Stress-induced changes imparted in a ‘dentin-bonded-crown’ material during sintering, annealing, ... more Stress-induced changes imparted in a ‘dentin-bonded-crown’ material during sintering, annealing, pre-cementation surface modification, and resin coating have been visualized by profilometry. The hypothesis tested was that operative techniques modify the stressing pattern throughout the material thickness. We polished the upper surfaces of 10 ceramic discs to remove surface imperfections before using a contact profilometer (40-nm resolution) to measure the ‘flatness’. Discs were re-profiled after annealing and after alumina particle air-abrasion and resin-coating of the ‘fit’ surface. Polished surfaces were convex, with a mean deflection of 8.4 ± 1.5 μm. Mean deflection was significantly reduced (P = 0.029) following alumina particle air-abrasion and increased (P < 0.001) on resin-coating. Polishing induced a tensile stress state, resulting in surface convexity. Alumina particle air-abrasion reduced the relative tensile stress state of the contralateral polished surface. Resin-pol...
This study was to investigate the influence of the bending test configurations and the crosshead ... more This study was to investigate the influence of the bending test configurations and the crosshead displacement speeds on the fracture toughness (K Ic) of dental porcelains obtained with the indentation strength in bending (ISB) method. Methods: The strength of the dental veneering porcelains Duceram and Sintagon Zx, Vickers' indented at a load of 2 kg was measured at a crosshead speed of 0.5 mm/min with three test configurations, which were 3-point, 4-point, and biaxial bending. Two more groups of Sintagon Zx were tested the same way, but at speeds of 0.1, and 0.05 mm/min, respectively. Both porcelains, the three crosshead speeds, and the three test configurations were compared statistically. Results: Duceram had a higher toughness than Sintagon Zx with all three test configurations and there was no significant difference between three test configurations with either porcelain. Within the crosshead speed groups of Sintagon Zx, a significant difference was found only in the 0.5 mm/min group between the 3point, and 4-point configurations. Within the configuration groups, significant differences were found between all speeds with the 3-point configuration and only between the highest and lowest speed with the 4-point and the biaxial tests. Conclusion: The crosshead displacement speed can cause statistically different results of fracture toughness obtained with the ISB method.
During the production of layered all-ceramic restorations transient and/or residual thermal stres... more During the production of layered all-ceramic restorations transient and/or residual thermal stresses may be formed which may affect a restoration&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s longevity. The aim of this study was to evaluate the influence of multiple firings on the thermal behavior of veneering porcelains and a ceramic core. The materials tested were: Empress 2 Core, Empress 2 Veneer and Eris glass-ceramics, Carrara Vincent and an experimental leucite-based veneering porcelain, Vitadur-Alpha aluminous porcelain, and two porcelains designed for titanium (i.e. Duceratin Dentine and Enamel). The thermal contraction coefficient of the materials was measured by means of dilatometery. The thermal contraction coefficient was measured during cooling and calculated over the temperature range of 450-20 degrees C by linear regression. One and two-way analysis of variance together with Tukey post-hoc tests were used as statistical analysis. Repeated firing affects the thermal contraction coefficients of Empress 2 Veneer, Carrara Vincent porcelain and the experimental porcelain. The thermal contraction coefficients of Empress 2 Core were significantly different from Vitadur-Alpha, Carrara Vincent, experimental porcelain, and Duceratin porcelains. The contraction coefficients of Empress 2 Veneer and Eris were closest to that of Empress 2 Core. The Empress 2 Core and Eris glass-ceramics, the aluminous porcelain and Duceratin porcelains showed better thermal stability after repeated firing than leucite porcelains. It can be concluded that due to the thermal stability of glass-ceramic materials, layered all-ceramic restorations of these materials may perform better.
The aim of this study was to compare three fracture toughness test methods, using four commercial... more The aim of this study was to compare three fracture toughness test methods, using four commercial dental porcelains. Materials and methods: The fracture toughness test techniques involved were: the single-edge-notched beam (SENB), the indentation strength method (IS), and a rather convenient ASTM standard for advanced ceramics, which is still rarely used in dental ceramic research, the Chevron-notched beam method (CN). Duceram, Duceram LFC, Sintagon Zx and Carrara Vincent were chosen for study. Data was analyzed by twoway and paired ANOVA. Result: No statistical difference was found between the CN and SENB methods with four dental porcelains, but IS was not always in statistical agreement with SENB or CN. Statistical agreement among all three methods occurred only with Duceram LFC. Conclusion: The different test methods did not always lead to the same ranking or values of fracture toughness. Yet the toughness results of the SENB method were comparable to those of the CN method for all the four dental porcelains tested in this study.
