Composite Resin Surfaces Research Articles

Effects of different saliva pH on hybrid composite resin surface roughness

Background: Currently, hybrid composite resin is the mostly used filling material to restore esthetic and function. During function, this material is in contact with various pH from food consumption, which is acidic and alkali which may effect the physical properties of composite resin, including surface roughness. Purpose: The research was conducted to determine the effect of pH in saliva on surface roughness of hybrid composite resin. Methods: This research used artificial saliva and composite resin samples divided into 3 groups based on different pH of immersion (pH 4, pH 7 and pH 10) for 30 days. Results: There were significant differences (p > 0.05) among those three treatment groups of hybrid composites soaked in artificial saliva with different pH for 30 days. And, with LSD test it is also known that there were significant differences between the artificial saliva with pH 4 and pH 7, whereas there was no significant difference between pH 4 and pH 10 and between pH 7 and pH 10. Conclusion: It can concluded that the changes of salivary pH affect the surface roughness of the hybrid composite resin. Acidic pH has increase the surface roughness of hybrid composite resin, whereas alkaline pH has no effects on the surface roughness of hybrid composite resin.Latar belakang: Saat ini tumpatan komposit merupakan bahan tumpatan yang paling sering digunakan untuk memperbaiki estetik dan fungsi. Dalam rongga mulut, bahan ini kontak dengan berbagai macam pH dari konsumsi makanan, baik asam maupun basa yang dapat mempengaruhi perubahan sifat fisik resin komposit, diantaranya yaitu kekasaran permukaan. Tujuan: Penelitian ini dilakukan untuk mengetahui tentang efek pH saliva terhadap kekasaran permukaan tumpatan resin komposit hybrid. Metode: Penelitian ini menggunakan saliva buatan yang dibagi dalam 3 kelompok sampel yaitu masing-masing dengan perendaman pH yang berbeda (pH 4, pH 7 dan pH 10)selama 30 hari. Hasil: Terdapat perbedaan yang bermakna (p > 0,05) antara kelompok perlakuan komposit hybrid yang telah direndam saliva buatan dengan berbagai pH selama 30 hari. Uji LSD menunjukkan adanya perbedaan yang signifikan antara perendaman pada saliva buatan antara pH4 dengan pH 7, sedangkan perbedaan yang tidak signifikan antara pH4 dengan pH 10 dan pH 7 dengan pH 10. Kesimpulan: Dapat disimpulkan bahwa perubahan pH saliva berpengaruh terhadap kekasaran permukaan resin komposit hybrid, pH asam meningkatkan kekasaran permukaan resin komposit hybrid, sedangkan pH basa tidak berpengaruh terhadap kekasaran permukaan resin komposit hybrid.

Streptococcus mutans Biofilm Adhesion on Composite Resin Surfaces After Different Finishing and Polishing Techniques

This study evaluated Streptococcus mutans biofilm adhesion on the surface of three composite resins (nanofilled, Filtek Z350, 3M ESPE, Salt Lake City, UT, USA; nanohybrid, Vit-1-escence, Ultradent Products, South Jordan, UT, USA; and microhybrid, Esthet X, Dentsply, Milford, DE, USA) following different finishing and polishing techniques. Sixty standardized samples (6 × 3 mm) of each composite were produced and randomly divided into three finishing and polishing treatments (n=20): 1) control group: composite resin surface in contact with Mylar matrix strips with no finishing or polishing performed, 2) Sof-Lex aluminum oxide disc technique (3M ESPE, and 3) carbide bur finishing and Astrobrush polishing technique (Ultradent). Half the samples of each group were incubated in human saliva for 1 hour, and all the samples were subjected to S mutans (ATCC 35688) biofilm development. The mean log of CFU/mL present in the S mutans biofilm was calculated, and data were statistically analyzed by three-way analysis of variance and the Tukey test (p<0.05). Human saliva incubation promoted a significant increase of bacterial adherence on all three of the composites' surfaces, regardless of the polishing treatment performed (p<0.05). Of the three, the nanofilled composite (Filtek Z350) had the lowest bacterial adherence with each of the finishing and polishing techniques despite the presence or absence of human saliva (p<0.05). Mylar matrix strips (control group) promoted the lowest bacterial adhesion on the surface of the microhybrid and nanofilled composites in the absence of human saliva.

