Chemical and morphological analysis of dentin irradiated by different high-power lasers: a systematic review

PURPOSE

This systematic review provides an overview of the main chemical and morphological alterations generated on dentin by different high-power lasers' irradiation.

METHODS

The review was registered in PROSPERO (CRD42023394164) and PRISMA guidelines were followed. The search strategy was conducted on MEDLINE (PubMed), Embase (Elsevier), and Web of Science (Clarivate) databases. The eligibility criteria were established according to the PICOS strategy, focusing on in vitro and ex vivo studies that assessed the chemical and morphological changes in dentin using five high-power lasers: Nd:YAG (1064 nm), Er:YAG (2940 nm), Er, Cr:YSGG (2780 nm), diode (980 nm), and CO2 (10,600 nm). Publication range was from 2010 to 2022. Data was summarized in tables and risk of bias was assessed by QUIN tool.

RESULTS

The search resulted in 2255 matches and 57 studies composed the sample. The methods most used to assess the outcomes were scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Raman. The studies presented "medium" and "low" risk of bias. The laser prevalently identified was the Er:YAG laser, associated with dentin ablation, absence of smear layer, and exposed tubules. The Nd:YAG laser generated vitreous surface and thermal damage, such as carbonization and cracks. The other lasers caused an irregular surface and no adverse thermal effects. Regarding the chemical structure, only the Er,Cr:YSGG laser caused collagen matrix reduction. The effects found were more intense with higher dosimetry.

CONCLUSION

Evidence available indicates that the irradiation of dentin with high-power lasers are related to morphological outcomes favorable to adhesive restorative procedures, with minimal changes in collagen matrix and mineral content. However, those observations should be carried carefully by clinicians and more clinical trials regarding the association of high-power laser irradiation and restorative procedure longevity are needed.

Objective assessment of the combined effect of exomass-related- and motion artefacts in cone beam CT

OBJECTIVES

To assess quantitatively the combined effect of exomass-related- and motion artefacts on voxel value parameters in cone beam CT (CBCT).

METHODS

A cylindrical phantom was manufactured, containing 21 tubes filled with a radiopaque solution, allowing the inclusion of three titanium implants in the periphery to induce exomass-related artefacts. The phantom was mounted on a robot simulating 0.75-, 1.5-, and 3 mm movements (nodding/lateral rotation/tremor). CBCT images with/without exomass and with/without movements were acquired in duplicate in three units: Cranex 3Dx, Orthophos SL-3D, and X1 (with motion-artefact correction). A cylindrical volume of interest was defined in each tube and voxel value mean and standard deviation were assessed. For each CBCT volume, the 21 mean voxel values were averaged providing the overall mean voxel value (MVV), and the standard deviation (among the 21 values) was calculated providing overall voxel value inhomogeneity (VVI). The standard deviation from each of the 21 volumes-of-interest were averaged, providing overall image noise (IN). The effect of the diverse tested situations was inferred from a repeated-measures analysis of variance, followed by Sidak's test (α = 0.05).

RESULTS

Overall, images acquired with exomass showed significantly (p ≤ 0.05) lower MVV, and higher VVI and IN. Motion artefacts aggravated exomass-related alterations. MVV and VVI were mostly affected by 3 mm nodding movements. Motion-artefact correction eliminated the deleterious effect of movement.

CONCLUSIONS

CBCT voxel-value parameters are altered by exomass-related artefacts, and this finding is aggravated in the presence of motion artefacts. Motion-artefact correction effectively eliminated the deleterious impact of movement.

Distribution of metal artifacts arising from the exomass in small field-of-view cone beam computed tomography scans

OBJECTIVES

To evaluate the distribution of metal artifacts from the exomass in small field-of-view (FOV) cone beam computed tomography (CBCT) scans.

STUDY DESIGN

An image phantom was scanned by using 3 CBCT units. Metal objects were positioned in the exomass, and additional CBCT scans were obtained. Mean gray values were obtained from 16 homogeneous areas and the standard deviation was calculated to quantify gray level inhomogeneity according to distinct zones of the FOV: total area and outer, inner, right, left, and mid-zones. The discrepancy between each zone and the total area was calculated to compare different CBCT units. Mean gray, gray level inhomogeneity, and discrepancy values were separately assessed by using analysis of variance (ANOVA) and Tukey's test (α = 0.05).

RESULTS

Overall, the mean gray values were significantly lower in the inner zone, and the gray level inhomogeneity values were significantly higher in the inner and mid-zones irrespective of the presence of metal objects in the exomass. The 3 CBCT units presented significantly different discrepancy values in most conditions.

CONCLUSIONS

The distribution of metal artifacts from the exomass follows the inherent gray value dispersion of CBCT images, with greater inhomogeneity in the inner zone of the FOV. This is exacerbated when metal objects are in the exomass.

Metallic materials in the exomass impair cone beam CT voxel values

OBJECTIVES

To assess the influence of artefacts arising from metallic materials in the exomass on cone beam CT (CBCT) voxel values.

METHODS

CBCT scans were taken of a phantom composed of 16 tubes filled with a homogeneous hyperdense solution and metallic materials of different compositions (titanium, cobalt-chromium and amalgam) and numbers (one, two and three). The phantom was centred in a 5 × 5 cm field of view such that the metallic materials were located in the exomass, using three CBCT units. Voxel values were obtained from the 16 homogeneous areas and averaged. Also, standard deviation was calculated to measure voxel value variability. Analysis of variance in a factorial scheme with additional treatment 3 × 3 + 3 (material × number + control) was performed, followed by Tukey's test for multiple comparisons, and Dunnett's test for comparisons with the control groups, at a level of significance of 5%.

RESULTS

Metallic material in the exomass significantly reduced the mean voxel value in the CS9300 and Picasso Trio units, and increased voxel value variability in all CBCT units. Amalgam was the material that induced significantly greater reduction of the mean voxel value in the CS9300 and Picasso Trio units, and significantly greater increase in the NewTom Giano. Voxel value variability was significantly greater for amalgam in all conditions. The presence of one cylinder induced significantly less pronounced effects on the mean voxel value and voxel value variability.

CONCLUSIONS

Artefacts arising from metallic materials in the exomass have a negative influence on CBCT voxel values.