Effect of external bleaching on color change of single shade resin composite versus nano fill resin composite in class v an in vitro study / submitted by Akram Gamal Mousa Diab, B.D.S. Future University (2017)

Supervisors, Prof. Dr. Essam Abdel Hafez Naguib, Professor and Head of Conservative Dentistry Department, Faculty of Oral and Dental Medicine, Future University in Egypt, Professor of Operative Dentistry, Faculty of Dentistry, Cairo University, Prof. Dr. Ahmed Zoheir El-Hoshy, Professor of Conservative Dentistry, Faculty of Dentistry, Cairo University, Dr. Ahmed Mohamed Fouad Khaled, Lecturer of Conservative Dentistry, Faculty of Oral and Dental Medicine, Future University in Egypt

Thesis (M.Sc.)-Future University, Faculty of Oral and Dental Medicine, Department of Conservative Dentistry, 2022.

Includes bibliographical references.

This study was carried out to investigate the effect of external bleaching on color change of single shade resin composite versus nano filled resin composite in class V.
A total of 20 caries-free human premolars of shade A3 were used for the study. Standardized class V cavities were prepared on the cervical third of the buccal surface of all teeth. After that, teeth were randomly divided into two groups 10 teeth each according to the type of resin composite used either single shade resin composite (Omnichroma) or nano filled resin composite (Z350 XT).
Cavities were restored with the resin composite assigned to their group, then all teeth were stored individually in tightly sealed plastic containers wrapped with black tape containing distilled water for 24 hours. Pre-bleaching assessment of the restoration color and the shade match between the tooth and restoration were done using VITA Easyshade.
Teeth were bleached and stored again for another 24 hours. Post-bleaching assessment of the restoration color and the shade match between the tooth and restoration were evaluated at 24 hours, one week and one month after bleaching.
The results of this current study showed that the effect of different storage time periods on the color change of Omnichroma was statistically significant between one month and 24 hours groups and between one month and one week groups. Further, the 24 hours and one week storage groups showed no statistically significant difference. Regarding the Z350 XT nanofilled composite, no statistically significant difference were found between all groups.
Considering the effect of different restorative materials on color change, there was no statistically significant difference between the two restorative materials at 24 hours and after one week. While there was a statistically significant difference between the two restorative materials after one month.
There was shade matching between tooth and restoration for Omnichroma before and after bleaching and throughout storage (no statistically significant difference between tooth shade and restoration shade). While for Z350 XT there was shade matching at baseline before bleaching while there was mismatch after 24 hours, one week and one month storage periods post-bleaching (statistically significant difference between tooth shade and restoration shade).
Under the limitations of the current study the following conclusions could be made:
1- Omnichroma single shade universal restorative material demonstrates structural color matching with the surrounding tooth structure both pre and post-bleaching procedures.
2- Storage time in distilled water up to one month post-bleaching had no detrimental effect on the dynamic color matching properties of Omnichroma single shade universal restorative material.
3- Nanofilled composite Z350 XT has a lower ability to continuously match the shade of the surrounding tooth structure after bleaching
Recommendations:
1- Omnichroma single shade resin composite maybe recommended for use in class V anterior restorations, especially in patients who might require bleaching procedures after restoration.
2- Further clinical studies are needed to assess the long term effects of the oral environment on Omnichroma single shade resin composite, regarding shade matching and color stability.

Text in English, abstracts in English and Arabic.