Transversal ultrahigh-resolution polarizationsensitive optical coherence tomography for strain mapping in materials.

Optical coherence tomography (OCT) and its extension, polarization-sensitive (PS-)OCT, are techniques for contactless and nondestructive imaging of internal structures. In this work, we apply PS-OCT for material characterization. We use a transversal scanning, ultra-high resolution (UHR-)PS-OCT setup providing cross-sectional as well as inplane information about the internal microstructure, the birefringence and the orientation of the optical axis within the material. We perform structural analysis and strain-mapping for different samples: we show the necessity of UHR imaging for a highly strained elastomer sample, and we discuss the effect of large birefringence on the PS-OCT images. Furthermore, we investigate high-aspect ratio photoresist moulds for the production of microelectromechanical parts (MEMS), demonstrating that transversal UHR-PSOCT is a promising tool for non-destructive strain-mapping.

[Histologic verification of the reliability of clinical caries diagnoses]. / Histologische Uberprüfung der Zuverlässigkeit klinischer Kariesdiagnosen.

The reliability of different investigators' assessment distinguishing carious cavities from caries-free ones was examined in an in vitro study. In 23 recently extracted human teeth caries was completely removed by the principal investigator, while in 17 teeth caries was only incompletely removed. On two occasions at an interval of 2 weeks, 5 investigators established the diagnosis "carious" or "caries-free" after clinical inspection using probe and mirror. Decalcified thin sections were examined in order to determine objectively if a tooth was caries-free or not. On an average, 8 out of 10 carious and 6 out of 10 caries-free cavities were correctly diagnosed. An analysis of the erroneous diagnoses showed that it was deep interproximal lesions that went unnoticed most frequently. Lesions at the enamel-dentin junction were also overlooked. False positive diagnoses were three times more frequent than false negative results. The reliability of caries detection (sensitivity 83.5%) was far higher than reported in the literature.

[Staining of carious dentin with Kariesdetektor]. / Die Anfärbung von kariösem Dentin mit dem Kariesdetektor (Säurerot in Propylenglykol).

In a histological study of the staining effect of the staining solution Kariesdetektor 60 human teeth with carious lesions of varying sizes were separated into one control half and one test half each immediately following their extraction. Non-decalcified thin ground sections were prepared with the aid of the saw-cut-and-grind technique. The test halves were stained with Kariesdetektor, the control preparations with toluidine blue. The staining effect of the disclosing dye was evaluated under the light microscope and compared with the control preparations. In enamel the disclosing dye stained all carious areas except the dark and the more peripheral transparent zones. In dentinal caries the zones of necrosis and penetration were safely stained. Zones of demineralization, dead tracts, and transparency zones were not stained. Kariesdetektor is a reliable optical aid in removing infected carious hard tooth structures.

[Studies into the effectivity of Caridex in caries removal]. / Untersuchungen über die Effektivität von Caridex bei der Kariesentfernung.

It was the goal of this study to find out if Caridex is a reliable method for removing dentine caries. Different lesions on 37 teeth were treated with the system and subsequently examined for caries. The macroscopic results were verified using undecalcified thin sections stained with toluidine blue and examined for residual caries under the light microscope. Even after applying the system for as long as 30 minutes there were only two cases where the floor of the cavity could be referred to as caries-free, while none of the enamel/dentin interfaces was caries-free in the cases treated. Histologically four preparations could be considered caries-free. The use of the Caridex system alone produced no satisfactory results.

Effect of a preventive program based on professional toothcleaning and fluoride application on caries and gingivitis.

The effect of a preventive program was studied in 12-14-yr-old children. 104 children (test group) participated in this program. After four visits in the first 6 wk, the children visited the oral hygienist five times a year to receive professional oral prophylactic treatment and instructions. Additionally a fluoride application (Duraphat) was given two times a year. Children of a control group (n = 117) received no prophylactic treatment. Diet was not controlled in either test or control group. After 2 yr mean caries increment amounted to 2.7 +/- 2.8 new DFS in the test group and 5.0 +/- 4.2 new DFS in the control group, respectively. The most pronounced differences between the two groups could be found on the proximal surfaces. In all, caries was reduced by 46% during the 2-yr period. Plaque accumulation and frequency of gingivitis were significantly reduced only in the test group (67% and 55%, resp.). The data revealed that the program reduced both caries and gingivitis to a remarkable extent.

[The stability of fluoride concentrations at the enamel surface]. / Untersuchungen zur Stabilität der Fluoridkonzentration an der Schmelzoberfläche.

A new method for in vitro fluoridisation of dental enamel is presented where commercial fluoride tablets of available fluoride compounds are subjected to comparative tests (Sodium fluoride, magnesium fluoride, or trisodiumhexafluoroferrate). Special consideration was given to stability of fluoride concentration on the enamel surface. Considerable differences were observed in the level of fluoride content directly after the last administration of fluoride and also the amount of fluoride concentration in 24 hours. The highest initial fluoride concentration was achieved with NaF (pH 4.0) and Na3FeF6 in combination with NaF, CaF2 and MgF2 (pH 4.0) whereas the greatest stability was reached with NaF.