Effect of thickness on the translucency of machinable and printable ceramic-glass polymer materials.

OBJECTIVES: To assess the translucency of machinable and printable ceramic-glass polymer materials with different thicknesses. METHODS: Five ceramic-glass polymer materials were tested: one 3D-printable material, Permanent Crown resin (3D), two machinable materials available at low translucency (LT) and high translucency (HT) levels, VITA Enamic (VE) HT/LT, and Cerasmart 270 (CS) HT/LT. A total of 100 specimens were produced across 10 subgroups (n = 10) with thicknesses of 1 mm and 1.5 mm. The colour coordinates of the specimens were measured against black and white backgrounds using a spectrophotometer. Translucency was quantified using the Relative Translucency Parameter (RTP), calculated via the CIEDE2000 formula. A two-way ANOVA followed by post-hoc tests with Bonferroni correction (α = 0.05) was used for statistical analysis. RESULTS: The RTP for both thicknesses were ranked as follows: CSHT > VEHT > CSLT > 3D > VELT. The RTP of the 3D was lower than that of the HT machinable materials (CSHT and VEHT) for both thicknesses (p < 0.05). No significant difference was observed between the RTP of 3D and CSLT at 1.5 mm (p = 1.000); however, at 1 mm, the RTP of the 3D was lower than that of the CSLT (p < 0.05). Notably, the 3D showed the least translucency difference with a 0.5 mm increase in thickness. CONCLUSIONS: Printable ceramic-glass polymer materials demonstrated lower translucency than HT machinable ceramic-glass polymer materials. Both the thickness and type significantly influenced the translucency of the LT machinable counterparts compared to the printable ceramic-glass polymer material. CLINICAL SIGNIFICANCE: Printable ceramic-glass polymer resins may be a suitable option for minimally invasive procedures, especially when attempting to mask undesirable-coloured abutments. When selecting HT machinable ceramic-glass polymers, clinicians should pay greater attention to the abutment colour and thickness of the restorative material.

Shear bond strength of permanent 3D-printed resin and milled zirconia to primary teeth using different luting agents.

PURPOSE: To evaluate the shear bond strengths (SBS) of permanent 3D-printed resin (PR) to primary dentin using different luting agents. METHODS: 90 primary teeth were prepared. 45 cylinders (3 x 3 mm) were printed using PR, and 45 cylinders were milled using a Z block (to control). The cylinders were bonded to primary dentin by using three types of luting agent [glass-ionomer cement (GIC), resin-modified glass-ionomer cement (RMGIC), and self-adhesive resin cement (SRC)]. The SBS values of the specimens were calculated, and the fracture modes were examined. RESULTS: There was a statistically significant difference between the three different luting agents that were used to lute the PR to primary dentin (P< 0.001). Changing the material (PR or Z) did not affect the SBS values of the luting agents (P> 0.05). The adhesive failure between cement and dentin in the PR-SRC group was significantly higher than the other groups (P< 0.001). The SBS values of the newly developed PR to primary dentin with RMGIC and SRC were similar, but GIC showed lower values than the others. CLINICAL SIGNIFICANCE: This laboratory study suggests that bond strength of the permanent 3D-printed resin can be like that of zirconia. As the resin-modified glass-ionomer cement and self-adhesive resin cement showed higher bond strength to primary teeth making the 3D-printed resin a treatment option.

A comparison of the shear bond strength between denture teeth and denture base resins manufactured either conventionally or with a 3D printer.

STATEMENT OF PROBLEM: Limited information is available on the shear bond strength (SBS) between denture teeth and denture base resins fabricated using a stereolithography (SLA) 3-dimensional (3D) printer. PURPOSE: The purpose of this in vitro study was to evaluate the SBS between denture teeth and the denture base resins produced with the conventional method and with a 3D printer. MATERIAL AND METHODS: Conventional or 3D printed denture teeth were included in the study. The denture base resins were manufactured either conventionally or with a 3D printer. Four subgroups were tested: conventional teeth-conventional base resin (CT-CB), conventional teeth-printed base resin (CT-PB), printed teeth-conventional base resin (PT-CB), and printed teeth-printed base resin (PT-PB). The maxillary molars were combined with Ø5×2.5-mm-cylindrical denture base resin. Shear bond testing was performed by applying a parallel force to the denture teeth-denture base resin interface by using a blade-edge chisel with a crosshead speed of 1 mm/min until failure occurred. SBS and elastic modulus (EM) were recorded. One-way ANOVA followed by the Dunnett T3 post hoc test was used for the statistical analysis (α=.05). The failure modes of the specimens were also analyzed. RESULTS: A statistically significant difference (P<.05) was found between the evaluated groups for the SBS and EM values. PT-PB showed the highest SBS value (15.4 ±2.7 MPa), and CT-PB showed the lowest (0.9 ±0.7 MPa). The PT-CB group showed the highest EM value (62.74 ±20.80 GPa), and the CT-PB group showed the lowest (29.46 ±28.40 GPa). The CT-CB and CT-PB specimens showed mostly adhesive failure; none of the PT-PB specimens showed adhesive failure. CONCLUSIONS: Three-dimensional printing led to a better bond between the denture teeth and the denture base resin compared with the conventional method. Although these findings need to be supported by clinical studies, the use of 3D printers is appropriate in the production of denture teeth and denture bases.

A Decision-Support System for Sustainable Water Distribution System Planning.

