Evaluation of objective masticatory performance: an experimental study in healthy adults

Abstract

This study aimed to objectively assess masticatory performance and to identify related factors among healthy adults. An experimental study was conducted on 75 healthy adults with a mean age of 51 years between January and June 2023. Masticatory performance was objectively assessed using the sieve method. Spearman correlation examined the association between masticatory performance and age, Functional Tooth Units (FTUs), and total Oral Behavior Checklist-21 (OBC-21) scores. Mann–Whitney U test was used to examine its relationship with sex. Linear Regression was performed to test each factor’s relationship with masticatory performance after controlling for other factors. Masticatory performance was associated with age (Spearman coefficient: -0.35, p = 0.002), and FTUs (Spearman coefficient: 0.66, p < 0.001), with higher FTU scores associated with a 30% improvement in chewing performance. Sex and OBC scores showed no significant effect on mastication performance. Multiple linear regression confirmed strong association between masticatory performance and FTUs (standardized ß = 0.670, p < 0.001). FTUs is the major determinant of masticatory performance. Restoring and preserving FTUs through dental care can significantly improve mastication, nutrition, and quality of life, particularly for older individuals.

Supplementary Information

The online version contains supplementary material available at 10.1007/s44445-025-00022-1.

Introduction

Mastication or chewing, is the process of breaking food into smaller, more digestible particles (Mishra et al. 2024; Sekundo et al. 2024). Such critical digestive procedure facilitates the mechanical breakdown of food increasing the surface area for enzymatic activity, and hence result in improved nutrient absorption (Bilt 2011; Chen et al. 2022; Mosca et al. 2015). Beyond its digestive role, mastication has significant implications for oral health, systematic health, and psychological well-being (Miquel-Kergoat et al. 2015; Hollis 2018; Kubo et al. 2015; Krishnamoorthy et al. 2018; Roohafza et al. 2016; Yamamoto and Shiga 2018).

Masticatory Performance (MP) refers to the ability of the oral apparatus to effectively crush, grind, and prepare food for swallowing and subsequent digestion after a predetermined number of mastication cycles (Bates et al. 1976; Gonçalves et al. 2021). MP is influenced by several factors including the condition of dentition, structural integrity of the oral cavity, functional capacity of the perioral muscles and the maximum bite force (Fan et al. 2023; Kosaka et al. 2018; Révérend et al. 2014).

Among these determinants, Functional Tooth Units (FTUs) emerge as a crucial measure of MP, reflecting the functional interaction between opposing teeth during chewing (Fan et al. 2023; Oohira et al. 2024; Bourdiol et al. 2020). FTUs take into account not only the presence of teeth but also their functional cooperation, providing a more comprehensive understanding of MP (Oohira et al. 2024; Bourdiol et al. 2020).

The distinction between performance and efficiency of mastication is pivotal. MP is used when “individuals are asked to chew or grind food for a predetermined chewing strokes” (Bates et al. 1976; Gonçalves et al. 2021; The Glossary of Prosthodontic Terms 2017). In contrast, efficiency refers to “the number of chewing cycles necessary to attain half of the original particle size” (Gonçalves et al. 2021; The Glossary of Prosthodontic Terms 2017; Glas et al. 2020). Therefore, masticatory performance reflects the individuals’ ability to break down food within a set number of strokes (Gonçalves et al. 2021), which highlights the capacity to achieve effective food breakdown under specific conditions or constraints.

Assessment of MP includes both subjective and objective evaluations (Gonçalves et al. 2021; Homsi et al. 2023; Elgestad Stjernfeldt et al. 2017). One of the objective techniques used is the sieve method which allows practitioners to quantitatively assess and classify patients according to their masticatory performance, represented by the percentage of food passing through the sieve (Ohara et al. 2003; Oliveira et al. 2014; Al-Ali et al. 1999). Previous studies have shown that individuals with reduced FTUs usually exhibit lower ability to masticate food, while those with higher FTUs were able to masticate more effectively and reported better health outcomes and enhanced quality of life (Fukuda et al. 2021; Tan et al. 2016; Milledge et al. 2021; Nedeljković et al. 2023).

