Biomedical subjects

D van Steenberghe

Publications and source records attributed to D van Steenberghe.

At least 127 records · Page 7Linked to original sources

PubMed1992

The importance of visual feedback on the accuracy of jaw and finger positioning in man.

The anatomical position of the mandible means that direct visual feedback is not possible. To clarify the role of visual information, several jaw- and finger-positioning tasks were designed, both in a 'free-movement' and an 'isolated' (arm or head fixed) state, with or without a visual feedback display of the target position. The subjects had to position the mandible or the index finger of the preferred hand on to a movable metal bar and to maintain a defined position coinciding with the target level provided on an oscilloscope screen. The position signal was tape recorded and computer analysed off-line. Digital filtering differentiated between the drift and the oscillations around the target (root mean square). The results demonstrated a lack of precision in the free-movement, finger-positioning task after withdrawal of visual feedback. For jaw opening and closing muscles, position control was less impaired when a visual feedback display was abolished. It was suggested that the efficiency of jaw positioning is not primarily determined by visual feedback.

Adult↗

PubMed1992

A study of 589 consecutive implants supporting complete fixed prostheses. Part I: Periodontal aspects.

Ninety-one consecutive edentulous patients who had been treated by means of fixed prostheses (n = 103) supported by Brånemark implants (n = 589) were examined. Eighteen fixtures (3%) failed to integrate. After a mean loading time of 32 (range 6 to 80) and 38 months (range 5 to 83) for fixtures in the maxilla and mandible, respectively, an additional 12 fixtures lost integration. The cumulative failure rate for individual fixtures after 6 years was 8.4% and 5% for maxillae and mandibles, respectively. Only one patient had to revert to complete dentures. For fixtures in the maxillae, the mean marginal bone loss was 0.7, 0.1, and 0.2 mm for each of the first 3 years of loading, respectively; for fixtures in mandibles, the corresponding values were 0.7, 0.2, and 0.1 mm. The loss in marginal bone height was equal in both jaws and was not related to bleeding on probing or to the preoperative resorption anatomy.

Adolescent↗

PubMed1992

A six-year prosthodontic study of 509 consecutively inserted implants for the treatment of partial edentulism.

A total of 509 consecutive Brånemark TM implants (Nobelpharma AB, Gothenburg, Sweden) were inserted in 146 patients between December 1982 and May 1989, on which 217 fixed partial dentures were planned. The cumulative failure rates after abutment connection were 3.9% and 4.1% for the maxillae and mandible, respectively. The lack of continuous prosthesis stability was limited to 4.1% for the maxillae and 5.4% for the mandible. The average annual marginal bone loss was 0.77 mm (SD = 1.0) and 0.96 mm (SD = 0.9) for the maxillae and mandible, respectively, during the first year and averaged 0.1 mm for the following years. The mode of connection between teeth and implants or the use of porcelain instead of composite resin as occlusal material did not influence the marginal bone height around the implants. Technical complications were most often related to the materials used. The results of a medium-term follow-up encourage the use of the Brånemark osseointegration system in the treatment of partial edentulism.

Adult↗

PubMed1992

A study of 589 consecutive implants supporting complete fixed prostheses. Part II: Prosthetic aspects.

In 91 consecutive edentulous patients, 103 jaws were treated with complete fixed prostheses supported by Brånemark Implants (n = 589). As a result of fixture loss in each of two patients (two jaws), an overdenture instead of a fixed prosthesis was installed. For one patient (two jaws), data were not available after abutment connection. At the end of the seventh year, the cumulative failure rates for the remaining 99 prostheses reached 4.9% for mandibles and 10.1% for maxillae. After loading, 12 fixtures showed signs of nonintegration, but only one patient had to revert to complete dentures. Neither the fixture location nor the cantilever length revealed a significant difference in marginal bone loss around the supporting fixtures. Patients with fixture-supported fixed prostheses in both jaws showed significantly more marginal bone loss than did those with only one fixed prosthesis opposed by either natural dentition (50%) or a complete denture (50%). Component complications were limited to fixture fracture (3/564), abutment screw fracture (5/564), and gold screw fracture (7/564). The predictability of Brånemark implants in the treatment of completely edentulous jaws is confirmed.

Alveolar Bone Loss↗

PubMed1992

Posterior jaw bone resorption in osseointegrated implant-supported overdentures.

