Influence of different pre-treatments on the resin infiltration depth into enamel of teeth affected by molar-incisor hypomineralization (MIH)

OBJECTIVES

This in vitro pilot study aimed to evaluate whether different pre-treatments (demineralization, deproteinization, (chemo-)mechanical reduction of the surface layer) influence the penetration depth of a resin infiltrant into MIH-affected enamel compared to initial carious lesions.

METHODS

Thirty extracted human permanent molars with non-cavitated initial carious lesions (n = 5) or MIH (n = 25) were chosen and randomly assigned to six experimental groups: IC: initial caries; M: MIH; MN: MIH, 5.25% sodium hypochlorite; MM: MIH, microabrasion; MA: MIH, air abrasion; MAN: MIH, air abrasion and 5.25% sodium hypochlorite. A modified indirect dual fluorescence staining method was adopted to assess the penetration depth (PD) of the resin infiltrant and the lesion depth (LD) by confocal laser scanning microscopy (CLSM). Exemplarily, scanning electron microscopic (SEM) images were captured. The relationship between group assignment and penetration/lesion depth was estimated using a linear mixed model incorporating the tooth as random effect (two observations/tooth). The significance level was set at p < 0.05.

RESULTS

For MIH-affected molars, the mean PD (in µm; median, [minimum-maximum]) were M (178.2 [32.5-748.9]), MN (275.6 [105.3-1131.0]), MM (48.7 [0.0-334.4]), MA (287.7 [239.4-491.7]), and MAN (245.4 [76.1-313.5]). Despite the observed differences in PD between the groups, these could not be statistically verified (Bonferroni, p = 0.322). The percentage penetration was significantly higher for IC than for MIH groups (Bonferroni, p < 0.05).

SIGNIFICANCE

Compared to IC, resin infiltration into MIH-affected enamel ist more variable. Different pre-treatments influence the resin penetration into developmentally hypomineralized enamel to a fluctuating level.

Management of permanent incisors affected by Molar-Incisor-Hypomineralisation (MIH) using resin infiltration: a pilot study

PURPOSE

To compare the aesthetic improvement of Molar-Incisor-Hypomineralisation (MIH) opacities treated by applying Icon-Etch for three cycles with the opacities treated by Icon-Etch for once, in the course of resin infiltration technique.

METHODS

Thirty incisors were sorted based on the colour of the opacities and then distributed according to the number of Icon-Etch cycles using a randomisation table into the groups: (1) White/Creamy one cycle, (2) White/Creamy three cycles, (3) Yellow/Brown one cycle, (4) Yellow/Brown three cycles. The primary outcomes of applying the resin infiltration to the opacities were compared amongst groups according to the parents' satisfaction, the amount of coverage, and the colour matching with the surrounding sound enamel. The stability of the results after 3 months was evaluated using a spectrophotometer.

RESULTS

The colour of the opacity pre-treatment affected the outcomes significantly (p < 0.05), compared according to the method of application (p > 0.05) in terms of parents' satisfaction. Whilst the multiple applications for Icon-Etch cycles showed more coverage amount in White/Creamy opacities than the application ones (p < 0.05); in colour matching, there was no statistically significant difference between the two methods (p > 0.05). For yellow/brown opacities, some negative results occurred with the single Icon-Etch cycle.

CONCLUSION

In MIH opacities, it is possible to rely on the resin infiltration as a minimally invasive method to achieve acceptable results, especially with multiple Icon-Etch cycles applications in the white/creamy opacities. The colour stability has not been affected by either the colour of the opacity or the number of cycles.

Esthetic Effects and Color Stability of Resin Infiltration on Demineralized Enamel Lesions: A Systematic Review

Aims and Objectives

The aim of this study was to systematically review the ability of resin infiltration to conceal demineralized enamel lesions to normal enamel translucency and to maintain color stability.

