Surface characterization and biological properties of regular dentin, demineralized dentin, and deproteinized dentin

Autologous Tooth Granulometry and Specific Surface Area with Three Grinding Methods: An In Vitro Study

A postextraction socket becomes a clinical challenge due to the fact that a series of changes associated with bone remodelling and resorption of the socket that occur after extraction, which limits the aesthetic and functional prognosis of implant-supported rehabilitations. It has been studied that the use of the autologous tooth-derived graft (ATDG) has regenerative properties and could therefore be useful for solving this type of problem. There is no consensus in the scientific literature on a standardized protocol for the use of the autologous tooth. Therefore, the aim of the present study was to evaluate the most relevant parameters to achieve the best properties of ground ATDG using three methods, namely Gouge forceps, electric grinder, and manual, that made up the study group (SG) and compared with the control group (CG) consisting of Bio-Oss®. The sample obtained by the electric grinder had the highest value of specific surface area (2.4025 ± 0.0218 m2/g), while the particle size as average diameter (751.9 µm) was the lowest and most homogeneous of the three groups. Therefore, the electric grinder allowed for obtaining ATDG with more regenerative properties due to its specific surface-area value and particle size in accordance with the xenograft with the greatest bibliographical support (Bio-Oss®). The higher specific surface increases the reaction with the physiological media, producing faster biological mechanisms.

Morphological aspects and distribution of granules composed of deproteinized bovine bone or human dentin into a putty mixture: an in vitro study

OBJECTIVE

The main aim of this study was to evaluate the morphological aspects and distribution of granules composed of deproteinized bovine bone mineral (DBBM) and human dentin-derived bone graft (HDBG) into a putty consistency mixture.

MATERIALS AND METHODS

DBBM or HDBG were mixed with an alginate-based hydrogel at two different granule/hydrogel ratio (1:1 and 1:3) and divided into four test groups while two control groups were composed of DBBM or HDBG free of hydrogel. Groups of specimens were cross-sectioned for morphological evaluation by scanning electron microscopy (SEM) at backscattered electrons mode. Details on the dimensions and pores' size of DBBM and HDBG were evaluated after mixing different amounts of particles and alginate-based hydrogels.

RESULTS

Microscopic analyses revealed a size of DBBM granules ranging from 750 up to 1600 μm while HDBG particles showed particle size ranging from 375 up to 1500 μm. No statistical differences were identified regarding the size of granules (p > 0.5). The mean values of pores' size of DBBM particles were noticed at around 400 μm while HDBG particles revealed micro-scale pores of around 1-3 μm promoted by the dentin tubules (p < 0.05). The lowest distance between particles was at 125 μm for HDBG and 250 μm for DBBM when the particle content was increased. On decreasing the particles' content, the distance between particles was larger for DBBM (~ 1000 μm) and HDBG (~ 1100 μm). In fact, statistically significant differences were found when the content of granules increased (p < 0.05).

CONCLUSIONS

The increased content of bioactive ceramic granules in a putty consistency mixture with hydrogel decreased the space among granules that can promote a high ceramic density and stimulate the bone growth over the healing process. Macro-scale pores on bovine bone mineral granules stimulate the formation of blood vessels and cell migration while the micro-scale pores of dentin-derived granules are proper for the adsorption of proteins and growth of osteogenic cells on the bone healing process.

CLINICAL SIGNIFICANCE

A high amount of bioactive ceramic granules should be considered when mixing with hydrogels as a putty material since that result in small spaces among granules maintaining the bone volume over the bone healing process. Deproteinized bovine bone mineral granules have macro-scale pores providing an enhanced angiogenesis while dentin-derived granules possess only micro-scale pores for the adsorption of proteins and proliferation of osteogenic cells on the bone healing process. Further studies should evaluate the combination of different bioactive ceramic materials for enhanced bone healing.

Photocrosslinkable gelatin-treated dentin matrix hydrogel as a novel pulp capping agent for dentin regeneration: I. synthesis, characterizations and grafting optimization

BACKGROUND

In recent years, treated dentin matrix (TDM) has been introduced as a bioactive hydrogel for dentin regeneration in DPC. However, no study has introduced TDM as a photocrosslinkable hydrogel with a natural photoinitiating system. Therefore, the present study aimed to explore the synthesis, characterizations and grafting optimization of injectable gelatin- glycidyl methacrylate (GMA)/TDM hydrogels as a novel photocrosslinkable pulp capping agent for dentin regeneration.

