Three-dimensional assessment of proximal contact enamel using optical coherence tomography

Equivalence study of the resin-dentine interface of internal tunnel restorations when using an enamel infiltrant resin with ethanol-wet dentine bonding

This preregistered ex vivo investigation examined the dentinal hybrid layer formation of a resinous infiltrant (Icon), with reference to both thickness (HLT) and homogeneity when combined with modified tunnel preparation (occlusal cavity only) and internal/external caries infiltration. The adhesives Syntac and Scotchbond MP were used as controls (Groups 1 and 3) or in combination with Icon (Groups 2 and 4). A split-tooth design using healthy third molars from 20 donors resulted in 20 prepared dentine cavities per experimental group. The cavity surfaces (n = 80) were etched (37% H3PO4), rinsed, and air-dried. Rewetting with ethanol was followed by application of the respective primers. After labeling with fluorescent dyes, either Syntac Adhesive/Heliobond or Scotchbond MP Adhesive was used alone or supplemented with Icon. HLT, as evaluated by scanning electron microscopy, did not significantly differ (P > 0.05), and confocal laser scanning microscopy revealed homogeneously mixed/polymerized resin-dentine interdiffusion zones in all groups. Icon can be successfully integrated into an ethanol-wet dentine bonding strategy, and will result in compact and homogeneous hybrid layers of comparable thickness considered equivalent to the non-Icon controls, thus allowing for preservation of the tooth's marginal ridge and interdental space in the case of internal/external infiltration of proximal caries.

Three Visual-Diagnostic Methods for the Detection of Enamel Cracks: An In Vitro Study

Tooth fractures are a common cause of tooth loss, frequently starting as enamel cracks. However, methods for the detection of enamel cracks are poorly investigated. The aim of the study was the validation of three clinical methods for the detection of enamel cracks: dental operating microscope (DOM), near-infrared transillumination (NIR), and fiber-optic transillumination (FOTI), with hard-tissue slices serving as controls. A total of 89 extracted teeth, set up as diagnostic models, were investigated, and the maximum crack depth was scored by two examiners. The actual crack depth was determined microscopically (25×) using horizontal sections. The accuracy of each method was analyzed using receiver operating characteristic (ROC) curves. Across all tooth surfaces, the area under the curve (AUC) amounted to 0.57 (DOM), 0.70 (FOTI), and 0.67 (NIR). For crack detection on vestibular/oral surfaces, the AUC was 0.61 (DOM), 0.78 (FOTI), and 0.74 (NIR); for proximal surfaces, it was 0.59 (DOM), 0.65 (FOTI), and 0.67 (NIR). However, the actual crack depth was underestimated with each method (p < 0.001). Under in vitro conditions, FOTI and NIR are suitable for detection of enamel cracks, especially on vestibular and oral tooth surfaces. However, an exact estimation of crack depth is not possible. Therefore, FOTI and NIR seem to be helpful for the clinical detection of enamel cracks.

Quantitative label-free optical technique to analyze the ultrastructure changes and spatiotemporal relationship of enamel induced by Msx2 deletion

New advances in the molecular mechanism of enamel mineralization reveal the practical significance of regenerative medicine in clinical transformation. Muscle segment homeobox 2 (MSX2), a transcription factor, is recently reported to be closely associated with the amelogenesis imperfecta (AI). To elucidate the biomineralization framework of AI enamel, herein, Msx2 gene mutant mice are investigated by dual-mode noninvasive spectroscopic analytical techniques for the first time. Optical coherence tomography (OCT) records the depth-resolved structural information of mice teeth, where a dramatic decrease in enamel thickness and quality occurred in Msx2 deficient (Msx2^-/- ) enamel. And it has the advantages of fast, noninvasive and low cost. Raman spectroscopy, a powerful molecular fingerprint tool, further witnesses an imbalance of inorganic and organic contents in Msx2^-/- enamel. In addition, abnormal expression of MSX2 also influences the spatial distribution of phosphate in enamel according to the Raman spectral imaging. Therefore, OCT integrated with Raman spectroscopy provides the quantitative label-free optical parameters of both the physical structure and chemical component in mice enamel, which strengthens the understanding of the biomineralization process underlying the Msx2-related amelogenesis imperfect.

