Fiber-reinforced packable resin composites in Class II cavities

OBJECTIVE: To evaluate the 6-year performance of two glass fiber-reinforced packable resin composites in Class II cavities. METHODS: Sixty-three participants received 87 medium to large, cervically dentin bordered, Class II restorations of two fiber-reinforced resin composites, 42 Nulite F (N) and 45 Alert (A). The restorations were evaluated clinically, according to slightly modified USPHS criteria at baseline, after 6 months, and yearly during 6 years. RESULTS: At 2 years the cumulative failure frequencies for N and A were 4.8% and 2.2%, respectively, which increased at 6 years to 25.0% and 12.8%. Reasons for failure were secondary caries, material and cusp fracture. The majority of the failures occurred after 3 years. Secondary caries occurred between 4 and 6 years. The incorporation of fibers resulted in very rough surface characteristics. CONCLUSIONS: A rather high failure rate was observed for one of the fiber-reinforced resin composites, while the other fulfilled the ADA criteria. The occurrence of most failures after 3 years indicated the necessity of long-term evaluations of new materials.     

Polymerization shrinkage of densely-filled resin composites

A new group of restorative materials called "packable" composites has recently been introduced. These products are essentially highly-filled or densely-filled hybrid resin composites. One of the many claims made about these materials is that they undergo less polymerization shrinkage than their conventional counterparts. This in vitro investigation compared the amount of linear shrinkage that occurs within a variety of densely filled resin composites (DFC) and conventional hybrid resin composites when cured with a visible halogen light. Six DFC resins (Alert, Ariston, P60, Prodigy, Solitaire and Surefil) and two hybrids (TPH-Spectrum, Z100) were used in this study. Dimensional change was measured in a linear direction using a calibrated light microscope. Eighty samples of resin composite were tested, resulting in eight groups of 10 samples (N=10) each. The one-way ANOVA with Student-Newman-Keuls post-hoc test was used to compare the shrinkage between groups, and Pearson's Correlation was used to test the relationship between filler characteristics and shrinkage. Alert and P-60 had significantly less shrinkage than Solitaire, Ariston, Prodigy, Z-100 and TPH-S. Thus, the shrinkage values of some DFC resins were significantly less and others were no different from conventional hybrid resins. There is a moderate association between filler volume and shrinkage. Filler size and resin chemistry are other factors that may also effect shrinkage.     

Polymerization shrinkage and contraction stress of dental resin composites

OBJECTIVE: The aim of this study was to evaluate the shrinkage, contraction stress, tensile modulus, and the flow factor of 17 commercially available dental resin composites. METHOD: The volumetric shrinkage measurements were performed by mercury dilatometry, and the contraction stress and tensile modulus were determined by means of stress-strain analysis. The statistical analysis was conducted by ANOVA and Tukey's post hoc test, and linear regression. RESULTS: Strong linear correlation for most resin composites were found for (i) contraction stress and shrinkage (ii) contraction stress and tensile modulus, and (iii) shrinkage and tensile modules. For most of the materials the unpolymerized resin content determines the amount of shrinkage, contraction stress and tensile modules. The pre-polymerized clusters in Heliomolar results in improved shrinkage/contraction stress properties. The shrinkage/contraction stress for Filtek Z100, Aelite Flo, and Flow-it was too high for the amount of resin in the resin composite. This was rationalized by high polymerization rates, a flow factor, and the nature of the resin. SIGNIFICANCE: High shrinkage and/or high contraction stress may lead to failure of the bond between the resin composites and the tooth structure. This study shows that the unpolymerized resin content determines the amount of shrinkage, contraction stress and tensile modules. Therefore, using pre-polymerized clusters will improve shrinkage/contraction stress properties, as was shown in Heliomolar, while high polymerization rates, and low flow factors have a deteriorative effect on the shrinkage/contraction stress properties.     

