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Biomedical subjects

J Härtel

Publications and source records attributed to J Härtel.

At least 19 recordsLinked to original sources
PubMed2004

The influence of pre- and intraoperative positioning of the condyle in the centre of the articular fossa on the position of the disc in orthognathic surgery. A magnetic resonance study.

OBJECTIVE: We investigated the changes in the temporomandibular joint (TMJ) after bilateral sagittal split osteotomy of the mandible for orthognathic surgery and the influence of positioning of the condylar process in the centre of the articular fossa before and during the operation for preventing changes in the TMJ postoperatively. STUDY DESIGN: A total of 28 patients with mandibular retrognathism had bilateral sagittal split osteotomies for mandibular advancement. In one group of 14 patients (28 TMJ), the condyles were placed in the centre of the articular fossa before and during the operation, and in the other group they were not. Differences on magnetic resonance imaging (MRI) were calculated and the results were evaluated. RESULTS: The main differences were found at maximal mouth opening. 15/28 TMJs (54%) that had not been positioned changed the position of the disc from physiological to anterior disc derangement with and without reduction postoperatively. In the 28 that had been positioned, changes were found in only 3 TMJs (11%) postoperatively. CONCLUSIONS: Fixing the condylar process in the centre of the articular fossa intraoperatively before bilateral sagittal split osteotomy is a factor in preventing postoperative structural changes in the temporomandibular joint.

Humans↗
PubMed2002

[Stimulating regeneration of bone defects by implantation of bioceramics and autologous osteoblast transplantation].

QUESTION: Does artificial stimulation of osteoconduction and osteogenesis lead to improved bone formation in defects of critical size? MATERIAL AND METHODS: Full-thickness, critical-sized defects in the anterior mandible were created in 24 adult mini-pigs. These defects were treated with a new kind of bioactive ceramic (60% hydroxylapatite and 40% beta-tricalcium phosphate), applied as a unique sol gel [9]. The bioceramic was tested alone and in combination with autologous osteoblasts. In a control group, periosteum was the only bone-producing source. After 5 weeks, the animals were sacrificed and the defects analyzed clinically, histologically, and by X-ray examination. The effects of periosteum, bioceramics, and osteoblasts were investigated in particular. RESULTS: The new bioceramic was degraded at the same speed as new bone was laid down. The rate of newly formed bone was highest in the bioceramic group at 72.3% (control group with periosteal covering only 59.3%). Additional transplantation of autologous osteoblasts did not result in faster bone production. CONCLUSION: It seems that this bioactive ceramic is successful as a bone replacement material and will be suitable as a carrier for osteoinductive substances such as bone morphogenetic proteins.

Animals↗
PubMed1999

The period of latency before a muscle receptor generates an action potential as a response to a muscle stretch.

Six primary (Ia) and seven secondary (II) muscle spindle afferents and eight Golgi tendon organ afferents (Ib) from the tibial anterior muscle of the cat, recorded at the dorsal roots, were subjected to a sinusoidal stretch of the host muscle, the frequency of which increased linearly from 2 to 80 Hz over four different lengths of time. Both the amplitude of the sinusoidal stretch and the prestretch of the muscle were varied. The phase of the action potentials was determined. The phase of the action potential, driven 1:1, increased linearly with frequency. From the gradient of the phase of this action potential the muscle-muscle receptor latency was determined, i.e., the period of latency between the stretch of the muscle and the occurrence of the action potential at the muscle nerve where it enters the muscle. The muscle-muscle receptor latency had values lying between 3 and 8 ms: it was dependent on the experimental parameters and became shorter as the conduction velocity of the afferent fiber increased. In three experiments the muscle latency was determined, i.e., the period of latency before the stretch was transferred from the tendon of the muscle to the proximal third of the muscle belly. The muscle was stretched sinusoidally under the same varying parameters as given above. The length changes occurring in the proximal third of the muscle were measured with a piezo element. The muscle latency was determined from the slope of the phase of the zero points of the sinusoidal piezo length changes; the phase increases linearly with frequency. The muscle latency had values lying between 6 and 15 ms: it was dependent on the experimental parameters. The muscle spindle latency, i.e., the period of latency between the stretch of the polar parts of the intrafusal muscle fibers and the recording of the action potentials from the spindle nerve near the spindle capsule, was determined from 5 Ia fibers and 1 II fiber of isolated muscle spindles. The isolated muscle spindle was stretched under the same varying parameters as given above. The muscle spindle latency was determined from the slope of the phase of the phase-locked action potential. The muscle spindle latency as measured by our method proved to be 0 ms. The latencies of the three elements and their dependence on the experimental parameters are discussed in the light of the transfer properties of the muscle and the muscle receptors.

