The Effects of Continual Intermittent Parathyroid Hormone Treatment on Human Periodontal Ligament Fibroblasts in an In Vitro Wound Repopulation Model.

INTRODUCTION: Periodontal ligament fibroblasts (PDLFs) play a vital role in periodontal regeneration. Parathyroid hormone (PTH) is important in catabolic regulation on osteoclasts; it also has anabolic effects on hard tissue formation. Using an in vitro wound repopulation model, this study investigated the effect of continual intermittent administration of PTH on PDLFs wound repopulation. Methods and Materials: PDLFs were grown in 12-well plates and divided into 0 (control), 5, 10, 20, 40, and 80 nM of PTH treatments. A 3-mm wound was created on confluent and synchronized cells. Six PTH treatments were initiated using serum-free medium with supplements. Cell repopulation was measured at four time points: 5, 10, 15, and 20 days. RESULTS: A 5% increase wound repopulation showed an enhancement on day 10 for all treatment groups as compared to control groups. On days 15 and 20, treatment groups showed a decrease in proliferation and migration compared to controls with significant decreases at concentrations of 40 and 80 nM. CONCLUSION: Continual intermittent treatment with PTH has the potential to enhance proliferation and migration of PDLFs for wound repopulation at early time points. A dose-dependent correlation was seen with a positive trend on day 10 while a significant decrease on day 20.

Ingestion of gastrolith mineralized matrix increases bone volume and tissue volume in mouse long bone fracture model.

PURPOSE: Fracture healing often requires extended convalescence as the bony fragments consolidate into restored viable tissue for load-bearing. Development of interventions to improve healing remains a priority for orthopaedic research. The goal of this study was to evaluate the ability of a naturally occurring matrix of amorphous calcium carbonate to affect fracture healing in an uninstrumented long bone model. METHODS: Complete transverse fracture was induced in the fibula of mature mice, followed by daily gavage of crushed gastrolith from crayfish at doses of 0 (control), 1 (1 MG), and 5 (5 MG) mg/kg. At Day 17, bones and sera were harvested. RESULTS: Morphologically, the 1 MG treated group had greater bone volume (BV), and both 1 MG and 5 MG had greater tissue volume (TV) than control (p < 0.05), as determined by µCT; BV/TV and mineral density did not yield a statistical difference. Histologically, regional variations in mineralized matrix were evident in all specimens, indicating a broad continuum of healing within the callus. Among serum proteins, bone-specific alkaline phosphatase, indicative of active mineralization, was greater in 5 MG than control (p < 0.05). Sclerostin, an inhibitor of osteogenesis, was lower in 5 MG than control (p < 0.05), also suggestive of enhanced healing. CONCLUSIONS: An increase in bone volume, tissue volume and cellular signaling for osteogenesis at 17 days following fibula fracture in this mouse model suggests that gastrolith treatment holds potential for improving fracture healing. Further study at subsequent time points is warranted to determine the extent to which the increase in callus size with gastrolith treatment may accelerate restoration of tissue integrity.

Effect of Sodium Lauryl Sulfate (SLS) on Primary Human Gingival Fibroblasts in an In Vitro Wound Healing Model.

OBJECTIVES: Sodium lauryl sulfate (SLS) is a surfactant used to decrease the surface tension of water. Most commercially available dentifrices contain 0.5-2.0% SLS. This study investigated the potential effect of SLS on oral wound healing using primary human gingival fibroblasts (HGFs). METHODS: HGFs cells were grown in12-well culture plates in DMEM medium. A 3 mm wound was created on confluent HGFs. The cells were challenged with 0 (the control group), 0.01, 0.02, 0.03, 0.04, or 0.05% SLS-containing media once daily for 2 minutes. The cells were stained on day 0, 2, 4, 6 and 8. The percent of wound fill area was measured. RESULTS: On day 2, 4, 6, and 8, the wound fill of the control group (0% SLS) was 15, 35, 67 and 98%, respectively; at 0.01% SLS, it was 10, 20, 65 and 84%; at 0.02%, it was 7, 10, 15 and 25%; at 0.03% SLS, it was only 5% and 8% on day 2 and 4. CONCLUSION: Our results showed a dose- and time-dependent inhibition on HGFs wound fill by SLS; however, future in vivo studies are needed to validate if our in vitro findings using SLS-free dentifrices to avoid the potential delay of wound healing.

