The Peri-Implant Sulcus Compared with Internal Implant and Suprastructure Components: A Microbiological Analysis

Purpose: A recent in vivo study has shown considerable contamination of internal implant and suprastructure components with great biodiversity, indicating bacterial leakage along the implant-abutment interface, abutment-prosthesis interface, and restorative margins. The goal of the present study was to compare microbiologically the peri-implant sulcus to these internal components on implants with no clinical signs of peri-implantitis and in function for many years. Checkerboard DNA-DNA hybridization was used to identify and quantify 40 species. Material and Methods: Fifty-eight turned titanium Brånemark implants in eight systemically healthy patients (seven women, one man) under regular supportive care were examined. All implants had been placed in the maxilla and loaded with a screw-retained full-arch bridge for an average of 9.6 years. Gingival fluid samples were collected from the deepest sulcus per implant for microbiological analysis. As all fixed restorations were removed, the cotton pellet enclosed in the intra-coronal compartment and the abutment screw were retrieved and microbiologically evaluated. Results: The pellet enclosed in the suprastructure was very similar to the peri-implant sulcus in terms of bacterial detection frequencies and levels for practically all the species included in the panel. Yet, there was virtually no microbial link between these compartments. When comparing the abutment screw to the peri-implant sulcus, the majority of the species were less frequently found, and in lower numbers at the former. However, a relevant link in counts for a lot of bacteria was described between these compartments. Even though all implants in the present study showed no clinical signs of peri-implantitis, the high prevalence of numerous species associated with pathology was striking. Conclusions: Intra-coronal compartments of screw-retained fixed restorations were heavily contaminated. The restorative margin may have been the principal pathway for bacterial leakage. Contamination of abutment screws most likely occurred from the peri-implant sulcus via the implant-abutment interface and abutment-prosthesis interface.

[The SPI implant system: clinical experience and one-year results]

The new Swiss implant system SPI became available three years ago and is used in combination with fixed and removable prosthetic reconstructions. In a pilot study the clinical procedures were evaluated and data of prosthetic complications of maintenance service were collected. 25 patients participated in the study with a total of 79 SPI implants during the time period from 2003-2004. 37 implants were located in the maxilla and 42 implants in the mandible. Two implants failed during the healing period, but no loaded implant was lost. Thus, the survival rate was 97.5% (77/79). 44 implants supported a fixed prosthesis, including nine single crowns and 33 implants were used in combination with removable partial denture. Four implants were used with ball anchor retention, 29 with bar support. The ELEMENT implant with the low implant shoulder allows very good esthetics. Prosthetic complications and maintenance service during the first year of function was comparable with other implant systems. Since the design of the abutment screws, healing caps and screwdriver was changed, the system has become easier in its application.

Stiffness, Strength, and Failure Modes of Implant-Supported Monolithic Lithium Disilicate Crowns: Influence of Titanium and Zirconia Abutments

PURPOSE The objective of this study was to evaluate stiffness, strength, and failure modes of monolithic crowns produced using computer-aided design/computer-assisted manufacture, which are connected to diverse titanium and zirconia abutments on an implant system with tapered, internal connections. MATERIALS AND METHODS Twenty monolithic lithium disilicate (LS2) crowns were constructed and loaded on bone level-type implants in a universal testing machine under quasistatic conditions according to DIN ISO 14801. Comparative analysis included a 2 × 2 format: prefabricated titanium abutments using proprietary bonding bases (group A) vs nonproprietary bonding bases (group B), and customized zirconia abutments using proprietary Straumann CARES (group C) vs nonproprietary Astra Atlantis (group D) material. Stiffness and strength were assessed and calculated statistically with the Wilcoxon rank sum test. Cross-sections of each tested group were inspected microscopically. RESULTS Loaded LS2 crowns, implants, and abutment screws in all tested specimens (groups A, B, C, and D) did not show any visible fractures. For an analysis of titanium abutments (groups A and B), stiffness and strength showed equally high stability. In contrast, proprietary and nonproprietary customized zirconia abutments exhibited statistically significant differences with a mean strength of 366 N (Astra) and 541 N (CARES) (P < .05); as well as a mean stiffness of 884 N/mm (Astra) and 1,751 N/mm (CARES) (P < .05), respectively. Microscopic cross-sections revealed cracks in all zirconia abutments (groups C and D) below the implant shoulder. CONCLUSION Depending on the abutment design, prefabricated titanium abutment and proprietary customized zirconia implant-abutment connections in conjunction with monolithic LS2 crowns had the best results in this laboratory investigation.

