Lower Polymerization Shrinkage Research Articles

Study on the polymerization shrinkage and mechanical-physical properties of dental resin composite modified by polyurethane dimechacrylate and glass flake fillers: Short title: Aging resistance for dental resin composites with low shrinkage

ObjectivesWe intend to explore the polymerization shrinkage and mechanical-physical properties of the dental resin composite modified by polyurethane oligomer PU-MA and glass flakes fillers, and provide some experimental information for developing new dental materials. MethodsBased on Bis-GMA/TEGDMA, the new dental resin composite was hand fabricated by combining PU-MA with different content (65 wt% ∼ 75 wt%) of glass flakes/Si-Al-borosilicate glass mixed fillers. The kinetics of polymerization shrinkage was investigated by using an experimental set-up based on laser triangulation. The mechanical-physical properties of specimens after 60 days water immersion and 5000 times thermo-cycles were measured by three-point bending test and micro vickers hardness tester. Data were submitted to one-way ANOVA/LSD-test (α = 0.05). Independent sample T test was used to analyze the data before and after aging. Two-way ANOVA was adopted to analyze the effect of composition and aging condition on the mechanical-physical properties (α = 0.05). ResultsPU-PG-75% performs lower volume shrinkage (1.35 %). As the increase of filler content, the water sorption and solubility increased and the depth of cure decreased significantly (P < 0.05). After aging, the flexural strength, elasticity modulus and vickers hardness of commercial products dropped obviously and PU-PG-75wt% was relatively stable. Conclusions20 wt% PU-MA could decrease the volume shrinkage of dental resin composite effectively. 60 days water immersion and 5000 times thermal cycles simultaneously resulted in a significant reduction in the flexural properties for experimental materials. PU-PG-75% may have the potential to be taken as a low shrinkage dental resin composite with good mechanical properties. Clinical SignificanceThis new synthesized composite could perform low polymerization shrinkage and better mechanical resistance, which may provide a new idea for improving the lifespan of direct restoration.

Characterization of dental light-curing resin composites incorporating multiple modified low-shrink monomers

ObjectivePolymerization shrinkage poses a significant challenge in dental resin composites. The objective of this study is to introduce spiroorthocarbonate monomer 3,9-dimethylene-1,3,5,7-tetraoxa-spiro[5,5]undecane (BMSOC) and epoxy resin monomer 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (ECHM-ECHC) into bisphenol-S-bis(3-methacrylato-2-hydroxy propyl)ether (BisS-GMA) based resin composites to develop composites with reduced shrinkage properties. MethodsBMSOC and BisS-GMA were synthesized and thoroughly mixed with ECHM-ECHC, followed by inorganic fillers and photoinitiators. Based on the composition of the resin matrix, five groups of experimental composites were prepared, with traditional bisphenol A-dimethacrylate glycidyl ester (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) based composite serving as the control. The polymerization properties, including degree of conversion (DC) and polymerization shrinkage (PS), as well as marginal microleakage, wettability, flexural strength (FS), flexural modulus (FM), and biocompatibility were evaluated. ResultsThe results demonstrated that compared with the control group, the PS of BisS-GMA based composites containing BMSOC and ECHM-ECHC were significantly reduced (P < 0.05), and the lowest PS (0.96 ± 0.08 %) was observed when the ratio of BisS-GMA: (Epoxy + BMSOC) was 4:6. Additionally, the experimental composites also exhibited improved DC, minimal microleakage, low hydrophilicity, enhanced mechanical properties, qualified in vivo biocompatibility, and slight/moderate in vitro biocompatibility. SignificanceThe resin composites incorporating multiple modified low-shrink monomers are promising for dental applications to prevent various clinical problems caused by PS and extend restoration longevity.

