Evaluation of polymerization characteristics and penetration into enamel caries lesions of experimental infiltrants

Antibacterial properties of mesoporous silica coated with cerium oxide nanoparticles in dental resin composite

Cerium oxide nanoparticles are known for their antibacterial effects resulting from Ce3+ to Ce4+ conversion. Application of such cerium oxide nanoparticles in dentistry has been previously considered but limited due to deterioration of mechanical properties. Hence, this study aimed to examine mesoporous silica (MCM-41) coated with cerium oxide nanoparticles and evaluate the antibacterial effects and mechanical properties when applied to dental composite resin. Cerium oxide nanoparticles were coated on the MCM-41 surface using the sol-gel method by adding cerium oxide nanoparticle precursor to the MCM-41 dispersion. The samples were tested for antibacterial activity against Streptococcus mutans via CFU and MTT assays. The mechanical properties were assessed by flexural strength and depth of cure according to ISO 4049. Data were analyzed using a t-test, one-way ANOVA, and Tukey's post-hoc test (p = 0.05). The experimental group showed significantly increased antibacterial properties compared to the control groups (p < 0.005). The flexural strength exhibited a decreasing trend as the amount of cerium oxide nanoparticle-coated MCM-41 increased. However, the flexural strength and depth of cure values of the silane group met the ISO 4049 standard. Antibacterial properties increased with increasing amounts of cerium oxide nanoparticles. Although the mechanical properties decreased, silane treatment overcame this drawback. Hence, the cerium oxide nanoparticles coated on MCM-41 may be used for dental resin composite.

Evaluation of experimental resin infiltrant containing nanohydroxyapatite on color stability and microhardness in demineralized enamel

OBJECTIVE

The aim of the study was to evaluate the effect of the addition of 10% nanohydroxyapatite in an experimental resin infiltrant on color stability and mineral loss.

MATERIAL AND METHODS

Bovine enamel blocks were randomized into five groups (n = 27/group): SE (sound enamel); ICL (initial caries lesion); I (Icon®); E (experimental infiltrant); EH (experimental infiltrant containing 10% nanohydroxyapatite). Color evaluation (n = 15) was performed and CIEL*a*b* values were obtained at points T0 (baseline), T1 (14 days immersed on coffee solution), and T2 (28 days immersed) and data were calculated ∆E00, ∆WID, ∆L*, ∆a*, and ∆b*. Cross-sectional microhardness (n = 12) was performed and lesion area (∆S) was calculated. Images were obtained with polarized light optical microscopy at 40 × magnification (n = 5).

RESULTS

In color stability results, there was significant difference between time (14 and 28 days); ICL demonstrated significant difference among treated groups in all measures (∆L*, ∆a*, ∆b*, ∆E00, ∆WID) regardless of time; I and E demonstrated similar behavior on those measures and EH differed from I in ∆L*. For ∆S, ICL group showed a significant difference compared to I and EH groups, but did not differ from E.

CONCLUSION

The nanohydroxyapatite incorporation suggested an effective mineral recovery on initial caries lesion in depth; however, it showed high color variation, such as Icon. In terms of ∆S, I and EH had lower mineral loss, suggesting a reinforcement on initial caries lesion.

CLINICAL RELEVANCE

Commercial and experimental infiltrants containing nanohydroxyapatite present low color stability and might reinforce mineral in initial caries lesion.

Influence of bioactive particles and onium salt on the physicochemical properties of experimental infiltrants

This study evaluated physicochemical properties of experimental infiltrants after addition of hydroxyapatite nanoparticles (HAp) or 58S bioactive glass (BAG) and diphenyliodonium hexafluorophosphate (DPI). The resin matrix was composed of TEGDMA/Bis-EMA (3:1), 0.5 mol% CQ, and 1 mol% EDAB. The blends received or not 0.5 mol% DPI and 10% wt BAG or HAp. Icon was used as commercial control. The groups were characterized by XRD, FT-IR spectrometry, and SEM before and after simulated body fluid (SBF) immersion for up to 7 days. Polymerization kinetics (n =3 ), water sorption and solubility (n=10), and viscosity (n = 3) were surveyed. For polymerization kinetics, the samples were polymerized for 5 min and the data were obtained from 40 s and 5 min. Statistical analysis was made using ANOVA and Tukey's test (a = 0.05). After 7 days of SBF immersion, XRD and FT-IR showed that the HAp crystalline phase was present only in the HAp groups. A lower degree of conversion (DC) and polymerization rate were observed for the Icon and BAG groups, whereas HAp showed higher values. For the BAG group, DPI increased polymerization rate and DC in 40 s. After 5 min, all groups presented DC above 80%. In groups with particles, the HAp groups exhibited higher viscosity, whereas DPI groups showed a decrease in viscosity. Icon had the highest water sorption. To conclude, BAG neither improved the physicochemical properties studied, nor did it show bioactive properties. The addition of DPI reduced viscosity caused by particle addition and also attenuated the DC decrease caused by BAG addition. The addition of bioactive particles to infiltrants should be seen with caution because they increase viscosity and may not bring major clinical improvements that justify their use. DPI might be indicated only if any component is added to the infiltrant to act as a compensation mechanism.

The Penetration Depth of Resin Infiltration Into Enamel: A Systematic Review

Aims and Objectives

Studies on resin infiltration and its penetration capability are becoming the focus of emerging dentistry. The depth of resin penetration could be a key determining factor in creating a diffusion barrier and in the success of infiltration. The aim of this review article was to evaluate the penetration depth of commercially available resin infiltration in early caries lesions and to identify factors that influence the penetration capability of resin infiltration.

