Demineralization-remineralization dynamics in teeth and bone

Quaternary ammonium silane, calcium and phosphorus-loaded PLGA submicron particles against Enterococcus faecalis infection of teeth: An in vitro and in vivo study

Refractory root canal infection of human teeth is the primary cause of dental treatment failure. Enterococcus faecalis is the major cause of refractory root canal infection. In the present study, poly(D,L-lactic-co-glycolide) (PLGA) submicron particles were used as carriers to deliver an antimicrobial quaternary ammonium silane (code-named K21) as well as calcium and phosphorus elements. The release profiles, antibacterial ability against E. faecalis, extent of infiltration into dentinal tubules, biocompatibility and in vitro mineralization potential of the particles were investigated. In addition, the antimicrobial effects of the particles against E. faecalis infection were evaluated in vivo in the teeth of beagle dogs. The encapsulated components were released from the PLGA particles in a sustained-release manner. The particles also displayed good biocompatibility, in vitro mineralization ability and antibacterial activity against E. faecalis. The particles could be driven into dentinal tubules of dentin slices by ultrasonic activation and inhibited E. faecalis colonization. In the root canals of beagle dogs, PLGA submicron particles loaded with K21, calcium and phosphorus demonstrated strong preventive effects against E. faecalis infection. The system may be developed into a new intracanal disinfectant for root canal treatment.

Effect of Two Methods of Remineralization and Resin Infiltration on Surface Hardness of Artificially Induced Enamel Lesions

Statement of the Problem:

The progression of incipient carious lesions may be simply prevented by non-invasive remineralization of lesions, eliminating the need for invasive and high-cost restorative procedures.

Purpose:

This study aimed to assess the effect of two commonly used remineralizing agents and resin infiltration on surface micro hardness of incipient enamel lesions at different time points.

Materials and Method:

In this in vitro study, 45 intact human maxillary central incisors were selected. After disinfection, enamel samples measuring 5x5x2.5 mm were cut out of the labial surface of the teeth. The surface of samples was polished and they were mounted in auto-polymerizing acrylic resin. According to Amaechi’s method, samples were immersed in acidified hydroxyethylcellulose system (pH= 4.5) for 96 hours to induce white spot lesions (WSLs). The baseline value of surface micro hardness of samples was measured using a Vickers hardness tester, then the samples were randomly divided into three groups (n=15) based on different remineralization methods: MI-Paste Plus, Remin Pro and ICON-Infiltrant according to the manufacturer’s instructions. All samples were stored in anti-dry mouth treatment agent during the experiment and their surface hardness was measured at 15 days (T1) and 20 weeks (T2).

Results:

The hardness of samples in MI-Paste Plus and Remin Pro groups significantly increased at both T1 and T2 (p< 0.001) but this increase was not significant in ICON group (p> 0.05).

Conclusion:

MI-Paste Plus and Remin Pro can efficiently increase the hardness of incipient enamel lesions.

The role of salivary contents and modern technologies in the remineralization of dental enamel: a narrative review

Human enamel once formed cannot be biologically repaired or replaced. Saliva has a significant role in remineralization of dental enamel. It not only has a buffering capacity to neutralize the oral cavity’s low pH generated after acidic encounters, but also acts as a carrier of essential ions, such as fluoride, calcium and phosphate, which have a positive role in enamel’s remineralization. This review discusses how salivary contents, like proteins and enzymes, have a natural role in enamel’s mineralization. In addition, the presence of ions, such as fluoride, calcium and phosphate, in saliva further enhances its capability to remineralize the demineralized enamel surface. The review further examines modern innovative technologies, based on biomimetic regeneration systems, including dentin phosphoproteins, aspartate-serine-serine, recombinant porcine amelogenin, leucine-rich amelogenin peptide and nano-hydroxyapatite, that promote enamel remineralization. Fluoride boosters like calcium phosphates, polyphosphates, and certain natural products can also play an important role in enamel remineralization.

The role of salivary contents and modern technologies in the remineralization of dental enamel: a narrative review

Human enamel once formed cannot be biologically repaired or replaced. Saliva has a significant role in remineralization of dental enamel. It not only has a buffering capacity to neutralize the oral cavity's low pH generated after acidic encounters, but also acts as a carrier of essential ions, such as fluoride, calcium and phosphate, which have a positive role in enamel's remineralization. This review discusses how salivary contents, like proteins and enzymes, have a natural role in enamel's mineralization. In addition, the presence of ions, such as fluoride, calcium and phosphate, in saliva further enhances its capability to remineralize the demineralized enamel surface. The review further examines modern innovative technologies, based on biomimetic regeneration systems, including dentin phosphoproteins, aspartate-serine-serine, recombinant porcine amelogenin, leucine-rich amelogenin peptide and nano-hydroxyapatite, that promote enamel remineralization. Fluoride boosters like calcium phosphates, polyphosphates, and certain natural products can also play an important role in enamel remineralization.

Probing Heterogeneity in Bovine Enamel Composition through Nanoscale Chemical Imaging using Atom Probe Tomography

OBJECTIVE

The aim of this study was to determine the heterogeneity in chemical composition of bovine enamel using atom probe tomography, and thereby evaluate the suitability of bovine enamel as a substitute for human enamel in in vitro dental research.

DESIGN

Enamel samples from extracted bovine incisor teeth were first sectioned using a diamond saw and then milled into needle-like samples (<100 nm diameter) by focused ion beam (FIB) coupled with a scanning electron microscope (SEM). These samples were analyzed in the atom probe to acquire three-dimensional (3D) images and quantify the atomic chemistry and distribution in bovine enamel.

RESULTS

For the first time, the atomic-level composition and clustering of major constituents and impurities within bovine enamel were determined and imaged. We discovered that the chemical composition of bovine enamel is spatially inhomogeneous at the atomic scale. The average bulk Ca/P ratio, ∼1.4, was in agreement with previously reported literature values from alternative conventional methods. When assessed locally at the atomic scale, the Ca/P ratio varied between 1.1 and 2.03. We also discovered that the Mg impurities were significantly segregated throughout the enamel, and such clustering influenced the variation of Ca/P ratios. The increase in Mg concentrations, near the Mg clusters, correlated with increased Ca and decreased P concentrations.

CONCLUSION

The presented findings of variability in local composition should be taken into account when interpreting dental research results from bovine enamel.