Epigallocatechin gallate-immobilized antimicrobial resin with rechargeable fluorinated synergistic composite for enhanced caries control

ObjectivesGiven the global prevalence of dental caries, impacting 2.5 billion individuals, the development of sophisticated prevention filling materials is crucial. Streptococcus mutans, the principal caries-causing strain, produces acids that demineralize teeth and initiate dental caries. To address this issue, we aimed to develop a synergistic resin-based composite for enhancing caries control. MethodsThe synergistic resin composite incorporates fluorinated kaolinite and silanized Al2O3 nanoparticle fillers into an epigallocatechin gallate (EGCG) immobilized urethane-modified epoxy acrylate (U-EA) resin matrix, referred to the as-prepared resin composite. The EGCG-modified TPGDA/U-EA network was synthesized by preparing methacrylate-functionalized isocyanate (HI), reacting it with EGCG to form HI-EGCG, and then incorporating HI-EGCG into the TPGDA/U-EA matrix. The lamellar space within the kaolinite layer was expanded through the intercalation of acrylamide into kaolinite, enhancing its capability to adsorb and release fluoride ions (F–). The layered structure of acrylamide/ kaolinite in the U-EA resin composite acts as a F– reservoir. ResultsThe physico-mechanical properties of the as-prepared resin composites are comparable to those of commercial products, exhibiting lower polymerization shrinkage, substantial F– release and recharge and favorable diametral tensile strength. The immobilized EGCG in the composite exhibits potent antimicrobial properties, effectively reducing the biofilm biomass. Furthermore, the synergistic effect of EGCG and fluorinated kaolinite efficiently counteracts acid-induced hydroxyapatite dissolution, thereby suppressing demineralization and promoting enamel remineralization. SignificanceOur innovative EGCG and fluoride synergistic composite provides enhanced antimicrobial properties, durable anti-demineralization, and tooth remineralization effects, positioning it as a promising solution for effective caries control and long-term dental maintenance.

Novel low-shrinkage dental resin containing microcapsules with antibacterial and self-healing properties

Dental resin restorations commonly fail because of fractures and secondary caries. The aim of this research was to synthesize a novel low-shrinkage dental resin with antibacterial and self-healing properties. The low-shrinkage dental resin was obtained by incorporating a 20 wt% anti-shrinkage mixture of an expanding monomer 3,9-diethyl-3,9-dimethylol −1,5,7,11-tetraoxaspiro[5,5] undecane and an epoxy resin monomer diallyl bisphenol A diglycidyl ether (1:1, referred as “UE”) and different mass fractions of self-healing antibacterial microcapsules (0%, 2.5%, 5%, 7.5%, and 10%) were incorporated into the matrix to prepare multifunctional dental resin. Polymerization shrinkage, mechanical properties, antibacterial activity, self-healing ability, and cytotoxicity of this dental resin were evaluated. The polymerization volumetric shrinkage of resin containing 20 wt% UE and 7.5 wt% microcapsules was reduced by 30.12% (4.13% ± 0.42%) compared with control. Furthermore, it exhibited high antibacterial activity and a good self-healing efficiency of 71% without adversely affecting the mechanical property and cell viability. This novel multifunctional dental resin with low polymerization shrinkage and excellent antibacterial activity and self-healing capability has potential application as a dental resin material to decrease the incidence of fractures and secondary caries.

Novel Dental Low-Shrinkage-Stress Composite with Antibacterial Dimethylaminododecyl Methacrylate Monomer.