International Journal of Dentistry and Oral Science, 2015
New ceramic materials and novel fabrication methods have been developed and introduced in dentist... more New ceramic materials and novel fabrication methods have been developed and introduced in dentistry with the aim to improve the longevity of dental ceramic restorations and to extent their use for more demanding clinical situations like construction of multi units posterior fixed partial dentures (FPDs). Dental ceramics have now reached a stage of development where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of the restorative systems in order to make an optimal choice in each specific clinical situation.
The effect of heat-pressing and subsequent pre-cementation (acid-etching) and resin-cementation o... more The effect of heat-pressing and subsequent pre-cementation (acid-etching) and resin-cementation operative techniques on the development of transient and residual stresses in different thicknesses of a lithium disilicate glass-ceramic were characterised using profilometry prior to biaxial flexure strength (BFS) determination. 60 IPS e.max Press discs were pressed and divested under controlled conditions. The discs were polished on one surface to thicknesses of 0.61±0.05, 0.84±0.08, and 1.06±0.07 mm (Groups A-C, respectively). The mean of the maximum deflection (acid-etching and resin-coating was determined using high resolution profilometery prior to BFS testing. Paired sample t-tests were performed (p<0.05) on the 20 individual samples in each group (Groups A-C) for each comparison. Differences between the baseline quantification and resin-cement coating deflection values and BFS values for Groups A-C were determined using a one-way ANOVA with post hoc Tukey tests (p<0.05). Ba...
The strength of all-ceramic restorations can be adversely affected by surface defects, leading to... more The strength of all-ceramic restorations can be adversely affected by surface defects, leading to restoration failures. Additionally, when a 2-layer all-ceramic restoration is required for esthetic purposes, part of the stronger ceramic core material is replaced by veneering porcelain.
The aim of this study was to characterize the relation of dimensional changes of dental ceramic m... more The aim of this study was to characterize the relation of dimensional changes of dental ceramic materials as function of temperature. The thermal dimensional behavior of one glass ceramic core, four commercially available veneering porcelains and two experimental veneering porcelain materials was determined on cooling from 450 C to 20 C by means of a vertical differential pushrod thermal dilatometer. The thermal dimensional behavior of the ceramic materials was expressed in three different ways: as linear relation with a linear line fitting procedure; as non-linear relation by a quadratic curve fitting procedure and according to ISO 9693 by a thermal expansion coefficient. For all ceramic materials except the one consisting of aluminum oxide fillers, the thermal dimensional behavior is best described with the polynomial function: Dl=l ¼ C þ a 1 T þ a 2 T 2 : The description of the thermal expansion coefficient according to the ISO standard on metal is not appropriate for the prediction of a thermal incompatibility of ceramic materials. Except for Vitadur Alpha, the ceramics materials tested showed non-linear expansion; their thermal dimensional behavior can be best described according to the quadratic relation method, second by the linear relation, third as recommended by ISO. r
New ceramic materials and novel fabrication methods have been developed and introduced in dentist... more New ceramic materials and novel fabrication methods have been developed and introduced in dentistry with the aim to improve the longevity of dental ceramic restorations and to extent their use for more demanding clinical situations like construction of multi units posterior fixed partial dentures (FPDs). Dental ceramics have now reached a stage of development where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of the restorative systems in order to make an optimal choice in each specific clinical situation. Keywords: Crystal Phase; Glass Phase; Glass-Ceramic; Veneering Porcelain; High Strength Ceramic; Polycrystalline Ceramic; Mechanical Properties; Optical Properties.
