Degree Of Polymerization Shrinkage Research Articles

Assessment of polymerization shrinkage of different bulk-fill resin composites

Objectives: This research was designed to evaluate the effect of polymerization shrinkage of different bulk-fill resin composites. Materials & Methods: Ninety extracted molars were prepared as specimens by having a box shape proximal cavity for the restoration of composite resins. The specimens were divided into three main groups (n=30), according to the resin composite materials used (sonic fill, flowable and packable bulk-fill). Profile projector was used for assessment of polymerization shrinkage Results: There is no significant difference between the variables. Sonic fill composite resin has lower polymerization shrinkage than flowable bulk-fill composite and packable bulk-fill composite. The marginal adaptation of sonically activated resin composite is more than the polymerization shrinkage of sonically activated resin composite, while the storage time of sonically activated resin composite is less in bulk-fill .Conclusions: Success of resin composites depends primarily on the degree of polymerization shrinkage as when the shrinkage decrease mostly the post-operative problems decrease.

Influence of shade of adhesive resin cement on its polymerization shrinkage

ABSTRACTResin cements have the ability to bond to the tooth structure and to several indirect restorative materials and they are available in different transparency and shades. However, polymerization shrinkage remains to be a problem that leads to gap formation at the margins of restoration, and accordingly microleakage may occur. The purpose of this study was to investigate the influence of the shade of adhesive resin cement on its polymerization shrinkage. Five shades (Group 1: universal; Group 2: brown; Group 3: clear; Group 4: opaque white; Group 5: opaque yellow) of a dual-cure composite cement system (Clearfil Esthetic Cement, Kuraray, Tokyo, Japan) were studied with 10 specimens of each shade. Volumetric shrinkages of the composite cements of these five shades were evaluated using a video-imaging device (Acu-Vol; Bisco, Inc.) by measuring the volumes before and after polymerization. Different shades displayed different volumetric shrinkages. Group 5 (2.62%) and Group 2 (3.96%) displayed the lowest and highest shrinkage percentages, respectively, with their respective shrinkage values being significantly different from those of the other groups (p < 0.05). The obtained results indicate that the shade of resin cement does affect its degree of polymerization shrinkage.

Clinical Evaluation of Class I Restorations Made with Composite with Low Degree of Polymerization Shrinkage

Clinical Evaluation of Class I Restorations Made with Composite with Low Degree of Polymerization Shrinkage

Microhardness and polymerization shrinkage of flowable resins that are light cured using a blue laser

This study evaluated the microhardness and polymerization shrinkage of flowable resins that are cured using different light sources. Seven flowable resins and two light sources (diode-pumped solid-state (DPSS) laser (LAS) and Optilux 501 (OP)) were chosen for the study. To evaluate the microhardness, a mold (height: 2 mm, inner diameter: 4 mm) was filled with resin and then light cured. The microhardness was measured at the top and bottom surfaces after aging for 24 h. The level of polymerization shrinkage was evaluated for 130 s (during and after the light curing) by measuring the dimensions of the cylindrical shape resin filling. The light intensity of the LAS and OP was approximately 520 mW/cm(2) and 800 mW/cm(2), respectively. The data for the microhardness and polymerization shrinkage were analyzed statistically. The microhardness (Hv) of the specimens at the top and bottom surface ranged from 25.3 ± 0.6 to 55.3 ± 1.0 and 28.0 ± 2.6 to 63.0 ± 2.3, respectively. Admira flow, Grandio flow, and Filtek Z350 flow showed a slightly higher microhardness at the bottom surface than that at the top surface. The degree of polymerization shrinkage (μm) of the specimens ranged from 30.5 ± 1.3 to 45.9 ± 0.6 for LAS and from 35.1 ± 1.5 to 47.1 ± 1.0 for OP. The values obtained using LAS and OP showed a statistical difference, but in many cases, the difference between the absolute values was minor.

