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Biomedical subjects

U Brägger

Publications and source records attributed to U Brägger.

At least 19 recordsLinked to original sources

Development of an opto-electronic positioning device for serial direct digital images of oral structures.

The aim of this study was to develop and test in vitro an opto-electronic positioning device for serial direct digital images of oral structures, i.e. to associate direct digital imaging with the principles of computer-aided surgery. This system registered positions of infrared light emitting diodes (LED) on carriers, establishing local coordinate systems. With LED markers attached on the sensor holder, the X-ray tube and a fix reference, the opto-electronic camera (Optotrak) registered the geometric source/detector relation. A specially designed tracking and guidance software was developed which enabled the operator to reposition the X-ray source. A graphical user interface guided the operator in aligning 2 circles to the reference axis, one indicating the origin of the beam, the other its tip. In addition, depth control was provided. An in vitro calibration was performed. A sensor holder/bite block carried the Sens-A-Ray sensor with a hair-cross. In front of the object a second hair-cross was fixed. A steel ball fixed to the center of the X-ray cone allowed to verify the alignment. The mean angulation error in the vertical plane was 0.06 degrees and 0.04 degrees in the horizontal one. Translation mean errors were small and ranged between -0.02 mm and 0.37 mm. The translation in the Z axis is negligible. This resulted in pairs of images suitable for digital subtraction. Although still in an experimental state, the results showed that opto-electronic navigation was useful to standardize projection geometry without any mechanical link and to achieve digital subtraction images based on direct digital imaging.

Equipment Design↗

Peri-implant microflora of implants with cemented and screw retained suprastructures.

The aims of this study were to compare clinical and microbiological features in the peri-implant area of implants carrying either screw retained or cemented suprastructures, and to investigate the relationship between the peri-implant microflora, the microbiota on the inner surface of removable suprastructures, and the periodontal microflora within the same subject. In 15 partially edentulous patients with ITI implants used as abutments for crown and bridge reconstructions, microbial samples were taken i) from the deepest periodontal pocket of each quadrant, ii) from the sulcus of the implants and iii) from the internal surface of the screw retained suprastructures. The samples were cultured using continuous anaerobic techniques. Five patients were found with both screw retained (S) and cemented (C) suprastructures. In these subjects the mean total cultivable counts were significantly higher in peri-implant samples from group C than in samples from group S. Furthermore, peri-implant samples of group S yielded a higher proportion of coccoid cells in the darkfield microscope and demonstrated absence of large spirochetes. From the 15 patients, Porphyromas gingivalis was detected in 10% of the periodontal samples and in only one peri-implant sample. Prevotella intermedia was detected in 33% of the periodontal and in 30% of the peri-implant samples. Fusobacterium spp. had a prevalence of 58% in the periodontal samples and was recovered from 50% of the peri-implant samples. Actinobacillus actinomycetemcomitans was not detected in any dental or peri-implant sample. In 1 case, however, the organism was recovered from the internal surface of the suprastructure. Linear regression analysis showed a significant relationship between the frequency of micro-organisms in peri-implant samples of group S and in samples from the inner surface of the suprastructure. Furthermore, there was a significant correlation between the incidence of micro-organisms in dental samples and i) in peri-implant samples of group S and ii) in samples from the internal suprastructure surface. These findings indicate, that the microbial leakage through the gap between the suprastructure and the abutment plays an important role in the bacterial colonization of the internal part of screw retained crowns and bridges. The study furthermore confirms the impact of the dental microflora on the microbial colonization of implants. This factor appears to be more important than the mode of fixation of the suprastructure.

Adult↗

Evaluation of postsurgical crestal bone levels adjacent to non-submerged dental implants.

In most of the studies on long-term radiographic evaluations of crestal bone levels adjacent to dental implants, no baseline radiographs taken immediately postsurgically had been obtained. The aim of this study was to test the reproducibility of a simple radiographic method for linear measurements of changes in bone levels and to evaluate changes in crestal bone levels adjacent to non-submerged ITI implants 1 year following the surgical procedure. From 128 patients enrolled in a clinical and radiographic longitudinal study 40 patients also had radiographs taken immediately postsurgically. They were, however, not obtained as "identical" images. The radiographs were mounted onto slides and projected on a screen. Mesially and distally from 57 implants triplicate linear measurements of the distance implant shoulder to bone crest were taken, using known dimensions of the implants as internal reference distances. The median difference of 213 (out of 228 possible) duplicate measurements was 0.00 mm (ranging from -1.72 mm to +1.47 mm when comparing the second to the third reading). Some 81% of the double measurements were within +/- 0.5 mm and the precision was 0.30 mm. In the immediate postoperative radiographs the median mesial bone level was located at 2.07 mm (distally 2.19 mm) from the implant shoulder. A statistically significant amount of bone loss in the first year was observed mesially (median = -0.78 mm) and distally (-0.85 mm) (Wilcoxon matched pairs signed rank test P < or = 0.001). No statistically significant influence of the implant location, the implant length, type of the implant (screw; cylinder) was observed (Kruskal-Wallis P > 0.05). The age of the patients was not correlated significantly to the amount of bone loss observed. In conclusion, methodological limitations existed when evaluating linear bone changes in non-identical radiographs using reference dimensions of the implants. The amount of postsurgical bone loss estimated in other studies was confirmed when using an immediate postoperative radiograph as a baseline.

