Casein phosphopeptide amorphous calcium phosphate and universal adhesive resin as a complementary approach for management of white spot lesions: an in-vitro study

Evaluation of NaOCl application prior to resin infiltrant or fluoride-containing resin varnish in the treatment of white spot lesions: An in vitro study

OBJECTIVE

The aim of this in vitro study is to investigate the effect of NaOCl (5.25 %) prior to resin infiltration and resin varnish on microhardness, surface roughness, and DIAGNOdent Pen values in the treatment of white spot lesions (WSLs).

METHODS

The artificial initial caries lesions were created in 160 human enamel samples. The demineralizated samples were divided into five groups: resin infiltration (ICON; DMG, Hamburg, Germany), NaOCl + ICON, resin varnish (Clinpro XT; 3M ESPE, Seefeld, Germany), NaOCl + Clinpro XT, and a negative control group. Enamel samples that underwent thermocycling aging were subjected to 5.000 cycles between 5-55 °C (N = 32, n = 16 for aging subgroups). Surface roughness (Ra), Vicker's microhardness (VHN), and DIAGNOdent Pen (Kavo, Biberach, Germany) (DDP) values were recorded at the baseline, after demineralization, after treatment, and after the thermal aging stages. The micro-CT analysis, microleakage, and Scanning Electron Microscope images were evaluated after treatment procedures and thermal aging. Robust ANOVA, Pearson's chi-square, and McNemar tests were used for statistical analysis. The significance level was p < 0.05.

RESULTS

The main effect of both group and stage was statistically significant for DDP, Ra, VHN, and micro-CT values. All treatment procedures improved the demineralized enamel compared to the negative control group (p < 0.001). The application of NaOCl (5.25 %) before resin infiltration increased microhardness but also in roughness. The resin-infiltrated groups showed less microleakage than the resin-varnish-treated groups (p < 0.001).

CONCLUSION

The application of NaOCl prior to resin infiltration or resin varnish did not result in any important alterations in the examined parameter values.

Evaluation of Broccoli Extract for Enhancing Primary Tooth Enamel Microhardness: An In Vitro Study

Background and Aims

Dental caries remains highly prevalent among children. This study aimed to evaluate the efficacy of aqueous broccoli extract in enhancing the microhardness of demineralized primary tooth enamel compared to a standard fluoride treatment.

Methods

An in vitro study was conducted using 30 extracted primary second molars, which were sectioned and polished. Baseline enamel microhardness was assessed using a Vickers hardness tester. Demineralization was induced using a cola drink (pH 4.5) for 8 min. The broccoli extract was prepared by air-drying fresh florets, stems, and leaves at room temperature, followed by aqueous extraction with distilled water and filtration. The samples were randomly assigned to receive a 10-min treatment with either aqueous broccoli extract (Group B) or 1.23% acidulated phosphate fluoride (APF) gel (Group F). Microhardness was measured posttreatment, and percentage changes between time points were compared using statistical analysis.

Results

After demineralization, broccoli extract, and fluoride gel significantly improved enamel microhardness. The broccoli extract group exhibited a greater recovery in microhardness (+44.95% vs. +20.78%, p = 0.008) compared to the fluoride gel group. However, the overall reduction in microhardness from baseline to final measurement showed no statistically significant difference between the two groups (p = 0.077).

Conclusion

Aqueous broccoli extract demonstrated comparable overall efficacy to fluoride gel in enhancing demineralized primary tooth enamel microhardness despite showing different patterns of demineralization and recovery. These findings suggest that broccoli extract may be a natural and effective alternative for enhancing enamel remineralization in pediatric caries prevention, warranting further clinical investigation.

Effects of Fluoride-containing Biomimetic Agents on Remineralization and Color Change of Enamel White Spot Lesions: An In Vitro Study

INTRODUCTION

The aim of this study was to evaluate the effects of fluoride-containing remineralization agents on enamel white spot lesions.

