Publications by authors named "Kurt Erdelt"

36 Publications

Effects of porcelain veneering methods on conformity of the marginal and internal fit of three-unit zirconia framework.

Odontology 2021 Mar 23. Epub 2021 Mar 23.

Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany.

The purpose of this study is to investigate the effects of porcelain veneering methods on the marginal and internal fit of a three-unit zirconia framework. A zirconia master model, in which the lower-left second premolar and the second left molar were used as the abutment, was obtained using an intraoral scanner. Based on the data, three-unit zirconia frameworks for fabricating all-ceramic bridges were designed and milled (FW group). Two types of all-ceramic bridge were fabricated by veneering porcelain onto these frameworks using the press-over technique (P group) and the layering technique (L group). The replica technique was used to measure the gap size between the abutments and the bridges. Measurements were taken in the marginal opening area (MO), chamfer area (CH), axial area (AX), and occlusal area (OC). Statistical analysis was performed using the Mann-Whitney U-test. There was no significant difference in MO and CH between the P and L groups. However, in AX, the L group had a significantly larger gap size than that of the P group (p = 0.003). In addition, compared with the FW group, the P group showed a significantly larger gap size in MO (p < 0.000), CH (p = 0.008), and OC (p < 0.000). These results indicate that the gap size increased after porcelain veneering using the press-over and layering techniques. In addition, the all-ceramic bridges fabricated using the press-over and layering techniques had approximately equal gap sizes in MO.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10266-021-00595-3DOI Listing
March 2021

Impact of Missing Teeth on Oral-Health-Related Quality of Life: A Prospective Bicenter Clinical Trial.

Int J Prosthodont 2021 Mar 18. Epub 2021 Mar 18.

Purpose: To investigate the effect of missing teeth on patients' oral health-related quality of life (OHRQoL).

Materials And Methods: A total of 151 patients participated in this prospective bicenter clinical study (mean age: 64.7 ± 10.5 years; 71 women). Four subgroups were defined based on the number of missing teeth. OHRQoL was assessed using the German version of the Oral Health Impact Profile-49/53 (OHIP-G49/53) and visual analog scale (VAS) questionnaires. The effect of missing teeth on OHIP (total and by dimension) and VAS scores before and after prosthetic treatment was investigated at baseline (T0), 1 week (T1), and 3 months (T2) after prosthetic treatment. Scores were analyzed using Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests. Correlations were assessed using Spearman rho correlation. The level of significance was set at P = .05.

Results: Initial OHIP and VAS scores were highest for patients with 11 to 28 missing teeth. Scores improved among all groups between T0 and T1/T2. After prosthetic rehabilitation (T1), improvements in total OHIP scores were greatest for patients with no missing teeth or with 11 to 28 missing teeth. Patients with no missing teeth or with 1 to 4 missing teeth before treatment had the lowest posttreatment OHIP scores. Total OHIP scores among the groups were in the same value range (P > .185). No direct correlation was found between the VAS and total OHIP scores.

Conclusion: OHIP and VAS scores for OHRQoL were associated with the number of missing teeth. Prosthetic treatment resulted in improved OHRQoL and oral function among all groups. The use of a VAS yielded additional detailed information.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.11607/ijp.7422DOI Listing
March 2021

Short communication: In vitro pilot study: Are monolithic 3Y-TZP zirconia crowns too strong for titanium Implants?

Int J Prosthodont 2021 Mar 3. Epub 2021 Mar 3.

Purpose: To report on pilot tests for a planned study on single implant-supported crowns made from different restorative materials using finite element analysis (FEA) and in vitro load-to-failure testing.

Materials And Methods: Within this pilot study, FEA was conducted using Ansys 2019 R2 to simulate stress and deformation for implant-supported crowns made of lithium disilicate ceramic (LiS2) and zirconia (3Y-TZP). Additionally, an in vitro load to failure test was conducted using two specimens per group to evaluate the failure mode and to confirm the findings from the FEA.

Results/conclusion: FEA revealed stress areas at the palatal cervical areas of the crowns. In the load to failure test, both hybrid abutment crowns made of LiS2 fractured (410 N and 510 N) before plastic deformation of the metal implant components occurred. The monolithic hybrid abutment crowns made of 3Y-TZP did not fracture until tests were interrupted at 646-N and 690-N occlusal force, when plastic deformation of the metal implant components was visually observed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.11607/ijp.7322DOI Listing
March 2021

Two-body wear and fracture behaviour of an experimental paediatric composite crown in comparison to zirconia and stainless steel crowns dependent on the cementation mode.

Dent Mater 2021 02 6;37(2):264-271. Epub 2020 Dec 6.

Department of Conservative Dentistry and Periodontology, University Hospital, Ludwig-Maximilians University Munich, Germany.

Objectives: The purpose of this in vitro study was to assess the two-body wear and fracture behaviour of an experimental additive manufactured composite crown in comparison to zirconia and stainless steel crowns and its cementation protocol for primary molars.

Material And Methods: Three different paediatric crowns - experimental composite crowns (CCs, 3M), zirconia crowns (ZCs, NuSmile), and stainless steel crowns (SSCs, 3M)-were cemented with an experimental resin-modified glass ionomer cement (RMGIC, 3M) and two self-adhesive cements (SACs; RelyX Unicem Automix 2, 3M; BioCem, NuSmile). Seven groups, each with eight specimens, were thermally cycled (55 °C/50 °C) and dynamically loaded (50N/ 1.2Hz) in a masticatory simulator with steatite antagonists. The areal and volumetric material loss of all specimens before and after 1,200,000 masticatory cycles was evaluated with a 3D profilometer. Light and scanning electron microscopy were used for qualitative analysis. Pairwise comparisons between all the groups were performed using the Mann-Whitney U test (p < 0.05).

Results: Microscopic imaging revealed different wear patterns for each material. Lowest fracture rates were documented for the CCs. In contrast, all the SSCs showed perforations. The CCs cemented with RMGIC showed the highest significant volumetric wear (6.3 ± 0.72 mm³), followed by the SSCs cemented with RMGIC (3.6 ± 1.79 mm³) and CCs cemented with SAC (3.5 ± 1.92 mm³). No significant differences were found in terms of the wear among all the other groups, ranging between 0.4 ± 0.25 and 0.6 ± 0.32 mm³.

Conclusion: The volume loss of the tested crowns differed for each material and was dependent on the type of cementation. With regard to in vitro wear and fracture patterns, cementation with SAC may increase the clinical performance of CC paediatric crowns.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.dental.2020.11.010DOI Listing
February 2021

Marginal and internal fit of three-unit fixed dental prostheses fabricated from translucent multicolored zirconia: Framework versus complete contour design.

J Prosthet Dent 2021 Feb 14;125(2):340.e1-340.e6. Epub 2020 Nov 14.

Professor, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany.

Statement Of Problem: Translucent multicolored zirconia materials enable more esthetic complete contour zirconia fixed dental prostheses (FDPs) than conventional zirconia, which exhibits low translucency and high opacity and is monochromatic. However, how the marginal and internal fit of translucent multicolored zirconia FDPs compare with those of traditional frameworks that require veneering is unclear.

