Effect of thermal cycling on fracture toughness of CAD/CAM materials.

PURPOSE: To compare the fracture toughness of four different CAD/CAM materials, (VM) Vitablocs Mark II, (IP) IPS e.max CAD, (LU) LAVA Ultimate, and (VE) Vita Enamic under long thermocycling conditions. METHODS: Each type of ceramic block was sectioned into beams (n=9) with dimensions of 14×3×2.5 mm (L × W × H). All four ceramics were submitted to different conditions: the desiccator or distilled water, each for 7 days. The third and fourth conditions involved the specimens being submitted to 60,000 and 120,000 thermocycles in water respectively. The dwelling time was 52 seconds at 5° and 55°C. A three-point bend test with a universal loading machine on notched samples was per-formed. Furthermore, a fractographic analyses was made by scanning electron microscopy (SEM) to determine if any of these conditions influenced the type of fracture. Data were analyzed by two-way ANOVA (α= 0.05). RESULTS: A significant difference in fracture toughness (P< 0.05) was found among the groups; IP (4.20±1.23) had the highest value followed by VE (2.02±0.39), which did not have a statistically significant difference from LU (1.96±0.42). The lower value and statistical difference for VM was 1.52±0.35. The ceramics performed better after they were hydrated, while the polymer-based materials had the fracture toughness means decreased after the thermocycles. CLINICAL SIGNIFICANCE: A significant difference in fracture toughness (P<0.05) was found among the groups; IP had the highest value followed by VE, which was not statistically significantly different from LU. The ceramics performed better after they were hydrated, while the polymer-based materials had fracture toughness means decreased after thermocycling.

Image quality evaluation of eight complementary metal-oxide semiconductor intraoral digital X-ray sensors.

PURPOSE: To evaluate the image quality generated by eight commercially available intraoral sensors. METHODS: Eighteen clinicians ranked the quality of a bitewing acquired from one subject using eight different intraoral sensors. Analytical methods used to evaluate clinical image quality included the Visual Grading Characteristics method, which helps to quantify subjective opinions to make them suitable for analysis. RESULTS: The Dexis sensor was ranked significantly better than Sirona and Carestream-Kodak sensors; and the image captured using the Carestream-Kodak sensor was ranked significantly worse than those captured using Dexis, Schick and Cyber Medical Imaging sensors. The Image Works sensor image was rated the lowest by all clinicians. Other comparisons resulted in non-significant results. CONCLUSIONS: None of the sensors was considered to generate images of significantly better quality than the other sensors tested. Further research should be directed towards determining the clinical significance of the differences in image quality reported in this study.

Lean management-the journey from toyota to healthcare.

The evolution of production systems is tightly linked to the story of Toyota Motor Company (TMC) that has its roots around 1918. The term "lean" was coined in 1990 following the exploration of the Toyota model that led to the "transference" thesis sustaining the concept that manufacturing problems and technologies are universal problems faced by management and that these concepts can be emulated in non-Japanese enterprises. Lean is a multi-faceted concept and requires organizations to exert effort along several dimensions simultaneously; some consider a successful implementation either achieving major strategic components of lean, implementing practices to support operational aspects, or providing evidence that the improvements are sustainable in the long term. The article explores challenges and opportunities faced by organizations that intend incorporating lean management principles and presents the specific context of the healthcare industry. Finally, the concepts of "essential few" and customer value are illustrated through a simple example of process change following lean principles, which was implemented in a dental school in the United States.

Relationship between broken appointments and dental students' clinical experience level.

As more dental schools adopt a comprehensive care model focused on patients' needs rather than a certain number of required procedures, clinic time utilization by students is coming under increasingly close scrutiny. This article presents an analysis of the influence of broken appointment rates on dental students' clinical experience levels. The total percentage of broken appointments experienced by each student from the classes of 2010 and 2011 at Case Western Reserve University School of Dental Medicine during his or her clinical education in the junior and senior years was determined, and the impact of the broken appointment rate on students' clinical experience levels was analyzed. The results show a statistically significant difference regarding the percentage of broken appointments between the classes of 2010 and 2011: 18.64 percent and 14.44 percent, respectively. When the rate of no-shows was compared to the students' clinical experience level, a weak but significant negative correlation was determined for the class of 2010 but not for the class of 2011. It is concluded that the rate of broken appointments accounts for a small part of the variability observed in the number of clinical procedures performed in the predoctoral clinic. When this rate is lowered below a threshold of 14.5 percent, broken appointments seem to have no influence on students' clinical experience level.

RT-PCR analysis of Candida albicans ALS gene expression in a hyposalivatory rat model of oral candidiasis and in HIV-positive human patients.

ALS gene expression was studied in the hyposalivatory rat model of oral candidiasis and in clinical specimens collected from HIV-positive patients to assess similarities in expression patterns between the model system and clinical isolates. Two Candida albicans strains, SC5314 and OY-2-76, were used in the rat model system and infection progressed for 3 or 5 days. The strains produced similar oral lesions at 3 days. At 5 days, strain OY-2-76 produced more superficial lesions containing relatively more yeast forms compared to invasive hyphal forms observed for strain SC5314. For all infections, the most severe lesions were observed on the tongue and gingiva overlying the mandible. ALS transcripts were easier to detect by RT-PCR later in infection and under other conditions where more fungal cells were present. Expression of ALS1, ALS2, ALS3 and ALS4 was observed in rats infected for 3 days with ALS5 and ALS9 transcripts detected after 5 days of infection. Expression of ALS6 was observed in a single specimen from a 5-day infection while ALS7 transcript was never found. Expression of all ALS genes was observed in oral clinical material collected from HIV-positive patients although ALS6 and ALS7 transcripts required an extra PCR amplification step to be detected. Overall, the patterns of ALS gene expression were similar between the rat model and human clinical specimens, suggesting that the model would be useful for studying the phenotype of al delta/al delta mutant strains.