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Purpose: High wear resistance of denture teeth preserves good occlusal relationship and sufficient parafunctional stability. This in-vitro investigation aimed to determine and compare the wear performance of different artificial denture teeth., Methods: Denture teeth of fifteen commercial products (n=8/group) were loaded in a pin-on-block design using steatite antagonists (d=3mm). Cyclic loading (50 N) was applied for 120,000 loadings (f=1.2Hz) with simultaneous thermal cycling (distilled water, 5°C/55°C, 2min/cycle). A loading cycle consisted of a vertical 1mm impact and a subsequent lateral 1mm sliding movement. Worn areas were digitalized (3-D-laser-scanning-microscope). Maximum and mean wear depth and surface roughness were determined and statistically compared (one-way Anova, Tukey-HSD test, α=0.05). Worn surfaces and cut specimens were investigated with scanning electron microscopy (SEM)., Results: Maximum wear varied between 475.1μm and 1232.2μm. Mean wear was between 241.1μm and 753.6μm with significant differences (p<0.001) between individual materials. Mean and maximum wear showed a significant correlation (Pearson's correlation coefficient: 0.942). Surface roughness increased between unworn to worn surface by 1.2μm (Ra, p=0.387) and by 41.7μm (Rz, p=0.000). All materials provided round or drop-shaped wear traces. Superficial analysis showed no cracks, chipping or fractures in the worn areas. Detailed evaluation of cut specimens with SEM exposed cracks on the bottom of the wear traces., Conclusions: Denture teeth showed significantly different in-vitro wear performance and increased roughness in the wear trace. Differences may be attributed to the composition of the materials, regarding both filler and polymer structure. The selection of teeth might contribute to enhanced in-vivo performance of the denture., (Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

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Objective: The aim of this study was to compare the fracture behavior of cantilever fixed dental prostheses (FDPs) fabricated from 3Y-TZP, 4Y-TZP, or 5Y-TZP zirconia. Method and materials: Posterior cantilever FDPs (three groups, each n = 16) were digitally designed and milled. After sintering, eight specimens/group were stored in demineralized water for 72 hours; eight specimens/group were subjected to accelerated aging using chewing simulation with thermal cycling (1,200,000 × 50 N; 2 × 3,000 × 5°C/55°C; H2O, 2 minutes/cycle) and finally stored in demineralized water for 24 hours. The cantilever FDPs were then statically loaded to failure to determine fracture load. Phase transformation towards the monoclinic phase was controlled with x-ray diffractometry. Results: One failure was identified after accelerated aging in the 5Y-TZP group. Fracture load decreased with increasing yttria content and decreasing bending strength. Accelerated aging using chewing simulation with thermal cycling caused a significant decline in fracture load. All FDPs failed in the area of the prepared tooth and in proximity to the cantilever, where the largest bending moment occurred. The yttria content had no influence on the type of fracture. With increasing yttria content, the relation between deformation and fracture load decreased only slightly. On the surface of FDPs that had been subjected to chewing simulation, no phase transformation towards the monoclinic phase (eg, low temperature degradation) was detected. Conclusion: Within the limitations of a laboratory study, the data indicate that 3Y-, 4Y-, and 5Y-TZP may be employed as material for the fabrication of permanent posterior cantilever FDPs. However, more data are necessary to finally advocate the application of 5-Y-TZP. [ABSTRACT FROM AUTHOR]

Denture prostheses are an ideal and extensive reservoir for microorganisms to attach to their surfaces. The aim of the study was to elucidate interactions between materials for the fabrication of denture bases and the attachment of microorganisms, focusing on respiratory pathogens and Candida species. Specimens (6 mm × 1 mm) with a standardized surface roughness (Sa = 0.1 µm) were prepared from heat-pressed polymethyl methacrylate (PMMA), CAD/CAM-processed PMMA, and CAD/CAM-processed polyether ether ketone (PEEK). The specimens were randomly placed in the vestibular areas of complete upper dentures in seven patients and were removed either after 24 h without any oral hygiene measures or after a period of four weeks. The microorganisms adherent to the surface of the specimens were cultivated and subsequently analyzed using mass spectrometry (MALDI-TOF). The means and standard deviations were calculated, and the data were analyzed using a two-way analysis of variance (ANOVA) and Tukey post-hoc test where appropriate (α = 0.05). There was a significant increase (p ≤ 0.004) in the total bacterial counts (CFU/mL) between the first (24 h) and the second (four weeks) measurements. Regarding quantitative microbiological analyses, no significant differences between the various materials were identified. Respiratory microorganisms were detected in all samples at both measurement time points, with a large variance between different patients. Only after four weeks, Candida species were identified on all materials but not in all participants. Candida species and respiratory microorganisms accumulate on various denture base resins. While no significant differences were identified between the materials, there was a tendency towards a more pronounced accumulation of microorganisms on conventionally processed PMMA. [ABSTRACT FROM AUTHOR]