Purpose: The purpose of this in vitro study was to compare the marginal and internal fit of frameworks and complete contour 3-unit FDPs fabricated from translucent multicolored zirconia.

Material And Methods: Frameworks with a thickness of 0.5 mm and complete contour FDPs with a thickness of 0.8 to 1.5 mm were manufactured by using a workflow similar to one from a zirconia master model (mandibular left second premolar-mandibular left second molar). Two polyvinyl siloxane replicas were made for each specimen to measure the marginal and internal fit. Measurement locations were mesial, lingual, buccal, and distal for each abutment. In these locations, the marginal opening (MO), chamfer area (CA), axial wall (AW), and occlusal area (OC) were measured. The data were analyzed with 2-way ANOVA and the Bonferroni post hoc test (α=.05).

Results: Frameworks showed significantly better mean ±standard deviation fit values than complete contour 3-unit FDPs at measurement areas MO (frameworks: 112 ±22 μm, complete contour FDPs: 144 ±37 μm) (P=.013), CA (frameworks: 89 ±12 μm, complete contour FDPs: 110 ±22 μm) (P=.006), and OC (frameworks: 182 ±36 μm, complete contour FDPs: 244 ±64 μm) (P=.008). At the measurement area AW (frameworks: 47 ±7 μm, complete contour FDPs: 50 ±9 μm of each location, no significant difference was observed between frameworks and complete contour FDPs (P=.361).

Conclusions: Design differences in 3-unit FDPs fabricated from translucent multicolored zirconia influenced the marginal and internal fit. Frameworks had smaller marginal fit than complete contour FDPs for translucent multicolored zirconia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.prosdent.2020.08.023DOI Listing
February 2021

Virtual education: Dental morphologies in a virtual teaching environment.

J Dent Educ 2020 Oct 8;84(10):1143-1150. Epub 2020 Jun 8.

Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany.

Objectives: Digital technology is already playing an increasingly important role in the education of students. The present investigation examined the acceptance of preclinical students for learning dental morphologies in virtual reality (VR).

Methods: The creation of the VR dental teaching environment was divided into 3 sections: (a) generation of the digital data; (b) creation of the VR dental learning environment for tooth morphologies; and (c) evaluation by preclinical students through questionnaires combined with visual analogue scale and fixed-answer options. Students of the Department of Prosthetic Dentistry of the University Hospital Munich were able to stay/interact in the VR dental learning environment for 10 minutes with VR headsets and hand controllers. The data were analyzed using the Kolmogorov-Smirnov test and exploratory data analysis using the median value and interquartile range.

Results: Of the students, 34.9% stated that they understand dental morphologies much better, 57.1% better, and 7.9% equally well compared to using the traditional textbook. The students would be willing to spend about 500 euros privately for the VR equipment. The haptic and auditive teaching elements were evaluated more positively than the purely visual ones of the integrated information boards.

Conclusions: Learning in the VR dental learning environment showed a high level of acceptance among all students and should be integrated as a fixed element in the dental curriculum. A further development for use independent of time and place is desirable.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jdd.12235DOI Listing
October 2020

In vivo wear of CAD-CAM composite versus lithium disilicate full coverage first-molar restorations: a pilot study over 2 years.

Clin Oral Investig 2020 Dec 12;24(12):4301-4311. Epub 2020 May 12.

Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336, Munich, Germany.

Objectives: To present a digital approach to measure and compare material wear behavior of antagonistic first molar restorations made of an experimental CAD/CAM composite (COMP) and lithium disilicate ceramic (LS2) in patients with reconstructed vertical dimension of occlusion (VDO) after generalized hard tissue loss.

Methods: A total of 12 patients underwent complete full jaw rehabilitation with full occlusal coverage restorations made either of COMP or LS2. The first molar restorations (n = 48) were chosen for wear examination. At annual recall appointments, polyether impressions were taken, and resulting plaster casts were digitalized using a laboratory scanner. Mean observation period was 371 days for first and 769 days for second year. The resulting 96 datasets were analyzed by superimposition of 3-D datasets using an iterative best-fit method. Based on the superimposition data, the wear rates of the occlusal contact areas (OCAs) were calculated.

Results: For antagonistic restorations made of COMP, the average wear rate was 24.8 ± 13.3 μm/month, while for LS2, it was 9.5 ± 4.3 μm/month in first year, with significant differences (p < 0.0001) between the materials. In second year, monthly wear rates decreased significantly for both materials: COMP (16.2 ± 10.7 μm/month) and LS2 (5.5 ± 3.3 μm/month). Statistical comparison between wear time showed significant differences for both materials: COMP p < 0.037 and LS2 p < 0.001. A logarithmic fit (COMP R = 0.081; LS2 R = 0.038) of the data was calculated to estimate the wear progression.

Significance: In patients with reconstructed VDO, restorations made of LS2 show a more stable wear behavior than ones out of experimental CAD/CAM composite. In cases of complete rehabilitation, load bearing CAD/CAM-composite restorations should be critically considered for application due to their occlusal wear behavior. However, when choosing a restorative material, not only the functional occlusal stability should be taken into account but also the prospect of minimally invasive treatment with maximum preservation of natural tooth structures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-020-03294-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7666668PMC
December 2020

Reproducibility of a magnet-based jaw motion analysis system.

Int J Comput Dent 2020 ;23(1):39-48

Background: The Dental Motion Decoder system (DMS-System) is a medical device based on magnetic field technology that records mandible movements. The data can be used to program an articulator or can be directly processed over a computer-aided design (CAD) interface. The present study aimed to assess the reproducibility of this system in vitro and in vivo.

Material And Methods: Protrusive and laterotrusive movements were simulated in vitro using an articulator (SAM SE) (Group M) and in vivo (Group P) on one test individual. Measurements were carried out in two ways: 1) Measurements were taken after initializing and referencing the system using the reference points (RPs) once, followed by 30 protrusive and laterotrusive movements (M1 and P1); and 2) Thirty individual measurements were recorded using the RPs before each measurement (M2 and P2). Values for the sagittal condylar path inclination angle (sCPIA) and the Bennett angle (BA) were exported and analyzed. The reproducibility of the system was evaluated using the standard deviations (SDs) of the measurement series (sCPIA and BA for M1, M2, P1, and P2).

Results: In vitro tests M1 (SD: sCPIA = 0.08 degrees; BA = 0.06 degrees) and M2 (SD: sCPIA = 0.26 degrees; BA = 0.11 degrees) showed significantly higher reproducibility (P < 0.001) compared with the in vivo measurements P1 (SD: sCPIA = 0.61 degrees; BA = 0.45 degrees) and P2 (SD: sCPIA = 1.4 degrees; BA = 0.65 degrees).

Conclusion: Within the limitations of the present study, the deviation in vitro, representing the reproducibility of the DMD-System, is smaller than the biologic variance observed in vivo. Therefore, reliable measurements under clinical conditions can be assumed.
View Article and Find Full Text PDF

Download full-text PDF

Source
March 2020

Clinical Performance of Anterior Full Veneer Restorations Made of Lithium Disilicate with a Mean Observation Time of 8 Years.

