References of "MAINJOT, Amélie"
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See detailInfluence of thermal expansion mismatch on residual stress profile in veneering ceramic layered on zirconia: Measurement by hole-drilling.
Mainjot, Amélie ULg; Najjar, Achref; Jakubowicz-Kohen, Boris D. et al

in Dental materials : official publication of the Academy of Dental Materials (2015)

OBJECTIVES: Mismatch in thermal expansion coefficient between core and veneering ceramic (Deltaalpha=alphacore-alphaveneer, ppm/ degrees C) is reported as a crucial parameter influencing veneer fractures ... [more ▼]

OBJECTIVES: Mismatch in thermal expansion coefficient between core and veneering ceramic (Deltaalpha=alphacore-alphaveneer, ppm/ degrees C) is reported as a crucial parameter influencing veneer fractures with Yttria-tetragonal-zirconia-polycrystal (Y-TZP) prostheses, which still constitutes a misunderstood problem. However, the common positive Deltaalpha concept remains empirical. The objective of this study is to investigate the Deltaalpha dependence of residual stress profiles in veneering ceramic layered on Y-TZP frameworks. METHODS: The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 0.7mm thick Y-TZP framework and a 1.5mm thick veneer layer. 3 commercial and 4 experimental veneering ceramics (n=3 per group) were used to obtain different Deltaalpha varying from -1.3ppm/ degrees C to +3.2ppm/ degrees C, which were determined by dilatometric analyses. RESULTS: Veneer fractures were observed in samples with Deltaalpha>/=+2.3 or </=-0.3ppm/ degrees C. Residual stress profiles measured in other groups showed compressive stresses in the surface, these stresses decreasing with depth and then becoming more compressive again near the interface. Small Deltaalpha variations were shown to induce significant changes in residual stress profiles. Compressive stress near the framework was found to decrease inversely to Deltaalpha. SIGNIFICANCE: Veneer CTE close to Y-TZP (+0.2ppm/ degrees C Deltaalpha) gived the most favorable stress profile. Yet, near the framework, Deltaalpha-induced residual stress varied inversely to predictions. This could be explained by the hypothesis of structural changes occurrence within the Y-TZP surface. Consequently, the optimum Deltaalpha value cannot be determined before understanding Y-TZP's particular behavior when veneered. [less ▲]

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See detailCeramic Materials for Dental Prostheses
MAINJOT, Amélie ULg

in Biomaterials (2014)

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See detailResidual stress profiles in veneering ceramic on Y-TZP, alumina and ZTA frameworks: Measurement by hole-drilling
Fukushima, K. A.; Sadoun, M. J.; Cesar, P. F. et al

in Dental materials (2014), 30(2), 105-111

OBJECTIVES: The residual stress profile developed within the veneering ceramic during the manufacturing process is an important predicting factor in chipping failures, which constitute a well-known ... [more ▼]

OBJECTIVES: The residual stress profile developed within the veneering ceramic during the manufacturing process is an important predicting factor in chipping failures, which constitute a well-known problem with yttria-tetragonal-zirconia polycrystal (Y-TZP) based restorations. The objectives of this study are to measure and to compare the residual stress profile in the veneering ceramic layered on three different polycrystalline ceramic framework materials: Y-TZP, alumina polycrystal (AL) and zirconia toughened alumina (ZTA). METHODS: The stress profile was measured with the hole-drilling method in bilayered disk samples of 19mm diameter with a 0.7mm thick Y-TZP, AL or ZTA framework and a 1.5mm thick layer of the corresponding veneering ceramic. RESULTS: The AL samples exhibited increasing compressive stresses with depth, while compressive stresses switching into interior tensile stresses were measured in Y-TZP samples. ZTA samples exhibited compressive stress at the ceramic surface, decreasing with depth up to 0.6mm from the surface, and then becoming compressive again near the framework. SIGNIFICANCE: Y-TZP samples exhibited a less favorable stress profile than those of AL and ZTA samples. Results support the hypothesis of the occurrence of structural changes within the Y-TZP surface in contact with the veneering ceramic to explain the presence of tensile stresses. Even if the presence of Y-TZP in the alumina matrix seems to negatively affect the residual stress profiles in ZTA samples in comparison with AL samples, the registered profiles remain positive in terms of veneer fracture resistance. [less ▲]