For several years, osseointegrated implant-supported overdentures have been used in the rehabilitation of full edentulism with excellent results, at least in the lower jaw. This study involved 3 groups of patients with different prosthetic reconstructions: (1) mandibular overdentures supported by 2 implants connected by a bar (30 patients), (2) mandibular fixed prostheses supported by 4-6 implants (25 patients) and (3) mandibular complete dentures without implant support as controls (85 patients). The primary aim of this study was to examine on orthopantomograms (by means of the area index to minimize distortion and magnification errors), posterior mandibular ridge resorption in the 3 treatment groups. The present data demonstrated a minimal posterior mandibular ridge resorption in patients with fixed implant-supported prostheses. A more considerable posterior ridge resorption was observed in the complete denture group and especially in the overdenture wearers. For the latter, the annual posterior jaw bone resorption after the post-extraction remodeling period of 6 months, was 2- to 3-fold that of full denture wearers. When patients were edentulous for more than 10 years, the difference between the 2 latter groups disappeared. It is suggested that although the overdenture design on 2 implants offers advantages from a financial and failure rate point of view, its indications in younger patients should cautiously be evaluated in a long-term perspective concerning posterior mandibular bone resorption.

Adolescent↗

PubMed1992

Fixture design and overload influence marginal bone loss and fixture success in the Brånemark system.

It has been documented that the long-term clinical outcome of the Brånemark system is very favourable. However, failures do occur before and after loading. This study examined the differences in marginal bone loss between standard and self-tapping fixtures and attempted to explain excessive marginal bone loss or loss of osseointegration during the first 3 years of loading. Marginal bone loss (scored on long cone radiographs) and fixture failure rate were compared for different fixture designs. For standard fixtures, in comparison with self-tapping fixtures, the failure rate was clearly higher before as well as after loading. However, for successful fixtures no difference in marginal bone loss was observed. For the conical fixtures an increased marginal bone loss around the smooth part was observed. The effect of fixture overload, marginal bone height and loss of osseointegration was examined in 69 patients with 1 and 15 patients with 2 fixed full prostheses, and in 9 patients with an overdenture in the upper jaw. Excessive marginal bone loss (more than 1 mm) after the first year of loading and/or fixture loss correlated well with the presence of overload due to a lack of anterior contact, the presence of parafunctional activity and osseointegrated full fixed prostheses in both jaws.

Adolescent↗

PubMed1992

Periodontal aspects of osseointegrated fixtures supporting a partial bridge. An up to 6-years retrospective study.

The present paper reports on the use of osseointegrated titanium fixtures (Brånemark) in partially edentulous patients. The tissue reactions around 509 implants in 97 upper and 71 lower jaws of 146 consecutive patients, rehabilitated by means of partial bridges--supported by implants only (60%) or by the combination of teeth and implants (40%)--were observed longitudinally. The mean number of implants per bridge was 2.40 (range 1-5) for the upper jaw and 2.06 (range 1-5) for the lower jaw respectively. Before loading, a total of 23 fixtures were lost, 15 in the upper and 8 in the lower jaw. This loss could partially be correlated to per- and post-operative complications and to fixture characteristics (length, self-tapping or not). After a loading time of 30 months (range 2 to 77 months), 6 implants, 2 in the upper and 4 in the lower jaw, showed symptoms of non-integration. The cumulative failure rate for the individual fixtures after a 6-year period reached 5.7 and 6.5% for the upper and lower jaw, respectively. The mean annual marginal bone loss, scored on standardized radiographs, was 0.9 mm during the 1st year and 0.1 mm the following years. This loss in marginal bone height was equal in the upper and lower jaws and not related to the type of occlusal material of the bridges. The present data showed that the cumulative failure rate for Brånemark implants supporting partial bridges can be limited to 6% after a 6-year period, and that the radiographic bone loss is comparable with that found around fixtures supporting full bridges.

Adult↗

PubMed1992

Morphology of neural endings in the human periodontal ligament: an electron microscopic study.

The ultrastructure of sensory nerve endings in the human periodontal ligament from 43 extracted teeth was studied using serial sections. Three types of nerve endings were found: free nerve endings (FNE), Ruffini-like endings and lamellated corpuscles. Free nerve endings stem from unmyelinated or from myelinated nerve fibers. The endings contain neurotubuli, neurofilaments and vesicles. Ruffini-like receptors were mostly found in the apical part of the periodontal ligament. In these Ruffini-like receptors a particularly abundant concentration of mitochondria appears. In some cases desmosome-like junctions are present between neurite and ensheathing cell. Lamellated corpuscles were also found in the periodontal ligament. The lamellae are extremely endocytotic and are in close contact with each other.

Adolescent↗

PubMed1992

Influence of temperature and foil hardness on interocclusal tactile threshold.