Time: 12:52 pm d e n t a l m a t e r i a l s 2 7 ( 2 0 1 1 ) 379-385 a v a i l a b l e a t w w w ... more Time: 12:52 pm d e n t a l m a t e r i a l s 2 7 ( 2 0 1 1 ) 379-385 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a Bi-axial flexure strength Profilometric evaluation a b s t r a c t Objectives. To characterize the stress induced deformation of bi-axial flexure strength (BFS) test specimens during processing to provide an insight into sintering effects and associated BFS determination. Methods. 40 Vitadur-Alpha and 80 IPS e.max Ceram disc-shaped specimens were condensed and a sintered on a silicon nitride refractory tray under controlled firing and cooling parameters. The mean of the maximum deflection (m) and Ra values (m) were determined using a high resolution profilometer and were related to the orientation of the measured surface within the furnace. BFS testing of the subsequent groups (n = 20) was performed and the data related to the measured deformation of the sintered specimens. A two-way analysis of variance (ANOVA) where factors were identified as surface state and firing orientation with post hoc Tukey's tests was complemented by pair-wise comparisons with a Student's t-test for each measurement (P < 0.05).
New ceramic materials and novel fabrication methods have been developed and introduced in dentist... more New ceramic materials and novel fabrication methods have been developed and introduced in dentistry with the aim to improve the longevity of dental ceramic restorations and to extent their use for more demanding clinical situations like construction of multi units posterior fixed partial dentures (FPDs). Dental ceramics have now reached a stage of development where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of the restorative systems in order to make an optimal choice in each specific clinical situation. Keywords: Crystal Phase; Glass Phase; Glass-Ceramic; Veneering Porcelain; High Strength Ceramic; Polycrystalline Ceramic; Mechanical Properties; Optical Properties.
Stress-induced changes imparted in a ‘dentin-bonded-crown’ material during sintering, annealing, ... more Stress-induced changes imparted in a ‘dentin-bonded-crown’ material during sintering, annealing, pre-cementation surface modification, and resin coating have been visualized by profilometry. The hypothesis tested was that operative techniques modify the stressing pattern throughout the material thickness. We polished the upper surfaces of 10 ceramic discs to remove surface imperfections before using a contact profilometer (40-nm resolution) to measure the ‘flatness’. Discs were re-profiled after annealing and after alumina particle air-abrasion and resin-coating of the ‘fit’ surface. Polished surfaces were convex, with a mean deflection of 8.4 ± 1.5 μm. Mean deflection was significantly reduced (P = 0.029) following alumina particle air-abrasion and increased (P < 0.001) on resin-coating. Polishing induced a tensile stress state, resulting in surface convexity. Alumina particle air-abrasion reduced the relative tensile stress state of the contralateral polished surface. Resin-pol...
This study was to investigate the influence of the bending test configurations and the crosshead ... more This study was to investigate the influence of the bending test configurations and the crosshead displacement speeds on the fracture toughness (K Ic) of dental porcelains obtained with the indentation strength in bending (ISB) method. Methods: The strength of the dental veneering porcelains Duceram and Sintagon Zx, Vickers' indented at a load of 2 kg was measured at a crosshead speed of 0.5 mm/min with three test configurations, which were 3-point, 4-point, and biaxial bending. Two more groups of Sintagon Zx were tested the same way, but at speeds of 0.1, and 0.05 mm/min, respectively. Both porcelains, the three crosshead speeds, and the three test configurations were compared statistically. Results: Duceram had a higher toughness than Sintagon Zx with all three test configurations and there was no significant difference between three test configurations with either porcelain. Within the crosshead speed groups of Sintagon Zx, a significant difference was found only in the 0.5 mm/min group between the 3point, and 4-point configurations. Within the configuration groups, significant differences were found between all speeds with the 3-point configuration and only between the highest and lowest speed with the 4-point and the biaxial tests. Conclusion: The crosshead displacement speed can cause statistically different results of fracture toughness obtained with the ISB method.
During the production of layered all-ceramic restorations transient and/or residual thermal stres... more During the production of layered all-ceramic restorations transient and/or residual thermal stresses may be formed which may affect a restoration&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s longevity. The aim of this study was to evaluate the influence of multiple firings on the thermal behavior of veneering porcelains and a ceramic core. The materials tested were: Empress 2 Core, Empress 2 Veneer and Eris glass-ceramics, Carrara Vincent and an experimental leucite-based veneering porcelain, Vitadur-Alpha aluminous porcelain, and two porcelains designed for titanium (i.e. Duceratin Dentine and Enamel). The thermal contraction coefficient of the materials was measured by means of dilatometery. The thermal contraction coefficient was measured during cooling and calculated over the temperature range of 450-20 degrees C by linear regression. One and two-way analysis of variance together with Tukey post-hoc tests were used as statistical analysis. Repeated firing affects the thermal contraction coefficients of Empress 2 Veneer, Carrara Vincent porcelain and the experimental porcelain. The thermal contraction coefficients of Empress 2 Core were significantly different from Vitadur-Alpha, Carrara Vincent, experimental porcelain, and Duceratin porcelains. The contraction coefficients of Empress 2 Veneer and Eris were closest to that of Empress 2 Core. The Empress 2 Core and Eris glass-ceramics, the aluminous porcelain and Duceratin porcelains showed better thermal stability after repeated firing than leucite porcelains. It can be concluded that due to the thermal stability of glass-ceramic materials, layered all-ceramic restorations of these materials may perform better.