Effect of a Benzalkonium Chloride Surfactant-Sodium Hypochlorite Combination on Elimination of Enterococcus faecalis.

INTRODUCTION: The purpose of this investigation was to determine the effect of a sodium hypochlorite-surfactant combination on the removal of Enterococcus faecalis from infected teeth. METHODS: Sixty-four extracted human single canal anterior teeth were prepared with rotary instrumentation and sterilized. Teeth were divided into 4 groups, N = 16. Three experimental groups were inoculated with E. faecalis and cultured for 21 days before use: positive control group, no irrigation; NaOCl group, irrigated with 5 mL 6% NaOCl; and NaOCl/BAK group, irrigated with 5 mL 6% NaOCl/0.008% benzalkonium chloride (BAK). The negative control group received medium only and no inoculate. Paper point sampling of the canals was obtained before irrigation (S1) for all 4 groups and for 2 groups after irrigation (S2) to determine remaining colony-forming units. After sampling, all teeth were split in half and evaluated for bacterial viability colony-forming units and penetration of dentinal tubules by using fluorescent vital dye staining and confocal laser scanning microscopy. RESULTS: Comparison of pre-irrigation and post-irrigation paper point samples from the 2 irrigated groups showed a significant reduction in bacterial canal load (P < .001, Kruskal-Wallis), with a significantly lower load in the NaOCl/BAK group than in the NaOCl group (P = .001, Mann-Whitney U test); 68.8% of the NaOCl/BAK samples gave no recoverable counts. In contrast, no significant difference between these groups was found for counts recovered from dentin. Confocal laser scanning microscopy showed no differences in tubule penetration. CONCLUSIONS: The addition of BAK to NaOCl significantly reduced the number of remaining bacteria within the canal after irrigation compared with NaOCl alone.

In vitro study of the adverse effect of nicotine and physical strain on human gingival fibroblasts as a model of the healing of wounds commonly found in the military.

BACKGROUND: Significant adverse effects on fibroblast growth and metabolism are observed with nicotine. We investigated the synergistic effects of nicotine and cyclical mechanical strain (CMS) on human gingival fibroblasts (HGFs) in a wound-healing model. METHODS: HGFs were isolated and grown in Dulbecco's modified Eagle's medium. Three-millimeter wounds were created on a confluent cell monolayer grown in a media containing 0, 1, 2, or 4 mM nicotine, with or without CMS. The applied deformation regimen remains constant for 6 days. On days 1, 2, 4, and 6, the cells were stained with hematoxylin and eosin Y for the evaluation of wound repopulation. RESULTS: The application of CMS alone demonstrates a biphasic response, with an initial stimulatory effect on wound repopulation (days 1-2) and less repopulation during the later phase (days 4-6). The addition of nicotine clearly demonstrated a time and inverse dose-dependent relationship on wound repopulation, with no effect during the early phase and reduced wound repopulation during the later phase. CONCLUSIONS: Initial treatment of HGF wounds with CMS resulted in faster wound repopulation regardless of nicotine presence. By day 6, wound healing of HGF exposed to both nicotine and CMS is delayed. These findings suggest that CMS and nicotine may affect fibroblasts and delay wound healing at other sites in the body as well.

The effectiveness of endodontic solvents to remove endodontic sealers.

Dental emergencies negatively affect troop readiness, especially during combat. Endodontic retreatment, when required, is especially challenging when the removal of endodontic sealer is required. In this study, we investigated the effectiveness of synthetic endodontic solvents to remove endodontic sealers. Fifty capillary tubes (2.7 mm ID×22 mm L), each filled to 15 mm with either Roth 801, AH Plus, MetaSEAL, or gutta-percha, were stored at 75% humidity for 14 days at 37°C. Ten capillary tubes containing each sealer were treated with either chloroform, xylene, EndoSolv R, EndoSolv E, or no solvent, and then penetrated with D3 ProTaper Universal Retreatment file on the same day. The time for the file to penetrate the length of each sealer was recorded, and the data statistically analyzed. Roth 801 failed to set and was not tested. The file took 3.4±0.1, 4.8±0.3, 5.7±0.4, 4.5±0.2, and 10.6±1.0 seconds (mean±SD) to penetrate gutta-percha using chloroform, xylene, EndoSolv R, EndoSolv E, or no solvent, respectively, and was performed by one endodontic resident at one sitting. The time for penetration of gutta-percha with any solvent was significantly faster (p≤0.05) than for AH Plus or MetaSEAL.The time for AH Plus ranged from 23.1±1.0 to 81.5±4.5 seconds. The time for MetaSEAL ranged from 97.2±6.1 to >180 seconds. EndoSolv E was the most effective solvent for AH Plus. It took significantly more time to remove MetaSEAL than AH Plus, regardless of the solvent used. Our study indicated that the use of the proper endodontic solvent makes complete removal of a sealer much more effective during retreatment.

