Ultrastructural characterization of tooth-biomaterial interfaces prepared with broad and focused ion beams

•  Current available techniques for transmission electron microscopy (TEM)   of tooth biomaterial interfaces are mostly ineffective for brittle   phases and impair integrated chemical and morphological   characterization.   Objectives. The aims of this study were (1) to determine the   applicability of new focused ion beam (FIB) and broad ion beam (BIB)   techniques for TEM preparation of tooth-biomaterial interfaces; (2) to   characterize the interfacial interaction with enamel and dentin of a   conventional glass-ionomer (Chem. l Superior, DeTrey Dentsply,   Germany), a 2-step self-etch (Clear. l SE, Kuraray, Japan) and a 3-step   etch-and-rinse (OptiBond FL, Kerr, USA) adhesives; and (3) to   characterize clinically relevant interfaces obtained from actual   Class-I cavities.   Methods. After bonding to freshly extracted human third molars,   non-demineralized and non-stained sections were obtained using the   FIB/BIB techniques and examined under TEM.   Results. The main structures generally disclosed in conventional   ultramicrotomy samples were recognized in FIB/BIB-based ones. There   were not any major differences between FIB and BIB concerning the   resulting ultrastructural morphology. FIB/BIB-sections enabled to   clearly resolve sub-micron hydroxyapatite crystals on top of hard   tissues and the interface between matrix and filler in all materials,   even at nano-scale. Some investigated interfaces disclosed areas with a   distinct "fog" or "melted look", which is probably an artifact due to   surface damage caused by the high-energy beam. Interfaces with enamel   clearly disclosed the distinct "keyhole" shape of enamel rods sectioned   at 90 degrees, delimited by a thin electron-lucent layer of inter-rod   enamel. At regions where enamel crystals ran parallel with the   interface, we observed a lack of interaction and some de-bonding along   with interfacial void formation.   Significance. The FIB/BIB methods are viable and reliable alternatives   to conventional ultramicrotomy for preparation of thin sections of   brittle and thus difficult to cut biomaterial-hard tissue interfaces.   They disclose additional ultrastructural information about both   substrates and are more suitable for advanced analytic procedures.

Keyword

FIB

BIB

Adhesion

Dental

Dentin

Enamel

TEM

Glass-ionomer

3-Step etch-and-rinse

2-Step self-etch

TECHNOLOGY

TEKNIKVETENSKAP

Publication and Content Type

ref (subject category)

art (subject category)