IMPACT OF SHORTENED DENTAL ARCH ON ORAL HEALTH-RELATED QUALITY OF LIFE.

BACKGROUND: A shortened dental arch (SDA) is an established treatment concept for patients with missing molars. However, little is known regarding long-term course of oral health-related quality of life (OHRQoL) in patients with SDA and the benefits from replacement of missing molars. OBJECTIVE: Purpose of this multi-center randomized clinical trial was to assess OHRQoL over a period of 15 years in patients with molar replacement by a removable partial denture (RPD) compared to patients with a restored SDA without molar replacement. METHODS: Patients at least 35 years of age with all molars missing in 1 jaw and at least the canine and one premolar present on each side were included. Patients received either a precision attachment-retained, RPD for replacement of missing molars (n = 79), or the dental arch ended with the second premolar (SDA) that had to be present or replaced by a cantilever fixed dental prosthesis (n = 71). Follow-up examinations continued for 15 years. OHRQoL was assessed with the 49-item Oral Health Impact Profile (OHIP). OHIP summary and dimension scores were longitudinally modeled in the statistical analyses to assess course of OHRQoL over time applying an intention-to-treat approach. In addition, scores for the OHRQoL dimensions Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact were analyzed. RESULTS: After an initial improvement in OHRQoL indicated by a mean decrease of 20.0 OHIP points with an effect size of 0.61 in the entire study population, OHRQoL stayed relatively constant over the entire follow-up period. Assuming a constant time and treatment effects over the study period, OHRQoL did not differ statistically significant between the 2 treatments (0.4 OHIP points; 95%-CI: 7.1 - 6.2). OHRQoL after treatment did not change notably over 15 years and was statistically nonsignificant as well (P = .872). Similar findings were observed in all 4 OHRQoL dimensions. CONCLUSIONS: In patients, missing all molars in one jaw OHRQoL improved providing RPD or restoring SDA to a clinically relevant degree. Treatment-related improvement remained mostly stable over a period of at least 15 years. Therefore, patients can be informed that both treatment concepts are equivalent concerning long-term OHRQoL. Accordingly, patients' preferences regarding treatment options should be granted priority in treatment decision making with the SDA treatment option being the default.

Rehabilitation of shortened dental arches: A fifteen-year randomised trial.

BACKGROUND: Few long-term studies on treatments in the shortened dental arch (SDA) are available. OBJECTIVE: The objective of this trial was to analyse the long-term success of two different treatment concepts. METHODS: Patients over 35 years of age with missing molars in one jaw and at least the canine and one premolar present on both sides were eligible. In the partial removable dental prosthesis (PRDP) group (N = 81), molars and missing second premolars were replaced by a precision attachment retained prosthesis. In the SDA group (N = 71), the dental arch ended with the second premolar that had to be present or replaced by a cantilever fixed dental prosthesis. Follow-up examinations were carried out over 15 years. RESULTS: A comprehensive outcome variable comprised four failure categories for which Kaplan-Meier survival (success) analyses were conducted. Half of the patients exhibited a continuous preservation of the per protocol prosthetic status that remained totally unaffected by complications for more than 10 years. The event-free success rates for moderate or worse failure implied a loss of the per protocol prosthetic status. The respective survival rates fell below 50% at 14.2 years in the PRDP group and 14.3 years in the SDA group. In none of the analyses, a significant group difference was found. CONCLUSIONS: In patients with an SDA condition, changes in the prosthetic status have to be expected. The affected proportion increases almost linearly from shortly after treatment and comprises the majority after 15 years. The influence of the examined treatments on success appears to be low.

Periodontal health in shortened dental arches: A 10-year RCT.

PURPOSE: This analysis focused on periodontal health in shortened dental arches (SDAs). METHODS: In a randomized controlled clinical trial, patients with missing molars in one jaw and at least one premolar and canine on both sides were eligible for participation. In the partial removable dental prosthesis (PRDP) group (n = 79), molars were replaced with a precision attachment retained PRDP. In the SDA group (n == 71), the SDA up to the second premolars was either left as is or restored with fixed dental prostheses. Outcome variables were vertical clinical attachment loss (CAL-V), pocket probing depth (PPD), bleeding on probing (BOP) and plaque index (PLI). For CAL-V and PPD, the changes at six measuring points per tooth were analyzed. For BOP and PLI, patient related rates were calculated for each point in time. Statistical methods included linear regression analyses. RESULTS: In the intention-to-treat (ITT) analysis for CAL-V in the study jaw, the 10 year patient related mean changes were 0.66 mm in the PRDP group and -0.13 mm in the SDA group. The resulting mean patient related group difference of 0.79 mm (95% CI: 0.20 mm-1.38 mm) was significant (p = 0.01). There were no significant differences in the ITT analyses for PPD. For BOP and PLI, significant group differences with more favorable results for the SDA group were found. CONCLUSIONS: In view of lacking substantial differences for CAL-V and PPD, the overall differences were considered of minor clinical relevance. The results add confirmatory evidence to the shortened dental arch concept and its clinical viability (controlled-trials.com ISRCTN97265367).