FTUs are not only significant contributor to maintaining individual health, it also affects a broad range of public health issues related to aging, socioeconomic factors, and access to dental care (Lyu et al. 2024). As populations age and oral health problems become more prevalent, maintaining an adequate number of functional tooth units becomes more challenging. However, it remains essential for proper nutrition, overall health, and sustaining quality of life (Naka et al. 2014; Cheng et al. 2023; Gil-Montoya et al. 2015; Adiatman et al. 2013). Despite the growing recognition of FTUs’ importance, majority of the studies have assessed this context among old populations (Cardoso et al. 2019; Chan et al. 2024). Although FTUs are known to have an impact on the MP, there is currently no empirical data establishing a direct relationship between FTUs and MP using the sieve method.

Furthermore, previous studies have demonstrated that age and sex can influence masticatory performance (MP) (Sekundo et al. 2024; Kosaka et al. 2018; Roccuzzo et al. 2025; Sano and Shiga 2021; Shiga et al. 2012). However, to date, no research has specifically investigated the direct relationship between MP as measured using the hard food sieve method and the influence of these demographic factors. As for oral behaviors, the Oral Behaviors Checklist 21 (OBC-21), a reliable self-reported instrument, is widely used to assess the frequency of parafunctional activities such as teeth clenching and grinding (Schiffman et al. 2014; Markiewicz et al. 2006). Such tool has been extensively applied in the context of Temporomandibular Disorders (TMDs) (Donnarumma et al. 2021; Bano et al. 2024; Zhong et al. 2024), though its association with MP in healthy individuals without TMD has not yet been explored.

Thus, the aim of this study was to assess MP among healthy adults using objective sieve method and to examine the relationship between MP and Functional Tooth Units (FTUs) in addition to other factors, including age, sex, and oral behaviors.

It is hypothesized that individuals with higher FTU scores will show enhanced MP compared to those with lower FTU scores, with a secondary objective of evaluating potential differences in MP based on sex, age, and total OBC-21 scores.

Materials and methods

An experimental study was conducted to assess MP using the sieve method among 75 healthy adults. Participants were approached at a University Clinic for general dental care in Trieste, Italy, between January 2023 and June 2023. In order to be eligible to take part in this study, individuals were required to meet the following inclusion criteria: good general health, defined as the absence of serious chronic conditions or acute illnesses that could interfere with daily functioning; exhibiting periodontal health with a Periodontal Screening and Recording (PSR) score of < 3; and being over 20 years with no upper age limit. Participants with implants and/or fixed prostheses were included in the study, whereas those wearing removable dentures were excluded. Individuals who did not meet these criteria were excluded from the study. Upon recruitment, sex balance was ensured to account for potential differences and maintain a representative sample. All participants were assessed by an orofacial pain expert according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) (Schiffman et al. 2014). None of the participants exhibited any limitation or pain in the Temporomandibular Joints (TMJs) or muscles upon performing mastication in addition to the absence of joint sounds during mastication.

The study adhered to ethical guidelines and was granted ethical approval from the Research and Ethics Committee (REC) of the Ateneo Units (IRB number: 125/24102022). All procedures were performed in conformity with the Declaration of Helsinki by the World Medical Association for medical research involving human participants (World Medical Association 2013; Shrestha and Dunn 2020). Only those who provided written informed consent were included.

Sample size calculation

The sample size was calculated based on a multiple linear regression model using G*Power version 3.1 (Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany). The required sample size was 43, calculated with an anticipated medium effect size (f² = 0.15), an alpha level (α) of 0.05, a desired power of 80%, and four predictors. To account for a 20% expected dropout rate, the total required sample size was increased to 52 participants. To ensure robust data for subgroup analysis, the final sample size was expanded to 75 participants. The larger sample size provides greater precision in the estimation of effects and enhances the generalizability of the findings.