Automated detection of fiducial screws from CT/DVT volume data for image-guided ENT surgery

This paper presents an automated solution for precise detection of fiducial screws from three-dimensional (3D) Computerized Tomography (CT)/Digital Volume Tomography (DVT) data for image-guided ENT surgery. Unlike previously published solutions, we regard the detection of the fiducial screws from the CT/DVT volume data as a pose estimation problem. We thus developed a model-based solution. Starting from a user-supplied initialization, our solution detects the fiducial screws by iteratively matching a computer aided design (CAD) model of the fiducial screw to features extracted from the CT/DVT data. We validated our solution on one conventional CT dataset and on five DVT volume datasets, resulting in a total detection of 24 fiducial screws. Our experimental results indicate that the proposed solution achieves much higher reproducibility and precision than the manual detection. Further comparison shows that the proposed solution produces better results on the DVT dataset than on the conventional CT dataset.

Implants with Original and Non-Original Abutment Connections

AIM: To test in vitro the mechanical resistance, rotational misfit and failure mode of three original implant-abutment connections and to compare them to two connections between non-original abutments connected to one of the original implants. MATERIAL AND METHODS: Three different implants with small diameters (3.3 mm for Straumann Roxolid, 3.5 mm for Nobel Biocare Replace and Astra Tech Osseospeed TX) were connected with individualized titanium abutments. Twelve implants from each system were connected to their original abutments (Straumann CARES, Nobel Biocare Procera, Astra Tech Atlantis). Twenty-four Roxolid implants were connected with non-original abutments using CAD/CAM procedures from the other two manufacturers (12 Nobel Biocare Procera and 12 Astra Tech Atlantis). For the critical bending test, a Zwick/Roell 1475 machine and the Xpert Zwick/Roell software were used. RESULTS: The rotational misfit varied when comparing the different interfaces. The use of non-original grade V titanium abutments on Roxolid implants increased the force needed for deformation. The fracture mode was different with one of the original connections. CONCLUSIONS: Non-original abutments differ in design of the connecting surfaces and material and demonstrate higher rotational misfit. These differences may result in unexpected failure modes.

Peri-implant inflammation defined by the implant-abutment interface

An implant-abutment interface at the alveolar bone crest is associated with sustained peri-implant inflammation; however, whether magnitude of inflammation is proportionally dependent upon interface position remains unknown. This study compared the distribution and density of inflammatory cells surrounding implants with a supracrestal, crestal, or subcrestal implant-abutment interface. All implants developed a similar pattern of peri-implant inflammation: neutrophilic polymorphonuclear leukocytes (neutrophils) maximally accumulated at or immediately coronal to the interface. However, peri-implant neutrophil accrual increased progressively as the implant-abutment interface depth increased, i.e., subcrestal interfaces promoted a significantly greater maximum density of neutrophils than did supracrestal interfaces (10,512 +/- 691 vs. 2398 +/- 1077 neutrophils/mm(2)). Moreover, inflammatory cell accumulation below the original bone crest was significantly correlated with bone loss. Thus, the implant-abutment interface dictates the intensity and location of peri-implant inflammatory cell accumulation, a potential contributing component in the extent of implant-associated alveolar bone loss.

The influence of non-matching implant and abutment diameters on radiographic crestal bone levels in dogs

BACKGROUND: It has been shown that different implant designs and different vertical implant positions have an influence on crestal bone levels. The aim of the present study was to evaluate radiographic crestal bone changes around experimental dental implants with non-matching implant-abutment diameters placed submucosally or transmucosally at three different levels relative to the alveolar crest. METHODS: Sixty two-piece dental implants with non-matching implant-abutment diameters were placed in edentulous spaces bilaterally in five foxhounds. The implants were placed submucosally or transmucosally in the left or the right side of the mandible. Within each side, six implants were randomly placed at three distinct levels relative to the alveolar crest. After 12 weeks, 60 crowns were cemented. Radiographs were obtained from all implant sites following implant placement, after crown insertion, and monthly for 6 months after loading. RESULTS: Radiographic analysis revealed very little bone loss and a slight increase in bone level for implants placed at the level of the crest or 1 mm above. The greatest bone loss occurred at implants placed 1 mm below the bone crest. No clinically significant differences regarding marginal bone loss and the level of the bone-to-implant contact were detected between implants with a submucosal or a transmucosal healing. CONCLUSIONS: Implants with non-matching implant-abutment diameters demonstrated some bone loss; however, it was a small amount. There was no clinically significant difference between submucosal and transmucosal approaches.

