Dentin remineralizing ability and enhanced antibacterial activity of strontium and hydroxyl ion co-releasing radiopaque hydroxyapatite cement

Antimicrobial and Antibiofilm Properties of Hydroxyapatite/Nano-Hydroxyapatite in Preventing Dental Caries: A Systematic Review

Controlling biofilm is a crucial strategy and an essential component of preventing dental caries. Considerable research has been conducted in recent years on the clinical application of hydroxyapatite (HAp) and hydroxyapatite nanoparticles (nHAp) in preventing dental caries. However, these studies have yet to investigate the effectiveness or mechanism of these substances as antibacterial and antibiofilm agents. This study aimed to provide a thorough analysis of the current evidence on the antibacterial and antibiofilm characteristics of HAp/nHAp in the prevention of dental caries. Searches were conducted across five databases: Cochrane Library, PubMed, Scopus, EBSCOhost, and ScienceDirect. Google Scholar was also searched. Titles, abstracts, and full text were evaluated following the guidelines set by the Preferred Reporting Item for Systematic Review and Meta-Analyses (PRISMA). A methodological quality assessment of the studies was conducted using the QUIN tool. The initial retrieval totaled 15,047 studies, from which 3,487 were excluded. A total of 11,560 studies were screened based on the title and abstract, resulting in 24 full-text studies considered potentially eligible for inclusion (κ = 0.9599). Finally, 19 studies met all the defined inclusion criteria and were included in this comprehensive systematic review (κ = 0.8837). HAp/nHAp demonstrates antimicrobial activities against gram-negative and gram-positive bacteria and fungi. However, nHAp's antibiofilm efficacy remains limited. Further investigation is required to improve the efficacy of antibacterial and antibiofilm agents.

Antimicrobial Potential of Strontium-Functionalized Titanium Against Bacteria Associated With Peri-Implantitis

OBJECTIVES

To explore the antimicrobial potential of strontium (Sr)-functionalized wafers against multiple bacteria associated with per-implant infections, in both mono- and multispecies biofilms.

MATERIALS AND METHODS

The bactericidal and bacteriostatic effect of silicon wafers functionalized with a strontium titanium oxygen coating (Sr-Ti-O) or covered only with Ti (controls) against several bacteria, either grown as a mono-species or multispecies biofilms, was assessed using a bacterial viability assay and a plate counting method. Mono-species biofilms were assessed after 2 and 24 h, while the antimicrobial effect on multispecies biofilms was assessed at Days 1, 3, and 6. The impact of Sr functionalization on the total percentage of Porphyromonas gingivalis in the multispecies biofilm, using qPCR, and gingipain activity was also assessed.

RESULTS

Sr-functionalized wafers, compared to controls, were associated with statistically significant less viable cells in both mono- and multispecies tests. The number of colony forming units (CFUs) within the biofilm was significantly less in Sr-functionalized wafers, compared to control wafers, for Staphylococcus aureus at all time points of evaluation and for Escherichia coli at Day 1. Gingipain activity was less in Sr-functionalized wafers, compared to control wafers, and the qPCR showed that P. gingivalis remained below detection levels at Sr-functionalized wafers, while it consisted of 15% of the total biofilm on control wafers at Day 6.

CONCLUSION

Sr functionalization displayed promising antimicrobial potential, possessing bactericidal and bacteriostatic ability against bacteria associated with peri-implantitis grown either as mono-species or mixed in a multispecies consortium with several common oral microorganisms.

Applications of Bioactive Strontium Compounds in Dentistry

Divalent cations have captured the interest of researchers in biomedical and dental fields due to their beneficial effects on bone formation. These metallic elements are similar to trace elements found in human bone. Strontium is a divalent cation commonly found in various biomaterials. Since strontium has a radius similar to calcium, it has been used to replace calcium in many calcium-containing biomaterials. Strontium has the ability to inhibit bone resorption and increase bone deposition, making it useful in the treatment of osteoporosis. Strontium has also been used as a radiopacifier in dentistry and has been incorporated into a variety of dental materials to improve their radiopacity. Furthermore, strontium has been shown to improve the antimicrobial and mechanical properties of dental materials, promote enamel remineralization, alleviate dentin hypersensitivity, and enhance dentin regeneration. The objective of this review is to provide a comprehensive review of the applications of strontium in dentistry.

