The Effect of Caries on the Chewing Ability of Children: A Scoping Review

Abstract Childhood caries might have several effects on the children's general health and growth, including chewing ability. This study aims to identify the evidences found regarding the effect of caries on the chewing ability of children through a scoping review. A scoping review literature search was performed in three databases (Scopus, PUBMED, and Web of Science) without restricting the publicized year. The selected articles were using human as its subjects and aiming to analyze the effects of caries on mastication ability in children. Ten articles matched the inclusion criteria of this review. All the articles suggested a deleterious effect of caries on masticatory performance, maximum bite force, swallowing threshold, and even masticatory behavior. Two of them stated that the effect was reversible by giving dental treatment. This scoping review concludes a negative effect of caries on the children's chewing ability.


Introduction
Dental caries is a chronic dental health problem which is, in fact, preventable.However, global reports state no improvement in children oral health over the past decades. 1According to a study, untreated dental cavity might be a caries predictor in the permanent dentition.Meanwhile, most parents/caregivers belief that caries denotes an acute disease that should be noticed only when there is a visible cavity or when the pain arise. 2 Unfortunately, when the dental pain arises, it might had already influenced the children's development both psychologically and physically, and their school and daily life achievements as well. 3Aside from pain, caries might also affect many other physiological functions of the body, including nutrition intake, chewing difficulty, delayed growth, 4,5 cognitive function, 6 and oral health-related quality of life (OHRQoL). 7Prior to understanding those impacts, a better understanding on the effect of caries to mastication ability and performance is required.Mastication poses the important stimulus for craniofacial growth and development, also in digestive process to obtain the required nutrition for health maintenance and growth. 8The thickness of occlusal and near contact area relates to the efficiency of mastication. 9,10An untreated caries means reduction in occlusal and proximal area, which are important for shredding foods.Moreover, pain might also arise as bolus makes contact with the dentinal tubules or the exposed pulp chamber.Thus, individual with worse caries might have worse mastication ability. 8The effect of caries to chewing ability on children has become interesting over decades.Early childhood denotes a crucial time to acquire mastication skill.Food diversity and textures is considered as crucial factors for mastication skill maturation. 11Thus, the effect of caries to chewing ability is naturally contrast to the adult.There are a couple of studies that focus on this area.Meanwhile, to the best of our knowledge, a study providing the whole picture of the effect of caries toward masticatory performance on children has not yet been available.Thus, this study aimed to identify the evidences found regarding the effect of caries on the chewing ability of children.

Methods
This review has been registered in PROSPERO with ID CRD42022309417.In the interest of answering the research question-"What is the effect of caries to the mastication ability of children?"-a review was performed on some particular selected articles.Those articles' eligibility was decided based on the following criteria: 1.All types of studies (observational and experimental studies); review articles are not included.2. Written in English.3. Studies with children and toddler as the subjects.4. Studies that performed all types of masticatory evaluation on children and toddler with or without caries.5. Outcome of study: mastication ability.
A sequential group discussion was performed in order to match the perception of operational definitions of variables and data extraction.Shall any problems and questions arise throughout the data extraction it will be discussed further by all the authors.

Search Strategy
Articles for the current review were acquired from databases (PUBMED, SCOPUS, and Web of Science), considering that they hold the most databases for biomedical and pharmaceutical literatures.Aside from that, PUBMED is known as the main tool to explore any literature relevant to biomed.The literature search was performed without restricting the year of publication, until January 13, 2022 with phrases complementary to caries, primary teeth car-ies, children, toddler, mastication performance, and mastication ability.

Study Selection
Data selection was performed by two authors independently, followed by identifying and removing duplicates.Articles screening was subsequently performed according to the inclusion criteria.Hereafter, full texts were further assessed for its eligibility.The assessment result from the two authors was combined.The critical appraisal for included studies was performed using the Joanna Briggs Institute Critical Appraisal tools for cohort, cross-sectional, and quasi-experimental studies.A discussion forum was opened as soon as any disambiguates or disagreements arise.The data of the included articles were recorded and tabulated.

Result
Following database search, a total of 182 articles were acquired and screened for its eligibility based on its title.As much as 20 duplicates were removed, and 146 articles were also removed because of different topic.Then, 18 articles were further assessed based on its abstract, eliminating 5 articles for having unmatched aim, and 1 article for not written in English.A number of 12 articles in full text were further assessed for its eligibility, removing 2 articles.In the end, a total of 10 articles were included in this study.The Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow diagram of the research search is shown in ►Fig. 1 for this analysis.

