Ines Willershausen

Influence of β-tricalcium phosphate granule size and morphology on tissue reaction in vivo.

In this study the tissue reaction to five different β-tricalcium phosphate (β-TCP)-based bone substitute materials differing only in size, shape and porosity was analyzed over 60 days, at 3, 10, 15, 30 and 60 days after implantation. Using the subcutaneous implantation model in Wistar rats both the inflammatory response within the implantation bed and the resulting vascularization of the biomaterials were qualitatively and quantitatively assessed by means of standard and special histological staining methods. The data from this study showed that all investigated β-TCP bone substitutes induced the formation of multinucleated giant cells. Changes in size, shape and porosity influenced the integration of the biomaterials within the implantation bed and the formation of tartrate-resistant acid phosphatase (TRAP)-positive and TRAP-negative multinucleated giant cells, as well as the rate of vascularization. While a high porosity generally allowed cell and fiber in-growth within the center of the bone substitute, a lower porosity resulted in a mosaic-like integration of the materials, with the granules serving as place holders. The number of multinucleated giant cells located in the implantation bed positively correlated with the vascularization rate. These data emphasize that all biomaterials investigated were capable of inducing the formation of TRAP-positive multinucleated giant cells as a sign of biomaterial stability. Furthermore, these cells directly influenced vascularization by secretion of vascular endothelial growth factor (VEGF), as well as other chemokines. Based on these findings, the role of multinucleated giant cells in the foreign body reaction to biomaterials might need to be reconsidered. This study demonstrates that variations in the physical properties of a bone substitute material clearly influence the (extent of the) inflammatory reaction and its consequences.

Association between chronic dental infection and acute myocardial infarction.

INTRODUCTION In patients with cardiovascular diseases several risk factors such as high blood pressure, diabetes, smoking and drinking habits, genetic disposition, and chronic inflammation must be considered. The aim of this study was to investigate whether there is a correlation between dental origin infections and the presence of an acute myocardial infarction (AMI). METHODS A total of 125 patients who had experienced a myocardial infarction and 125 healthy individuals were included in this study. The oral examination was carried out following the consent of the ethics committee and the National Board for Radiation Protection and included the number of teeth, endodontically treated teeth, periodontal screening index (PSI), clinical attachment level, and radiographic apical lesions (radiograph examination). The medical examination included, among others, blood glucose level, C-reactive protein (CRP) serum levels, and leukocyte number. RESULTS The study demonstrated that patients with AMI exhibited an unfavorable dental state of health. After statistical adjustment for age, gender, and smoking, they exhibited a significantly higher number of missing teeth (P = .001), less teeth with root canal fillings (P = .0015), a higher number of radiologic apical lesions (P = .001), and a higher PSI value (P = .001) compared with individuals without myocardial infarction. The medical data showed a nonsignificant correlation between CRP and the number of radiologic apical lesions. CONCLUSIONS This study presents evidence that patients who have experienced myocardial infarction also exhibit an unfavorable dental state of health in comparison to healthy patients and suggests an association between chronic oral infections and myocardial infarction.

Evaluation of the tissue reaction to a new bilayered collagen matrix in vivo and its translation to the clinic

This study evaluates a new collagen matrix that is designed with a bilayered structure in order to promote guided tissue regeneration and integration within the host tissue. This material induced a mild tissue reaction when assessed in a murine model and was well integrated within the host tissue, persisting in the implantation bed throughout the in vivo study. A more porous layer was rapidly infiltrated by host mesenchymal cells, while a layer designed to be a barrier allowed cell attachment and host tissue integration, but at the same time remained impermeable to invading cells for the first 30 days of the study. The tissue reaction was favorable, and unlike a typical foreign body response, did not include the presence of multinucleated giant cells, lymphocytes, or granulation tissue. In the context of translation, we show preliminary results from the clinical use of this biomaterial applied to soft tissue regeneration in the treatment of gingival tissue recession and exposed roots of human teeth. Such a condition would greatly benefit from guided tissue regeneration strategies. Our findings demonstrate that this material successfully promoted the ingrowth of gingival tissue and reversed gingival tissue recession. Of particular importance is the fact that the histological evidence from these human studies corroborates our findings in the murine model, with the barrier layer preventing unspecific tissue ingrowth, as the scaffold becomes infiltrated by mesenchymal cells from adjacent tissue into the porous layer. Also in the clinical situation no multinucleated giant cells, no granulation tissue and no evidence of a marked inflammatory response were observed. In conclusion, this bilayered matrix elicits a favorable tissue reaction, demonstrates potential as a barrier for preferential tissue ingrowth, and achieves a desirable therapeutic result when applied in humans for soft tissue regeneration.