Residents’ journal review

As restorative composite materials improve, the need to bond to existing restorations for orthodontic treatment is likely to increase. The purpose of this study was to evaluate the in-vitro shear bond strength of orthodontic brackets bonded to aged restorative composite resin surfaces treated with various surface-roughening methods. Ninety composite resin discs (Filtek Supreme XT, 3M ESPE, St Paul, Minn) (6 × 2 mm) were compressed on a glass slide, light-cured, and treated for 300 hours with an accelerated aging procedure. Each disc was randomly assigned to a different prebonding-procedure group: (1) control with no surface treatment, (2) 38% phosphoric acid, (3) 9.6% hydrofluoric acid, (4) airborne aluminum trioxide particle abrasion, (5) sodium bicarbonate particle abrasion, or (6) roughing with a diamond bur. After the prebonding procedure, metal brackets were bonded with adhesive (Transbond XT, 3M Unitek, Monrovia, Calif). All samples were stored in water for 7 days at 37°C and then thermocycled 1000 times (5°C-55°C). Shear bond strength was recorded as the maximum load to debond the brackets. The results showed that treatment with phosphoric acid was not significantly different from no pretreatment. All other treatment methods had significantly better shear bond strengths than did the control, but no statistical differences were found among the 4 other methods. The authors concluded that surface roughening was an effective pretreatment in bonding to aged composite surfaces and that clinically adequate shear bond strengths were found by using either hydrofluoric acid, sodium bicarbonate, aluminum trioxide particle abrasion, or a diamond bur.

Influence of several fibre‐reinforced composite restoration techniques on cusp movement and fracture strength of molar teeth

To compare mean cusp movement in molar teeth with endodontic access and mesial-occlusal-distal (MOD) cavities before and after restoration with several fibre-reinforced composite restoration techniques under loading and to evaluate the effect of restoration technique on fracture strength. Reference points were marked at the mesial cusp ridges of extracted human mandibular molar teeth. Digital images were taken under loading (300 N) using a stereomicroscope (Leica MZ16A; Wetzlar, Germany). Three-dimensional (3D) distances between the reference points were recorded (Leica, Stereo-Explorer, 2.1) as controls. Standard MOD cavities were prepared and restored as follows (n = 10), group 1: composite restoration (Clearfil AP-X; Kuraray, Tokyo, Japan); group 2: cavity lined with polyethylene fibre (Ribbond, Ribbond Inc., Seattle, WA, USA) in combination with flowable resin (Protect-Liner F; Kuraray, Tokyo, Japan) before composite restoration; group 3: polyethylene fibre inserted on occlusal surface of the tooth from buccal to lingual after finishing the composite restoration; group 4: missing walls were restored with composite resin and inner surfaces of the axial walls were then reinforced with polyethylene fibre placed circumferentially before the composite restoration. The restored teeth were re-loaded, digital images were re-taken and the 3D distance between the reference points was recorded in μm. Comparisons of the restoration techniques, the effectiveness of restoration for each group were analysed statistically (Kruskall-Wallis, paired-samples t-test). The teeth were then loaded until failure (5 mm min(-1) ), the data were recorded (N) and analysed statistically (Kruskall-Wallis test). A significant difference occurred amongst the groups in terms of cusp movement (P = 0.018). All the groups revealed a decrease in inter-cuspal width when compared to their initial records. The mean values of these decreases were as follows: group 1 17.6 (P = 0.003), group 2 6.7 (not sig), group 3 6.6 (not sig) and group 4 0.85 (not sig) μm. No significant difference was found amongst the fracture strength values (P = 0.22). In group 1, 90% of the fractures were non-restorable, whereas in group 3 100% of the fractures were restorable. Regardless of restoration technique, fibre reinforcement of composite restorations decreased cusp movement in molar teeth with MOD and endodontic access cavities but did not affect fracture strength.

