Nano-filled Resin-modified Glass Ionomer Research Articles

Finite Element Analysis of the Mechanical Performance of Non-Restorable Crownless Primary Molars Restored with Intracoronal Core-Supported Crowns: A Proposed Treatment Alternative to Extraction for Severe Early Childhood Caries

Early childhood caries (ECC) involve extensive coronal tooth structure loss, and tooth reconstruction remains highly challenging. To fulfill preclinical assessment, the present study investigated the biomechanics of non-restorable crownless primary molars that were restored by stainless steel crowns (SSC) using different composite core build-up materials. Computer-aided design-integrated 3D finite element and modified Goodman fatigue analyses were performed to determine stress distribution, risk of failure, fatigue life and dentine-material interfacial strength for the restored crownless primary molars. A dual-cured resin composite (MultiCore Flow), a light-cured bulk-fill resin composite (Filtek Bulk Fill posterior), a resin-modified glass-ionomer cement (Fuji II LC) and a nano-filled resin-modified glass-ionomer cement (NRMGIC; Ketac N100) were used as core build-up composite materials in the simulated models. The finite element analysis showed that types of core build-up materials affected the maximum von Mises stress only in the core materials (p-value = 0.0339). NRMGIC demonstrated the lowest von Mises stresses and revealed the highest minimum safety factor. The weakest sites were along the central grooves regardless of type of material, and the ratio of shear bond strength to maximum shear stress at the core-dentine interface of the NRMGIC group was lowest among the tested composite cores. However, all groups provided lifetime longevity from the fatigue analysis. In conclusion, core build-up materials differentially influenced the von Mises stress (magnitude and distribution) and the safety factor in crownless primary molars restored with core-supported SSC. However, all materials and the remaining dentine of crownless primary molars provided lifetime longevity. The reconstruction by core-supported SSC, as an alternative to tooth extraction, may successfully restore non-restorable crownless primary molars without unfavorable failures throughout their lifespan. Further clinical studies are required to evaluate the clinical performance and suitability of this proposed method.

Microleakage comparision in class V Cavities using different glass ionomer cements

Aim: The aim of this study was to compare the microleakage of Conventional Glass Ionomer Cement(CGIC),Resin Modified Glass Ionomer Cement (RMGIC)and Nano-Filled Resin Modified Glass Ionomer Cement (RMGIC). Materials and Methods: forty five sound extracted human molar teeth were selected. Teeth were randomly divided into three groups of 15 teeth each and restored as follows: Group 1-CGIC; Group 2-RMGIC; and Group 3-Nano-filled RMGIC. Datas were analyzed using Kruskal-Wallis and Wilcoxon tests. Results: There was no statistically significant differences in dye leakage between the three restorative materials for occlusal margins (P = 0.465).At the gingival margins, Group 3 showed significantly less microleakage than Groups 1 (P = 0.008) and 2 (P = 0.041). The degree of microleakage in the gingival margins of each group was higher than that found in occlusal margins. Conclusions: No material was able to completely eradicate microleakage at enamel, dentin, or cementum margin. Nano-filled RMGIC show significantly less microleakage as compared to other two cements at gingival margins.

Three-year performance of a nano-filled resin-modified glass ionomer cementin class II primary molar restorations.

To compare the clinical failure rate of two resin-modified glass ionomer cements (RMGICs) used for Class II primary molar restorations over a 3-year period. Healthy, cooperative children aged 4-8years with carious, asymptomatic primary molars requiring class II restorations received either nano-filled (Ketac Nano, 3M ESPE) or regular (Vitremer, 3M ESPE) RMGIC restorations. These were blindly assessed semiannually for 3years using the modified USPHS criteria with all-cause failure as primary outcome and failure for each criterion as secondary outcome. Data was analysed with Fisher's exact tests and survival analysis with robust standard errors at 5%. Outcome assessment included 159 teeth at 12months, 141 teeth at 24months, and 98 teeth at 36months. No difference in all-cause failure was found between regular and nano-filled RMGIC at 12 (8.6% versus 14.1%), 24 (9.0% versus 14.9%) or 36months (7.4% versus 20.5%) (P > 0.05). The nano-filled RMGIC retained better its anatomical form and the regular RMGIC likewise its marginal integrity (P < 0.05), but only in the acceptable range (Alpha-Bravo). Overall, survival analysis found no significant difference for all-cause failure [hazard ratio (HR) 0.58; 95% confidence interval (CI) 0.25-1.31; P = 0.19] or any secondary outcomes other than contact point integrity. Finally, subgroup analysis by jaw indicated that the regular RMGIC performed better than the nano-filled RMGIC for mandibular molars (HR 0.36; 95% CI 0.13-0.96; P = 0.04), but further data are needed. Nano-filled RMGIC showed less occlusal wear but more mild marginal defects than regular RMGIC, but these findings were of limited clinical significance and both materials performed favourably for 3years.

