Remineralising effect of 45S5 bioactive glass on artificial caries in dentine

Ion release, cytocompatibility and microbial inhibition of a novel varnish containing fluoride-doped bioactive glass ceramics: an in vitro study

OBJECTIVES

The study aimed to develop and evaluate in vitro a varnish containing fluoride-doped glass ceramics capable of inhibiting oral microorganisms, releasing hydroxyapatite-forming ions, and ensuring biocompatibility.

MATERIALS AND METHODS

For the production of the experimental varnish (VE), composed of hydrogenated rosin, 10% and 20% by weight of glass ceramics with composition S53P4 (CF0) and doped with F- ions (CF5 and CF10) were incorporated. The EVs were characterized by Rheology, Scanning Electron Microscopy (SEM), FTIR, ion release (fluoride and calcium ions), cytotoxicity on VERO cells, and antimicrobial effect on S. mutans, S. aureus and C. albicans and anti-biofilm effect on S. mutans. The data were analyzed by One-Way ANOVA and Kruskal-Wallis test (P = 0.05).

RESULTS

Homogeneous varnishes with good viscosity were obtained. Varnishes with 20% CF demonstrated biocompatibility and minimum inhibitory concentration (MIC) at concentrations lower than 10 mg/mL and 3.12 mg/mL, respectively, except for C. albicans. An anti-biofilm effect on S. mutans was observed for the varnishes with 20% CF. All varnishes with CF released more F- than the commercial varnish, with V20CF10 standing out, which released 4 times more F- ions in a quarter of the time.

CONCLUSIONS

The V20CF10 varnish is a promising material for dental use in the treatment of early caries lesions, due to its biocompatibility, antimicrobial properties, and release of hydroxyapatite-forming ions.

CLINICAL RELEVANCE

The use of a new varnish that combines antimicrobial properties with hydroxyapatite-forming ion release may prevent or halt the progression of dental caries lesions, offering greater efficacy than currently available varnishes.

Physio-Mechanic and Microscopic Analyses of Bioactive Glass-Based Resin Infiltrants

This study aimed to investigate the efficacy and durability of bioactive glass-based dental resin infiltrants. Resin infiltrants were formulated by combining photoinitiated dimethacrylate monomers with three variations of bioactive glass: 45S5 Bioglass (RIS), boron-substituted (RIB), fluoride-substituted (RIF), and pure resins (PR), whereby TOOTH group (TH) and ICON (CN) served as commercial control groups. Teeth samples were prepared, and experimental and control infiltrants were applied on demineralized human-extracted teeth. All the samples were subjected to immersion in artificial saliva and pH cycling for 30 days. The samples from another group underwent tooth brushing simulation for 9600 cycles. Following artificial saliva immersion, the samples' hardness values showed that RIB had the highest values (318.44 ± 3.83) while PR (212.52 ± 9.02) had the lowest values. After immersing into the pH cycling solution, the RIF showed the highest hardness (286.86 ± 5.11), while the lowest values for the CN (143.76 ± 3.50). After the tooth brushing simulation, the teeth samples with RIB showed maximum microhardness values (312.06 ± 16.30) and the weakest for the TH (189.60 ± 6.43). The commercial and experimental enamel resin infiltrants showed almost similar results overall, with RIB demonstrating better microhardness and comparable surface roughness. In contrast, RIF proved more resistant to pH cycling, exhibited higher microhardness, and performed better in surface roughness analysis. These findings suggest that resin infiltrant materials, especially RIF, have promising potential for effectively and esthetically managing white spot lesions.

Applications of smart materials in minimally invasive dentistry - some research and clinical perspectives

OBJECTIVES

Dental caries is one of the most prevalent bacteria-induced non-communicable diseases globally. It is known to be the top oral health burden in both developing and developed nations. There is substantial literature on the disease process and there is still debate on the extent of caries removal needed and the adequacy of the materials available to restore the lost tooth structure. The current review discusses the disease process together with the contemporary management of the carious lesion and also presents substantial evidence on novel materials and techniques that make minimally invasive dentistry predictable.

METHODS

The written work presented shows the most relevant literature for the management of dental caries focusing on novel materials used in minimally invasive dentistry.

RESULTS

There is still much to learn about specific antimicrobial and caries prevention mechanisms of novel materials. Materials that respond to a single or a few stimuli remain "weakly intelligent" in the face of the complex microenvironment in the oral cavity. Engineered systems that combine artificial intelligence and chemical engineering, are expected to possess higher intelligence, self-healing capabilities as well as environmental adaptability, and may be future promising research directions.

SIGNIFICANCE

The targeted approach in managing dental caries will hopefully have a better clinical outcome. The strategies discussed are alternatives to the contemporary approach and will improve the clinical management.

Remineralization Effect of Bioactive Glass With and Without Fluoride and Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) on Artificial Dentine Caries: An In Vitro Study

Background/objectives Dentine hypersensitivity (DH) is a common dental condition marked by transient, sharp pain arising from dentinal exposure. Bioactive materials are capable of remineralization. This study aims to explore the remineralization effect of bioactive glass (BAG) with and without fluoride and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), using dentine discs as the test substrate. Materials and methods In this in vitro experimental study, 28 dentine discs were prepared from premolar teeth. Artificial caries were induced by subjecting the dentine discs to demineralization in acid for 72 hours. After demineralization, the discs were treated with various remineralizing dentifrices to evaluate their effects. The dentine discs (n=28) were divided into four groups: group 1 = BioMin (BioMin Technologies, London, United Kingdom), group 2 = NovaMin/Sensodyne Repair (GlaxoSmithKline plc, London, England, United Kingdom), group 3 = Recaldent (CPP-ACP; GC Orthodontics Inc., Alsip, Illinois, United States), and group 4 = deionized water (control group). All discs underwent a 28-day remineralization process using the respective dentifrices assigned to each group. The microhardness of the discs was measured using Vickers microhardness testing at three stages: baseline, post-demineralization, and post-remineralization. Results There was no significant difference in terms of microhardness between groups both at the baseline (F (3, 24) = 1.079, p = 0.995) and after the demineralization process (F (3, 24) = 1.310, p = 0.294). However, a significant difference was identified between the groups after the remineralization process (F (3, 24) = 34.008, p = 0.001). Additionally, the least significant difference (LSD) multiple comparison test was performed. There were significant differences identified in the remineralization condition, with group 1 having the highest values, followed by group 2, group 3, and group 4. Conclusion The results indicate that the remineralization effect on artificially induced dentine caries was more pronounced with bioactive glass containing fluoride compared to bioactive glass without fluoride and CPP-ACP.