Acidity-induced release of zinc ion from BioUnionTM filler and its inhibitory effects against Streptococcus mutans

BioUnion filler incorporated into restorative/coating materials is a new bio-functional glass powder. The most unique function of BioUnion filler is its ability to release Zn²⁺ in acidic environments. In this study, the ion release profile of BioUnion filler under acidic conditions and its antibacterial effects against Streptococcus mutans were evaluated. The concentrations of Zn²⁺ released from BioUnion fillers into acetic acids were greater than those released into water. S. mutans inhibition by BioUnion fillers was greater with sucrose than without sucrose, reflecting a decrease in suspension pH in response to the addition of sucrose. Exposure to acids increased Zn²⁺ release from BioUnion fillers, and the fillers after repeated exposure to acids demonstrated inhibitory effects against S. mutans. These findings suggest that BioUnion filler accelerated the release of Zn²⁺ under acidic conditions, which induced bactericidal/inhibitory effects against S. mutans.

Is there evidence for Novamin application in remineralization?: A Systematic review

Background

Calcium sodium phosphor-silicate material, a type of bio-glass was originally developed as an implant material to regenerate bone and recently adapted for use in oral care products (NovaMin Technology Inc.). Novamin is used for many dental problems like hypersensitivity, gingivitis, bleeding, non-carious lesions, carious lesions, whitening and is currently emerging as one of the treatment modality for the remineralization of the tooth. Since the prescription of these novel materials to the patients are based on cost effectiveness, efficacy and effectiveness, a clinician should make decision based on best available evidence. Hence, the objective of this review is to find out the current evidence available on the use of Novamin as an agent for remineralization.

Materials and methods

Relevant articles were searched and screened from several databases including PubMed, Cochrane review, Science Direct and trip which were published till 1988 to July 2017; The articles relevant to the objective of this review were included (RCT's) and articles out of interest of this review were excluded. The primary outcome for the chosen studies is the remineralization capacity of Novamin. Data extraction is done independently and jointly by 3 authors using data collection forms. Studies obtained were evaluated using the Cochrane Collaboration tools for accessing risk bias. The assessment of the quality of the evidence and the bias risk was obtained using the Grading of Recommendations Assessment Development and evaluation System.

Results

The articles from the database obtained for further review was N = 1. According to the study reviewed, the baseline comparisons using decalcification index obtained between Novamin study group (ReNew) and the control group (Crest) yield a P-value of 0.97 whereas after a 3 months interval follow up the value is 0.0403 suggesting there was a trend towards improvement in white spot lesions in the control group and at 6 months' time point the p-value is 0.81 concluding that there are no significant difference of remineralization process obtained by using traditional toothpaste and Novamin.

Conclusion

Review shows that Novamin has significantly less clinical evidence to prove its effectiveness as a remineralization agent in treating both carious and non-carious lesion. Hence, better designed clinical trials should be carried out in the future before definitive recommendations can be made.

Effects of lemon essential oil and limonene on the progress of early caries: An in vitro study

OBJECTIVE

The purpose of this study was to investigate the effects of Lemon essential oil (LEO) and Limonene (LIM) in the progress of early caries.

DESIGN

LEO and LIM were selected as experimental medicine, while sodium fluoride (NaF) and deionized water (DW) were positive and blank controls, respectively. Bovine incisors were used to establish enamel and dentin early caries models by demineralization method in vitro. Then specimens were subjected to pH cycling. Calcium and phosphate release of demineralizing solution were measured by an automatic biochemical analyzer; Surface microhardness tester and energy dispersive X-ray spectrometer were used to detect the surface microhardness recovery and calcium- phosphate ratio on tooth surface; Degraded collagen matrix by collagenase was investigated by assaying hydroxyproline.

RESULTS

Calcium release of dentin demineralizing solution of LEO group was lower than DW group's and higher than NaF group's. Both of LEO and LIM groups, the surface microhardness recovery were significantly lower than those of NaF group, which were similar to DW group. Dentin surface calcium- phosphate ratio of LEO and LIM groups were lower than those of NaF group and higher than those of DW group. Hydroxyproline concentration in the remineralizing solution of LEO and LIM groups were lower than DW groups' and higher than NaF groups'.

CONCLUSIONS

LEO and LIM have influence on the progress of dentin early caries, which can stabilize its structure by inhibiting collagen degradation. Meanwhile, these medicines may provide a new drug choice for the prevention and treatment of early root caries.

Polymeric and inorganic nanoscopical antimicrobial fillers in dentistry

Failure of dental treatments is mainly due to the biofilm accumulated on the dental materials. Many investigations have been conducted on the advancements of antimicrobial dental materials. Polymeric and inorganic nanoscopical agents are capable of inhibiting microorganism proliferation. Applying them as fillers in dental materials can achieve enhanced microbicidal ability. The present review provides a broad overview on the state-of-the-art research in the field of antimicrobial fillers which have been adopted for incorporation into dental materials over the last 5 years. The antibacterial agents and applications are described, with the aim of providing information for future investigations. STATEMENT OF SIGNIFICANCE: Microbial infection is the primary cause of dental treatment failure. The present review provides an overview on the state-of-art in the field of antimicrobial nanoscopical or polymeric fillers that have been applied in dental materials. Trends in the biotechnological development of these antimicrobial fillers over the last 5 years are reviewed to provide a backdrop for further advancement in this field of research.

Nanoscale chemical and mechanical heterogeneity of human dentin characterized by AFM-IR and bimodal AFM

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AFM-IR technique was used to detect the chemical heterogeneity of human dentin for the first time.

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The heterogeneity of mechanical properties of human dentin was explored by AFM AM-FM technique.

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A band at 1336 cm⁻¹ assigned to S Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]>O stretching vibrations was found only in peritubular dentin.

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Peritubular dentin had a higher Young’s modulus (32.25 ± 4.67 GPa) than intertubular dentin.

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AFM-IR and AFM AM-FM are useful for understanding the mineral deposition mechanisms of dentin.

Human dentin, as an important calcified tissue in the body, plays significant roles in withstanding masticatory forces and has a complex hierarchical organization. Understanding the composition and ultrastructure of dentin is critical for elucidating mechanisms of biomineralization under healthy and pathological states. Here, atomic force microscope infrared spectroscopy (AFM-IR) and AFM-based amplitude modulation-frequency modulation (AM-FM) techniques were utilized to detect the heterogeneity in chemical composition and mechanical properties between peritubular and intertubular dentin at the nanoscale. AFM-IR spectra collected from peritubular and intertubular dentin contained similar vibrational bands in the amide regions (I, II and III), suggesting that collagen may exist in both structures. A distinctive band at 1336 cm⁻¹ indicative of SO stretching vibrations was detected only in peritubular dentin. AFM-IR imaging showed an uneven distribution of chemical components at different locations, confirming the heterogeneity of dentin. The Young’s modulus of peritubular dentin was higher, and was associated to a higher mineral content. This study demonstrated distinctive chemical and mechanical properties of peritubular dentin, implying the different development and mineralization processes between peritubular and intertubular dentin. AFM-IR is useful to provide compositional information on the heterogeneity of human dentin, helping to understand the mineral deposition mechanisms of dentin.

