A common congenital abnormality that is seen in approximately 1 in 700 live births is cleft lip and palate (CLP). ¹ Cleft lip in association with the palate is twice as common as either cleft lip or palate alone. These malformations alter the middle third of the face to varying extents. They may occur in isolation, for example in nonsyndromic patients, or can be part of a group of abnormalities such as in syndromic cases. ¹

The anatomical and physiological variations such as tooth malposition, nasal septum deviation, or stenosis of the nasal vestibule in the maxillary sections put patients with CLP at an increased risk of oral diseases. In addition, the probability of caries intensifies as patients with CLP are unable to maintain oral hygiene due to the inability to eliminate soft foods consumed during surgical and orthodontic treatment. ² , ³

The most common oral health concern in patients with CLP is dental caries. Prevention and early detection are paramount for the multidisciplinary management of patients with CLP. ⁴ Prevalence of dental caries and caries experience is depicted using the decayed, missing, and filled teeth (DMFT) index that numerically describes the prevalence of past and present caries and is calculated by totaling the number of decayed (D), missing due to caries (M), filled (F), and teeth (T). Caries experience in the permanent dentition is denoted by upper case letters (DMFT) and lower case letters are used to represent caries experience in the primary dentition (dmft). ¹ Zhu et al. ⁵ discovered a greater occurrence of caries in patients with CLP than those with cleft lips with/without alveolus. ⁵ It is well documented in the literature that higher plaque levels and caries rates are seen in the maxillary anterior teeth. ² , ⁶ , ⁷ , ³⁴ This may be attributed to difficulty in brushing, lack of flexibility of the surgically corrected lip, limited access to teeth located within the cleft structure, and the patient's anxiety about brushing around the cleft area. The scarcity of guidance that caregivers receive on nutrition and oral hygiene may also lead to higher caries rates. ² Caregivers of children affected with CLP often consider dental care to be less important than medical and surgical care. ⁸ The high expense of dental treatment and the fact that many CLP patients must travel far distances for treatment further limit their access to dental care. It has been postulated that the structure of the cleft region, surgery and surgical scar tissues, limited movement of the lips, and enamel defects interfere with the maintenance of adequate oral hygiene in patients with CLP. ⁹

Literature has found high caries prevalence due to poor oral hygiene ¹⁰ , ¹¹ in children with CLP compared to healthy children of the same age, in disparity to the outcome of studies conducted by Moura et al. and Parapanisiou et al. ¹² , ¹³ These inconsistencies have been linked to factors such as the limited sample size and wide age range, the lack of a control group, and the inability to differentiate between the various types of cleft. Despite multiple investigations, there is scarce literature on how site-specificity in patients with CLP influences caries prevalence. ⁴ Antonarakis et al. 2013 ⁴ performed a systematic review with meta-analysis to analyze the prevalence of caries in nonsyndromic patients with cleft lip and/or palate and concluded that nonsyndromic patients with CLP tend to have higher caries prevalence, both in the permanent and the deciduous dentition, in comparison with matched non-CLP controls. ⁴ Worth et al. 2017 ¹ did another meta-analysis to determine if individuals with an orofacial cleft were at a higher risk of caries. The study concluded that people with cleft lip and/or palate had greater caries prevalence, both in the primary and permanent dentition. ¹ In addition, Hasslöf and Twetman conducted a systematic analysis in 2007 ¹⁴ that included case–control studies but could not reach a conclusive decision about the association of CLP with caries prevalence. ¹⁴

This revised review will provide an overview of the latest research in this field and also give a complete re-appraisal of previous literature. The goal of the present article was to include published studies that examined caries prevalence in patients with unilateral CLP (UCLP) and bilateral CLP (BCLP) to find out whether there exists a quantitative difference in caries experience among them. To the best of our knowledge, no prior attempt has been made to conduct a meta-analysis to assess the difference in caries prevalence between patients with UCLP and BCLP.

Using the established Preferred Reporting Items for Systematic Reviews and Meta-Analysis checklist, ¹⁵ the systematic review protocol was framed [Refer to [Supplementary Table 1[SUPPORTING:1]]].

Utilizing the population, intervention, comparison, and outcomes framework of systematic review, the review question was formulated that defines the population (nonsyndromic CLP patients), intervention (recording DMFT index), comparison (nonsyndromic UCLP and BCLP patients), and outcome (DMFT score).

The formulated research question was “Is caries prevalence site-specific in patients with CLP?” The review protocol was registered on PROSPERO with registration number CRD2021292425.

