Literature Review Writing 2021: How to write a review of Literature fast WITH example in 30 minutes. (Ways to find literature to review)

Welcome, you were probably redirected here from YouTube to view an example of a literature review. However, if you are not from YouTube, you need to click here and watch the video first. 

I promised several things in that video, one of which is a template that I use for my data extraction. I apologise for the nature of this website, there will be an upgrade soon. You can copy the template or modify it. Use either excel, word doc or google docs but I love excel best.

Now to the example I promised, just scroll down and read through. That was the chapter 2 for  my masters thesis, so don’t bother thinking about copying it. It won’t end well. This is the first example, the link to the second example is in my YouTube description box. Make sure to head back there and check it out. 

CHAPTER TWO

 LITERATURE REVIEW

Dental caries remains a major global health problem with a skewed distribution and massive economic and health implications (Balaji, 2018). For the prevalence to be controlled, there is a need to determine the effectiveness of the commonly used fluoridation technique, particularly in the low and middle-income countries where funding is of utmost importance. Over the years, researchers have tried to reduce the prevalence of dental caries with various fluoridation methods of which water fluoridation and fluoridated toothpaste are the most common. These techniques have been applied in various settings like schools, communities and families (Innes and Robertson, 2018; Kapoor,2014).

Iheozor-Ejiofor et al. (2015) conducted a systematic review on water fluoridation for the prevention of dental caries. Iheozor-Ejiofor et al. (2015) included a total of 155 studies in the review while 107 of the studies had sufficient data for quantitative synthesis. Although with very little contemporary evidence meeting the inclusion criteria. The result showed that the introduction of water fluoridation caused a reduction in caries severity. However, 71% of these included studies were conducted before 1975 and the widespread use of fluoride toothpaste. There might have been temporal changes in the effect because of changes in several factors. Also 97% of the studies had high risk of bias and a significant between-study variation. There is insufficient evidence to evaluate the effect of stopping water fluoridation will have on caries level. The reviewers stated that the observational nature of the study designs limits the confidence level in the size of the effect estimated.

Putting into consideration the effect diet has on dental caries, Armfield et al. (2013) compared the association between sugar-sweetened beverage (SSBs), dental caries and water fluoridation among children in Australia between ages 5 to 16 years. The aim of the study was to determine whether exposure to water fluoridation modifies the effect of SSBs on dental caries. The study used a stratified clustered sampling method involving 16,508 children. Their caries activity was assessed by dental staffs and the study utilized a questionnaire filled by parents to gather other history of sugar consumption about the child. The use of a questionnaire exposes the study to bias because of self-reporting. The study confirms the effectiveness of water fluoridation even though consumption of SSBs is a major risk factor for dental caries. Increased exposure to fluoridated water decreased the association between SSBs consumption and dental decay.

The effectiveness of water fluoridation even in high-risk caries areas was confirmed in a cross-sectional study conducted by Koh et. al (2015) evaluated the pre and post-water fluoridation effect on caries experience in primary dentition in a community-based setting. The pre-fluoridation group consisted of 201 children, age 4.0 to 9.9 years that were randomly selected while the post-fluoridation consisted of 256 children of the same age range and data gotten from the same clinic. However, it was not stated if the post-fluoridation group were randomly selected and, the sex distribution was not indicated. The period between pre-fluoridation (1998 to December 2008) and post-fluoridation (January 2011 to December 2012) is wide as factors may have changed over time. The dental caries prevalence and experience was measured using the DMFT/dmft index which is a valid standardised tool by the World Health Organization for use in epidemiological studies (Khamis, 2016). The study was single-blind peer reviewed with only one reviewer. The study concluded that water fluoridation caused a reduction in caries prevalence from 87% to 75% and a 19% drop in caries experience. These are quite significant. However, this study was done in a community in Australia, therefore cannot be generalised worldwide.

The frequency of dental healthcare services following water fluoridation was also used to assess the effectiveness of water fluoridation. Cho et al. (2016) conducted a cohort study on healthcare utilization for dental caries based on implementation of dental care services in North Korea. The sampling data used in the study was from the national health insurance to evaluate the impact of water fluoridation on the nation. The study concluded that the implementation of water fluoridation is associated with reduction in the utilization of dental health care services and improved oral health especially dental caries. However, there was no specific data indicating the reduction in severity of dental caries or the tool used to measure the caries in the sample. Furthermore, other factors that could affect health outcomes like type of toothpaste, frequency of tooth brushing, and lifestyles were not considered. The fluoride level in the water and actual volume consumed were not considered. The data included 472, 250 patients but the gender of these patients were not revealed. The study was carried out in North Korea. Therefore, it cannot be generalised to the rest of the world.