Histologic Evaluation of Osseous Regeneration Following Combination Therapy With Platelet-Rich Plasma and Bio-Oss in a Rat Calvarial Critical-Size Defect Model.

Platelet-rich plasma (PRP) is an autogenous source of growth factors shown to facilitate human bone growth. Bio-Oss, an osteoconductive xenograft, is used clinically to regenerate periodontal defects, restore dental alveolar ridges, and facilitate sinus-lift procedures. The purpose of this study was to analyze whether a combination of PRP and Bio-Oss would enhance bone regeneration better than either material alone. PRP and/or Bio-Oss were administered in an 8-mm critical-size defect (CSD) rat calvarial model of bone defect between 2 polytetrafluoroethylene membranes to prevent soft tissue incursion. Eight weeks after the induction of the CSD, histologic sections were stained with hematoxylin and eosin stain and analyzed via light microscopy. Qualitative analyses revealed new bone regeneration in all 4 groups. The Bio-Oss and PRP plus Bio-Oss groups demonstrated greater areas of closure in the defects than the control or PRP-only groups because of the space-maintaining ability of Bio-Oss. The groups grafted with Bio-Oss showed close contact with new bone growth throughout the defects, suggesting a stronger graft. The use of PRP alone or in combination with Bio-Oss, however, did not appear to enhance osseous regeneration at 8 weeks. Areas grafted with Bio-Oss demonstrated greater space-maintaining capacity than controls, and PRP was an effective vehicle for placement of the Bio-Oss. However, at 8 weeks this study was unable to demonstrate a significant advantage of using PRP plus Bio-Oss over using Bio-Oss alone.

Gender and age differences in growth factor concentrations from platelet-rich plasma in adults.

The use of platelet-rich plasma (PRP) to facilitate healing of orthopedic-related injuries has gained popularity; however, the clinical benefits are not consistent. Differences may result from variations in growth factor (GF) levels in normal populations. The purpose of this study was to determine if GF levels present in activated PRP preparations differed by gender and age (≤ 25 versus >25 years) in a healthy population (N = 102). All GFs analyzed (epidermal growth factor [EGF], hepatocyte growth factor [HGF], insulin growth factor-1 [IGF-1], platelet-derived growth factor-AB [PDGF-AB], platelet-derived growth factor-BB [PDGF-BB], transforming growth factor beta-1 [TGFß-1], and vascular endothelial growth factor) had higher levels for females and for those ≤ 25 years old. Of the GFs tested, four of seven were significantly higher (p < 0.05) for females (EGF, HGF, IGF-1, PDGF-BB), the most significant being IGF-1 (female, 85.0; male, 69.3 ng/mL; p < 0.01). Five of seven GFs achieved significance (p < 0.05) for people ≤ 25 years old (EGF, IGF-1, PDGP-AB, PDGF-BB, and TGFß-1), with IGF and PDGF-AB achieving p < 0.001 (≤ 25 years, 85.1; >25 years, 56.8, and ≤ 25 years, 7.66; >25 years, 5.77 ng/mL, respectively). Finally, for both genders, most of the GFs were positively correlated with all GFs. This study demonstrated that both age and gender account for variations in specific GFs present in PRP, and this may partially explain some of the inconsistent results of PRP clinical trials.

Evaluation of a new filing system's ability to maintain canal morphology.

