Enamel Repair Research Articles

A Novel Nano-Hydroxyapatite Agarose-Based Hydrogel for Biomimetic Remineralization of Demineralized Human Enamel: An in-vitro Study.

This study aims to investigate the biomimetic effect of agarose hydrogel loaded with enamel matrix derivative (EMD-agarose) alone or in combination with nano-hydroxyapatite (n-HA-EMD-agarose) on the remineralization of human demineralized enamel. Extracted human mandibular third molars were sectioned into 54 buccal and lingual halves. Acid-resistant nail varnish was applied to each half, except for two enamel windows. Enamel surface microhardness, energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) analyses were conducted to evaluate enamel surfaces at baseline, following demineralization with 37% phosphoric acid, and after each hydrogel application and remineralization for two, four, and six days. Remineralization was performed using a phosphate solution at 37°C. At day 6 following remineralization, a statistically significant higher mean microhardness was recorded in n-HA-EMD-agarose hydrogel (260.87 ± 3.52) as compared to EMD-agarose hydrogel (244.63 ± 2.76) (p = 0.027). Similarly, n-HA-EMD-agarose hydrogel showed a higher mean calcium (46.31 ± 2.78), phosphorous (24.92 ± 0.826), and fluoride (0.909 ± 0.053) weight percentage compared to EMD-agarose hydrogel calcium (19.64 ± 1.092), phosphorous (19.64 ± 1.092), and fluoride (0.7033 ± 0.0624) weight percentage (p < 0.05). Further, SEM analysis revealed a substantial deposition of n-HA following the application of the n-HA-EMD-agarose hydrogel, whereas the EMD-agarose exhibited a relatively smooth enamel surface with less visible enamel rods due to mineral deposition. The combined n-HA-EMD-agarose hydrogel demonstrated improved surface microhardness of the remineralized enamel and enhanced mineral content deposition, indicating its potential as a biomimetic approach for dental enamel repair.

Biomimetic Remineralization of Dental Hard Tissues via Amyloid‐Like Protein Matrix Composite with Amorphous Calcium Phosphate

AbstractNumerous remineralizing coatings aim to prevent or treat early enamel lesions and occlude exposed dentinal tubules (DTs). Nevertheless, the pace of remineralization is inadequate, and the mechanical robustness of the newly established mineral layer fails to match the inherent strength. In this study, a biomimetic mineralization strategy aimed at replicating key events in biological mineralization, specifically focusing on the organic–inorganic composite matrix, is proposed. The material utilizes Tris(2‐carboxyethyl)phosphine (TCEP), which serves a dual role: stabilized amorphous calcium phosphate (ACP) (ACP@TCEP) nanoparticles as its inorganic component, and catalyzing the cleavage of intramolecular disulfide bonds in poly(ethylene glycol) (PEG) grafted lysozyme (lyso‐PEG) to facilitate the formation of an amyloid‐like protein matrix composite with ACP (ACP@lyso‐PEG nanocomplexes). ACP@lyso‐PEG nanocomplexes can rapidly and efficiently form an enamel‐like remineralization layer on the surface of damaged dental hard tissue, reaching ≈4.205 µm thickness after 3 days of acid‐etched enamel. Furthermore, achieving a depth of DTs occlusion exceeding 60 µm after 5 days, using a simple immersion process. The resulting mineralized layer exhibits mechanical strength comparable to natural teeth. This study introduces a conceptual biomimetic mineralization strategy for effective enamel repair or DTs occlusion in clinical practices, and offers potential insights into the mechanisms of biomineral formation.

The Impact of the Gender on the Pulp Vitality Testing for the Various Types of the Conducting Media: An Original Research