Influencia del acondicionamiento de la dentina con ácido poliacrílico en la resistencia al cizallamiento de un cemento de ionómero de vidrio modificado con resina con tecnología de nano relleno.

Purpose: This in vitro study aimed to evaluate the influence of dentin conditioning with polyacrylic acid on the shear bond strength of the nano-filled resin-modified glass ionomer cement Ketac N100 (3MESPE). Material and methods: Eighteen bovine incisors were randomly divided into two groups (n=18): group 1, without dentin surface treatment, and group 2, with dentin surface treated with 10% polyacrylic acid for 15 seconds. In both groups the primer was applied before the application of the nano-filled resin-modified glass ionomer cement (Ketac N100) and light-cured for 20 seconds. After 24 hours, the specimens were submitted to thermocycling for 350 cycles, and the teeth were immersed in distilled water at room temperature. After 24 hours, specimens were tested for shear bond strength at 1mm/minute crosshead speed. The collected data were analyzed using the non-parametric test of Mann Whitney (p&lt;0.05). Results: There was a significant difference in shear bond strength values between the treatment and control groups, the group with dentin conditioning with 10% polyacrylic acid showed higher shear strength values than the group without dentin treatment. Conclusion: Application of 10% polyacrylic acid on dentin increases the shear bond strength values of nano-filled resin-modified glass ionomer cement.

Histologic Evaluation of Artificial Floors Under MTA and Nano-Filled Resin-Modified Glass Ionomer Used to Repair Furcation Perforations in Dogs.

Objective:This study aimed to compare the tissue reaction of two repair materials for furcation perforations, nano-filled resin modified glass ionomer (Nano-FRMGI) and mineral trioxide aggregate (MTA), used with or without an artificial floor.Methods:A total of 96 teeth in 6 dogs were used for this study. After access cavities, root canals were prepared and obturated with gutta percha using cold lateral condensation technique. Perforations were then created on the floors of the pulp chambers. The perforations divided into four groups n=24/group that were sealed with MTA alone, MTA with calcium sulphate artificial floor (CSAF), FRMGI alone and Nano-FRMGI with CSAF. All access cavities were filled with composite resin. Two dogs were sacrificed at 1, 3, and 6 month. The experimental tooth along with the surrounding alveolar bone were cut in block sections and histologically evaluated for tissue response. Data were analyzed by Chi-square (P≤0.05).Results:MTA and MTA with CSAF showed more bone and cementum apposition when compared to Nano-FRMGI at 6-month interval. MTA and MTA with CSAF showed less bone resorption, epithelium proliferation and inflammation compared to Nano-FRMGI at 6-month interval.Conclusion:MTA with CSAF or MTA-alone show better outcomes in the repair of pulp chamber floor perforation.

Assessment of Microleakage Using Dye Penetration Method in Primary Teeth Restored with Tooth-colored Materials: An In Vitro Study

