• Proceedings of the KACD Conference
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• 2003.11a
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• pp.563-563
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• 2003

The purpose of present study was to evaluate the polymerization shrinkage stress and cuspal deflection in maxillary premolars resulting from polymerization shrinkage of composites and compomers. 1)Measurements of polymerization shrinkage stress. For measurements of polymerization shrinkage stress, Stress measuring machine(R＆B, Daejon, Korea) was used. Composites and compomers which were used in this study were as follows：(omitted)

• Restorative Dentistry and Endodontics
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• v.26 no.2
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• pp.134-140
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• 2001

The polymerization shrinkage of composite resins is an important drawback although the composites have many advantages-more esthetic and conservative than metallic restoratives etc. The purposes of this research were to develop a new measurement method and to manufacture an instrument that can measure the initial dynamic volumetric shrinkage of composite resins during polymerization. The instrument was basically an electromagnetic balance that constructed with a force transducer using position sensitive photo detector(PSPD) and a negative feedback servo amplifier of proportional-derivative(PD) controller. The volumetric change of composites during polymerization was detected continuously as buoyancy change in distilled water by means of Archimedes's principle. It was converted to continuous electrical voltage signal in real time. The signal was properly conditioned and filtered and then it was stored in computer by a data acquisition(DAQ) board. By using this electronic instrument. the dynamic patterns of the polymerization shrinkage of eight commercial(Z-100, DenFil, AeliteFil, Z-250, P-60, SureFil, Synergy compact, and Tetric ceram) composite resins were measured and compared. The results were as follows. 1. From this project of developing instrument, the ability has been achieved that can acquire and process data of electrical signal transformed from various physical phenomenon by using temperature, displacement. photo. and force transducer. As a consequence, the instrumentation and measurement system used to analyze the physical characteristics of various dental materials in dental research field can be designed, manufactured and implemented in lab. 2. This instrument has some advantages. It was insensible to temperature change and could measure true dynamic volumetric shrinkage in real time without complicated process. It showed accuracy and high precision results with small standard deviation. 3. The polymerization shrinkage of composites was significantly different between brands and ranged from 2.47％ to 3.89％, The order of polymerization shrinkage was as follows, in order of increasing shrinkage, SureFil, P60, Z250, Z100, Synergy compact. DenFil, Tetric ceram, and AeliteFil. 4. The polymerization shrinkage rate per unit time, dVol％/dt, showed that the instrument can provide an indirect research method for polymerization reaction kinetics.

• Restorative Dentistry and Endodontics
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• v.28 no.4
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• pp.348-353
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• 2003

The purpose of present study was to evaluate the polymerization shrinkage stress and amount of linear shrinkage of composites and compomers for posterior restoration. For this purpose, linear polymerization shrinkage and polymerization stress were measured. For linear polymerization shrinklage and polymerization stress measurement, custom made Linometer (R&B, Daejon, Korea) and Stress measuring machine was used (R&B, Daejon, Korea). Compositers and compomers were evaluated: Dyract AP (Dentsply Detrey, Gumbh. German) Z100 (3M Dental Products, St. Paul. USA) Surefil (Dentsply Caulk, Milford, USA) Pyramid (Bisco, Schaumburg, USA) Synergy Compact (Coltene, Altstatten, Switzerland), Heliomolar (Vivadent/Ivoclar, Liechtenstein), and Compoglass (Vivadent Ivoclar/Liechtenstein) were used. 15 measurements were made for each material. Linear polymerization shrinkage or polymerization stress for each material was compared with one way ANOVA with Tukey at 95% levels of confidence. For linear shrinkage: Heliomolar, Surefil

• Restorative Dentistry and Endodontics
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• v.35 no.1
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• pp.51-58
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• 2010

Dental composites have improved significantly in physical properties over the past few decades. However, polymerization shrinkage and stress is still the major drawback of composites, limiting its use to selected cases. Much effort has been made to make low shrinking composites to overcome this issue and silorane-based composites have recently been introduced into the market. The aim of this study was to measure the volumetric polymerization shrinkage kinetics of a silorane-based composite and compare it with conventional methacrylate-based composites in order to evaluate its effectiveness in reducing polymerization shrinkage. Five commercial methacrylate-based (Beautifil, Z100, Z250, Z350 and Gradia X) and a silorane-based (P90) composites were investigated. The volumetric change of the composites during light polymerization was detected continuously as buoyancy change in distilled water by means of Archemedes' principle, using a newly made volume shrinkage measurement instrument. The null hypothesis was that there were no differences in polymerization shrinkage, peak polymerization shrinkage rate and peak shrinkage time between the silorane-based composite and methacrylate-based composites. The results were as follows: 1. The shrinkage of silorane-based (P90) composites was the lowest (1.48%), and that of Beautifil composite was the highest (2.80%). There were also significant differences between brands among the methacrylate-based composites. 2. Peak polymerization shrinkage rate was the lowest in P90 (0.13%/s) and the highest in Z100 (0.34%/s). 3. The time to reach peak shrinkage rate of the silorane-based composite (P90) was longer (6.7 s) than those of the methacrylate-based composites (2.4-3.1 s). 4. Peak shrinkage rate showed a strong positive correlation with the product of polymerization shrinkage and the inverse of peak shrinkage time (R = 0.95).

