Biomedical subjects

D van Steenberghe

Publications and source records attributed to D van Steenberghe.

At least 145 records · Page 8Linked to original sources

PubMed1991

Periotest: an objective clinical diagnosis of bone apposition toward implants.

Implant mobility as an indicator of failing close bone apposition is generally known. Whereas a clearly visible mobility can always be correlated with an interposition of soft tissue, the range from a clinically firm implant to just tangible implant mobility represents the actual problem zone. Thirty consecutive patients who had mandibles restored with osseointegrated implants ad modum Brånemark were tested with the Periotest device for damping characteristics of the implants and the peri-implant tissues as a whole. The mean Periotest value (PTV) was -1.74. The characteristics of the mandible, the peri-implant tissue, and the abutment length are the determining factors for the PTV. Fixture length, dolder bar, and length of time in function had no significant influence on the PTV.

Adult↗

PubMed1990

Computed tomography in the preoperative planning of oral endo-osseous implant surgery.

Computed tomography (CT) is a well-established aid in the preoperative assessment of the dimension of mandible and maxilla for endo-osseous implant installation. CT is a valuable tool for the measurement of the alveolar ridge and recognition of the course of the inferior alveolar nerve canal. In the present study, three different techniques were examined: normal CT images with coronal and sagittal slices, standard reconstructions based on axial slices, and multiplanar reconstruction and display (MPR/MPD), also based on axial slices. Six dissected human jaw bones were examined with these three techniques. Afterwards, these jaws were sawn, and the real values were measured. Comparing these scores with the radiological measurements, the standard reconstruction technique seemed the most reliable method in the preoperative examination of the jaw bone quality and bone proportion.

Dental Implantation, Endosseous↗

PubMed1990

Comparative antiplaque activity of sanguinarine and chlorhexidine in man.

This clinical investigation examined the effect of a sanguinarine extract on bacterial plaque growth in man. Three different mouthrinses were examined: (i) Veadent containing 0.03% sanguinarine and 0.2% zinc chloride (test rinse); (ii) a vehicle solution containing all the excipients of Veadent except the 0.03% sanguinarine (control rinse); (iii) Hibident a 0.2% chlorhexidine digluconate formulation (positive control rinse). The trial in which 12 dental students participated, was designed as a single-blind, cross-over study. During 3 experimental periods of 18 days, the participants refrained from mechanical oral hygiene and rinsed twice a day with one of the above mentioned solutions. Between experimental phases, a wash-out period of 11 days was instituted. In each subject, 4 teeth were randomly selected for assessment. Clinical evaluations were performed at days 1 (0, 4, 8, 12 hours), 2, 4, 11 and 18. The plaque on the buccal surfaces of the selected teeth was disclosed with neutral red 0.05% and colour slides taken. The % of the tooth surface covered with plaque was calculated planimetrically from these colour slides. The present results show an excellent anti-plaque effect with Hibident, a very small effect with Veadent and a negligible effect with the vehicle solution without the sanguinarine. These findings would suggest that the Veadent mouthrinse would have at most only a limited role as a plaque inhibitor.

Adult↗

PubMed1990

The influence of surface free energy and surface roughness on early plaque formation. An in vivo study in man.

Previous in vivo studies suggested that a high substratum surface free energy (s.f.e.) and an increased surface roughness facilitate the supragingival plaque accumulation. It is the aim of this clinical trial to explore the "relative" effect of a combination of these surface characteristics on plaque growth. 2 strips, one made of fluorethylenepropylene (FEP) and the other made of cellulose acetate (CA) (polymers with surface free energies of 20 and 58 erg/cm2, respectively) were stuck to the labial surface of the central incisors of 16 volunteers. Half the surface of each strip was smooth (Ra +/- 0.1 microns) and the other half was rough (Ra +/- 2.2 microns). The undisturbed plaque formation on these strips was followed over a period of 6 days. The plaque extension at day 3 and 6 was scored planimetrically from color slides. Finally, of 6 subjects samples were taken from the strips as well as from a neighbouring smooth tooth surface (s.f.e. 88 erg/cm2; Ra +/- 0.14 microns). These samples were analysed with a light microscope to score the proportion of coccoid cells, and small, medium, and large rods or fusiform bacteria. At day 3, a significant difference in plaque accumulation was only obtained when a rough surface was compared with a smooth surface. However, at day 6, significantly less plaque was recorded on FEP smooth (19.4%) when compared with CA smooth (39.5%). Between FEP rough (96.8%) and CA rough (98.2%), no significant difference appeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1990

CT scan standard reconstruction technique for reliable jaw bone volume determination.