Action Potentials↗
PubMed1999

Dental implants in alveolar cleft patients: a retrospective study.

Since 1994, 15 cleft patients have received dental implants after treatment of the alveolar clefts by osteoplastic measures. Altogether 23 dental implants were undertaken. Twelve implants were inserted after tertiary osteoplasty, 7 with simultaneous repeat-osteoplasty, and another 4 implants following two-stage re-osteoplasty. In 11 patients with a total of 17 implants clinical and radiological follow-ups were performed. An individual crown was constructed on each of the implants. The radiological evaluation revealed that 70% of the implants were fully embedded in bone. All implants except one remained in situ and stable. Thus, the success rate was 96% retention. It is believed that a dental implant in the alveolar cleft may be lost because of its unfavourable location in terms of stability and function or because it was inserted too late. Scars resulting from previous surgery can also play a role in the failure of an implant. Therefore it is proposed that dental implants should not be inserted later than 6 to 8 weeks following osteoplasty of the cleft alveolus.

Adolescent↗
PubMed1994

[The late results following velopharyngoplasty. A data comparison of the 2 cleft centers of Hamburg and Rostock].

Speech results were evaluated in 349 patients following velopharyngoplasty in all cases according to Sanvenero-Rosselli. Velopharyngoplasty was performed several years after palatoplasty in either the Rostock or the Hamburg cleft centers. Comparison of the data revealed that the outcome after velopharyngoplasty in relation to speech was more or less the same in the patients from both centers. In 90% of the patients with clefts of the lip, alveolus, and palate, and in over 90% of those patients with only cleft palates, voice sound was at a level between 1 and 2 on a scale to 3 and on average levels of 1.46 and 1.53 were achieved. These results document that the surgery, when combined with close interdisciplinary team work with the speech therapist, culminated in the successful rehabilitation of cleft patients at both cleft centers.

Child↗
PubMed1994

Incidence of velopharyngoplasty following various techniques of palatoplasty.

A total of 474 patients with cleft palates were treated at the Department for Maxillofacial Surgery of Rostock University from 1971 to 1991. In 145 cases velopharyngoplasty was indicated. Primary velopharyngoplasty was performed on 36 and secondary velopharyngoplasty on 109 patients. In our opinion today primary velopharyngoplasty should be the exception. Intravelar veloplasty according to Kriens (1970) created particularly favorable conditions for good velar function so that secondary pharyngoplasty was only rarely indicated. Secondary pharyngoplasty should be performed and timed only in agreement with the speech therapist.

Alveolar Process↗
PubMed1994

[Fractures of the facial skull in the growth period and concomitant injuries].

From 1968 to 1990, 135 children up to the age of 14 years were treated as in-patients for fractures of the facial skull. Most had been sustained in traffic accident. Other associated lesions were seen in 80 patients. In 21 of these we observed general surgical traumas or fractures of the base of the skull, and in 23 patients cerebral traumas were detected. Treatment was instituted an average of 1.7 days after the trauma in the case of patients with no associated injuries and of 5.6 days in the case of those with other injuries. Definitive treatment had been applied within 6 days after the accident in 80% of patients with other injuries and/or with fractures of the skull base.

