Biomedical subjects

S Hassfeld

Publications and source records attributed to S Hassfeld.

77 records · Page 5Linked to original sources

PubMed1995

Intraoperative navigation in oral and maxillofacial surgery.

Surgical procedures in the oral and maxillofacial region may be difficult in areas of complex anatomy. Up to now, surgical planning has been based almost exclusively on the surgeon's experience and on the interpretation of 2-dimensional (2D) radiologic information. Our experiences with a commercially available 3D navigation system (Viewing Wand, ISG, Mississauga, Ontario, Canada) is reported upon. The system consists of a mechanical operating arm with 6 joints and 6 degrees of freedom working as a 3D digitizer and is interfaced to a computer graphics workstation. After registration of the position of the patient's head in relation to the tip of the instrument on the navigation arm, the surgeon can observe the 3D position and direction of the instrument in use on the monitor, i.e. on the computed tomography and/or magnetic resonance tomography images of the patient taken before. In 40 interventions performed so far, the accuracy was 2 mm and better. 3 cases are presented in this paper. The system facilitates surgery especially in anatomically complicated situations without the risk of damaging neighbouring structures. Planning of surgical interventions is much easier. By using computer assisted simulation and navigation systems, we expect an improvement in quality and a reduction in surgical risks. Thus, "looking ahead" surgery has become possible. More extensive and more radical interventions are likely to be performed in the near future. Responsibility for the surgical intervention, however, remains exclusively with the surgeon.

Carcinoma, Adenoid Cystic↗

PubMed1992

[Jaw opening reflex: a new electrophysiologic method for objective assessment of trigeminal sensory disorders. I. Method and normal values].

Retrospective analysis of trigeminal nerve evoked potentials in 40 consecutive patients, most of them with traumatic nerve lesions, showed that in 12 cases no trigeminal nerve SEP were obtainable, and 11 of the remaining 28 patients had normal trigeminal nerve SEP. Therefore the jaw-opening reflex was investigated as a potential tool for electrophysiologic analysis of facial sensory disturbances. The jaw-opening reflex was investigated in 60 healthy subjects (31 female, 29 male) aged 23-82 years. It was elicited by electrical 0.1 ms square wave pulses delivered to the lower and upper lips and to the infraorbital region on either side at a rate below 1 per 5s. The EMG responses were recorded from the bilateral masseter and temporalis muscles at a moderate voluntary activation. Under these conditions, the jaw-opening reflex reveals itself as two inhibitory pauses of the ongoing EMG on both sides, the onset latency of the first EMG-suppression being 10-15 ms, and of the second 35-50 ms. Particular attention was paid to the stimulus strength at threshold (TR) to evoke the jaw-opening reflex. We found that the jaw-opening reflex was constantly evoked by weak stimuli applied to the 2nd and 3rd trigeminal branches. Bilateral reflex responses with unilateral stimulation were a regular finding. The reflex responses increase with increasing stimulus strength (Fig. 1). Moderate to forcible activation of the jaw closing muscles is a prerequisite for optimum recordings of the jaw-opening reflex (Fig. 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

[Comparison of two methods for conscious sedation in maxillofacial surgery with local anesthesia].

A randomised, prospective study was conducted to compare the efficiency and safety of methods for intravenous conscious sedation in patients undergoing oral surgery under local analgesia. 150 systemically healthy patients (ASA Class I and II) participated. Three groups were formed: group 1 received 0.05 mg/kg midazolam; group 2 0.05 mg/kg midazolam, 1.5 mg/kg tramadol, 50 mg alizaprid; group 3 0.05 mg/kg midazolam, 0.2 mg/kg nalbuphine, 50 mg alizaprid. Blood pressure, heart rate and oxygen saturation were measured throughout the procedure. The results confirmed that the use of nalbuphine (group 3) allows a reduction in the mean dosage of midazolam required to produce satisfactory sedation and effected a more rapid recovery time compared to group 12 and 2. With the combination nalbuphine and alizaprid nausea and vomiting could be reduced for the most part compared to group 2.

Procedural Sedation↗

PubMedDate not supplied

Digital radiography of interproximal caries: effect of different filters.

The aim of this study was to compare the effect of different image processing modes (filters) on reproducibility and validity of the assessment of interproximal carious lesions on digitized radiographic images. Standardized radiographs of 34 extracted teeth exhibiting interproximal caries were obtained. All radiographs were digitized and using the FRIACOM-software the central depth (CD) of each carious lesion was measured on the unchanged radiographic image and after use of five different filters with 7fold and 18fold magnification. All measurements were repeated after 1 week to estimate reproducibility. Histometric CD assessments provided a gold standard for comparison with the radiographic measurements (validity). Neither reproducibility nor validity of CD measurements were improved by one of the filters. Measurements of dentinal lesions showed a statistically higher variability than those of enamel lesions (p<0.001). 18fold magnification provided more valid CD measurements than 7fold magnification (p<0.001). In this study digital manipulations of radiographic images failed to result in statistically significantly improved reproducibility or validity of CD measurements.

Dental Caries↗

PubMedDate not supplied

AIDA: Web agents to support dental treatment planning.

Dental treatment planning is highly dependent on the educational background and personal experience of the dentist and on the thoroughness with which findings are taken. The objective of research in the AIDA (Artificially Intelligent Dental Agents) project is therefore the analysis of dental decision making and the design of a decision-supportive software module to test the decision-making process and make it transparent for both dentists and patients. In the AIDA project (aida.uni-hd.de), an expert system has been set up to identify treatment alternatives with integrated decision rationale for experts, practicing dentists, and eventually also patients. It is based on a top-down structure for dental decision-making, which was developed to standardize argumentation. For prosthetic dentistry, how one uses individual patient findings to arrive at possible treatment alternatives was clarified in greater detail. The planning rules for fixed prostheses have already been integrated into a software agent. Other modules should soon specify and verify these suggestions in terms of further fields of dentistry (e.g., restorative dentistry). In the near future, AIDA will be able to deliver dentally-founded justifications for every individual decision.

Decision Making, Computer-Assisted↗