Ca2+ release and buffering effects of synthetic hydroxyapatite following bacterial acid challenge

Caries Etiology and Preventive Measures

Caries is a widespread disease in both children and adults. Caries is caused by the conversion of fermentable carbohydrates by plaque bacteria into acids on the tooth surface. Thus, it is important to focus on sugar reduction and plaque control. For efficient plaque removal/control, state-of-the-art toothpastes contain various active ingredients such as antimicrobial agents (e.g., chlorhexidine, stannous salts, and zinc salts), abrasives (e.g., calcium carbonate, calcium phosphates, and hydrated silica), surfactants (e.g., sodium lauryl sulfate and sodium methyl cocoyl taurate), and natural compounds (e.g., polyphenols and xylitol). Agents with pH-buffering and calcium-releasing properties (e.g., calcium carbonate and calcium phosphates) and biomimetic actives (e.g., hydroxyapatite) reverse the effects of the acids. Additionally, modern toothbrushes (i.e., electric toothbrushes) as well as dental floss and interdental brushes significantly help remove plaque from dental surfaces including interproximal surfaces. In conclusion, modern concepts in caries prevention should focus not only on tooth remineralization alone but also on the control of all the key factors involved in caries development.

Antimicrobial properties of glass-ionomer cement incorporated with nano-hydroxyapatite against mutans streptococci and lactobacilli under orthodontic bands: An in vivo split-mouth study

Background

Fixed orthodontic appliances enhance dental plaque accumulation. Glass ionomer (GI) is among the most popular orthodontic cement. It possesses antibacterial properties; however, its antibacterial activity may not be sufficient for caries prevention. Although evidence shows that the addition of 8wt% nano-hydroxyapatite (nHA) may enhance the antibacterial properties of GI, no clinical study has been conducted in this respect. Thus, this study aimed to assess the subgingival accumulation of Streptococcus mutans (S. mutans) and Lactobacillus acidophilus (L. acidophilus) around orthodontic bands cemented with conventional GI and GI reinforced with 8wt% nHA.

Materials and Methods

This split-mouth clinical trial was conducted on 20 patients requiring a lingual arch. The patients were randomly assigned to two groups. In group 1, the right molar band was cemented with pure Fuji I (GC), and the left was cemented with Fuji I containing 8wt% nHA. In group 2, the right molar band was cemented with Fuji I containing 8wt% nHA, and the left was cemented with Fuji I. After 3 months, subgingival sampling was performed by sterile paper points. S. mutans and L. acidophilus were cultured on MSB and MRS agar, and colonies were counted by a colony counter. Data were analyzed by independent samples t-test using SPSS 25 at a 0.05 level of significance.

Results

The mean counts of S. mutans, aerobic and anaerobic lactobacilli, and total bacterial around orthodontic bands cemented with Fuji I containing 8wt% nHA were significantly lower than those around orthodontic bands cemented with pure Fuji I (P < 0.05).

Conclusion

The addition of 8wt% nHA to GI cement can enhance its antibacterial properties for the cementation of orthodontic bands, decrease the accumulation of cariogenic bacteria, and probably decrease the incidence of caries in orthodontic patients.

The composition of the dental pellicle: an updated literature review

Background

The dental pellicle is a thin layer of up to several hundred nm in thickness, covering the tooth surface. It is known to protect the teeth from acid attacks through its selective permeability and it is involved in the remineralization process of the teeth. It functions also as binding site and source of nutrients for bacteria and conditioning biofilm (foundation) for dental plaque formation.

Methods

For this updated literature review, the PubMed database was searched for the dental pellicle and its composition.

Results

The dental pellicle has been analyzed in the past years with various state-of-the art analytic techniques such as high-resolution microscopic techniques (e.g., scanning electron microscopy, atomic force microscopy), spectrophotometry, mass spectrometry, affinity chromatography, enzyme-linked immunosorbent assays (ELISA), and blotting-techniques (e.g., western blot). It consists of several different amino acids, proteins, and proteolytic protein fragments. Some studies also investigated other compounds of the pellicle, mainly fatty acids, and carbohydrates.

