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Biomedical subjects

R Mericske-Stern

Publications and source records attributed to R Mericske-Stern.

At least 19 recordsLinked to original sources
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↗
PubMed2000

Prosthodontic considerations.

The prosthodontic section of the 1997 ITI Consensus Conference in Vitznau, Switzerland, examined a broad spectrum of issues related to the prosthodontic phase of dental implant therapy. Topics included diagnosis and treatment planning, considerations for the use of ITI prosthodontic components, management of the partially edentulous patient, management of the edentulous patient, implant occlusion, and the use of narrow- and wide-body implants. The management of partially and totally edentulous patients will be discussed in separate papers. This paper is written so that each major consensus point discussed by the prosthodontic section is the first sentence of a paragraph. The remainder of each paragraph serves as background information or justification for the consensus statement. It should be noted that agreement on all points was reached by voting within the prosthodontic section. Many of the consensus statements were reached unanimously, while some were reached through compromise and split vote. Not all of the points presented here were presented to the plenum session on the final day of the conference.

Cementation↗
PubMed2000

Prosthetic management of the partially dentate patient with fixed implant restorations.

The aim of this chapter is to discuss the current prosthetic management of the partially dentate patient by means of fixed implant restorations in the scope of the ITI(R) Dental Implant System. For that purpose, the related statements defined by the participants of the prosthodontic section of the 1997 ITI Consensus Conference in Vitznau, Switzerland, will be presented, completed by explanatory comments where appropriate. Distinct conceptual differences will be made between the esthetic zone (areas of the dental arches where esthetic considerations are of primary concern) and the non-esthetic zone (regions of the jaws where esthetic aspects do not represent a priority), and between single tooth replacement and multiple unit implant restorations. Furthermore, it is underlined that current clinical concepts should be based on both predictable treatment outcome and cost-effectiveness. In this context, a straightforward surgical and prosthetic protocol is generally preferred in posterior locations of the oral cavity, using a nonsubmerged implant placement comprising an easily accessible implant shoulder location, and subsequently cemented implant restorations, basically according to a traditional prosthodontic approach. In esthetically demanding indications, where normally a distinctly submucosal implant shoulder location is advocated, screw-retained restorations are preferred, based on prefabricated prosthetic components (e.g. machined cast-on copings) to assure optimum surface properties and contour, and to achieve adequate marginal adaptation.

Bicuspid↗
PubMed2000

In vivo force measurements on maxillary implants supporting a fixed prosthesis or an overdenture: a pilot study.

STATEMENT OF PROBLEM: In this preliminary study, an attempt was made to measure in vivo forces simultaneously on 5 maxillary implants with different types of superstructure. MATERIAL AND METHODS: Force measurements were carried out on 1 test patient with 5 ITI implants in the edentulous maxilla. A screw-retained fixed complete denture and an overdenture were fabricated for comparative measurements of forces. The overdenture could be mounted to 2 different types of bars. The measuring method was used with piezo-electric force transducers that were directly mounted onto the implants. This allowed for simultaneous measurements of forces in 3 dimensions, ie, in axial and transverse directions. Static and functional forces such as maximum biting (clenching), biting on a bite plate, and chewing food were registered. All measurements were repeated in the same way 2 years later. RESULTS: The registered forces exhibited similar force patterns with both types of superstructure and both types of bars for overdenture connection. The force magnitudes were significantly different for the 3 dimensions (P<.05) with highest forces along the implant axis. On the posterior implants, force magnitudes were significantly higher (P<.05) than on the anterior implants in all 3 dimensions. On the anterior implants, under some test conditions, the transverse force components reached up to 100% of the axial force or even exceeded it during the chewing of food. During maximum biting, no upward force (tensile force) was found on any implant with the fixed complete denture, but upward force was found on one anterior implant with the overdenture. When chewing food, small force magnitudes in upward directions were regularly found with both superstructures. The force patterns between the first and second registrations showed similar trends, and no obvious differences were found. CONCLUSION: From these results it was concluded that similar patterns of force transmission onto the implants are observed with a fixed complete denture and an overdenture connected to maxillary implants. The bar design did not significantly influence the force pattern.

Calibration↗
PubMed2000

[Testing dental implants with an in vivo finite element model].