Characteristics of the Studies
The effect of caries toward chewing ability in children was first published in 2004, and the most publication was recorded from 2016 to 2020, with eight articles being published over that period.The included studies were from Asia, Europe, and South America.The largest portion of publication in this study were from South America (40%), followed by Asia (30%) and Europe (30%).Most of the articles were came from Brazil (4), and two articles came from France, one from Saudi Arabia, one from India, one from Singapore, and one from Turkey.The average respondents used for those studies were 171, with the maximum number being 676 and the minimum number being 25 respondents.Seven of the 10 studies were cross-sectional observational studies, two were cohort studies, and one quasi-experimental study.The subject of the studies was varied between primary and mixed dentitions, with sample age ranging from 3 to 12 years old.Only one study used target in the phase of early permanent dentition.The included articles varied from cross-sectional, cohort, and quasi-experimental studies.

The cross-sectional studies
The cross-sectional studies are summarized in ►Table 1.
Most of the studies used the Decay, Missing, and Filling (DMFT) index 7,11 and International Caries Detection and Assessment System [11][12][13] to assess caries condition.Other clinical oral condition assessment was performed using Caries Assessment Spectrum and Treatment, 16 radiographic imaging, 14 and manually counting the number of carious lesion and plaque index. 15Some studies also evaluated occlusion using the International Orthodontic Treatment Needs (IOTN) index 11,13 and Dental Aesthetic Index, 7 number of masticatory units, sucking habits, 13 orofacial dysfunction using the Nordic Orofacial Test-Screening (NOT-S) questionnaire, the presence of abscess, or other oral condition resulting from untreated caries using the PUFA index. 11Some studies also collected other data that are expected to affect masticatory function, such as anthropometric measurement with body mass index (BMI) 12 or body weight and height. 145][16] Aside from masticatory performance, Souto-Souza et al also evaluated the children swallowing threshold. 13A study by Linas et al was the only one that evaluated masticatory function via mastication capability and masticatory behavior. 11Some studies also evaluated children's food consistency by dietary log that were filled by the parents/caregivers 12 and their OHRQoL. 7ll of these studies found a negative correlation between caries and masticatory function.Although there were no difference value of maximum bite force between caries and caries-free group, caries still might reduce the masticatory performance in children. 14Meanwhile, other studies found that the maximum occlusal bite force value decreases with the progression of the caries spectrum of first permanent molars. 16Aside from caries, Consolação Soares et al also stated a negative influence on masticatory performance of preschool children that came from higher frequency of sweet beverage consumption and higher BMI. 12 Another study also stated that a higher number of tooth loss correlated with an inferior masticatory performance in older children. 7The presence of dental cavity not only interfere with children's chewing ability, but also alter their masticatory behavior, such as food refusal, using tongue to crush food against the palate. 11

The cohort studies
Two prospective cohort studies were included in this study with children aged from 2 to 6 years old as the subject.Both studies used children suffering from early   18 The two studies performed clinical oral examination and caries assessment using the DMFT index.However, Collado et al added several aspect to be explored, such as orofacial dysfunction assessment using NOT-S, orofacial dysmorphology assessment using the IOTN index, and OHRQoL assessment using the Early Childhood Oral Health Impact Scale. 17The treatment given to children with ECC were multiple teeth extraction, 18 restoration, endodontic treatments, and crown under general anesthesia. 17Masticatory evaluation was done by assessing interarch functional contact; an elastomer impression was made, and then scanned using image analysis software.A month after treatment, follow-up was performed and found that the deteriorated orofacial function and quality of life caused by ECC were reversible by giving a conservative dental treatment. 17While the other study that evaluated masticatory function with mixing ability test and assessment of oral processing behavior found the children's mastication function in 3 months after treatment follow-up were unchanged, which was probably due to the loss of masticatory units following the treatment. 18The summary of the cohort studies is shown in ►Table 2.

