Age-related changes in oral motor-control strategies during unpredictable load demands in humans

Effect of Apical Microsurgery on Force Regulation of Incisor Teeth during Unpredictable Force Control Task

BACKGROUND

Apical microsurgery (AMS) involves removal of the root-end which can affect the force regulation of teeth.

OBJECTIVE

To investigate the force regulation of incisor teeth treated with AMS during the unpredictable force control task in comparison to their contralateral teeth with complete root apices, in humans.

METHODS

Fifteen eligible participants (8 women and 7 men; mean age 52.9 ± SD 4.4 years) performed a standardized unpredictable force control task which involved pulling and holding a force transducer with AMS-treated incisors and its contralateral control teeth (n =30 teeth). A series of four load masses: 100, 200, 50, and 300 gm were attached to the force transducer through a string in an unpredictable manner. The force profile obtained was divided into initial and later time-segments. The peak force and peak force rate during the initial time-segment, and the holding force and coefficient of variability during the later time-segments were calculated and compared by the repeated measures analysis of variance.

RESULTS

During the initial time-segment, the peak force and peak force rate were significantly lower in the AMS-treated teeth than in the controls (P = 0.001, P = 0.013, respectively). However, during the later time-segment, no significant differences in the holding force nor the coefficient of variability were observed between the AMS-treated teeth and their controls (P = 0.755, P = 0.213, respectively).

CONCLUSION

In contrast to incisors with complete normal root apices, AMS-treated incisors do not show robust changes in force regulation.

Effect of malocclusion on jaw motor function and chewing in children: a systematic review

Objective

To investigate the effects of dental/skeletal malocclusion and orthodontic treatment on four main objective parameters of chewing and jaw function (maximum occlusal bite force [MOBF], masticatory muscle electromyography [EMG], jaw kinematics, and chewing efficiency/performance) in healthy children.

Materials and methods

Systematic searches were conducted in MEDLINE (OVID), Embase, and the Web of Science Core Collection. Studies that examined the four parameters in healthy children with malocclusions were included. The quality of studies and overall evidence were assessed using the Joanna Briggs Institute and GRADE tools, respectively.

Results

The searches identified 8192 studies; 57 were finally included. The quality of included studies was high in nine studies, moderate in twenty-three studies, and low in twenty-five studies. During the primary dentition, children with malocclusions showed similar MOBF and lower chewing efficiency compared to control subjects. During mixed/permanent dentition, children with malocclusion showed lower MOBF and EMG activity and chewing efficiency compared to control subjects. The jaw kinematics of children with unilateral posterior crossbite showed a larger jaw opening angle and a higher frequency of reverse chewing cycles compared to crossbite-free children. There was a low to moderate level of evidence on the effects of orthodontic treatment in restoring normal jaw function.

Conclusions

Based on the limitations of the studies included, it is not entirely possible to either support or deny the influence of dental/skeletal malocclusion traits on MOBF, EMG, jaw kinematics, and masticatory performance in healthy children. Furthermore, well-designed longitudinal studies may be needed to determine whether orthodontic treatments can improve chewing function in general.

Clinical relevance

Comprehensive orthodontic treatment, which includes evaluation and restoration of function, may or may not mitigate the effects of malocclusion and restore normal chewing function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00784-021-04356-y.

Age and sex differences in oral functions from junior high school to young adulthood: A cross-sectional study

BACKGROUND

As oral function requires maintenance throughout life, it needs to be understood across age groups; however, few studies have investigated this in young individuals.

OBJECTIVES

To clarify age and sex differences in maximum occlusal force, maximum tongue pressure and tongue-lip motor function; and the relationship among these oral functions in junior high school students and young adults.

METHODS

This cross-sectional study investigated oral functions in students aged 12-13 years, 14-15 years old and 16-17 years old (S1, S2 and S3), and young adults aged 20-40 years (YA). We analysed age group differences in each sex and sex differences in each age group. Multiple linear regression analysis was performed for each sex using the maximum occlusal force as the dependent variable to investigate the associations among different oral functions.

RESULTS

In 522 children and 100 young adults, there were significant increases in oral functions with age in males and a significant decrease in maximum tongue pressure between S2 and S3 in females. Maximum occlusal force and tongue pressure were higher in males than in females in S3 and YA; tongue-lip motor function was higher in females than in males in S1. In multiple linear regression analysis, tongue-lip motor function and age group were significant factors in both sexes and in males, respectively.

CONCLUSION

Maximum occlusal force, maximum tongue pressure and tongue-lip motor function increased with increasing age groups in males. Our findings provide a basis for assessing oral function across age groups.

Cognitive changes and neural correlates after oral rehabilitation procedures in older adults: a protocol for an interventional study

BACKGROUND

Epidemiological studies show an association between masticatory function and cognitive impairment. This has further strengthened the notion that tooth loss and impaired masticatory function may be risk factors for dementia and cognitive decline. Animal experiments have indicated a causal relationship and several possible mechanisms have been discussed. This evidence is, however, lacking in humans. Therefore, in the current interventional study, we aim to investigate the effect of rehabilitation of masticatory function on cognition in older adults.

METHODS

Eighty patients indicated for prosthodontic rehabilitation will be randomly assigned to an experimental or a control group. Participants will conduct neuropsychological assessments, masticatory performance tests, saliva tests, optional magnetic resonance imaging, and answer questionnaires on oral health impact profiles and hospital anxiety and depression scale before, 3 months, and 1 year after oral rehabilitation. The difference between the two groups is that the control group will be tested an additional time, (at an interval of about 3 months) before the onset of the oral rehabilitation procedure. The primary outcome is a change in measures of episodic memory performance.

DISCUSSION

Although tooth loss and masticatory function are widespread in older people, it is still an underexplored modifiable risk factor potentially contributing to the development of cognitive impairment. If rehabilitation of masticatory function shows positive effects on the neurocognitive function, this will have great implications on future health care for patients with impaired masticatory status. The present project may provide a new avenue for the prevention of cognitive decline in older individuals.

TRIAL REGISTRATION

The protocol for the study was retrospectively registered in ClinicalTrials.gov Identifier: NCT04458207, dated 02-07-2020.