The Effect of Formulated Dentin Remineralizing Gel Containing Hydroxyapatite, Fluoride, and Bioactive Glass on Dentin Microhardness: An In Vitro Study

Objectives

This study aimed to develop a gel with dentin-remineralizing properties, integrating nano-hydroxyapatite (nHA), sodium fluoride (NaF), and bioactive glass (BG).

Materials and Methods

The enamel layer of 40 bovine incisors was removed. The samples were allocated into four groups of 10 each, based on varying concentrations of nHA, BG, and NaF in the gel compositions (wt%): (1) 2.5%-7.5%-0.05%, (2) 5%-5%-0.05%, (3) 7.5%-2.5%-0.05%, and (4) a control group with a base gel lacking remineralizing agents. After 8 hr of demineralization, the dentin surface microhardness was measured at depths of 30, 60, and 140 µm. After a 20-day pH cycling, the percentage of surface microhardness recovery (SMHR%) was measured and compared among the groups using the ANOVA and Tukey HSD post hoc tests (α = 0.05). Scanning electron microscopy analysis evaluated each specimen's superficial morphology.

Results

At all depths, the SMHR% of the Group 2 and Group 3 was significantly higher than the control group (p  < 0.05). The SMHR% Group 1 (67.39% ± 29.34%) was significantly higher than the control group (-21.24% ± 51.72%) only at the depth of 30 μm (p = 0.047). Group 3 had higher SMHR% than Group 2 at all depths; however, the difference was not statistically significant. Moreover, the SMHR% of Group 3 was significantly higher than that of Group 1 at depths of 30 μm (187. 94% ± 68.95% vs. 67.39% ± 29.34%; p = 0.005) and 60 μm (179.55% ± 75.96% vs. 64.34% ± 41.96%; p = 0.043). Surface deposition and tubule occlusion were observed in the Groups 2 and 3 samples, which was more prominent in the latter.

Conclusions

Combining 7.5% nHA, 2.5% BG, and 0.05% NaF could potentially remineralize primary carious lesions.

Protecting primary teeth from dental erosion through bioactive glass

OBJECTIVES

The present study aimed to evaluate the effectiveness of bioactive glass (BAG) in preventing dental erosion in primary teeth.

METHODS

Enamel and dentin specimens (2 × 2 × 2 mm) were obtained from extracted primary teeth, which were randomly divided into the following groups based on the pretreatments (n = 12): DW (deionized water), NaF (2 % sodium fluoride), 2BAG (2 % BAG), 4BAG (4 % BAG), 6BAG (6 % BAG), and 8BAG (8 % BAG). The specimens were immersed in the respective solutions for 2 min and subjected to in vitro erosive challenges (4 × 5 min/d) for 5 d. The erosive enamel loss (EEL), erosive dentin loss (EDL), and the thickness of the demineralized organic matrix (DOM) were measured using a contact profilometer. The surface microhardness (SMH) was measured, and the percentage of SMH loss (%SMHL) was calculated. The surface morphology and mineral composition were evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively.

RESULTS

After the erosive challenges, the EEL, EDL, and%SMHL of the 2BAG, 4BAG, 6BAG, and 8BAG groups significantly reduced, with the greatest reduction was observed in the 6BAG (EEL: 6.5 ± 0.2 μm;%SMHL in enamel: 12.8 ± 2.6; EDL: 7.9 ± 0.3 μm; %SMHL in dentin: 22.1 ± 2.7) and 8BAG groups (EEL: 6.4 ± 0.4 μm;%SMHL in enamel: 11.0 ± 1.9; EDL: 7.8 ± 0.5 μm; %SMHL in dentin: 22.0 ± 2.5) (P < 0.05). With increasing BAG concentrations, the number of surface deposits containing Ca, P, and Si increased.

CONCLUSIONS

6BAG was the most effective for preventing dental erosion in primary teeth and showed a particularly strong potential for dentin erosion prevention.

CLINICAL SIGNIFICANCE

Bioactive glass, especially at a 6 % concentration, has proven effective in reducing erosive tooth wear and surface microhardness loss while also protecting demineralized organic matrix in primary dentin.

Marginal integrity of prototype bioactive glass-doped resin composites in class II cavities

OBJECTIVES

This in vitro study examined the marginal integrity of experimental composite materials doped with bioactive glass (BG).

MATERIALS AND METHODS

Class-II MOD cavities were prepared and restored with one of the following composite materials: a commercial composite material as a reference (Filtek Supreme XTE), an experimental composite doped with BG 45S5 (C-20), and an experimental composite doped with a fluoride-containing BG (F-20). Six experimental groups (n = 8) were used, as each of the three composites was applied with (+) or without (-) a universal adhesive (Adper Scotchbond Multipurpose). All specimens were subjected to thermocycling (10,000 x, 5-55 °C) and then additionally stored in artificial saliva for eight weeks. Scanning electron micrographs of the mesial and the distal box were taken at three time points (initial, after thermocycling, and after eight weeks of storage in artificial saliva). The margins were classified as "continuous" and "non-continuous" and the percentage of continuous margins (PCM) was statistically analyzed (α = 0.05).