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See detailInfluence of firing time and framework thickness on veneered Y-TZP discs curvature.
Jakubowicz-Kohen, Boris D.; Sadoun, Michael J.; Douillard, Thierry et al

in Dental materials : official publication of the Academy of Dental Materials (2014), 30(2), 242-248

OBJECTIVES: The objective of the present work was to study the curvature of very thinly, veneered Y-TZP discs of different framework thicknesses submitted to different firing times. METHODS: Fifteen 20-mm ... [more ▼]

OBJECTIVES: The objective of the present work was to study the curvature of very thinly, veneered Y-TZP discs of different framework thicknesses submitted to different firing times. METHODS: Fifteen 20-mm-wide Y-TZP discs were produced in three different thicknesses: 0.75, 1, 1.5mm. One disc from each group was left unveneered while the others were layered with a 0.1mm veneering ceramic layer. All discs underwent five firing cycles for a total cumulative firing time of 30min, 1, 2, 5 and 10h at 900 degrees C. The curvature profile was measured using a profilometer after the veneering process and after each firing cycle respectively. A fitted curve was then used to estimate the, curvature radius. The coefficient of thermal expansion (CTE) measurements were taken on veneering, ceramic and Y-TZP beam samples that underwent the same firing schedule. Those data were used to calculate the curvature generated by CTE variations over firing time. RESULTS: All bilayered samples exhibited a curvature that increased over firing time inversely to framework thickness. However non-veneered samples did not exhibit any curvature modification. SIGNIFICANCE: The results of the present study reveal that even a very thin veneer layer (0.1mm) can induce a significant curvature of Y-TZP discs. The dilatometric results showed that Tg and CTE, variations are not sufficient to explain this curvature. A chemical-induced zirconia volume, augmentation located at the framework sub-surface near the interface could explain the sample, curvature and its increase with firing time. [less ▲]

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See detailY-TZP and in-mouth low thermal degradation: a pilot prospective clinical study.
KOENIG, Vinciane ULg; El Mokaddam, F; Wulfman, Claudine et al

Poster (2014)

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See detailThermal mismatch influence on residual stress in veneer on zirconia
MAINJOT, Amélie ULg; Najjar, Achref; Jakubowicz-Kohen, Boris et al

in Dental Materials (2014)

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See detailEchecs des prothèses dentaires et implantaires en zircone: le point sur les facteurs de risque
DUPONT, Nathalie ULg; KOENIG, Vinciane ULg; VAN HEUSDEN, Alain ULg et al

in Revue Médicale de Liège (2014), (hors-série 2014),

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See detailInfluence of firing time and framework thickness on layered Y-TZP discs curvature
Jakubowicz, Boris; MAINJOT, Amélie ULg; Sadoun, Michael

in Dental Materials (2013, December), 29(E25-E26),

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See detailResidual stress in veneering ceramic layered on Y-TZP, alumina, and ZTA polycrystalline ceramics
Fukushima, Karen; Sadoun, Michael; Cesar, Paulo et al

in Dental Materials (2013, December), 29(E10-E11),

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See detailA new in vitro protocol to study HGF/HGK attachment and proliferation on prostheses materials
GRENADE, Charlotte ULg; MAINJOT, Amélie ULg; VAN HEUSDEN, Alain ULg et al

in Dental Materials (2013, December), 29(E15-E16),

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See detailLe point sur l'émaillage de la zircone: aspects cliniques et scientifiques
MAINJOT, Amélie ULg

Conference (2013, January 25)

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See detailClinical risk factors related to failures with zirconia-based restorations: An up to 9-year retrospective study.
Koenig, Vinciane; Vanheusden, Alain ULg; Le Goff, Stephane O. et al

in Journal of dentistry (2013), 41(12), 1164-74

OBJECTIVES: The first objective of this study was to retrospectively evaluate zirconia-based restorations (ZBR). The second was to correlate failures with clinical parameters and to identify and to ... [more ▼]