Purpose: To survey dentists in Germany regarding their preferred cementation regimen for fixed dental prostheses (FDPs) fabricated from various restorative materials. Materials and Methods: An online survey was developed for completion by dentists in Germany between 08/2019 and 02/2020. The questionnaire gathered information about the cementation regimen (conventional, including the acid-base cements zinc-oxide phosphate or any glass-ionomer cement; self-adhesive; adhesive; don't know) that the participant would preferably select for the insertion of single- or multi-unit FDPs fabricated from various restorative materials. Data were also collected on demographic and personal characteristics. Results: A total of 721 dentists completed the survey, and the data from 688 questionnaires were included in the analysis. Conventional cementation was the option of choice for restorations fabricated from alloy/porcelain-fused- to-metal among 91.0% of the participants and for restorations fabricated from polycrystalline ceramics among 42.9% of the participants. Adhesive cementation was preferred for restorations fabricated from feldspathic/leucite-reinforced glass ceramics (77.9%), lithium-disilicate glass ceramics (67.5%), zirconia-reinforced lithium-silicate glass ceramics (42.0%), and CAD/CAM resin composites (63.8%). Uncertainties regarding the appropriate cementation protocol for restorations fabricated from CAD/CAM resin composites were reported by 15% of the participants. More than 20% of the participants selected a technique that is less or not at all recommended for the cementation of restorations fabricated from zirconia-reinforced lithium-silicate glass ceramic and CAD/CAM resin composites. Conclusion: The results of the survey suggest that dentists in Germany select the cementation regime depending on the restorative material. Some of the participating dentists selected cementation regimens that are less or not at all recommended for restorations fabricated from zirconia-reinforced lithium-silicate glass ceramic and CAD/CAM resin composites, or were not sure about the appropriate cementation protocol. [ABSTRACT FROM AUTHOR]

Background: Information on the prevalence of temporomandibular disorders (TMD) or possible/probable bruxism in seniors is heterogeneous and sparse. Objectives: To elucidate the prevalence of TMD and possible/probable bruxism in German adults aged 60 years and older. Methods: Participants of the Interdisciplinary Longitudinal Study of Adult Development and Aging (ILSE) born between 1950–1952 (C1) and 1930–1932 (C2) were examined in 2014–2016 (fourth wave). The participants were surveyed and clinically examined by one calibrated examiner. Two questions of the Patient Health Questionnaire (PHQ) were utilised to evaluate self‐reported bruxism. The clinical examination included signs of probable bruxism and the RDC/TMD examination protocol. Results: Data from 191 participants were available. No RDC/TMD diagnosis was made in 83.2%. Of the participants, 15.2% received a single diagnosis and 1.6% multiple diagnoses that included disc displacements (9.4%) and degenerative joint diseases (8.9%). A total of 24.7% reported bruxism that included self‐reported awake bruxism in 11.9% and sleep bruxism in 16.2%. Wear was clinically identified in 27.2% of the participants. No sex‐related differences were observed. Significant differences were detected for probable bruxism between C1 (14.1%) and C2 (54.3%). Conclusion: In the German population aged 60 years and older, the prevalence of TMD is 16.8%. TMD is characterised by temporomandibular joint disorders, including disc displacements and degenerative joint disorders. Bruxism was observed in a quarter of the old population. [ABSTRACT FROM AUTHOR]