RESULTS

In most experimental groups, thermocycling led to a significant decrease in PCM, while the additional 8-week aging had no significant effect. F-20 + performed significantly better (p = 0.005) after 8 weeks storage in artificial saliva than the reference material with adhesive, while no statistically significant differences were observed at the other two time points. C-20 + exhibited significantly better PCM than the reference material with adhesive after thermocycling (p = 0.026) and after 8 weeks (p = 0.003).

CONCLUSIONS

Overall, the experimental composites with BG showed at least as good marginal adaptation as the commercial reference, with an indication of possible re-sealing of marginal gaps.

CLINICAL RELEVANCE

Maintaining or improving the marginal integrity of composite restorations is important to prevent microleakage and its likely consequences such as pulp irritation and secondary caries.

A Comparative In Vitro Physicochemical Analysis of Resin Infiltrants Doped With Bioactive Glasses

Objective This study aimed to investigate the longevity and effectiveness of bioactive glass (BAG)-based dental resin infiltrants. Materials and methods The three types of BAG - 45S5 bioglass (RIS), boron-substituted (RIB), and fluoride-substituted (RIF) - were incorporated with photoinitiated dimethacrylate monomers to create experimental resin infiltrants. ICON® (CN; DMG-America, Ridgefield Park, NJ) and pure resin (PR) were used as control groups in this study. Disc-shaped samples were prepared for the experimental and control groups. The samples were challenged with the pH cycle and immersed in the artificial saliva for 30 days. On Day 0 and Day 30, the pH cycle and artificial saliva immersion, Vicker's microhardness, surface roughness, and surface morphology were investigated. Results The RIF group's disc samples showed the highest Vicker's microhardness values (78.20 ±0.06) on Day 30 of artificial saliva immersion, whereas the CN group's values were the lowest (55.99 ±0.24). Following the pH cycling, the RIF displayed the highest hardness (64.15 ±1.89) whereas the CN group's values were the lowest (33.47 ±1.28). Regarding surface roughness, on Day 30, the RIB resin group exhibited the highest (1.14 ±0.001 µm). In contrast, the CN resin showed the lowest (1.07 ±0.06 µm) values, while immersed in the artificial saliva solution. In the same duration of time, in the pH cycling solution, PR showed the least (0.85 ±0.89 µm), while RIF showed the highest roughness value (0.94 ±0.54 µm). Morphological analysis revealed that following the artificial saliva immersion, the RIB, CN, and PR exhibited smoother surfaces compared to the RIS and RIF groups. However, when immersed in the pH cycling solution, RIB and RIF showed more resistance against acid attack. Conclusions Our results revealed that the experimental resin groups performed much better than the commercial resin infiltrants following artificial saliva and pH cycling challenges.

Biomimetic dentin remineralization using eggshell derived nanohydroxyapatite with and without carboxymethyl chitosan - An in vitro study

The objective of this study was to evaluate the synergistic effect of eggshell-derived nanohydroxyapatite (EnHA) and carboxymethyl chitosan (CMC) in remineralizing artificially induced dentinal lesions. EnHA and CMC were synthesized using simple chemical processes and characterized using FTIR, XRD, HRSEM-EDX, TEM, DLS and TGA/DTA analyses. A total of 64 pre-demineralized coronal dentin specimens were randomly subjected to following treatments (n = 16):artificial saliva (AS), EnHA, CMC, and EnHA-CMC, followed by pH cycling for 7 days. HRSEM-EDX, Vickers-indenter, and micro-Raman analyses were used to assess surface-topography, microhardness, and chemical analysis, respectively. All tested materials demonstrated non-cytotoxicity when assessed on hDPSCs using MTT assay. FTIR, XRD and thermal analyses confirmed the characteristics of both EnHA and CMC. EnHA showed irregular rod-shaped nanoparticles (30-70 nm) with the presence of Ca,P,Na, and Mg ions. Dentin treated with EnHA-CMC exhibited complete tubular occlusion and highest microhardness whereas the AS group revealed the least mineral deposits (p < 0.05). No significant differences were observed between EnHA and CMC groups (p > 0.05). In addition, molecular conformation analysis revealed peak intensities in collagen's polypeptide chains in dentin treated with CMC and EnHA-CMC, whereas other groups showed poor collagen stability. The results highlighted that EnHA-CMC aided in rapid and effective biomineralization, suggesting its potential as a therapeutic solution for treating dentin caries.

Enamel Matrix Derivative, 58S5 Bioactive Glass, and Fluoride Varnish for Enamel Remineralization: A Multi-analysis Approach

PURPOSE

This study aimed to evaluate the enamel remineralization efficacy of enamel matrix derivative (EMD), experimental bioactive glass (BAG), and fluoride varnish in vitro.

METHODS AND MATERIALS

Artificial initial caries lesions were developed on fifty human enamel specimens using demineralization solution (pH 4.5, 37°C, 96 hours). Specimens were randomly assigned to five groups (n=10): I-5% NaF varnish (Enamelast), II-experimental 58S5 BAG+37% phosphoric acid (PA), III-EMD (Emdogain) + Ethylenediaminetetraacetic Acid (EDTA), IV-EMD+37% PA, V-Control (untreated). All remineralization agents were applied with pH cycling for seven days. The specimens were scanned by spectral domain optical coherence tomography (SD-OCT) at baseline, at demineralization, and after pH cycling. Lesion depths were measured using image analysis software (ImageJ). Lesions were evaluated using surface microhardness (SMH) and two fluorescence methods (FluoreCam and DIAGNOdent Pen [DDPen]). The data were statistically analyzed by Kruskal Wallis, Friedman, and Wilcoxon tests (α=0.05).