INTRODUCTION: The manufacturer of the Hyflex CM endodontic files claims the files remain centered within the canal, and if unwound during treatment, they will regain their original shape after sterilization. The purpose of this study was to evaluate and compare the canal centering ability of the Hyflex CM and the ProFile ISO filing systems after repeated uses in simulated canals, followed by autoclaving. METHODS: Sixty acrylic blocks with a canal curvature of 45° were stained with methylene blue, photographed, and divided into 2 groups, H (Hyflex CM) and P (ProFile ISO). The groups were further subdivided into 3 subgroups: H1, H2, H3; P1, P2, P3 (n = 10). Groups H1 and P1 were instrumented to 40 (.04) with the respective file system. Used files were autoclaved for 26 minutes at 126°C. After sterilization, the files were used to instrument groups H2 and P2. The same sterilization and instrumentation procedure was repeated for groups H3 and P3. Post-instrumentation digital images were taken and superimposed over the pre-instrumentation images. Changes in the location of the center of the canal at predetermined reference points were recorded and compared within subgroups and between filing systems. RESULTS: Statistical differences in intergroup and intragroup transportation measures were analyzed by using the Kruskal-Wallis analysis of variance of ranks with the Bonferroni post hoc test. There was a difference between Hyflex CM and ProFile ISO groups, although it was not statistically significant. Intragroup differences for both Hyflex CM and ProFile ISO groups were not significant (P < .05). CONCLUSIONS: The Hyflex CM and ProFile ISO files equally maintained the original canal's morphology after 2 sterilization cycles.

Effect of rhBMP-2 dose on bone formation/maturation in a rat critical-size calvarial defect model.

BACKGROUND: Application of recombinant human bone morphogenetic protein-2 (rhBMP-2) has been associated with significant adverse events in craniofacial settings, including swelling and seroma formation. Recent work has demonstrated an inverse relationship between bone formation/maturation and rhBMP-2 dose, frequency/severity of adverse events increasing with rising dose. OBJECTIVE: The objective of this study was to determine the most effective dose for rhBMP-2 soak-loaded onto an absorbable collagen sponge (ACS) carrier for bone formation/maturation using an established defect model. METHODS: One hundred sixty-eight outbred male Sprague-Dawley rats, age 11-13 weeks, weight 325-375 g randomized into seven groups of 24 subdivided into groups of eight, were used to provide radiographic and light microscopy observations of bone formation/maturation and aberrant healing events at 2, 4 and 8 weeks following application of rhBMP-2/ACS into critical-size, ø8-mm, through-through, calvarial osteotomy defects for a dose of 1.25, 2.5, 5.0, 10.0 and 20.0 µg rhBMP-2/defect, or serve as ACS or sham-surgery controls. RESULTS: rhBMP-2 dosages ≥ 2.5 µg/defect showed histological defect closure >90% within 2 weeks, and complete resolution within 4 weeks. Adverse healing events including swelling, excessive bone formation or seroma formation could not be determined with certainty in this defect model. Notably ACS control sites showed complete defect closure at the 8-week healing interval. CONCLUSIONS: rhBMP-2/ACS accelerates local bone formation in the rat critical-size through-through calvarial defect model once reaching an osteoinductive dose threshold. This threshold may already be reached at a 1.25-/2.5-µg dose in this model. No further enhancement to bone formation/maturation may be observed adding rhBMP-2 above the 2.5-µg dose. The 1.25-20.0 µg dose range did not invoke appreciable aberrant healing events.

Variance of matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) concentrations in activated, concentrated platelets from healthy male donors.

BACKGROUND: The use of autologous blood concentrates, such as activated, concentrated platelets, in orthopaedic clinical applications has had mixed results. Research on this topic has focused on growth factors and cytokines, with little directed towards matrix metalloproteinases (MMPs) which are involved in post-wound tissue remodeling. METHODS: In this study, the authors measured the levels of MMP-2, MMP-9 and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), in activated platelets derived from blood of healthy, male volunteers (n = 92), 19 to 60 years old. The levels of the natural inhibitors of these proteases, tissue inhibitor of metalloproteinase 1 (TIMP-1), TIMP-2 and TIMP-4 were also assessed. RESULTS: Notably, there was no significant change in concentration with age in four of six targets tested. However, TIMP-2 and TIMP-4 demonstrated a statistically significant increase in concentration for subjects older than 30 years of age compared to those 30 years and younger (P = 0.04 and P = 0.04, respectively). CONCLUSION: TIMP-2 and TIMP-4 are global inhibitors of MMPs, including MMP-2 (Gelatinase A). MMP-2 targets native collagens, gelatin and elastin to remodel the extracellular matrix during wound healing. A decreased availability of pharmacologically active MMP-2 may diminish the effectiveness of the use of activated, concentrated platelets from older patients, and may also contribute to longer healing times in this population.