Materials and Methods

A literature search was performed in four databases (PubMed, Science Direct, Scopus, and Web of Science) and manual searching from 2009 to December 2022. Eligibility criteria included in vitro studies pertaining to factors affecting the penetration depth of resin infiltration into the enamel. The risk of bias assessment was done by using checklist for reporting in vitro studies (CRIS).

Results

The initial search resulted in a total of 297 studies. Twenty-nine were assessed for eligibility, and 23 were selected in the qualitative synthesis. According to the CRIS guidelines, all of the studies were classified as moderate risk of bias. The penetration of resin infiltration is influenced by the enamel surface treatment with hydrochloric acid, formulations containing triethylene glycol dimethacrylate (TEGDMA), the addition of ethanol, penetration time, duration of penetration time, saliva contamination, caries activity, and type of tooth. The hypermineralized surface layer needs to be removed for better resin perfusion.

Conclusion

The key to optimal resin infiltration depends on the enamel surface treatment with hydrochloric acid and application technique, infiltration duration, formulation of TEGDMA and ethanol in the resin composition, as well as the type and caries activity of involved teeth. Resin infiltration has superior penetrability compared to fissure sealant, casein phosphopeptide-amorphous calcium phosphate nanocomplexes, flowable composite, adhesive and fluoride varnish. Resin penetration depth may be a critical factor in forming a diffusion barrier and the effectiveness of infiltration in halting the progression of caries.

Application of laser on enamel surface with three types of bioactive glasses-based resin infiltrants: An in vitro study

OBJECTIVE

The study aimed to evaluate and compare the surface micro-hardness, roughness, color, and morphology of enamel after Er,Cr:YSGG laser irradiation, followed by application of three types of bioactive glasses-based resin infiltrants, and the samples groups were challenged with the pH cycle.

METHODOLOGY

Experimental photoactivated resin infiltrants were synthesized using dimethacrylate resins, whereby three different types of bioactive glasses (BGs), i.e., 45S5, fluoridated-BG (F-BG), and borosilicate-BG (B-BG), were incorporated into the resin system. Initially, white spot lesions were created artificially on the toosth enamel surface, then irradiated with Er,Cr:YSGG laser. Then, the resin-only and BG-based resins were infiltrated on the enamel surface. All samples were pH challenged for 14 days, and the micro-hardness, surface roughness, surface morphology, and color stability (ΔE) analyses were conducted before and after the 14 days pH challenge.

RESULTS

After laser irradiation, the micro-hardness was significantly high with 45S5 group compared to resin-only (p = 0.021), F-BG (p = 0.042), and B-BG (p = 0.001) groups. After the pH challenge, the micro-hardness values for all groups were reduced significantly (p ≤ 0.05). The surface roughness was least with the resin-only group and showed a non-significant difference with F-BG (p = 0.34) and significant differences with both B-BG (p = 0.005), and 45S5 (p = 0.010) groups. After the pH cycle, the roughness of all groups was increased significantly (p ≤ 0.05), except B-BG group showed a non-significant difference (p = 0.528). The B-BG group showed significantly high ΔE between day 0 and baseline compared to resin-only (p = 0.0008), F-BG (p = 0.017), and 45S5 (p = 0.029), whereas between day 14 and baseline, the lowest ΔE value was observed for B-BG (14.2 ± 2.10) and maximum for the resin-only (20.57 ± 2.47) group. The SEM images showed pitting on the surface of all resin infiltrant groups after 14 days of pH challenge.

CONCLUSION

The morphological difference was observed after the laser irradiation on the enamel surface. The differences in micro-hardness, surface roughness, and color were observed after the application of experimental resin infiltrants and significant differences were observed after the pH challenge.

An Insight into Enamel Resin Infiltrants with Experimental Compositions

Resin infiltration is a conservative treatment of initial enamel carious lesions. Only one infiltrant material is available on the market (Icon, DMG), and research is now investigating new chemical compositions so as to further exploit the benefits of the resin infiltration technique. A literature search of the articles testing the effects of different formulations on mechanical properties, resin penetration ability, remineralizing, and antibacterial activities was conducted. Of 238 articles, 29 resulted in being eligible for the literature review. The formulations investigated were all different and consisted in the inclusion of hydrophobic monomers (i.e., BisEMA, UDMA), solvents (ethanol, HEMA), alternative etchants (PAM) or molecules with antibacterial or bioactivity features (i.e., AgNP, YbF_3, MTZ, chitosan, DMAMM, HAp, MC-IL, NACP, PUA, CHX) and microfilled resins. Information on the long-term performances of the tested experimental materials were scarce. The combination of TEGDMA with hydrophobic monomers and the inclusion of a solvent alternative to ethanol reinforced mechanical properties of the materials. Hybrid-glass materials demonstrated an enhanced remineralization capacity. Techniques such as tunnelization increased the penetration depth and preserved the recourse to less-conservative treatments. Combining the min-invasive infiltrant approach with remineralizing and bacteriostatic properties would be beneficial for therapeutic and economical aspects, according to the principles of minimally invasive dentistry.