METHODS AND MATERIALS

Twenty bovine incisors were cut mesio-distally and occluso-gingivally, creating 80 specimens, and divided into four groups (n=20/group): 1) control (no treatment); 2) fluoride varnish (Voco Profluoroid 5% NaF Varnish, VOCO Dental, Cuxhaven, Germany); 3) CPP-ACFP (MI Paste Plus with Recaldent, GC Corporation, Tokyo, Japan),; 4) self-assembling peptide (P11-4F, CURODONT Repair Fluoride Plus, Credentis AG, Windisch, Switzerland). After a three-week demineralization-remineralization cycle, white spot lesions were observed on the specimens. Before applying the remineralization agents, baseline demineralization values were determined using DIAGNOdent 2095, QLF-D Biluminator, SEM-EDS (KaVo Dental, Charlotte, NC, USA), and color values were measured by Vita EasyShade (Vita Zahnfabrik, Bad Säckingen, Germany). Remineralization agents were applied once, following the manufacturers' instructions. The remineralization capacities of these agents and their effects on color change were evaluated at four time points: baseline (T0), demineralization (T1), and remineralization on the seventh (T2) and 30th (T3) days.

RESULTS

After 30 days, CPP-ACFP and P11-4F showed significantly greater Ca (% by weight), F (% by weight), and Ca/P ratio than the fluoride varnish group (p<0.05). SEM images revealed that in the groups where the remineralization agent was applied, the pores and tubules were blocked, and the surfaces were covered, whereas these findings were not observed in the control group. Based on QLF-D Biluminator data, P11-4F application provided more successful fluorescence changes compared to CPP-ACFP and fluoride applications and was statistically more effective in reducing lesion volume and maximum fluorescence loss (p<0.05). Significant differences were observed among the four groups at the seventh (T2) and 30th days (T3) in the laser fluorescence evaluation with DIAGNOdent (p<0.05). On the seventh day, the fluoride group exhibited greater effectiveness than the control group, while on the 30th day, the CPPACFP group demonstrated superior improvement over the control group (p<0.05). According to color change results, applying a remineralization agent was found to be a statistically successful method in restoring the tooth's original color (p<0.05). However, there were no significant differences among the treatment groups (p>0.05).

CONCLUSIONS

CPP-ACFP and P11-4F demonstrated positive effects on remineralization at the seventh and 30th days. Applying a remineralization agent is a viable option for blocking pores and tubules on demineralized enamel. The color change related to the use of the remineralization agent showed a positive effect over time.

Assessment of Change in Enamel Color and Surface Hardness Following the Use of ICON Resin Infiltration and Remineralizing Agent: An In Vitro Study

This study aimed to evaluate the change in enamel color and surface micro-hardness following the use of resin-infiltration concept material (ICON) and casein phosphopeptide-amorphous calcium fluoride phosphate (CPP-ACFP) remineralizing agent. Fifty-four extracted human third molars were collected and randomly divided into three groups: group A: control with no surface treatment; group B: treated using ICON; and group C: treated using CPP-ACFP. The change in color and micro-hardness of the enamel surface were measured using spectrophotometer and Vickers hardness number, respectively. The measurements were taken at three timelines; baseline (BL), after demineralization (DM), and after surface treatment (TX). The three groups showed no significant differences in enamel color change after demineralization (p < 0.05). However, after surface treatment in relation to the baseline, groups B and C had a significant increase in color change compared to the control group (p < 0.05), and group B showed a statistically significant increase in enamel color changes compared to group C. Additionally, all groups exhibited a significant reduction in enamel micro-hardness after demineralization in comparison to their baseline (p < 0.05). Group C showed a significant increase in micro-hardness after surface treatment compared to groups A and B (p < 0.05), while group B showed a significant decrease in enamel micro-hardness compared to groups A and C (p < 0.05). These findings suggest that teeth treated with CPP-amorphous calcium fluoride phosphate (CPP-ACFP) show a significant improvement in enamel surface color after demineralization compared to the teeth treated with resin infiltration (ICON) and the non-treated teeth. Additionally, enamel surfaces treated with CPP-ACFP show significant enamel hardness regaining, while resin infiltration (ICON) compromises enamel surface hardness.