Adolescent↗

Guided tissue regeneration for the treatment of intraosseous defects using a biabsorbable membrane. A controlled clinical study.

The aim of this controlled, clinical study was to evaluate guided tissue regeneration using a bioabsorbable membrane in periodontal intraosseous defects. Forty patients, each contributing one defect > or =4 mm in depth participated. The control group (18 individuals) received conventional flap therapy, while the test group (22 individuals) was treated using the bioabsorbable membrane, Guidor. Clinical assessments were made by one examiner, blinded with respect to treatment group, at baseline, 6 and 12 months following surgery. Baseline probing pocket depths of 7.7+/-1.4 mm in the membrane group and 7.6+/-1.9 mm in the control group were measured. Twelve month results showed a significant clinical attachment level gain in both control (1.1+/-1.8 mm), and membrane group (1.3+/-2.1 mm). Probing pocket depth reduction of 2.6+/-1.9 mm and 2.7+/-1.9 mm was observed in the respective groups. Bone sounding showed a non-significant gain of 0.4+/-1.8 mm and 0.6+/-1.4 mm at membrane and control sites, respectively. Radiographic evaluation confirmed these results. There were no significant differences found between treatment groups for any of the tested variables. Smoking had a negative effect on healing in both groups. In conclusion, clinical and radiographic results indicate that guided tissue regeneration using a bioabsorbable membrane at intraosseous defects did not predictably achieve greater clinical attachment level gain nor bone gain when compared to conventional flap therapy.

Absorption↗

Evaluation of tetracycline fiber therapy with digital image analysis.

The aims of the present study were to assess radiographically the effects of scaling/root planing combined with antibiotic therapy using tetracycline fibers (TCF): (I) on alveolar bone density and linear descriptors and (II) on supracrestal soft tissue density. 19 subjects with generalized adult periodontitis (with at least 20 teeth present, at least 4 teeth with pockets >4 mm and bleeding upon controlled force probing) and high cultural counts of Porphyromonas gingivalis were recruited from a pool of 57 patients. The full mouth treatment group (FT) consisted of 10 patients, who underwent a full mouth supra-gingival scaling and prophylaxis treatment and were instructed to rinse 2x daily with a 0.1% chlorhexidine solution. 1 week later, tetracycline-hydrochloride-containing fibers (Actisite periodontal fiber) were applied around all teeth. After 7-12 days, the fibers were removed and all teeth were scaled and root planed under local anaesthesia. The chlorhexidine rinsing continued for another 2 months. In 9 subjects (local treatment group LT), 2 teeth with periodontal lesions with pocket probing pepth (PPD) > or =5 mm were treated by placement of tetracycline fibers, which remained in place for 7 to 12 days. Upon removal of the fibers, scaling and root planing was performed on these 2 teeth, while the rest of the dentition remained untreated, and no chlorhexidine rinse was applied. 2 of the untreated teeth revealing similar periodontal lesions were chosen to represent sites affected by untreated periodontitis (NT). In this group, a limited local treatment was performed (2 teeth) with the inherent potential for recolonization from the untreated pocket sites. Standardized periapical radiographs were obtained from the 4 monitored sites within each patient at baseline (before treatment) and 2 and 6 months thereafter. One radiograph was exposed in a standard way for bone assessment. The second radiograph was underexposed, at about a 1/5 of the original exposure time to allow the evaluation of soft tissue. Mean changes in the linear parameters and changes in density (CADIA) observed at multiple sites within each patient and treatment group were used as the best estimate of treatment outcome. Over the observation period of 6 months, a significant difference in bone height changes was found between the untreated sites (median loss -0.29 mm) and the sites from full-mouth treated patients (median gain 0.24 mm, p=0.008). When comparing the baseline to the 6 months radiographs, a loss in bone density was observed for the untreated group (median=-2.13 CADIA). Both treatment groups revealed a gain in density (median=1.58 and 2.43 CADIA for the locally and the full-mouth treated groups, respectively). Differences in density were significant, both between the nontreated and locally treated sites (p=0.026) and between the nontreated sites and the sites from the full mouth treated patients (p=0.002). The analysis of the soft tissues showed a similar pattern of changes in density to those seen in the bone defect. At 2 months, there was a tendency for loss in density for the nontreated group (median=-0.17 CADIA) that continued over the 6 month period (median=-0.31 CADIA). A significant increase in density was observed for the full-mouth treated sites (median=1.57 and 0.64 CADIA for the 2 and 6 months radiographs, respectively). A significant increase was also observed for the locally treated group when compared to the untreated sites (median=0.13 and 0.10 CADIA for the 2 and 6 months radiographs, respectively). Comparing untreated sites with full-mouth treated sites, a significant difference was observed for CADIA measurements (p<0.001). No significant difference was observed comparing locally treated and untreated sites (p=0.24). It was concluded that scaling and root planing combined with TCF therapy can result in increased bone density and alveolar bone height. Full-mouth treatment seemed to result in more pronounced gains compared to local tre