The finite element method (FEM) makes it possible to simulate biomechanical situations on a computer. In the present study the so-called voxel method [9, 14, 17, 18, 19] was used for the construction of the mandible model. For this, the relationship between the biological tissue (e.g. bone) and the corresponding attenuation coefficient of CT data (Hounsfield units = HU) were utilized. The CT data were obtained from an edentulous patient provided with a prosthesis borne on two titanium implants. In a parallel study, the bite forces of the same individual were measured. These were recorded digitally in three dimensions (cranio-caudal, anterior-posterior and left-right) The forces determined by a special program were then transferred to the FEM model implants. We were able to show that a bar joining the implants had a far greater effect on maximum equivalent stress than was expected from the measuring data alone. The highest stress at maximum occlusive force was lowered by 704% on using the connecting bar. On chewing, a stress reduction of 59.9% was observed. The reduction in stress achieved by the bar could, we believe, prolong the life of the implant.

Biomechanical Phenomena↗
PubMed1999

Clinical experience with one-stage, non-submerged dental implants.

This review article describes the scientific documentation of one-stage, non-submerged dental implants. In the past 25 years, numerous in vivo studies have demonstrated that non-submerged titanium implants achieve osseointegration as predictable as that of submerged titanium implants. This observation was confirmed in prospective clinical studies, mostly done with the ITI Dental Implant System. ITI implants have been widely documented for up to 10 years of prospective follow-up at various centers. All studies showed success rates well above 90%. In summary, the non-submerged approach is a true alternative to the original healing modality with submerged titanium implants. The non-submerged approach offers several clinical advantages: (i) the avoidance of a second surgical procedure and less chair time per patient, resulting in overall reduced treatment cost; (ii) the lack of microgap at the bone crest level, leading to less crestal bone during healing and resulting in a more favorable crown-to-implant length ratio; and (iii) a simplified prosthetic procedure, presenting an ideal basis for cemented implant restorations. Due to these significant clinical advantages, the non-submerged approach will become more important in implant dentistry in the near future, particularly in implant sites without esthetic priority.

Alveolar Process↗
PubMed1998

Treatment outcomes with implant-supported overdentures: clinical considerations.

Three indications for implant-supported overdentures are defined, namely, the edentulous maxilla, the edentulous mandible, and the compromised situation. These indications for overdentures are related to three patient groups: (1) a younger segment of patients among the older population with maxillary complete dentures, (2) elderly completely edentulous patients who request better stabilization of the mandibular denture, and (3) patients with acquired or congenital defects. The aim of this article is to discuss treatment strategies and clinical considerations with respect to three specific indications for overdentures.

Adaptation, Physiological↗
PubMed1997

Force distribution on implants supporting overdentures: the effect of distal bar extensions. A 3-D in vivo study.

Force distribution on mandibular implants supporting overdentures was registered in vivo by means of piezo-electric transducers that allow for simultaneous force measurements in 3 dimensions. The anchorage device for connecting the overdenture to the implants was a U-shaped bar to which distal extensions were soldered bilaterally. Force patterns were analyzed under different test conditions such as maximum force when biting in centric occlusion, maximum biting with the unilateral use of a bite plate, parafunction and chewing bread. Maximum force measured in centric occlusion and on the ipsilateral implant with the use of bite plate was increased in the vertical dimension, compared to transverse dimensions. On the contralateral implant, equally low values were found, in all 3 dimensions. Transverse force components reached 5 to 35% of the vertical magnitudes. With the use of the bite plate on the ipsilateral implant, force magnitudes in the vertical direction and in the backward-forward direction were significantly higher (P < 0.01, P < 0.00) compared to measurements in centric occlusion. Chewing and grinding resulted in lower vertical forces compared to maximum biting, while transverse forces in the backward forward direction reached force magnitudes that resembled the vertical component (50 to 100%). The prevalent (> 95%) or exclusive force direction in the vertical dimension, registered on both implants was downward. However, with the unilateral use of the bite plate, upward directions were found on the contralateral implant as an effect of distal bar extensions. This was in contrast to previous results where upward force directions were not found. In transverse dimensions, the specific influence of bar extensions was recognised in backward directions on the contralateral implant. In comparison with previous results, it was concluded that, in vivo, the effect of distal bar extensions was of much lesser influence regarding force magnitudes and force directions than was expected.

Aged↗
PubMed1997

Long-term evaluation of non-submerged ITI implants. Part 1: 8-year life table analysis of a prospective multi-center study with 2359 implants.