RESULTS

According to SD-OCT results, fluoride varnish was found to be the most effective agent in reducing lesion depth (p=0.005). All agents increased the SMH values after pH cycling. No significant difference was found among fluoride varnish, BAG, and EMD+PA groups. These SMH values were significantly higher than EMD+EDTA and control groups (p<0.001). All groups showed lower DDPen scores compared with the control group (p<0.001), however, no significant difference was found among the remineralization agents. In FluoreCam assessment, size and intensity values of all treated groups showed improvement. However, there was no significant difference between the treatment groups in terms of FluoreCam size measurements (p=0.186).

CONCLUSION

58S5 BAG and EMD+PA have remineralization capacity as effective as fluoride varnish. EMD+PA showed better SMH and lesion intensity results than EMD+EDTA.

Promoting bond durability by a novel fabricated bioactive dentin adhesive

OBJECTIVE

To prepare a bioactive dentin adhesive and investigate its effect on promoting bonding durability of dentin.

METHODS

The mineralization of the bioactive glass with high phosphorus (10.8 mol% P2O5-54.2 mol% SiO2-35 mol% CaO, named PSC) and its ability to induce type I collagen mineralization were observed by SEM and TEM. The Control-Bond and the bioactive dentin adhesive containing 20 wt% PSC particles (PSC-Bond) were prepared, and their degree of conversion (DC), microtensile bond strength (μTBS), film thickness and mineralization performance were evaluated. To evaluate the bonding durability, dentin bonding samples were prepared by Control-Bond and PSC-Bond, and mineralizated in simulated body fluid for 24 h, 3 months, and 6 months. Then, the long-term bond strength and microleakage at the adhesive interface of dentin bonding samples were evaluated by microtensile testing and semiquantitative ELIASA respectively.

RESULTS

The PSC showed superior mineralization at 24 h and induced type I collagen mineralization to some extent under weakly alkaline conditions. For PSC-Bond, DC was 62.65 ± 1.20%, μTBS was 39.25 ± 4.24 MPa and film thickness was 17.00 ± 2.61 μm. PSC-Bond also formed hydroxyapatite and maintained good mineralization at the bonding interface. At 24 h, no significant differences in μTBS and interface microleakage were observed between the Control-Bond and PSC-Bond groups. After 6 months of aging, the μTBS was significantly higher and the interface microleakage was significantly lower of PSC-Bond group than those of Control-Bond group.

SIGNIFICANCE

PSC-Bond maintained bond strength stability and reduced interface microleakage to some extent, possibly reducing the occurrence of secondary caries, while maintaining long-term effectiveness of adhesive restorations.

Effect of bioactive glass particles on mechanical and adhesion properties of resin cements

PURPOSE

The aim of this study is to evaluate the mechanical and adhesive properties of three different resin cements with bioactive glass (BAG) incorporated in two different ratios.

METHODS

BAG was added to different resin cements (3M Rely-X Ultimate, GC Link Ace, and GC Link Force) in different ratios (5% and 10% by weight). The three-point flexural strength, microhardness, and bond strength properties were evaluated. The fracture types of the groups were then analyzed using a stereo microscope. The data were analyzed using a multifactorial analysis of variance and Tukey's post-hoc tests (α < 0.05).

RESULTS

The addition of BAG reduced the flexural strength of the resin cements (P < 0.05).The effect of BAG addition on the Vickers microhardness value was significantly different for each cement group (P < 0.05). In addition, with the exception of the GC link force group (10% BAG addition), the BAG addition decreased the bond strength of cements to dentin in all the groups (P = 0.171).

CONCLUSIONS

The results of this study confirmed that different resin cements comprising different ratios of BAG exhibited different flexural strength, hardness, and bond-strength properties. Since the bond strength values increased with the addition of 10% BAG in the GC Link Force cement group, the effects of different BAG compositions could be worth investigating in future studies.

Dentine tubule occlusion effect of hydrolyzed casein in a bioactive glass-based dental desensitizing gel

OBJECTIVES

The effectiveness of three different groups of polyethylene glycol (PEG)-based gels containing powders on dentin hypersensitivity (DH) treatment were assessed and compared with Actimins® as commercial reference group.

METHODS

Hydroxyapatite nanorods (nHA) and sol-gel-derived 45S5 bioglass (SGD 45S5) powders were synthesized through hydrothermal and sol-gel methods, respectively. First, 25 demineralized dentin disks were divided into five groups. Then, the prepared gels based on 45S5 bioglass with and without hydrolyzed casein (HC) as experimental, nHA gel and Actimins® as positive and commercial reference groups were applied twice a day on disks by a micro applicator. To mimic the oral environment, treated disks were immersed in artificial saliva in a water bath at 37 °C for 7 days. However, in the negative control group, no agent was applied on the samples. FE-SEM, EDS, AFM, and XRD were performed to assess tubule occlusion. One-way ANOVA test was used for statistical analysis and p*<0.05 was set as the significance level.

RESULTS

The nHA with an average aspect ratio of 2.77 and the SGD 45S5 powders with a polygonal morphology and the average size of 48.64±11.38 µm were synthesized. After treatment, tubule occlusion in HC-SGD 45S5 and nHA gels were shown to be higher than other groups. The root mean square roughness (Rrms) of the above-mentioned gels showed to be 121.54±9.25 nm, and 312.6 ± 9 nm, respectively.

CONCLUSION

The nHA containing group exhibited the highest tubule occlusion efficiency (i.e., tubule diameter of 0.92±0.32 µm) with a superior mineral precipitation. HC as a novel material demonstrates to be potentially beneficial in DH treatment.

CLINICAL SIGNIFICANCE

DH as a common issue may be reduced or eliminated by occlusion of patent dentinal tubules. There are various types of desensitizing agents capable of controlling the DH by the occlusion of patent dentinal tubules. The desensitizing gels developed in this study showed to be promising for clinical and home-use applications.