The effect of irradiation modes on polymerization and microleakage of composite resin

The aim of this study was to investigate the effect of light irradiation modes on polymerization shrinkage, degree of cure and microleakage of a composite resin. VIP (Bisco Dental Products, Schaumburg, IL, USA) and Optilux 501 (Demetron/Kerr, Danbury, CT, USA) were used for curing Filtek Z-250 (3M Dental Products, St. Paul., MN, USA) composite resin using following irradiation modes: VIP (Bisco) 200mW/ (V2), 400mW/ (V4), 600mW/ (V6), Pulse-delay (200 mW/ 3 seconds, 5 minutes wait, 600mW/ 30seconds, VPD) and Optilux 501 (Demetron/Kerr) C-mode (OC), R-mode (OR). Linear polymerization shrinkage of the composite specimens were measured using Linometer (R&B, Daejeon, Korea) for 90 seconds for V2, V4, V6, OC, OR groups and for up to 363 seconds for VPD group (n=10, each). Degree of conversion was measured using FTIR spectrometer (IFS 120 HR, Bruker Karlsruhe, Germany) at the bottom surface of 2 mm thick composite specimens V2, Y4, V6, OC groups were measured separately at five irradiation times (5, 10, 20, 40, 60 seconds) and OR, VPD groups were measured in the above mentioned irradiation modes (n=5 each). Microhardness was measured using Digital microhardness tester (FM7, Future-Tech Co., Tokyo, Japan) at the top and bottom surfaces of 2mm thick composite specimens after exposure to the same irradiation modes as the test of degree of conversion(n=3, each). For the microleakage test, class V cavities were prepared on the distal surface of the ninety extracted human third molars. The cavities were restored with one of the following irradiation modes : V2/60 seconds, V4/40 seconds, V6/30 seconds, VPD , OC and OR. Microleakage was assessed by dye penetration along enamel and dentin margins of cavities. Mean polymerization shrinkage, mean degree of conversion and mean microhardness values for all groups at each time were analyzed using one-way ANOVA and Duncan's multiple range test, and using chi-square test far microleakage values. The results were as follows : . Polymerization shrinkage was increased with higher light intensity in groups using VIP (Bisco) : the highest with 600mW/, followed by Pulse-delay, 400mW/ and 200mW/ groups, The degree of polymerization shrinkage was higher with Continuous mode than with Ramp mode in groups using Optilux 501 (Demetron/Kerr). . Degree of conversion and microhardness values were higher with higher light intensity. The final degree of conversion was in the range of 44.7 to 54.98% and the final microhardness value in the range of 34.10 to 56.30. . Microleakage was greater in dentin margin than in enamel margin. Higher light intensity showed more microleakage in dentin margin in groups using VIP (Bisco). The microleakage was the lowest with Continuous mode in enamel margin and with Ramp mode in dentin margin when Optilux 501 (Demetron/Kerr) was used.

Polymerization Shrinkage of Restorative Resins Using Laser and Visible Light Curing

This in vitro investigation compared the amount of linear shrinkage that occurs when a light-cured composite resin is cured with a visible light source, and also with an argon laser. When composite resins are light-cured, they undergo a certain degree of polymerization shrinkage, which can be clinically significant and affect the efficacy of the restoration. A new protocol utilizes laser curing instead of conventional visible light. Two hybrid composite resins were used, Z100 and TPH-Spectrum. Dimensional change was measured in a linear direction, using a calibrated light-microscope. A total of 40 samples of composite resin was tested using two curing lights, and two hybrid composite resins, resulting in four groups of 10 samples (n = 10) each. According to manufacturer instructions, curing time for the laser was 10 sec, and for visible light was 40 sec. With TPH-Spectrum, the mean shrinkage with visible light was 0.583% compared to that with laser light which was 0.591%. With Z100, the mean shrinkage with visible light was 0.565%, compared to that with laser light which was 0.551%. There was no significant difference in amount of shrinkage of hybrid composite resins between using visible light or laser light. There was also no significant difference in shrinkage between the two hybrid composites for either light source.