Structural analysis of reactionary dentin formed in response to polymicrobial invasion

Abstract

In response to microbial invasion of dentin odontoblasts secrete an altered calcified matrix termed reactionary dentin (Rd). 3D reconstruction of focused-ion-beam scanning electron microscopy (FIB-SEM) image slices revealed helical tubular structures in Rd that contrasted with regular cylindrical tubules characteristic of dentin from healthy teeth and affected so-called physiological dentin (Pd) lying exterior to Rd. This helical structure in Rd provided effective constriction of tubule lumen diameter that formed a barrier to bacterial advance towards the dental pulp. SEM of resin cast preparations revealed altered extension of odontoblast processes through Rd. The distribution of key mineral elements was studied by combination of 3D reconstruction of focused-ion-beam based X-ray microanalysis (FIB-EDS), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). There was a marked redistribution of calcium and phosphorous in Rd together with an increase of diffusely deposited magnesium compatible with the mineral deposition phase of synthesis of this altered matrix. Changes in tubule structure and mineral content characteristic of Rd are consistent with reduced hardness and lower elastic modulus reported for this matrix. Findings provide insight into the unique structure of Rd synthesised as a primary response to infection.

Glial Network Responses to Polymicrobial Invasion of Dentin

“…Considering both expression profile and anatomical proximity to odontoblasts, seracytes may play a role in modulating the reported plasticity of the odontoblastic layer [Hattyasy, 1961;Byers et al, 2003;Mitsiadis et al, 2011] possibly by neural differentiation [Anthony et al, 2004] that is compatible with the extensive networks formed in response to caries. Thus, while odontoblasts in mature teeth have been considered as terminally differentiated cells, they show remarkable adaptation to carious insult, particularly in the synthesis of reactionary dentin in a gradient of response extending from the zone of most extensive microbial penetration of dentin [Farahani et al, 2010;Charadram et al, 2012Charadram et al, , 2013. Evidence was obtained that GFAP + networks mediated this gradient response [Farahani et al, 2010].…”

“…In response to degradation of dentin matrix and subsequent polymicrobial invasion [Hahn and Liewehr, 2007;Veerayutthwilai et al, 2007], odontoblast secretion patterns are markedly altered to produce a new dentin matrix termed reactionary dentin. The helical structure of the tubules in reactionary dentin matrix appears to impede bacterial invasion along patent dentinal tubules and is therefore considered protective [Charadram et al, 2013]. Of note, reactionary dentin is deposited in a gradient decreasing in depth according to distance from the zone of microbial invasion.…”

Excellent Preservation of Archaeological, Mercury‐Enriched Dental Remains

“…) or that from pulp to dentin and enamel, provided that odontoblasts migrated from the dentin to enamel (Charadram et al . ). In addition, albeit the presence of sulphur was small, we do not discard the plausible formation of HgS (Cervini‐Silva et al .…”

“…Notably, Hg accumulated preferentially inside the spheres (≤39%), yet the contents of Hg in tubules, attributed to fractures in the tubules, occurred between the pulp and crowns (Hörsted-Bindslev et al 1997). Reportedly, such tubules contributed to the migration of Hg from the enamel to dentin (Harris et al 2008) or that from pulp to dentin and enamel, provided that odontoblasts migrated from the dentin to enamel (Charadram et al 2013). In addition, albeit the presence of sulphur was small, we do not discard the plausible formation of HgS (Cervini-Silva et al 2013;Emslie et al 2015).…”

Avaliação da citotoxicidade, proliferação celular e expressão gênica de macrófagos e células indiferenciadas da polpa dentária estimuladas com Papacárie Duo®

“…A dentina é permeada por túbulos que convergem à medida que caminham para áreas dentinárias mais internas e, portanto, o diâmetro dos túbulos dentinários varia em função da distância em relação à superfície da câmara coronária (Pashley e Carvalho, 1997). Assim, materiais aplicados sobre o complexo dentino-pulpar podem ser biocompatíveis se aplicados sobre cavidades rasas e de média profundidade onde a permeabilidade da dentina é menor, porém podem apresentar efeitos indesejáveis ao tecido pulpar quando em cavidades mais profundas, pois a espessura e as características morfológicas da dentina remanescente favorecem a difusão transdentinária dos componentes químicos dos materiais, os quais podem ser tóxicos ao tecido pulpar ou ainda interferir negativamente no processo de reparo (Marshall et al, 1997 Os odontoblastos são células que frente à injúrias pulpares, passam a produzir matriz dentinária próxima aos locais lesados na tentativa de proteger o tecido pulpar da infecção microbiana (Charadram et al, 2013). A capacidade de resposta do complexo dentino-pulpar ocorre graças à estimulação desses odontoblastos, que sintetizam e secretam a matriz dentinária reacional.…”