Purpose: To investigate changes in oral health prior to and after conversion of fractured abutment teeth in double crown-retained removable dental protheses (DC-RDPs) into root-anchored ball attachments.Materials and Methods: Twenty patients were supplied with one root-anchored ball attachment after abutment tooth fracture. The Oral Health Impact Profile (OHIP-49) was completed by the patients prior to and after treatment to assess changes in perceived oral health.Results: Changes in OHIP were statistically and clinically significant (28.90 points prior to treatment and 13.80 points after treatment), especially in cases with a minor number of remaining double crowns.Conclusion: The conversion of fractured abutment teeth in DC-RDPs into root-anchored ball attachments can be an effective strategy for improving perceived oral health. [ABSTRACT FROM AUTHOR]

In the study the influence of different dental technical tools on the surface temperature and phase composition of fixed dental prostheses (FDPs) made of yttria-partially stabilized zirconia polycrystals (3Y-/4Y-/5Y-PSZ) was investigated. FDPs were fabricated by using computer-aided manufacturing (CAM). The FDPs were treated with a contra-angle handpiece equipped with different burs and polishers. The resulting surface temperatures were measured with a thermographic camera, and the resulting phase transformations were investigated by X-ray diffraction and quantified by Rietveld refinement. Processing with burs resulted in no phase transformation, but a preferred orientation shift. Using coarse polisher induced a phase transformation to the rhombohedral phase, while fine polishers produced no relevant phase transformations and no preferred orientation shift. Compared to the monoclinic phase (ca. 9% theoretical volume increase), which is associated with low-temperature degradation (LTD), the rhombohedral phase is much more voluminous (ca. 15% theoretical volume increase) and distorted and, therefore, has a greater degradation potential. [ABSTRACT FROM AUTHOR]

In this prospective clinical trial we observed the 2-year clinical performance of posterior tooth-supported multi-unit fixed dental prostheses (FDP) fabricated from zirconia with monolithic occlusal surfaces. Fifty multi-unit FDPs were inserted in 50 patients. After two years of clinical service, 43 restorations were reexamined as one patient had died and six patients were not available for recall. Two biological (root canal treatment: 12 and 14 months) and one technical (debonding: 12 months) complications occurred. According to the Kaplan–Meier analysis, the success rate was 93.7%, and the survival rate was 100%. The six patients who were not available for regular 2-year follow-up were examined after the official 2-year recall interval, and none of the FDPs presented complications or failures. Within the limitations of the current study, the use of multi-unit FDPs with monolithic occlusal surfaces fabricated from zirconia can be recommended for short-term use in the posterior area. [ABSTRACT FROM AUTHOR]

Objectives: This study aimed to survey dentists in Germany to identify their favored materials for the fabrication of tooth-supported single crowns (SCs) depending on the location of the abutment teeth and the preparation margin. Materials and methods: The survey included questions regarding demographic characteristics of dentists/their dental practice and preferred restorative materials for the fabrication of SCs for abutment teeth 16, 11, 34, and 36 with either supra- or subgingival preparation margins. Results: Between August 2019 and February 2020, 721 dentists participated in the survey; responses from 33 dentists were excluded from data analysis because the dentists did not work in Germany or provided less than one fixed dental prosthesis/month. Dentists favored ceramic materials independent of the location of the abutment tooth and preparation margin (56.6–92.2%). CAD/CAM resin composites or full metals were preferred by only a few participants. A significantly higher proportion of dentists recommended porcelain fused to metal for subgingival preparation margins than for supragingival margins (p < 0.001). Characteristics of dentists/dental practices influenced a single scenario (11 subgingival) that was dependent on the dentist's time since graduation. When asked to specify the ceramic materials, numerous participants wrote a free response (5.7–7.8%) or did not answer (0.7–4.8%). Conclusions: Dentists in Germany selected restorative materials for SCs depending on the clinical scenario. Since numerous dentists did not specify the ceramic materials, postgraduate information and education might help to extend expertise. Clinical relevance: The results of this survey provide insight into the favored materials of dentists for the fabrication of tooth-supported SCs. [ABSTRACT FROM AUTHOR]

