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Biomedical subjects

G Boering

Publications and source records attributed to G Boering.

At least 37 records · Page 2Linked to original sources
PubMed1995

In vivo degradation and biocompatibility study of in vitro pre-degraded as-polymerized polyactide particles.

The degradation of high molecular weight as-polymerized poly(L-lactide) (PLLA) is very slow; it takes more than 5.6 yr for total resorption. Moreover, the degradation products of as-polymerized PLLA bone plates, consisting of numerous stable particles of high crystallinity, are related with a subcutaneous swelling in patients 3 yr postoperatively. In order to avoid these complications, polymers were developed that are anticipated to have comparable mechanical properties but a higher degradation rate and do not degrade into highly stable particles that can induce a subcutaneous swelling. On chemical grounds it can be expected that copolymerization of PLLA with 4% D-lactide (PLA96) or by modifying PLLA through cross-linking (CL-PLLA) will lead to less stable particles and a higher degradation rate. To evaluate the long-term suitability of these as-polymerized polymers, the biocompatibility of the degradation products should be studied. Considering the very slow degradation rate of as-polymerized PLLA, in vitro pre-degradation at elevated temperatures was used to shorten the in vivo follow-up periods. In this study, the biocompatibility and degradation of as-polymerized PLLA, PLA96 and CL-PLLA were investigated by implanting pre-degraded particulate materials subcutaneously in rats. Animals were killed after a postoperative period varying from 3 to 80 wk. Light and electron microscopical analysis and quantitative measurements were performed. The histological response of all three pre-degraded materials showed a good similarity with in vivo implanted material. Pre-degraded PLLA induced a mild foreign body reaction and showed a slow degradation rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Patient satisfaction with implant-retained mandibular overdentures. A comparison with new complete dentures not retained by implants--a multicentre randomized clinical trial.

OBJECTIVES: The aim of this study was to establish the treatment outcome of full denture treatment with or without implant support, in which the outcome assessment focuses on the patient's subjective evaluation ('denture-satisfaction'). DESIGN: A multicenter randomized clinical trial. SUBJECTS: Thirty-two men and 118 women (mean age 56 +/- 9, range 35-84 years) participated in the study. The mean height of the mandible was 13 +/- 2 mm, measured on a lateral cephalometric radiograph. The patients were randomly assigned to either a group treated with implant-retained mandibular overdentures and a new maxillary denture, or to a control group treated with a new set of complete dentures. MAIN OUTCOME MEASURES: Denture satisfaction was assessed using questionnaires focusing on denture-related complaints and 'a general satisfaction rate'. RESULTS: Based on the baseline data, from the 'denture complaints' questionnaire six interpretable factors could be extracted. One factor did not vary following treatment and was excluded from the outcome analysis. At the 1-year evaluation three out of five factors showed significantly better scores for the group treated with implants than for the control-group. The same was found for the general satisfaction rate. CONCLUSION: For patients with a severely resorbed mandible, overdentures retained by dental implants appear to provide a more satisfactory solution to their denture-related problems.

Adult↗
PubMed1995

Evaluation of temporomandibular joint prostheses: review of the literature from 1946 to 1994 and implications for future prosthesis designs.

PURPOSE: This article describes the useful elements of applied temporomandibular joint (TMJ) prostheses and discusses the factors necessary to be addressed in an appropriate TMJ prostheses design. MATERIALS AND METHODS: Information about TMJ prostheses was gathered by a literature search. Only designs with the primary intention of true joint replacement were selected. The designs were divided in fossa-eminence, condylar, and total joint replacements, which are reviewed separately. RESULTS: A fossa-eminence prosthesis can be fixed by a metal plate screwed to the root of the zygomatic arch. A condylar prosthesis can be fixed by a metal plate screwed to the mandibular ramus and fitted by bending the plate or using different sizes. All reviewed designs resulted in a loss of translational movements of the mandible, especially in an anterior direction. Although the recent designs use the same materials as are used in hip and knee joint prostheses, the wear properties of the existing TMJ prostheses are still unknown. CONCLUSIONS: A future prosthesis must imitate the anterior movement of the mandible when the mouth is opened and also allow some mediolateral movement. The fitting to the skull is still a major problem, as is the combination of the required motions and low wear rates. To confirm good clinical performance of a new TMJ prosthesis, long-term follow-up studies are necessary.

Evaluation Studies as Topic↗
PubMed1995

TMJ articular disc position and configuration 30 years after initial diagnosis of internal derangement.

