Biegefestigkeit von Verblendkeramiken für Zirkoniumdioxid : hat die Prüfmethode einen Einfluss auf die Werte?

Die klinische Zuverlässigkeit von Zirkoniumdioxid-Restaurationen wird diskutiert. Das Hauptproblem scheint die erhöhte Frakturrate der Verblendungen zu sein. Die Festigkeit der Verblendkeramiken ist dabei einer der Faktoren, die die Stabilität der gesamten Restauration bestimmen. Deshalb war es das Ziel der vorliegenden Untersuchung, die Biegefestigkeit von Verblendkeramiken für Zirkoniumdioxid vergleichend zu untersuchen. Die Festigkeitswerte wurden mit drei verschiedenen Messmethoden ermittelt und denjenigen von Verblendmassen für die Metallkeramik gegenübergestellt

Time efficiency and efficacy of a centralized computer-aided-design/computer-aided-manufacturing workflow for implant crown fabrication: A prospective controlled clinical study

OBJECTIVE To assess time efficiency and the efficacy of the prosthetic manufacturing for implant crown fabrication in a centralized workflow applying computer aided design and computer aided manufacturing (CAD-CAM). MATERIAL AND METHODS Fifty-nine patients with one posterior implant each, were randomly allocated to either a centralized digital workflow (c-DW, test) or a laboratory digital workflow (l-DW, control). Patients were excluded from efficiency and efficacy analyses, if any additional restoration than this single implant crown had to be fabricated. A customized titanium abutment and a monolithic zirconia crown were fabricated in the c-DW. In the l-DW, models were digitalized for CAD-CAM fabrication of a monolithic zirconia crown using a standardized titanium base abutment. Time for impression, laboratory operating and delivery time were recorded. The efficacy of the prosthetic manufacturing was evaluated at try-in and at delivery. Data was analyzed descriptively. Statistical analyses using student's unpaired t- and paired Wilcoxon were performed (p < 0.05). RESULTS At impression taking, 12 patients (c-DW) and 19 patients (l-DW) were included. The impression time was 9.4±3.5 min (c-DW) and 15.1 ± 4.6 min (l-DW) (p < 0.05). The laboratory operating time was 130 ± 31 min (c-DW) and 218.0±8 min (l-DW) (p < 0.05). The delivery time was significantly longer in the c-DW (5.9 ± 3.5 1 days) as compared to the l-DW (0.5±0.05 days). At try-in and at delivery, efficacy of prosthetic manufacturing was similar high in both workflows. CLINICAL RELEVANCE The c-DW was more time efficient compared to the lab-DW and rendered a similar efficacy of prosthetic manufacturing

Computer‐assisted bone augmentation, implant planning and placement: An in vitro investigation

Aim To assess in vitro the workflow for alveolar ridge augmentation with customised 3D printed block grafts and simultaneous computer-assisted implant planning and placement. Methods Twenty resin mandible models with an edentulous area and horizontal ridge defect in the region 34–36 were scanned with cone beam computed tomography (CBCT). A block graft for horizontal ridge augmentation in the region 34–36 and an implant in the position 35 were digitally planned. Twenty block grafts were 3D printed out of resin and one template for guided implant placement were stereolithographically produced. The resin block grafts were positioned onto the ridge defects and stabilised with two fixation screws each. Subsequently, one implant was inserted in the position 35 through the corresponding template for guided implant placement. Optical scans of the study models together with the fixated block graft were performed prior to and after implant placement. The scans taken after block grafting were superimposed with the virtual block grafting plan through a best-fit algorithm, and the linear deviation between the planned and the achieved block positions was calculated. The precision of the block fixation was obtained by superimposing the 20 scans taken after grafting and calculating the deviation between the corresponding resin blocks. The superimposition between the scans taken after and prior to implant placement was performed to measure a possible displacement in the block position induced by guided implant placement. The (98–2%)/2 percentile value was determined as a parameter for surface deviation. Results The mean deviation in the position of the block graft compared to the virtual plan amounted to 0.79 ± 0.13 mm. The mean deviation between the positions of the 20 block grafts measured 0.47 ± 0.2 mm, indicating a clinically acceptable precision. Guided implant placement induced a mean shift of 0.16 ± 0.06 mm in the position of the block graft. Conclusions Within the limitations of this in vitro study, it can be concluded that customised block grafts fabricated through CBCT, computer-assisted design and 3D printing allow alveolar ridge augmentation with clinically acceptable predictability and reproducibility. Computer-assisted implant planning and placement can be performed simultaneously with computer-assisted block grafting leading to clinically non-relevant dislocation of block grafts

