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PubMed2000

The development of the ITI DENTAL IMPLANT SYSTEM. Part 2: 1998-2000: Steps into the next millennium.

In 1998 and 1999, the ITI DENTAL IMPLANT SYSTEM underwent its greatest modification since it came into existence. Prosthetic possibilities with regard to implant position transfer and master-cast manufacturing have been considerably enlarged by synOcta, surgical instruments have been improved in a multitude of ways and, by introducing SLA, the sand-blasted, large grit, acid-etched surface for oral implants which shortens time to loading by 50%, the ITI and Straumann have achieved a major breakthrough in surface technology.

Dental Abutments↗
PubMed2000

The scientific basis for and clinical experiences with Straumann implants including the ITI Dental Implant System: a consensus report.

Successful endosseous implant therapy requires integration of the implant with bone, soft connective tissue and epithelium. This report from a consensus conference on Straumann dental implants including the ITI Dental Implant System documents the interaction of these nonsubmerged one-piece implants with the oral tissues and reviews clinical studies supporting the high success achievable with these implants in patients. Light and electron microscopy reveal that epithelial structures similar to teeth are found around the implants. A connective tissue zone exists between the apical extension of the junctional epithelium and the alveolar bone. This connective tissue comprises a dense circular avascular zone of connective tissue fibers surrounded by a loose vascular connective tissue. The histologic dimensions of the epithelium and connective tissue comprising the biologic width are similar to the same tissues around teeth. The nonsubmerged one-piece design of the Straumann implants, which have been used for over 20 years, has set a standard in implant dentistry, with other implants now being manufactured and placed using similar techniques. Straumann implants have an endosseous portion that is either coated with a well-characterized and well-documented titanium plasma-sprayed surface or is sandblasted and acid attacked. Both surfaces have been shown to have advantages for osseous integration compared to machined and other smoother implant surfaces. These advantages include greater amounts of bone-to-implant contact, more rapid integration with bone tissue, and higher removal torque values. The lack of component connection at or below the alveolar crest provides additional benefits. Component connection at the alveolar crest, as seen with submerged implants, results in microbial contamination, crestal bone loss and a more apical epithelial location. Numerous human clinical trials document the successful use of Straumann implants in a variety of indications and areas of the mouth. These include prospective long-term trials using strict criteria of success and life table analyses. Taken together, the clinical studies reveal that Straumann implants can be used predictably in partially edentulous and completely edentulous maxilla and mandibles with high success rates. Furthermore, the animal and microscopic studies reviewed provide a scientific basis for the integration of Straumann implants with bone, connective tissue and epithelium.

Animals↗
PubMed2000

Biological complications with dental implants: their prevention, diagnosis and treatment.

Biofilms form on all hard non-shedding surfaces in a fluid system, i.e. both on teeth and oral implants. As a result of the bacterial challenge, the host responds by mounting a defence mechanism leading to inflammation of the soft tissues. In the dento-gingival unit, this results in the well-described lesion of gingivitis. In the implanto-mucosal unit, this inflammation is termed "mucositis". If plaque is allowed to accumulate for prolonged periods of time, experimental research has demonstrated that "mucositis" may develop into "periimplantitis" affecting the periimplant supporting bone circumferentially. Although the bony support may be lost coronally, the implant still remains osseointegrated and hence, clinically stable. This is the reason why mobility represents an insensitive, but specific diagnostic feature of "periimplantitis". More sensitive and more reliable parameters of developing and existing periimplant infections are "bleeding on probing", "probing depths" and radiographic interpretation of conventional or subtraction radiographs. Depending on the diagnosis made continuously during recall visits, a maintenance system termed Cumulative Interceptive Supportive Therapy (CIST) has been proposed.

Animals↗
PubMed2000

Mechanical complications of dental implants.

Adverse occlusal forces can result in mechanical complications of implant components. While unacceptably high incidences of mechanical failures have been reported for the two-stage external hex screw-type implant systems, the standard-diameter ITI solid-screw implant does not seem to be vulnerable to these problems. The 8 degrees Morse taper has eliminated abutment screw loosening and fracture. The incidence of prosthetic screw loosening has been minimized by the 45 degrees bevel on the implant shoulder and by the 1.5 mm vertical abutment walls. The design of the standard-diameter solid-screw ITI implant and the material used in its fabrication (cold worked type IV cp titanium) have eliminated fixture fracture. However, because there have been some reported instances of fractures involving reduced-diameter and hollow implants, these designs should be used with caution.