Current dental resins exhibit polymerization shrinkage causing microleakage, which has the potential to cause recurrent caries. Our objectives were to create and characterize low-shrinkage-stress (LSS) composites with dimethylaminododecyl methacrylate (DMADDM) as an antibacterial agent to combat recurrent caries. Triethylene glycol divinylbenzyl ether and urethane dimethacrylate were used to reduce shrinkage stress. DMADDM was incorporated at different mass fractions (0%, 1.5%, 3%, and 5%). Flexural strength, elastic modulus, degree of conversion, polymerization stress, and antimicrobial activity were assessed. The composite with 5% DMADDM demonstrated higher flexural strength than the commercial group (p < 0.05). The addition of DMADDM in BisGMA-TEGDMA resin and LSS resin achieved clinically acceptable degrees of conversion. However, LSS composites exhibited much lower polymerization shrinkage stress than BisGMA-TEGDMA composite groups (p < 0.05). The addition of 3% and 5% DMADDM showed a 6-log reduction in Streptococcus mutans (S. mutans) biofilm CFUs compared to commercial control (p < 0.001). Biofilm biomass and lactic acid were also substantially decreased via DMADDM (p < 0.05). The novel LSS dental composite containing 3% DMADDM demonstrated potent antibacterial action against S. mutans biofilms and much lower polymerization shrinkage-stress, while maintaining excellent mechanical characteristics. The new composite is promising for dental applications to prevent secondary caries and increase restoration longevity.

Preparation and characterization of silica based nanoclusters as reinforcement for dental applications

AbstractAs composite resins become the most extensively utilized material in the field of cosmetic and restorative dentistry, several strategies to overcome dental composites' challenges such as long‐term mechanical failure and secondary caries are continuously being developed. Among them, the design of suitable fillers to optimize their clinical performance has been given priority in addressing those shortcomings. In this study, silica‐based nanoclusters were synthesized and used as fillers to prepare UV curable dental composites was assessed. Nanoclusters were prepared by prepolymerization followed by pulverization and sieving of commercial silica nanoparticles with triethylene glycol dimethacrylate monomer. The composites were then made by filling 55:25:20 weight ratio of urethane dimethacrylate, bisphenol A glycidyl methacrylate, and triethylene glycol dimethacrylate, respectively with varying concentration of nanoclusters. The clusters and composites were characterized by SEM, TGA, and FTIR analyzes. The results have shown a significant improvement of physical and mechanical properties in composites containing nanoclusters. Increasing nanocluster concentration caused a reduction in composite polymerization shrinkage, water absorption and solubility as well as limited rise of flexural strength. At 50% filler load, nanoclusters doped composites exhibited higher flexural strength than nanoparticles doped composites. Furthermore, the blending of nanoclusters with nanoparticles as fillers produced the composites having the lowest polymerization shrinkage (2.2%) and the highest flexural strength (113.91 MPa). Overall, the synthesized nanoclusters have shown greater performance in comparison with the current available silica nanoparticles.

Investigation of Thermal-Induced Changes in Molecular Order on Photopolymerization and Performance Properties of a Nematic Liquid-Crystal Diacrylate.

Polymerization shrinkage and associated stresses are the main reasons for dental restorative failure. We developed a series of liquid crystal diacrylates and dimethacrylates which have markedly low polymerization shrinkage. In order to fully understand the effects of temperature-induced changes of molecular order on the photopolymerization process and performance properties of the generated polymers, the photopolymerization of a difunctional acrylate, 2-t-butyl-1,4-phenylene bis (4-(6-(acryloyloxy)hexyloxy)benzoate), which exists in the nematic liquid crystalline phase at room temperature, was investigated as a function of photopolymerization temperature over the nematic to isotropic range. Morphological studies suggested that a mesogenic phase was immediately formed in the polymer even if polymerization in thin films occurred above the nematic-to-isotropic (N→I) transition temperature of the monomer (Tn-i = 45.8 °C). Dynamic mechanical analysis of 2 × 2 mm cross-section bar samples polymerized at 60 °C showed reduced elastic moduli, increased glass transition temperature and formation of a more crosslinked network, in comparison to polymers formed at lower polymerization temperatures. Fractography analysis showed that polymers generated from the nematic liquid crystalline phase underwent a different fracture pattern in comparison to those generated from the isotropic phase. Volumetric shrinkage (2.2%) found in polymer polymerized from the nematic liquid crystalline phase at room temperature was substantially less than the 6.0% observed in polymer polymerized from an initial isotropic phase at 60 °C, indicating that an organized monomer can greatly contribute to reducing cure shrinkage.

