Enamel microcracks in terms of orthodontic treatment: A novel method for their detection and evaluation

Teeth Microcracks Research: Towards Multi-Modal Imaging

This perspective is an overview of the recent advances in teeth microcrack (MC) research, where there is a clear tendency towards a shift from two-dimensional (2D) to three-dimensional (3D) examination techniques, enhanced with artificial intelligence models for data processing and image acquisition. X-ray micro-computed tomography combined with machine learning allows 3D characterization of all spatially resolved cracks, despite the locations within the tooth in which they begin and extend, and the arrangement of MCs and their structural properties. With photoluminescence and micro-/nano-Raman spectroscopy, optical properties and chemical and elemental composition of the material can be evaluated, thus helping to assess the structural integrity of the tooth at the MC site. Approaching tooth samples having cracks from different perspectives and using complementary laboratory techniques, there is a natural progression from 3D to multi-modal imaging, where the volumetric (passive: dimensions) information of the tooth sample can be supplemented by dynamic (active: composition, interaction) image data. Revelation of tooth cracks clearly shows the need to re-assess the role of these MCs and their effect on the structural integrity and longevity of the tooth. This provides insight into the nature of cracks in natural hard materials and contributes to a better understanding of how bio-inspired structures could be designed to foresee crack propagation in biosolids.

Effects of the conventional, soft start, and pulse delay modes produced by light-emitting diode device on metal brackets bond strength and enamel damage: An in vitro comparative study

OBJECTIVES

This study aimed to compare the bond strength and enamel damage following debonding of metal brackets cured by different light-curing modes: conventional, soft start, and pulse delay modes.

MATERIAL AND METHODS

Sixty extracted upper premolars were randomly divided into three groups according to the used light-curing mode. Metal brackets were bonded with a light-emitting diode device employing different modes. Group 1: conventional mode (10s mesial+10 s distal); group 2: soft start mode (15s mesial+15s distal); group 3: pulse delay mode (3s mesial+3s distal, followed by 3min of no photoactivation, then 9s mesial+9s distal). Radiant exposure was the same in all study groups. Shear bond strengths of the brackets were tested with a universal testing machine. A stereomicroscope was used to determine the number and length of enamel microcracks. One-Way ANOVA and Kruskal-Wallis tests were used to detect significant differences in shear bond strength and microcracks number and length among groups.

RESULTS

The soft start and pulse delay modes produced significantly greater shear bond strength than the conventional mode (19.46±4.90MPa; 20.47±4.97MPa; 12.14±3.79MPa, respectively, P<0.001). However, there was no significant difference between the soft start and pulse delay groups (P=0.768). The number and length of microcracks increased significantly after debonding in all study groups. The change in microcracks length was not different among study groups.

CONCLUSION

The soft start and pulse delay modes produced greater bond strength than the conventional mode without predisposing enamel to higher risk of damage. Conservative methods for debonding are still required.

The influence of age and orthodontic debonding on the prevalence and severity of enamel craze lines

BACKGROUND

Craze lines may cause esthetic concerns, especially when noted on the incisors. Various light sources with additional recording apparatus have been proposed to visualize craze lines, but a standardized clinical protocol is yet to be determined. This study aimed to validate the application of near-infrared imaging (NIRI) from intraoral scans to evaluate craze lines and to determine the influence of age and orthodontic debonding on their prevalence and severity.

METHODS

The NIRI of maxillary central incisors from a full-mouth intraoral scan and photographs from an orthodontic clinic (N = 284) were collected. The prevalence of craze lines and influence of age and orthodontic debonding history on severity were evaluated.

RESULTS

Craze lines were detected reliably as white lines distinguishable from dark enamel using the NIRI from intraoral scans. The craze line prevalence was 50.7%, which was significantly higher in patients 20 years or older than in patients younger than 20 years (P < .001), with more frequent severe craze lines for those 40 years or older than in patients younger than 30 years (P < .05). Prevalence or severity was similar between patients with and without an orthodontic debonding history regardless of the type of appliance.

