Modes of Action and Clinical Efficacy of Particulate Hydroxyapatite in Preventive Oral Health Care − State of the Art

Clinical Evaluation of the Effect of Nanohydroxyapatite Lozenge on the pH of Dental Plaque

Purpose

This study investigated the influence of nanohydroxyapatite-containing (nanoHAP) lozenge on plaque pH following sucrose intake.

Patients and Methods

Sixteen adult subjects were enrolled in this double-blind crossover study composed of four interventions: (1) 10% w/v sucrose solution, (2) 10% w/v sorbitol solution, (3) nanoHAP lozenge, and (4) 10% w/v sucrose solution challenge followed by nanoHAP lozenge. Following the determination of each subject's resting plaque pH, the pH was measured at different time intervals from 3 to 30 minutes from the start of intervention, with 7 days interval between the applications of different interventions. The data were analyzed using the analysis of variance and Tukey's test (α < 0.05).

Results

While sorbitol produces no change in plaque pH, nanoHAP-lozenge increased the plaque pH from a baseline of 7.0 ± 0.3 (mean ± sd) to 7.8 ± 0.2 (mean ± sd) within 30 minutes. Sucrose lowered the plaque pH from a baseline of 7.0 ± 0.4 (mean ± sd) to the lowest minimum of 5.1 ± 0.1 (mean ± sd) at the 7th minute, rising above the critical pH of enamel dissolution (5.5) at 12th minute and the baseline pH in more than 30 minutes. With lozenge intervention following sucrose challenge, plaque pH rose to 5.5 in 8 min, and to the baseline pH in 24 min. The cH area (Hydrogen ion concentration area) produced by sucrose (1.82 sq. units) was significantly (p < 0.05) greater than that produced when sucrose was challenged with lozenge (0.48 sq. units).

Conclusion

Nanohydroxyapatite-containing lozenge increased plaque pH, reduced plaque pH drop in the presence of sucrose, and facilitated the rapid recovery of plaque pH after sucrose intake.

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.

Case Report on Caries Assessment Using Intraoral Scanner Compared with Bitewing Radiographs

Dental caries remains one of the main reasons patients seeing their dentist. They either show up for preventive measures, diagnostics, or treatment of present caries lesions. To date, diagnostics are performed visually, supported by using bitewing radiographs. While radiographic diagnostics should only be performed on a biannual basis, and some caries process will not be seen with visual diagnostics, there remains a lack in regular checkups. Therefore, different technical applications can be used for regular diagnostics. One of those is the near-infrared imaging (NIRI) technology. In this case report, a patient presented with incipient caries lesions. These lesions were diagnosed visually, radiographically, and using NIRI. After diagnosis of incipient caries lesions, the patient was advised to use a hydroxyapatite toothpaste and a hydroxyapatite gel for the remineralization of the lesions and prevention of caries progression. The patient was followed up for 6 months with regular checkups in between. Visual diagnostics and NIRI were used to detecting the caries progress. After 6 months, bitewing radiographs were used in addition. In this clinical investigation we were able to show for the first time that NIRI and bitewing radiographs are able to detect and follow incipient caries lesions. Additionally, this study highlights that hydroxyapatite-containing oral care products are able to arrest and remineralize the caries process.

Bioactivity and remineralization potential of modified glass ionomer cement: A systematic review of the impact of calcium and phosphate ion release

This systematic review investigates the effectiveness of calcium and phosphate ions release on the bioactivity and remineralization potential of glass ionomer cement (GIC). Electronic databases, including PubMed-MEDLINE, Scopus, and Web of Science, were systematically searched according to PRISMA guidelines. This review was registered in the PROSPERO database. Five eligible studies on modifying GIC with calcium and phosphate ions were included. The risk of bias was assessed using the RoBDEMAT tool. The incorporation of these ions into GIC enhanced its bioactivity and remineralization properties. It promoted hydroxyapatite formation, which is crucial for remineralization, increased pH and inhibited cariogenic bacteria growth. This finding has implications for the development of more effective dental materials. This can contribute to improved oral health outcomes and the management of dental caries, addressing a prevalent and costly oral health issue. Nevertheless, comprehensive longitudinal investigations are needed to evaluate the clinical efficacy of this GIC's modification.

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.