Assessment of Masticatory Performance

The test food chosen was raw carrot, prepared in cylindrical samples measuring 1 cm in thickness and 2 cm in diameter. Parallel to recommendations from previous studies, the central part of the carrot was used to maintain consistent texture and composition (Woda et al. 2010).

Upon collecting the chewed samples, laboratory containers with lids were used. For the analysis, the single sieve method was chosen using a two-sieve system. The upper sieve had a mesh size of 4 mm in diameter (Fig. 1), while the lower sieve contained fine meshes designed to capture only the smallest fragments (Fig. 2). This filtration process, resembling a “waterfall” effect, ensured the separation of fine particles. The volume of the sieved fragments was then measured using a graduated syringe (Elgestad Stjernfeldt et al. 2017; Bilt and Fontijn-Tekamp 2004).

Fig. 1.

Upper sieve with 4 mm mesh size

Fig. 2.

Lower sieve with fine meshes designed to capture only the smallest fragments

Patients were instructed to chew the carrot sample for 20 strokes (Bonnet et al. 2019). Afterwards, the chewed sample was collected, and participants rinsed their mouths with 150–200 ml of water, which was also collected for analysis (Bonnet et al. 2019).

The chewed sample was passed through the sieve with the 4 mm diameter mesh under a constant water jet to separate the fragments. The filtered fragments were collected, and their volume was measured. Finally, the percentage of fragments that passed through the sieve was calculated, providing the masticatory performance for each participant (Bilt and Fontijn-Tekamp 2004; Bonnet et al. 2019).

Assessment of Functional Tooth Units (FTUs)

During the physical examination, Functional Tooth Units (FTUs) were evaluated. Natural teeth, implants, and fixed prostheses were considered, with the assessment focusing exclusively on posterior teeth, including premolars and molars, while excluding third molars.

In order to describe the differences between MP and FTUs, participants were divided into 2 groups based on their FTU count. Group 1 comprised participants with more than 7 FTUs, while Group 2 included those with 7 or fewer FTUs.

Assessment of oral behaviors

To evaluate the impact of oral habits on MP, patients were asked to complete the Italian version of the"Oral Behavior Checklist-21"(OBC-21) (Ohrbach 2014). This tool was originally validated in English to collect data on the prevalence and frequency of oral habits (Markiewicz et al. 2006). The OBC-21 has been translated and culturally adapted into multiple languages, including Portuguese, Italian, German, and Malaysian (Schiffman et al. 2014; Ohrbach 2014; Barbosa et al. 2018; John et al. 2006; Tedin Ng et al. 2022; Donnarumma et al. 2018; Österlund et al. 2018). The OBC-21 consists of 21 items, which are divided into two categories: sleep-time behaviors and awake-time behaviors. Each item is rated on a 5-point scale (0 to 4) based on the frequency of the behavior over the past month. Sleep-time behaviors are rated from"none of the time"to"4–7 nights/week,"while wake-time behaviors range from"none of the time"to"all of the time."The total score, ranging from 0 to 84, is obtained to categorize patients’ risk levels:"No risk"(score of 0),"Low risk"(scores 1–24), and"High risk"(scores 25–84). Refer to the supplementary file for detailed OBC-21.

Statistical analysis

The Shapiro–Wilk test was used to examine the normality of the data. The test indicated a significant p-value (0.016), which implies that the dependent variable (MP) does not follow a normal distribution. Descriptive statistics were reported for continuous variables as means ± standard deviations, while categorical variables were presented as frequencies and percentages. Spearman’s correlation was employed to assess the relationship between MP and key factors, including age, FTUs, and total OBC-21 scores. Mann–Whitney U was employed to assess the relationship between MP and sex. Multiple Linear Regression analyses were performed to test each factor’s relationship with MP. All statistical analyses were performed using SPSS version 26 (IBM Corp., Armonk, NY, USA). A p-value < 0.05 was considered statistically significant.

Results

A total of 75 participants were included in the study. As per sex, 49.3% were females (37 participants), and 50.7% were males (38 participants). The mean age of the participants was 51 years (SD ± 17.4).