Adolescent↗
PubMed1991

Incidence of cleft lip, alveolus and palate forms.

The different cleft forms of 1,450 cleft lip, alveolus and/or palate patients have been analyzed. Randomized groups of 50 plus the next 50 patients and so forth have been examined. The resulting 29 groups reveal a maximum of 139 different clinical cleft forms. The prediction of a possible maximum was made with the exponential formula y = a. (1-eb.x). The tendency of the prognosis levels at a maximum of 169 different cleft forms in and above 4900 patients.

Alveolar Process↗
PubMed1990

[Experimental animal studies on the possibilities of bone reconstruction using preserved allogenic material].

Preserved allogeneic bone is possibly to repair the permanent shortness in autogeneic bone tissue in clinical practice. Complications as to the incorporation were observed after using lyophilised allogeneic implants. These were attributes to immunologic defense reaction. Demineralised bone caused a more intensive bone regeneration histologically than lyophilised bone. The clinical test of a superficial demineralised lyophilised preserved bone with osteoinductive potency and structural stability is recommended.

Animals↗
PubMed1990

[Late results of corrective surgery of protruding external ears].

In the period 1974-1984 corrections of the external ear were carried out on 343 patients using the Haecker/Joseph method for flattening and the Converse method for anthelixplasty. Check-ups on 147 patients revealed late results to be "improved to very good" in 92.5% of cases on the basis of metrical data and aesthetic appraisal of the corrected external ear. Provided that there is a firm indication and exact pre-operative diagnosis combined with good surgical technique and post-operative care, these two methods represent well-tried procedures with a high success rate.

Child↗
PubMed1988

[The healing of osteotomies of the lower jaw and the adaptation of the masticatory muscles after miniplate osteosynthesis in rabbits. I. Radiologic and histological evaluation of the lower jaw].

Radiographic and histological investigations were carried out on a total of 15 rabbits after lower-jaw osteotomy and miniplate osteosynthesis. After the removal of the lower jaw (4, 8, 12 and 24 weeks) consolidation of the osteotomy surfaces without complications was observed in all animals. Radiographic examinations showed that callus formation in the operated area increased as the experiment proceeded. Histological observations made clear that only secondary bone-fracture healing resulted which must be attributed to the operation technique. These findings show that the lower jaw of the rabbit is very well suited to experimental research on miniplate osteosynthesis.

Animals↗
PubMed1988

[Osteotomy healing of the lower jaw and the adaptation of the masticatory muscles after miniplate osteosynthesis in rabbits. II. Response pattern of the masticatory muscles (M. masseter)].

16 operated 4 control animals of both sexes were included in the study following osteotomy of the lower jaw and subsequent miniplate osteosynthesis. In addition, muscle tissue excised from 8 rabbits was evaluated at the time of the operation as additional normal material. The study was conducted over 4, 8, 12 and 24 weeks, after which periods the animals were killed and their left and right masseters examined and compared in histological, histochemical and morphometric terms. The masticatory muscles of the control rabbits displayed a marked sex dimorphism. The males had strikingly large, predominantly type-2 fibres, whereas the fibre diameters in the females were found to differ less clearly, with type-1 fibres being predominant. In terms of muscle regeneration, it was found that following soft-part trauma small localized defects (biopsy) had healed completely after 12 weeks. In the residual parenchyma, signs of adaptation to a changed mastication as a result of the experimental operation (osteotomy of the lower jaw, miniplate osteosynthesis, muscle biopsy) could be identified. Atrophy as a result of non-use was found to occur to a limited extent, whereas the number of type-2C fibres and fibre type transformations were raised significantly. After the surgery, the organization of the impaired muscle fibres was aided by a stabilization and rest positioning of the parts concerned. The muscle fibres reinnervation that followed was supported by functional exercise and nerve impulses.

Animals↗