• Restorative Dentistry and Endodontics
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• v.29 no.4
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• pp.346-352
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• 2004

The purpose of present study was to evaluate the polymerization shrinkage stress and cuspal deflection in maxillary premolars resulting from polymerization shrinkage of composites and compomers. Composites and compomers which were used in this study were as follows: Dyract AP, Z100, Surefil. Pyramid, Synergy Compact, Heliomolar, Heliomolar HB, and Compoglass F. For measuring of polymerization shrinkage stress, Stress measuring machine (R&B, Daejon, Korea) was used. One-way ANOVA analysis with Duncan's multiple comparison test were used to determine significant differences between the materials. For measuring of cuspal deflection of tooth, MOD cavities were prepared in 10 extracted maxillary premolars. And reduction of intercuspal distance was measured by strain measuring machine (R&B, Daejon, Korea) One-way ANOVA analysis with Turkey test were used to determine significant differences between the materials. Polymerization shrinkage stress is $\mathbb{\ulcorner}$Heliomolar, Z100, Pyramid < Synergy Compact Compoglass F < Dyract AP < Heliomolr HB, surefil$\mathbb{\lrcorner}$ (P < 0.05). And cuspal delfelction is $\mathbb{\ulcorner}$Z100, Heliomolar, Heliomolar HB, Synergy Compact Surefil. < Compoglass F < Pyramid, Dyract AP$\mathbb{\lrcorner}$ (P < 0.05). Measurements of ploymerization shrinkage stress and those of cuspal deflection of the teeth was different. There is no correlation between polymerization shrinkage stress and cuspal deflection of the teeth(p > 0.05).

• Composites Research
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• v.26 no.3
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• pp.182-188
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• 2013

The purpose of this study was to measure the volumetric polymerization shrinkage kinetics and stress of a silorane-based dental restorative composite and compare it with those of conventional methacrylate-based dental composites. Two methacrylate-based composites (Z250, Z350 flowable) and one silorane-based composite (P90) were investigated. The volumetric polymerization shrinkage of the composites during light curing was measured using a laboratory-made volume shrinkage measurement instrument based on the Archimedes' principle, and the polymerization stress was also determined with the strain gage method. The shrinkage of silorane-based composites (P90) was the lowest, and that of Z350 flowable was the highest. Peak polymerization shrinkage rate was the lowest in P90 and the highest in Z350 flowable. The time to reach peak shrinkage rate of P90 was longer than those of the methacrylate-based composites. The polymerization shrinkage stress of P90 was lower than those of the methacrylate-based composites.

• Restorative Dentistry and Endodontics
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• v.27 no.5
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• pp.488-492
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• 2002

The purpose of this study was to evaluate the effectiveness of plasma arc curing (PAC) unit for composite and compomer curing. To compare its effectiveness with conventional quartz tungsten halogen (QTH) light curing unit, the polymerization shrinkage rates and amounts of three composites (Z100, Z250, Synergy Duo Shade) and one compomer, that had been light cured by PAC unit or QTH unit, was compared using a custome made linometer. The measurement of polymerization shrinkage was peformed after polymerization with either QTH unit or PAC unit. In case of curing with the PAC unit, the composite was light cured with Apollo 95E for 6s, the power density of which was recorded as 1350 mW/$\textrm{cm}^2$ by Coltolux Light Meter. For light curing with QTH unit, the composite was light cured for 30s with the XL2500, the power density of which was recorded as 800 mW/$\textrm{cm}^2$ by Coltolux Light Meter. The amount of linear polymerization shrinkage was recorded in the computer every 0.5s for 60s. Ten measurements were made for each material. The amount of linear polymerization shrinkage for each material in 10s and 60s which were cured with PAC or QTH unit were compared with t test. The amount of polymerization shrinkage in the tested materials were compared with 1way ANOVA with Duncan's multiple range test. As for the amounts of polymerization shrinkage in 60s, there was no difference between PAC unit and QTH unit in Z250 and Synergy Duo Shade. In Z100 and Dyract AP, it was lower when it was cured with PAC unit than when it was cured with QTH unit (p<0.05). As for the amounts of polymerization shrinkage in 10s, there was no difference between PAC unit and QTH unit in Z100 and Dyract AP. The amounts of polymerization shrinkage was significantly higher when it was cured with PAC unit in Z250 and Synergy Duo Shade (p<0.05). The amounts of polymerization shrinkage in the tested materials when they were cured with QTH unit were Z250 (6.6um) < Z100 (9.3um), Dyract AP (9.7um) < Synergy Duo Shade (11.2um) (p<0.05). The amount of polymerization shrinkage when the materials were cured with PAC unit were Dyract AP (5.6um) < Z100 (8.1um), Z250(7.0um) < Synergy Duo Shade (11.2um) (p<0.05).

