have a negative effect on osseointegration (OI) of dental implants. Using an ovariectomized (OVX) rat model, the extent of OI using histologic and histomorphometric analysis (HMA) under a variety of OVX conditions was assessed. Five experimental groups (n = 7 rats per group) were used: 1) OP control, 2) OI control, () OI followed by OVX treatment to induce OP (OI-->OP), 4) OP induction followed by OI (OP-->OI), and 5) OP induction simultaneously with OI (OI = OP). Using undecalcified plastic-embedded cross-sections of the implant site, HMA was performed to determine the percent of bone contact (BC) at the implant-tissue interface and percent of bone area (BA) immediately (1.5-mm diameter) surrounding the implant site. The presence of Bone Sialoprotein (BSP), an important extracellular matrix component of bone, was evaluated using immunohistochemical staining procedures. The implant control resulted in the highest level of OI (BC = 79%; BA = 87%), whereas all groups in which OVX was performed resulted in a significant reduction in BA (70-75%). High levels of BC were observed in established OP conditions (OP-->OI; BC = 79%); however, following OI, induction of OP conditions (OI-->OP) led to a significant reduction in BC (50%). In each of the OP treatment groups, a diminution of cortical bone, increased trabecularization of the host bone site, and loss of staining of BSP was observed. The results of this work indicate that although OI is possible under a variety of OP-like conditions simulating implant placement, the long-term biomechanical stability of implants under these conditions could be compromised and remains unclear. Further research to understand implant use in the complex bone environment under OP-like conditions is encouraged.

Osteogenesis involves the recruitment of multipotent mesenchymal cells and the progressive differentiation of these cells into osteoblasts. The transcription factor Runx2 regulates osteoblast differentiation and expression of genes necessary for the development of a mineralized phenotype. The purpose of this study was to determine if preosteoblast cell differentiation associated with Runx2 and osteocalcin gene expression was influenced by implant surface microtopography. Human embryonic palatal mesenchymal cells (HEPM cells) were cultured on grooved or roughened cpTi implant discs. Cell phenotypes were evaluated with epifluorescent microscopy. Real-time PCR was used for quantitative analysis of Runx2 and osteocalcin gene expression. HEPM cells mineralized when grown on rough and grooved implant surfaces relative to tissue culture plastic. Real-time PCR showed significant (p < 0.05) increases in Runx2 and osteocalcin gene expression in cells cultured on rough and grooved implant microtopographies. These results suggest that preosteoblast cell differentiation is affected by implant surface microtopographies during osseointegration of dental implants. (C) 2004 Wiley Periodicals, Inc.

The transcription factor Cbfa1 regulates osteoblast differentiation and expression of genes necessary for the development of a mineralized phenotype. The purpose of this study was to determine if Cbfa1 and BSPII gene expression are influenced by implant surface microtopography. Osteoblasts were cultured on 600-grit (grooved) or sandblasted (roughened) cpTi implant discs. Mineralization was evaluated by Alizarin-Red-S staining. Real Time PCR was used for quantitative analysis of Cbfa1 and BSPII gene expression. Enhanced mineralization was seen in osteoblasts grown on roughened implant surfaces relative to tissue culture plastic. Real Time PCR showed significant (P < 0.05) increases in Cbfa1 gene expression in cells grown on roughened, as compared with grooved, implant surfaces. BSPII gene expression was also increased on rough surfaces in the UMR cells, but was reduced in the rat calvarial osteoblast cultures. These results suggest that osteoblast gene expression and mineralization are affected by roughened implant surface microtopographies during osseointegration of dental implants.