BULK FILL COMPOSITE RESIN RESTORATION TECHNIQUES REPLACE INCREMENTAL TECHNIQUES

Introduction: Shrinkage during the polymerization process is the main disadvantage of using composite resins because it creates pressure between the tooth and the restoration which causes failure of the adhesion of the composite resin to the tooth, micro-fissures, and cuspid deflection. Review: To reduce shrinkage that occurs, it is known that conventional composite resins must be inserted into the cavity incrementally or in layers with a maximum thickness of 2 mm per layer. However, the incremental insertion method has several disadvantages, namely that it requires a longer clinical time for restoration. To overcome the shortcomings of these conventional composites, Bulk-fill composite resin was introduced. Composite bulk fill is a sophisticated technology that allows composites to be directly placed on the restoration, has a low polymerization shrinkage to reduce micro-leakage, reduces stress in the presence of elasticity, increases the depth of at least 4 mm translucent at the time of application, is very conducive to light transmission, is more flowable to allow adaptation to the cavity, including cervical margins, it is easy to apply with minimal handling and is resistant to large stresses. Conclusion: With the characteristics possessed by the Bulk-fill composite resin, it is known that the bulk-fill technique in addition to reducing the clinical application time, can also improve the edge adaptation between the restoration and the tooth compared to the incremental technique, without reducing its physical strength.

Novel Antibacterial Copolymers Based on Quaternary Ammonium Urethane-Dimethacrylate Analogues and Triethylene Glycol Dimethacrylate.

The growing scale of secondary caries and occurrence of antibiotic-resistant bacterial strains require the development of antibacterial dental composites. It can be achieved by the chemical introduction of quaternary ammonium dimethacrylates into dental composites. In this study, physicochemical and antibacterial properties of six novel copolymers consisting of 60 wt. % quaternary ammonium urethane-dimethacrylate analogues (QAUDMA) and 40 wt. % triethylene glycol dimethacrylate (TEGDMA) were investigated. Uncured compositions had suitable refractive index (RI), density (dm), and glass transition temperature (Tgm). Copolymers had low polymerization shrinkage (S), high degree of conversion (DC) and high glass transition temperature (Tgp). They also showed high antibacterial effectiveness against S. aureus and E. coli bacterial strains. It was manifested by the reduction in cell proliferation, decrease in the number of bacteria adhered on their surfaces, and presence of growth inhibition zones. It can be concluded that the copolymerization of bioactive QAUDMAs with TEGDMA provided copolymers with high antibacterial activity and rewarding physicochemical properties.

Effect of preheating on polymerization shrinkage strain of BIS-GMA free and containing resin composite restorative materials (in vitro study)

BackgroundThis study investigated the effect of preheating of bulk-fill BIS-GMA free and containing resin composite on post-gel shrinkage strain. In a split Teflon mold, sixty resin composite specimens were prepared with dimensions 7 mm length × 4 mm width × 4 mm height. Thirty specimens of each tested restorative materials were prepared, ten specimens for each selected temperature used in the study (room temperature 23 °C, 50 °C and 65 °C). The resin composite was monitored for post-gel shrinkage strain for 3 min after light irradiation using strain gauges. For pairwise comparisons, Duncan’s multiple range test was used to analyze the data after two-way ANOVA. The p ≤ 0.05 significance level was chosen.ResultsViscalor thermoviscous bulk-fill composite Bis-GMA containing had the lowest polymerization shrinkage strain values in the three different temperatures. There was a statistically significant difference between groups according to material used at different temperatures. Both tested materials showed the highest shrinkage strain when preheated at 65 °C.ConclusionsWhile the technology of thermoviscous is introduced to deliver the viscosity of a flowable resin composite so reducing the polymerization strain, it actually had adverse effect on it. Preheating of bulk-fill BIS-GMA free resin composite either to 50 °C or 65 °C had no effect on decreasing the polymerization shrinkage strain. Polymerization shrinkage strain of bulk-fill BIS-GMA contains resin composite either without or with preheating far superior to that of BIS-GMA free resin composite.