An artificial biofilm induced secondary caries model for in vitro studies

The aim of this study was to establish a new in vitro model for biofilm induced secondary caries studies using an oral biofilm reactor. An approximately 2 × 3 × 2 mm(3) sized dentino-enamel Class I cavity was prepared in the middle of a square-shaped specimen from the mid-labial portion of bovine incisors. The cavities were partially filled with either Clearfil AP-X with SE-Bond or Clearfil AP-X without any bond. Artificial biofilms were then formed on the resin composite filled surfaces using three species of oral bacteria in an oral biofilm reactor for 20 hours followed by 7- or 30-day incubation periods. The lesions were clearly visible on fluorescence microscopy and by scanning electron microscopy in the enamel at the interface of resin restorations in all samples. The data from image analysis showed that the lesion size was largest in the No-bond samples with statistically significant differences (p < 0.05). Demineralization along the cavity wall extended deeper in No-bond compared to SE-Bond samples and penetration was significantly deeper in No-bond 30-day samples. A primary artificial secondary caries model was established using biofilms for in vitro studies and the significance of using a bonding system could also be verified.

Effect of two prophylaxis methods on adherence of Streptococcus mutans to microfilled composite resin and giomer surfaces

Surface attributes of a restoration play an important role in adherence of plaque bacteria. Prophylaxis methods may be involved in modification of or damaging the restoration surface. The aim of the present study was to evaluate the effect of two prophylaxis methods on adherence of Streptococcus mutans to the surface of two restorative materials. A total of 60 specimens were prepared from each material; a microfilled composite resin (HelioProgress) and a giomer (Beautifil II). For each material, the specimens were randomly divided into three groups (n=20). Group 1: no prophylaxis treatment (control); Group 2: prophylaxis with pumice and rubber cup; Group 3: prophylaxis with air-powder polishing device (APD). The surfaces of selected specimens from each group were evaluated under a scanning electron microscope (SEM), and the surface topography formed by the two prophylaxis methods was determined by atomic force microscopy (AFM). Adherence of Streptococcus mutans to the surface of specimens was determined by the plate counting method following immersion in a bacterial innoculum for 4 hours, rinsing and sonication. Data were analyzed by two-way ANOVA and post hoc Tukey test for multiple comparisons. Statistical significance was set at P<0.05. Bacterial adherence was significantly affected by both factors: restorative material type and prophylaxis method (P<0.0005). Mean bacterial adhesion was significantly higher in composite groups compared to corresponding giomer groups. Within each material, bacterial adherence was significantly lower in the control group compared to prophylaxis groups. Prophylaxis with pumice and rubber cup resulted in a significantly lower bacterial adherence compared to prophylaxis with APD. Based on the results of the present study, giomer specimens demonstrated lower bacterial adherence compared to composite resin specimens. In both materials, the highest bacterial adherence was observed with prophylaxis with APD, pumice and rubber cup and the control group, respectively.

The roughness, microhardness, and surface analysis of nanocomposites after application of topical fluoride gels

Objectives Application of acidulated phosphate fluoride (APF) gels has long been considered to cause deterioration of composite surfaces. The aims of this study were to demonstrate that nanocomposite surfaces were not affected by some APF gels and to investigate the possible underlying mechanisms. Methods The elemental composition and viscosity of 3 acidulated phosphate fluoride (APF) agents (60 Second Taste Gel, Topex, and Zap) and 1 neutral fluoride agent (pH7 Gel) were analyzed. Subsequently, 320 specimens of 3 nanocomposites (Premisa, Filtek Z350, and Grandio) and a microhybrid composite (Estelite Sigma) with 80 specimens for each composite were randomly divided into 5 groups ( n = 16) and treated with 4 fluoride gels as well as distilled water which served as the control. Fluoride gels were applied on composite resin surfaces 4 times, 30 min each time. The roughness and microhardness were measured after treatments. Qualitative examination of the surface degradation of the composites was carried out with Fourier transforming infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Results Topex and Zap did not cause surface changes of composite resins, the possible reason being ascribed to the presence of magnesium aluminum silicate (MAS) clays. In contrast, 60 Second Taste Gel treatments caused significant roughness increase, microhardness decrease, more prominent filler dissolution, and IR spectral changes of Premisa, Filtek Z350, and Grandio. Estelite Sigma was less affected by the 4 fluoride gels. Significance The composite surfaces were not affected by Topex or Zap even after extended treatments. These two APF gels may be more suitable for clinical applications.

