Biomedical subjects

Norbert Gutknecht

Publications and source records attributed to Norbert Gutknecht.

5 recordsLinked to original sources

PubMed2006

Comparative evaluation of the effects of Nd:YAG and Er:YAG laser in dentin hypersensitivity treatment.

Dentin hypersensitivity (DH) is one of the most common complications that affect patients after periodontal therapy. So far, many investigators have successfully used different types of laser on DH treatment. The aim of this study was to evaluate the comparative effect of Nd:YAG laser and Er:YAG laser on human teeth desensitization. A group of nine patients with a total of 63 chronic hypersensitive teeth were selected. Each one of them should at least have three hypersensitive teeth. These teeth were randomly allocated into three groups. Group 1, Nd:YAG laser (1 W, 15 Hz, 60 s, two times); group 2, Er:YAG laser (100 mJ, 3 Hz, 60 s, two times); and group 3 serves as control group without any treatment. Assessment of pain was performed by a visual analysing scale (VAS) after stimulation of sensitive tooth by using the sharp tip of an explorer. This test was performed before treatment, immediately after that and at 1-, 3- and 6-month intervals after treatment by one blinded examiner. Analysis of VAS score between the three groups at the time of treatment did not show any significant difference (p = 0.506). However, by using repeated-measurement analysis of variance test, significant differences were seen in the three groups between before-treatment VAS score and after treatment (p < 0.0005). This statistically significant difference in the control group demonstrated a placebo effect. However, the effect of using Nd:YAG and Er:YAG lasers was stronger than this placebo effect, so that after removing the effect of the placebo, differences immediately after, 1, 3 and 6 months post treatment between all three groups still were statistically highly significant (p < 0.0005). Compared to the Er:YAG laser group, using Nd:YAG laser resulted in a significant reduction of VAS score at each follow-up examination (p < 0.0005). Although using Nd:YAG and Er:YAG laser in desensitization of hypersensitive teeth showed a placebo effect limited to a short time, results of this study demonstrated that both of these lasers have an acceptable therapeutic effect. The observed effects seemed to last for at least 6 months. It was concluded that Nd:YAG laser is more effective than Er:YAG laser in reduction of patients' pain.

Analysis of Variance↗

PubMed2005

Temperature evolution on human teeth root surface after diode laser assisted endodontic treatment.

The thermal rise threshold of an 810-nm semi-conductor diode laser on the root surface when used in root canals in vitro for laser assisted root canal treatment is investigated in this study. A total of 50 human single-rooted extracted teeth were included. For this study, the canals were enlarged up to an apical size of ISO#50 file. Laser irradiation was performed with six different settings. Specimens were irradiated at 0.6-1 W output power at the distal end of the fiber and about 1-1.5 W output power in the continuous mode (CW) as two groups. In the third group, 0.6-1 W output power, 10 ms pulse length (PL) and 10 ms interval duration (ID) were selected. In three other groups 1-1.5 W output power were used with different PL and ID as following: PL 10 and ID 10 ms, PL 10 and ID 20 ms and PL 20 and ID 20 ms. The total irradiation time was from 5 to 20 s per canal with a 200 mum in diameter and 25 mm long tip. After laser treatment, the temperature changes at the outer root surface were registered by means of NiCr-Ni measuring sensors and a T 202 thermometer. The safe temperature threshold for applying this diode laser in root canal is considered as 7 degrees C increase. To avoid increasing the temperature changes at the outer root surface related to this threshold, following total irradiation times were found: 0.6-1 W output power (10 ms PL/10 ms ID): 20 s (s), 1-1.5 W output power (10 ms/10 ms and 20 ms/20 ms): 15 s, 0.6-1 W output power CW and 1-1.5 W output power (20 ms PL/10 ms ID): 10 s and 1-1.5 W output power CW: 5 s. In the first three groups, 5 s irradiation and 5 s rest period avoided a temperature increase above the threshold of 7 degrees C).

