In vitro and clinical evaluation of optical coherence tomography for the detection of subgingival calculus and root cementum

Marginal adaptation analysis of CAD/CAM resin crown with non-invasive methods

OBJECTIVES

This study compared the silicone replica method with swept-source optical coherence tomography (SS-OCT) to analyze marginal adaptation and investigated the effect of the light incidence angle of SS-OCT on measurement precision.

MATERIALS AND METHODS

A typodont-prepared mandibular right first molar was scanned using an intraoral scanner (Trios 3). Fourteen crowns were fabricated from CAD/CAM resin blocks (Katana Avencia P) using a 5-axis milling machine (DWX-50). Marginal adaptation at the buccal, lingual, mesial, and distal points was assessed using the silicone replica method and SS-OCT at light incidence angles of 60°, 75°, and 90°. Statistical comparisons were performed using two-way analysis of variance (ANOVA) and t-tests with Bonferroni correction, and t-tests at a significance level of 0.05.

RESULTS

At 60°, SS-OCT showed significantly larger marginal discrepancies than the silicone replica method at the buccal, lingual, and mesial points (p < 0.05). At 75°, only the lingual point showed a significantly larger value than the silicone replica method (p < 0.05). At 90°, no significant differences were observed between the SS-OCT and silicone replica methods (p > 0.05). Marginal discrepancy values increased as the angle changed from 90° to 75° to 60°, with significant differences between 60° and 75° and between 60° and 90° at the buccal and lingual points (p < 0.05).

CONCLUSIONS

SS-OCT is a viable alternative to the silicone replica method for assessing marginal adaptation at an incidence angle of 90 °.

CLINICAL RELEVANCE

SS-OCT, a non-invasive method, has the potential to be applied clinically for evaluating marginal fit in indirect restorations in vivo.

High-precision and non-invasive measurement of crestal bone level by optical coherence tomography

Background/purpose

Identifying crestal bone level (CBL) on the buccal and lingual aspects poses challenges in conventional dental radiographs. Given that optical coherence tomography (OCT) has the capability to non-invasively provide in-depth information about the periodontium, this in vitro study aimed to assess whether OCT can effectively identify periodontal landmarks and measure CBL in the presence of gingiva.

Materials and methods

An in-house handheld scanning probe connected to a 1310-nm swept-source OCT (SS-OCT) system, along with self-developed algorithms were employed to measure the CBL in dental models with artificial gingiva. Markers were positioned 0.5 mm above the artificial gingival margin (SG) and the crestal bone (SC) on both the mid-buccal and mid-lingual sides of 28 plastic teeth. The distances between the paired SG and SC were measured in the OCT images after correcting for the optical path through the covering artificial gingiva. These measurements were subsequently compared to the ground truth values obtained using a 2.5D inspection system.

Results

The mean difference in CBL measured by SS-OCT and 2.5D was 0.008 mm (95 % CI: -0.092 to 0.108 mm). Statistical analysis using a three-way ANOVA indicated that the measurement differences were not significant across maxillary/mandible, anterior/posterior, and buccal/lingual dimensions. Furthermore, these differences were not associated with gingival thickness (α = 0.05).

Conclusion

The proposed SS-OCT system demonstrated its capability to accurately and non-invasively assess CBL through artificial gingiva. Moreover, it facilitated the semi-automatic delineation of critical periodontal landmarks on OCT en face images, highlighting its potential for clinical applications.

Quantitative Evaluation of Caries and Calculus with Ultrahigh-Resolution Optical Coherence Tomography

Dental caries on the crown's surface is caused by the interaction of bacteria and carbohydrates, which then gradually alter the tooth's structure. In addition, calculus is the root of periodontal disease. Optical coherence tomography (OCT) has been considered to be a promising tool for identifying dental caries; however, diagnosing dental caries in the early stage still remains challenging. In this study, we proposed an ultrahigh-resolution OCT (UHR-OCT) system with axial and transverse resolutions of 2.6 and 1.8 μm for differentiating the early-stage dental caries and calculus. The same teeth were also scanned by a conventional spectral-domain OCT (SD-OCT) system with an axial resolution of 7 μm. The results indicated that early-stage carious structures such as small cavities can be observed using UHR-OCT; however, the SD-OCT system with a lower resolution had difficulty identifying it. Moreover, the estimated surface roughness and the scattering coefficient of enamel were proposed for quantitatively differentiating the different stages of caries. Furthermore, the thickness of the calculus can be estimated from the UHR-OCT results. The results have demonstrated that UHR-OCT can detect caries and calculus in their early stages, showing that the proposed method for the quantitative evaluation of caries and calculus is potentially promising.