In the present multi-center study, non-submerged ITI implants were prospectively followed to evaluate their long-term prognosis in fully and partially edentulous patients. In a total of 1003 patients, 2359 implants were consecutively inserted. Following a healing period of 3-6 months, the successfully integrated implants were restored with 393 removable and 758 fixed restorations. Subsequently, all consecutive implants were documented annually up to 8 years. At each examination, the clinical status of all implants was evaluated according to predefined criteria of success. Therefore, the data base allowed the evaluation of 8-year cumulative survival and success rates for 2359 implants. In addition, cumulative success rates were calculated for implant subgroups divided per implant type, implant length, and implant location. Furthermore, the actual 5-year survival and success rates could be determined for 488 implants. During the healing period, 13 implants did not successfully integrate, whereas 2346 implants fulfilled the predefined criteria of success. This corresponds with an early failure rate of 0.55%. During follow-up, 19 implants were classified as failures due to several reasons. In addition, 17 implants (approximately 0.8%) demonstrated at the last annual examination a suppurative periimplant infection. Including 127 drop out implants (= 5.4% drop out rate) into the calculation, the 8-year cumulative survival and success rates resulted in 96.7% and 93.3%, respectively. The analysis of implant subgroups showed slightly more favorable cumulative success rates for screw type implants (> 95%) compared to hollow-cylinder implants (91.3%), and clearly better success rates for mandibular implants (approximately 95%) when compared to maxillary implants (approximately 87%). The actual 5-year survival and success rates of 488 implants with 98.2% and 97.3%, respectively, were slightly better than the estimated 5-year cumulative survival and success rates of 2359 implants indicating that the applied life table analysis is a reliable statistical method to evaluate the long-term prognosis of dental implants. It can be concluded that non-submerged ITI implants maintain success rates well above 90% in different clinical centers for observation periods up to 8 years.

Adolescent↗
PubMed1996

In vivo measurements of some functional aspects with mandibular fixed prostheses supported by implants.

Maximal occlusal force and oral tactile sensibility were recorded in 21 edentulous patients wearing maxillary complete dentures and mandibular fixed prostheses supported by Brånemark implants. Bite force was measured with a miniature force transducer between antagonistic molars and premolars, and the passive tactile sensibility of the fixtures was recorded in the horizontal and vertical directions with spring balances. The active tactile sensibility was tested using steel foils (100 to 10 microns). The range of maximal occlusal force recorded was from 35 to 330N with highest values observed on the second premolars (mean 143N). Significantly lower forces were found on molars and first premolars (p < 0.01). The detection threshold of minimal pressure was about 330 g in the horizontal, and 388 g in the vertical direction. This difference was not statistically significant. The average number of incorrect assessments when testing steel foils was 16.6 errors, out of 100 recordings. Similar results when using these 3 test modalities had been found on overdentures supported by two mandibular implants and occluding with maxillary complete dentures. The results of this study suggest that mandibular implants supporting fixed prostheses are not likely to improve oral tactile sensibility and maximal occlusal force in the presence of maxillary complete dentures.

Aged↗
PubMed1996

Simultaneous force measurements in 3 dimensions on oral endosseous implants in vitro and in vivo. A methodological study.

A novel piezo-electric force transducer was developed that is mounted directly on ITI-implants and allows for simultaneous force measurements in 3 dimensions. The reliability of this measuring method in vitro and in vivo was evaluated. For test and calibration measurements 5 edentulous patients with 2 mandibular implants were selected and master casts obtained with original implants in situ. Preload of the abutment screw was measured with a torque controller by repeated tightening and loosening. The introduction of additional preloads when bar connectors or telescopes were mounted was examined on the casts and in the mouth. Tests were carried out to identify the influence of screw tensions on force measurements by loading the implants in vertical and transverse directions. Calibration measurements in vivo and in vitro were carried out by means of a spring balance. A regression model was calculated to analyze the influence of the applied preload on measured forces. The mean preload value was 315, ranging from 200 to 480N. A significant correlation of applied loads to measured forces was found (r = 0.99). It was independent of the preload in vertical direction but dependent in transverse direction. No additional tension of the abutment screw was ever observed when bars were mounted. Calibration measurements with the spring balance showed that bars contribute to load sharing between the implants. Comparable results were found for all measurements in vitro and in vivo. It was concluded that the new piezo-electric transducer is an adequate instrument to measure forces in 3 dimensions on ITI-implants.

Dental Abutments↗
PubMed1996

3-D in vivo force measurements on mandibular implants supporting overdentures. A comparative study.

