Gerhard Wahl

Regulation of NAMPT in Human Gingival Fibroblasts and Biopsies

Adipokines, such as nicotinamide phosphoribosyltransferase (NAMPT), are molecules, which are produced in adipose tissue. Recent studies suggest that NAMPT might also be produced in the tooth-supporting tissues, that is, periodontium, which also includes the gingiva. The aim of this study was to examine if and under what conditions NAMPT is produced in gingival fibroblasts and biopsies from healthy and inflamed gingiva. Gingival fibroblasts produced constitutively NAMPT, and this synthesis was significantly increased by interleukin-1β and the oral bacteria P. gingivalis and F. nucleatum. Inhibition of the MEK1/2 and NFκB pathways abrogated the stimulatory effects of F. nucleatum on NAMPT. Furthermore, the expression and protein levels of NAMPT were significantly enhanced in gingival biopsies from patients with periodontitis, a chronic inflammatory infectious disease of the periodontium, as compared to gingiva from periodontally healthy individuals. In summary, the present study provides original evidence that gingival fibroblasts produce NAMPT and that this synthesis is increased under inflammatory and infectious conditions. Local synthesis of NAMPT in the inflamed gingiva may contribute to the enhanced gingival and serum levels of NAMPT, as observed in periodontitis patients. Moreover, local production of NAMPT by gingival fibroblasts may represent a possible mechanism whereby periodontitis may impact on systemic diseases.

Long-term effects of vertical bone augmentation: a systematic review

ABSTRACT Extraction, periodontitis, or trauma can cause a reduction on the alveolar ridge. This could result in an insufficient alveolar bone width and height. Different techniques of vertical bone augmentation are described in literature. However, nowadays there is not enough evidence against lateral augmentation procedures to verify if these techniques are stable over a long period of time. Objective This review analyses the different techniques that are used to vertically augment the bone and evaluate if these techniques are stable over a long period of time. Material and Methods The MEDLINE-PubMed database was searched from its earliest records until December 22, 2014. The following search term was used: Alveolar Ridge augmentation [MESH]. Several journals were hand searched and some authors were contacted for additional information. The primary outcome measure that was analyzed was marginal bone level change around dental implants in the augmented sites, and the secondary outcomes were survival and success rates of dental implants placed in the augmented sites. Results The search yielded 203 abstracts. Ultimately, 90 articles were selected, describing 51 studies meeting the eligibility criteria. The marginal bone level change for the inlay technique and vertical guided bone regeneration are in agreement with the success criteria. Alveolar distraction showed more marginal bone level change after the first year of loading, and for the inlay technique very few studies were available. Conclusions Based on the available data in the current existing studies with a follow-up period of at least 4 to 5 years, one can summarize that there seems to be a trend that the onlay technique, alveolar distraction, and vertical guided bone regeneration are stable for at least 4 to 5 years.

Comparison of the Accuracy of Cone Beam Computed Tomography and Medical Computed Tomography: Implications for Clinical Diagnostics with Guided Surgery

PURPOSE This study compared the accuracy of cone beam computed tomography (CBCT) and medical-grade CT in the context of evaluating the diagnostic value and accuracy of fiducial marker localization for reference marker-based guided surgery systems. MATERIALS AND METHODS Cadaver mandibles with attached radiopaque gutta-percha markers, as well as glass balls and composite cylinders of known dimensions, were measured manually with a highly accurate digital caliper. The objects were then scanned using a medical-grade CT scanner (Philips Brilliance 64) and five different CBCT scanners (Sirona Galileos, Morita 3D Accuitomo 80, Vatech PaX-Reve3D, 3M Imtech Iluma, and Planmeca ProMax 3D). The data were then imported into commercially available software, and measurements were made of the scanned markers and objects. CT and CBCT measurements were compared to each other and to the caliper measurements. RESULTS The difference between the CBCT measurements and the caliper measurements was larger than the difference between the CT measurements and the caliper measurements. Measurements of the cadaver mandible and the geometric reference markers were highly accurate with CT. The average absolute errors of the human mandible measurements were 0.03 mm for CT and 0.23 mm for CBCT. The measurement errors of the geometric objects based on CT ranged between 0.00 and 0.12 mm, compared to an error range between 0.00 and 2.17 mm with the CBCT scanners. CONCLUSIONS CT provided the most accurate images in this study, closely followed by one CBCT of the five tested. Although there were differences in the distance measurements of the hard tissue of the human mandible between CT and CBCT, these differences may not be of clinical significance for most diagnostic purposes. The fiducial marker localization error caused by some CBCT scanners may be a problem for guided surgery systems.