A novel dental infiltration resin based on isosorbide-derived dimethacrylate with high biocompatibility, hydrolysis resistance, and antibacterial effect

Objectives: The available infiltration resin has raised biosafety and treatment stability concerns because of the cytotoxicity of the main component, TEGDMA, and its susceptibility to hydrolysis in the oral environment. This study aimed to develop a TEGDMA-free infiltration resin to overcome these drawbacks. Methods: Using the synthetic bioderived monomer bis(methacrylate) isosorbide (IBM) and the zwitterionic compound 2-methacryloyloxyethyl phosphorylcholine (MPC), a novel infiltrant IBMA was developed and preferentially selected. We investigated the performance of the IBMA resin regarding cytotoxicity, antibiofilm adhesion, and hydrolysis resistance and further verified its ability to restore the demineralized enamel and stability of the infiltrated area under artificial aging conditions. Results: Compared with the commercial TEGDMA-based infiltration resin ICON, IBMA not only demonstrated similar enamel morphologic and esthetic restorative effects in chalky lesions but also exhibited favorable cell viability, durable Streptococcus mutans UA159 biofilm-repellent performance, and higher enamel microhardness (204.0 ± 5.12 HV) of the infiltrated enamel. Specifically, because of the high crosslink density [(47.77 ± 5.76) ×103 mol/mm3] and low water sorption [12.79 ± 2.56 µg/mm3] of the polymer network, the IBMA resin was more resistant to hydrolysis than ICON, which prevents the disruption of the infiltrant's micropore-blocking effect after aging. Enamel lesions treated with IBMA demonstrated good color stability after the tea-staining challenge, which was significantly better than that in the ICON group. Conclusion: Based on these findings, the IBMA resin exhibits favorable cell viability, hydrolysis resistance, and biofilm-repellent properties, which alleviates the defects of traditional TEGDMA systems. Therefore, it is a better alternative for microinvasive treatment involving early caries and enamel whitish discoloration.

Resin-based materials to control human dentin permeability under erosive conditions in vitro: A hydraulic conductance, confocal microscopy and FTIR study

OBJECTIVES

To characterize the behavior of three different polymeric agents before and after an erosive challenge on dentin permeability, to analyze their degradation in both conditions, and to analyze their degree of conversion (DC).

METHODS

The permeability of human dentin disks (1.0 ± 0.2 mm) was measured with smear layer, after its removal, after treatment (LpTreat) with Gluma Desensitizer, PRG Barrier Coat (PBC) or Icon infiltrant (n = 11/group) and after exposure to citric acid (LpEro) (6%, pH 2.1, 1 min). The specimens were analyzed under a Laser Scanning Confocal Microscope (n = 2/group) and the products' DC were calculated. Data were subjected to 2-way repeated measures ANOVA and post-hoc Bonferroni (permeability analysis), to paired t-test (for specimens treated with Icon) and to t-test (DC analysis) (α < 0.05).

RESULTS

Icon showed the lowest LpTreat and LpEro values, while PBC and Gluma did not differ from each other under these conditions. Icon and PBC showed LpEro similar to a dentin with smear layer. Under the Laser Scanning Confocal Microscope, more deposits were noticeable on dentin after treating with PBC. Gluma presented the deepest penetration in dentin. The DC of PBC was the highest.

SIGNIFICANCE

Icon caused the highest reduction on permeability values, followed by PBC and Gluma. PBC generated more deposits covering dentin and seemed to be more efficient after an erosive challenge. The association of a polymeric resin with inorganic ion-releasing fillers seem to be a great strategy to manage dentin hypersensitivity under erosive conditions.

Monomer Release from Dental Resins: The Current Status on Study Setup, Detection and Quantification for In Vitro Testing

Improvements in mechanical properties and a shift of focus towards esthetic dentistry led to the application of dental resins in various areas of dentistry. However, dental resins are not inert in the oral environment and may release monomers and other substances such as Bisphenol-A (BPA) due to incomplete polymerization and intraoral degradation. Current research shows that various monomers present cytotoxic, genotoxic, proinflammatory, and even mutagenic effects. Of these eluting substances, the elution of BPA in the oral environment is of particular interest due to its role as an endocrine disruptor. For this reason, the release of residual monomers and especially BPA from dental resins has been a cause for public concern. The assessment of patient exposure and potential health risks of dental monomers require a reliable experimental and analytical setup. However, the heterogeneous study design applied in current research hinders biocompatibility testing by impeding comparative analysis of different studies and transfer to the clinical situation. Therefore, this review aims to provide information on each step of a robust experimental and analytical in vitro setup that allows the collection of clinically relevant data and future meta-analytical evaluations.

Effects of hybrid inorganic-organic nanofibers on the properties of enamel resin infiltrants - An in vitro study

This in vitro study aimed to evaluate the overall mechanical properties of resin infiltrants doped with bioactive nanofibers and their ability in inhibiting enamel demineralization or achieving remineralization of the adjacent enamel to white spots. A commercial resin infiltrant (ICON, DMG) was doped with hybrid inorganic-organic nanofibers and analyzed for degree of conversion (DC, n = 3) and surface hardness (SH, n = 6). Subsequently, enamel specimens (6 × 4 × 2 mm³) were prepared and submitted to a demineralizing/remineralizing process to produce a subsurface caries-like lesion. The specimens were treated with one of the following materials: ICON infiltrant, DMG (control); ICON + nanofibers of poly-lactic acid (PLA)-filled with silica (PLA-SiO₂); ICON + nanofibers of (PLA)-filled with calcium incorporated into a silica network (SiO₂-CaP). Then, the specimens were subjected to a pH-cycling demineralizing/remineralizing model for 7 days at 37 °C. The %ΔSH change (after treatment), %SH loss and %SH recovery (after pH-cycling regimen) were calculated after SH evaluation (n = 9/group). The Ca/P weight ratio before and after pH-cycling regimen was evaluated through SEM/EDX. The results of DC were analyzed through the T-test (p < 0.05). ANOVA followed by Tukey's test (p < 0.05) was performed for hardness and EDX. A significant SH increase was observed in the ICON/SiO₂CaP group (p < 0.05). The ICON/PLA-SiO₂ presented higher DC values than the control group (p = 0.043). All groups presented significant difference in %ΔSH (p < 0.05), although the specimens treated with ICON/SiO₂CaP presented greater values. Regarding the %SHL and %SHR, the ICON/SiO₂CaP and ICON/PLA-SiO₂ were significantly different compared to the control group (p < 0.001). However, no difference was observed between the ICON/SiO₂CaP and ICON/PLA-SiO_2. The Ca/P ratio showed that the ICON/SiO₂CaP and ICON/PLA-SiO₂ after the pH-cycling regimen differed from sound enamel and modified infiltrants before pH-cycling. In conclusion, tailored hybrid nanofibers may be incorporated into enamel resin infiltrants without compromise the mechanical properties of such experimental materials. These latter can inhibit the demineralization of enamel and increase its hardness during pH-clycling challange.