To describe the differences between MP and FTUs, participants were categorized into 2 groups. Group 1 included 49 participants with FTUs greater than 7, while Group 2 consisted of 26 participants with FTUs equal to or less than 7. The mean FTUs for Group 1 was 10.51 (SD ± 1.58), whereas for Group 2, the mean FTUs was 4.73 (SD ± 1.73). The MP, represented by the percentage of food passing through the sieve, was significantly higher in Group 1 (51.4%) compared to Group 2 (22.0%). This resulted in an average difference of 30% in the percentage of food passing through the sieve between the two groups, emphasizing the relationship between FTUs and MP. Detailed results are presented in Table 1.

Table 1.

Group statistics for FTUs and % of food passed

Statistics	Group	FTUs	% of food passed through the sieve
Mean	1	10.51	51.4
	2	4.73	22.0
Median	1	10.0	52.9
	2	5.00	20.3
Standard deviation	1	1.58	18.3
	2	1.73	13.5
Minimum	1	8	12.0
	2	1	6.25
Maximum	1	12	84.6
	2	7	47.8

FTUs Functional Tooth Units

Correlation analysis was conducted to examine the relationship between MP, measured by the percentage of food passing through the sieve, and various factors. The analysis revealed a significant negative association between age and MP (r =  -0.35, p = 0.002), suggesting that as age increases, MP decreases. Additionally, a strong positive correlation was found between MP and FTUs (r = 0.66, p < 0.001), indicating that higher FTUs are associated with greater MP. In contrast, no significant correlation was observed between MP and OBC-21. Mann–Whitney U test showed no significant association between sex and MP. The detailed results of the bivariate analysis are presented in Table 2.

Table 2.

Association testing between masticatory performance (% food passed) and various factors (bivariate analysis)

Variable	Test	P-value
Age	Spearman’s Correlation	0.002, r = -0.35
FTUs	Spearman’s Correlation	< 0.001, r = 0.66
Total OBC-21 Score	Spearman’s Correlation	0.19
Sex	Mann–Whitney U	0.633

FTUs Functional Tooth Units, OBC-21 Oral Behaviors Checklist-21

Further analysis using a linear regression model (Table 3) revealed that MP was only affected by the total number of FTUs (standardized ß = 0.670, p < 0.001).

Table 3.

Results of multiple linear regression of factors associated with masticatory performance

Outcome variable	Predictor variable	ß	Standardized ß	p-values	95% Confidence Interval Lower bound Upper Bound		VIF
Masticatory Performance (% food passed)	Age	0.07	0.05	0.61	- 0.21	0.35	1.71
	FTUs	4.62	0.68	< 0.001	3.16	6.09	1.51
	Total OBC-21	0.23	0.10	0.25	- 0.17	0.63	1.16

FTUs Functional Tooth Units, OBC-21 Oral Behavior Checklist-21

Discussion

The study findings provide strong evidence that Functional Tooth Units (FTUs) are crucial to MP. The significant, strong positive correlation between FTU scores and the percentage of food passing through the sieve emphasizes the need for functional dentition to ensure effective food breakdown. These results are in conformity with other studies that have highlighted the relationship between FTUs and mixing ability index, nutrient intake, quality of life, and overall health, especially in the older population (Fukuda et al. 2021; Tan et al. 2016; Milledge et al. 2021; Kim 2021). Furthermore, the observed 30% difference in food passage between the high- and low-FTU groups further highlights the benefits of maintaining a higher number of FTUs for achieving optimal mastication and improving nutritional outcomes.

Age was found to have an impact on MP, where increased age was found to affect oral function and resulted in poorer MP (Sekundo et al. 2024; Kosaka et al. 2018; Roccuzzo et al. 2025). However, age was not found to be truly significant when performing regression analysis, suggesting that FTUs, which decrease upon aging, are the major determinant for MP. Previous studies have shown that the decline in MP among the aging population can be explained by various contributing factors, including tooth loss, decreased occlusal force, changes in the quality and quantity of saliva, and motor impairments (Peyron et al. 2017; Iyota et al. 2020; Xu et al. 2019).