Eligibility criteria

Strict inclusion criteria were set to identify relevant articles from the database. The identification and filtering of articles were performed by two examiners (S. S. and A. G.). Full text of relevant articles was obtained and independently screened by both reviewers. Inclusion criteria were based on studies that described different types of clefts, only considered nonsyndromic UCLP and BCLP patients, included either permanent or primary dentition or both, and reported data in the form of DMFT/dmft score for different types of clefts in the form of mean and standard deviation (SD). Only articles published in English from inception to November 2021 were considered. Exclusion criteria were based on the elimination of studies that did not describe the type of cleft, studies that evaluated syndromic UCLP and BCLP patients, and studies that did not categorize data individually for each cleft type rather results were given in terms of cleft and noncleft groups. Studies, in which the aim did not match the aim of the review and studies with the presence of any confounding factor that interfered with the outcome were also excluded. Case reports, letters, short communications, case series, and reviews were eliminated.

Outcome assessed

Caries experience was assessed using the DMFT index in permanent dentition or dmft in the case of deciduous dentition in patients with UCLP and BCLP. The outcome was given in mean and SD.

Information sources and search

To identify relevant articles that met the specified inclusion criteria, a MEDLINE/PubMed, Scopus, and EBSCOhost search were carried out. Manual screening and selection of studies were also done through references to selected studies. The search was implemented by two examiners (J. W. and S. S.) in November 2021. MeSH (Medical Subject Headings) was paired with “AND” and “OR” to establish a database ([cleft lip palate]) AND [caries prevalence]). Titles and abstracts were first screened against the inclusion and exclusion criteria. Full texts were independently obtained and evaluated for the second screening by the two researchers (S. S. and J. W.). Any discrepancies were resolved by a craniofacial research expert (P. B.). Figure 1depicts a flowchart of the process of selection of included studies. Figure 1

Preferred Reporting Items for Systematic Reviews and Meta-Analysis flowchart of included studies. CLP: Cleft lip and palate.

Study selection

The search database yielded a total of 858 articles Figure 1. Duplicate studies were removed and abstracts of the remaining 456 articles were screened. Of these, 21 articles underwent screening by reading full-text articles. At the end of the screening, only three articles that fulfilled the inclusion criteria were included in the present analysis. Eleven studies were excluded as data were not given for individual sub-types of clefts and instead, results represented only cleft and noncleft groups. ³ , ⁶ , ⁸ , ¹⁰ , ¹² , ¹⁹ , ²⁰ , ²¹ , ²² , ²³ Five studies with CLP patients that did not segregate results among UCLP and BCLP were also excluded. ¹³ , ²⁴ , ²⁵ , ²⁶ , ²⁷ One study considered only UCLP patients. ²⁸ One study had to be excluded due to the presence of a confounding factor, in which the association of caries prevalence and carbohydrate intake of patients with CLP was evaluated. ²⁹

Study description

To generate a complete brief approximation of the difference in caries experience between patients with UCLP and BCLP, a random effects meta-analysis was done. Since the studies involved different populations throughout the world, random effects meta-analysis was employed to account for variance in caries prevalence outcomes. For a study to be a part of a meta-analysis, it must give an account of the sample size and mean dmft/DMFT for each group, and either the SD, standard error (SE), SE of difference, or P value. Meta-analysis was conducted using Revman 5.3. The analysis involved studies comparing patients with UCLP and BCLP patient groups in terms of caries prevalence for both permanent and primary dentition.

Characteristics of included studies

The data for included studies were extracted from the included studies under the following headings: author and year, sample size, age group, types of clefts, results, and conclusion. The data from the included studies were collected in the age group ranging from 4 to 16 years. It was unclear among included studies whether any surgical intervention, prior dental treatment, or any follow-up was taken into consideration before recording DMFT. All the studies concluded that patients with BCLP were more susceptible to caries than patients with UCLP. ⁹ , ¹⁶ , ¹⁷

Synthesis of results

Figure 2a and Figure 2b show forest plot illustrations of random effect meta-analysis of included studies for the primary dentition (dmft) and permanent dentition (DMFT), respectively. In the current analysis, the standard mean difference obtained for primary teeth in mixed dentition was 0.36 (95% confidence interval [CI]: 0.69–0.03) and for permanent dentition was 0.57 (95% CI: 1.03–0.11). The variation was statistically significant for caries experience in the permanent dentition evaluated using a DMFT score with a P = 0.01 and moderate statistical heterogeneity among included studies with (I ²-34%, P < 0.05). On the other hand, the difference was also statistically significant in primary teeth with mixed dentition using dmft with a P = 0.03 and no statistical heterogeneity among included studies with (I ²-0%, P < 0.05). The result of the meta-analysis indicates that patients with BCLP have higher caries prevalence. The funnel plot as per [Supplementary Figure 1[SUPPORTING:2]] and [Supplementary Figure 2[SUPPORTING:3]] was visually symmetrical suggesting a lack of publication bias. Figure 2