Determinations of interocclusal tactile threshold levels so far have involved neither appropriate psychophysical approaches nor an assessment of the mechanical and thermal properties of the foils used. Twenty subjects (12 females) aged 18 to 50 (mean age 35) were tested for their absolute threshold level (RL). Both the method of limits and the staircase method were applied to determine the active or passive RL. For the active RL assessment, foils of different thicknesses were placed between edge-to-edge opposed incisors during gentle biting. Inner ear receptors of the blindfolded subjects were blocked by broad band noise applied through earphones, because vibrations induced by occlusal contact and conducted through bone might be perceived by these receptors. The foils presented were aluminum (Al), tin (Sn), polyester (PE) and calibrated steel (St) (thickness ranging from 8 to 50 microns) which offer different physical and thermal properties. The range of RL of the group varied between 8 microns for aluminum to 46 microns for polyester for 50% correct assessments. Increasing the foil temperature from room temperature (20 degrees C) to body temperature (35 degrees C) significantly increased the RL for conducting materials (one-way blocked ANOVA). These results indicate that temperature exchange takes place while presenting conducting foils at 20 degrees C (cold stimulus) interocclusally, which influences the RL by activating thermosensitive receptors. The passive RL determination with classical von Frey-hairs resulted in a mean axial RL of 3.0 g. Both psychophysical RL assessments (method of limits, staircase method) gave reproducible and similar results as ascertained by ANOVA. Furthermore, a positive correlation was established between active and passive RL (Pearson correlation test).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

A multicenter study of overdentures supported by Brånemark implants.

Nine clinical centers participated in a prospective study of overdentures supported by Brånemark implants in the maxilla or mandible. The study initially comprised 133 patients provided with 117 implants placed in the maxilla and 393 implants placed in the mandible. The preliminary results indicate a success rate in the mandible comparable with the reports on fixed prostheses. Conversely, overdenture treatment in the maxilla seems to be less favorable than previous reports of fixed restorations. The differences between the fixed and the present overdentures in the maxilla were mainly based on differences in patient selection and bone quality. A total of 32 implants was mobile and removed and another 29 implants were lost to follow-up because of patient dropout up to the first annual checkup after denture placement. A higher implant failure rate occurred in the maxilla. Mucosal reactions were also more unfavorable around implants placed in the maxilla.

Adult↗

PubMed1991

The precision of motor control in human jaw and limb muscles during isometric contraction in the presence of visual feedback.

Experiments showed that the human capacity to maintain a particular isometric force in the presence of visual feedback during a force-level, pursuit-tracking experiment is less developed for the jaw-closing muscles than for the limb muscles. This finding may indicate that the projection on the trigeminal motoneurone pool from visual inputs is poor, or that the trigeminal effector system itself is less finely tuned.

Adult↗

PubMed1991

Prosthetic aspects of osseointegrated fixtures supporting overdentures. A 4-year report.

Eighty-six consecutive patients, provided with 84 resilient and two nonresilient overdentures (six in the upper and 80 in the lower jaw), were examined. The overdentures were supported by a total of 173 osseointegrated titanium fixtures (the standard Branemark abutment), with a mean loading time of 19.1 months (range 4 to 48 months). In each jaw only two fixtures anchored the overdentures. No failures occurred during the observation period but two fixtures were lost before loading. The radiographic annual bone loss around fixtures in the lower jaw was -0.8 mm for the first year and less than -0.1 mm for the following years. The change in marginal bone height did not correlate with parameters such as the occlusion and articulation pattern, the presence or absence of a soft liner around the abutments, and the magnitude of the interabutment distance. The patients' reactions to overdenture treatment were, on the whole, positive concerning chewing function, phonetics, and comfort. The need for maintenance care of the clip-bar attachment was minimal.

Adult↗

PubMed1991

Masseteric post-stimulus EMG complex following mechanical stimulation of osseointegrated oral implants.

Periodontal receptors can be located in the periodontal ligament itself, the alveolar bone, the periosteum and the gingiva. The aim of the present study was to quantify the contribution of the periodontal ligament receptors in eliciting a reflex response in human masseter muscles. Surface EMG recordings were made in 17 human subjects, fully or partially edentulous, and all provided with osseointegrated oral implants ad modum Brånemark. They maintained a constant clenching level. Mechanical stimulation of an oral implant in the upper central incisor region failed to elicit a reflex in fully edentulous subjects with oral implants in both jaws. The absence of a reflex response strongly suggests that the receptors in the periodontal ligament itself are mainly responsible for the reflex. Stimulation of the same area in subjects with oral implants in the upper jaw and natural teeth in the lower jaw elicited a reflex response in most subjects. Since they were instructed to clench in full habitual occlusion, transmission from the stimulated area to periodontal receptors of natural teeth is very probable.

Confidence Intervals↗

PubMed1991

Periodontal aspects of osseointegrated fixtures supporting an overdenture. A 4-year retrospective study.

