Marginal and Internal Precision of Zirconia Four-Unit Fixed Partial Denture Frameworks Produced Using Four Milling Systems.

BACKGROUND: CAD/CAM systems enable the production of fixed partial dentures with small and reproducible internal and marginal gaps. PURPOSE: The purpose of this study was to evaluate the reproducibility of the marginal and internal adaptations of four-unit fixed partial denture frameworks produced using four CAD/CAM systems. MATERIALS AND METHODS: Prepared dies of a master model that simulated the loss of the first left molar were measured. Fifteen frameworks were manufactured using four CAD/CAM systems (A-D). The internal fit was determined by the replica technique, and the marginal gap was determined by microscopy. ANOVA was carried out to detect significant differences, and the Bonferroni adjustment was performed. The global level of significance was set at 5%. RESULTS: The mean gap size ranged from 84 to 132 µm (SD 43-71 µm). The CAD/CAM systems showed significant variance (p < 0.001), and system A (VHF) showed the smallest gaps. The smallest gaps for each system were in the molar part and in the marginal region of the frameworks (p < 0.001). CONCLUSIONS: The CAD/CAM systems showed significantly different gap sizes, particularly between premolars and molars and among the marginal, axial and occlusal regions. All of the systems are suitable for clinical application.

Does the Modification of the Apical Geometry of a Dental Implant Affect Its Primary Stability? A Comparative Ex Vivo Study.

(1) Background: Primary stability-one fundamental criterion for the success of dental implants-is influenced by implant geometry even if the effect of apical shape modifications on implant primary stability has not yet been examined. Therefore, the aim of the ex vivo study was to compare primary stability of implants differing in apically located screw threads (J-line) or a flat tip (K-line) only. (2) Methods: 28 implants of each group of the same diameter (4.3 mm) were randomly inserted into porcine bone blocks. The first group (9, 11 and 13 mm) was inserted into "hard", the second (11 mm) into "soft" bone, here using a normal and an undersized drilling protocol. Insertion torque (Ncm), Periotest® value, resonance frequency (implant stability coefficient, ISQ) and push-out force (N) were measured. (3) Results: In "hard" bone, primary stability increased with increasing length in both groups but it was significantly higher in J-line (p < 0.03). An undersized preparation of the implant bed in "soft" bone resulted in a significant increase in primary stability in both groups. Here, J-line also showed a significantly increased primary stability when compared to equally prepared K-line (insertion torque: 37 Ncm vs. 26 Ncm; Periotest®: -6.5 vs. -4.3; push-out force: 365 N vs. 329 N; p < 0.05 each). (4) Conclusions: Primary stability is significantly higher with increasing implant length and apically located screw threads as well as with undersized drilling protocols. When preparing the implant site and subsequently selecting the implant system, modifying factors such as implant geometry (also at the tip) should be taken into account.

Activation of Human Osteoblasts via Different Bovine Bone Substitute Materials With and Without Injectable Platelet Rich Fibrin in vitro.

INTRODUCTION: The aim of the in vitro study was to compare the effect of four bovine bone substitute materials (XBSM) with and without injectable platelet-reach fibrin for viability and metabolic activity of human osteoblasts (HOB) as well as expression of alkaline phosphatase (ALP), bone morphogenetic protein 2 (BMP-2), and osteonectin (OCN). MATERIALS AND METHODS: Cerabone® (CB), Bio-Oss® (BO), Creos Xenogain® (CX) and MinerOss® X (MO) ± i-PRF were incubated with HOB. At day 3, 7, and 10, cell viability and metabolic activity as well as expression of ALP, OCN, and BMP-2, was examined. RESULTS: For non-i-PRF groups, the highest values concerning viability were seen for CB at all time points. Pre-treatment with i-PRF increased viability in all groups with the highest values for CB-i-PRF after 3 and 7 and for CX-i-PRF after 10 days. For metabolic activity, the highest rate among non-i-PRF groups was seen for MO at day 3 and for CB at day 7 and 10. Here, i-PRF groups showed higher values than non-i-PRF groups (highest values: CB + i-PRF) at all time points. There was no difference in ALP-expression between groups. For OCN expression in non-i-PRF groups, CB showed the highest values after day 3, CX after day 7 and 10. Among i-PRF-groups, the highest values were seen for CX + i-PRF. At day 3, the highest BMP-2 expression was observed for CX. Here, for i-PRF groups, the highest increase was seen for CX + i-PRF at day 3. At day 7 and 10, there was no significant difference among groups. CONCLUSION: XBSM sintered under high temperature showed increased HOB viability and metabolic activity through the whole period when compared to XBSM manufactured at lower temperatures. Overall, the combination of XBSM with i-PRF improved all cellular parameters, ALP and BMP-2 expression at earlier stages as well as OCN expression at later stages.