In vitro analysis of the cytotoxicity and the antimicrobial effect of four endodontic sealers

IntroductionThe aim of this study was to investigate in vitro the cytotoxicity and antibacterial properties of four different endodontic sealers using human periodontal ligament fibroblast cell proliferation and visual analysis of growth inhibition.MethodsA silicone (GuttaFlow), silicate (EndoSequence BC), zinc oxide eugenol (Pulp Canal Sealer EWT) and epoxy resin (AH Plus Jet) based sealer were incubated with PDL fibroblasts (104 cells/ml, n = 6) up to 96 h. Cell proliferation (RFU) was determined by means of the Alamar Blue assay. Cell growth and morphology was visualized by means of fluorescent dyes. Possible antibacterial properties of the different sealers were visualized by means of SEM (Enterococcus faecalis; Parvimonas micra).ResultsFibroblast proliferation depended on sealer and cultivation time. After 72 and 96 h GuttaFlow and EndoSequence BC showed relatively non-cytotoxic reactions, while Pulp Canal Sealer EWT and AH Plus Jet caused a significant decrease of cell proliferation (p < 0.001). Visualization of cell growth and morphology with various fluorescent dyes supplemented the results. No antibacterial effect of EndoSequence BC to P. micra was found, whereas GuttaFlow showed a weak, Pulp Canal Sealer EWT and AH Plus Jet extensive growth inhibition. Also, no antibacterial effect of GuttaFlow, EndoSequence BC or AH Plus Jet to E. faecalis could be detected.ConclusionsThese in vitro findings reveal that GuttaFlow and EndoSequence BC can be considered as biocompatible sealing materials. However, prior to their clinical employment, studies regarding their sealing properties also need to be considered.

Histological and histomorphometrical analysis of a silica matrix embedded nanocrystalline hydroxyapatite bone substitute using the subcutaneous implantation model in Wistar rats

The clinical suitability of a bone substitute material is determined by the ability to induce a tissue reaction specific to its composition. The aim of this in vivo study was to analyze the tissue reaction to a silica matrix-embedded, nanocrystalline hydroxyapatite bone substitute.The subcutaneous implantation model in Wistar rats was chosen to assess the effect of silica degradation on the vascularization of the biomaterial and its biodegradation within a time period of 6 months. Already at day 10 after implantation, histomorphometrical analysis showed that the vascularization of the implantation bed reached its peak value compared to all other time points. Both vessel density and vascularization significantly decreased until day 90 after implantation. In this time period, the bone substitute underwent a significant degradation initiated by TRAP-positive and TRAP-negative multinucleated giant cells together with macrophages and lymphocytes. Although no specific tissue reaction could be related to the described silica degradation, the biomaterial was close to being fully degraded without a severe inflammatory response. These characteristics are advantageous for bone regeneration and remodeling processes.

Implantation of silicon dioxide-based nanocrystalline hydroxyapatite and pure phase beta-tricalciumphosphate bone substitute granules in caprine muscle tissue does not induce new bone formation

BackgroundOsteoinductive bone substitutes are defined by their ability to induce new bone formation even at heterotopic implantation sites. The present study was designed to analyze the potential osteoinductivity of two different bone substitute materials in caprine muscle tissue.Materials and methodsOne gram each of either a porous beta-tricalcium phosphate (β-TCP) or an hydroxyapatite/silicon dioxide (HA/SiO2)-based nanocrystalline bone substitute material was implanted in several muscle pouches of goats. The biomaterials were explanted at 29, 91 and 181 days after implantation. Conventional histology and special histochemical stains were performed to detect osteoblast precursor cells as well as mineralized and unmineralized bone matrix.ResultsBoth materials underwent cellular degradation in which tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like cells and TRAP-negative multinucleated giant cells were involved. The ß-TCP was completely resorbed within the observation period, whereas some granules of the HA-groups were still detectable after 180 days. Neither osteoblasts, osteoblast precursor cells nor extracellular bone matrix were found within the implantation bed of any of the analyzed biomaterials at any of the observed time points.ConclusionsThis study showed that ß-TCP underwent a faster degradation than the HA-based material. The lack of osteoinductivity for both materials might be due to their granular shape, as osteoinductivity in goat muscle has been mainly attributed to cylindrical or disc-shaped bone substitute materials. This hypothesis however requires further investigation to systematically analyze various materials with comparable characteristics in the same experimental setting.

Non-cross-linked collagen type I/III materials enhance cell proliferation: in vitro and in vivo evidence

Objective To analyze Mucograft®(MG), a recently introduced collagen matrix, in vitro and in vivo, and compare it with BioGide®(BG), a well-established collagen membrane, as control. Material and Methods A detailed analysis of the materials surface and ultra-structure was performed. Cellular growth patterns and proliferation rates of human fibroblasts on MG and BG were analyzed in vitro. In addition, the early tissue reaction of CD-1 mouse to these materials was analyzed by means of histological and histomorphometrical analysis. Results MG showed a three-fold higher thickness both in dry and wet conditions, when compared to BG. The spongy surface of BG significantly differed from that of MG. Cells showed a characteristic proliferation pattern on the different materials in vitro. Fibroblasts tended to proliferate on the compact layers of both collagens, with the highest values on the compact side of BG. In vivo, at day three both materials demonstrated good tissue integration, with a mononuclear cell sheet of fibroblasts on all surfaces, however, without penetrating into the materials. Conclusions The findings of this study showed that MG and BG facilitate cell proliferation on both of their surfaces in vitro. In vivo, these two materials induce a comparable early tissue reaction, while serving as cell occlusive barriers.