Exploring the Microbiome of Healthy and Diseased Peri-Implant Sites Using Illumina Sequencing

Aim To compare the microbiome of healthy (H) and diseased (P) peri-implant sites and determine the core peri-implant microbiome. Materials and Methods Submucosal biofilms from 32 H and 35 P sites were analyzed using 16S rRNA sequencing (MiSeq, Illumina), QIIME and HOMINGS. Differences between groups were determined using Principal Coordinate Analysis (PCoA), t-tests and Wilcoxon rank sum test and FDR-adjusted. The peri-implant core microbiome was determined. Results PCoA showed partitioning between H and P at all taxonomic levels. Bacteroidetes, Spirochetes and Synergistetes were higher in P, while Actinobacteria prevailed in H (p\u3c0.05). Porphyromonas and Treponema were more abundant in P and while Rothia and Neisseria were higher in H (p\u3c0.05). The core peri-implant microbiome contained Fusobacterium, Parvimonas and Campylobacter sp. T. denticola and P. gingivalis levels were higher in P, as well as F. alocis, F fastidiosum and T. maltophilum (p\u3c0.05). Conclusion The peri-implantitis microbiome is commensal-depleted and pathogen-enriched, harboring traditional and new pathogens. The core peri-implant microbiome harbors taxa from genera often associated with periodontal inflammation

A prospective, controlled clinical trial evaluating the clinical radiological and aesthetic outcome after 5 years of immediately placed implants in sockets exhibiting periapical pathology

OBJECTIVE: The aim was to compare the clinical, aesthetic and radiological outcome of immediately placed implants in sockets with or without periapical pathology 5 years after placement. MATERIALS AND METHODS: Twenty-seven patients were followed 5 years after immediate implant placement (test-group: 12 patients with periapical pathologies; control-group: 15 patients without periapical pathology). Clinical (FMBS, FMPS, CAL, keratinized mucosa), aesthetical (length of clinical crown, Papilla index), and radiological (vertical distance implant shoulder to first bone to implant contact (IS-BIC)) parameters were assessed. Both 95% confidence intervals, as well as results of statistical tests (one-sample, two-sample, paired t-test) were provided. RESULTS: After 5 years the implant survival rate was 100% for all 27 implants. In the test group the width of the keratinized mucosa increased significantly over the observation period (0.8 ± 1.0 mm). Concerning aesthetic parameters at the 3-month as well as at the 5-year examination no statistically significant difference could be found between the two groups. In the control-group the papilla mesial and distal to the implant increased statistically significant during the observation period by 0.5 ± 0.5 and 0.4 ± 0.6 index score points, respectively. The position of the gingival margin at the implant site and the two neighboring teeth remained stable. At the 5-year visit IS-BIC measured between 1.4 ± 0.5 mm (mesial, control) and 1.7 ± 0.7 mm (distal, test), no significant difference could be found between the two groups. Over the observation period no statistically significant change of IS-BIC could be found in the test- as well as in the control-group. None of the examined radiographs revealed any signs of retrograde peri-implantitis. CONCLUSION: The replacement of teeth exhibiting periapical pathologies by implants placed immediately after tooth extraction can be a successful treatment modality with no disadvantages in clinical, aesthetical and radiological parameters to immediately placed implants into healthy sockets

Success of 6-mm Implants with Single-Tooth Restorations: A 3-year Randomized Controlled Clinical Trial