Engineered Biomaterials Trigger Remineralization and Antimicrobial Effects for Dental Caries Restoration

Dental caries is the most prevalent chronic disease globally, significantly impacting individuals' quality of life. A key reason behind the failure of implanted restorations is their biological inactivity, meaning they are unable to form crosslinks with the surrounding tooth structures, thus making patients susceptible to implant loss and recurrent tooth decay. For the treatment of caries, antibacterial medicine and remineralization are effective means of treating the recurrence of caries. Owing to the rapid progression in the biomaterials field, several biomaterials have been reported to display antimicrobial properties and aid in dentin remineralization. Bioactive materials hold considerable potential in diminishing biofilm accumulation, inhibiting the process of demineralization, enabling dentin remineralization, and combating bacteria related to caries. Bioactive materials, such as fluoride, amorphous calcium phosphate, bioactive glass, collagen, and resin-based materials, have demonstrated their effectiveness in promoting dentin remineralization and exerting antibacterial effects on dental caries. However, the concentration of fluoride needs to be strictly controlled. Although amorphous calcium phosphate can provide the necessary calcium and phosphorus ions for remineralization, it falls short in delivering the mechanical strength required for oral mastication. Resin-based materials also offer different advantages due to the complexity of their design. In this review, we delve into the application of advanced bioactive materials for enhancing dentin remineralization and antibacterial properties. We eagerly anticipate future developments in bioactive materials for the treatment of dental caries.

Remineralizing Ability of Resin Modified Glass Ionomers (RMGICs): A Systematic Review

The selective caries removal approach leads to the need to use materials with the ability to remineralize remaining partially demineralized dentin. Among the materials proposed are resin-modified glass ionomer cements (RMGICs). The aim of this systematic review was to evaluate, based on in vitro experimental studies, whether RMGICs are suitable for remineralizing affected dentin. A systematic literature search was performed in four databases, followed by article selection, data extraction, and quality assessment. Studies assessing the remineralizing potential of RMGICs on dentin were included in our review. Studies which compared such properties between different RMGICs or with other materials were also eligible. The studies report the remineralizing ability of RMGICs, albeit with differences between different commercial products. RMGICs show a similar ability to conventional GICs to remineralize affected dentin, fulfilling the function for which they are designed. Moreover, the incorporation of additives, such as bioactive glass (BAG) or CCP-ACP, improves their remineralizing potential. The results of this review support the use of RMGICs as restorative materials after selective caries removal.

Theobromine versus casein phospho-peptides/Amorphous calcium phosphate with fluoride as remineralizing agents: effect on resin-dentine bond strength, microhardness, and morphology of dentine

BACKGROUND

This study aimed to assess the impact of theobromine and casein phospho-peptides/amorphous calcium phosphate with fluoride (CPP-ACPF) on the resin-dentine bond strength, microhardness, and dentine morphology.

METHODS

A total of 18 sound human molars for micro-tensile bond strength (µTBS), 20 sound human premolars for microhardness, and 30 premolars for Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) were used. Based on the pre-treatment used, teeth were split into six groups; sound dentine, demineralized dentine, and demineralized dentine treated with theobromine (Sigma Aldrich) and MI paste plus (GC International, USA) for two-time intervals; 5 min and 1 month. The bonded teeth were sectioned to produce 1 mm² resin-dentine sticks which were evaluated for µTBS using a universal testing device (Instron 3365, USA). The dentine microhardness was tested by using the Vickers microhardness tester (Nexus 4000 TM, Netherlands). The pre-treated dentine surface was examined using SEM/EDX (Neoscope JCM-6000 plus Joel benchtop SEM, Japan). µTBS results were analysed with two-way ANOVA. Microhardness and EDX results were analysed with two-way mixed model ANOVA. The significance level was set at (p ≤ 0.05).

RESULTS

While both remineralizing materials at the two-time intervals demonstrated µTBS comparable to sound dentine (46.38 ± 12.18), the demineralized group demonstrated statistically the lowest µTBS (p < 0.001). Whether used for 5 min or 1 month, theobromine significantly increased the microhardness (50.18 ± 3.43) and (54.12 ± 2.66) respectively (p < 0.001), whereas MI paste only increased the hardness (51.12 ± 1.45) after 1 month (p < 0.001).

CONCLUSIONS

The pre-treatment of demineralized dentine with theobromine for 5 min or 1 month could enhance its bond strength and microhardness while for MI paste plus, only 1-month application was efficient to ensure remineralization.

The Effect of Nanosilver Sodium Fluoride on the Mechanical and Physiochemical Properties of Artificially Demineralised Dentin

PURPOSE

To synthesise and characterise nanosilver sodium fluoride (NSSF) and assess the effect of applying this formulation in vitro on artificially demineralised root dentin lesions, compared with the application of silver diamine fluoride (SDF), sodium fluoride (NAF) or no treatment, in terms of mechanical, chemical and ultrastructural properties.

MATERIALS AND METHODS

NSSF was prepared using 0.5 wt% chitosan solution. On 40 extracted human molars, the buccal aspect of the cervical thirds of roots were prepared and divided into 4 groups of 10 each: control (no treatment), NSSF, SDF and NaF (n = 10). The specimens were examined using scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS). Fourier transform infrared spectroscopy (FTIR), surface and cross-sectional microhardness and nano-indentation tests were performed to determine the mineral and carbonate content, microhardness, and nanohardness, respectively. Statistical analysis was performed to determine the differences between the different treatment groups for the set parameters using parametric and non-parametric tests. Tukey's and Dunnet's T3 post-hoc tests were further used for multiple comparisons between groups (α = 0.05).