Influence of a bioceramic root end material and mineral trioxide aggregates on fibroblasts and osteoblasts.

OBJECTIVE The biocompatibility of materials used in endodontic treatment is of high importance, because they can come in contact with periradicular tissues and there is a risk of possible systemic toxicity. The aim of the present study was to investigate the in vitro reaction to a bioceramic based root end material in comparison to mineral trioxide aggregates (MTA) as the established gold standard. DESIGN The root end materials grey MTA Angelus (GMTA), white MTA Angelus (WMTA), ProRoot MTA, and EndoSequence Root Repair Material (ERRM) were incubated with human periodontal ligament fibroblasts and osteoblasts (10(4)cells/ml) for up to 96h. Cell proliferation (RFU) was determined by means of the Alamar Blue assay. In addition, fluorescence staining was carried out to visually monitor cell growth and morphology. RESULTS For most of the observational time period of up to 96h, there was no statistically significant difference between the proliferation rates of the control cells and those in contact with ERRM. In contrast, the mineral trioxide based materials caused from 24 to 96h significantly lower proliferation rates in comparison to the controls (p<0.001). For proliferation rates of cells in contact with MTAs and ERRM significant differences were observed throughout the whole observation time for the osteoblasts, but only up to 24h for the human periodontal ligament fibroblasts. CONCLUSION Within the limits of this study the results suggest that the bioceramic root end material is biocompatible, but needs to be investigated in clinical studies before it can be recommended as retrograde sealer in endodontic practice.

Gingival crevicular fluid MMP-8-concentrations in patients after acute myocardial infarction

BackgroundThe aim of this study was to determine the presence of matrix metalloproteinase-8 in the gingival crevicular fluid (GCF) of patients after acute myocardial infarction (AMI).MethodsA total of 48 GCF samples from 20 AMI patients, hospitalized at the Department of Cardiology and Angiology of the Johannes Gutenberg University Mainz, were investigated. Besides the myocardial infarction all patients suffered from chronic periodontal disease. Fifty-one GCF samples from 20 healthy age matched individuals with similar periodontal conditions served as controls. The dental examination included the assessment of oral hygiene, gingival inflammation, probing pocket depth, clinical attachment level and X-ray examination. The study was only carried out after the positive consent of the regional ethic commission. A quantitative assessment of aMMP-8 levels in the gingival crevicular fluid was performed with the help of the DentoAnalyzer (Dentognostics GmbH, Jena, Germany), utilising an immunological procedure.ResultsThe aMMP-8 concentrations found in the gingival crevicular fluid of the AMI patients significantly differed (p = 0.001; mean value 30.33 ± 41.99 ng/ml aMMP-8) from the control group (mean value 10.0 ± 10.7 ng/ml aMMP-8). These findings suggest that periodontal inflammation in AMI patients might be associated with higher MMP-8-values compared to the healthy controls.ConclusionsThe acute myocardial infarction seems to influence the degree of periodontal inflammation, thus the measurement of the gingival crevicular fluid MMP8 levels seems to be a helpful biochemical test to obtain information about the severity of the periodontal disease.

Survey of root canal irrigating solutions used in dental practices within Germany.

AIM Irrigant usage information in relation to years of professional experience was collected from general dentists in different German federal states by means of a questionnaire. METHODOLOGY A short survey concerning endodontic treatment and use of irrigants was mailed to 4240 dentists or delivered to 3720 dental offices as an extra page in a journal in eight German states. Detailed information concerning the most frequently used irrigants, their concentrations, the spectrum of disinfectants used in root canal treatment concepts for vital and nonvital pulps, main topics of continuing education as well as years of professional experience was collected. The statistical analysis of differences found amongst the dentists in relation to professional experience or federal state was performed using the chi-square test. RESULTS Of a total of 7960 invitations, 1630 replies were evaluated (response rate 20.5%). The majority of the dentists (57.3%) had >20 years of professional experience, 23% had >30 years. Dentists with long-standing professional experience (20-30 years) used H2 O2 significantly more often than dentists with less experience (P < 0.001), and of the older colleagues (>30 years of professional experience), 14.6% never used NaOCl, whilst the younger colleagues almost always used it (P < 0.001). Differences were also found for the usage of irrigants amongst dentists from the various German states. CONCLUSIONS Whilst NaOCl was used in almost all states, regional differences were found regarding the choice of additional irrigants, which were mainly determined by the irrigation protocols taught at different universities.