• Restorative Dentistry and Endodontics
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• v.27 no.2
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• pp.135-141
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• 2002

Objectives : The aim of this study is to evaluate the effect of light intensity variation on the polymerization rate of composite resin using IB system (the experimental equipment designed by Dr. IB Lee) by which real-time volumetric change of composite can be measured. Methods : Three commercial composite resins [Z100(Z1), AeliteFil(AF), SureFil(SF)] were photopolymerized with Variable Intensity Polymerizer unit (Bisco, U.S.A.) under the variable light intensity (75/150/225/300/375/450mW$^2$) during 20 sec. Polymerization shrinkage of samples was detected continuously by IB system during 110 sec and the rate of polymerization shrinkage was obtained by its shrinkage data. Peak time(P.T.) showing the maximum rate of polymerization shrinkage was used to compare the polymerization rate. Results : Peak time decreased with increasing light intensity(p<0.05). Maximum rate of polymerization shrinkage increased with increasing light intensity(p<0.05). Statistical analysis revealed a significant positive correlation between peak time and inverse square root of the light intensity (AF:R=0.965, Zl:R=0.974, SF:R=0.927). Statistical analysis revealed a significant negative correlation between the maximum rate of polymerization shrinkage and peak time(AF:R=-0.933, Zl:R=-0.892, SF:R=-0.883), and a significant positive correlation between the maximum rate of polymerization shrinkage and square root of the light intensity (AF:R=0.988, Zl:R=0.974, SF:R=0.946). Discussion and Conclusions : The polymerization rate of composite resins used in this study was proportional to the square root of light intensity Maximum rate of polymerization shrinkage as well as peak time can be used to compare the polymerization rate. Real-time volume method using IB system can be a simple alternative method to obtain the polymerization rate of composite resins.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.6
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• pp.735-742
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• 2007

Statement of problem. Although a number of previous investigations have been carried out on the polymerization shrinkage-strain kinetics of provisional crown and fixed partial denture (FPD) materials, the effect of the changes of liquid monomer to powder ratio on its polymerization shrinkage-strain kinetics has not been reported. Purpose. The purpose of this study was to investigate the influence of liquid monomer to powder ratio of polymer-based provisional crown and FPD materials on the polymerization shrinkage-strain kinetics. Material and methods. Chemically activated acrylic provisional materials (Alike, Jet, Snap) were investigated. Each material was mixed with different liquid monomer to powder ratios by volume (1.0:3.0, 1.0:2.5, 1.0:2.0, 1.0:1.5, 1.0:1.0). Time dependent polymerization shrinkage- strain kinetics of all materials was measured by the bonded-disk method as a function of time at $23^{\circ}C$. Five recordings were taken for each ratio. The results were statistically analyzed using one-way ANOVA and the multiple comparison Scheffe test at the significance level of 0.05. Trends were also examined by linear regression. Results. At 5 minutes after mixing, the polymerization shrinkage-strains of all materials ranged from only 0.01% to 0.49%. At 10 minutes, the shrinkage-strain of Alike was the highest, 3.45% (liquid monomer to powder ratio=1.0:3.0). Jet and Snap were 2.69% (1.0:2.0) and 1.58% (1.0:3.0), respectively (P>0.05). Most shrinkage (94.3%-96.5%) occurred at 30 minutes after mixing for liquid monomer to powder ratio, ranging from 1.0:3.0 to 1.0:1.0. The highest polymerization shrinkage-strain values were observed for the liquid monomer to powder ratio of 1.0:3.0. At 120 minutes after mixing, the shrinkage-strain values were 4.67%, 4.18%, and 3.07% for Jet, Alike, and Snap, respectively. As the liquid monomer to powder ratio increased, the shrinkage-strain values tend to be decreased linearly (r=-0.769 for Alike, -0.717 for Jet, -0.435 for Snap, $r^2=0.592$ for Alike, 0.515 for Jet, 0.189 for Snap; P<0.05). Conclusion. The increase of the liquid monomer to powder ratio from 1.0:3.0 to 1.0:1.0 had a significant effect on the shrinkage-strain kinetics of polymer-based crown and FPD materials investigated. This increased the working time and decreased the shrinkage-strain during polymerization.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.9-15
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• 2007

As the development of nanotechnology, the use of composite resins which containing nanofillers becomes popular. The purpose of this study was to test the degree of polymerization of nanofillercontaining composite resins. For the study, three different nanofiller-containing composite resins and two different light-curing units were used. To evaluate the degree of polymerization, the maximum polymerization shrinkage taking place during the light curing, and the microhardness, after the light curing, were measured. As results, two light-curing units exhibited a similar emission spectrum to that of the included photoinitiator, camphorquinone. The only difference between the light-curing units were the width of the emission spectrum. Three different composite resins showed different microhardness values. Among them, Grandio showed the greatest microhardness value. However, there was less microhardness difference on the top and bottom surfaces due to the difference of the light-curing units. The maximum polymerization shrinkage values were also similar in the tested specimens regardless of the difference of the light-curing units. However, Grandio showed the least polymerization shrinkage. According to the manufacturers' data, Grandio showed the highest filler content(vol%).