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Bulk fill vs incremental layering in posterior restorations: Systematic review
d e n t a l m a t e r i a l s 3 3 S ( 2 0 1 7 ) e1–e92
they are used in a variety of clinical dental situations as restorative, lining, luting and sealing materials. The self-hardening setting reaction takes place between a glass powder and a poly(acrylic acid) and involves the formation of ionically cross-linked acidic polymer chains featuring multivalent counter ions leached from the glass. The novel glass powder composition reported here, based on SiO2 -B2 O3 -K2 O-CaOAl2 O3 , is produced with the melt-quenching technique. The borosilicate system exhibits a strong tendency to phase separate after a thermal heat treatment; one of the phases created is more reactive and susceptible to acid attack and will be leached out from the glass earlier. The GIC setting time is thus related to the acid susceptibility of the glass and it is proposed that a controlled phase separated glass can improve the workability and final properties of the cement thanks to the controlled formation of the acid susceptible phase. The other phase in the glass can remain in the cement improving the mechanical properties of the dental restorative material. Materials and methods: Factorial Experimental Design (FED) approach sets up a series of samples covering an interesting compositional range for the final purpose of the research. The heat-treated borosilicate powders are dissolved in an acid solution (HNO3 , pH 2.5) and the ions leaching is checked using ICP analysis at different time points. SEM analyses before and after an acid leaching (HNO3 , 1 M) are directed to study the surface microstructure and phase separation on the bulk glasses. Glass powders were selected and mixed with poly(acrylic acid) to study the influence on the mechanical properties. Results: The glass composition influences the colour appearance of the samples, probably due to a different mechanism of phase-separation. A complete characterization of the glass dissolution kinetics reveals the effect of the composition on the ions leaching. Al2 O3 increases the network connectivity and durability stabilizing the glass structure. The B2 O3 /CaO ratio influences the calcium and potassium leaching. SEM studies show different surface microstructures. The glass composition influences flexural strength and hardness of the final material. Conclusions: The results show the connection between the compositional feature of the glasses and their leaching behaviours. This is a useful tool for designing an ideal glass system with the tailored characteristic in order to improve the properties of the glass ionomer cements and enhance the understanding of their setting mechanism. http://dx.doi.org/10.1016/j.dental.2017.08.091 91 Bulk fill vs incremental layering in posterior restorations: Systematic review A.D. Loguercio ∗ , Y.L. Gruber, R.T. Jitumori, T.E. Bakaus, G.M. Gomes, A. Reis State University of Ponta Grossa, Brazil Purpose/aim: To systematically review the risk and intensity of postoperative sensitivity, risk of fractures, marginal adaptation and marginal discoloration in posterior composite resin restorations placed with bulk or incremental filling.
e47
Materials and methods: A comprehensive search was performed in the MEDLINE via PubMed, Scopus, Web of Science, LILACS, BBO and Cochrane Library. The abstracts of IADR (1990–2016), unpublished and ongoing trials registries were also searched, as well as, dissertations and theses. Study selection: We included randomized clinical trials that compared the bulk and incremental filling of composite resins for restoration of posterior cavities in adult patients. The risk of bias tool of the Cochrane Collaboration was used to assess the risk of bias of the included studies. Random effects model was used for the meta-analyses. Results: After duplicates removal and non-eligible articles, 8 studies remained for qualitative synthesis. Two studies were judged to be “low” risk of bias, and six at “unclear” risk of bias. No evidence of difference between techniques was observed for postoperative sensitivity, risk of fractures, marginal adaptation and marginal discoloration in any of the study follow-ups (p > 0.05). Conclusions: Both restoration techniques do not influence the postoperative sensitivity up to 1 month in posterior restorations, as well as, fracture and marginal discrepancies until 6 years of clinical evaluation. http://dx.doi.org/10.1016/j.dental.2017.08.092 92 Development of a hoop-strength test for a crown-like model geometry R. Belli 1 , S. Csato 1 , A. Petschelt 1 , D. Klein 2 , S. Tremmel 2 , U. Lohbauer 1,∗ 1
Friedrich-Alexander University Erlangen-Nuremberg (FAU), Research Laboratory for Dental Biomaterials, Erlangen, Germany 2 Friedrich-Alexander University Erlangen-Nuremberg (FAU), Institute for Mechanical Technology (KTmfk), Erlangen, Germany Purpose/aim: To develop a test using a standardized sphero-cylindrical geometry as an analogue for dental crowns, where an opening hoop stress is induced to the margins to simulate different clinical scenarios. Materials and methods: Metallic abutments having a sphero-cylindrical shape with 10 mm in diameter and 7 mm in height were fabricated with a 0.5 mm inner radius between the axial and marginal walls and two marginal thicknesses: 1 and 2 mm. These abutments were sputtered and scanned to generate a CAD model, upon which a sphero-cylinder “crown” was modelled having a final thickness of 0.7 and 1.6 mm throughout and a rounded inner margin. A finite element model of the crown geometry was built simulating the loading of a conical (7◦ ) piston from the crown opening by touching the rounded inner margin circumferentially to induce hoop-stresses. Experimental tests imitating this set-up were conducted in a universal testing machine for a lithium disilicate (e.max CAD, Ivoclar-Vivadent) and a feldspar ceramic (Vitablocs Mark II, Vita Zahnfabrik) in the two aforementioned thicknesses. The forces at fracture were used as input in the finite element simulation to obtain the maximum principal
