Application of a standard autoclaving protocol does not harm structural integrity of two-piece zirconia abutments under detachment force testing.

OBJECTIVE: Aim was to assess the influence of a standard autoclaving protocol on the retention of zirconia abutments glued on titanium bases in two-piece implant abutments. MATERIALS AND METHODS: Twenty-four CAD/CAM-generated zirconia abutments were adhesively cemented on prefabricated titanium bases. Before mechanical and thermal aging, the specimens were divided into two groups. Group 1 was subjected to a standard steam autoclaving protocol and Group 2 remained untreated (control). The tensile strength in all specimens was evaluated by a standardized pull-off test limited to a maximum force of 1000 N. RESULTS: Eleven samples in both groups could be subjected to pull-off testing. Ten samples in Group 1 and three samples in Group 2 failed, while all others reached the maximum pull-off force. This difference was statistically significant. The mean retention values for the failed samples were 694.53 ± 369.10 N in Group 1 and 890.78 ± 25.90 N in Group 2. This difference was not statistically significant. CONCLUSIONS: A standard autoclaving protocol does not reduce detachment force of two-piece zirconia abutments. CLINICAL RELEVANCE: Clinical sterilization processes as recommended by regulatory authorities seem to be harmless to the structural integrity of two-piece zirconia implant abutments, at least with regard to the retention of the components.

All-Ceramic Zirconium Dioxide Implant Abutments for Single-Tooth Replacement in the Posterior Region: A 5-Year Outcome Report.

PURPOSE: To assess the clinical performance of a prefabricated all-ceramic zirconium dioxide implant abutment for single-tooth replacement in the posterior region. MATERIALS AND METHODS: Forty implants (Xive S plus screw type, Dentsply Sirona Implants) were inserted into the posterior region in 24 patients and were provided with zirconium dioxide abutments (Cercon abutment, Dentsply Sirona Implants). The licensed range of indications for these abutments is limited to the maxillary and mandibular anterior teeth. The following parameters were used to document the state of the soft tissue: modified Plaque Index; modified Sulcus Bleeding Index; and pocket depth. Mesial and distal bone levels were determined on radiographs during the prosthetic treatment and at the 5-year recall. RESULTS: A total of 34 functioning implants were followed up over a 5-year interval. Two patients wearing three abutments were lost to follow-up. In total, five abutments exhibited a rotational misfit during the observation period, causing significant gingival discoloration and damage to the implants. In the remaining restorations, the soft and hard tissue parameters were indicative of a low inflammatory status. Compared to the baseline situation, partly significant bone apposition could be observed. CONCLUSION: The observed specific type of failures after 5 years in function for full zirconia posterior implant abutments cannot be recommended, at least not in combination with the implant system used in this study.

Influence of Connector Diameter on Fracture Load of CAD/CAM-Processed Monolithic Lithium Disilicate Fixed Partial Dentures.

PURPOSE: To investigate the influence of connector diameter on the mechanical load to fracture in monolithic three-unit lithium disilicate fixed partial dentures (FPDs). MATERIALS AND METHODS: A total of 24 FPDs were designed and manufactured using computer-aided design/computer-assisted manufacturing (CAD/CAM) with connector diameters of 16 mm2, 12 mm2, or 9 mm2 (Groups A, B, and C, respectively; n = 8 for each group). After thermal and mechanical aging, the FPDs were subjected to mechanical load-to-fracture assessment. RESULTS: Fracture loads of Groups B (834 ± 105 N) and C (796 ± 41 N) were significantly lower compared to Group A (990 ± 65 N). CONCLUSION: Connector dimensions proved to be crucial for fracture resistance of monolithic lithium disilicate FPDs.

Differential Behavior of Fibroblasts and Epithelial Cells on Structured Implant Abutment Materials: A Comparison of Materials and Surface Topographies.

