Fatigue Loading Test on Screw-Retained Lithium Disilicate Crowns Adhesively Cemented on Titanium Abutment

Round 1

Reviewer 1 Report

Dear authors,

General comments

This manuscript was investigated to mechanical properties and microleakage between implant abutment made of titanium and superstructure made of lithium disilicate via dynamic loading test. Consequently, the failure of resin cement to bond to the superstructure on titanium implant abutment was mainly happened.

At first, reviewer strongly informed the authors that the form of scientific paper should be kept; for example, the Table, and how to describe chemical substances. As this journal “Crystals” is scientific journal, the authors should read the instruction of submission. At second, experimental design was far from reality. Also, there are some problem in this paper as follows. Please response and revise the contents.

Major points

• The reviewer could not know what the objective of this study is. If the authors would like to know the fatigue fracture load of crown made of lithium disilicate-glass ceramics on titanium implant abutment, the fatigue cyclic curve and Weibull distribution will be shown. If the authors would like to know the durability of bonding strength between the glass ceramic crown and the abutment, the retention force will be shown. If microleakage is happened to be coused to adaptation of crown to abutment, the reviewer could not know what the factor in this experiment was. Therefore, the objective could not reflect to experimental design.
• L127-130 The reviewer could not know that the load was applied at an angle of 30° from Figure 2. The authors should show the schema of cross-sectional appearance. Additionally, the reviewer appeared to have a straight bond between crown and abutment in Figure 3. Therefore, the load applied to the crown was directly transmitted to the abutment.
• In Figure 3, where did the authors see the stain on glass ceramics? That is, the authors are expecting glass-ceramics to stain? Generally, the glass-ceramics are believed not to discolor with dye penetration. The authors should show clearly show what is dyed.
• In Table 2, the thickness of cement was quite thickened. Normally, the thickness is considered to be acceptable up to 100 μm (less than 0.1 mm thick) clinically. The design of ceramic crown was wrong to experiment. Some literatures have reported the strength and thickness of cement, adaptation of crown, abutment materials in experiment, and the occlusion affected the fracture of crown. Therefore, the authors should be clearly described the problem and difference in Discussion. Otherwise, the readers and reviewer could not finoriginality of this article
• In conclusion, the authors wrote that the seal between the abutment and crown was important. However, the data corresponding to sealing could not find in this article. Also, there are many kinds of “ceramic restoration”. The authors should revise correctly.
• In References, the authors should be checked to journal name (abbreviation?), year, volume, pages.

Author Response

Dear reviewer,

Thank you for your valuable comments. We have complied with all recommendations. Please find attached our answers.

Author Response File: Author Response.pdf

Reviewer 2 Report

In lines 127-128  Authors wrote about choosen loading force on a level 50 N for incisors and 150 N for the premolar and molar teeth so my quwstion is why those forces and on what scientific sources the values were taken.

In Table 2 Authors wrote that if the remaining thickness between implant abutment and ceramic wall is less than 0,5 mm it can be considered the restoration has high risk of fracture. If so maybe there should be made some corrections on the CAD stage with modeling the restorations? Ale in lines 163-165 there was showed measures for numerical models, but do the Authors realized measures for phisical models, which was testes with masticatory simulation?

Author Response

Dear reviewer,

Thank you for your valuable comments. We have complied with all recommendations. Please find attached our answers.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors

The manuscript is largely revised. However, reviwer should requrie more revision as following one point. 

>Q. L127-130 The reviewer could not know that the load was applied at an angle of 30° from Figure 2. The authors should show the schema of cross-sectional appearance. Additionally, the reviewer appeared to have a straight bond between crown and abutment in Figure 3. Therefore, the load applied to the crown was directly transmitted to the abutment.
>A. All samples were subjected to dynamic loading in a computer-controlled dual-axis chewing simulator (Chewing Simulator CS-4; SD-Mechatronik, Westerham, Germany) Scheme and methodology are based on and presented in ISO 14801:2016(E). We have made that clarification in the manuscript.

The authors suggested to methology according to ISO 14801:2016. However, ISO 14801 shows the "Dynamic loading test for endosseous dental implants". including straight type and angle type. Essential mistake is that this ISO document is at test of implant body, not supersturcure and abutment.  Also, the Figures 2-4, the main points are connection between abutment and implant body. Therefore, the authors should show the schema of dyanamic loading test, and explain in detail.

Best 

Author Response

Dear reviewer 

Please find attached our answer

Author Response File: Author Response.pdf