Bioactive ceramic-based materials: beneficial properties and potential applications in dental repair and regeneration

Bioactive ceramics, primarily consisting of bioactive glasses, glass-ceramics, calcium orthophosphate ceramics, calcium silicate ceramics and calcium carbonate ceramics, have received great attention in the past decades given their biocompatible nature and excellent bioactivity in stimulating cell proliferation, differentiation and tissue regeneration. Recent studies have tried to combine bioactive ceramics with bioactive ions, polymers, bioactive proteins and other chemicals to improve their mechanical and biological properties, thus rendering them more valid in tissue engineering scaffolds. This review presents the beneficial properties and potential applications of bioactive ceramic-based materials in dentistry, particularly in the repair and regeneration of dental hard tissue, pulp-dentin complex, periodontal tissue and bone tissue. Moreover, greater insights into the mechanisms of bioactive ceramics and the development of ceramic-based materials are provided.

Mechanical properties of simulated dentin caries treated with metal cations and L-ascorbic acid 2-phosphate

This pH cycling study aimed to investigate the effects of L-Ascorbic acid 2-phosphate (AA2P) salts of Mg, Zn, Mn, Sr, and Ba on the surface microhardness, compressive strength, diametral tensile strength (DTS), and solubility of root canal dentin. 186 cylindrical dentin specimens from 93 teeth were fortified with optimal concentrations of AA2P salts of Mg (0.18 mM), Zn (5.3 µM), Mn (2.2 × 10-8 M), Sr (1.8 µM), and Ba (1.9 µM). Saline was used as the control group. These dentin specimens underwent a 3-day cycling process simulating dentin caries formation through repeated sequences of demineralization and remineralization. Surface microhardness at 100 and 500 µm depths (n = 10/subgroup), scanning electron microscopy (n = 3/group), compressive strength (n = 10/group), DTS (n = 6/group), and solubility (n = 5/group) tests were performed to analyze the dentin specimens. Data were analyzed using Kolmogorov-Smirnov, one-way ANOVA, and Post Hoc Tukey tests (p < 0.05). The control group had significantly lower microhardness at both depths (p < 0.001), reduced DTS (p = 0.001), decreased compressive strength (p < 0.001), and higher weight loss (p < 0.001) than all other groups. The Sr group had the highest compressive strength and microhardness among all the groups. The microhardness was significantly higher for the 500 µm depth than the 100 µm depth (p < 0.001), but the difference in microhardness between depths across groups was not significant (p = 0.211). All fortifying solutions provided some protection against artificial caries lesions. Therefore, these elements might have penetrated and reinforced the demineralized dentin against acid dissolution.

Glass ionomer cement with calcium-releasing particles: Effect on dentin mineral content and mechanical properties

OBJECTIVE

to evaluate the effect a glass ionomer cement (GIC) containing hydroxyapatite (HAp) or calcium silicate (CaSi) particles on mineral content and mechanical properties of demineralized dentin. Ion release and compressive strength (CS) of the cements were also evaluated.

METHODS

GIC (Fuji 9 Gold Label, GC), GIC+ 5%HAp and GIC+ 5%CaSi (by mass) were evaluated. Ion release was determined by induced coupled plasma optical emission spectroscopy (Ca2+/Sr2+) or ion-specific electrode (F-) (n = 3). A composite (Filtek Z250, 3 M ESPE) was used as control in remineralization tests. Demineralized dentin discs were kept in contact with materials in simulated body fluid (SBF) at 37 °C for eight weeks. Mineral:matrix ratio (MMR) was determined by ATR-FTIR spectroscopy (n = 5). Dentin hardness (H) and elastic modulus (E) were determined by nanoindentation (n = 10). CS was tested after 24 h and 7d in deionized water (n = 12). Data were analyzed by ANOVA/Tukey test (α = 0.05).

