The effect of two different types of forces on possible root resorption in relation to dentin phosphoprotein levels: a single-blind, split-mouth, randomized controlled trial

Background The purpose of this 2-arm-parallel split-mouth trial was to evaluate and compare the extent of possible root resorption using dentin phosphoprotein levels in gingival crevicular fluid between controlled continuous and intermittent orthodontic force groups. Materials and methods A sample of 16 maxillary first premolars from 8 patients requiring bilateral extractions of the upper first premolars as part of their orthodontic treatment were recruited. A buccally directed continuous force of 150 g, reactivated after 28 days, was applied to the upper first premolar on one side for 8 weeks. On the contralateral first premolar, a buccally directed intermittent force (21 days on, 7 days off) of the same magnitude was applied for the same period. Gingival crevicular fluid samples were collected at the beginning of the study, 1st, 3rd, 4th and 5th week, and at the end of the study to quantify and compare dentin phosphoprotein levels in both groups. Results Dentin phosphoprotein levels showed a higher concentration in the continuous force group than the intermittent force group in week 4 and 8 of sample collection; where the differences were statistically significant (95% CI 0.007–0.14; P < .04) and (95% CI 0.02–0.17; P < .04) respectively. No harm was observed. Conclusions Dentin phosphoprotein was found to be a useful early biomarker to detect and monitor root resorption, showing that the application of an intermittent orthodontic force caused less root resorption than a continuous force. Trial registration NCT04825665 ClinicalTrials.gov. Registered 1 April 2021—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04825665.

Organic Matrix of Enamel and Dentin and Developmental Defects

The anatomical crown of the tooth is covered by enamel and root is covered by cementum. The dentin forms the major part of the tooth. The dentin structure is very similar to that of the bone both physically and chemically which is why many scientists have wondered about using its properties for developing a novel bone graft material. In contrast with hard and brittle enamel dentin is viscoelastic. The organic structure of dentin which is about 35% is composed of mainly type I collagen embedded in mucopolysaccharides ground substance. Approximately half of the non-collagenous composition consists of hyperphosphorylated proteins. The acidic glycoproteins, Gla-proteins, serum proteins, proteoglycans etc. composes the remaining part. The dentin matrix consists of many similar proteins as that of bone like dentin phosphoprotein, dentin sialoprotein etc.. The matrix also consists of many growth factors. Any external disturbance like an infection, trauma, calcium or phosphorous metabolic changes can lead to defective amelogenesis. Mutational changes can lead to defect in dentin. An early diagnosis can result in a satisfactory treatment plan contributing to functional and esthetical compensation.

Potential for Drug Repositioning of Midazolam for Dentin Regeneration

Drug repositioning promises the advantages of reducing costs and expediting approvalschedules. An induction of the anesthetic and sedative drug; midazolam (MDZ), regulatesinhibitory neurotransmitters in the vertebrate nervous system. In this study we show the potentialfor drug repositioning of MDZ for dentin regeneration. A porcine dental pulp-derived cell line(PPU-7) that we established was cultured in MDZ-only, the combination of MDZ with bonemorphogenetic protein 2, and the combination of MDZ with transforming growth factor-beta 1. Thedifferentiation of PPU-7 into odontoblasts was investigated at the cell biological and genetic level.Mineralized nodules formed in PPU-7 were characterized at the protein and crystal engineeringlevels. The MDZ-only treatment enhanced the alkaline phosphatase activity and mRNA levels ofodontoblast differentiation marker genes, and precipitated nodule formation containing a dentinspecificprotein (dentin phosphoprotein). The nodules consisted of randomly orientedhydroxyapatite nanorods and nanoparticles. The morphology, orientation, and chemicalcomposition of the hydroxyapatite crystals were similar to those of hydroxyapatite that hadtransformed from amorphous calcium phosphate nanoparticles, as well as the hydroxyapatite inhuman molar dentin. Our investigation showed that a combination of MDZ and PPU-7 cellspossesses high potential of drug repositioning for dentin regeneration.

Transgenic expression of dentin phosphoprotein inhibits skeletal development

Dentin sialophosphoprotein (DSPP) is proteolytically processed into an NH₂-terminal fragment called <em>dentin sialoprotein</em> (DSP) and a COOH-terminal fragment known as <em>dentin</em> <em>phosphoprotein</em> (DPP). These two fragments are believed to perform distinct roles in formation of bone and dentin. To investigate the functions of DPP in skeletal development, we generated transgenic mice to overexpress hemagglutinin (HA)-tagged DPP under the control of a 3.6 kb type I collagen (Col1a1) promoter (designated as <em>Col1a1-HA-DPP</em>). The Col1a1-HA-DPP transgenic mice were significantly smaller by weight, had smaller skeletons and shorter long bones than their wild type littermates, as demonstrated by X-ray radiography. They displayed reduced trabecular bone formation and narrower zones of proliferative and hypertrophic chondrocytes in the growth plates of the long bones. Histological analyses showed that the transgenic mice had reduced cell proliferation in the proliferating zone, but lacked obvious defects in the chondrocyte differentiation. In addition, the transgenic mice with a high level of transgene expression developed spontaneous long bone fractures. In conclusion, overexpressing DPP inhibited skeletal development, suggesting that the balanced actions between the NH₂- and COOH-terminal fragments of DSPP may be required for normal skeletal development.