Oral health最新文献

A biologic and esthetic rationale has been presented along with a simplified controlled technique to achieve predictable results (Figures 13A and 13B). The clinician is constantly faced with the challenge of developing room for esthetic material while preserving the biologic objectives. Using the three essential anterior tooth preparation keys (incisal edge, reduction requirements, and the biologic zone) enhances predictability. Developing the incisal edge relative to the dynamics of facial esthetics provides the initial starting point of tooth preparation. The reduction requirements are designed to satisfy the mechanical principles, address the pulpal concerns, and preserve the structural requirements of the tooth. The biologic zone can be developed by using the total dentogingival complex measurements and will clinically aid in the determination of cervical limitations to providing intracrevicular margin location.

Purpose: The purpose of this study was to record the fluoride released measured in parts per million of four fluoride composite resins for five years.

Materials and methods: Four fluoridated composites were separated into four groups. Two composite resins with high viscosity were core materials, Ti-Core with titanium (group 1) and Ti-Core Natural (group 2) and the other two resins studied were low viscosity post cements Flexi-Flow cement with titanium (group 3) and Flexi-Flow Natural (group 4). The fluoride release was studied under four experimental conditions. Three replications were studied in each condition. Fluoride release was measured for 260 weeks (5 years).

Statistical methods: A one-way analysis of variance (ANOVA) was used to compare the average weekly release followed by a Student-Newman-Keuls (SNK) pairwise multiple comparison test. All results were considered statistically significant if p < 0.05.

Results: The ANOVA analysis released a significant statistical interaction between group and week (p < 0.0001). Further analysis showed that the average weekly release for Ti-Core with titanium did not differ from Ti-Core Natural, and that Ti-Core with titanium and Ti-Core Natural differed from both Flexi-Flow Natural and Flexi-Flow with titanium, which were not different from one another.

Conclusions: Ti-Core with titanium (Group 1) and Ti-Core Natural (Group 2) released a greater amount of fluoride than Flexi-Flow with titanium (Group 3) and Flexi-Flow Natural (Group 4). The fluoride released from these fluoridated resin composites are similar to reported ranges of other fluoride releasing dental restoration materials.

Our recommendation is a 90-105 mm macro lens focusing from 1:1 to infinity and a minimum aperture of f/32. A reputable brand should be preferred: Nikon, Canon, Minolta, Sigma etc.... A 105 mm macro lens allows for adequate working distance (approx. 130 mm for a straight view at 1:1 magnification). A 105 mm macro lens induces insignificant perspective distortion and has a large range of aperture. Lastly, it provides for a magnification scale ranging from 1:1 to infinity and is optically excellent. The working distance of current camera systems extends approximately from 4 4/8" or 114 mm, to 7" or 180 mm, at 1:1 magnification. Again these differences are mainly due to lens design and mounted components, (filters, bracket, lighting systems). A minimum of 5" or 125 mm of working distance is desirable for physical access of your camera and proper illumination of the photographed object. However, adequate lighting also depends upon the type and location of your lighting system especially for higher magnification photographs. Part II will examine the different lighting systems on the market and try to decide which is most adapted to your needs. It will answer your questions about the use of the operatory light while focusing, the red eye problem and the use of polarizing filters to decrease the amount of reflection from the flash.