Fracture Resistance of Teeth Restored with Newer Methacrylate-Based Dental Composite Materials: An In Vitro Study

Introduction: Composite have evolved significantly due to the increase in the demand for a more esthetic and conservative approach in dentistry. Modifications have been made on the filler particle size and loading, followed by alterations in the resin matrix substance. Methacrylate-based composite with the addition of nanoparticles to the filler has been introduced in the market, providing improved esthetics and lower polymerization shrinkage. The present study was done to compare the fracture resistance of teeth restored using two newer methacrylate-based composite materials, along with the flexural strength of the composites. Methods: Sixty mandibular premolars were divided into two control groups of 10 teeth each and two experimental groups of 20 teeth. Group I − intact teeth with no preparations (n = 10), Group II − prepared but unrestored teeth (n = 10), Group III − teeth prepared and restored with a stackable nanohybrid methacrylate-based composite material (IPS Empress DirectTM), and Group IV − teeth prepared and restored with a packable submicron methacrylate-based composite material (Brilliant EverglowTM), respectively. The teeth were embedded in resin-filled PVC rings, and a compressive loading test was carried out for all groups at a cross-head speed of 0.5 mm/min. The flexural strengths of the two composite materials were also analyzed using three-point bending test using Universal Testing Machine. The statistical significance (P < 0.05) of the differences between the experimental groups was analyzed by ANOVA and Tukey post hoc test. Results: The mean fracture resistance was highest in Group IV (1877.37 ± 494.79) followed by Group III (1763.69 ± 392.51), Group I (1607.08 ± 283.48), and Group II having the least (1442.08 ± 373.66). The mean fracture resistance overall differed significantly between the four groups (P = 0.048). Tukey test showed fracture resistance differed significantly between Group II and Group IV (P = 0.042) and no significance among other groups. Conclusion: Fracture resistance was highest in the group restored with the packable submicron hybrid composite material. The packable submicron methacrylate-based composite material also showed higher flexural strength than stackable nanohybrid composite material.

X-ray microtomography analysis of gaps and voids in the restoration of non-carious cervical lesions with different composite resins.

Resin composites are the most widely used material for restoring cervical defects. However, the high failure rate of these restorations is still a concern. The aim of this in vitro study was to evaluate, using microtomography (μCT), the interfacial gap and voids formation in Class V cavities in premolars restored with materials with lower polymerization shrinkage combined with different restorative techniques. Cervical defects were created in 30 intact premolar and were randomly distributed to be restored by one of the following techniques (n = 6): Composite resin with two increments (CR), organic modified polymer (ORMOCER) with single (OR1) or two increments (OR2, or low viscosity bulk-fill composite resin with single (BF1) or two increments (BF2). Each tooth was scanned before filling to determine the volume of interest (VOI) to be applied in the second μCT after restoration and to control the cavity volume among the groups. In the μCT after filling, the volume of interfacial gaps and voids was calculated for each group. The groups were compared using one-way and Tukey HSD post hoc test (α = 0.05). It was possible to identify higher gap formation in the OR1 group and higher void formation in CR group (P < 0.05). OR2 group showed better results than the group with one increment. BF2 showed the best filling capacity. It was possible to conclude that the material and the number of increments directly influenced the internal adaptation and voids formation of Class V restorations.

The Influence of Various Photoinitiators on the Properties of Commercial Dental Composites.