PURPOSE: This study evaluates disc position and configuration on magnetic resonance imaging (MRI) in temporomandibular joints (TMJs) with a long history of internal derangement. PATIENTS AND METHODS: Sagittal T1-weighted MRIs of 55 TMJs that were diagnosed with internal derangement approximately 30 years ago were made with the mouth closed and open, and the position and configuration of the articular disc were determined. For comparison, a control group consisting of 15 asymptomatic TMJs without clinical signs of internal derangement or of other TMJ disorders were studied in the same way. RESULTS: Anterior disc position was found in 90% of the TMJs with a history of internal derangement. Reducing disc displacement was found in one third of these TMJs, whereas permanent displacement was found in two thirds. In four joints, no disc was discernible. In one of the joints of the control group, a permanent disc displacement was found; normal disc position was found in all other joints of the control group. A biconcave disc configuration, which was considered normal, was found only in TMJs with normal disc position or with reducing discs. CONCLUSION: It was concluded that, after 30 years of displacement, the TMJ disc can be clearly identified on MRI in most cases. If the disc becomes permanently displaced, its configuration deviates from the normal biconcave configuration, and its anteroposterior length decreases. Convex and folded appearances of the disc are common in this situation. However, the disc usually maintains its biconcave configuration as long as it resumes its position on top of the condyle during mouth opening, even if this condition lasts for several decades.

Aged↗
PubMed1995

Normal cartilage structure, biochemistry, and metabolism: a review of the literature.

PURPOSE: To understand the possible significance of the presence of proteases, cytokines, growth factors, and arachidonic acid metabolites in the osteoarthritic temporomandibular joint (TMJ), a review of the normal physiologic processes and participating factors in the normal TMJ is established, based on knowledge of structure, biochemistry and metabolism of normal cartilage in general.

Arachidonic Acid↗
PubMed1995

Patient satisfaction and chewing ability with implant-retained mandibular overdentures: a comparison with new complete dentures with or without preprosthetic surgery.

PURPOSE: The objective of this study was to compare denture satisfaction and chewing ability of edentulous patients treated with dental implant-retained overdentures or with full dentures with or without previous preprosthetic surgery. PATIENTS AND METHODS: This study was a controlled clinical trial. Thirty-eight men and 52 women participated in the study. The mean height of the anterior mandible was 21 mm (range, 16 to 25 mm), measured on a lateral cephalometric radiograph. The subjects were randomly assigned to the three treatment modalities. The main outcome measures were denture satisfaction and chewing ability, which were assessed using questionnaires focusing on denture-related complaints and the ability to chew different types of food, and an overall denture satisfaction score. RESULTS: Based on the baseline data from the "denture complaints" and "chewing ability" questionnaires, nine interpretable factors could be extracted. Two factors did not vary following treatment and were excluded from the outcome analysis. At the 1-year evaluation five of seven factors showed significantly better scores for the two surgical groups than for the control group. The same was found for the overall denture satisfaction rate. CONCLUSION: Overdentures retained by dental implants or complete dentures made after a vestibuloplasty and deepening of the floor of the mouth provide a more satisfactory solution for denture-related problems than complete dentures alone. For the scale "functional complaints lower denture," the overdenture group showed even a significantly better score than the preprosthetic surgery group.

Cephalometry↗
PubMed1995

The structure, biochemistry, and metabolism of osteoarthritic cartilage: a review of the literature.

PURPOSE: To understand the possible significance of the presence of proteases, cytokines, growth factors, and arachidonic acid metabolites in the osteoarthritic temporomandibular joint (TMJ), the pathogenesis of TMJ osteoarthritis (OA) is discussed, based on knowledge of structure, biochemistry and metabolism of osteoarthritic cartilage in general, and a classification of TMJ OA is presented.

Arachidonic Acids↗
PubMed1995

Calcium pyrophosphate dihydrate crystal deposition disease: a review of the literature and a light and electron microscopic study of a case of the temporomandibular joint with numerous intracellular crystals in the chondrocytes.

The pathogenesis of calcium pyrophosphate dihydrate (CPPD) crystal deposition disease of synovial joints is still unclear, although overproduction of extracellular pyrophosphate (PPi) is thought to play a key role. We studied the light and electron microscopic appearances of a case of CPPD crystal deposition disease of the temporomandibular joint (TMJ) in search of new clues for its pathogenesis. Light microscopic examination of CPPD-containing material from the joint space revealed cartilaginous nodules with various degrees of crystallization. Transmission electron microscopic examination revealed numerous extra- as well as intracellular crystals and crystal shaped spaces in the chondrocytes. Other striking ultrastructural features of the chondrocytes included the presence of many mitochondria, frequently containing crystalline material, and the presence of highly dilated rough endoplasmic reticulum and large glycogen islands. The presence of intramitochondrial crystals may hypothetically imply a derangement in mitochondrial adenosine triphosphate or PPi metabolism. The finding of intracellular CPPD crystals in chondrocytes points to the existence of an intracellular pathway of CPPD crystal formation in CPPD crystal deposition disease of the TMJ and possibly in CPPD crystal deposition disease in general.

