Influence of denture treatment on brain function activity

The Relationship between Removable Dental Prostheses and Brain Activity in Elderly Individuals: Systematic Review

BACKGROUND

There is an increasing body of literature associating edentulism with cognitive impairment. The aim of this systematic review was to summarize the available data, emphasizing the role of removable dental prostheses in preventing cognitive deterioration and promoting brain health in elderly individuals.

AIM

This systematic review investigates the relationship between the use of removable dental prostheses and physiological or adaptive changes at the cerebral level in partially and completely edentulous patients.

METHODS

A systematic review was conducted following PRISMA guidelines, with an initial search across PubMed, Scopus, and Web of Science databases. Studies published up to June 2023 in English were considered. A risk of bias assessment was performed for included studies.

RESULTS

Of the 86 studies initially screened, 13 met the inclusion criteria. Findings indicate a positive association between the use of removable dental prostheses and improved cognitive function, with potential therapeutic implications for managing cognitive decline.

CONCLUSION

Removable dental prostheses play a crucial role in enhancing neurological health and preventing cognitive decline, making them an important consideration in the management of neurodegenerative diseases.

To Study the Effect of Anterior Palatal Surface Modifications of Complete Denture on Speech Intelligibility Oral Perception and Cortical Brain Function Activity: An In Vivo Study

BACKGROUND

 The classic maxillary full denture covers the whole palate, preventing the tongue from touching the denture base tissues itself. Thus, it has deleterious effects on cortical brain function and the ability to understand spoken language.

AIM

 This study aimed to determine the effect of anterior palatal surface modifications of the complete denture on speech intelligibility oral perception and cortical brain function activity.

METHODS AND MATERIALS

 This study compared the speech clarity, oral discernment, and cortical mind capability activity of complete denture wearers in three study groups: a) complete denture wearers with a small opening (SO) in the maxillary front palatal base; b) complete denture patients who wear regular complete denture; c) complete denture patients who did not wear complete denture; and d) complete denture patients who wear a functionally contoured modified palate (FCMP). Patients with no teeth at all underwent four phases of testing to assess their cognitive abilities and speech quality (pitch and volume). In the first phase, partial dentures were used. During phase 2, a conventional full denture was inserted. In the third phase, a palatal base denture was functionally altered. In phase 4, dentures with a little aperture at the front of the palatal base were used.  Results: The values of pitch and intensity of sound in category A with FCMP modification I were 180.76 ± 24.12 and 73.27 ± 9.74, respectively. On the other hand, the values of pitch and intensity of sound in category B with FCMP modification I were 185.41 ± 27.29 and 73.91 ± 8.31, respectively. The values of pitch and intensity of sound in category A with SO modification II were 188.52 ± 21.11 and 76.13 ± 5.21, respectively. On the other hand, the values of pitch and intensity of sound in category B with SO modification II were 194.59 ± 24.02 and 75.21 ± 6.12, respectively. The findings for values of pitch and intensity were statistically significant among the four phases (p < 0.001). The highest speech intelligibility and cortical brain function were observed in phase 4 in both categories A and B, with the highest scores by experts of 3.21 and 3.42, respectively. Conclusion: Based on the findings of this in vivo investigation, it can be concluded that using modified dentures (modification types I and II) following denture installation improves speech intelligibility, oral perception, and cortical brain function activity.

The Impact of Masticatory Function on Cognitive Impairment in Older Patients: A Population-Based Matched Case-Control Study

PURPOSE

The aim of this study was to investigate the association between the changes in masticatory function and cognitive impairment by analyzing longitudinal data of older Korean patients.

MATERIALS AND METHODS

Patients aged over 60 years with dental records between 2005 to 2010 (baseline; T1) and 2014 to 2020 (follow-up; T2) were selected in a single medical center. Based on the dementia diagnosis after T2, the cohort was classified into two groups, the dementia group (n=122) and the control group (n=366). Changes in masticatory function were calculated using the total functional tooth unit (T-FTU) in both groups. The incidence of tooth extraction (%) and the subsequent rehabilitation during the observation period were also evaluated.