On the other hand, the study results demonstrate the lack of relationship between MP and oral behaviors. Such findings suggest that while oral habits are prevalent and have proven their relevance to Temporomandibular Disorders (TMDs) (Donnarumma et al. 2021), they may not directly affect the mechanical performance of mastication. However, oral behaviors like clenching and unilateral chewing, often associated with psychological stress (Bano et al. 2024; Zhong et al. 2024), could have long-term consequences on masticatory function.

The study also found no significant correlation between MP and sex. Although previous studies have highlighted sex-related differences in MP, particularly in terms of the amount of glucose extracted and maximal occlusal bite force (Sano and Shiga 2021; Shiga et al. 2012), none of these studies employed the sieve method to assess MP, which may explain the differences in the results.

This experimental study has employed a reliable and objective sieve method to assess MP; thus, the findings can be considered valid and reliable. Moreover, the sample size was further increased to ensure robust findings and strengthen the study results. Additionally, the balanced distribution between male and female participants helped control for sex as a potential confounding factor when analyzing the relationship between MP and other variables.

Despite these valuable insights, several limitations should be acknowledged. Upon assessment, the participants’ dietary history was not considered, and participants were required to chew the test food for predetermined stroke numbers regardless of individual variability in masticatory habits, thus acting as a potential confounding factors. Additionally, experimental settings vary from natural chewing conditions, compromising the ecological validity of the results. Moreover, assessing MP was limited to a single food type (raw carrot), limiting the generalizability of the findings to other foods with varying textures. The lack of orthodontic assessments, including malocclusion, arch integrity, and teeth alignment, further restricts the scope of conclusions. Finally, since the study was conducted among individuals residing in a single geographic area with similar food habits, applying those results to a diverse population may be constrained. Future research should address these limitations to provide a broader understanding of the factors affecting MP.

From a clinical perspective, interventions directed towards preserving or restoring FTUs, including fixed prostheses, dental implants, and preventive dental care, could significantly improve both oral and systemic health, as well as quality of life, especially in the aging population with higher rates of edentulism (Yamamoto and Shiga 2018; AlSaggaf et al. 2024). Promoting the need for routine dental visits among the general population could enhance the oral health-related outcomes and ensure the permanence of dental integrity (Mohd Khairuddin et al. 2024). Furthermore, as malocclusion can impair MP, preserving dental alignment and arch integrity through orthodontic interventions can gradually enhance performance by correcting misalignments (Zanon et al. 2022; Lee et al. 2023).

Conclusion

This study confirms the direct relationship between FTUs and MP and highlights the clinical implications for clinical practice, while no significant differences were found based on age, sex, or OBC-21 scores. Future research should explore FTUs'impact on other health outcomes, assess the role of malocclusion in masticatory function, and evaluate restorative interventions to improve MP.

Supplementary Information

Below is the link to the electronic supplementary material.

Abbreviations

DC/TMD

Diagnostic Criteria for Temporomandibular Disorders

FTUs

Functional Tooth Units

MP

Masticatory Performance

REC

Research and Ethics Committee

OBC-21

Oral Behavioral Checklist-21

PSR

Periodontal Screening and Recording

SD

Standard Deviation

TMDs

Temporomandibular Disorders

TMJs

Temporomandibular Joints

Authors’ contributions

Concept and design aspects were led by BR, MH, and LC. Data acquisition and statistical analysis were conducted by BR, MH, and MM. Analysis and interpretation of the data were performed collectively by BR, MH, MM, and LC. BR was responsible for drafting the manuscript which was critically revised for important intellectual content by MH, MM and LC. All authors reviewed and approved the final manuscript.

Funding

Not applicable.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declaration

Ethics approval and informed consent to participate

The study adhered to ethical guidelines and was granted ethical approval from the Research and Ethics Committee (REC) of the Ateneo Units (IRB number: 125/24102022) and adhered to ethical guidelines. All procedures were performed in conformity with the Declaration of Helsinki by the World Medical Association for medical research involving human participants. Participants were fully informed about the purpose and methods of the study, and only those who provided written informed consent were included.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.