In Vitro Models Used in Cariology Mineralisation Research-A Review of the Literature

BACKGROUND

Dental caries remains a significant global health problem. One of the fundamental mechanisms underlying the development and progression of dental caries is the dynamic process of demineralisation/remineralisation. In vitro models have played a critical role in advancing our understanding of this process and identifying potential interventions to prevent or arrest dental caries. This literature review aims to provide a structured oversight of in vitro mineralisation models which have been used to study the tooth demineralisation/remineralisation process.

METHODS

Publications from 2019 to 2023 were screened to identify articles reporting the use of in vitro models to study the demineralisation/remineralisation of tooth caries. The included studies were methodologically assessed for their information on (i) substrate, (ii) lesion formation, and (iii) mineralisation models.

RESULTS

The most reported substrates used in the studies were human teeth along with bovine incisors. Acetic/lactic buffers were the most common solutions to induce caries lesions. pH cycling was the most frequently used mineralisation model for simulating the daily change within the oral environment. This review discussed the advantages and limitations of various approaches.

CONCLUSIONS

Standardisation of in vitro mineralisation models is crucial for enabling effective comparison between studies and advancing caries research.

Incidence, severity, and risk factors for white spot lesions in adolescent patients treated with clear aligners

OBJECTIVES

This study was aimed to clarify the incidence, severity, and clinical risk factors for white spot lesions (WSLs) in adolescent patients treated with clear aligners.

METHODS

Pre-treatment and post-treatment intraoral photographs of 203 adolescent patients undergoing clear aligner therapy were retrospectively evaluated to assess the occurrence and severity of WSLs. Information on patients' general oral condition and orthodontic treatment was collected from clinical medical documents, retrospective questionnaires, and ClinCheck® software. Independent risk factors and model performance were determined by multivariate logistic regression and receiver operating characteristic curve analysis.

RESULTS

Thirty-five percent of adolescent patients developed WSLs during clear aligner treatment. Logistic regression analysis revealed that the presence of WSLs before treatment (OR 2.484, 95% CI 1.245-4.957), frequency of drinking carbonated beverages (OR 1.508, 95% CI 1.045-2.177), and number of anterior attachments (OR 2.192, 95% CI 1.502-3.198) were risk factors for the occurrence of WSLs in adolescent patients treated with clear aligners (P < .05), whereas the number of times they brushed each day (OR 0.656, 95% CI 0.454-0.947) and frequency of aligner cleaning after eating while wearing them (OR 0.611, 95% CI 0.433-0.861) were protective factors against WSLs (P < .05).

CONCLUSIONS

The incidence of WSLs was high in adolescent patients treated with clear aligners. Few brushings each day, pre-treatment WSLs, a high frequency of drinking carbonated beverages, a low frequency of aligner cleaning after eating while wearing them, and a high number of anterior attachments are strongly associated with the development of WSLs in adolescent patients treated with clear aligners.

Evaluation of incipient enamel-carious-like lesion treated with hydroxyapatite-chitosan nanocomposite hydrogel

BACKGROUND

Non-invasive restoration of tooth enamel is a topic of high relevance in dental material science. Multiple approaches have been proposed to reach optimum reconstruction results. The current study was performed to evaluate the cross-sectional microhardness besides mineral quality and content in artificially induced carious enamel after treatment with hydroxyapatite-chitosan (HAp-CS) nanocomposite gel.

METHODS

Artificially carious lesions were induced by immersion of teeth in acidic carboxymethyl cellulose gel (pH 4.95-5) for 24- and 72-hours periods. Two different compositions of HAp-CS nanocomposite hydrogel were prepared with two different ratios 50/50 (%) and 70/30 (%), respectively. Additionally, sodium fluoride gel (1000 ppm concentration) was prepared and used as reference. Gels were applied to carious lesions twice/day for 3 min/each. After 45 days of application, surface morphology, energy dispersive x-ray spectroscopy, micro-Raman analysis in addition to cross-sectional microhardness were evaluated. Statistical analysis was performed using two-way ANOVA and Tukey's post hoc statistical tests.

RESULTS

Surface morphological evaluation of treated surfaces showed obliteration of surface irregularities. Groups demineralized for 24 hours and treated with 70/30 (HAp-CS) showed highest significant cross-sectional-microhardness (P ≤ 0.05). Evaluated subsurface cross-sectional microhardness showed better mineral quality for groups demineralized for 24 hours and treated with HAp-CS nanocomposite gels.