Development and design of a novel loading device for the investigation of bone adaptation around immediately loaded dental implants using the reindeer antler as implant bed

The assessment of the behavior of immediately loaded dental implants using biomechanical methods is of particular importance. The primary goal of this investigation is to optimize the function of the implants to serve for immediate loading. Animal experiments on reindeer antlers as a novel animal model will serve for investigation of the bone remodeling processes in the implant bed. The main interest is directed towards the time and loading-dependant behavior of the antler tissue around the implants. The aim and scope of this work was to design an autonomous loading device that has the ability to load an inserted implant in the antler with predefined occlusal forces for predetermined time protocols. The mechanical part of the device can be attached to the antler and is capable of cyclically loading the implant with forces of up to 100 N. For the calibration and testing of the loading device a biomechanical measuring system has been used. The calibration curve shows a logarithmic relationship between force and motor current and is used to control the force on the implant. A first test on a cast reindeer antler was performed successfully.

Immunohistochemical analysis of the gingiva with periodontitis of type I plasminogen deficiency compared to gingiva with gingivitis and periodontitis and healthy gingiva.

OBJECTIVE Type I plasminogen deficiency (Plgdef) is an uncommon chronic inflammation of mucous membranes. Gingival enlargements usually proceed with progressive periodontal destruction and tooth-loss. Plasmin(ogen)-independent enzymatic mechanisms for fibrin clearance have already been discussed in the literature. Our primary objective was to verify, immunohistochemically, the occurrence of different enzymatic factors involved in tissue breakdown of inflamed compared to healthy gingiva. Secondly, we tried to find out, if these patients have a similar microbiological profile to the patients with known gingivitis and periodontitis. MATERIALS AND METHODS Immunohistochemical analysis of enzymes elastase, plasminogen (plg), cathepsin G, matrix-metalloproteinase (MMP)-3 and MMP-7 and of glycoprotein fibrinogen were performed with gingival tissues from 3 healthy controls, 8 patients with Plgdef and 3 patients with gingivitis and periodontitis. Furthermore, plaque from 5 patients with plasminogen deficiency were also obtained to determine the microbiological profile. RESULTS Significantly high numbers of elastase positive leukocytes were detected in all samples. Staining for MMP-3 and MMP-7 was seen in samples with gingivitis and periodontitis with a stronger staining in samples with periodontitis by Plgdef. Fibrinogen was detectable in all samples. Staining for plg was stronger in samples with periodontitis than in other samples. Staining for cathepsin G was weak in gingivitis and periodontitis. Subgingival microbial flora showed elevated colony forming units of Prevotella intermedia/nigrescens, Fusobacterium spp., Eikenella corrodens, Porphyromonas gingivalis and viridans streptococci. CONCLUSION Strong staining of elastase, MMP-3 and MMP-7 and weak staining of plg in Plgdef samples supports the plasmin(ogen) - independent fibrin clearance. Similar subgingival microbiological flora was observed in periodontitis with Plgdef as in other periodontal diseases. Further investigations should determine the exact pathomechanism and focus on effective treatment methods of this entity.

Clinical and radiographic outcome of dental implants supporting fixed prostheses: the relevance of cortical bone formation.

Purpose:To evaluate the hard and the soft tissue parameters around implants supporting fixed prostheses over a period of 5 years and the possible association to the increase in periimplant bone density (IPBD). Material and Methods:A total of 39 dental implants placed in 29 patients were included in the study. Periimplant clinical (gingival index, probing depth, keratinized mucosa, sulcus fluid flow rate) and radiographic variables (bone loss, bone density) were collected, and the data analysis performed. Results:Periimplant hard and soft tissue parameters remained stable throughout the follow-up period. Of the 39 implants, 20 demonstrated IPBD. The mean distance between first bone-to-implant contact and the microgap for implants with and without IPBD was significantly different at 1-year, 2-year, and 5-year follow-up. The evidence of IPBD demonstrated no influence on the periimplant soft tissue parameters. All mean values of bone density for implants with IPBD were higher than those for implants without IPBD throughout the whole observation period. Conclusion:All implants were clinically successful over the period of follow-up. IPBD might be more indicative of a stable periimplant bone level.