RESULTS

The control group (no treatment) was found to have statistically significantly lower mean scores for surface and cross-sectional microhardness compared with all other test groups (NaF, NSSF and SDF) (p < 0.05). Spearman's rank correlation test showed statistically insignificant differences between the mineral-to-matrix ratio (M:M) and carbonate content of all groups (p < 0.05).

CONCLUSIONS

Treatment of root lesions with NSSF yielded comparable results to SDF and NaF under in-vitro conditions.

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.

Theobromine versus Casein phospho-peptide/Amorphous Calcium Phosphate with Fluoride as remineralizing agents: Effect on resin-dentine bond strength, microhardness, and morphology of dentine.. [DOI: 10.21203/rs.3.rs-2722167/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: This study aimed to assess the impact of theobromine and casein phospho-peptides/amorphous calcium phosphate with Fluoride (CPP/ACPF) on the resin-dentine bond strength, microhardness, and dentine morphology. Methods: Based on the pre-treatment used, 18 sound human third molars were split into six groups.; sound dentine, demineralized dentine, and demineralized dentine treated with theobromine and MI paste plus for two-time intervals; 5 minutes and 1 month. The bonded teeth were sectioned to produce 1 mm2 resin-dentine sticks which were evaluated for micro-tensile bond strength (µTBS) using a universal testing device. The dentine microhardness was tested by using the Vickers microhardness tester. The pre-treated dentine surface was examined using Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). µTBS results were analysed with two-way ANOVA. Microhardness and EDX results were analysed with two-way mixed model ANOVA. Results: While both remineralizing materials at the two-time intervals demonstrated µTBS comparable to sound dentine, the demineralized group demonstrated statistically the lowest µTBS. Whether used for 5 minutes or 1 month, theobromine significantly increased the microhardness, whereas MI paste only increased the hardness after 1 month. Conclusions: The pre-treatment of demineralized dentine with theobromine and MI paste plus could enhance its bond strength and microhardness.

Micro-Raman spectroscopy analysis of dentin remineralization using eggshell derived nanohydroxyapatite combined with phytosphingosine

The aim of this study was to assess the remineralization efficacy of chicken eggshell-derived nano-hydroxyapatite (CEnHAp) combined with phytosphingosine (PHS) on artificially induced dentinal lesions. PHS was commercially procured whereas CEnHAp was synthesized using microwave-irradiation method and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution scanning electron microscopy-energy-dispersive X-ray spectroscopy (HRSEM-EDX), and transmission electron microscopy (TEM). A total of 75 pre-demineralized coronal dentin specimens were randomly treated with one of the following test agents (n = 15 each): artificial saliva (AS), casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), CEnHAp, PHS, and CEnHAp-PHS under pH cycling for 7, 14, and 28 days. Vickers microhardness indenter, HRSEM-EDX, and micro-Raman spectroscopy methods were used to assess the mineral changes in the treated dentin samples. Data were submitted to Kruskal-Wallis and Friedman's two-way analyses of variance (p < 0.05). HRSEM and TEM analysis depicted irregular spherical structure of the prepared CEnHAp with a particle size of 20-50 nm. The EDX analysis confirmed the presence of Ca, P, Na and Mg ions. The XRD pattern showed the characteristic crystalline peaks for hydroxyapatite and calcium carbonate that are present in the prepared CEnHAp. Dentin treated with CEnHAp-PHS revealed highest microhardness values along with complete tubular occlusion compared to other groups at all test time intervals (p < 0.05). Specimens treated with CEnHAp showed increased remineralization than those treated with CPP-ACP followed by PHS and AS groups. The intensity of mineral peaks, as observed in the EDX and micro-Raman spectra, confirmed these findings. Further, the molecular conformation of the collagen's polypeptide chains, and amide-I and CH₂ peaks attained peak intensities in dentin treated with CEnHAp-PHS and PHS whereas other groups revealed poor stability of collagen bands. Microhardness, surface topography, and micro-Raman spectroscopy analyses revealed that dentin treated with CEnHAp-PHS have an improved collagen structure and stability as well as highest mineralization and crystallinity.

Bioactive Materials for Caries Management: A Literature Review

Researchers have developed novel bioactive materials for caries management. Many clinicians also favour these materials, which fit their contemporary practice philosophy of using the medical model of caries management and minimally invasive dentistry. Although there is no consensus on the definition of bioactive materials, bioactive materials in cariology are generally considered to be those that can form hydroxyapatite crystals on the tooth surface. Common bioactive materials include fluoride-based materials, calcium- and phosphate-based materials, graphene-based materials, metal and metal-oxide nanomaterials and peptide-based materials. Silver diamine fluoride (SDF) is a fluoride-based material containing silver; silver is antibacterial and fluoride promotes remineralisation. Casein phosphopeptide-amorphous calcium phosphate is a calcium- and phosphate-based material that can be added to toothpaste and chewing gum for caries prevention. Researchers use graphene-based materials and metal or metal-oxide nanomaterials as anticaries agents. Graphene-based materials, such as graphene oxide-silver, have antibacterial and mineralising properties. Metal and metal-oxide nanomaterials, such as silver and copper oxide, are antimicrobial. Incorporating mineralising materials could introduce remineralising properties to metallic nanoparticles. Researchers have also developed antimicrobial peptides with mineralising properties for caries prevention. The purpose of this literature review is to provide an overview of current bioactive materials for caries management.

Combined remineralizing effect of arginine and fluoride on artificially demineralized human primary dentin evaluated using quantitative light induced fluorescence

Introduction

One the most common chronic dental diseases affecting children is dental caries. Dentin caries is a condition in which caries has progressed to the dentin and caused a significant depth of lesion. Clinical studies have revealed that an increased caries risk is associated with a decreased alkali-producing capacity of the microbial populations colonizing the oral cavity of adults, which arginine somewhat compensates for.