The aim of this article was to compare the biomechanical properties of commercial composites containing different photoinitiators: Filtek Ultimate (3M ESPE) containing camphorquinone (CQ); Estelite Σ Quick (Tokuyama Dental) with CQ in RAP Technology®; Tetric EvoCeram Bleach BLXL (Ivoclar Vivadent AG) with CQ and Lucirin TPO; and Tetric Evoceram Powerfill IVB (Ivoclar Vivadent AG) with CQ and Ivocerin TPO. All samples were cured with a polywave Valo Lamp (Ultradent Products Inc.) with 1450 mW/cm2. The microhardness, hardness by Vicker’s method, diametral tensile strength, flexural strength and contraction stress with photoelastic analysis were tested. The highest hardness and microhardness were observed for Filtek Ultimate (93.82 ± 17.44 HV), but other composites also displayed sufficient values (from 52 ± 3.92 to 58,82 ± 7.33 HV). Filtek Ultimate not only demonstrated the highest DTS (48.03 ± 5.97 MPa) and FS (87.32 ± 19.03 MPa) but also the highest contraction stress (13.7 ± 0.4 MPa) during polymerization. The TetricEvoCeram Powerfill has optimal microhardness (54.27 ± 4.1 HV), DTS (32.5 ± 5.29 MPa) and FS (79.3 ± 14.37 MPa) and the lowest contraction stress (7.4 ± 1 MPa) during photopolymerization. To summarize, Filtek Ultimate demonstrated the highest microhardness, FS and DTS values; however, composites with additional photoinitiators such as Lucirin TPO and Ivocerin have the lowest polymerization shrinkage. These composites also have higher FS and DTS and microhardness than material containing CQ in Rap Technology.

Synthesis and characterization of ladder structured ormocer resin of siloxane backbone and methacrylate side chain

Available resin-based hard tissue restorations are highly influenced by the problems associated with post-polymerization shrinkage and toxicity of uncured monomers. To address this scenario, we have synthesized an ormocer resin (LSM) of inorganic siloxane backbone using the monomer 3-(trimethoxy silyl)propyl methacrylate (3-TMSPM) by modified sol gel method. The synthesized polycondensed LSM resin is fashioned with three-dimensional network of ladder structured Si-O-Si backbone which grow continuously to form higher molecular weight (Mn-18956 KDa) prepolymer. Four membered siloxane rings along with intact methacrylates constituted the monomeric unit of the prepolymer LSM. High thermal stability indicated the presence of intense siloxane network whereas low glass transition temperature and melting peak demonstrated the flexibility and partial crystallinity of the LSM resin. Low linear polymerization shrinkage (LPS) of cured LSM resin (0.422 ± 0.04%) witnessed the presence of inorganic siloxane backbone and performed better than cured bisphenol glycidyl methacrylate (BisGMA)composite (0.916 ± 0.09%). Non-cytotoxicity and cytocompatibility of the cured LSM resin proved the eligibility of the resin for hard tissue restorative applications.

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.

Fabrication and characterization of low-shrinkage dental composites containing montmorillonite nanoclay.

Dental composites are aesthetic materials widely used in Dentistry for replacing hard dental tissues lost due to caries or traumas. The aim of this study was to fabricate low-shrinkage dental composite charged with nanoclay fillers (montmorillonite Cloisite®-MMT) and evaluate their cytotoxicity and physicomechanical properties. Four dental composites were produced from the same organic matrix: Bis-GMA/TEGDMA (30wt.%). The filler system was constituted of BaSi, SiO2, and MMT in the following concentrations (wt.%): 93.8/6.2/0, 89.1/5.9/5, 86.7/5.8/7.5, and 84.4/5.6/10 (E0: 0; E5: 5%; E7.5: 7.5%; E10: 10% of MMT nanoclays). The following properties were tested: in vitro cytotoxicity, flexural strength, elastic modulus, volumetric shrinkage, water sorption, water solubility, and hygroscopic expansion. Scanning electron microscopy was used to characterize composites' topography. Data were analyzed by one-way ANOVA and Tukey's HSD post hoc test (p < 0.05). MMT nanoclays did not affect the cytotoxicity. E5 and E7.5 groups showed a significant decrease in polymerization shrinkage while maintained the overall physicomechanical properties. The inclusion of 5 and 7.5wt.% of MMT nanoclays allowed the fabrication of dental composites with low cytotoxicity and low polymerization shrinkage, without jeopardizing the overall behaviour of their physicomechanical properties (flexural strength, elastic modulus, water sorption, water solubility, and hygroscopic expansion). These aspects suggest that the usage of MMT nanoclays could be an effective strategy to formulate new dental composites with clinical applicability.