The aim of the study was to test whether implants of 6 mm in length perform equally well as 10-mm implants in terms of survival and marginal bone-level changes when supporting single crowns. Patients with a posterior single-tooth gap were randomly allocated to either the placement of a 6-mm (test) or 10-mm implant (control). The treatment protocol allowed for internal sinus lift but not for lateral bone augmentation. After a healing period of 10 wk, implants were loaded with screw-retained single crowns. Survival rates, number of pockets ≥5 mm, and bleeding-on-probing were assessed clinically. The change of marginal bone level and crown-to-implant ratios were analyzed by 2 examiners. Longitudinal intragroup analyses for marginal bone levels were performed applying the Wilcoxon signed rank test. Intergroup differences at baseline and at 3 y were compared using the Mann-Whitney U test. The effect of implant length and crown-to-implant ratio on changes of marginal bone level also was determined. Of 94 implants placed (47 test and 47 control), 78 implants (40 test and 38 control) were available for follow-up examination at 3 y of loading. One test implant was lost during the second year. Hence, implant survival was not significantly different between the 2 groups after 3 y (98% test; 100% control). We found no significant change in the crestal bone level from baseline to 3 y for test and control implants with -0.19 ± 0.62 mm and -0.33 ± 0.71 mm, respectively. The intergroup difference was not significant. Crown-to-implant ratios were not associated with a statistically significant difference in marginal bone loss. However, the number of sites with pockets ≥5 mm was significantly higher in the test group. Based on the 3-y assessment, the use of 6-mm implants can be considered a viable option when reconstructing posterior single tooth gaps (German Clinical Trials Registry: DRKS00006290)

Five-Year Survival of Short Single-Tooth Implants (6 mm): A Randomized Controlled Clinical Trial

The aim of the present study was to evaluate whether 6-mm dental implants in the posterior segments of either jaw perform equally well in terms of clinical and radiographic outcomes when compared with 10-mm implants after 5 y of loading. Patients with single-tooth gaps in the posterior area who were scheduled for implant therapy were randomly assigned to a group receiving either a 6- or 10-mm implant. After a healing period of 10 wk, implants were loaded with a screw-retained single crown and followed up at yearly intervals. Of 96 patients, 86 could be recalled after 5 y. The implant survival rates amounted to 91% (95% confidence interval: 0.836 to 0.998) for the 6-mm group and 100% for the 10-mm group ( P = 0.036). Median crown-to-implant (C/I) ratios were 1.75 (interquartile range [IQR], 1.50 to 1.90) for the 6-mm group and 1.04 (IQR, 0.95 to 1.15) for the 10-mm group, whereas the median marginal bone levels measured -0.29 mm (IQR, -0.92 to 0.23) for the 6-mm group and -0.15 mm (IQR: -0.93 - 0.41) for the 10-mm group after 5 y. The C/I ratio turned out to be statistically significant ( P < 0.001), whereas marginal bone levels showed no significant difference between the groups. The 6-mm implants exhibited significantly lower survival rates than the 10-mm implants over 5 y, whereas there was no difference between upper and lower jaws in terms of survival ( P = 0.58). Lost implants did not show any sign of marginal bone loss or peri-implant infection previous to loss of osseointegration. High C/I ratio and implant length had no significant effect on marginal bone level changes or technical and biological complications (German Clinical Trials Registry: DRKS00006290)

A Novel Function of DELTA-NOTCH Signalling Mediates the Transition from Proliferation to Neurogenesis in Neural Progenitor Cells