CONCLUSION

The prevalence of craze lines in the maxillary central incisor was 50.7%, with a higher prevalence in adults than in adolescents. Orthodontic debonding did not affect the severity of craze lines.

PRACTICAL IMPLICATIONS

Craze lines were reliably detected and documented by means of applying NIRI from intraoral scans. Intraoral scanning can provide new clinical information on enamel surface characteristics.

Revelation of microcracks as tooth structural element by X-ray tomography and machine learning

Although teeth microcracks (MCs) have long been considered more of an aesthetic problem, their exact role in the structure of a tooth and impact on its functionality is still unknown. The aim of this study was to reveal the possibilities of an X-ray micro-computed tomography ([Formula: see text]CT) in combination with convolutional neural network (CNN) assisted voxel classification and volume segmentation for three-dimensional (3D) qualitative analysis of tooth microstructure and verify this approach with four extracted human premolars. Samples were scanned using a [Formula: see text]CT instrument (Xradia 520 Versa; ZEISS) and segmented with CNN to identify enamel, dentin, and cracks. A new CNN image segmentation model was trained based on "Multiclass semantic segmentation using DeepLabV3+" example and was implemented with "TensorFlow". The technique which was used allowed 3D characterization of all MCs of a tooth, regardless of the volume of the tooth in which they begin and extend, and the evaluation of the arrangement of cracks and their structural features. The proposed method revealed an intricate star-shaped network of MCs covering most of the inner tooth, and the main crack planes in all samples were arranged radially in two almost perpendicular directions, suggesting that the cracks could be considered as a planar structure.

The Use of Fiber-optic Transillumination in the Diagnosis of Fracture Line in Teeth: A Method of Standardization in Fracture Strength Studies

The use of fiber optic transillumination (FOTI) has been witnessed in the clinical scenario for many decades but has not been used in in vitro studies. The present paper highlights the use of FOTI as a method of standardization while conducting fracture strength studies in vitro.

How to cite this article

Chanchala HP, Godhi BS, Saha S. The Use of Fiber-optic Transillumination in the Diagnosis of Fracture Line in Teeth: A Method of Standardization in Fracture Strength Studies. Int J Clin Pediatr Dent 2022;15(4):475-477.

Three-dimensional non-destructive visualization of teeth enamel microcracks using X-ray micro-computed tomography

Although the topic of tooth fractures has been extensively analyzed in the dental literature, there is still insufficient information about the potential effect of enamel microcracks (EMCs) on the underlying tooth structures. For a precise examination of the extent of the damage to the tooth structure in the area of EMCs, it is necessary to carry out their volumetric [(three-dimensional (3D)] evaluation. The aim of this study was to validate an X-ray micro-computed tomography ([Formula: see text]CT) as a technique suitable for 3D non-destructive visualization and qualitative analysis of teeth EMCs of different severity. Extracted human maxillary premolars were examined using a [Formula: see text]CT instrument ZEISS Xradia 520 Versa. In order to separate crack, dentin, and enamel volumes a Deep Learning (DL) algorithm, part of the Dragonfly's segmentation toolkit, was utilized. For segmentation needs we implemented Dragonfly's pre-built UNet neural network. The scanning technique which was used made it possible to recognize and detect not only EMCs that are visible on the outer surface but also those that are buried deep inside the tooth. The 3D visualization, combined with DL assisted segmentation, enabled the evaluation of the dynamics of an EMC and precise examination of its position with respect to the dentin-enamel junction.

In vivo examination of enamel microcracks after orthodontic debonding: Is there a need for detailed analysis?

INTRODUCTION

Our aim was to assess changes in the number of enamel microcracks (EMCs) after removing metal brackets in teeth with and without visible EMCs before the bonding procedure.