PURPOSE: The aim of this study was to compare the proliferation and attachment behavior of fibroblasts and epithelial cells on differently structured abutment materials. MATERIALS AND METHODS: Three different surface topographies were prepared on zirconia and titanium alloy specimens and defined as follows: machined (as delivered without further surface modification), smooth (polished), and rough (sandblasted). Energy-dispersive X-ray spectroscopy, topographical analysis, and water contact angle measurements were used to analyze the surface properties. Fibroblasts (HGF1) and epithelial cells (HNEpC) grown on the specimens were investigated 24 hours and 72 hours after seeding and counted using fluorescence imaging. To investigate adhesion, the abundance and arrangement of the focal adhesion protein vinculin were evaluated by immunocytochemistry. RESULTS: Similar surface topographies were created on both materials. Fibroblasts exhibited significant higher proliferation rates on comparable surface topographies of zirconia compared with the titanium alloy. The proliferation of fibroblasts and epithelial cells was optimal on different substrate/topography combinations. Cell spreading was generally higher on polished and machined surfaces than on sandblasted surfaces. Rough surfaces provided favorable properties in terms of cellular adhesion of fibroblasts but not of epithelial cells. CONCLUSIONS: Our data support complex soft tissue cell-substrate interactions: the fibroblast and epithelial cell response is influenced by both the material and surface topography.

Post-endodontic treatment of incisors and premolars among dental practitioners in Saarland: an interactive Web-based survey.

OBJECTIVES: The aim of the present study was to evaluate the trend of dental practitioners in the federal state of Saarland in Germany in regard to restoring endodontically treated teeth using a Web-based survey. MATERIALS AND METHODS: An interactive Web-based survey instrument was developed, including seven clinical scenarios, presented by photographs of natural incisor and premolar with different types of cavities. Following a decision tree adapted to the clinical treatment, questions on different aspects of the post-endodontic treatment were asked. All 615 members of the Saarland Dental Association (SDA) were asked to participate in the survey. RESULTS: A total of 33 % completed the survey. The majority of the participants believed in the reinforcement effect of the ferrule design, as well as the post placement. The vast majority of the responding practitioners (92 %) adapted their treatment strategies to a high extent to the destruction degree of the endodontically treated tooth. Fiber-reinforced composite (FRC) posts are the most popular prefabricated post type, regardless of the cavity size and tooth localization. Significant differences between the dentists according to the degree of experience were detected only for the use of glass-ionomer cements as core buildup material. CONCLUSIONS: The predominant post-endodontic treatment strategies of German dental practitioners are only partly in agreement with the current literature. There is a clear trend toward the increasing use of metal-free post and core materials. CLINICAL SIGNIFICANCE: Although the participants showed a general adoption of modern materials and techniques, different patterns of post-endodontic treatment were revealed that were not consistent with approaches supported by the literature.

Fracture behavior of metal-ceramic fixed dental prostheses with frameworks from cast or a newly developed sintered cobalt-chromium alloy.

OBJECTIVES: The aim of this study was to investigate the fracture behavior of metal-ceramic bridges with frameworks from cobalt-chromium-molybdenum (CoCrMo), which are manufactured using conventional casting or a new computer-aided design/computer-aided manufacturing (CAD/CAM) milling and sintering technique. MATERIALS AND METHODS: A total of 32 metal-ceramic fixed dental prostheses (FDPs), which are based on a nonprecious metal framework, was produced using a conventional casting process (n = 16) or a new CAD/CAM milling and sintering process (n = 16). Eight unveneered frameworks were manufactured using each of the techniques. After thermal and mechanical aging of half of the restorations, all samples were subjected to a static loading test in a universal testing machine, in which acoustic emission monitoring was performed. Three different critical forces were revealed: the fracture force (F max), the force at the first reduction in force (F decr1), and the force at the critical acoustic event (F acoust1). RESULTS: With the exception of the veneered restorations with cast or sintered metal frameworks without artificial aging, which presented a statistically significant but slightly different F max, no statistically significant differences between cast and CAD/CAM sintered and milled FDPs were detected. Thermal and mechanical loading did not significantly affect the resulting forces. CONCLUSIONS: Cast and CAD/CAM milled and sintered metal-ceramic bridges were determined to be comparable with respect to the fracture behavior. CLINICAL SIGNIFICANCE: FDPs based on CAD/CAM milled and sintered frameworks may be an applicable and less technique-sensitive alternative to frameworks that are based on conventionally cast frameworks.

