Effect of Mixing and Impression Techniques Using Vinyl Polysiloxane (VPS) on the Accuracy of Fixed Partial Dentures

Round 1

Reviewer 1 Report

I do not think it is realistic to use a bur to remove 2 mm of putty in the two-stage technique.  It is clear from the photograph that the wash is not 2mm thick.  i am concerned that 22.8% of castings were misfits - this seems exceptionally high and very different from dental practice.  This may be due to the test regime that was employed; "rocking test" and "probe test" re very subjective.  What would be interesting to know is how many of these "misfit" restorations were actually cemented in the patient's mouth.  Was any adjustment needed to the restorations prior to this?  If  a misfit was cemented in place clinically then this might indicate that the degree of misfit was not clinically important.  There was no example of a radiograph showing a typical misfit.  Radiographs have the problem that one can only assess interproximal regions.  

Author Response

I do not think it is realistic to use a bur to remove 2 mm of putty in the two-stage technique.  It is clear from the photograph that the wash is not 2mm thick.

- the text was clarify "round low-speed bur number 6 with diameter of 1.8mm.(DentsplyDeTreyGmbh), in order to create controlled space (up to 2 mm) for wash material"

  i am concerned that 22.8% of castings were misfits - this seems exceptionally high and very different from dental practice.  This may be due to the test regime that was employed; "rocking test" and "probe test" re very subjective.  What would be interesting to know is how many of these "misfit" restorations were actually cemented in the patient's mouth.  Was any adjustment needed to the restorations prior to this?  If  a misfit was cemented in place clinically then this might indicate that the degree of misfit was not clinically important.  There was no example of a radiograph showing a typical misfit.  Radiographs have the problem that one can only assess interproximal regions. 

• these are the methods  used to validate the fit of  metal frameworks, according to the prosthodontic department guidelines based on the literatura :
• Assif D. et al. Comparison of methods of clinical evaluation of the marginal fit of complete cast gold crowns. J Prosthet Dent. 1985;54:20-24.
• Abduo, J.et al. Assessing the fit of implant fixed prostheses: A critical review. Int J Oral MaxillofacImpl 2010,25,506-515.
•  

Reviewer 2 Report

Dear Authors,

I read your manuscript, the topic is interesting, but some issues need clarification.

Best regards

Comments for author File: Comments.pdf

Author Response

issuses such as research design ,methods and results were clarified

Reviewer 3 Report

This is a research study and the selection should be based in certain criterion, not random selection :” Two impression techniques were randomly”

 

The list of references is quite old, and only 1 ref is new one. I suggest using more novel references in order to endorse the novelty of this work

Please avoid block citation, “[11-18] “ “[29,32,34,36,38,40]”;and so on -  max 2-3 is OK

A citation is required for this standard “ISO 4823”4

The “Materials and methods” part is very superficial treated as there are missing details of measurements and criterion for misfit

“The putty was allowed to set for 6 minutes” is any justification for setting 6 minutes ?

Not clear how was measured and achieved “21/92 metal frameworks (22.8%) were found ill-fitted (22.8%).” Please provide details and in which consideration was made .

Many time is presented the “the misfit” but not clear the measurement technique used

This part “Moreover the mechanical mixing is preferred by the dental staff due to accessibility of this method” is repeated twice in introduction and discussion

Even there is a section of discussion but it is not interpreted in details against your results rather is present mostly literature data ; For example you stated “Clinical situation and anatomical limitations such as..” but there is no evidence between your results and how they were generated and if they were or not influenced by the limitation indicated in literature .

Your conclusion is just a sentence without any details; therefore I suggest to present a proper section of conclusion which should be linked to your results and indicate some quantitative details

Author Response

thanks for the comments ,our response are below and also were included in the manuscript:

This is a research study and the selection should be based in certain criterion, not random selection :” Two impression techniques were randomly”

- text was changed according to the suggestaion 

 

The list of references is quite old, and only 1 ref is new one. I suggest using more novel references in order to endorse the novelty of this work

Please avoid block citation, “[11-18] “ “[29,32,34,36,38,40]”;and so on -  max 2-3 is OK

- corrected at the manuscript

A citation is required for this standard “ISO 4823”4

The “Materials and methods” part is very superficial treated as there are missing details of measurements and criterion for misfit

- was clarified at the text

“The putty was allowed to set for 6 minutes” is any justification for setting 6 minutes ?

