Polymerization shrinkage of microfilled composites determined by laser beam scanning

Fano, Vincenzo; Ortalli, I.; Pizzi, Silvia; Bonanini, Mauro

doi:10.1016/s0142-9612(96)00171-8

Cited by 43 publications

(14 citation statements)

References 9 publications

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“…The linear shrinkage was measured by a laser-scanned described in [8] The materials reported in table I can be divided into two groups having different properties. A group is made up of Provil specimens with different viscosities (P = putty, M = medium, L = light), Express putty and Elite putty soft.…”

Section: W1mentioning

confidence: 99%

Evaporation in addition impression silicones

Fano

Ortalli

1995

Il Nuovo Cimento D

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Summary. --The effect of weight loss on the dimensional stability of some addition-polysiloxanes used as impression materials in dentistry is studied. We show that polymerization is not the only factor affecting the shrinkage of these materials. An explanation for the time-dependent weight functions is given.PACS 81.70 -Materials testing. PACS 87.90 -Other topics in biophysics, medical physics, and biomedical engineering. Polysiloxane-based impression materials, which cure by addition reaction, are considered materials with superior properties in dentistry [1]. Several works report that they show little dimensional change with time [2][3][4], when compared with the polysulphides and condensation silicones. This is because the addition polymerization does not produce volatile by-products [5,6]. Recently, it has been suggested [7] that the shrinkage is a complicated function of time: the early shrinkage, that proceeds exponentially for very few hours, is affected by the polymerization reaction. However, depending on the sample thickness, the long-term shrinkage, which is not exponential, finishes after one or more days. The knowledge of all the factors affecting the dimensional variation is closely related to the accuracy of the impressions and is a condition required to improve the material quality.In this work the possible evaporation of volatile components was tested by monitoring the weight of addition impression silicones. Their weight loss with time can be ascribed to evaporation. To confirm this phenomenon, we tested the weight variation of samples having similar shapes but different thicknesses. In contrast with the polymerization, which does not depend on thickness, the ratio W/W1 (where W = = W1 -W2, W1 is the sample weight measured at zero-time, W2 is the weight after t time) is larger for thin samples, compared with the thick ones, in the early stages of the evaporation.The influence of evaporation on the dimensional stability was assessed by examining the linear shrinkage as a function of time, for materials showing different

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Section: W1mentioning

confidence: 99%

Evaporation in addition impression silicones

Fano

Ortalli

1995

Il Nuovo Cimento D

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“…Shrinkage measurements using non-contact methods have been carried out by other investigators using, for example, laser beam scanning or videoimaging techniques (Fano et al, 1997;Sharp et al, 2003). With these techniques, the external dimensions of the composite specimen are recorded continuously during the polymerization process, from which the overall or bulk material shrinkage can be obtained.…”

Section: Introductionmentioning

confidence: 99%

Application of digital image correlation to full-field measurement of shrinkage strain of dental composites

Lau

Fok

2013

J. Zhejiang Univ. Sci. A

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Abstract:Objectives: Polymerization shrinkage of dental composites remains a major concern in restorative dentistry because it can lead to micro-cracking of the tooth and debonding at the tooth-restoration interface. The aim of this study was to measure the full-field polymerization shrinkage of dental composites using the optical digital image correlation (DIC) method and to evaluate how the measurement is influenced by the factors in experiment setup and image analysis. Methods: Four commercial dental composites, Premise Dentine, Z100, Z250 and Tetric EvoCeram, were tested. Composite was first placed into a slot mould to form a bar specimen with rectangular-section of 4 mm×2 mm, followed by the surface painting to create irregular speckles. Curing was then applied at one end of the specimen while the other part were covered against curing light for simulating the clinical curing condition of composite in dental cavity. The painted surface was recorded by a charge-coupled device (CCD) camera before and after curing. Subsequently, the volumetric shrinkage of the specimen was calculated with specialist DIC software based on image cross correlation. In addition, a few factors that may influence the measuring accuracy, including the subset window size, speckle size, illumination light and specimen length, were also evaluated. Results: The volumetric shrinkage of the specimen generally decreases with increasing distance from the irradiated surface with a conspicuous exception being the composite Premise Dentine as its maximum shrinkage occurred at a subsurface distance of about 1 mm instead of the irradiated surface. Z100 had the greatest maximum shrinkage strain, followed by Z250, Tetric EvoCeram and then Premise Dentine. Larger subset window size made the shrinkage strain contour smoother. But the cost was that some details in the heterogeneity of the material were lost. Very small subset window size resulted in a lot of noise in the data, making it difficult to discern the general pattern in the strain distribution. Speckle size did not seem to have obvious effect on the volumetric shrinkage strain along specimen length; however, larger speckles resulted in higher level of noise or heterogeneity in the shrinkage distribution. Compared with bright illumination, dimmer lighting produced larger standard deviations in the measured shrinkage, indicating a higher level of noise. The longer the specimen, the greater was the rate of reduction with distance from the irradiated surface, especially for the longitudinal strain. Significance: The image correlation method is capable of producing full-field polymerization shrinkage of dental composites. The accuracy of the measurements relies on selection of optimal parameters in experimental setup and DIC analysis.

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“…This method is valid only when the isotropic contraction of sample is guaranteed. In other cases, exaggerated or diminished shrinkage data may result (5, 6, 12–14). In reality, because the geometric limitation of the measurement apparatus with a structure where the disc‐shaped composite specimen is sandwiched between two glass plates, the radial contraction of the thin disc shaped sample must be limited.…”

Section: Introductionmentioning

confidence: 99%

A new method to measure the polymerization shrinkage kinetics of light cured composites

Lee

Cho

Son

et al. 2005

J of Oral Rehabilitation

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This study was undertaken to develop a new measurement method to determine the initial dynamic volumetric shrinkage of composite resins during polymerization, and to investigate the effect of curing light intensity on the polymerization shrinkage kinetics. The instrument was basically an electromagnetic balance that was constructed with a force transducer using a position sensitive photo detector (PSPD) and a negative feedback servo amplifier. The volumetric change of composites during polymerization was detected continuously as a buoyancy change in distilled water by means of the Archimedes' principle. Using this new instrument, the dynamic patterns of the polymerization shrinkage of seven commercial composite resins were measured. The polymerization shrinkage of the composites was 1.92 approximately 4.05 volume %. The shrinkage of a packable composite was the lowest, and that of a flowable composite was the highest. The maximum rate of polymerization shrinkage increased with increasing light intensity but the peak shrinkage rate time decreased with increasing light intensity. A strong positive relationship was observed between the square root of the light intensity and the maximum shrinkage rate. The shrinkage rate per unit time, dVol%/dt, showed that the instrument can be a valuable research method for investigating the polymerization reaction kinetics. This new shrinkage-measuring instrument has some advantages that it was insensitive to temperature changes and could measure the dynamic volumetric shrinkage in real time without complicated processes. Therefore, it can be used to characterize the shrinkage kinetics in a wide range of commercial and experimental visible-light-cure materials in relation to their composition and chemistry.

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Polymerization shrinkage of microfilled composites determined by laser beam scanning

Cited by 43 publications

References 9 publications

Evaporation in addition impression silicones

Evaporation in addition impression silicones

Application of digital image correlation to full-field measurement of shrinkage strain of dental composites

A new method to measure the polymerization shrinkage kinetics of light cured composites

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