196 Brånemark implants in 86 consecutive patients rehabilitated by means of overdentures (6 upper jaws, 80 lower jaws) were observed longitudinally. In each jaw, only 2 implants were used to anchor the overdenture. 2 implants in the lower jaw showed some mobility at the abutment installation and were removed immediately. During the loading period (mean loading time 19.1 months ranging from 4 to 48 months), none of the implants showed any signs of non-integration. The marginal tissue reaction and plaque accumulation were monitored using conventional indices. Clinical methods and standardized radiographs were used to evaluate the bone level and density. The numbers of approximal surfaces without plaque (40%) or with gingival inflammation (55%) were almost constant throughout the study. The probing pocket depths remained within the range of 2.7 to 3.2 mm during the observation time, whereas the distance of the gingival margin from the top of the abutment clearly increased (from 1.8 to 2.9 mm). For loaded lower jaw implants connected to each other with a straight bar, a radiographic bone loss of 0.8 mm was observed during the first postsurgical year followed by a mean annual bone loss of less than 0.1 mm. For the "sleeping" fixtures, 50% less bone loss was recorded. For loaded but not interconnected implants in the upper jaw, the bone loss during the first 6 months reached 2.0 mm. The loss in marginal bone height did not clearly correlate with parameters such as the plaque index, the gingivitis index, the presence or absence of gingiva around the abutment, or the implant length. The present data, with an observation time up to 4 years, showed that the failure rate for Brånemark implants supporting overdentures in the lower jaw can be limited to 1%. However, the use of 2 unconnected fixtures in the upper jaw cannot presently be advocated since considerable bone loss was observed.

Adult↗

PubMed1991

The rehabilitation of oral defects by osseointegrated implants.

So far, preprosthetic surgery for oral defects improved prosthetic retention problems for only a limited amount of time and led to many side-effects. The alternative offered by the osseointegration technique developed by P.-I. Brånemark changed the concept of preprosthetic surgery dramatically. By means of a few permucosal titanium screws, bridges or overdentures can be retained even in cases of advanced jaw bone resorption. When the latter is extreme, an autologous free bone graft fixed by means of self-tapping titanium implants can offer the necessary support for sometimes elaborate prosthetic reconstructions. The marginal bone loss around Brånemark implants is very limited after a 1st year of bone remodelling, even when an autologous transplant has been used.

Dental Implantation, Endosseous↗

PubMed1991

Discriminating power of five plaque indices.

Since plaque plays a major role in the development of periodontal inflammation, special attention is paid to its composition and quantity. Several indices have been designed for the quantification of the supragingival plaque. The aim of the present study was to compare the utility and discriminating power of five such plaque indices. In 14 subjects, three teeth were selected randomly on which the undisturbed plaque formation was studied over a period of 96 hours. This examination was performed twice, the first time after induction of gingivitis and a second time starting with a healthy gingiva. It is known that in the presence of gingival inflammation, the plaque growth rate slightly increases. Plaque formation was estimated at several visits with the following indices: Harrap index, Quigley and Hein index, Navy index modified by Clemmer and Barbano, Navy index modified by Hancock and Wirthlin, and a planimetrical plaque scoring system. The path of the plaque growth curve was found to depend on the selected plaque index, going from an exponential curve (planimetry) over an sigmoidal curve (Harrap index, Navy index modified by Hancock and Wirthlin) to a nearly linear relation (Quigley and Hein, Navy index modified by Clemmer and Barbano). By comparing the plaque scores on patients with healthy gingiva with those from patients with inflamed gingiva, it was found that the planimetrical plaque index had a clearly higher discriminating power. It was concluded that the choice of an index for the measurement of the plaque extension depends on the goals of the study.

Adult↗

PubMed1991

The influence of gingival inflammation, tooth type, and timing on the rate of plaque formation.

The undisturbed supragingival plaque formation was recorded twice over a 100 hours period in 14 healthy dental students; first after induction of gingival inflammation and a second time starting from a healthy gingiva. During each experimental segment plaque formation was recorded on 42 randomly selected and clean teeth at the start and after 6, 12, 24, 30, 36, 48, 54, 60, 72, 84, and 96 hours. Four hours later all teeth up to the first molars were examined. The presence of disclosable plaque was calculated planimetrically as percent of the total labial surface area of the tooth. The rate of plaque formation was found to be significantly greater (P = 0.001) in the presence of gingival inflammation (+ 29.0%). Moreover, this study indicates an important variation in the plaque growth rate within the dentition; the highest scores were found for the upper premolars, the upper molars, and the lower front teeth. Finally, the rate of plaque formation was found to decrease during the night.

Adult↗

PubMed1991

Oral implants.

Today, more and more evidence suggests that even small changes in hardware for oral implants may jeopardize its biocompatibility. Even the manner in which the hardware is sterilized can influence cellular adhesion. This review discusses the surface characteristics, configuration, and success rates of various oral implants, as well as the complications that can result following implantation.

Dental Implantation, Endosseous↗