- corrected in the text

Not clear how was measured and achieved “21/92 metal frameworks (22.8%) were found ill-fitted (22.8%).” Please provide details and in which consideration was made .Many time is presented the “the misfit” but not clear the measurement technique used

-was clarified at secton 2.4 Metal framework fit verification

This part “Moreover the mechanical mixing is preferred by the dental staff due to accessibility of this method” is repeated twice in introduction and discussion

- corrected

Even there is a section of discussion but it is not interpreted in details against your results rather is present mostly literature data ; For example you stated “Clinical situation and anatomical limitations such as..” but there is no evidence between your results and how they were generated and if they were or not influenced by the limitation indicated in literature .Your conclusion is just a sentence without any details; therefore I suggest to present a proper section of conclusion which should be linked to your results and indicate some quantitative details

- it was emphziesd and clarified at the Discussion

Round 2

Reviewer 1 Report

The authors have not addressed my previous concerns

Author Response

I do not think it is realistic to use a bur to remove 2 mm of putty in the two-stage technique.  It is clear from the photograph that the wash is not 2mm thick.

- The use of Nr.6 bur was done in order to create wash space up to 2 mm for wash material ,as we found previously in an vitro study  that a wash space up to 2 mm is preferable for accuracy  (ref.14)

• at the picture of the 2 stage impression it can be seen that all the preparation is covered by wash material while in the 1 stage picture parts of the prepared teeth are covered only by the putty
• It was clarified at the text.

 

• i am concerned that 22.8% of castings were misfits - this seems exceptionally high and very different from dental practice.  This may be due to the test regime that was employed; "rocking test" and "probe test" re very subjective.  What would be interesting to know is how many of these "misfit" restorations were actually cemented in the patient's mouth.  Was any adjustment needed to the restorations prior to this?  If  a misfit was cemented in place clinically then this might indicate that the degree of misfit was not clinically important.  There was no example of a radiograph showing a typical misfit.  Radiographs have the problem that one can only assess interproximal regions.

   21/92 metal frameworks (22.8%) were found ill-fitted while 71 metal frameworks were found to be accurate (77.2%). these are the general results 'specific results were: In 44 patients, the one-step mixing technique was used, the misfit was detected in 5/44 of the metal frameworks when the machine mixing of the putty was performed (11.4%) and in 9/44  of the frameworks when the hand mixing of putty was applied (20.4%).

  In 48 of the cases, the two- stage impression technique was used and the misfit was detected in 1/48 metal framework when the automatic mixing was applied (2.1%), and 6/48 metal frameworks was found ill-fitted when the hand mixing was used (12.5%). (Table 3) which are more realists 

  regarding the comments about the misfit verifications methods the text was changed and clarified according to the comments :"The accuracy of the FPD`s restorations was tested clinically and radiologically.  Three common accuracy assessments methods were used to validate the fit of all the metal frameworks, according to the prosthodontic department guidelines: probe test (using a dental probe to confirm vertical and horizontal restoration marginal fitting , at the buccal and lingual/palatal aspect ); tactile sense test (“rocking test” for verifying the metal framework stability , at the restorations  masio-distal aspects) and radiographic test performing bitewing radiograph to verify restorations  interproximal adaptation. [43-44] Misfit of the metal framework was diagnosed when one of the three accuracy assessment methods was found to be defective and demarcated as inaccurate restoration leading to redoing the impression"

Reviewer 3 Report

please address my concerns

Author Response

Thanks very much for the comments   ,our response are below and also were included in the manuscript:

- This is a research study and the selection should be based in certain criterion, not random selection :” Two impression techniques were randomly”

- - text was changed according to the suggestions:

“The putty mixing techniques was chosen randomly according to the operator`s preference and was one of the two following mixing methods: “

“  The data of the current study was recovered from patient`s files (retrospective study) and subjected   

     to statistical analysis.”

