Comparison of the effect of conventional and implant-retained overdentures on brain activity and cognition in a geriatric population - A Functional MRI study

DO ORAL CARE AND REHABILITATION IMPROVE COGNITIVE FUNCTION? A SYSTEMATIC REVIEW OF CLINICAL STUDIES

OBJECTIVES

An increasing number of studies have identified an association between oral health status and cognitive function. However, the effect of oral interventions, including oral health care, dental treatment and oral motor exercises, on cognitive function remains unclear. This systematic review examined whether oral interventions contribute to the long-term improvement of cognitive status.

METHODS

Four databases were searched (MEDLINE, Web of Science, Cochrane Library, and ICHUSHI Web) to identify randomized and nonrandomized controlled trial studies and prospective cohort studies from inception until 1 September 2023, published in English or Japanese. The Cochrane risk of bias tool for randomized controlled trials and the risk of bias assessment tool for nonrandomized studies were used to assess bias risk.

RESULTS

A total of 20 articles were included in the qualitative analysis; 13 articles were published in English, and 7 were published in Japanese. The implemented interventions were oral care in 8 studies, dental treatment in 8 studies, and oral motor exercise in 4 studies. One study found a significant effect on attention following oral care intervention. Some dental treatments influenced cognitive function, although a clear positive effect was not determined. In 1 study, attention and working memory improved in the chewing exercise group.

CONCLUSIONS

Several studies verified the improvement effects of oral interventions, such as oral care, dental treatment, and oral motor exercise, on cognitive function or impairment. However, there was still a lack of conclusive evidence that such an intervention clearly improved cognitive function. To clarify the effects of oral interventions on cognitive function, it is necessary to examine participants, interventions, and outcome measures in detail.

The effect of single-implant overdentures on cognitive function in older adults: A 3-year follow-up report

OBJECTIVE

To investigate the occurrence of mild cognitive impairment in edentulous patients up to 3 years after they received single-implant overdentures (1-IODs).

METHODS

This was a follow-up study for a crossover randomized controlled trial comparing 1-IODs and conventional complete dentures, with patient satisfaction as the primary outcome. In the present study, the cognitive function of the patients, measured with the Japanese version of the Montreal cognitive assessment (MoCA-J), was evaluated as the secondary outcome at baseline and 2 months, 1 year, 2 years, and 3 years after 1-IOD placement. The total and domain (memory, executive function, visuospatial skills, language, attention, and orientation) MoCA-J scores of the patients at each timepoint were analyzed and compared.

RESULTS

Twenty-two patients with edentulous mandibles received 1-IODs. Within-group comparisons revealed that the total MoCA-J scores at 1 year and 3 years after 1-IOD placement were significantly increased compared with baseline scores. Additionally, the memory domain scores at all timepoint were significantly increased compared with the baseline scores, and the executive function domain scores at the 2-month, 2-year and 3-year timepoint were significantly increased compared with the baseline scores.

CONCLUSION

Patients with edentulous mandibles who underwent 1-IOD placement showed significantly improved total scores of MoCA-J after 1 year and 3 years of wearing 1-IODs. In addition, they showed significantly improved memory domain scores at 2 months, 1 year, 2 years, and 3 years after 1-IOD placement and executive function domain scores at 2 months, 2 years, and 3 years after 1-IOD placement.

CLINICAL SIGNIFICANCE

The results of this study suggest that 1-IOD treatment for older adults, especially those with edentulous mandibles, may prevent cognitive decline regardless of the condition of the maxilla.

Functional Neuroplasticity of Adults with Partial or Complete Denture Rehabilitation with or without Implants: Evidence from fMRI Studies

Tooth loss may affect food ingestion and, consequently, nutrition intake. The neuroimaging literature using functional magnetic resonance imaging (fMRI) was reviewed to summarize the changes in brain functions in response to denture rehabilitation in patients with partial or complete edentulous dentition. Overall, this review covered nine fMRI studies on denture rehabilitation. Eight recruited complete edentulous patients, whereas one recruited partially edentulous patients. The risk-of-bias assessment revealed concerns regarding all nine studies. Due to the heterogeneity of the studies and the lack of brain coordinates reported, a meta-analysis could not be conducted, and this review could only summarize the findings without statistical validation. The evidence from jaw-clenching studies suggested that implant-supported fixed dentures could be the best option, as compared to implant-supported overdentures and complete dentures, as it was associated with higher brain activity levels in various brain regions, including those corresponding to the primary sensory (postcentral gyrus) and motor cortices (precentral gyrus). Gum-chewing studies indicated that perhaps the medial and middle frontal gyri were associated with food comminuting and food mixing, which could be improved by the full replacement of the dental arch, instead of only partial replacement. All the fMRI studies described the functional neuroplasticity of the patients undergoing denture rehabilitation and suggested that certain rehabilitation options were more beneficial in restoring masticatory functions, as well as their associated brain activity levels.