Regaining apical patency after obturation with gutta-percha and a sealer containing mineral trioxide aggregate.

INTRODUCTION: MTA Fillapex (Angelus Solucoes Odontologicas, Londrina PR, Brazil) was introduced as a mineral trioxide aggregate (MTA)-based sealer used for endodontic obturation. There is a lack of research that evaluates the ability of different solvents to soften MTA-based sealers during retreatment. This study tested the ability of 4 commonly used endodontic solvents to soften gutta-percha and MTA Fillapex to allow for the re-establishment of apical patency. METHODS: Eighty-six extracted maxillary anterior teeth were instrumented to the working length to a size 45 (.04 taper size). Teeth were divided into 2 groups (n = 43 for each group). MTA Fillapex was placed into all canals. Group 1 was obturated with gutta-percha to the working length, and group 2 was obturated 2 mm short of the working length to ensure the apical 2 mm was filled with sealer only. Both groups were divided into 4 subgroups (n = 10). The remaining teeth served as the control group. Each subgroup was exposed to 1 of the following solvents: chloroform, Endosolv R (Septodont, Saint-Maur, France), Endosolv E (Septodont), or eucalyptol. RESULTS: Patency was re-established in 100% of the teeth in groups 1 and 2 when tested with chloroform or Endosolv E, 80% of the teeth in group 1 and 90% in group 2 when tested with eucalyptol, and 10% of the teeth in group 1 and 50% in group 2 tested when with Endosolv R. The chi-square test indicated there was a statistical difference between Endosolv R and the other tested solvents for both groups. CONCLUSIONS: Chloroform, Endosolv E, and Eucalyptol soften GP and MTA Fillapex sufficiently to aid in re-establishing apical patency during endodontic retreatment.

Synthesis of osteotropic hydroxybisphosphonate derivatives of fluoroquinolone antibacterials.

1-Hydroxybisphosphonate derivatives of ciprofloxacin, gatifloxacin and moxifloxacin have been synthesized using Cu(I) catalyzed azide-alkyne 1,3-dipolar cycloaddition reaction. The 1,2,3-triazol linked hydroxybisphosphonate derivative of ciprofloxacin exhibited antibacterial activity comparable to the parent antibiotic and all fluoroquinolone-bisphosphonates displayed osteotropic properties in a bone model.

The effects of enamel matrix derivative and cyclic mechanical strain on human gingival fibroblasts in an in vitro defect healing model.

Gingival fibroblasts (GFs) play a considerable role in the maintenance of the gingival apparatus as well as in connective tissue repair. Mobility of a periodontal wound or soft tissue graft can impair connective tissue healing from the GFs. Enamel matrix derivative (EMD) is an enamel matrix protein used clinically for periodontal regeneration of intrabony defects and furcations, as well as treatment of gingival margin recessions. The goal of this project was to compare the effects of varying concentrations of EMD, with and without cyclic mechanical strain, on cellular wound fill of human GFs using an in vitro defect healing model. GFs were seeded and cultured in six-well flexible-bottomed plates. A 3-mm wound was created in the central portion of each confluent well. Three wells were treated with each EMD concentration of 0 Μg/mL (control), 30 Μg/mL, 60 Μg/mL, or 120 Μg/mL. The plates were placed in an incubator containing a strain unit to subject test plates to cyclic strain. An identical set of control plates were not flexed. Cells were examined on days 4, 8, 12, and 16. Microphotographs were taken and wound fill measurements made using image analysis software. The percent wound fill was calculated. All nonflexed plates, regardless of EMD concentration, reached > 90% defect fill at similar rates by day 16. However, in the flexed plates, EMD had a significant negative effect on defect fill. The defect fill was 55.7% for 0 Μg/mL EMD, 48.2% for 30 Μg/mL EMD, 36.7% for 60 Μg/mL EMD, and 34.1% for 120 Μg/mL EMD on day 16 for the flexed GFs. EMD, in concentrations as high as 120 Μg/mL, did not significantly affect the amount of defect fill with nonflexed GFs. However, when the GFs were flexed, the addition of EMD had a significant negative effect on defect fill in a dose-dependent manner.

