Usefulness of an occlusal force device incorporating a microcomputer

Abstract

This study was conducted to clarify the usefulness of a newly developed occlusal force device. An arbitrary load was applied to the device 100 times, and the measured values were recorded. The loading and measured values were extremely close, and the error rate was fairly small. There was a close relationship between the occlusal force measured with a device based on the dental prescale and that measured using the new device. These results suggest that the newly developed device can measure and evaluate occlusal force with a degree of accuracy equivalent to the dental prescale.

Introduction

Occlusal force is an important and widely used index for objective evaluation of masticatory function. Currently, occlusal force is assessed in two ways: that for the entire dentition and that for individual teeth. In the former case, a dental prescale (GC Inc., Tokyo, Japan) is employed, but after measurement the data must be scanned and then analyzed, which is time consuming and requires extensive and expensive equipment. A simple alternative to the dental prescale is to count the number of remaining teeth without the use of instrumentation, but this method does not represent the occlusal force accurately.

To solve these problems, the authors have developed a prototype device that can measure occlusal force easily [Japanese Patent 5990552 B2, Sep 14, 2016] [1].

However, this had the disadvantage of requiring connection to a PC for measurement, and was unable to display occlusal force in real time. Therefore, a new device incorporating a microcomputer was developed. The device uses a program to estimate the actual occlusal force value from the value output by the sensor.

The purpose of the present study was to clarify the usefulness of the newly developed occlusal force device, and to investigate the loading and measured values after application of loads ranging from 100 N to 1,000 N. In addition, the maximum occlusal force of healthy dentate adults was measured and analyzed using the new device and a bite-force analysis system employing a dental prescale.

Materials and Methods

Outline of the newly developed occlusal force device

The newly developed occlusal force device (abbreviated hereafter as device A) was calibrated by applying measured values within a load range of 100-1,000 N to the sensor part of the device, and a program uploaded to the microcomputer was used to calculate and display the value of the applied load.

The sensor characteristics were estimated from the pre-recorded measured values, and a calculation formula suitable for the sensor was incorporated into the program, enabling highly precise calculation and display of the applied load value (Fig. 1).

Fig. 1 Newly developed occlusal force device

A: structure of the sensor part of the device, Ba: sensor body, Bb: After attaching the heat-shrunk cover, C: occlusal force device

Recording method

Experiment 1

A load between 100 N and 1,000 N was applied 100 times to the sensor part of device A using a load device, and the measured values were recorded.

Experiment 2

One hundred ninety-four healthy dentate adults with natural dentition (86 males, 108 females; age range 21-59 years; average age 42.6 years) participated. Informed consent was obtained from all of the subjects after they were provided with an explanation about the general nature of the study.

After selecting an appropriate size, the prescale (Dental Prescale II; GC Inc.) was inserted into the oral cavity to fit the entire dentition within the boundaries of the film. Subjects were asked to perform maximum clenching of the teeth for approximately 3 s at the intercuspal position. The maximum occlusal force was calculated using device B (Bite force analysis system; GC Inc.) with the filter ON to automatically clean the recorded data [2].

The occlusal force of the first molar was measured when the subject maintained maximum clenching for approximately 3 s using device A. The cover of device A was disposable and sterilized with ethylene oxide gas before measurement. Recordings were made with device A on both the right and left sides. The sum of the occlusal force on the habitual chewing side and the occlusal force on the non-habitual chewing side was calculated and taken as the maximum occlusal force.

Statistical analysis

All data were analyzed using statistical software (SPSS for Windows 27.0, IBM Corp., Armonk, NY, USA). First, the presence or absence of a correlation between load values and measured values was investigated, as well as the error rate ([measured value – load value]/load value). Next, the presence or absence of a correlation was investigated between the maximum occlusal forces of device A and device B. In addition, the presence or absence of a gender difference in the measured maximum occlusal force was investigated. The statistical methods used included the Shapiro-Wilk test to confirm normality, Pearson’s correlation coefficient for the relationship between the two devices, and independent t-tests for comparisons between males and females. All differences with a P-value of <0.05 were considered significant.

Results

Experiment 1: The 100 load values between 100 N and 1,000 N and the measured values were all extremely similar, and showed a significant positive correlation (r = 0.9998, y = 1.009 x + 4.160, P < 0.001) (Fig. 2). The error rate was 1.9 ± 0.9%, which is considered small.

Experiment 2: The mean values and standard deviations of the maximum occlusal forces for males and females with devices A and B are shown in Table 1a.

A significant positive correlation was found between the maximum occlusal force measured with device A and the maximum occlusal force measured with device B (male: r = 0.737, P < 0.001; female: r = 0.747, P < 0.001) (Table 1b). With both devices, the maximum occlusal force was significantly greater for males than for females (P < 0.001) (Table 1c).