Influence of superstructure geometry on the mechanical behavior of zirconia implant abutments: a finite element analysis.

To predict the clinical performance of zirconia abutments, it is crucial to examine the mechanical behavior of different dental implant-abutment connection configurations. The international standard protocol for dynamic fatigue tests of dental implants (ISO 14801) allows comparing these configurations using standardized superstructure geometries. However, from a mechanical point of view, the geometry of clinical crowns causes modified boundary conditions. The purpose of this finite element (FE) study was to evaluate the influence of the superstructure geometry on the maximum stress values of zirconia abutments with a conical implant-abutment connection. Geometry models of the experimental setup described in ISO 14801 were generated using CAD software following the reconstruction of computerized tomography scans from all relevant components. These models served as a basis for an FE simulation. To reduce the numerical complexity of the FE model, the interaction between loading stamp and superstructure geometry was taken into account by defining the boundary conditions with regard to the frictional force. The results of the FE simulations performed on standardized superstructure geometry and anatomically shaped crowns showed a strong influence of the superstructure geometry and related surface orientations on the mechanical behavior of the underlying zirconia abutments. In conclusion, ISO testing of zirconia abutments should be accompanied by load-bearing capacity testing under simulated clinical conditions to predict clinical performance.

Fracture resistance of a selection of full-contour all-ceramic crowns: an in vitro study.

This study aimed to evaluate the fracture resistance of monolithic single crowns made from zirconia (ZI), lithium disilicate (LS2), or feldspar ceramic (FC). Five groups of crowns representing a maxillary first molar were made with the appropriate dimensions according to the manufacturer's instructions. The ZI and LS2 crowns were luted adhesively or cemented conventionally on a metal abutment tooth analog. The feldspar ceramic crowns were luted adhesively. All specimens underwent axial loading until fracture. The crowns in the ZI groups possessed the highest fracture resistance independent of the mode of fixation.

Pre-fabricated zirconium dioxide implant abutments for single-tooth replacement in the posterior region: success and failure after 3 years of function.

OBJECTIVE: Zirconia implant abutments have gained a much broader clinical use over the past few years. The aim of the present study was to assess the clinical performance of a pre-fabricated zirconium dioxide implant abutment for single-tooth replacement in the posterior region. MATERIALS AND METHODS: Forty implants of the XiVE(®) S plus screw type (DENTSPLY Friadent, Mannheim, Germany) were inserted in the posterior region of 24 patients and provided with zirconium dioxide abutments (FRIADENT(®) CERCON(®) Abutment, DENTSPLY Friadent). The following parameters were used to document the state of soft tissue: modified plaque index, modified sulcus bleeding index and pocket depth. Mesial and distal bone levels were determined on radiographs during the prosthetic treatment and at the 36-month recall. RESULTS: Thirty-seven implants could be followed up after 36 months in function. One patient wearing two abutments was lost to follow-up. One abutment exhibited a rotational misfit after 2 years in function. A further abutment showed the same failure at the 36-months recall appointment. In the remaining 36 implants the soft and hard tissue parameters were indicative of a low inflammatory status. Compared to the baseline situation, a partly significant bone apposition could be observed. Chipping of parts of the veneering ceramic was registered in 22% of the remaining implant restorations. CONCLUSIONS: The use of zirconia abutments in this study lead to mainly healthy peri-implant hard and soft tissue conditions but, considering the observed failures after 3 years in function, clinical long-term results should be awaited before recommending full zirconia implant abutments in a posterior indication.

Fracture behavior of zirconia implant abutments is influenced by superstructure-geometry.