ABSTRACT Introduction: To identify gender-based differences in pulpal sensory thresholds in human teeth utilizing various conducting media. Materials and Methods: The study involved 50 participants of both genders equally distributed. The maxillary central incisors were the teeth selected for the intervention. The three conducting media that were put to the test were Colgate Sensitive Pro-Relief Enamel Repair Toothpaste (CS), Himalaya herbals sensitivity toothpaste (HS), and Lignox 2% gel (LG). Subject’s sensory threshold readings as well as the Visual analogue scale (VAS) scores were noted at the tiniest sensation they experienced. Following an ANOVA, a post hoc analysis was performed to confirm the significance between the three media. Results: Lox 2% Jelly significantly reduced sensory threshold values compared to the other conducting media (P &lt; 0.001). Comparing the sensory threshold values of the sexes showed that men have greater values. Male and female readings differed significantly in the Lox 2% Jelly group (P = 0.021), whereas Colgate Sensitive Pro-Relief Enamel Repair Toothpaste, Himalaya herbals sensitivity toothpaste (P &lt; 0.001) groups showed highly significant variances. All the three conducting media had a highly significant variance for the VAS scores. (P &lt; 0.001). Conclusion: The conducting material used and gender affect the pulpal sensory thresholds to electric impulses produced by EPT.

Peptide Amphiphile‐Mediated Assembly and Fusion of Anisotropic Amorphous Particles for Enamel Remineralization

AbstractEnamel remineralization, which attempts to generate a mineral layer structurally similar to native enamel and restore its mechanical properties, remains a significant challenge. Here, rationally designed peptide amphiphile (PA) molecules bind to amorphous calcium phosphate (ACP) particles via electrostatic interactions, imparting anisotropic properties that drive PA‐modified ACP to form spindle‐shaped aggregates. Furthermore, some residual PA molecules may further regulate crystallization and facilitate the formation of well‐aligned hydroxyapatite bundles. Additionally, the involvement of PA can mediate the ordered deposition and fusion of ACP on the enamel surface, and construct the crystalline‐amorphous mineralization front with a continuous structure. This mineralization front ensures epitaxially oriented growth of enamel crystals and achieves a structurally ordered mineral layer similar to that of native enamel, while the mechanical performance is effectively restored. More significantly, the thickness of the newly formed mineral layer can be augmented through cyclic remineralization, benefitting the design of products intended for practical enamel repair.

Biomimetic Self-Maturation Mineralization System for Enamel Repair.

Enamel repair is crucial for restoring tooth function and halting dental caries. However, contemporary research often overlooks the retention of organic residues within the repair layer, which hinders the growth of dense crystals and compromises the properties of the repaired enamel. During the maturation of natural enamel, the organic matrix undergoes enzymatic processing to facilitate further crystal growth, resulting in a highly mineralized tissue. Inspired by this process, a biomimetic self-maturation mineralization system is developed, comprising ribonucleic acid-stabilized amorphous calcium phosphate (RNA-ACP) and ribonuclease (RNase). The RNA-ACP induces initial mineralization in the form of epitaxial crystal growth, while the RNase present in saliva automatically triggers a biomimetic self-maturation process. The mechanistic study further indicates that RNA degradation prompts conformational rearrangement of the RNA-ACP, effectively excluding the organic matter introduced earlier. This exclusion process promotes lateral crystal growth, resulting in the generation of denser enamel-like apatite crystals that are devoid of organic residues. This strategy of eliminating organic residues from enamel crystals enhances the mechanical and physiochemical properties of the repaired enamel. The present study introduces a conceptual biomimetic mineralization strategy for effective enamel repair in clinical practice and offers potential insights into the mechanisms of biomineral formation.

Self-assembled branched polypeptides as amelogenin mimics for enamel repair.

The regeneration of demineralized enamel holds great significance in the treatment of dental caries. Amelogenin (Ame), an essential protein for mediating natural enamel growth, is no longer secreted after enamel has fully matured in childhood. Although biomimetic mineralization based on peptides or proteins has made significant progress, easily accessible, low-cost, biocompatible and highly effective Ame mimics are still lacking. Herein, we construct a series of amphiphilic branched polypeptides (CAMPs) by facile coupling of the Ame's C-terminal segment and poly(γ-benzyl-L-glutamate), which serves to simulate the Ame's hydrophobic N-terminal segment. Among them, CAMP15 is the best biomimetic mineralization template with great self-assembly performance to guide the oriented crystallization of hydroxyapatite and is capable of inhibiting the adhesion of Streptococcus mutans and Staphylococcus aureus on the enamel surfaces. This work highlights the potential application of amphiphilic branched polypeptide as Ame mimics in repairing defected enamel, providing a promising strategy for prevention and treatment of dental caries.