Shear bond strength of orthodontic brackets to aged resin composite surfaces: effect of surface conditioning

The aim of this study was to investigate the effects of surface conditioning protocols on the shear bond strength (SBS) of metal brackets to aged composite resin surfaces in vitro. Ninety composite resin discs, 6 mm in diameter and 2 mm in height, were prepared and treated with an ageing procedure. After ageing, the specimens were randomly assigned to one of the following groups: (1) control with no surface treatment, (2) 38 per cent phosphoric acid gel, (3) 9.6 per cent hydrofluoric acid gel, (4) airborne aluminium trioxide particle abrasion, (5) sodium bicarbonate particle abrasion, and (6) diamond bur. The metal brackets were bonded to composite surfaces by means of an orthodontic adhesive (Transbond XT). All specimens were stored in water for 1 week at 37°C and then thermocycled (1000 cycles, 5-55°C) prior to SBS testing. SBS values and residual adhesive on the composite surface were evaluated. Analysis of variance showed a significant difference (P = 0.000) between the groups. Group 6 had the highest mean SBS (10.61 MPa), followed by group 4 (10.29 MPa). The results of this study suggest that a clinically acceptable bond strength can be achieved by surface conditioning of aged resin composite via the application of hydrofluoric acid, aluminium trioxide particle abrasion, sodium bicarbonate particle abrasion, or a diamond bur.

Weibull analysis of bond strength of orthodontic buccal tubes bonded to resin composite surface with various techniques

The objective of this study was to analyze the survival probabilities of various surface preparation techniques for bonding buccal tubes on resin composite surface. Resin composite specimens (hybrid), 33 per group were prepared. 8 experimental groups were (1) sandblast 90 μm; (2) sandblast 50 μm; (3) abrasion using diamond bur; (4) hydrofluoric acid etching for 1 min (HF 1 min); (5) HF 2 min; (6) HF 3 min; (7) 37% orthophosphoric etching for 10 min (H 3PO 4 10 min) and (8) control (unetched surface). Plastic conditioner was applied then buccal tubes were bonded. Shear bond strength was tested with the universal testing machine and the Weibull analysis was performed. The results at a stress level of 7.8 MPa and 10 MPa, revealed the probabilities of survival for sandblast 50 μm (100%, 99.9%), sandblast 90 μm (99.7%, 98.7%), diamond bur (98.3%, 93.4%), HF 2 min (95.9%, 85.3%), HF 1 min (78.3%, 61.4%), HF 3 min (70.6%, 46.3%), H 3PO 4 10 min (61.4%, 44.5%) and control (26.3%, 6.9%), respectively. Therefore, surface preparation by sandblast (50 μm and 90 μm), or diamond bur followed by plastic conditioner were highly effective for bonding orthodontic buccal tubes on hybrid resin composite surface. HF 2 min was acceptable. However, HF 1 min, 3 min, H 3PO 4 etching and unetched surface could not achieve adequate bond survival.

Effect of hydrogen peroxide topical applications on enamel and composite resin surfaces

Effect of hydrogen peroxide topical applications on enamel and composite resin surfaces

Immediate repair bond strengths of microhybrid, nanohybrid and nanofilled composites after different surface treatments

Objectives To evaluate immediate repair bond strengths and failure types of resin composites with and without surface conditioning and characterize the interacting composite surfaces by their surface composition and roughness. Methods Microhybrid, nanohybrid and nanofilled resin composites were photo-polymerized and assigned to four groups: (1) no conditioning (Control), (2) no conditioning, polymerized against a Mylar strip (Control, with strip), (3) intermediate adhesive resin (IAR) application, and (4) chair-side silica coating, silanization and intermediate resin application (SC). Resin composites, similar as their substrates, were adhered onto the substrates. Shear force was applied to the interface in a universal testing machine and failure types were evaluated under light microscopy. Surface characterization was done by contact angle measurements, X-ray photoelectron spectroscopy, scanning electron and atomic force microscopy. Results Significant effects of the resin composite type and surface conditioning were observed. Conditioning the composites with their IARs does not result in significant improvements in bond strength compared to the control with strip (bond strengths between 14.5 and 20.0 MPa). SC increased the bond strength in all composites except TE by an average 8.9 MPa, while in all composites the surface roughness increased from 7 to 384 μm. Failure types in this group were exclusively cohesive. Physico-chemical modelling of the composite surfaces showed that the surfaces were dominated by the resin matrix, with a major increase in silica-coverage after SC for all composites. Conclusion Intermediate adhesive resin conditioning did not improve the composite-to-composite immediate repair strength. Silica coating and silanization followed by its corresponding IAR, strongly increased repair bond strengths and provided exclusively cohesive failures in the substrate in all composites.