Conclusions

The dental pellicle is composed mainly of different proteins, but also fatty acids, and carbohydrates. Analysis with state-of-the-art analytical techniques have uncovered mainly acidic proline-rich proteins, amylase, cystatin, immunoglobulins, lysozyme, and mucins as main proteins of the dental pellicle. The pellicle has protective properties for the teeth. Further research is necessary to gain more knowledge about the role of the pellicle in the tooth remineralization process.

Caries-preventing effect of a hydroxyapatite-toothpaste in adults: a 18-month double-blinded randomized clinical trial

Background

Dental caries is a worldwide challenge for public health. The aim of this 18-month double-blinded, randomized, clinical trial was to compare the caries-preventing effect of a fluoride-free, hydroxyapatite toothpaste (test) and a toothpaste with sodium fluoride (1450 ppm fluoride; positive control) in adults.

Methods

The primary endpoint was the percentage of subjects showing no increase in overall Decayed Missing Filled Surfaces (DMFS) index. The study was designed as non-inferiority trial. Non-inferiority was claimed if the upper limit of the exact one-sided 95% confidence interval for the difference of the primary endpoint DMFS between test and control toothpaste was less than the predefined margin of non-inferiority (Δ ≤ 20%).

Results

In total, 189 adults were included in the intention-to-treat (ITT) analysis; 171 subjects finished the study per protocol (PP). According to the PP analysis, no increase in DMFS index was observed in 89.3% of subjects of the hydroxyapatite group and 87.4% of the subjects of the fluoride group. The hydroxyapatite toothpaste was not statistically inferior to a fluoride toothpaste with regard to the primary endpoint.

Conclusion

Hydroxyapatite was proven to be a safe and efficient anticaries agent in oral care.

Clinical trial registration

NCT04756557.

Clinical Evidence of Biomimetic Hydroxyapatite in Oral Care Products for Reducing Dentin Hypersensitivity: An Updated Systematic Review and Meta-Analysis

Dentin hypersensitivity (DH) is a very common dental problem that can have a negative impact on the quality of life and can lead to invasive dental procedures. Prevention of DH and control of symptoms are highly desirable. Hydroxyapatite (HAP) has been shown in vitro to block dentinal tubules and in vivo to be a safe and effective additive in oral care products that reduce DH clinically. This study's aim was to conduct a systematic review and meta-analysis of the current evidence that HAP-containing oral care products reduce DH. Databases were searched, and only clinical trials in humans were included; studies conducted in vitro or on animals were not included. Publications in a foreign language were translated and included. We found 44 published clinical trials appropriate for systematic analysis. More than half of the trials had high-quality GRADE scores. HAP significantly reduced dentin hypersensitivity compared to placebo (39.5%; CI 95% [48.93; 30.06]), compared to fluoride (23%; CI 95% [34.18; 11.82]), and with a non-significant tendency compared to other desensitizing agents (10.2%; CI 95% [21.76; -19.26]). In conclusion, the meta-analysis showed that HAP added to oral care products is a more effective agent than fluoride in controlling dentin hypersensitivity and may be superior to other desensitizers.

Overview on Adjunct Ingredients Used in Hydroxyapatite-Based Oral Care Products

Hydroxyapatite, Ca₅(PO₄)₃(OH), is a biomimetic active ingredient, which is used in commercial oral care products such as toothpastes and mouthwashes worldwide. Clinical studies (in vivo) as well as in situ and in vitro studies have shown the preventive effects of hydroxyapatite in various field of oral care. In some products, hydroxyapatite is combined with other active ingredients, to achieve an additional antibacterial effect or to promote gum health. This review analyzes the efficacy of six selected natural and nature-inspired ingredients that are commonly used together with hydroxyapatite. These additional actives are either antibacterial (lactoferrin, xylitol, and zinc) or promote gum health (allantoin, bisabolol, and hyaluronic acid). A systematic literature search was performed, and all studies found on each ingredient were analyzed. In summary, all analyzed ingredients mentioned in this review are well described in scientific studies on their beneficial effect for oral health and can be used to expand the preventive effect of hydroxyapatite in oral care products.

Remineralization of molar incisor hypomineralization (MIH) with a hydroxyapatite toothpaste: an in-situ study

AIM

This randomized, double-blind, crossover, in-situ study, compared the efficacy of toothpastes based on microcrystalline hydroxyapatite (HAP; fluoride-free) or fluoride, in remineralizing molar incisor hypomineralization (MIH).