Materials and Methods

A literature search of PubMed, MEDLINE, Web of Science, and Scopus databases and a manual search of articles from 2009 to 2021 for randomized controlled trials (RCTs) and clinical efficacy trials (nonrandomized) were performed. Methodological quality and risk of bias (RoB) of included papers was assessed using Cochrane Collaboration Risk of Bias Tool 2.0 for RCTs and ROBINS-I (Risk Of Bias In Non-randomized Studies of Interventions) tool for nonrandomized studies.

Results

A total of 352 titles and abstracts were reviewed. Eight RCTs and three clinical efficiency studies were included in this review. The masking effects of the demineralized enamel lesion were reported immediately after resin infiltration, and the color stability of this material was up to 24 months, with no adverse effects noted. For RCTs, four studies were classified as "some concerns" and four were as "low RoB." For nonrandomized studies, all of the studies presented an overall moderate RoB.

Conclusion

Resin infiltration achieves the best esthetic outcomes compared with microabrasion and remineralization therapy. Color stability was achieved with this material for up to 24 months and no adverse effects were noted. Factors contributing to the esthetic outcomes of the resin include the elimination of the hypermineralized surface layer, the homogeneity of the resin itself, and polishing after resin infiltration. Longitudinal follow-up and improved control of confounding variables should characterize future high-quality systematic reviews.

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.

Evaluation of Infiltrant Application in the Course of Root Cementum Caries with Different Methods of Surface Preparation—An In Vitro Study

The aim of this study is to evaluate the depth of penetration of an experimental preparation with the characteristics of a dental infiltrant into the decalcified root cementum tissue and observation of the root cementum tissue subjected to a single and repeated twice hydrochloric acid etching process. The study material consisted of 20 human teeth (the study group—12 demineralised teeth, the control group—8 teeth). A commercially available Icon preparation and an experimental preparation were used for the study with addition 2% of YF3 (yttrium trifluoride) added as an indicator to facilitate microscopic observation. Each tooth was divided into two zones, blue (Icon) and red (experimental preparation). The teeth were divided into two subgroups—in the first subgroup, the etching preparation was applied once, in the second subgroup twice, and at the end the teeth were infiltrated with the experimental preparation and the Icon preparation. The study of tooth longitudinal section morphology and chemical composition was performed with the use of a Hitachi S-3400N scanning electron microscope. Microscopic observations show that the applied YF3 tracer in most cases agglomerates and remains in the form of conglomerates on the surface of the root cementum. Single particles of YF3 are visible, penetrating through the cementum tissues into the root dentine structure. The degree of tissue infiltration with the resin (depth of penetration into decalcified tissues) is visible at a depth of approx. 80–120 μm. In the test group subjected to a single etching process, good penetration of both resins was noticeable, however, excessive erosion of the root surface was evident in several of the specimens—indicating that damage occurred as a result of the etching process. In the test group subjected to two etching processes, excessive erosion of the cementum is visible in each deposit.

In vitro effect of resin infiltrant on resistance of sound enamel surfaces in permanent teeth to demineralization

OBJECTIVE

To investigate the effect of resin infiltrant on resistance of sound permanent enamel surfaces to demineralization.

METHOD

Eighty healthy premolars were sectioned to obtain enamel blocks from the buccal surface. Specimens with baseline surface microhardness values of 320-370 were selected. The experimental group were treated with resin infiltrant, while the control group was not. Specimens from each group were artificially demineralized and the surface microhardness values were measured again. Confocal laser scanning microscopy was used to measure the depth of demineralization and detect the penetration ability of the resin infiltrant. The specimens were subjected to a simulated toothbrushing abrasion test. Scanning electron microscopy was used to observe changes in the surface morphology of specimens after each of these procedures.