Aside the dental service utilization, an Iranian study has shown that age-sex specific and sequela-specific disability-adjusted life years (DALYs) resulting from dental caries is preventable through water fluoridation. The result of this study by Abtahi et al. (2018) showed that approximately 20% of the national dental caries DALYs were preventable by water fluoridation. The data on burden of disease resulting from dental caries extracted from the Global Burden of Disease study in 2016. The limitation of estimated data values from this database also applies to this study. Also, certain sequela like difficulty in eating because of tooth loss is not limited to dental caries only, as periodontal disease may be the cause. The result gotten from this study is an indication of the role water fluoridation plays in promoting dental public health and compensate inequality at a national level.

An inequitable effect of community water fluoridation on dental caries was demonstrated in the study by McLaren et al. (2016a) in Calgary, Canada. The study compared socioeconomic patterns of dental caries in children during a period of fluoridated water supply (2009/2010) and following its discontinuation (2013/2014). The study recorded increasing inequality in dental caries following discontinuation of community water fluoridation. Although, the study had limited socio-economic information available at both point in time (before and after cessation)   

There had been so many debates about cessation of water fluoridation and its effect with several countries going ahead to implement it. McLaren et al. (2016b) explored the short-term implication of water fluoridation cessation on dental caries in Alberta, Canada. A pre-post cross-sectional study design was used involving grade 2 schoolchildren in 2004/2005 and 2013/2014 in two similar cities within Alberta. This affected potential cofounders being ruled out because the comparative analysis used pre-cessation data taken several years before cessation data was collected. Furthermore, no data was collected on inter-examiner or intra-examiner reliability even though the assessment team was reported to have had extensive training and calibration. The result showed increased caries activity in primary teeth during the cessation period. The dental caries activity in permanent teeth was not worsened but this could be because of the short-time frame of the study.

Similar to the result of water cessation in the study by McLaren et al. (2016b), Seppa, Karkkainen and Hausen (2000) conducted a study on the change in dmft score following cessation of water fluoridation. It was a cross-sectional survey of two communities. One community had never received fluoridated water supply while the other community stopped water fluoridation in 1992 (after using since 1959). Although it was difficult to draw conclusion because of the study design used. The caries score was higher in the community that had previously been receiving fluoridated water than the community that never did. This is an interesting result as it would have been expected that the community who never received water fluoridation should have higher caries rate.

From an economic perspective, Ran and Chattopadhyay (2016) conducted a systematic review to determine if the intervention is of any cost benefit. 564 studies were identified between 1995 and 2013 but only 10 studies met the inclusion criteria. The result indicates that the economic benefit of water fluoridation exceeds other intervention cost. However, there might have been an underestimation of the costs and benefit because of the nature of the intervention which resulted in estimation of the both values.

The most common adverse effect of water fluoridation is dental fluorosis. This has been the main reason for cessation of the intervention in some countries like China.  Firmino et al. (2018) conducted an ecological study to determine the relationship between dental caries, dental fluorosis and water fluoridation among 12-year-old school children in Brazil. The survey took place between 2009 and 2010 involving 7328 twelve-year olds of both gender. The research showed a lower prevalence of dental caries with optimally fluoridated water. However, the ecological study design limits the application of finding at individual level but may be useful for international data comparison. Furthermore, other sources of fluoride exposure like toothpaste were not controlled

In assessing the effectiveness of fluoride toothpastes, a systematic review and meta-analysis of varying concentration of fluoride toothpaste for the prevention of dental caries in children and adolescent was conducted by Walsh et al. (2010) and included randomised controlled trials and cluster-randomised controlled trial study design. 75 studies were included in the review while 66 of these studies met the meta-analysis criteria with publication date ranging from 1955 to 2008. However, many these studies were categorised as ‘unclear’ because they failed to give adequate information on the method of randomisation and process of treatment allocation. Generally, the studies were largely bias-free except for randomisation and allocation concealment. The result of the meta-analysis showed that the preventive effect of fluoride toothpaste against dental caries is increased significantly with higher fluoride concentration. The review also had few studies examining the effect in deciduous dentition.