HMU Fluorinze Mouthwash Enhances Enamel Remineralization: An In Vitro Study

BACKGROUND:

Fluoride therapy has long been used extensively to prevent dental caries. Fluoride appears in a variety of dental care products such as mouth rinses, dentifrices, gels, etc. HMU Fluorinze is the first mouthwash containing fluoride in Vietnam.

AIM:

This research was conducted to evaluate the efficacy of HMU Fluorinze mouthwash on remineralizing enamel in laboratory conditions.

METHODS:

20 third molar teeth were cleaned and covered with nail polish, except for a 3 x 3 mm square on their buccal surfaces. These teeth underwent two steps: demineralization using Coca-cola and remineralization for 20 daysusing standard calcifying solution (control group) and standard calcifying solution + HMU Fluorinze mouthwash 2 times/day (experimental group). The index measured of enamel structure after demineralization and remineralization was assessed by a DIAGNOdent pen 2190.

RESULTS

The indices measured of the control group and experimental group at baseline were 3.65 ± 0.76 and 3.35 ± 0.64 respectively. After demineralization the control group measured 21.78 ± 4.48 and the experimental group, 20.25 ± 2.26. Following remineralization, the control group scores were 6.30 ± 1.03 and the experimental group, 3.90 ± 1.24, demonstrating statistical significance (p < 0.01) between the two groups. After 20 days, the results for the experimental group did not differ from the original results (p = 0.272), in contrast with the control group (p < 0.01).

CONCLUSION

Results show that HMU Fluorinze mouthwash is better at remineralizing than standard calcifying solution.

Comparative analysis of the remineralization potential of CPP-ACP with Fluoride, Tri-Calcium Phosphate and Nano Hydroxyapatite using SEM/EDX - An in vitro study

Background

In recent years, the non-invasive management of non cavitated caries lesions using remineralization systems to repair the enamel have received more attention from the scientific community. Aim: To quantitatively evaluate the remineralization potential of Casein phosphopeptide-amorphous calcium phosphate-fluoride(CPP-ACPF), Tri-calcium phosphate(TCP) & Nano-hydroxyapatite(nHAP) using Scanning Electron Microscopy(SEM) and Energy dispersive X-ray Analysis(EDX).

Material and Methods

40 enamel specimens were prepared, and immersed in demineralising solution at a pH of 4.4 for 96 hours at 37°C, to induce artificial carious lesions. Remineralization was carried out for a period of 30 days using CPP-ACPF, TCP, nHAP. The specimens were evaluated for calcium and phosphorus content using SEM-EDX.

Results

The Ca/P mass % after remineralization was significantly higher with CPP-ACP-F and TCP-F followed by nHAP.

Conclusions

CPP-ACP-F and TCP can promote significant remineralization of incipient carious lesions. These are excellent delivery vehicles available in a slow release amorphous form to localize calcium, phosphate and fluoride at the tooth surface.

Key words:Remineralization, in vitro; CPP-ACP fluoride, Nano-hydroxyapatite, Tri-calcium phosphate, SEM/ EDX.

Early detection of enamel demineralization by optical coherence tomography

Enamel is the outermost layer of the tooth that protects it from invasion. In general, an acidic environment accelerates tooth demineralization, leading to the formation of cavities. Scanning electron microscopy (SEM) is conventionally used as an in vitro tool for the observation of tooth morphology changes with acid attacks. Yet, SEM has intrinsic limitations for the potential application of in vivo detection in the early demineralization process. In this study, a high-resolution optical coherence tomography (OCT) system with the axial and transverse resolutions of 2.0 and 2.7 μm in teeth has been utilized for characterizing the effect of the acidic environment (simulated by phosphoric acid) on the enamel topology. The scattering coefficient and the surface roughness of enamel can be directly derived from the OCT results, enabling a quantitative evaluation of the topology changes with demineralization. The dynamic process induced by the acid application is also recorded and analyzed with OCT, depicting the evolution of the demineralization process on enamel. Notably, the estimated enamel scattering coefficient and surface roughness significantly increase with the application time of acid and the results illustrate that the values of both parameters after demineralization are significantly larger than those obtained before the demineralization, illustrating both parameters could be effective to differentiate the healthy and demineralized teeth and determine the severity. The obtained results unambiguously illustrate that demineralization of the tooth surface can be successfully detected by OCT and further used as an indicator of early-stage cavity formation.

Surface analysis of etched enamel modified during the prenatal period

Structural changes in the enamel surface subjected to induced demineralization and assessment of the influence of prenatal administration of β-hydroxy β-methylbutyrate (HMB) on enamel resistance were investigated. The examination was conducted on five sets of teeth from one-day-old spiny mice (Acomys cahirinus), one from the control and four from the experimental groups. Surface structure, molecular arrangement and crystalline organization of offspring's enamel both before and after etching were studied. Obtained results revealed that the physical and molecular arrangements of enamel were altered after the prenatal supplementation, and significantly affected its final structure and resistance against acid action. The enamel of incisors from the offspring which mothers were supplemented with HMB in a high dose (0.2 g/kg_bw) and in the late period of gestation (26th-39th day) showed the highest endurance against acid treatment demonstrating only vestigial changes in their surface structure after acid action. Comparing to the remaining experimental groups, it was characterized by a reduced roughness and fractal dimension, significantly lower degree of demineralization and simultaneous lack of notable differences in the Raman spectra before and after acid etching. The results suggest that an increased enamel resiliency was the effect of a relatively high degree of mineralization and higher organization of the surface.

Histological comparison of three apatitic bone substitutes with different carbonate contents in alveolar bone defects in a beagle mandible with simultaneous implant installation

Since bone apatite is a carbonate apatite containing carbonate in an apatitic structure, carbonate content may be one of the factors governing the osteoconductivity of apatitic bone substitutes. The aim of this study was to evaluate the effects of carbonate content on the osteoconductivity of apatitic bone substitutes using three commercially available bone substitutes for the reconstruction of alveolar bone defects of a beagle mandible with simultaneous dental implant installation. NEOBONE, Bio-Oss, and Cytrans that contain 0.1, 5.5, and 12.0 mass% of carbonate, respectively, were used in this study. The amount of newly formed bone in the upper portion of the alveolar bone defect of the beagle's mandible was 0.7, 6.6, and 39.4% at 4 weeks after surgery and 4.7, 39.5, and 75.2% at 12 weeks after surgery for NEOBONE, Bio-Oss, and Cytrans, respectively. The results indicate that bone-to-implant contact ratio was the largest for Cytrans. Additionally, the continuity of the alveolar ridge was restored in the case of Cytrans, whereas the continuity of the alveolar ridge was not sufficient when using NEOBONE and Bio-Oss. Both Cytrans and Bio-Oss that have a relatively larger carbonate content in their apatitic structure was resorbed with time. We concluded that carbonate content is one of important factors governing the osteoconductivity of apatitic bone substitutes.