RESULTS

No significant differences between the experimental and control groups were observed in the baseline microhardness values or in the experimental group after resin infiltration compared with the baseline conditions. After artificial demineralization, the microhardness value in the control group was significantly lower than that in the experimental group (266.0 (±34.5) compared with 304.0 (±13.0), P = 0.017). Confocal laser scanning microscopy results showed that the demineralization depth in the control group was significantly deeper than that in the experimental group (97.9 (±22.8) µm vs. 50.4 (±14.3) µm, P < 0.001), and that resin infiltrant completely penetrated the acid-etched demineralized area of the tooth enamel with a mean penetration depth of 31.6 (±9.0) µm. Scanning electron microscopy showed that the surface morphology was more uniform and smoother after simulated toothbrushing. The enamel surface structure was more severely destroyed in the control group after artificial demineralization compared with that of the experimental group.

CONCLUSION

Resin infiltrant can completely penetrate an acid-etched demineralized enamel area and improve resistance of sound enamel surfaces to demineralization. Our findings provide an experimental basis for preventive application of resin infiltrant to sound enamel surfaces to protect tooth enamel against demineralization.

Success of resin infiltration treatment on interproximal tooth surfaces in young adults-A practice-based follow-up study

Objectives

Arresting active initial caries lesions is part of the modern caries controlling system. Resin infiltration (RI) system has been found a promising method in arresting interproximal initial lesions. The aim was to investigate whether RI arrests progression of active caries lesions.

Materials and methods

Participants (n = 20) of the retrospective study were patients in the Dental Teaching Unit, City of Oulu, Finland, mean age 26 years (SD5.2). Indication for RI was radiographically diagnosed progressing (ICDAS 1–3) interproximal lesions (n = 54). RI treatments were performed in 2015–2017. Controls were initial lesions in the same bitewing radiographs without RI or other treatment (n = 24). For analyzes teeth were categorized as lower and upper premolars and molars. The change in lesions during the follow‐up period was recorded surface wise as follows: deterioration / improvement from ICDAS score 3/improvement from ICDAS score 2/improvement per se/at follow‐up, lesion was less diffuse/no change. The changes in each tooth surface were analyzed between RI intervention and control teeth by using Chi‐square test. Proportions of successful and failed surfaces were given.

Results

The mean length of follow‐up period was 17.4 m (SD7.2). Arresting of caries lesions (ICDAS scores 2 and 3) was distinctly better in RI group (63.0%) compared with the controls (29.1%). The situation progressed among 29.2% of the controls whereas the respective proportion among the intervention group was 14.8%. Progression of lesions was more distinct in all tooth groups in the control group. Outcome was successful despite the lesion depth.

Conclusions

Resin infiltration seems effective in arresting progression of initial caries lesions with monitoring period of 1.5 years.

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.

Adhesive systems effect over bond strength of resin-infiltrated and de/remineralized enamel

Background: The purpose of this study was to evaluate the effect of different bonding agents on bond-strength to demineralized enamel after remineralizing treatments and resin infiltration. Methods: Buccal enamel of 120 bovine incisors was polished and then were divided into five experimental groups: SE (sound enamel); DE (demineralized enamel); AS (demineralized enamel immersed in artificial saliva for eight weeks); NaF (demineralized enamel treated with 0.05% sodium fluoride solution (one minute) for eight weeks); Ic (demineralized enamel infiltrated with a low-viscosity resin (Icon-DGM). These groups were subdivided according to adhesive system used: self-etching adhesive Adper Easy One (3M/ESPE) and etch-and-rinse adhesive Single Bond (3M/ESPE). The composite resin blocks were fabricated using a Teflon matrix. A thermomechanical cycling machine was used to carry out the artificial aging of the specimens and thus were sectioned into sticks. The microtensile tests were performed using a universal testing machine at a cross-head speed of 1 mm/min. Data (in MPa) were subjected to two-way ANOVA and Tukey's tests (5%). Results: Significant differences were found for both factors tested and interactions (p<0.05). Tukey's test results of µTBS (mean ± SD) were: etch-and-rinse SE (28.79±3.93); DE (30.41±7.22); AS (29.03±3.33); NaF (29.81±4.06)a; Ic (29.47±5.5);  and self-etching SE (30.37±6.96); DE (14.62±4.47); AS (9.79±2.32); NaF (9.36±2.31); Ic (30.78±8.68).   Conclusions: Resin infiltration did not affect the bond strength of demineralized enamel for both adhesive systems tested. For etch-and-rinse adhesive, no differences were observed for the tested groups. For self-etching adhesive, only the resin-infiltrated group showed similar bond strength to sound enamel. Both etch-and-rinse and self-etching adhesive systems can be used in resin-infiltrated enamel, if a composite restoration needs to be further performed. In enamel that has undergone the de/remineralization process, the use of a total-etch adhesive might be preferable for the restorative procedure.

