Comparison of oral stereognosis in relation to age and the use of complete dentures

Effects of tongue lesions and palatal coverage on oral sensory functions

STATEMENT OF PROBLEM

Oral stereognosis (OS) plays a significant role in the oral rehabilitation of patients with edentulism, as it influences their adaptation to new prostheses. Because of the essentially tactile characteristic of oral sensory perception, the tongue and palate appear to have a crucial function in OS. However, little is known about the influence of tongue lesions on OS and sensorial function. In addition, controversies remain regarding the role of the palate.

PURPOSE

The purpose of this clinical study was to evaluate whether tongue lesions and palatal coverage are disruptive to OS and gustatory function.

MATERIAL AND METHODS

Seventy participants (mean age=30.7 ±6.7 years) were divided into a tongue lesion group (experimental; n=35) and a control group (n=35). The tongue lesion group included participants with geographic, fissured, or hairy tongue. OS was evaluated with the oral stereognosis ability (OSA) test. Gustatory function was assessed with exposure to flavored solutions. After completing the above tests, the participants received a palate covering device, and then OS and gustatory function were immediately reevaluated. Data were analyzed with the Mann-Whitney and Wilcoxon tests (α=.05).

RESULTS

OSA and gustatory function scores did not differ among the tongue lesion and control groups with and without palatal coverage (all P>.05). After palatal coverage, the tongue lesion group took more time to perform the OSA test than the control group (P<.05).

CONCLUSIONS

Neither the presence of tongue lesions nor palatal coverage influenced OS or gustatory function. The OSA test response times were longer for the tongue lesion group after they had received palatal coverage.

Palatal coverage and oral stereognosis: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Complete denture wearers present with less sensory function than dentate individuals because of the loss of periodontal receptors. However, the role of the palatal receptors on such function is still unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the influence of palatal coverage associated with complete dentures or palatal devices on oral stereognosis in edentulous or dentate adults.

MATERIAL AND METHODS

Eight major literature databases and the nonpeer-reviewed literature were searched up to December of 2021. Randomized clinical trials and nonrandomized clinical trials comparing oral stereognosis in edentulous or dentate participants using conventional complete dentures or implant-supported prostheses or those using palatal devices were included. Bias was assessed with Cochrane tools (ROBINS-I and RoB 2.0). Meta-analyses were conducted to compare oral stereognosis before and after palatal coverage (α=.05). Certainty of the evidence was verified using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

Of 14 included studies, the risk of bias was considered low for 9 studies and moderate for 5 studies. Despite the very low certainty of evidence, meta-analyses showed no differences in oral stereognosis immediately after complete denture insertion (standardized mean difference [SMD]=0.302; 95% confidence interval [CI]: -0.124, 0.728; P=.165; I2=92.4%). Oral stereognosis scores improved after ≥1 month of complete denture use compared with initial evaluations without them. Qualitative analysis indicated that oral stereognosis was not influenced by palatal coverage shortly after complete denture installation and that oral stereognosis scores improved over time after prosthesis use.

CONCLUSIONS

Oral stereognosis improved with the use of palate-covering prostheses over time. However, because of the very low certainty of evidence, the statement must be interpreted with caution.

Somatosensory innervation of healthy human oral tissues

The oral somatosensory system relays essential information about mechanical stimuli to enable oral functions such as feeding and speech. The neurochemical and anatomical diversity of sensory neurons across oral cavity sites have not been systematically compared. To address this gap, we analyzed healthy human tongue and hard-palate innervation. Biopsies were collected from 12 volunteers and underwent fluorescent immunohistochemistry (≥2 specimens per marker/structure). Afferents were analyzed for markers of neurons (βIII tubulin), myelinated afferents (neurofilament heavy, NFH), and Merkel cells and taste cells (keratin 20, K20). Hard-palate innervation included Meissner corpuscles, glomerular endings, Merkel cell-neurite complexes, and free nerve endings. The organization of these somatosensory endings is reminiscent of fingertips, suggesting that the hard palate is equipped with a rich repertoire of sensory neurons for pressure sensing and spatial localization of mechanical inputs, which are essential for speech production and feeding. Likewise, the tongue is innervated by afferents that impart it with exquisite acuity and detection of moving stimuli that support flavor construction and speech. Filiform papillae contained end bulbs of Krause, as well as endings that have not been previously reported, including subepithelial neuronal densities, and NFH+ neurons innervating basal epithelia. Fungiform papillae had Meissner corpuscles and densities of NFH+ intraepithelial neurons surrounding taste buds. The differing compositions of sensory endings within filiform and fungiform papillae suggest that these structures have distinct roles in mechanosensation. Collectively, this study has identified previously undescribed neuronal endings in human oral tissues and provides an anatomical framework for understanding oral mechanosensory functions.