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.

Enhancing adhesion and alignment of human gingival fibroblasts on dental implants.

BACKGROUND: Promoting the directional attachment of gingiva to the dental implant leads to the formation of tight connective tissue which acts as a seal against the penetration of oral bacteria. Such a directional growth is mostly governed by the surface texture. MATERIAL AND METHODS: In this study, three different methods, mechanical structuring, chemical etching and laser treatment, have been explored for their applicability in promoting cellular attachment and alignment of human primary gingival fibroblasts (HGFIBs). RESULTS: The effectiveness of mechanical structuring was shown as a simple and a cost-effective method to create patterns to align HGIFIBs. CONCLUSION: Combining mechanical structuring with chemical etching enhanced both cellular attachment and the cellular alignment.

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.

Impact of shortened dental arch on oral health-related quality of life over a period of 10 years - A randomized controlled trial.

OBJECTIVES: To compare oral health-related quality of life (OHRQoL) in patients with either molar replacement by partial removable dental prostheses (PRDP) or with restored shortened dental arches (SDA) over a period of 10 years. METHODS: In this multi-center RCT, a consecutive sample of 215 patients with bilateral molar loss in at least one jaw was initially recruited in 14 prosthodontic departments. Of those patients, 150 could be randomly allocated to the treatment groups (SDA: n = 71; PRDP: n = 79), received the allocated treatment, and were available for follow-up assessments. OHRQoL was assessed using the 49-item version of the Oral Health Impact Profile (OHIP) before treatment (baseline) and at follow-ups after treatment (4-8 weeks and 6, 12, 24, 36, 48, 60, 96, and 120 months). To investigate the course of OHRQoL over time, we longitudinally modelled treatment and time effects using mixed-effects models. RESULTS: OHRQoL substantially improved from baseline to first follow-up in both groups indicated by a mean decrease in OHIP scores of 20.0 points (95%-CI: 12.5-27.5). When compared to the SDA group, OHRQoL in the PRDP group was not significantly different (-0.6 OHIP points; 95%-CI: -7.1 to 5.9) during the study period when assuming a constant time effect. OHRQoL remained stable over the 10 years with a statistically insignificant time effect (p = 0.848). CONCLUSIONS: For patients requesting prosthodontic treatment for their lost molars, treatments with SDA or PRDP improve clinically relevantly OHRQoL and maintain it over a period of 10 years with no option being superior to the other. CLINICAL SIGNIFICANCE: Since there was no significant difference between the two treatment options over the observation period of 10 years, and since results have stayed stable over time, patients can be informed that both treatment concepts are equivalent concerning OHRQoL.

Influence of the preparation design and artificial aging on the fracture resistance of monolithic zirconia crowns.

PURPOSE: The aim of this study was to evaluate the fracture resistance and fracture behavior of monolithic zirconia crowns in accordance with the preparation design and aging simulation method. MATERIALS AND METHODS: An upper first molar was prepared sequentially with three different preparation designs: shoulderless preparation, 0.4 mm chamfer and 0.8 mm chamfer preparation. For each preparation design, 30 monolithic zirconia crowns were fabricated. After cementation on Cr-Co alloy dies, the following artificial aging procedures were performed: (1) thermal cycling and mechanical loading (TCML): 5000 cycles of thermal cycling 5℃-55℃ and chewing simulation (1,200,000 cycles, 50 N); (2) Low Temperature Degradation simulation (LTD): autoclave treatment at 137℃, 2 bar for 3 hours and chewing simulation; and (3) no pre-treatment (control group). After artificial aging, the crowns were loaded until fracture. RESULTS: The mean values of fracture resistance varied between 3414 N (LTD; 0.8 mm chamfer preparation) and 5712 N (control group; shoulderless preparation). Two-way ANOVA analysis showed a significantly higher fracture loads for the shoulderless preparation, whereas no difference was found between the chamfer preparations. In contrast to TCML, after LTD simulation the fracture strength of monolithic zirconia crowns decreased significantly. CONCLUSION: The monolithic crowns tested in this study showed generally high fracture load values. Preparation design and LTD simulation had a significant influence on the fracture strength of monolithic zirconia crowns.

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.