Fig. 2 Experiment 1: relationship between load value and measured value

Table 1 Results of experiment 2

a
	Device A			Device B
	habitual	non-habitual	sum
Male	543.1 ± 116.3 N	494.1 ± 105.3 N	1031.5 ± 212.3 N	1036.9 ± 213.8 N
Female	475.3 ± 108.3 N	418.6 ± 99.3 N	891.4 ± 187.1 N	902.8 ± 190.5 N
b
	Device A	Device B	r-value	P-value
Male	1031.5 ± 212.3 N	1036.9 ± 213.8 N	0.737	<0.001
Female	891.4 ± 187.1 N	902.8 ± 190.5 N	0.747	<0.001
c
	Male	Female	P-value
Device A	1031.5 ± 212.3 N	891.4 ± 187.1 N	<0.001
Device B	1036.9 ± 213.8 N	902.8 ± 190.5 N	<0.001

a: Mean and standard deviation of the maximum occlusal force for device A and device B. b: Relationship between device A and device B in males and females. c: Independent t-tests for comparisons between males and females. Habitual: habitual chewing side, Non-habitual: non-habitual chewing side

Discussion

The majority of previous studies of occlusal force have focused on individual teeth than on the overall dentition. The GM10 occlusal force meter (Nagano Keiki Inc., Tokyo, Japan) has been commercially available in Japan and widely used for individuals of all ages, from children [3] to the elderly [4], because it has the advantage of allowing simple, immediate measurement of individual tooth occlusal force for multiple times. However, production of this device has been discontinued. In addition, it has been pointed out that the thickness and extreme hardness of the bitten part during measurement may cause pain in the temporomandibular joint and tooth chipping. To solve these problems, the authors devised a prototype device that can measure the occlusal force of individual teeth, and has a polyvinyl chloride disk placed over the cover of the measurement part, making it easier to bite. Furthermore, incorporation of a program that can estimate sensor characteristics has improved its accuracy and enabled the sensor to be used in the field. Due to these features, the developed occlusal force device can be said to be new and original.

It is important that measurements taken with the occlusal force device must match the applied load value. When the load value and the measured value match perfectly, a positive correlation is observed, and both the correlation coefficient and regression equation coefficient are 1. The results of this study showed that the correlation coefficient was 0.9998 and the regression equation coefficient was 1.009, both being extremely close to 1, indicating that the occlusal force device calculated a value that closely approximated the applied load. The error rate was also extremely small at less than 2%. Based on these findings, it seems reasonable to conclude that the newly developed occlusal force device is capable of providing measurements with high accuracy.

The occlusal force of individual teeth can be measured for the first molar, molars, premolars, etc., but the first molar is that most commonly used [3,4,5]. Therefore, in this study, the maximum occlusal force at the first molars on both sides using a load device and the maximum occlusal force of the entire dentition were measured using a dental prescale.

When the relationship between the two was examined for maximum occlusal force, and a positive correlation was found between the two. This indicates that the measured maximum occlusal force for the first molars on both sides can be used to represent the maximum occlusal force of the entire dentition obtained using the dental prescale.

It is known that there are gender differences in maximum occlusal force for the entire dentition. The present results confirmed similar gender differences in individual tooth occlusal force. Therefore, the reference value (mean value – standard deviation × 2) [6] for individual tooth occlusal force at the first molar must be set separately for males and females. On the basis of the present results, it seems reasonable to consider that this value should be approximately 610 N (310 N on the habitual chewing side) for males and approximately 520 N (260 N on the habitual chewing side) for females.

Abbreviations

PC: personal computer

Ethical Statements

This retrospective chart review study involving human participants was conducted in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study was conducted with the approval of the Ethics Committee of the School of Life Dentistry, Nippon Dental University (approval number: NDU-T2020-31).

Conflicts of Interest

The authors have no conflicts of interest to declare in relation to this study.

Funding

Not applicable

Author Contributions

HS: conceptualization, methodology, data curation, data acquisition, writing, review, editing, and supervision, KN: conceptualization, data acquisition, formal analysis, validation, methodology and editing, MK: data acquisition, HU: data acquisition, MY: data acquisition, YIS: data acquisition and editing. All authors have read and agreed to publish this version of the manuscript.

ORCID iD

HS*: [e-mail], https://orcid.org/0009-0003-1431-3454

KN: [e-mail], https://orcid.org/0009-0003-1891-7415

MK: [e-mail], https://orcid.org/0009-0006-3253-3786

HU: [e-mail], https://orcid.org/0009-0007-2096-1334

MY: [e-mail], https://orcid.org/0000-0003-1353-9702

YIS: [e-mail], https://orcid.org/0000-0003-3982-8369

Data Availability Statements

The datasets analyzed for the present study are not publicly available due to ethical restriction, but are available from the corresponding author on reasonable request.

References

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