The reproducibility of electronic color measurements of the marginal gingiva.

INTRODUCTION: This study evaluated the reproducibility of electronic color determination system evaluations of the marginal gingiva, which could be important for adhesive cervical fillings or prosthetic restorations that imitate the gingiva. MATERIAL AND METHODS: In 50 subjects, the L*, a*, and b* color coordinates were evaluated five times at a point in the marginal area of a central incisor using different electronic color determination systems: (SP) Shadepilot, (ES) Easyshade, (CE) Crystaleye, and (SV) X-Rite. The mean color difference (ΔE) and its standard deviation between the five measurements from each participant were calculated separately for each device. Further ICC for interdevice reliability was determined. RESULTS: The L*, a*, and b* color coordinates and ΔE values differed significantly among the systems (p < 0.001). Within each patient and measurement system, ΔE ranged from 1.4 to 3.2 (SD 1.1-2.5), L* from 2.6 to 5.7 (SD 2.6-5.7), a* from 11.9 to 21.3 (SD 3.6-3.9), and b* from 15.1 to 28.9 (SD 1.7-4.3). Interdevice reliability ranged between 0.675 and 0.807. CONCLUSIONS: Color determination of the marginal gingiva using the electronic tooth color determination systems tested herein showed limited reproducibility. The results obtained with the different measurement systems differed enormously. CLINICAL RELEVANCE: These results show that the electronic color measurement devices tested allow no high reproducible determination of color coordinates of the marginal gingiva.

A collagen membrane influences bone turnover marker in vivo after bone augmentation with xenogenic bone.

BACKGROUND: The aim was to compare early biochemical and histological osseous healing of chronic mandibular defects regenerated with bovine bone substitute with and without collagen membrane in vivo. METHODS: Eight weeks after formation of a lateral full-thickness perforating bone defect in the mandible of 40 rabbits, bovine bone substitute with ("+";n = 20) and without ("-";n = 20) collagen membrane was applied. Blood and bone was collected 24, 72 h, 7, 14 and 21 days after surgery. Total acid phosphatase, bone acid phosphatase, total alkaline phosphatase and bone alkaline phosphatase activities were compared between groups. Formation of new bone was quantified histologically for all time points. RESULTS: Twenty-four hours after surgery, bone alkaline phosphatase was significantly elevated in "+" group when compared to "-" (p=0.012). After 72 hours, all bone turnover markers except for total acid phosphatase (p=0.078) where significantly elevated in "+" (all p < 0.05). Fourteen days after surgery, the significant highest values for all bone turnover markers were detected in "-" (all p < 0.05). A significant difference in favor of group "-" could also be detected after 3 weeks in terms of both acid phosphatases (p < 0.05). In histology, no significant differences could be detected. CONCLUSION: Bone regeneration with bovine bone substitute material and collagen membrane shows a significantly earlier bone remodeling activity but does not seem to influence formation of new bone in histological samples.

Potential risk factors for early and late dental implant failure: a retrospective clinical study on 9080 implants.