Assessment of demineralized tooth lesions using optical coherence tomography and other state-of-the-art technologies: a review

Tooth demineralization is one of the most common intraoral diseases, encompassing (1) caries caused by acid-producing bacteria and (2) erosion induced by acid of non-bacterial origin from intrinsic sources (e.g. stomach acid reflux) and extrinsic sources (e.g. carbonated drinks). Current clinical assessment based on visual-tactile examination and standardized scoring systems is insufficient for early detection. A combination of clinical examination and technology is therefore increasingly adapted. This paper reviews various procedures and technologies that have been invented to diagnose and assess the severity of tooth demineralization, with focus on optical coherence tomography (OCT). As a micron-resolution non-invasive 3D imaging modality, variants of OCT are now available, offering many advantages under different working principles for detailed analytical assessment of tooth demineralization. The roles, capabilities and impact of OCT against other state-of-the-art technologies in both clinical and research settings are described. (139 words).

Intraoral optical coherence tomography and angiography combined with autofluorescence for dental assessment

There remains a clinical need for an accurate and non-invasive imaging tool for intraoral evaluation of dental conditions. Optical coherence tomography (OCT) is a potential candidate to meet this need, but the design of current OCT systems limits their utility in the intraoral examinations. The inclusion of light-induced autofluorescence (LIAF) can expedite the image collection process and provides a large field of view for viewing the condition of oral tissues. This study describes a novel LIAF-OCT system equipped with a handheld probe designed for intraoral examination of microstructural (via OCT) and microvascular information (via OCT angiography, OCTA). The handheld probe is optimized for use in clinical studies, maintaining the ability to detect and image changes in the condition of oral tissue (e.g., hard tissue damage, presence of dental restorations, plaque, and tooth stains). The real-time LIAF provides guidance for OCT imaging to achieve a field of view of approximately 6.9 mm × 7.8 mm, and a penetration depth of 1.5 mm to 3 mm depending on the scattering property of the target oral tissue. We demonstrate that the proposed system is successful in capturing reliable depth-resolved images from occlusal and palatal surfaces and offers added design features that can enhance its usability in clinical settings.

A handheld fiber-optic probe to enable optical coherence tomography of oral soft tissue

This study presents a highly miniaturized, handheld probe developed for rapid assessment of soft tissue using optical coherence tomography (OCT). OCT is a non-invasive optical technology capable of visualizing the sub-surface structural changes that occur in soft tissue disease such as oral lichen planus. However, usage of OCT in the oral cavity has been limited, as the requirements for high-quality optical scanning have often resulted in probes that are heavy, unwieldy and clinically impractical. In this paper, we present a novel probe that combines an all-fiber optical design with a light-weight magnetic scanning mechanism to provide easy access to the oral cavity. The resulting probe is approximately the size of a pen (10 mm 140 mm) and weighs only 10 grams. To demonstrate the feasibility and high image quality achieved with the probe, imaging is performed on the buccal mucosa and alveolar mucosa during routine clinical assessment of six patients diagnosed with oral lichen planus. Results show the loss of normal tissue structure within the lesion, and contrast this with the clear delineation of tissue layers in adjacent inconspicuous regions. The results also demonstrate the ability of the probe to acquire a three-dimensional data volume by manually sweeping across the surface of the mucosa. The findings of this study show the feasibility of using a small, lightweight probe to identify pathological features in oral soft tissue.

