Preventive Effects of Laser Irradiation and Dentin Bonding Agent Application on Tooth Discoloration Induced by Mineral Trioxide Aggregate

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The introduction presents a background to the topic in question, which is of clinical relevance. It is pointed out there is a gap in the existing literature as few studies have evaluated the impact of pre-application of laser irradiation in preventing tooth discoloration. The methodology was described in detail, in which the tooth color assessment was analyzed using a standard method and presented in the literature. The results are consistent with the literature, presented in tables and graphs and with what was found. Although the discussion has been developed carefully and is well described, it can still be increased by mentioning the main risk factors responsible for tooth discoloration caused by MTA-blood contact, and making it clearer and highlighting the role of the Nd:YAG laser as an agent to prevent this color change.

Author Response

• Dear reviewer, thank you for your positive and informing feedback. With the line of your suggestions following information about discoloration caused by MTA-blood contact are added;

“When collagen undergoes a reaction with bismuth oxide, a transformation occurs, leading to the formation of a black sediment. Furthermore, the oxidation of bismuth oxide results in the destabilization of its oxygen molecule, prompting a reaction with carbon dioxide present in the atmosphere. This reaction yields bismuth carbonate, known for its discoloration properties. Another conceivable pathway for discoloration induced by MTA involves the oxidation of iron within the set material, associated with the phase of calcium aluminoferrite present in the cement powder. “

 

• For the highlighting of the laser role, the following sentences are also added;

“      Nd YAG laser is frequently preferred in the treatment of dentine sensitivity due to its highly effective dentinal tubule occlusion and high penetration depth effects. Additionally, Nd:YAG laser, when applied with appropriate parameters, also reduces unwanted side effects such as cracks and pulp damage in teeth.^{18, 29}”

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

First of all, highlighting the importance of the study presented and its scientific relevance.

[ ] It would be crucial to have the values of the initial results for all groups before any procedure. The results presented are after bond and laser procedures...  it is important control initial color of groups specimes.  The authors dont´t believe that a difference betwenn them can influence the stability and modifications of samles color... we don't know if the teeth allocated to each group didn't have differents color values...The authors should add these results.

[ ] small content errors to correct... Error in the means results, and in the authors' comma [ ] Authores state that the greatest discoloration degree is always at 6 months... but in clearfill it is not they should correct this sentence... [ ] Regarding the luminosity results, the clearfil is the one that seems to decrease... why the authors don´t relate this relationship with the luminosity value? this discussion of luminosity it is essential [ ] related to laser group, it is important to clarify the machine and application time... [ ] The laser group also presents statistically significant lower luminosity but this is not mentioned in the discussion [ ] The abstract is unclear and erroneous. The authors mention groups differences in results but laser group is not statistically significant... This may be dubious for the reader. in addition, we do not have the initial reduction of all teeth without any intervention, it was important. The initial value may influence the results over time and color stability. I would like the authors to mention these variables If possible, integrate these results into the article or at least refer to these issues as limitations and biases of the article.

  

Author Response

• Dear reviewer, the material method has been revised according to your suggestions. We hope that we have comprehended your feedback and met your expectations. Thank you for your valuable input and consideration.

 

“In this in vitro study, we tried to distribute the initial colors of the teeth in a standard way to each experimental group by measuring them with a spectrophotometer. An equal number of color tones were distributed to each group (three teeth color A2, two teeth color B1, two teeth color B2, and three teeth color A3 in the same experimental group). In addition, the color changes within each tooth in the T0-T1-T2-T3 and T4 intervals were examined. It is seen that the initial groupings were made in the same way in similar studies in the literature.”

• Jesus LS, Reis TLDS, Machado BGMM, Costa ALMD, Savaris JM, Volpato CAM, Bortoluzzi EA, Teixeira CDS, Fernandes PCDSV, Garcia LDFR. Dental and composite resin discoloration induced by different hydraulic calcium silicate-based cements: two-year in vitro assessment. J Appl Oral Sci. 2023 Apr 28;31:e20220444. doi: 10.1590/1678-7757-2022-0444. PMID: 37132699; PMCID: PMC10159045

de Jesus LS, Volpato CAM, Bortoluzzi EA, da Silveira Teixeira C, Rossetto HL, de Carvalho Panzeri Pires-de-Souza F, da Fonseca Roberti Garcia L. Tooth discoloration induced by the different phases of a calcium aluminate cement: One-year assessment. J Esthet Restor Dent. 2021 Oct;33(7):999-1009. doi: 10.1111/jerd.12739. Epub 2021 Apr 30. PMID: 3392907

• Dear reviewer, we thank for your opinions. We revised due to your suggestions.

“The highest degree of discoloration in each experimental group was observed at the end of the 6th month, as compared to the 1st month, except Clearfil SE Bond group (P<0.05).  “

• Dear Reviewer, the laser device informations and application time of the laser group are added to the methodology part as follows;

“Group 5: (Laser irradiation) The internal walls of the pulp chamber in this group were irradiated using Nd:YAG laser (Fotona, Lightwalker, USA). Lasers were used with 1 W power, at an energy level of 100 mJ per pulse, and a repetition rate of 10 Hz, for 10 sec, firing interval 250 msn. A 300-mm quartz fibre was used with pre-established movements in the occluso–apical and mesiodistal directions and vice versa.”

• Dear Reviewer, the related part was also added to discussion part as a limitation of the study.