Encapsulation of a novel peptide derived from histatin-1 in liposomes against initial enamel caries in vitro and in vivo.

Biomimetic mineralization mediated by proteins and peptides is a promising strategy for enamel repair, and its specific application model needs more research. In this work, we exploited a liposomal delivery system for a novel peptide (DK5) derived from histatin-1 (DK5-Lips) as a new biomimetic mineralization strategy against initial enamel caries. The DK5-Lips was prepared using calcium acetate gradient method and then the in vitro release, salivary stability, and cytotoxicity were studied. Initial enamel caries was created in bovine enamel blocks and subjected to pH-cycling model treated with DK5-Lips. Surface microhardness testing, polarized light microscopy (PLM), and transverse microradiography (TMR) were analyzed. Then the biocompatibility of DK5-Lips was evaluated in the caries model of Sprague-Dawley rats, and the anti-caries effect was assessed using Micro-CT analysis, Keyes scores, and PLM in vivo. DK5-Lips provided a mean particle size of (97.63 ± 4.94)nm and encapsulation efficiency of (61.46 ± 1.44)%, exhibiting a sustained release profile, excellent stability in saliva, and no significant toxicity on human gingival fibroblasts (HGFs). The DK5-Lips group had higher surface microhardness recovery, shallower caries depth, and less mineral loss in bovine enamel. Animal experiments showed higher volume and density values of residual molar enamel, lower Keyes score, and shallower lesion depth of the DK5-Lips group with good biocompatibility. As a safe and effective application model, DK5-Lips could significantly promote the remineralization of initial enamel caries both in vitro and in vivo. The potential of liposome utilization as vehicle for oral delivery of functional peptides may provide a new way for enamel restoration.

High-resolution Raman spectroscopy reveals compositional differences between pigmented incisor enamel and unpigmented molar enamel in Rattus norvegicus

Dental enamel is a peculiar biological tissue devoid of any self-renewal capacity as opposed to bone. Thus, a thorough understanding of enamel composition is essential to develop novel strategies for dental enamel repair. While the mineral found in bone and dental enamel is generally viewed as the biologically-produced equivalent of hydroxy(l)apatite, the formation of these bioapatites is controlled by different organic matrix frameworks—mainly type-I collagen in bone and amelogenin in enamel. In lower vertebrates, such as rodents, two distinct types of enamel are produced. Iron-containing pigmented enamel protects the continuously growing incisor teeth while magnesium-rich unpigmented enamel covers the molar teeth. Using high-resolution Raman spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy, this work explores the differences in acid phosphate (HPO42−), carbonate (CO32−), hydroxyl (OH−), iron, and magnesium content of pigmented incisor enamel and unpigmented molar enamel of Sprague Dawley rats. Bundles of hydroxy(l)apatite nanowires comprise the enamel prisms, where prisms in pigmented enamel are wider and longer than those in unpigmented molars. In contrast to magnesium-rich unpigmented enamel, higher mineral crystallinity, and higher HPO42− and OH− levels are hallmark features of iron-rich pigmented enamel. Furthermore, the apparent absence of iron oxides or oxy(hydroxides) indicates that iron is introduced into the apatite lattice at the expense of calcium, albeit in amounts that do not alter the Raman signatures of the PO43− internal modes. Compositional idiosyncrasies of iron-rich pigmented and nominally iron-free unpigmented enamel offer new insights into enamel biomineralisation supporting the notion that, in rodents, ameloblast function differs significantly between the incisors and the molars.