Effect of systemic parathyroid hormone (1-34) and a beta-tricalcium phosphate biomaterial on local bone formation in a critical-size rat calvarial defect model.

OBJECTIVE: The objective of this study was to evaluate local bone formation following systemic administration of parathyroid hormone (1-34) (PTH), a surgically implanted synthetic beta-tricalcium phosphate (beta-TCP) bone biomaterial serving as a matrix to support new bone formation. MATERIALS AND METHODS: Critical-size, 8 mm, calvarial through-and-through osteotomy defects were surgically created in 100 adult male Sprague-Dawley rats. The animals were randomized into five groups of 20 animals each to receive one of the following treatments: PTH (15 microg PTH/kg/day; subcutaneously), PTH/beta-TCP, beta-TCP, or particulate human demineralized freeze-dried bone (DFDB), and sham-surgery controls. Ten animals/group were euthanized at 4 and 8 weeks post-surgery for radiographic and histometric analysis. RESULTS: The histometric analysis showed that systemic PTH significantly enhanced local bone formation, bone fill averaging (+/-SE) 32.2+/-4.0% compared with PTH/beta-TCP (15.7+/-2.4%), beta-TCP (12.5+/-2.3%), DFDB (14.5+/-2.3%), and sham-surgery control (10.0+/-1.5%) at 4 weeks (p<0.014). Systemic PTH showed significantly enhanced bone formation (41.5+/-4.0%) compared with PTH/beta-TCP (22.4+/-3.0%), beta-TCP (21.3+/-4.4%), and with the sham-surgery control (23.8+/-4.2%) at 8 weeks (p<0.025). The DFDB group showed significantly increased bone formation from 4 (14.5+/-2.3%) to 8 weeks (32.0+/-3.2%) (p<0.006). The PTH/beta-TCP and beta-TCP groups both showed limited biomaterials resorption. The radiographic analysis was not diagnostic to distinguish local bone formation from the radiopaque beta-TCP biomaterial. CONCLUSIONS: Systemic administration of PTH significantly stimulates local bone formation. Bone formation was significantly limited by the beta-TCP biomaterial.

Radiographic interpretation of experimental lesions in radicular tooth structure of human maxillary anterior teeth.

External resorption is often first detected radiographically. Early detection can lead to timely intervention and improvement of treatment outcome. The purpose of this study was to determine the minimal radicular defect size in maxillary anterior teeth that is radiographically detectable. Six teeth were selected in a cadaver maxilla (#6-11) and extracted. The teeth were then replanted in the maxilla, and three horizontally angled radiographs (0 degrees , 30 degrees from the mesial, and 30 degrees from the distal) were exposed as a baseline. Then, a sequence of tooth removal, placement of a 0.1-mm deep defect in the interproximal and midroot surface, tooth replantation, and radiograph exposure was begun and repeated eight times. Each time the defect depth was increased by 0.1 mm. Ten clinicians interpreted the subsequent radiographs to determine if they visualized a defect on each tooth and the location of the defect. The evaluators' ability to detect experimental lesions according to the depth of the defect was shown to be statistically significant for both tooth type and location of the radicular defect (analysis of variance, p < 0.05). The average size of defect needed for radiographic visualization was as follows: central incisor (0.28 mm on the interproximal [IP] and 0.74 mm on the midroot [MR] [palatal], lateral incisor (0.39 mm on the IP and 0.55 mm on the MR); and canine [0.45 mm on the IP and 0.71 mm on the MR). Based on the results of this study, the minimal defect size detected was 0.28 mm to 0.74 mm depending on defect location and tooth selected.

An acute osteomyelitis model in traumatized rat tibiae involving sand as a foreign body, thermal injury, and bimicrobial contamination.