BACKGROUND: The aim of this study was to analyze potential risk factors for early and late dental implant failure (DIF) in a clinical cohort trial. In a private practice, 9080 implants were inserted during a period of 10 years. In case of DIF, data were classified into early and late DIF and compared to each other in regard of gender, age, site of implantation, implant geometry, and patients' systemic diseases. RESULTS: Three hundred fifty-one implants failed within the observation period (survival rate: 96.13%). Early DIF occurred in 293 implants (83.48%) compared to late DIF in 58 implants (16.52%). Significant earlier DIF was seen in the mandible (OR = 3.729, p < 0.001)-especially in the posterior area-and in younger patients (p = 0.017), whereas an increased likelihood of late DIF was associated with maxillary implants (OR = 3.729, p < 0.001) and older patients. CONCLUSIONS: Early DIF is about twice as common as late DIF. Main risk factors for early DIF are implant location in the (posterior) mandible as well as younger age. On contrary, late DIF is rather associated with older patients, cancellous bone quality, and longer implants.

Implant primary stability depending on protocol and insertion mode - an ex vivo study.

BACKGROUND: Dental implant primary stability is thought to be a fundamental prerequisite for the long-term survival and success. The aim of this study was to analyze the influence of protocol and insertion mode on dental implant stability ex vivo. One hundred and twenty implants were inserted either manually or machine-driven into porcine mandibles by a standard or over-dimensioned protocol. Dental implant stability was measured via resonance frequency analysis (RFA), insertion torque (IT), and torque out (TO). RESULTS: Statistically significant higher IT and TO values were seen after standard protocol insertion (p < 0.05), whereas manual and machine-driven insertion mode showed equivalent values. CONCLUSIONS: The over-dimensioned protocol exceeded the primary stability values recommended for immediate implant insertion; therefore, it could be recommended as well.

Immobilization of BMP-2, BMP-7 and alendronic acid on titanium surfaces: Adhesion, proliferation and differentiation of bone marrow-derived stem cells.

This study analyzed the influence of titanium (TiO2 ) surface modifications with two osteogenic proteins (BMP-2, BMP-7) and an anti-osteoclastic drug (alendronic acid [AA]) on sandblasted/acid-etched (SLA) and plain TiO2 (PT) on cell adhesion, proliferation and differentiation (alkaline phosphatase [AP] and osteocalcin [OC]) of bone-marrow derived stem cells (BMSCs) after 1, 3 and 7 days in-vitro. Initially, AA surfaces showed the highest cell number and surface coverage. At day 3 and 7, BMP and AA-modified surfaces exhibited a significantly enhanced cell growth. For proliferation, at days 3 and 7, an enhancement on BMP-2, BMP-7 and AA-surfaces was seen. At day 7, SLA also showed a higher proliferation when compared to PT. Initially, AP expression was elevated on SLA and AA surfaces. At days 3 and 7, a significant increased AP expression was seen for SLA, BMP-2, BMP-7 and AA discs. For OC, SLA and AA surfaces had the highest expression after 1 day whereas after 3 and 7 days a significant difference was recorded for SLA, BMP-2, BMP-7 and AA. In conclusion, a beneficial biological effect of a chemical immobilization method of BMP-2, BMP-7 and alendronate onto titanium surfaces on BMSCs was proven.

Evaluation of symptomatic maxillary sinus pathologies using panoramic radiography and cone beam computed tomography-influence of professional training.

BACKGROUND: A comparison of panoramic radiography (PAN) alone and PAN together with small field of view cone beam computed tomography (sFOV-CBCT) for diagnosis of symptomatic pathologies of the maxillary sinus was carried out by clinicians of different experience. METHODS: Corresponding radiographic images (PAN/sFOV-CBCT) of 28 patients with symptomatic maxillary sinus pathologies were chosen and analyzed by two general practitioners (GP), two junior maxillofacial surgeons (MS1), and three senior maxillofacial surgeons (MS2) via questionnaire. RESULTS: Visibility of maxillary pathologies in PAN was significantly different between the groups (GP 39%, MS1 48%, MS2 61%; p < 0.05). The number of incidental findings varied within examiner groups in PAN with a significant increase in MS2 (p = 0.027). The majority of examiners rated an additional sFOV-CBCT as "reasonable"/"required" with a significant influence of the examining groups (GP 98.2%, MS1 94.6%, MS2 80.9%; p = 0.008). In 58% of cases, an additional sFOV-CBCT was seen as "affecting therapy" with significant differences between the groups (GP 68%, MS1 50%, MS2 55%; p < 0.001). CONCLUSIONS: PAN alone is not sufficient for the evaluation of pathologies of the maxillary sinus. But, depending on the examiners' clinical experience, it remains a useful diagnostic tool. Along with the observers' training, significant benefits of an additional sFOV-CBCT for evaluation of symptomatic maxillary sinus pathologies were detected.