METHODS

Two lesion-bearing enamel blocks were produced from each of thirty extracted permanent molars diagnosed with MIH. Sixty produced blocks were randomly assigned to two groups (30/group): 20% HAP or 1450 ppm fluoride toothpaste. Each group was subdivided into, etched (n = 20), with lesion surface treated with 32% phosphoric acid-etchant for 5 s, and unetched (n = 10). Blocks were cemented into intra-oral appliances (2 blocks/appliance) worn full-time by 15 subjects. Subjects used the toothpastes in a two-phase crossover manner, lasting 14 days per phase, after one-week washout period. Baseline and post-treatment mineral density (MD) was quantified using microcomputed tomography.

RESULTS

Overall, both groups showed statistically significant (paired t-test; p < 0.001) net-gain when MD was compared pre-treatment and post-treatment. HAP: pre-treatment (1.716 ± 0.315) and post-treatment (1.901 ± 0.354), Fluoride: pre-treatment (1.962 ± 0.363) and post-treatment (2.072 ± 0.353). Independent t-test demonstrated a practically significantly (≥10%) higher percentage remineralization with HAP toothpaste (26.02 ± 20.68) compared with fluoride toothpaste (14.64 ± 9.60). Higher percentage remineralization was observed in etched than unetched samples.

CONCLUSION

The tested toothpaste based on hydroxyapatite can remineralize MIH lesions. Pre-treating the tooth surface with acid-etchant enhanced remineralization.

Advanced Drug Delivery Platforms for the Treatment of Oral Pathogens

The oral cavity is a complex ecosystem accommodating various microorganisms (e.g., bacteria and fungi). Various factors, such as diet change and poor oral hygiene, can change the composition of oral microbiota, resulting in the dysbiosis of the oral micro-environment and the emergence of pathogenic microorganisms, and consequently, oral infectious diseases. Systemic administration is frequently used for drug delivery in the treatment of diseases and is associated with the problems, such as drug resistance and dysbiosis. To overcome these challenges, oral drug delivery systems (DDS) have received considerable attention. In this literature review, the related articles are identified, and their findings, in terms of current therapeutic challenges and the applications of DDSs, especially nanoscopic DDSs, for the treatment of oral infectious diseases are highlighted. DDSs are also discussed in terms of structures and therapeutic agents (e.g., antibiotics, antifungals, antiviral, and ions) that they deliver. In addition, strategies (e.g., theranostics, hydrogel, microparticle, strips/fibers, and pH-sensitive nanoparticles), which can improve the treatment outcome of these diseases, are highlighted.

Incorporation of Fluoride into Human Teeth after Immersion in Fluoride-Containing Solutions

Toothpastes and mouth rinses contain fluoride as a protective agent against caries. The aim of this study was to determine the degree of fluoride-uptake by human tooth mineral during immersion into fluoride-containing aqueous solutions as different pH. Human teeth were immersed in fluoride-containing solutions to assess the extent of fluoride incorporation into tooth enamel. A total of 16 extracted teeth from 11 patients were immersed at 37 °C for one minute into aqueous fluoride solutions (potassium fluoride; KF) containing either 250 ppm or 18,998 ppm fluoride (1-molar). Fluoride was dissolved either in pure water (neutral pH) or in a citrate buffer (pH 4.6 to 4.7). The elemental surface composition of each tooth was studied by energy-dispersive X-ray spectroscopy in combination with scanning electron microscopy and X-ray powder diffraction. The as-received teeth contained 0.17 ± 0.16 wt% fluoride on average. There was no significant increase in the fluoride content after immersion in 250 ppm fluoride solution at neutral or acidic pH values. In contrast, a treatment with a 1-molar fluoride solution led to significantly increased fluoride concentrations by 0.68 wt% in water and 9.06 wt% at pH 4.7. Although such fluoride concentrations are far above those used in mouth rinses or toothpastes, this indicates that fluoride can indeed enter the tooth surface, especially at a low pH where a dynamic dissolution-reprecipitation process may occur. However, precipitations of calcium fluoride (globuli) were detected in no cases.