RESULTS

Ca2+ and Sr2+ release was higher for the modified materials (p < 0.05). Only GIC+ 5%HAp showed higher F- release than the control (p < 0.05). All groups showed statistically significant increases in MMR, with no differences among them after 8 weeks (p > 0.05). No differences in dentin H or E were observed among groups (p > 0.05). HAp-modified GIC showed increased initial CS, while adding CaSi had the opposite effect (p < 0.05). After 7 days, GIC+ 5%CaSi presented lower CS in relation to control and GIC+ 5%HAp (p < 0.05).

SIGNIFICANCE

GIC modification with HAp or CaSi affected CS and increased ion release; however, none of the groups showed evidence of dentin remineralization in comparison to the negative control.

The Effect of Doping on the Electrical and Dielectric Properties of Hydroxyapatite for Medical Applications: From Powders to Thin Films

Recently, the favorable electrical properties of biomaterials have been acknowledged as crucial for various medical applications, including both bone healing and growth processes. This review will specifically concentrate on calcium phosphate (CaP)-based bioceramics, with a notable emphasis on hydroxyapatite (HA), among the diverse range of synthetic biomaterials. HA is currently the subject of extensive research in the medical field, particularly in dentistry and orthopedics. The existing literature encompasses numerous studies exploring the physical-chemical, mechanical, and biological properties of HA-based materials produced in various forms (i.e., powders, pellets, and/or thin films) using various physical and chemical vapor deposition techniques. In comparison, there is a relative scarcity of research on the electrical and dielectric properties of HA, which have been demonstrated to be essential for understanding dipole polarization and surface charge. It is noteworthy that these electrical and dielectric properties also offer valuable insights into the structure and functioning of biological tissues and cells. In this respect, electrical impedance studies on living tissues have been performed to assess the condition of cell membranes and estimate cell shape and size. The need to fill the gap and correlate the physical-chemical, mechanical, and biological characteristics with the electrical and dielectric properties could represent a step forward in providing new avenues for the development of the next-generation of high-performance HA-doped biomaterials for future top medical applications. Therefore, this review focuses on the electrical and dielectric properties of HA-based biomaterials, covering a range from powders and pellets to thin films, with a particular emphasis on the impact of the various dopants used. Therefore, it will be revealed that each dopant possesses unique properties capable of enhancing the overall characteristics of the produced structures. Considering that the electrical and dielectric properties of HA-based biomaterials have not been extensively explored thus far, the aim of this review is to compile and thoroughly discuss the latest research findings in the field, with special attention given to biomedical applications.

Assessment of physical/mechanical properties and cytotoxicity of dual-cured resin cements containing Sr-bioactive glass nanoparticles and calcium phosphate

The aim was to develop dual-cured resin cements containing Sr-bioactive glass nanoparticles (Sr-BGNPs; 5 or 10 wt%) and monocalcium phosphate monohydrate (MCPM; 3 or 6 wt%). Effects of additives on degree of monomer conversion (DC), biaxial flexural strength/modulus, shear bond strength (SBS), mass/volume change, color stability, ion release, and cytotoxicity were examined. Controls included material without reactive fillers and Panavia SA Plus (PV). Experimental cements showed higher DC than PV regardless of light activation (p<0.05). Mean SBS and color stability were comparable between experimental cements and PV. Cell viability upon the exposure to sample extracts of experimental cements was 80%-92%. High additive concentrations led to lower strength and modulus than PV (p<0.05). The additives increased mass change, reduced color stability, and promoted ion release. The experimental resin cements demonstrated acceptable mechanical/chemical properties and cytotoxicity. The additives reduced the strength but provided ion release, a desirable action to prevent recurrent caries.