Primary Stability of Cylindrical and Conical Dental Implants in Relation to Insertion Torque-A Comparative Ex Vivo Evaluation.

INTRODUCTION: The aim of this ex vivo study was to investigate the influence of different insertion torques on primary stability of a conical and a cylindrical implant system. MATERIALS AND METHODS: Thirty-two dental implants (Astra Tech OsseoSpeed 5.0 S × 11 mm cylindrical [n = 16] and 5.0 × 11 mm conical [n = 16]) were inserted with 20, 30, 40, and 45 N·cm into fresh porcine bone of mixed trabecular-cortical quality. Before insertion, bone quality was assessed via cone beam tomography. After insertion, resonance frequency analysis was reported using the implant stability quotient (ISQ). Implant insertion depths were evaluated, and the implants were pushed out of the bone by force (measured in N). All experiments were done with n = 4 per group. RESULTS: The highest ISQ (mean 78.25 ± 2.9) and pushout values (mean 675 N ± 5.8) were measured for the cylindrical implant after insertion using 30 N·cm. The conical implant showed the highest primary stability by means of ISQ (mean 76.25 ± 2.2) and pushout force (mean 502.5 N ± 9.6) after an insertion torque of 40 N·cm. If more insertion force was used, primary stability was reduced in all cases. CONCLUSION: The data indicate that different forms of an implant system need different insertion torques to obtain an optimal primary stability. These results have to be verified clinically.

A novel method for evaluating periodontal recession: a feasibility study.

PURPOSE: To evaluate whether a three-dimensional (3D) optical method currently used for the production of dental restorations could be applied to the simultaneous evaluation of the height and width of periodontal recessions, and determine the reproducibility and accuracy of the method for evaluating periodontal recession. MATERIALS AND METHODS: The height and width of periodontal recessions scratched onto stone replicas were recorded using a 3D optical method, a periodontal probe, and a caliper. RESULTS: No difference was found between measurements obtained using the methods tested (p > 0.05). However, measurements using the 3D optical method showed the highest reproducibility. CONCLUSION: The 3D optical method allowed the accurate and reproducible evaluation of the height and width of periodontal recessions. The next step should be the development of fully automated soft-tissue monitoring software to increase time savings.

Mechanical anchorage and peri-implant bone formation of surface-modified zirconia in minipigs.

AIM: To test the hypothesis that peri-implant bone formation and mechanical stability of surface-modified zirconia and titanium implants are equivalent. MATERIALS AND METHODS: Twelve minipigs received three types of implants on either side of the mandible 8 weeks after removal of all pre-molar teeth: (i) a zirconia implant with a sandblasted surface; (ii) a zirconia implants with a sandblasted and etched surface; and (iii) a titanium implant with a sandblasted and acid-etched surface that served as a control. Removal torque and peri-implant bone regeneration were evaluated in six animals each after 4 and 13 weeks. RESULTS: The titanium surface was significantly rougher than both tested zirconia surfaces. Mean bone to implant contact (BIC) did not differ significantly between the three implant types after 4 weeks but was significantly higher for titanium compared with both zirconia implants after 13 weeks (p<0.05). Bone volume density (BVD) did not differ significantly at any interval. Removal torque was significantly higher for titanium compared with both zirconia surfaces after 4 and 13 weeks (p<0.001). The sandblasted and etched zirconia surface showed a significantly higher removal torque after 4 weeks compared with sandblasted zirconia (p<0.05); this difference levelled out after 13 weeks. CONCLUSIONS: It is concluded that all implants achieved osseointegration with similar degrees of BIC and BVD; however, titanium implants showed a higher resistance to removal torque, probably due to higher surface roughness.