OBJECTIVES: The purpose of this in vitro study was to evaluate the influence of the superstructure-geometry on the fracture behavior of zirconia abutments (Compartis, DeguDent GmbH, Hanau, G). MATERIALS AND METHODS: Four different groups (n = 8) representing anterior single crown replacement were prepared. In groups 1 and 2, the implants were restored with customized all-ceramic abutments and anatomically shaped crowns (chromium cobalt alloy). Groups 3 and 4 received crowns with a geometry according to the international standard ISO 14801 (dynamic fatigue test for endosseous dental implants) with a spherical contact area. Groups 2 and 4 were subjected to mechanical aging in a chewing simulator (50 N × 1,200,000 cycles). Static loading until fracture was performed using a universal testing device at an angle of 30° to the implant axis. Fracture patterns were analyzed using SEM. RESULTS: In group 2, only one specimen survived mechanical aging. In group 4, one specimen fractured during the chewing simulation. Groups 1 and 2 showed significantly lower load-bearing capacity than groups 3 and 4. Artificial aging did not influence the fracture resistance. The SEM analysis revealed fatigue-related fracture patterns in those specimens, which failed during artificial aging. CONCLUSIONS: Drawing conclusions from ISO testing concerning clinical performance appears to be critical as anatomic superstructure geometries induce different fracture behaviors. CLINICAL RELEVANCE: ISO testing of zirconia abutments should be accompanied by load-bearing capacity testing under simulated clinical conditions to predict clinical performance.

Influence of proximal contacts and FRC posts on the fracture behavior of premolars with class II composite restorations: an in-vitro study.

The purpose of this study was to evaluate the influence of the number of proximal contacts and fiber-reinforced composite (FRC) post insertion on the fracture behavior of endodontically treated premolars with class II (MOD) cavities and direct composite restorations. Forty-eight single-rooted human premolars were endodontically treated and prepared with standardized MOD (mesio-occluso-distal) cavities. One-half of the teeth additionally received FRC-posts (DT Light SL) luted with Panavia F resin cement. All of the specimens were restored with direct composite restorations, and the teeth were embedded in proximal contact with either zero, one or two adjacent tooth-replicas. Eight sound premolars served as control. After thermomechanical ageing, the samples were loaded until fracture at an angle of 30°. The sound teeth showed the highest mean fracture load. Teeth with one or two proximal contacts and FRC-posts showed only statistically insignificantly lower values. All of the other groups had significantly lower values.

Clinical success rates for polyether crown impressions when mixed dynamically and statically.

The purpose of this study is to compare success rates of dual-viscosity impressions for two types of mixing techniques of the polyether elastomeric impression material. Additionally, influencing parameters on the success rates should be evaluated. The expectation was that there would be no difference between the success rates for the two mixing techniques. Two centres enrolled 290 subjects (727 teeth) into the trial. Patients were randomized for the two types of mixing techniques. One step, dual-viscosity impressions were made with either statically mixed Impregum Soft tray material (SAM) or dynamically mixed Impregum Penta H DuoSoft (DMM). Low viscosity Impregum Garant L DuoSoft was used for both groups. Gingival displacement involved the use of two braided cords. Full-arch trays were used exclusively. Both critical defects and operator errors were assessed for the first impression taken by trained dentists. The primary outcome was impression success. For comparison of the two mixing techniques, the odds ratio for success and the corresponding one-sided 95% confidence interval was calculated by a logistic regression model. To account for the dependence between several teeth within one patient, the method of general estimating equations was used. The overall impression success rate was 35.4%. Both mixing techniques showed equal success rates indicated by an OR of 1.0 and a lower limit of the one-sided 95% confidence interval of 0.71. Using this result to develop the corresponding interval for the difference, it could be shown that the success rate using SAM was at most 8.2% lower than that when using DMM with a probability of 95%. Multivariate logistic regression analysis of other potential influencing factors showed position of finish line (p = 0.008, supra compared to mixed), blood coagulation disorder (p = 0.021) and the level of training of the clinician (student vs dentist, p=0.008) to have an independent influence on the success rate. Dynamic mechanical mixing and the new static mixing of polyether tray material showed nearly equal success rates in the study even though success rates were comparatively low (DMM, 35.3%; SAM, 35.4%).