PURPOSE. The aim of the current study was to analyze treatment concepts of a cohort of German dentists for planning, fabrication, and maintenance of implant-supported fixed and removable restorations. MATERIALS AND METHODS. A questionnaire including queries about experiences with implant-supported restorations as well as prosthetic and maintenance treatment concepts for supplying patients with fixed and removable implantsupported prosthetic restorations was developed and sent to 350 dental offices registered in the municipal area of Leipzig, Germany. RESULTS. An overall total of 62 returned questionnaires were included in the analyses, which relates to a response rate of 17.7%. Participating dentists were more involved in the prosthetic aspects of implant dentistry rather than surgery, while prosthetic concepts such as backward planning, digital processing, and application of all-ceramic materials were not commonly performed. Simple attachments were preferred over complex retention systems in removable implant-supported restorations. Tooth/implant-supported fixed denture prostheses as well as removable denture prostheses with supporting posterior implants were not regarded as a favorable treatment option. CONCLUSION. Within the limitations of the study, the data indicate that dentists favor simple and conventional treatment approaches in implant prosthetics. Prosthetic aspects in the planning of implant-supported restorations are often neglected. Prosthetic treatment guidelines and aspects should commonly be considered in the planning phase of implant-supported prosthetic restorations, and awareness should be increased in postgraduate education. [ABSTRACT FROM AUTHOR]

This study investigated the handling properties and clinical performance of two commercially available resin materials with slight differences in filler composition for the fabrication of fixed interim restorations. In a dental university setting, patients requiring prosthetic treatment were supplied with fixed interim restorations fabricated from two commercially available resin materials. To clarify the handling properties of the resin materials, dentists and undergraduate students completed a questionnaire. Prior to insertion of the definitive restoration, the interim restorations were analyzed by calibrated examiners using a modification of the United States Public Health Service criteria. Eighty-two fixed interim restorations with a mean clinical service period of 44.5 (±28.3) days were included, including 39 single crowns, 30 fixed denture prostheses, 10 blocked crowns, and 3 partial coverage restorations. No significant differences between the two materials in the rating of their handling properties were identified, with the exception of the parameter "surface". Failures due to fractures were observed in 13% of the interim restorations. No significant differences between the materials in the rating of the clinical performance were identified. These results indicate that slight changes in the filler composition of commercial formulations account for few differences in handling properties and clinical performance. [ABSTRACT FROM AUTHOR]

This laboratory study aimed to investigate the effect of doping an acrylic denture base resin material with nanoparticles of ZnO, CaO, and TiO2 on biofilm formation. MATERIALS AND METHODS. Standardized specimens of a commercially available cold-curing acrylic denture base resin material were doped with 0.1, 0.2, 0.4, or 0.8 wt% commercially available ZnO, CaO, and TiO2 nanopowder. Energy dispersive X-ray spectroscopy (EDX) was used to identify the availability of the nanoparticles on the surface of the modified specimens. Surface roughness was determined by employing a profilometric approach; biofilm formation was simulated using a monospecies Candida albicans biofilm model and a multispecies biofilm model including C. albicans, Actinomyces naeslundii, and Streptococcus gordonii. Relative viable biomass was determined after 20 hours and 44 hours using a MTT-based approach. RESULTS. No statistically significant disparities were identified among the various materials regarding surface roughness and relative viable biomass. CONCLUSION. The results indicate that doping denture base resin materials with commercially available ZnO, CaO, or TiO2 nanopowders do not inhibit biofilm formation on their surface. Further studies might address the impact of varying particle sizes as well as increasing the fraction of nanoparticles mixed into the acrylic resin matrix. [ABSTRACT FROM AUTHOR]

Objectives: Removable dentures with different denture teeth may provide different performance and resistance in implant and gingival situations, or anterior and posterior applications. Materials and methods: Two situations of removable dentures were investigated: gingiva (flexible) and implant (rigid) bearing. For simulating the gingiva/jaw situation, the dentures were supported with flexible lining material. For the implant situation, implants ( d = 4.1 mm) were screwed into polymethylenmethacrylate (PMMA) resin. Two commercial (Vita-Physiodens MRP, SR Vivodent/Orthotyp DCL) and two experimental materials (EXP1, EXP2) were investigated in anterior (A) and posterior (P) tooth locations. Chewing simulation was performed, and failures were analyzed (microscopy, SEM). Fracture strength of surviving dentures was determined. Results: Only EXP1 revealed failures during chewing simulation. Failures varied between anterior and posterior locations, and between implant (P:4x; A:7x) or gingiva (P:1x; A:2x) situations. Kaplan-Meier log-rank test revealed significant differences for implant situations ( p < 0.002), but not for gingiva bearing ( p > 0.093). Fracture testing in the implant situation provided significantly highest values for EXP2 (1476.4 ± 532.2 N) in posterior location, and for DCL (1575.4 ± 264.4 N) and EXP2 (1797.0 ± 604.2 N) in anterior location. For gingival bearing, significantly highest values were found for DCL/P (2148.3 ± 836.3 N), and significantly lowest results for EXP1/A (308.2 ± 115.6 N). For EXP1 + EXP2 + Vita/P and for EXP1/A no significant differences were found between implant- or gingiva-supported situations. Conclusions: Anterior and posterior teeth showed different material-dependent in vitro performance, further influenced by implant/gingiva bearing. While an implant in anterior application increased fracture strength of two materials, it decreased fracture values of 3/4 of the materials in posterior application. Clinical relevance: Survival of denture teeth may be influenced by material, oral position, and bearing situation. [ABSTRACT FROM AUTHOR]