Polymerization shrinkage and shrinkage stress development in ultra-rapid photo-polymerized bulk fill resin composites

ObjectiveTo determine the polymerization shrinkage (%) and shrinkage stress (MPa) characteristics of ultra-rapid photo-polymerized bulk fill resin composites.MethodsTwo ultra-rapid photo-polymerized bulk fill (URPBF) materials: PFill and PFlow were studied, along with their comparators ECeram and EFlow. PFill contains an addition fragmentation chain transfer (AFCT) agent. The URPBR materials were irradiated using two different 3 s high irradiance protocols (3000 and 3200 mW/cm² based on Bluephase PowerCure and VALO LCUs, respectively) and one 10 s standard protocol (1200 mW/cm² based on a Bluephase PowerCure LCU). Bonded disk and Bioman II instruments were used to measure Polymerization shrinkage % and shrinkage stress MPa, respectively, for 60 min at 23 ± 1 °C (n = 5). Maximum shrinkage-rate and maximum shrinkage stress-rate were also calculated for 15 s via numerical differentiation. The data were analyzed via multiple One-way ANOVA and Tukey post-hoc tests (α = 0.05).ResultsPFill groups, regardless of their irradiance protocol, showed significantly lower PS than the comparator, ECeram (p < 0.05). However, PFlow irradiated via different protocols, was comparable to EFlow and ECeram (p > 0.05). PFill consistently produced stress results which were significantly lower than ECeram (p < 0.05) and were comparable for both high irradiance protocols (p > 0.05). PFlow only exhibited significantly higher shrinkage stress when polymerized with the 3 sVALO protocol (p < 0.05).The maximum shrinkage strain-rate (%/s) was significantly lower in PFill-10s and PFill-3s groups (using PowerCure LCU) compared to ECeram. However, no differences were seen between PFlow and EFlow (p > 0.05). The maximum shrinkage stress-rate of PFill and PFlow was comparable between different irradiation protocols, as well as to their comparator ECeram (p > 0.05).SignificanceHigh irradiation protocols over ultra-short periods led to slightly lower shrinkage strain but slightly higher stress, possibly due to reduced network mobility. The AFCT agent incorporated in PFill composite seemed to reduce shrinkage stress development, even with high irradiance protocols.     

Margin quality and microleakage of Class II composite resin restorations

Margin quality and isotope microleakage analyses of Class II restorations placed in extracted human molars were compared using various composite resins and placement techniques. At occlusal margins, the traditional (experimental) composite resin restoration placed by the incremental technique showed less microleakage than did the traditional (commercial) [corrected] composite resin restoration placed by the bulk technique. In each group, the occlusal and proximal adaptations had significantly higher "excellent margin" than did the cervical adaptation. Thus, the marginal adaptation at the cervical aspect of conventional Class II composite resin restorations may present a problem with respect to microleakage.     

Factors associated with microleakage in Class II resin composite restorations

This in vitro study investigated the correlation between factors related to cavosurface marginal adaptation and microleakage in Class II cavities restored with a light- or chemical-activated resin composite. Standardized cavities were prepared in 40 molars that were randomly divided between both materials. Each of the groups was, in turn, divided, so that the restorations were placed by incremental and bulk techniques. The resultant four groups (n = 10), each with material/technique variations, had their marginal gaps measured by environmental scanning electron microscopy at randomly selected facial and lingual points of the proximal box of each restoration. After sectioning the teeth, interfacial dye penetration was assessed by light stereomicroscopy according to an ordinal scale at the same locations as for the marginal gaps. In a general linear model with microleakage as a dependent variable, no correlation between marginal gap size and microleakage was found (p = 0.802), although the interaction of the material and placement technique (p = 0.028) and material alone (p = 0.063) influenced microleakage. The model explained 63% of the variation in microleakage. It was concluded that, irrespective of the possible role of marginal gap in the occurrence of microleakage, the choice of material and placement technique are important determining factors in microleakage.     

Polymerization shrinkage and shrinkage force kinetics of high- and low-viscosity dimethacrylate- and ormocer-based bulk-fill resin composites

Odontology - The aim of the present study was to investigate polymerization shrinkage, shrinkage force development, and degree of monomer conversion of high- and low-viscosity dimethacrylate- and...     

In vitro microleakage of packable composites in Class II restorations.