Determination of the frictional coefficient of the implant-antler interface: experimental approach.

Abstract The similar bone structure of reindeer antler to human bone permits studying the osseointegration of dental implants in the jawbone. As the friction is one of the major factors that have a significant influence on the initial stability of immediately loaded dental implants, it is essential to define the frictional coefficient of the implant-antler interface. In this study, the kinetic frictional forces at the implant-antler interface were measured experimentally using an optomechanical setup and a stepping motor controller under different axial loads and sliding velocities. The corresponding mean values of the static and kinetic frictional coefficients were within the range of 0.5–0.7 and 0.3–0.5, respectively. An increase in the frictional forces with increasing applied axial loads was registered. The measurements showed an evidence of a decrease in the magnitude of the frictional coefficient with increasing sliding velocity. The results of this study provide a considerable assessment to clarify the suitable frictional coefficient to be used in the finite element contact analysis of antler specimens.

Sika deer antler as a novel model to investigate dental implant healing: A pilot experimental study

Dental implants are important tools for restoring the loss of teeth. The rapid growth and periodic regeneration of antlers make Sika deer a good and less invasive alternative model for studying bone remodelling in mammals. We developed a special loading device for antlers and analysed the bone reaction around unloaded implants and under immediate loading conditions until osseointegration occurred. In micro-computed tomography images, the density of antler tissue around the implants increased as the loading time increased. This finding was histologically confirmed by the good osseointegration observed in unloaded and loaded specimens. Antler tissue displays a similar healing process to human bone. The use of an antler model is a promising alternative for implant studies that does not require animal sacrifice.

Numerical investigation of bone remodelling around immediately loaded dental implants using sika deer (Cervus nippon) antlers as implant bed

Abstract This study combines finite element method and animal studies, aiming to investigate tissue remodelling processes around dental implants inserted into sika deer antler and to develop an alternative animal consuming model for studying bone remodelling around implants. Implants were inserted in the antlers and loaded immediately via a self-developed loading device. After 3, 4, 5 and 6 weeks, implants and surrounding tissue were taken out. Specimens were scanned by μCT scanner and finite element models were generated. Immediate loading and osseointegration conditions were simulated at the implant-tissue interface. A vertical force of 10 N was applied on the implant. During the healing time, density and Young’s modulus of antler tissue around the implant increased significantly. For each time point, the values of displacement, stresses and strains in the osseointegration model were lower than those of the immediate loading model. As the healing time increased, the displacement of implants was reduced. The 3-week immediate loading model (9878 ± 1965 μstrain) illustrated the highest strains in the antler tissue. Antler tissue showed similar biomechanical properties as human bone in investigating the bone remodelling around implants, therefore the use of sika deer antler model is a promising alternative in implant biomechanical studies.

Characterization of a diet-induced obesity rat model for periodontal research

ObjectivesObesity is associated with periodontitis, but the mechanisms underlying this association have yet to be unraveled. The present investigation was to evaluate a common rat model, in which obesity is induced by high-fat, high-sucrose diet (HFSD), for its applicability in periodontal research.Materials and methodsTen male Wistar rats were fed a 3-month HFSD along with a matching control group. Afterwards, the body weight, adipocyte morphology, leptin and adiponectin levels in adipose tissue, gingiva, and serum as well as the serum levels of triglyceride, cholesterol, and glucose were analyzed. For statistical analyses, parametric and non-parametric tests were applied (p < 0.05).ResultsBody weight was significantly higher in the HFSD group after dieting as compared to control. HFSD caused a significant increase in serum triglyceride, low-density lipoprotein cholesterol, and leptin levels and a significant decrease in high-density lipoprotein cholesterol. Furthermore, adipose tissue from HFSD rats exhibited significantly larger adipocytes, displayed a significant upregulation of leptin and, surprisingly, elevated adiponectin levels, which is in contrast to chronic obesity in humans. Although leptin and adiponectin were also observed in gingival biopsies, no obvious differences between the groups were found.ConclusionsAlthough this rat diet-induced obesity model is characterized by changes typical of obesity, it also has limitations, which have to be considered when data, especially with regard to adipokines, are extrapolated to humans.Clinical relevanceThe rodent diet-induced obesity model may be useful for unraveling pathomechanisms underlying the association between obesity and periodontal destruction but conclusions have to be drawn with caution.