The Influence of Diet on Oxidative Stress and Inflammation Induced by Bacterial Biofilms in the Human Oral Cavity

The article is a concise compendium of knowledge on the etiology of pathogenic microorganisms of all complexes causing oral diseases. The influence of particular components of the diet and the role of oxidative stress in periodontal diseases were described. The study investigated the bacteriostatic effect of the diet of adults in in vivo and in vitro tests on the formation of bacterial biofilms living in the subgingival plaque, causing diseases called periodontitis. If left untreated, periodontitis can damage the gums and alveolar bones. Anaerobic bacteria, called periopathogens or periodontopathogens, play a key role in the etiopathogenesis of periodontitis. The most important periopathogens of the oral microbiota are bacteria of all complexes, including the red complex. The obtained results suggest the possibility of using a specific diet in the prevention and treatment of periodontal diseases-already treated as a disease of civilization. The quoted article is an innovative compilation of knowledge on this subject and it can be a valuable source of knowledge for professional hygienists, dentists, peridontologists, dentistry students and anyone who cares about proper oral hygiene. The obtained results suggest the possibility of using this type of diet in the prophylaxis of the oral cavity in order to avoid periodontitis.

In-vivo usefulness of optical coherence tomography in atrophic-erosive oral lichen planus: Comparison between histopathological and ultrastructural findings

Oral lichen planus (OLP) is a common premalignant chronic inflammatory disorder. Optical Coherence Tomography (OCT) provides a real-time, non-invasive, and in-situ optical signature using light of varying wavelengths to examine tissue. Aim of the present study was to assess the possible role of OCT as diagnostic tool for atrophic-erosive OLP by examining OCT scans of healthy buccal mucosa, and comparing their ultrastructural features with those of a buccal mucosa affected by atrophic-erosive OLP, using their histopathological counterparts as the gold standard. Through grayscale (enface scan) and an application in which the vascularization of the tissue is visible (dynamic scan), it was possible to distinguish the healthy from the lichenoid pattern from 20 controls (12 M; 8 F; mean age: 41.32 years) and 20 patients with histologically confirmed atrophic-erosive OLP (7 M; 13 F; mean age: 64.27 years). In detail, mean width of stratified squamous epithelium (EP) and lamina propria (LP) were evaluated. Among controls, EP and LP showed a mean width of 300 (±50) and of 600 (±50) μm respectively; among cases, disruption of membrane basement prevented from any measurement. Furthermore, a differential pattern of EP and LP emerged between the two groups: a light-grayish, hypo-reflective, homogeneous area of EP recurring in controls turned into a hyper-reflective, non-homogeneous area among cases. Dynamic scan showed a differential profile of LP vascularization, varying from a hypo-reflective red area with small blood vessels in the control group, to a hypo/hyper-reflective area, completely overrun by a denser, wider blood flow amid OLP cases. Although histopathological examination remains the gold standard for OLP diagnosis, OCT could be a potentially helpful tool for the clinician and the pathologist, since it allows analysis of the vascularization of the sample without adversely affecting histological processing.

Swept-source optical coherence tomographic observation on prevalence and variations of cemento-enamel junction morphology

To investigate the prevalence of different patterns of cemento-enamel junction (CEJ) morphology under swept-source optical coherence tomography (SS-OCT). One hundred extracted human teeth were used consisting of incisors, premolars, and molars. Each sample was observed for every 500 μm circumferentially along CEJ and OCT images of the pattern were noted. Microscopic observations were done for the representative sample using confocal laser scanning microscope (CLSM) and transmission electron microscope (TEM). The OCT images exhibited four CEJ patterns: edge-to-edge (type I), exposed dentin (type II), cementum overlapping enamel (type III), and enamel overlapping cementum (type IV). The prevalence of CEJ patterns was further statistically considered for mesial, distal, buccal, and lingual surfaces. The real-time imaging by SS-OCT instantly determined CEJ morphology. CLSM and TEM observation revealed morphological features along CEJ, which corresponded to OCT images of CEJ anatomy. OCT results showed 56.8% of type I pattern predominantly found on proximal surfaces, followed by 36.5% of type II pattern on buccal and lingual surface, 6.4% of type III pattern, and 0.3% of type IV pattern. There was a significant difference in prevalence of CEJ patterns among different types of teeth, but there was no statistically significant difference among the four surfaces in each type of teeth. OCT is a non-invasive diagnostic tool to examine the CEJ patterns along the entire circumference. OCT observation revealed even minor dentin exposure that would need clinical and home procedures to prevent any symptoms.