CONCLUSIONS

Nanocomposite gel with 70/30 (HAp-CS) could efficiently improve cross-sectional microhardness and both minerals composition and quality for lesions demineralized for 24 hours. More severely induced lesions, as demineralized for 72 hours, need more powerful agent compositions and/or prolonged application protocols for improvement.

An In Vitro Study Comparing the Antibacterial and Mechanical Properties of Zinc Oxide-Based Nanofillers in Orthodontic Adhesives for White Spot Lesion Prevention in Fixed Orthodontic Therapy

Introduction Preventing enamel demineralization (white spot lesions or WSLs) around the brackets during and after orthodontic therapy has been a challenging problem. Zinc oxide (ZnO) nanoparticles (NPs) show antibacterial effects against cariogenic bacteria Streptococcus (S.) mutans. Materials and methods In this study, researchers modified Transbond XT adhesive (Sigma Aldrich, St. Louis, Missouri, USA) by adding different concentrations of ZnO nanoparticles, i.e., 0.1% and 0.5wt%, in two experimental groups and a control group. We performed Fourier transform infrared spectroscopy and scanning electron microscopy for physio-structural characterization and investigated antibacterial ability by disc diffusion and colony-forming tests. We conducted shear bond strength and adhesive remnant index to determine the mechanical characteristics. Results The development and size of the inhibition zone were greatly dependent on the concentration of ZnO nanoparticles in the disc agar diffusion test. All ZnO NP-based experimental adhesives reduced the colony numbers for S. mutans. For S. mutans, the composite comprising 0.5wt% ZnO nanoparticles significantly reduced colony counts. The control group exhibited the maximum mean shear bond strength, whereas 0.5wt% nanoparticles composite had the lowest number. Conclusion Adding ZnO as nanofillers imparts antibacterial properties to the orthodontic adhesives. An increase in the concentration of ZnO nanoparticles in orthodontic adhesive increases its antibacterial properties. We found the shear bond strength of the novel composite with up to 0.5wt% ZnO nanoparticles to be in a clinically acceptable range.

Evaluation of Antimicrobial Efficiency, Shear Bond Strength, and Adhesive Remnant Index of TiO2 Infiltrated Orthodontic Adhesive - An In Vitro Study

Background

Enamel demineralization is an unavoidable adverse effect encountered with bonding brackets in orthodontic therapy. Introducing nanoparticles into the composite adhesive paste can prevent enamel demineralization. Titanium dioxide (TiO2) is known to exhibit direct antimicrobial efficiency. This study aimed to assess the antibacterial efficiency and shear bond strength (SBS) of an orthodontic bonding composite infiltrated with TiO2 nanoparticles.

Materials and Methods

This in vitro study evaluated the efficiency of TiO2 nanoparticle-incorporated light-curing orthodontic composite paste (ENLIGHT, ORMCO). Twenty extracted premolars were randomly and equally allocated to the two study groups, N = 10. While a conventional composite was utilized for the bonding brackets in Group I, a TiO2-incorporated composite was used in Group 2. The adhesive remnant index (ARI) scores given by Artun and Bergland et al. and SBS were determined. Furthermore, the antimicrobial efficiency was estimated using the minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) and agar well diffusion assay for six composite disc specimens. The results were statistically analyzed using the chi-square test and Student's t test, at P < 0.05.

Results

After 24 h of curing, no statistical mean difference was observed between the two groups in terms of ARI or SBS scores (P > 0.05). However, there was a significant increase in the antimicrobial efficiency of Group II when compared with Group I (P < 0.05).

Conclusion

TiO2 nanoparticle-incorporated orthodontic composites improve the antimicrobial efficiency with no significant change in the SBS. The ARI scores indicate the presence of 50% remnant orthodontic composite on the tooth enamel surface post debonding.

