Histological Evaluation of Pulpal Response and Dentin Bridge Formation After Direct Pulp Capping Using Recombinant Amelogenin and Mineral Trioxide Aggregate (MTA).

The purpose of the study was to compare and histologically investigate pulpal response and dentin bridge formation after direct pulp capping using recombinant amelogenin and mineral trioxide aggregate (MTA). Recombinant amelogenin protein and MTA were used as pulp capping materials in 120 teeth from eight mongrel dogs. Dogs were sacrificed at two different evaluation times. Regenerative changes were evaluated histologically. At two weeks, in contrast to the MTA group, most of the amelogenin group showed moderately formed hard tissue formation and the pulp tissue was completely filling the entire pulp chamber. These results were statistically significant. At two months, all the samples of the amelogenin group showed complete dentin bridge formation and the pulp chamber was filled entirely with tissue-mimicking the authentic pulp in all the specimens of the amelogenin group. These results were statistically significant. In conclusion, direct pulp capping by recombinant amelogenin protein resulted in significantly better regeneration of the dentin-pulp complex than MTA.

Amelogenin as a regenerative endodontic molecule for immature teeth with apical periodontitis. An experimental study.

Vitality of the dentin-pulp complex depends on cell activity and signalling processes. Amelogenin protein regulates cell signalling pathways during tooth development by activating the Wnt/ß-catenin intercellular signalling pathway. This study aimed to regenerate a vascularized pulp using recombinant amelogenin protein, in necrotic root canals by cell homing. Access opening was performed for a total of 120 root canals and were left open to become contaminated with oral microbes for 14 days then cleaned. Canals were divided into 2 groups; in the First group, the canals were filled with amelogenin, while in the 2nd group the canals were left empty. Samples were evaluated histologically and with immunodetection of Sox2, Oct4, Vascular endothelial growth factor (VEGF), Wnt1a, Wnt 3a, Wnt 10b, and Glial Fibrillary Acidic Proteins (GFAP). IC50 was used to determine the cytotoxicity of amelogenin. Regenerated dense cellular tissue was seen in the apical part of amelogenin-treated root canals, and regenerated delicate vascularized tissue was observed in the radicular and pulp chamber. Cells found in the regenerated soft tissue expressed Wnt family members that regulate stem cell pluripotency. Also, Sox2 and Oct4, Pluripotency markers, could be identified in the newly formed apical papilla and dental follicle. Furthermore, VEGF in the regenerated pulps indicated neovascularization. While the GFAP immune reactivity demonstrated that the neuro-sensory organ was being replicated in the regenerated dental pulps. Finally, IC50 test showed that recombinant amelogenin protein has a safe dose at high-level concentrations. Recombinant amelogenin protein induces pulp regeneration most likely from the Sox2 identified stem cells within the apical papilla and can enhance apex formation in non-vital immature teeth.

Regeneration of Neural Networks in Immature Teeth with Non-Vital Pulp Following a Novel Regenerative Procedure.

BACKGROUND AND OBJECTIVES: Recombinant amelogenin protein (RAP) was reported to induce soft-tissue regeneration in canine infected endodontically treated permanent teeth with open apices. To characterize identities of the cells found in the RAP regenerated tissues compared to authentic pulp by identifying: 1) stem cells by their expression of Sox2; 2) nerve fibers by distribution of the axonal marker peripherin; 3) axons by their expression of calcitonin gene-related peptide (CGRP); 4) the presence of astrocytes expressing glial fibrillary acidic proteins (GFAP). METHODS: A total of 240 open-apex root canals in dogs were used. After establishment of oral contamination to the pulp, the canals were cleaned, irrigated, and 120 canals filled with RAP, and the other 120 with calcium hydroxide. RESULTS: After 1, 3, and 6 months, teeth were recovered for immune-detection of protein markers associated with native pulp tissues. Regenerated pulp and apical papilla of RAP group revealed an abundance of stem cells showing intense immunoreactivity to Sox2 antibody, immunoreactivity of peripherin mainly in the A-fibers of the odontoblast layer and immunoreactivity to CGRP fibers in the central pulp region indicative of C-fibres. GFAP immunoreactivity was observed near the odontoblastic, cell-rich regions and throughout the regenerated pulp. CONCLUSIONS: RAP induces pulp regeneration following regenerative endodontic procedures with cells identity by gene expression demonstrating a distribution pattern similar to the authentic pulp innervation. A- and C-fibers, as well as GFAP specific to astrocytic differentiation, are recognized. The origin of the regenerated neural networks may be derived from the Sox2 identified stem cells within the apical papilla.

Characterization of the apical bridge barrier formed following amelogenin apexification.