An interactive decision-support system (DSS) can help experts prepare water resource management plans for decision makers and stakeholders. The design of the proposed prototype incorporates visualization techniques such as circle views, grid layout, small multiple maps, and node simplification to improve the data readability of water distribution systems. A case study with three urban water management and sanitary engineering experts revealed that the proposed DSS is satisfactory, efficient, and effective.

[Molecular typing of clinical Candida krusei isolates by using restriction endonuclease analysis of genomic DNA and polymerase chain reaction]. / Candida krusei klinik izolatlarinin genomik DNA restriksiyon enzim analizi ve polimeraz zincir reaksiyonu ile tiplendirilmesi.

Candida krusei is inherently resistant to fluconazole and is an important pathogen responsible for nosocomial candidiasis especially in patients with hematological malignancy. Despite the growing clinical importance of C. krusei infections, little is known of its genetic diversity and molecular epidemiology. Therefore, differentiating between C. krusei isolates is of importance for a better understanding of the epidemiology, mode of transmission and pathogenesis of the organism. We investigated the use of two different methods (restriction endonuclease analysis of genomic DNA (REAG) with Hinfl and polymerase chain reaction by using Arno1 and Arno2 primers) for molecular typing of 56 C. krusei isolates from 56 patients. Ten different types (A-J) were determined by REAG. Depending on the patterns of isolates, the number of the bands varied from 12 to 15 and the size of the fragments varied from 2.0 kb to 6.2 kb. Of the isolates 71.4% were gathered under three major patterns (D, F, H). In the second method, PCR amplified different sizes of fragments varied approximately from 1 kb to 2 kb, which yielded 13 types (a-m) from 56 patients. Four major patterns (d, f, h, k) were observed for 58.9% of the isolates. The genotypes detected by REAG and PCR methods were found to be same in 43 isolates out of 56. As the banding patterns of the isolates were found to be similar in this study, it was thought that an exogenous origin could be the source of infections caused by C. krusei isolates. Both REA of genomic DNA and PCR analysis seem to be useful for the typing of C. krusei, however PCR assay can be preferred as it is a simple and rapid method. As a result, further studies are required for the validation of reproducibility and discriminatory power of these methods.

[The frequency of PER-1 type extended spectrum beta-lactamases in nosocomial isolates of Pseudomonas aeruginosa]. / Hastane kaynakli Pseudomonas aeruginosa izolatlarinda PER-1 türü genislemis spektrumlu beta-laktamaz enzimlerinin sikligi.

The aim of this study was to determine the frequency of PER-1 type extended-spectrum beta-lactamase (ESBL) in nosocomial Pseudomonas aeruginosa strains isolated in Hacettepe University Adult Hospital. Sixty-seven non-duplicate P. aeruginosa isolates from patients with nosocomial infections between January 2002 and December 2004 were included in the study. The isolates were identified at species-level by Sceptor (Becton Dickinson, USA) system, and all the strains were stored at -80 degrees C until further testing. Polymerase chain reaction (PCR) was performed for the detection of (bla)PER-1 genes, and PFGE analysis was used to investigate their genetic relatedness. The antimicrobial susceptibilities of the PER-1 positive isolates were determined by Etest (AB Biodisk, Solna, Sweden) method. According to the results of PCR, 22.7% (15/67) of the isolates were positive for PER-1 enzyme. Those 15 (bla)PER-1 positive isolates showed eight different PFGE patterns, indicating the presence of multiple clones. Of the PER-1 positive P. aeruginosa isolates, nine were resistant to imipenem/meropenem, and 11 were resistant to piperacillin-tazobactam and tobramycin. The epidemiological investigation of multidrug resistant P. aeruginosa should give important clues for the initial empirical therapy, especially in certain geographic locations where ESBL-producing P. aeruginosa strains seemed to be highly prevalent.

[Molecular characterization of BRO beta-lactamases of Moraxella catarrhalis strains isolated from carrier children]. / Tasiyici çocuklardan izole edilen Moraxella catarrhalis suslarinda BRO beta-laktamazlarin moleküler tiplendirilmesi.

Nasopharyngeal carriage of Moraxella catarrhalis is a risk factor for upper respiratory tract infections and otitis media. In this study, we aimed to characterize BRO beta-lactamases of M. catarrhalis strains isolated from 64 children without any symptoms of respiratory disease. Gram negative diplococci grown on selective media and which are catalase, oxidase, DNase, nitrate reduction positive, glucose, maltose, sucrose and lactose fermentation negative, were diagnosed as M. catarrhalis. Antibiotic susceptibility testing was performed by agar dilution method recommended by NCCLS. BRO beta-lactamases were differentiated by restriction enzyme analysis method. The resistance rate for ampicillin was 18.8% and all the isolates were found to be sensitive to amoxicillin-clavulanate, cefazolin, cefaclor, azithromycin and ciprofloxacin. Out of 64 M. catarrhalis isolates, 57 (89%) were found beta-lactamase positive with nitrocefin disk test (Remel, USA). The presence of BRO beta-lactamases in these 57 strains (89%) was also confirmed by restriction enzyme analysis, while 7 (11%) of them were found to be negative. Among the positive strains, 47 (73.4%) were typed as BRO-1, and 10 (15.6%) were typed as BRO-2. The characterization of BRO beta-lactamases of M. catarrhalis strains in carrier children is important since the high rate of carriage predisposes to respiratory tract infections. As a result, BRO beta-lactamase typing will guide the treatment regimen against the respiratory infections that can occur due to M. catarrhalis in carrier children.