Adult↗

Computer-assisted densitometric image analysis of digital subtraction images: in vivo error of the method and effect of thresholding.

The aim of the present study was to assess the in vivo error of the method as well as the effect of thresholding when obtaining and evaluating standardized periapical radiographs for computer-assisted densitometric image analysis (CADIA). Twenty healthy volunteers participated in an experimental gingivitis study in which neither mechanical nor chemical plaque control was performed for 21 days. Two pairs of standardized periapical radiographs were taken at days 0 (baseline) and 21 (follow-up), one from a maxillary area (15 volunteers) and one from a mandibular molar/premolar area (17 volunteers). Each baseline radiograph was digitized and its image displayed on a monitor. The follow-up radiograph was then superimposed and digitized as well. After gray level correction, subtraction radiographic images were produced. The difference in gray level between the baseline and the follow-up image was calculated within each region of interest (ROI) at each picture point (pixel). In bone ROI, changes in density reflected the amount of change due to methodological errors plus the basic bone remodeling over 3 weeks. For gingival ROI, changes in density reflected the methodological error plus a possible change in soft tissue density during the experimental gingivitis. Within all of the ROI, some pixels indicated a change in gray level. A change in gray level was then thresholded; i.e., only changes >5 and then >10 gray levels were registered and used for calculation of the CADIA values. With a threshold of 5, 44/45 maxillary bone ROI and 60/66 mandibular bone ROI showed a change in density, while 41/45 maxillary gingiva ROI and 26/66 mandibular gingiva ROI indicated a change in density. With a threshold of 10, 16/45 maxillary bone ROI and 12/66 mandibular bone ROI indicated a change in density, while 13/45 maxillary gingiva ROI and 1/66 mandibular gingiva ROI indicated a change. The amounts of changes in density calculated in the various ROI were low even when applying no threshold, ranging from -0.279 to 0.621. Applying a threshold of 5, the CADIA values ranged from -0.234 to 0.727. With a threshold of 10, the changes in density ranged from -0.318 to 0.133. In vivo, CADIA of standardized radiographs indicated change in density due to methodological errors. Application of thresholds may avoid false-positive diagnoses. When applying CADIA in clinical research, the range of change to be expected due to methodological limitations as well as the threshold for true change should be evaluated. These thresholds may differ in various areas of the mouth, i.e., bone or gingival, maxillary/mandibular, anterior/posterior ROI.

Absorptiometry, Photon↗

Associations between clinical parameters assessed around implants and teeth.