White spot lesions in fixed orthodontic treatment: Etiology, pathophysiology, diagnosis, treatment, and future research perspectives

White spot lesions (WSLs) refer to localized areas of hypo-mineralization limited to the enamel of the teeth surface, which is noticeable clinically to the naked eye on drying of the teeth. During fixed orthodontic treatment, it is very hard for the patient to maintain excellent oral hygiene as the brackets, bands, wires, elastics, and other appliances and attachments worn intra-orally provide a platform for food retention, plaque formation, and then colonization by acidogenic bacteria like Streptococcus mutans and Lactobacillus. This review aims to elaborate and focus on etiology, pathophysiology, diagnosis, treatment aspect, and future scope for research about the WSLs occurring due to fixed orthodontic treatment.

A Comprehensive Narrative Review of Nanomaterial Applications in Restorative Dentistry: Demineralization Inhibition and Remineralization Applications (Part I)

Nanotechnology is extensively employed in various aspects of dentistry, including restorative dentistry, because of its substantial improvement and promising potential in the clinical efficacy of restorative materials and procedures. The main purpose of this review is to explore the different uses of nanomaterials in restorative dentistry. The review is divided into two parts: the current review (Part 1) focuses on the prevention of demineralization and promotion of remineralization, while the upcoming review (Part 2) will discuss the reinforcement of restorative materials and their therapeutic applications. Nanofillers are added to dental materials to boost their antibacterial, anticaries, and demineralization inhibitory capabilities. Additionally, they improve remineralization and enhance both mechanical properties and therapeutic features. The nanoparticles (NPs) used to increase antibacterial and remineralization inhibitions can be classified into two main groups: inorganic and organic NPs. Examples of inorganic NPs include silver, zinc oxide, titanium oxide, and gold. Examples of organic NPs include silica, quaternary ammonium salt monomers, and chitosan NPs. Furthermore, the nanofillers utilized to enhance the process of remineralization include various types such as metals, nano-hydroxyapatite, nano-amorphous calcium phosphate (ACP), dicalcium phosphate NPs, casein phosphopeptide-ACP (CPP-ACP), and calcium fluoride NPs. These uses underscore the potential applications of NPs in restorative dentistry, although there are still some limitations to address.

Long term remineralizing effect of casein phosphopeptide amorphous calcium phosphate in white spot lesions: A systematic review and meta-analysis

BACKGROUND

White spot lesions (WSLs) appear as white, opaque areas on the teeth and are caused by a demineralization of the enamel.

OBJECTIVE

The purpose of this systematic review and meta-analysis was to determine whether casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) has beneficial effects on WSLs and provides remineralizing benefits that are superior to those of placebo or no treatment.

METHODS

Following a thorough analysis of the literature across major online sources, 103 papers - 54 of which underwent in-depth evaluation - were found. We used inclusion and exclusion criteria to choose research articles that were appropriate for our review.

RESULTS

10 papers met this review's requirements and were subsequently included. As compared to the controls, CPP-ACP demonstrated increased efficacy in treatment of WSLs in terms of remineralisation and other parameters which included microhardness tests and enamel surface roughness. The forest plots present the results of meta-analyses comparing the effect of CPP-ACP versus control/other agents on white spot lesions (WSLs). In terms of odds ratios (OR), CPP-ACP showed a small increase in the odds of WSLs compared to control/other agents. In-vitro studies showed no significant difference in relative risk (RR) between CPP-ACP and control/other agents. Randomized control trials indicated a small increase in the risk of WSLs with CPP-ACP treatment, but the overall effect was not statistically significant.

CONCLUSION

There was evidence to support the use of CPP-ACP over other agents for WSL prevention or treatment, but further research is needed to confirm these findings.

Surface topography and spectrophotometric assessment of white spot lesions restored with nano-hydroxyapatite-containing universal adhesive resin: an in-vitro study

BACKGROUND

White spot lesion (WSL) is a main shortcoming accompanied by orthodontic treatment. It impairs the esthetic, surface hardness, and surface texture of enamel. So, this study was conducted to analyze the surface characteristics and color change of white spot lesions treated with nano-hydroxyapatite (nHA)-enriched universal adhesive resin.