“An equal number of color tones were distributed to each group based on colors A2, B1, B2, and A3. The initial luminosity values were recorded but not considered for the allocation of the groups. For this reason, in the result part, luminosity change was evaluated within each group, rather than between the groups.”

• The abstract is reorganized, and the related topics are corrected.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

What is the novelty of this study?

 

Could you please explain how blood initiates the discoloration with MTA? I mean the mechanism.

Could you please explain the Bismuth oxide’s color change effect in contact with collagen?

I think the authors should reconsider the study design.

All the best

Comments on the Quality of English Language

Please check for grammatical errors and typos. 

Author Response

What is the novelty of this study?

• Dear Reviewer,

Firstly, I would like to express my gratitude for your interest in our work and the insightful feedback provided. In this context, I would like to offer a more detailed and explanatory perspective on the novelty of our research.

Our study aims to contribute significantly to the field by investigating the efficacy of pre-application of Nd:YAG laser irradiation and different dentin bonding agents (DBAs) in preventing tooth discoloration induced by MTA. This emphasis on the pre-application of these interventions and the comparative analysis of different dentin bonding agents distinguish our study. It provides novel insights into potential strategies to mitigate discoloration risks associated with MTA usage in regenerative endodontics, as well as valuable information on the varying efficacies of different dentin bonding agents in this context. There is no study in the literature that compare the different bonding agents and laser in the prevention effect of tooth discoloration.

 

Could you please explain how blood initiates the discoloration with MTA? I mean the mechanism. Could you please explain the Bismuth oxide’s color change effect in contact with collagen?

The following statements are added;

“ When collagen undergoes a reaction with bismuth oxide, a transformation occurs, leading to the formation of a black sediment. Furthermore, the oxidation of bismuth oxide results in the destabilization of its oxygen molecule, prompting a reaction with carbon dioxide present in the atmosphere. This reaction yields bismuth carbonate, known for its discoloration properties. Another conceivable pathway for discoloration induced by MTA involves the oxidation of iron within the set material, associated with the phase of calcium aluminoferrite present in the cement powder. “

I think the authors should reconsider the study design.

All the best

Thank you for your feedback and suggestions. Authors did the best to revise the manuscript with the directions of the reviewers. We greatly appreciate your time and consideration.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you.

I think the author misunderstood my comments. 

In this study design, the authors used fresh blood to examine the discoloration. The known mechanism of discoloration is associated with collagen and Bismuth Oxide. Are those collagens from blood or Dental tissue? 

I apologize, I am not convinced with the revision. Please revise your study design to justify blood-associated discoloration. 

Thank you.

 

Comments on the Quality of English Language

Please have careful proofreading to avoid simple typos and grammatical errors. 

Author Response

• Dear Reviewer, Thank you for your revision. Your concern is quite logical and understandable. We are pleased to have a chance to rewrite it. Following explanation about blood-associated discoloration of MTA is added to the introduction part;

“ The mechanisms underlying the blood-associated discoloration of Mineral Trioxide Aggregate (MTA) remain unclear. One potential explanation for discoloration resulting from contact between blood and MTA may involve the interaction between erythrocytes and unset MTA. The gradual hydration process of MTA might facilitate the absorption and subsequent hemolysis of erythrocytes from the blood, leading to both material and subsequent tooth discoloration (Felman, 2013). Notably, discoloration linked to collagen-bismuth oxide has been documented as well (Mozynska, 2017). Nevertheless, it is important to highlight that MTA without bismuth oxide can also induce discoloration in the presence of blood, potentially due to the porosity of the cement or the hypothesis of heme absorption from hemoglobin (Torabinejad, 2018). Research indicates that the heme group is a prosthetic group composed of a ferrous (Fe2+) ion located at the center of a large heterocyclic organic ring called porphyrin. This structure is formed by four pyrrolic groups interconnected by methine bridges (Dean, 2005). Over time, blood in contact with the cement undergoes a natural redox reaction leading to the conversion of Fe2+ (with a red color) to ferric (Fe3+), which imparts a dark brown color. This transformation may contribute to the darkening of the cement and, subsequently, tooth discoloration (Felman, 2013; Guimarães, 2015)."

 

• Mozynska J, Metlerski M, Lipski M, Nowicka A: Tooth Discoloration Induced by Different Calcium Silicate-based Cements: A Systematic Review of In Vitro Studies. J Endod 2017;43(10):1593-601. Available from: http://www.ncbi.nlm.nih.gov/pubmed/28864217.
• Torabinejad M, Parirokh M, Dummer PM. Mineral trioxide aggregate and other bioactive endodontic cements: An updated overview – Part II: Other clinical applications and complications.Int Endod J. 2018;51:284–317
• FELMAN, Daniel; PARASHOS, Peter. Coronal tooth discoloration and white mineral trioxide aggregate.Journal of endodontics, 2013, 39.4: 484-487.
• Dean L. Blood Groups and Red Cell Antigens. Bethesda, MD: National Center for Biotechnology Information; 2005.
• Guimarães, B. M., Tartari, T., Marciano, M. A., Vivan, R. R., Mondeli, R. F. L., Camilleri, J., & Duarte, M. A. H. (2015). Color stability, radiopacity, and chemical characteristics of white mineral trioxide aggregate associated with 2 different vehicles in contact with blood.Journal of endodontics, 41(6), 947-952.

 

 

 

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

Looks good.

Comments on the Quality of English Language

Proofreading is required.