Assessment of orofacial muscle strength, masticatory and swallowing function in children indicated for orthodontic treatment.

doi:10.21203/rs.3.rs-3305556/v1

Objectives

To evaluate orofacial muscle strength, masticatory and swallowing function in children indicated for orthodontic treatment.

Materials and Method

Sixty-two volunteers were equally divided into an experimental group (mean age:14.9 ± 2.8, 15 girls) and a control group (15.2 ± 2.3, 15 girls) based on their orthodontic treatment needs. The orofacial muscle strength was measured by recording the maximum voluntary bite force (MVBF), tongue and cheek pressure. Additionally, the participants also performed a food comminution and mixing ability tests to measure their masticatory performance. Swallowing function was assessed with a standardized Test of Masticating and Swallowing Solids (TOMASS).

Results

The results showed significant differences in the MVBF (P = 0.009) but no differences in tongue pressure (P = 0.208) and cheek pressure (P = 0.925) between the groups. The results also showed no significant differences in food comminution test and mixing ability test between the two groups (P = 0.553, P = 0.269, respectively). The results of the TOMASS test showed significant differences in the number of bites to eat the cracker (P = 0.003) but no significant differences in number of chewing cycles (P = 0.855), number of swallows (P = 0.149) or duration to eat the cracker (P = 0.275).

Conclusions

Patients indicated for orthodontic treatments show poor orofacial muscle strength in terms of lower MVBF with the age and sex matched controls. However, the patient group does not show any signs of impaired masticatory or swallowing function.

Clinical relevance:

A comprehensive assessment of oral functions in children can enhance clinicians' evaluation of orthodontic treatment needs. MVBF could be a simple and useful tool to evaluate the orthodontic treatment needs.

Hard viscoelastic

test food

malocclusion

bite force

tongue pressure

cheek pressure

The mastication process involves the ingestion of food morsels, placing them between the upper and lower teeth, and applying the necessary force to crush the food into smaller pieces. The masticatory process also stimulates salivary production that helps to lubricate the food morsel and producing coherent, soft, and moistened bolus that is ready for swallowing. This complex, rhythmic and semiautomatic process is further affected by other factors such as food hardness [1–3] texture, taste, number of chewing cycles, bite force, masticatory muscle activity [4, 5] and other related factors that produce successful food morsel breakdown [6].

Growing children have significant morphological changes in the orofacial structures involved in chewing. The skeletal mass, skeletal shape, muscle mass, and muscle geometry frequently undergo dramatic alterations because of growth. These growth alterations confront the nervous system with dynamically changing systems that must be regulated. The sensorimotor control of chewing behavior may also be significantly challenged by alterations in the orofacial anatomy [7–9]. Additionally, these alterations could be linked to problems with jaw and occlusion function (i.e., malocclusion). Considering the changes in the orofacial structures, it might be important for growing children to learn and modify their chewing behavior and adapt to the changing oral motor demands. It was shown that chewing parameters such as maximum bite force [10, 11], jaw muscle activity [9], and jaw kinematics gradually alter with the development of the orofacial structures and are mostly impacted by the dentition state [12, 13]. Further, it has been shown that while the jaw sensorimotor regulation and chewing function develop gradually with age, a transition to the adult-type of masticatory behavior occurs in the late-mixed to early-permanent dentition stages in children with normal occlusion [7–9, 13–15].

Malocclusion is ranked as one of the most significant oral health conditions by the World Health Organization (WHO). It is widely accepted that the muscles of the tongue, lips, and cheeks are primarily responsible for the forces acting on the teeth. These pressures have a variety of tasks, including directing tooth eruption, affecting occlusal development, and preserving the stability and structure of the dental arch [16, 17]. Malocclusion may also lead to functional difficulties. Functional measures such as bite force, chewing performance, chewing efficiency and jaw movements are affected by malocclusions. Therefore, it is important to both subjectively and objectively evaluate the determinants of oral functions such as mastication and swallowing. Further, the severity of malocclusion and the corresponding orthodontic treatment is primarily allocated based on index for orthodontic treatment needs (IOTN) in most countries. In Sweden, a similar classification uses anatomical anomalies such as the magnitude of overjet, overbite, crossbite, without considering loss (impaired) of function. A fair assessment of the functional measurement such as bite force, chewing and swallowing performance in children would provide the clinicians more clinical tools in better evaluating the treatment needs.