Dental Implants↗
PubMed2001

Clinical evaluation and prosthetic complications of single tooth replacements by non-submerged implants.

The aim of the present study was to evaluate single tooth replacements by non-submerged implants. In the time period from 1990 to 1998, 72 patients were consecutively admitted for treatment with a total of 109 solid screw ITI-implants supporting single crowns. All crowns were ceramic to metal fused with a ceramic occlusal surface and mounted to the octa-abutment. The mean observation time was 4.3 years, ranging from >1 to 9 years. The implants were monitored regularly by periimplant parameters. Periapical radiographs using the parallel technique were taken after the healing period and in 1999 for comparative measurements. No implant was lost during the healing phase, while 3 failures occurred after a loaded period of 2.5 and >5 years, respectively. The 5-year cumulative survival rate was 99.1%. In the course of the study, only 2 implants exhibited marginal inflammation that required treatment. The radiographically measured distance (DIB) from the implant shoulder to the first implant-bone contact was significantly increased in 1999 and different between the two readings. However, this difference in DIB was not significant between implants with a short (1 year) and long (>5 years) observation period. It was concluded that changes in the crestal bone level occur mostly in the first postsurgical year. Prosthetic complications were rare, mostly encountered in the first year after loading and often limited to re-tightening of the occlusal screw.

Adult↗
PubMed2001

Retrospective analysis of the influence of abutment structure design on the success of implant unit. A 3-year controlled follow-up study.

A comparative study of 96 Spline and Threadloc implants is presented. The authors examined the possibility of the failure of the retaining screws of two different antirotational systems (the Threadloc system with hexagonal polyhedral extension and the Spline system), and the possible incorrect link between the abutment and the transfer. After an observation period of 36 months starting from the day of prosthesis insertion, three single Threadloc fixtures (20%) and five pairs of joint Threadloc fixtures (5.7%) presented problems and a partial prosthetic screw loosening. For the Spline series fixtures, no screw loosening was encountered. Regarding the safety of the link between abutment and implant, the best results were obtained from the Spline system, which did not hinder the dentist in positioning the link with the abutment. This is the result of the different geometries of the two antirotational mechanisms which are present on the two fixtures. It is believed that the precise contact between the abutment and the fixture avoids the triggering of a phlogistic process, which can develop into periimplantitis. Therefore, when hex systems are used, an x-ray, which verifies this correct situation, is always recommended during the follow-up.

Adult↗
PubMed2001

A meta-analytic, quantitative assessment of osseointegration establishment and evolution of submerged and non-submerged endosseous titanium oral implants.

Two implant placement methods are used in oral implantology: submerged (S, two-stage surgical procedure) and non-submerged (NS, one-stage surgery). However, a quantitative assessment of their influence on implant osseointegration, summarising the whole present experience, is not directly possible, owing to the lack of normalisation of the published results. To overcome this difficulty, selection criteria have been applied to the latter in a process of a meta-analysis of specialised literature, in order to authorise a pooled treatment with an adequate statistical method. Survival life tables are established (up to 15 and 10 years respectively for S and NS implants placed in normal situations) for extended samples (13049 S and 5515 NS implants). Early (before loading) failure rates and 95% confidence level ranges of cumulative implant survival rates are shown. For both categories, the quality of the placement stage remains critical to ensure optimal osseointegration behaviour. Both categories match current survival requirements, but with a quite different behaviour over time. NS implants, while osseointegrating better initially, are subject to causes of osseointegration loss, which persist over a longer period of time. Implant design characteristics (including the type of surface) seem to be more relevant than the placement procedure for the implant's behaviour. This is in agreement with recent histological and preliminary clinical results, and should be confirmed by further studies.

Dental Implantation, Endosseous↗
PubMed2002

A long-term follow-up of 76 Bränemark single-tooth implants.