In vitro investigation of the performance of different restorative materials under cast circumferential clasps for removable dental prostheses.

OBJECTIVES: The objective of this in vitro study was to investigate the behavior of different composite restorative materials under the load of cast circumferential clasps for removable dental prostheses (RDPs). METHODS: In 60 human molars, standardized mesial-occlusal-distal cavities were prepared. The cavities were restored with the following materials: Definite, Tetric Ceram, SureFil, Heliomolar RO, Ariston pHc, and Oralloy, and provided with a rest seat. The rest seats were subjected to 5,000 cycles of thermal cycling and 1,200,000 masticatory cycles in a mastication simulator via cobalt-chromium circumferential clasps cast to standardized frameworks in a laboratory model designed to simulate the biomechanics of a free-end denture base. Fracture analysis of the restorations was performed by light microscopy. Before and after loading, material wear was measured with a 3D-laser scanner, and an analysis of the marginal quality was performed in an SEM at ×200 applying the replica technique. RESULTS: No significant differences in the fracture behavior among the composite materials were found; the amalgam control group showed a significantly higher fracture resistance. Regarding the wear of the materials, the composites Definite and SureFil exhibited a behavior similar to that of amalgam. The other composites demonstrated higher wear rates. The initial marginal quality was significantly worse for Ariston pHc. The marginal adaptation decreased significantly after thermal and mechanical loading for Definite and Ariston pHc. CONCLUSIONS: In terms of the investigated aspects of mechanical performance, the tested composites seemed to be inferior to amalgam. Further clinical studies are needed to evaluate the ability of composite restorations to provide support for RDP clasps. CLINICAL RELEVANCE: The use of composites as direct restoration materials should be avoided in teeth, which serve as abutments for clasp-retained RDPs.

Influence of fatigue testing and cementation mode on the load-bearing capability of bovine incisors restored with crowns and FRC posts.

The aim of the study was to evaluate the influence of fatigue and cementation mode on the fracture behaviour of endodontically treated bovine incisors restored with fiber-reinforced-composite (FRC) posts and crowns. Forty-eight endodontically treated incisors were restored with FRC posts, composite build-ups, and cast crowns. In 16 teeth, each of the posts were cemented conventionally with KetacCem (3M Espe) or adhesively with Panavia F (Kuraray) or RelyXUniCem (3M Espe). One-half of the specimens in each group were subjected to thermal cycling with 10,000 cycles at 5-55°C and mechanical aging, loading the specimens in 1,200,000 cycles with 50 N. Fracture resistance was determined by loading the specimens until fracture at an angle of 45°. The loading test showed that cementation mode and fatigue testing had an influence on the load bearing capability. Before fatigue testing no statistically significant differences between the different cementation modes could be detected. After fatigue testing, conventionally cemented FRC posts lead to statistically significant higher fracture loads compared to adhesively luted posts. Most specimens fractured in a favourable way, independent from the type of cementation.

Fracture behavior of straight or angulated zirconia implant abutments supporting anterior single crowns.

The aim of the study was to evaluate the influence of artificial aging on the fracture behavior of straight and angulated zirconia implant abutments (ZirDesign™; Astra Tech, Mölndal, Sweden) supporting anterior single crowns (SCs). Four different test groups (n = 8) representing anterior SCs were prepared. Groups 1 and 2 simulated a clinical situation with an ideal implant position (left central incisor) from a prosthetic point of view, which allows for the use of a straight, prefabricated zirconia abutment. Groups 3 and 4 simulated a situation with a compromised implant position, requiring an angulated (20°) abutment. OsseoSpeed™ implants (Astra Tech) 4.5 mm in diameter and 13 mm in length were used to support the abutments. The SCs (chromium cobalt alloy) were cemented with glass ionomer cement. Groups 2 and 4 were thermomechanically loaded (TCML = 1.2 × 106; 10,000 × 5°/55°) and subjected to static loading until failure. Statistical analysis of force data at the fracture site was performed using nonparametric tests. All samples tested survived TCML. Artificial aging did not lead to a significant decrease in load-bearing capacity in either the groups with straight abutments or the groups with angulated abutments. The restorations that utilized angulated abutments exhibited higher fracture loads than the restorations with straight abutments (group 1, 280.25 ± 30.45 N; group 2, 268.88 ± 38.00 N; group 3, 355.00 ± 24.71 N; group 4, 320.71 ± 78.08 N). This difference in load-bearing performance between straight and angulated abutments was statistically significant (p = 0.000) only when no artificial aging was employed. The vast majority of the abutments fractured below the implant shoulder.