METHODS

Before bonding, 13 patients having teeth with visible EMCs and 13 subjects whose teeth were free of EMCs were included in the study. All patients were asked to complete a questionnaire with a detailed medical history at the beginning of treatment and after removing metal brackets. The number of teeth with visible EMCs and the number of premolars without EMCs were recorded for each subject twice, that is, before bonding and after debonding, together with the tooth sensitivity assessments elicited by compressed air and cold testing.

RESULTS

The number of visible EMCs in premolars increased after removing metal brackets. EMCs were recorded in at least 25.0% of all evaluated teeth for the patients having teeth with and without visible EMCs at the beginning of treatment. However, the changes in the number of visible EMCs were not significantly different (P = 0.619) between the groups. For the subjects with visible EMCs, tooth sensitivity caused by cold was registered nearly 3 times more often after removing brackets compared with the patients without EMCs prior bonding.

CONCLUSIONS

Formation of EMCs was noticed after debonding. Changes in the number appeared to be similar for the subjects with and without visible EMCs before bonding. Higher incidence of EMCs was associated with more frequent tooth sensitivity perceptions after removing brackets.

The orthodontic bonding properties of human enamel after cryopreservation

The aim was to investigate the effect of cryopreservation on the enamel bonding properties of orthodontic brackets. Sixty-six human premolars were randomly allocated to a control group or a cryopreserved group. Conventional stainless-steel orthodontic brackets were bonded with a light cure adhesive on the buccal side of the premolars. The shear bond strength (SBS) was determined at a crosshead speed of 1 mm/min. The SBS and adhesive remnant index (ARI) were evaluated respectively by an independent samples t test and Fisher's exact test (α≤0.05). The mean failure load was lower in the cryopreserved group. However, this difference in SBS was not significant (p=0.443). In both groups, the ARI mostly indicated a failure at the enamel-adhesive interface. The mean ARI scores for both groups were not significantly different (p=0.099). Within the limitations of this macro bond strength testing, it can be concluded that cryopreservation does not significantly affect the bonding properties of enamel.

A Novel Method Using Confocal Laser Scanning Microscopy for Three-Dimensional Analysis of Human Dental Enamel Subjected to Ceramic Bracket Debonding

The aim of this in vitro study was to present a method using confocal laser scanning microscopy for three-dimensional analysis of human dental enamel subjected to ceramic bracket debonding. The labial enamel surfaces of three upper central incisors were prepared and mounted in the form of standardized specimens. A sample repositioning protocol was established to enable surface measurement and analysis before and after bracket debonding. Observations were made of representative areas measuring 1,280 × 1,280 μm2, in the center of the enamel samples, as well as of the total topography (2,500 × 3,500 μm) of the bonding areas provided by the equipment software. Noncontact three-dimensional high-resolution image analyses revealed the capabilities of the employed technique and methodology to permit the examination of specific characteristics and alterations on the surfaces, before and after the debonding and finishing procedures. The new protocol was effective to provide qualitative and quantitative assessments of changes on the same dental surfaces at different trial times. The methodology constitutes a feasible tool for revealing the effects of debonding of ceramic brackets on sound and previously injured dental enamel surfaces.

Effect of different debonding techniques on shear bond strength and enamel cracks in simulated clinical set-ups

OBJECTIVE

The aim of this study was to evaluate the relationship between debonding forces and enamel cracks length change between different debonding techniques.

METHODS

80 extracted premolar teeth with intact buccal enamel were divided into five groups. In each group, enamel cracks were evaluated by stereomicroscope before and after debonding. All teeth were bonded with metal brackets by self-cure adhesive (3M, USA) and then debonded by bracket debonding plier, fixed on the UTM machine, through five methods based on location of plier on brackets: OGwing (occlusogingival), MDwing (mesiodistal), Oblique, OGbase (occlusogingival) and Cusp-base.

RESULTS

Based on non-parametric distribution of data, there was no significant difference between groups in ARI and enamel cracks length change. The highest shear bond strength for debonding presented in OG base method (25.25 ± 8.4) and the difference was statistically significant (P-value = 0.029). There was no linear relationship between shear bond strength and cracks length change and also between ARI and cracks length change.