Int J Prosthodont 2020 Jan/Feb;33(1):14-21

Purpose: To evaluate the survival and complication rates of full veneer restorations after up to 11 years of clinical service.

Materials And Methods: Six patients (four men, two women, median age 42.3 ± 4.7 years) were restored with a total of 40 adhesively luted anterior full veneers (maxilla: 36; mandible: 6; mostly canine to canine) made of lithium disilicate ceramic. Patients were treated between July 2007 and January 2014. All restorations were examined during annual recall visits using the modified United States Public Health Service criteria for color match, marginal discoloration, secondary caries, marginal integrity, surface texture, and restoration fracture, rated as Alpha, Bravo, or Charlie. Data were statistically analyzed using Kaplan-Meier estimation with log-rank test.

Results: Time of clinical service was 68 to 139 months (median: 8.1 ± 2.0 years) without any dropouts. Full veneer restorations in the anterior dentition presented a survival rate of 100% and a complication rate of 12.5% due to reparable minor chippings (technical complication/restoration fracture rated Bravo) of four restorations (one after 11 months, one after 20 months, and two after 66 months) and a crack in one restoration (after 38 months) due to trauma. No further technical (debonding or discoloration) or biologic (secondary caries) complications occurred.

Conclusion: Based on the present results, minimally invasive anterior full veneer restorations might be considered as a reliable treatment option, but further clinical data are essential.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.11607/ijp.6465DOI Listing
December 2019

Influence of speed sintering on the fit and fracture strength of 3-unit monolithic zirconia fixed partial dentures.

J Prosthet Dent 2020 Sep 25;124(3):380-386. Epub 2019 Nov 25.

Assistant Professor, Department of Prosthetic Dentistry, University Hospital, Ludwig Maximilian University of Munich, Munich, Germany. Electronic address:

Statement Of Problem: Speed sintering has been introduced to enable single-visit monolithic zirconia prostheses. However, the fit and fracture load of zirconia 3-unit monolithic fixed partial dentures (FPDs) after speed sintering are unknown.

Purpose: The purpose of this in vitro study was to test the properties of zirconia 3-unit monolithic FPDs after speed sintering and to compare the properties with conventional sintering.

Material And Methods: A calibrated operator digitized an in vitro model with a complete coverage preparation of a maxillary right second premolar and second molar (n=12) by using the CEREC AC Omnicam (Dentsply Sirona) scanner. Twelve zirconia FPDs were designed (CEREC SW 4.1.1), and for each data set (n=12), 1 FPD was designed and milled 4 times (MCXL Premium; CEREC Zirconia; Dentsply Sirona), resulting in 4 identical monolithic FPDs (N=48). The FPDs were divided into 2 groups according to the sintering procedure (n=24): speed sintering (group S) by using the SpeedFire (Dentsply Sirona) and the conventional sintering (group C) by using the inFire HTC speed (Dentsply Sirona). All the FPDs were glazed by using glaze-spray and fired according to the sintering group. The SpeedFire (Dentsply Sirona) was used for group S, and the VACUMAT 6000M (VITA Zahnfabrik) was used for group C. The fit of the FPDs was evaluated with the replica technique by using polyvinyl siloxane and analyzed according to the measurement areas: marginal gap, chamfer area, axial wall, and occlusal area. Subsequently, groups S and C were further subdivided, and 12 specimens per group underwent artificial aging by thermomechanical loading in a mastication machine (50 N for 1.2×10 times at a frequency of 1.7 Hz and a thermal change in distilled water from 5 °C to 50 °C every 120 seconds), resulting in additional subgroups: group SA and group CA. For all the FPDs (groups S, C, SA, and CA), a fracture load measurement was conducted. The Kolmogorov-Smirnov test was used to examine the values of the fit and fracture load for normal distribution. The Mann-Whitney U test for the fit and a 2-way ANOVA for the fracture load were used to detect the differences among the groups (α=.05).

Results: Group S showed a better marginal (P=.018) and occlusal (P<.001) fit than group C. For the fracture load values, no significant difference was found because of the sintering procedure (P=.070) or the interaction of the sintering procedure and artificial aging (P=.484). Artificial aging showed an impact (P=.024) with significantly lower values after aging.

Conclusions: Speed-sintered FPDs had equal and better values for the fit and fracture load than conventional sintering.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.prosdent.2019.09.003DOI Listing
September 2020

Mechanical stability of all-ceramic abutments retained with three different screw materials in two-piece zirconia implants-an in vitro study.

Clin Oral Investig 2020 May 3;24(5):1801-1806. Epub 2019 Sep 3.

Department of Prosthodontics, University of Munich, Goethestr 70, 80336, Munich, Germany.

Objectives: To measure the abutment rotation and fracture load of two-piece zirconia implants screwed with three different abutment screw materials.

Material And Methods: Thirty-six zirconia implants with 36 zirconia abutments were distributed into 3 test groups: group G connected with gold screws, group T with titanium screws, and group P with peek screws. In the first part of the study, the rotation angle of the abutments was measured. The second part of the study measured the maximum fracture force of adhesively bonded lithium disilicate crowns after artificial aging and fracture modes were reported.

Results: In group G, the median rotation angle was 8.0°, in group T 11.6°, and in group P 9.5°. After artificial aging, no screw loosening, crown, abutment, or implant fracture occurred. The median fracture force in group G was 250 N, in group T 263 N, and in group P 196 N.

Conclusions: Rotation angles and fracture loads of two-piece zirconia implants with gold, titanium, or peek screws showed no significant differences; however, fracture loads showed inferior results for group P.

Clinical Relevance: The indication for the material peek as an abutment screw is still questionable and should be considered carefully.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-019-03043-3DOI Listing
May 2020

Digital impressions in dentistry-accuracy of impression digitalisation by desktop scanners.

Clin Oral Investig 2020 Mar 13;24(3):1249-1257. Epub 2019 Jul 13.

Department of Prosthetic Dentistry, University Hospital of the LMU Munich, Goethestraße 70, 80336, Munich, Germany.

Objectives: To test if the partially digital workflow by digitalisation of the impression reveals a comparable accuracy as the indirect digitalisation of the gypsum cast for 4-unit fixed dental prostheses (FDPs).

Materials And Methods: A titanium model with a tapered full veneer preparation of a molar and premolar was used as analysis model. To receive a virtual three-dimensional reference dataset (REF), it was digitised by industrial computed tomography. Three impression materials were used with individual impression trays (N = 36, n/material = 12): (1) PE (Impregum Penta), (2) PVS-I (Imprint 4 Penta: Super Quick Heavy plus Super Quick Light), and (3) PVS-D (Dimension Penta: H Quick plus L). For partially digital workflow (group IMP), two desktop scanners were used: (1) D810 (3Shape D810) and (2) ZZ (Zirkonzahn S600ARTI). For indirect digitalisation (group CAST), gypsum master casts were manufactured and digitalised using the same desktop scanners. Virtual datasets were superimposed by best fit algorithm, and accuracy was analysed by calculating the Euclidean distances (ED) to the REF (Geomagic Qualify). Statistic was determined (Kruskal-Wallis H test, Mann-Whitney U post hoc analysis, two-sample Kolmogorov-Smirnov test, p < 0.05).

