Use of addictive substances is among the most challenging and complex health problems leading to a wide range of cardiovascular, mental and psychological, metabolic, endocrine, and infectious disorders (1). Addiction to new drugs and industrial substances not only gives rise to many social and economic problems, but also causes damage to oral health (2). Opioids, as the most commonly used drug in Iran, include opium, syrup, heroin, and codeine used orally, by inhalation, or by injection. Other substances used in Iran include cannabis (from the cannabis group), stimulants such as methylphenidate (under the brand name of Ritalin from the amphetamine group), ecstasy (from the amphetamine group), as well as cocaine and LSD (from the hallucinogenic group) (2). The use of narcotics or stimulants causes dry mouth or xerostomia, which in turn reduces the saliva pH and increases the formation of plaque and dental plaque. All these factors increase the incidence of tooth decay and periodontal disease (1). Moreover, narcotic and stimulant addiction can increase the tendency to intake simple sugars, which is an effective factor in causing caries and bruxism and increasing tooth sensitivity and necrotic gingivitis (3). Given that narcotic or stimulant addiction reduces motivation and self-confidence, addicts and those treated with methadone have lower rates of oral hygiene than non-addicts (4). Mental problems such as depression caused by drug addiction can eventually lead to neglect oral care and follow-up of dental treatment except in emergencies (5, 6).

Health-related quality of life is specifically associated with quality of life in relation to health and disease, which is a multidimensional concept. Oral health quality of life is one of these dimensions since oral diseases have been proven to affect the quality of life (1). Oral health-related quality of life is defined as an individual's personal assessment of the effects of functional, physical, and social factors as well as experience of oral pain and discomfort on different aspects of their life (7). Given the role that oral conditions play in people's social relations, appearance, self-confidence, as well as speaking, chewing, tasting, and swallowing processes, they affect one's pleasure experienced from life. Therefore, the status of oral health-related quality of life affects people's lives in both physical and mental dimensions (8).

The seriousness and importance of dental problems in treating substance abusers necessitate establishment of an accessible dental care program. For example, the toothache interfering with the process of addiction treatment may cause relapse in addicts. In addition, poor appearance and improper functioning of the dental problems can cause isolation and non-compliance with the treatment and care process (9).

So far, few studies were conducted on oral health and its related quality of life among the addicts worldwide (10–12) and in Iranian cities of Yazd, Mashhad, Isfahan, and Tehran (13–19). Some of these studies concluded that drug abuse increased DMFT and Plaque Control Record indices (14). As they noted, stimulants and morphine were the most commonly used drug among women and men, respectively (16). Furthermore, the oral and dental treatment needs of the addicted population are wide and should be followed up (14, 15). Akbari et al. (13) also reported an urgent need to plan dental treatments in the population of addicts at the time of withdrawal. In this regard and since no research has ever investigated oral health status related to narcotic and stimulant abuse in Ahvaz City, the present study was conducted. The aim was to determine the quality of life related to oral health of narcotic and stimulant addicts who referred to maintenance methadone therapy (MMT) centers in Ahvaz City in 2020.

The mean age of addicts who referred to addiction treatment centers in Ahvaz was 36.03 ± 8.98 years and 97 addicts (52%) were under 36 years old. In terms of using toothbrush, 128 addicts (68%) rarely brushed their teeth, 127 (67.9%) did not have any dental visits for more than 3 years, and 86 addicts (46.1%) had more than five teeth lost. Table 1 represents other demographic characteristics of the participants along with the relationship of these characteristics with the mean quality of life related to oral health.

Table 1 shows that the mean scores of qualities of life related to oral health were not significantly different between levels of study factors such as age, educational level, employment status, background disease, economic status, dental visit, use of toothbrush or number of lost teeth (P < 0.05).

The mean scores of qualities of life related to oral health and its dimensions were also determined based on the type of substance used; i.e., narcotics or stimulants (Table 2).

The results obtained from Table 2 show a statistically significant difference between the quality of life related to oral health based on the type of substance used (narcotic or stimulant drugs) (P < 0.05). In other words, the mean quality of life related to oral health was higher in narcotic addicts than stimulant users. Moreover, a significant difference was found between narcotic and stimulant users with regard to the scores of mental distresses (P = 0.001), mental disability (P = 0.001), and physical disability (P = 0.019) dimensions.

Later, intensity of the relationship was examined between the dimensions of oral health-related quality of life and the overall score of OHIP-14 in terms of the substance type. Figures 1–3 illustrate the theoretical model obtained.

