Nano eggshell‐based slurry as a direct pulp‐capping material: In vitro characterization and histopathological assessment in an experimental animal model

Abstract

AimPulp vitality is essential for tooth integrity. Following pulp exposure, choosing a suitable pulp‐capping material is crucial to maintain pulp vitality. However, the reparative dentine bridge created by calcium hydroxide (Ca(OH)2) is generally porous and incomplete. The aim of the current study is to assess the in vitro and in vivo bioactivities of nano eggshell‐based slurry (NES), using NES as a direct pulp‐capping material, compared with Ca(OH)2 in rabbit animal model.MethodologyNano eggshell powder (NE) was characterized for particle morphology, chemical composition and ion release. In vitro bioactivity was tested by immersion in simulated body fluid (SBF) for 7 days. For histopathological evaluation, 36 adult New Zealand rabbits (72 pulp exposures) were divided into nine groups (n = 8) according to the pulp‐capping material (NES, Ca(OH)2 and no capping as negative control group) and the animals were sacrificed after 7, 14 or 28 days. The pulps of the two lower central incisors were exposed and then directly capped by Ca(OH)2 or NES or left untreated. The cavities were then sealed with glass ionomer cement. Teeth were collected for histopathological evaluation using an optical microscope. Pulp haemorrhage, inflammation, fibrosis and calcific bridge formation were assessed. Results were statistically analysed using anova and Tukey's tests.ResultsNano eggshell particles were spherical with a 20 nm diameter and were composed mainly of calcite. Statistical analysis showed that there was a significant increase in the release of all investigated ions between days 1 and 28, except for copper. NES group showed a significantly higher release of all elements as compared to Ca(OH)2. Environmental scanning electron microscope micrographs of NES incubated for 7 days in SBF showed the formation of HAp with a Ca/P ratio (1.686). For histopathological evaluation, the difference between groups was statistically significant. At day 28, 75% of the pulps of the Ca(OH)2 group showed mild calcific bridge in comparison with 100% moderate calcific bridge in the NES group. The NES group showed significantly less inflammation at days 7 and 28, and higher fibrosis at day 7 compared with Ca(OH)2.ConclusionsNano eggshell‐based slurry represents a promising novel direct pulp‐capping material with favourable pulp tissue response.

Histological Characterization of Modified Calcite Paste as Pulpotomy Material in Partially Pulpotomized Rabbit Incisors

“…In the MC group, the pulp tissue shows normal architecture with the absence of diffuse calcification, vacuoles and blood vessel hyalinization compared to the control group which indicates the MC paste is highly biocompatible and doesn't have an adverse effect upon degradation, these findings agree with four weeks findings of the pulp of rabbit incisors after capped with eggshell slurry, where mild inflammatory response and complete dentin bridging was found in 100% of the teeth at 28-day post capping. 31,40 In general, the mild alkaline pH, sustained release of calcium ions and the anti-inflammatory effect of the acetate group seem to support the hypothesis that MC cement is an effective material for capping exposed pulps.…”

“…31,33,34 the evaluation is done in two-time point after 1week to evaluate the initial pulp response and after 4 weeks to evaluate the final tissue response as the rabbit incisors are continuously growing and these period were established by previous studies. 31,40,41 In 1 st week period, in the non-capped control group, Although RMGIC cements used to seal the cavity were not in direct contact with the pulp, it's impossible to exclude that they didn't have any effect on the inflammatory process. However, 83.3% of the control group showed moderate pulpal inflammation, which may be due to traumatic exposure procedure, 42 as well as the cytotoxic effect of resin-modified glass ionomer 43 .…”

“…46,47 Furthermore, on day 7 control group showed the formation of scanty calcified tissue at the periphery of the exposure site may refer to the high regenerative capacity of rabbit pulp which is not hindered by the presence of bacteria due to the good sealing ability of RMGIC, these data agree with previous studies that shows the dentin bridge formation can be seen in control and experimental group using rabbit incisors at the day 7 after pulp exposure. 39,40 Meanwhile, in the MC group on day 7, most of the specimens showed mild inflammation and absence of necrotic layer response, indicating the biocompatibility of the MC novel paste, these data greed with the findings of in vivo study where the pure calcium carbonate slurry used to as pulpotomy paste for rat molar which shows mild inflammatory response after 7 days and formation of dentin bridge, 40 also present finding in a line with a recent study which using eggshell slurry as capping material in rabbit incisors, the biocompatibility and bioactivity of eggshell owing to high CaCO 3 content which may reach upto 95%by weight. 31 However, the mild inflammatory response to MC may attributed to the mild Alkaline pH of the modified calcite cement due to the release of acetate and bicarbonate group from the paste, 48 which may induce the low-grade inflammatory response of rabbit incisors pulp, this finding agrees with the finding of in vivo study using eggshell paste as capping material to traumatically exposed rabbit incisors 31 .…”