BACKGROUND: Recombinant amelogenin protein (RAP) is reported to induce complete root apex formation in dog model when used as apexification therapy. It also induces pulp regeneration in 85% of the treated group. Thus, the aim of this study was to investigate the nature of the remaining regenerated calcified tissues of the RAP group that showed no pulp regeneration compared to the calcium hydroxide treated group (CH). METHODS: A total of 240 dogs' open apex root canals were used, after establishment of canals contamination. Canals were cleaned, irrigated, and filled with RAP as an apexification material and compared with CH. Treated teeth were assessed by H&E, trichrome staining, and/or immunohistochemistry technique, at 1, 3, and 6 months. RESULTS: A time-dependent increase in the calcified tissue barrier was observed in the apex of the RAP-treated group compared to the CH-treated group. The newly formed dentin in this RAP group was mainly tubular dentin and was functionally attached to the bone by periodontal ligament, while the CH group showed dentin-associated mineralized tissue (DAMT) associated with the newly formed apical barrier. CONCLUSIONS: Out results suggest that RAP can be used as novel apexification material, resulting in a thickening and strengthening of the canal walls, and achieving apical closure.

Recombinant Amelogenin Protein Induces Apical Closure and Pulp Regeneration in Open-apex, Nonvital Permanent Canine Teeth.

INTRODUCTION: Recombinant DNA-produced amelogenin protein was compared with calcium hydroxide in a study of immature apex closure conducted in 24 young mongrel dogs. METHODS: Root canals of maxillary and mandibular right premolars (n = 240) were instrumented and left open for 14 days. Canals were cleansed, irrigated, and split equally for treatment with recombinant mouse amelogenin (n = 120) or calcium hydroxide (n = 120). RESULTS: After 1, 3, and 6 months, the animals were sacrificed and the treated teeth recovered for histologic assessment and immunodetection of protein markers associated with odontogenic cells. After 1 month, amelogenin-treated canals revealed calcified tissue formed at the apical foramen and a pulp chamber containing soft connective tissue and hard tissue; amelogenin-treated canals assessed after 3- and 6-month intervals further included apical tissue functionally attached to bone by a periodontal ligament. In contrast, calcified apical tissue was poorly formed in the calcium hydroxide group, and soft connective tissue within the pulp chamber was not observed. CONCLUSIONS: The findings from this experimental strategy suggest recombinant amelogenin protein can signal cells to enhance apex formation in nonvital immature teeth and promote soft connective tissue regeneration.

Histological evaluation of enamel matrix derivative as a pulpotomy agent in primary teeth.

PURPOSE: The purpose of this study was to evaluate histologically the effect of an enamel matrix derivative as a pulpotomy agent in primary canines. METHODS: Ten carious primary canines among teeth deemed for serial extraction were selected for this study. Emdogain gel was used as the pulp dressing material on the amputated pulp stumps. Teeth were extracted postoperatively after: (1) 1 week; (2) 2 weeks; and (3) 6 months. The extracted teeth were examined histologically to assess the response of the pulp to Emdogain gel after the pulpotomy procedure. RESULTS: Of the teeth extracted after 1 week, the amputated pulpal surface was lined by a thin, nearly continuous cellular layer. Generalized congestion was accompanied by an increase in angiogenesis. Of the teeth extracted after 2 weeks, most showed small islands of dentin-like tissue at different stages of mineralization. Of the teeth extracted after 6 months, several different histological pictures were viewed. Most of the teeth showed coalescing islands of dentin-like tissue trying to bridge the full width of the coronal pulp at the interface between the wounded and unharmed pulp tissue below the amputation site. CONCLUSION: Based on these experiments, Emdogain gel shows promising results as a valuable material for use in pulpotomy procedures, especially in the primary dentition.

Comparison of mineral trioxide aggregate and formocresol as pulp-capping agents in pulpotomized primary teeth.

PURPOSE: The aim of this study was to use clinical, radiographic, and histologic examinations to compare the relative success of gray mineral trioxide aggregate (MTA), white MTA, and formocresol as pulp dressings in pulpotomized primary teeth. METHODS: Twenty-four children, each with at least 3 primary molars requiring pulpotomy, were selected for this study's clinical and radiographic portion. An additional 15 carious primary teeth planned for serial extraction were selected for this study's histologic portion. All selected teeth were evenly divided into 3 test groups and treated with pulpotomies. Gray MTA was used as the pulp dressing for one third of the teeth, white MTA was the dressing for one third, and the remaining one third were treated with formocresol. The treated teeth selected for the clinical and radiographic evaluations were monitored periodically for 12 months. The treated teeth selected for histologic study were monitored periodically and extracted 6 months postoperatively. RESULTS: Four children with 12 pulpotomized teeth failed to return for any follow-up evaluations in the clinical and radiographic study. Of the remaining 60 teeth in 20 patients, 1 tooth (gray MTA) exfoliated normally and 6 teeth (4 white MTA and 2 formocresol) failed due to abscesses. The remaining 53 teeth appeared to be clinically and radiographically successful 12 months postoperatively. Pulp canal obliteration was a radiographic finding in 11 teeth treated with gray MTA and 1 tooth treated with white MTA. In the histologic study, both types of MTA successfully induced thick dentin bridge formation at the amputation sites, while formocresol induced thin, poorly calcified dentin. Teeth treated with gray MTA demonstrated pulp architecture nearest to normal pulp by preserving the odontoblastic layer and delicate fibrocellular matrix, yet few inflammatory cells or isolated calcified bodies were seen. Teeth treated with white MTA showed a denser fibrotic pattern, with more isolated calcifications in the pulp tissue along with secondary dentin formation. CONCLUSIONS: Gray MTA appears to be superior to white MTA and formocresol as a pulp dressing for pulpotomized primary teeth.