Introduction

People's appearance plays a key role in their social interactions; subsequently, the color of teeth is the most important determinant of patient satisfaction [ 1]. Recently, dental procedures have undergone changes especially in Western societies, because dental caries have been decreased, the numbers of remaining teeth have been increased, and the patients' demand for cosmetic dentistry is increasing [ 2- 3]. The first report on tooth bleaching is cited in Zakaria Razi's Book of Al-Mansouri [ 4]. Feinman [ 5] developed the first bleaching method, using hot oxygenated water. Tooth bleaching in Iran started in 1335 at the School of Medicine and since then has been practiced by the Iranian dental schools [ 6].

Bleaching can be done with the use of carbamide peroxide, hydrogen peroxide, and sodium perborate with or without light activation. There are various techniques of vital bleaching, including bleaching in the office by high concentrations of bleaching materials with soft tissue protection or at-home bleaching by lower concentrations of bleaching materials [ 7- 9]. Some negative effects such as nausea, tooth sensitivity, and gingivitis have been reported with the procedure [ 10- 13].

Azodo and Ogbomo [ 14] and Mehl et al. [ 15] have reported that the arrangement and the size of teeth were important determinants of dental satisfaction for the Benin university students. Maghaireh et al. [ 16] found that 69.3% of patients were satisfied with the appearance of their teeth. However, Akarslan et al. [ 17] showed that among the patients referred to the dental School in Turkey, 55.1% were dissatisfied with tooth color and 42.7% with tooth appearance, while 29.9% of the patients were dissatisfied with tooth crowding and 23.3% of people concealed their teeth while smiling. Samorodnitzky-Naveh et al. [ 18] highlighted that the main factor in tooth beauty was tooth color, although 37.3% of the patients were not satisfied with the appearance of their teeth. According to Subait et al. [ 19] among 238 students in Saudi Arabia, 15% of the students were dissatisfied with tooth appearance, 62% with tooth color, 62% of them had tendency to bleaching and 32% wanted to have orthodontic treatment.

Increasing demand for tooth bleaching and lack of a similar study in Kerman provide a new investigation to assess the knowledge of the students about dental bleaching in Shahid Bahonar University of Kerman.

Materials and Method

This descriptive-analytical cross-sectional study was conducted on the students of electrical, civil, industrial, chemistry, mechanics, metallurgy, computer and mining engineering, at Shahid Bahonar University of Kerman.

Data collection tool was a questionnaire that consisted of demographic information (gender, age, field of study, brushing frequency, dental flossing, and dental visits), some questions about tooth color satisfaction, importance of teeth appearance, tendency to do bleaching, history of dental bleaching and satisfaction, source of information, and eight questions about the knowledge of dental bleaching. The reliability and validity coefficient of the questionnaire were 0.81 and 0.79, respectively, using ICC formula. Sample size was based on the below formula: n= (z^2*p(1-p)) /d^2, considering z= 1.96, d= 0.05 and p= 0.5, was calculated to be 400, but some questions had been missed by the respondents, thus final analysis was performed on only 384 questionnaires. After collecting the questionnaires, the data were coded and entered into SPSS statistical software version 21, using descriptive statistics tests (Mean, Standard deviation, frequency, and percentage of frequency). The independent t-test, chi-square and logistic regression test was performed at significant level 0.05.

The participants were assured that they would not be named in any part of the research and the project would be completely voluntary and with their consent.

 This proposal is registered under the IR.KMU.REC. (1397, 441) and was approved by Kerman University of Medical Sciences Ethics Committee.

Results

In this study, 59.55% of participants were male and 40.45% were female students (Table 1). In terms of oral hygiene behavior, 49.8% individuals brushed twice daily, 47% used dental floss and 35.3% had dental visits less than 6 months ago. In addition, 17.5% of the participants were reported to have smoking habit and 13, 5% were consuming hookah (Table 2).

Overall, 87% of people considered the appearance of teeth important and very important, whereas, 26.75% of the participants were dissatisfied and completely dissatisfied with the color of their teeth.

Only 44.33% of participants that had access to Internet presented more information on tooth bleaching and 14.09% gained their information by consulting their dentist. Moreover, 13.5% of the participants did bleaching and 69% (42.33% of females and 57.97% of males) tended to do it. The highest tendency (47.41%) for bleaching was in dental office and the least favorable method was the use of bleaching tapes (1.44%). The most correct answer was about the difference between bleaching and scaling and root planning (SRP) (52.1%).