Recently a systematic review concluded that children with malocclusion tend to show lower maximum voluntary bite force and jaw muscle activity and impaired jaw kinematics compared to normal healthy control [18]. Therefore, we hypothesized that children indicated for orthodontic treatment will have poor orofacial muscle strength and show signs of impaired masticatory and swallowing function compared to their healthy controls. The aim of the current study was to evaluate orofacial muscle strength, masticatory and swallowing function in children indicated for orthodontic treatment and compare them with their age and sex matched healthy controls.

The study was carried out in accordance with the declaration of Helsinki II and was approved by the Regional Ethical Review Board, (Dnr 2021/01044), Stockholm, Sweden. Participants and their parents were provided with a detailed description of the study aims and data collection process before being invited to participate in the study. Upon obtaining written informed consent, participants were recruited into the study if they were willing to participate. Additionally, participants were informed that they could discontinue the study at any time during the data collection process.

Study participants

The study was carried out at the Orthodontic Specialist Clinic, Karolinska Institutet, Sweden. A priori power and sample size calculation were conducted using G*Power version 3.1.9.7 to determine the number of participants required to test the study hypothesis. The results of the sample size calculation showed that a sample of 58 (29 in each group) participants was needed to achieve 60% power for detecting a medium effect size at a significance criterion of α = 0.05. Accordingly, sixty-two participants were equally distributed into an experimental and a control group based on their treatment allocation. Participants in experimental group (n = 31, age = 14.9 ± 2.8 years, age range: 11 to 22 years, 15 girls and 16 boys) were indicated for orthodontic treatment diagnosed by orthodontic specialist (see Table 1) according to Socialstyrelsens index. The Socialstyrelsens index was developed in 1966 by orthodontic section of the Swedish dental society and Swedish medical board and addresses subjective and objective needs for the treatment. It consists of four grades with grade one being the little need of treatment and grade four being urgent need for treatment [19]. The participants in control group (n = 31, age = 15.2 ± 2.3 years, age range: 11 to 21 years, 15 girls and 16 boys) were children visiting the dental clinic for their routine dental check and not indicated for orthodontic treatment. The participants were in permanent dentition stage, with no previous history of orthodontic treatment, healthy periodontal status, and without ongoing active carious lesion or any other ongoing. The participants included in the study neither reported any serious or chronic oral, orofacial /systemic diseases nor were on any kind of medications, at the start of the experiment.

Study protocol

The single experimental session lasted for about 30 minutes. All participants (from both groups) were seated upright on an office chair comfortably in presence of their parents. All participants performed a series of objective and subjective measurements to evaluate the orofacial muscle strength, masticatory, and swallowing function. The orofacial muscle strength was evaluated by measuring tongue pressure, cheek pressure, lip pressure, and maximum voluntary muscle force (MVBF). The masticatory efficiency and performance were evaluated by food comminution and mixing ability tests. The swallowing function was evaluated by a standardized Test of Masticating and Swallowing Solids (TOMASS). Lastly, the subjective evaluation of potential limitations in oral functions was evaluated with the Jaw function limitation scale (JFLS-20) questionnaire.

Objective assessments

Orofacial muscle strength

Maximum voluntary bite force

Maximum voluntary bite force was evaluated by force metal transducer (Hottinger Bruel & Kjaer). The force magnitude was measured in Newtons (N) by using metal gauge-based bite force transducer. The examiner places the force transducer on the area around the first molar of the preferred chewing side and ask the participant to “bite/clench the teeth as hard as comfortably possible”. Three bite force recording were taken, and the mean of the three readings was taken.

Tongue pressure, Lip pressure and Cheek pressure

The orofacial muscles were examined using the IOPI (IOPI Medical LLC, Carnation, WA). The pressure magnitude was measured in Kilopascal (kPa) by using balloon muscle pressure transducer. For tongue pressure, the examiner placed the balloon of the pressure transducer between the tongue and the palate and ask the participant to press the balloon with the tongue against the palate as hard as comfortably possible”. For lip pressure, the examiner placed the balloon of the transducer between the lips around the central incisors in the vestibule between the teeth and the lips and ask the participant to “clench the lips together as hard as comfortably possible”. For cheek pressure, the examiner placed the balloon of the transducer on the area around the first molar in the buccal vestibule and ask the participant to clench the cheeks as hard as comfortably possible”. For each test, three pressure readings were taken, and the mean of the three readings was calculated.