In a previous study (Haas et al. 1995), we reported on preliminary results of 76 Brånemark implants placed in 71 patients with single-tooth gaps. The present study examines the results of the same group over a longer period of time: 55 implants were followed for more than 5 years, 12 for a period between 4 and 5 years and 1 implant for 46 months. One patient died 3 years after implant placement. Five patients lost their implant within 24 months after insertion. The drop-out rate was 2 implants in 2 patients. The recall rate was thus 97%. Of the 5 implant failures, 2 were located in the maxilla and 3 in the mandible. The Kaplan-Meier survival probability was 93% after 120 months. 74% of the sites showed healthy peri-implant soft tissue conditions. At 15 implants (22%) a bone resorption of more than 2 mm was observed on intraoral radiographs. The mean bone resorption was 1.8 mm in the maxilla and 1.3 mm in the mandible and did not increase with time (Pearson correlation coefficient: r = -0.06, P = 0.59). Abutment loosening occurred in 7 implants (10%), however all abutments that were fixed with a defined torque subsequently remained stable. Thus the favourable preliminary results could be maintained over an average 66 months, indicating that if implant loss happens it seems to occur during the first 2 years after insertion.

Adult↗
PubMed2002

Resonance frequency assessment of dental implant stability with various bone qualities: a numerical approach.

Resonance frequency analysis (RFA) has been used by several investigators to assess the boundary conditions of dental implants. The goal of the current study was to determine the vibrating behavior of a dental implant under various surrounding bone conditions. A 3D finite element (FE) model of a cylinder-type titanium implant was developed. In this model, the implant was embedded into a cubic section of bone. The model was first validated using a series of modal testing experiments. The effects of bony conditions on the resonance frequencies of the implant were computed with different bone types and bone densities. Our results show that the resonance frequency of the implant with type III surrounding bone decreased linearly (r = -0.996, P < 0.01) from 17.9 kHz (without loss in bone density) to 0.6 kHz (90% loss in bone density) when the bone densities were decreased. On the other hand, without bone loss, the highest resonance frequency value (36.1 kHz) was found when the implant was placed into type I surrounding bone. In contrast, the resonance frequency of the implant with type IV bone quality was found to be 9.9 kHz, which is almost four-fold less than that found in the type I model. These results suggest that RFA could serve as a non-invasive diagnostic tool for detecting the stability of dental implants during the healing stages and in subsequent routine follow-up care after treatment.

Animals↗
PubMed2002

Implant osseointegration in the irradiated mandible. A comparative study in dogs with a microradiographic and histologic assessment.

This research focuses on the effects of radiotherapy on the osseointegration of dental implants placed before or after radiotherapy in 11 male beagles. After the extraction of all mandibular premolars 1st and 2nd molars, three dogs were implanted without radiotherapy (Control group), four dogs were irradiated 4 weeks after implantation (IrA group) and four dogs were irradiated 8 weeks before implantation (IrB group). Eight implants were placed in each dog, in an alternating pattern: four nonsubmerged ITI Bonefit titanium plasma spray-coated and four submerged Steri-Oss hydroxyapatite-coated. The irradiated dogs received 4.3 Gy daily for 10 days. Two different fluorescent markers were administered at the time of implantation and of irradiation. The dogs were sacrificed 6 months after implantation, i.e. 5 months after radiotherapy for the IrA group and 8 months for the IrB group. Each mandible was submitted to histological and microradiographic analysis. Bone formation occurred around 85 of the 88 implants and consisted mostly of the successive deposit of woven and lamellar bone. Both irradiated groups showed obvious bone remodeling in alveolar bone as well as in the basilar part of the mandible. Nevertheless, in the IrA group, the resorption phenomena predominated over osteogenesis. The balance between these two opposite processes seemed to be restored 8 months after the end of radiotherapy (IrB group). In spite of focal lesions of radiation-specific bone destruction emphasized in some irradiated dogs, we conclude from our results that osseointegration of dental implants is possible in irradiated bone tissue.

Alveolar Bone Loss↗
PubMed2002

Evaluation of implants placed with barrier membranes. A restrospective follow-up study up to five years.

This follow-up study evaluated clinical and radiographic parameters of dental implants placed in combination with guided bone regeneration with barrier membranes. All implants functioned well up to 60 months after insertion. Forty-one patients, with a total of 72 augmented implants, who participated in a regular maintenance protocol, were investigated. Annual Periotest values (median value, - 3) revealed stable periimplant conditions and sustained osseointegration. At 6 months and annually thereafter up to five years, the radiographic evaluation yielded mean bone losses of 0.8, 1.25, 1.39, 1.42, 1.42 and 1.39 mm, respectively, with a range from 0 to 3.5 mm. No implant failures or losses were recorded. The results demonstrated stable periimplant conditions up to five years after membrane-protected osseous regeneration, with no significant differences in the radiographic bone level in regard to region, jaw or bone graft. Premature membrane exposure resulted in a significantly higher crestal bone loss up to 24 months. The newly formed bone appeared to be able to withstand functional loading for up to 60 months in a predictable manner.