TEKNIK RESTORASI RESIN KOMPOSIT BULK FILL MENGGANTIKAN TEKNIK INKREMENTAL

Introduction. Shrinkage during the polymerization process is the main disadvantage of using composite resins because it creates pressure between the tooth and the restoration which causes failure of the adhesion of the composite resin to the tooth, micro-fissures, and cuspid deflection. Review. To reduce shrinkage that occurs, it is known that conventional composite resins must be inserted into the cavity incrementally or in layers with a maximum thickness of 2 mm per layer. However, the incremental insertion method has several disadvantages, namely that it requires a longer clinical time for restoration. To overcome the shortcomings of these conventional composites, Bulk-fill composite resin was introduced. Composite bulk fill is a sophisticated technology that allows composites to be directly placed on the restoration, has a low polymerization shrinkage to reduce micro-leakage, reduces stress in the presence of elasticity, increases the depth of at least 4 mm translucent at the time of application, is very conducive to light transmission, is more flowable to allow adaptation to the cavity, including cervical margins, it is easy to apply with minimal handling and is resistant to large stresses. Conclusion. With the characteristics possessed by the Bulk-fill composite resin, it is known that the bulk-fill technique in addition to reducing the clinical application time, can also improve the edge adaptation between the restoration and the tooth compared to the incremental technique, without reducing its physical strength

EFEITO DO ACABAMENTO E POLIMENTO SOBRE A TOPOGRAFIA SUPERFICIAL DE UMA RESINA COMPOSTA CONVENCIONAL E UMA BULK FILL

Introdução: Os compostos resinosos são materiais bastante presentes no dia a dia da clínica odontológica. Apesar de suas vantagens e ótimas propriedades, as resinas compostas convencionais ainda apresentam limitações, como o maior tempo clínico e falhas na adesão. Dessa forma tem-se o surgimento das resinas Bulk-Fill que entre as suas vantagens e propriedades temos: menor tempo clínico, baixa contração de polimerização, maior translucidez, além de propriedades que levam a sua melhor manipulação, tempo clínico e topografia superficial. Objetivo: Avaliar a topografia superficial de restaurações realizadas com diferentes tipos de resina composta antes e após submetê-las a diferentes sistemas de acabamento e polimento. Metodologia: Foram confeccionados 100 corpos de prova (CP), sendo 50 de cada composto resinoso, apresentando cinco grupos (n=10) sorteados de forma aleatória, de acordo com o sistema de acabamento e polimento (AP) empregado. Foram utilizadas as resinas Filtek Z350 XT (3M ESPE, St. Paul, MN, EUA) e a Bulk Fill Filtek One Bulk Fill (3M ESPE, St. Paul, MN, EUA) e os sistemas de acabamento e polimento: Discos de Lixa Sof-Lex Pop On Kit (DL); Discos Diamantado Espiral Sof-Lex (DE); Ponta Enhance (PE) e Broca Carbide Multilaminada nº 0283F (BM), que foram comparados com superfície deixada pela Tira de Poliester (Controle Negativo – CN). Após 7 dias de armazenamento em água destilada, os CP foram submetidos a análise da superfície por meio do Microscópio Eletrônico de Varredura (MEV). Resultados: Os CP da resina Bulk Fill tiveram como melhor resultado o sistema de AP com BM e resultado não satisfatório com DE, enquanto o PE e DL tiveram resultados semelhantes. Os CP da resina Filtek Z350 XT tiveram melhor aspecto visual de lisura superficial no grupo CN e pior resultado no grupo com DE. Conclusões: Dessa forma, o sistema que apresentou melhor resultado foi com a BM na resina Bulk Fill, enquanto a Filtek Z350 XT apresentou-se melhor no grupo C. Porém, ainda são necessários mais estudos que possam levar em considerações outras variações na metodologia empregada para se chegar em um protocolo de acabamento e polimento mais eficiente.