Computed tomography can assist the surgeon in planning the exact three-dimensional positioning of endosseous implants in the jaw bone. This study examined the reliability of three CT techniques: direct imaging (normal coronal and sagittal slices), standard reconstruction (based on axial slices), and multiplanar reconstruction and display (also based on axial slices). The three imaging techniques were used to estimate the bone height, bone width, and maximal implant length in six dissected human jaw bones. These jaws were then sawed perpendicular to their axis to enable measurement of real values for comparison. The sagittal and coronal slices frequently were overestimated, especially in the canine and premolar regions. The mean absolute deviation was 1.4 mm. Standard reconstruction offered the most reliable cross-sectional images, with a mean absolute deviation of 0.5 mm. The multiplanar reconstruction and display technique frequently demonstrated underestimations (mean absolute deviation was 2.3 mm). The standard reconstruction technique seems to be the method of choice in preoperative radiographic examination of patients before implant placement.

Alveolar Process↗

PubMed1990

Applicability of osseointegrated oral implants in the rehabilitation of partial edentulism: a prospective multicenter study on 558 fixtures.

Nine clinical centers using the Brånemark System participated in a prospective study of 159 partially edentulous patients between 18 and 70 years of age. Clinical parameters evaluated were plaque index, gingivitis, pocket depth, bleeding index, tooth mobility, and stomatognathic function. Initially, 558 fixtures were placed and 521 remained in the study following prosthesis placement (199 prostheses in 154 patients). Fixtures were lost or unaccounted for because of nonintegration prior to prosthesis fabrication (19), patient withdrawal (11), prosthodontic reasons (6), and failure during prosthetic procedures (1). Failure was primarily attributable to unfavorable bone quality, sex (more in males), and smaller fixture size. Complications and failure related to other patient characteristics are presented. After 1 year of a 5-year study, preliminary results suggest that a success rate equal to or better than that obtained with edentulous patients may be expected.

Adult↗

PubMed1990

[Osseointegrated implants ad modum Brånemark in the oral rehabilitation of patients with advanced periodontal breakdown].

Despite the achievements of modern periodontology, partially or completely edentulous mouths are unavoidable. The rehabilitation of such patients is a great challenge in oral health care. The state of the art of osseointegrated implants according to Brånemark is described. Both full dentures and fixed partial dentures are discussed, with special emphasis on microbiological issues. The hypotheses are supported by substantial published evidence, and the problems discussed are further exemplified by a number of clinical case reports. The authors conclude that osseointegration according to Brånemark is an effective long-term method for oral rehabilitation, and that the failure rate is low. One reservation that has to be made is that we are still waiting for the results of long-term studies on patients who are edentulous due to advanced adult periodontitis. This is the only way to evaluate in more detail the robustness of the tissues around the implantation site.

Dental Implants↗

PubMed1990

[The implant/tissue interface in a clinical perspective].

For a proper insight in the implant/tissue interface of permucosal oral implants it is good to refer to the tooth/periodontium interface. Although there are evident differences such as the lack of a periodontal ligament with its possibilities for eruption and migration and elaborate neural endings, it seems that classical periodontal parameters are the yardstick to discriminate failure from success of oral implants. Long cone radiographs and mobility assessment seem the only available clinical tools to detect a scar tissue interposition. On the other hand, their discrimination power is insufficient to prove close bone apposition. Further studies are needed to interpret the observations that around failing implants the subgingival microflora resembles that of active adult periodontitis. Periodontologists can learn a lot from the implant/periodontium interface to get a better understanding of the tooth/periodontium complex.

Dental Implants↗

PubMed1989

Single motor unit and surface electromyogram analysis of human jaw-closing muscle reflexes after tapping an upper tooth.

