Comparison of Dehydrated Human Amnion-Chorion and Type 1 Bovine Collagen Membranes in Alveolar Ridge Preservation: A Clinical and Histological Study.

Alveolar ridge preservation maintains ridge dimensions and bone quality for implant placement. The aim of this randomized controlled clinical study is to compare the use of a human amnion-chorion membrane to a collagen membrane in an exposed-barrier ridge preservation technique. Furthermore, this study will determine if intentional membrane exposure compromises ridge dimensions and bone vitality. Forty-three patients requiring extraction and delayed implant placement were randomly assigned into either the experimental or control group. Twenty-one participants received human amnion-chorion membrane (test) during ridge preservation while 22 participants received the collagen membrane (control). In both groups, demineralized freeze-dried bone allografts were used to graft the socket and primary closure was not achieved. The patients underwent implant placement after an average healing period of 19.5 weeks, and 2.7 × 8-mm core bone specimens were obtained for histomorphometric analyses. The clinical ridge dimensions were measured after extraction and at the time of delayed implant placement. No significant difference was observed in the mean vital bone formation between the experimental (51.72 ± 8.46%) and control (49.96 ± 8.31%; P > .05) groups. The bone height and width did not differ, as determined by clinical measurements (P > .05). Using either a human amnion-chorion membrane or type 1 bovine collagen as the open barrier did not change healing, compromise ridge dimensions, or affect bone vitality between the 2 groups.

Influence of mini-screw diameter and loading conditions on static and dynamic assessments of bone-implant contact: An animal study.

OBJECTIVES: The goal was to compare static versus dynamic bone-implant interface histology of mini-screws and to evaluate its relation to diameter and load. SETTING AND SAMPLE POPULATION: Canine animal model. MATERIAL AND METHODS: Custom-machined, titanium alloy (Ti6AI4V) mini-screws (n = 70) of 1.60, 2.00, 3.00 and 3.75 mm diameter were placed into edentulous sites in five skeletally mature beagle dogs. Using a split-mouth design, no load (NL) was applied to one side while a 2N load (L) was applied by calibrated coil springs on the other side. Intravenous bone labels were administered 21 and 7 days prior to sacrifice. Dogs were euthanized 90 days after screw placement. Bone sections were analysed under bright-field and epifluorescent light. The region of interest was defined as the bone within the threads of the screws. The following parameters were quantified: (a) Static-bone volume/tissue volume (BV/TV %) and bone-implant contact (BIC, %); (b) Dynamic-labelled bone/bone volume (LB/BV, %), and dynamic BIC (DBIC, %). RESULTS: BV/TV ranged from 71.2% to 85.0% of the screw surface. BIC ranged from 45.7% to 55.4% of the screw surface and was not affected by diameter (P = 0.66). In contrast, the percentage of DBIC did not vary with the applied load (P = 0.41); however, it correlated significantly with the diameter of the screw (P = 0.001). CONCLUSION: The percentage of DBIC that is actively remodelling increases with increasing diameter of the screw. Dynamic histomorphometry is more sensitive to detecting changes in bone-implant contact when compared to static measurements.

Novel application and validation of in vivo micro-CT to study bone modelling in 3D.

OBJECTIVES: The aim is to highlight a novel three-dimensional (3D) imaging methodology using micro-CT scans to visualize and measure bone modelling in an animal model. In order to validate the new methodology, we compared the 3D imaging method to traditional two-dimensional (2D) histomorphometry to assess growth changes in the jaws of a rodent. SETTING AND SAMPLE POPULATION: Rodent animal models. MATERIAL AND METHODS: Eleven rats were obtained from a larger previously published study. Sixty undecalcified histological sections from the maxilla and corresponding high-resolution in vivo micro-CT reconstructions were obtained. Bone modelling changes on specific alveolar surfaces were measured using traditional histomorphometry. Measurements of bone growth were also obtained via 3D Slicer software from 3D micro-CT generated models from the same plane containing the histological images. Both qualitative and quantitative 3D methods were compared to traditional histological measurements. Quantitative agreement between methods was categorized as follows: poor (>150 µm), good (150-100 µm) and excellent (<100 µm). RESULTS: Both qualitative (88.3%) and quantitative (86.7%) 3D measurements showed excellent agreement, when compared to histomorphometric measurements. Only 1.7% and 5% of the comparisons exhibited poor agreement (>150 µm) for qualitative and quantitative methods, respectively. DISCUSSION: The new 3D superimposition method compares very favourably with traditional histology. It is likely that in the future, such methods will be used in studies of bone adaptation. CONCLUSION: The 3D micro-CT qualitative and quantitative methods are reliable for measuring bone modelling changes and compare favourably to histology for the specific application described.