Physical and Mechanical Properties of Resins Blends Containing a Monomethacrylate with Low-polymerization Shrinkage.

Objectives The aim of this study was to evaluate the Knoop hardness (KH), cross-link density (CLD), water sorption (WS), water solubility (WSB), and volumetric shrinkage (VS) of experimental resins blends containing a monomethacrylate with low-polymerization shrinkage. Materials and Methods A blend of bisphenol glycidyl methacrylate (BisGMA) as base monomer was formulated with (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA), Bis-GMA/isobornyl methacrylate (IBOMA), or Bis-GMA/TEGDMA/IBOMA in different concentrations (40, 50, or 60 wt%). The camphorquinone (CQ)/2-(dimethylamino) ethyl methacrylate (DMAEMA) was used as the photoinitiator system. The KH and CLD were measured at the top surface using an indenter. For WS and WSB, the volume of the samples was calculated in mm 3 . The samples were transferred to desiccators until a constant mass was obtained (m1) and were subsequently immersed in distilled water until no alteration in mass was detected (m2). The samples were reconditioned to constant mass in desiccators (m3). WS and WSB were determined using the equations m2 − m3/V and m1 − m3/V, respectively. VS results were calculated with the density parameters before and after curing. Statistical Analysis Data were submitted to ANOVA and Tukey’s test (α = 0.05). Results The resins containing IBOMA showed lower VS results. TEGDMA 40% and TEGDMA/IBOMA 20/20 wt% showed higher KH values. The IBOMA groups showed lower CLD, while TEGDMA groups had higher values of CLD. The BisGMA/TEGDMA resin presented the highest values of WS, and for WSB, all groups showed no significant differences among themselves. Conclusion The monomethacrylate with low-polymerization shrinkage IBOMA used alone or in combination with TEGDMA may decrease VS, WS, and CLD values.

Novel Urethane-Dimethacrylate Monomers and Compositions for Use as Matrices in Dental Restorative Materials.

In this study, novel urethane-dimethacrylate monomers were synthesized from 1,3-bis(1-isocyanato-1-methylethyl)benzene (MEBDI) and oligoethylene glycols monomethacrylates, containing one to three oxyethylene groups. They can potentially be utilized as matrices in dental restorative materials. The obtained monomers were used to prepare four new formulations. Two of them were solely composed of the MEBDI-based monomers. In a second pair, a monomer based on triethylene glycol monomethacrylate, used in 20 wt.%, was replaced with triethylene glycol dimethacrylate (TEGDMA), a reactive diluent typically used in dental materials. For comparison purposes, two formulations, using typical dental dimethacrylates (bisphenol A glycerolate dimethacrylate (Bis-GMA), urethane-dimethacrylate (UDMA) and TEGDMA) were prepared. The monomers and mixtures were tested for the viscosity and density. The homopolymers and copolymers, obtained via photopolymerization, were tested for the degree of conversion, polymerization shrinkage, water sorption and solubility, hardness, flexural strength and modulus. The newly developed formulations achieved promising physico-chemical and mechanical characteristics so as to be suitable for applications as dental composite matrices. A combination of the MEBDI-based urethane-dimethacrylates with TEGDMA resulted in copolymers with a high degree of conversion, low polymerization shrinkage, low water sorption and water solubility, and good mechanical properties. These parameters showed an improvement in relation to currently used dental formulations.