Aims

To evaluate the remineralizing efficacy of fluoridated toothpaste, with fluoride-arginine containing toothpaste on demineralized dentin of primary teeth using quantitative light-induced fluorescence™.

Materials and Methods

Forty-five primary molars were decoronated and sectioned to prepare dentin specimens and mounted in an acrylic block in a uniform manner using a customized acrylic jig. Samples were randomized into three groups, were subjected to demineralization to create artificial dentin caries lesion. Following this, all the 45 samples were subjected to multispecies bacterial pH cycling for 21 days. All the specimens were evaluated for postdemineralization, pH cycling day 7, 14, and 21 on QLF™.

Results

On day 21, maximum fluorescence gain was observed by the positive control group followed by the arginine and negative control group. The variation observed between positive control and arginine group was found to be statistically significant.

Conclusions

An in vitro development of artificial caries such as demineralized lesion on primary dentin sample using plaque biofilm was observed successfully under QLF after 72 h. Arginine in combination with fluoride showed almost similar remineralization of demineralized primary dentin compared to fluoride alone after 21 days of multispecies bacterial pH cycling.

Ceramic Nanomaterials in Caries Prevention: A Narrative Review

Ceramic nanomaterials are nanoscale inorganic metalloid solids that can be synthesised by heating at high temperatures followed by rapid cooling. Since the first nanoceramics were developed in the 1980s, ceramic nanomaterials have rapidly become one of the core nanomaterials for research because of their versatility in application and use in technology. Researchers are developing ceramic nanomaterials for dental use because ceramic nanoparticles are more stable and cheaper in production than metallic nanoparticles. Ceramic nanomaterials can be used to prevent dental caries because some of them have mineralising properties to promote the remineralisation of tooth tissue. Ceramic minerals facilitate the remineralisation process and maintain an equilibrium in pH levels to maintain tooth integrity. In addition, ceramic nanomaterials have antibacterial properties to inhibit the growth of cariogenic biofilm. Researchers have developed antimicrobial nanoparticles, conjugated ceramic minerals with antibacterial and mineralising properties, to prevent the formation and progression of caries. Common ceramic nanomaterials developed for caries prevention include calcium-based (including hydroxyapatite-based), bioactive glass-based, and silica-based nanoparticles. Calcium-based ceramic nanomaterials can substitute for the lost hydroxyapatite by depositing calcium ions. Bioactive glass-based nanoparticles contain surface-reactive glass that can form apatite crystals resembling bone and tooth tissue and exhibit chemical bonding to the bone and tooth tissue. Silica-based nanoparticles contain silica for collagen infiltration and enhancing heterogeneous mineralisation of the dentin collagen matrix. In summary, ceramic nanomaterials can be used for caries prevention because of their antibacterial and mineralising properties. This study gives an overview of ceramic nanomaterials for the prevention of dental caries.

Promotion Effect of Carboxymethyl Chitosan on Dental Caries via Intrafibrillar Mineralization of Collagen and Dentin Remineralization

Objective: To observe ultrastructural changes during the process of carboxymethyl chitosan (CMC)-mediated intrafibrillar mineralization, we evaluated the biomimetic remineralization potential of CMC in type-I collagen fibrils and membranes, and further explored the bond strength as well as the bond interfacial integrity of the biomimetic remineralized artificial caries-affected dentin (ACAD). Methods: A mineralized solution containing 200 μg/mL CMC was used to induce type-I collagen biomimetic remineralization in ACAD, while traditional mineralization without CMC was used as a control. The process and pattern of mineralization were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) as well as structured illumination microscopy (SIM). The Vickers hardness test was used to quantify the dentin hardness, while the microtensile bond strength (µTBS) test was used to assess the bond strength and durability. The bond interfacial integrity was evaluated by a confocal laser scanning microscope (CLSM). Results: TEM, SEM, and SIM images showed that CMC had a positive effect on stabilizing amorphous calcium phosphate (ACP) and promoting intrafibrillar mineralization, while extrafibrillar mineralization was formed without CMC. Furthermore, hardness evaluation and µTBS proved that CMC significantly increased dentin hardness and bond strength. CLSM indicated that CMC could create a significantly better bond interfacial integrity with less of a micro-gap in ACAD. Significance: CMC possessed the ability to promote intrafibrillar mineralization and remineralization in demineralized caries dentin lesions, as well as improve bond performance, which implied its potential in carious dentin demineralization or dentin hypersensitivity and possibly even as a possible material for indirect pulp-capping, to deal with deep caries. Highlights: CMC possessed the ability to induce intrafibrillar mineralization effectively; the bond strength and bond durability of demineralized caries dentin were improved via CMC-induced remineralization; the CMC-induced remineralization complex is a potential material for indirect pulp-capping, to deal with deep caries.

Effects of 45S5 bioactive glass on the remineralization of early carious lesions in deciduous teeth: an in vitro study

Background

Early childhood caries has been designated as a serious public health problem. The traditional restoration method is very challenging, especially in uncooperative patients. Non-invasive therapy, like remineralization agents, which have been developed to reverse the demineralization progress at the early stage of caries, may be a better choice. This study aimed to evaluate the remineralization efficacy of different concentrations of 45S5 bioactive glass (BAG) on artifical carious lesions of deciduous enamel.

Methods

65 caries-like enamel lesions of the deciduous teeth were assigned to 5 groups (n = 13) and transported to a 14 days pH-cycling: Group A: 2%BAG, Group B: 4%BAG, Group C: 6%BAG, Group D: 8%BAG, and Group E: deionized water (DDW, negative control). 8 sound (Group F) and 8 demineralized teeth (Group G) were prepared for contrast. The recovery power of mechanical property was evaluated by Vickers hardness test through the recovery of enamel microhardness (%REMH). Surface morphology, mass fraction of Ca and P ions, and Ca/P atomic ratio were analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDX). Moreover, Fourier transform infrared spectroscopy equipped with attenuated total reflectance was used to identify the chemical structure of newly formed compounds.

