Background

Oral health is a fundamental component of general health and wellbeing. Among various oral diseases, dental caries continues to affect a large number of populations around the globe even though tremendous attempts to raise awareness have been made but still the trend is on the higher side. Dental caries is recognized as a disease of ancient times. It may affect anyone, irrespective of ethnicity, age, gender, or socioeconomic status. Management of dental caries nowadays largely depends upon its risk assessment hence it is very important to map out its prevalence in any given population [1,2,3,4]. According to the World Health Organization (WHO), dental caries remains a major problem for almost every country in the world. There are many definitions of dental caries [5]. However, it is largely accepted as a multifactorial disease initiated by interactions between fermentable carbohydrates, acidogenic bacteria, and numerous host factors, comprising saliva [6, 7]. The principal cause of caries is the acid development of dietary carbohydrates that are fermented by bacteria in saliva and plaque. Possible cariogenic bacteria are usually found in relatively small amounts in healthy saliva and plaque. However, there will be a proliferation of acid-tolerant bacteria in some biological and environmental disorders, such as increased frequency of fermentable carbohydrate consumption, low pH conditions [8, 9].

Dental caries is a well-known burden on health. Untreated carious lesions can be painful and may lead to functional limitation, as well as disability [10, 11]. While dental caries is mostly preventable, the occurrence of dental caries amongst adults is high, affecting almost 35% of the world's population, making it the most predominant health condition around the world [12]. Dental caries, along with periodontal diseases are a well-known cause of tooth loss, and in some cases even edentulism causing major functional limitation, and impairment [13,14,15]. As a result, dental caries has long been a worldwide burden on oral health [5]. Not only does it affect oral health, it too harms the quality of life and overall health, particularly in low-income countries [16]. According to the WHO, 60–90% of children are affected by dental caries [17]. Dental caries affects all age groups, although children are affected to a greater extent than adults. To solve this dilemma, part of the solution is to accurately estimate the current burden in a given geographical location and prepare for robust dental education/health promotion programs. Data on the prevalence of caries is maintained in the WHO Country Area Profile Program database. There are, however, a few limitations: data for all age groups and all WHO countries are not available; and if data is available it is not regularly updated.

The extent of disease distribution offers a unique context for planning strategies and designing public health policies. A systematic review and meta-analysis are one of the most vital research methods for obtaining an accurate estimation of disease indicators in a society. In this study, a meta-analysis was planned to deliver evidence-based information based on which suitable health care strategies can be established to get a whole representation of the situation of dental caries amongst the Pakistani population.

Based on our knowledge, we did not find any national/regional level studies or any meta-analyses to report the prevalence of dental caries in Pakistan's general population. Therefore, this systematic review and meta-analysis were conducted to estimate the proportion of dental caries in the Pakistani population by using data from already published studies.

Methods

Search strategy

Literature in the English language was searched from January 1970 to June 2020 primarily from PubMed, Scopus, and Web of science using the following MESH Keywords: "Prevalence", "Dental Caries", "Dental Decay" and "Severity". Additional studies were sought from gray literature google scholar, and researchgate. Besides, we also explored the reference lists of identified articles to find further relevant studies. Literature was searched using various search strategies such as prevalence, severity, dental caries, and/or prevalence, severity, dental decay, Pakistan and/or dental caries, prevalence, severity, and/or dental caries, severity, prevalence, Pakistan and/or dental decay, prevalence, severity, and/or dental decay, severity, prevalence, Pakistan.

Inclusion and exclusion criteria

We included the studies (a) that provided the prevalence of dental caries in the Pakistani population of any sex or age group. We excluded those articles that (a) did not provide the prevalence of dental caries or data from where prevalence cannot be calculated (b) did not publish in English language (c) involved review articles, case reports, book chapters, and letter.

Selection of studies

The total number of studies found were 9083 that include from PubMed (n = 58), Scopus (n = 1071), and Web of Science (n = 5903). The additional studies found through other sources were (n = 2051). The Reference Management Software Package (Endnote X9) was used to check the duplication and 7013 studies were removed. Studies (n = 1569) were conducted other than the Pakistani population. The remaining (n = 501) were further screened and finally, (n = 39) studies were selected for full text read. Of those (n = 7) articles did not report the prevalence and (n = 2) were review articles. Finally, (n = 30) studies were matching the objective and were satisfying the inclusion criteria for this meta-analysis and were included (Fig. 1).