The present study aimed to assess the microleakage in primary teeth restored with tooth-colored materials using the dye penetration method. A total of 60 healthy primary molar teeth were included in this study and standardized class II mesio-occlusal cavities were prepared on the samples. Consequently, these teeth were randomly divided into three experimental groups (n = 20 each group) such as group I: nano-filled resin-modified glass-ionomer, group II: nanocomposite resin, and group III: Cention N. After completing all the restorations, the restored teeth were subjected to 100 cycles of thermocycling. Next, all the surfaces of the tooth, except the restoration and a 1-mm zone adjacent to the restoration's margins, were covered with two coats of nail varnish. The coated teeth were then submerged in a 0.5% basic fuchsin dye solution. The teeth were then sectioned along the center of each restoration mesiodistally. Each part was visualized under a stereomicroscope at ×40 magnifications to assess microleakage. Out of all the included restorative materials, the least microleakage was demonstrated by teeth restored by the nano-filled resin-modified glass-ionomer (RMGI) group (1.05 ± 0.21) followed by the Cention N group (1.84 ± 0.14) and the nanocomposite resin group (3.10 ± 0.03). A statistical method involving the analysis of variance revealed a statistically significant difference among the different restorative materials. Multiple comparisons among the restorative materials showed a statistically significant difference between groups I and II and groups II and III restorative materials (p < 0.05). The dye penetration score 1 was more [11(55%)] for the nano-filled RMGI group, score 3 was more [12(60%)] for the nanocomposite resin group, and score 2 was more [9(45%)] for the Cention N group. The present study showed significantly less microleakage associated with the nano-filled resin-modified glass ionomer group than nanocomposite resin and Cention N groups. Since many years, dentists have encountered a challenging problem with cervical lesions. Thus, an interdisciplinary treatment approach is the appropriate option in the management of carious teeth that involve gingival recession and cervical extension.

Comparative efficacy of nanofilled and microfilled resin-modified glass ionomer as pits and fissure sealant in permanent molar teeth

The purpose of the present study was to compare the efficacy of nanofilled and microfilled resin- modified glass ionomer as pits and fissure sealants in permanent molar teeth. Ninety six teeth having fissure at the occlusal surface were randomly divided into two groups: Group I: Treated by nanofilled resin-modified glass ionomer sealant and Group II: Treated by microfilled resin- modified glass ionomer sealants. Clinical assessment was performed by modified Ryge´s criteria by means of retention, color match, marginal adaptation at 3, 6, and 12 months follow-up visit. Chi-square test was used for testing differences between the two groups; a value of p&lt;0.05 was considered as statistically significant. The results revealed that at 12 months observation period, nanofilled resin-modified glass ionomer sealant showed better retention, color stability and marginal adaptation than that of microfilled resin-modified glass ionomer sealants. Furthermore, the differences between two groups in respect to marginal adaptation and color match were statistically significant (p&lt;0.05). It can be concluded that nanofilled resin-modified glass ionomer sealant could be a better alternative to microfilled resin- modified glass ionomer sealant.

Effect of Adhesive Pretreatments on Marginal Sealing of Aged Nano-ionomer Restorations.

Background and aims. Nano-ionomer (NI) interacts with tooth structures superficially, and there is a concern about the enamel bonding ability of mild self-etch Ketac primer. This study compared the effect of different adhesive procedures (self-etching and etch-and-rinse approach) on long-term marginal microleakage of nano-filled resin-modified glass-ionomer (NI) cervical restorations.Materials and methods. Class V cavities were prepared on 72 maxillary premolars. The teeth were divided into six groups: G1: No treatment (NC); G2: Ketac primer (K primer); G3: Etchant + Ketac primer (E+K primer); G4: Self-etch adhesive (Bond Force); G5: Etchant + Bond Force (E+Bond Force); G6: Etchant + Adper Single Bond (Etch and rinse adhesive). All the cavities were restored with Ketac N100. The samples were stored in water for 6 months and thermocycled for 2000 cycles. Marginal sealing was assessed using dye penetration technique. Data were analyzed with non-parametric tests (α=0.05).Results. All the adhesive pretreatments resulted in a lower marginal leakage than that of NC (P≤0.01), except for E+Bond Force at the dentin margin. There was no significant difference between K primer and Bond Force. Microleakage differed significantly between K primer pretreatment and E+K primer (P=0.003), E+Bond Force (P=0.002) and etch-and-rinse adhesive (P=0.001) at the enamel margin, but it did not differ at the dentin margin. E+ Bond Force group showed insignificantly lower leakage at the enamel margin and significantly higher leakage at the dentin margin (P=0.02).Conclusion. Etch-and-rinse adhesive and selective enamel etching along with self-etch adhesive/Ketac primer might improve marginal sealing of aged nano-ionomer restoration.