Preface to COAST 2018 Innovators' Workshop: Bridging the biology and technology gap in orthodontics and craniofacial care.

OBJECTIVE: A third focused workshop explored how to transfer novel findings into clinical orthodontic practice. SETTING AND SAMPLE POPULATION: Participants met at the Scottsdale Plaza Resort, 12-16 September 2018 for the Consortium for Orthodontic Advances in Science and Technology 2018 Innovators' Workshop. Thirty speakers and four lunch-hour focus group leaders shared and exchanged information with approximately 45 registered attendees. MATERIAL AND METHODS: This Innovators' Workshop was organized according to five themed sessions which covered: (a) The relevance of genetics, biology and environment to therapeutic outcomes; (b) Application of bioinformatics in craniofacial research; (c) Regeneration with and for orthodontic treatment; (d) Technology in precision orthodontics; and (e) Muscle, joint, and airway: Growth, function and pain. RESULTS: The papers that comprise this supplemental issue exemplify the important outcomes of the 2018 COAST Workshop. In addition, matters identified as important needs include improved understanding of neural, skeletal and muscle tissue crosstalk in early craniofacial growth; standardized methods for three-dimensional radiographic and surface landmark and reference plane identification, measurements and serial superimpositioning techniques for use in the clinic; sharing and making available existing data sets (eg, cone beam computed tomography images, genotype-phenotype data); evidence of the usefulness and effectiveness of new devices; guidelines of what to measure to characterize the airway; more information about the influences of the soft tissues on craniofacial morphology; and information about effective digital work flows applied to clinical and educational settings. CONCLUSIONS: Progress in bridging the biology-technology gap has identified new needs for improvements in orthodontics and craniofacial care.

A rodent model using skeletal anchorage and low forces for orthodontic tooth movement.

INTRODUCTION: Nonhuman animal models have been used extensively to study orthodontic tooth movement (OTM). However, rodent models have disadvantages, including a reported reduction in bone volume during OTM. The purpose of this study was to determine the viability of a skeletal anchorage and the effect of low force (∼3 cN) on interradicular bone volume during OTM. METHODS: Ninety Sprague-Dawley rats were divided into 5 time points. A miniscrew and a nickel titanium coil spring placed a load of 3 cN (experimental) or 0 cN (sham) on the maxillary first molar in a split-mouth design. Displacement of the first molar and bone volume/total volume (BV/TV) in the interradicular region were quantified. RESULTS: The success rate of the miniscrew was 98.9% (89 out of 90). Linear and angular tooth movement increased steadily (mean 0.1 mm/wk, 0.48 mm at 40 days). BV/TV was significantly reduced between the tooth movement and non-tooth movement sides in the 3 cN group: by 13%, 23%, 15%, 23%, and 16% at 3, 7, 14, 28, and 40 days, respectively. CONCLUSIONS: Our model resulted in efficient OTM without skeletal anchorage failure. BV/TV reduction was lower than in previous reports. This novel validated model is likely to be the basis for future studies.

Compensations in Bone Morphology and the Dentition in Patients With Untreated Unilateral Cleft Lip and Palate: A Cone-Beam Computed Tomographic Analysis.