Synergistic effect of ion-releasing fillers on the remineralization and mechanical properties of resin-dentin bonding interfaces

In modern restorative dentistry, adhesive resin materials are vital for achieving minimally invasive, esthetic, and tooth-preserving restorations. However, exposed collagen fibers are found in the hybrid layer of the resin-dentin bonding interface due to incomplete resin penetration. As a result, the hybrid layer is susceptible to attack by internal and external factors such as hydrolysis and enzymatic degradation, and the durability of dentin bonding remains limited. Therefore, efforts have been made to improve the stability of the resin-dentin interface and achieve long-term clinical success. New ion-releasing adhesive resin materials are synthesized by introducing remineralizing ions such as calcium and phosphorus, which continuously release mineral ions into the bonding interface in resin-bonded restorations to achieve dentin biomimetic remineralization and improve bond durability. As an adhesive resin material capable of biomimetic mineralization, maintaining excellent bond strength and restoring the mechanical properties of demineralized dentin is the key to its function. This paper reviews whether ion-releasing dental adhesive materials can maintain the mechanical properties of the resin-dentin bonding interface by supplementing the various active ingredients required for dentin remineralization from three aspects: phosphate, silicate, and bioactive glass.

Addition of metal chlorides to a HOCl conditioner can enhance bond strength to smear layer deproteinized dentin

OBJECTIVES

To evaluate the effect of smear layer deproteinization using hypochlorous acid (HOCl) with/without metal chlorides (SrCl₂ and ZnCl₂) on the microtensile bond strength (µTBS) of two simplified adhesives to dentin.

METHODS

Human dentin surfaces with a standardized smear layer were pretreated using a 105 ppm HOCl solution with/without SrCl₂ (0.05 M, 0.1 M, 0.2 M, 0.4 M) or ZnCl₂ (0.05 M, 0.1 M, 0.2 M) for 5 s, 15 s, or 30 s. After the deproteinizing solution was washed out with water for 5 s, 15 s, or 30 s, pretreated surfaces were bonded with one-step self-etch adhesive Bond Force II or universal adhesive Clearfil Universal Bond Quick, and µTBS was measured after 24 h. Additionally, the deproteinizing effects of HOCl solutions with/without the metal chlorides were compared by measuring changes in the amide:phosphate ratio using attenuated total reflection Fourier transform infrared spectroscopy. Statistical analysis was performed using multifactor ANOVA, Tukey's post hoc tests and t-tests (p < 0.05).

RESULTS

Pretreatment with pure HOCl for 15 s and 30 s significantly decreased the amide:phosphate ratio (p < 0.05), indicating effective deproteinization, but the µTBS of both adhesives increased significantly only if HOCl was washed out for 30 s (p < 0.05). Increasing the concentrations of metal chlorides enabled shortening of the wash-out time down to 5 s while maintaining the improved µTBS (p < 0.05). The deproteinizing effect of HOCl was not significantly altered by the addition of metal chlorides (p > 0.05).

SIGNIFICANCE

The effectiveness of smear layer deproteinization using HOCl can be improved by the addition of metal chlorides, as their increasing concentration allowed to shorten the wash-out time from 30 s down to 5 s.

Functional role of inorganic trace elements in dentin apatite tissue-Part 1: Mg, Sr, Zn, and Fe

Many essential elements exist in nature with significant influence on dentin and bone apatite tissue. Hydroxyapatite (HAp) is the major inorganic crystalline structure of dentin that provides a site for various physiological functions such as surface layer ion exchange. Decades of apatite research have shown that enamel is a high-substituted crystalline apatite, but recent findings suggest that dentin apatite may play a more important role in regulating ion exchange as well as mineral crystallinity. This article is the first part of a review series on the functional role of inorganic trace elements including magnesium, strontium, zinc, and iron in dentin hydroxyapatite. The morphology, physiology, crystallinity, and solubility of these elements as they get substituted into the HAp lattice are extensively discussed. An electronic search was performed on the role of these elements in dentin apatite from January 2007 to September 2021. The relationship between different elements and their role in the mineral upkeep of dentin apatite was evaluated. Several studies recognized the role of these elements in dentinal apatite composition and its subsequent effects on morphology, crystallinity, and solubility. These elements are of great importance in physiological processes and an essential part of living organisms. Magnesium and strontium stimulate osteoblast activity, while zinc can improve overall bone quality with its antibacterial properties. Iron nanoparticles are also vital in promoting bone tissue growth as they donate or accept electrons in redox reactions. Thus, understanding how these elements impact dentin apatite structure is of great clinical significance.