Effect of complete dentures on oral stereognostic ability in edentulous patients: A systematic review

Aim:

Oral stereognosis is an important sensation for a human being to percept any type of materials that are introduced in the oral cavity. It is defined as the ability of an individual to recognize objects using only tactile sensation without using vision, audition, balance, somatic function, taste, or smell. The primary purpose of this review was to evaluate the effect of complete dentures on oral stereognostic ability in edentulous subjects.

Settings and Design:

Systematic review based on PRISMA guidelines.

Materials and Methods:

A systematic search of the electronic databases like PubMed and Web of Science was done using keywords – “stereognosis,” “oral stereognosis,” “complete denture,” and “complete edentulism.” In addition to this, a manual search of references mentioned in the articles and gray literature was done. Data extraction and assessment were done by two independent reviewers.

Statistical Analysis Used:

Qualitative analysis.

Results:

The literature search yielded a total of 61 articles. Thirteen duplicate articles were removed and 36 articles were rejected after initial screening of titles and abstracts. A total of 12 articles were selected for full text reading and 5 of them were included for qualitative analysis.

Conclusion:

All the included studies showed complete denture treatment therapy improved stereognostic ability in terms of correct identification of test pieces and time taken to identify the objects. There is also a direct relationship between the adaptability of dentures and stereognostic ability.

Activation of Prefrontal Cortex in Process of Oral and Finger Shape Discrimination: fNIRS Study

Background

The differences in the brain activities of the insular and the visual association cortices have been reported between oral and manual stereognosis. However, these results were not conclusive because of the inherent differences in the task performance-related motor sequence conditions. We hypothesized that the involvement of the prefrontal cortex may be different between finger and oral shape discrimination. This study was conducted to clarify temporal changes in prefrontal activities occurring in the processes of oral and finger tactual shape discrimination using prefrontal functional near-infrared spectroscopy (fNIRS).

Methods

Six healthy right-handed males [aged 30.8 ± 8.2 years (mean ± SD)] were enrolled. Measurements of prefrontal activities were performed using a 22-channel fNIRS device (ETG-100, Hitachi Medical Co., Chiba, Japan) during experimental blocks that included resting state (REST), nonsense shape discrimination (SHAM), and shape discrimination (SHAPE).

Results

No significant difference was presented with regard to the number of correct answers during trials between oral and finger SHAPE discrimination. Additionally, a statistical difference for the prefrontal fNIRS activity between oral and finger shape discrimination was noted in CH 1. Finger SHAPE, as compared with SHAM, presented a temporally shifting onset and burst in the prefrontal activities from the frontopolar area (FPA) to the orbitofrontal cortex (OFC). In contrast, oral SHAPE as compared with SHAM was shown to be temporally overlapped in the onset and burst of the prefrontal activities in the dorsolateral prefrontal cortex (DLPFC)/FPA/OFC.

Conclusion

The prefrontal activities temporally shifting from the FPA to the OFC during SHAPE as compared with SHAM may suggest the segregated serial prefrontal processing from the manipulation of a target image to the decision making during the process of finger shape discrimination. In contrast, the temporally overlapped prefrontal activities of the DLPFC/FPA/OFC in the oral SHAPE block may suggest the parallel procession of the repetitive involvement of generation, manipulation, and decision making in order to form a reliable representation of target objects.