RESULTS

In the dementia group, T-FTU significantly decreased from T1 to T2 (9.81±2.78 to 9.11±3.16, respectively, p=0.008), while no significant change was observed in the control group. During the mean observation period of 9 years, significantly more teeth were extracted and neglected to be prosthetically restored in the dementia group than in the control group. Regression analysis revealed that the number of missing teeth neglected [odds ratio (OR)=1.195, 95% confidence interval (CI)=1.025-1.393, p=0.023] and previous alcohol consumption (OR=4.445, 95% CI=1.831-1.795, p=0.001) were the most significant risk factors of dementia.

CONCLUSION

There might be a causative relationship between the neglected missing dentition and the onset of dementia.

A prospective association between tooth status and cognitive performance among older adults in Europe

OBJECTIVES

This study set out to examine both the longitudinal association between tooth status and cognitive performance among older adults in Europe, and the mediating effects of loneliness and quality of life on this association.

METHODS

We conducted a prospective analysis using data from 38,614 participants aged 50 or older, taken from the Survey of Health, Ageing and Retirement in Europe (SHARE) of 2013 (baseline) and 2015 (follow up). Bootstrapping with resampling strategies was used for testing a multiple mediator model.

RESULTS

The average age of participants was 66.9 (SD = 9.4). About 23% of the participants had full sets of their own teeth and 38.2% had missing teeth fully replaced by dental implants or dentures. Participants who had partially replaced teeth (B = 0.038, p < 0.001), and with fully replaced teeth (B = 0.041, p < 0.001), or had all their teeth in place (B = 0.055, p < 0.001), had better cognitive performance compared to those who did not replace their missing teeth. It was also found that quality of life and loneliness partially mediated these relationships - Having all teeth in place or replacing all or partially missing teeth was found to affect cognitive performance also via improved quality of life and through lower loneliness.

CONCLUSION

In later life, poor tooth status can be directly associated with cognitive decline and indirectly linked to cognitive performance, in light of decreasing quality of life and increasing loneliness. Clinicians should be aware of both the impact of poor tooth status on cognitive status and the implications for the wellbeing of older adults.

Effect of Molar Occlusal Balance on Cognitive Function in the Elderly

BACKGROUND

Elderly people with dementia, who are increasing at a rate comparable to the rate at which theelderly population is growing, are becoming a serious social problem in Korea. Therefore, the purpose of this study was to investigate the association between molar occlusal balance and cognitive function among Koreans aged 65 years and older.

METHODS

A total of 308 participants aged 65 years and older who attended a senior center were recruited for the study with their consent. The Korean version of the Mini-Mental State Examination (MMSE-DS) was used to assess cognitive function, and masticatory ability was measured according to the ability to chew food, the number of remaining teeth, and the self-perceived perceived masticatory function. Relative molar occlusal balance was measured using the T-scan Ⅲ system. All collected data were analysed using SPSS version 23.0.

RESULTS

There was a significant association between cognitive function and molar masticatory ability (P < .05). The participants with relative molar occlusal balance had a higher MMSE-DS score when compared to those with relative incision occlusal balance, adjusted for sociodemographic factors and number of remaining teeth, subjective masticatory ability, chewing ability, occlusion time, and denture use. Cognitive function was higher when relative molar occlusion was greater compared to anterior occlusion in anterior-posterior teeth balance.

CONCLUSIONS

Cognitive function in elderly people was higher when the relative molar occlusal balance was greater. Mastication with posterior teeth may have a more important effect on stimulation of cognitive function. Therefore, oral health care focusing on maintenance of molar teeth may be crucial for elderly persons.

The Effect of Alteration of Vertical Dimension of Occlusion on Brain Activity in Complete Denture Wearers