Results: ZZ showed for positive deviations superior accuracy for IMP than for CAST. PE and PVS-I showed superior accuracy than PVS-D. D810 showed partially significant better performance with PVS-I and PVS-D than ZZ.

Conclusions: The partially digital workflow by digitalisation of the impression can be used for clinical indications of small-span fixed dental prostheses. However, for this indication, the impression material and the desktop scanner are more decisive for the accuracy of virtual model datasets.

Clinical Relevance: Despite the rapid advancement of the computer-aided technology for dental therapy purposes, the implementation of this technique is not as fast as the technical development. In order to combine the well-established procedure to use elastomeric materials for a conventional impression and to avoid the drawbacks of casting it by gypsum, the digitalisation of the impression itself by a desktop scanner may be a logical procedure as an access point to the digital workflow. However, there is only limited information about the accuracy of this partially digital workflow by the digitalisation of modern impression materials in comparison to the well-known process of indirect digitalisation of gypsum casts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-019-02995-wDOI Listing
March 2020

Residual monomer elution from different conventional and CAD/CAM dental polymers during artificial aging.

Clin Oral Investig 2020 Jan 16;24(1):277-284. Epub 2019 May 16.

Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336, Munich, Germany.

Objectives: Analyze and quantify the residual monomer elution of nine conventional and CAD/CAM (computer-aided design/computer-aided manufacturing) dental polymers during artificial aging.

Materials And Methods: A total of 360 square-shaped specimens (14 × 12 × 2 ± 0.05 mm) were fabricated from eight CAD/CAM polymer blanks (n = 40): Avadent Base material, Avadent Teeth material, PMMA Multi blank, PMMA Mono blank, Temp Premium, Telio CAD, Ceramill Temp, Shofu Block HC, and conventional polymer PalaXpress. Specimens were aged in distilled water for 60 days at 37 °C and the evaluation of the residual monomer elution was made through UV spectrophotometry. Statistical analysis was carried out in the SPSS software. One-way ANOVA and Scheffé post hoc test were applied (α < 0.05).

Results: Aging time significantly changed the elution in all groups, except for PalaXpress. Statistically significant differences of elution were found between the materials. Shofu Block HC presented the highest, whereas PMMA Multi blank A3 and Mono blank A1 presented the lowest elution after the 60th day of aging.

Conclusions: CAD/CAM dental polymers as well as the conventional polymer PalaXpress eluted residual monomer within aging time. The differences in elution were material-dependent; still, the maximum elution found is below the specified threshold of ISO standard 20795-1.

Clinical Relevance: With the evolution of CAD/CAM technology, material's manufacturers have invested in the development of polymeric materials with higher resistance and stability to produce indirect restorations using CAD/CAM. It is expected that these materials present lower elution of residual monomer than conventional polymers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-019-02947-4DOI Listing
January 2020

Can lithium disilicate ceramic crowns be fabricated on the basis of CBCT data?

Clin Oral Investig 2019 Oct 6;23(10):3739-3748. Epub 2019 Feb 6.

Department of Prosthodontics, University Hospital, LMU, Munich, Germany.

Objectives: Evaluating the fit of CAD/CAM lithium disilicate ceramic crowns fabricated on basis of direct and indirect digitalization of impressions by CBCT or of dental casts.

Material And Methods: A metal model with a molar chamfer preparation was digitized (n = 12 per group) in four ways: IOS-direct digitalization using an Intra-Oral scanner (CS3600), cone-beam computed tomography scan (CBCT 1)-indirect digitalization of impression (CBCT-CS9300), CBCT 2-indirect digitalization of impression (CBCT-CS8100), and Extra-Oral scanner (EOS)-indirect digitalization of gypsum-cast (CeramillMap400). Accuracy of 3D datasets was evaluated in relation to a reference dataset by best-fit superimposition. Marginal fit of lithium disilicate crowns after grinding was evaluated by replica technique. Significant differences were detected for 3D accuracy by Mann-Whitney U and for fit of crowns by One-way ANOVA followed by Scheffe's post hoc (p = 0.05).

Results: 3D analysis revealed mean positive and negative deviations for the groups IOS (- 0.011 ± 0.007 mm/0.010 ± 0.003 mm), CBCT 1 (- 0.046 ± 0.008 mm/0.093 ± 0.004 mm), CBCT 2 (- 0.049 ± 0.030 mm/0.072 ± 0.015 mm), and EOS (- 0.023 ± 0.007 mm/0.028 ± 0.007 mm). Marginal fit presented the results IOS (0.056 ± 0.022 mm), CBCT 1 (0.096 ± 0.034 mm), CBCT 2 (0.068 ± 0,026 mm), and EOS (0.051 ± 0.017 mm).

Conclusions: The marginal fit of EOS and IOS, IOS and CBCT 2, and CBCT 2 and CBCT 1 showed statistical differences. The marginal fit of CBCT 1 and CBCT 2 is within the range of clinical acceptance; however, it is significant inferior to EOS and IOS.

Clinical Relevance: The use of a CBCT enables clinicians to digitize conventional impressions. Despite presenting results within clinical acceptable levels, the CBCT base method seems to be inferior to Intra-Oral scans or to scanning gypsum models regarding the resulting accuracy and fit.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-019-02802-6DOI Listing
October 2019

Computable translucency as a function of thickness in a multi-layered zirconia.

J Prosthet Dent 2019 Apr 4;121(4):683-689. Epub 2018 Dec 4.

CDT, Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany.

Statement Of Problem: Determining the relationship between variable thicknesses and the translucency of dental ceramics is essential for optimizing esthetics in different clinical situations.

Purpose: The purpose of this in vitro study was to analyze the relationship between layer thickness and translucency of 2 multi-layered monolithic zirconia materials and to develop an equation by which the grade of translucency can be calculated dependent on the materials' layer thicknesses in advance.

Material And Methods: Two semisintered multi-layered zirconia blanks, namely KATANA Zirconia Super Translucent Multi-Layered Disk (Noritake Dental Supply Co, Ltd) and Zirconia Ultra Translucent Multi-Layered Disk (UTML) (Noritake Dental Supply Co, Ltd), were sectioned (N=96) to separate the 4 layers (n=12 per layer): enamel layer, transition layer 1, transition layer 2, body layer. All specimens were sintered in a furnace (M2 Plus; Thermo-Star) at 1500°C for 2 hours and automatically polished under water cooling up to P2400 for the thicknesses of 1.6, 1.3, 1.0, 0.7, and 0.4 mm. Transmittance of visible light was measured using a spectrophotometer (Lambda 35; Perkin Elmer). Data were analyzed using the Kolmogorov-Smirnov, 2-way ANOVA, and Scheffé post hoc tests (α=.01) and curve fitting.

Results: Analyzing the fitting of the values of the 8 material groups to the linear, exponential, and logarithmic curves, 7 of the 8 groups (not UTML body layer) fitted the most (R-square value closer to 1.0) to the logarithmic curve. Constants were obtained from the distance to the x-axis and the curvature.