Development of New Experimental Dental Enamel Resin Infiltrants-Synthesis and Characterization

The aim of the present study was to obtain experimental infiltration materials, intended for the treatment of dental white spots, and to investigate them. Two series of infiltrants (P1–P6)/(P1F–P6F) were obtained, based on different monomer mixtures, without/with glass filler (with fluoride release ability). Each infiltrant from the second series contained the same amount of glass powder, and each infiltrant from the (P–PF) group contained the same resin composition. The characteristics of the experimental infiltrants were investigated by degree of conversion (DC), mechanical strength, water sorption (WS), and fluoride release, in addition to residual monomer for (P1F–P6F) infiltrants. The results were compared with those obtained for commercial Icon infiltrant. For the experimental infiltrants, without/with filler, the recorded DC was in the range of 58.27–89.70%/60.62–89.99%, compared with Icon (46.94%) 24 h after polymerization. The release of fluoride depends on the permeability of the polymer matrix, with respect to the water sorption, which may help to diffuse ions in the storage medium but which can also influence the release of residual monomers. The highest flexural strengths were recorded for the (TEGDMA/HEMA/Bis-GMA) infiltrants (133.94 ± 16.389 MPa/146.31 ± 7.032 MPa). The best experimental infiltrants were P2 and P2F (Bis-GMA/HEMA/TEGDMA).

Minimally Invasive Therapies for the Management of Dental Caries—A Literature Review

In recent years, due to a better understanding of the caries pathology and advances in dental materials, the utilization of non-invasive and minimally invasive techniques that delay/obviate the need for traditional restorations has started gaining momentum. This literature review focuses on some of these approaches, including fluoride varnish, silver diamine fluoride, resin sealants, resin infiltration, chemomechanical caries removal and atraumatic restorative treatment, in the context of their chemistries, indications for use, clinical efficacy, factors determining efficacy and limitations. Additionally, we discuss strategies currently being explored to enhance the antimicrobial properties of these treatment modalities to expand the scope of their application.

The influence of lesion characteristics on application time of an infiltrate applied to MIH lesions on anterior teeth: An exploratory in vivo pilot study

OBJECTIVES

To evaluate the factors that influences the kinetics of resin infiltration of molar incisor hypomineralisation (MIH) lesions on permanent anterior teeth.

METHODS

Demarcated MIH lesions with homogeneous and heterogeneous lesion body appearance, Types 1 (n = 14) and 2 (n = 18), respectively, were selected. After removal of the lesion surface layer using a tapered diamond finishing bur, the lesions were etched and ethanol was applied to the lesions and it was determined if the lesion was still visible or not. Images were taken just prior infiltrant (Icon; DMG) application (T₀), during the infiltration process (T_x) and when infiltration had ceased progressing or opacity disappearance was clinically apparent (T_max). Surface-area measurements of the opacity and infiltrated area were calculated and the infiltration proportion (IP_x) was calculated over the infiltration time.

RESULTS

Type 1 and positive ethanol test lesions showed significantly lower mean T_max (3.4 min) in comparison with Type 2 and negative ethanol test lesions (9.9 min) [Student t-test/Fisher's exact test; p < .01]. A non-linear correlation was observed (R² = 0.88) indicating that the IP_x was rapid at the beginning of resin application, decreasing over time.

CONCLUSION

In comparison with Type 1 and positive ethanol test lesions, Type 2 and negative ethanol test lesions require longer application time to infiltrate.

CLINICAL SIGNIFICANCE

MIH-lesion type and the 'ethanol test' were reliable predictive factors for the application time required for infiltrating MIH lesions on permanent anterior teeth.

A modified TEGDMA-based resin infiltrant using polyurethane acrylate oligomer and remineralising nano-fillers with improved physical properties and remineralisation potential

OBJECTIVES

This study aimed to modify an experimental triethylene glycol dimethacrylate (TEGDMA) based resin infiltrant using PUA oligomer and two remineralising fillers, including fluorohydroxyapatite (FHA) and fluoride-doped bioactive glass (FD-BG), to improve the mechanical and physical properties and induce remineralising potential.

MATERIALS AND METHODS

The polyurethane acrylate oligomer (PUA) was synthesised and characterised. Experimental resin infiltrant was prepared by mixing 10% of synthesised PUA with 88% TEGDMA. Water contact angle, penetration coefficient, and penetration depth were then measured. The FHA and FD-BG fillers were synthesised and characterised. To prepare nano-filled resin infiltrant, 5% of each powder was mixed with the prepared resin infiltrant. The prepared resin infiltrants were characterised to evaluate their degree of conversion, mechanical properties, water sorption, and solubility. The ion release of filled resin was also assessed. The non-infiltrated and infiltrated enamel specimens underwent fourteen days of pH-cycling, and a surface microhardness was done to assess the resistance to demineralisation.

RESULTS

The results showed that the addition of PUA to TEGDMA increased the mechanical properties and decreased water sorption and solubility. The addition of synthesised FD-BG fillers to resin infiltrant significantly improved the resistance to demineralisation of enamel samples compared with other groups (p ≤ 0.001). The FHA fillers also improved the resistance to demineralisation; however, the produced changes were not statistically meaningful (p > 0.05).

