SEM Evaluation of Enamel Surface Changes and Enamel Microhardness around Orthodontic Brackets after Application of CO2 Laser, Er,Cr:YSGG Laser and Fluoride Varnish: An In vivo Study

Can acid produced from probiotic bacteria alter the surface roughness, microhardness, and elemental composition of enamel? An in vitro study

Probiotics are live microorganisms that upon administration in adequate amounts provide various health benefits to the host. Probiotics are "lactic acid-producing bacteria" as they release large amounts of organic acids, particularly lactic acids, in their surrounding environment. Although the acids produced by probiotics are beneficial for gastrointestinal and vaginal health, the acidogenic nature of probiotics has raised concerns among dental professionals, especially concerning their effect on the enamel and dentin. Previous studies have found that probiotics can lower the pH of the saliva and cause essential elements like Calcium and Phosphorus to leach from the enamel. This can alter the surface topography of enamel and increase the risk of enamel defects. Studies have also noted that probiotic bacteria can replace cariogenic bacteria and lower the risk of tooth decay. However, the effect of acid produced by probiotics on the enamel surface remains unclear. Hence, the present study aims to evaluate the effect of probiotics on the surface roughness, microhardness, and elemental composition of enamel compared to 0.1 M Lactic acid (demineralizing agent). Twenty enamel sections were randomly divided into groups and subjected to a pH cycling model using a probiotic suspension and 0.1 M lactic acid. The changes in the surface roughness, microhardness, surface morphology, and elemental composition of the enamel with regard to Carbon, Oxygen, Sodium, Hydrogen, Magnesium, Phosphorus, Fluoride, Chlorine, and Calcium of the enamel were evaluated before and after the emersion in both the groups. The results showed a significant increase in the mean surface roughness in the probiotic group before and after the exposure. The microhardness of the enamel decreased along with altered arrangement of the enamel prisms, increased striations, scratch marks, and pitting after exposure to the probiotic group. A decrease in the atomic/weight% for Calcium, Phosphorous, Fluoride, Aluminium, and Oxygen and an increase in the weight/atomic% for Carbon, Nitrogen, and Sodium were noted compared to the baseline in the probiotic solution. The results in the probiotic group were comparable to the 0.1 M lactic acids. The pH changed from 5.78 to 3.06 at the end of 24 h in the probiotic group. Based on these findings, we conclude that exposure to probiotics can affect microhardness and surface roughness and cause leaching of essential elements like Calcium and Phosphorous from the enamel.

In vitro controlled elemental analysis to evaluate the combined effect of acidulated phosphate fluoride with Er:YAG and diode lasers

Background

Acidulated phosphate fluoride (APF) application is used for dental caries prevention. Combining APF with different laser wavelengths increases acid resistance in enamel.

Aim

To assess the effects of Er:YAG (2940 nm) laser and diode (940 nm) laser after the application of APF on morphology and mineral content of enamel surfaces of human teeth in vitro.

Materials and Methods

Twenty (20) freshly extracted third molar crowns were collected and split longitudinally into halves. Ten (10) halves were given to each of the following groups: group 1 (control), group 2 (application of 1.23% APF gel only), group 3 (diode laser; 1 W for 60 sec, contact mode after APF gel), and group 4 (Er:YAG; 80 mJ, 0.8 W, 10 Hz; in pulsed mode for 10 sec after APF gel). Specimens were morphologically examined by scanning electron microscope (SEM), and mineral content was analysed by energy dispersive X-ray (EDX). Collected data were statistically analysed by ANOVA.

Results

Morphologic results were superior in group 3 followed by group 2 and group 1 with the least change in group 4. EDX of calcium (Ca), phosphorous (P), and Ca/P ratio weight % showed the highest value with no statistical significance between groups 2 and 1, and higher with statistical significance in groups 3 and 4 in descending order. Carbon weight % showed highest results in group 4 then 3, 2, and 1. Fluoride weight % showed highest statistical results in group 4 then 2, 3, and 1.

Conclusion

The diode laser showed superior morphological results after APF application compared to the Er:YAG laser. The Er:YAG increased fluoride absorption on outer enamel surfaces.