Treatment of various degrees of white spot lesions using resin infiltration-in vitro study

BACKGROUND

This study was conducted to evaluate the efficiency of resin infiltration to improve the color of white spot lesions (WSLs) and to estimate the effect of different numbers of etching and resin infiltrant applications on the color change of WSLs with various depths. Ninety-six sound extracted premolars were subjected to acid attack inducing different depths of WSLs. Using a DIAGNOdent, teeth were divided into four main groups according to the depth of the WSLs: shallow enamel, deep enamel, shallow dentine, and deep dentine without cavitation. Then each of the main groups was subdivided into four groups: six teeth each with different protocols of resin infiltration as follows: 1 etching + 1 infiltrant application (EA), 1 etching + 2 infiltrant applications (EAA), 2 etchings + 1 infiltrant application (EEA), 2 etchings + 2 infiltrant applications (EEAA). Spectrophotometric analysis was measured at baseline (T0), after inducing the WSLs (T1), and following resin infiltration application (T2) for each group.

RESULTS

In shallow enamel, EA produced the least mean color difference (1.62 ± 0.85), with high significant difference (P < 0.001), when compared with the clinically detectable threshold (ΔE = 3.7). While in deep enamel, EAA showed the least mean color change (1.95 ± 0.4), with P < 0.001 when compared with the critical value. Also, in shallow dentine, the least mean change was noticed with EAA (3.0 ± 0.45), with P < 0.001 when compared with the clinical color detection threshold. Furthermore, in deep dentine, EAA had the least mean difference (3.76 ± 0.6) but with no significant difference, when compared with the clinically detectable threshold.

CONCLUSIONS

As the WSL got deeper, the color of the lesion became more clinically visible. In shallow enamel, the best treatment option was one etching with one resin infiltrant application. For deep enamel and shallow dentine, one etching with two applications of infiltrant gave the best lesion masking. In deep dentine, it is advisable to perform one etching with two infiltration steps, taking in consideration that all deep dentine lesions without cavitation were partially masked, remained clinically detectable, and might require more invasive restorative procedures.

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.

Surface Roughness of Initial Enamel Caries Lesions in Human Teeth After Resin Infiltration

BACKGROUND

Low viscosity resin infiltration of initial caries lesions is a modern microinvasive method to treat initial cries lesions. However, only scarce information is available about the long-term surface alterations of infiltrated lesions.

METHODS

Twenty-eight premolar teeth exhibiting non-cavitated initial caries lesions (International Caries Detection and Assessment System (ICDAS code 1&2)) were divided into two groups, one of which was infiltrated with resin, and the other remained untreated. The teeth underwent two thermocycling procedures. The surface roughness was determined quantitatively, and the results were evaluated statistically. In addition, the surfaces of the lesions were investigated by scanning electron microscopy (SEM), and the surface was analyzed visually with respect to surface irregularities.

RESULTS

The results showed a reduction in the surface roughness that was significant after 2500 thermocycles compared to the untreated surface. In the control specimens, no change in the surface roughness was found. The qualitative SEM data also showed a smooth surface after thermocycling, which supported the statistical findings.

CONCLUSION

After thermocycling, resin-infiltrated enamel surfaces become smoother and had no additional risk for plaque accumulation.