Remineralization Strategies for Teeth with Molar Incisor Hypomineralization (MIH): A Literature Review

Molar incisor hypomineralization (MIH) is a highly prevalent dental developmental disorder with a significant health burden for patients and high treatment needs, yet no comprehensive review article on all remineralization systems as a non-invasive treatment approach for MIH has been published. Typical characteristics of MIH-affected teeth are a lower mineral density and lower hardness compared to healthy teeth leading to sensitivity and loss of function. Thus, the use of formulations with calcium phosphates to remineralize MIH-affected teeth is reasonable. This review presents an up-to-date overview of remineralization studies focusing on active ingredients investigated for remineralization of MIH, i.e., casein phosphopeptide amorphous calcium phosphate (CPP-ACP), casein phosphopeptide amorphous calcium fluoride phosphate (CPP-ACFP), hydroxyapatite, calcium glycerophosphate, self-assembling peptide, and fluoride. Overall, 19 studies (in vitro, in situ, and in vivo) were found. Furthermore, an additional search for studies focusing on using toothpaste/dentifrices for MIH management resulted in six studies, where three studies were on remineralization and three on reduction of sensitivity. Overall, the studies analyzed in this review showed that MIH-affected teeth could be remineralized using calcium phosphate-based approaches. In conclusion, calcium phosphates like CPP-ACP, calcium glycerophosphate, and hydroxyapatite can be used to remineralize MIH-affected teeth. In addition to MIH-remineralization, CPP-ACP and hydroxyapatite also offer relief from MIH-associated tooth sensitivity.

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.

Comparative assessment of the remineralization characteristics of nano-hydroxyapatite extracted from fish scales and eggshells

OBJECTIVES

Dentine hypersensitivity (DH) is a common concern in dentistry that has the potential to restrict daily activities and harm a person's quality of life. In this study, the remineralization characteristics of nano-hydroxyapatite (nHAp) extracted from waste eggshells and fish scales were comparatively assessed.

MATERIALS AND METHODS

The extraction methods used to obtain nHAp from both fish scales and eggshells are also described. The effect of the extraction process and bio-waste source on the physicochemical characteristics of the nHAp such as Ca/P ratio, functional groups, crystallinity and phase change, and surface morphology are presented in the study. The remineralization properties were evaluated using dentine models (n = 15). A field scanning electron microscope was used to evaluate the effectiveness of the dentine tubules occlusion. The percentage occluded area for all the specimens was evaluated statistically using a one-way analysis of variance (α = 0.05).

RESULTS

The results showed that there were variations in the physicochemical characteristics of the nHAp extracted, including the crystallinity, particle size, and surface morphology, and buffering effects against citric acids. The EnHAp extracted from eggshells had higher crystallinity, superior buffering effects, and smaller particle size compared to the nHAp extracted from fish scales, making it a more favourable material for remineralization of teeth. The statistical evidence showed that there were statistically significant differences in the dentine occluding properties measured in the nHAp (p < 0.001). The highest mean % occluded area was measured with the EnHAp group.

CONCLUSIONS

The findings of this study provide insights into the use of bio-waste materials for the development of sustainable and effective products for oral health care.

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.

Influence of the Amount of Toothpaste on Cleaning Efficacy: An In Vitro Study

OBJECTIVES

 The aim of this in vitro study was to test the influence of the amount of toothpaste on enamel cleaning efficacy.

MATERIALS AND METHODS

 The hydrated silica-based test toothpaste (radioactive dentin abrasion: 60.19 ± 1.35) contained all ingredients of a regular fluoride toothpaste. The cleaning efficacy of four different toothpaste amounts (1.00 g, 0.50 g [both "full length of brush"], 0.25 g ["pea-size"], and 0.125 g ["grain of rice-size"]) diluted in 1.00 mL water were each tested for different brushing times (10, 30, 60, 120, 180, and 300 seconds) using a standardized staining model on human molars with a brushing machine. Photographic documentation and colorimetric measurements were conducted, respectively, initially, after staining and after each brushing step. Colorimetric measurements were used to calculate the stain removal (in %).

STATISTICAL ANALYSIS

 Results were analyzed by one-way analysis of variance with post hoc Tukey test and Levene's test for analysis of homogeneity of variance. The level of significance α was set at ≤ 0.05.