OBJECTIVES: The first objective of this study was to retrospectively evaluate zirconia-based restorations (ZBR). The second was to correlate failures with clinical parameters and to identify and to analyse chipping failures using fractographic analysis. METHODS: 147 ZBR (tooth- and implant-supported crowns and fixed partial dentures (FPDs)) were evaluated after a mean observation period of 41.5+/-31.8 months. Accessorily, zirconia implant abutments (n=46) were also observed. The technical (USPHS criteria) and the biological outcomes of the ZBR were evaluated. Occlusal risk factors were examined: occlusal relationships, parafunctional habits, and the presence of occlusal nightguard. SEM fractographic analysis was performed using the intra-oral replica technique. RESULTS: The survival rate of crowns and FPDs was 93.2%, the success rate was 81.63% and the 9-year Kaplan-Meier estimated success rate was 52.66%. The chipping rate was 15% and the framework fracture rate was 2.7%. Most fractographic analyses revealed that veneer fractures originated from occlusal surface roughness. Several parameters were shown to significantly influence veneer fracture: the absence of occlusal nightguard (p=0.0048), the presence of a ceramic restoration as an antagonist (p=0.013), the presence of parafunctional activity (p=0.018), and the presence of implants as support (p=0.026). The implant abutments success rate was 100%. CONCLUSIONS: The results of the present study confirm that chipping is the first cause of ZBR failure. They also underline the importance of clinical parameters in regards to the explanation of this complex problem. This issue should be considered in future prospective clinical studies. CLINICAL SIGNIFICANCE: Practitioners can reduce chipping failures by taking into account several risk parameters, such as the presence of a ceramic restoration as an antagonist, the presence of parafunctional activity and the presence of implants as support. The use of an occlusal nightguard can also decrease failure rate. [less ▲]

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See detail3D-Characterization of the veneer-zirconia interface using FIB nano-tomography.
MAINJOT, Amélie ULg; Douillard, Thierry; Gremillard, Laurent et al

in Dental materials : official publication of the Academy of Dental Materials (2013), 29(2), 157-65

OBJECTIVES: The phenomena occurring during zirconia frameworks veneering process are not yet fully understood. In particular the study of zirconia behavior at the interface with the veneer remains a ... [more ▼]

OBJECTIVES: The phenomena occurring during zirconia frameworks veneering process are not yet fully understood. In particular the study of zirconia behavior at the interface with the veneer remains a challenge. However this interface has been reported to act on residual stress in the veneering ceramic, which plays a significant role in clinical failures such as chipping. The objective of this study was thus to investigate the veneer-zirconia interface using a recent 3D-analysis tool and to confront these observations to residual stress measurements in the veneering ceramic. METHODS: Two cross-sectioned bilayered disc samples (veneer on zirconia), exhibiting different residual stress profiles in the veneering ceramic, were investigated using 2D and 3D imaging (respectively Scanning Electron Microscopy (SEM) and Focused Ion Beam nanotomography (FIB-nt), associated with chemical analysis by Energy Dispersive X-ray Spectroscopy (EDS). RESULTS: The observations did not reveal any structural change in the bulk of zirconia layer of both samples. However the presence of structural alterations and sub-surface microcracks were highlighted in the first micrometer of zirconia surface, exclusively for the sample exhibiting interior tensile stress in the veneering ceramic. No interdiffusion phenomena were observed. SIGNIFICANCE: FIB nanotomography was proven to be a powerful technique to study the veneer-zirconia interface. The determination of the origin and the nature of zirconia alterations need to be further studied. The results of the present study support the hypothesis that zirconia surface property changes could be involved in the development of tensile stress in the veneering ceramic, increasing the risk of chipping. [less ▲]

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See detailWhat future for zirconia in prosthodontics : state of the art and research outcomes
MAINJOT, Amélie ULg

Scientific conference (2012, May)

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See detailResidual Stress in Veneering Ceramic
MAINJOT, Amélie ULg

Conference (2012, April 04)

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See detailWhat future for zirconia in prosthodontics : state of the art and research outcomes
MAINJOT, Amélie ULg

Scientific conference (2012)

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