Conclusions: The methodology of this study provided the materials' specific constants a and b by analyzing the translucency behavior of KATANA Super Translucent Multi-Layered Disk and Ultra Translucent Multi-Layered Disk in different thicknesses, allowing further translucency calculation by applying the developed formula and the constants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.prosdent.2018.08.013DOI Listing
April 2019

Retentive force of PEEK secondary crowns on zirconia primary crowns over time.

Clin Oral Investig 2019 May 6;23(5):2331-2338. Epub 2018 Oct 6.

Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany.

Objectives: The purpose of the present study was to evaluate the retentive forces of CAD/CAM-fabricated polyetheretherketone (PEEK) secondary crowns on zirconia primary crowns over an artificial aging period representing 10 years of clinical service and compare them to electroformed secondary crowns made from pure gold.

Material And Methods: Implant-supported zirconia primary crowns (N = 20) were CAD/CAM milled and provided either with electroformed secondary crowns (group ZE; N = 10) or CAD/CAM-fabricated PEEK secondary crowns (group ZP; N = 10). All secondary crowns were attached to a casted tertiary structure to ensure adequate stability. A universal testing machine was used to determine the retentive force values at baseline and after 1, 3, 5, and 10 years of simulated aging in the presence of artificial saliva. Data were analyzed applying Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U test. Level of significance was set at p < 0.05.

Results: Retentive forces were not different for the groups ZE and ZP at baseline (median ZE 2.85 N; ZP 2.8 N; p ≤ 0.218). Because retentive force values changed significantly over simulation time for group ZE (Kruskal-Wallis; p ≤ 0.028), the values between the test groups ZE and ZP differed significantly (Mann-Whitney U) at 5 years (ZE 3.03 N; ZP 2.76 N; p ≤ 0.003) and 10 years (ZE 3.1 N; ZP 2.78 N; p ≤ 0.011).

Conclusions: PEEK secondary crowns exhibit stable retentive force values over 10 years of simulated aging showing no signs of deterioration while the retentive force values of electroformed secondary crowns increase over time.

Clinical Relevance: PEEK might be a suitable alternative to proven metallic materials for the fabrication of secondary crowns.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-018-2657-xDOI Listing
May 2019

Marginal adaptation of lithium disilicate ceramic crowns cemented with three different resin cements.

Clin Oral Investig 2019 Jan 17;23(1):315-320. Epub 2018 Apr 17.

Department of Prosthodontics, Gerodontology and Craniomandibular Disorders, Charité - Universitätsmedizin Berlin, CC3, Berlin, Germany.

Objectives: The cementation process and cementation materials have an influence on the marginal adaptation of restorations. The gap could be affected by thermal and mechanical loading (TCML). The computerized x-ray microtomography (μCT) method offers the possibility of measuring the marginal gap without destruction of the restoration. The aim of this study was to evaluate the marginal gap (MG) and the absolute marginal discrepancy (AMD) before and after TCML.

Materials And Methods: Thirty-nine human premolars were prepared for full ceramic crowns made of lithium disilicate. The crowns were cemented by three different resins-Panavia F 2.0, Variolink II, and Relyx Unicem. The MG and AMD were evaluated by μCT before and after TCML.

Results: Panavia F 2.0 had the lowest MG (before 118 μm-after TMCL 124 μm) and AMD (before 145 μm-after TMCL 154 μm), followed by Relyx Unicem (MG: before 164 μm-after TCML 155 μm; AMD: before 213 μm-after TMCL 209 μm) and Variolink II (MG: before 317 μm-after TMCL 320 μm; AMD: before 412 μm-after TMCL 406 μm). The differences were statistically significant before and after TCML. Rather than TCML, it appeared the resin cement was responsible for differences between the MG and AMD before and after TCML.

Conclusions: μCT is an accurate technique for assessing cemented restorations. Panavia F 2.0 has the lowest MG and AMD before and after TCML.

Clinical Relevance: The resin material that features a three-step protocol (Variolink II) produced higher MG and AMG values than the Panavia or Relyx Unicem varieties with less or no intermediate steps at all.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-018-2438-6DOI Listing
January 2019

Load bearing capacity, fracture mode, and wear performance of digitally veneered full-ceramic single crowns.

Int J Comput Dent 2017;20(3):245-262

Objectives: Computer-aided technologies can help to minimize clinical complications of zirconia-based restorations such as veneering porcelain fractures. The aim of this study was to evaluate different veneering approaches for zirconia single crowns regarding contact wear, fracture strength, and failure mode.

Methods: Six different types of computer-aided design (CAD) crowns were manufactured and conventionally cemented on 10 metal dies each: three groups with a zirconia framework and a CAD/CAM-fabricated veneering cap ("digital veneering system": DVS, CAD-on, Infix CAD), zirconia-based crowns with pressed veneering caps (Infix Press), zirconia framework containing the dentin layer with only the incisal enamel material added (dentin-core), and conventional substructure with powder buildup veneering porcelain (layering technique). All specimens were submitted to artificial aging (120,000 mechanical cycles, 50 N load, 0.7-mm sliding movement, 320 thermocycles). After contact wear was measured with a laser scanning system, fracture resistance and failure mode were examined using a universal testing machine and a scanning electron microscope. Statistical analysis was performed at a significance level of 5%.

Results: No statistical difference was revealed regarding the contact wear of the restorations (P = 0.171; ANOVA). No significant difference was found regarding the fracture resistance of the crowns (P = 0.112; ANOVA). Failure analysis revealed three different failure patterns: cohesive veneering fracture, adhesive delamination, and total fracture, with a characteristic distribution between the groups.

Significance: All tested specimens survived artificial aging and exhibited clinically acceptable wear resistance and fracture resistance. Digital veneering techniques offer a promising, time- and cost-effective manufacturing process for all-ceramic restorations and may usefully complement the digital workflow.
View Article and Find Full Text PDF

Download full-text PDF

Source
November 2017

Mechanical performance of cement- and screw-retained all-ceramic single crowns on dental implants.

Clin Oral Investig 2018 Mar 15;22(2):981-991. Epub 2017 Jul 15.

Department of Prosthodontics, Charité University Medicine Berlin, Assmannshauserstr. 4-6, 14197, Berlin, Germany.

Objectives: This in-vitro study was performed to compare the contact wear, fracture strength and failure mode of implant-supported all-ceramic single crowns manufactured with various fabrication and fixation concepts.

Materials And Methods: Fifty dental implants (Conelog Ø 4,3mm/L11mm, Camlog Biotechnologies AG) were embedded and treated with all-ceramic molar single-crowns. Three groups received hand-layered zirconia crowns (IPS e.max Ceram/ IPS e.max ZirCAD, Ivoclar Vivadent AG): CZL (cement-retained zirconia-based layered) group crowns were cemented conventionally, SZL (screw-retained zirconia-based layered) group crowns were screw-retained, MZL (modified zirconia-based layered) group crowns showed a different coping design with screw retention. The specimens of SST (screw-retained sintering-technique) and SFL (screw-retained full-contour lithium-disilicate) group were CAD/CAM (Computer-aided design/computer-aided manufacturing) fabricated in the sintering technique (IPS e.max ZirCAD/IPS e.max CAD, Ivoclar Vivadent AG) and full-contour of lithium disilicate (IPS e.max CAD, Ivoclar Vivadent AG) respectively and screw-retained. All specimens underwent artificial aging, load until failure and a scanning electron microscopy (SEM) analysis. The received data were statistically compared (one-way ANOVA; Student-Newman-Keuls test; Mann-Whitney U-test) at a significance level of 5%.