Relationship between oral stereognostic ability and dietary intake in older Japanese adults with complete dentures

PURPOSE

Oral stereognostic ability (OSA) is a useful indicator of oral perception to recognize food characteristics during mastication. Previous studies have shown associations between dietary intake and oral health status, such as taste perception. However, the effect of oral sensory ability on dietary intake is unclear. The purpose of this study was to investigate the association between oral sensory ability and dietary intake in older Japanese complete denture wearers.

METHODS

This cross-sectional study included 164 participants aged 69-71 or 79-81years old, wearing both maxillary and mandibular complete dentures. OSA test was used to evaluate oral tactile perception. Diet during the preceding month was assessed using a self-administered diet history questionnaire. Multivariable linear regression analysis was conducted to assess the association between OSA score and food and nutrient intake after adjusting for age, sex, socioeconomic factors, and occlusal force.

RESULTS

The bivariate analysis showed that OSA score was significantly and positively correlated with intake of green and yellow vegetables and negatively correlated with intake of cereals among examined foods. OSA score was also positively correlated with intake of vitamins A, B₂, and C and α-tocopherol (as a substitute for vitamin E) among examined nutrients. After adjusting for age, sex, socioeconomic factors, and occlusal force, OSA score remained significantly associated with intake of green and yellow vegetables and α-tocopherol.

CONCLUSIONS

OSA was significantly associated with intake of green and yellow vegetables in older complete denture wearers.

Influence of lower complete denture use on masseter muscles and masticatory function: A longitudinal study

BACKGROUND

Edentulism can reduce mastication, leading to changes in food pattern, with possible consequences to masticatory muscle thickness.

OBJECTIVES

This study verified masticatory function and oral perception in subjects who did not use lower CDs, and whether the insertion of new upper and lower CDs would improve such variables.

METHODS

Fifteen edentulous elderly who wore only the upper CD were selected and received new upper and lower CD. Volunteers were evaluated at baseline and after 1, 3 and 6 months of new prosthesis use. Masticatory performance (MP) was assessed by the sieving method (X₅₀ values). Masseter thickness (MT) was evaluated by ultrasonography. Oral sensorial ability (OSA) was assessed by oral stereognosis test and maximum tongue pressure (MTP) was verified by pressure sensors. Data were submitted to repeated measures ANOVA and Tukey-Kramer posthoc tests (α = 0.05). Correlation between OSA and MTP was verified by Person's correlation.

RESULTS

X₅₀ and MTP decreased (P < 0.05) after 1 month and remained stable (P > 0.05) for next assessments. After 3 months, MT in rest position was increased (P < 0.05), while during maximum voluntary contraction 1 month was enough to increase MT (P < 0.05). There were no differences for OSA (P > 0.05) and no correlation between OSA and MTP.

CONCLUSION

Masticatory performance and masseter thickness of elderly who did not use the lower dentures were improved after 2 months using new upper and lower CDs. However, new CDs in both dental arch decreased MTP. Brazilian Registry of Clinical Trials (ReBEC #RBR-37gdst).

Impact of cognitive function on oral perception in independently living older people

OBJECTIVES

Oral tactile perception is important for better mastication, appetite, and enjoyment of food. However, previous investigations have not utilized comprehensible variables thought to have negative effect on oral perception, including aging, denture wearing, and cognitive function. The aim of this study was to elucidate the impact of cognitive function on oral perception in independently living older individuals.

MATERIALS AND METHODS

The study sample was comprised of 987 participants (466 males, 521 females; age 69-71 years). Oral examinations, assessments of cognitive function in preclinical level by Montreal Cognitive Assessment (MoCA)-J, and determination of oral stereognostic ability as an indicator of oral perception were performed. Related variables were selected by univariate analyses; then, multivariate logistic regression model analysis was conducted.