A RCT conducted by Tickle et al. (2017) to prevent children from becoming caries active over a 36-month period. Randomisation was done using computer-generated random numbers and there was allocation concealment.  Total of 1248 children were recruited but 1096(549 intervention and 547 control) were used in final analysis. The interventions were fluoride varnish, toothbrush, 50ml tube of 1450ppm fluoride and standardized oral hygiene instructions while the control was advice only. Examiners bias was avoided because the external examiners were calibrated and blinded to the study groups. The result showed that 34% of the intervention group became caries active compared to 39% in the control group.  More significantly, the caries activity measured by the standardised dmft index in the intervention group was 7.2 while it was 9.6 in the control group.  However, the study failed to evaluate if the children were caries-free but showed a slow caries progression in those who had caries.

Petersen et al. (2015) conducted a non-randomised controlled trial in a two-year school-based intervention to assess oral health promotion program combined with supervised tooth brushing using a toothpaste containing 1450ppm fluoride concentration. A total of 3,706 pre-school children were recruited from 15 south Thailand schools: 8 schools consisting of 1,766 children as controls and 7 schools with a total of 1,940 children belonged to the intervention groups. The intervention schools were further classified into cooperative schools (5) and non-cooperative schools (2) based on their adherence and participation to the tooth brushing activities. The sex distribution was not stated. The study documented a significant effect from use of fluoridated toothpaste with approximately 41% caries incidence reduction in the cooperative schools.

A randomised clinical study by Newby et al. (2013) to compare the effect of three varying concentration of fluoride toothpaste to placebo in halting dental caries progression. The varying concentration were 1,426 ppm fluoride, 1000 ppm fluoride, 500ppm fluoride and 0ppm fluoride (placebo).  It was a single-blind, crossover study involving 55 subjects, 24 males and 31 females within the age range of 11 to 14 years. The test result showed that all three concentration of fluoride toothpaste increased enamel remineralisation, fluoride uptake and acid resistance following a single brushing thereby capable of preventing caries progression. However, the duration immediate effect seen in this study is somewhat questionable. There is a conflict of interest as four of the nine authors are employees of GlaxoSmithKline Consumer Healthcare, a company that funded the study.

Another systematic review conducted by Wright et al. (2014) confirmed the efficacy of fluoride toothpaste in children younger than 6 years old. The reviewed further showed a decrease in fluorosis when fluoride toothpaste was commenced after the age of 2 years. The review includes 17 clinical trials and not RCTs. The result gotten from this review may not be generalised to all children as most of the studies were conducted in high risk populations. Another limitation in this review is that the studies included were at high risk of bias because of the study designs.

Fluorosis as an adverse effect of fluoridation is commoner in water fluoridation than fluoride toothpaste. In measuring fluorosis in Mexican children, Molina-Frechero et al. (2015) evaluated 239 students. Mean age was 11 ± 0.82 and 51% were male. More than half of the population had a type of fluorosis. 29.3% had very mild fluorosis, 20.9% had mild fluorosis, 6.7% had moderate fluorosis while 2.1% had severe type of fluorosis. The mean fluorosis score was 0.887 ± 0.956. The study concluded that the association between frequent brushing using toothpaste high in fluoride concentration and lack of parental supervision during toothbrushing may be a contributing factor to the severity of fluorosis. However, one limitation of the study is that the data used to determine frequency of brushing, type of toothpaste and supervision during study was obtained from a questionnaire filled by the parent. The data collected is prone to self-report bias. Additionally, the study was conducted for a small fraction of Mexico children and cannot be generalised to the rest of the world. Contrary to the findings of Molina-Frechero, a review by Pretty (2016) presented available evidence to promote the use of high concentration of fluoride in toothpaste particularly in high caries risk children. The systematic review showed good level of support to toothpaste up to 2800ppmF.

Several literatures have explored either water fluoridation or fluoride toothpaste and has found them effective against caries prevention. Various concentrations have also been explored with several conclusions been drawn. Majority of the reviews available on water fluoridation and fluoride toothpaste made use of studies that were conducted several decades ago. However, there is no review that has evaluated their effectiveness using studies done within the last decade. There is a need fro a review that can be related to the state of this present society. As the two most popular and commonly used form of fluoridation, it is important to compare their effectiveness against dental caries prevalence as it will help health policy and decision makers make informed decisions.

Don’t forget to head back to YouTube for the second example. Cheers.