By using univariate and multivariate analysis, 17.88% of female and 12% of male students have done bleaching treatment, which was not statistically significant (p< 0.111). The percentage of students who did bleaching was not different between married and single ones (p= 0.771), although female students heard more about dental bleaching (p< 0.001). There was no statistically significant difference in the number of participants performed bleaching in different fields. There was a significant difference, regarding the dissatisfaction of tooth color in the students with a tendency to do bleaching (76.21%) and those without a tendency to do bleaching (2.1%), (p<0.001). The mean score of knowledge and health behavior were higher in the students who heard about bleaching (p< 0.001, p< 0.001) and have done bleaching (p= 0.030, p< 0.012).

Statistically, there was a significant difference between the amount of hygienic behavior and gender. Female students had significantly better hygienic behavior (p= 0.007). There was no significant difference (p= 0.000) between other variables including gender, field of study, and marital status (Table 3).

Logistic regression test showed that among all the variables, the only variable that had significant statistical relationship with one's tendency to do bleaching was tooth color dissatisfaction, which has increased for 1.87 times.

Discussion

This survey and the study of Dozic et al. [ 20] showed that the desire to have an attractive smile and white teeth, have currently become an important need. In the current study, 87% of people considered the appearance of teeth important and very important. Only, 26.75% of the participants were dissatisfied and completely dissatisfied with the color of their teeth, which is less than 76.4 % reported by Nomay [ 21].

The satisfaction rates of teeth color were reported to be 66.3% by Maghaireh et al. [ 16], 36.6% by Lanjert et al. [ 22], 43.1% by Al-Zarea et al. [ 23], 42.8% by Yu et al. [ 24], 32% by Nomay [ 21], and 26.6% by Subait et al. [ 19]. Their reported results were lower than the results yielded by our study (87 %), even though the tooth color may be the primary cause of dissatisfaction with tooth appearance [ 17].

In the current study, there was no statistically significant relationship between variables including gender, field of study, and age with dental color satisfaction. According to Vallittu et al. [ 25], color satisfaction has been shown to be age-dependent. The results of the study by Akarslan et al. [ 17] indicated that people with higher degrees of education and higher self-esteem were more satisfied with the color of their teeth.  The reason for the lack of statistical correlation between color satisfaction with age and education in this investigation is probably related to the same range of age, education level and being young middle-aged.

In addition, 49.75% of the participants (Figure 1) were satisfied and quite satisfied with the appearance of their teeth. Various studies [ 31, 17, 26- 28 ] in different countries have reported different levels of satisfaction, including 42.2% in Malaysia [ 31 ], 57.3% in Turkey [ 17 ], 65 % in Palestine [ 26 ], 65.5 % in Jordan [ 27 ], and 76% in England (76%) [ 28 ]. Compared to our study, Yu et al. [ 24 ] showed, 53.6% of Chinese students were dissatisfied with the appearance of their teeth.

Figure 1. Frequency distribution of individuals according to tooth color and appearance satisfaction

According to our study, there was no statistically significant relationship between dental appearance satisfaction with educational field, age, and gender, but Strajnić et al. [ 29] found that with increasing education level, satisfaction with the appearance of teeth was also increased. As such, in our study, five completely satisfied to completely dissatisfied question options were used to measure the degree of tooth color satisfaction. This investigation shows that 13.5% of participants had done bleaching, while Hatherell et al. [ 30] revealed that 28.44% of the students had done bleaching, which was more than our study. This study also indicates that 69% of participants tended to do bleaching similar to that of Hatherell et al. [ 30], whereas 66.37% of students in the United Kingdom wanted to do tooth bleaching (Table 3). The tendency to do bleaching in the Al-Zarea study [ 23] was, 80.9%, Akarslan et al. [ 17], 49% Tin-O-o et al. [ 31], 55.3%, Nomay [ 21], 77% and Subait 80% [ 19].

In the study of Maghaireh et al. [ 16], the most tendency for improving the appearance of teeth was tooth bleaching and it also was the most favorable treatment in Riyadh, London and Malaysia [ 19, 31- 32].

In our study, female students were more likely to do bleaching, although the difference was not statistically significant. This can be attributed to the studied population and methods of assessing the tooth color satisfaction. In addition, 58.25% of students had heard about bleaching, but female students had significantly more hearing.

The main source of information in 44.33% of participants was Internet and the next levels were dentists, friends, and acquaintances (Figure 2), which is somehow higher than the results (35.8 %) reported by Azodo et al. [ 14 ] in Nigeria. The reason for this difference may be due to greater access to the Internet in the current study.

Figure 2. Frequency distribution of individuals according to source of information

Additionally, the most tendency was to do bleaching in the office (47.41%), thus dentists appear to be aware of the success rate of treatment and its limitations before any bleaching procedure.