Durability of bond strength of glass-ionomers to enamel

PurposeTo evaluate the shear bond strength of a new generation of glass ionomer (Glass Carbomer) to enamel versus a nano-filled resin-modified glass ionomer (ketac Nano) and a conventional type after different storage periods. Materials & methodsCrowns of 36 sound and freshly extracted human permanent molars were sectioned mesiodistally into two halves. The convex buccal or lingual surface was gently ground with water cooled 200-, 400-, and 600-grit silicon carbide abrasive papers successively to obtain flat enamel surfaces. The prepared specimens (n = 72) were divided into three main groups (24 each): I (Ionofil Molar), II (Ketac Nano) III (Glass Carbomer). The specimens in each group were subdivided into three subgroups A, B & C according to the storage period in artificial saliva. Shear bond strength between enamel surface and the bonded material was measured using a universal testing machine at a cross head speed of 0.5 mm/min. All the debonded interfaces were examined under both binocular stereo microscope at 40× and SEM at 200× to determine the mode of failure. ResultsKetac Nano recorded the highest shear bond strength values (9.30 ± 0.67, 12.07 ± 0.76, 6.7 ± 0.73) followed by Ionofil Molar, recording (5.25 ± 0.62, 7.82 ± 1.42, 5.91 ± 0.87) while the lowest values were found in Glass Carbomer specimens, recording (2.17 ± 0.63, 6.66 ± 0.68, 5.72 ± 0.79). There was a highly significant difference in shear bond strength values among the three different storage periods in all the tested materials (P < 0.0001). A positive correlation was recorded (R = 9.3) between the adhesive mode of failure and shear bond strength while a negative correlation was recorded (R = 4.5) between the cohesive mode of failure and shear bond strength using Spearman's correlation test. ConclusionsStorage time was a factor which significantly influenced both shear bond strength and mode of failure especially in Glass Carbomer specimens.

Comparative evaluation of microleakage of nano-filled resin-modified glass ionomer: An in vitro study.

Objective:This in vitro study evaluated the microleakage of a nano-filled resin-modified glass ionomer and a high viscosity glass-ionomer restorations in class V cavities.Materials and Methods:Thirty-two class V cavities prepared on the buccal and lingual surfaces of 16 sound, third molar teeth were randomly assigned into two groups and restored by one of the glass ionomer material; Group A: A high viscosity (Ketac Molar, 3M ESPE) Group B: A nano-filled resin-modified (Ketac N100, 3M ESPE) glass ionomer. One clinician prepared all the cavities. The materials were used according to the manufacturers’ recommendations. The restored teeth were then stored in distilled water at 37°C for 24 h, thermocycled at 5-55°C for 1000 cycles. The specimens were immersed in aqueous solution of Indian ink dye for 48 h at room temperature. They were embedded in resin polyester and sectioned longitudinally in a buccolingual direction. Microleakage was assessed according to the depth of dye penetration along the restoration. The extent of dye penetration at the occlusal and gingival margins was assessed using a stereo microscope. Randomly selected samples from each group were prepared for scanning electron microscope evaluation. The data were statistically analyzed with Friedman and Wilcoxon signed ranks tests.Results:There were statistically significant differences between the microleakage scores of the two groups for both occlusal and gingival scores (P = 0.001). Occlusal and gingival scores for high viscosity glass ionomer (P = 0.024) and nanoionomer (P = 0.021) using Wilcoxon signed ranks tests showed statistically significant differences. High viscosity glass ionomer showed significantly less microleakage compared to the nano-filled resin-modified glass-ionomer (RMGIs) at occlusal margin (P = 0.001). No significant differences were found between the groups at gingival margin (P = 0.0317).Conclusion:Within the limitations of this in vitro study, nano-filled RMGIs restorations did not perform better than high viscosity glass ionomer in class V cavities in terms of microleakage assessment.