Purpose The overall aim of this project was to study osteoblast cell attachment on titanium surfaces with varying surface roughness. Materials and Methods Commercially pure titanium surfaces were prepared by polishing through 600-grit sandpaper, sandblasting, or sandblasting followed by acid etching to produce surfaces of varying roughness, as determined by scanning electron microscopy and atomic force microscopy. In vitro cell attachment of MC3T3-E1 osteoblasts was performed on the prepared surfaces in both serum-containing and serum-free media conditions. Results Cell attachment was directly related to the average surface roughness, with the highest levels of cell attachment observed on sandblasted and sandblasted-acid-etched surfaces. Similar patterns of cell attachment were observed when serum-free conditions were employed. Conclusions Combined surface analytical and cell/molecular biological techniques are powerful tools to broaden our understanding of biological events occurring at the implant-tissue interface. Data acquired from these in vitro techniques provide a translational application to in vivo clinical models leading to the next generation of dental implants.

PURPOSE:The purpose of this study was to evaluate the short-term wound healing and repair at the tissue/cement interface with different hydroxyapatite cement formulations.MATERIALS AND METHODS:Three groups of Sprague-Dawley rats were implanted with HAC for 3, 7, or 14 days. The medial femur-tibia sites on each leg of the animals were used to create four separate 1.5-mm defects, which were filled with HAC (Bone-Source, Howmedica-Leibinger, Inc.) mixed with either water (W) as a control, an accelerant (0.1 M sodium phosphate, SP), or a stabilizer (1% hydroxypropylmethyl cellulose, HPMC) as diluents. At the appropriate postimplantation times, the animals were euthanized and tissue-implant blocks were prepared for qualitative histopathologic evaluations.RESULTS:Osseoconduction around and into the HAC was observed with all three cement formulations and the control (unfilled) site by day 7 and continued through day 14. The histologic staining did not reveal resorption lacunae or other cellular activities characteristic of osteoclast degradation of HAC. These results suggests that other processes, perhaps physical-chemical in nature, contributed to the initial degradation of the HAC following surgical placement. Structural stability of HAC was noted when using HPMC as the diluent. However, when either W or SP were employed, dissociation (washout) of the HAC into the surrounding tissue was noted.CONCLUSION:HAC is prone to in situ physical-chemical breakdown before the completion of the setting reaction. Diluents designed to stabilize or accelerate the HAC mixture appeared to improve the handling properties of the HAC without compromising the biological characteristics of the cement.

Objective: To test the elastic wall concept utilizing adhesive resins of varying stiffness in a low- and high-C-factor cavity design after short- and long-term water storage.Methods: A flat and box-shaped cavity was restored on occlusal dentin with a resin composite using a filled and unfilled adhesive resin from which microtensile specimens with a 0.5 mm(2) cross-sectional area were formed. After storage for 30- and 150-days the microtensile bond strength (mu TBS) was determined in a Zwick materials testing machine and the subsequent debond pathway was examined under scanning electron microscopy. Fisher's exact test was used to determine differences in joint and substrate failure modes and a Weibull regression model with gamma frailties was used to test for differences between failure distributions. Tests for three way and two-way interactions were also completed for storage time, C-factor and adhesive. All tests were at 95% confidence levels.Results: The characteristic strength (TBS degrees) for the Optabond FL adhesive applied on a flat cavity was 47.57 and 20.90 MPa and a box-shaped cavity was 49.26 and 17.49 MPa for short- and long-term storage, respectively, while the corresponding TBS degrees for the unfilled Optibond adhesive on the flat cavity design was 36.93 and 32.68 MPa and in a box-shaped cavity was 32.84 and 15.46 MPa. Combining all groups according to storage time revealed a three-fold increase in the debond pathway including the bottom of the hybrid layer.Significance: Evidence suggests that the durability of the bonded joint is threatened by hydrolysis and the most susceptible region is the bottom half of the hybrid layer and in low C-factor cavity designs a more flexible adhesive resin liner was more durable. (C) 2001 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.

