Load-bearing capacity of 3D-printed incisor partial-coverage crowns made from zirconia and composite.

PURPOSE: This study investigated the fracture resistance of 0.5-mm-thick restorations for minimally invasive therapy. Anterior partial-coverage crowns composed of three-dimensional (3D)-printed 3-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP; Lithacon 3Y210, Lithoz) and 3D-printed composite (Varseo Smile Crown plus, Bego) were compared with a control group made from milled 3Y-TZP (Cercon ht, DentsplySirona). METHODS: Three groups each with 27 restorations were produced. For milled 3Y-TZP partial-coverage crowns, drill compensation was needed so the milling bur could access the inner surface at the incisal edge. Restoration fit was verified by cross-sectioning 12 specimens in each group. The remaining 15 restorations were sandblasted (Al2O3, 0.1 MPa) and adhesively cemented (Panavia SA, Kuraray) onto CoCr teeth. Static load-to-failure tests were performed. The load was induced on the incisal edge. The forces needed to fracture the specimens were analyzed using the Welch analysis of variance and post hoc Dunnet-T3 tests. The Weibull parameters were also calculated. RESULTS: Drill compensation increased cement thickness at the loading area by 200 µm in milled 3Y-TZP restorations compared with the 3D-printed partial-coverage crowns. Fracture resistance was the highest in 3D-printed 3Y-TZP restorations (1570±661N) followed by milled 3Y-TZP (886±164N) and 3D-printed composite partial-coverage crowns (570±233 N). Milled 3Y-TZP was associated with a substantially higher Weibull modulus (m=6) than the 3D-printed materials (m=2), suggesting greater reliability. CONCLUSIONS: Fracture resistance increased with tighter fit, demonstrating the benefit of the geometric freedom associated with 3D-printing. Future research should focus on making 3D-printed 3Y-TZP more reliable to increase its safety in clinical use.

Comparison between interocclusal registration using silicone bite registration material and intraoral scanner on clenching strength.

INTRODUCTION: The purpose of this study was to clarify the influence of clenching strength on interocclusal registration using intraoral scanner (IOS). METHODS: Subjects were eight volunteers. Two experimental conditions were light clenching (LC) and 40% maximum voluntary clenching (MVC). The conventional silicone bite registration and IOS were used for comparison. Occlusal contact areas (OCA) for different clenching strengths were compared, along with variation of measured values (VMV) between recording methods. RESULTS: Significant differences were observed between conditions on OCA and between methods on VMV. CONCLUSION: Clenching strength influenced interocclusal registration using IOS. Int J Prosthodont. 10.11607/ijp.8445.

Simultaneous prosthodontic treatment for crowns of natural teeth and dental implants using digital technology: A case report.

The aim of this clinical report was to describe the improvement of masticatory disorders with the use of digital technology to simultaneously perform prosthodontic treatment of natural teeth and edentulous areas. Computer-guided implant surgery was performed, and crown prostheses and implant superstructures were fabricated simultaneously using digital technology.

Factors Affecting the Decision-making of Direct Pulp Capping Procedures among Dental Practitioners: A Multinational Survey from 16 Countries with Meta-analysis.

INTRODUCTION: Direct pulp capping (DPC) procedures require the placement of a bioactive material over an exposure site without selective pulp tissue removal. This web-based multicentered survey had 3 purposes: (1) to investigate the factors that affect clinicians' decisions in DPC cases, (2) to determine which method of caries removal is preferred, and (3) to evaluate the preferred capping material for DPC. METHODS: The questionnaire comprised 3 sections. The first part comprised questions regarding demographic features. The second part comprised questions on how treatment plans change according to factors such as nature, location, number and size of the pulp exposure, and patients' age. The third part composed of questions on the common materials and techniques used in DPC. To estimate the effect size, the risk ratio (RR) and 95% confidence interval (CI) were calculated using a meta-analysis software. RESULTS: A tendency toward more invasive treatment was observed for the clinical scenario with carious-exposed pulp (RR = 2.86, 95% CI: 2.46, 2.32; P < .001) as opposed to the clinical scenario with 2 pulp exposures (RR = 1.38, 95% CI: 1.24, 1.53; P < .001). Complete caries removal was significantly preferred to selective caries removal (RR = 4.59, 95% CI: 3.70, 5.69; P < .001). Among the capping materials, calcium silicate-based materials were preferred over calcium hydroxide-based materials (RR = 0.58, 95% CI: 0.44, 0.76; P < .05). CONCLUSIONS: While carious-exposed pulp is the most important factor in clinical decisions regarding DPC, the number of exposures has the least impact. Overall, complete caries removal was preferred over selective caries removal. In addition, the use of calcium silicate-based materials appears to have replaced calcium hydroxide-based materials.

