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Biomedical subjects

P Schärer

Publications and source records attributed to P Schärer.

At least 19 recordsLinked to original sources
PubMed2001

Immediate occlusal loading of Brånemark implants applied in various jawbone regions: a prospective, 1-year clinical study.

BACKGROUND: The original protocol for dental implant treatment ad modum Brånemark was based on submerged healing prior to loading. For patients, immediate implant function could reduce cost and increase attractiveness of implant treatment. PURPOSE: The goal of this study was to evaluate the short-term success rate of immediately loaded implants placed in various regions of the jaws. MATERIALS AND METHODS: Forty-one patients received a total of 127 immediately loaded implants (76 maxillary and 51 mandibular). Seventy-one percent of the patients received their prosthetic restoration the same day and the others within 11 days. All prosthetic constructions were in full contact in centric occlusion. Clinical follow-up examinations were performed at 1 week, 2 weeks, and at 1, 2, 3, 6, and 12 months after implant loading. The study was completed 1 year after loading. RESULTS: Twenty-two implants were lost in 13 patients (including 7 maxillary implants lost in 1 patient). The cumulative success rate of the implants was 82.7% after 1 year of prosthetic loading. All sites with implant losses were re-implanted, using a two-stage technique, with no further complications reported. Ninety-one percent of implants placed in regions other than the posterior maxilla were successful compared with 66% of implants placed in the posterior maxilla. Implants in patients with a parafunctional habit (bruxers) were lost more frequently than those placed in patients with no parafunction (41% vs. 12%). Implants subjected to guided bone regeneration were more successful compared with those not subjected to regeneration procedures (90% vs. 67%). CONCLUSIONS: The immediate loading concept is a realistic treatment alternative in various jawbone regions except for the posterior part of the maxilla. High occlusal loads should be considered a risk factor. On the other hand, implants in combination with bone defects frequently are penetrating cortical layers to a higher extent, thereby contributing to implant stability during the healing phase and consequently do not inevitably jeopardize the treatment result. However, further controlled clinical studies with larger sample sizes need to be performed to evaluate the influence of different parameters on treatment outcome.

Adult↗
PubMed2001

Alveolar ridge augmentation with Bio-Oss: a histologic study in humans.

The aim of the present study was to investigate the healing of alveolar ridge defects augmented with cancellous bovine bone mineral. In six partially edentulous patients, bone augmentation was necessary prior to implant placement because of severe alveolar ridge resorption. The defect sites, all located in the maxilla, were filled with Bio-Oss and covered with the resorbable collagen membrane Bio-Gide. Biopsies were obtained from the defect sites 6 to 7 months following grafting and were processed for ground sectioning. The histologic analysis revealed that the Bio-Oss particles occupied 31% of the total biopsy area. An intimate contact between woven bone and Bio-Oss was detected along 37% of the particle surfaces. A mixed type of bone was found; it contained woven bone and parallel-fibered bone, which demonstrates features of remodeling activity. Signs of resorption of the grafting material were observed in the histologic sections, which indicates that the material takes part in the remodeling process. It is suggested that Bio-Oss may be a very suitable material for staged localized ridge augmentation in humans.

Adult↗
PubMed2001

Reliability and strength of all-ceramic dental restorations fabricated by direct ceramic machining (DCM).

All-ceramic dental bridges for the molar region are not yet available at reasonable costs. The novel direct ceramic machining (DCM) process allows an easy, reliable and rapid fabrication for all-ceramic dental restorations with high mechanical strength and good biocompatibility. In DCM, an enlarged framework is easily milled out of a pre-fabricated porous ceramic blank made of zirconia. After sintering to full density, no further time-consuming hard machining with diamond tools is needed. For individual esthetical requirements, the framework is coated with a veneer porcelain. Compared to the commercially available In-Ceram Alumina and IPS Empress2 restorations, the mechanical strength of zirconia frameworks is twice as high, allowing the restorations to bear the high mastication forces in the molar region. In terms of reliability, zirconia bridges fabricated by the DCM process are also superior to In-Ceram Alumina and IPS Empress2. A clinical study of three-unit dental bridges in the molar region found no problems after the first year of observation.

Aluminum Oxide↗
PubMed2000

Soft tissue correction of a single-tooth pontic space: a comparative quantitative volume assessment.