CONCLUSIONS

Based on the results, the PUA+TEGDMA+ FD-BG/FHA composite can be used as an alternative material for pure TEGDMA in enamel infiltration approaches owing to its better mechanical properties, lower water sorption and solubility, and also remineralisation potential.

CLINICAL SIGNIFICANCE

A resin infiltrant with remineralisation potential, lower water sorption and solubility and higher mechanical properties may enhance the management of early caries lesions.

Influence of Incorporating Zirconium- and Barium-based Radiopaque Filler Into Experimental and Commercial Infiltrants

OBJECTIVES

To evaluate how adding different concentrations of particles (barium or zirconium oxide 25%/45% by weight) to a commercial infiltrant (Icon) and an experimental infiltrant influences cohesive strength (CS), degree of conversion (DC), water sorption (WS), solubility (SL), radiopacity, and penetration depth.

METHODS AND MATERIALS

Microtensile CS (n=10) was evaluated using a universal testing machine. DC (n=5) was evaluated in a Fourier-transform infrared spectrometer. Polymerized samples were dissected, weighed, and stored to obtain the final mass for WS and SL tests (n=10). Radiopacity analysis (n=5) was performed using a digital radiography system. Penetration depth analysis (n=5) was performed by confocal laser scanning microscopy. Analyses were performed using the R program, with a significance level of 5%, except for the penetration depth analyses, which were evaluated only qualitatively.

RESULTS

The groups with 45% zirconium showed greater CS values, regardless of the infiltrant. Among the groups with no particle addition, those of the experimental infiltrant presented higher DC than those of Icon. The experimental infiltrant presented lower WS than Icon. All groups had SL below the ISO recommended levels. Radiopacity higher than 2.24 mmAl (enamel radiopacity) was observed only in the groups with 45% zirconium. All the groups achieved similar penetration depth, but the groups containing experimental infiltrant appear to have had longer tag extensions.

CONCLUSIONS

Addition of 45% of zirconium presented good results for CS and WS, as well as SL below the ISO recommended standard, adequate radiopacity, and penetration depth similar to the other groups.

Study of Cytotoxic Properties of an Experimental Preparation with Features of a Dental Infiltrant

Microinvasive dentistry is based on the treatment of early carious lesions with the use of dental infiltrants. The commercially available Icon dental infiltrant does not contain any bacteriostatic component. An experimental preparation enriched with the missing component was synthesised. The aim of this study was to evaluate the cytotoxicity of the experimental preparation. Mouse fibroblasts of the L-929 lineage were used for the in vitro study. Cell morphology and viability were assessed. In the cytotoxicity analysis, it was shown that the experimental preparation (42.8 ± 10.3) after 24 h at two-fold dilution showed similar cytotoxicity to Icon (42.7 ± 8.8) (p > 0.05), while at four-fold dilution experimental preparation (46.7 ± 3.1), it was less toxic than Icon (34.2 ± 3.1) (p < 0.05). The experimental preparation has the potential to provide an alternative to the Icon commercial preparation. Further research is needed to evaluate the cytotoxicity of the experimental preparation over a longer period of time.

Response of pulp cells to resin infiltration of enamel white spot-like lesions

OBJECTIVES

To investigate the trans-enamel and trans-dentinal biological effects of treating enamel white spot-like lesions (EWSLs) with resin infiltration components (RICs) on odontoblast-like cells (MDPC-23) and human dental pulp cells (HDPCs).

METHODS

EWSLs were induced in 60 enamel/dentin discs (4.0 ± 0.2 mm thick) using S. mutans. The discs were adapted into artificial pulp chambers and MDPC-23 were seeded on the dentin surface. The components of a resin infiltration system (Icon) were applied individually or in combination on the enamel surface as following (n = 10/treatment): Etch, Infiltrant, Etch+Infiltrant, or Etch+Dry+Infiltrant. The application of water or hydrogen peroxide served as negative and positive controls, respectively. After 72 h, MDPC-23 viability was evaluated. The extracts were exposed for 72 h to pre-cultured MDPC-23 and HDPCs in 96-well plates to evaluate cell viability, alkaline phosphatase activity (ALP), mineralized nodule formation (MN), and the expression of inflammatory cytokines (ICs) and mineralization-related genes (MRs). Data were analyzed by ANOVA complemented with Tukey or Games-Howell post-hocs (α = 5%).

RESULTS

Cell viability, ALP activity, and MN formation were significantly reduced in response to the RICs, presenting intermediate values compared to positive and negative controls. Likewise, ICs were upregulated, whereas MRs were downregulated. Among the RICs, the Etch component caused the most notorious detrimental effects.

SIGNIFICANCE

Resin infiltration of EWSLs negatively affected the metabolism of pulp cells in vitro. Therefore, even though resin infiltration is a micro-invasive therapy for non-cavitated caries in enamel, it should be closely followed up seen that components may diffuse and unbalance pulp homeostasis.

Experimental self-etching resin infiltrants on the treatment of simulated carious white spot lesions

OBJECTIVES

To evaluate the penetration depth (μm) of experimental resin infiltrants containing different percentages of triethylene glycol dimethacrylate (TEGDMA) and phosphoric acid 2-hydroxyethyl methacrylate ester (PAM) in artificial carious white spot lesions (WSL).

METHODS

WSL were produced in 65 bovine flat enamel specimens by pH cycling protocol, which were treated with either Icon (control) or experimental acidic infiltrants based on different percentages of TEGDMA and PAM monomers (acidic), and their association or not with previous acid-etching with phosphoric acid. Ten readings using Confocal Laser Scanning Microscopy were conducted on each specimen and the penetration depth was calculated from the surface until the deepest point with the fluorescent dye Rhodamine B (0.02 mg/mL). The pH and the viscosity of the experimental infiltrants were also tested. Data were statistically analyzed with two-way ANOVA and Tukey tests (α < 0.05).