OBJECTIVES: To evaluate the microleakage in Class II resin restorations at different margins and the polymerization shrinkage of the composites used. METHOD AND MATERIALS: Four standardized Class II (3 x 5 x 2 mm) cavities were prepared in 32 teeth. The sample had the gingival margin either 1 mm below or above the cementoenamel junction. Teeth were divided and restored according to the following protocols: (1) Single Bond + P60; (2) Prime & Bond NT + Surefil; (3) Bond-1 + Alert; and (4) Prime & Bond 2.1 + TPH. After 7 days, the specimens were thermocycled (500 cycles between 5 to 55 degrees C with a 15-second dwell time), immersed in 0.5% methylene blue for 24 hours, sectioned, and evaluated (both surfaces) at the gingival margin by two examiners, using a 0 to 3 marginal infiltration score system. The polymerization shrinkage of the composites (n = 6) was evaluated by the disk deflective method. Microleakage data was evaluated by nonparametric repeated measures ANOVA. The percentage of polymerization shrinkage was evaluated by ANOVA and Tukey's test. RESULTS: Only protocol 3 showed a significant difference between enamel and cementum margin. No difference was detected among the protocols in the enamel margin. Only protocol 1 provided a good seal in the cementum margin. All packable composites showed lower polymerization shrinkage than the hybrid tested. CONCLUSION: All protocols are able to prevent dye penetration in enamel margins; however, protocol 1 is preferable to reduce the microleakage in the cementum margin. The packable composites showed lower polymerization shrinkage compared to the hybrid resin.     

Polymerization shrinkage of visible-light-cured composites

This study investigated the long-term dimensional changes of a conventional and a polyacid-modified composite resin and the effects of hydration on polymerization shrinkage. A strain-monitoring device was used to measure the linear polymerization shrinkage of the composites in the free state when stored in water at 37 degrees C or air at 26 degrees C over a one-month period. Results showed that the polymerization reaction of both conventional and polyacid-modified composite resins was accompanied by a dimensional shrinkage change. The rate of shrinkage for both composites was greatest during the polymerization reaction and continued after removal of the curing light. When stored in water, the greatest shrinkage was noted at one hour for both materials. This was followed by a slow uptake of water and expansion from one day to one month. The polyacid-modified composite had significantly less polymerization shrinkage than the conventional composite after one month of storage in water.     

Evaluation of the microleakage at the proximal walls of Class II cavities restored using resin composite and precured composite inserts.

OBJECTIVE: This in vitro study compared the microleakage of resin composite restorations placed in Class II cavity preparations using an incremental placement technique with and without the addition of precured resin composite inserts. METHOD AND MATERIALS: Sixty standardized mesio-occlusal and disto-occlusal cavities were prepared in 30 recently extracted molar teeth. Twenty cavities were restored by employing the incremental placement technique (group I), and 40 cavities were restored using the incremental placement in the presence of precured composite inserts of two sizes: 1 x 3 mm (group II) and 1.25 x 3 mm (group III). The restored teeth were thermocycled for 250 cycles in water baths set at temperatures of 5 degrees C and 50 degrees C using a 30-second dwell time, stained, and sectioned horizontally at the middle of the restoration. Following sectioning, each specimen was microscopically examined at x 4 magnification. The extent of dye penetration at the tooth/restoration interface was scored for each test group, and the scores obtained were subjected to one-way analysis of variance (ANOVA) and Tukey's pairwise comparison at a 95% significance level. RESULTS: The current investigation showed statistically significant differences in dye penetration between the three test groups. CONCLUSION: The use of precured resin composite inserts with the incremental placement technique in the restoration of Class II cavity preparations seems to improve the marginal seal of the proximal walls of finished restorations.     

Gingival microleakage of Class II resin composite restorations with fiber inserts

PURPOSE: This investigation evaluated the effect of glass and polyethylene fiber inserts on the microleakage of Class II composite restorations with gingival margins on root surfaces. METHODS: Fifty-four intact molars were sterilized with Gamma irradiation and mounted in acrylic bases. Class II slot cavities were made on both proximal sides of each tooth (3 mm wide, 1.5 mm deep) with the gingival margin on the root surface. The teeth were divided into nine groups, according to the technique of restoration and type of bonding agent. Filtek P-60 (3M/ESPE) was used to restore all cavities. Two types of fiber inserts were used: glass fiber (Ever Stick, StickTech) and polyethylene (Ribbond-THM), with three bonding agents being employed: Scotch Bond Multipurpose (3M/ESPE), Clearfil SE Bond (Kuraray) and Xeno IV (Dentsply). In the experimental groups, 3 mm long fiber inserts were inserted into restorations at the gingival seat. The control groups had no fiber inserts. The restorations were made incrementally and cured with LED light (UltraLume5, Ultradent). The restored teeth were stored in water for two weeks, then thermocycled for 3000 cycles (5 degrees C and 55 degrees C). The tooth surfaces were sealed with nail polish, except at the restoration margins. The teeth were immersed in 2% procion red dye solution, sectioned and dye penetration was assessed to determine the extent of microleakage according to a six-point scale. RESULTS: The fiber groups generally showed reduced microleakage scores compared to the control groups. The Clearfil SE Bond (Kuraray)/Filtek P-60 (3M/ESPE) combination produced the lowest degree of microleakage, irrespective of fiber type. However, the glass fiber groups were more consistent in reducing microleakage than the polyethylene groups. CONCLUSIONS: The use of fiber inserts significantly reduced gingival microleakage in Class II composite restorations with gingival margins in dentin, irrespective of the adhesive used. Clearfil SE Bond (Kuraray)/Filtek P60 (3M/ESPE) produced the lowest microleakage scores.     