Fungal biofilms may contribute to the occurrence of denture stomatitis. The objective of the study was to investigate the biofilm formation and morphology of Candida albicans in biofilms on the surface of denture base materials. Specimens were prepared from different denture base materials. After determination of surface properties and salivary pellicle formation, mono- and multispecies biofilm formation including Candida albicans ATCC 10231 was initiated. Relative amounts of adherent cells were determined after 20, 44, 68 and 188 h; C. albicans morphology was analysed employing selective fluorescence microscopic analysis. Significant differences were identified in the relative amount of cells adherent to the denture base materials. Highest blastospore/hyphae index suggesting an increased percentage of hyphae was observed in mono- and multispecies biofilms on the soft denture liner, which did not necessarily respond to the highest relative amount of adherent cells. For both biofilm models, lowest relative amount of adherent cells was identified on the methacrylate-based denture base material, which did not necessarily relate to a significantly lower blastospore/hyphae index. The results indicate that there are significant differences in both biofilm formation as well as the morphology of C. albicans cells in biofilms on the surface of different denture base materials. [ABSTRACT FROM AUTHOR]

Objective This study aimed to evaluate the adhesion and proliferation of Candida albicans on denture base materials with different resin chemistries. Materials and methods Standardised specimens were prepared from different denture base materials (i.e. Palapress vario, Paladon 65, Castdon, Sherapress, Eclipse and Mucopren) and subjected to thermal cycling to simulate an artificial ageing process. After the determination of surface roughness and surface free energy, Candida albicans adherence and proliferation on the surface of denture base materials were simulated by subsequent incubation with Candida albicans ATCC 10231 for either 24 h or 196 h with and without prior simulation of salivary pellicle formation. Results Regardless of the presence of a salivary pellicle or the incubation time, the results indicate that the proliferation of Candida albicans is significantly dependent on the material that is used for the fabrication of denture bases ( p < 0.001). A significantly higher proliferation of Candida albicans was observed on the surface of denture base materials with the highest polar contribution to surface free energy (i.e. Eclipse, Mucopren), and this result supports the assumption that there might be a relationship between the polar contribution to surface free energy of the substratum material and Candida albicans proliferation. Conclusion The results obtained from this study indicate that Candida albicans proliferation in particular is not necessarily increased on denture base materials that are subjected to thermal cycling. [ABSTRACT FROM AUTHOR]

doi: 10.1111/j.1741-2358.2010.00394.x Analysis of veneer failure of removable prosthodontics Abstract Objective: This retrospective study aimed to analyse the failure rate of the facings of double crown-retained dentures. Materials and methods: The clinical reports of 575 patients, who received double crown-retained removable dentures with a total of 1807 double crowns between 1984 and 2007, were included in the study. The 575 prostheses were attached to telescopic crowns using a friction fit (FF; n = 1999), conical crowns (CC; n = 61), or parallel-sided telescopic crowns with a clearance fit (CF; n = 315). Survival probabilities for the veneers were investigated using the Kaplan-Meier method; Cox regression analysis was carried out to determine the influence of the double crown used for retention, type of antagonist, and localisation. Results: Veneer failure occurred in 7.0% of FF, 27.9% of CC, and 4.4% of CF. The risk of veneer failure was 2.3 times higher for CC than for FF ( p = 0.042); no significant differences were found between CF and FF ( p = 0.363). No significant influences on the localisation of the denture ( p = 0.534) or the type of antagonist ( p = 0.341) were found. Conclusion: CC-based double crowns have a higher risk of veneer failure than FF and CF, which may be due to high tensile stresses occurring in the cervical area of their outer copings. [ABSTRACT FROM AUTHOR]