Masticatory efficiency and performance

Food comminution text

Masticatory efficiency means the number of masticatory cycles needed to reduce foods to specific size and masticatory performance means evaluating the particle size distribution of food when chewed for a given number of cycles [20]. Two trials of the food comminution test were completed by each participant, and the experiment was being recorded on video. The first trial was assessing masticatory efficiency and second trail was assessing masticatory performance. The participants were asked to eat standardized, hard viscoelastic, test food prepared in the laboratory described in previous studies [5, 13, 21, 22]. For the first trial of test food, the participants were asked to chew and eat the test food naturally and indicate when the test food has been completely swallowed. The chewing cycles and duration were recorded. For the second trial of the test food, the participants were asked to eat the candy and stopped abruptly after 10 chewing cycles and spit out the candy along with all the remnants in a petri dish. A thirty ml of water was added to the Petri dish and gently separate the pieces (if any) without breaking them. image captured with android phone camera with adequate natural lighting and with the flash in fixed distance from the camera to the Petri dish (about 1.5 feet). The number of pieces of the test food were measured according to previous study [23]. A better masticatory performance was indicated by having more particles.

Mixing ability test

Mixing ability test was used to assess masticatory performance. A standard two- sides chewing gum Vivident Fruitswing® “Karpuz/Asai Üzümü” (Vivident) (Perfetti van Melle), was used to measure mixing ability test [24, 25]. The participants were asked to chew on chewing gum on their preferred chewing side. The examiner silently counts the number of chewing cycles. After twenty chewing cycles, the participant is asked to spit out the chewing gum. The chewed gum is placed on a cellophane paper and is flattened to a wafer of 1 mm using a customized template guide. Image captured for the two sides of the wafer with android phone camera with adequate natural lighting and without the flash in fixed distance from the camera to the wafer (about 1.5 feet). One examiner scanned and analyzed each sample in accordance with prior study [26, 27]. As a measure of the mixing capacity, the Variance of hue (VOH) was determined by specialist software in accordance with the prior recommendations. Poorer mixing ability is indicated by a greater VOH value.

Swallowing Function

Test of masticating and swallowing solids

Test of masticating and swallowing solids was tested using two crackers. The participants were asked to eat two Göteborg Saltiner crackers separately. The experiment was being recorded on video. The content of the cracker was: wheat flour / wheat flour, sunflower oil / sunflower oil, wheat starch / wheat starch, sugar, salt, baking powder / leavening agent (deer antler salt E 503, sodium bicarbonate), malt extract (grain / BYG), fermented beetroot extract. The participants were asked to eat a cracker “as quickly as is comfortably possible”, and then to say their name out loud to confirm oral cavity clearance and completion of the task. The task is timed using a timer. Four measurements were recorded: the number of discrete bites, chewing cycles, swallows per whole cracker and total time to complete the whole cracker were measured for each cracker. The mean of each measurement was calculated.

Subjective assessment

Jaw function limitation scale

The standardized and validated Jaw Functional Limitation Scale was used to examine the subjective assessments of the jaw (masticatory) function (JFLS-20). JFLS-20 is an organ-specific tool for evaluating the masticatory system's functional state. The 20-item scale assesses the total functional limitation of the masticatory system, considering vertical mobility, verbal and nonverbal communication, and mastication behavioral imitation. The widely regarded Swedish version, which has strong reliability and validity, was used [28–30]. The participants rated their limitation for each item on a scale from 0 to 10, with 0 representing no limitation and 10 representing severe limitation. Four behaviors were calculated: total score for JFLS-20, mastication, jaw mobility and verbal and emotional communication. The mean values of each domain represent the score for each domain.

Statistical analysis

The data were analyzed with SPSS (IBM SPSS Statistics for Windows, Version 25.0. Armonk, NY: IBM Corp) statistical software program. The assumption of normality was checked by the Shapiro–Wilk test. All normally distributed data were analyzed with parametric tests while non-normally distributed data were analyzed with non-parametric tests. Data related to tongue pressure, cheek pressure, maximum voluntary bite force, and total time to eat cracker in TOMASS were normally distributed. Thus, an unpaired t-test was performed to evaluate the differences between the two groups. All other variables (lip pressure, number of chewing cycles, duration of chewing sequence and number of pieces of food comminution test, variance of hue of mixing ability test, number of bites, cycles, and swallows of TOMASS test, the total score of JFLS, mastication, jaw mobility and verbal and emotional communication of JFLS) were skewed, thus Mann–Whitney U-test was chosen for the analysis.

All participants were able to perform all the clinical tests in reliable manner without any difficulty. However, one participant swallowed the test food during the food comminution test only after seven chewing cycles. Therefore, the participant was asked to repeat the task and spit out the chewed test food only after seven chewing cycles. The lip pressure in most participants was not reliable therefore it was excluded from the analysis and has not been reported.

