PubMed Health⌕ Search

Biomedical subjects

G Boering

Publications and source records attributed to G Boering.

At least 19 recordsLinked to original sources
PubMed1992

Secondary retention of permanent molars: an assessment of ankylosis by scanning electron and light microscopy.

Secondary retention refers to the cessation of eruption of a tooth after emergence. This may be the result of pathological changes in the periodontal ligament. The aim of this study was to describe the morphological and histological aspects of the radicular surface of secondarily retained permanent molars. The roots of 12 secondarily retained molars and two control molars, were examined by means of scanning electron microscopy (SEM) and light microscopy (LM) in order to analyse the occurrence and localisation of ankylosis. With SEM it was observed that the root surface of retained molars showed local areas covered with bonelike tissue. LM of these areas showed that this tissue was bone in direct contact with the root surface (ankylosis). In 11 cases, the areas of ankylosis were observed in the bifurcation area and at the interradicular root surface. In the remaining case, ankylosis was located at the outer root surface. The results of this study endorse the assumption that focal ankylosis is an important factor in secondary retention. Treatment recommendations must be based on this fundamental principle, because orthodontic movement of ankylotic molars is not possible.

Adolescent↗
PubMed1992

Three-dimensional visualization of the temporomandibular joint: a computerized multisectional autopsy study of disc position and configuration.

To demonstrate disc position and disc configuration of the temporomandibular joint, three-dimensional multisectional computer reconstructions were made of 20 autopsy specimens (11 female, 9 male; mean age, 40.4 years). The presence of a distinct occlusion was the only criterion for selection. Normal disc position was found in 13 joints, partial anterior disc position was found in 5 joints, and complete anterior disc position was seen in 2 joints. Fifteen joints had biconcave disc configuration and 5 joints had deformed discs. Considering the high incidence of disc position deviating from the normal superior position, it is suggested that in some cases a so-called abnormal disc position can be regarded as within the limits of anatomic and physiological variability.

Adult↗
PubMed1992

Secondary retention of permanent molars: a report of five families.

The aetiopathogenesis of secondary retention is not fully understood, but heredity is involved in at least some cases. In this study first-degree relatives of 52 patients with secondary retention of permanent molars were screened for the presence of the same phenomenon in their dentition. Familial occurrence could be shown in five families. The pedigrees are compatible with autosomal dominant inheritance. HLA phenotypes and blood groups ABO, rhesus and P1 were studied in two families. The lod scores for linkage with secondary retention were added to previously reported information. The lod score for linkage for blood group system P increased from +0.940 to +1.475 at a recombination fraction of 5 per cent. It is concluded that secondary retention of permanent molars is an aetiologically heterogeneous condition in which some cases are caused by the presence of an abnormal autosomal dominant gene.

Adult↗
PubMed1992

Computer-aided optimization of choice and positioning of bone plates and screws used for internal fixation of mandibular fractures.

The present study describes a biomechanical integrated model of the mandibular system in which the maxilla and mandible, the masticatory muscles, and the temporomandibular joints are regarded as one system. In this model, strains in plate-osteosynthesis devices for internal fixation of mandibular fractures can be minimized by optimizing their positions. The model evaluates maximal bite force strategies on all possible dental elements; it uses a linear programming technique and a muscle architecture model, resulting in muscle recruitment patterns. The shape of a "standard" lower jaw is digitized by means of a three-dimensional (3-D) coordinate retrieval device and drawn on a computer screen after its dimensions have been changed according to the clinical case at hand. The 3-D location of the fracture as well as the anatomic restrictions for screw placement can be indicated on the screen. Osteosynthesis devices can be indicated in terms of dimensions, number, and material properties.

Biomechanical Phenomena↗
PubMed1992

Classification of temporomandibular joint osteoarthrosis and internal derangement. 1. Diagnostic significance of clinical and radiographic symptoms and signs.

In the clinical setting, diagnosis primarily depends on the history and present status of the patient, and on the examiner's expertise in physical examination and interpretation of conventional radiographs. In order to evaluate the diagnostic significance of clinical and radiographic variables, the authors used magnetic resonance imaging as the 'golden standard' for articular disk position. A total of 90 temporomandibular joints (TMJs) were available for the study. Group I (representing 'normal' disk position) comprised eight joints (8.9%); group II (representing reducing disk), 34 joints (37.8%); and group III (non-reducing disk), 48 joints (53.3%). Nine anamnestic, 15 clinical, and three radiographic variables obeyed pre-defined univariate selection criteria. Relatively high sensitivities were found for clicking-related variables in MR-group II, and for variables related to movement restriction in MR-group III. None of the symptoms or signs appeared to be pathognomonic for either one of the diagnostic groups. Principal component analysis revealed 13 factors that could be grouped into three major categories, representing impairment of joint mechanics, joint pain and tenderness, and radiographically detectable degenerative changes, respectively. Discriminant analyses showed that symptom combinations, which included clinical variables related to joint mechanics, appeared to provide the most useful diagnostic information. It is concluded that reducing and permanent disk displacement can be distinguished in many cases using clinical and radiographic variables. However, there is considerable variability within these groups. To establish a specific clinical diagnosis, a more detailed classification of osteoarthrosis and internal derangement is desirable.

Adolescent↗
PubMed1992

Classification of temporomandibular joint osteoarthrosis and internal derangement. 2. Specific diagnostic criteria.

Separate entities of temporomandibular joint osteoarthrosis and internal derangement are operationally defined. Criteria are based on an analysis of the diagnostic significance of symptoms and signs, principles of synovial joint pathology in general, and on therapeutic considerations. The primary goal was to enable identification of characteristic stages of osteoarthrosis and internal derangement using diagnostic tools readily available in practice.

Cartilage, Articular↗
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↗
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↗