OBJECTIVE: The purpose of this study was to quantitatively assess dentoalveolar and skeletal compensations in patients with untreated unilateral cleft lip and palate (UCLP). We hypothesized that there are significant skeletal and dental adaptations in UCLP cases compared to a comparison maxillary crossbite group. DESIGN: A convenience retrospective sample of 30 patients with UCLP and a comparison group of 30 patients with unilateral posterior crossbite without CLP. Cone-beam computed tomography scans (CBCTs) were used to evaluate dental and skeletal compensations. In addition, alveolar bone thickness was measured at 2-mm increments in mesiodistal and faciolingual cross-sectional views along the long axis of the central incisors. Alveolar bone height was measured, and the percentage of root length supported by bone was calculated. RESULTS: Compensations for unilateral cleft lip and palate were restricted to the cleft site and adjacent structures. Dental compensations include alteration in the position of cleft-adjacent maxillary incisors and maxillary canines. No gross skeletal compensations were found. Alveolar support of cleft adjacent incisors was similar to controls except for measurements in the most coronal and apical regions. The cleft group contralateral incisors exhibited buttressing effects and had significantly higher alveolar thickness in the coronal half of the tooth. There was less (5%) alveolar coverage of the cleft-facing aspect of the central incisor root than all other incisors. CONCLUSION: The bone adaptation to the presence of a cleft was localized in the vicinity of the cleft, and adaptations in the mandible were not apparent.

Soft Tissue Changes Measured With Three-Dimensional Software Provides New Insights for Surgical Predictions.

PURPOSE: Although computer-aided craniofacial reconstructions allow for simulation of hard tissue changes, the prediction of the final soft tissue facial changes remains a challenge. The purpose of the present study was to evaluate the 3-dimensional (3D) soft tissue changes in patients undergoing 2-jaw orthognathic surgery. PATIENTS AND METHODS: For the present retrospective cohort study, 40 consecutive patients (11 men and 29 women; mean age 23.5 ± 4.9 years) who had undergone 2-jaw orthognathic surgery were selected. We obtained the medical and dental records from 3 weeks before surgery and 6 months after surgery. We used image processing software to segment, superimpose, and quantify the hard and soft tissue displacements in 3 dimensions before and after surgery at 15 paired locations. The soft tissue and hard tissue changes were determined through quantification of homologous landmark displacements between the preoperative and postoperative computed tomography data. We measured the 3D soft and hard tissue changes and the anteroposterior, inferosuperior, and transverse components of the changes. We quantified the ratios between the soft and hard tissue changes, tested Pearson's correlation between these changes, and developed a predictive regression equation for the observations at each location. RESULTS: We found that soft tissue movement followed the hard tissue movement, with a correlation nearly equal to 0.9 (range 0.85 to 0.98), suggesting that in general the soft tissues of the maxillary and mandibular landmarks are affected similarly by the skeletal movements. The anteroposterior component of the soft tissue 3D displacements followed the hard tissue movement with a ratio greater than 0.9 and with high correlation (r > 0.9) in the mandible. CONCLUSION: The results of the present study provide surgeons with a ratio of hard to soft tissue change and the strength of the correlations, which will allow for more accurate 3D predictions for both midline and lateral structures in bimaxillary orthognathic surgical cases. In addition, predictive equations for various landmarks were developed and can be used in computer-based prediction programs to aid in treatment planning of soft tissue changes.

Aging, inflammation, immunity and periodontal disease.

The increased prevalence and severity of periodontal disease have long been associated with aging, such that this oral condition affects the majority of the adult population over 50 years of age. Although the immune system is a critical component for maintaining health, aging can be characterized by quantitative and qualitative modifications of the immune system. This process, termed 'immunosenescence', is a progressive modification of the immune system that leads to greater susceptibility to infections, neoplasia and autoimmunity, presumably reflecting the prolonged antigenic stimulation and/or stress responses that occur across the lifespan. Interestingly, the global reduction in the host capability to respond effectively to these challenges is coupled with a progressive increase in the general proinflammatory status, termed 'inflammaging'. Consistent with the definition of immunosenescence, it has been suggested that the cumulative effect of prolonged exposure of the periodontium to microbial challenge is, at least in part, a contributor to the effects of aging on these tissues. Thus, it has also been hypothesized that alterations in the function of resident immune and nonimmune cells of the periodontium contribute to the expression of inflammaging in periodontal disease. Although the majority of aging research has focused on the adaptive immune response, it is becoming increasingly clear that the innate immune compartment is also highly affected by aging. Thus, the phenomenon of immunosenescence and inflammaging, expressed as age-associated changes within the periodontium, needs to be more fully understood in this era of precision and personalized medicine and dentistry.

Bone biology-related gingival transcriptome in ageing and periodontitis in non-human primates.