The influence of light-curing time on the bacterial colonization of resin composite surfaces

Objectives Bacterial colonization of composite surfaces represents the main factor in the etiology of secondary caries around adhesive restorations. The authors’ aim was to evaluate the influence of light-curing time on mutans streptococci colonization (MS) of a resin composite material. Methods Specimens obtained from a dental resin composite were divided into 12 groups and light-cured with the same light source respectively for 10, 20, 30, 40, 60 or 80 s using two different curing-power levels: 400 and 800 mW/cm 2. A wild strain of MS was isolated and a 24-h-monospecific biofilm, adherent to the surfaces of the samples, was obtained. A colorimetric technique (MTT assay), based on the reduction of a yellow tetrazolium salt to a purple formazan, was used to evaluate the biomass adherent to the specimen surfaces. ANOVA and Scheffé’s tests were used to statistically analyze the results. Results Two-way ANOVA demonstrated there was no interaction between curing-time factor and curing-power factor ( p = 0.970); one-way ANOVA was used to analyze separately the data obtained from each curing-power level. Both levels showed highly significant differences ( p < 0.0001) among the different curing time groups. The non-parametric test for trend showed in both levels the existence of a highly significant trend ( p < 0.0001) for bacterial colonization reduction as curing time increases. Significance A reduced curing time seems to be responsible for increased in vitro colonization of composite surfaces by MS; this phenomenon is likely to be related to the presence of unpolymerized monomers on the material surface.

Effect of hydrogen peroxide topical application on the enamel and composite resin surfaces and interface

The objective of the present study was to analyze the superficial roughness and the interface between enamel and composite resin restorations after dental bleaching procedure. Black's class V cavities were made and restored with composite resin, and the whole set, enamel-restorative material, was treated with 35% hydrogen peroxide. Seven procedures of 30 min each were performed. A profilometric assessment was carried out before and after the treatment of each sample, and roughness scores were obtained. Treated and untreated samples were analyzed under scanning electronic microscope and images of their surface were obtained. The treatment with 35% hydrogen peroxide caused no alteration in the interface between enamel and composite resin, Tetric Ceram, fillings and the topical application of 35% hydrogen peroxide on enamel and composite resin, Tetric Ceram, caused an alteration of their surface topography, featuring a predominance of depressions after the bleaching treatment.

Surface Characterization and Biocompatibility of Restorative Resin Containing Nanoparticles

Composite resins that are used to restore hard tissues have several drawbacks including the accumulation of biofilm on teeth and restorations. Recently, quaternary ammonium poly(ethylene imine) (QA-PEI) nanoparticles were developed for additional antibacterial activity of restorative composite resins. QA-PEI nanoparticles were synthesized from cross-linked poly(ethylene imine) that was N-alkylated with octyl halide, followed by quaternary methylation with methyl iodide. QA-PEI particles that were embedded in restorative composite resin at 1% w/w resulted in the complete growth inhibition of Streptococcus mutans. Moreover, the antibacterial activity was retained for at least 3 months. The active substances on the surface of the restorative composite resin that were incorporated with QA-PEI particles were detected by X-ray photoelectron spectroscopy (XPS) and confocal microscopy measurements. The in vitro cytotoxicity tests showed a similar effect on the viability of the cell line that was tested with composites including modified and unmodified dental composite resins. In vivo toxicity studies, which were assessed on Wistar rats by the implantation of modified composite specimens, revealed no inflammation response 1 week after the implantation of restorative composite resin that was embedded with up to 2% w/w QA-PEI.