The mechanical stimulation of an upper tooth elicited reflex responses in masseter and temporalis motor units, which were recorded with both surface and needle electromyograms (EMGs) simultaneously. The subjects maintained one of the recorded motor units, which was the latest recruited unit, at a constant firing frequency, varying from 12 to 25 Hz. After a latency of 10 ms, all 19 motor units were inhibited for a period, the duration of which depended on the prestimulus firing frequency. A motor unit with a low firing frequency was inhibited for a longer time than a faster firing one. At the end of this inhibition there was an increased probability of firing recorded, in the form of a time-locked clustering of action potentials. Furthermore, in three motor units, all firing at a frequency of about 25 Hz, the first interspike interval after the inhibition was regularly half the duration of the mean prestimulus interspike interval. The timing of the last action potential before the stimulus influenced significantly the reflex responses in all motor units.

Action Potentials↗

PubMed1989

A retrospective multicenter evaluation of the survival rate of osseointegrated fixtures supporting fixed partial prostheses in the treatment of partial edentulism.

Whether the excellent prognosis of the osseointegration technique also applies for the rehabilitation of partially edentulous jaws was investigated through a multicenter retrospective study. Six centers from three continents participated in the study, which included 133 fixtures in 38 patients. Forty fixtures were installed in the upper jaw and 93 in the lower jaw. The observation time varied between 6 and 36 months after prosthetic reconstruction. Clinical evaluation included mobility measurement of the restorations and control of infectious or neurologic complication. Radiologically the absence of radiolucency around the fixtures was checked by a single observer who also calculated the distance between the marginal bone and the top of the fixture. Fifty-eight percent of the prostheses were connected to natural teeth. The success rate for the individual fixtures in the upper and lower jaws was 87% and 92%, respectively. The most failures occurred before the prosthetic rehabilitation. The mean maximum distance between the margin of the bone and the fixture-abutment junction was 2.5 mm. Since only two of the 53 fixed prostheses were lost during the observation period, and since most fixture losses occurred before the prosthetic phase of the treatment, this study supports the concept that osseointegrated prostheses can also be applied to the rehabilitation of partial edentulism.

Adolescent↗

PubMed1989

Comments on standardization of reflex measurements in human masseter muscle, including silent periods.

The following comments are given on the guidelines suggested by Türker (1988) for studies on oral reflexes using the surface EMG of the masseter muscles in man, including the silent period. (i) Attention should not be confined to electrical stimulation since mechanoreceptors in the periodontium, especially in the periodontal ligament, can only be activated by mechanical stimulation of a tooth. Furthermore, different modes of stimulation and stimulation sites do not yield equivalent reflex complexes. Weak and transient mechanical stimulation of a tooth while clenching at a low level of 5 or 10% MVC is a selective model (89%) to study the influence of periodontal receptors. (ii) Statistical criteria should be applied on rectified and averaged EMG records to prevent any subjective bias in the measurements of reflex variables. Whether a period of increased EMG activity is due to clustering of action potentials of motor units firing of which was delayed by a preceding inhibition, or to a real excitatory influence, can be assessed by applying statistical criteria on averaged and subsequently rectified records. (iii) The clenching level should be less than 25% of MVC to avoid muscle fatigue, and to elicit pronounced reflexes with a weak and therefore more selective stimulus. (iv) The stimulus intensity should be much less than six times the threshold if selectivity for mechanoreceptors is desired. Furthermore, periods of increased activity in surface EMG resulting from a weak stimulus are probably due to real excitatory influences and not to clustering of motor unit action potentials after an inhibition. (v) Jaw separation and the use of a force transducer are not always advantageous. If mechanical stimulation is applied to a tooth, clenching in full habitual occlusion causes a complete suppression of the influence of muscle spindles. A shift in activity between the various elevator muscles, and hence a change in activity of the muscle studied, may occur during an experimental session if biting force is used as a feedback. Such a shift is not relevant if feedback is carried out on rectified and low-pass filtered (1.6 Hz) EMG of the muscle studied.

Bias↗

PubMed1989

Is early plaque growth rate constant with time?