ОЦЕНКА КАЧЕСТВЕННЫХ, КОЛИЧЕСТВЕННЫХ И ОРГАНОЛЕПТИЧЕСКИХ ПАРАМЕТРОВ НОВОЙ ЗУБНОЙ ПАСТЫ С РЕМИНЕРАЛИЗУЮЩИМ КОМПОНЕНТОМ

Subject. The subject of this study is “DentaSwiss Enamel Repair &amp; Protect” treatment-and-prophylactic toothpaste.&#x0D; Objective. The purpose of this study is to evaluate organoleptic properties of the new “DentaSwiss Enamel Repair &amp; Protect” treatment-and-prophylactic toothpaste, and its effects on the functional activity of minor salivary glands and oral mucosa.&#x0D; Methodology. The study was carried out by the Department of Therapeutic Dentistry and Propedeutics of Dental Disease together with the Department of General Chemistry, Ural State Medical University of the Ministry of Health of the Russian Federation. The study involved 65 volunteer patients recruited from the dental students (24 young male adults, 41 young adult women; the average age of patients was 21.25 ± 1.65 years old). The assessment of mixed saliva was performed for the following parameters: the qualitative analysis of such characteristics of saliva secretions such as color, transparency, presence of inclusions, the hydrogen-ion concentration, the functional activity of minor salivary glands, microcrystallization of mixed saliva.&#x0D; Conclusions. The research results showed that the use of “DentaSwiss Enamel Repair &amp; Protect” toothpaste reliably changes the pH-value, the functional activity of minor salivary glands and microcrystallization of mixed saliva which consequently enhances remineralizing effects of mixed saliva and the ability of the tooth enamel to restore. On all parameters, organoleptic properties of “DentaSwiss Enamel Repair &amp; Protect” toothpaste were highly ranked by the study participants scoring the average of 9.95 ± 0.05.

Mimicking amelogenesis to remineralize enamel through co-assembly of PTL fibrils and CMC/ACP

Enamel remineralization has important clinical value for the prevention and minimally invasive treatment of early enamel caries. Enamel matrix proteins (EMPs) are believed to play a key role in amelogenesis to regulate the growth and organization of enamel. Three “key events” of amelogenesis indicated the co-assembly of EMPs composed of amyloid amelogenin (templating protein) and non-amelogenin (non-templating protein) with amorphous calcium phosphate (ACP), followed by the transformation into the crystalline phase with the help of proteolytic enzymes. Herein, a biomimetic microenvironment is constructed, adhesive phase-transited lysozyme fibrils (PTL fibrils) mimicking amelogenin template through amyloid-like lysozyme aggregation, acid carboxymethyl chitosan (CMC) and sodium hypochlorite (NaClO) mimicking non-amelogenin and proteolytic enzymes, respectively. Based on the synchronous self-assembly and mineralization, the full process of the three “key events” of biomineralization were reverted in vitro by slowly raising the pH of the system through dialysis, in-situ regenerating enamel-like crystals with properly oriented structure and mechanical properties that are close to natural enamel independent of additional mineral ions. Especially, the present study proposed the crucial role of the amyloid conformation transition of amelogenin and supported a promising biomimetic strategy for enamel repair.

Calcium Phosphate Nanoclusters for the Repair of Tooth Enamel Erosion.

The artificial repair of tooth enamel is still an urgent requirement because it has a complicated and well-arranged structure. Herein, calcium phosphate nanoclusters (CaP NCs) were synthesized, via a facile approach, for application in the repair of tooth enamel erosion. Structural and optical characterizations validated the successful preparation of spherical CaP NCs, with an average size of 2.1 ± 0.11 nm. By evaporating the ethanol and triethylamine (TEA) solvents, pure CaP was produced, which was further used to repair the tooth enamel. Simulated caries lesions were achieved via phosphoric acid etching to cause damage to enamel rods. After repair, the damaged enamel rods were directly covered with CaP. According to microhardness testing, after repair with CaP NCs, the hardness value of the tooth enamel with acid etching increased to a similar level to that of normal tooth enamel. The results of the microhardness test indicated that CaP NCs revealed great potential for repairing tooth enamel erosion. Our work demonstrates a promising potential for treating the early stage of tooth erosion with CaP NCs. Based on these findings, we believe that stable CaP NCs can be employed as a precursor for the tunable, effective repair of tooth enamel in the near future.

Phosphorylated and Phosphonated Low-Complexity Protein Segments for Biomimetic Mineralization and Repair of Tooth Enamel.