The second method of bleaching was using bleach toothpaste (25.29%), although Wash et al. [ 33] and Joiner et al. [ 34] have shown that tooth discoloration may occur after regular use of toothpaste containing bleach material. Among our participants, only 1.4% of people tended to use bleach tape for bleaching.

Data analysis indicated that there was no significant difference between the age of the subjects and their knowledge of bleaching. This contrasts the results of Al-Nomay et al. [ 21] who studied different age groups, whereas our results were rather based on the similar age groups.

There was no significant difference between participants' knowledge of dental bleaching in terms of gender and field of study. These results are not in line with Al-Nomay et al. study [ 21] that showed women were significantly more aware of the subject.

This study showed that 52.1% of students knew the difference between bleaching and SRP, even though our research had "no idea" option too (Table 4).

In addition, 25.9% of the students answered yes to the question of side effects of bleaching, which is less than 46 % reported by Diklić et al. [ 35]. Regression analysis showed that the tooth color satisfaction increased the odds of tendency for doing bleaching to 1.87 times. This may be due to the age range of the participants, the uniformity of their education, and appropriate health behavior. However, tooth color dissatisfaction can influence people's decision to do bleaching.

Despite the results of this study, the most confounding factors which affect the tendency to do bleaching, include the treatment cost, the long multiple visits for in-office bleaching, and tooth sensitivity with nausea after each visit of tooth bleaching. In addition, the participants of our study were at the same age range and education, which could be effective on our results. Therefore, further investigations are needed concerning the knowledge and tendency of the public population to do dental bleaching.

Conclusion

The present investigation highlights that 35.5% of the subjects were satisfied with the color, 49.75% with the appearance of the teeth. Moreover, 69% had a tendency to do bleaching and the knowledge level about bleaching and its alternative treatments was moderate.

