Evaluation of the Surface Roughness and Accelerated Aging of CAD/CAM Materials

PURPOSE

To compare the influence of surface roughness and accelerated aging on the mechanical properties of polymer-based and ceramic CAD/CAM materials.

MATERIALS AND METHODS

Three polymers (Lava Ultimate [LVU], VITA ENAMIC [ENA], and Shofu Block HC [SFB]) and one ceramic (IPS Empress CAD [EMP]) were selected for this study. The specimens were treated with the aim of measuring surface roughness (Ra [mm]) and its influence on the mechanical properties. The treatments were: polishing (POL); etching with 9.6% hydrofluoric acid for 90 seconds (ETC); airborne-particle abrasion with 50-μm aluminum oxide at 2-bar pressure (SBT); and airborne-particle abrasion with 50-μm aluminum oxide at 2-bar pressure plus etching with 9.6% hydrofluoric acid (SAC) for 90 seconds. Before and after the accelerated aging (AA) protocol (30,000 cycles, 5°C and 55°C), the specimens were subjected to the 3-point bending test. The data were analyzed with two-way and three-way ANOVA and post hoc Tukey test (P < .05).

RESULTS

The surface roughness ranged from 0.24 μm to 1.96 μm, with statistically significant differences (P < .05). The highest surface roughness, in descending order, was exhibited by: LVU > SFB > EMP > ENA. The AA demonstrated an influence on the flexural strength of LVU, ENA, and SFB. The surface treatment did not affect the flexural moduli of the materials tested. The LVU and SFB showed decreased moduli of resilience after the AA; however, modulus of resilience was not influenced by surface treatment.

CONCLUSION

The polymer-based materials were affected by AA. In addition, surface treatment could jeopardize their mechanical properties in certain conditions.

Students' satisfaction with electrical handpieces in an educational setting

OBJECTIVE

This article presents the evaluation and outcome of improvements carried out at Case Western Reserve School of Dental Medicine (CWRU) based on feedback provided by students during implementation of electrical handpieces technology in the school.

METHODOLOGY

Students were surveyed in February 2010 (first survey) regarding their satisfaction with the existing clinical set-up for electrical handpieces. Following a change in clinical setting and integration of the control box into the dental unit in November 2010, students were administered the same survey as in February 2010 (second survey).

RESULTS

There was an increased level of satisfaction with electric handpieces in the new clinical setting; these levels were significant regarding the ergonomics of the handpiece and clinical setting, operation of the handpiece, and technical maintenance. There was a significant shift from those who were categorically against using electrical handpieces after graduation towards those were 'not sure' regarding the adoption of electric technology in their practice.

CONCLUSIONS

Specifically improving the clinical setting of a control box for electrical handpieces can influence overall student perception regarding the quality of handpieces and their operation.

Antifungal resistance of candidal biofilms formed on denture acrylic in vitro

Denture biofilms represent a protective reservoir for oral microbes. The study of the biology of Candida in these biofilms requires a reliable model. A reproducible model of C. albicans denture biofilm was developed and used to determine the susceptibility of two clinically relevant C. albicans isolates against 4 antifungals. C. albicans, growing as a biofilm, exhibited resistance to amphotericin B, nystatin, chlorhexidine, and fluconazole, with 50% reduction in metabolic activity (50% RMA) at concentrations of 8, 16, 128, and > 64 microg/mL, respectively. In contrast, planktonically cultured C. albicans were susceptible (50% RMA for the same antifungals was obtained at 0.25, 1.0, 4.0, and 0.5 microg/mL, respectively). In conclusion, results obtained by means of our biofilm model show that biofilm-associated C. albicans cells, compared with cells grown in planktonic form, are resistant to antifungals used to treat denture stomatitis.

Clinical implications of drugs taken by our patients

An awareness of the various medications commonly prescribed for patients to self-administer will assist clinicians to anticipate the most commonly encountered medical diagnoses; will give clues to a patient's physical and emotional ability to undergo and respond to dental care; will alert clinicians to potential drug-drug and drug-disease interactions, and to the presence of drug-induced illness; and provide invaluable information that will help the clinician identify high-risk patients who may experience a life-threatening medical emergency while in the dental office.