RESULTS

 The cleaning efficacy decreased significantly when using smaller toothpaste amounts. Stain removal after 120 seconds brushing time was: 77.4 ± 5.0% (1.00 g toothpaste), 75.7 ± 3.4% (0.50 g toothpaste), 54.1 ± 6.7% (0.25 g toothpaste), and 48.2 ± 7.1% (0.125 g toothpaste), respectively.

CONCLUSION

 In this in vitro study the cleaning efficacy of a medium-abrasive, hydrated silica-based toothpaste was analyzed. Note that 1.00 g toothpaste showed for all brushing times a significantly higher cleaning efficacy than 0.25 g toothpaste and 0.125 g toothpaste.

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.

Electrophoresis-Aided Biomimetic Mineralization System Using Graphene Oxide for Regeneration of Hydroxyapatite on Dentin

Graphene oxide (GO) is an emerging luminescent carbon nanomaterial with the ability to foster hydroxyapatite (HA). A specially designed electrophoresis system can be used to accelerate the mineralization process. The aim of this study was to promote HA crystal growth on demineralized dentin using a GO incorporated electrophoresis system. GO was successfully synthesized by carbonization of citric acid and its presence was confirmed by Fourier transform infrared and UV-visible spectrophotometry evaluation. Dentin slices were placed in demineralized solution and divided into control (without the electrophoresis system) and experimental group. Demineralized dentin slices in the experimental group were remineralized using the electrophoresis system for 8 h/1.0 mA, with one subgroup treated without GO and the other with GO. Energy dispersive spectroscopy evaluation showed that the calcium/phosphate ratio of the crystal formed in control and experimental group with addition of GO was close to natural hydroxyapatite. However, scanning electron microscopy evaluation showed that the exposed dentinal tubules were occluded with rod-like crystals, which is similar to native enamel morphology, in the experimental group with addition of GO compared to the flake-like crystal in the control group. Mechanical evaluation revealed that the nanohardness and modulus of remineralized dentin were significantly higher in the experimental group. In conclusion, GO is a promising material to remineralize dentin and the introduction of an electrophoresis system can accelerate its process.

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.

Influence of childhood asthma on dental caries: A longitudinal study

OBJECTIVES

The study investigated the influence of childhood asthma on dental caries development and caries risk factors among children with asthma in Slovenia.

MATERIAL AND METHODS

The study population consisted of 2-17 years old children (n = 138), who had used anti-asthmatic medicines for at least 1 year. Controls were their non-asthmatic siblings (n = 140). International Caries Detection and Assessment System-II was used to assess caries status. After 3 years, 106 baseline participants (53 asthmatic and 53 siblings) were reexamined. Questionnaires completed by parents and data from the patients' medical records provided information on demographics, child's medical history, medication usage, and oral health behaviors. Additional 308 asthmatic children were examined to assess caries risk factors among children with asthma.

RESULTS

Asthmatic children had significantly higher mean d12 fs and D12 MFS (p ≤ 0.05), and fewer caries-free individuals (p ≤ 0.01). In asthmatic children, 3 years mean increment in D12 MFS was significantly higher (p ≤ 0.05). Furthermore, progression over 3 years from sound tooth surfaces to decayed cavitated and filled lesions in primary and permanent teeth were present in significantly higher (p ≤ 0.05) percentage, and likewise transition from decayed cavitated lesions to missing tooth surfaces because of caries in primary teeth, and from filled to filled non-cavitated and cavitated lesions in permanent teeth. Lower caries experience in asthmatic children was associated with lower doses of inhaled glucocorticoid use, leucotriene antagonist use, and daily milk and cheese consumption.

CONCLUSIONS

Asthmatic children who had used anti-asthmatic medicines had higher caries experience and higher caries progression over 3 years in both primary and permanent dentitions. Besides anti-asthmatic medicines, other factors were associated with higher caries experience in asthmatic children.

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.