AIM: Cellular and molecular immunoinflammatory changes in gingival tissues drive alveolar bone loss in periodontitis. Since ageing is a risk factor for periodontitis, we sought to identify age-related gingival transcriptome changes associated with bone metabolism in both healthy and in naturally occurring periodontitis. MATERIALS AND METHODS: Adult (12-16 years) and aged (18-23 years) non-human primates (M. mulatta) (n = 24) were grouped into healthy and periodontitis. Gingival tissue samples were obtained and subjected to microarray analysis using the Gene Chip Macaque Genome Array. Gene expression profiles involved in osteoclast/osteoblast proliferation, adhesion and function were evaluated and compared across and between the age groups. QPCR was also performed on selected genes to validate microarray data. RESULTS: Healthy aged tissues showed a gene profile expression that suggest enhancement of osteoclastic adhesion, proliferation/survival and function (SPP1, TLR4, MMP8 and TFEC) and impaired osteoblastic activity (SMEK3P and SMAD5). The gingival transcriptome in both adult and aged animals with naturally occurring periodontitis (FOS, IL6, TLR4, MMP9, MMP10 and SPP1 genes) was consistent with a local inflammatory response driving towards bone/connective tissue destruction. CONCLUSION: A pro-osteoclastogenic gingival transcriptome is associated with periodontitis irrespective of age; however; a greater bone-destructive molecular environment is associated with ageing in healthy tissues.

Bone ingrowth and initial stability of titanium and porous tantalum dental implants: a pilot canine study.

PURPOSE: To investigate if a dental implant system with a midsection covered by 3-dimensionally porous tantalum material would exhibit stability comparable with a traditional threaded titanium alloy implant system and whether bone would grow into the porous section. METHODS: Three experimental and 3 control implants were placed in the individual mandibles of 8 dogs. Resonance frequency analysis assessed implant stability at 0, 2, 4, 8, and 12 weeks of healing. Histomorphometric and backscattered scanning electron microscopic analyses examined the presence of bone ingrowth into the experimental implant's porous section and bone-to-implant contact along the titanium surfaces of both implants. RESULTS: Implant stability did not significantly differ during 0 to 12 weeks of healing. Progressive tissue mineralization developed inside porous sections from weeks 2 to 12. Porous implants exhibited a combination of progressive osseointegration along their titanium surfaces and bone ingrowth inside their porous tantalum sections. CONCLUSIONS: Cortical and apical implant threads, combined with the porous section, were able to stabilize the experimental implant to the same degree as the fully threaded control implant.

Statins Modulate Microenvironmental Cues Driving Macrophage Polarization in Simulated Periodontal Inflammation.

Periodontal disease (PD) is a chronic inflammatory disorder characterized by the destruction of connective tissue, tooth loss, and systemic infections. Clinically, treatment of PD includes control of the etiologic factors via several modalities: initial therapy including scaling and root planing (SRP), corrective phase of surgical treatment, both with and without adjunct antimicrobial/pharmacological agents, followed by a maintenance/supportive periodontal therapy phase. Each treatment phase aims to control oral biofilm by addressing risk factors and etiology. Monotherapy of systemic antibiotics is insufficient compared to their use as an adjunct to SRP. The critical issue of systemic antimicrobial usage includes adverse patient outcomes and increased bacterial resistance. Therefore, alternative adjuncts to periodontal therapy have been sought. Statins are widely prescribed for the treatment of hypercholesterolemia and cardiovascular disease. Statins have demonstrated anti-inflammatory properties and immunomodulatory effects, and a few retrospective studies showed that statin patients exhibit fewer signs of periodontal inflammation than subjects without the medication. Despite the available clinical studies on the local administration of statins for PD, no studies have reported the macrophage polarization response. We have developed a gingival fibroblast-macrophage co-culture model to track macrophage response when exposed to a battery of microenvironmental cues mimicking macrophage polarization/depolarization observed in vivo. Using our model, we demonstrate that simvastatin suppresses macrophage inflammatory response and upregulates tissue homeostasis and M2 macrophage markers. Our findings support the usage of statins to mitigate periodontal inflammation as a valid strategy.

Bone damage associated with orthodontic placement of miniscrew implants in an animal model.

