The American Dental Association has encouraged dentists to update their knowledge about nutritional recommendations related to oral health [16]. However, this topic has been largely ignored by most dental clinicians [17]. This study assessed the knowledge, attitude, and practice of dentists and senior dental students in Yazd city, Iran regarding nutrition counseling. The mean knowledge score was 7.12 ± 1.75 for dentists and 6.48 ± 1.2 for dental students out of 9. The mean knowledge score of both groups was acceptable, which was in agreement with the results of Vaidya et al, [16] who assessed the knowledge level of nutrition science students, but was different from the findings of Dolatkhah et al, [18] who assessed the knowledge level of medical students and Bapat et al, [7] who assessed the knowledge level of nutrition science students. Also, Abdullah et al. [19] discussed that dental students only had knowledge about the basics of nutrition in dentistry and there is still need for further instruction of nutritional topics in dental curricula.
In the present study, the mean knowledge score of participants had no significant correlation with their gender, which was in agreement with previous studies [1, 2, 7, 18, 20]. Also, the mean knowledge score of participants in the present study had no significant correlation with age which was in agreement with the results of Alamri et al, [20] and Dolatkhah et al [18].
In the current study, the mean knowledge score of dentists was significantly higher than that of dental students (P = 0.03). Similar results were reported by Abdullah et al, [19] who reported higher knowledge score of senior compared with freshman dental students, and Chalmuri et al, [2] and Vaidya et al, [16] who reported higher knowledge score of graduates compared with dental students, Bapat et al, [7] who reported higher knowledge score of third-year dental students of nutrition compared with freshman students, and Dolatkhah et al, [18] who reported higher knowledge score of externs than interns.
The mean knowledge score of dentists had no significant correlation with their work experience, which has not been evaluated in any other study to compare our results with, and assessment of this parameter was a strength of this study.
In the present study, 62.2% of dentists and 55% of students believed that anti-oxidants can effectively decrease inflammation in periodontitis, which is correct, since antioxidants have anti-inflammatory properties and can decrease inflammation in periodontitis [21, 22]. They can prevent and enhance the treatment of periodontitis as well [23]. Also, calcium supplementation can positively affect the management of periodontal disease [24]. Moreover, optimal calcium content can decelerate tooth loss and alveolar ridge resorption [25, 26]. In the present study, 45.9% of dentists and 37.5% of dental students were aware of the correlation of low calcium intake and higher severity of periodontal disease.
Obesity can cause xerostomia, caries, and periodontitis [8]. Several cross-sectional studies reported an association between obesity and periodontitis [27, 28]. Also, increased BMI and lipid percentage are associated with higher risk of periodontitis [29]. In the present study, 75.5% of dentists and 65% of students were aware of the association of obesity and increased risk of periodontal disease, and 62.2% of dentists and 50% of dental students believed that obesity was associated with higher risk of caries. Evidence shows that periodontitis can lead to hypertension [30–33], and treatment of periodontitis decreases the systolic and diastolic blood pressures by 12 and 10 mmHg, respectively [34]. Also, 73.5% of dentists and 62.5% of dental students in the present study reported hypertension as a side effect of periodontal disease.
In the current study, 69.4% of dentists and 37.5% of dental students believed that consumption of sugary substances alone had higher cariogenic effect than their consumption with meals; however, only 1.7% of nutrition science students in the study by Bapat et al. [7] agreed with this statement. In the present study, 77.6% of dentists and 76.5% of dental students believed that fruit juices were more cariogenic than whole fruits, and 70.4% of dentists and 55% of dental students thought that drinks with natural or added sugars were more cariogenic than sweet solid foods. In a study by Shah et al, [35] 73% of dental students linked the consumption of fruit juices to caries, while 1.7% of students in the study by Bapat et al. [7] agreed with this statement. In the present study, 93.9% of dentists and 92.5% of dental studies correctly believed that frequency of consumption of sugary foods was more important than total amount of consumption in caries development. However, in the study by Bapat et al, [7] 91.6% of students did not agree with this statement. This difference may be due to the fact that dentists and dental students pay more attention to nutritional topics related to oral health compared with nutrition science students.
Regarding the advantages of nutrition counseling, 68.4% of dentists and 62.5% of students believed that nutrition counseling reveals the nutritional patterns that compromise the masticatory system and oral health, and 41.8% of dentists and 30% of students believed that it can help estimate the success of treatment. In a study by Ritchie et al, [28] participants believed that nutrition counseling can help predict the treatment prognosis and success of treatment.