Bone Remineralization around Dental Implants following Conservative Treatment after Peri-Implantitis

The aim of this case report is to show that bone remineralization around dental implants with a history of peri-implantitis is possible after irritant factors are removed and only conservative treatment is performed. Patient came to the clinic after three years of dental implant placement complaining about swelling, sensitivity and gingiva color changes at the posterior part of the maxilla. During radiographic and intraoral examinations peri-implantitis of the #24 implant site was diagnosed. The surgical treatment method was rejected and performed conservative treatment instead. The outcome is promising; periapical radiographs three months later showed bone remineralization as well as stable bone after 10 years. A key clinical message: Bone remineralization around dental implants with a history of peri-implantitis is possible after irritant factors are removed and conservative treatment performed.

The Application of the Logistic Equation Model to Predict the Remineralization Characteristics of Desensitizing Paste

Objectives

A mathematical model making using of the Verhulst logistic equation was developed to predict the remineralization behaviors of desensitizing paste.

Methods

The input parameter used for the model was obtained experimentally by brushing twenty-one simulated dentin specimens for seven days with three sample groups, namely, EB@TiO₂, Colgate Pro-relief, and Sensodyne repair (n = 7). A field emission scanning electron microscope (FESEM) and ImageJ software were used to observe and measure the % occluded ratio of the dentin surface. The model fittings for the three sample groups were carried out using the built-in MATLAB least-squares fitting routine fmincon in the optimization toolbox.

Results

The results suggest that the experimental parameter were in agreement with the model. It was found that the logistic equation model can make a future prediction of the remineralization pattern for EB@TiO₂ and Colgate Pro-relief. It was, however, found that the trajectory for the Sensodyne repair was a bit complex, thus making the prediction difficult.

Conclusions

Overall, the salient feature of this study suggests that the logistic equation could be used to predict the remineralization behavior of desensitizing paste in the management of sensitive tooth.

Early crestal bone loss: Is it really loss?

Bone remineralization around dental implants might be possible after early crestal bone loss.

Effectiveness of Theobromine on Enamel Remineralization: A Comparative In-vitro Study

Background

Remineralizing agents demonstrate potential to reverse early carious lesions. Theobromine containing dentifrices claim to remineralize enamel lesions effectively. The aim of this in-vitro study was to evaluate and compare the remineralization potential of dentifrices containing theobromine, 0.21% sodium fluoride (NaF) with functionalized tricalcium phosphate (f-TCP) and amine fluoride on artificial enamel caries.

Materials and methods

Sound extracted human premolars were demineralized to produce deep artificial carious lesions. The teeth were sectioned longitudinally and allocated to three treatment groups with nine specimens in each group: Group A (NaF + f-TCP), Group B (amine fluoride), and Group C (theobromine). The specimens were then subjected to pH cycling for seven days. Confocal laser scanning microscopy (CLSM) was utilized to record the patterns of demineralization and remineralization. One-way ANOVA and paired t-test were used to analyze changes in lesion depth. The level of significance was set at p<0.05.

Results

All three dentifrices effectively remineralized artificial carious lesions (paired t-test, p<0.001). Of the groups, Group A (54.97%) reported the highest percentage change in lesion depth values followed closely by Group B (51.51%) and Group C (31.71%), respectively.

Conclusion

Within this in-vitro study, theobromine containing dentifrice was effective in remineralizing lesions of enamel. However, theobromine demonstrated less remineralization potential in comparison to dentifrices containing NaF + f-(TCP) and amine fluoride.

The Oral Bacterial Microbiome of Interdental Surfaces in Adolescents According to Carious Risk

Adolescence is closely associated with a high risk of caries. The identification of specific bacteria in an oral microniche, the interdental space of the molars, according to carious risk can facilitate the prediction of future caries and the anticipation of the progression or stabilization of caries in adolescents. A cross-sectional clinical study according to the bacteriological criteria of interdental healthy adolescents and carious risk factors-low and high-using a real-time polymerase chain reaction technique was conducted. The presence of 26 oral pathogens from the interdental microbiota of 50 adolescents aged 15 to 17 years were qualitatively and quantitatively analyzed. Bacteria known to be cariogenic (Bifidobacterium dentium, Lactobacillus spp., Rothia dentocariosa, Streptococcus cristatus, Streptococcus mutans, Streptococcus salivarius, Streptococcus sobrinus, and Streptococcus wiggsiae) did not present differences in abundance according to carious risk. Periodontal bacteria from the red complex are positively correlated with carious risk. However, only 3 bacteria-S. sobrinus, E corrodens and T. forsythia-presented a significant increase in the highest group. Estimating the risk of caries associated with bacterial factors in interdental sites of molars in adolescents contributes to the better definition of carious risk status, periodicity and intensity of diagnostic, prevention and restorative services.

Remineralization potential of dentifrice containing nanohydroxyapatite on artificial carious lesions of enamel: A comparative in vitro study

BACKGROUND

A carious lesion is the accumulation of numerous episodes of demineralization and remineralization, rather than a unidirectional demineralization process. Tooth destruction can be arrested or reversed by the frequent delivery of fluoride or calcium/phosphorous ions to the tooth surface. Nanohydroxyapatite particle-containing dentifrices are the newer generation of products which claim to remineralize enamel lesions effectively. The aim of this study was to evaluate and compare the remineralization ability of dentifrices containing nanohydroxyapatite, NovaMin, and amine fluoride on artificial enamel caries.

MATERIALS AND METHODS

In this in vitro study, extracted sound premolars were placed in a demineralizing solution to produce deep artificial carious lesions. The teeth were then sectioned longitudinally and divided into three groups (n = 16 in each group): Group A (nanohydroxyapatite), Group B (NovaMin), and Group C (fluoride). The sections were then subjected to pH cycling for 7 days. Polarized light microscopy was utilized to record the depth of the lesions before and after treatment with the selected dentifrices. Changes in the mean lesion depth were statistically analyzed by one-way ANOVA and t-test. The level of significance was assessed at P < 0.05.