The multfactorial nature of bone injuries in modern warfare and emergency trauma patients warrants enhancement of existing models. To develop a more appropriate model, rat tibiae (n = 195) were mechanically injured, divided into 2 groups (with or without thermal injury), and contaminated with a range of Staphylococcus aureus (Cowan 1) inocula. In some experiments, S. aureus inocula also contained Escherichia coli or foreign bodies (sand or soil). The primary outcome measure was the amount of S. aureus remaining in the tibia (tibial bacterial load) 24 h after contamination, reported as log10 cfu/g bone. S. aureus showed ID50 and ID95 values of 72 and 977 cfu, respectively. Values were lower than seen previously by using S. aureus strain SMH. S. aureus tibial bacterial loads were higher in tibiae with mechanical and thermal injury (log10 4.15 +/- 0.27 cfu/g) versus mechanical injury alone (log10 3.1 +/- 0.47 cfu/g, P = 0.028). The addition of E. coli to the S. aureus inoculum had no effect on tibial bacterial loads (S. aureus only, log10 4.24 +/- 0.92 cfu/g; S. aureus + E. coli, log10 4.1 +/- 1.0 cfu/g, P = 0.74). Sand, added as a foreign body, increased tibial bacterial load. Combined mechanical and thermal trauma of the tibia is associated with increased S. aureus tibial bacterial loads, increasing the risk of acute osteomyelitis. Understanding the interplay of mechanical and thermal injuries, bimicrobial contamination, and foreign bodies may improve our understanding of traumatic bone injuries and the pathogenesis of osteomyelitis.

Influence of matrix-suspended demineralized bone on osseous repair using a critical-sized defect in the rat (Rattus norvegicus) calvarium.

Demineralized freeze-dried bone (DFDB) in matrix form must be rehydrated with a carrier medium which allows for easy manipulation during periodontal surgery. The purpose of this study was to evaluate how human DFDB suspended in a polyol matrix affects new bone formation in the rat calvarium critical-sized defect (CSD) model. Fifty-five adult male Harlan Sprague-Dawley rats were assigned to 1 of 5 treatment groups: polyol, 100% DFDB, 47% DFDB/polyol, 47% DFDB, or an unfilled control. They were then placed into 8-m calvarial CSDs. The bone donor source company for the DFDB and DFDB/polyol groups was the same. Calvaria were harvested 10 weeks after surgery and evaluated histomorphometrically. The diameter of bone particles from the 3 groups containing DFDB was measured by scanning electron microscopy. There was no statistically significant difference in the percentage of bone fill between any of the groups, although the 100% DFDB group exhibited the most bone fill. The 47% DFDB/polyol and 47% DFDB groups had similar amounts of bone formation. The average size of the demineralized bone particles from the 100% DFDB group was significantly smaller than that of the other 2 groups containing DFDB. Adding a polyol to DFDB produced similar osseous regeneration in the rat calvarium defect model vs DFDB alone. Yet from a clinical standpoint, the polyol enhanced graft handling and stability. Graft particle size may have an effect on bone fill.

Comparative study of the variability of 0.06 tapered rotary endodontic files to current taper standards.

This study compared the taper variation among Profile, Guidance, and EndoSequence 0.06 tapered rotary files to current standards. Fifteen files of sizes 35, 40, and 45 from each manufacturer were evaluated for a total of 135 files. A digital image of the first 4 mm of each file was captured with light microscope at 22x, calibrated for 0.001-mm accuracy, and analyzed. The diameter of each file was measured at 1 and 4 mm, and the taper was calculated. Of the 3 file systems, 100% of the Profile files, 97.8% of the Guidance files, and 86.7% of the EndoSequence files fell within +/-0.02 taper. All file systems demonstrated variability within their groups. A series of chi(2) analyses indicated that manufacturers tend to produce Guidance and Profile tapers slightly under the ideal 0.06 taper (P < .05). The tapers of EndoSequence files were just as likely to be over or under the advertised 0.06 taper (P > .05).

Unevenness of the apical constriction in human maxillary central incisors.

This study examined the incisoapical extent of the apical constriction in 45 human maxillary central incisors. The null hypothesis was that the apical constriction is a flat ring. Our working hypothesis was that the constriction is actually uneven or "skewed" as it traces a path around the circumference of the canal. Teeth were split and imaged with 25x magnification, and the most apical and coronal limits of the apical constriction were identified and measured. Analysis of the data indicates that a majority (>70%) of maxillary central incisors exhibit an unevenness or "skew" of the apical constriction of greater than 100 microm in the incisoapical dimension, with a maximum measured skew of 385 microm. On the basis of the results of this study, a statistically significant (P < .05) variation in the longitudinal position of the apical constriction around its circumference was confirmed in maxillary central incisors.