Biomimetic mineralization based on self‐assembly has made great progress, providing bottom‐up strategies for the construction of new organic–inorganic hybrid materials applied in the treatment of hard tissue defects. Herein, inspired by the cooperative effects of key components in biomineralization microenvironments, a new type of biocompatible peptide scaffold based on flexibly self‐assembling low‐complexity protein segments (LCPSs) containing phosphate or phosphonate groups is developed. These LCPSs can retard the transformation of amorphous calcium phosphate into hydroxyapatite (HAP), leading to merged mineralization structures. Moreover, the application of phosphonated LCPS over phosphorylated LCPS can prevent hydrolysis by phosphatases that are enriched in extracellular mineralization microenvironments. After being coated on the etched tooth enamel, these LCPSs facilitate the growth of HAP to generate new enamel layers comparable to the natural layers and mitigate the adhesion of Streptococcus mutans. In addition, they can effectively stimulate the differentiation pathways of osteoblasts. These results shed light on the potential biomedical applications of two LCPSs in hard tissue repair.

Novel trends, challenges and new perspectives for enamel repair and regeneration to treat dental defects.

Dental enamel is the hardest tissue in the human body, providing external protection for the tooth against masticatory forces, temperature changes and chemical stimuli. Once enamel is damaged/altered by genetic defects, dental caries, trauma, and/or dental wear, it cannot repair itself due to the loss of enamel producing cells following the tooth eruption. The current restorative dental materials are unable to replicate physico-mechanical, esthetic features and crystal structures of the native enamel. Thus, development of alternative approaches to repair and regenerate enamel defects is much needed but remains challenging due to the structural and functional complexities involved. This review paper summarizes the clinical aspects to be taken into consideration for the development of optimal therapeutic approaches to tackle dental enamel defects. It also provides a comprehensive overview of the emerging acellular and cellular approaches proposed for enamel remineralization and regeneration. Acellular approaches aim to artificially synthesize or re-mineralize enamel, whereas cell-based strategies aim to mimic the natural process of enamel development given that epithelial cells can be stimulated to produce enamel postnatally during the adult life. The key issues and current challenges are also discussed here, along with new perspectives for future research to advance the field of regenerative dentistry.

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 &lt; 0.05). Enamel surface hardness was increased only by nano-hydroxyapatite toothpastes after in situ treatment compared with the baseline (p &lt; 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 &lt; 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 Growth on Amelogenin‐Amelotin Recombinamers

AbstractStrategies to improve hydroxyapatite mineralization for enamel repair are essential for tissue regeneration. Amelogenin and amelotin (AMTN) are enamel matrix proteins playing critical roles in enamel formation. Amelogenin acts as a scaffold for hydroxyapatite, while AMTN (specifically its ‘SSEEL’ domain) is necessary for proper enamel mineralization. The functional relationship between recombinant AMTN and amelogenin, and their combined ability to guide uniaxial hydroxyapatite growth in vitro has been investigated recently. However, incorporation of the active domain of AMTN within recombinant amelogenins has not been studied yet. Here we describe the synthesis of modified amelogenin by inserting, internally and at its C‐terminus, the mineralizing AMTN‐derived motif SSEEL. C‐terminus modified amelogenin promoted hydroxyapatite formation, whereas internal incorporation of the motif initially resulted in amorphous calcium phosphate formation. Here we show that modified amelogenin with the mineralizing AMTN‐motif SSEEL can promote hydroxyapatite growth. These results give new insights for mineralized tissue regeneration using recombinamer proteins.

Facile Synthesis of In Situ Formable Alginate Composite Hydrogels with Ca2+-Induced Healing Ability.