doi: 10.1111/j.1741-2358.2011.00485.x Candida albicans biofilm formation on soft denture liners and efficacy of cleaning protocols Objective: The aim of this study was to investigate Candida albicans biofilm formation on denture liners and to analyse the efficacy of cleaning protocols. Material and methods: Specimens were prepared from four silicone-based soft denture liners. After artificial ageing and surface free energy determination, specimens were incubated with saliva (2 h) and Candida albicans ATCC 10231 for either short- (2.5 h) or long-term (24 h) biofilm formation. Adherent cells were determined either after incubation of specimens with Candida albicans or after treatment with different denture cleaning protocols. Statistical analysis was performed using one-way anova and the Games-Howell test (α = 0.05). Results: For both short- and long-term biofilm formation, similar amounts of Candida albicans cells were found on the surface of the different liners ( p = 0.295 and 0.178, respectively). For both short- and long-term biofilm formation, the highest cleaning efficacy was observed for sodium hypochlorite (NaOCl; p < 0.01). The efficacy of the chemical denture cleaner in removing long-term Candida albicans biofilms was significantly lower than the efficacy of removal by brushing ( p < 0.001). Conclusion: Different silicone-based soft denture liners yield similar Candida albicans biofilm formation on their surface. The highest efficacy for the removal of Candida albicans biofilms was identified for NaOCl. Chemical denture cleaners appear to have rather low efficacy to remove mature Candida albicans biofilms. [ABSTRACT FROM AUTHOR]

The aim of this in vitro study was to investigate the two-body wear of different ceramics. Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists, respectively. Specimens were loaded in a pin-on-block design with a vertical load of 50 N for 1.2 × 10 cycles; ( f = 1.6 Hz; lateral movement, 1 mm; mouth opening: 2 mm). Human enamel was used as a reference. Three zirconia ceramics, three veneering porcelains, two glass-infiltrated and one lithium disilicate ceramic were investigated. Veneering and lithium disilicate ceramics were glazed before testing. Surface roughness Ra (SP6, Perthen-Feinprüf, G) and wear depth were determined using a 3D scanner (Laserscan 3D, Willytec, G). SEM (Quanta FEG 400, FEI, USA) pictures of the worn specimens and antagonists were made for evaluating wear performance. Veneering porcelain provided wear traces between 71.2 and 124.1 μm (enamel antagonist) and 117.4 and 274.1 μm (steatite). Wear of the steatite antagonists varied between 0.618 and 2.85 mm². No wear was found for zirconia and glass-infiltrated substructure ceramics. Also, no wear was found for the corresponding antagonists. Wear of specimens and antagonists was strongly material dependent. No visible wear was found on zirconia and glass-infiltrated ceramics. Porcelain and lithium disilicate ceramic showed a comparable or lower wear than the enamel reference. Antagonist wear was found to be lower when specimens were made of substructure oxide ceramics instead of veneering porcelain. From the point of wear testing, zirconia may be used for the fabrication of fixed dental prosthesis without veneering. [ABSTRACT FROM AUTHOR]

The mechanical properties of luting agents are determined by the mixing ratio of powder and liquid. The purpose of this in vitro study was to evaluate the therapeutic range of zinc carboxylate cements by investigating the mechanical properties of such cements when formulated using erroneous powder/liquid ratios. Using the recommended powder/liquid ratio as a standard, four different mixing ratios (25% and 50% more or less powder) were used to prepare each carboxylate cement (Aqualox, Carboco, Durelon). A veneering composite (Sinfony) was used as control. Vickers hardness and three-body abrasion were evaluated. In each carboxylate cement, both a 25% and 50% increase in liquid content resulted in significantly lower Vickers hardness, whereas a higher powder content altered the saturation concentration but did not result in increased hardness; this effect was particularly obvious in Carboco. Durelon showed a linear relationship between wear and powder/liquid ratio, whereas Carboco and Aqualox displayed a more exponential increase in wear in mixings with an increased liquid content. The mechanical properties of carboxylate cements were altered in mixtures with an increased liquid content, but not in those with a high powder content. Mixing ratio errors greater than 25% may significantly affect the clinical performance of carboxylate cements. [ABSTRACT FROM AUTHOR]