METHODS

G-GMA/TDM hydrogel was photocrosslinked using a new two-component photoinitiating system composed of riboflavin as a photoinitiator under visible light and glycine as a first time coinitiator with riboflavin. The grafting reaction conditions of G-GMA/TDM e.g. GMA concentration and reaction time were optimized. The kinetic parameters e.g. grafting efficiency (GE) and grafting percentage (GP%) were calculated to optimize the grafting reaction, while yield (%) was determined to monitor the formation of the hydrogel. Moreover, G-GMA/TDM hydrogels were characterized by swelling ratio, degradation degree, and cytotoxicity. The instrumental characterizations e.g. FTIR, 1H-NMR, SEM and TGA, were investigated for verifying the grafting reaction. Statistical analysis was performed using F test (ANOVA) and Post Hoc Test (P = 0.05).

RESULTS

The grafting reaction dramatically increased with an increase of both GMA concentration and reaction time. It was realized that the swelling degree and degradation rate of G-GMA/TDM hydrogels were significantly reduced by increasing the GMA concentration and prolonging the reaction time. When compared to the safe low and moderate GMA content hydrogels (0.048, 0.097 M) and shorter reaction times (6, 12, 24 h), G-GMA/TDM with high GMA contents (0.195, 0.391 M) and a prolonged reaction time (48 h) demonstrated cytotoxic effects against cells using the MTT assay. Also, the morphological surface of G-GMA/TDM freeze-dried gels was found more compacted, smooth and uniform due to the grafting process. Significant thermal stability was noticed due to the grafting reaction of G-GMA/TDM throughout the TGA results.

CONCLUSIONS

G-GMA/TDM composite hydrogel formed by the riboflavin/glycine photoinitiating system is a potential bioactive and biocompatible system for in-situ crosslinking the activated-light pulp capping agent for dentin regeneration.

Dentin extracellular matrix loaded bioactive glass/GelMA support rapid bone mineralization for potential pulp regeneration

The study aims to develop a novel dentin extracellular matrix (dECM) loaded gelatin methacrylate (GelMA)-5 wt% bioactive glass (BG) (Gel-BG) hydrogel for dental pulp regeneration. We investigate the role of dECM content (2.5, 5, and 10 wt%) on the physicochemical characteristics and biological responses of Gel-BG hydrogel in contact with stem cells isolated from human exfoliated deciduous teeth (SHED). Results showed that the compressive strength of Gel-BG/dECM hydrogel significantly enhanced from 18.9 ± 0.5 kPa (at Gel-BG) to 79.8 ± 3.0 kPa after incorporation of 10 wt% dECM. Moreover, we found that in vitro bioactivity of Gel-BG improved and the degradation rate and swelling ratio reduced with increasing dECM content. The hybrid hydrogels also revealed effectual biocompatibility, >138 % cell viability after 7 days of culture; where Gel-BG/5%dECM was most suitable. In addition, the incorporation of 5 wt% dECM within Gel-BG considerably improved alkaline phosphatase (ALP) activity and osteogenic differentiation of SHED cells. Taken together, the novel bioengineered Gel-BG/dECM hydrogels having appropriate bioactivity, degradation rate, osteoconductive and mechanical properties represent the potential applications for clinical practice in the future.

Treated Dentin Matrix in Tissue Regeneration: Recent Advances

Tissue engineering is a new therapeutic strategy used to repair serious damage caused by trauma, a tumor or other major diseases, either for vital organs or tissues sited in the oral cavity. Scaffold materials are an indispensable part of this. As an extracellular-matrix-based bio-material, treated dentin matrixes have become promising tissue engineering scaffolds due to their unique natural structure, astonishing biological induction activity and benign bio-compatibility. Furthermore, it is important to note that besides its high bio-activity, a treated dentin matrix can also serve as a carrier and release controller for drug molecules and bio-active agents to contribute to tissue regeneration and immunomodulation processes. This paper describes the research advances of treated dentin matrixes in tissue regeneration from the aspects of its vital properties, biologically inductive abilities and application explorations. Furthermore, we present the concerning challenges of signaling mechanisms, source extension, individualized 3D printing and drug delivery system construction during our investigation into the treated dentin matrix. This paper is expected to provide a reference for further research on treated dentin matrixes in tissue regeneration and better promote the development of relevant disease treatment approaches.