Dental caries have plagued humans for many years. At present, photocrosslinking resin is commonly used in clinics to repair narrow tooth defects, but the ultraviolet light used in this process has unavoidable cytotoxicity. In situ hydrogels with a similar structure to that of the natural extracellular matrix have gradually attracted attention in the field of hard tissue repair engineering. The injectable molding properties of hydrogel also give it the potential to fill irregularly shaped or fine tissue defects. Through a rapid and facile Michael addition reaction, we prepared maleic chitosan (CS-maleic anhydride [MA]) and thiolated alginate (sodium alginate [SA]-SH) to form a CS-MA/SA-SH hydrogel. To endue its mineralize ability, β-glycerophosphate calcium phosphate and calcium carbonate as the precursor of hydroxyapatite (HAp) were premixed in the hydrogel at certain ratios. This kind of hydrogel can quickly form into different shapes within 10 min. It is worth noting that external Ca2+ can react with the residual carboxyl groups of SA and provide the hydrogel with a self-healing ability. At the same time, we creatively propose a method that uses alkaline phosphatase to promote the mineralization of HAp in hydrogels, to achieve the purpose of regenerating hard tissue in situ. By examining the properties of hydrogels at different concentrations of calcium and phosphorus salts, we find that the CS-MA/SA-SH hydrogel with 50% (wt.%) inorganic matter presented the best self-healing properties, excellent mineralization of highly crystallized Hap, and has ideal cell compatibility. The potential application of the CS-MA/SA-SH hydrogel in repairing exposed dentin tubules in decayed teeth was explored through preliminary in vitro dental restoration experiments. Obviously, the penetration depth through dentin tubules was better than that of commercial dental sensitizers. In addition, the HAp morphology was affected by the local environment. We believe that this hydrogel can utilize tissues for dental regeneration and mineralization, and the healing ability provides the hydrogel flexibility for further application in hard tissue regeneration. Impact statement In this article, we report a simple, gentle, and rapid method for the synthesis of new, in situ-formable polysaccharide-based hydrogels that are capable of healing through the Michael addition reaction, which does not require any crosslinking agents. The rapid healing ability of the hydrogel can be obtained within 1 min by introducing calcium ions, giving the hydrogel the possibility of self-healing in the cap-enriched state. Second, we conferred in vitro mineralization of hydrogels and used a simple novel "enzyme-promoted" approach. Simulated mineralization using human body-enriched alkaline phosphatase as an inducer, allowing hydrogels rich in calcium glycerophosphate and calcium chloride to be highly similar to natural hydroxyphospholipids in a simulated body fluid environment at 37°C, stone-structured, and well-shaped thin-section mineralized products. Finally, we use the self-healing hydrogel with in vitro mineralization ability to carry out simple repair and mineralization regeneration of enamel and dentin, and this result is related to the tooth desensitizing agent commonly used in Chinese dental clinics. Comparison of commercial hydrogels further proves that this polysaccharide-based hydrogel is not only convenient for clinical operation in oral prosthesis but also has obvious advantages in the sealing of enamel by dental tubules and the enhancement of tooth hardness.

Development of strontium-doped nano hydroxyapatite dentifrice and compare its remineralising potential with a topical cream containing casein phosphopeptide- amorphous calcium phosphate - An In Vitro study.

To develop and evaluate the efficacy of synthesised strontium-doped nano hydroxyapatite dentifrice and compare its remineralizing potential with a topical cream containing Casein Phospho Peptide - Amorphous Calcium Phosphate, in remineralizing artificial carious lesion on enamel. Enamel specimens of 4 x 4 x 1 mm were prepared from 90 freshly extracted teeth. Specimens were divided into 3 groups of 30 samples each, based on the type of dentifrice applied that is a control group (Group I) and two experimental groups (Groups II, III). Surface topography and the calcium/phosphorous ratio of all sound specimen were evaluated using Scanning electron microscope and Energy Dispersive X-ray Analysis (SEM-EDAX). The samples in group I and each of the experimental groups were subjected to demineralisation and the calcium/phosphorous ratio of the demineralized specimen were analysed. The samples were then subjected to remineralisation using different agents in each group. Samples in the control group (Group I) were brushed with a conventional dentifrice. In the experimental groups, Group II topical cream with Casein Phosphopeptide and Amorphous Calcium phosphate (CPP-ACP) was used and in Group III laboratory synthesized Strontium-doped nanohydroxyapatite paste (Sr-nHAP), respectively for 28 consecutive days. The samples in the both the control and the two experimental groups were again subjected to SEM-EDAX analysis to analyse the calcium phosphorus ratio following remineralisation cycle. Groupwise comparison of the data was done with one way ANOVA followed by Tukeys Post hoc Test. Both experimental groups (II, III) showed statistically significant remineralisation potential after demineralisation, compared to the control group I. Intergroup comparison showed that the samples in Group III showed the higher remineralisation potential than Group II and was statistically significant. Both CPP- ACP containing tooth cream as well as Sr doped nHAp showed remineralisation potential. Sr doped nanohydroxyapatite showed better remineralisation than CPP ACP and can be considered for enamel repair in incipient carious lesions.