Mechanisms of setting reactions and interfacial behavior of a nano-filled resin-modified glass ionomer

ObjectivesIn order to improve the short-comings of glass ionomers such as polishability and esthetics while preserving their excellent clinical bonding effectiveness, nanofiller technology has been introduced in a paste-paste resin-modified glass ionomer (nano-filled RMGI, Ketac Nano, KN, 3M ESPE). One objective of this study was to investigate if the introduction of nanotechnology had any significant effect on the setting reaction of the nanoionomer compared to a control RMGI, Vitremer (VM, 3M ESPE). Another objective was to determine the mechanism of bonding of KN in combination with its primer (KNP) to the tooth. MethodsFourier-Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses were performed on KN and VM during the setting of the GIs. FTIR and XPS were also used to study the reaction of the primer of KN (KNP) with hydroxyapatite (HAP). Shear adhesion to dentin and enamel was measured with KN and compared with several RMGIs and one conventional glass ionomers (CGI). The interfaces were examined with scanning electron microscopy (SEM). ResultsFTIR data show that KN undergoes both acid-base and methacrylate setting reactions of classical RMGIs. XPS and FTIR studies of the interaction KNP with HAP shows the formation of calcium-polycarboxylate bond. Shear adhesion and failure mode of KN to enamel and dentin were similar to the other RMGIs and CGI. SEM images of KN with tooth structure showed a tight interface with a thin but distinct layer of 2–3 microns attributed to the primer. This was also observed for VM but not for the other three materials. ConclusionsKN showed two setting reactions expected in true RMGIs. The adhesion with dentin and enamel was similar to other glass-ionomers. The formation of calcium-polycarboxylate was also evident. This chemical bonding is a significant factor in the excellent long-term adhesion of these materials.

Microleakage of Silorane-based Resin Composite in Comparison with Methacrylate-based Composite in Class II Open Sandwich Restorations: An in vitro Study

ABSTRACT Introduction This in vitro study aimed to evaluate the effect of different monomer systems on microleakage in class II composite open sandwich restorations with and without a separating agent placed between the nanofilled resin modified glass ionomer and the resin. Materials and methods Class II cavity preparations were prepared in maxillary premolars (n = 240) and the cervical limit of the proximal box was below the cementoenamel junction. Group 1 was restored with silorane-based composite and group II was restored with methacrylate-based composite. All specimens were subjected to thermocycling and examined for microleakage after in 50% silver nitrate solution. The recorded results of dye penetration were statistically analyzed using Chisquare test. Results Methacrylate-based composite (Filtek Z 350, 3M, St Paul, MN, USA) exhibited the highest dye penetration and silorane-based composite (Filtek P90 Low Shrink Posterior Restorative, 3M, St Paul, MN, USA) showed the lowest dye penetration among the restorative materials. However, specimens with separating agent showed almost no leakage between the RMGIC and tooth interface. Conclusion Forces of polymerization shrinkage are stronger than the bond between glass ionomer cement and tooth interface and the use of silorane technology in open sandwich restoration will decrease microleakage and improve clinical performance. How to cite this article Hegde MN, Hegde N, Hegde ND. Microleakage of Silorane-based Resin Composite in Comparison with Methacrylate-based Composite in Class II Open Sandwich Restorations: An in vitro Study. World J Dent 2012;3(2):145-149.

Comparative evaluation of microleakage in Class V cavities using various glass ionomer cements: An in vitro study

Aim: The study aimed to evaluate the microleakage of nano-filled resin-modified glass ionomer restorative (nano-filled RMGI) in comparison with that of conventional glass ionomer cement (CGIC), and resin-modified glass ionomer cement (RMGIC). Materials and Methods: Forty-five standardized Class V cavity preparations were prepared on sound extracted human molar teeth. Teeth were randomly assigned to three experimental groups of 15 teeth each and restored as follows: Group 1, CGIC; Group 2, RMGIC; and Group 3, nano-filled RMGI. The specimens were placed in a solution of 2% Rhodamine-B dye for 24 h at room temperature under vacuum. Staining along the tooth restoration interface was recorded. Results were analyzed using Kruskal-Wallis and Wilcoxon tests. Results: There were no statistically significant differences in dye leakage between all the three restorative materials for occlusal margins (P = 0.464). Group 3 showed significantly less microleakage compared to Group 1 (P = 0.007) and Group 2 (P = 0.040) at the gingival margins. The degree of microleakage in the gingival margins of each group was more than that found in occlusal margins. Conclusions: No material was able to completely eliminate microleakage at enamel, dentin, or cementum margin. Nano-filled RMGI showed least microleakage compared to other two cements at gingival margins. Clinical Relevance to Interdisciplinary Dentistry Cervical lesions have been a restorative challenge for dentists for many years. An interdisciplinary treatment approach is the appropriate choice in cases where there is gingival recession and cervical lesions. Glass ionomer cements have been commonly used for restoration of cervical lesions. Nano-filled resin-modified glass ionomer cement can be used for the restoration of cervical lesions, as it has a better marginal sealing ability compared to conventional glass ionomer and resin-modified glass ionomer cements.