they are used in a variety of clinical dental situations as restorative, lining, luting and sealing materials. The self-hardening setting reaction takes place between a glass powder and a poly(acrylic acid) and involves the formation of ionically cross-linked acidic polymer chains featuring multivalent counter ions leached from the glass. The novel glass powder composition reported here, based on SiO2 -B2 O3 -K2 O-CaOAl2 O3 , is produced with the melt-quenching technique. The borosilicate system exhibits a strong tendency to phase separate after a thermal heat treatment; one of the phases created is more reactive and susceptible to acid attack and will be leached out from the glass earlier. The GIC setting time is thus related to the acid susceptibility of the glass and it is proposed that a controlled phase separated glass can improve the workability and final properties of the cement thanks to the controlled formation of the acid susceptible phase. The other phase in the glass can remain in the cement improving the mechanical properties of the dental restorative material. Materials and methods: Factorial Experimental Design (FED) approach sets up a series of samples covering an interesting compositional range for the final purpose of the research. The heat-treated borosilicate powders are dissolved in an acid solution (HNO3 , pH 2.5) and the ions leaching is checked using ICP analysis at different time points. SEM analyses before and after an acid leaching (HNO3 , 1 M) are directed to study the surface microstructure and phase separation on the bulk glasses. Glass powders were selected and mixed with poly(acrylic acid) to study the influence on the mechanical properties. Results: The glass composition influences the colour appearance of the samples, probably due to a different mechanism of phase-separation. A complete characterization of the glass dissolution kinetics reveals the effect of the composition on the ions leaching. Al2 O3 increases the network connectivity and durability stabilizing the glass structure. The B2 O3 /CaO ratio influences the calcium and potassium leaching. SEM studies show different surface microstructures. The glass composition influences flexural strength and hardness of the final material. Conclusions: The results show the connection between the compositional feature of the glasses and their leaching behaviours. This is a useful tool for designing an ideal glass system with the tailored characteristic in order to improve the properties of the glass ionomer cements and enhance the understanding of their setting mechanism. http://dx.doi.org/10.1016/j.dental.2017.08.091 91 Bulk fill vs incremental layering in posterior restorations: Systematic review A.D. Loguercio ∗ , Y.L. Gruber, R.T. Jitumori, T.E. Bakaus, G.M. Gomes, A. Reis State University of Ponta Grossa, Brazil Purpose/aim: To systematically review the risk and intensity of postoperative sensitivity, risk of fractures, marginal adaptation and marginal discoloration in posterior composite resin restorations placed with bulk or incremental filling.
e47
Materials and methods: A comprehensive search was performed in the MEDLINE via PubMed, Scopus, Web of Science, LILACS, BBO and Cochrane Library. The abstracts of IADR (1990–2016), unpublished and ongoing trials registries were also searched, as well as, dissertations and theses. Study selection: We included randomized clinical trials that compared the bulk and incremental filling of composite resins for restoration of posterior cavities in adult patients. The risk of bias tool of the Cochrane Collaboration was used to assess the risk of bias of the included studies. Random effects model was used for the meta-analyses. Results: After duplicates removal and non-eligible articles, 8 studies remained for qualitative synthesis. Two studies were judged to be “low” risk of bias, and six at “unclear” risk of bias. No evidence of difference between techniques was observed for postoperative sensitivity, risk of fractures, marginal adaptation and marginal discoloration in any of the study follow-ups (p > 0.05). Conclusions: Both restoration techniques do not influence the postoperative sensitivity up to 1 month in posterior restorations, as well as, fracture and marginal discrepancies until 6 years of clinical evaluation. http://dx.doi.org/10.1016/j.dental.2017.08.092 92 Development of a hoop-strength test for a crown-like model geometry R. Belli 1 , S. Csato 1 , A. Petschelt 1 , D. Klein 2 , S. Tremmel 2 , U. Lohbauer 1,∗ 1
Friedrich-Alexander University Erlangen-Nuremberg (FAU), Research Laboratory for Dental Biomaterials, Erlangen, Germany 2 Friedrich-Alexander University Erlangen-Nuremberg (FAU), Institute for Mechanical Technology (KTmfk), Erlangen, Germany Purpose/aim: To develop a test using a standardized sphero-cylindrical geometry as an analogue for dental crowns, where an opening hoop stress is induced to the margins to simulate different clinical scenarios. Materials and methods: Metallic abutments having a sphero-cylindrical shape with 10 mm in diameter and 7 mm in height were fabricated with a 0.5 mm inner radius between the axial and marginal walls and two marginal thicknesses: 1 and 2 mm. These abutments were sputtered and scanned to generate a CAD model, upon which a sphero-cylinder “crown” was modelled having a final thickness of 0.7 and 1.6 mm throughout and a rounded inner margin. A finite element model of the crown geometry was built simulating the loading of a conical (7◦ ) piston from the crown opening by touching the rounded inner margin circumferentially to induce hoop-stresses. Experimental tests imitating this set-up were conducted in a universal testing machine for a lithium disilicate (e.max CAD, Ivoclar-Vivadent) and a feldspar ceramic (Vitablocs Mark II, Vita Zahnfabrik) in the two aforementioned thicknesses. The forces at fracture were used as input in the finite element simulation to obtain the maximum principal