Surface Properties and Color Stability of Resin-Infiltrated Enamel Lesions

OBJECTIVES

To examine the surface topographies, microhardness, and color stability of resin-infiltrated enamel lesions before and after aging challenges in vitro using three-dimensional laser scanning profilometry, surface microhardness testing, spectrophotometry, and scanning electron microscopy.

METHODS

Forty human third molars were embedded in epoxy resin, and each tooth was prepared to have two white spot lesions and one sound enamel area. One white spot lesion received resin infiltration and the other was untreated. Ten specimens were subjected to thermocycling for 10,000 cycles, 10 specimens were immersed in coffee solutions, and 10 specimens were placed in water storage. Surface area roughness (Sa), Vickers microhardness (VHN), and CIE L*a*b* color values were measured on sound enamel, resin-infiltrated lesions, and untreated lesions before and after aging. The surface morphology of resin-infiltrated lesions was observed after aging under scanning electron microscopy and compared with 10 specimens that were not subjected to aging challenge.

RESULTS

Resin infiltration increased the surface microhardness of the enamel lesions from 89.3 to 212.0 VHN. The surface microhardness of resin-infiltrated enamel lesions was not significantly affected by aging. The surface roughness of resin-infiltrated lesions (0.32-0.37 μm) was greater than that of sound enamel (0.05-0.06 μm) and untreated lesions (0.12-0.13 μm). Thermocycling and water storage further increased surface roughness of resin-infiltrated surfaces. Resin-infiltrated enamel lesions showed greater discoloration than sound enamel surfaces. Surface microfissures and microcracks were observed on resin-infiltrated enamel lesions after thermocycling.

CONCLUSIONS

Surface hardness of enamel lesions increased significantly after resin infiltration and remained stable following thermocycling. Surface roughness and color stability of resin-infiltrated enamel lesions were less than ideal and might further deteriorate after aging in the oral environment.

Effect of thermal cyclic stress on acid resistance of resin-infiltrated incipient enamel lesions in vitro

This study aimed to examine the effect of thermal cycling on gap formation at the interface between infiltrated resin (ICON(®)) and enamel lesion and on the durability of anti-demineralization efficacy to predict the future performance. SS-OCT technique was examined to determine whether it has the potential to detect the gap. Bovine enamel lesions were prepared, and the infiltrated resin was applied to the lesion. Resin-infiltrated lesion specimens were thermal cycled 10,000 cycles and further demineralized in pH 4.5 buffer for 7 days. Released Ca (mg/cm(2)) was quantified by Ca electrode. The SS-OCT technique was applied to detect the gap, and SEM observation was performed to determine the presence of the gap. There was no significant difference in the amount of Ca release before and after the thermal cycling, suggesting long-lasting anti-demineralization efficacy of the resin. SS-OCT and SEM observations indicated no apparent gap formation after the thermal cycling.

Enamel surface alterations after repeated conditioning with HCl

Background

The aim of this study was to investigate the influence of etching time with 15 % hydrochloric acid (HCl) on the enamel surface destruction by studying the resulting roughness and erosion depth.

Methods

The vestibular surfaces of 12 extracted, caries free human incisors were divided into four quadrants, and each quadrant was etched with 15 % HCl for different numbers of etching cycles (1×2, 2×2, 3×2 and 4×2 min). Surface roughness and erosion depth were measured quantitatively with optical profilometry, and the surface morphology was imaged with scanning electron microscopy (SEM).

Results

After two minutes of 15 % HCl application a median enamel substance loss of 34.02 μm was observed. Lengthening of etching time (2×2, 3×2 and 4×2 min) resulted in significantly increase in erosion depth to each additionally, between 13.28 -15.16 μm (p < 0.05) ending up in a total median enamel surface loss of 77 μm. Regarding surface roughness no significant (p > 0.05) difference was found between unetched enamel and the etched enamel surfaces.

Conclusion

Repeated 15 % HCl conditioning of the enamel surface increases the depth of the etched surface erosion. However, the total erosion depth is rather shallow and therefore negligible.