The present study aimed at evaluating the quality of life related to oral health in patients who referred to MMT centers. The findings showed that the quality of life associated with oral health was significantly lower in people who use stimulants than narcotics. Although this rate of discrepancy was not severe, a significant difference was observed between scores of the two groups of drug abusers in the areas of mental disability, mental distress, and physical disability. More specifically, the effect of oral problems caused by using stimulants was higher on dimensions of quality of life, such as distraction, stress, peace disturbance, confusion in group, life dissatisfaction, and inability to perform activities. In other words, stimulants affect mental health and quality of life related to oral health negatively. Consistent with these findings, Nazemi et al. (22) reported that different dimensions of mental health (anxiety and social dysfunction) were significantly associated with the OHIP-14 index. Our findings on Figure 1 also corroborate this point. According to Figure 2, in addicts who use narcotics, physical disability was most associated with quality of life related to health. These results confirm the findings reported in the literature indicating that the type of substances applied affect the status of oral health indicators (23). This finding can be justified by mentioning that the most common oral lesions caused by using stimulants include dry mouth (16, 24, 25), spongy gingiva, and erythematosus with margin (16) that plays the most important role in the decline of their oral health (16). Islami et al. showed that the means of ruxism, rampant carries, xerostomia, attrition, and DMFT were higher in people with a history of using amphetamines stimulants (25). In contrast, missing teeth and caries had a significant relationship with drug abuse (26).

Generalized pigmentation was observed only in methamphetamine users. According to the literature, the duration of drug withdrawal was significantly associated with the incidence of oral lesions, so that less pigmented lesions were observed in addicts who have quit their addiction even for 1 month. In other words, increased duration of withdrawal improved the pink color, firmness, and stippled knife edge margin of the gum (16). Eslami et al. (25) conducted a study in Tabriz noting that abuse of stimulants (amphetamines and methamphetamines) was higher than narcotics (opium syrup) in women. This pattern change can explain higher incidence of oral health-related psychological problems followed by using stimulants. In this regard, many other factors may be influential, including the effect of addiction treatment methods, such as methadone therapy and withdrawal duration (16). A study was investigated amphetamine-dependent people and found that they intook more sugary foods, crumbs (instead of main meals), and drank cranberry drinks compared with the healthy individuals. Drug addicts believed that substance use reduced their appetite and increased their cravings for sugar (27). In the present study, only one fourth of those who referred to the substance abuse centers had been visited by dental professionals during the past year and a significant percentage of participants reported lack of a history of visits to dentists over the last 3 years. In Boston, about half of men and women who were addicted to drugs had more than a year since their last dental visit or were unable to recall the time of their last visit (28). According to the results of other studies, it seems that referring to dentists to receive educational and medical services is low among drug addicts around the world.

By comparing the results of this study with those reported in the literature, it can be claimed that the type of substance used by addicts is probably a more decisive factor than other personal variables in terms of the quality of life related to oral health. This finding can be justified by mentioning that quality of life related to oral health showed no significant difference not only among different levels of age, education, employment, economic status, marriage, and chronic illness, but also in other underlying factors such as a history of dental visits or the use of toothbrushes. Such discrepancy in the findings may be attributed to the sample size or the participants' characteristics since they were selected among patients who referred to MMT centers through available sampling method. Therefore, findings of the study are not generalizable to the population. In the studies by Shekarchizadeh et al. (8), Mahnaz Heydari (29), Ahmadi et al. (17), Esfahanizadeh (28), and Darvishpour Kakhki et al. (30) a significant relationship was found between the quality of health-related life and factors such as education, age, gender, and teeth condition (8, 29–31). This finding is in contrary to the findings of the present study. Given that the participants of the above-mentioned studies included women, retired, or elderlies of different cities, differences in the results can be attributed to diversity in their nutritional, environmental, cultural, or genetic factors. However, results of the studies by Akbari (13), Khabazian (32), Gholami (31), and Khatmi Nasab (33) are consistent with our findings in reporting that age and education had no relationship with quality of life related to oral health (13, 31–34). In this study, the total score of the oral health-related quality of life was 34.89 ± 6.50. Considering that these mean scores were received from the addicts who referred to addiction treatment centers, our findings cannot be representative of all addicts in Ahvaz. Moreover, substance use rates are naturally higher among the large population of addicts who are homeless and sleep on the street. As a result, future researchers are recommended to investigate addicts who are not in medical centers to provide a more comprehensive viewpoint in this area.

Based on the findings, the quality of life index related to oral health is more unfavorable in stimulant users than narcotic users. Therefore, authorities are recommended to focus their interventions and research programs to improve health-related quality of life in addicts, especially stimulant users.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

The studies involving human participants were reviewed and approved by Ahvaz Jundishapur University of Medical Sciences of Ethics Committee. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements.

MC was principal investigators of the study. MC and HM were advisors of the study and performed the statistical analysis. FS was collected the data and drafted the manuscript. All authors contributed to the design, data analysis, assisted in the preparation of the final version of the manuscript, read, and approved the final version of the manuscript.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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