Study of the Intra-Coronal Pressure Generated by Internal Bleaching Agents and Its Influence on Temporary Restoration

Round 1

Reviewer 1 Report

thank you for your well-written article.

here are some questions.

1. It would be nice if the background and purpose of the study could be strengthened a little more in the introduction. Is the purpose of this study to evaluate temporary sealing according to oxygen expansion for each bleaching material?
2. In the discussion, I would like you to describe more the clinical significance that can be drawn from the results of this study. Do you want to say that oxygen expansion increases when HP is applied, so temporary sealing should be more careful?

Author Response

Dear reviewer,

Thank you very much for the corrections. You will find the corrections made underlined in yellow.

• It would be nice if the background and purpose of the study could be strengthened a little more in the introduction. Is the purpose of this study to evaluate temporary sealing according to oxygen expansion for each bleaching material?

Reply: First of all, thank you very much for your corrections. This correction seems very appropriate, we have strengthened the introduction to better justify the purpose of this study.

"The reactive oxygen released during the whitening process has been associated with both the whitening capacity and the toxicity of the agents, depending on the concentration of HP and the duration of the treatment [25]. It has been shown in some studies that there is microleakage of the temporary coronal sealant after internal bleaching, which has certain drawbacks such as conditioning the desired results and the leakage of HP and reactive oxygen into the oral cavity [26-28]. If the expected success is not achieved during the first session, the treatment time is prolonged, and the possibility of coronal leakage may increase due to inserting another temporary restoration when renewing the bleaching agent. This may compromise the endodontic treatment and the viability of the tooth with the related aesthetic consequences, since it is generally performed on the teeth of the anterior sector [29]. Furthermore, it has been shown that leakage of HP in high concentrations into the oral cavity can easily cause burns to mucosal and periodontal tissues [30]. The aim of this in vitro study was to evaluate in vitro and compare the oxygen expansion that takes place after the reaction of the bleaching agents HP 30% and SP with dental tissues from inside the pulp chamber."

• In the discussion, I would like you to describe more the clinical significance that can be drawn from the results of this study. Do you want to say that oxygen expansion increases when HP is applied, so temporary sealing should be more careful?

Reply: Thank you very much for your corrections. We have described the importance indicated in the discussion.

"This study highlights the clinical importance of understanding the bleaching reaction inside the tooth with each agent in order to choose the best possible temporary sealing material for each condition. Since oxygen expansion increases with higher HP, sealing with high concentrations of HP must be thorough."

 

Author Response File: Author Response.docx

Reviewer 2 Report

After critically reviewing this Research Article titled "Study of the intra-coronal pressure generated by internal bleaching agents and its influence on temporary restoration", I detected some MINOR flaws, which determined my recommendation of “ACCEPT UNDER REVIEW”. Below please find my detailed comments.

The authors studied the expansion of oxygen in vitro that occurs when bleaching agents come into contact with hard dental tissues, the bleaching agentes studied were hydrogen peroxide (HP) and sodium perborate (SP), and a combination of both agentes.

The study is well written and conducted, with well-described methodology, including approval by the ethics committee of the host institution, with minor flaws and easily corrected and appropriate for the objectives of the work. Statistical analyzes of the results obtained were well conducted.

The results obtained were very promising and the discussions were relevant to the results achieved.

• Authors should write the meaning of the abbreviations HP and SP [hydrogen peroxide (HP) and sodium perborate (SP)] in the abstract.
• In item 2.3 Experimental Groups: the information contained in Table 1 is repeated in the first paragraph of the same topic. Authors should exclude the table, as it does not add any new information.
• Figure 2 is not cited in the text, nor its importance in the results is detailed.
• Important information is missing from Figure 2, such as "days" on the X axis and the measurement unit used on the Y axis, whether mm or another measurement.

The limitations of the study were not well pointed out and, if it is possible, should be written in the end of the article.

Author Response

Dear reviewer,

Thank you very much for the corrections. You will find the corrections made underlined in green.

 

 

• Authors should write the meaning of the abbreviations HP and SP [hydrogen peroxide (HP) and sodium perborate (SP)] in the abstract.

Reply: Thank you very much for your corrections. In addition, the abstract has been improved.

 

The following bleaching groups were used: Hydrogen peroxide (HP) 30% (n=30), Sodium Perborate (SP) with distilled water (n=30), a mixture of HP 30% with SP (n=30) and a control group (n=30).

• In item 2.3 Experimental Groups: the information contained in Table 1 is repeated in the first paragraph of the same topic. Authors should exclude the table, as it does not add any new information.

Reply: Thank you very much for your comment, we agree with you, table 1 has been deleted to avoid repeating information already indicated.

• Figure 2 is not cited in the text, nor its importance in the results is detailed.

Reply: Thank you very much for your correction. Figure 2 has been quoted and the significance of the results has been detailed.

"Figure 2 shows the evolution of the average expansion observed in each bleaching agent over the first 10 days. This figure shows the discreet, stable and irrelevant progress of oxygen expansion in the SP group, which contrasts with the HP group, where a significant and strong expansion is observed from the first day. Also, the average expansion of the HP 30% + SP group sits between the aforementioned two groups, neither reaching the levels of the HP 30% nor evolving as weakly as in the SP group. (Figure 2)"

• Important information is missing from Figure 2, such as "days" on the X axis and the measurement unit used on the Y axis, whether mm or another measurement.