Weibull analysis of shear/peel bond strength of orthodontic buccal tubes bonded to five resin composites

Bonding orthodontic buccal tube on a large resin composite restoration of molar tooth can result in easier bond failure than bonding to intact enamel. The resin composite type may be one of several factors that influence the bond strength. The objective of this study was to analyze the survival probabilities of buccal tubes bonded to various resin composites. Resin composite discs, 33 specimens for each group were prepared as follows: (1) nanofill (Filtek Supreme), (2) compomer (F2000), (3) hybrid (Z100), (4) packable (P60) and (5) flowable (Filtek Flow). The surface was etched with 9.6% hydrofluoric acid, followed by plastic conditioner application. Orthodontic buccal tubes were then bonded. Shear/peel bond strength was tested with the universal testing machine. The Weibull analysis was performed to indicate the survival probability for each resin composite type. Scanning electron microscope comparison of unetched and etched surface of resin composite was demonstrated. The probabilities of survival at a stress level of 7.8 MPa ranked from highest to lowest as follows: hybrid (95.87%), packable (95.38%), flowable (91.81%), compomer (69.95%) and nanofill (36.03%). The survival probabilities of orthodontic buccal tube bonded on hybrid, packable and flowable resin composite were substantially high, while that of nanofill resin composite was remarkably low. From scanning electron microscope, different surface topography of etched surface exhibited unequal resistance to acid etching among different resin composites. Therefore, type of resin composite surface accounted for the differences seen in the survival probabilities of orthodontic buccal tubes.

Optical density and chemical composition of microfilled and microhybrid composite resins

This study evaluated the optical density of two microfilled and two microhybrid resins, as well as the composition of these materials with regard to their optical density. Cavities prepared in 12 2-mm- or 4-mm-thick acrylic plastic plates were filled with Z250 (3M-ESPE), A110 (3M-ESPE), Charisma (Heraeus-Kulzer) and DurafillVS (Heraeus-Kulzer). The resin increments (2-mm-thick) were light-cured for 40 s. Three 0.12-s radiographic exposures were made of each #2 acrylic plastic plate. DenOptix system optical plates were used to obtain the digital images. Three readings of the composite resin surface were made in each radiograph, totalizing 216 readings. The mean of highest and lowest grey-scale values was obtained. Two specimens of each composite resin were prepared for SEM analysis of the chemical elements related to optical density, using energy dispersive x-ray analysis (EDX). The results were subjected to Shapiro-Wilk's test, ANOVA, Tukey's test at 1% level of significance and Pearson's correlation. The mean grey-scale values at 2 mm and 4 mm were: Z250 = 154.27a and 185.33w; A110 = 46.77b and 63.05y; Charisma = 163.40c and 200.46z; DurafillVS = 43.92b and 58.99x, respectively. Pearson's test did not show any positive correlation between optical density and percentage weight of optical density chemical elements. It was concluded that the microhybrid resins had higher optical density means than the microfilled resins; among the evaluated resins, Charisma had the highest optical density means.

Evaluation of Flowable Resin Composite Surfaces Eroded by Acidic and Alcoholic Drinks

The purpose of this study was to evaluate the morphological changes of the surfaces of flowable resins eroded by orange juice and alcohol drinks. The tested products were Beautifil Flow BF02 and BF10, Clearfil Majesty LV, Filtek Supreme XT Flowable Restorative, Unifil LoFlo Plus and Filtek Supreme. Filler percentages of flowable resins were calculated after the latter were incinerated at 750 degrees C. Specimens were shaped into a disk form with a diameter of 10 mm and a thickness of 1 mm. Morphological changes were evaluated for the following types of flowable resin surfaces: polished surface, surfaces eroded by 100% orange juice, wine and whisky. Filler percentages of the tested flowable resins ranged between 42 and 78%. Surface degradation was observed for the specimens immersed in acidic and alcoholic drinks, and it was thought that the lower the filler percentage, the greater was the surface degradation. Decomposition of the matrix resin and fallout of the fillers were observed in flowable resins that eroded with acidic and alcoholic drinks.