The aim of this study was to compare three fracture toughness test methods, using four commercial... more The aim of this study was to compare three fracture toughness test methods, using four commercial dental porcelains. Materials and methods: The fracture toughness test techniques involved were: the single-edge-notched beam (SENB), the indentation strength method (IS), and a rather convenient ASTM standard for advanced ceramics, which is still rarely used in dental ceramic research, the Chevron-notched beam method (CN). Duceram, Duceram LFC, Sintagon Zx and Carrara Vincent were chosen for study. Data was analyzed by twoway and paired ANOVA. Result: No statistical difference was found between the CN and SENB methods with four dental porcelains, but IS was not always in statistical agreement with SENB or CN. Statistical agreement among all three methods occurred only with Duceram LFC. Conclusion: The different test methods did not always lead to the same ranking or values of fracture toughness. Yet the toughness results of the SENB method were comparable to those of the CN method for all the four dental porcelains tested in this study.
International Journal of Dentistry and Oral Science, 2015
New ceramic materials and novel fabrication methods have been developed and introduced in dentist... more New ceramic materials and novel fabrication methods have been developed and introduced in dentistry with the aim to improve the longevity of dental ceramic restorations and to extent their use for more demanding clinical situations like construction of multi units posterior fixed partial dentures (FPDs). Dental ceramics have now reached a stage of development where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of the restorative systems in order to make an optimal choice in each specific clinical situation.
The effect of heat-pressing and subsequent pre-cementation (acid-etching) and resin-cementation o... more The effect of heat-pressing and subsequent pre-cementation (acid-etching) and resin-cementation operative techniques on the development of transient and residual stresses in different thicknesses of a lithium disilicate glass-ceramic were characterised using profilometry prior to biaxial flexure strength (BFS) determination. 60 IPS e.max Press discs were pressed and divested under controlled conditions. The discs were polished on one surface to thicknesses of 0.61±0.05, 0.84±0.08, and 1.06±0.07 mm (Groups A-C, respectively). The mean of the maximum deflection (acid-etching and resin-coating was determined using high resolution profilometery prior to BFS testing. Paired sample t-tests were performed (p<0.05) on the 20 individual samples in each group (Groups A-C) for each comparison. Differences between the baseline quantification and resin-cement coating deflection values and BFS values for Groups A-C were determined using a one-way ANOVA with post hoc Tukey tests (p<0.05). Ba...
The strength of all-ceramic restorations can be adversely affected by surface defects, leading to... more The strength of all-ceramic restorations can be adversely affected by surface defects, leading to restoration failures. Additionally, when a 2-layer all-ceramic restoration is required for esthetic purposes, part of the stronger ceramic core material is replaced by veneering porcelain.
The aim of this study was to characterize the relation of dimensional changes of dental ceramic m... more The aim of this study was to characterize the relation of dimensional changes of dental ceramic materials as function of temperature. The thermal dimensional behavior of one glass ceramic core, four commercially available veneering porcelains and two experimental veneering porcelain materials was determined on cooling from 450 C to 20 C by means of a vertical differential pushrod thermal dilatometer. The thermal dimensional behavior of the ceramic materials was expressed in three different ways: as linear relation with a linear line fitting procedure; as non-linear relation by a quadratic curve fitting procedure and according to ISO 9693 by a thermal expansion coefficient. For all ceramic materials except the one consisting of aluminum oxide fillers, the thermal dimensional behavior is best described with the polynomial function: Dl=l ¼ C þ a 1 T þ a 2 T 2 : The description of the thermal expansion coefficient according to the ISO standard on metal is not appropriate for the prediction of a thermal incompatibility of ceramic materials. Except for Vitadur Alpha, the ceramics materials tested showed non-linear expansion; their thermal dimensional behavior can be best described according to the quadratic relation method, second by the linear relation, third as recommended by ISO. r
New ceramic materials and novel fabrication methods have been developed and introduced in dentist... more New ceramic materials and novel fabrication methods have been developed and introduced in dentistry with the aim to improve the longevity of dental ceramic restorations and to extent their use for more demanding clinical situations like construction of multi units posterior fixed partial dentures (FPDs). Dental ceramics have now reached a stage of development where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of the restorative systems in order to make an optimal choice in each specific clinical situation. Keywords: Crystal Phase; Glass Phase; Glass-Ceramic; Veneering Porcelain; High Strength Ceramic; Polycrystalline Ceramic; Mechanical Properties; Optical Properties.
