Dentin wetting by three adhesive systems: influence of etching time, temperature and relative humidity.

OBJECTIVES: The purpose of this study was to investigate the wetting properties of three adhesives systems on etched dentin surfaces submitted to a brief air-drying procedure, as in clinical conditions. The influence of two clinical parameters (surface temperature and surrounding hygrometry) on wetting was investigated. METHODS: Two total-etch adhesives (Excite Vivapen and Adper Scothbond 1XT) and one self-etching adhesive (GC-G Bond) were used. Superficial and deep dentin slice were obtained from six caries-free extracted third molars. Before the adhesive deposition, the dentin samples were etched with 37% phosphoric acid for different time durations. The surface topography was characterised by atomic force microscopy (AFM) observations and the wetting properties of dentin were studied by contact angle measurements. RESULTS: Unlike clinical expectations, the contact angles increased with the acid exposure time, and consequently with both surface roughness and the organic-mineral ratio of the dentin components. The wetting properties were clearly more sensitive to the surrounding relative humidity than the temperature. The contact angles values were reduced by about 50% when the relative humidity increased from 37% to 80% and by about 15% when the temperature was raised from 25 degrees C to 37 degrees C. CONCLUSION: Acid-etched dentin exposed to a brief air-drying appears as the key parameter to control the wetting properties of total-etch adhesive-dentin systems. The experimental results seem to be well described by the Cassie-Baxter approach, and suggest that dentinal tubules through an adhesive repellent contribution should account for the observed wettability decreases.

Dentinal tubules driven wetting of dentin: Cassie-Baxter modelling.

We investigate the wetting properties of dentin surfaces submitted to a phosphoric acid etching followed by an air drying procedure, as in clinical situations of adhesive dentistry. The surface topography of the etched surfaces was characterized by AFM, and the wetting properties of water on these rough and heterogeneous surfaces were studied, by contact angle measurements. We showed that the contact angle increases with the acid exposure time and consequently with both surface roughness and the organicmineral ratio of the dentin components. From the whole results, obtained on dentin and also on synthesized hydroxyapatites samples, we inferred a water contact angle of ~133° on the dentinal tubule. These experimental results may be described by the Cassie-Baxter approach, and it is suggested that small air pockets could be formed inside the dentinal tubules.

The effect of incomplete patient follow-up on the reported results of AVM radiosurgery.

BACKGROUND: The reported efficacy of AVM radiosurgery--80-85% 2-year obliteration rate--is based exclusively on the results of follow-up arteriography in a small percentage of treated patients; it is therefore inaccurate. We examined the effect of incomplete follow-up on the results of AVM radiosurgery. METHODS: We reviewed the results of AVM radiosurgery in 82 patients after a minimum of 24 months of follow-up. Patients were not preselected to undergo arteriography on the basis of any other imaging study. Data were analyzed using the Kaplan-Meier method and stratified by size of AVM. Results were compared with those obtained from the same data using the reporting techniques described in the literature. RESULTS: When data analysis was limited to patients who had follow-up arteriography, the 2-, 3-, and 4-year obliteration rates were 37%, 73%, and 84% after a minimum 24-month follow-up. Using Kaplan-Meier analysis the 2-, 3-, and 4-year obliteration rates were 32%, 55%, and 55% (95% CI = +/-18%), respectively. The 2-year obliteration rate was 43% for AVMs <30 mm in diameter and 16% for AVMs >30 mm in diameter, respectively. CONCLUSION: If data analysis is limited to the patients who undergo follow-up arteriography, the obliteration rate of AVM radiosurgery is overestimated. The actual 2-year obliteration rate if all data is considered is in the range of 40% rather than the commonly reported 80%. Therefore, treated patients are exposed to the risk of intracerebral hemorrhage for a longer period than previously appreciated. Compulsive long-term follow-up is required to document the true AVM obliteration rate after treatment by radiosurgery.

Hemodynamic effects of ketamine in children undergoing cardiac catheterization.

Ketamine is used to supplement sedation during cardiac catheterization. We studied ketamine-induced circulatory changes in 28 acyanotic children (18 of whom had left-to-right shunts), aged 4-161 months (mean, 33 months). Oxygen consumption (VO2) was measured continuously. In the 18 patients with shunts, the pulmonary to systemic flow ratio fell slightly (2.3 +/- 1.1 to 1.8 +/- 0.4, p less than 0.05). In all patients, the ratio of pulmonary (PVR) to systemic vascular resistance (SVR) rose from 0.16 +/- 0.09 to 0.28 +/- 0.21, p less than 0.001. Ketamine increases VO2, heart rate, cardiac output, and pulmonary arterial pressure (PAP). The rise in PAP is more consistent than the rise in PVR; resistance changes were greatest in patients with elevated resting PVR (r = 0.54). Caution should be used in administering ketamine to selected subjects; moreover, ketamine can confuse interpretation of cardiac catheterization data, especially if VO2 is assumed and not measured.