Human Enamel Fluorination Enhancement by Photodynamic Laser Treatment

Poor oral hygiene leads to serious damages of theteeth’s surface enamel such as micro-abrasions and acid erosion. These alterations combined with bacterial plaque result in cavity appearance. Prophylactic measures include various techniques for enamel surface restoration. Fluorination is one of the most important treatments for this purpose. Therefore, in the present research, we investigated the classical fluorination treatment compared with laser photodynamic fluorination performed on human enamel samples with poor surface quality. Three sample groups were investigated: veneer (F), inlay (I), and crowns (C). The general morphologic aspect was investigated by scanning electron microscopy (SEM), and the specific details such as the fine microstructure and nanostructure were investigated by atomic force microscopy (AFM) of the surface roughness. The samples were also investigated by Fourier transformed infrared attenuated total reflectance (FTIR-ATR) to evidence the fluorination effect on the enamel surface. Results showed that all initial samples had an altered state with micro-abrasions and erosion with mineral loss, which increase the surface roughness. The F group was the most damaged, having a higher roughness, and the I group was less damaged. Classic fluorination treatment partially restored the enamel by local re-mineralization, but did not obtain the parameters of healthy enamel. However, a significant decrease of the roughness was observed (statistical relevance p = 0.001 with the Breusch–Pagan Test). This fact was supported by the presence of newly formed fluorides in the FTIR-ATR spectra. The photodynamic laser fluorination restores the enamel in an enhanced manner by a strong re-mineralization, which implies a significant roughness value decrease comparable to healthy enamel. The Breusch–Pagan Test confirmed the relevance with p = 0.001. This is due to an extended re-mineralization abundant in fluoride crystals as observed by AFM and FTIR. Statistical p-values regarding laser application were in the range of 0.02–0.06, supporting its relevance in the fluorination effect. The final conclusion is that the photodynamic effect is able to favor the newly formed fluoride deposition onto the affected sites of the enamel surface.

Single-component orthodontic adhesives: comparison of the clinical and in vitro performance

OBJECTIVES

To investigate the clinical and in vitro performance of single-component orthodontic adhesives under metal brackets.

MATERIALS AND METHODS

Bimaxillary orthodontic treatment was required for sixty patients and 60 premolar teeth were divided into three groups (n: 20). The single-component orthodontic adhesives Biofix and GC Ortho Connect (GC) that did not require primers were compared to the control group using Transbond XT, which was applied with a primer. For each patient, total bonding time was measured. The Adhesive Remnant Index (ARI_(Bracket)) score was noted over 12 months. In vitro tests were used to evaluate specimens, shear bond strength (SBS), ARI_(Bracket), and Enamel Surface Index (ESI). After in vitro debonding, the enamel surface and bracket base were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

RESULTS

Clinical failure rate with primer was 9.0%, while it was 8.0 and 10.0 for GC and Biofix, respectively. The mean in vitro SBS values of the Biofix, GC, and Transbond XT groups were 8.21, 8.07, and 7.37 MPa, respectively. There were no statistically differences in clinical failure (p = 0.160) and SBS values (p = 0.158). Mean differences in bond-up time per jaw were 9.65, 10.51, and 11.97 min, which were statistically significant (p = 0.0001).

CONCLUSION

Single-component adhesives had acceptable SBS values and enamel effects according to SEM-EDX analysis. Clinically, bonding failure was not shown statistically inferior to bonding with primer. There was also a significant difference in bond-up times.

CLINICAL RELEVANCE

Considering an intensely working clinic with bonding processes for at least two jaws per day, this means a saving of the chair time of 1 patient per week. However, better saliva contamination and moisture control with lack of the primer stage and, thereby, an acceptable bracket failure rate will bring clinically significant results with less chair time for clinicians.

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.

Laser-assisted prevention of enamel caries: a 10-year review of the literature

Since the invention of lasers in dentistry, investigations in caries prevention by the use of laser radiation have been proposed. There are several mechanisms stated for this purpose such as photothermal and/or photochemical interaction processes with the enamel. Alone or in conjugation with topical fluoride application, this treatment modality may improve enamel acid resistance in high-caries-risk populations. Data collection was done by searching the keywords caries, prevention, and laser in PubMed, Embase, Web of Science, Cochrane Library, and Google Scholar. Lasing protocols of the collected literature and their effectiveness as well as examination methods used to verify treatment outcomes have been evaluated. One hundred eighteen publications were found for the last 10 years. The wavelengths investigated for caries prevention are mainly located in the near and the mid-infrared spectral range. In the evaluated period of time, investigations using CO₂; Er:YAG; Er,Cr:YSGG; Er:YLF; fundamental, second, and third harmonic generations of Nd:YAG; diodes; and argon ion lasers were found in the databases. Accounting for 39% of the literature, CO₂ laser was the most examined system for this purpose. Reviewing the literature in this narrative review showed that all laser systems presented a positive effect in varying degrees. Laser irradiation could be an alternative or synergistic to topical fluoridation for enamel caries prevention with longer lasting effect. Further research should be focused on selecting proper laser settings to avoid damage to enamel and developing effective evidence-based clinical protocols.