Fig. 1
figure 1

Flowchart showing selection of studies. Total number of studies found were 9083 that include from PubMed (n = 58), Scopus (n = 1071) and Web of science (n = 5903).The additional studies found through other sources were (n = 2051). The Reference Management Software Package (Endnote X9) was used to check the duplication and 7013 studies were removed. Studies (n = 1569) conducted other than Pakistani population. The remaining (n = 501) was further screened and finally (n = 39) studies was selected for full text read. Of those (n = 7) articles did not reported prevalence and (n = 2) were a review articles. Finally, (n = 30) studies were matching the objective and was satisfying the inclusion criteria for this meta-analysis and were included

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Data abstraction

After doing the initial search, title papers and abstracts of identified articles were explored for relevance and appropriateness to the study question of the present study. The full text of the included studies was obtained. Two field-based experts (A.A.S. and E.F) independently worked on duplication and abstraction of data from each study using a standardized form. The information relating to the prevalence of dental caries, sample size, methodology, year of study, and region/ city was recorded.

Data analysis

The pooled estimate of dental caries in Pakistan was calculated with a 95% confidence interval (CI) and data was displayed with both random-effects model and fixed-effects model. The random-effects model of the meta-analysis was considered more appropriate for the current study. In case of substantial heterogeneity among included studies, random-effects model weights study more equally and are considered more appropriate. Cochran’s Q test (χ2) and the I2 statistic were used to calculate the variance between study and heterogeneity in estimates. Cochran Q was reported as χ2 while I2 was reported in the form of percentages. A higher percentage indicated from I2 statistic showed high heterogeneity between estimates of individual studies (I2 < 25% shows low heterogeneity; 30–70% = moderate heterogeneity and > 75% shows high heterogeneity). Forest plot was used to present the combined prevalence estimate of dental caries with a 95% confidence interval (CI). The analysis was conducted by using MedCalc statistical software version 19.5.3.

Quality assessment

Two independent reviewers (J.A and A.A.M) assessed the quality of included studies. Joanna Briggs Institute (JBI) critical appraisal checklist for prevalence studies was used to ascertain the risk of bias in included studies [18]. JBI appraisal checklist is based on 9 items and each item is assessed by scoring (yes = 1), (no = 0), and (unclear or not applicable = 0). The total score obtained of each study was presented as percentages and each study was categorized according to different levels of risk of bias (high risk of bias if 20–50% items scored yes, moderate risk of bias if 50–80% items scored yes, and low risk of bias if 80–100% items scored yes as per JBI checklist) as shown in Table 1 and Fig. 2.

Table 1 Risk of bias in the current study
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Fig. 2
figure 2

Items of JBI Critical Appraisal Checklist of included studies. JBI appraisal checklist is based on 9 items and each items is assessed by scoring (yes = 1), (no = 0), and (unclear or not applicable = 0).The total score obtained of each individual study was presented as percentages and each study was categorized according to different levels of risk of bias (high risk of bias if 20–50% items scored yes, moderate risk of bias if 50–80% items scored yes, and low risk of bias if 80–100% items scored yes as per JBI checklist)

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Results

A total of 27,878 subjects were included in the meta-analysis from 30 studies conducted from 2009 to 2020 on the prevalence of dental carries in Pakistan. Of those studies, 13 (43%) were from Punjab province, 11 (37%) from Sindh, 2 studies each from Khyber Pakhtunkhwa (KPK) (7%) and Baluchistan (7%), and 2 (7%) studies from Islamabad. The proportion of selected studies according to the province are classified in (Table 2). In the context of cities, there were 7 studies from Karachi, 4 from Lahore, 3 studies from Hyderabad, 2 studies each from Peshawar, Multan, Islamabad, Quetta, and Rawalpindi while one study each from Sialkot, Bahawalpur, Faisalabad, Bhakkar, Sargodha, and Khairpur city (Table 2).

Table 2 The characteristics of included studies in meta-analysis
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The prevalence estimate of dental caries in terms of proportion (random effect model) was 56.62% (95% CI: 49.54 to 63.57). The value of I2 was 99.13% (95% CI: 99.02 to 99.23) and (I2 > 75%) indicating high heterogeneity among the selected studies and due to this reason, aggregate data of random effect model was selected for meta-analysis. Possible reasons for the high level of heterogeneity could be because of variability in the data reported amongst the studies included in the meta-analysis. Other probable reasons may include a difference in characteristics of participants, as well as the use of the various method of caries detection, or could be because of high publication bias. The mean proportion of random and fixed effects models, along with Cochran’s Q value with P-value is reported in Table 3.

Table 3 Summary of included studies with variables and prevalence estimate of dental caries in Pakistan
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The prevalence estimate (random effect model) of dental caries in Punjab was 55.445% (95% CI: 44.174 to 66.44), in Sindh 58.946% (95% CI: 43.796 to 73.274) while in Baluchistan and KPK combined was 51.168% (95% CI: 22.930 to 79.004). The prevalence estimate of dental caries in major cities of the countries was as following: Karachi 61.988% (95% CI: 45.504 to 77.161), Lahore 57.604% (95% CI: 47.727 to 67.183), while Islamabad and Rawalpindi combined was 57.377% (95% CI: 32.642 to 80.287). The prevalence estimate of different provinces and cities of Pakistan is shown in Fig. 3.