The in situ potential of synthetic nano-hydroxyapatite for tooth enamel repair

This study was designed to evaluate whether nano-hydroxyapatite toothpastes with or without fluoride would be more advantageous than a fluoride toothpaste in the repair of eroded enamel in situ. Twenty-one subjects participated in this single-blind, randomized, cross-over design study with three 7-day treatment phases. In each phase, the subjects wearing a palatal appliance containing five sterilized enamel specimens used either one of the two test regimens (1% nano-hydroxyapatite toothpaste and 2.25% nano-hydroxyapatite/1450 parts per million (ppm) fluoride toothpaste) or one control (1400 ppm fluoride toothpaste). Enamel specimens were extraorally demineralized (4 × 5 min/day) and were intraorally treated with the toothpastes (2 × 2 min/day). The nano-hydroxyapatite toothpaste groups exhibited significantly higher surface microhardness than did the standard fluoride toothpaste group (p < 0.05). Enamel surface hardness was increased only by nano-hydroxyapatite toothpastes after in situ treatment compared with the baseline (p < 0.05). Morphological analysis demonstrated an apatite-type crystal deposition on the eroded enamel surface produced by nano-hydroxyapatite toothpastes, while fluoride toothpaste failed to show any significant surface deposition. Chemical analysis showed a higher content of calcium and phosphorus in the enamel surface treated with nano-hydroxyapatite toothpastes compared with that in the control one (p < 0.05). It is concluded that home use of nano-hydroxyapatite containing toothpastes may have a protective effect against erosion at the enamel surface.

Hydroxyapatite in Oral Care Products-A Review

Calcium phosphate compounds form the inorganic phases of our mineralised tissues such as bone and teeth, playing an important role in hard tissue engineering and regenerative medicine. In dentistry and oral care products, hydroxyapatite (HA) is a stable and biocompatible calcium phosphate with low solubility being used for various applications such as tooth remineralisation, reduction of tooth sensitivity, oral biofilm control, and tooth whitening. Clinical data on these products is limited with varied results; additionally, the effectiveness of these apatite compounds versus fluoride, which has conventionally been used in toothpaste, has not been established. Therefore, this review critically evaluates current research on HA oral care, and discusses the role and mechanism of HA in remineralisation of both enamel and dentine and for suppressing dentine sensitivity. Furthermore, we position HA’s role in biofilm management and highlight the role of HA in dental applications by summarising the recent achievement and providing an overview of commercialised HA dental products. The review also indicates the existing limitations and provides direction for future research and commercialisation of apatite-based oral care products.

SEM/EDS Evaluation of the Mineral Deposition on a Polymeric Composite Resin of a Toothpaste Containing Biomimetic Zn-Carbonate Hydroxyapatite (microRepair®) in Oral Environment: A Randomized Clinical Trial

Toothpastes containing biomimetic hydroxyapatite have been investigated in recent years; the behavior of this material in the oral environment has been evaluated directly on dental enamel showing a marked remineralizing activity. To propose microRepair^®-based toothpastes (Zn-carbonate hydroxyapatite) for the domiciliary oral hygiene in patients with dental composite restorations, the aim of this study was to evaluate the deposition of Zn-carbonate hydroxyapatite on a polymeric composite resin with Scanning Electron Microscopy/Energy-Dispersive X-ray Spectrometry (SEM/EDS) analysis. Twenty healthy volunteers underwent the bonding of 3 orthodontic buttons on the vestibular surfaces of upper right premolars and first molar. On the surface of the buttons, a ball-shaped mass of composite resin was applied and light-cured. Then, the volunteers were randomly divided into two groups according to the toothpaste used for domiciliary oral hygiene: the Control toothpaste containing stannous fluoride and the Trial toothpaste containing microRepair^®. The buttons were debonded after 7 days (T1—first premolar), after 15 days (T2—second premolar), and after 30 days (T3—first molar) to undergo the SEM/EDS analysis. The deposition of calcium, phosphorus, and silicon was assessed through EDS analysis and data were submitted to statistical analysis (p < 0.05). SEM morphologic evaluation showed a marked deposition of the two toothpastes on the surfaces of the buttons. EDS quantitative analysis showed an increase of calcium, phosphorus, and silicon in both the groups, with a statistically significant difference of calcium deposition at T3 for the Trial group. Therefore, the use of toothpaste containing Zn-carbonate hydroxyapatite could be proposed as a device for domiciliary oral hygiene because the deposition of hydroxyapatite on polymeric composite resin could prevent secondary caries on the margins of restorations.

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.

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.