MATERIALS AND METHODS

Eighty sound human permanent molars crowns were sectioned into two halves, producing 160 specimens. 16 specimens were left untreated, and 144 specimens were artificially-demineralized to generate WSLs. The specimens were classified according to the treatment approach applied as follows: I; Sound enamel, Group II; artificially-created WSLs, Group III; ICON resin-restored WSLs, Group IV; Universal adhesive resin-restored WSLs, Group V; 0.5 wt% nHA-containing universal adhesive resin-restored WSLs, Group VI; 1 wt% nHA-containing universal adhesive resin- restored WSLs, and Group VII; 3 wt% nHA-containing universal adhesive resin-restored WSLs, Group VIII; 5 wt% nHA-containing universal adhesive resin-restored WSLs, Group IX; 7 wt% nHA-containing universal adhesive resin-restored WSLs, and Group X; 10 wt% nHA-containing universal adhesive resin-restored WSLs. Some surface characteristics and color changes were assessed. Data was collected and analyzed statistically using ANOVA and the Tukey test at p < 0.05.

RESULTS

Surface microhardness of WSLs was significantly improved with all investigated ratios of nHA-containing universal adhesive (p < 0.0001), with the highest mean belonging to 10 wt% nHA-containing universal adhesive resin treated WSLs. All ratios of nHA-containing universal adhesive resin significantly reduced the surface roughness of WSLs (p < 0.0001). The investigated ratios of 1, 3, 5, 7, and 10 wt% nHA-containing universal adhesive resin treatment approach could mask the WSLs significantly (p < 0.0001).

CONCLUSIONS

Nano-hydroxyapatite-containing universal adhesive is a promising contemporary approach for the management of WSLs, coupled both the remineralizing concept and the minimally invasive resin infiltration.

Surface roughness and microhardness of enamel white spot lesions treated with different treatment methods

Objective

To analyse the surface roughness and microhardness of artificial enamel white spot lesions before and after WSL formation, after treatment (Opalsutre™ microabrasion, Sylc® bioactive glass, and ICON® resin infiltration), and after pH cycling with the help of the profilometer surface roughness tester and the digital Vickers microhardness tester.

Materials and methods

Seventy-five extracted molars were used to acquire one hundred specimens. 50 specimens were randomly assigned to five groups (n = 10) for the surface roughness study: 1) Sound group, 2) WSL group, 3) micro abrasion (MA; Opalustre, Ultradent, South Jordan, UT, USA), 4) bioactive glass 45S5 Sylc powder (Sylc; Denfotex Research Ltd, Inverkeithing, UK), and 5) ICON resin infiltration (ICON; DMG, Hamburg, Germany). An additional 25 specimens were used to obtain 50 enamel slabs for the surface microhardness study, which were also assigned to the same groups. All groups underwent a final stage of pH cycling. Surface roughness and surface microhardness measurements were performed at different stages for all groups.

Results

Regarding surface roughness, ICON significantly reduced the surface roughness compared to Opalustre and Sylc, with no significant difference between Opalustre and Sylc. In terms of surface microhardness, ICON showed the highest improvement, followed by Sylc and then Opalustre. Both surface roughness and microhardness were significantly affected by demineralization, partially improved after treatment, and then regressed significantly after pH cycling.

Conclusion

ICON resin infiltrant can be considered as a superior treatment option for improving surface roughness and microhardness, while Opalustre demonstrated relatively the poorest performance compared to the other treatment options. It is noteworthy that the pH cycling procedure had an adverse impact irrespective of the treatment option used.

Peptides in Dentistry: A Scoping Review

Currently, it remains unclear which specific peptides could be appropriate for applications in different fields of dentistry. The aim of this scoping review was to scan the contemporary scientific papers related to the types, uses and applications of peptides in dentistry at the moment. Literature database searches were performed in the following databases: PubMed/MEDLINE, Scopus, Web of Science, Embase, and Scielo. A total of 133 articles involving the use of peptides in dentistry-related applications were included. The studies involved experimental designs in animals, microorganisms, or cells; clinical trials were also identified within this review. Most of the applications of peptides included caries management, implant osseointegration, guided tissue regeneration, vital pulp therapy, antimicrobial activity, enamel remineralization, periodontal therapy, the surface modification of tooth implants, and the modification of other restorative materials such as dental adhesives and denture base resins. The in vitro and in vivo studies included in this review suggested that peptides may have beneficial effects for treating early carious lesions, promoting cell adhesion, enhancing the adhesion strength of dental implants, and in tissue engineering as healthy promotors of the periodontium and antimicrobial agents. The lack of clinical trials should be highlighted, leaving a wide space available for the investigation of peptides in dentistry.