References

1. Mon T, Norkhafizah S, Nurhidayati H. Factor influencing patient satisfaction with dental appearance and treatments they desire to improve aesthetics. BMC Oral Health. 2011; 11:6.
2. Hathere S, Lynch CD, Burke FM, Ericson D, Gilmour AS. Attitudes of final-year dental students to bleaching of vital and non-vital teeth in Cardiff, Cork, and Malmö. J Oral Rehabil. 2011; 38:263-269.
3. Terry DA, Geller W. Esthetic and restorative dentistry: material selection and technique. Milan: Quintessence Publishing Co Inc; 2012.
4. Abu Bakr Muhammad Ibn Zakariya Al-Razi. The Book of Medicine Dedicated to Mansur. Publication of the Center for Ethics and Medical History of Tehran University of Medical Sciences: Research and proposition by Hazem Bakri Sedighi and translation by Majid Ebrahim Zaker; 2008.
5. Feinman RA. Reviewing vital bleaching and chemical alterations. J Am Dent Assoc. 1991; 122:55-56.
6. Karbasi Kheir M. Overview of dental history in Iran. Med Hist J. 2014; 4:137-154.
7. Haywood VB, Heymann HO. Nightguard vital bleaching. Quintessence International. 1991; 22:515-523.
8. Paliska J, Stipetić A, Tarle Z, Ristić M, Ban T, Vujičić N, et al. Colorimetric Assessment of Different Tooth Whitening Procedures. Acta Stomatol Croat. 2011; 45:258-267.
9. Sulieman M, MacDonald E, Rees JS, Newcombe RG, Addy M. Tooth bleaching by different concentrations of carbamide peroxide and hydrogen peroxide whitening strips: an in vitro study. J Esthet Restor Dent. 2006; 18:93-100.
10. Kwon SR, Ko SH, Greenwall LH, Goldstein RE, Haywood VB. Tooth whitening in esthetic dentistry: Principles and techniques. London: Quintessence Publishing Co; 2009.
11. Klarić E, Par M, Profeta I, Matošević D, Tarle Z. Postoperative sensitivity after two in-office bleaching methods. Acta Stomatol Croat. 2011; 45:100-109.
12. Li Y, Greenwall L. Safety issues of tooth whitening using peroxidebased materials. Br Dent J. 2013; 215:29-34.
13. Klarić E, Marcius M, Ristić M, Sever I, Prskalo K, Tarle Z. Surface changes of enamel and dentin after two different bleaching procedures. Acta Clin Croat. 2013; 52:419-429.
14. Azodo CC, Ogbomo AC. Self-evaluated dental appearance satisfaction among young adults. Ann Med Health Sci Res. 2014; 4:603-607.
15. Mehl C, Wolfart S, Vollrath O, Wenz HJ, Kern M. Perception of dental esthetics in different cultures. Int J Prosthodont. 2014; 27:523-529.
16. Maghaireh GA, Alzraikat H, Taha NA. Satisfaction with dental appearance and attitude toward improving dental esthetics among patients attending a dental teaching center. J Contemp Dent Pract. 2016; 17:16-21.
17. Akarslan Z, Sadik B, Erten H, Karabulut E. Dental esthetic satisfaction, received and desired dental treatments for improvement of esthetics. Indian Journal of Dental Research. 2009; 20:195-200.
18. Samorodnitzky-Naveh GR, Geiger SB, Levin L. Patients satisfaction with dental esthetics. J Am Dent Assoc. 2007; 138:805-808.
19. Subait AA, Ali A, Hammad ZA, Alrumaih A, Al-Malki M, Al-faqih A, et al. Dental Aesthetics and Attitudes among University Students in Saudi Arabia, A Cross-sectional study. J Dent and Oral Disord. 2016; 2:1022.
20. Dozić A, Zukanović A, Bajsman A, Sečić S, Petaros A. Spectrophotometric Evaluation of Color Alterations of Teeth Exposed to Different Conditions in Time. Acta Stomatol Croat. 2011; 45:247-257.
21. Nomay N. Public attitude and awareness towards their teeth color and dental bleaching in Saudi Arabia: A cross-sectional survey. Journal of Public Health and Epidemiology. 2016; 8:45-52.
22. Lajnert V, Kovačević Pavičić D, Pezo H, Stevanović A, Jović T, Šnjarić D, et al. Patients’ general satisfaction with the appearance of anterior maxillary teeth. Vojnosanit Pregl. 2017; 74:520-525.
23. Al-Zarea BK. Satisfaction with appearance and the desired treatment to improve aesthetics. Int J Dent. 2013; 2013:912368.
24. Yu H, Cheng SL, Zhou JY, Cheng H. A survey on general knowledge and influencing factors of dental aesthetics among three universities students in Fuzhou city. Shanghai Kou Qiang Yi Xue. 2017; 26:510-515.
25. Vallittu PK, Vallittu AS, Lassila VP. Dental aesthetics: A survey of attitudes in different groups of patients. J Dent. 1996; 24:335-338.
26. Younis A, Al-Omiri MK, Hantash RO, Alrabab’Ah M, Dar-Odeh N, Abu HO, et al. Relationship between dental impacts on daily living, satisfaction with the dentition and personality profiles among a Palestinian population. Odontostomatol Trop. 2012; 35:21-30.
27. Karasneh J, Al-Omiri MK, Al-Hamad KQ, Al Quran FA. Relationship between patient′s oral health-related quality of life, satisfaction with dentition, and personality profiles. J Contemp Dent Pract. 2009; 10:E049-E056.
28. Alkhatib MN, Holt R, Bedi R. Age and perception of dental appearance and tooth colour. Gerodontology. 2005; 22:32-36.
29. Strajnić L, Bulatović D, Stančić I, Živković R. Self-perception and satisfaction with dental appearance and aesthetics with respect to patients’ age, gender, and level of education. Srp Arh Celok Lek. 2016; 144:580-589.
30. Hatherell S, Lynch CD, Burke FM, Ericson D, Gilmour AS. Attitudes of final-year dental students to bleaching of vital and non-vital teeth in Cardiff, Cork, and Malmö. J Oral Rehabil. 2011; 38:263-269.
31. Tin-Oo MM, Saddki N, Hassan N. Factors influencing patient satisfaction with dental appearance and treatments they desire to improve aesthetics. BMC Oral Health. 2011; 11:6.
32. Al-Shiekh L, Muhammed MED, Muhammed AER, El-Huda MA, Hashim NT. Evaluation of dental students’ oral hygiene attitude and behavior using HU-DBI in Sudan. Science Postprint. 2015; 1:1-4.
33. Wash TF, Rawlinson A, Wildgoose D, Marlow I, Haywood J, Ward JM. Clinical evaluation of the stain removing ability of a whitening dentifrice and stain controlling system. J Dent. 2005; 33:413-418.
34. Joiner A, Philpotts CJ, Alonso C, Ashcroft AT, Sygrove NJ. A novel optical approach to achieving tooth whitening. J Dent. 2008; 36 Suppl 1:s8-s14.
35. Diklić D, Klarić Sever E, Galić N, Spajić J, Prskalo K. Attitudes of Students of Different Schools of University of Zagreb on Tooth Bleaching. Acta stomatol Croat. 2016; 50:301-309.