Effect of treated filler loading on the photopolymerization inhibition and shrinkage of a dimethacrylate matrix

This study shows how treated filler loading influences the photopolymerization of a dimethacrylate comonomer mixture, regarding, in particular, shrinkage and inhibition under atmospheric oxygen, present in oral environment. Bis-GMA/TEGDMA (75/25 wt.%) resins were loaded with hybrid filler (Ba aluminosilicate glass and pyrogenic silica), treated with gamma-methacryloxy(propyl)trimethoxysilane, at 0-50 wt.% and light cured over a total of 30 s (45 mW/cm2). Degree of double-bond conversion (DC), obtained using FTIR, decreased with filler content. 1H MAS spectra (293-340 K) and STRAFI images (293 K) were obtained as a function of irradiation time and filler concentration. 1H signals of unreacted methacrylate groups were more intense for higher loaded resins and resonances from -CH2SiO2(OH) (T2) and -CH2SiO3- (T3) units, also observed by 29Si NMR, were resolved and suggest the presence of T2-resin bonds. 1D images show a reduction on polymerization contraction and reaction inhibition at the composite resin surface with filler loading. 2D resin images present a highly mobile surface layer, hence with lower DC.

Streptococcus mutans biofilm changes surface-topography of resin composites

Objectives Polymerized resin composites and nonpolymerized monomers are reported to accelerate bacterial growth. Furthermore, in vivo, resin composite restorations accumulate more plaque than other restorative materials. The purpose of this study was to test the hypothesis that bacteria–composite surface interaction causes changes in surface-topography. Methods Resin composite disks were polymerized between two glass slides. Streptococcus mutans cells were brought in contact with and grown on the disks for 1 day, 1 week or 1 month. The disks were analyzed using atomic force microscopy. One-month-aged composite specimens were assayed for changes in micro-hardness and bacterial outgrowth. Results Atomic force microscopy analysis revealed a time-dependent increase in root mean square (RMS) roughness ( p < 0.0001). S. mutans outgrowth was accelerated following direct contact with the surface of aged composites, with no changes in micro-hardness. Significance Our results show that S. mutans growth on resin composite increases surface roughness without affecting micro-hardness. The change in surface integrity may further accelerate biofilm accumulation.

Evaluation on the abrasion resistance of a surface sealant

The purpose of this study was to evaluate the abrasion resistance of surface penetrating sealant which was applied on a composite resin restoration and to provide proper time to reapply sealant on composite resin surface. Two hundred rectangular specimens, sized , were made of Micronew (Bisco, Inc., Schaumburg, IL, U.S.A) and divided into two groups; F group (n = 10) was finished with coarse and medium grit of Sof-Lex discs and BisCoverwas applied B group (n = 190) after finishing with discs. B group was again subdivided into nineteen subgroups From B-1 group to B-18 group were subjected to toothbrush abrasion test using a distilled water-dentifrice slurry and toothbrush heads B-IM group was not subjected to toothbrush abrasion test. Average surface roughness (Ra) of each group was calculated using a surface roughness tester (Surfcorder MSE-1700: Kosaka Laboratory Ltd., Tokyo, Japan) . A representative specimen of each group was examined by FE-SEM (S-4700: Hitachi High Technologies Co., Tokyo, Japan). The data were analysed using cluster analysis, paired t-test, and repeated measure ANOVA. The results of this study were as follows; 1. Ra off group was and B-IM group was . Ra became higher from B-1 group to B-18 group . 2. Final cluster center of Ra was in cluster 1 , in cluster 2 and in cluster 3 (. There were significant difference among Ra of three clusters. 3 Ra of B-IM group was decreased 210.72% than Ra of F group. Ra of B-8 group and B-15 group was increased 35.49% and 51.35% respectively than Ra of B-IM group. 4. On FE-SEM, B-IM group showed the smoothest resin surface. B-8 group and B-15 group showed vertically shallow scratches , and wide and irregular vertical scratches on composite resin surface respectively. Within a limitation of this study, finished resin surface will be again smooth and glazy if BisCover would be reapplied within 8 to 14 months after applying to resin surface.