A complete account of the whole developmental process of neurogenesis involves understanding a number of complex underlying molecular processes. Among them, those that govern the crucial transition from proliferative (self-replicating) to neurogenic neural progenitor (NP) cells remain largely unknown. Due to its sequential rostro-caudal gradients of proliferation and neurogenesis, the prospective spinal cord of the chick embryo is a good experimental system to study this issue. We report that the NOTCH ligand DELTA-1 is expressed in scattered cycling NP cells in the prospective chick spinal cord preceding the onset of neurogenesis. These Delta-1-expressing progenitors are placed in between the proliferating caudal neural plate (stem zone) and the rostral neurogenic zone (NZ) where neurons are born. Thus, these Delta-1-expressing progenitors define a proliferation to neurogenesis transition zone (PNTZ). Gain and loss of function experiments carried by electroporation demonstrate that the expression of Delta-1 in individual progenitors of the PNTZ is necessary and sufficient to induce neuronal generation. The activation of NOTCH signalling by DELTA-1 in the adjacent progenitors inhibits neurogenesis and is required to maintain proliferation. However, rather than inducing cell cycle exit and neuronal differentiation by a typical lateral inhibition mechanism as in the NZ, DELTA-1/NOTCH signalling functions in a distinct manner in the PNTZ. Thus, the inhibition of NOTCH signalling arrests proliferation but it is not sufficient to elicit neuronal differentiation. Moreover, after the expression of Delta-1 PNTZ NP continue cycling and induce the expression of Tis21, a gene that is upregulated in neurogenic progenitors, before generating neurons. Together, these experiments unravel a novel function of DELTA–NOTCH signalling that regulates the transition from proliferation to neurogenesis in NP cells. We hypothesize that this novel function is evolutionary conserved

A Model of Ischemia-Induced Neuroblast Activation in the Adult Subventricular Zone

We have developed a rat brain organotypic culture model, in which tissue slices contain cortex-subventricular zone-striatum regions, to model neuroblast activity in response to in vitro ischemia. Neuroblast activation has been described in terms of two main parameters, proliferation and migration from the subventricular zone into the injured cortex. We observed distinct phases of neuroblast activation as is known to occur after in vivo ischemia. Thus, immediately after oxygen/glucose deprivation (6–24 hours), neuroblasts reduce their proliferative and migratory activity, whereas, at longer time points after the insult (2 to 5 days), they start to proliferate and migrate into the damaged cortex. Antagonism of ionotropic receptors for extracellular ATP during and after the insult unmasks an early activation of neuroblasts in the subventricular zone, which responded with a rapid and intense migration of neuroblasts into the damaged cortex (within 24 hours). The process is further enhanced by elevating the production of the chemoattractant SDf-1α and may also be boosted by blocking the activation of microglia. This organotypic model which we have developed is an excellent in vitro system to study neurogenesis after ischemia and other neurodegenerative diseases. Its application has revealed a SOS response to oxygen/glucose deprivation, which is inhibited by unfavorable conditions due to the ischemic environment. Finally, experimental quantifications have allowed us to elaborate a mathematical model to describe neuroblast activation and to develop a computer simulation which should have promising applications for the screening of drug candidates for novel therapies of ischemia-related pathologies

Flexural strength of veneering ceramics for zirconia

OBJECTIVES: The flexural strengths of veneering ceramics for zirconia were compared. METHODS: With 10 different veneering ceramics for zirconia (test group) and three different veneering ceramics for the metal-ceramic technique (control group) three-point flexural strength and biaxial flexural strength according to ISO 6872: 1995 as well as four-point flexural strength according to EN 843-1: 2005 were measured (n=10). Statistical analysis was performed with one-way ANOVA and post hoc Scheffé test (SPSS, p<0.05). RESULTS: For the test group, three-point flexural strength ranged between 77.8+/-8.7 and 106.6+/-12.5MPa without any statistically significant differences, biaxial flexural strength between 69.1+/-4.8 and 101.4+/-10.5MPa with three homogeneous groups and four-point flexural strength between 59.5+/-6.2 and 89.2+/-9.5MPa with five homogeneous groups. The control group showed three-point flexural strength values ranging from 93.3+/-13.5 to 149.4+/-20.5MPa, biaxial flexural strength values from 93.4+/-10.0 to 141.2+/-11.6MPa, and four-point flexural strength values from 82.7+/-8.5 to 116.9+/-9.8MPa. In every case, the results of the four-point flexure test were significantly lower than those obtained in the three-point flexure test. The three-point flexural strengths of the test group are similar to those of two ceramics of the control group. The flexural strength of one ceramic of the control group significantly exceeded the strengths of all other ceramics investigated. CONCLUSION: Three-point flexural strength values of veneering ceramics for zirconia are similar to those of veneering ceramics for the metal-ceramic technique. The four-point flexure test among all three tests showed highest discrimination between the different ceramic materials