Fig. 3
figure 3

Prevalence estimate of dental caries in provinces and cities of Pakistan. The prevalence estimate (random effect model) of dental caries in Punjab was 53.95%, in Sindh 58.135% while in Baluchistan and KPK combined was 51.17% The prevalence estimate of dental caries in major cities of the countries was as following: Karachi 60.83%, Lahore 57.51%, while Islamabad and Rawalpindi combined was 57.38%

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The proportion estimate was calculated for the primary, mixed and permanent dentition as shown in the additional files (Additional file 1: Tables S1, Additional file 2: S2, Additional file 3: S3 and Additional file 4: Figure S1, Additional file 5: Fig. S2). The prevalence estimate (random effect model) of dental caries in primary dentition was 50.493% (95% CI: 43.867 to 57.110), in mixed dentition 61.183% (95% CI: 43.796 to 73.274) while in permanent dentition was 57.184% (95% CI: 26.288 to 85.251).

The Forest plot (Fig. 4) is displaying the proportion prevalence of dental caries of each study included in the meta-analysis. The highest prevalence of dental caries was reported by Badar et al. [32] in Bahawalpur while the lowest was reported by Malik et al. [24] in Karachi.

Fig. 4
figure 4

Forest plot showing effect of different studies and overall effect at 95% CI regarding dental caries from (2009–2020). Forest plot is displaying the proportion prevalence of dental caries of each study included in meta-analysis. The highest prevalence of dental caries was reported by Badar et al. in Bahawalpur while lowest was reported by Malik et al. in Karachi

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The funnel plot (Fig. 5) shows the effect estimates of the included studies against their measure of precision or size of the studies. The funnel plot is showing asymmetry that is indicating heterogeneity and reporting bias. Moreover, poor methodological design and studies with smaller sample sizes can also lead to asymmetry. Other than the aforementioned reasons, the additional likelihood of asymmetry could be due to language bias (reporting of study in English language only) and citation bias (in which positive outcomes are used more to cite and readily available in scientific databases).

Fig. 5
figure 5

Funnel plot showing prevalence of dental caries as proportion. The funnel plot shows the effect estimates of the included studies against their measure of precision or size of the studies. The funnel plot is showing asymmetry that is indicating heterogeneity and reporting bias

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Discussion

The present study concentrated on all the articles reporting the prevalence of dental caries among a Pakistani population. Thirty studies met the inclusion requirements and were included in this systematic review. Prevalence of dental caries was displayed overall, as well as for primary, mixed and permanent dentition separately. Most of the included studies were of high risk, and some of them did not mention the age groups of the participant or even the method used for detecting dental caries. Within all mentioned limitations to our best knowledge, this is the first meta-analysis on dental caries for the Pakistani population. It will help in providing a proportion estimate of dental caries for the Pakistani population. Additionally, it is indicated that most of the studies on dental caries in a Pakistani population contain a high level of bias. Future studies should be carefully designed.

Even though the current research reported useful information in terms of prevalence and seriousness of dental caries in Pakistani individuals, it is clear that most of the studies were conducted in Punjab and Sindh, with some studies conducted in Baluchistan, KPK, and Islamabad. The present meta-analysis, however, may not be indicative of the population as a whole. It may, however, be argued that there are similar socioeconomic and cultural backgrounds among the participants.

The utilize of numerous methodologies such as diagnosis, sample size, and recording procedures, randomization, and form of study was another potential weakness that is typical in dental caries studies. Heterogeneity and publication bias are other inevitable shortcomings of most meta-analysis research, which was also evident in the current meta-analysis. We used Cochran’s Q test (χ2) and the I2 statistic for verifications: the funnel plots showed asymmetrical shape at the bottom in prevalence studies indicating the presence of publication bias, which was confirmed by the insignificant result of Cochran’s Q test (χ2) and the I2 statistic.

By visual inspection of the forest plot, heterogeneity can be estimated. Where there is a low correlation in confidence intervals for the outcomes of individual studies, this usually indicates the existence of statistical heterogeneity [49]. Therefore, we used a random-effects model for the calculation of proportion estimate of dental caries, While the confidence interval quantifies the precision of the point estimate, the true dispersion of effect sizes is discussed by the prediction interval. Two problems are unique and not synonymous. Therefore, we should also estimate the prediction interval if we use a random-effects model to make inferences that are more insightful in meta-analyses [50].

DMFT index is the most used index for the measurement of dental caries at the population level. According to Castro et al. [51], most of the study participants thought to use some other index yet continued to use it as according to them, they could not found a more reliable method of measurement of dental caries. Almost all indices have limitations. To date, DMFT is a widely used and accepted method of measuring dental caries at the community level. It can only detect cavitated lesions and cannot account for incidence [52].