RESULTS

The lesion depth decreased significantly by 10.56% in Group A, 6.73% in Group B, and 9.58% in Group C (paired t-test, P < 0.001). When comparisons were made across the groups, no statistical significance was found between the Groups A, B, and C (ANOVA test, P > 0.05).

CONCLUSION

All three dentifrices were found to be effective in remineralizing artificial carious lesions. Nanohydroxyapatite dentifrice produced significantly better results compared to fluoride- and NovaMin-containing dentifrices, instigating for its use in the management of early carious lesions.

Remineralization, Regeneration, and Repair of Natural Tooth Structure: Influences on the Future of Restorative Dentistry Practice

Currently, the principal strategy for the treatment of carious defects involves cavity preparations followed by the restoration of natural tooth structure with a synthetic material of inferior biomechanical and esthetic qualities and with questionable long-term clinical reliability of the interfacial bonds. Consequently, prevention and minimally invasive dentistry are considered basic approaches for the preservation of sound tooth structure. Moreover, conventional periodontal therapies do not always ensure predictable outcomes or completely restore the integrity of the periodontal ligament complex that has been lost due to periodontitis. Much effort and comprehensive research have been undertaken to mimic the natural development and biomineralization of teeth to regenerate and repair natural hard dental tissues and restore the integrity of the periodontium. Regeneration of the dentin-pulp tissue has faced several challenges, starting with the basic concerns of clinical applicability. Recent technologies and multidisciplinary approaches in tissue engineering and nanotechnology, as well as the use of modern strategies for stem cell recruitment, synthesis of effective biodegradable scaffolds, molecular signaling, gene therapy, and 3D bioprinting, have resulted in impressive outcomes that may revolutionize the practice of restorative dentistry. This Review covers the current approaches and technologies for remineralization, regeneration, and repair of natural tooth structure.

Trans,trans-farnesol, an antimicrobial natural compound, improves glass ionomer cement properties

A series of experiments were conducted to characterize a novel restorative material. We explored the effect on biological, physical and chemical properties of glass ionomer cement (GIC) adding-the naturally occurring tt-farnesol (900 mM). Two groups were accomplished for all assays: GIC+tt-farnesol and GIC (control). Biological assays: 1) agar diffusion against some cariogenic bacteria; 2) S. mutans biofilm formation and confocal laser scanning microscopy-CLSM. 3) gtfB, gtfC, gtfD, gbpB, vicR, and covR expression; 4) MTT and microscopic morphology. Physical properties assays: 1) roughness; 2) hardness; 3) compressive strength and 4) diametral tensile strength. Chemical assay: Raman spectroscopy. The adding of tt-farnesol to GIC led to larger zones of inhibition (p<0.05), biofilms with a short-term reduction in bacterial viability but similar biomass (p>0.05). Polysaccharides levels increased over time, similarly over groups (p>0.05). Viable and non-viable S. mutans were seen on the specimens’ surface by CLSM but their virulence was not modulated by tt-farnesol. The tt-farnesol increased the HaCaT cell viability without impact on compressive and diametral tensile strength and roughness although the hardness was positively affected (p<0.05). Raman confirmed the presence of tt-farnesol. The incorporation of tt-farnesol into GIC inhibited the growth of cariogenic bacteria but had a little effect on the composition, structure and physiology of the biofilm matrices. Also, the tt-farnesol increased the hardness and the biocompatibility of the GIC, not influencing negatively other physical properties of the restorative material.

Oral microbial biofilms: an update

Human oral cavity (mouth) hosts a complex microbiome consisting of bacteria, archaea, protozoa, fungi and viruses. These bacteria are responsible for two common diseases of the human mouth including periodontal (gum) and dental caries (tooth decay). Dental caries is caused by plaques, which are a community of microorganisms in biofilm format. Genetic and peripheral factors lead to variations in the oral microbiome. It has known that, in commensalism and coexistence between microorganisms and the host, homeostasis in the oral microbiome is preserved. Nonetheless, under some conditions, a parasitic relationship dominates the existing situation and the rise of cariogenic microorganisms results in dental caries. Utilizing advanced molecular biology techniques, new cariogenic microorganisms species have been discovered. The oral microbiome of each person is quite distinct. Consequently, commonly taken measures for disease prevention cannot be exactly the same for other individuals. The chance for developing tooth decay in individuals is dependent on factors such as immune system and oral microbiome which itself is affected by the environmental and genetic determinants. Early detection of dental caries, assessment of risk factors and designing personalized measure let dentists control the disease and obtain desired results. It is necessary for a dentist to consider dental caries as a result of a biological process to be targeted than treating the consequences of decay cavities. In this research, we critically review the literature and discuss the role of microbial biofilms in dental caries.

Salivary Factors Related to Caries in Children with Autism

Many predisposing factors to caries are present in autism, however, it is unlikely that autistic patients exhibit higher caries indexes than the rest of the population.

OBJECTIVE

To evaluate salivary factors related to caries in autistic patients.

STUDY DESIGN

34 autistics and 34 controls aged between 4-13 years old were included. Decayed, missing, and filled teeth (DMFT) index and oral hygiene simplified index (IHO-S) were assessed, as well as, pH, total proteins, phosphate, calcium and IgA in saliva. All data were analyzed by chi² and Student t tests for independent samples. P values<0.05 were considered statistically significant.

RESULTS

Autistic patients showed less caries than controls (p≤0.001), DMFT was 1±1 and 3±2 respectively (p≤0.001). In relation to IHO-S, values increased (p=0.008) in autistic patients (2.25±0.78) compared to controls (1.79±0.59), however Salivary ph means were similar (7.20±0.48 and 7.27±0.34 respectively). Decreased calcium levels (p=0.013) were observed in autistics (0.621±0.35 mmol/L) compared to controls (0.89±0.51 mmol/L), but phosphate levels were similar (6.17±4.22 M, 5.51±4.86 M respectively). When total proteins of saliva were assessed, autistics showed a slight increment (2.65±1.81 mg/mL) compared to controls (2.24±1.27 mg/mL) and zymography showed a higher proteolytic activity in autistic children. Finally, IgA concentration reached 116.55±90.97 μg/mL in autistics and 161.61 ± 193.37μg/mL (p=0.527) in the control group.

CONCLUSIONS

Even though patients with autism exhibited a poorer oral hygiene, caries indexes were lower, calcium levels in saliva were found to be lesser and phosphate levels higher.