Adult↗
PubMed2003

Correlation of insertion torques with bone mineral density from dental quantitative CT in the mandible.

OBJECTIVE: The aim of this study was to establish a correlation between bone mineral density measured preoperatively with dental computed tomography (CT), and insertion torque of screw-shaped dental implants. MATERIAL AND METHODS: In eight human mandibles obtained postmortem, bone mineral density (BMD) was measured with dental quantitative CT (DQCT) and correlated with insertion torque values at 45 implant sites during insertion of screw-shaped dental implants (Brånemark System MKIII, Nobel Biocare, AB, Göteborg, Sweden). RESULTS: A significant correlation (r=0.86, P<0.001) between BMD and torque values was observed, indicating that local BMD at a specific implant position is related to the supportive capacity of the jawbone. BMD exhibited no correlation with bone height or position. CONCLUSION: The noninvasive assessment of BMD using a DQCT scan employing a low-dose protocol may be used to estimate expected primary stability depending on BMD, implant type and preparation procedure. These data may therefore help the surgeon to select the optimum implant position, implant type and operation technique.

Absorptiometry, Photon↗
PubMed2003

Implant stability and histomorphometry: a correlation study in human cadavers using stepped cylinder implants.

The aim of the present study was to determine the correlation between the primary stability of dental implants placed in edentulous maxillae and mandibles, the bone mineral density and different histomorphometric parameters. After assessing the bone mineral density of the implant sites by computed tomography, 48 stepped cylinder screw implants were installed in four unfixed human maxillae and mandibles of recently deceased people who had bequeathed their bodies to the Anatomic Institute I of the University of Erlangen-Nuremberg for medical-scientific research. Peak insertion torque, Periotest values and resonance frequency analysis were assessed. Subsequently, histologic specimens were prepared, and bone-to-implant contact, the trabecular bone pattern factor (TBPf), the density of trabecular bone (BV/TV) and the height of the cortical passage of the implants were determined. The correlation between the different parameters was calculated statistically. The mean resonance frequency analysis values (maxilla 6130.4+/-363.2 Hz, mandible 6424.5+/-236.2 Hz) did not correlate with the Periotest measurements (maxilla 13.1+/-7.2, mandible -7.9+/-2.1) and peak insertion torque values (maxilla 23.8+/-2.2 N cm, mandible 45.0+/-7.9 N cm) (P=0.280 and 0.193, respectively). Again, no correlations could be found between the resonance frequency analysis, the bone mineral density (maxilla 259.2+/-124.8 mg/cm(3), mandible 349.8+/-113.3 mg/cm3), BV/TV (maxilla 19.7+/-8.8%, mandible 34.3+/-6.0%) and the TBPf (maxilla 2.39+/-1.46 mm-1, mandible -0.84+/-3.27 mm-1) (P=0.140 and 0.602, respectively). However, the resonance frequency analysis values did correlate with bone-to-implant contact of the oral aspect of the specimens (maxilla 12.6+/-6.0%, mandible 35.1+/-5.1%) and with the height of the crestal cortical bone penetrated by the implants in the oral aspect of the implant sites (maxilla 2.1+/-0.7 mm, mandible 5.1+/-3.7 mm) (P=0.024 and 0.002, respectively). The Periotest values showed a correlation with the height of the crestal cortical bone penetrated by the implants in the buccal aspect of the implant sites (maxilla 2.5+/-1.2 mm, mandible 5.4+/-1.2 mm) (P=0.015). The resonance frequency analysis revealed more correlations to the histomorphometric parameters than the Periotest measurements. However, it seems that the noninvasive determination of implant stability has to be improved in order to give a more comprehensive prediction of the bone characteristics of the implant site.

Aged↗
PubMed2003

The anchorage of Brånemark and ITI implants of different lengths. I. An experimental study in the canine mandible.

