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Biomedical subjects

G Boering

Publications and source records attributed to G Boering.

At least 73 records · Page 4Linked to original sources
PubMed1992

Temporomandibular joint osteoarthrosis and generalized joint hypermobility.

Peripheral joint mobility of temporomandibular joint (TMJ) osteoarthrosis and internal derangement patients (n = 25) and of a control group (n = 29) was measured according to a rigidly standardized protocol, in order to study the relationships between TMJ osteoarthrosis and internal derangement and generalized joint hypermobility. No significant differences in peripheral joint mobility between the two groups were found. Therefore, generalized joint hypermobility cannot be considered as a predisposing factor for TMJ osteoarthrosis.

Adolescent↗
PubMed1992

[Chronic facial pain due to nerve injury. Deafferentation pain].

Patients presenting chronic facial pain are very common. After profound examination a significant cause for this pain often cannot be found. Some patients are suffering from this pain due to injury of a sensible nerve and then it is called deafferentation pain. This somatic disorder can give different complaints. Pain can develop as a result of formation of neuromas 'cross-talking' of nerves and alterations in the central nerve system. It seems to be difficult to make clinical features to diagnose deafferentation pain and differentiate it from pain disorders where the psychic suffering seems to be very important. The treatment is based mainly on the reduction of the conducting of abnormal pulses by the damaged or changed nerves.

Chronic Disease↗
PubMed1992

[Secondary retention of permanent molars. I. Clinical, radiologic and histologic characterization].

The clinical, radiographical and histological aspects of secondary retention in permanent molars were studied in a group of 53 patients with 81 secondarily retained permanent molars. First molars turned out to be affected most frequently. The mean infraocclusion at the patients' first visit was 4.3 mm. After six months, infraocclusion had increased in adolescents. It seemed to be stable in adults. Tilting of adjacent teeth was observed in 39 cases of secondary retention. A solid, clear percussion sound and a partial absence of the periodontal ligament space on radiographs was only noted in less than 20% of the affected molars, while histological examination of 38 removed molars revealed that local areas of ankylosis were present in all cases. During a follow-up period of four years, six new cases of secondary retention were observed in the same population.

Adolescent↗
PubMed1992

[Secondary retention of permanent molars. II. Therapy].

The efficacy of 5 treatment modalities for secondary retention of permanent molars was evaluated in 62 patients with 92 affected molars. The results showed that a prosthetic build up is a proper treatment if secondary retention develops late in or after the growth spurt. In these cases the extent of infraocclusion is slight and relatively stable. If secondary retention starts before the growth spurt, immediate removal of the retained molar followed by orthodontic treatment to close the diastema gives maximal success. When secondary retention develops during the growth spurt, the tooth affected has to be observed at six monthly intervals. In such cases, no active treatment is indicated if the extent of infraocclusion is minor and stable. In all other cases the affected molar should be removed, followed by orthodontic closure of the diastema.

Adolescent↗
PubMed1991

The effects of different steam-sterilization programs on material properties of poly(L-lactide).

As-polymerized poly(L-lactide) test rods were sterilized by seven different specially designed computer-operated autoclaving programs. As a control, common hospital sterilization was performed. In all cases, the molecular weight decreased after sterilization. A short time high-temperature sterilization led to less molecular weight decrease than a low sterilization temperature cycle with a longer sterilization time. Regular hospital sterilization significantly reduced the elongation at break and also resulted in a decrease of 35% in tensile strength. The program causing minimal damage to the material properties was studied in detail. This program, with a sterilization period of 60 s and 129 degrees C, was effective for PLLA sterilization and also looks very promising for sterilization of other thermo- and moisture-labile polymers.

Humans↗
PubMed1991

Degradation of and tissue reaction to biodegradable poly(L-lactide) for use as internal fixation of fractures: a study in rats.

Samples of high-molecular-weight poly(L-lactide) (PLLA) (Mv = 9.0 x 10(5), a biomaterial developed for plates and screws used in internal fixation of jaw fractures, were implanted subcutaneously in the backs of rats to study tissue reaction to PLLA and to follow the degradation process. The PLLA seemed to follow the degradation pattern typical of biodegradable polyesters. After pure hydrolysis up to about 104 wk, phagocytic activity of macrophages was found at about 143 wk. Full resorption of PLLA was not demonstrated in this study. Except for the early and final parts of the implant period, no acute or chronic inflammatory reaction was observed. No implant was rejected. It is estimated that more than 3 yr will be required for total resorption of PLLA. For bone-healing this long period is of no practical importance. There is no need for removal of PLLA after fracture healing as is the case with metal fixation devices. Thus, PLLA has potential application in internal fixation of fractures and osteotomies in the maxillofacial region and other fractures that are not too heavily loaded in the human body.