A Novel Dental Sealant Containing Dimethylaminohexadecyl Methacrylate Suppresses the Cariogenic Pathogenicity of Streptococcus mutans Biofilms

Cariogenic oral biofilms are strongly linked to dental caries around dental sealants. Quaternary ammonium monomers copolymerized with dental resin systems have been increasingly explored for modulation of biofilm growth. Here, we investigated the effect of dimethylaminohexadecyl methacrylate (DMAHDM) on the cariogenic pathogenicity of Streptococcus mutans (S. mutans) biofilms. DMAHDM at 5 mass% was incorporated into a parental formulation containing 20 mass% nanoparticles of amorphous calcium phosphate (NACP). S. mutans biofilms were grown on the formulations, and biofilm inhibition and virulence properties were assessed. The tolerances to acid stress and hydrogen peroxide stress were also evaluated. Our findings suggest that incorporating 5% DMAHDM into 20% NACP-containing sealants (1) imparts a detrimental biological effect on S. mutans by reducing colony-forming unit counts, metabolic activity and exopolysaccharide synthesis; and (2) reduces overall acid production and tolerance to oxygen stress, two major virulence factors of this microorganism. These results provide a perspective on the value of integrating bioactive restorative materials with traditional caries management approaches in clinical practice. Contact-killing strategies via dental materials aiming to prevent or at least reduce high numbers of cariogenic bacteria may be a promising approach to decrease caries in patients at high risk.

Chlorogenic acid- loaded calcium phosphate chitosan nanogel as biofilm degradative materials

This work describes an effort to develop an antimicrobial agent (chlorogenic acid - CGA) loaded porous nanogel based on calcium phosphate-chitosan (CaPNP@Chi) nanogel with biofilm degradative properties and has potential applications in restorative dentistry. The nanogel was prepared by ionic gelation of calcium phosphate nanoparticles and chitosan in the ratio of 1.25: 1. Chlorogenic acid was loaded to the nanoparticles as an ethanolic solution and the encapsulation efficiency determined by chromatographic techniques. The particle size and morphology of CaPNP@Chi and CaPNP@Chi@CGA was determined by dynamic light scattering and scanning electron microscopic techniques. The minimum inhibitory concentration against S. aureus and K. pneumoniae was determined through the well diffusion method. The biofilm formation and biofilm decay were studied through staining assays. The toxicity, if any of the nanogel was assessed by MTT assay against HaCaT cells. All data were statistically analyzed. The composite had a CGA encapsulation efficiency of 70% and was thermally stable up to 124 °C. The zone of inhibition was found to be 18.7 mm ± 0.6 against S. aureus. CaPNP@Chi@CGA showed a 68% increase in biofilm degradation when compared with the untreated group. Results obtained in this study suggest that the positively charged nanogel interacted with the bacterial cell membrane and brought about the disruption of the cell membrane. Also, CaPNP@Chi@CGA was observed to be nontoxic up to 40 μg/mL to HaCaT cells. These results support the potential of CaPNP@Chi@CGA nanogel for biofilm degradation and its application as filling material in restorative dentistry.

Remineralization of Artificial Dentin Caries Using Dentin and Enamel Matrix Proteins

To assess the remineralizing potential of dentin matrix proteins and enamel matrix derivatives (DMPs and EMDs) after application on artificially induced dentin lesions, given the hypothesis that these materials increase the mineral uptake, binding, and mineralization. Forty-eight caries-free human premolars were used. Teeth were cut, polished, and embedded, leaving an open window on the root surface, of which one-third was covered with a flowable composite to preserve the healthy untreated dentin. Then, samples were demineralized in Buskes solution for 33 days. A micro-CT scan prior to treatment was performed. Next, the samples were randomly allocated into four groups: (A) An untreated negative control (CON), (B) application of porcine dentin matrix proteins (DMP), (C) treatment with enamel matrix derivatives (EMD, Emdogain, Straumann), and (D) amine fluoride application (AMF, Elmex fluid, GABA). All samples were placed in artificial saliva for 21 days. A second micro-CT scan was performed, after which the change in gray scaling within a defined region of interest (0.25 mm³) was analyzed. ANCOVA was applied to discover statistical differences between the different treatments. Both, treatment with AMF; (P = 0.011 versus CON) as well as with DMP (P = 0.043 versus CON) yielded a statistically significant difference compared to the control treatment. EMD treatment was not found to differ (P > 0.05). Mainly the top layer of the defects showed clear signs of remineralization, which was also evident in CON. This study was able to visually confirm the remineralization potential of demineralized dentin especially after DMP application, which, however, did not outperform AMF. Based on this, additional studies combining proteins and fluorides are now warranted and ongoing.

Evaluating the buffering and acid-resistant properties of eggshell-titanium dioxide composite against erosive acids

OBJECTIVE:

This paper reports on the buffering and acid-resistant properties of a modified eggshell-titanium composite against citric acid attack.

MATERIALS AND METHODS:

Eggshell-titanium EB-TiO₂ was prepared by ball-milling eggshell powder and titanium dioxide. Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM) were used to characterize EB-TiO₂. The buffering property against citric acid at pH values of 2, 4, and 5 was measured using a pH meter. Five brands of toothpaste (Colgate, Colgate Sensitive, Aquafresh, Oralwise, and Sensodyne) were used to assess the acid-resistant properties of EB-TiO₂. Enamel models were simulated by dissolving each brand of toothpaste with eggshell (control) and EB-TiO₂. The samples were exposed to citric acid of pH 2. The average slope (kPa/s) was measured using a pressure sensor. An analysis of variance was used to analyze the kPa/s values (α =.05).

RESULTS:

The FTIR and XRD analyses suggest the surface modification of EB-TiO₂. The TEM image revealed spherical-shaped particles in EB-TiO₂. The pH test results showed that the buffering properties of eggshell and EB-TiO₂ were comparable. Significant differences were observed in the acid resistance properties of the samples exposed to citric acids ( P < .05). The Colgate toothpaste infused with eggshell powder had the highest mean kPa/s values, whereas Sensodyne infused with EB-TiO₂ had the lowest kPa/s values.

CONCLUSION:

The salient features of this study indicate that modification of eggshell with titanium dioxide does not affect its carbonate buffering properties. Connecting the kPa/s values to acid-resistant properties, EB-TiO₂ effectively reduces erosive attacks when added to toothpaste.

Changes in salivary pH following consumption of different varieties of date fruits

Objective

Consumption of date fruits leads to chemical changes in saliva, including variations in pH values. We conducted this study to assess the effect of the consumption of different types of dates on salivary pH.