RESULTS

The material factor and the interaction material*acid-etching were statistically significant. The lowest penetration depth was observed for the samples treated with the commercial infiltrant after etching with 15% hydrochloric acid. When specimens were pre-treated with PA, highest penetration was seen for specimens treated with 100% TEGDMA, which differed from all other groups. The lowest penetration was seen for those treated with 50:50 TEGDMA:PAM infiltrants. When specimens were not previously etched, highest penetration was seen for Icon, which differed only from those treated with 25% TEGDMA 75% PAM, where the lowest values were seen. The values of viscosity increased and the pH decreased with the addition of PAM in the infiltrant formulations.

CONCLUSION

the association between TEGDMA and PAM seems to allow similar infiltration depth reached by Icon infiltrant without acid etching the enamel surface.

Can composition and preheating improve infiltrant characteristics and penetrability in demineralized enamel?

The composition of infiltrants can influence their physical properties, viscosity and depth of penetration (DP). Strategies are used to increase the DP, such as the addition of diluents or the use of heat. This study aimed to evaluate the effect of preheating and composition on physical properties and DP of infiltrants in demineralized enamel. The groups were assigned, and the following experimental formulations were made: 25%BisEMA +75%TEGDMA; 25%BisEMA +65%TEGDMA +10%ethanol; 25%BisEMA +65%TEGDMA +10%HEMA; 100%TEGDMA; 90%TEGDMA +10%ethanol; 90%TEGDMA +10%HEMA. The samples were photoactivated at two temperatures (25°C and 55°C). Degree of conversion (DC) was performed using an infrared spectrophotometer. Elastic modulus (E), flexural strength (FS) and contact angle (CA) tests were also performed. The DP of an infiltrant in demineralized enamel was determined by confocal laser scanning microscopy (CLSM) using an indirect labeling technique. The data were analyzed by two-way ANOVA and Tukey's test. DC increased after preheating in all the groups; however, 90%TEGDMA+10%ethanol showed the lowest DC for both temperatures, and the lowest E. Preheating did not influence E or FS. The CA increased at 55°C for most groups, but decreased for groups containing HEMA. Temperature did not seem to influence DP, and Icon showed the lowest DP values. The 100%TEGDMA composition showed more homogeneous penetration, whereas Icon showed heterogeneous and superficial penetration. The preheating technique does not improve all properties in all the material compositions. The composition of a material can influence and improve its properties.

The Use of Resinous Infiltrants for the Management of Incipient Carious Lesions: a Literature Review

AbstractThe objective of this work was to analyze scientific evidence from a literature review pertaining to the effectiveness of resinous infiltrants for minimally invasive treatment of incipient carious lesions. Studies published between 2002 and 2019 were queried from the following databases: Capes, PubMed, Medline, BBO, Lilacs and SciELO. The search keywords included "Dental Caries", "Tooth Remineralization", "Dental Leakage". Most of the studies found resin-infiltrating treatment to be a viable option for the minimally invasive treatment of incipient carious lesions; this treatment was able to fulfill the primary expected effects: inhibition of carious progression and the lesions esthetic improvement. However, some issues need to be clarified to improve the safety of this treatment because it can be recommended in clinical practice. In conclusion, the use of resinous infiltrants has been reported as promising for the treatment of incipient carious lesions. However, there is a need for long-term studies to confirm the effectiveness of this treatment to determine its applicability for clinical use. Keywords: Dental Caries. Dental Leakage. Tooth Remineralization. ResumoO objetivo desse trabalho foi analisar evidências científicas, por meio de uma revisão de literatura, sobre a eficácia do uso de infiltrantes resinosos para o tratamento minimamente invasivo de lesões cariosas incipientes. A seleção do material literário utilizado foi realizada por pesquisa sobre o tema nas bases de dados: portal de periódicos Capes, PubMed, Medline, BBO, Lilacs e SciELO, abrangendo prioritariamente, o período de 2002 a 2019. Para busca nas bases de dados foram utilizadas palavras-chave como “Cárie Dentária”, “Remineralização Dentária”, “Infiltração Dentária”, assim como suas correspondentes na língua inglesa.  A maioria dos estudos encontrados aponta o tratamento infiltrante resinoso como uma opção viável para o tratamento minimamente invasivo de lesões cariosas incipientes sendo capaz de cumprir os principais efeitos esperados: inibição da progressão cariosa e melhoria estética das lesões. Entretanto, alguns impasses necessitam ser esclarecidos para que o tratamento seja recomendado com mais segurança na prática clínica. Conclui-se que o uso de infiltrantes resinosos tem sido relatado como promissor para o tratamento de lesões cariosas incipientes, contudo há necessidade de novas pesquisas e estudos a longo prazo para confirmar sua eficácia em todos aspectos desejáveis para seu uso clínico. Palavras-chave: Cárie Dentária. Infiltração Dentária. Remineralização Dentária.

Is Resin Infiltration a Microinvasive Approach to White Lesions of Calcified Tooth Structures?: A Systemic Review

Aim

The treatment of white lesions should aim at arresting the lesion progression of carious lesions and improving the esthetics by diminishing the opacity of the developmental disturbances of a tooth. The objective of this review was to present the scientific basis, the principles of resin infiltration and to discuss its inherent clinical applications.

Data sources

Data were identified by PubMed searches. Papers published in English between 2010 and 2015 were selected and most up-to-date or relevant references were chosen.

Conclusion

The resin infiltration technique, while promising, needed more clinical evidence for conclusive findings. However, based on available laboratory and clinical studies, it seems convincing that resin infiltration of enamel lesions should aim at arresting the progression of white spot lesions. Combining this microinvasive approach with a substantial caries remineralization program may provide therapeutic benefits and significantly reduce both long term restorative needs and costs, thus complementing the concept of minimum intervention dentistry.