INTRODUCTION: The purposes of this study were to quantify bone damage associated with insertion of 2 types of miniscrew implants and to relate the amount of bone damage to monocortical plate thickness. METHODS: Nondrilling (n = 28) and self-drilling (n = 28) miniscrew implants (6 × 1.6 mm, Dentaurum, Newtown, Pa), and pilot holes (n = 26) were placed bilaterally in the maxillae and the mandibles of 5 adult dogs immediately after death. Bone blocks were cut, bulk stained with 1% basic fuchsin, embedded in methyl methacrylate, sectioned, and mounted. Monocortical plate thickness was measured adjacent to the miniscrew implant insertion site. Damage amounts were quantified at distances of 0 to 0.5 mm (adjacent region) and 0.5 to 1 mm (distant region) from the bone-implant interface. Total fractional damaged area (%), fractional microcracked area (%), and fractional diffuse damaged area (%) were quantified by using standard histomorphometric methods. RESULTS: The mean monocortical plate thickness of the specimens from the mandible (2.2 mm) was significantly (P <0.001) greater than that of the maxillary specimens (0.9 mm). In the mandible, the 3 damage parameters were greater with self-drilling miniscrew implants than with nondrilling miniscrew implants; however, there were no differences in the damage parameters in the maxilla. CONCLUSIONS: Bone damage accumulation is related to the type of miniscrew implant and the thickness of the bone.

Post-Expansion and end of treatment outcomes of semi-rapid maxillary expansion with a modified removable appliance.

Context: Maxillary expansion is the mainstay therapy for maxillary transverse deficiency. There has been a constant search for the most effective yet biologically friendly method of maxillary expansion, alternatives being, slow, rapid and semi rapid. Aims: The purpose of this study was to explore the outcome of palatal expansion achieved using a removable plate and low continuous forces brought about by a semi rapid screw activation protocol. Settings and Design: Retrospective study. Methods and Material: Plaster models of 56 consecutive patients treated for maxillary expansion were obtained pre-treatment (T0), post-expansion (T1), and post fixed appliance treatment (T2). The radiographic images of the models were traced using Image J software. Linear and angular measurements were evaluated to measure transverse change. Statistical Analysis Used: Interclass Correlation Coefficient [ICC] and Dahlberg's formula were used for reliability test. The differences in the mean values between the three duration groups [T0, T1 and T2] were analysed using Analysis of Variance (ANOVA). For multiple comparisons, a post hoc Tukey honestly significant difference (HSD) test was performed. Results: Significant increase in inter-molar, alveolar and palatal linear widths were observed from T0 to T1 with significant relapses from T1 to T2, with an overall net gain remaining at T2. Similarly, significant increases in all angular measurements were observed from T0 to T1 with significant relapses from T1 to T2 and an overall insignificant change at T2 as compared to T0. Conclusion: The appliance and protocol were effective in producing transverse expansion with minimal molar and alveolar tipping.

Effects of short-term zoledronic acid treatment on bone remodeling and healing at surgical sites in the maxilla and mandible of aged dogs.

PURPOSE: It is unknown whether zoledronic acid (ZA) interferes with initial bone healing at extraction and implant sites. The goal of this study was to examine the effect of short-duration ZA on bone remodeling and healing after surgical insult in an aged dog model. MATERIALS AND METHODS: Four 2- to 3-year-old male dogs were administered ZA (0.1 mg/kg per month for 4 months), and 3 age-matched untreated dogs received no drug. In both groups, after the ZA-treated group had completed receiving the drug, the third premolar was extracted unilaterally and 2 orthodontic mini-implants per jaw per dog were placed on the ipsilateral side. After a 6-week healing period, a pair of calcein bone labels were administered. Bone sections from the mandible, maxilla, rib, and femur were obtained. The percent necrosis in the alveolar and basal regions of tooth-supporting bone was assayed by lactate dehydrogenase, and dynamic histomorphometric parameters were quantified and analyzed by use of mixed models. RESULTS: All extraction sites healed uneventfully, and no lesions resembling osteonecrosis were detected. The total percent necrosis was limited to less than 1% for all the bone sites examined. The ZA reduced bone remodeling at both surgical sites (extraction sites and mini-implant site) and nonsurgical sites. Although there was a significant (P < .05) increase in bone formation rate at the surgical sites in the untreated group, this increase was not significant (P = .3) in the ZA-treated group. CONCLUSIONS: Bone remodeling occurs in ZA-treated animals at surgical sites. ZA dramatically reduced bone turnover, but no exposed lesions resembling osteonecrosis developed at extraction and mini-implant sites after the 4-month drug duration.