Animals↗
PubMed1991

Tissue responses to degenerative changes in the temporomandibular joint: a review.

The articular cartilage covering of the mandibular condyle and the articular eminence, as well as the tissue of the articular disc, may be affected by degenerative changes associated with osteoarthrosis. Degenerative changes of cartilage alter its physical properties and, as a result, affect its ability to withstand compressive and shearing stresses. Increased friction between the articular surfaces may impair joint movement and may elicit compensatory or pathologic responses of the cartilage and the adjacent tissues, such as capsule and ligaments, synovial membrane, subchondral bone, and associated musculature. In this review, these structural changes are described and related to common signs and symptoms of craniomandibular dysfunction, such as clicking, locking and instability, pain and tenderness, restricted ranges of mandibular motion, crepitation, deformity, muscle wasting, and changes of occlusion.

Adaptation, Biological↗
PubMed1991

Clinical, radiographic and histological characteristics of secondary retention of permanent molars.

Secondary retention refers to the cessation of eruption of a tooth after emergence neither due to a physical barrier in the path of eruption nor as a result of an abnormal position. In this study, the clinical and radiographic features of 81 secondary retained permanent molars in a group of 53 patients were evaluated. Retained molars removed for therapeutic reasons (n = 38) were examined histologically to detect any areas of ankylosis. The first molars in the mandible and maxilla were most frequently affected. The mean infraocclusion at the patients' first visit was 4.3 +/- 1.9 mm. After 6 months, infraocclusion increased in adolescents but was stable in adults. Tilting of the adjacent teeth was observed in 39 cases. A sharp, solid percussion sound and a partial absence of the periodontal ligament space on radiographs were noted in less than one-fifth of the affected molars, while histological evaluation revealed that local areas of ankylosis were present in all cases. From the data relating to the 38 molars removed for therapeutic reasons, the sensitivity of the percussion test and radiographic evaluation was found to be 29 and 21 per cent respectively. During a period of 4 years, six new cases of secondary retention were observed in the same population. From this study it is concluded that secondary retention of permanent molars seems to be associated with focal ankylosis and that percussion tests and radiographs are not sufficiently reliable to exclude the presence of ankylotic areas. The presence of ankylotic areas and tendency of infraocclusion to increase in adolescents but to be stable in adults have major implications for therapy.

Adolescent↗
PubMed1991

A comparative study of electromyograms of the masseter, temporalis, and anterior digastric muscles obtained by surface and intramuscular electrodes: raw-EMG.

Electromyographic activity was synchronously recorded by surface and intramuscular electrodes in the same muscle. The activity of the left masseter, left temporalis, and both bellies of the anterior digastric muscle was studied by this double registration technique. In rest position no electromyographic activity could be detected in any of the muscles by both techniques. Both techniques give comparable results in cyclic jaw movements. In isometric contractions, however, differences in the registered activity were observed between the surface electrode on the depressor group muscles and the intramuscularly recorded anterior digastric muscles. Silent periods evoked in the elevator muscles were of slightly longer duration when recorded by intramuscular electrodes than when recorded by surface electrodes. A protruded position of the mandible results in a silent period of longer duration than the position of the mandible in maximal occlusion during clenching for both techniques.

Adult↗
PubMed1991

Eruption disturbances of permanent molars: a review.

Eruption disturbances of permanent molars may become clinically and radiographically manifest as impaction, primary retention or secondary retention. This may result in clinical problems such as malocclusion and loss of neighboring teeth due to caries and periodontal disease. Which of these disorders will develop, depends primarily on the eruptive stage. Factors that may interfere with the eruptive stages (i.e. follicular growth, pre-emergent eruptive spurt, postemergent eruptive spurt, juvenile occlusal equilibrium, circumpubertal occlusal eruptive spurt, adult occlusal equilibrium) and the clinical consequences of that interference are reviewed. Treatment recommendations are given.

Humans↗
PubMed1991

[Retrospective evaluation of the staple-bone-implant].

Sixty-four patients with denture problems, were treated with the staple-bone-implant, within a period of five years. The implant is indicated for patients having a severe resorbed mandibula (8-15 millimeter) to create a better stability and function with the new denture. The implant, the operative and prosthetic procedures, the methods and the results are presented. Until now a success rate of 92% can be mentioned.

Alveolar Bone Loss↗
PubMed1990

Temporomandibular joint direct sagittal computed tomography: evaluation of image-processing modalities.