Methods

We recruited 15 children (aged 6–15 years) who were instructed to consume one piece of specific types of dates (Safree, Nabtat Seif, Khalas, Sukkari, and Segae) for 5 consecutive days. On the 6th and 7th days, the children consumed a quarter of a grapefruit (positive control) and chewed on a sterilised cotton pellet (negative control), respectively. Salivary samples from unstimulated kids were collected at least 1 h after breakfast every day and the salivary pH was recorded.

Results

When compared with the pH values before date consumption, the lowest mean salivary pH value among the date-consuming groups 5 min after salivary stimulation was noted after the consumption of Khalas (6.26), followed by those after consumption of Safree (6.31), Nabtat Seif (6.36), Segae (6.44), and Sukkari (6.45). The highest difference in mean values was observed for Khalas (.47), followed by those for Sukkari (.45), Nabtat Saif (.44), Segae (.38), and Safree (.35). The pH of saliva collected after grapefruit consumption was the lowest, whereas chewing cotton pellets led to an increased salivary pH.

Conclusion

This study showed a decrease in the salivary pH following date consumption, but not to a value as low as the critical value. These findings suggest that dates do not have detrimental effects on salivary parameters.

A New SLC10A7 Homozygous Missense Mutation Responsible for a Milder Phenotype of Skeletal Dysplasia With Amelogenesis Imperfecta

Amelogenesis imperfecta (AI) is a heterogeneous group of rare inherited diseases presenting with enamel defects. More than 30 genes have been reported to be involved in syndromic or non-syndromic AI and new genes are continuously discovered (Smith et al., 2017). Whole-exome sequencing was performed in a consanguineous family. The affected daughter presented with intra-uterine and postnatal growth retardation, skeletal dysplasia, macrocephaly, blue sclerae, and hypoplastic AI. We identified a homozygous missense mutation in exon 11 of SLC10A7 (NM_001300842.2: c.908C>T; p.Pro303Leu) segregating with the disease phenotype. We found that Slc10a7 transcripts were expressed in the epithelium of the developing mouse tooth, bones undergoing ossification, and in vertebrae. Our results revealed that SLC10A7 is overexpressed in patient fibroblasts. Patient cells display altered intracellular calcium localization suggesting that SLC10A7 regulates calcium trafficking. Mutations in this gene were previously reported to cause a similar syndromic phenotype, but with more severe skeletal defects (Ashikov et al., 2018;Dubail et al., 2018). Therefore, phenotypes resulting from a mutation in SLC10A7 can vary in severity. However, AI is the key feature indicative of SLC10A7 mutations in patients with skeletal dysplasia. Identifying this important phenotype will improve clinical diagnosis and patient management.

Dental remineralization via poly(amido amine) and restorative materials containing calcium phosphate nanoparticles

Tooth decay is prevalent, and secondary caries causes restoration failures, both of which are related to demineralization. There is an urgent need to develop new therapeutic materials with remineralization functions. This article represents the first review on the cutting edge research of poly(amido amine) (PAMAM) in combination with nanoparticles of amorphous calcium phosphate (NACP). PAMAM was excellent nucleation template, and could absorb calcium (Ca) and phosphate (P) ions via its functional groups to activate remineralization. NACP composite and adhesive showed acid-neutralization and Ca and P ion release capabilities. PAMAM+NACP together showed synergistic effects and produced triple benefits: excellent nucleation templates, superior acid-neutralization, and ions release. Therefore, the PAMAM+NACP strategy possessed much greater remineralization capacity than using PAMAM or NACP alone. PAMAM+NACP achieved dentin remineralization even in an acidic solution without any initial Ca and P ions. Besides, the long-term remineralization capability of PAMAM+NACP was established. After prolonged fluid challenge, the immersed PAMAM with the recharged NACP still induced effective dentin mineral regeneration. Furthermore, the hardness of pre-demineralized dentin was increased back to that of healthy dentin, indicating a complete remineralization. Therefore, the novel PAMAM+NACP approach is promising to provide long-term therapeutic effects including tooth remineralization, hardness increase, and caries-inhibition capabilities.

The Effect of Sensory Innervation on the Inorganic Component of Bones and Teeth; Experimental Denervation - Review

The effect of the nervous system on bone remodelling has been described by many studies. Sensory and autonomic nerves are present in the bone. Immunohistochemical analysis of the bone have indicated the presence of neuropeptides and neurotransmitters that act on bone cells through receptors. Besides carrying sensory information, sensory neurons produce various neuropeptides playing an important role in maintaining bone and tooth pulp homeostasis, and dentin formation. Bone tissue and teeth contain organic and inorganic components. Bone cells enable bone mineralization and ensure its formation and resorption. Studies focused on the effects of the nervous system on the bone are proceeded using various ways. Sensory denervation itself can be achieved using capsaicin causing chemical lesion to the nerve. Surgical ways of causing only sensory lesion to nerves are substantially limited because many peripheral nerves are mixed and contain a motor component as well. From this point of view, the experimental model with transection of inferior alveolar nerve is appropriate. This nerve provides sensory innervation of the bone and teeth of the mandible. The purpose of our paper is to provide an overview of the effects exerted by the nervous system on the inorganic component of the bone and teeth, and also to present an overview of the used experimental models. As we assume, the transection of inferior alveolar nerve could be reflected in changed contents and distribution of chemical elements in the bone and teeth of rat mandible. This issue has not been studied so far.

The Associations of Maternal and Neonatal Vitamin D with Dental Development in Childhood

BACKGROUND

Vitamin D influences the formation and mineralization of teeth.

OBJECTIVE

To investigate the association of maternal and neonatal vitamin D concentrations with the dental development of 10-y-old children, in a population-based prospective cohort study among 3,770 mothers and children in the Netherlands.

METHODS

Maternal venous blood samples were collected in the second trimester (median 20.4 weeks of gestation; range: 18.5-23.2 wk) whereas umbilical cord blood samples were collected immediately after delivery (median 40.1 weeks of gestation; range 35.9-42.3 wk). Dental development was defined using the Demirjian method. Multivariate regression models were built to analyze the studied associations.

