Remineralising effects of fluoride varnishes containing calcium phosphate on artificial root caries lesions with adjunctive application of proanthocyanidin

Effects of proanthocyanidin-functionalized hydroxyapatite nanoparticles on dentin bonding

OBJECTIVES

To evaluate the effect of proanthocyanidin-functionalized hydroxyapatite nanoparticles (nHAp_PA) used as pretreatment at different concentrations on the microtensile bond strength (µTBS) and endogenous enzymatic activity (MMPs) on pH-cycled dentin after 24 h and 6 months of artificial aging.

MATERIALS AND METHODS

Fifty human sound dentin blocks were randomly assigned to 5 groups (n = 10): (i) negative control (no treatment); (ii) positive control (pH-cycling); (iii) pH-cycling + 2% nHAp_PA for 60s; (iv) pH-cycling + 6.5% nHAp_PA for 60s; (v) pH-cycling + 15% nHAp_PA for 60s. A self-etch adhesive was used for bonding procedures before resin composite build-ups. Specimens were tested with the µTBS test after 24 h and 6 months of laboratory storage. The proteolytic activity in each group was evaluated with gelatin zymography and in situ zymography. Data were statistically analyzed (p < 0.05).

RESULTS

At 24 h, the µTBS of the experimental groups were significantly higher than the controls (p ≤ 0.001), and no differences were observed between different concentrations (p > 0.05). Artificial aging significantly decreased bond strength in all groups (p ≤ 0.008); however, nHAp_PA 2% still yielded higher bonding values than controls (p ≤ 0.007). The groups pretreated with nHAp_PA exhibited lower MMP-9 and MMP-2 activities compared to the positive control group and almost the same enzymatic activity as the negative control group. In situ zymography showed that after 6 months of aging, nHAp_PA 2% and nHAp_PA 6,5% decreased enzymatic activity as well as the negative control.

CONCLUSIONS

Dentin pretreatment with nHAp_PA increased the bonding performance of a self-etch adhesive and decreased MMP-2 and MMP-9 activities after 6 months.

Frontiers of Global Research Trend on Root Caries: A Bibliometric Analysis

OBJECTIVE

This study aimed to examine the global research trend and frontiers in the field of root caries.

METHODS

Two independent investigators searched the Web of Science Core Collection to include journal articles published on root caries from 1994 to 2023. They examined citation trends of the selected publications and performed bibliometric analysis using VOSviewer. Cooccurrence and cocitation analysis were used to calculate the burst strength of the most cited keywords and the most cited publications.

RESULTS

This study included 1144 publications (1004 scientific research articles and 140 review articles) for bibliometric analysis. The number of publications from 2018 to 2023 was 404, accounting for 35% (404/1144) over the last 30 years. The annual citation count showed a gradual upward trend with a surge from 2018. The cooccurrence analysis classified the publications into four clusters which were in vitro studies, prevention, microbiology, and epidemiology. Cocitation analysis revealed silver diamine fluoride, systematic review, and randomized clinical trial were the three main keywords; and their citation burst strength (period) were 17.2 (2017-2023), 9.4 (2015-2023), and 6.9 (2018-2023), respectively. Noninvasive treatment of root caries (narrative review), aetiology of root caries (narrative review), and use of silver diamine fluoride in arresting root caries (clinical trial) were the topics (publication type) of the three most cited publications; and their burst strength (period) were 8.9 (2017-2020), 5.9 (2017-2021), and 4.7 (2015-2018), respectively.

CONCLUSION

This study highlights the recent growing research interest in root caries, particularly on its microbiology, prevention, and the use of silver diamine fluoride.

Immediate and Sustained Root Caries Prevention of Fluoride Varnish Combined with Toothpastes

The aim of this study was to determine the immediate and sustained effect of a fluoride varnish and its combinations with toothpastes in preventing root caries development using a salivary microcosm in vitro model. Human root dentin specimens (n = 150) were randomly divided into 5 experimental protocols (n = 30): (1) Fluoride Varnish (V); (2) V followed by Paste One (V + PO); (3) V followed by Paste Plus (V + PP); (4) V followed by PO and PP (V + PO + PP); and (5) No treatment (control). One varnish layer was applied on the specimens (except for the control group) and kept for 18 h. Then, the varnish was removed and toothpaste treatments were initiated according to experimental groups. For the short-term incubation model (n = 15), the specimens were also immediately subjected to 7-day cariogenic challenge. For that, human saliva was used as bacterial inoculum and McBain artificial saliva containing 2% sucrose as growth medium. The other half of the specimens (n = 15) were used to study the varnish's sustained effect by long-term incubation (8 weeks) before cariogenic challenge. The protocols' anti-caries properties were evaluated by dentin porosity (rhodamine intensity; RI) and mineral density, while their anti-biofilm effects were evaluated using biofilm's biomass and viability assays. For short- and long-term incubation models, all experimental regimens resulted in statistically significant decreases (p < 0.05) in the RI (up to 180 μm and 120 μm, respectively) as well as higher mineral density compared to No treatment (p < 0.001). V + PO + PP and/or V + PO resulted in statistically lower RI compared to V for some depths (p < 0.05) in both models. There were changes in RI and mineral density within groups over time. All experimental treatments exhibited anti-biofilm effects. All prevention protocols exhibited immediate and sustained anti-caries effect against root caries development. The combination of a fluoride varnish with PO resulted in superior additional anti-caries effects.

Prevention of Root Caries Using Oxalic Acid

Certain dentin hypersensitivity treatment materials include oxalic acid to coat dentin surfaces with minerals, while certain organic acids possess a remineralization effect. Herein, an organic acid that inhibits the demineralization and coating of root surfaces was evaluated. Specimens were produced using five non-carious extracted bovines. Four different acids were used: oxalic acid (OA), malonic acid (MA), polyacrylic acid (PA), and succinic acid (SA). Each acid was applied to the root surface and washed using distilled water or a remineralization solution, and the surface was observed using scanning electron microscopy (SEM). All the surfaces of each specimen, barring the polished surface, were covered with wax and immersed in an automatic pH cycling system for two weeks. Dentin demineralization was analyzed using transverse microradiography (TMR) before and after pH cycling. SEM analysis demonstrated that the three acid groups demineralized the dentin surface, whereas the OA group generated crystals covering the dentin surface, even in a distilled water environment. TMR analysis revealed that the OA groups showed significantly lower integrated mineral loss compared with the other groups, even in the distilled water environment. The results suggest that OA generates insoluble calcium oxalate crystals on the dentin and suppresses demineralization even under low saliva conditions.

Development of Root Caries Prevention by Nano-Hydroxyapatite Coating and Improvement of Dentin Acid Resistance

There is no established method for optimizing the use of dentin to prevent root caries, which are increasing in the elderly population. This study aimed to develop a new approach for root caries prevention by focusing on bioapatite (BioHap), a new biomaterial, combined with fluoride. Bovine dentin was used as a sample, and an acid challenge was performed in three groups: no fluoride (control group), acidulated phosphate fluoride treatment (APF group), and BioHap + APF treatment (BioHap group). After applying the new compound, the acid resistance of dentin was compared with that of APF alone. The BioHap group had fewer defects and an increased surface hardness than the APF group. The BioHap group had the smallest lesion depth and least mineral loss among all groups. Using a scanning electron microscope in the BioHap group showed the closure of dentinal tubules and a coating on the surface. The BioHap group maintained a coating and had higher acid resistance than the APF group. The coating prevents acid penetration, and the small particle size of BioHap and its excellent reactivity with fluoride are thought to have contributed to the improvement of acid resistance in dentin. Topical fluoride application using BioHap protects against root caries.