Dental Adhesive Interfaces Reinforced with Magnetic Nanoparticles: Evaluation and Modeling with Micro-CT versus Optical Microscopy

Abstract

Dental adhesives are used in a wide range of applications, including to place direct composite restorations in frontal or posterior teeth. One of the most frequent causes for the failure of composite resin restorations is microleakages. The first aim of this work is to introduce a new type of self-etched dental adhesive doped with magnetic nanoparticles (MPs) synthetized in the laboratory. The scope is to produce adhesives with a minimized width/thickness to decrease the risk of microleakages. The second aim is to assess the width/thickness of the adhesive layer in all the characteristic areas of the teeth using both the less precise but most common optical microscopy and the more accurate and volumetric micro-Computed Tomography (CT) investigations. Twenty extracted teeth have been divided into four groups: Group 1 includes ‘blank’ samples with adhesives that are not doped with MPs; Group 2 includes samples with adhesives doped with MPs; Groups 3 and 4 include samples with adhesives doped with MPs that are subjected to an active magnetic field for 5 and 10 min, respectively. Microscopy investigations followed by micro-CT and EDAX are performed on the adhesive. While a rather good agreement is obtained between the microscopy and micro-CT results, the capability of the latter to offer a full volumetric reconstruction of the layer is exploited to analyze the adhesion of the four considered dental materials. Thus, from micro-CT results the graphs of the surface areas as functions of the adhesive layer width are modeled mathematically, as well as the volume of sealants, for each of the four groups. To our knowledge, it is the first time that such a methodology is used. Characteristic parameters are extracted and the ascertainment of the optimal parameter that should be utilized for such assessments is discussed. The study demonstrates the adhesion improvement produced for Groups 3 and 4, where MPs are used. It also concludes that the magnetic field should be applied to the adhesive material for the longest possible exposure time (with a trade-off with the clinical duration of the treatment).

Micro-CT and Microscopy Study of Internal and Marginal Gap to Tooth Surface of Crenelated versus Conventional Dental Indirect Veneers

“…This synthetic parameter was deduced with this analytic method for the first time to our knowledge in [ 28 ]. It allows making a rigorous and simple comparison between the capability of the two different types of veneers to provide dental preparation as tight as possible.…”

“…These investigations allow obtaining the graphs of the surface area with regard to the thickness/width of dental cement. Considering the simplest possible functions that can approximate these graphs on portions (i.e., parabolic or linear), they can be deduced following the methodology developed in [ 28 , 35 ].…”

“…These investigations allow obtaining the graphs of the surface area with regard to the thickness/width of dental cement. Considering the simplest possible functions that can approximate these graphs on portions (i.e., parabolic or linear), they can be deduced following the methodology developed in [28,35]. The investigation in the sagittal plane is performed by moving the axis from the mesial to the distal surface, completing the 3D analysis of the wall width.…”

“…The latter must also be used for a porosity analysis, which is necessary to assess avoiding leakages, micro-infiltration, and fissures within the cement layer. Such micro-CT investigations come in the context of their use for a range of studies, including dental adhesives [ 28 ] or bone regeneration [ 29 , 30 ], coupled with other investigation methods, for example, microscopy [ 28 ] or optical coherence tomography (OCT) [ 31 ].…”

Emerging Technologies for Dentin Caries Detection—A Systematic Review and Meta-Analysis

“…Despite being a more objective method than the visual examination, radiographic examination may underestimate the caries lesions' depth [11,13,14]. An emerging technology that has shown potential for dental imaging applications is optical coherence tomography (OCT) [12,[15][16][17]. Moreover, it has applications in imaging caries at all stages of progression, and dentin structures, as well [18][19][20][21].…”