Two-in-one strategy: a remineralizing and anti-adhesive coating against demineralized enamel

Tooth enamel is prone to be attacked by injurious factors, leading to a de/remineralization imbalance. To repair demineralized enamel and prevent pulp inflammation caused by biofilm accumulation, measures are needed to promote remineralization and inhibit bacterial adhesion on the tooth surface. An innovative material, poly (aspartic acid)-polyethylene glycol (PASP-PEG), was designed and synthesized to construct a mineralizing and anti-adhesive surface that could be applied to repair demineralized enamel. A cytotoxicity assay revealed the low cytotoxicity of synthesized PASP-PEG. Adsorption results demonstrated that PASP-PEG possesses a high binding affinity to the hydroxyapatite (HA)/tooth surface. In vitro experiments and scanning electron microscopy (SEM) demonstrated a strong capacity of PASP-PEG to induce in situ remineralization and direct the oriented growth of apatite nanocrystals. Energy dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD) and Vickers hardness tests demonstrated that minerals induced by PASP-PEG were consistent with healthy enamel in Ca/P ratio, crystal form and surface micro-hardness. Contact angle tests and bacterial adhesion experiments demonstrated that PASP-PEG yielded a strong anti-adhesive effect. In summary, PASP-PEG could achieve dual effects for enamel repair and anti-adhesion of bacteria, thereby widening its application in enamel repair.

Enamel Repair with Amorphous Ceramics.

Developing high-performance materials in physiological conditions to clinically repair stiff tissue for long lifespan remains a great challenge. Here, an enamel repair strategy is reported by efficiently growing a biocompatible ZrO2 ceramic layer on defective enamel through controllable hydrolysis of Zr4+ in oral-tolerable conditions. Detailed analysis of the grown layer indicates that the grown ZrO2 ceramic is amorphous without grain boundary and dislocation, which endows the repaired enamel with natural enamel comparable mechanical performance (modulus ≈82.5 GPa and hardness ≈5.2 GPa). Besides, the strong chemical connection between unsaturated coordinated Zr4+ in amorphous structure and PO4 3- greatly strengthen the crystalline-amorphous interface of the repaired enamel to endure the long-time mastication damage. Moreover, these ZrO2 ceramics provide hydrophilic, electronegative, and smooth surfaces to resist the adhesion and proliferation of cariogenic bacteria. The hybrid amorphous-crystalline interface design with advantages in biomechanical compatibility would promote the evolution of a variety of cutting-edge functional materials for medical and engineering application.

Evaluation of remineralization potential and cytotoxicity of a novel strontium-doped nanohydroxyapatite paste: An in vitro study.

Background:The focus of caries management has shifted to the early detection of caries and noninvasive methods of management of incipient lesions with novel remineralizing agents.Aim:The aim of this study is to evaluate and compare the remineralization potential of a novel laboratory synthesized strontium-doped nanohydroxyapatite (SrnHAp) paste to a commercially available regular dentifrice.Materials and Methods:Sixty enamel specimens (4 mm × 4 mm × 1 mm) were divided into two groups based on the type of dentifrice applied: Group I – regular toothpaste and Group II – SrnHAp paste. Calcium/phosphorous ratio of all sound specimens was evaluated using Scanning Electron Microscopy-Energy Dispersive X-ray analysis. Samples in both groups were subjected to demineralization, and the calcium/phosphorous ratio was analyzed. The samples were then subjected to remineralization using the specific agents in each group, and the mean calcium–phosphorus ratio was assessed. Cytotoxic evaluation of both pastes was done by direct microscopic observation and MTT assay.Statistical Analysis:Comparison of mean calcium and phosphorous values of sound enamel, demineralized, and remineralized specimen in Groups I and II was done using the one-way ANOVA and Tukeys post hoc test. Intergroup comparison after remineralization was done using the Student's t-test.Results and Conclusion:Group II showed higher remineralization potential than Group I and was statistically significant. Cytotoxicity of novel paste was less compared to the regular toothpaste. SrnHAp showed better remineralization than regular toothpaste and can be considered for enamel repair in incipient carious lesions.