In the present study, 79.6% of dentists and 72.5% of dental students agreed with the statement that nutrition counseling should be included in dental preventive programs. In a study by Hseiki et al, [36] 94.8% of primary care physicians believed that proper nutrition and diet is important in prevention of many disease conditions. In the study by Abdullah et al, [19] 86.3% of dental students pointed to the significance of nutrition counseling, and in a study by Rajesh Nidhi and Ramakrishnan [1] 92.8% of dental students believed that nutrition counseling is an inseparable part of routine dental procedures. In the study by Alamri et al, [20] 91.4% of dental students declared that nutrition is a key element in oral health, and 75.5% agreed that nutrition counseling is imperative in dentistry. In the study by Sivakumar et al, [17] 75% of dental students agreed that nutrition is a critical part of healthcare, and in the study by Dolatkhah et al, [18] 73.5% of medical students stated that nutrition counseling should be included in routine care of patients. In a study by Morge et al, [37] 71.7% of medical students agreed that nutrition counseling should be part of routine care. Despite the presence of positive attitude towards this topic, assessment of practice in the present study revealed that 61.2% of dentists and 35% of dental students believed that time consuming nature of nutrition counseling, and 46.9% of dentists and 57.5% of dental students stated that not having adequate information in this regard were the main obstacles against provision of nutrition counseling to their patients. Also, time consuming nature of counseling was reported as the main obstacle by 36.3% of dental hygienists in a study by Cole et al, [38] 36.3% of dental students in the study by Sivakumar et al, [17] and 62.4% of primary care physicians in the study by Hseiki et al [36]. Regarding children, Sim et al. [39] reported that the main obstacle against nutrition counseling to parents about their children was lack of interest of parents, while Wright and Casamassimo [40] reported that the main concern was the reaction of parents. However, only 13.3% of dentists and 12.5% of students were worried about the reaction of patients in the present study.
Lack of self-confidence to provide nutrition counseling was reported by 9.2% of dentists in the present study and 17.5% of students, while this rate was 35.1% in dental students in the study by Shah et al [35].
In this study, 39.8% of dentists and 52.5% of dental students reported referral of patients to a nutritionist in case they could not provide nutrition counseling to them. This rate was 39.1% in the study by Sivakumar et al, [17] 53.7% in the study by Hseili et al, [36] and 20% in the study by Rajesh Nidhi and Ramakrishnan [1]. Of all, 51% of dentists and 62.5% of students in the present study complained that they did not receive adequate information regarding nutrition in their education. This rate was 49.6% in the study by Hseili et al, [36] 25.7% in the study Abdullah et al, [19] 42% in the study by Sivakuamr et al, [17] and 64.9% in the study by Shah et al [35]. Such a wide range of variation can be due to different educational curricula. In the present study, 37.8% of dentists and 50% of students claimed that they acquired their current information through miscellaneous non-academic studies, which points to the insufficient quality of education in this regard. This rate was 18% in the study by Cole et al [38]. Other studies did not address this topic [1, 2, 7, 16, 18–20, 35]. In the current study, 7.1% of dentists and 0% of dental students reported recording of weight and BMI of patients. This rate was 61.2% in the study by Hseiki et al, [36] 72.6% in the study by Morge et al, [37] and 20% in the study by Bell et al [41]. Such a wide range of variation can be due to the fact that Hseilki et al, [36] and Morge et al. [37] evaluated primary care physicians and medical graduates.
Of all, 86.7% of dentists evaluated in the current study reported no participation in continuing education courses regarding nutrition. This rate was 72.9% in the study by Alamri et al, [20] 90.5% in the study by Dolatkhah et al, [18] and 72.9% in the study by Rajesh Nidhi and Ramakrishnan [1] which were close to the value in the present study.
Also, only 27.6% of dentists and 22.5% of dental students reported prescription of supplements for patients. This rate was 50.7% in the study by Alamri et al, [20] and 42.3% in the study by Sivakuamr et al, [17] that were higher than the value in the present study, which may be due to their stronger belief in efficacy of supplements in oral health promotion.
The optimal efficacy of probiotics for reduction of caries, periodontal health, and reduction of mouth malodor has been well documented [42–44]. Nonetheless, 60.2% of dentists and 62.5% of dental students declared that they did not recommend consumption of probiotics to their patients. Also, 58.2% of dentists and 42.5% of dental students did not advise their overweight and obese patients to lose weight.
In the present study, 61.2% of dentists and 62.5% of dental students instructed the patients regarding postoperative diet, and 57.1% of dentists and 75% of students reported that they would inform patients seeking tooth extraction about its adverse health consequences.
Periodontal disease has been linked to inadequate intake of calcium and vitamin D [45–47]. Also, low level of vitamin D is correlated with recurrent aphthous ulcers [48]. However, 71.4% of dentists and 57.5% of dental students reported that they would not recommend measurement of vitamin D serum level in patients with periodontal disease and bone loss. Also, 78.6% of dentists and 85.5% of dental students did not recommend vitamin D supplementation to patients with aphthous ulcers and progressive bone loss. Moreover, 82.7% of dentists and 87.5% of dental students had never received nutrition counseling to possibly improve their attitude in this respect. Also, a higher percentage of dentists with shorter work experience reported referral of patients to a nutritionist, reported their academic courses as one important source of their information about nutrition, and prescribed probiotics for their patients, which may be due to their knowledge retention.
This study was conducted in Yazd city. Thus, the results cannot be generalized to the entire population of dentists and dental students nationwide. Future studies on dentists and dental students in other cities are required.
Implications for Research and Practice
Retraining courses or practical workshops can be planned to improve the performance of dentists and dental students in the field of nutritional counseling.