Influence of artificial aging on the load-bearing capability of straight or angulated zirconia abutments in implant/tooth-supported fixed partial dentures.

PURPOSE: The aim of the study was to evaluate the influence of artificial aging on the fracture behavior of straight and angulated zirconia implant abutments used in ZirDesign (Astra Tech) implant/tooth-supported fixed partial dentures (FPDs) in the maxilla. MATERIALS AND METHODS: Four different test groups (n = 8) representing anterior implant/tooth-supported FPDs were prepared. Groups 1 and 2 simulated a clinical situation with an ideal implant position (maxillary left central incisor) from a prosthetic point of view, which allowed for the use of a straight, prefabricated zirconia abutment. Groups 3 and 4 simulated a situation with a compromised implant position that required an angulated (20-degree) abutment. OsseoSpeed implants (4.5 3 13 mm, Astra Tech) as well as metal tooth analogs (maxillary right lateral incisor) with simulated periodontal mobility were mounted in polymethyl methacrylate. The FPDs (chromium-cobalt alloy) were cemented with glass ionomer. Groups 2 and 4 were thermomechanically loaded and subjected to static loading until failure. Statistical analysis of force data at the fracture site was performed using nonparametric tests. RESULTS: All samples survived thermomechanical loading. Artificial aging did not lead to a significant decrease in load-bearing capacity in either the straight abutments or the angulated abutments. The restorations that used angulated abutments exhibited higher fracture loads than the restorations with straight abutments (group 1: 209.13 ± 39.11 N; group 2: 233.63 ± 30.68 N; group 3: 324.62 ± 108.07 N; group 4: 361.75 ± 73.82 N). This difference in load-bearing performance was statistically significant, both with and without artificial aging. All abutment fractures occurred below the implant shoulder. CONCLUSIONS: Compensation for angulated implant positions with an angulated zirconia abutment is possible without reducing the load-bearing capacity of implant/tooth-supported anterior FPDs.

Zirconium dioxide implant abutments for posterior single-tooth replacement: first results.

BACKGROUND: Prefabricated implant abutments made of zirconium dioxide (yttria-stabilized polycrystalline tetragonal zirconia; Y-TZP) have proved to be useful in the esthetically demanding anterior region and may also be useful for premolar and molar replacement because of their obvious positive impact on the health of peri-implant soft tissues. METHODS: Forty screw implants were inserted in the posterior region of 24 patients and provided with prefabricated all-ceramic abutments made of zirconium dioxide Y-TZP. Zirconia-based crowns were used as superstructures. The following parameters were used to document the state of soft tissue: the modified plaque index (mPI), sulcus fluid flow rate (SFFR), modified sulcus bleeding index (mSBI), and probing depth (PD). Additionally, implant stability was measured using an electronic mobility testing device. RESULTS: All implants (N = 40) followed up after 6 months in function were osseointegrated and showed good stability. In the presence of good oral hygiene (mPI: 0.3), the parameters SFFR (16) and mSBI (0.7) were indicative of stable and healthy soft tissue. The mean PD was highest at the distal points of measurement (2.4 mm) and was generally at a low level. Neither implant loss nor crown fractures occurred. Chipping of parts of the veneering ceramic was registered in three cases (7.5%). CONCLUSIONS: After 6 months in function, no mechanical failure was registered in any of the all-ceramic abutments. On clinical investigation, the peri-implant soft tissues were largely healthy and devoid of inflammation.