Diagnosis of Occlusal Caries with Dynamic Slicing of 3D Optical Coherence Tomography Images

Detecting the extent of occlusal caries is a clinically important but challenging task required for treatment decision making. The aim of this study was to assess the diagnostic power of 3D swept-source optical coherence tomography (OCT) for evaluation of occlusal caries in comparison with X-ray radiography. Extracted human molars not exhibiting American Dental Association (ADA) criteria advanced caries were mounted in a silicone block and digital dental radiographs were captured from the buccal side. Subsequently, occlusal surfaces were scanned with a prototype Yoshida Dental OCT. Thirteen examiners evaluated the presence and extent of caries on radiographs and dynamically sliced 3D OCT video images, using a 4 level scale—0: intact; 1: enamel demineralization without cavitation; 2: enamel caries with cavitation; 3: dentin caries with or without cavitation. Sensitivity, specificity and area under operating characteristic curves (Az) were statistically analyzed (α = 0.05). Reliability analysis showed an excellent agreement among the 13 examiners for both methods. The OCT presented a significantly higher sensitivity and Az value for the detection of caries compared to radiographs (p < 0.05). Radiography showed especially low sensitivity for dentin caries (0–2 versus 3). Dynamic slicing of 3D OCT volumes is a powerful adjunct tool to visual inspection to diagnose the dentin occlusal caries in vitro.

Ex vivo investigation on internal tunnel approach/internal resin infiltration and external nanosilver-modified resin infiltration of proximal caries exceeding into dentin

This ex vivo proof-of-concept study aimed to investigate the effect of nanosilver particles (AgNP) added to a conventional infiltrant resin (Icon) on external penetration into natural proximal enamel caries exceeding into dentin after internal tunnel preparation and internal infiltration. Carious lesions (ICDAS codes 2/3) of extracted human (pre-)molars revealing proximal caries radiographically exceeding into dentin (E2/D1 lesions) were preselected. Then, 48 of those specimens showing demineralized areas transcending the enamel-dentin border as assessed by means of near-infrared light transillumination (DIAGNOcam) were deproteinized (NaOCl, 5%). Using an internal tunnel approach, occlusal cavities central to the marginal ridge were prepared. Excavation of carious dentin, total etch procedure (H3PO4, 40%), and internal resin infiltration (FITC-labeled) followed, along with final restorations (flowable composite resin). Outer lesion surfaces were etched (HCl, 15%) prior to external infiltration (RITC-labeled). Group 1 (control; n = 24) used non-modified infiltrant, while an infiltrant/AgNP mixture (20 nm; 5.5 wt%) was used with experimental Group 2 (n = 24). Non-infiltrated pores of cut lesions were stained (Berberine), and specimens were analyzed using confocal laser scanning microscopy. Compared to the non-filled infiltrant, incorporation of AgNP had no effect on the resin's external penetration. Between the groups, no significant differences regarding internal or external infiltration could be detected, and non-infiltrated lesion areas did not differ significantly (p>0.109; t-test). The internal tunnel preparation in combination with both an internal resin infiltration and an additional external infiltration approach using a nanosilver-modified infiltrant resin leads to increased infiltrated lesion areas, thus occluding and adhesively stabilizing the porous volume of the demineralized enamel. While exerting antimicrobial effects by the nanosilver particles, this approach should have the potential as a viable treatment alternative for proximal lesions extending into dentin, thus avoiding the sacrifice of sound enamel, postponing the frequently inevitable restoration/re-restoration cycle of conventional proximal caries treatment, and improving dental health.