SEM and FT-MIR Analysis of Human Demineralized Dentin Matrix: An In Vitro Study

Recently, the demineralized dentin matrix has been suggested as an alternative material to autologous bone grafts and xenografts for clinical purposes. The aim of this study was to investigate the effect of different times of demineralization on the chemical composition and the surface morphology of dentinal particles. Extracted teeth were ground and divided into 5 groups based on demineralization time (T0 = 0 min, T2 = 2 min, T5 = 5 min, T10 = 10 min, and T60 = 60 min) with 12% EDTA. The analysis was performed using Fourier-Transform Mid-Infrared spectroscopy (FT-MIR) and Scanning Electron Microscopy (SEM) (p < 0.05). The FT-MIR analysis showed a progressive reduction of the concentration of both PO43− and CO32− in the specimens (T0 > T2 > T5 > T10 > T60). On the contrary, the organic (protein) component did not undergo any change. The SEM examination showed that increasing the times of demineralization resulted in a smoother surface of the dentin particles and a higher number of dentinal tubules.

Physicochemical and Morphological Characterization of Dentin from Deciduous and Permanent Teeth Processed by Different Methods for Tissue Regeneration

The composition of autogenous dentin differs from that of extracted deciduous and permanent teeth, as graft material must undergo procedures prior to implantation. The aim of this study was to characterize the physicochemical and morphological properties of dentin from deciduous (DTs) and permanent teeth (PTs) that had been demineralized (DMA), deproteinized (DPA), and decellularized (DSA). The dentin particles were DMA with ethylenediaminetetraacetic acid (EDTA), DPA with isopropanol, and DSA with sodium dodecyl sulfate (SDS). Sound dentin (SD) was used as the control group. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) and X-ray diffraction (XRD) were used to examine the surface and physicochemical properties of the dentin. DMA and DPA dentin had lower concentrations of calcium and protein respectively than SD, showing a significant difference compared with DMA and DPA dentin from DTs and PTs (p < 0.05). In the DSA dentin, it was possible to eliminate the cellular residues of dentin from DTs and PTs, and the gene GAPDH was not expressed. The results of FTIR and XRD revealed a different physicochemical composition according to the dentin processing. EDS demonstrated that DMA dentin obtained the lowest values of calcium and phosphate, and the micrographs obtained by SEM exhibited a porous matrix structure in DMA dentin to a greater degree than in DPA or DSA dentin. The physicochemical properties and morphology of dentin as an autograft material differ depending on whether the teeth are deciduous or permanent; the processing method conditions the characteristics of the dentin substrate as a matrix for tissue regeneration.

Bio-Morphological Reaction of Human Periodontal Ligament Fibroblasts to Different Types of Dentinal Derivates: In Vitro Study

Understanding the biological and morphological reactions of human cells towards different dentinal derivate grafting materials is fundamental for choosing the type of dentin for specific clinical situations. This study aimed to evaluate human periodontal ligament fibroblasts (hPLF) cells exposed to different dentinal derivates particles. The study design included the in vitro evaluation of mineralized dentine (SG), deproteinized and demineralized dentine (DDP), and demineralized dentine (TT) as test materials and of deproteinized bovine bone (BIOS) as the positive control material. The materials were kept with the hPLF cell line, and the evaluations were made after 24 h, 72 h, and 7 days of in vitro culture. The evaluated outcomes were proliferation by using XTT assays, the morphological characteristics by light microscopy (LM) and by the use of scanning electron microscopy (SEM), and adhesion by using confocal microscopy (CLSM). Overall, the experimental materials induced a positive response of the hPLFs in terms of proliferation and adhesion. The XTT assay showed the TT, and the SG induced significant growth compared to the negative control at 7 days follow-up. The morphological data supported the XTT assay: the LM observations showed the presence of densely packed cells with a modified shape; the SEM observations allowed the assessment of how fibroblasts exposed to DDP and TT presented cytoplasmatic extensions; and SG and BIOS also presented the thickening of the cellular membrane. The CLMS observations showed the expression of the proliferative marker, as well as and the expression of cytoskeletal elements involved in the adhesion process. In particular, the vinculin and integrin signals were stronger at 72 h, while the actin signal remained constantly expressed in all the follow-up of the sample exposed to SG material. The integrin signal was stronger at 72 h, and the vinculin and actin signals were stronger at 7 days follow-up in the sample exposed to DDP material. The vinculin and integrin signals were stronger at 72 h follow-up in the sample exposed to TT material; vinculin and integrin signals appear stronger at 24 h follow-up in the sample exposed to BIOS material. These data confirmed how dentinal derivates present satisfying biocompatibility and high conductivity and inductivity properties fundamental in the regenerative processes. Furthermore, the knowledge of the effects of the dentin’s degree of mineralization on cellular behavior will help clinicians choose the type of dentine derivates material according to the required clinical situation.