Results: Mouth-motion fatigue testing caused two abutment fractures (SST group and SZL group) and two chipping events (CZL group). Specimens of MZL group showed statistically significant less contact wear compared to the other groups (p<0.001). There was no statistical difference between the groups in terms of the maximum fracture load. SEM-analysis showed a more homogenous structure and surface of CAD/CAM fabricated specimens towards manually veneered components.

Conclusions: The mode of retention did not influence the fracture resistance but the failure patterns of the specimens. CAD/CAM milled lithium-disilicate crowns seemed to be a preserving factor for dental implants.

Clinical Relevance: The mode of retention and veneering influences the mechanical performance of implant-supported single crowns.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-017-2178-zDOI Listing
March 2018

Fracture resistance of different implant abutments supporting 
all-ceramic single crowns after aging.

Int J Comput Dent 2017;20(1):53-64

Objective: To test the mechanical properties of three different restorative materials for implant abutments supporting all-ceramic single crowns.

Materials And Methods: Thirty implants with butt-joint connections were distributed into three test groups: Group A with 10 one-piece zirconia abutments, Group U with 10 titanium abutments, and Group T with 10 titanium-zirconia hybrid abutments. Monolithic zirconia single crowns were cemented and artificially aged. The crowns were loaded at a 30-degree angle in a universal testing machine until fracture or bending. Additionally, after removal of the restorations, the implant-abutment interface of the fixtures was inspected using a scanning electron microscope (SEM).

Results: In Group A, the abutments failed on average at 336.78 N, in Group U at 1000.12 N, and in Group T at 1296.55 N. The mean values between Groups T and U (P = 0.009), and between Group A and Groups T and U (P < 0.001) were significantly different. The abutments in Group A failed early due to fractures of the internal parts and parts close to the implant neck. In Groups T and U, failures occurred due to bending of the implant neck.

Conclusion: This experimental study proves that hybrid and titanium abutments have similar mechanical properties. One-piece abutments made of zirconia showed significantly lower fracture resistance.
View Article and Find Full Text PDF

Download full-text PDF

Source
June 2017

Accuracy and reproducibility of four cone beam computed tomography devices using 3D implant-planning software.

Int J Comput Dent 2017;20(1):21-34

Objective: To measure the deviations of four different cone beam computed tomography (CBCT) devices in three dimensions by means of a three-dimensional (3D) implant-planning program.

Materials And Methods: A master radiographic template with two vertical, two transverse, and two sagittal radiopaque markers was fabricated for a human dry skull. The lengths of the markers were measured with a high-precision caliper. The skull and the template were scanned in each of the four CBCT devices (1. Gendex GXCB-500; 2. Sirona Galileos Comfort; 3. Sirona Orthophos XG 3D; 4. Carestream CS 9300) 19 times (10 scans without moving the skull, and 9 scans with repeated repositioning of the skull in the device, according to the manufacturers' instructions). A 3D implant-planning program was used to measure the lengths of the six markers digitally. Actual and digital measurements were compared to determine device-specific errors. The repositioning of the skull examined the reproducibility of the CBCT devices. Linear measurements were analyzed statistically (P < 0.05).

Results: Mean deviations without moving the skull (vertical/sagittal/transverse) for device 1 were 0.023 mm/
0.000 mm/0.025 mm (0.07%/0.19%/0.24%), for device 2 were 0.410 mm/0.115 mm/0.080 mm (-1.75%/0.32%/
0.88%), for device 3 were -0.665 mm/-0.215 mm/
-0.675 mm (-2.71%/-1.82%/-4.42%), and for device 4 were -0.045 mm/-0.135 mm/-0.410 mm (-0.45%/
-1.54%/-2.57%). The overall mean deviation for device 1 was 0.028 mm (0.16%), for device 2 was 0.072 mm (-0.95%), for device 3 was 0.518 mm (-2.97%), and for device 4 was -0.197 mm (-1.53%). The mean deviation after repositioning for device 1 was 0.004 mm (-0.65%), for device 2 was -0.250 mm (0.95%), for device 3 was 0.496 mm (-2.66%), and for device 4 was -0.265 mm (-1.92%). Thus, apart from device 3, the deviations increased.

Conclusion: Deviations from the actual measurements were detected with each device. Therefore, respecting safety distances when placing implants is crucial.
View Article and Find Full Text PDF

Download full-text PDF

Source
June 2017

Accuracy and mechanical performance of passivated and conventional fabricated 3-unit fixed dental prosthesis on multi-unit abutments.

J Prosthodont Res 2017 10 7;61(4):403-411. Epub 2017 Feb 7.

University of Munich, Department of Prosthodontics, Goethestr. 70, 80336 Munich, Germany.

Purpose: The aim of this study was to evaluate the fit and mechanical stability of conventional versus passive fitting 3-unit fixed dental prosthesis (FDP) screw-retained on implants.

Methods: Twenty acrylic models, each with two embedded implants, were fabricated and functioned as patient-models. Impressions were taken and 20 all-ceramic FDPs were pre-fabricated on the plaster casts. Respectively 10 FDPs were fixed on the plaster casts (group 1) and on the patient-models for passive fitting (group 2). The fit of each FDP was checked on the patient-model by means of visual control (grades 1-10) and microscopic examination. Furthermore, specimens were artificially aged for possible prosthodontic failures, followed by a fracture strength test.

Results: Group 2 [1.4 (±0.3)] showed significantly (p<0.001) better results in the visual examination of the marginal fit compared to group 1 [6.3 (±2.4)]. The microscopic marginal misfit was 160μm (±80μm) at the abutment margin and 150μm (±80μm) at the axial wall of the abutment for group 1, respectively, 0μm and 0μm up to 17μm for group 2 (p<0.001). No failure of the FDPs could be observed during artificial aging in both groups. The fracture load showed no significant difference (p=0.60) between group 1 [2583N (±664N)] and group 2 [2465N (±238N)].

Conclusions: Visual and microscopic examination detected huge differences in marginal fit between groups 1 and 2. However, no statistically verifiable differences could be detected in long-term stability of implant-supported FDPs irrespective of the fit.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jpor.2016.12.011DOI Listing
October 2017

Fit of 4-unit FDPs from CoCr and zirconia after conventional and digital impressions.

Clin Oral Investig 2016 Mar 30;20(2):283-9. Epub 2015 Jun 30.

Department of Prosthodontics, Dental School of the Ludwig-Maximilian University of Munich, Goethestrasse 70, 80336, München, Germany.

Objectives: To evaluate the marginal and internal fit of CAD/CAM-generated frameworks for 4-unit, fixed dental prostheses (FDPs) from zirconia (Z) and cobalt-chromium alloy (C) made with conventional (CI) and digital impressions (DI).