Influence of molding angle on the trueness and defects of removable partial denture frameworks fabricated by selective laser melting.

PURPOSE: To examine the effect of molding angle on the trueness and defects associated with removable partial denture (RPD) frameworks fabricated by selective laser melting (SLM). METHODS: A plaster model of a partially edentulous mandibular arch classified as Kennedy class II modification 1 was used. After obtaining the 3D data of the model (design data), a framework was designed using CAD software. Based on the design data, three different molding angle conditions (0°, 45°, and -45°) were set in the CAM software. The frameworks were fabricated by SLM under each condition, and 3D data were captured (fabrication data). The design and fabrication data were superimposed using 3D inspection software to verify the shape errors. The number of support structures was then measured. To examine the internal defects, micro-computed tomography (µCT) was performed for void analysis. Surface roughness was measured using a laser microscope. RESULTS: The overall shape errors of the RPD framework were smaller under the 0° condition compared with the others, and the largest number of support structures was observed at 0°. Many internal defects were observed in the large components of the framework at 45° and -45°. The surface roughness was the smallest at -45°. CONCLUSION: The trueness and defects associated with the RPD frameworks were affected by the difference in the SLM molding angle.

The Role of Digital 3D Scanned Models in Dental Students' Self-Assessments in Preclinical Operative Dentistry.

The aim of this study was to determine how dental student self-assessment and faculty assessment of operative preparations compared for conventional visual assessment versus assessment of scanned digital 3D models. In 2016, all third-year students in the Class of 2018 (N=35) at Harvard School of Dental Medicine performed preclinical exams of Class II amalgam preparations (C2AP) and Class III composite preparations (C3CP) and completed self-assessment forms; in 2017, all third-year students in the Class of 2019 (N=34) performed the same exams. Afterwards, the prepared typodont teeth were digitally scanned. Students self-assessed their preparations digitally, and four faculty members graded the preparations conventionally and digitally. The results showed that, overall, the students assessed their preparations higher than the faculty assessments. The mean student-faculty gaps for C2AP and C3CP in the conventional assessments were 11% and 5%, respectively. The mean digital student-faculty gap for C2AP and C3CP were 8% and 2%, respectively. In the conventional assessments, preclinical performance was negatively correlated with the student-faculty gap (r=-0.47, p<0.001). The correlations were not statistically significant with the digital assessments (p=0.39, p=0.26). Students in the bottom quartile significantly improved their self-assessment accuracy using digital self-assessments over conventional assessments (C2AP 10% vs. 17% and C3CP 3% vs. 10%, respectively). These results suggest that digital assessments offered a significant learning opportunity for students to critically self-assess themselves in operative preclinical dentistry. The lower performing students benefitted the most, improving their assessment ability to the level of the rest of the class.

Biomechanical comparison between 2 guided-growth constructs.

BACKGROUND: Correction of deformity using guided growth with plate and screw constructs has shown good results in the correction of angular deformities in children. Some recent reports have shown device failure, perhaps because of increased patient weight as seen in Blount disease. The purpose of our study was to compare the strength to failure between 2 similar devices, the Orthofix 8-plate manufacturer 1 (M-1) and Biomet Peanut plate manufacturer 2 (M-2), using 2 different screw types: solid and cannulated. METHODS: A model of bone was developed using 30-pcf solid polyurethane foam as cancellous bone and high-density polyethylene as cortical bone. A 10.0-mm defect was created through the polyurethane foam and was spanned by a plate and screw system. Under the assumption that device failure is caused by cyclical loading, each device underwent fatigue testing on an MTS Bionix machine with a 4-Hz micromotion of 5.0 mm at -500-N compression, and the number of cycles to failure was recorded. RESULTS: All devices failed at the screw shaft; plates did not break under any circumstances. The highest mean number of cycles to failure was seen with the M-2 device using solid, stainless-steel screws (22,614 cycles; SD, 6885). On comparing with titanium screws, solid screws were significantly stronger in both the M-1 (P=0.002) and M-2 devices (P=0.013). The M-2 device with cannulated screws was noted to be significantly stronger than the M-1 device with cannulated screws (P=0.036). CONCLUSIONS: This study reveals a significant increase in strength in one titanium cannulated guided-growth system over another. Solid screws are also shown to be significantly stronger than cannulated screws. Long-term clinical data will be required to determine whether this difference results in lower failure rates. CLINICAL RELEVANCE: Use of a stronger guided-growth device may be of benefit for correction of deformity in children who are heavier, such as those with Blount disease. Comparative clinic trials will be needed to confirm the advantage of one device over another.