Orofacial muscle strength

The mean MVBF for the experimental group was 307.9 ± 137.9 and control group was 411 ± 162.2. The mean tongue pressure for the experimental group was 42.8 ± 10.8 and control group was 47.2 ± 16.3. The mean cheek pressure for the experimental group was 20 ± 7.1 and control group was 19.8 ± 5.3. The results of the statistical analysis showed significantly lower MVBF in the experimental group compared to the control group (P = 0.009). However, there was no statistically significant differences in the tongue (P = 0.208) and cheek pressure (P = 0.925) between the two groups.

Masticatory efficiency

The mean number of chewing cycles and the duration of chewing sequence was 21.2 ± 10.1 and 18.2 ± 6.8, respectively for the experimental group. Similarly, the mean number of chewing cycles and the duration of chewing sequence was 23.2 ± 10.9 and 19.5 ± 9.7, respectively for the control group. However, there was no significant difference in the chewing cycles (P = 0.490) and the duration of chewing sequence (P = 0.714) between the two groups

Masticatory performance

The mean number of pieces of the food comminution test for the experimental group was 3.5 ± 2.4 and 4.5 ± 4.4 for the control group. The mean number of Variance of hue (VOH) of mixing ability test for the experimental group was 0.24 ± 0.14 and control group was 0.20 ± 0.07. The results of the statistical analysis showed no significant difference between the two groups in either the food comminution (P = 0.553) or the mixing ability test (P = 0.269)

Swallowing Function

The mean number of bites, chewing cycles, number of swallows and total time of TOMASS test for the experimental group was 2.7 ± 0.9, 33.4 ± 7.9, 2.8 ± 0.8 and 33.1 ± 8.4 and control group was 2.1 ± 0.6, 32.6 ± 9.7, 2.5 ± 0.9 and 30.6 ± 9.2 respectively. The results of the statistical analysis showed significantly higher number of bites (P = 0.003) in experimental group compared to the control group. However, there was no statistically significant differences between the two groups in chewing cycles (P = 0.855), number of swallows (P = 0.149) and total time (P = 0.275).

Subjective assessment

The mean total JFLS-20 score for the experimental group was 14.2 ± 17.8 and 11.1 ± 15.9 for the control group. The results of the statistical analysis showed no significant difference between the two groups in the total score of JFLS-20 (P = 0.623). The mean score of mastication, jaw mobility, and verbal and emotional communication of JFLS-20 for the experimental group was 3.7 ± 5.0, 2 ± 3.9 and 7.6 ± 11.4 and control group was 3.2 ± 5.4, 1.6 ± 3.0 and 6.2 ± 9.2 respectively. The results of the statistical analysis showed no significant difference between the two groups in mastication (P = 0.453), jaw mobility (P = 0.734) and verbal and emotional communication (P = 0.988).

A summary of the mean and SD of all the measured variables are presented in Table 2.

The study showed that the MVBF was significantly lower in patients indicated for orthodontic treatment than the age and sex-matched control group not indicated for orthodontic treatment. However, the results also showed that there were no significant differences in the tongue pressure, cheek pressure, masticatory efficiency and performance, and subjective assessment of jaw function. The results also showed no significant differences in the swallowing function except for number of bites in the TOMASS test. Overall, the results of the current study imply that patients indicated for orthodontic treatments show poor orofacial muscle strength in terms of lower bite force compared to the age matched controls. However, the patient groups do not show any signs of impaired masticatory or swallowing function.

Orofacial muscle strength (including bite force) is an indicator of functional state of the masticatory system [31, 32]. The current study showed that orofacial muscle strength parameters were similar in both group except for MVBF. Previous studies have shown lower MVBF in children with malocclusions [33–36]. For example, it was reported that children with class I or II malocclusion had lower maximum bite force than children with normal occlusion [35]. Another study showed that children in mixed dentition with posterior crossbite had lower maximum bite force than non-crossbite children [33, 34]. Similarly, patients with posterior crossbite tend to show lower maximum voluntary bite force than healthy counterparts with normal occlusion [36]. Therefore, children with malocclusions and indicated for orthodontic treatment show decreased orofacial muscle strength and in terms of lower MVBF in comparison to children not indicated for orthodontic treatment.

The results of the current study also showed that there was no significant difference in the tongue and cheek pressure between the two groups. These findings are consistent with previous studies which have shown that tongue and cheek pressures in patients with class II division 2 malocclusion was not different in comparison to a control group [37]. However, it has also been shown that cheek pressure increases significantly in patients who have had maxillary constrictions after rapid maxillary expansion in comparison to pretreatment phase [38]. The reason for finding no significant differences in tongue and cheek pressure in the current study maybe due to the different types, degree, and severity of malocclusion in the current patient group (mentioned below).