The quasi-experimental study
The only quasi-experimental study included in this study observed the differences of occlusal bite force before and 24 hours after treating carious teeth with glass ionomer cement (GIC) restoration (►Table 3).The study divided the samples into three groups, caries in all quadrants, caries in upper/lower jaw on the right side, and caries in upper/lower jaw in the left side.Following 24 hours of GIC restoration, they found an increased value of occlusal bite force in all groups.A significant increase of bite force value was also recorded in the free-caries side. 19

Key Findings
Mastication denotes a rhythmical automatic movement, where the food is mixed and crushed with saliva, forming a bolus to be swallowed.It is a complex mechanism involving opening and closing movement of the jaw, saliva secretion, combined with tongue movement to mix the food. 20The overall finding that can be learned from the included study is caries, either involving anterior or posterior teeth, had influence on the children's ability to chew food.2][23] Fortunately, some studies proved that the negative effect is reversible.Applying GIC restoration to the carious teeth were able to increase the value of occlusal bite force. 19This result is supported by two prospective studies using children suffering from ECC as the subjects, comparing their ability to chew food before and after receiving dental treatment under general anesthesia. 17,18The studies recorded a successful oral function restoration, including mastication, following dental treatment. 17While the other study found an increase of chewing difficulty corresponded to the increased total number of extracted teeth.However, the study assumed that the children had ability to adapt to gain the most optimal masticatory function. 18

Significance of the Findings and Possible Mechanisms
In children, aside from nutritional status, mastication also plays a role in growth process.Studies observing chewing cycle identified well-developed mastication efficiency at the age of 8 months, and for harder solid foods, the earliest maturation identified was at 24 months old.Meanwhile, the studies observing kinematics jaw movement found that by the age of 18 months, children will have well-controlled jaw movement during chewing process. 22Considering the continuous change of occlusion during primary dentition, in order to illustrate and confirm appropriate growth and development of stomatognathic system, its functional determinants should be established. 19The oral health state and a particular sensory input from teeth, denotes a decisive key for mastication capability and behavior.Carious lesion progressively affects the tooth structural integrity.Open occlusal or proximal contacts mean losing occlusal force, which also reduce the area to grind the food.Thus, the existence of decayed teeth may alter the children's ability to chew foods with different texture.Besides, children might also modify their masticatory behavior, like extending the chewing time and having chewing-side or certain food preference.Aside from decreasing occlusal force, pain arising from caries also promotes sensitivity during grinding the food.Therefore, whether due to food preference or swallowing bolus in large particles, nutritional consequences should be expected. 11,14,23Dental caries in children is also at risk of causing preferred chewing side (PCS). 246][27][28] The loss of masticatory units due to the progression of caries can alter the chewing frequency and the bolus granulometry.These factors are responsible for the declining sensory input from the teeth receptors that are required to control muscle and jaw movement during mastication.The adverse effect of caries on maximum bite force associated with input from periodontal tissue mechanoreceptors due to the inadequate occlusal conditions. 14Although the children had the ability to form mastication behavioral adaptation, the measures were not enough to atone this shortcoming. 11The reversible effect was proven by two prospective studies and one experimental study.Treating carious lesion means restoring the functional occlusal contact, thus the sensory input from teeth become available again.By restoring the tooth anatomical support, oral function will be recovered, leading to progressing natural occlusal equilibration. 17,19mitations of this Review The included articles were mostly observational studies, since this study focused on the effect of a disease.This might prevent us to draw the causal inferences between caries and mastication ability.Besides, the included studies use various methods of masticatory function assessment, in various dentition state (primary, mixed, and early permanent dentitions), which makes it quite challenging to conclude.

Future Research
In order to get the detailed view of the caries effect toward the children's ability to chew, further research can focus on how strong the caries impact on each dentition state.A study that compares the effect of caries on children with primary, mixed, and early permanent dentition group is recommended.Besides, a study that observes a long-term effect of caries during childhood, both treated and untreated, toward mastication ability or behavior in adulthood is also worth considering.

Conclusion
Finally, it can be concluded that dental caries, specifically the untreated ones, might alter the children's ability to chew.The masticatory function deteriorates as the caries progress.
Treating the carious lesion may restore the effect.This finding is expected to be used as reference and principal rationale to give dental treatment as soon as carious lesion is detected.

Fig. 1
Fig. 1 Flowchart diagram of the research search.

Table 1
The summary of the cross-sectional studies caries (ECC) that required treatment under general anesthesia.The study by Collado et al compared any changes with those with no caries, 17 while Khong et al evaluated the dental treatment effect without comparing with a control group.
Abbreviations: BMI, body mass index; DMFT, Decay, Missing, and Filling index; ICDAS, International Caries Detection and Assessment System; IOTN, International Orthodontic Treatment Needs; MP, masticatory performance; NOT-S, Nordic Orofacial Test-Screening; OHRQoL, oral health-related quality of life; WHO, WORLD Health Organization.childhood

Table 2
The summary of the cohort studies

Table 3
The summary of the quasi-experimental study