BACKGROUND: The establishment of appropriate vertical dimension of occlusion (VDO) is paramount for successful and functioning complete dentures (CDs). AIM: The aim of this study was to assess the effect of alteration of VDO on the brain activity in CD wearers. MATERIALS AND METHODS: Ten completely edentulous patients participated in this study. Each patient received three sets of CDs: one control set and two duplicates’ CDs. The control CDs was designed with appropriate VDO (control - VDO), while the duplicate CDs were designated as followed: one with VDO lowered by –3 mm (low - VDO) the other one VDO was increased by +5 mm (high - VDO). The effect of alteration of VDO on brain activity was assessed by measuring alpha waves changes using electroencephalogram (EEG) before and after chewing gum. Statistical analysis was carried out using one-way ANOVA and dependent t-test. The significance level was set at p < 0.05. RESULTS: There was a significant increase in the alpha waves mean values after chewing (p < 0.05) gum compared to before except for low - VDO CDs (p > 0.05). The control-VDO revealed a statistically significant higher mean values compared to the duplicate dentures. CDs with high - VDO showed higher mean value than low - VDO dentures, however, it was statistically insignificant (p > 0.05). CONCLUSION: Appropriate determination of VDO is not only important for the success of CDs but also for the functional augmentation of brain activity.

Tooth loss, cognitive impairment and chronic cerebral ischemia

BACKGROUND/PURPOSE

Vascular factor is an important risk factor in the process of cognitive impairment or dementia. Tooth loss could cause impairments of spatial learning and memory in mice, and nitric oxide (NO) and its synthase might be involved in the process. The objectives of this study were to investigate and compare the behavioral impairments between the Wistar rats with tooth loss and those with chronic ischemia and to determine the changes in nitric oxide (NO) and its synthases under those two conditions.

MATERIALS AND METHODS

The Morris water maze was used to test the spatial learning and memory abilities in the Wistar rats 8 weeks after the molar extraction procedure and the occlusion of 2 blood vessels to produce cerebral ischemia. The changes in NO and its synthases were evaluated using the Griess assay, Western blotting, and immunohistochemistry.

RESULTS

Similar impairments in the spatial learning and memory of Wistar rats were found after tooth loss and the induction of cerebral ischemia. The levels of NO and iNOS in the rat hippocampus increased, and the levels of eNOS decreased. Conclusion: For Wistar rats, the results of cognitive impairments related to tooth loss and those that occur due to chronic cerebral ischemia were statistically not significant and that NO, iNOS and eNOS in the hippocampus are involved in both cases.

Effect of occlusal rehabilitation on spatial memory and hippocampal neurons after long-term loss of molars in rats

Experimental loss of occlusal support caused by the extraction or grinding of molar teeth has been reported to foment the impairment of learning and memory in laboratory animals. The purpose of this study was to examine the effect of occlusal reconstruction after long-term loss of molars on spatial memory by using 8-arm radial maze and by assessing histopathological changes of neuron density in the hippocampus. Experimental dentures were inserted into the oral cavities of molarless rats to recover the occlusal support. Age-matched groups of control, molarless and denture-wearing rats were trained to perform the maze tasks. The difference of the error incidence in the maze task was evaluated between three groups. The difference of neuron density between three groups was also evaluated at the end of the maze task. Serum corticosterone levels were also measured to estimate the chronic stress, which could be caused by extraction, insertion of the experimental denture or any experimental procedure. The error incidence in the denture-wearing group was significantly higher than that of the control group, but significantly lower than that of the molarless group. Significant differences of neuron density were observed between three groups in each of the hippocampal CA1, CA3 and DG subfields. No significant difference of the serum corticosterone levels between three groups could be observed. From the results of this study, it was suggested that the recovery of occlusal support would bring amelioration of cognitive impairment concomitant with long period loss of molars in rats.

Interactions between occlusion and human brain function activities

There are few review articles in the area of human research that focus on the interactions between occlusion and brain function. This systematic review discusses the effect of occlusion on the health of the entire body with a focus on brain function. Available relevant articles in English from 1999 to 2011 were assessed in an online database and as hard copies in libraries. The selected 19 articles were classified into the following five categories: chewing and tongue movements, clenching and grinding, occlusal splints and occlusal interference, prosthetic rehabilitation, and pain and stimulation. The relationships between the brain activity observed in the motor and sensory cortices and movements of the oral and maxillofacial area, such as those produced by gum chewing, tapping and clenching, were investigated. It was found that the sensorimotor cortex was also affected by the placement of the occlusal interference devices, splints and implant prostheses. Brain activity may change depending on the strength of the movements in the oral and maxillofacial area. Therefore, mastication and other movements stimulate the activity in the cerebral cortex and may be helpful in preventing degradation of a brain function. However, these findings must be verified by evidence gathered from more subjects.