Time: 12:52 pm d e n t a l m a t e r i a l s 2 7 ( 2 0 1 1 ) 379-385 a v a i l a b l e a t w w w ... more Time: 12:52 pm d e n t a l m a t e r i a l s 2 7 ( 2 0 1 1 ) 379-385 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a Bi-axial flexure strength Profilometric evaluation a b s t r a c t Objectives. To characterize the stress induced deformation of bi-axial flexure strength (BFS) test specimens during processing to provide an insight into sintering effects and associated BFS determination. Methods. 40 Vitadur-Alpha and 80 IPS e.max Ceram disc-shaped specimens were condensed and a sintered on a silicon nitride refractory tray under controlled firing and cooling parameters. The mean of the maximum deflection (m) and Ra values (m) were determined using a high resolution profilometer and were related to the orientation of the measured surface within the furnace. BFS testing of the subsequent groups (n = 20) was performed and the data related to the measured deformation of the sintered specimens. A two-way analysis of variance (ANOVA) where factors were identified as surface state and firing orientation with post hoc Tukey's tests was complemented by pair-wise comparisons with a Student's t-test for each measurement (P < 0.05).
New ceramic materials and novel fabrication methods have been developed and introduced in dentist... more New ceramic materials and novel fabrication methods have been developed and introduced in dentistry with the aim to improve the longevity of dental ceramic restorations and to extent their use for more demanding clinical situations like construction of multi units posterior fixed partial dentures (FPDs). Dental ceramics have now reached a stage of development where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of the restorative systems in order to make an optimal choice in each specific clinical situation. Keywords: Crystal Phase; Glass Phase; Glass-Ceramic; Veneering Porcelain; High Strength Ceramic; Polycrystalline Ceramic; Mechanical Properties; Optical Properties.
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Papers by Giuseppe Isgro
where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge
of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of the restorative systems in order to make an optimal choice in each specific clinical situation.
Keywords: Crystal Phase; Glass Phase; Glass-Ceramic; Veneering Porcelain; High Strength Ceramic; Polycrystalline Ceramic; Mechanical Properties; Optical Properties.
the longevity of dental ceramic restorations and to extent their use for more demanding clinical situations like construction
of multi units posterior fixed partial dentures (FPDs). Dental ceramics have now reached a stage of development
where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge
of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of
the restorative systems in order to make an optimal choice in each specific clinical situation.
Keywords: Crystal Phase; Glass Phase; Glass-Ceramic; Veneering Porcelain; High Strength Ceramic; Polycrystalline Ceramic;
Mechanical Properties; Optical Properties.
where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge
of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of the restorative systems in order to make an optimal choice in each specific clinical situation.
Keywords: Crystal Phase; Glass Phase; Glass-Ceramic; Veneering Porcelain; High Strength Ceramic; Polycrystalline Ceramic; Mechanical Properties; Optical Properties.
the longevity of dental ceramic restorations and to extent their use for more demanding clinical situations like construction
of multi units posterior fixed partial dentures (FPDs). Dental ceramics have now reached a stage of development
where it is possible to make long-span metal free posterior FPDs. Dentists and dental technicians should have knowledge
of advances in dental ceramic materials and fabrication methods available to understand advantages and disadvantages of
the restorative systems in order to make an optimal choice in each specific clinical situation.
Keywords: Crystal Phase; Glass Phase; Glass-Ceramic; Veneering Porcelain; High Strength Ceramic; Polycrystalline Ceramic;
Mechanical Properties; Optical Properties.