Biodegradable Carbonate Apatite Nanoparticle as a Delivery System to Promote Afatinib Delivery for Non-Small Cell Lung Cancer Treatment

Nanomedicine-based drug-delivery systems have significant interest in cancer treatment, such as improving the stabilities and biocompatibilities, precise targeting, and reducing toxicities for non-cancerous cells. Herein, this study presents the synthesis and characterisation of carbonate apatite nanoparticles (nCA) and encapsulated afatinib (AFA) as promising drug delivery candidates for lung cancer treatment. nCA/AFA was synthesised and physicochemically characterised, then the encapsulation capacity, drug loading, and cumulative drug release profile were evaluated. Powder X-ray diffraction (PXRD) confirmed that the synthesised nCA is apatite. Fourier-transform infrared spectroscopy (FTIR) results confirmed the drug loading into the nanoparticles. High-resolution transmission electron microscopy (HR-TEM) determined the morphology of nCA and nCA/AFA and the diameters of 47.36 ± 3.16 and 42.97 ± 2.78 nm, respectively, without an unaltered nCA phase. Encapsulation efficiency (%) and drug loading (%) were 55.08% ± 1.68% and 8.19% ± 0.52%. Brunauer–Emmett–Teller (BET) and dynamic light-scattering (DLS) results revealed that the synthesised nCA is mesoporous, with a surface area of 55.53 m²/g, and is negatively charged. Atomic force microscopy (AFM) showed increasing roughness of nCA/AFA compared to nCA. The drug release from the nano-formulation nCA/AFA demonstrated slow and sustained release compared to the pure drug. Accordingly, nCA/AFA represents a promising drug delivery system for NSCLC treatment.

Hydroxyapatite as Remineralization Agent for Children's Dental Care

Children are prone to develop dental caries. This is supported by epidemiological data confirming early childhood caries (ECC) as a highly prevalent disease affecting more than every second child worldwide. ECC is known to result from an imbalance between re- and demineralization where demineralization dominates due to frequent acid production by cariogenic bacteria present in oral biofilms. The application of oral care formulations containing remineralizing agents helps to prevent dental caries. As young children are sensitive and usually swallow (intended or unintended) a majority of toothpaste or other oral care products during daily dental care, all ingredients, especially the actives, should be non-toxic. Biomimetic hydroxyapatite [HAP; Ca5(PO4)3(OH)] is known to have favorable remineralizing properties combined with an excellent biocompatibility, i.e., it is safe if accidently swallowed. Several clinical trials as well as in situ and in vitro studies have shown that HAP remineralizes enamel and dentin. Remineralization occurs due to deposition of HAP particles on tooth surfaces forming mineral-mineral bridges with enamel crystals, but also indirectly through calcium and phosphate ions release as well as HAP's buffering properties in acidic environments (i.e., in plaque). HAP induces a homogenous remineralization throughout the subsurface enamel lesions. This review summarizes the current evidence showing HAP as an effective remineralizing agent in oral care products for children. Additional studies showing also further beneficial effects of HAP such as the reduction of biofilm formation and the relief of hypersensitivity in children with molar incisor hypomineralization (MIH). It can be concluded that HAP is an effective and safe remineralizing agent for child dental care.

Bone Regeneration and Oxidative Stress: An Updated Overview

Bone tissue engineering is a complex domain that requires further investigation and benefits from data obtained over past decades. The models are increasing in complexity as they reveal new data from co-culturing and microfluidics applications. The in vitro models now focus on the 3D medium co-culturing of osteoblasts, osteoclasts, and osteocytes utilizing collagen for separation; this type of research allows for controlled medium and in-depth data analysis. Oxidative stress takes a toll on the domain, being beneficial as well as destructive. Reactive oxygen species (ROS) are molecules that influence the differentiation of osteoclasts, but over time their increasing presence can affect patients and aid the appearance of diseases such as osteoporosis. Oxidative stress can be limited by using antioxidants such as vitamin K and N-acetyl cysteine (NAC). Scaffolds and biocompatible coatings such as hydroxyapatite and bioactive glass are required to isolate the implant, protect the zone from the metallic, ionic exchange, and enhance the bone regeneration by mimicking the composition and structure of the body, thus enhancing cell proliferation. The materials can be further functionalized with growth factors that create a better response and higher chances of success for clinical use. This review highlights the vast majority of newly obtained information regarding bone tissue engineering, such as new co-culturing models, implant coatings, scaffolds, biomolecules, and the techniques utilized to obtain them.