The anchorage of machined Brånemark and ITI TPS-coated implants of various lengths was investigated in an animal model. Brånemark fixtures 7 and 10 mm long and ITI implants 6 and 10 mm long were inserted in the mandible of dogs and were reverse-torqued after 3 months of healing. The failing mode was different for the two implant systems. For the ITI implants, loosening coincided with the peak reverse-torque values. For the Brånemark fixtures, two reverse-torque values were identified and recorded, a 'start to rotate' and a peak value. The 'start to rotate' values for the 7 and 10 mm Brånemark fixtures were 36.67 and 38.57 Ncm, respectively, the peak values were 61.88 and 69.13 Ncm. The increase in implant length from 7 to 10 mm did not significantly improve the anchorage. The mean reverse-torque values for the 6- and 10-mm ITI implants were 104.66 and 192.25 Ncm, respectively; the difference was statistically significant. The mean removal torque of the 6-mm ITI implant was higher than the 7- and 10-mm Brånemark implants. It is suggested that the distinct anchorage magnitude and the distinct loosening patterns registered for both implant systems might be related to the various surface states. The latter might account for the different failure tendencies mentioned in the literature for short Brånemark and ITI implants.

Analysis of Variance↗
PubMed2000

Bone healing around implants placed in a jaw defect augmented with Bio-Oss. An experimental study in dogs.

The present experiment was carried out to study some tissue reactions around implants that were placed in an edentulous ridge which had been augmented with deproteinized natural bovine cancellous bone mineral. In 4 male beagle dogs, the premolars in the right side of the mandible were extracted and a large buccal ridge defect was created by mechanical means. The bone plate at the lingual aspect of the defect was left intact. 5 months later, the distal 2/3 of the defect area was augmented with Bio-Oss (Geistlich Sons Ltd, Wolhusen, Switzerland) mixed with a fibrin sealer (Tisseel, Immuno AG, Vienna, Austria). After 3 months of healing, 3 fixtures (Astra Tech AB, Mölndal, Sweden; TiO-blast; 8x3.5 mm) were installed in the mandible; 2 were placed in the augmented portion and I was placed in the non-augmented portion of the defect. After a healing period of 3 months, abutment connection was performed and a plaque control period initiated. 4 months later, the dogs were sacrificed and each implant region was dissected. The tissue samples were dehydrated, embedded in plastic, sectioned in the bucco-lingual plane and examined in the light microscope. It was observed that osseointegration failed to occur to implant surfaces within an alveolar ridge portion previously augmented with Bio-Oss. In the augmented portion of the crest, the graft particles were separated from the host tissue as well as from the implant by a well-defined connective tissue capsule. Although the lingual aspect of all fixtures (test and control) was in contact with hard tissue at the time of installation, after 4 months of function, a deep vertical bone defect frequently had formed at the lingual surface of the implants. It was concluded that in this model (i) Bio-Oss failed to integrate with the host bone tissue and (ii) no osseo-integration occurred to the implants within the augmented portion of the crest.

Alveolar Ridge Augmentation↗
PubMed2003

External and occlusal trauma to dental implants and a case report.

Dental implants subjected to traumatic forces can survive. Cortical bone seems to provide a protective energy-absorbing mechanism in the collagen polymer that helps to prevent microcracking and fracture of bone. The collagen polymer has cross-linking bonds that break and absorb the energy of a traumatic impact so as not to cause damage to the main polymer chain. A case reported demonstrates that a traumatic force damaged the implant prosthetic crown, but not the bone encasing the implant or the integration of the implant.

Adult↗
PubMed2002

Crowns and other extra-coronal restorations: preparations for full veneer crowns.

Preparations for full veneer crowns is the eighth in the series on crowns and other extra-coronal restorations. Whilst handpiece skills are important, many other factors combine to ensure provision of a satisfactory full veneer crown (also termed 'full coverage crown'). Our aim in writing this article is to consider the principles which influence crown preparation, seasoned with clinical advice our undergraduate and postgraduate students have found useful.

Composite Resins↗
PubMed1993

Dental anomalies--are adhesive castings the solution?

Adhesive cast restorations placed without tooth preparation were used to restore the teeth of patients affected by either amelogenesis or dentinogenesis imperfecta. Twelve patients aged between 7 and 18 years were treated and in total 64 cast restorations were placed. At the time of cementation, the vertical dimension was increased by the thickness of restorative material placed on the functioning surfaces of the restored teeth. Full occlusion was restored for all individuals, with only one casting being lost. The castings have been placed for intervals between 10 and 54 months.

Acrylic Resins↗