Materials And Methods: A titanium model was digitized with an intraoral scanner (DI, LAVA™ C.O.S.; 3M ESPE; Seefeld, Germany; n = 12). Additionally, 12 conventional impressions were taken, and referring plaster casts were digitized by a laboratory-scanner (CI, LAVA™ Scan ST; 3M ESPE; n = 12). Frameworks were fabricated (3M ESPE) from cobalt-chromium (DI-C, n = 12; CI-C, n = 12) and zirconia (DI-Z, n = 12; CI-Z, n = 12) from the same datasets. A replica technique was applied to measure the accuracy. The Mann-Whitney U statistical test was applied to detect statistical differences between each material and methodology groups in terms of fit.

Results: Frameworks from DI-C (median 19.07 μm) showed significantly better marginal fit than CI-C (median 64.64 μm, p < 0.001). Frameworks from DI-Z (median 52.50 μm) showed significantly better marginal fit than CI-Z (median 72.94 μm, p = 0.001). Additionally, frameworks from DI-C showed a significantly better marginal fit than DI-Z (p < 0.001).

Conclusions: CI and DI led to a clinically acceptable marginal fit of 4-unit FDPs from cobalt-chromium and zirconia. DI leads to better marginal fit of the cobalt-chromium frameworks; however, no effect on zirconia was found.

Clinical Relevance: The results indicate that DI is suitable for fabricating 4-unit, cobalt-chromium and zirconia frameworks with regard to fit requirements.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-015-1513-5DOI Listing
March 2016

Light transmittance by a multi-coloured zirconia material.

Dent Mater J 2015 23;34(3):310-4. Epub 2015 Apr 23.

Comprehensive Dental Care, Oral Implant Center, Niigata Hospital, Nippon Dental University.

Full-contour zirconia restorations are gaining in popularity. Highly translucent zirconia materials and multi-coloured zirconia blocks might help to overcome the aesthetic drawbacks of traditional zirconia. This study evaluated the transmittance of visible light (400-700 nm) through the four different layers (Enamel Layer EL, Transition Layer 1 TL1, Transition Layer 2 TL2, Body Layer BL) of a multi-coloured zirconia block (KATANA™ Zirconia Multi-Layered Disc (ML)) using a spectrophotometer. Forty specimens (thickness of 1±0.05 mm) from each layer were examined and statistically evaluated at a confidence-level of 5%. Light transmittance was expressed as a percentage of the through-passing light. The following mean values (SD) were found: EL 32.8% (1.5), TL1 31.2% (1.3), TL2 25.4% (1.3) and BL 21.7% (1.1). Significant differences were found between all groups (ANOVA, Student-Newman-Keuls). This multi-coloured zirconia block showed four layers with different light transmittance capabilities. It might therefore be useful for enhancing the aesthetic appearance of full-contour zirconia restorations made from this material.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4012/dmj.2014-238DOI Listing
February 2017

Full-arch prostheses from translucent zirconia: accuracy of fit.

Dent Mater 2014 Aug 2;30(8):817-23. Epub 2014 Jun 2.

Department of Prosthodontics, Ludwig-Maximilians University, Munich, Germany. Electronic address:

Objectives: The aim of this study was to evaluate the marginal and internal fit of single crowns, compared to 14-unit frameworks made of translucent yttria-stabilized zirconia. We hypothesized that there is an influence of the type of restoration on the marginal and internal fit.

Methods: Eight teeth (FDI locations 17, 15, 13, 11, 21, 23, 25 and 27) of a typodont maxillary model were provided with a chamfer preparation to accommodate a 14-unit prosthesis or four single crowns (SCs). Ten 14-unit fixed dental prostheses (FDPs) and 40 single crowns were fabricated using a computer aided design (CAD)/computer aided manufacturing (CAM) system with pre-sintered translucent yttria-stabilized zirconia blanks. The restorations were cemented onto twenty master dies, which were sectioned into four pieces each. Then, the marginal and internal fits were examined using a binocular microscope. In order to detect the differences between the two types of restorations a non-parameteric test (Mann-Whitney-U) was carried out; to detect differences between the abutment teeth and the abutment surfaces non-parametric tests (Kruskal-Wallis) and pairwise post hoc analyses (Mann-Whitney-U) were performed after testing data for normal distribution (method according to Shapiro-Wilk). Level of significance was set at 5%.

Results: The mean (SD) marginal opening gap dimensions were 18 μm (14) for the single crowns and 29 μm (27) for the 14-unit FDPs (p<0.001). Abutment 21 of the FDPs showed statistical differences concerning the location of the teeth in both marginal and internal fit (p<0.001). The measured gaps (types I-IV) revealed statistical differences between all types, when comparing SCs to the FDPs (p<0.001).

Significance: Single crowns showed significantly better accuracy of fit, compared to the 14-unit FDPs. However, both restorations showed clinically acceptable marginal and internal fit.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.dental.2014.05.001DOI Listing
August 2014

Retention forces of 14-unit zirconia telescopic prostheses with six double crowns made from zirconia--an in vitro study.

Clin Oral Investig 2014 May 21;18(4):1173-1179. Epub 2013 Aug 21.

Department of Prosthodontics, Ludwig-Maximilians University, Goethestraße 70, 80336, Munich, Germany.

Objectives: The aim of this study was to evaluate the retention forces (RFs) of zirconia double-crown systems, with primary and secondary crowns made from zirconia in vitro.

Materials And Methods: Ten maxillary models with six abutment teeth were prepared. Sixty inner crowns were fabricated from pre-sintered zirconia with a taper of 0°. Ten 14-unit telescopic prostheses (removable partial dentures, RDPs) were fabricated, using the same computer-aided design/computer-aided manufacturing system as that used for the inner crowns. The removal test was performed in a standardized setup using a universal testing device at a crosshead speed of 10 mm/min. Ten separation cycles were carried out for each single primary crown as well as for each 14-unit RDP in the presence of artificial saliva. The results were imported into a statistic program and analysed by a one-way ANOVA and post hoc tests. The level of significance was set at 5 %.

Results: The mean RFs of the single double-crown systems were in the range of 0.611-2.895 N, whereas the RFs for the whole RDP varied between 8.1 and 13.6 N. RF was dependent on the abutment tooth (p < 0.001) and on the model (p < 0.001).

Conclusions: The results of this study indicate that the manufacturing of full-zirconia double-crown systems is possible as well as reproducible. The RFs are comparable to those reported from casted and electroformed double-crown systems.

Clinical Relevance: It has been shown that the RFs of the presented telescopic system are comparable to existing double-crown systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-013-1093-1DOI Listing
May 2014

Marginal and internal fit of four-unit zirconia fixed dental prostheses based on digital and conventional impression techniques.

Clin Oral Investig 2014 29;18(2):515-23. Epub 2013 May 29.

Department of Operative Dentistry, Federal University of Santa Catarina, Av. Universitária Qd. 60, Lt. 08. Residencial Macedônia, Torre 1, apt. 1004, Santa Isabel, Anapólis, Goiás, Brazil, 75083350,

Objectives: The aim of this in vitro study was to evaluate the marginal and internal fit of CAD/CAM-generated four-unit zirconia fixed dental prostheses made with digital and conventional impressions.