CONCLUSION

Despite the lower cracks length change in Cusp-base method than other groups, there wasn't significant difference between debonding methods. Also the amount of debonding forces and ARI do not affect the changes of cracks length.

Evaluation of Enamel Topography after Debonding Orthodontic Ceramic Brackets by Different Er,Cr:YSGG and Er:YAG Lasers Settings

In the last decade, the success of lasers in simplifying many dental procedures has heightened the need for research in the orthodontic field, in order to evaluate the benefits of laser-assisted ceramic brackets debonding. Conventional ceramic brackets removal delivers a high shear bond strength (SBS), which might lead to enamel damage. Nowadays, debonding ceramic brackets by Er:YAG laser seems a viable alternative technique; however, there is no data on the use of Er,Cr:YSGG in the literature. We aimed to evaluate the difference in enamel topography derived from different erbium laser settings used during debonding. One hundred and eighty bovine incisors teeth were randomly divided into fifteen experimental groups, according to different erbium laser settings using scanning methods. SBS testing was performed after debonding; stereomicroscopic and SEM analyses were done after cleaning the remaining adhesive so as to assess the incidence of enamel microcracks formation and enamel loss. There were no statistically significant differences between the proportions of teeth with normal enamel topography within the control group when compared with any of the Er:YAG groups. However, the proportion of teeth with a normal enamel topography in Er,Cr:YSGG was 4 W/20 Hz (83.3%) and in Er:YAG was 5 W/20 Hz (91.7%), which was statistically significantly higher than the control group (41.7%). The selection of erbium lasers' optimal parameters during debonding influences the enamel topography. When considering the evaluation of both microscopic and statistical analyses, irradiation by Er:YAG (120 mJ/40 Hz) displayed a significant reduction in microcracks compared with conventional debonding, even though some microstructural changes in the enamel could be noted. Er,Cr:YSGG (4 W/20 Hz) respected the enamel topography the most out of the studied groups.

Enamel microcracks in the form of tooth damage during orthodontic debonding: a systematic review and meta-analysis of in vitro studies

Objectives

To evaluate and compare the enamel microcracks (EMCs) characteristics (qualitative and quantitative) in the form of tooth damage before and after debonding from human teeth of in vitro studies.

Eligibility criteria

Laboratorial studies evaluating EMCs characteristics before and after debonding metal and ceramic brackets from human teeth with intact buccal enamel.

Information sources

An electronic search of four databases (all databases of the Cochrane Library, CA Web of Science, MEDLINE via PubMed, and Google Scholar) and additional manual searches were carried out, without language restrictions. Studies published between 2000 and 2017 years were selected. Reference lists of the included articles were screened, and authors were contacted when necessary.

Risk of bias

The following six parameters were analyzed: blinding of examiner and outcome assessment, incomplete outcome data before bonding and after debonding, selective outcome reporting, and incomplete reporting of EMCs assessment.

Included studies

Out of 430 potentially eligible studies, 259 were screened by title and abstract, 180 were selected for full-text analysis, 14 were included in the systematic review. Seven studies were selected for the meta-analysis.

Synthesis of results

The results for EMCs characteristics were expressed as mean differences (MDs) with their 95 per cent confidence intervals (CIs), and calculated from random-effects meta-analyses. Debonding was associated with the increase in number (three studies, MD = 3.50, 95% CI, 2.13 to 4.87, P < 0.00001), length (seven studies, MD = 3.09 mm, 95% CI, 0.75-5.43, P < 0.00001), and width (three studies, MD = 0.39 µm, 95% CI, -0.01 to 0.79, P = 0.06) of EMCs. Considerable statistical heterogeneity was found for two forest plots evaluating the changes of number and length characteristics during debonding.

Conclusions

There is weak evidence indicating length and width of EMCs increase following bracket removal and the scientific evidence concerning quantitative evaluation of the number parameter before and after debonding is insufficient. However, there is a strong evidence that after debonding the number of EMCs is likely to increase.

Registration

No registration was performed.