Objective: In in vitro tests, metals and resins are frequently used as substitutes for human teeth. This study aims at determining the suitability of various materials for substituting human incisors in load capability tests. Method: Veneering composite (Adoro; n = 16) and non‐precious CoCr‐alloy (NPA; n = 16) were used for manufacturing 32 identical specimens based on the model of a maxillary central incisor resin tooth (Morita). Sixteen human incisors served as a control group. After root canal treatment, all specimens were restored with fiber‐reinforced composite posts and core build‐ups. For each group, eight specimens were chosen randomly and restored either with identical NPA crowns or with all‐ceramic crowns. Specimens were exposed to thermal cycling and mechanical loading (TCML) until failure. Statistical analysis was conducted using the Kruskal–Wallis test and the Bonferroni‐adjusted Mann Whitney U‐test. Results: In ceramic crowns, the highest median fracture resistance was found in alloy tooth substitutes (430 N) and natural incisors (426 N), which both showed a significantly higher fracture resistance than composite tooth substitutes (162 N). In alloy crowns, alloy tooth substitutes exhibited the highest fracture resistance (348 N), but no statistically significant difference could be detected between natural incisors (158 N) and composite tooth substitutes (117 N). No artificial tooth substitute showed fracture patterns similar to those of natural incisors. Significance: Mechanical parameters are significantly influenced by the type of restoration and the restorative material used. In in vitro tests, the range of artificial tooth substitutes suitable for the replacement of human incisors is limited by load capability. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2009 [ABSTRACT FROM AUTHOR]

The aim of this in vitro study was to analyse the performance of CAD/CAM resin-based composites for the fabrication of long-term temporary fixed dental prostheses (FDP) and to compare it to other commercially available alternative materials regarding its long-term stability. Four CAD/CAM materials [Structur CAD (SC), VITA CAD-Temp (CT), Grandio disc (GD), and Lava Esthetic (LE)] and two direct RBCs [(Structur 3 (S3) and LuxaCrown (LC)] were used to fabricate three-unit FDPs. 10/20 FDPs were subjected to thermal cycling and mechanical loading by chewing simulation and 10/20 FDPs were stored in distilled water. Two FDPs of each material were forwarded to additional image diagnostics prior and after chewing simulation. Fracture loads were measured and data were statistically analysed. SC is suitable for use as a long-term temporary (two years) three-unit FDP. In comparison to CT, SC featured significantly higher breaking forces (SC > 800 N; CT < 600 N) and the surface wear of the antagonists was (significantly) lower and the abrasion of the FDP was similar. The high breaking forces (1100–1327 N) of GD and the small difference compared to LE regarding flexural strength showed that the material might be used for the fabrication of three-unit FDPs. With the exception of S3, all analysed direct or indirect materials are suitable for the fabrication of temporary FDPs. [ABSTRACT FROM AUTHOR]

Background: The influence of typical manufacturing regimes for producing fixed dental prostheses (FDPs) from yttria partly-stabilized zirconia polycrystals (3Y/4Y/5Y-TZP) on the phase composition is quantified. Methods: Fixed dental prostheses (FDPs) were designed using a CAD process and machined from different Y-TZP blanks from two manufacturers differing in yttria contents. Subsequent to sintering, the FDPs were glaze fired and air-blasted using alumina particles. Phase composition was determined with X-ray diffraction and quantified with Rietveld refinement. Results: The blanks from VITA Zahnfabrik (VITA YZ HT, VITA YZ ST, VITA YZ XT) and Dental Direct (DD Bio ZX2, DD cube ONE, DD cube X2) featured a rhombohedral portion with rather small crystallites and a small monoclinic portion for 3Y/4Y-TZPs, which increased after machining and disappeared after sintering. Glaze firing and air-blasting with alumina particles had no significant influence on the phase composition. Conclusion: The phase history of dental zirconia is revealed, which may have implications on further processing and aging of the FDP (e.g. low temperature degradation) in mouth. [ABSTRACT FROM AUTHOR]