Bonding Nano-filled Resin-modified Glass Ionomer to Dentin Using Different Self-etch Adhesives

To investigate the shear bond strength of the nano-filled resin-modified glass ionomer (RMGI) to dentin using different self-etch adhesives. Two resin-based restorative materials, a nano-filled RMGI (Ketac Nano-100, 3M ESPE) and a restorative composite (Grandio, VOCO) were bonded to bovine dentin using four self-etch adhesives (Futurabond M, VOCO; Adper Easy Bond, 3M ESPE; G Bond, GC Corp; and One Coat, Coltène). One hundred bovine anterior teeth were used in this study. Subsequent to labial enamel removal, each adhesive was applied according to manufacturer instructions. Fifty teeth were restored with the nano-filled RMGI and the other 50 were restored with the resin composite. Cylinders of 3×2 mm from the two restorative materials were bonded to dentin, and the specimens were stored in distilled water for 24 hours. Shear bond strength testing was performed in a universal testing machine at a crosshead speed of 0.5 mm/min. Two randomly selected specimens from each group were chosen for evaluation by scanning electron microscopy (SEM). Failure modes were evaluated using the stereomicroscope. All data for shear bond strength in MPa were expressed as mean ± standard deviation (SD). Statistical analysis was carried out using SAS program (SAS, 1988). Two-way analysis of variance revealed that the adhesives, the restorative materials, and their interactions (adhesives and restorative materials) had a significant effect on the shear bond strength to bovine dentin. Self-etch adhesives used in this study can adequately bond the nano-filled RMGI to dentin.

The Effect of the Pre-Conditioning Step on the Shear Bond Strength of Nano-Filled Resin-Modified Glass-Ionomer to Dentin

The purpose of this study was to evaluate the effect of the pre-conditioning step using different dentin conditioners on the shear bond strength (SBS) of the nano-filled resin-modified glass ionomer (RMGI) to dentin. Twenty-four human molars were used in this study. Subsequent to teeth sectioning in the mesio-distal direction and creation of the smear layer, the teeth were divided into six groups with and without the pre-conditioning step. Dentin surfaces were restored with RMGI cylinders and the specimens were stored in distilled water at 37ºC for 24 hours. SBS test were performed using a Universal Testing Machine at a crosshead speed of 0.5 mm/minute. Statistical analysis was performed using One-Way ANOVA followed by Duncan's Multiple Range Test. RMGI/dentin interface was evaluated using SEM operated at 12 Kv at 2000X magnification. 35% phosphoric acid and EDTA yielded significantly higher SBS (12.0±1.8 and 11.9±4.4 MPa, respectively), compared to all tested groups. In addition, 25% polyacrylic acid (8.6±3.1 MPa) reported significantly higher SBS than the nano-filled RMGI when applied according to manufacturer instructions (5.5±2.2 MPa). When nano-filled RMGI was applied without its nano-primer, or directly over 25% polyacrylic acid conditioned dentin exhibited 100% pre-test failure, and their SBS were expressed as 0.0±0.0 MPa. SEM revealed that the nano-primer was unable to decalcify and hybridize the dentin surface. Based on the results of the current study, the pre-conditioning step effectively improves the SBS of nano-filled RMGI to dentin. The self-adhesiveness of nano-filled RMGI was not proved in this study.

Fluoride release profile of a nanofilled resin-modified glass ionomer cement

The present study aimed to compare the fluoride (F-) release pattern of a nanofilled resin-modified glass ionomer cement (GIC) (Ketac N100 - KN) with available GICs used in dental practice (resin-modified GIC - Vitremer - V; conventional GIC - Ketac Molar - KM) and a nanofilled resin composite (Filtek Supreme - RC). Discs of each material (n=6) were placed into 4 mL of deionized water in sealed polyethylene vials and shaken, for 15 days. F- release (μg F-/cm²) was measured each day using a fluoride-ion specific electrode. Cumulative F- release means were statistically analyzed by linear regression analysis. In order to analyze the differences among materials and the influence of time in the daily F- release, 2-way ANOVA test was performed (α=0.05). The linear fits between the cumulative F- release profiles of RC and KM and time were weak. KN and V presented a strong relationship between cumulative F- release and time. There were significant differences between the daily F- release overtime up to the third day only for GICs materials. The daily F- release means for RC were similar overtime. The results indicate that the F- release profile of the nanofilled resin-modified GIC is comparable to the resin-modified GIC.