RESULTS

Univariate analyses revealed that number of teeth, removable dentures usage, and cognitive function respectively had a significant relationship with stereognostic score. Next, the subjects were classified into good and poor perception groups (lowest 17.4%) according to oral stereognostic ability. Logistic regression analysis revealed that lower cognitive function was significantly associated with poor oral perception (OR = 0.934, p = 0.017) after controlling for other variables.

CONCLUSIONS

Cognitive decline even in preclinical stage was associated with reduced oral perception after controlling for gender, tooth number and denture use in independent living older people.

CLINICAL RELEVANCE

This study suggested that preclinical level of change in cognitive function affected oral perception. Dental practitioners and caregivers may need to pay attention to reduced oral perception among older people even if they do not have trouble in daily life.

Evaluation of Oral Stereognosis in Relation to Tactile Ability and Patient Satisfaction

We investigated the oral stereognostic ability (OSA) of dentate individuals, conventional complete denture patients, and maxillary implant-supported denture patients with bar attachments. Stereognosis tests were carried out, and the relationship between OSA and patient satisfaction was assessed with a satisfaction survey: the Turkish version of the oral health impact profile-14 (OHIP-TR-14). To compare differences in oral sensory function among individuals with natural dentition, complete denture wearers, and maxillary implant-supported denture wearers, tactile awareness (thickness perception threshold) and pressure awareness (threshold of lateral loading) were assessed. According to the results, the oral perception level of natural dentate patients was higher than that of the complete denture group and maxillary implant-supported complete denture group at the end of the study. There was no statistically significant difference in OHIP-TR-14 scores between the maxillary implant-supported complete denture group and the complete denture group ( P < .05). The control group perceived the applied lateral and vertical forces statistically earlier than the other groups ( P < .001). There was no statistically significant difference between the complete denture and maxillary implant-supported denture groups in terms of the lateral pressure threshold or thickness tactile threshold ( P > .05). At the end of the study it was concluded that there was no correlation between oral perception levels and satisfaction in patients with complete dentures and patients with maxillary implant-supported complete dentures. The control group, compared with the complete denture and maxillary implant-supported complete denture groups, perceived the lateral and vertical forces statistically earlier than the other groups.

Does shape discrimination by the mouth activate the parietal and occipital lobes? - near-infrared spectroscopy study

A cross-modal association between somatosensory tactile sensation and parietal and occipital activities during Braille reading was initially discovered in tests with blind subjects, with sighted and blindfolded healthy subjects used as controls. However, the neural background of oral stereognosis remains unclear. In the present study, we investigated whether the parietal and occipital cortices are activated during shape discrimination by the mouth using functional near-infrared spectroscopy (fNIRS). Following presentation of the test piece shape, a sham discrimination trial without the test pieces induced posterior parietal lobe (BA7), extrastriate cortex (BA18, BA19), and striate cortex (BA17) activation as compared with the rest session, while shape discrimination of the test pieces markedly activated those areas as compared with the rest session. Furthermore, shape discrimination of the test pieces specifically activated the posterior parietal cortex (precuneus/BA7), extrastriate cortex (BA18, 19), and striate cortex (BA17), as compared with sham sessions without a test piece. We concluded that oral tactile sensation is recognized through tactile/visual cross-modal substrates in the parietal and occipital cortices during shape discrimination by the mouth.

Rate-related kinematic changes in younger and older adults

AIMS

This study aimed to investigate the effects of speech rate changes on kinematic characteristics and stability of speech movements in younger and older speakers using electromagnetic midsagittal articulography.

PATIENTS AND METHODS

Eight young adults and 8 older adults engaged in a series of syllable repetition tasks of /pa/, /sa/ and /ta/ obtained at self-paced slow, habitual and fast speech rates, as well as in a series of metronome-guided speech rates, ranging from 2 to 4 syllables per second. The kinematic parameters duration, amplitude and peak velocity were obtained for opening and closing movements.

RESULTS

Older speakers were able to increase speech rate to the same degree or higher compared to younger speakers in both pacing conditions. Kinematic data show that older adults increased duration and decreased peak velocity in closing movements of alveolar constrictions at slower rates more prominently than younger adults. The results on movement stability revealed no differences between age groups.