Findings from the previous studies have shown that individuals with normal occlusion have better masticatory performance than those who were treated and untreated malocclusion [39]. Children with anterior open bite tend to have lower masticatory performance compared to children without open bite [40]. It has been reported that chewing efficiency and swallowing function were worse in individuals with malocclusion, especially if the malocclusion was severe [41]. One study showed that children with normal occlusion had better masticatory efficiency and ability than class II malocclusion [42]. Another study presented that individuals with normal occlusion had better masticatory performance than individuals with malocclusion [43]. However, our findings show that participants indicated for orthodontic treatment and the control group had similar masticatory efficiency and performance. Although these findings contradict some of the earlier findings, yet they are consistent with some of the other previous studies. For example, it has been shown that mild form of class I and II malocclusion have little or no impact on masticatory performance [44]. Further, another study concluded that individuals with malocclusion were similar to normal cases in masticatory performance except for class III cases [45]. Therefore, it is suggested that orofacial muscle strength (lip, cheek, and tongue), masticatory and swallowing function may be affected differently with different degrees, severity, and specific diagnosis of malocclusion. The participants who were indicated for orthodontic treatment in the current study had various kinds of malocclusions with different severity based on Socialstyrelsens index. Therefore, no differences were observed between the individuals indicated for orthodontic treatment and their controls. It is suggested that future studies should consider proper stratification of the study population based on the diagnosis and severity of malocclusion.

The hard viscoelastic food comminution test has shown promising results to evaluate masticatory performance in older people with dental implants [15, 46]. The hard viscoelastic test food used in the current study is perceived to be more difficult and complex to chew compared to other (plastic) foods, as they require more chewing and more muscle effort [22] compared to other test foods. Moreover, the hard viscoelastic test food requires stronger jaw muscle activity and greater degree of jaw sensorimotor control during chewing [5, 13, 47]. Therefore, it is suggested that the food comminution test along with other previously used tests such as two-color chewing gum mixing ability test and measures of orofacial muscle strength could be good clinical indicators of the state of the masticatory system of the patients undergoing orthodontic treatment.

Test of mastication and swallowing solids (TOMASS) was developed for use in a treatment study for swallowing impairment associated with Parkinson’s disease [48]. It was presented as a reliable emerging clinical tool for quantification of solid bolus ingestion [49]. Up to date, no previous studies have investigated the swallowing function in relation with malocclusion. Our results showed that swallowing function was not significantly different between the two groups except for number of bites to eat the cracker. Even though there is significant difference in the number of bites to eat the cracker, the difference does not seem to have a greater clinical relevance. However, the mean numbers of each parameter in TOMASS test in the current study are close to the normative data of children in Italy and Portugal even though the type of cracker used in Italy and Portugal was different than the cracker used in our study [49–52]. Therefore, it is inferred that the participants in the current study do not show any signs of swallowing problems or impairments.

The subjective assessment of mastication, jaw mobility and verbal and emotional communication domains from the JFLS showed no significant difference between the two groups. Both groups showed no major limitation in JFLS. It was reported that the prevalence for each item of JFLS in the adult Swedish community was low [53]. Further, age and gender had no influence on the jaw function limitations [53]. Previous study compared jaw function limitation scale among different orofacial conditions [30]. It was shown that Temporomandibular disorder had the highest limitation in mastication and jaw mobility followed by malocclusion, burning mouth syndrome and Sjogren syndrome while Temporomandibular disorder and malocclusion had the highest limitation in verbal and emotional communication [30]. Therefore, the study group does not present any clinical signs of TMD or orofacial pain and hence does not report any limitation of jaw function.

In conclusion, children indicated for orthodontic treatments based on the Socialstyrelsen criteria do show signs of poor orofacial muscle strength in terms of lower bite force compared with the age and sex matched controls. However, the patient groups do not show any signs of impaired masticatory or swallowing function. It is suggested that the orofacial muscle strength, masticatory and swallowing function may be dependent on the different degrees/types or the severity of malocclusions. It is also suggested that the orthodontic evaluation for treatment allocation would benefit if the above-mentioned objective measures of the functioning state of the masticatory systems are incorporated in the diagnosis procedures, and MVBF could be a simple and useful tool to evaluate the orthodontic treatment needs.

Ethics approval and consent to participate.