STATEMENT OF PROBLEM: Various augmentation procedures are recommended for the correction of localized alveolar ridge defects. However, no study has quantitatively evaluated the results of these procedures to date. PURPOSE: This study compared 2 soft tissue augmentation surgeries commonly used to alter contours of single-tooth pontic space by quantifying 3-dimensional volume changes with the optical projection Moiré method at 1 and 3.5 months after surgery. MATERIAL AND METHODS: Twenty-four patients required surgery. Each patient had a localized alveolar ridge defect, corresponding to a mesial-distal width of 1 single tooth. The defect of 12 patients was corrected with a subepithelial connective tissue graft; the remaining 12 patients were treated by receiving a free full-thickness gingival graft, which included epithelium and connective tissue with fatty tissue. Six unoperated defects of 6 patients formed the control group. For each defect, an impression was made before treatment, at 1 and 3.5 months after surgery to measure the volume changes on the dental casts with a validated projection Moiré system. Volume change was assessed relative to the preoperative dimension at the buccal and crestal aspects of the single-tooth pontic space. RESULTS: At 3.5 months postsurgery, mean volumetric gain for the connective tissue group with 159 mm(3) (SD +/- 80) was significantly greater (P =.027) than for free full-thickness gingival graft group with 104 mm(3) (SD +/- 31). CONCLUSION: The applied projection Moiré method proved its applicability in assessing 3-dimensional volume changes of pontic spaces with a single-tooth width. Volumetric assessment after 1 and 3.5 months revealed significantly greater volume gain with the subepithelial connective tissue graft in comparison to the free full-thickness gingival graft.

Adipose Tissue↗
PubMed2000

Long-term survival estimates of cast gold inlays and onlays with their analysis of failures.

The aim of the present study was to assess the clinical behaviour of cast gold restorations with respect to define a gold control against current and future ceramic and composite restorations. The study sample included 50 patients with 303 cast gold restorations. All restorations were cemented with a non-adhesive technique. A total of 303 restorations were evaluated clinically and radiographically using modified United States Public Health Service criteria. Restorations recorded as having an A- or a B-rating were defined as successful. Of the 303 restorations, 42 were judged as failures, which resulted in a failure rate of 13.8% for a mean observation time (+/- s.d.) of 18.7 ( +/- 9.5) years. The estimated Kaplan-Meier survival rates (s.e.) were 96.1% (+/- 1.1%) at 10 years, 87.0% (+/- 2.2%) at 20 years and 73.5% (+/- 5.4%) at 30 years. In total, biological reasons were counted 25 times in comparison to 17 technical reasons for those 42 failed cast gold restorations, with 17 secondary caries (40%) as the most common biological reason and with 13 retention losses (31%) as the most common technical reason. The endodontically treated tooth was exclusively identified as a risk factor. The restoration type (inlay versus onlay) did not influence the survival rate.

Confidence Intervals↗
PubMed2000

[Clinical study of zirconium oxide bridges in the posterior segments fabricated with the DCM system].

Today's dental reconstructive therapeutic concepts require restoration of high esthetic quality and excellent biocompatibility. Full ceramic reconstructions accomplish these requirements but only for anterior teeth and premolars. For all-ceramic bridges the mechanical strength was insufficient to withstand the posterior chewing forces. Frequently the interdental connectors cracked, and the only way to prevent these fractures was to overconture the connectors to a size of approx. 16 mm2. The high-tech ceramic zirconia is a potential alternative for three-to five-unit full ceramic bridges in the functionally loaded posterior segments. Experimental zirconia bridges which were fabricated using the DCM system (Direct Ceramic Machining System at the ETH Zurich, were tested in vitro. The frameworks were digitally enlarged by 20% and were easily milled from a presintered yet porous zirconia blank. After the milling process, the framework was densely sintered and shrank to its original size. Due to these positive in-vitro results a clinical investigation was started. 22 veneered zirconia bridges were luted; 19 molars and 25 premolars were prepared. The connectors, max. 7 mm2, of all these bridges, have been functionally loaded by antagonists. After a mean observation time of 385 days (307 days to 488 days), all 22 bridges did not show any cracks in the framework or in the veneering porcelain. The patients commented particularly on the low heat conduction rate of zirconia. The only endodontic problem which occurred could not be directly connected to the type of bridge framework. The reliability of zirconia bridges in this investigation was connected to the DCM-Process. No statement about other zirconia-systems can be made on the results of this study.

Dental Alloys↗
PubMed1999

Factors influencing the success of GBR. Smoking, timing of implant placement, implant location, bone quality and provisional restoration.