[Implant-borne prosthesis for an edentulous maxilla with a large maxillectomy defect--a step-wise therapy concept]. / Implantatgetragene Versorgung eines ausgedehnten Resektionsdefektes der Maxilla. Ein mehrstufiges Therapiekonzept.

Due to the great variety of maxillectomy defects standardized restorative treatment protocols are rarely documented. For the practitioner it is from highest importance to consider the specific defect morphology and, even more important, the individual needs of affected patients. The presented case shows the planning and realization of the restoration of a maxilla with an extended resection defect following tumor surgery. Because the demanding patient remained edentulous after extraction of the residual teeth for periodontal reasons, an implant retained obturator prosthesis was inserted. Following interdisciplinary planning a treatment protocol with stepwise extraction, augmentation and implant insertion in the os zygomaticum as well as in the residual alveolar ridge was carried out, which make successive adjustment of the temporary obturator prosthesis possible. This procedure resulted in a long lasting treatment duration, but made also a sufficient temporary restoration during healing periods feasible. The definitive restoration was retained by a bar splinting four implants in the residual alveolar ridge and a special retentive anchoring abutment on two implants in the os zygomaticum.

Survival of glass fiber post restorations over 5 years.

PURPOSE: To evaluate the survival of glass fiber reinforced composite post (GFP) restorations and to identify risk factors for restoration failure. METHODS: GFPs of three consecutively placed post systems, two tapered and one parallel-sided, were adhesively luted and the core was built with a resin composite. Teeth served as abutment teeth according to the prosthetic treatment plan. 149 GFP in 121 patients (age: 53 +/- 15 year; 50 men; 71 women) were followed for 5-79 months (mean +/- SD: 50 +/- 21 months). Cox proportional hazards models were used to evaluate the association between several clinical variables and the failure rate. RESULTS: After exclusion of endodontic failures (n = 3), significantly higher failure rates were found for restorations of anterior teeth compared to posterior teeth (hazard regression (HR): 2.8; 95% confidence interval (CI): 1.4; 5.8; P = 0.004). Restorations in teeth with no proximal contacts compared to at least one proximal contact, single crowns compared to fixed partial dentures and less than two remaining cavity walls had a HR of 2.4 (CI: 0.8-7.1), 2.4 (CI: 0.6-8.7), and 1.5 (CI: 0.6-3.8), respectively. However, these correlations were not statistically significant (P > 0.05).

[Implant-supported prostheses for the edentulous patient after partial maxillectomy--clinical considerations in the choice of retention elements--2 case reports]. / Implantatgestützte Restauration der zahnlosen, teilresezierten Maxilla. Klinische Uberlegungen zur Auswahl prothetischer Halteelemente--2 Kasuistiken.

The prosthetic rehabilitation of edentulous patients following hemimaxillectomy proves to be functionally unsatisfactory in many cases because of a heavily changed oral morphology and oral communication with the nasal and maxillary sinus cavities, which makes it difficult to achieve a sufficient retention and stability of the restoration using a conventional obturator denture. Using implants as anchorage increases comfort considerably for patients wearing such restorations. Due to the wide variety of the individual anatomy of the defect area and the residual parts of intact maxilla clinicians are confronted with advanced challenges according the preprosthetic planning and technical realization. Moreover, a close interdisciplinary cooperation between prosthetic dentistry and maxillofacial surgery is necessary to guarantee a successful treatment. By the means of two patients the rehabilitation with implant-borne dentures is demonstrated. Considering individual demands one patient was treated with telescopic crowns, the other with a bar system. The procedure of the prosthetic rehabilitation is presented. Aspects which arise from the specific case situations should be of special interest. In spite of the problematic initial situation the rehabilitation of the patients resulted in esthetically and functionally sufficient restorations.