Tomographic evaluation of direct pulp capping using a novel injectable treated dentin matrix hydrogel: a 2-year randomized controlled clinical trial

OBJECTIVES

To assess clinically and radiographically the success of pulp capping procedure done in traumatically exposed permanent posterior teeth using a novel injectable treated dentin matrix hydrogel (TDMH), Biodentine, and MTA and to evaluate the formed dentin bridge under the capping materials using CBCT imaging.

MATERIALS AND METHODS

45 patients subjected to accidental traumatic pulp exposures by undergraduate dental students are allocated for this study. For each patient, a pulp capping procedure was done. TDMH was formed of TDM powder and sodium alginate to be injected and then hardened in the defect area. Patients were assigned to 3 groups: TDMH, Biodentine, and MTA, respectively, and returned to the clinic after 3, 6, 12, 18, and 24 months for clinical and radiographic examinations. Tomographic data, including thickness and density of formed dentin bridges, were evaluated at the end of the study period compared to the base line. Pulp sensitivity was evaluated throughout the study period using thermal testing and electric pulp tester.

RESULTS

During the follow-up period, all patients were asymptomatic with no clinical signs and symptoms and revealed no radiographic signs of pathosis. However, tomographic evaluation showed the tested materials to have different levels of impact on formed dentin bridges with TDMH group resulted in significantly superior dentin bridges of a higher radiodensity and thickness than Biodentine and MTA.

CONCLUSIONS

TDMH has a greater potential to induce dentin bridge formation than Biodentine and MTA under standardized conditions. Additionally, CBCT imaging was confirmed as a non-invasive and inclusive approach to evaluate the formed dentin bridges after pulp capping procedure.

CLINICAL RELEVANCE

Direct pulp capping can be done successfully with this novel injectable pulp capping material in future clinical applications.

TRIAL REGISTRATION

PACTR201901866476410.

Histological evaluation of the regenerative potential of a novel treated dentin matrix hydrogel in direct pulp capping

OBJECTIVES

To produce a novel injectable treated dentin matrix hydrogel (TDMH) to be used as a novel pulp-capping agent for dentin regeneration compared with Biodentine and MTA.

MATERIALS AND METHODS

Thirty intact fully erupted premolars scheduled to be extracted for orthodontic reasons were included. Pulps were mechanically exposed in the middle of the cavity floor. TDMH was composed of TDM powder (500-μm particle size) and sodium alginate as an injectable scaffold. The capped teeth were divided into three equal groups (n = 10): TDMH, Biodentine, and MTA respectively. Clinical examination and assessment of periapical response were performed. The teeth were extracted after 2-weeks and 2-month intervals, stained with hematoxylin-eosin, and categorized by using a histologic scoring system. Statistical analysis was performed using chi-square and Kruskal-Wallis test (p = 0.05).

RESULTS

All teeth were vital during observation periods. Histological analysis after 2 months showed complete dentin bridge formation and absence of inflammatory pulp response with no significant differences between groups. However, the formed dentin was significantly thicker with the TDMH group with layers of well-arranged odontoblasts that were found to form a homogenous tubular structure with numerous dentinal tubule lines showing a positive trend to dentin regeneration.

CONCLUSIONS

TDMH could achieve dentin regeneration and conservation of pulp vitality and might serve as a feasible natural substitute for silicate-based cements in restoring in vivo dentin defect in direct pulp-capping procedure.

TRIAL REGISTRATION

PACTR201901866476410.

