Effect of hydroxyapatite film formed by powder jet deposition on dentin permeability

Abstract

A powder jet deposition (PJD) process can be used to create a thick hydroxyapatite (HA) film on the surface of a human tooth. This study aimed to investigate in vitro the ability of an HA film, applied using PJD, to diminish dentin permeability. Discs of human coronal dentin were cut perpendicular to the tooth axis and the smear layer was removed by EDTA treatment. The HA film was created by accelerating HA particles, calcinated at 1200°C, onto the dentin discs at room temperature and atmospheric pressure. The surfaces and cross-sections of the HA PJD-treated samples were observed using scanning electron microscopy. Their permeability was indirectly recorded with a split-chamber device utilizing a chemiluminescence technique. MS-coat, a commercial dentin-desensitizing agent, was also evaluated for its effect on reducing liquid flow through the dentin. The scanning electron microscopy images showed that the HA particles were successfully deposited onto the dentin and solidly into the dentin tubules. The permeability of dentin after application of the HA films was significantly lower than that following application of MS-coat. This study showed the potential clinical application of PJD techniques in desensitizing dentin hypersensitivity.

Development of Powder Jet Deposition Technique and New Treatment for Discolored Teeth

“…The specimens were first immersed in distilled water at 37 °C for 1 day. After the immersion, the specimens underwent 500 thermal cycles [2]. To evaluate their microstructure, the cross section of the HA layers was observed by SEM.…”

“…The specimens were fixed on a stage, with their enamel surface perpendicular to the nozzle. The layers were polished using diamond polishing paste (Dia Polisher Paste; GC, Tokyo, Japan) and a felt wheel for 30 s with intermittent pressure of 5,000 g [2]. To evaluate the microstructure, the cross section of the HA layers was observed by SEM (JSM-6500F, JEOL, Tokyo, Japan).…”

“…Two water baths were maintained at 5 °C and 55 °C. Each cycle consisted of 20 s immersion in each water bath and a travel time of 10 s. The water baths were constantly stirred with stirrers, and the variation in the temperature of each water bath was within 1 °C of the set temperature [2,14]. The specimens were first immersed in distilled water at 37 °C for 1 day.…”

“…To evaluate the mechanical properties of the layers, micro-Vickers hardness was measured using a dynamic microhardness tester (FM-ARS 9000; Future-Tech, Kawasaki, Japan). A load of 100 gf was applied for 5 s using a pyramid-shaped die; the depth of the impression was used to calculate the hardness of the specimens [2,15]. Furthermore, the bonding strength of the HA layers to the enamel substrates was evaluated using a micro-tensile test (Romulus; Quad Group, Spokane, WA, USA) [2,16].…”

“…Even if the adhesion technique is properly applied, these differences in properties between restorative materials and tooth substance can give rise to different mechanical, thermal, or chemical stresses in the oral cavity and can lead to clinical problems such as drop-off of the restorative material from the tooth or secondary caries [1]. In our previous studies, we presented the possibility of applying a layer of HA as a new restorative material with chemical, compositional, and mechanical properties corresponding to the tooth substance [2,3]. A newly developed advanced technology called powder jet deposition (PJD) was used to create the HA layers.…”