Early plaque growth and plaque topography were studied in 15 young adults with a healthy periodontium during a 4-day period of no oral hygiene. After perfect tooth-cleaning, the recolonisation of the buccal surfaces of 48 teeth (front teeth and premolars) was recorded at the start and after 6, 12, 24, 30, 36, 48, 54, 60, 72, 84 and 96 h. At each visit, reproducible colour slides of the buccal tooth surfaces were taken after plaque disclosure. Plaque extension was calculated planimetrically as a % of the total surface area of the tooth. At the end of the experimental period, an average of 27.7% of the surface area was covered by plaque. The early plaque growth followed an exponential curve with a slight tendency for saturation at 96 h. During the night, the plaque growth rate decreased by up to 50%. Clear differences in plaque growth rate were observed between types of teeth, and the plaque growth pattern seemed to be closely correlated to irregularities of the tooth surface. The discontinuity in plaque growth and the influence from the tooth surface roughness have important implications for oral hygiene planning.

Adult↗

PubMed1989

The influence of surface free-energy on planimetric plaque growth in man.

The purpose of this study was to examine the change in plaque area over nine days in vivo on four materials with different surface free-energies (s.f.e.). Twelve healthy dental students participated in a cross-over, split-mouth, double-blind study. Supragingival plaque formation was recorded over a nine-day period, on four different materials: fluorethylenepropylene (Teflon) (FEP), parafilm (PAR), cellulose acetate (CA), and enamel (E) with s.f.e. of 20, 26, 57, and 88 erg/cm2, respectively. Strips made from the first three materials were stuck to the buccal surface of an upper incisor. The remaining incisor was carefully polished and served as an enamel surface. The increase in plaque was evaluated after three, six, and nine days. A planimetrical analysis was used so that the plaque area could be expressed as a percentage of the total buccal tooth surface. This procedure was repeated on each subject, so that at the end, each pair of central or lateral incisors received the four tested materials. The results indicated that the adherence of micro-organisms on pellicle-coated substrata was influenced by the material's s.f.e.; there was an association between the s.f.e. of the substrata and the supragingival plaque extension in vivo. High surface free-energy substrata in the oral cavity attracted more micro-organisms than did low energetic materials. Additionally, the bacterial adhesion seemed very weak on surfaces with a low s.f.e.

Adult↗

PubMed1989

[Surgical and non-surgical approach to deep periodontal pockets].

Deepened pockets are a challenge because they offer an anaerobic niche and because of their inaccessibility to personal plaque control measures. Scaling and root planing followed by regular professional plaque removal are effective in arresting the progress of most chronic adult periodontitis. Only when pockets remain inflamed after repeated thorough professional treatment during several months can a surgical pocket elimination technique be used. The results will depend on the type of attachment loss (horizontal vs. irregular) the root anatomy (furcations) and the training level of the operator, general practitioner or periodontologist. There is an increasing trend in the anterior parts of the oral cavity (monoradicular teeth easily accessible for plaque control) to use the Widman technique. Long-term data concerning the stability of this new attachment are lacking. Gingivectomy is less elaborate, does not imply a high-level sterile environment like for mucoperiosteal flap surgery, but leads to phonetic and esthetic side-effects when used in frontal areas. In the distal areas the apically displaced and the shortened repositioned flap techniques are effective in a long-term perspective if regular postoperative monitoring is respected. Discussion remains concerning the stability of a new connective tissue attachment vs. a long epithelial attachment. A recent breakthrough is the so-called Guided Tissue Regeneration where by means of a submucosally membrane the periodontal ligament cells are allowed to regenerate the different periodontal tissue compartments. Preliminary results are very encouraging but need further evaluation.

Dental Plaque↗

PubMed1988

Interactive periodontal and acoustic influences on the masseteric post-stimulus electromyographic complex in man.