Comparative evaluation of platelet-rich fibrin, platelet-rich fibrin + 50 wt% nanohydroxyapatite, platelet-rich fibrin + 50 wt% dentin chips on odontoblastic differentiation - An in vitro study-part 2

AIM

The purpose of this study was to investigate the effects of platelet-rich fibrin (PRF) modified with bioactive radiopacifiers-nanohydroxyapatite (nHA) and dentin chips (DC) on odontoblastic differentiation in human dental pulp cells (HDPCs).

SUBJECTS AND METHODS

PRF was modified with 50wt% of nHA (G bone-SHAG31, Surgiwear Company) and 50 wt% of DC. HDPSCs differentiation and mineralization by the groups ([Group A - Control (Dimethyl sulfoxide), Group B - PRF, Group C - PRF + nHA, Group D - PRF + DC]) were assessed. ELISA was done to quantify the interleukin (IL)-6 and IL-8 cytokine expression. The odontoblastic differentiation was determined by the expression of odontogenesis-related genes and the extent of mineralization using alizarin red S staining.

STATISTICAL ANALYSIS USED

One-way ANOVA with post hoc Tukey-honestly significant difference tests were applied to assess the significance among various groups.

RESULTS

The level of inflammatory cytokines (IL-6 and IL-8) expression by Group D (PRF + 50 wt% DC) was higher compared to Group B (PRF) and Group C (PRF + 50 wt% DC). Group C (PRF + 50 wt% nHA) induced more mineralization nodules compared to other groups. The integrated density value for the DSPP and DMP-1 protein expression by Group C (PRF + 50 wt% nHA) and Group D (PRF + 50 wt% DC) was higher compared to Group B (PRF).

CONCLUSIONS

The results suggest that the addition of bioactive radiopacifiers into PRF has a synergistic effect on the stimulation of odontoblastic differentiation of HDPCs, hence inducing mineralization.

[Dentin matrix in tissue regeneration: a progress report]

Lesions on tissues and organs critically affect quality of life, due to severe tissue defects that are threatening. Tissue repair and functional reconstruction are concurrent challenges in modern medicine. Tissue engineering brings hope for tissue and organ regeneration. Scaffolds provide a microenvironment for cell growth, proliferation and differentiation. Moreover, scaffolds influence the size and morphology of regenerated tissues. Dentin matrix, which is a natural bioactive and biocompatible scaffold, has become a research hotspot in recent years and has been widely used in tissue engineering. Studies on the use of dentin matrix as scaffolds have made a series of important progress in tooth root, periodontal, dental pulp and bone regeneration. This review demonstrates the biological characteristics of dentin matrix as bioactive scaffolds, describes the application of dentin matrix in tissue regeneration and provides a theoretical basis for the use of a dentin matrix in clinical applications.

Effect of sodium chloride on gene expression of Streptococcus mutans and zeta potential of demineralized dentin

Purpose

In this work, the effects of sodium chloride (NaCl) on gene expression of planktonic Streptococcus mutans cells are investigated. Also assessed are the effects of NaCl on zeta potential of sound and demineralized dentin.

Methods

The relative level of glucosyltransferase B (gtfB), gtfC and gtfD transcription of S. mutans in the presence of NaCl was evaluated by quantitative polymerase chain reaction (qPCR). The osmolality of varying salt (NaCl) concentrations and their influence on the zeta potential of sound and demineralized dentin was investigated as well.

Results

NaCl significantly reduced the expression of gtfB and C genes in planktonic S. mutans; whereas, gtf D gene expression significantly increased in the presence of NaCl (P < 0.05). NaCl at concentrations of 37.5 mg/ml reduced zeta potential of demineralized dentin, while no significant decrease of zeta potential was found when sound dentin was exposed to this concentration.

Conclusion

NaCl reduces the expression of some gtfs in S. mutans and increases negative potential charge of demineralized dentin.

Surface characteristics of three commercially available grafts and adhesion of stem cells to these grafts

BACKGROUND

Reconstruction of bone defects is often performed using bone autografts. However, limitations associated with the use of autografts led to the use of bone substitute materials.

OBJECTIVES

The purpose of this study was to compare the surface characteristics of three commercially available grafts namely allografts, xenografts and alloplasts.