The aim of the present study was to clinically assess the peri-implant and periodontal conditions 1 year after placement of oral implants (ITI Dental Implant System) in partially edentulous patients. In all, 127 patients (median age 50 years, range 17 to 79) were examined. They were all treated according to a concept of comprehensive dental care and had received fixed partial dentures (FPD). Significant differences were observed between implants and contralateral control teeth with respect to mean pocket probing depth (PPD) (2.55 mm at implants/2.02 mm at teeth), mean probing attachment level (PAL) (2.97 mm/2.53 mm) and bleeding on probing (BOP) (24%/12%) (Wilcoxon matched pairs sign rank test, P < or = 0.01), whereas mean modified plaque index (0.22/0.30), mean modified bleeding index (0.35/0.44) and mean recession (-0.42 mm/-0.51 mm) did not significantly differ between implants and teeth. Compared to control teeth, the width of keratinized mucosa at implants was significantly smaller at lingual, but not at buccal aspects. Regression analyses showed no significant association between the amount of keratinized mucosa and degree of inflammation. Recession, PPD and PAL were slightly influenced by the amount of keratinized mucosa indicating greater resistance to probing. Grouping the implants according to various lengths, type of fixation of the FPD or combination with natural teeth did not result in statistically significant different clinical parameters, whereas grouping according to different localization within the oral cavity did. For example, the mean PAL in 83 anterior implants was 2.52 mm, whereas 175 posterior implants had a mean PAL of 3.18 mm (Mann-Whitney U-test, P < or = 0.01). Regression analyses between the mean PAL for all implants in each patient and the mean PAL of the corresponding dentition revealed an r2 of 0.23 (P < or = 0.01). Using multiple regression analysis, the mean PAL of the implants showed to be significantly influenced by the combined factors "fullmouth" PII, "fullmouth" BOP and mean PAL of all teeth. The results of this study suggest that in partially edentulous patients the overall periodontal condition may influence the clinical condition around implants and thus reinforces the importance of periodontal treatment prior to and supportive periodontal therapy after the incorporation of osseointegrated oral implants.

Adolescent↗

Comparison of periodontal and peri-implant probing by depth-force pattern analysis.

The purpose of this study was to compare the tissue resistance to probing and the accuracy of depth determination at different force levels around implants and teeth. In 11 subjects 1 implant and 1 tooth at a comparable location and with comparable probing depth were investigated. The sites were located on either the mesial or distal aspect of the tooth and the implant. A probing device was used which allowed simultaneous monitoring of probing force and probe penetration and which standardized the insertion pathway for repeated measurements. The probing instrument was fitted with an attachment for an aiming device to take a radiograph with the probe tip in the sulcus, using a standardized projection geometry. Probing depth values were determined at 0.25, 0.50, 0.75, 1.00 and 1.25 N probing force. The standard error of the individual measurement (Si), evaluated by comparison of repeated measurements in the same session, was 0.2 mm on implants and 0.1 mm on teeth. For implants there was a trend for slightly better reproducibility at higher force levels. Curve analysis of depth force patterns showed that a change in probing force had more impact on the depth reading in the peri-implant than in the periodontal situation. The mean distance between the probe tip and the peri-implant bone crest amounted to 0.75 +/- 0.60 mm at 0.25 N probing force. It is concluded that peri-implant probing depth measurements are more sensitive to force variation than periodontal pocket probing.

Dental Implantation, Endosseous↗

Particulate bioglass as a grafting material in the treatment of periodontal intrabony defects.

The present clinical trial was designed to evaluate the effects of a bioactive glass, Perioglas, in the treatment of periodontal intrabony defects. 20 patients, 23-55 years of age (44 sites), with intrabony defects completed the 1-year study. Teeth with furcation involvement were excluded. After completion of initial therapy, defects were randomly assigned to either a test or control procedure. Following flap reflection, root planing and removal of chronic inflammatory tissue in both groups, the test defects were restored with the bioactive glass particulate material. Mucoperiosteal flaps were replaced, sutured and a periodontal dressing was used. All the patients received postoperative antibiotics and analgesics and were seen at 1 week for suture removal. Follow-up was then carried out weekly and at 3 months, 6 months, 9 months and 1 year post-surgery. Plaque score, bleeding score, probing pocket depth (PPD), probing attachment level (PAL) and gingival recession were recorded at baseline, 3 months and 1 year. Standardised radiographs for computer-assisted densitometric image analysis (CADIA) were taken at baseline, immediately post-operatively and at 1 year. The CADIA data showed a significant increase (F-ratio: 15.67, p < 0.001) in radiographic density and volume between the defects treated with the Perioglas when compared to those treated with surgical debridement only. PPD and PAL showed significant improvements in both experimental and control sites, with a greater trend to improvement in the experimental sites. It was concluded that this bioactive glass is effective as an adjunct to conventional surgery in the treatment of intrabony defects.

Absorptiometry, Photon↗

Effect of the NSAID flurbiprofen on remodelling after periodontal surgery.