Post-stimulus electromyogram (EMG) complexes (PSECs) were studied in the full-wave rectified and averaged EMGs of the masseter muscles in 15 subjects, who clenched at a controlled level. The PSECs, a series of downward- and upward-going waves reflecting inhibitory and excitatory influences upon the masseteric motoneurones, were elicited by mechanical stimulation of a tooth. The stimuli selectively activated mechanoreceptors in the periodontium and, by bone-conduction, acoustic receptors. Application of acoustic masking during the periods of stimulation revealed a series of inhibitory and excitatory acoustic influences in the PSEC, which were absent after local electrical stimulation of receptors in the periodontium or their afferents. By applying local anaesthesia to the periodontium of a mechanically stimulated tooth, the durations of the acoustic influences were on the average reduced by 76%. In subjects whose PSECs consistently included a second inhibitory period, the duration of the acoustic influences with respect to that of the PSEC (30%) was larger than otherwise (13%), suggesting a central gating of periodontal pathways which can block both periodontal and acoustic influences. The acoustic influences, of which the appearance in the PSEC largely depends upon activated periodontal pathways, represent a new finding of audio-motor reflexes.

Acoustic Stimulation↗

PubMed1988

Bilateral post-stimulus electromyographic complexes in human masseter muscles after stimulation of periodontal mechanoreceptors of bi- and unilaterally-innervated teeth.

These complexes (PSECs) were studied in full-wave rectified and averaged EMG in 13 subjects, who jaw-clenched at a controlled level. The PSECs were elicited by mechanical and electrical stimulation of receptors or their afferents in the unilaterally- and bilaterally-innervated periodontium of the upper first premolars and an upper central incisor. To exclude any contribution from acoustic receptors, subjects were exposed to high-intensity noise during mechanical stimulation. Comparison of peak amplitude and area from PSEC waves in normalized EMG amplitude-time plots suggests extensive crossing of the midline by periodontal afferent information. The small variation in latency of the first inhibitory wave on the two sides suggests that there are no additional synapses in the crossed pathway. Latency differences and wave incidence on the two sides of the later inhibitory and excitatory periods varied markedly between subjects suggesting that influences from higher centres affect masseteric motoneurones. In five subjects stimulation of periodontal receptors around different teeth resulted in different PSEC wave sequences.

Adult↗

PubMed1988

Periodontal aspects of osseointegrated oral implants modum Brånemark.

The osseointegration method developed by Brånemark offers new perspectives in the rehabilitation of partial and total edentulism in cooperation with the prosthodontist or general practitioner. The success rates over 90 and even 95 per cent in the upper and lower jaws, respectively, have been confirmed by several teams on series of consecutive patients. Ongoing research will allow discrimination between those systems that really osseointegrate predictably and those that do this irregularly or only demonstrate a close bone apposition. There is an urgent need for follow-up studies on consecutive patients of 5 or preferably 10 years before unrestricted clinical applications are granted. There are attractive research perspectives offered by the osseointegration principle in the field of periodontology. Fundamental questions concerning bacterial colonization of hard surfaces in the oral cavity, epithelial downgrowth, ankylosis, and others can be addressed and extrapolated to the treatment of periodontal pathologies around teeth.

Alveolar Process↗

PubMed1987

Plaque removing effect of a convex-shaped brush compared with a conventional flat brush.

The plaque-removing effect of a convex-shaped multitufted brush was compared with that of a conventional flat multitufted brush. Two group (five and seven dental students, respectively), well instructed in the modified Bass technique, participated in a blind, splitmouth, crossover study during two consecutive experimental periods of 96 hours of undisturbed plaque growth. After each of these periods, a supervised brushing session was performed, followed by toothpick utilization. Plaque removal was evaluated using the modified Navy Plaque Index (MNPI) and planimetry. A 4% erythrosin solution was used as a disclosing agent. Planimetrically, the flat Oral B brush appeared significantly more effective than the convex shaped Ph brush (P less than 0.001). This superiority was even enhanced after the use of toothpicks (P less than 0.0005). The differences between the brushes, however, were too small to be detected by the less discriminating MNPI. Although it has been claimed that the convex brush could assure approximal plaque control, the results indicate that for the convex-shaped, as well as for the flat brush, an approximal aid is essential for good plaque control. The hypothesis that the design of the convex-shaped brush could facilitate the modified Bass technique for the average patient could not be proven in this study.

Adult↗