Cartilage, Articular↗
PubMed1995

Radiographic signs of temporomandibular joint osteoarthrosis and internal derangement 30 years after nonsurgical treatment.

The aim of this study was to evaluate with radiographs the long-term status of temporomandibular joints that were treated nonsurgically for reducing disk displacement (group 1) or permanent disk displacement (group 2) 30 years ago. Transcranial and transpharyngeal radiographs were made before (T1), 2 to 4 years after (T2), and 30 years after (T3) nonsurgical treatment in 65 former patients with temporomandibular joint osteoarthrosis. To control the results for aging 35 matched subjects (group 3) underwent the same radiographic examination. The number and severity of radiographically visible degenerative changes increased significantly from T1 through T2 to T3 in group 1 and in group 2. The increase in these changes was not simply caused by aging, because in approximately three quarters of the temporomandibular joints in group 3, no radiographically visible degenerative changes were found. At all occasions group 2 showed significantly more severe changes than group 1. At T3 in 64% of the temporomandibular joints in group 1, no or only slight radiographically visible degenerative changes were observed, whereas in 86% of the temporomandibular joints in group 2, moderate to severe changes were observed. A persisting reducing disk displacement in part of the temporomandibular joints in group 1 might explain this significant difference. In 79% of the temporomandibular joints with moderate to severe radiographically visible degenerative changes at T1, no or only slight progression in the extent of these changes was seen between T2 and T3. Apparently a radiographically stable end stage may be reached within a few years after permanent displacement in most cases. It was concluded that in temporomandibular joints with reducing disk displacement, no or only slight radiographically visible degenerative changes develop, even if this condition persists for several decades. On the other hand, in temporomandibular joints with permanent disk displacement, radiographically visible degenerative changes are extensive in the vast majority of cases.

Case-Control Studies↗
PubMed1995

Symptoms of temporomandibular joint osteoarthrosis and internal derangement 30 years after non-surgical treatment.

To evaluate the long-term condition of temporomandibular joints (TMJs) affected by osteoarthrosis and internal derangement, 99 patients treated non-surgically between 1958 and 1962 were recalled for follow-up. The patients, 16 men and 83 women (mean age 58.2 years) with either reducing or permanent disk displacement, were submitted to a structured interview concerning previous treatment, masticatory function, and the presence of symptoms of osteoarthrosis and internal derangement of the masticatory system, and of complaints of the musculoskeletal system in general. A control group, consisting of eight men and 27 women (mean age 58.9 years) without complaints of the masticatory system, matching the patient group for sex, age and state of dentition, was included in the study to avoid simply documenting age-related joint conditions. Satisfaction with the treatment outcome was high. Chewing ability of the the patients did not differ from that of the controls, although patients more often expected pain and difficulty with opening the mouth wide. The main TMJ symptoms of the patients had decreased significantly; patients reported joint noises more often than controls. It is concluded that, despite some persisting symptoms, the non-surgical treatment approach of TMJ osteoarthrosis and internal derangement provides long-lasting satisfactory subjective results and is well-accepted by the patients.

Cartilage, Articular↗
PubMed1995

Angle of mouth opening measurement: reliability of a technique for temporomandibular joint mobility assessment.

The maximal interincisal distance added to the vertical overlap is generally used as a measure for temporomandibular joint mobility. However, the length of the mandible also has an influence on this measure. The angle of mouth opening as a measure of temporomandibular joint mobility is independent of the length of the mandible. The aim of the study was to develop a mandibular goniometer to measure the angle of mouth opening and to test its reliability. Ten subjects, two males and eight females (mean age 28.1 years) participated in the study. The measurements were performed during four independent sessions of three measurements each. The results were analysed with ANOVA. Intra-observer variability was found to be 2.0 degrees when the result of all the measurements were analysed, and were found to be 1.2 degrees when the mean value of the sessions were used for analysis. Based on the results of this study it can be concluded that the angle of mouth opening can be measured reliably.

Adult↗
PubMed1995

Temporomandibular joint mobility assessment: a comparison between four methods.