The aim of the present experiment was to assess the effect of the administration of the NSAID flurbiprofen (Froben) on tissue healing after periodontal surgery. Sites from patients with the same treatment modality (modified Widman flap) but receiving a placebo drug and sites within each patient not exposed to surgery served as controls. Nineteen patients suffering from moderate to severe periodontal disease were recruited and they signed informed consent forms. These patients required periodontal surgery as assessed at the periodontal re-evaluation. The sites chosen for the study were all diagnosed with PPD > or = 5 mm and were bleeding on probing. During the healing phase 10 patients received 50 mg Froben 3 times per day for 30 d whereas 9 patients received a placebo drug. Two sites with PPD > or = 5 mm after initial therapy and bleeding on probing served as surgical sites, whereas 2 similar sites were not exposed to surgery. The study design was set up double-blind. The radiographic examination consisted of 2-4 standardized vertical bitewings obtained at the periodontal re-evaluation (BL) at 1, 3 and 6 months post-surgically for digital subtraction and computer assisted densitometric image analysis (CADIA). The regions of interest analysed were mesial or distal crestal sites. Minimal remodelling activity was observed radiographically after periodontal surgery in both patient groups. There were no statistically significant differences between the four groups of sites regarding the mean changes in density when analysing the pairs of radiographs 0-1, 0-3, 0-6 months. A frequency analysis was performed to list the number of sites with different ranges of density change. No differences in the distributions of the numbers of sites were observed when comparing the 4 site groups (Kolmogorov-Smirnov, p > 0.05). A significant reduction of the probing pocket depth and a significant amount of clinical attachment gain was noted at the surgically treated sites irrespective of whether the patients had used flurbiprofen or placebo. Whereas the pathways leading to bone resorption in periodontally diseased sites have been shown, in other studies, to be influenced by NSAID, the results of the present study could not justify general administration of Froben for the purpose of reduction of bone resorption after periodontal surgical procedures in patients with adult periodontitis.

Absorptiometry, Photon↗

Clinical trials on therapies for peri-implant infections.

Peri-implant infections are pathological conditions which are normally localized in the soft tissues surrounding an oral implant. They may range from a rather localized mucositis lesion reflecting the host response to a bacterial challenge to a more advanced lesion "termed peri-implantitis" when previously osseointegrated oral implants have been partially disintegrated; i.e. have lost alveolar bone around the implant. Usually these lesions start as a result of plaque accumulation and show similar progression as observed around teeth. Muscositis seems to be a prerequisite for the following peri-implantitis. However, the factors involving the transition to a more advanced lesion are still not known. Logically, the therapy for peri-implant infection has to be related to antibacterial treatment prior to the attempt to surgically regenerate peri-implant alveolar bone lost as a result of the infection. In order to diagnose these lesions at an early stage frequent assessments of clinical parameters are needed during maintenance therapy. The anti-infective treatment may intercept the development of the lesion. Following mechanical debridement of plaque deposits the application of efficacious antiseptics (chlorhexidine) is a necessity. Following this, antibiotics may cumulatively be applied to control the infection. Only a few longitudinal studies have documented the efficacy of such treatment regimens, and controls have generally not been available for ethical reasons. In regenerating the lost jaw bone only case reports are available today. Controlled animal studies will have to be performed to document the possibility of re-osseointegration and the factors influencing predictability.

Animals↗

Subtraction radiography in oral implantology.

Radiographic examinations in connection with implant installation are important means to diagnose changes in the bone tissue following implantation. During the healing and early remodeling phases, a slight reduction of the marginal bone height occurs in the first year after implantation, which is followed by an even smaller annual mean loss in bone height. Conventional radiographs, however, are of limited value for reliable assessment of subtle alveolar bone changes, although methods were developed to standardize the projection geometry of serial radiographs from implants to improve the accuracy in detecting changes of the peri-implant bone height. Newer radiographic diagnostic methods should not only comprise the possibility of metric assessment of bone height but also further information on changes in density. This report emphasizes the potential of digital subtraction radiography as a sensitive diagnostic tool in peri-implant diagnosis. Minute peri-implant density changes may occur in the healing phase after implant installation, after loading, and during the maintenance phase.

Alveolar Bone Loss↗

The significance of bone in periodontal disease.

Although the connective tissue attachment represents the key issue in periodontal health or disease and in periodontal therapy, the assessment of alveolar bone changes renders valuable indirect evidence for periodontal stability, progression of disease, or repair mechanisms. In periodontal disease bacterial products trigger host cells to release mediators, which may imbalance the steady state between resorption of bone and apposition of osteoid. Modulation of the hosts prostaglandin or interleukin-I synthesis by drug therapy could support the antimicrobial concept of periodontal therapy. Cross-sectional and long-term assessments of alveolar bone have been used to estimate the progression rate of periodontal disease. Inherent limitations of bone assessments in radiographs have to be considered when drawing conclusions from measurements that represent remodeling in periodontal lesions after therapy. Both bone quantity and quality seem to be of secondary importance with respect to the progression of disease, as well as response to therapy. Other risk factors that affect the microbial ecology and/or the hosts immune system seem to be the primary determinants for the periodontal health status.

Alveolar Bone Loss↗