Physical/Mechanical and Antibacterial Properties of Orthodontic Adhesives Containing Calcium Phosphate and Nisin

Enamel demineralization around orthodontic adhesive is a common esthetic concern during orthodontic treatment. The aim of this study was to prepare orthodontic adhesives containing monocalcium phosphate monohydrate (MCPM) and nisin to enable mineralizing and antibacterial actions. The physicomechanical properties and the inhibition of S. mutans growth of the adhesives with added MCPM (5, 10 wt %) and nisin (5, 10 wt %) were examined. Transbond XT (Trans) was used as the commercial comparison. The adhesive containing a low level of MCPM showed significantly higher monomer conversion (42–62%) than Trans (38%) (p < 0.05). Materials with additives showed lower monomer conversion (p < 0.05), biaxial flexural strength (p < 0.05), and shear bond strength to enamel than those of a control. Additives increased water sorption and solubility of the experimental materials. The addition of MCPM encouraged Ca and P ion release, and the precipitation of calcium phosphate at the bonding interface. The growth of S. mutans in all the groups was comparable (p > 0.05). In conclusion, experimental orthodontic adhesives with additives showed comparable conversion but lesser mechanical properties than the commercial material. The materials showed no antibacterial action, but exhibited ion release and calcium phosphate precipitation. These properties may promote remineralization of the demineralized enamel.

Ultrastructural changes of bovine tooth surfaces under erosion in presence of biomimetic hydroxyapatite

Enamel and dentin are susceptible to acids from food sources leading to dental erosion, a global problem affecting millions of individuals. Particulate hydroxyapatite (HAP) on the tooth surface can influence the effects of acid attacks. Standardized bovine enamel and dentin samples with artificial saliva are used in an in vitro cyclic demineralization–remineralization protocol to analyze the structural changes experienced by tooth surfaces using high-resolution scanning electron microscopy and to evaluate the potential of a HAP-based oral care gel in the protection of teeth from erosive attacks. The interfaces between HAP particle and enamel HAP crystallites are investigated using focused ion beam preparation and transmission electron microscopy. The results show that erosion with phosphoric acid severely affects enamel crystallites and dentin tubules, while artificial saliva leads to remineralization effects. The HAP-gel forms a microscopic layer on both enamel and dentin surfaces. Upon acid exposure, this layer is sacrificed before the native tooth tissues are affected, leading to significantly lower degrees of demineralization compared to the controls. This demonstrates that the use of particulate HAP as a biomaterial in oral care formulations can help protect enamel and dentin surfaces from erosive attacks during meals using a simple and effective protection principle.

The use of hydroxyapatite toothpaste to prevent dental caries

Dissolution of hydroxyapatite from the tooth structure at low pH can lead to the irreversible destruction of enamel and dentin, which if left untreated can result in pain and tooth loss. Hydroxyapatite toothpastes contain hydroxyapatite particles in micro- or nanocrystalline form that have been shown to deposit and restore demineralized enamel surfaces. As such, they are currently being explored as a fluoride-free anti-caries agent. This narrative review article aims to summarize the recent findings of the research investigating the remineralization potential of HAP toothpaste in vitro, in situ and in vivo, as well as some other applications in dentistry.

Anti-caries evaluation of a nano-hydroxyapatite dental lotion for use after toothbrushing: An in situ study

OBJECTIVES

The aim of this randomized, double-blind, two-arm crossover in situ study was to investigate whether nano-hydroxyapatite (nanoHAP) dental lotion (Apagard Deep Care) applied immediately after tooth-brushing with nanoHAP toothpaste (Apagard M-plus) enhances the remineralization promotion and the demineralization inhibition efficacies of nanoHAP toothpastes.