Results

% REMH were (42.65 ± 1.35), (52.59 ± 2.96), (57.40 ± 1.72), (52.91 ± 2.55), (12.46 ± 2.81) in 2%BAG, 4%BAG, 6%BAG, 8%BAG, and DDW groups respectively. Micro-spherical particles were deposited in all BAG groups and 6% BAG showed the densest and most uniform surface. EDX analysis identified significantly higher Ca(wt%) and P(wt%) in four BAG groups than in the demineralized group (p < 0.005), while 6% BAG showed the highest mineral gain efficacy. The infrared spectrum demonstrated that newly mineralized crystals were consisted of type-B hydroxycarbonate apatite.

Conclusion

BAG possessed a promising remineralization effect on artificial lesions in deciduous enamel by recovering enamel surface mechanical property, morphology and chemical elements. Among them, 6% BAG performed the greatest overall efficacy. Acting as a new caries-arresting biomaterial, 45S5 BAG has the potential to facilitate the adaptation of better carious prevention strategies in children.

Traditional Microscopic Techniques Employed in Dental Adhesion Research-Applications and Protocols of Specimen Preparation

Microscopy is a traditional method to perform ex vivo/in vitro dental research. Contemporary microscopic techniques offer the opportunity to observe dental tissues and materials up to nanoscale level. The aim of this paper was to perform a literature review on four microscopic methods, which are widely employed in dental studies concerning the evaluation of resin-dental adhesive interfaces-confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The literature search was performed using digital databases: PubMed, Web of Science and Scopus. On the basis of key words relevant to the topic and established eligibility criteria, finally 84 papers were included in the review. Presented microscopic techniques differ in their principle of operation and require specific protocols for specimen preparation. With regard to adhesion studies, microscopy assists in the description of several elements involved in adhesive bonding, as well as in the assessment of the condition of enamel surface and the most appropriate etching procedures. There are several factors determining the quality of the interaction between the substrates which could be recognized and a potential for further implementation of microscopic techniques in dental research could be recognized, especially when these techniques are used simultaneously or combined with spectroscopic methods. Through such microscopy techniques it is possible to provide clinically relevant conclusions and recommendations, which can be easily introduced for enamel-safe bonding and bonding protocols, as well as optimal pretreatments in dentine preparation.

Effects of bioactive glass with high phosphorus content on mineralization of type I collagen fibrils

PURPOSE

To study effects of bioactive glass with high phosphorus content (10.8% P₂O₅, 54.2% SiO₂, 35% CaO, mol%, named PSC) on mineralization of type I collagen fibrils.

METHODS

(1) PSC, and PSC combining 0.1 mg/mL, 0.5 mg/mL, or 1.0 mg/mL polyacrylic acid (PAA), were used to induce the mineralization of self-assembled type I collagen fibrils. After 3 and 7 days of mineralization, collagen fibrils were observed by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). (2) PSC suspension was dialyzed in simulated body fluid (SBF), or in SBF containing 0.1 mg/mL, 0.5 mg/mL, or 1.0 mg/mL PAA, to form amorphous calcium phosphate (ACP), then observed by TEM.

RESULTS

(1) PSC and PSC combining 0.1 mg/mL or 0.5 mg/mL PAA induced mainly extrafibrillar mineralization. PSC combining 1.0 mg/mL PAA induced both extrafibrillar and intrafibrillar mineralization. (2) The ACP induced by PSC or PSC combining 0.1 mg/mL PAA partly formed lattice structure after 24 h. The particle size of the ACP induced by PSC combining 0.5 mg/mL PAA was 100-150 nm, and that induced by PSC combining 1.0 mg/mL PAA was 30-50 nm.

CONCLUSION

PSC induced mainly extrafibrillar mineralization, and PSC combining an appropriate concentration (1.0 mg/mL) of PAA induced both extrafibrillar and intrafibrillar mineralization.

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.

The effects of strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization

OBJECTIVES

This study investigated the effects of a new strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization.

METHODS

We designed an in vitro experiment with calcium phosphate (CaCl₂·2H₂O + K₂HPO₄ in buffer solution) with different concentrations of strontium-doped bioactive glass (1 mg/mL or 5 mg/mL), and different concentrations of fluoride (0 ppm, 1 ppm or 5 ppm). Tris-buffered saline served as negative control. After incubation at 37 ℃ for 48 h, the shape and organization of crystals were examined by transmission electron microscopy (TEM) and electron diffraction. Structure of the crystals was assessed by powder X-ray diffraction (P-XRD) and unit cell parameters were calculated. Characterization of the crystals were performed by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR).

RESULTS

TEM and selected-area electron diffraction revealed that the precipitates in all experimental groups were crystalline apatite. There was an interaction between strontium and fluoride with different concentrations on crystal thickness (p = 0.008). P-XRD indicated the formation of strontium-substituted-fluorohydroxyapatite and strontium-substituted-hydroxyapatite in the groups with both bioactive glass and fluoride. Expansion or contraction of crystal unit cell was influenced by the concentrations of strontium and fluoride. Raman spectra showed strong phosphate band at 960 cm^-1 in all experimental groups and displayed no obvious shift. FTIR results confirmed the formation of apatite.

CONCLUSIONS

The results of this study suggest that strontium-doped bioactive glass and fluoride have synergistic effects on hydroxyapatite crystallization.

CLINICAL SIGNIFICANCE

Strontium-doped bioactive glass and fluoride have synergistic effects on hydroxyapatite crystallization by producing strontium-substituted-hydroxyapatite and strontium-substituted-fluorohydroxyapatite with enhanced bioactivity and reduced solubility which could be beneficial for caries management.