复合树脂收缩应力研究进展

复合树脂具有较好的美观性，因此临床应用越来越广泛。但树脂聚合时的收缩应力却影响临床效果，也是人们研究复合树脂的一个焦点。本文就复合树脂收缩应力的产生、影响因素、降低收缩应力的方法及研究收缩应力常用的方法做一综述。     

Effect of resin coating on dentin bonding of resin cement in Class II cavities

This study was designed to evaluate the efficacy of resin coating on the regional microtensile bond strength (MTBS) of a resin cement to the dentin walls of Class II cavities. Twenty mesio-occlusal cavities were prepared in human molars. In 10 cavities, a resin coating consisting of a self-etching primer bonding system, Clearfil SE Bond, and a low-viscosity microfilled resin, Protect Liner F, was applied. The other 10 teeth served as a non-coating group. After impression taking and temporization, they were kept in water for one day. Composite inlays were then cemented with a dual-cure resin cement, Panavia F 2.0, and stored in water for one day. Thereafter, MTBSs were measured. Two-way ANOVA (p=0.05) revealed that the MTBS of resin cement to dentin was influenced by resin coating, but not by regional difference. In conclusion, application of a resin coating to the dentin surface significantly improved the MTBS in indirect restorations.     

Three different methods to evaluate microleakage of packable composites in Class II restorations

This in vitro study compared three different methods to evaluate detectable levels of microleakage in Class II restorations placed with five commercially available packable resin composites: Alert, Glacier, Pyramid, Solitaire 2 and SureFil. A flowable resin composite, Flow-It, was used to line all packable composites. The hybrid resin composite Z100 was also included. The adhesive system used with all groups was Scotchbond MultiPurpose Plus. Standard Class II cavities were prepared on the mesial (enamel margins) and distal (dentin margins) sides of the teeth with no communication between them. Based on a power analysis, 180 permanent human molars were randomly assign to each of six groups with 30 specimens per group. All restorative materials were placed following manufacturers' recommendations. Following restoration and thermocycling, the specimens were stored at room temperature in solutions of 45Ca, methylene blue and rhodamine B, sequentially. Microleakage was ordinal scored as 1 (no penetration), 2 (penetration up to one-third of the cervical floor), 3 (penetration beyond one-third of the cervical floor to the axial wall) and 4 (penetration along the axial wall) by two independent evaluators. Analysis of the occlusal surfaces was also accomplished following the same scheme. In this study, tracers/dyes were evaluated for differences in penetration using generalized estimating equation methodology applied to cumulative logistic regression models. The results showed that Rhodamine B detected more microleakage than 45Ca or methylene blue, and 45Ca generally detected more microleakage than methylene blue.     

Influence of different restorative techniques on microleakage in Class II cavities with gingival wall in cementum

This study compared marginal leakage of Class II cavities with gingival margin in cementum using different techniques. Twenty-four recently extracted third molars were used. Proximal standard box cavities were prepared in both mesial and distal surfaces. The gingival margin was located apical to the cemento-enamel junction. All the preparations and restorations were performed by the same operator. Standard cavities were randomly divided into three groups (n = 16) and restored as follow: Group 1-light-cured composite resin; Group 2-self-cured composite resin + light-cured composite resin and Group 3-amalgam + light-cured composite resin. After polishing, the teeth were thermocycled and their gingival margins exposed to dye. Specimens were sectioned and leakage scores observed in accordance with a standard ranking. Data were subjected to statistical analysis (Kruskal-Wallis). Results showed that the amalgam/resin composite combination demonstrated the least leakage.