Reply: Thank you very much for your correction. Information has been added to the graph to make it easier to understand.

• The limitations of the study were not well pointed out and, if it is possible, should be written in the end of the article.

Reply: Thank you very much for your correction. It has been indicated in the end of the discussion.

"However, although the study has been carried out very thoroughly and meticulously, it has certain limitations inherent to an in vitro experimental study, such as temperature (since oral temperature is higher). The degree of coronal filtration should be checked with other studies for each bleaching agent and the actual effect on bleaching capacity should be evaluated."

 

 

Author Response File: Author Response.docx

Reviewer 3 Report

Journal Name: Applied Science

Title: Study of the intra-coronal pressure generated by internal bleaching agents and its influence on temporary restoration

In the current article, the authors studied hydrogen peroxide and sodium perborate bleaching agent's effects in dental applications.  

 

Article accept as it is with minor corrections.

 

1. The first line of the abstract is not clear authors need to mention which mechanism they are discussing.
2. The abstract is not clear and has to be improved
3. Authors need to discuss the importance and disadvantages of dental bleaching in a more detailed way
4. Is there any other chemical compounds other than hydrogen peroxide and sodium perborate to use as a dental bleaching agent
5. The font size of the texts present in Figure 1 has to be improved.
6. How authors are accounting bleaching efficacy
7. The conclusion is too small
8. Please check the grammatical and syntax error
9. What is the error limits of the experiments has to be explained
10. What are the reasons for deviation in results?

Author Response

Reviewer 3

Dear reviewer,

Thank you very much for the corrections. You will find the corrections made underlined in blue.

• The first line of the abstract is not clear authors need to mention which mechanism they are discussing.
• The abstract is not clear and has to be improved

Reply: Thank you very much for this corrections. We have amended both corrections concerning the abstract.

Abstract: Intracoronal bleaching is a treatment that whitens non-vital teeth from within the pulp chamber, a procedure by which oxygen and free radicals are released. This in vitro study analyzes and compares the oxygen expansion produced when different bleaching agents encounter dental tissues during this type of bleaching. 120 lower incisors were included and prepared to achieve conditions as close as practicable to internal bleaching with Walking Bleach technique. The access cavity of the lingual surface was prepared to seal glass tubes with oil inside them by adhesive restoration once the bleach was placed inside the pulp chamber. The following bleaching groups were used: Hydrogen peroxide (HP) 30% (n=30),Sodium Perborate (SP) with distilled water (n=30), a mixture of HP 30% with SP (n=30) and a control group (n=30). After 10 days, the oil displacement that took place through the tube due to oxygen release was measured daily. Displacement of the oil was observed in all groups except the control group. The final mean expansion at 10 days was 335.24 ± 76.85 mm for the HP 30% group, 8.40 ± 1.74 mm for the SP group, and 183.07 ± 49.93 mm for the HP30%+SP mixture. Significant statistical differences were observed between the three groups using the Games-Howell post-hoc test, where HP30% caused the greatest expansion and SP the least expansion. These results suggest that the higher the amount of HP in the sample, the more oxygen expansion is observed, so that temporary restoration must be performed more carefully to avoid displacement.

• Authors need to discuss the importance and disadvantages of dental bleaching in a more detailed way

Reply: Thank you very much for your correction. It has been indicated in the discussion.

• Is there any other chemical compounds other than hydrogen peroxide and sodium perborate to use as a dental bleaching agent

Reply: Thank you very much for your correction.

• The font size of the texts present in Figure 1 has to be improved.

Reply: Thank you very much for your correction. The font size has been increased for better readability.

• How authors are accounting bleaching efficacy

Reply: The efficacy of bleaching is not an objective of this study. We observed the expansive behavior that occurs when oxygen is released as a result of the reaction of the bleaching agents with the dental tissues, a factor that may influence its efficacy. This fact gives rise to possible future studies.

• The conclusion is too small

Reply: Thank you very much for your correction. We have extended the conclusion

"The results of the present in vitro experimental study show that oxygen release occurs with all bleaching agents. However, significant differences were observed between the different agents used, with HP 30% showing the highest oxygen expansion and SP with distilled water the lowest. The HP group. 30% + SP group showed a significantly lower expansion than HP 30% but significantly higher than SP. It is suggested that the degree of oxygen expansion depends on the amount of HP available in the preparation, as it is the active agent in all samples. Therefore, the provisional restoration should provide a more effective seal with higher concentrations of HP to avoid mismatch and the resulting problems it could cause."

• Please check the grammatical and syntax error

Reply: Thank you very much for your correction. Some errors noted have been corrected.

• What is the error limits of the experiments has to be explained.

Reply: Thank you very much for your correction. It has been indicated in the discussion.

"However, although the study has been carried out very thoroughly and meticulously, it has certain limitations inherent to an in vitro experimental study, such as temperature (since oral temperature is higher). The degree of coronal filtration should be checked with other studies for each bleaching agent and the actual effect on bleaching capacity should be evaluated."

• What are the reasons for deviation in results?

Reply: Hydrogen Peroxide (HP) is a very unstable compound. This could lead to some deviation in the results due to the characteristics of this bleaching agent, which could be equally found in any study using HP.

Author Response File: Author Response.docx