METHODS

This in vitro study was conducted on beta-tricalcium phosphate (β-TCP) alloplast, a mixture of demineralized bone matrix and mineralized bone allograft (DBM&MBA) and natural bovine bone mineral (NBBM) xenograft. Presence of apatite groups on the surface of samples was assessed by X-ray diffraction (XRD) while the presence of functional groups was evaluated using Fourier transform infrared spectroscopy (FTIR). Also, dental pulp stem cells (DPSCs) were cultured on the surface of samples and their adhesion was evaluated under a scanning electron microscope (SEM).

RESULTS

The FTIR showed a relatively similar pattern for NBBM and TCP samples and a different pattern in DBM&MBA. The results of XRD analysis also showed similarities between NBBM and TCP with sharper peaks than the DBM&MBA sample. The SEM micrographs showed that at 24 hours, no cell was detectable on the surface of NBBM sample; whereas, elongated cells were noted on the surface of TCP and DBM&MBA samples.

CONCLUSIONS

The patterns of β-TCP and NBBM samples in XRD and FTIR spectroscopy showed high resemblance but they had different behaviors with respect to cell adhesion.

tBHQ Suppresses Osteoclastic Resorption in Xenogeneic-Treated Dentin Matrix-Based Scaffolds

Extracellularmatrix (ECM)-based scaffolds are important for their potential therapeutic application. Treated dentin matrix (TDM), a kind of ECM, seeded with allogeneic dental follicle stem cells (TDM/aDFC) provides a suitable inductive microenvironment for tooth root regeneration. Considering the limited sources, xenogeneic TDM (xTDM) is a possible alternative to allogeneic TDM; however, xTDM-based scaffold presents severe osteolysis and resorption lacunae causing regenerated tooth root failure. Immune response-induced excessive osteoclastogenesis plays a critical role in xenogeneic scaffold osteolysis and resorption. The impact of antioxidant, tert-butylhydroquinone (tBHQ), on xTDM/aDFCs-induced osteoclastogenesis and osteoclastic resorption in vivo and in vitro are investigated. tBHQ upregulates heme oxygenase-1 release and downregulates high mobility group box 1 mRNA expression. mRNA expression of other osteoclast-related genes including nuclear factor-kappa Bp65, receptor activator of nuclear factor kappa-B, nuclear factor of activated T-cells cytoplasmic 1, cathepsin K, and integrin β3, also decreases significantly. Furthermore, tBHQ-treated xTDM/aDFCs scaffolds implanted into rhesus macaques show reduced osteolysis and osteoclastic resorption by microcomputed tomography and tartrate-resistant acid phosphatase staining. tBHQ-induced suppression of xTDM/aDFC-induced osteoclastogenesis and osteoclastic resorption presents a new strategy for the regeneration of biological tooth root and could be applied to the regeneration of other complex tissues and organs.

Demineralized dentin and enamel matrices as suitable substrates for bone regeneration

Background

In recent decades, tooth derivatives such as dentin (D) and enamel (E) have been considered as potential graft biomaterials to treat bone defects. This study aimed to investigate the effects of demineralization on the physical-chemical and biological behavior of D and E.

Methods

Human D and E were minced into particles (Ø<1 mm), demineralized and sterilized. Thorough physical-chemical and biochemical characterizations of native and demineralized materials were performed by SEM and EDS analysis and ELISA kits to determine mineral, collagen type I and BMP-2 contents. In addition, MG63 and SAOS-2 cells were seeded on tooth-derived materials and Bio-Oss®, and a comparison of cell responses in terms of adhesion and proliferation was carried out.

Results

The sterilization process, as a combination of chemical and thermal treatments, was found to be effective for all materials. On the other hand, D demineralization allowed preserving the collagen content, while increasing BMP-2 bioavailability. D and demineralized D (dD) displayed excellent biocompatibility, even greater than Bio-Oss®. Conversely, the high mineral content displayed by E, as confirmed by EDS analysis, inhibited cell proliferation. Of note, even though the demineralization process was somehow less effective in E than in D, demineralized E (dE) displayed increased BMP-2 bioavailability and improved performance in vitro compared with native E.

Conclusions

Our results substantiate the idea that the demineralization process lead to an increase of BMP-2 bioavailability, thus paving the way toward development of more effective, osteoinductive tooth-derived materials for bone regeneration and replacement.