Compared to thermoplastic manufacturing techniques, computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies make it easier to process modern restorative and prosthetic materials with improved material properties. In dentistry, tooth-colored alternatives to metal-based frameworks for application in removable dental prostheses (RDP) emerged. With regard to this aspect, the current article provides an overview of the specific material properties of polyoxymethylene (POM). Furthermore, it reviews scientific literature indexed in PubMed and Web of Science that focuses on RDPs fabricated from POM within the last 10 years. Finally, a prosthetic rehabilitation of a patient with a RDP fabricated from POM is illustrated and observations during a follow-up over 10 months are described. Scientific data and clinical observations indicate that polyoxymethylene is a promising material that bridges gaps in dental therapeutic options. While survival time may be limited due to wear, POM might be a favorable option for application in semi-permanent restorations. [ABSTRACT FROM AUTHOR]

Demographic changes in the industrialized countries require that dentists adapt to the growing and heterogeneous group of elderly patients and develop concepts for the dental care of fit, frail, and dependent old and very old people. In general, dental care for old and very old people should be based on their individual everyday life. As a result of demographic changes, improved oral hygiene at home, and the establishment of professional teeth and denture cleaning, tooth loss occurs increasingly in higher ages, which implies that first extensive prosthetic rehabilitation with fixed or/and removable dental prostheses is shifting to a higher average age than ever before. This phenomenon requires that the individual diseases, potential multimorbidity and polypharmacy, and associated limitations are taken into consideration. Against this background, the current survey aims to summarize epidemiological trends associated with tooth loss, using Germany as a highly representative country for demographic changes as an example. Furthermore, the current narrative summary outlines general principles that should be followed in dental care, treatment of geriatric patients, and outlines current therapeutic options in prosthetic dentistry. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the clinical properties of tooth-colored computer-aided design/computer-aided manufacturing (CAD/CAM) materials for the fabrication of a 3-unit fixed dental prostheses (FDPs) in the same clinical scenario. A 53-year-old female patient was supplied with a 3-unit FDP to replace a second premolar in the upper jaw. Restorations were fabricated from 3 mol%, 4 mol%, and 5 mol% yttrium oxide zirconia, zirconia with translucency gradient, indirect composite resin, polyetheretherketone (PEEK), and polyetherketoneketone (PEKK). Milling time, weight, and radiopacity were investigated. Esthetics were examined following the US Public Health Service criteria (USPHS). The milling time for zirconia was twice as high as for the indirect composite resin, PEEK, or PEKK. The latter materials had a weight of 2 g each, while zirconia restorations yielded 5 g. Zirconia presented intense radiopacity. PEEK and PEKK required veneering and an opaquer was applied to the PEKK framework. All FDPs showed acceptable esthetics. PEEK and PEKK restorations were featured by a grayish shimmering. A variety of CAD/CAM materials are available to fabricate 3-unit FDPs with esthetically acceptable results. In the esthetic zone, PEEK and PEKK require veneering and an opaquer might be applied. Milling time, weight, and radiopacity were relatively high for zirconia FDPs. [ABSTRACT FROM AUTHOR]

The aim of the current study was to relate an artificial aging protocol for the analysis of dental materials to their clinical performance. 20 fixed interim restorations (crowns and fixed denture prostheses (FDPs)) fabricated from two commercially available resin-based composites (RBCs) and a previous clinical trial served as templates for the fabrication of duplicate restorations. Duplicates were subjected to artificial aging using thermal cycling and mechanical loading. Subsequent to wear analysis, templates and duplicates were loaded to fracture and were examined using thermal gravimetric analysis (TG) and differential scanning calorimetry (DSC). For both RBCs, a relevant uptake of water was identified, which was more pronounced in the duplicates. Tribological analyses indicated relevant signs of wear in both templates and duplicates. While qualitative analyses indicated macroscopically similar wear traces in templates and duplicates, data showed that wear of FDPs was underrated in the laboratory analyses. The results of the current study suggest that chewing simulation allows a proper estimation of aging processes in materials for the fabrication of fixed interim restorations. However, simulation parameters should be continuously improved using data derived from clinical settings to enhance the quality of the simulation protocols. [ABSTRACT FROM AUTHOR]