Computed tomography (CT) is a useful method for examination of the temporomandibular joint because it allows visualization of the articular disk. In computed tomography many factors play an important role in image reconstruction and image processing. The use of image-processing modalities (such as window variation and level detection) has far-reaching consequences on the display and interpretation of the direct sagittal CT image of the temporomandibular joint (TMJ). In this study, the most important image reconstruction and processing factors were studied for use in the diagnosis of internal derangements and other disorders of the TMJ. Optimal values for the setting of the CT system for the different techniques are discussed.

Humans↗
PubMed1990

Temporomandibular joint computed tomography: development of a direct sagittal technique.

Radiology plays an important role in the diagnosis of temporomandibular disorders. Different techniques are used with computed tomography offering simultaneous imaging of bone and soft tissues. It is therefore suited for visualization of the articular disk and may be used in patients with suspected internal derangements and other disorders of the temporomandibular joint. Previous research suggests advantages to direct sagittal scanning, which requires special positioning of the patient and a sophisticated scanning technique. This study describes the development of a new technique of direct sagittal computed tomographic imaging of the temporomandibular joint using a specially designed patient table and internal light visor positioning. No structures other than the patient's head are involved in the imaging process, and misleading artifacts from the arm or the shoulder are eliminated. The use of the scanogram allows precise correction of the condylar axis and selection of exact slice level.

Adolescent↗
PubMed1990

Treatment of the retained permanent molar.

The effect of five different treatments for retained permanent molars was evaluated in 59 patients to develop a rational guideline for adequate therapy. The results showed that a prosthetic buildup is the proper treatment if retention develops after the growth spurt, because in these cases the extent of infraocclusion is slight and relatively stable. If retention develops before the growth spurt, immediate removal of the retained molar followed by orthodontic treatment is the way to maximal success. When retention develops during the growth spurt, the tooth affected has to be observed at 6-month intervals. In such a case, no active treatment is indicated if the neighboring teeth show no tilting and the extent of infraocclusion is minor and stable. In all other cases, the teeth affected have to be removed, followed by orthodontic closure of the edentulous space. Finally, all patients must be screened regularly, because in this investigation, new cases of retention were observed relatively frequently.

Adolescent↗
PubMed1990

Spontaneous reeruption of a secondarily retained permanent lower molar and an unusual migration of a lower third molar.

Secondary retention refers to cessation of eruption of a tooth after its emergence. It occurs mainly in the deciduous dentition, but it is also seen on rare occasions in the permanent dentition. Although ankylosis has been suggested as the main etiologic factor, the exact biologic mechanism of secondary retention is not yet known. This article presents a case of spontaneous reeruption of a secondarily retained permanent molar, which is very rare. It also describes an unusual migration of a lower third molar in the same patient.

Adult↗
PubMed1990

Influence of resorbable poly(L-lactide) bone plates and screws on the dose distributions of radiotherapy beams.

Metallic bone plates have been shown to affect radiation in vitro. Although no damage has ever been demonstrated in vivo these plates may cause dose enhancements and shielding of the adjacent tissue. Resorbable high molecular weight as-polymerized poly(L-lactide) (PLLA) bone plates have recently been used for reconstruction in the maxillofacial area. To determine their influence on dose distribution, a 4-hole bone plate and screws of PLLA were exposed to electron and photon beams. A tissue-equivalent phantom of perspex was irradiated and measurements were made with LiF thermoluminescent dosimeters. No significant changes in dose deviations could be determined when the dose distribution in the homogeneous phantom was compared with that of the phantom in which the PLLA material was placed. From this study it can be concluded that the PLLA material can be regarded as tissue-equivalent and can, thus, be safely used for fracture fixation of bone fragments when postoperative irradiation is anticipated.

Bone Plates↗
PubMed1990

A standardized technique for the placement of electrodes in the two heads of the lateral pterygoid muscle.

The results of electromyographic research on the two heads of the lateral pterygoid muscle depend largely on correct placement of the electrodes. Measurements were carried out on 24 male and 27 female skulls of known age and sex to determine the direction and depth of penetration for the placement of wire electrodes in the two heads of the lateral pterygoid muscle separately. The method of placement was simulated on human dissecting room material. With the use of a modified dental facebow, endodontic needles were placed in the direction of the two heads of the lateral pterygoid muscle in 11 human cadavers. The point of penetration was the most cranial point of the lower border of the zygomatic arch, lateral to the sigmoid notch of the mandible; after dissection over 80% of the needles proved to be placed correctly. The technique has since been used over 60 times on both heads of the lateral pterygoid muscle in volunteering dental students, dentists, and patients with symptoms of craniomandibular dysfunction. The technique interferes with the maximal opening of the mouth, which was reduced by about 10 mm. Subjects suffered slight inconveniences after the removal of the electrodes at the end of the test procedures. These inconveniences consisted of stiffness in the jaws and muscle soreness. Hematomas or infections did not occur.

Cephalometry↗