Bone response to loaded implants with non-matching implant-abutment diameters in the canine mandible

BACKGROUND: One way to evaluate various implant restorations is to measure the amount of bone change that occurs at the crestal bone. The objective of this study was to histologically evaluate the alveolar bone change around a bone-level, non-matching implant-abutment diameter configuration that incorporated a horizontal offset and a Morse taper internal connection. METHODS: The study design included extraction of all mandibular premolars and first molars in five canines. After 3 months, 12 dental implants were placed at three levels in each dog: even with the alveolar crest, 1 mm above the alveolar crest, and 1 mm below the alveolar crest. The implants were submerged on one side of the mandible. On the other side, healing abutments were exposed to the oral cavity (non-submerged). Gold crowns were attached 2 months after implant placement. The dogs were sacrificed 6 months postloading, and specimens were processed for histologic and histometric analyses. RESULTS: Evaluation of the specimens indicated that the marginal bone remained near the top of the implants under submerged and non-submerged conditions. The amount of bone change for submerged implants placed even with, 1 mm below, and 1 mm above the alveolar crest was -0.34, -1.29, and 0.04 mm, respectively (negative values indicate bone loss). For non-submerged implants, the respective values were -0.38, -1.13, and 0.19 mm. For submerged and non-submerged implants, there were significant differences in the amount of bone change among the three groups (P <0.05). The percentage of bone-to-implant contact for submerged implants was 73.3%, 71.8%, and 71.5%. For non-submerged implants, the respective numbers were 73.2%, 74.5%, and 76%. No significant differences occurred with regard to the percentage of bone contact. CONCLUSIONS: Minimal histologic bone loss occurred when dental implants with non-matching implant-abutment diameters were placed at the bone crest and were loaded for 6 months in the canine. The bone loss was significantly less (five- to six-fold) than that reported for bone-level implants with matching implant-abutment diameters (butt-joint connections).

Precision of fit and retention force of cast non-precious-crowns on standard titanium implant-abutment with different design and height

OBJECTIVE The cost-effectiveness of cast nonprecious frameworks has increased their prevalence in cemented implant crowns. The purpose of this study was to assess the effect of the design and height of the retentive component of a standard titanium implant abutment on the fit, possible horizontal rotation and retention forces of cast nonprecious alloy crowns prior to cementation. MATERIALS AND METHODS Two abutment designs were examined: Type A with a 6° taper and 8 antirotation planes (Straumann Tissue-Level RN) and Type B with a 7.5° taper and 1 antirotation plane (SICace implant). Both types were analyzed using 60 crowns: 20 with a full abutment height (6 mm), 20 with a medium abutment height (4 mm), and 20 with a minimal (2.5 mm) abutment height. The marginal and internal fit and the degree of possible rotation were evaluated by using polyvinylsiloxane impressions under a light microscope (magnification of ×50). To measure the retention force, a custom force-measuring device was employed. STATISTICAL ANALYSIS one-sided Wilcoxon rank-sum tests with Bonferroni-Holm corrections, Fisher's exact tests, and Spearman's rank correlation coefficient. RESULTS Type A exhibited increased marginal gaps (primary end-point: 55 ± 20 μm vs. 138 ± 59 μm, P < 0.001) but less rotation (P < 0.001) than Type B. The internal fit was also better for Type A than for Type B (P < 0.001). The retention force of Type A (2.49 ± 3.2 N) was higher (P = 0.019) than that of Type B (1.27 ± 0.84 N). Reduction in abutment height did not affect the variables observed. CONCLUSION Less-tapered abutments with more antirotation planes provide an increase in the retention force, which confines the horizontal rotation but widens the marginal gaps of the crowns. Thus, casting of nonprecious crowns with Type A abutments may result in clinically unfavorable marginal gaps.