Resin Infiltration of Fissure Caries with Various Techniques of Pretreatment in vitro

The resin infiltration technique might be used for occlusal caries lesions in order to arrest their progression. This in vitro study evaluated the influence of various modifications of the infiltration technique on the penetration abilities of the infiltrant into occlusal lesions. Extracted human molars and premolars (n = 140) with non-cavitated white spot lesions were randomly allocated to 7 groups. As control, specimens were etched with 15% hydrochloric acid (HCl) gel for 120 s and resin infiltrated for 180 s (Icon; DMG). As modification HCl gel reduced in surface tension and viscosity with and without abrasives was applied using 3 different types of brushes either to oscillate or rub the HCl gel onto the enamel surface. The median maximum lesion depth was 1,232 µm (interquartile range 882-1,513). Compared with the control procedure [23% (16/50)] a higher percentage penetration was observed if the HCl gel was mixed with a small amount of abrasives were rubbed into the fissures using a modified brush with stiff bristles that were adjusted to the fissure relief for either 120 s [100% (64/100)] or 30 s [98% (61/100); p < 0.05; Mann-Whitney test]. All other experimental treatments resulted in penetration results in-between. It can be concluded that the use of an abrasive HCl gel in conjunction with a modified brush mostly enhances resin infiltration into fissure caries lesions. © 2014 S. Karger AG, Basel

Modification of surface pretreatment of white spot lesions to improve the safety and efficacy of resin infiltration

Objective

A low-viscosity resin (infiltrant) was used to inhibit the progression of white spot lesions (WSLs) and resolve associated esthetic issues. An alternative pretreatment was explored to increase the pore volume of the surface layer of the WSLs. Also, the penetration effects of the infiltrant were evaluated for various pretreatments.

Methods

Sixty two artificial lesions were fabricated on bovine teeth. As a positive control, 15% HCl gel was applied for 120 seconds. Further, 37% H₃PO₄ gel was applied for 30 seconds using three methods. The samples were divided as follows: H₃PO₄ only group, H₃PO₄ sponge group, and H₃PO₄ brush group. The acid was gently rubbed with the applicators (i.e., a sponge or brush) throughout the application time. To compare the effects of resin infiltration, twenty paired halves of specimens were treated with an infiltrant (ICON®).

Results

Thicknesses of the removed surface layers and infiltrated areas were evaluated by confocal laser scanning microscope. The positive control and the 37% H₃PO₄ brush group failed to show significant differences in the removed thickness (p > 0.05); however, the mean percentage of the infiltrated area was higher in the 37% H₃PO₄ brush group (84.13 ± 7.58%) than the positive control (63.51 ± 7.62%, p < 0.001). Scanning electron microscope observations indicate higher pore volumes for the 37% H₃PO₄ brush group than for the positive control.

Conclusions

Application of 37% H₃PO₄ with a brush for 30 seconds increased the pore volume of WSL surface layers and the percentage of infiltrated areas in comparison to the use of 15% HCl for 120 seconds.

Resin infiltration into differentially extended experimental carious lesions

Resin infiltration of initial caries lesions is a novel method of caries therapy. However, it has some limitations. Therefore, further experimental studies are needed to improve resin infiltration. It was the aim of this investigation to study resin infiltra-tion into different experimental carious lesions. Caries-free extracted human molars and premolars were demineralized for 3, 6, 9 and 12 days and infiltrated with resin. Prior to infiltration, the teeth were incubated with sodium fluorescein. After em-bedding, serial sections were cut through the experimental lesions, and the penetration of the resin was measured with fluo-rescence microscopy. Two infiltrated teeth from each time interval were not embedded and cut. Infiltration of the resin was then studied with EDS element analysis. The results showed that with increasing demineralization time, the lesion expansion was also increasing, and the resin infiltration was always almost complete. From these results it can be concluded that artifi-cial standardized caries-like lesions are suitable for experimental studies of resin infiltration.