Experimental formation of dentin-like structure in the root canal implant model using cryopreserved swine dental pulp progenitor cells

Objectives: The purpose of the present study was to present histological and immunohistochemical evidence demonstrating the regenerative capacity of swine dental pulp stem cells (S-DPSCs) seeded on organic or synthetic scaffolds and implanted as hybrid root implants in the jaw bone of mini pigs.Methods: Immature permanent incisor teeth and unerupted premolars at the early root-forming stage were extracted from three seven-month-old mini-pigs and mesenchymal stem / progenitor cells were isolated from dental pulp. Cells were cryopreserved in liquid nitrogen. Σeeth were processed for histological analysis in serial sections. Relationships between the anatomical zones of dental mesenchyme at the root apex were morphologically evaluated in hematoxylin-eosin and immunohistochemically stained for Tenascin-C and Syndecan-1 sections. A year later, new permanent incisor and premolar teeth were extracted, pulp tissue was removed and pieces of root canals of the extracted teeth, containing collagen or PLGA scaffolds seeded with the autologous cryopreserved DPSCs, were implanted into the fresh post-extraction socket of the mini pig jaw. The resulting constructs were harvested after 6 and 10 weeks and evaluated by histological and mmunohistochemical analyses.Results: Stem / progenitor cells isolated either from dental pulp or apical papilla tissue were found to be positive for CD90, CD105 and CD146 and negative for STRO-1 CD29 & CD31. Syndecan-1 immunostaining was detected in the odontoblastic layer along the newly deposited root dentine and the dental pulp around the capillaries. Tenascin-C was intensely expressed in the subodontoblastic cell region along the newly deposited root dentine and the whole dental pulp parenchyme. Apical papilla and dental follicle were negative for both antibodies. 6 weeks postoperatively, the central canal space of the root implants showed degrading scaffold material. New extracellular matrix had been deposited in a polar predentin-like pattern on the canal dentinal walls by cuboidal non-polarized cells. 10 weeks postoperatively, newly formed organic matrix had been consistently deposited on the canal walls. The presence of a continuous layer of polarized cells showing typical columnar morphology, adjacent to the newly deposited organic matrix was evident.Conclusions: The interactions of S-DPSCs with the dentin matrix of roots implanted in the jawbone of mini pigs constitute a model to study in vivo organization and differentiation potential of DPSCs. Expression patterns of the molecules Tenascin and Syndecan are very different between dental pulp and apical papilla tissues. Furthermore, it seems evident that cell surface markers are not able to identify by flow cytometry, individual dental stem / progenitor cell populations isolated from developmentally different areas

Dentinogenic Specificity in the Preclinical Evaluation of Vital Pulp Treatment Strategies: A Critical Review

Reviews on the clinical performance of vital pulp treatment strategies and capping materials repeatedly showed an insufficient grade of evidence concerning their therapeutic validity. The biological mechanisms underlying the regenerative potential of pulp-dentin complex have attracted much attention during the last two decades, since new pulp treatment modalities have been designed and tested at the preclinical level. It has been recognized that evaluation should be based on the specific ability of therapeutic interventions to signal recruitment and differentiation of odontoblast-like cells forming a matrix in a predentin-like pattern, rather than uncontrolled hard tissue deposition in a scar-like form. The aim of the present article was to critically review data from histological experimental studies on pulp capping, published during the last 7 decades. A comprehensive literature search covering the period from 1949 to 2015 was done using the Medline/Pubmed database. Inclusion of a study was dependent on having sufficient data regarding the type of capping material used and the unit of observation (human permanent tooth in vivo or animal permanent dentition; primary teeth were excluded). The post-operatively deposited matrix was categorized into three types: unspecified, osteotypic, or dentin-like matrix. One hundred fifty-two studies were included in the final evaluation. Data from the present systematic review have shown that only 30.2% of the 152 experimental histological pulp capping studies described the heterogenic nature of the hard tissue bridge formation, including osteotypic and tubular mineralized tissue. Structural characteristics of the new matrix and the associated formative cells were not provided by the remaining 106 studies. Analysis showed that more careful preclinical evaluation with emphasis on the evidence regarding the dentinogenic specificity of pulp therapies is required. It seems that selection of appropriate vital pulp treatment strategies and pulp capping materials would be further facilitated in terms of their therapeutic validity if international consensus could be reached on a select number of mandatory criteria for tissue-specific dentinogenic events

Shear Bond Strength of Ah26 to Human Dentin Treated with Dimethyl Sulfoxide (Dmso)

The purpose of this study was to examine the bond strength of AH26 to human coronal dentin exposed to DMSO. A total of 70 dentin specimens were equally divided into two groups. Each dentin surface was pre-treated with 2 mL of 2.5% NaOCl, 3 mL of EDTA 17%, and distilled water. One group was finally rinsed with 50% DMSO. Following the AH26 application, the bond strength was tested by subjecting the samples to a shear load at a crosshead speed of 0.5 mm/min using universal testing equipment. The results according to paired samples t-test indicated that there was a statistically insignificant difference between the two groups. Therefore, DMSO had no effect on the bond strength of AH26 root sealer to dentin