In osteoporosis, the regenerative capacity of bone is compromised, which may involve altered osteoblast (OB) activity. This could be attributed to an inappropriate synthesis and assembly of an extracellular matrix (ECM), altered cell adhesion to the ECM, or be due to inappropriate downstream activation of adhesion-mediated signaling cascades through proteins such as focal adhesion kinase (FAK). The purpose of our study was to compare early adhesion-mediated events using previously described and characterized clinically derived OBs obtained from human patients undergoing major joint arthroplasty for osteoporosis or osteoarthritis. The presence or absence of osteoporosis was established with a radiographic index. Using light microscopy and crystal violet staining, we show that OB cells derived from sites of osteoporosis do not attach and spread as well as non-osteoporotic (OP) OB cells. OP cells initially have a more rounded morphology, and show significantly less (P < 0.001) attachment to serum-coated tissue culture plastic over a 24 h time period. Immunofluorescent labeling after 24 h of attachment showed that OP OB focal adhesions (FAs) and stress fibers were less defined, and that the OP cells were smaller and had a more motile phenotype. When normalized protein lysates were Western blotted for phosphotyrosine (PY) a band corresponding to pp125FAK was identified. FAK tyrosine phosphorylation was evident at 6 h in both the OP and non-OP OBs, but decreased or was absent through 24 h in OP OBs. These results suggest early adhesion-mediated events, such as cell adhesion, attachment, and FAK signaling via PY may be altered in OP OBs.

Objective: To determine the failure mode between dentin-adhesive resin-resin composite bonded joint produced with a chevron-notch short-bar (CNSB) and microtensile test methods.Methods: Forty teeth were randomly selected for microtensile and forty for CNSB specimen fabrication and stored in 0.5% chloramine T at 37 degreesC until respective static load to failure testing at 30 and 180 days. Failure modes were categorized by SEM and tested with Fisher's exact test. Within respective mechanical testing methods the probability of failure curve distributions being significantly different were analyzed by the Wald chi-square statistic.Results: The characteristic fracture toughness at 30- and 180-day storage was 0.82 and 0.87 MPa m(1/2), while the Weibull Modulus (m) for the failure distributions, was 4.60 and 4.56, respectively. No significant difference was demonstrated in the failure distributions between these groups (p = 0.45). The characteristic tensile strength (mu TBS degrees) at 30- and 180-day storage was 52.53 and 14.71 MPa with an m of 3.04 and 1.56, respectively. Failure distributions for mu TBS groups were significantly different (p < 0.001). K-IvM failure modes, regardless of storage time, were within the adhesive joint with 30-day debonds primarily through the top region of the hybrid layer (THL) and after 180-days involving the bottom of the hybrid layer (BHL). The 30-day TBS group demonstrated a propensity to debond in dentin or resin composite substrates but after 180-days storage debonds again involved the BHL.Significance: The weak links in the dentin-adhesive resin-resin composite bonded joint may be the interphase regions between the THL and the adhesive resin and the BHL and dentin. (C) 2001 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.

OBJECTIVE Our goal in this investigation was to examine the mandibular bone density and radiographic textural changes and the relationship between mandibular and spinal bone mineral density in an osteoporotic rabbit model. STUDY DESIGN Three adult female New Zealand white rabbits in each of 4 groups received daily injections of cortisone acetate at a dosage of 0.0 (control), 3.0, 7.5, or 15.0 mg/kg for 4 weeks. The rabbits were then killed, and the mandible and spine of each animal were removed. Digital radiographs (70 kVp, 10 mA, 8 impulses) of the hemimandibles and spines were made. Lateral and anteroposterior bone densities of the lumbar spine (L2) were calculated, and average mandibular interdental bone density, fractal dimension, and gradient values were calculated. RESULTS Correlation analysis revealed that cumulative steroid dose was strongly related to mandibular bone density (r = -0.80, P <.01), moderately related to mandibular fractal dimension (r = -0.61, P <. 05), and moderately related to anteroposterior lumbar spine density (r = -0.64, P <.05). Moderate correlations were found between mandibular interdental bone density and spinal density (r = 0.56, P <.05), but mandibular fractal dimension was not related to spinal density. CONCLUSIONS In osteoporotic female rabbits, mandibular bone mineral density decreases in relation to spinal density and cumulative steroid dose. Mandibular fractal dimension decreases with cumulative steroid dose but is not significantly related to either mandibular density or spinal density.