METHODS

64 sound enamel blocks and 64 blocks bearing artificially-produced initial caries were produced from human permanent molar teeth. During each treatment period, lasting 14 days per arm, two blocks, one sound and one lesion-bearing, were exposed to either 5% nanoHAP-containing or placebo dental lotion after tooth-brushing with 5% nanoHAP toothpaste, via an intra-oral appliance worn by 30 adults in each of the study groups. Baseline and post-test mineral loss were quantified using transverse microradiography (TMR). One-sided t-test of one group mean was used for intragroup comparison, while two-sided t-test of two independent means was used to compare the two dental lotions.

RESULTS

Pairwise comparison (baseline vs. post-test) indicated significant (p<.001) remineralization by nanoHAP toothpaste in both groups. However, when compared against each other, there was a significantly (p<.001) greater percentage of remineralization with nanoHAP lotion [58.4(±1.8)%] than with placebo lotion [37.7(±2.2)%]. TMR examination showed absolute demineralization inhibition in sound enamel blocks exposed to either lotions.

CONCLUSIONS

Toothpaste containing 5% nanoHAP effectively remineralized initial caries and inhibited demineralization of healthy enamel; however, the application of a dental lotion containing 5% nanoHAP after brushing resulted in superior remineralization compared to a placebo lotion.

CLINICAL SIGNIFICANCE

Dental lotion containing 5% nanohydroxyapatite used immediately after toothbrushing with 5% nanohydroxyapatite toothpaste can serve as an adjunct to enhance the clinical benefits of the toothpaste.

Cariogenic Biofilms: Development, Properties, and Biomimetic Preventive Agents

Oral biofilms will build up within minutes after cleaning of the dental hard tissues. While the application of remineralizing agents is a well-known approach to prevent dental caries, modern oral care products offer also additional active agents to maintain oral health. Human saliva contains many different organic and inorganic compounds that help to buffer organic acids produced by cariogenic microorganisms. However, most oral care products only contain remineralizing agents. To improve the benefit of those products, further active ingredients are needed. Books, review articles, and original research papers were included in this narrative review. Putting all these data together, we give an overview of oral biofilms and active compounds used in modern oral care products to interact with them. The special focus is on inorganic compounds and their interaction with oral biofilms. While organic compounds have several limitations (e.g., cell toxicity), inorganic compounds based on calcium and/or phosphate (e.g., sodium bicarbonate, hydroxyapatite, calcium carbonate) offer several advantages when used in oral care products. Calcium release can inhibit demineralization, and the release of hydroxide and phosphate ions might help in the buffering of acids. Therefore, the focus of this review is to summarize the scientific background of further active ingredients that can be used for oral care formulations.

The Potential of Hydroxyapatite Toothpaste to Prevent Root Caries: A pH-Cycling Study

PURPOSE

The effectiveness of a hydroxyapatite (HAP) toothpaste and a fluoride toothpaste in preventing root tissue demineralization (root caries) was compared using an established pH-cycling caries model.

MATERIALS AND METHODS

Sixty dentin blocks were produced from the root tissue of extracted human teeth and were assigned to 3 test groups (n=20/group): 10% hydroxyapatite toothpaste (HAP), 1450 ppm fluoride toothpaste (fluoride), and artificial saliva (artsaliva). Early root caries lesions were developed in each sample by 7-day demineralization using a pH-cycling caries model. The daily cyclic treatment regimen consists of two 2-minute toothpaste-slurry treatment periods, one 6-hour acid challenge using acidified gel (pH 4.5), and then storage in remineralizing solution (artsaliva) for the rest of the time. Demineralization was assessed as the amount of mineral loss (∆z) using transverse microradiography (TMR). Pairwise comparisons (between treatments) were performed using analysis of variance (ANOVA), and then Tukey's HSD for multiple comparisons. All p-values are considered significant if p<0.05.

RESULTS

Both ANOVA and Tukey's HSD indicated no significant (ANOVA; n=20) difference in mean ∆z among the groups, with least ∆z (±Sd) in the HAP (1117±366) compared to fluoride (1392±334) and artsaliva (1406±223). Relative to control, HAP and fluoride inhibited root demineralization by 21% and 6%, respectively.