Comparative evaluation of decalcifying agents for dissolution of pulp stones: An in vitro study

Background:

Despite constant advances in science, obscurity remains in the efficient removal of pulp stones to aid in successful root canal treatment. In this context, chemical means of dissolving pulp stones were explored.

Aim:

The aim of this study is to evaluate and to compare the efficacy of decalcifying agents on the dissolution of pulp stones.

Materials and Methods:

The study was divided into two groups for pulp stone analysis (21 samples) and dentin analysis (54 samples). Twenty-one pulp stones from patients aged 18–70 who underwent root canal treatment were collected and divided into three subgroups (n = 7) randomly. They were subjected to chemical treatment in a labeled glass container with 5 ml of the respective chemical agents, such as 17% ethylenediaminetetraacetic acid solution (positive control), no treatment (negative control), and newly developed Physiological Simulated Decalcifying Agent (PSDA). At the end of the study period (24 h), the samples were removed, rinsed with deionized water, and subjected to physical analysis, scanning electron microscopy (SEM), and Energy –dispersive X-ray spectroscopy (EDS) analysis. Under dentin analysis, 54 maxillary premolars scheduled for orthodontic extraction without caries or extensive restorations were selected, following which 2-mm thick transverse dentinal sections at the cementoenamel junction level were obtained and randomly divided into two groups for SEM (n = 21) and microhardness analysis (n = 33). The samples were subjected to respective chemical treatment groups similar to pulp stones for 24 h and analyzed using SEM, EDS, and microhardness analysis.

Results:

Postchemical treatment with the newly developed decalcifying solution, the pulp stones showed the absence of nodular crystallites and surface softening under SEM and a decrease in the calcium level under EDS analysis. Concerning the microhardness of dentin, no significant changes could be observed.

Conclusion:

The newly explored PSDA was found to be efficacious in the decalcification of pulp stones at a clinically relevant time of 24 h, without significantly affecting the structural integrity and the hardness values of dentin.

Factors influencing the drug release from calcium phosphate cements

Thanks to their biocompatibility, biodegradability, injectability and self-setting properties, calcium phosphate cements (CPCs) have been the most economical and effective biomaterials of choice for use as bone void fillers. They have also been extensively used as drug delivery carriers owing to their ability to provide for a steady release of various organic molecules aiding the regeneration of defective bone, including primarily antibiotics and growth factors. This review provides a systematic compilation of studies that reported on the controlled release of drugs from CPCs in the last 25 years. The chemical, compositional and microstructural characteristics of these systems through which the control of the release rates and mechanisms could be achieved have been discussed. In doing so, the effects of (i) the chemistry of the matrix, (ii) porosity, (iii) additives, (iv) drug types, (v) drug concentrations, (vi) drug loading methods and (vii) release media have been distinguished and discussed individually. Kinetic specificities of in vivo release of drugs from CPCs have been reviewed, too. Understanding the kinetic and mechanistic correlations between the CPC properties and the drug release is a prerequisite for the design of bone void fillers with drug release profiles precisely tailored to the application area and the clinical picture. The goal of this review has been to shed light on these fundamental correlations.