Materials And Method: A titanium master model was used. For group conventional impression (CI), 12 polyether impressions of the master model with Impregum(TM) were made. For group digital impression (DI), 12 digital impressions of the master model using Lava(TM) C.O.S. system were made. The replica technique was applied. The Mann-Whitney U statistical test was applied to detect statistical differences between the groups, in terms of marginal and internal fit. Face-by-face comparisons between groups were also carried out.

Results: Groups DI and CI presented mean marginal fit of 63.96 and 65.33 μm, respectively, and showed no statistically significant difference. Groups DI and CI presented significantly different internal fit with mean values of 58.46 and 65.94 μm, respectively. Group DI showed statistically significantly lower values for marginal and internal fit on premolar mesial face, and on molar distal and palatal faces.

Conclusions: Frameworks fabricated from digital and conventional impressions showed clinically acceptable marginal fit. Frameworks fabricated from digital impression demonstrated better internal fit than ones fabricated from conventional impression. Reviewing each retainer face, digital impression showed better marginal and internal fit at the premolar mesial and molar distal faces.

Clinical Relevance: The results of this in vitro study show that digital impressions made with the Lava(TM) C.O.S. system and its digital workflow are suitable for fabricating four-unit zirconia frameworks, with regard to marginal and internal fit requirements.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-013-0987-2DOI Listing
December 2015

Retentive strength of two-piece CAD/CAM zirconia implant abutments.

Clin Implant Dent Relat Res 2014 Dec 25;16(6):920-5. Epub 2013 Mar 25.

Ludwigshafen, Germany.

Purpose: The purpose of this study is to evaluate the retention of two-piece computer-aided design (CAD)/computer aided manufacturing (CAM) zirconia abutments after artificial aging under simulated oral conditions using three different types of resin-based luting agents.

Material And Methods: Twenty-one CAD/CAM-generated zirconia copings (CERCON Compartis, Degudent, Hanau, Germany) were bonded to a prefabricated secondary titanium implant insert (XiVE Ti-Base, Dentsply Friadent, Mannheim, Germany), using three different types of resin-based luting agents: group A: Panavia 21 (Kuraray Co, Kurashiki, Japan); group B: Multilink Implant (Ivoclar Vivadent, Schaan, Liechtenstein); and group C: SmartCem2 (Dentsply DeTrey, Konstanz, Germany). The bonding surfaces of the titanium inserts and the zirconia ceramic copings were air-abraded and cleaned in alcohol. All specimens were stored in distilled water for 60 days and subsequently thermal-cycled 15,000 times (5-55 °C). The dislodging force of the copings along the long axis of the implant/abutment complex was recorded using a universal testing machine with 2 mm/min crosshead speed. Data were analyzed descriptively and by performing the Kruskal-Wallis test.

Results: The mean retention values were 924.93 ± 363.31 N for Panavia 21, 878.05 ± 208.33 N for Multilink Implant, and 650.77 ± 174.92 N for SmartCem2. The Kruskal-Wallis test indicated no significant difference between the retention values of the tested luting agents (p = 0.1314). The failure modes of all tested two-piece abutments were completely adhesive, leaving the detached zirconia coping and titanium insert undamaged.

Conclusion: The use of resin-based luting agents in combination with air abrasion of titanium inserts and zirconia copings led to a stable retention of two-piece CAD/CAM abutments. The bonding stability of the investigated luting agents exceeded the general limits of fracture resistance of two-piece zirconia abutments. A notable difference between the mean retention values of the tested bond materials was shown. However, the statistical analysis revealed that this difference was not significant.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/cid.12060DOI Listing
December 2014

In vitro fatigue and fracture strength testing of one-piece zirconia implant abutments and zirconia implant abutments connected to titanium cores.

Int J Oral Maxillofac Implants 2013 Mar-Apr;28(2):488-93

University of Munich, Department of Prosthodontics, Munich, Germany.

Purpose: The purpose of this study was to determine the fatigue and fracture strength of zirconia implant abutments connected to titanium cores (ZrTi) and one-piece zirconia implant abutments (Zr).

Materials And Methods: Thirty-two implants were secured into epoxy resin blocks and connected with abutments. Eight specimens of each group (Zr with a diameter of 3.75 mm [Zr3.75] or 5.5 mm [Zr5.5] and ZrTi with a diameter of 3.75 mm [ZrTi3.75] or 5.5 mm [ZrTi5.5]) were thermally cycled from 5°C to 55°C and loaded with 100,000 cycles at 120 N at 30 degrees off-axis. All specimens were then tested for fracture resistance using a compressive load at 30 degrees off-axis.

Results: Abutment fracture or screw loosening was not observed during thermal cycling and cyclic loading. The median fracture resistance values and standard deviations were 526 N (± 32 N) for group Zr3.75, 1,241 N (± 269 N) for group ZrTi3.75, 1,894 N (± 137 N) for group Zr5.5, and 2,225 N (± 63 N) for group ZrTi5.5. Statistically significant differences in fracture strength were found between Zr and ZrTi for each implant diameter.

Conclusions: Zirconia implant abutments connected to titanium cores showed higher fracture strength compared to one-piece zirconia abutments. Hence, they might be preferable for clinical use.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.11607/jomi.2772DOI Listing
February 2014

Clinical study evaluating the discrepancy of two different impression techniques of four implants in an edentulous jaw.

Clin Oral Investig 2013 Nov 6;17(8):1929-35. Epub 2012 Dec 6.

Private Practice for Oral Surgery, Josef-Heilingbrunnerstrasse 2, 93413, Cham, Germany,

Objectives: Precise implant-supported prosthodontics requires accurate impressions. Many in vitro studies comparing different implant impression techniques were performed. The purpose of this in vivo study was to compare the discrepancy of two different impression techniques of implants clinically.

Material And Methods: Four implants were inserted nearly bilateral in ten edentulous jaws. From each jaw, two different impressions (A, transfer; B, splinted pick-up) were taken. Respectively two stone casts of each jaw were produced and scan bodies were mounted on the lab analogues to digitize the casts. One scan body of the digitized casts was each superimposed and the deviations of the remaining three scan bodies were measured three dimensionally. The fit of the suprareconstructions was evaluated clinically on both casts and in the mouth.

Results: The mean discrepancy of scan body 2 was 192 μm (±96), 282 μm (±97) for scan body 3, and 366 μm (±114) for scan body 4. The discrepancies between two scan bodies were statistically significant (p ≤ 0.010; ANOVA test). Comparing the data with the span between the scan bodies, a linear regression line could be drawn to show the dependency between the misfit and the length of the span. Clinically, the fit on the cast produced by the splinted pick-up technique was favorable.

Conclusions: The discrepancy between the splinted pick-up impression technique and the transfer technique were in a range with clinical influence.

Clinical Relevance: For better accuracy of implant-supported prosthodontics, the splinted pick-up technique should be used for impressions of four implants evenly spread in edentulous jaws.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-012-0885-zDOI Listing
November 2013