Force transmission onto implants supporting overdentures was measured in vivo by means of piezoelectric transducers that allow for simultaneous force registrations in 3 dimensions. The transducers are directly mounted onto the implants, beneath the anchorage device. The force registrations were analyzed with regard to the anchorage device and retention mechanism of overdenture support. The 3 types of denture anchorage were a U-shaped bar, a round clip-bar and single telescopes. Forces were measured in the following test situations: maximum force when biting in centric occlusion, maximum bite force during biting on a bite plate, grinding and chewing bread. Multiple regression showed that the vertical component of maximum forces was dependent on the anchorage device and test situation. The transverse components reached 10 to 50% of the vertical force magnitude. With the bite plate in situ maximum forces measured in vertical direction were significantly higher or the ipsilateral implant with telescopes than with bars (p < 0.01 and p < 0.001). Chewing and grinding resulted in lower vertical forces compared to maximum biting. In transverse dimensions, mainly in the anterior-posterior direction, registered forces reached magnitudes that resembled the vertical component (50 to 100%). Force magnitudes of chewing and grinding were similar for all three anchorage devices. However, differences were observed between bars and telescopes with regard to the direction of transverse force components. The results of this study do not suggest the preference of one specific anchorage system or retention mechanism for overdenture support. However, rigid bars contribute to load sharing and stress distribution onto the implants.

Aged↗
PubMed1995

Periotest measurements and osseointegration of mandibular ITI implants supporting overdentures. A one-year longitudinal study.

The Periotest values of mandibular implants, registered before and after loading by overdentures, were compared. Thirty edentulous patients with 60 Bonefit ITI implants were selected with an average age of 69 years. The Periotest values were measured 1) after a healing period of 3 months and 2) after the overdentures had been worn for a period of 12 months. Periodontal parameters were recorded at both examinations. Furthermore, 17 biopsies of mandibular bone taken from the implant sites during implant surgery were analyzed to assess the bone density. The histomorphometric evaluation was done using a point count method. At the end of the healing period, all registered Periotest values were negative, ranging from -1 to -8 with an average of 4.08. One year later, all measurements showed negative values again, ranging from -2 to -8 with an average of 4.97. The difference was statistically significant. Seventeen biopsies of mandibular bone were evaluated to determine the density. The range of bone density was from 22.4% and 90.9%. There was no correlation found between bone density and Periotest values. However, a significant correlation could be observed between mandibular atrophy and bone density.

Aged↗
PubMed1994

Overdentures with roots or implants for elderly patients: a comparison.

Roots maintained under the denture base preserve the alveolar ridge, provide sensory feedback and improve the stability of the dentures. Furthermore, with the use of copings and precision attachments, retention of the denture is provided. Overdentures are a favored treatment modality for elderly patients with few remaining teeth because adaptation to wearing dentures is facilitated. Recently, overdenture treatment with the use of implants has become popular for edentulous elderly patients who are maladaptive to complete dentures. Although the biologic basis of implants installed in the bone is different from roots surrounded by a periodontal membrane, the prosthetic concept is similar. Tactile sensibility is reduced because of the absence of periodontal receptors. However, oral function with overdentures supported by roots or implants is comparable and does not seem to depend on the presence of a periodontal membrane. Comparison of studies demonstrates a higher tendency for success when overdentures are supported by implants than by roots. This is particularly true for mandibular overdentures, whereas for maxillary implants, more frequent failures are observed with low bone quality and short implants. This study discusses results and special applications with regard to an elderly population who will profit from the benefit of overdenture therapy.

Adult↗
PubMed1994

Peri-implant mucosal aspects of ITI implants supporting overdentures. A five-year longitudinal study.

Sixty-six ITI implants placed in the mandible of 33 edentulous elderly patients (mean age: 69 years) were observed longitudinally for 5 years. The implants served as overdenture anchorage either by means of a connecting bar or single spherical attachments. During the study period, 2 implants failed (one because of a peri-implant lesion and one because of a fracture) and had to be removed. At the beginning of the study, all implants were osseointegrated and had successfully been in function for 3-5 months. Oral hygiene practices and the peri-implant mucosal status were assessed according to the criteria of conventional periodontal parameters. Approximately 50% of the implants had been installed into lining mucosa and hence were to surrounded by keratinized mucosa. The peri-implant mucosal tissue was maintained healthy during the whole observation period, and no or only minimal loss of attachment was observed. The probing depths averaged approximately 3 mm. At the end of the study, orthopantomographic radiographs were obtained from all patients to assess the peri-implant bony structures. Small local angular bony defects were detected on 16 implants (22%) in 12 patients. Slightly increased probing depths were observed when angular bony defects were present. Loss of attachment was significantly less frequent when the implants had been placed following a prolonged period of edentulousness (> 5 years). This study demonstrated that advanced age, reduced dexterity of elderly patients and environmental conditions of overdentures do not represent a higher risk for the development of peri-implant lesions.

Aged↗