Cure behaviour of visible light activated dental composites

Maffezzoli, Alfonso; Terzi, Roberto; Nicolais, L.

doi:10.1007/bf00120292

Cited by 26 publications

(31 citation statements)

References 22 publications

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“…Under these conditions, the kinetic constant of the propagation reaction, the radical efficiency and, consequently, the overall rate of reaction decrease to zero for a value of a lower than 1. This kinetic behaviour may be modelled using a simple pseudo-autocatalytic expression, obtained by modifying a kinetic equation previously proposed for free-radical polymerization of unsaturated polyester and acrylic thermosetting resins [5,13]:…”

Section: Initiation and Inhibitionmentioning

confidence: 99%

“…In fact, the glass transition temperature, continuously increasing during cure, approaches the isothermal cure temperature thereby strongly reducing the molecular mobility. Under these conditions, the reaction becomes diffusion controlled and the termination step of the polymerization is governed by the strong reduction in the molecular mobility caused by vitrification [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

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Polymerization kinetics of acrylic bone cements by differential scanning calorimetry

Maffezzoli

1996

Journal of Thermal Analysis

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Bone cements arc widely used for the fixation of metallic prostheses in orthopaedics and to form replacements for skull defects in neurosurgery. Acrylic bone cements are based on a mixture of methyl methacrylate (MMA) and a fine powder of polymethyl methacrylate (PMMA).The polymerization of the bone cement occurs in contact with the bone and the prosthesis which act as the boundaries of a bulk polymerization reactor. The kinetic behaviour of the bone cement plays a fundamental role for the final performance of the implant.In this paper, the isothermal and non-isothermal polymerization behaviour of a commercial bone cement is described. A simple phenomenological model, accounting for the autoaeceleration effect, for a diffusion controlled termination mechanism and for the reaction between inhibitor and initiator, is proposed. The reaction kinetics is analysed by DSC. DSC data are used for the determination of the rates of polymerization under isothermal and non-isothermal conditions. The experimental data are processed to calculate the parameters of the proposed phenomenological kinetic model. The analytical and numerical details related to the integration of the model are discussed.

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Section: Initiation and Inhibitionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polymerization kinetics of acrylic bone cements by differential scanning calorimetry

Maffezzoli

1996

Journal of Thermal Analysis

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“…The bulk isothermal rate of reaction model that depends on conversion has been used effectively by Maffezzoli and co-workers. 12,13 Racz et al showed that an analogy between the classical Avrami approach for phase transformations and the kinetic phenomena that occur during photocuring of polymer and copolymer resins gives rise to a simple algebraic two-parameter expression for the extent of cure versus time that matched cross-linking chemical conversion quite well.…”

Section: Introductionmentioning

confidence: 99%

A study of localized curing of glass‐filled composites using microhardness measurements

Abedian

Garcı́a-Godoy

2005

J of Applied Polymer Sci

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Extent of cure of hybrid composite systems is examined by conducting hardness measurements at different stages of the photopolymerization reaction and obtaining kinetic parameters that matched the experimental data. The materials are commercial dental composites based on bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane resins with different photoinitiator concentrations as well as filler particle sizes and combinations. Samples (five per group) were made using nylon molds (2.5 ϫ 5 mm) of the tested composites. The samples were light cured with a constant-power light source for durations up to 20 s. After curing, all samples underwent Vicker's hardness testing of top and bottom surfaces. While there are significant differences in the polymerization behavior between the top and bottom locations for the tested composites, the corresponding growth exponent n, a kinetic parameter in the kinetic theory, is very close in all cases. For the tested materials the coefficient factor k is much lower for the bottom surfaces compared with the top surfaces. This reduction in the value of k is more severe for the material with a higher concentration of the photoinitiator as well as a higher percentage of glass filler particles in the wavelength range affecting the photopolymerization. It is argued that a relationship between k and the irradiation intensity can be used to quantify the decay of irradiated light with its penetration into the composites. The comparisons can be used to draw preliminary conclusions on the parameters controlling the effective depth of cure in a hybrid composite.

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“…However, most traditional kinetic models consider only the isothermal behaviour, while light curing of dental composites is a fast and highly non-isothermal bulk polymerization. The analysis of the isothermal cure of a methacrylate-based commercial dental composite, activated by visible light, presented in the first part of this study [5], has lead to the determination of very low final glass transition temperatures (Tg) in the cured parts. This result appears in contrast with the good performances shown by these materials used for dental restorations.…”

Section: Introductionmentioning

confidence: 99%

Cure behaviour of visible light activated dental composites

Maffezzoli

Terzi²,

Nicolais

1995

J Mater Sci: Mater Med

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In this paper, the non-isothermal cure behaviour of a dental composite, activated by visible light, is described using a heat transfer model that, coupled with a reaction kinetic expression, is able to predict the temperature and the degree of reaction in the composite. The temperature and the degree of reaction profiles inside the composite are calculated, as a function of the cure time, taking into account the system geometry, the thermal diffusivity of the composite, and the resin reaction rate. Material properties, boundary and initial conditions and the kinetic behaviour are the input data of the heat transfer model. Once the degree of reaction is known, the glass transition temperature profiles across the thickness of the composite are calculated. Experimentally measured glass transition temperatures are used for the evaluation of an extinction coefficient capable of accounting for the effects of the light absorption through the thickness on the polymerization kinetics. Finally, the effects of the non-isothermal cure conditions on the application of these materials in dental restorations are discussed.

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Cure behaviour of visible light activated dental composites

Cited by 26 publications

References 22 publications

Polymerization kinetics of acrylic bone cements by differential scanning calorimetry

Polymerization kinetics of acrylic bone cements by differential scanning calorimetry

A study of localized curing of glass‐filled composites using microhardness measurements

Cure behaviour of visible light activated dental composites

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