 

-The list of references is quite old, and only 1 ref is new one. I suggest using more novel references in order to endorse the novelty of this work

Please avoid block citation, “[11-18] “ “[29,32,34,36,38,40]”;and so on - max 2-3 is OK

- - corrected at the manuscript ( block citations were divided , novel references were marked)

-A citation is required for this standard “ISO 4823”4

-- The standard was removed from the text  

 

The “Materials and methods” part is very superficial treated as there are missing details of measurements and criterion for misfit

- - was added and clarified at the text:

“ Three common accuracy assessments methods were used to validate the fit of all the metal frameworks, according to the prosthodontic department guidelines: probe test (using a dental probe to confirm vertical and horizontal restoration marginal fitting , at the buccal and lingual/palatal aspect ); tactile sense test (“rocking test” for verifying the metal framework stability , at the restorations  masio-distal aspects) and radiographic test performing bitewing radiograph to verify restorations  interproximal adaptation. [43-44] Misfit of the metal framework was diagnosed when one of the three accuracy assessment methods was found to be defective and demarcated as inaccurate restoration leading to redoing the impression”

“The putty was allowed to set for 6 minutes” is any justification for setting 6 minutes ?

- corrected in the text :

“ The putty was allowed to set according to the manufacturer  recommendation time”

Not clear how was measured and achieved “21/92 metal frameworks (22.8%) were found ill-fitted (22.8%).” Please provide details and in which consideration was made  .Many time is presented the “the misfit” but not clear the measurement technique used

-- was clarified at section 2.4 Metal framework fit verification:

“Three common accuracy assessments methods were used to validate the fit of all the metal frameworks, according to the prosthodontic department guidelines: probe test (using a dental probe to confirm vertical and horizontal restoration marginal fitting , at the buccal and lingual/palatal aspect ); tactile sense test (“rocking test” for verifying the metal framework stability , at the restorations  masio-distal aspects) and radiographic test performing bitewing radiograph to verify restorations  interproximal adaptation. [43-44] Misfit of the metal framework was diagnosed when one of the three accuracy assessment methods was found to be defective and demarcated as inaccurate restoration leading to redoing the impression”

  21/92 metal frameworks (22.8%) were found ill-fitted while 71 metal frameworks were found to be accurate (77.2%). these are the general results 'specific results were: In 44 patients, the one-step mixing technique was used, the misfit was detected in 5/44 of the metal frameworks when the machine mixing of the putty was performed (11.4%) and in 9/44 of the frameworks when the hand mixing of putty was applied (20.4%). In 48 of the cases, the two- stage impression technique was used and the misfit was detected in 1/48 metal framework when the automatic mixing was applied (2.1%), and 6/48 metal frameworks was found ill-fitted when the hand mixing was used (12.5%). (Table 3) which are more realists

 

-This part “Moreover the mechanical mixing is preferred by the dental staff due to accessibility of this method” is repeated twice in introduction and discussion

-- corrected at the text :

“Likewise, there is a clear preference for the automatic mixing among the medical staff (clinicians and assistants) considering the convenience of the machine method.[36] Furthermore, automatic mixing is considered to be more economical compared to hand mixing, thanks to minor waste of the impression material. [37-40]”

“  Moreover  the mechanical mixing is preferred by the dental staff due to ease of use.

Additional factor persuading the operator in using mixing technique for impression material is the accessibility of the mixing  machine  .[36]”

 

- Even there is a section of discussion but it is not interpreted in details against your results rather is present mostly literature data ; For example you stated “Clinical situation and anatomical limitations such as..” but there is no evidence between your results and how they were generated and if they were or not influenced by the limitation indicated in literature .Your conclusion is just a sentence without any details; therefore I suggest to present a proper section of conclusion which should be linked to your results and indicate some quantitative details

- The quantitative details were added and  clarified at the Discussion:

“ Previous in vitro studies have shown that different mixing techniques have an effect on impression quality and have found that machine mixing improves impression quality.[39,40] This findings are consistent with our study results ,in which emphasize the fact that mechanical mixing produced significantly( P = 0.04) more accurate metal framework restorations than hand mixing. The clinically outcome show that hand mixing led to twice as many metal frameworks misfit, compared to machine mixing (31.1% vs.14.1%). “

“ Similar to previous in vitro studies results, the present study have shown a significant difference in PFD`s metal frameworks fit accuracy when comparing two common impression techniques. While the one-step technique has the benefits of being faster it also has led to fabrication of twice as many ill-fitted metal frameworks, compared to two-stage impression technique (31.8% vs. 14.6%).  “

