A New Laser-Processing Strategy for Improving Enamel Erosion Resistance

In the present study, a new automatic laser-processing strategy allowing standardized irradiation of natural tooth areas was investigated. The objective was to find a combination of laser parameters that could cause over a 600°C temperature increase at the enamel surface while not damaging enamel, avoiding temperature change above 5.5°C in the pulp and increasing enamel erosion resistance. Seventy-seven bovine enamel samples were randomly divided into 6 laser groups and 1 negative control (C/no treatment/ n = 11). A scanning strategy (7 × 3 mm) was used for the CO₂ laser treatment (λ = 10.6 µm, 0.1-18 J/cm²) with different pulse durations-namely, 20 µs (G20), 30 µs (G30), 55 µs (G55), and 490 µs (G490), as well as 2 modified pulse distances (G33d, G40d). Measurements of temperature change were performed at the surface (thermal camera/50 Hz), at the underside (thermocouples), and at the pulp chamber using a thermobath and human molars ( n = 10). In addition, histology and X-ray diffraction (XRD/ n = 10) were performed. Erosion was tested using an erosive cycling over 6 d, including immersion in citric acid (2 min/0.05 M/pH = 2.3) 6 times daily. Surface loss was measured using a profilometer and statistical analysis with a 2-way repeated-measures analysis of variance (α = 0.05). Only G20 fulfilled the temperature requirements at the surface (619 ± 21.8°C), at the underside (5.3 ± 1.4°C), and at the pulp (2.0 ± 1.0°C), and it caused no mineral phase change and significant reduction of enamel surface loss (-13.2 ± 4.0 µm) compared to C (-37.0 ± 10.1 µm, P < 0.05). A laser-scanning strategy (20 µs/2 kHz/1.25 J/cm², 3.4 mm/s) has been established that fulfilled the criteria for biological safety and significantly increased enamel erosion resistance (64%) in vitro.

Causes of altered liver function tests - the role of alpha-1 antitrypsin

BACKGROUND

Altered liver function tests are a common finding in clinical practice. Our retrospective study aimed to identify the diagnoses in a non-selected cohort of patients with altered liver tests and to investigate whether alpha-1 antitrypsin genotyping should be part of the diagnostic workup.

PATIENTS AND METHODS

501 patients who were admitted to our outpatient clinic for further evaluation of altered liver function tests were included in the study. The patients underwent a standardized diagnostic program with history taking, physical examination, laboratory tests and ultrasonography. Liver biopsy was performed if appropriate.

RESULTS

More than 50 % of the patients had nonalcoholic fatty liver disease. Alcoholic and drug-induced liver injury were found in 8.6 % and 7 % of patients, respectively. Chronic hepatitis B and C, autoimmune liver disease and inherited causes of liver disease made up for approximately 16 % of the diagnoses. The remaining patients were diagnosed with kryptogenic liver disease or had miscellaneous diagnoses. In 3.7 % of the genotyped patients, the alpha-1 antitrypsin genotype PiMZ was found.

CONCLUSION

Nonalcoholic fatty liver disease is nowadays the most frequent cause of altered liver tests. Alcoholic liver disease might be underrepresented in our study since these patients less often seek medical attention or the diagnosis is already made by the primary care physician. Drug-induced liver injury was found in more patients than expected and might therefore be underdiagnosed in practice. The alpha-1 antitrypsin genotype PiMZ was found in absence of other possible causes of liver disease, indicating that the PiMZ genotype is itself a risk factor for liver disease. Genotyping for alpha-1 antitrypsin should therefore be done when other causes for altered liver function tests have been ruled out.

Designing optical free-form surfaces for extended sources

LED lighting has been a strongly growing field for the last decade. The outstanding features of LED, like compactness and low operating temperature take the control of light distributions to a new level. Key for this is the development of sophisticated optical elements that distribute the light as intended. The optics design method known as tailoring relies on the point source assumption. This assumption holds as long as the optical element is large compared to the LED chip. With chip sizes of 1 mm² this is of no concern if each chip is endowed with its own optic. To increase the power of a luminaire, LED chips are arranged to form light engines that reach several cm in diameter. In order to save costs and space it is often desirable to use a single optical element for the light engine. At the same time the scale of the optics must not be increased in order to trivially keep the point source assumption valid. For such design tasks point source algorithms are of limited usefulness. New methods that take into account the extent of the light source have to be developed. We present two such extended source methods. The first method iteratively adapts the target light distribution that is fed into a points source method while the second method employs a full phase space description of the optical system.