Microleakage and Shear Punch Bond Strength in Class II Primary Molars Cavities Restored with Low Shrink Silorane Based versus Methacrylate Based Composite using Three Different Techniques

This in vitro study aimed to evaluate the gingival microleakage in class II cavities in primary molars restored with a low shrink silorane resin composite (Filtek P90) or a nanohybride composite resin (Filtek supreme XT) using three different techniques, (total bonding, closed or open sandwich techniques) lined by nano-filled resin modified glass ionomer cement RMGIC (Ketac N100). Additionally, the shear punch bond strength between the two types of composite and KNIO0 was also examined. For microleakage test, two standardized class II slot cavities were prepared in proximal surfaces of 60 sound extracted primary molars which were divided into 2 groups of 30 each according to the type of composite. Each group was subdivided into 3 groups (n = 10) according to the restorative technique used. The restored teeth were examined for microleakage after immersion in 2% methylene blue dye using stereomicroscope at 20 X. Microleakage scores among the groups were compared using Kruskal Wallis test followed by pair wise Mann Whitney U test at P < or = 0.05. Thirty disc specimens were prepared for determining the shear punch bond strength between the two composite materials and the KN100. Specimens were divided into 5 groups (n = 6) according to the adhesive protocol. The differences in mean bond strength values in MPa between groups were statistically analyzed using ANOVA followed by pair wise Tukey Post hoc test at P < or = 0. 05. Mode of failure was also evaluated for all groups. Both the silorane resin and nano-composite resin showed superior marginal seal with the total bonding technique compared to closed and open sandwich techniques. The recorded mean shear punch bond strength values showed no statistical significant difference between the two resin composites without or with their adhesive bonding systems when bonded to the nano-ionomer. All specimens showed cohesive mode of failures except for silorane resin with Adper Easy Bond Self Etch Adhesive (AEBSEA) which showed adhesive mode of failure. The best marginal seal was obtained with the total bonding technique using both resin composites. The shear punch bond strength between KN100 and the two composite materials was not affected by either of the used adhesive bonding agent.

Bonding effectiveness and interfacial characterization of a nano-filled resin-modified glass-ionomer

Glass-ionomers (GIs) exhibit excellent clinical bonding effectiveness, but still have shortcomings such as polishability and general aesthetics. The aims of this study were (1) to determine the micro-tensile bond strength (μTBS) to enamel and dentin of a nano-filled resin-modified GI (nano-RMGI; Ketac N100, 3M-ESPE), and (2) to characterize its interfacial interaction with enamel and dentin using transmission electron microscopy (TEM). Methods The nano-RMGI was used both with and without its primer, while a conventional RMGI restorative material (conv-RMGI; Fuji II LC, GC) and a packable conventional GI cement (conv-GI; Fuji IX GP, GC) were used as controls. After bonding to freshly extracted human third molars, microspecimens of the interfaces were machined into a cylindrical hourglass shape and tested to failure in tension. Non-demineralized TEM sections were prepared and examined from additional teeth. Results The μTBS to both enamel and dentin of nano-RMGI and conv-GI were not statistically different; the μTBS of non-primed nano-RMGI was significantly lower, while that of conv-RMGI was significantly higher than that of all other groups. TEM of nano-RMGI disclosed a tight interface at enamel and dentin without surface demineralization and hybrid-layer formation. A thin filler-free zone (<1 μm) was formed at dentin. A high filler loading and effective filler distribution were also evident, with localized areas exhibiting nano-filler clustering. Conclusions The nano-RMGI bonded as effectively to enamel and dentin as conv-GI, but bonded less effectively than conv-RMGI. Its bonding mechanism should be attributed to micro-mechanical interlocking provided by the surface roughness, most likely combined with chemical interaction through its acrylic/itaconic acid copolymers.