Short-term zoledronic acid reduces trabecular bone remodeling in dogs.

The effects of zoledronic acid, a bisphosphonate, on the trabecular bone remodeling (TBR) of the mandibular condyle are unknown. The objectives of this study were to quantify and compare TBR in the mandibular condyle and vertebrae of 2- to 3-yr-old dogs and to evaluate the effects of short-term zoledronic acid on TBR. Bone samples from two, age-matched groups of dogs [seven dogs were given no treatment (NT group) and seven dogs were treated with four total infusions of zoledronic acid administered monthly (ZOL group)] were analyzed using histomorphometry. Trabecular bone remodeling and microarchitecture were quantified and analyzed statistically. Physiologic TBR, quantified in the NT group, was significantly higher (more than sixfold) in the vertebrae than in the mandibular condyle. Trabecular bone remodeling in the vertebrae of dogs of the ZOL group was 96% lower than in dogs of the NT group. By contrast, TBR in the mandibular condyle of dogs in the ZOL group was statistically equivalent to that of dogs in the NT group. Our results demonstrate that the physiological TBR in aged dogs is vastly different in the mandibular condyle compared to that in the vertebra. A higher level of physiologic TBR in the vertebra than in the mandibular condyle results in greater reduction of TBR in response to short-term treatment with zoledronic acid.

Relationships of viscosity with contact hardness and modulus of bone matrix measured by nanoindentation.

Creep is an active form of time-dependent viscoelastic deformation that occurs in bone tissue during daily life. Recent findings indicate bone mineralization, which is involved in determining the elastic and plastic properties of bone matrix, can also contribute in controlling its viscoelastic property. Nanoindentation viscosity was used as a direct measure for the capacity of a material to resist viscous-like flow under loading. The objectives of this study were to examine (1) whether the nanoindentation viscosity obtained using the traditional viscoelastic Voigt model can describe creep response of bone matrix and (2) how the nanoindentation viscosity is related to contact hardness and elastic modulus. The Voigt model accurately described the creep behavior of bone matrix (r(2)>0.96, p<0.001). The nanoindentation viscosity had strong relationships with nanoindentation contact hardness (r(2)=0.94, p<0.001) and modulus (r(2)=0.83, p<0.001) independent of tissue ages of osteonal bone matrix. The strong positive relationships of nanoindentation viscosity with contact hardness and modulus can be interpreted as increases in the mineral portion of bone matrix may limit the interfibril motion of collagen while enhancing the mechanical stability of bone. We suggest that previous nanoindentation results can be reanalyzed to characterize the viscoelastic creep using the Voigt model.

Inhibition of osteoclastogenesis by opsonized Porphyromonas gingivalis.

A crucial step in the pathogenesis of periodontal disease (PD) is activation of osteoclasts (OC) by numerous virulence factors produced by Porphyromonas gingivalis (Pg). To understand pathogenesis of periodontal disease and the role of specific adaptive immune responses, effects of antibodies on Pg-induced OC differentiation and function were investigated. Human peripheral blood-derived monocytes were differentiated in vitro to osteoclasts in the presence or absence of: a) Pg; b) antibodies to Pg; and c) antibody-opsonized Pg. Findings suggest significant induction of osteoclastogenesis by Pg when compared to control cultures, whereas opsonization decreased osteoclastogenesis by 45%. Immune receptor gene expression profile in the presence of opsonized Pg showed marked up-regulation of TLR1 (3-fold) and TLR2 (2-fold) along with FcγRIIB (2-fold) and FcγRIII receptors (5-fold), but not TLR4 and FcRγ receptors. Interestingly, blocking FcγRIIB, but not FcγRIII receptor, reversed the inhibitory effects of opsonized Pg suggesting a critical role played by FcγRIIB in osteoclastogenesis. Furthermore, opsonized Pg transformed OC precursors to a "macrophage phenotype" suggesting a bone protective role of the immune complexes in modulating osteoclastogenesis, probably by competing as an agonist for PRRs, and inducing selective activation of FcγRs with simultaneous suppression of FcRγ which regulates bone resorptive process. Further defining effective antibody isotypes, avidity, and antigenic specificity could improve targets for eliciting protective immunity.