CONCLUSION

Within the limit of the present study, the tested toothpaste containing 10% HAP is an effective root caries control toothpaste. Toothpaste containing 10% HAP was slightly more effective in preventing tooth demineralization than 1450 ppm fluoride provided as sodium fluoride. Thus, this study shows that HAP toothpastes can serve as an effective alternative to fluoride toothpastes for root caries management.

Drug Delivery (Nano)Platforms for Oral and Dental Applications: Tissue Regeneration, Infection Control, and Cancer Management

The oral cavity and oropharynx are complex environments that are susceptible to physical, chemical, and microbiological insults. They are also common sites for pathological and cancerous changes. The effectiveness of conventional locally-administered medications against diseases affecting these oral milieus may be compromised by constant salivary flow. For systemically-administered medications, drug resistance and adverse side-effects are issues that need to be resolved. New strategies for drug delivery have been investigated over the last decade to overcome these obstacles. Synthesis of nanoparticle-containing agents that promote healing represents a quantum leap in ensuring safe, efficient drug delivery to the affected tissues. Micro/nanoencapsulants with unique structures and properties function as more favorable drug-release platforms than conventional treatment approaches. The present review provides an overview of newly-developed nanocarriers and discusses their potential applications and limitations in various fields of dentistry and oral medicine.

Impact of a toothpaste with microcrystalline hydroxyapatite on the occurrence of early childhood caries: a 1-year randomized clinical trial

The aim of this trial was to determine whether a toothpaste with microcrystalline hydroxyapatite is not inferior to a fluoride toothpaste in prevention of caries in children. This double-blinded randomized control trial compared two toothpastes regarding the occurrence of caries lesions using International Caries Detection and Assessment System (ICDAS) ≥ code 1 on the primary dentition within 336 days. The test group used a fluoride-free hydroxyapatite toothpaste three times daily while control group used a toothpaste with fluoride. 207 children were included in the intention-to-treat analysis; 177 of them finished the study per protocol. An increase in caries ICDAS ≥ code 1 per tooth was observed in 72.7% of the hydroxyapatite-group (n = 88), compared with 74.2% of the fluoride-group (n = 89). The exact one-sided upper 95% confidence limit for the difference in proportion of participants with ICDAS increase ≥ 1 (-1.4%) was 9.8%, which is below the non-inferiority margin of 20% demonstrating non-inferiority of hydroxyapatite compared to the fluoride control toothpaste. This RCT showed for the first time, that in children, the impact of the daily use of a toothpaste with microcrystalline hydroxyapatite on enamel caries progression in the primary dentition is not inferior to a fluoride control toothpaste (Clinical Trials NCT03553966).

Whitening Effects of a Novel Oral Care Gel with Biomimetic Hydroxyapatite: A 4-Week Observational Pilot Study

The whitening effects of an oral care gel based on particulate microcrystalline hydroxyapatite, Ca₅(PO₄)₃(OH), were tested in a 4-week observational pilot study. Patients were recruited from two dental practices in Germany. Participants were asked to complete a questionnaire regarding their personal perception of their tooth color and brightness as well as the level of dentin hypersensitivity at the baseline and after 4 weeks of twice daily use of an oral care gel with hydroxyapatite. Data of 25 patients with a mean age of 46 ± 16 years were analyzed. Various subjective whitening parameters showed a tendency to be improved after the 4-week use. Additionally, patients reported that symptoms of dentin hypersensitivity were significantly reduced (p < 0.05, 95% confidence interval (CI): (0.8; 2.4)), and the tooth surface was significantly smoother (p < 0.05, 95% CI: (0.54; 1.6)). In conclusion, microcrystalline hydroxyapatite is a promising whitening agent for oral care formulations and represents a biomimetic alternative to other whitening agents for daily dental care.

In Vitro Whitening Effect of a Hydroxyapatite-Based Oral Care Gel

Objective  Oral care formulations aim to prevent oral diseases such as dental caries and gingivitis. Additionally, desire for white teeth still exists across all age groups. It is known that most whitening toothpastes are highly abrasive and can be harmful to teeth and gingiva. Therefore, a gel formulation with biomimetic hydroxyapatite (HAP; Ca ₅ [PO ₄ ] ₃ [OH]) as active ingredient was developed. This formulation was tested with respect to its tooth whitening properties in an in vitro study.