The study was carried out in accordance with the declaration of Helsinki II and was approved by the Regional Ethical Review Board, (Dnr 2021/01044), Stockholm, Sweden.

Consent for publication

Informed consents were obtained from either the participants or/and their parents.

Availability of data and material

Upon reasonable request, data can be obtained from the corresponding author.

Competing interests

All authors declare that they do not have any competing interests or any conflict of interests.

Funding

The research project is supported by grants from Stockholm County Council and Karolinska Institutet (SOF: Styrgruppen för Odontologisk Forskning) and Karolinska Institutet research foundation grants.

Authors' contributions

The study was conceived, designed, and directed by AK and AG. RA, MP and AS collected the data for the experimental and control group. RA and AK analysed the data and drafted the first draft. AS and MP designed the tables. All authors contributed and approved the final draft. AG was overall responsible for the conduct and supervision of the study.

Acknowledgments

Sincere gratitude is expressed to King Abdelaziz University, Saudi Cultural Office in Berlin for their support. The authors thank Hanan Omairi and Stephanie Ammerman for their help in recruiting the participants.

Peyron, M.A., et al., Oral declines and mastication deficiencies cause alteration of food bolus properties. Food & function, 2018. 9(2): p. 1112-1122.
Peyron, M.A., et al., Age-related changes in mastication. Journal of oral rehabilitation, 2017. 44(4): p. 299-312.
Al-Manei, K., et al., Food Hardness Modulates Behavior, Cognition, and Brain Activation: A Systematic Review of Animal and Human Studies. Nutrients, 2023. 15(5).
Grigoriadis, A., et al., Effect of Sudden Deprivation of Sensory Inputs From Periodontium on Mastication. Frontiers in neuroscience, 2019. 13: p. 1316-1316.
Grigoriadis, A., R.S. Johansson, and M. Trulsson, Adaptability of mastication in people with implant-supported bridges. J Clin Periodontol, 2011. 38(4): p. 395-404.
van der Bilt, A., et al., Oral physiology and mastication. Physiology & Behavior, 2006. 89(1): p. 22-27.
Almotairy, N., et al., Developmental and age-related changes in sensorimotor regulation of biting maneuvers in humans. Physiology & behavior, 2020. 219: p. 112845.
Almotairy, N., et al., Age-related changes in oral motor-control strategies during unpredictable load demands in humans. European journal of oral sciences, 2020. 128(4): p. 299-307.
Almotairy, N., et al., Development of the jaw sensorimotor control and chewing - a systematic review. Physiology & Behavior, 2018. 194: p. 456-465.
Tsai, H.H., Maximum bite force and related dental status in children with deciduous dentition. J Clin Pediatr Dent, 2004. 28(2): p. 139-42.
Kaur, H., et al., Effect of various malocclusion on maximal bite force- a systematic review. J Oral Biol Craniofac Res, 2022. 12(5): p. 687-693.
Brennan, D.S., A.J. Spencer, and K.F. Roberts-Thomson, Tooth loss, chewing ability and quality of life. Qual Life Res, 2008. 17(2): p. 227-35.
Almotairy, N., A. Kumar, and A. Grigoriadis, Effect of food hardness on chewing behavior in children. Clin Oral Investig, 2021. 25(3): p. 1203-1216.
Almotairy, N., A. Kumar, and A. Grigoriadis, Motor control strategies during unpredictable force control tasks in humans. Journal of Oral Rehabilitation, 2020. 47(10): p. 1222-1232.
Homsi, G., et al., Subjective and objective evaluation of masticatory function in patients with bimaxillary implant-supported prostheses. J Oral Rehabil, 2023. 50(2): p. 140-149.
Weinstein, S., et al., On An Equilibrium Theory Of Tooth Position. The Angle Orthodontist, 1963. 33(1): p. 1-26.
PROFFIT, W.R., Equilibrium Theory Revisited: Factors Influencing Position of the Teeth. The Angle Orthodontist, 1978. 48(3): p. 175-186.
Alshammari, A., et al., Effect of malocclusion on jaw motor function and chewing in children: a systematic review. Clinical Oral Investigations, 2022. 26(3): p. 2335-2351.
Linder-Aronson, S., Orthodontics in the Swedish Public Dental Health Service. Trans Eur Orthod Soc, 1974: p. 233-40.
Bates, J.F., G.D. Stafford, and A. Harrison, Masticatory function - a review of the literature. III. Masticatory performance and efficiency. J Oral Rehabil, 1976. 3(1): p. 57-67.
Grigoriadis, A., et al., Effect of Sudden Deprivation of Sensory Inputs From Periodontium on Mastication. Front Neurosci, 2019. 13: p. 1316.
Peyron, M.A., C. Lassauzay, and A. Woda, Effects of increased hardness on jaw movement and muscle activity during chewing of visco-elastic model foods. Exp Brain Res, 2002. 142(1): p. 41-51.
Homsi, G., et al., Assessment of masticatory function in older individuals with bimaxillary implant-supported fixed prostheses or with a natural dentition: A case-control study. J Prosthet Dent, 2021.