Effect of Strontium-Doped Bioactive Glass on Preventing Formation of Demineralized Lesion

This study investigated the effect of strontium-doped bioactive glass (SBAG) on the formation of dental demineralized lesions. Materials and methods: The study materials were 48 sound human tooth specimens with both dentine and enamel, divided equally into four groups: Group 1 (SBAG), Group 2 (SBAG+Fluoride), Group 3 (Fluoride), and Group 4 (Water as control). After 14 days of pH cycling, the surface morphology of the specimens was observed by scanning electron microscopy. Crystal characteristics of the precipitates were assessed by X-ray diffraction (XRD). Micro-CT was used to measure the mineral loss and the depths of the demineralized lesions formed. Results: Exposure of collagen in inter-tubular areas in dentine was seen in the control group (Group 4) but not in Groups 1 to 3. In Group 2, there were obvious granular particles on the surface of the dentine. XRD revealed precipitation of apatites on the surface of the tooth specimens in Groups 1 to 3. The mean lesion depths in dentine were 81.80 μm, 30.68 μm, 39.04 μm, and 146.36 μm in Groups 1 to 4, respectively (p < 0.001). Lesions in enamel were only found in the control group. The mean mineral loss values in the dentine lesions were 1.25 g/cm³, 0.88 g/cm³, 0.87 g/cm³, and 1.65 g/cm³, in Groups 1 to 4, respectively (p < 0.001). Conclusion: Strontium-doped bioactive glass has a preventive effect on the formation of demineralized lesions in enamel and dentine.

A Novel Fast-Setting Strontium-Containing Hydroxyapatite Bone Cement With a Simple Binary Powder System

In recent years, strontium-substituted calcium phosphate bone cement (Sr-CPC) has attracted more and more attentions in the field of bone tissue repair due to its comprehensive advantages of both traditional CPC and Sr ions. In this study, a crucial Sr-containing α-Ca_{3 - x} Sr _x (PO₄)₂ salt has been synthesized using a simplified one-step method at lower synthesis temperature. A novel Sr-CPC has been developed based on the simple binary Sr-containing α-Ca_{3 - x} Sr _x (PO₄)₂/Ca₄(PO₄)₂O cement powder. The physicochemical properties and hydration mechanism of this Sr-CPC at various Sr contents were intensively investigated. The setting product of this Sr-CPC after a set for 72 h is a single-phase Sr-containing hydroxyapatite, and its compressive strength slightly decreased and its setting time extended with the increase of Sr content. The hydration process included the initial formation of the medium product CaHPO₄⋅2H₂O (30 min∼1 h), the following complete hydration of Ca₄(PO₄)₂O and the initially formed CaHPO₄⋅2H₂O (2∼6 h), and the final self-setting of α-Ca_{3 - x} Sr _x (PO₄)₂ (6 h∼). The compressive strength of Sr-CPC, which was closely related to the transformation rate of Sr-containing hydroxyapatite, tended to increase with the extension of hydration time. In addition, Sr-CPC possessed favorable cytocompatibility and the effect of Sr ions on cytocompatibility of Sr-CPC was not obvious at low Sr contents. The present study suggests α-Ca_{3 - x} Sr _x (PO₄)₂ is a kind of vital Sr-containing salt source which is useful to develop some novel Sr-containing biomaterials. In addition, the new Sr-containing cement system based on this simple binary α-Ca_{3 - x} Sr _x (PO₄)₂/Ca₄(PO₄)₂O cement powder displayed an attractive clinical application potential in orthopedics.

Remineralizing effect of a new strontium-doped bioactive glass and fluoride on demineralized enamel and dentine

OBJECTIVE

To investigate the remineralizing effect of a strontium-doped bioactive glass (HX-BGC) and fluoride on demineralized enamel and dentine.

MATERIALS

Sixty demineralized human tooth specimens were allocated to four groups. Group 1 received 5% HX-BGC, Group 2 received 5% HX-BGC and 1450 ppm fluoride, Group 3 received 1450 ppm fluoride, and Group 4 received deionized water as negative control. The specimens were subjected to pH cycling for 14 days. The surface morphology, lesion depths, crystal characteristics and collagen matrix degradation of the specimens were assessed by scanning electron microscopy (SEM), micro-computed tomography (mico-CT), X-ray diffraction (XRD), and spectrophotometry with a hydroxyproline (HYP) assay, respectively.