 

 

Round 3

Reviewer 3 Report

Please address my concerns

Author Response

Acording to the comments suggested the following changes were done in the text:

• English editing
• Introduction ,research design ,results and Discussion and conclussions. were improved.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

1. The current study investigates the effect of applying different mixing techniques on the accuracy of impressions made from vinyl polysiloxane which is a silicone based material which is a general category of polymers consisting of a silicon-oxygen backbone with organic groups. For this the authors assess the mixing influence by assessing metal framework clinical fit of fixed partial restorations. The authors used manual mixing (using hands) and mechanical mixing using putty material. The authors found that mechanical mixing provides better accuracy and two stage technique was more accurate which were recommended as a combination for best impression fabrication.
2. Please consider reviewing the abstract and highlight the novelty, major findings and conclusions.
3. Introduction is very short and must be improved. The authors must provide comprehensive literature review which discusses past studies same or similar to this work. Report what they did and what were their main findings then explain how does the current study brings new knowledge and difference to the field.
4. After line 66 the authors must answer the following question: What is the research gap did you find from the previous researchers in your field? Mention it properly. It will improve the strength of the article.
5. Please combine lines 67-72 in one paragraph
6. Line 45/55/66/170 bulk citations are not advised and must be reduced or removed completely unless the authors give full credit to each of the studies. This is not acceptable at all.
7. The materials and method section must be improved, provide full details of the experimental work, Images of test equipment and tools used in the study. Photos of the impressions produced using hand and mechanical mixing techniques..etc.
8. The results are merely described and is limited to comparing the experimental observation. The authors are encouraged to include a discussion section and critically discuss the observations from this investigation with existing literature.
9. This paper lacks any basic foundations for a scientific paper, it seems like it was written quickly without any consideration for the basic requirements of a scientific paper therefore it can not be accepted.
10. 10 authors for 6 pages?

Author Response

Thanks for the comments' corrections were done accordingly 

all changes point by point were colored in yellow in the text 

1. Please consider reviewing the abstract and highlight the novelty, major findings and conclusions. - Done 
2. Introduction is very short and must be improved. The authors must provide comprehensive literature review which discusses past studies same or similar to this work. Report what they did and what were their main findings then explain how does the current study brings new knowledge and difference to the field.- was improved
3. After line 66 the authors must answer the following question: What is the research gap did you find from the previous researchers in your field? Mention it properly. It will improve the strength of the article.- done
4. Please combine lines 67-72 in one paragraph- Done
5. Line 45/55/66/170 bulk citations are not advised and must be reduced or removed completely unless the authors give full credit to each of the studies. This is not acceptable at all.- citations in line 66& 170 were changed
6. The results are merely described and is limited to comparing the experimental observation. The authors are encouraged to include a discussion section and critically discuss the observations from this investigation with existing literature.- done at the discussion part
7. 10 authors for 6 pages?- each author activity was  described

 

Reviewer 2 Report

 

Dear Authors,

 

The topic of the article is great of interest. However your manuscript presents lots of criticalities:

 

Authors need to revise the title it is un clear.

 

Abstract: Abstract should be revised, rewritten and make it more fluent and appealing.

 

Keywords: To ensure a properly research in medical databases, use MeSH terms to find  appealing keywords that could be helpful in finding your article.

 

“The 46 working time of impression material can also be affected by the mixing technique. [26] 47 In general, the mixing techniques can be divided into two major categories: mechanical 48 mixing and hand mixing techniques.”  Please provide a proper description of the two techniques. What kind of devices could be used for the mechanical technique?

“In addition, 52 due to more uniform blending of the base with the catalyst, machine mixing enhances 53 the polymerization reaction and generates homogeneity of the impression material with 54 superior physical properties especially with high viscosity materials. ”Citation is missing. Please cite.

 

“Various impression techniques have been proposed to improve the accuracy of VPS pressions. The putty-wash impression can be made using two principal techniques: putty-wash one step technique and putty-wash 2 step technique. Some studies sug- gested that the impressions accuracy does not depend on the impression technique, [41,42] while many other studies concluded that the impression technique is an im- portant factor that affects the impressions accuracy.” I would like to suggest the authors to improve these sentences describing the two techniques and then explain the current literature findings

Please revise the introduction section make it more fluent.