Epidemiology of MRSA and current strategies in Europe and Japan.

The prevalence of health-care associated infections caused by multi-drug resistant organisms has significantly increased over the past decade. Among these organisms, Methicillin-resistant Staphylococcus aureus (MRSA) plays a prominent and increasing role. Because of consequences for patients and the economic burden in course of prolonged treatment following MRSA infections and additional indirect costs for e.g. isolation or antiseptic treatment, this trend will further damage European health-care systems.In 2006, a workshop was initiated at the 8(th) International Congress of the German Society of Hospital Hygiene held in Berlin. The aim of this workshop was to give an overview of the current situation of MRSA in selected European countries and to elaborate on potential strategies to prevent MRSA-infections and dissemination. A questionnaire encompassing 20 questions addressed topics such as epidemiology, current measures and future prospects was distributed to representatives from various European countries and Japan. A variety of widely different answers was obtained. It was shown that in all countries prevalence of MRSA is on a rising tide. This trend is observable in all European countries, albeit less strong in The Netherlands, Slovenia, France, Austria and Scandinavian countries. It was conclude that prevention strategies in a united and expanding European Community will become of utmost importance and that rapid screening strategies, e.g. PCR, might be of assistance in such an approach. A potential strategy to improve infection control measures could be the requirement of health-insurance providers to sign contracts only with hospitals able to proof having an infection control management in place.

The pharmacokinetics and safety of ABT-751, a novel, orally bioavailable sulfonamide antimitotic agent: results of a phase 1 study.

PURPOSE: Microtubules play a critical role in many cellular functions, including cell division and mitosis. ABT-751 is a novel sulfonamide antimitotic that binds to the colchicine site on beta-tubulin that leads to a block in the cell cycle at the G2M phase, resulting in cellular apoptosis. ABT-751 was investigated in this phase 1 trial designed to assess its maximum tolerated dose (MTD), dose-limiting toxicity (DLT), tolerability, and pharmacokinetics. EXPERIMENTAL DESIGN: ABT-751 was administered on a daily (q.d.) or twice daily (b.i.d.) oral schedule for 7 days every 3 weeks to 39 patients with refractory solid tumors. Toxicity was monitored weekly. Plasma and urine ABT-751 and metabolite pharmacokinetics were determined. RESULTS: The MTD for the q.d. schedule was 250 mg/d. DLTs during cycle 1 were abdominal pain, constipation, and fatigue. The MTD on the b.i.d. schedule was 150 mg. Cycle 1 of therapy with the 175 mg b.i.d. schedule was tolerated without DLT. However, six of seven patients reported grade 3 toxicity (ileus, constipation, abdominal pain, or fatigue), which occurred in cycle 2 or 3. ABT-751 was absorbed after oral administration with an overall mean T(max) of about 2 hours. The pharmacokinetics of ABT-751 were dose-proportional and time-independent. There was minimal accumulation of ABT-751 after multiple q.d. and b.i.d. doses. Efficacious concentrations, as determined from preclinical models (0.5-1.5 microg/mL), were achieved in all subjects. ABT-751 metabolism occurred primarily by glucuronidation and sulfation. No complete or partial tumor responses were noted, but one patient had a minor response, and four patients had stable disease lasting at least 6 months. CONCLUSIONS: The MTD and recommended phase 2 doses for ABT-751 were 250 mg q.d. and 150 mg b.i.d. on a 7-day schedule given every 3 weeks, due to subsequent cycle toxicities at 175 mg b.i.d. dosing. Toxicities were abdominal pain, constipation, and neuropathy.