Changes in mechanical properties of bone within the mandibular condyle with age.

The purpose of the study was to compare indentation modulus (IM) and hardness of condylar bone in young and adult dogs. In addition we desired to examine histologic sections for bone formation activity in the two groups. Mandibular condyles were obtained from adult (1- to 2-year-old) and young (approximately 5-m old) dogs. Two sections/condyle were obtained and one was processed for histomorphometry and the other for mechanical analyses. Indents were made on moist condylar trabecular bone to a depth of 500 nm at a loading rate of 10 nm/s using a custom-made hydration system to obtain IM and hardness. Histomorphometric analyses measured the bone volume/total volume (BV/TV%) and ratio of labeled to unlabeled bone within the condyle. Data were analyzed using a repeated-measures factorial analysis of variance and Tukey-Kramer method. Overall, the IM of the adult condyles (10.0+/-3.4 GPa, Mean+/-SD) were significantly (P<0.0001) higher than in young dogs (5.6+/-2.6 GPa). There was a greater bone mass in the young (60.2%) versus the adult condyles (42%). Also, significantly more labeled bone in the young (66.1%) condylar bone suggested higher bone forming activity than in adult condyles (27.5%). With age there is a change in mass and material properties in the trabecular bone of the mandibular condyle in dogs.

Alveolar process anabolic activity in C3H/HeJ and C57BL/6J inbred mice.

BACKGROUND: The purpose of this study was to characterize bone activity of the alveolar process in C3H/HeJ (C3H) and C57BL/6J (B6) inbred mice. Based on observations in other animal species, we hypothesized that the bone-formation rate/bone surface (BFR/BS) is greater in the alveolar process compared to the body of the mandible and that the bone anabolic activity is greater in the alveolar process of the mandible than in the maxilla. We also examined the alveolar process of C3H and B6 mice for the presence of secondary osteons. METHODS: Jaws from 17-week-old C3H and B6 female mice (N = 15/group) were harvested. Histomorphometric parameters were evaluated in sections from the alveolar process, each of which included at least one molar root. RESULTS: In C3H and B6 mice, BFR/BS was not significantly different (P >0.05) between the alveolar process and the body of the mandible. In C3H mice, BFR/BS was significantly greater (P = 0.05) in the mandible compared to the maxilla. BFR/bone volume (BV) was not significantly different (P >0.05) between C3H mandible and maxilla. In the B6 inbred mouse, BFR/BS and BFR/bone volume (BV) were not significantly different (P >0.05) between jaws. After analyzing 165 bone sections, we identified 25 secondary osteons. CONCLUSIONS: The surface anabolic activity was not different between the body and the alveolar process of the mandible. The surface activity was greater in the C3H mandible than in the maxilla. Although secondary osteonal bone remodeling existed in the C3H and B6 alveolar bone, this process was not a consistent finding.

Testing of a bioactive, moldable bone graft substitute in an infected, critically sized segmental defect model.

Large infected bone defects, often resulting from high energy traumas, are difficult to treat due to their variability in complexity and location. Standard treatment for infected bone defects begins with a protocol that includes a series of debridements in conjunction with an extended course of systemic antibiotics. Only after the infection has been eliminated will repair of the defect commence, typically with implantation of autologous bone. To address some of the shortcomings of the standard treatment methods, such as serial procedures, limited grafting material, and the need for a second surgical site for autologous bone, a sequential, dual drug-releasing, moldable, calcium sulfate-based bone graft substitute was developed previously. In the present studies, the effectiveness of the material for treating both the infection with vancomycin and bone defect with simvastatin was evaluated in vivo using a critically sized, infected segmental defect model in rat femurs. Although the infection was not fully eliminated, the local release of vancomycin increased survivorship of infected animals by 464% compared to nontreated controls. Infected animals receiving antimicrobial treatment showed comparable amounts of new bone formation within the defect site when compared to noninfected controls. Incorporating agents capable of disrupting established biofilms into bone graft substitutes may enhance effectiveness in treating a biofilm infection within a bone defect. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1878-1886, 2018.