AIM should be rewritten making it more appealing.

Materials and Methods section is well written and understandable.

“Hang mixing led to twice as many metal frameworks misfit, compared to machine mix- 165 ing (31.1% vs.14.1%). The mechanical mixing allows better control of the amounts and 166 the proportions of the impression material used, facilitates polymerization reaction, re- 167 duces the number and the size of the bubbles incorporated in the impression material 168 and avert contamination. Moreover the mechanical mixing is preferred by the dental 169 staff due to accessibility of this method” These sentences need to be supported by current literature. 

Discussion should be revised and extended. (Too short)

Limitation of the study should be inserted at the end of the discussion section

Conclusion section must be entirely revised making it more appealing.

English spell revision is necessary.

 

Best Regards.

Comments for author File: Comments.pdf

Author Response

Authors need to revise the title it is un clear. - Done

 

Abstract: Abstract should be revised, rewritten and make it more fluent and appealing.- Done

 

Keywords: To ensure a properly research in medical databases, use MeSH terms to find  appealing keywords that could be helpful in finding your article.- Done

 

“The 46 working time of impression material can also be affected by the mixing technique. [26] 47 In general, the mixing techniques can be divided into two major categories: mechanical 48 mixing and hand mixing techniques.”  Please provide a proper description of the two techniques. What kind of devices could be used for the mechanical technique?

“In addition, 52 due to more uniform blending of the base with the catalyst, machine mixing enhances 53 the polymerization reaction and generates homogeneity of the impression material with 54 superior physical properties especially with high viscosity materials. ”Citation is missing. Please cite.

 

“Various impression techniques have been proposed to improve the accuracy of VPS pressions. The putty-wash impression can be made using two principal techniques: putty-wash one step technique and putty-wash 2 step technique. Some studies sug- gested that the impressions accuracy does not depend on the impression technique, [41,42] while many other studies concluded that the impression technique is an im- portant factor that affects the impressions accuracy.” I would like to suggest the authors to improve these sentences describing the two techniques and then explain the current literature findings

Please revise the introduction section make it more fluent. -Done

AIM should be rewritten making it more appealing.-Done

Materials and Methods section is well written and understandable.

“Hang mixing led to twice as many metal frameworks misfit, compared to machine mix- 165 ing (31.1% vs.14.1%). The mechanical mixing allows better control of the amounts and 166 the proportions of the impression material used, facilitates polymerization reaction, re- 167 duces the number and the size of the bubbles incorporated in the impression material 168 and avert contamination. Moreover the mechanical mixing is preferred by the dental 169 staff due to accessibility of this method” These sentences need to be supported by current literature. 

Discussion should be revised and extended. (Too short)

Limitation of the study should be inserted at the end of the discussion section

Conclusion section must be entirely revised making it more appealing.

English spell revision is necessary.-Done

 

Reviewer 3 Report

Dear authors,

I have appreciated the work and the present study is interesting. Although it is not an unprecedented study, it reveals that technology can help to obtain better results when well applied.By the way, my main concerns about the work are:

• Minor Comments - English usage and style need to be fixed
• Major Comments - I suggest the Authors to consider to include an reference if in the hand mixing technique gloves were used or not because the negative effect of latex on vinyl poly siloxane is known.
  
  

Best regards

Author Response

• Minor Comments - English usage and style need to be fixed - Done 
• Major Comments - I suggest the Authors to consider to include an reference if in the hand mixing technique gloves were used or not because the negative effect of latex on vinyl poly siloxane is known. - added to the text

Round 2

Reviewer 1 Report

the authors did not answer or abide to the recommendations and requriements raised in the previou review suc has reducing bulk citations! 14 references in one line...

Also the paper lacks any in depth analysis, literature review is minimal, it is better suited for a communication rather than a journal article. 

Also no figures in the materials and method section make it difficult to follow up how thes tests were carried out.

the reviewer advise against accepting this article for publication 

Reviewer 2 Report

Dear Authors, 

thank you for your reply

I will suggest the editor to accept the manuscript in current form

Best regards