The overall quality of evidence in the selected studies was classified as moderate, with the majority of the studies achieving a moderate risk of bias. Seven studies were found to have low risk. In the present meta-analysis study, the prevalence of dental caries in primary, mixed and permanent teeth studied in this study. In the primary dentition, the prevalence of caries was 50.493%, and mixed dentition was 61.183%, whereas it was around 57.184% of the permeant dentition. During the start of 1980s The World Health Organization alongside FDI World dental federation formulated goals to control the spread of dental caries and mentioned that 50% of children between the ages of 5 and 6 should be free of dental caries by the year 2000 [53]. However, till date in most countries, the prevalence of dental caries in children reported to be very high. This situation creates troubling conditions for tooth decay in adulthood and would also place enormous costs for tooth restoration on the health sector in the country. The overall prevalence estimate of the proportion of dental caries (random effect model) was 56.32%. The identified factors for dental caries are poor oral hygiene habits, intake of cariogenic diet, and low socioeconomic status [54]. The above findings demonstrated high levels of both prevalence and severity in terms of caries. In various included studies, the prevalence of dental caries was reported to be varied. This is in agreement with the finding of Richardson et al. [55] that reported the frequency of dental caries in various studies differs significantly, because of many factors, including (1) subjects studied; their age, and the accessibility for examination; (2) racial and cultural factors; (3) socio-economic status; and (4) diagnostic criteria. Also, the prevalence of dental caries is typically incomparable with another in one region, so it is not possible to extrapolate findings from one ethnic group within that group [55].

As a result of many clinical studies and preventive initiatives focused on caries prevention, developed countries have less caries prevalence and a decrease in caries levels in contrast to countries with good oral health systems such as the Scandinavian countries, dental caries is still a continuing oral health issue [56]. There exists a continuous need of measuring the incidence/prevalence of dental caries. The findings of the 2013 Child Dental Health Survey in England, Wales, and Northern Ireland showed that the prevalence of caries was 31% in five-year-old kids [57]. Treatment needs for dental caries depend upon the changing pattern of a disease over time. A study from the United States reported that the prevalence of dental caries in school-going children was low since the 1960s, however, the incidence seems to be slightly increased from 24 to 28% during the late 1980s to 2004. [58]. That is why regular monitoring of disease prevalence's overtime is of essential importance. A study on 2214 Australian children aged 5 to 8 years reported the prevalence of dental caries to be lower than the current pooled prevalence of 56.32% [59].

Generally, the prevalence of dental caries in the current study was 56.32%. There were high differences within the included studies with the lowest of 8% stated by Malik et al. [24] and the highest of 97% exhibited by Badar et al. [32]. A generally low level of reported prevalence can be because of widespread usage of fluoridated toothpaste [60] and the introduction of a national oral health program [61]. Other probable reasons for such variance can be due to the various geographical areas, the variations between the individuals included in the analysis, and sample size. Oral health policies, fluoridation of community water, and oral hygiene products often play a role in the variability between countries [62]. In most provinces of Pakistan, low levels of water fluoridation were observed, likewise, only 22 percent of the Libyan population receives fluoridated water [63]. Consumption of foods containing sugar is high and easily available everywhere like schools, offices in Pakistan which can be one of the probable causative factors for a higher rate of dental caries in the country.

Some remarkable points were noted during the quality evaluation, which should be considered for future studies by researchers. More specifically, the occurrence of caries in deciduous and permanent dentition should be reported separately. Along with the mean prevalence of the age groups included in the report, the prevalence of caries for individual ages should also be indicated.

The present meta-analysis found studies with certain methodological flaws such as sampling technique, sample size. Besides that, we also noticed a strong publication bias. Another probable limitation observed was the geographical distribution of studies that contain data on prevalence was mainly reported from larger cities of the country. A substantial region of Pakistan is still unexposed, and there still can be an unexplained prevalence of dental caries. It could therefore be assumed that the findings obtained could not present an accurate picture of the prevalence of dental caries in Pakistan. There is a need for national-level population-based studies with equal representation from urban and rural areas of the country. In addition, future epidemiological studies should be conducted to explore various determinant factors of dental caries in the countries. It will help the policymaker in managing the burden of dental caries in the Pakistani population.

Conclusions

Within the limitations of this study, it can be concluded that in Pakistan dental caries is a serious dental public health issue. Dental caries in Pakistan was found to be approximately 60%. Most of the studies on dental caries are of poor quality and contain a high amount of bias. To get a precise image of the prevalence of dental caries amongst subjects in the area, additional studies documenting dental caries from all cities are needed.

Therefore, in Pakistan, the level of dental caries should be a priority, and oral health care investment should be devoted to the preparation of oral health policies and programs. That will enhance the oral health-related quality of life of this demographic part.