RESULTS

SEM images showed the enamel surface was smooth with regularly arranged enamel rods in Groups 1-3. Granular grains were observed in both inter-tubular and intra-tubular dentine in Groups 1-3. The mean lesion depths in enamel were 80.8 μm, 50.6 μm, 72.7 μm and 130.7 μm in Groups 1-4, respectively (p < 0.001), and those in dentine were 152.6 μm, 140.9 μm, 165.4 μm and 214.1 μm, respectively (p < 0.001). The differences in mean mineral loss in enamel and in dentine between the four study groups follow the same pattern as that of the differences in lesion depth. XRD illustrated apatite formation in each group. There were no significant differences in the HYP concentrations among the four groups (p = 0.261).

CONCLUSION

Combined use of HX-BGC and fluoride can reduce mineral loss and promote remineralization of demineralized enamel and dentine through the precipitation of newly formed apatite.

CLINICAL SIGNIFICANCE

Adjunctive use of HX-BGC may enhance the remineralization effect of fluoride in the management of early dental caries lesions.

Antimicrobial Potential of Strontium Hydroxide on Bacteria Associated with Peri-Implantitis

Background: Peri-implantitis due to infection of dental implants is a common complication that may cause significant patient morbidity. In this study, we investigated the antimicrobial potential of Sr(OH)₂ against different bacteria associated with peri-implantitis. Methods: The antimicrobial potential of five concentrations of Sr(OH)₂ (100, 10, 1, 0.1, and 0.01 mM) was assessed with agar diffusion test, minimal inhibitory concentration (MIC), and biofilm viability assays against six bacteria commonly associated with biomaterial infections: Streptococcus mitis, Staphylococcus epidermidis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Escherichia coli, and Fusobacterium nucleatum. Results: Zones of inhibition were only observed for, 0.01, 0.1, and 1 mM of Sr(OH)₂ tested against P. gingivalis, in the agar diffusion test. Growth inhibition in planktonic cultures was achieved at 10 mM for all species tested (p < 0.001). In biofilm viability assay, 10 and 100 mM Sr(OH)₂ showed potent bactericidal affect against S. mitis, S. epidermidis, A. actinomycetemcomitans, E. coli, and P. gingivalis. Conclusions: The findings of this study indicate that Sr(OH)₂ has antimicrobial properties against bacteria associated with peri-implantitis.

Farnesal-loaded pH-sensitive polymeric micelles provided effective prevention and treatment on dental caries

BACKGROUND

Farnesol is a sesquiterpene from propolis and citrus fruit that shows promising anti-bacterial activity for caries treatment and prevention, but its hydrophobicity limits the clinical application. We aimed to develop the novel polymeric micelles (PMs) containing a kind of derivative of farnesol and a ligand of pyrophosphate (PPi) that mediated PMs to adhere tightly with the tooth enamel.

RESULTS

Farnesal (Far) was derived from farnesol and successfully linked to PEG via an acid-labile hydrazone bond to form PEG-hyd-Far, which was then conjugated to PPi and loaded into PMs to form the aimed novel drug delivery system, PPi-Far-PMs. The in vitro test about the binding of PPi-Far-PMs to hydroxyapatite showed that PPi-Far-PMs could bind rapidly to hydroxyapatite and quickly release Far under the acidic conditions. Results from the mechanical testing and the micro-computed tomography indicated that PPi-Far-PMs could restore the microarchitecture of teeth with caries. Moreover, PPi-Far-PMs diminished the incidence and severity of smooth and sulcal surface caries in rats that were infected with Streptococcus mutans while being fed with a high-sucrose diet. The anti-caries efficacy of free Far can be improved significantly by PPi-Far-PMs through the effective binding of it with tooth enamel via PPi.

CONCLUSIONS

This novel drug-delivery system may be useful for the treatment and prevention of dental caries as well as the targeting therapy of anti-bacterial drugs in the oral disease.