Body Temperature↗

PubMed2005

Effects of Er:YAG and Nd:YAG lasers on dentin permeability in root surfaces: a preliminary in vitro study.

OBJECTIVE: This in vitro study evaluated the effects of Nd:YAG and Er:YAG lasers on reducing dentin permeability by sealing opened tubules. BACKGROUND DATA: According to hydrodynamic theory, dentine hypersensitivity occurs when dentin is exposed with tubules opened. Consequently, a painful sensation occurs due to an intensification of the dentinal permeability. Treatment, therefore, should be based on a decrease of this permeability, achieved by the obliteration of dentinal tubules. The Nd:YAG laser is known for its capacity to seal dentinal tubules; however, few studies concerning treatment with Er:YAG laser are available. METHODS: The Nd:YAG laser was used, based on two parameters: (A) 1.0 W, 10 Hz, and (B) 1.5 W, 15 Hz. The Er:YAG laser was used at 60 mJ, 2 Hz, four applications of 20 sec each, at 6 mm from the surface. After irradiation, all samples were immersed in 1% Rodamine B dye solution, in order to evaluate the penetration of the dye solution and observe the decrease/increase of dentinal permeability after the laser treatment. RESULTS: The laser conditions used in the present study decreased the permeability as follows: (a) when using the Er:YAG laser at 60 mJ, 2 Hz in 26.05%, and (b) when using the Nd:YAG laser at 1.5 W, 15 Hz in 19.03%--with no statistical difference between them. Additionally, the Nd:YAG laser at 1.0 W, 10 Hz, decreased permeability in 4.59%, with a smaller effect. CONCLUSIONS: According to the results of this in vitro study, the Er:YAG laser at 60 mJ, 2 Hz, and the Nd:YAG laser at 1.5 W, 15 Hz are useful for decreasing dentin permeability.

Analysis of Variance↗

PubMed2004

Multireflection pumping concept for miniaturized diode-pumped solid-state lasers.

An innovative pump concept for diode-pumped, solid-state lasers is introduced as an example for an Er:YSGG laser, permitting its miniaturization. Embedded in a multireflective pump cavity, the laser crystal is simultaneously side and end pumped. Specially calculated and shaped deflecting optics distribute the coaxially input pumping light homogeneously over the lateral surface of the crystal, therefore reducing the size of the laser head, including the optical resonator, to a length of 27.5 mm and an outside diameter of 12.5 mm. The differential efficiency achieved is between 8.7% and 24%. The laser emits energy of 15.7 mJ at an absolute efficiency of 9.1% and a repetition rate of 4 Hz.

Equipment Design↗

PubMed2004

Influence of the spatial beam profile on hard tissue ablation, part II: pulse energy and energy density distribution in simple beams.

When calculating applied flux densities in practice, the beam profile of a laser is often erroneously assumed to be homogeneous. In addition, there is usually no consistency in the choice of a suitable measuring method for determining the beam diameter. This failure to observe the inhomogeneous intensity distribution within the beam cross-section, combined with the imprecise knowledge of the beam diameter, leads to flux densities being stated that represent mean values at best. The present paper gives definitions for the flux densities of simple, radially symmetrical beam cross-sections, taking the top-hat and Gaussian profiles as examples. In connection with the inhomogeneous energy distribution in the Gaussian beam, a concept of integral and local energy density is discussed, which differs from the customary definition of the energy density as a constant. Also presented are the consequences of the mathematical concepts in terms of measurement, giving particular consideration to the case where the energy density as the measured variable matches the integral energy density. The significance of the integral and local energy density for hard-tissue ablation is described, based on the practical example of the ablation of dental hard substance. The central result is that the integral flux density is directly accessible as a measured variable, while the effect on the tissue is determined by the local flux density. If the form of the beam is known, the integral flux density can be converted into the local flux density.

Dental Enamel↗