How to cite this article

Manoharan V, Kumar AS, et al. Is Resin Infiltration a Micro invasive Approach to White Lesions of Calcified Tooth Structures?: A Systemic Review. Int J Clin Pediatr Dent 2019;12(1):53-58.

In vitro effect of a resin infiltrant on different artificial caries-like enamel lesions

OBJECTIVES

A resin infiltrant was employed for the treatment of active white spot lesions due to its ability to penetrate into the enamel pores and prevent the progression of the lesion. However, limited information is available about its mechanical effect on different artificial enamel lesions as well as on its resistance to further demineralization. Therefore, this study aimed to evaluate the effects of the Icon® infiltrant on different artificial caries-like enamel lesions and its resistance to new acid challenges.

DESIGN

Artificial lesions were produced in bovine enamel using three different protocols (demineralization/remineralization cycling, DE-RE; 8% methylcellulose gel, MC; and methyl ethyl diphosphonate solution, MHDP; n = 13). The specimens were treated with Icon® and subjected to a new acid challenge using DE-RE cycling. The surface and cross-sectional hardness were evaluated in sound, demineralized, treated and further demineralized enamel areas. Data were statistically analyzed using ANOVA and Tukey's test (p < 0.05).

RESULTS

All of the demineralizing protocols produced subsurface artificial caries lesions. The infiltrant was able to partially recover the surface hardness and prevent further surface hardness loss in enamel previously demineralized using the DE-RE and MHDP protocols. In regard to cross-sectional hardness, no positive effect was found.

CONCLUSIONS

The effect of the infiltrant depends on the type of lesion created in vitro, and its action is limited to the lesion surface.

Resin infiltration of deproteinised natural occlusal subsurface lesions improves initial quality of fissure sealing

The aim of this ex vivo study was to evaluate the infiltration capability and rate of microleakage of a low-viscous resin infiltrant combined with a flowable composite resin (RI/CR) when used with deproteinised and etched occlusal subsurface lesions (International Caries Detection and Assessment System code 2). This combined treatment procedure was compared with the exclusive use of flowable composite resin (CR) for fissure sealing. Twenty premolars and 20 molars revealing non-cavitated occlusal carious lesions were randomly divided into two groups and were meticulously cleaned and deproteinised using NaOCl (2%). After etching with HCl (15%), 10 premolar and 10 molar lesions were infiltrated (Icon/DMG; rhodamine B isothiocyanate (RITC)-labelled) followed by fissure sealing (G-ænial Flo/GC; experimental group, RI/CR). In the control group (CR), the carious fissures were only sealed. Specimens were cut perpendicular to the occlusal surface and through the area of the highest demineralisation (DIAGNOdent pen, KaVo). Using confocal laser-scanning microscopy, the specimens were assessed with regard to the percentage of caries infiltration, marginal adaption and internal integrity. Within the CR group, the carious lesions were not infiltrated. Both premolar (57.9%±23.1%) and molar lesions (35.3%±22.1%) of the RI/CR group were uniformly infiltrated to a substantial extent, albeit with significant differences (P=0.034). Moreover, microleakage (n=1) and the occurrence of voids (n=2) were reduced in the RI/CR group compared with the CR group (5 and 17 specimens, respectively). The RI/CR approach increases the initial quality of fissure sealing and is recommended for the clinical control of occlusal caries.

Evaluation of Surface Roughness Characteristics Using Atomic Force Microscopy and Inspection of Microhardness Following Resin Infiltration with Icon®

OBJECTIVE

The aim of this study was to evaluate the surface roughness via atomic force microscopy (AFM) as well as to evaluate the microhardness values of Icon^® in comparison with sound and demineralized enamel in a large subject group.

MATERIALS AND METHODS

Enamel samples were prepared from sound bovine incisors and randomly allocated into either AFM (n = 60) or microhardness (n = 60) groups. The AFM group was divided into control (n = 30) and Icon^® (n = 30) subgroups. The microhardness group was also divided into three subgroups: control (n = 20), demineralization (n = 20) and Icon^® (n = 20) groups. The demineralization and Icon^® subgroups were subjected to a demineralizing solution (pH: 4, 2 hours). Following the formation of shallow white spot lesions and application of the infiltrant, each sample was examined according to its parameter.

RESULTS

AFM images suggested that Icon^® had a significantly rougher surface than the control group. When the AFM results were evaluated numerically, it was evident that the Icon^® group possessed statistically higher Sa, Sq, mean height, and maximum deviation values compared to the control group. The mean Vickers hardness values of all groups were determined to be significantly different from one another. Hardness values in the demineralization group were determined to be significantly lower than the control and Icon^® groups. No statistically significant difference was observed between mean Vickers hardness values for the contol and Icon^® groups.

CONCLUSIONS

The present in vitro study shows that more studies are required to improve the surface quality of this infiltrant material.

CLINICAL SIGNIFICANCE

The present in vitro study shows that the resin infiltration technique results in increased microhardness of demineralized enamel. However, it was observed that the infiltrant material creates a significantly rougher surface compared to healthy, untreated enamel. (J Esthet Restor Dent 29:201-208, 2017).

Effect of monomer blend and chlorhexidine-adding on physical, mechanical and biological properties of experimental infiltrants

OBJECTIVES

The aim of the study was to evaluate antimicrobial inhibition zone, degree of conversion (DC) and Knoop hardness (KH) of experimental infiltrants. Experimental low viscosity monomer blends were prepared and chlorhexidine diacetate salt (CHX) (0.1% or 0.2%) was added comprising the groups: G1) TEGDMA; G2) TEGDMA/0.1CHX; G3) TEGDMA/0.2CHX; G4) TEGDMA/UDMA; G5) TEGDMA/UDMA/0.1CHX; G6) TEGDMA/UDMA/0.2CHX; G7) TEGDMA/BISEMA; G8) TEGDMA/BISEMA/0.1CHX; G9) TEGDMA/BISEMA/0.2CHX. Icon^® was used as control group.