Influence of Er, Cr: YSGG (2780 nm) and Nanosecond Nd: YAG Laser (1064 nm) Irradiation on Enamel Acid Resistance: Morphological and Elemental Analysis

BACKGROUND:

Enamel demineralisation is an initial step of the serious dental problem including dental caries, white spot lesions and dental erosion.

AIM:

Compare the effect of Er, Cr: YSGG (λ = 2780 nm) and nanosecond Nd: YAG (λ = 1064 nm) laser on enamel acid resistance.

MATERIAL AND METHODS:

Thirty non-carious human premolars, extracted for orthodontic reasons, were used. The experimental groups (n = 10 each group) were: Group I, untreated (control); Group II, Er, Cr: YSGG laser irradiation (0.75 W, 20 Hz, 140 μs, 10 s); Group III, nanosecond pulsed Nd: YAG laser irradiation (0.8 W, 10 Hz, 7 ns, 10 s). Scanning electron microscope and Energy Dispersive X-ray Spectroscopy (EDX) were used to assess acquired enamel resistance to PH cycling.

RESULTS:

After subjecting the three experimental groups to PH cycling, scanning electron microscopic examination revealed irregular porous dissoluted enamel surface in group I. However, groups II and III demonstrated partially dissoluted enamel surface. EDX analysis demonstrated the lowest mean percentage decrease in calcium and phosphorus content in group II followed by group III, then the highest mean percentage decrease was observed in untreated group I. One-way ANOVA revealed significant differences (p < 0.0001) between the tested groups.

CONCLUSIONS:

Both Er, Cr: YSSG and nanosecond Nd: YAG laser irradiation were able to improve the acid resistance of enamel. However, enamel surface treated with Er, Cr: YSSG laser showed the lowest mean percentage decrease of calcium and phosphorus (highest acid resistance).

Effect of Er,Cr:YSGG on Remineralization Using CPP - ACPF (MI - Paste Plus) after Enamel Erosion Caused by Carbonated Soft Drink in Primary Teeth: In-Vitro Study

BACKGROUND:

Erosion is a widespread phenomenon with higher predilection in primary dentition.

AIM:

The aim of the present study is to assess the remineralising effect of Er,Cr:YSGG laser application combined with CPP-ACPF after erosive demineralisation by Coca-Cola in primary teeth.

METHODS:

Fifty teeth (n = 10) were divided into; Group I: Artificial saliva, (Saliva natural, Medac, UK), Group II: CPP-ACPF (MI Paste Plus, GC Corp, USA), Group III: Er,Cr:YSGG (Waterlase iPlus, USA), Group IV: CPP-ACPF + Er,Cr:YSGG, Group V: Er,Cr:YSGG + CPP-ACPF. Teeth were immersed in Coca-Cola for 10 min, 5 times/day for 5 days. DIAGNOdent (DD) measurements were taken before and after the experiment.

RESULTS:

There was a significant increase in DD readings after erosive-treatment cycles in all test groups. The highest reading was in samples immersed in artificial saliva, and the lowest was in those subjected to combined CPP-ACPF and Er,Cr:YSGG laser application, regardless of the sequence used. There was no significant difference between samples immersed in artificial saliva, and after CPP-ACPF application. Similarly, there was no significant difference between samples treated by combined treatment of CPP-ACPF and Er,Cr:YSGG application. However, there was a significant difference between samples immersed in artificial saliva or treated with CPP-ACPF application and those subjected to combined treatment CPP-ACPF along with Er,Cr:YSGG.

CONCLUSION:

Combining Er,Cr:YSGG laser and CPP-ACPF paste significantly increased enamel remineralisation, regardless of the sequence implemented. Saliva naturally and CPP-ACPF application had a comparable effect on remineralisation.