CONCLUSIONS

The results suggest that an age-related difference in speed-accuracy trade-off can be ruled out. Differences in kinematic characteristics point towards the possibility that older adults aimed to facilitate a closed-loop control system to maintain movement stability at slower speech rates.

Altered oral sensory perception in tongue thrusters with an anterior open bite

The aim of this study was to evaluate oral sensory perception in patients with an anterior open bite (AOB) and associated tongue thrusting activity. This study was performed in the Department of Orthodontics, Government Dental Hospital, Chennai, on 30 subjects (16 females and 14 males) aged from 12 to 17 years with an AOB associated with a tongue thrust and in a control group of 100 subjects (53 females and 47 males aged from 12 to 17 years) with a normal occlusion and no oral habits. Stereognosis and two-point discrimination (2PD) were employed for evaluation of oral sensory perception. Statistical comparison was undertaken using a Student's t-test. Stereognostic ability was altered in children with an AOB associated with a tongue thrust (t = 15.2, probability of occurrence P < 0.01). The mean oral stereognostic score in the control group was 31.8 and in tongue thrusters 25.3. The AOB group also showed a diminished 2PD threshold at the tip of the tongue [control group 1.08 mm, tongue thrusters with an AOB 1.64 mm (t = 7.3, P < 0.01)]. This finding highlights the fact that the tongue plays a vital role in oral sensory perception. Oral stereognostic tests and 2PD as diagnostic tools are valuable in the evaluation of oral sensory perception.

Decrease in stereognostic ability of the tongue with age

Rehabilitation of eating and swallowing functions from the viewpoint of quality of life should attempt to restore not only the physical, but also sensory function. As the size and shape of the intra-oral bolus of food provides oral sensory information important for eating and swallowing, we investigated the stereognostic ability of the tongue in 269 young adults (mean age: 24.5 years) and 60 seniors (mean age: 80.5 years); all of whom had no eating or swallowing complaints. Assessment of the stereognostic ability involved identifying 20 differently shaped test pieces placed in the oral cavity. The young adults identified a significantly higher number of differently shaped test pieces than the seniors (mean correct number of responses: 16.5 and 10.1 respectively; P < 0.001). Gender and the presence of palatal covers did not have any significant effect on stereognostic ability. The test pieces were categorized into six groups based on the shape. When the young adults misidentified a piece, they often selected another piece within the same group, almost never selecting a piece from another group. The seniors, however, chose test pieces from different groups. Moreover, to determine whether stereognosis could be improved through training, we conducted training involving four senior subjects in their 80s, who correctly identified 10 or fewer pieces. After the training, the number of correct answers increased significantly (P < 0.05). These findings indicate that seniors show decreased stereognostic ability of the tongue compared with young adults and suggest the possibility of recovering the ability using our training method.

Influence of palatal surface shape of dentures on food perception

The purpose of this study was to clarify the influence of the palatal surface shape of dentures on food perception. Eighteen healthy dentulous subjects (mean age, 24 years) were investigated. Four types of experimental plate were used: (i) a tailor-made plate, (ii) an average-model plate, (iii) a smooth plate, and (iv) a wrinkle plate. Test foods consisted of Bavarian cream cubes containing one to three mustard seeds and six raw carrot pieces of different shapes. Bavarian cream cubes with three seeds were used for analysis. Other foods were used as dummy foods. Subjects were required to wear experimental plates and press test foods placed on the anterior area of the tongue against the experimental plates. We measured time required to perceive number of spherical bodies, rate of correct answers, and level of perception with each type of experimental plate using a 100-mm visual analogue scale. The results showed a significant difference in response time between the average-model plate and the other experimental plates, with response time longest for the average-model plate. On the other hand, no significant differences in rate of correct answers regarding number of spherical bodies or level of perception were found among the experimental plates. When incisive papilla, palatine suture and palatal rugae based on the standard Japanese shape were replicated on the palatal surface of the plates, the time required for food perception during ingestion was prolonged in comparison to plates with other palatal surface shapes.