Effects of an orthodontic primer containing amorphous fluorinated calcium phosphate nanoparticles on enamel white spot lesions

OBJECTIVES

The study investigated the effects of an orthodontic primer containing amorphous fluorinated calcium phosphate (AFCP) nanoparticles on enamel white spot lesions (WSLs).

MATERIALS AND METHODS

The AFCP nanoparticles were prepared and incorporated into Transbond XT Primer. Thirty-two human enamel slices were highly polished and randomly divided into four groups: no part covered (control), half covered with a primer containing 0 wt%, 25 wt%, and 35 wt% AFCP. Subsequently, samples were challenged by a modified pH-cycling and characterized by color measurement, micro-computed tomography, and scanning electron microscope (SEM). The bonding properties of the primers containing AFCP were assessed using shear bond strength test, and the mouse fibroblasts (L929) were employed to evaluate the cytotoxicity.

RESULTS

When the enamel was challenged by pH cycling, 25 wt% and 35 wt% AFCP groups exhibited less color change (ΔE) and less mineral loss than the control and 0 wt% AFCP groups. The SEM images showed that the original microstructural integrity and mineral deposition rate of the enamel surface were better in the 25 wt% and 35 wt% AFCP groups. In particular, the 35 wt% AFCP group exhibited the best performance after 3 weeks of pH cycling. The shear bond strength and cell viability revealed no significant difference among the tested groups (P > 0.05).

CONCLUSION

Using the primer containing 35 wt% AFCP might be a promising strategy for preventing the occurrence and development of WSLs during orthodontic treatment.

A remineralizing orthodontic etchant that utilizes calcium phosphate ion clusters

This study aimed to investigate whether a phosphoric acid (H3PO4) solution containing calcium phosphate ion clusters (CPICs) could minimize enamel damage during long-term bracket bonding by dissolving the enamel surface and promoting enamel remineralization. The experimental design is as follows: first, three experimental etchants (H3PO4, CPICs-incorporated H3PO4 solution-I, and CPICs-incorporated H3PO4 solution-II) and two bonding resins (conventional orthodontic resin and self-adhesive orthodontic resin) were used in combination to create six groups, respectively. Each of these six groups was then divided into two sub-groups based on the presence or absence of thermocycling (TC). Twenty samples were assigned to each of the 12 groups (independent variables), and thus a total of 240 metal bracket-attached human premolars were used in this experiment. Bracket debonding was performed on each of 20 premolars in 12 groups, and shear bond strength (SBS) and adhesive remnant index (ARI) values were measured as dependent variables. Next, the three experimental etchants were applied (independent variables) to each of the three enamel samples, and the remineralization of the enamel surface was investigated as a dependent variable. The enamel surface was observed using electron scanning and atomic force microscopy. Furthermore, X-ray diffraction, energy dispersive spectroscopy (EDX) spectrum X-ray spectroscopy, and elemental mapping were performed, and the Knoop microhardness scale was measured. Therefore, the experiment was performed in two steps: SBS and ARI measurements for 12 groups, followed by observation of the enamel surface and microhardness measurements, according to the three types of etchants. As a result of the experiment, first, when the bracket was debonded, SBS did not decrease, and residual adhesive was hardly observed in the C2A group (before TC), C2A, and C1C groups (after TC) (p &lt; 0.001). Second, the experimental etchant containing CPICs achieved remineralization while demineralizing the enamel. This was verified through SEM/EDX, element mapping, XRD, and AFM. Also, the roughness and microhardness of the enamel surface were better in the remineralized surface by the experimental etchant containing CPICs (p &lt; 0.017). The CPICs-incorporated H3PO4 solution reduced ARI while maintaining SBS during bracket debonding, regardless of whether TC was performed or the type of resin. The etchant containing CPICs was also shown to remineralize the enamel and increase its microhardness.