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Biomedical subjects

W H Raab

Publications and source records attributed to W H Raab.

At least 19 recordsLinked to original sources
PubMed1992

Temperature related changes in pulpal microcirculation.

During dental treatment temperatures can be reached which might possibly damage the tooth pulp. To determine the effect of both thermal stimulation on pulpal microcirculation and local anesthesia on thermoregulation we measured the pulpal blood flow by using laser Doppler flowmetry. Experiments were carried out on lower incisors of Wistar rats anaesthetized with thiopental. The rats were divided into three groups, with one remaining untreated, and the others being either desensitized with capsaicin or sympathectomized with guanethidine. In a range between 33 degrees C and 42 degrees C there was no substantial change in blood flow, which, however, was the case below 33 degrees C. Up to 49 degrees C an increase could be recorded in both untreated and guanethidine pretreated animals, whereas the capsaicin groups showed almost no reaction. This increase in blood flow can be blocked reversibly by local anaesthesia. For this purpose we tested articain 5% and mepivacain 3%, both without constrictor. Intravital microscopic studies show that the temperature related increase in blood flow is also associated with plasma extravasation. From these results we draw the conclusion that pulpal thermoregulation is linked to nociceptive sensory neurons and can be described as "neurogenic inflammation".

Anesthesia, Dental↗
PubMed1991

[Acute and chronic toothache].

Toothache occurs as a result of pulpal and periodontal diseases. Due to the nature of their innervation pain is the only means for both pulp and dentine to react to all kinds of external stimuli. The actual mechanism of sensory transmission, however, has not been clarified, yet. In contrast to this, the innervation of the periodontium offers a wide range of mechano-sensitive receptors. Chronic dental pain is mainly the result of inflammatory reactions. Nerve sprouting, summation, convergence in the trigeminal system and regional inflammatory conditions modulate the local pain process, thus complicating diagnosis. The differential diagnostic clarification with regard to neuralgiform and ENT-diseases therefore requires special care with case history and status. Although there have been advances in pain research over the last few years, no fundamental development in dental diagnosis has been brought about, yet. Probing, sensitivity- and percussion testing as well as x-ray exposure are still the most important diagnostic tools for the dental practitioner.

Acute Disease↗
PubMed1991

[Pulp reactions during Erbium YAG laser irradiation of hard tooth structure].

The Er:YAG Laser is an effective tool for removing hard tooth structure without causing any measurable degree of thermal damage. In view of the fact that the process of ablation basically depends on thermal effects, pulpal microcirculation was studied by Laser-Doppler flowmetry during Er:YAG Laser irradiation. Rat incisors were used to demonstrate that pulp damage can be avoided if correct laser parameters are used for preparing enamel and dentin.

Animals↗
PubMed1991

[Studies on the perception of periodontal stimuli].

The stimulation of the periodontium causes a reflex response of the jaw muscles and at the same time a perceptive reaction of the central nervous system. The aim of our study was to develop a method for the objective assessment of the subjective perception experienced after stimulating the periodontium. Seven healthy volunteers took part in these experiments in the course of which mechanical stimuli (2.5 N, 750 microseconds) were applied perpendicular to the tooth, thus leading to a stimulation of the periodontium. Sensory evoked potentials of the periodontium (SEP-PA) elicited from the EEG served as an objective measure of perception. A computerized analysis of the data thus obtained allows an assessment of the change in perception following repeated periodontal stimulation at different rates.

Electroencephalography↗
PubMed1991

[Difference reflectometry might permit process control for dental laser applications].

Difference reflectometry is a new method for assessing material surfaces by measuring the relative amount of light reflected within a range of 300-720 nm. The in vivo and in vitro results of the present study indicate that it is possible to transfer this measuring principle to dental applications. Reflexion measurements allow the detection of hard tooth structures and their pathologic alterations with adequate exactness. With the aid of this method it is possible to differentiate between carious hard tissues and clinically healthy tissues by color and surface structure during excavation. It also allows a reliable demarcation from oral soft tissues. Due to its high measuring frequency it may be used as on-line process control. In contrast to other spectrometric methods it requires a minimum of equipment and is easy to handle.

Dental Caries↗
PubMed1991

[The influence of brushing methods on wedge-shaped defects].

By experimentally brushing 20 teeth vertically to the tooth axis under a pressure of 2 N only lesions in cementum or dentine could be obtained. There was no case in which enamel was damaged by our brushing experiments. Therefore, defects appearing clinically cannot be explained by wrong tooth brushing techniques. There were several parallel lesions (similar to a saw blade) to be found as well as confluent hard tissue losses. Both indicate the direction of the movement of the tooth brush. The smallest defect to be measured in coronal-apical direction was 2.25 mm, the biggest 6.7 mm. The depth of the defects ranged front 239.9 microns to 493.2 microns. A correlation between Vicker's hardness and substance abrasion could not be proved, nor was the clinical appearance of wedge-shaped defects to be achieved by means of our experimental device. The formation of enamel defects cannot be explained by mere mechanical abrasion due to tooth brushing. In our opinions the formation of wedge-shaped defects implies a multicausal process.

Dental Enamel↗
PubMed1990

[Reactive changes in the periodontal microcirculation under orthodontic forces].