(a) Forest plot for permanent dentition (decayed, missing, and filled teeth [DMFT]), (b) Forest plot for deciduous dentition (DMFT). DMFT: Decayed, missing, and filled teeth, CI: Confidence interval, SD: Standard deviation.

This study focused on the difference in caries prevalence among patients with UCLP and BCLP. So far, such a segregated analysis has not been performed and highlights an area of focus for health promotion and disease prevention activities for cleft patients. The findings of this meta-analysis show that patients with BCLP have higher dmft and DMFT scores than patients with UCLP. This could be associated with the massive envelopment of anatomical structures in clefts. ³⁰

Past craniofacial research has already established a link between higher caries prevalence in cleft patients than noncleft. ¹ , ³ , ⁵ , ⁶ , ⁸ , ¹⁰ , ¹⁴ , ²⁰ , ²⁴ , ³¹ Similarly, our literature search revealed studies that showed that higher caries prevalence was associated with BCLP. Up until now, however, this evidence was inconclusive. Previous theories stated that the predisposition of patients with CLP to acquire caries is a consequence of poor oral health. Reasons given for this included (1) Deficiency in flexibility caused by invasive lip repair and (2) The structure of the cleft causing discomfort while brushing that poses a challenge in maintaining good oral hygiene. ¹¹ Furthermore, crowding, a higher frequency of supernumerary teeth, and an underdeveloped maxilla with arch space deficiency make brushing and flossing more challenging and effective cleaning of the teeth by the tongue and saliva. In past studies and in our findings, no statistically significant association between gender and caries experience has been shown. ⁹ , ¹²

Another paramount factor is food impaction commonly seen in patients with CLP, as food tends to escape through the nose and regurgitate into the oral cavity. This tends to increase the risk of caries development as substrates for cariogenic bacteria are present in the mouth more frequently and for longer periods. ² , ²⁴ Enamel hypoplasia, which has shown to be of higher prevalence in CLP patients. ² Socioeconomic status is an additional factor associated with increased caries prevalence in patients with CLP. Cleft patients born into low socioeconomic status or those born in low-and middle-income countries with low access to specialized cleft care exhibit increased caries prevalence. Attention must be given to the issue of health inequities. ²⁹ , ³² Oral health IQ of the primary caregivers may also explain higher caries rates; parents may feed their children snacks high in added sugars to console them to be empathetic in light of the CLP. ⁴ Furthermore, patients with CLP tend to retort to mocking at school as a result of their dental malposition by showing less interest in their oral hygiene. ⁴

The findings of the conducted meta-analysis point toward the site-specific nature of caries prevalence in patients with CLP which draws attention to the need for routine dental checkups. Previous literature reports a higher incidence of UCLP than BCLP, however, caries prevalence is higher in BCLP due to reasons previously discussed. ³³ , ³⁴ Although the overall incidence of bilateral BCLP is less, its negative impact on oral hygiene, the increased caries prevalence, and the negative effect on quality of life should not be neglected. Therefore, it is paramount to focus on future cleft care initiatives and research on-site specificity of caries prevalence in CLP patients.

Limitations

However, there were a few limitations of this study. First, the population group and type of dentition compared were heterogeneous. This could affect the outcome as the occurrence of caries maybe more in a particular type of population. Caries prevalence also is dictated by the type of dentition, for example, bottle feeding and inability to maintain proper hygiene might result in higher caries prevalence in deciduous dentition in comparison to permanent. The second limitation can be that the review is based on only three articles due to a lack of literature that provides the proper result concerning different types of clefts. This also indicates the scope for further randomized controlled trials that involve data on both UCLP and BCLP patients.

The outcome of the study indicates that there is a higher occurrence of caries in patients with BCLP than UCLP in both permanent and primary dentition. From the findings of the study, one can state that caries prevalence in patients with CLP is site-specific. Therefore, there is a need for special care and attention in CLP patients to maintain good oral hygiene and prevent the decay of teeth at a young age.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors of this manuscript declare that they have no conflicts of interest, real or perceived, financial or nonfinancial in this article.