Materials and Methods  Enamel samples were allocated to either group (a) HAP gel, (b) whitening mouth rinse with phosphates, or (c) negative control (distilled water). Test products were applied by finger (a) or were rinsed (b, c) for 1, 3, and 9 (b and c only) cycles, respectively.

Results  Color changes (ΔE) were measured spectrophotometrically. Group (a) showed a significant increase in color changes with respect to whitening after one cycle (mean ΔE = 5.4 [±2.66], p  ≤ 0.006) and three cycles (mean ΔE = 11.2 [±3.11], p < 0.0001) compared to groups (b) and (c). For group (b), a significant increase in color change was measured after three (mean ΔE = 2.77 [±1.01], p = 0.02) and nine cycles (mean ΔE = 3.27 [±1.61], p = 0.006) compared to (c). Group (c) showed only minor and statistically insignificant color changes.

Conclusion  This in vitro study demonstrated a significantly higher ad hoc whitening effect of the HAP gel compared to the mouth rinse and water after short-time application.

Comparison of hydroxyapatite and fluoride oral care gels for remineralization of initial caries: a pH-cycling study

OBJECTIVE

The present in vitro study investigated if simulated daily use of hydroxyapatite-based gel (15% HAP) remineralizes early caries lesions as effective as weekly use of high fluoride (12,500 ppm) concentration gel, comparing them with artificial saliva alone.

MATERIALS AND METHODS

Three tooth blocks were produced from each of 20 bovine teeth. Caries-like lesion was created on each block by 4-day demineralization in acidified gel. The blocks were randomized into three remineralization groups (20 blocks/group); Hydroxyapatite-based gel (Karex gelée, 15% HAP, fluoride-free), fluoride-based gel (Elmex gelée, 12,500 ppm F-), and artificial saliva (AS). Remineralization was conducted using pH-cycling model for 28 days with storage in AS. The pH cycling model consisted of 2 h demineralization once daily for all groups, and 3 min HAP gel application once daily, 3 min fluoride gel application once weekly, or remain in AS only respectively. Baseline and post-test mineral loss were quantified using microradiography.

RESULTS

Paired t-tests (baseline vs. post-Test) indicated significant (p < 0.0001) remineralization in all groups. When compared against each other using Games-Howell's multiple comparison test, no significant difference in remineralization was observed between the two gels, but both gels exhibited significantly (p < 0.001) higher percentage mineral gain (HAP:39 ± 7%; fluoride:41 ± 11%) than AS alone (6 ± 2%).

CONCLUSION

Hydroxyapatite-based gel (15% HAP) was as effective as fluoride-based gel (12,500 ppm F-) in remineralizing initial caries lesion.

Daily Application of a Toothpaste with Biomimetic Hydroxyapatite and Its Subjective Impact on Dentin Hypersensitivity, Tooth Smoothness, Tooth Whitening, Gum Bleeding, and Feeling of Freshness

The aim of this observational study was to analyze the effect of a toothpaste with biomimetic zinc hydroxyapatite (HAP) on subjective parameters after a four-week home use. Patients with subjective dentin hypersensitivity were recruited at three dental practices in Germany and received a questionnaire with visual analogue scales and Likert scales both at baseline and follow-up. The questionnaire was specifically developed for this study and focused on questions about subjective parameters like dentin hypersensitivity, tooth surface texture, tooth color, and freshness after toothbrushing. Patients answered the questionnaire both at baseline and after a four-week home use (follow-up) of the HAP toothpaste. Data of 46 patients were analyzed by paired t-test and non-parametric Wilcoxon signed-rank test, respectively. Subjective parameters on dentin hypersensitivity were reduced after the four-week use of the HAP toothpaste (p < 0.001). Additionally, patients assessed their tooth surface as smoother (p < 0.001), tooth color as whiter (p = 0.003), and reported a stronger feeling of freshness after toothbrushing (p = 0.014) after four-week use of the HAP toothpaste compared to the previously used toothpaste. In conclusion, the tested toothpaste with biomimetic HAP is well-suited for individuals suffering from dentin hypersensitivity, because subjective symptoms on dentin hypersensitivity were reduced. Additionally, patients reported smoother and whiter teeth after using the HAP toothpaste.