The aim of this retrospective clinical study was to evaluate the influence of different factors on the outcome of GBR treatment. 75 patients, who were not randomly assigned to the investigated parameters for clinical reasons, were included in the study. They presented with defect sites around implants and were treated with a xenogenic grafting material and a resorbable collagen membrane. The defect morphology was described, its dimension was measured and calculated at the time of implant installation and at re-entry. The success of GBR treatment was related to several clinical variables and possible correlations were evaluated. Defect sites around maxillary implants showed significantly more bone fill (96%) compared to those in the mandible (78%). The insertion of a provisional restoration during the healing period was also associated with significantly better results than when no provisional was inserted. Immediate and short-term delayed implant placements showed the best results both with 92% bone fill, when compared with long-term delayed placements with 80% bone fill (n.s.). In sites with type I bone quality (compact bone), a reduced bone fill was observed (64%). The results indicate that successful bone fill can be achieved with GBR; this is more feasible in the maxilla, when a provisional restoration is used. Early implant placement timings seem to be preferable due to the alveolar ridge preservation, more favorable defect morphologies and a higher regenerative capacity.

Absorbable Implants↗
PubMed1998

Sinus elevation procedures in the resorbed posterior maxilla. Comparison of the crestal and lateral approaches.

OBJECTIVES: The purpose of this study was to compare three different methods for sinus elevation: (1) the lateral antrostomy as a two-step procedure, (2) the lateral antrostomy as a one-step procedure, and (3) the osteotome technique with a crestal approach. Indication criteria were defined, based on the residual bone height measured from computed tomography scans, for the sake of applying the appropriate technique. STUDY: In 30 patients designated for implant treatment in the resorbed posterior maxilla, 79 implants were placed in combination with a bone-grafting material for sinus augmentation. The final bone heights were measured from panoramic radiographs or post-operative computed tomography scans. RESULTS: The success rate for the osteotome technique was 95% during the 30-month study period; no failures occurred in any site treated with a lateral antrostomy. The gain in bone height was comparable for the one-step (median = 10 mm) and two-step (median = 12.7 mm) lateral antrostomies. These sites exhibited a significantly greater increase in bone height (p < 0.001) than did the sites in which the osteotome technique was applied (mean = 3.5 mm). The histologic sections showed both bone apposition in intimate contact with the bone-grafting material particles and initial signs of its remodeling. CONCLUSIONS: The results indicate that the osteotome technique can be recommended when more than 6 mm of residual bone height is present and an increase of about 3 to 4 mm is expected. In cases of more advanced resorption a one-step or two-step lateral antrostomy has to be performed.

Adult↗
PubMed1998

Perfusing dentine with horse serum or physiologic saline: its effect on adhesion of dentine bonding agents.

Freshly prepared dentine specimens of human teeth were perfused with either horse serum or physiologic saline. After application of AllBond2, ART Bond, Syntac or an experimental dentine bonding agent called P-Bond, a composite cylinder was added and cured at the same time. After 1500 thermal cycles with constant imitation of intrapulpal pressure, the shear bond strengths were measured. Resulting shear bond strength values were analysed with Students t-test or Mann-Whitney Test. The values for AllBond2 were not significantly different. The values for ART Bond (P < 0.05) and for Syntac (P < 0.05) were significantly higher if the dentine was perfused with horse serum. For P-Bond (P < 0.001) the values were significantly higher if the dentine was perfused with physiologic saline. According to these results it does not seem to be appropriate to take a clear decision as to which of the two perfusing media investigated might be more suitable to imitate in vivo conditions.

Animals↗
PubMed1998

A retrospective study of combined fixed-removable reconstructions with their analysis of failures.

The survival rate and the reasons for failures of 130 combined fixed-removable reconstructions (CFR), incorporated in 112 patients, were assessed. Each CFR reconstruction was classified depending on its attachments: 76 reconstructions were attached with rigid, precise attachments, and constituted the rigid group; 54 reconstructions were attached with either semi-precision or individual attachments and were defined as the semi-rigid group. Of the 130 reconstructions, 41 were determined as complete successes, 39 as partial successes and 50 as failures, leading to 37 major repairs and to 13 new reconstructions. Three reconstructions failed due to technical reasons, 36 due to biological reasons and for 11 reconstructions, both categories of reasons were responsible for their failure. In total, technical reasons were counted 15 times in comparison to 73 biological reasons for those 50 failed reconstruction, with 29 fractured abutment teeth as the most common biological reason. Within the rigid group, 45 failed reconstructions were observed, whereas within the semi rigid group only 5 failures occurred, leading to an 8-year survival estimate (+/- SD) of 30.1% (+/- 6.9%) for the rigid group and 93.1% (+/- 3.9%) for the semi rigid group. Beside the attachment type, the anatomy of the partially edentulous tooth arch in form of the free-end situation and the dentate opposing jaw were identified as risk factors.

Adult↗
PubMed1998

A new all-ceramic post and core system: clinical, technical, and in vitro results.