METHODS

Specimens of resin blends were made (n=9) to accomplished DC and KH. Pour plate was accomplished to evaluate antimicrobial groups' activity against Streptococcus mutans (SM) and Lactobacillus acidophilus (LA). Data obtained were submitted to two-way ANOVA and Tukey tests for blends comparisons and Dunnett's test for comparisons between experimental infiltrants and Icon^® (p<0.05).

RESULTS

In relation to antimicrobial effect, uncured blends showed higher antibacterial activity than cured ones for the most of blends. After polymerization, G5 showed the highest inhibition zone against SM and, G3 and G6 against LA. Concerning KH, TEGDMA/UDMA-based blends showed the highest values of KH number and it was influenced by monomeric base, regardless CHX concentration. DC was not affected by monomer blend composition, neither for CHX concentration. The antimicrobial activity was affected by monomeric base, CHX concentration and polymerization. Experimental infiltrants presented similar or higher performance than Icon^® for the properties evaluated.

SIGNIFICANCE

White spot lesion infiltration with low viscosity monomer blends (infiltrants) is an alternative to stop initial caries lesions progression. The incorporation of an antimicrobial agent as chlorhexidine diacetate salt in infiltrants composition could enhance the performance of these materials.

Evaluation of sorption/solubility, softening, flexural strength and elastic modulus of experimental resin blends with chlorhexidine

OBJECTIVES

To evaluate physical-chemical properties of experimental diacetate chlorhexidine (CHX)-added resin blends.

METHODS

Blends were formulated: G1)TEGDMA; G2)TEGDMA/0.1%CHX; G3)TEGDMA/0.2%CHX; G4)TEGDMA/UDMA; G5)TEGDMA/UDMA/0.1%CHX; G6)TEGDMA/UDMA/0.2%CHX; G7)TEGDMA/BisEMA, G8)TEGDMA/BisEMA/0.1%CHX; G9)TEGDMA/BisEMA/0.2%CHX. Icon(®) was the control group. For sorption/solubility (SS), cylindrical specimens (n=5) were prepared and their weight obtained. The specimens were immersed in deionized water for 7days at 37°C and their weight was verified again. SS were calculated using accepted formulas. For softening, cylindrical specimens (n=10) were prepared and initial Knoop hardness number (KHN) obtained. The specimens were immersed in absolute ethanol for 24h at 37°C and final KHN accomplished. Softening values were calculated by KHN reduction percentage. For elastic modulus (EM) and flexural strength (FS) bar specimens were prepared (n=10) and values obtained with a universal device (three point, 5mm distance, 0.5mm/min, load of 50N). The data was analyzed using one-way ANOVA and Tukey test (α=5%).

RESULTS

TEGDMA/BisEMA blends and Icon(®) showed the lowest sorption from blends (p>0.05), and Icon(®) was the most soluble material (p<0.01). TEGDMA/UDMA/0.1%CHX showed the highest softening, similar to Icon(®) (p>0.05). For EM, all blends were different than Icon(®) (p<0.01). For FS, TEGDMA blends were similar to Icon(®), showing the lowest averages (p>0.05).

CONCLUSIONS

Monomers chemical characteristics influenced the physical-chemical properties of experimental blends more than CHX. Between the blends tested, UDMA blends presented satisfactory results for assays evaluated.

CLINICAL SIGNIFICANCE

Infiltrants CHX-added could arrest and reinforce initial caries lesions, and the antimicrobial effect could prevent new lesions in sound enamel adjacent to the infiltrated area.

Influence of Staining Solution and Bleaching on Color Stability of Resin Used for Caries Infiltration

OBJECTIVE

The objective of this study was to evaluate the color stability of Icon-infiltrated white spot lesions after staining and the bleaching effect on the infiltrated and stained surfaces.

METHODS AND MATERIALS

Enamel-dentin specimens (N=30, 5 × 5 × 3 mm, 1-mm enamel + 2-mm dentin thickness) were prepared from bovine incisors and randomly allocated into three groups (n=10): control, demineralized, and infiltrated. Artificial enamel subsurface lesions were created using 50 mL of 0.05 M acetate buffer solution. Specimens were produced by Icon application in enamel caries-like lesions, according to the manufacturer's instruction. Baseline color readings were assessed using a spectrophotometer, and CIE L*a*b* measurements of each specimen were performed using a white background. To simulate extrinsic dietary staining, specimens were placed into a 4-mL coffee infusion, three times daily for 15 minutes, for 14 days. After the staining procedure, color measurements were performed again. Then, bleaching procedures were performed using 16% carbamide peroxide gel for four hours daily for 21 days, and a final color assessment was performed. To compare the baseline and final measurements, t-test was used (α =0.05). The statistical comparison between the groups was performed using the one-way analysis of variance and Tukey tests (α =0.05).

RESULTS

Coffee staining provided a significant reduction of L* values and an increase of a* and b* in all groups (control, decayed, and infiltrated). The bleaching procedure provided a significant increase in L* and decrease of a* and b* values in all groups. There was no significant difference in ΔE values between decayed and infiltrated groups before bleaching, and after bleaching, the infiltrated group showed the lowest ΔE values.

CONCLUSION

It can be concluded that enamel infiltrated with Icon presents significant alteration of color after staining when compared with sound enamel. However, if there is discoloration of the infiltrant, the bleaching treatment can be used successfully.