The influence of intrusive forces on the periodontal microcirculation exerted as conventional through brackets on the teeth is demonstrated with laser Doppler flowmetry. This noninvasive method shows that forces of 0.1 N on the human upper incisor cause a decrease of the periodontal perfusion of 20% which shall regain its initial level after 50-80 seconds. With an intrusive force of 0.5 N the perfusion decreases 42% within two to three seconds, which however shall not even regain its original level after ten minutes. Immobilisation of the teeth and infiltrative anaesthesia with vasoconstrictor were carried out in order to specify these measurements.

Adult↗
PubMed1990

[SEM study of radiogenic caries].

The present SEH study could show that radiogenic caries is accompanied by morphological changes at the dentine-enamel junction. These changes appear as lacunar defects of up to 300 microns in size. This kind of defect was found in 28 of 32 teeth which were exposed to radiation of more than 40 Gy. In a control group with caries of the smooth surfaces no comparable results could be obtained.

Dental Caries↗
PubMed1990

[Sensory and inflammatory reaction mechanisms in the dental pulp].

Laser-Doppler-flowmetry is used to show whether electrical stimulation of the rats tooth pulp leads to reactions such as neurogenic inflammations. Following electrical stimulation, a flow reduction with a subsequent flow increase can be observed After experimental elimination it can be shown that both sympathetic and nociceptive fibres are involved in this reaction. Thus the neurogenic inflammation of the dental pulp is a mechanism allowing early and localised reactions to noxious stimuli.

Animals↗
PubMed1990

[The effects of local anesthesia on the thermoregulation of the tooth pulp].

Laser Doppler flowmetry was used to measure the effects of local anesthesia on the thermoregulation of the tooth pulp. Heat affecting the pulp is physiologically offset by a reactive increase in blood flow. An increase in temperature from 35 degrees C to 45 degrees C results in an increase in blood flow by 100%, on an average. Local anesthetics produce a reversible block of this protective mechanism, thus eliminating more or less the reactive increase in blood flow. Under local anesthesia the defence power of the tooth pulp against noxious temperatures seems to be considerably reduced.

Anesthesia, Local↗
PubMed1990

[A procedure for testing local anesthetics].

A method for testing intensity and duration of the effect of local anaesthetics is presented. The assessment of effectiveness is based on the subjective perception threshold after painful electrical tooth pulp stimuli. With respect to its practical applicability the method is tested in a clinical study using three commercial local anaesthetics. The results prove the possibility of giving reproducible and quantitative statements concerning the time course and intensity of anaesthesia. Using this method, only a restricted number of subjects is necessary for estimating the differences in the basic features of different local anaesthetics.

Acetanilides↗
PubMed1990

[Vitality tests of the tooth pulp using laser Doppler flowmetry].

Laser-Doppler flowmetry allows a non-invasive assessment of the microcirculation in circumscribed tissue areas. However, measurements in intact human teeth prove to be extensive, as far as instrumental equipment and time requirements are concerned. Therefore we developed an application system which allows us to transfer the principle of measurement under clinical conditions. Thus we were able to prove that the signal recorded can be regarded as a specific expression of pulpal microcirculation. A comparison between vital teeth and root-filled teeth shows that the signal to noise ratio is sufficiently high to allow a definite assessment of pulp vitality.

Dental Pulp↗
PubMed1990

[Pulp toxicity of luting cements].

With the aid of laser-Doppler-flowmetry we are able to determine changes in the microcirculation of the tooth pulp. This method can also be used for testing the histocompatibility of dental materials. The zinkoxiphosphate cement Tenet and the glass ionomer cement Ketac-Cem are examined for tissue tolerance. This is done by determining the incisal and apical changes in pulpal microcirculation. Tenet has almost no discernible effect on pulpal microcirculation. Ketac-Cem causes a longlasting hyperaemia in half of the cases which seems to depend on the depth of cavity preparation.

Animals↗
PubMed1990

[Assessment of tooth pulp reaction to dental materials in an animal experiment].

Laser Doppler flowmetry is a useful method for quantifying changes in microcirculation. The present study is designed to clarify if this method may also be used to assess the biocompatibility of dental materials. The experiments carried out on rats' incisors have shown that it is possible to record circulatory reactions occurring in the direct vicinity of the site of application. The reactive change in microcirculation in the apical part clearly differs from the local reaction at the site of application. A modification of the experimental set up allows the synchronous recording of blood flow in the apical and the incisal parts of the pulp. Calcium hydroxide is used to illustrate the local and the overall circulatory reaction of the dental pulp.

Animals↗
PubMed1990

[Pulp toxicity of the acid components of acid-base reaction cements].

Laser-Doppler-flowmetry enables us to assess microcirculatory changes in the tooth pulp. This method can also be used for testing the histocompatibility of dental materials. The acid components of Tenet and Ketac-Cem are examined for tissue tolerance. This is done by assessing the incisal and apical changes in pulpal microcirculation. The phosphoric acid of Tenet causes an almost complete collapse of the incisal microcirculation just a short time after its application. The tartrate of Ketac-Cem causes long-lasting hyperaemia, whereas the acryl-maleinate-copolymer has no discernible effects.

Animals↗
PubMed1989

[Temperature-dependent changes in the microcirculation of the dental pulp].

Laser Doppler flowmetry was used to study the changes in the blood flow within the dental pulp as a reaction to thermal stimuli between 17 degrees C and 57 degree C. Temperatures below 31 degrees C resulted in a reduction, temperatures above 43 degrees C in an increase in blood flow. Temperatures higher than 49 degrees C caused irreversible damage to the pulp's microcirculation. Experimental nerve blocks showed that the reactive increase is linked to the afferent rather than the sympathetic innervation of the tooth pulp.

Dental Pulp↗