Root-filled teeth with fractured or discolored coronal aspects invariably need to be restored by crowns. The prepared abutment tooth is usually reinforced by a metallic post and core system. The grayish discoloration of the root, and consequently of the gingiva, caused by the metal color may be an enormous esthetic disadvantage in the anterior teeth. In 1993 ceramic posts made of zirconia were introduced by the authors, allowing a new all-ceramic concept for nonvital abutment teeth. A new ceramic post and core system has now been developed with the idea of further improving esthetic appearance. In this system the core material is heat pressed directly onto the zirconia post. This article describes the material and the fabrication procedures (chairside and in the laboratory) of the system. Clinical results are presented. The retention of the core material is evaluated by in vitro tests.

Aluminum Silicates↗
PubMed1997

Effect of cleaning dentine with soap and pumice on shear bond strength of dentine-bonding agents.

This in vitro study reports on the cleaning effect of different soaps on the shear bond strength of various dentine-bonding agents. Human teeth were coated with provisional cements for 24 h or for 14 days. After removing the provisional cements with a scaler, the dentinal surface was cleaned with a cotton pellet and non-fluoridated flour of pumice and soap for 10 sec. Different dentine-bonding agents and a luting resin were bonded to the dentinal surface according to manufacturers' instructions with the bonding agent and the composite material being light-cured at the same time. The bonding agents were tested under intrapulpal pressure and with thermal cycling to imitate physiological conditions. Compared with cleaning the dentine with water and pumice, all soaps investigated in this study decreased the shear bond strength values of the tested dentine-bonding agents considerably.

Dental Bonding↗
PubMed1997

Effect of provisional cements on the bond strength of various adhesive bonding systems on dentine.

Temporization of prepared teeth is needed for protection of the pulp and the restoration of the patients' aesthetic and functional needs. When zinc-oxyphosphate cement is used, eugenol-containing provisional cements are preferred because of their sedative effect to the pulp and because of their acceptable compressive strength. However, prior to definitive adhesive cementation with composite luting resins and dentine bonding agents the use of eugenol-containing provisional cements has to be considered critical because eugenol severely disturbs the polymerization of resinous materials. The purpose of this study was to compare shear bond strength values of various adhesive luting systems on dentine which had been in contact with various provisional cements prior to dentine bonding. The results show that the provisional cements which were used considerably decreased some of the bond strength values of the dentine bonding systems tested. Freegenol and Fermit, however, seem to have beneficial effects on the SBS values of Syntac and ART Bond. The only bonding system which produces acceptably high average SBS values with a eugenol-containing provisional cement was P-Bond.

Adhesives↗
PubMed1997

Film thickness of various dentine bonding agents.

Curing dentine bonding agents create a film thickness on the surface of teeth which are prepared for all-ceramic crowns. The aim of this study was to investigate if the film thickness of dentine bonding agents (DBAs) is acceptable with the fit of definitive restorations of 50-100 microm. AllBond 2, Syntac, ART Bond, P-Bond (an experimental DBA), and the Primer of AllBond 2 were applied onto teeth which were prepared with standardized all-ceramic crown preparations. The DBAs were applied onto the prepared tooth surfaces according to manufacturers' instructions and under a standardized simulation of intrapulpal pressure. After curing the DBAs, the teeth were cut mesiodistally and orolingually and the film thickness was measured under a light microscope. Only the film thicknesses of AllBond 2 and P-Bond were low enough and, therefore, would enable curing to take place immediately after their application.

Acid Etching, Dental↗
PubMed1997

Short-term results of IPS-Empress full-porcelain crowns.

PURPOSE: A leucite-reinforced, glass-ceramic material was recently introduced for clinical use. In this clinical trial, IPS-Empress material was tested in the form of full-porcelain crowns. MATERIALS AND METHODS: Thirty-four patients were restored with 78 full-porcelain crowns. After etching the crowns with hydrofluoric acid, they were silanized and luted using dentin bonding agents and resin composite cement, which was primarily a dual-cured type. The 41 anterior and 37 posterior crowns were evaluated clinically with a mirror and probe, radiographically, and using clinical photographs, according to the modified United States Public Health Service criteria. Restorations having neither charlie nor delta criteria were defined as successful, and their survival rate was calculated according to Kaplan-Meier analysis. RESULTS: The mean observation period for the 78 restorations was 19.7 +/- 8.5 months. Seventy-four crowns were defined as successful. Four restorations failed because of fractures. Three of the four failures occurred in the first 2 months after cementation. The survival rate was estimated to be 95% successful after 2 years in service. Eighty percent of the crowns demonstrated an excellent esthetic result. CONCLUSIONS: The initial clinical results of this esthetic full-porcelain crown system are encouraging. However, because of fatigue phenomena for all ceramic materials, a longer observation period is needed to provide a definitive prognosis about the long-term clinical behavior.

Aluminum Silicates↗