Temporomandibular joint (TMJ) mobility is assessed in different ways. Measurement of the interincisal distance in maximal mouth opening added to the vertical overlap of the dentition, i.e. linear mouth opening (LMO); measurement of angular displacement of the mandible relative to the cranium at maximal mouth opening, i.e. angle of mouth opening (AMO); assessment of the condylar position relative to the articular eminence performed on transpharyngeal radiographs in maximal mouth opening, i.e. condylar mobility (CM); measurement of angular displacement of the mandible at maximal mouth opening relative to the closed mouth position of the mandible, assessed on transpharyngeal radiographs in maximally opened and in closed mouth position, i.e., radiographic angle of mouth opening (RAMO). To compare these TMJ mobility assessment methods and to analyse the relationship between LMO, AMO and mandibular length (ML), 28 healthy volunteers (13 females, 15 males), mean age 29-6 years (range 21-41) with a symmetrical mouth opening pattern were assessed. LMO, AMO, ML, and RAMO were measured and CM was assessed on transpharyngeal radiographs. LMO and AMO were strongly and significantly related (r = 0.71). LMO was significantly influenced by AMO and ML. No significant differences between AMO and RAMO were found. CM was strongly and significantly related to AMO (r = 0.72) and weakly but significantly related to LMO (r = 0.42). Based on the results of this study recommendations are made regarding the appropriate application of TMJ mobility assessment methods.

Adult↗
PubMed1995

[The educational continuum and the specialization in oral diseases and jaw surgery].

Throughout the world can be seen a strong development towards the requirement of both a dental and a medical degree for oral and maxillofacial surgeons. Such requirements call for a critical review of the various parts of the curriculum and the optimum educational continuity in the sequence dentistry--medicine--oral and maxillofacial surgery.

Curriculum↗
PubMed1995

Detection of lymph node metastases of squamous-cell cancer of the head and neck with FDG-PET and MRI.

UNLABELLED: The uptake of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) in neck lymph nodes of twelve patients with a squamous-cell carcinoma of the oral cavity was studied with PET in order to detect and locate lymphogenic metastases. METHODS: The results of FDG-PET imaging were compared with clinical, MRI and histopathologic findings. Standardized uptake values (SUV) were also calculated. RESULTS: A sensitivity of 91% and a specificity of 88% were calculated for FDG-PET. In contrast, a sensitivity of 36% and a specificity of 94% were calculated for MRI. Calculated SUVs for reactive lymph nodes, metastatic lymph nodes and the primary tumor were undifferentiated. CONCLUSION: Using FDG-PET, lymph node metastases of squamous-cell carcinomas of the oral cavity can be visualized with a high sensitivity and specificity. FDG-PET can be an improvement in the evaluation of the neck.

Aged↗
PubMed1995

Complications after mandibular third molar extraction.

The records of 1,797 patients were retrospectively examined to analyze the possible relationships between postoperative complications following mandibular third molar extraction and parameters such as age, sex, indication for surgery, position of the molar, surgical experience, surgical technique, and postoperative care. Older patients tended to suffer more often from complications. Surgery performed while there were signs of pericoronal inflammation also resulted in more complications. There was no statistically significant difference in the mean complication rate arising from surgery performed by staff members and the rate when surgery was performed by residents. There seems to be no reason for patients to return routinely for removal of resorbable sutures or other postoperative care because this practice does not result in a decrease in postoperative symptoms.

Adolescent↗
PubMed1994

Overdentures supported by two IMZ implants in the lower jaw. A retrospective study of peri-implant tissues.

Between 1987 and 1990, 57 edentulous patients were treated with overdentures supported by 2 endosseous IMZ implants connected by a bar in the lower jaw. The condition of the peri-implant tissue was evaluated for a loading period ranging from 12 to 57 months (mean 30 months and median 24 months). The evaluation parameters included Plaque Index, Bleeding Index, Gingiva Index, pocket depth, dysesthesia of chin or lip, peri-implant bone loss and loss of implants. During the healing phase prior to the construction of an overdenture, 3 implants were lost. After a healing period of 6 months, these implants were successfully replaced. During the follow-up period, a Plaque Index < or = 1 was observed in 45 patients and an abundance of plaque and calculus was observed in 1 patient. Heavy or profuse bleeding and severe gingival inflammation was observed in 3 patients. The mean pocket depth was 3.6 +/- 1.7 mm. None of the patients experienced lip or chin dysesthesia. Marginal bone loss was observed around 30 (26%) implants. From this study it is concluded that, once proper osseointegration is obtained, 2 IMZ implants connected with a bar in the lower jaw supply a proper base for the support of an overdenture; the condition of the peri-implant tissues is steady and independent of the follow-up time.

Adult↗