RESULTS

High concentrations of 25-hydroxyvitamin D [25(OH)D] during midpregnancy (β: -0.04; 95% CI: -0.08, -0.01) and at birth (β: -0.06; 95% CI: -0.10, -0.02) were associated with a lower dental age in children. The children of mothers with severe vitamin D deficiency [25(OH)D <25.0 nmol/L] during midpregnancy exhibited a higher dental age (β: 0.14; 95% CI: 0.03, 0.24) and higher developmental stages of the mandibular first premolar (β: 0.32; 95% CI: 0.04, 0.60) compared with the children of mothers with optimal values of 25(OH)D (≥75.0 nmol/L). Children with vitamin D deficiency [25(OH)D 25.0-49.9 nmol/L] at birth exhibited a higher dental age (β: 0.11; 95% CI: 0.01, 0.20), higher developmental stages of the mandibular second premolar (β: 0.27; 95% CI: 0.02, 0.51), and higher developmental stages of the mandibular second molar (β: 0.24; 95% CI: 0.00, 0.48) compared with children with sufficient-to-optimal values of 25(OH)D (≥50.0 nmol/L) at birth.

CONCLUSION

Higher maternal and neonatal 25(OH)D concentrations are associated with decelerated dental development in childhood. The lower the vitamin D level during midpregnancy or at birth, the higher the dental age of children, and the higher the developmental stages of the mandibular teeth.

Monitoring demineralization and remineralization of human dentin by characterization of its structure with resonance-enhanced AFM-IR chemical mapping, nanoindentation, and SEM

OBJECTIVE

This research aimed at monitoring demineralization and remineralization of dentin and its collagen matrix at the nanoscale by amorphous, microcrystalline, and in situ formed hydroxyapatite.

METHODS

The concurrent use of the resonance-enhanced atomic force microscopy coupled with infrared probe (AFM-IR) chemical mapping, nano-indentation, and scanning electron microscopy (SEM) provides a detailed insight into the structure of human dentin, as well as to the processes of its partial demineralization and remineralization.

RESULTS

The resonance-enhanced AFM-IR chemical mapping of dentin has shown to be a useful method to follow distribution of its collagen and hydroxyapatite components at the micro- and nanoscale levels, especially in conjunction with SEM imaging and nanoindentation. Dentin with a higher extent of natural dentin tubule occlusion tends to be harder and less elastic. The relative affinity of the collagen and hydroxyapatite components of dentin toward hydroxyapatite depends on its type (amorphous, microcrystalline, or formed in-situ). The gel mineralization technique allows for an even and controlled growth of hydroxyapatite guided by the completely demineralized collagen matrix of dentin.

SIGNIFICANCE

The observed trends of the affinity of collagen toward different forms of hydroxyapatite helps develop new remineralizing formulations. The employed methods of characterization may provide an insight to the natural processes of bone mineralization guided by its both hydroxyapatite and protein constituents.

Analysis of Calcium Levels in Groundwater and Dental Caries in the Coastal Population of an Archipelago Country

BACKGROUND:

The coastal region is the largest region in Indonesia as a country of the archipelago. Characteristics of groundwater content in coastal areas are very influential on dental health, especially dental caries. The main elements contained in 1-1000 mg/litre groundwater are calcium, magnesium, sodium, potassium, chlorine, bicarbonate, and sulfate groups. Calcium is an essential ingredient for living organisms that play a role in the formation of bone and tooth along with permeability of cell walls.

AIM:

This study aimed to analyse the relationship between calcium in groundwater with dental caries.

METHOD:

Analytical observational study with cross-sectional approach was implemented was coastal communities in Watu Ulo Jember Regency in February 2018 (3,686 inhabitants), with sample criteria of the minimum age of 12 years and consumed groundwater as drinking water at least 2 years by purposive side. The variables in this study were calcium levels as the independent variable and dental caries as the dependent variable. Calcium was measured using the spectrophotometric method. Caries measurements were performed using the DMF-T index. Data were presented descriptively in the table and analysed by Spearman Correlation test to analyze the relationship between groundwater calcium with dental caries.

RESULTS:

Average groundwater calcium content was 126.75 mg/litre (high category), and average dental caries was 2.2 (low category). Spearman correlation analysis showed p = 0.029 (p < 0.000), which means there was a correlation between groundwater calcium level with dental caries.

CONCLUSION:

There is a positive relationship between the calcium content of groundwater with dental caries.

Study of physico-chemical properties and in vitro antimicrobial activity of hydroxyapatites obtained from bone calcination

Hydroxyapatite was obtained by bone calcinations. To study the calcination process, bovine and porcine bones were first autoclaved to remove fat and other non-bone tissues. They were then heated in an alumina pan in an oxidizing atmosphere of air, where simultaneous thermal analysis curves were recorded. To prepare the hydroxyapatites, bone samples were calcined at 850 °C and 1000 °C using a muffle furnace for 1 h. The obtained materials were powdered using mortar and pestle, and sifted in a sieve (60 mesh) without any additional purification or chemical treatment. The materials obtained were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The antimicrobial properties of these materials were determined through direct contact tests against Staphylococcus aureus. The natural hydroxyapatites obtained by bone calcination inhibited S. aureus growth, with the material obtained by calcination of bovine bones at 1000 °C, showing the best antimicrobial activity. These results indicated that bone wastes can be used to obtain hydroxyapatites with antimicrobial activity.

The application of nanogenerators and piezoelectricity in osteogenesis

Bone is a complex organ possessing both physicomechanical and bioelectrochemical properties. In the view of Wolff's Law, bone can respond to mechanical loading and is subsequently reinforced in the areas of stress. Piezoelectricity is one of several mechanical responses of the bone matrix that allows osteocytes, osteoblasts, osteoclasts, and osteoprogenitors to react to changes in their environment. The present review details how osteocytes convert external mechanical stimuli into internal bioelectrical signals and the induction of intercellular cytokines from the standpoint of piezoelectricity. In addition, this review introduces piezoelectric and triboelectric materials used as self-powered electrical generators to promote osteogenic proliferation and differentiation due to their electromechanical properties, which could promote the development of promising applications in tissue engineering and bone regeneration.

In Vivo Rodent Models for Studying Dental Caries and Pulp Disease

Dental caries is an infectious oral disease caused primarily by complex interactions of cariogenic oral flora (biofilm) with dietary carbohydrates on the tooth surface over time. Streptococcus mutans and Streptococcus sobrinus (S. mutans and S. sobrinus) are the most prevalent cariogenic species within the oral biofilm and considered the main etiological agents of caries. Pulp exposure and infection can be caused by trauma, carious lesion, and mechanical reasons. Pulp response to these exposures depends on the state of the pulp as well as the potential bacterial contamination of pulp tissue. Herein, we describe the process of using two in vivo rodent models to study the progression of dental caries and pulp disease: a nutritional microbial model and a pulp disease induction model. The progression of the carious lesion and pulpal infections in both models was assessed by micro-CT imaging and histomorphometric analysis. Moreover, the pulp disease induction models can be used to compare and assess the antibacterial and reparative properties of the different pulp capping materials.