Wallace, S., et al., Impact of prosthodontic rehabilitation on the masticatory performance of partially dentate older patients: Can it predict nutritional state? Results from a RCT. J Dent, 2018. 68: p. 66-71.
Silva, L.C., et al., Reliability of a two-colour chewing gum test to assess masticatory performance in complete denture wearers. J Oral Rehabil, 2018. 45(4): p. 301-307.
Schimmel, M., et al., A novel colourimetric technique to assess chewing function using two-coloured specimens: Validation and application. J Dent, 2015. 43(8): p. 955-64.
Schimmel, M., et al., A two-colour chewing gum test for masticatory efficiency: development of different assessment methods. J Oral Rehabil, 2007. 34(9): p. 671-8.
Lund, J.P. and A. Kolta, Generation of the central masticatory pattern and its modification by sensory feedback. Dysphagia, 2006. 21(3): p. 167-74.
Larsson, P., Methodological studies of orofacial aesthetics, orofacial function and oral health-related quality of life. Swed Dent J Suppl, 2010(204): p. 11-98.
Ohrbach, R., P. Larsson, and T. List, The jaw functional limitation scale: development, reliability, and validity of 8-item and 20-item versions. J Orofac Pain, 2008. 22(3): p. 219-30.
Koc, D., A. Dogan, and B. Bek, Bite force and influential factors on bite force measurements: a literature review. Eur J Dent, 2010. 4(2): p. 223-32.
Bakke, M., Bite Force and Occlusion. Seminars in Orthodontics, 2006. 12(2): p. 120-126.
Castelo, P.M., et al., Maximal bite force, facial morphology and sucking habits in young children with functional posterior crossbite. J Appl Oral Sci, 2010. 18(2): p. 143-8.
Castelo, P.M., et al., Masticatory muscle thickness, bite force, and occlusal contacts in young children with unilateral posterior crossbite. Eur J Orthod, 2007. 29(2): p. 149-56.
Roldán, S.I., et al., Are maximum bite forces of subjects 7 to 17 years of age related to malocclusion? Angle Orthod, 2016. 86(3): p. 456-61.
Sonnesen, L., M. Bakke, and B. Solow, Bite force in pre-orthodontic children with unilateral crossbite. Eur J Orthod, 2001. 23(6): p. 741-9.
Partal, I. and M. Aksu, Changes in lips, cheeks and tongue pressures after upper incisor protrusion in Class II division 2 malocclusion: a prospective study. Prog Orthod, 2017. 18(1): p. 29.
Halazonetis, D.J., E. Katsavrias, and M.N. Spyropoulos, Changes in cheek pressure following rapid maxillary expansion. Eur J Orthod, 1994. 16(4): p. 295-300.
Henrikson, T., E. Ekberg, and M. Nilner, Can orthodontic treatment improve mastication? A controlled, prospective and longitudinal study. Swed Dent J, 2009. 33(2): p. 59-65.
Corrêa, E.C., et al., Masticatory evaluation of anterior open bite malocclusion using the colorimetric capsule method. Gen Dent, 2018. 66(6): p. 56-59.
Freitas, H.V., et al., Alterations of oral functions and dental malocclusions in adolescents: a cross-sectional population-based study. Cien Saude Colet, 2021. 26(suppl 3): p. 5261-5272.
Henrikson, T., E.C. Ekberg, and M. Nilner, Masticatory efficiency and ability in relation to occlusion and mandibular dysfunction in girls. Int J Prosthodont, 1998. 11(2): p. 125-32.
English, J.D., P.H. Buschang, and G.S. Throckmorton, Does malocclusion affect masticatory performance? Angle Orthod, 2002. 72(1): p. 21-7.
Barrera, L.M., et al., Mixed longitudinal evaluation of masticatory performance in children 6 to 17 years of age. Am J Orthod Dentofacial Orthop, 2011. 139(5): p. e427-34.
Shiere, F.R. and R.S. Manly, The effect of the changing dentition on masticatory function. J Dent Res, 1952. 31(4): p. 526-34.
Homsi, G., et al., Assessment of masticatory function in older individuals with bimaxillary implant-supported fixed prostheses or with a natural dentition: A case-control study. The Journal of Prosthetic Dentistry, 2021.
.
Athukorala, R.P., et al., Skill training for swallowing rehabilitation in patients with Parkinson's disease. Arch Phys Med Rehabil, 2014. 95(7): p. 1374-82.
Frank, U., et al., International standardisation of the test of masticating and swallowing solids in children. J Oral Rehabil, 2019. 46(2): p. 161-169.
Huckabee, M.L., et al., The Test of Masticating and Swallowing Solids (TOMASS): reliability, validity and international normative data. Int J Lang Commun Disord, 2018. 53(1): p. 144-156.
Krishnamurthy, R., et al., The Test of Masticating and Swallowing Solids (TOMASS): Normative data for the adult Indian population. Data Brief, 2021. 35: p. 106958.
Hägglund, P., et al., The Test of Masticating and Swallowing Solids (TOMASS): Normative data for two crackers available in the Scandinavian and international markets. Int J Speech Lang Pathol, 2021. 23(3): p. 329-337.
Oghli, I., et al., Prevalence and normative values for jaw functional limitations in the general population in Sweden. Oral Dis, 2019. 25(2): p. 580-587.

Table 01

Distribution of children indicated for orthodontic treatment with respect to sagittal, vertical, and transverse relationship.
Variable	Study Group (%)
Sagittal relationship
Class I malocclusion	52
Class II malocclusion	45
Class III malocclusion	3
Vertical relationship
Normal overbite	45
Deep bite	45
Open bite	10
Transverse relationship
Crossbite*	29
Normal	71
*Anterior and posterior crossbite

Table 02

Summary of the mean and standard deviation (SD) of all the measured variables.
Variable	Study Group (Mean ± SD)	Reference group (Mean ± SD)	P value
Demographic and physical characteristics
Age	14.9 ± 2.8	15.2 ± 2.3	P = 0.394
Sex	16 Boys, 15 Girls	16 Boys, 15 Girls
Orofacial muscle strength
Bite force	307.9 ± 137.9	411 ± 162.2	P = 0.009
Tongue pressure	42.8 ± 10.8	47.2 ± 16.3	P = 0.208
Cheek pressure	20 ± 7.1	19.8 ± 5.3	P = 0.925
Masticatory function
Chewing cycles (n)	21.2 ± 10.1	23.2 ± 10.9	P = 0.490
Chewing duration	18.2 ± 6.8	19.5 ± 9.7	P = 0.714
Comminution test (n)	3.5 ± 2.4	4.5 ± 4.4	P = 0.553
Mixing ability (VOH)	0.24 ± 0.14	0.20 ± 0.07	P = 0.269
Swallowing function
TOMASS bites (n)	2.7 ± 0.9	2.1 ± 0.6	P = 0.003
TOMASS chewing cycles (n)	33.4 ± 7.9	32.6 ± 9.7	P = 0.855
TOMASS swallow (n)	2.8 ± 0.8	2.5 ± 0.9	P = 0.149
TOMASS time (sec)	33.1 ± 8.4	30.6 ± 9.2	P = 0.275
Subjective evaluation (JFLS-20)
Total score	14.2 ± 17.8	11.1 ± 15.9	P = 0.623
Mastication	3.7 ± 5.0	3.2 ± 5.4	P = 0.453
Jaw mobility	2 ± 3.9	1.6 ± 3.0	P = 0.734
Verbal and emotional communication	7.6 ± 11.4	6.2 ± 9.2	P = 0.988
TOMASS: Test of masticating and swallowing solids, VOH: Variance of hue, JFLS: Jaw function limitation scale

No competing interests reported.

Assessment of orofacial muscle strength, masticatory and swallowing function in children indicated for orthodontic treatment.

Status:

Version 1

Abstract

Objectives

Materials and Method

Results

Conclusions

Clinical relevance:

Introduction

Material and Methods

Study participants

Study protocol

Objective assessments

Orofacial muscle strength

Maximum voluntary bite force

Tongue pressure, Lip pressure and Cheek pressure

Masticatory efficiency and performance

Food comminution text

Mixing ability test

Swallowing Function

Test of masticating and swallowing solids

Subjective assessment

Jaw function limitation scale

Statistical analysis

Results

Orofacial muscle strength

Masticatory efficiency

Masticatory performance

Swallowing Function

Subjective assessment

Discussion

Declarations

References

Tables

Additional Declarations

Status:

Version 1