Association Between Reduced Posterior Occlusal Contact and Alzheimer's Disease Onset in Older Japanese Adults: Results from the LIFE Study

BACKGROUND

An association between poor oral health and cognitive decline has been reported. Most of these studies have considered the number of teeth as a criterion, only a few studies have analyzed the relationship between occlusal status and Alzheimer's disease (AD).

OBJECTIVE

To elucidate whether posterior occlusal contact is associated with AD, focusing on the Eichner classification, among an older population aged 65 years or older in Japan.

METHODS

This study used monthly claims data of National Health Insurance in Japan from April 2017 to March 2020. The outcome was newly diagnosed AD defined according to ICD-10 code G30. The number of teeth was estimated by dental code data, and occlusal contact was divided into three categories, namely A, B, and C, according to the Eichner classification. Multivariate Cox proportional hazards models were used to analyze the association between a new diagnosis of AD and the Eichner classification.

RESULTS

A total of 22,687 participants were included, 560 of whom had newly diagnosed AD during a mean follow-up period of 12.2 months. The AD participants had a lower proportion of Eichner A and a higher proportion of Eichner C. After adjusting for covariates, hazard ratios (95% confidence intervals) with Eichner B and C were 1.34 (1.01-1.77) and 1.54 (1.03-2.30), respectively.

CONCLUSION

In older people aged≥65 years old, reduced posterior occlusal contact as well as tooth loss have an impact on AD. This study emphasizes the importance of paying attention to occlusal contacts to reduce the risk of AD.

Occlusal Changes with Clear Aligners and the Case Complexity Influence: A Longitudinal Cohort Clinical Study

BACKGROUND

Clear aligners (CA) are used 22 h daily, creating a bite-block effect. This work aims to (i) analyze occlusal changes before the beginning of treatment, after the first set of CA and after the use of additional aligners; (ii) compare planned occlusal contacts with the ones obtained after the first set of CA; (iii) analyze the occlusal changes occurred after reaching the orthodontic goals after 3 months of using CA only at night; (iv) evaluate and characterize which tooth movements did not allow the treatment to be completed at the end of the first set of aligners, and finally (v) verify the possible relation between the changes in occlusal contact and areas and parameters such as case complexity and facial biotype.

MATERIALS AND METHODS

A quantitative, comparative, and observational longitudinal cohort study design was implemented to evaluate the clinical data and the complexity levels of cases receiving CA. A non-probabilistic and convenience sample of 82 individuals was recruited. The orthodontic malocclusion traits were classified as simple, moderate, or complex corrections based on the basis of the Align^® recommendations with the Invisalign^® evaluation tool. According to the Invisalign^® criteria, patients need only one complex problem for their case to be classified as complex. Meshlab^® v. 2022.02, ClinCheck^® version Pro 6.0, My-Itero^® version 2.7.9.601 5d plus, and IBM^® SPSS Statistics software (Statistical Program for Social Sciences), version 27.0 for Windows were the software^® used.

RESULTS

A statistically significant decrease in area and occlusal contacts number were observed from before the start of orthodontic treatment (T0) to the end of treatment (T1). The changes in the occlusal area (from T0 to T1) were statistically different between hyperdivergent (28.24 [15.51-40.91]) and hypodivergent (16.23 [8.11-24.97]) biotypes (p = 0.031). A significant difference between the hyperdivergent (4.0 [2.0-5.0]) and normodivergent (5.5 [4.0-8.0]) group was found in T1 for the anterior contacts (p = 0.044). Anterior contacts obtained were significantly higher than the planned (p = 0.037) Between T1 and T2 statistically significant increases of occlusal areas, posterior and total contacts were observed.

CONCLUSIONS

Occlusal contact and area were decreased, either at the end of the first set or after the use of additional aligners. Anterior occlusal contacts obtained were higher than planned as opposed to posterior occlusal contacts obtained. The hardest tooth movements to achieve to complete the treatment were distalization, rotation, and posterior extrusion. After completing orthodontic treatment (T1) to 3 months after (T2) using additional aligners only at night, posterior occlusal contacts were significantly increased, which could be due to the natural settling of the teeth in this period.

Number and localization of occlusal contact areas on natural posterior teeth without dental findings - evaluations of the regional baseline study (SHIP-1) with the Greifswald Digital Analyzing System (GEDAS)

Sufficient occlusion is a basic prerequisite for the functional efficiency of the occlusal surfaces. Exactly where and in what number the occlusal contacts in the posterior region should be present for this purpose is controversial. The present study investigated the number and location of occlusal contacts on posterior teeth without dental findings, ie, without caries or restorative restorations such as fillings, crowns, etc. Such natural posterior teeth were present in 709 subjects (males (m) = 446: 48.9 ± 13.04 years, females (f) = 283: 52.4 ± 14.23 years) of a subject collective of 1223 subjects (m = 648, f = 575) of the regional baseline study 'Study of Health in Pomerania 1' (SHIP-1). Silicone bite registrations in habitual intercuspation (IP) were evaluated, whereby the test persons were asked to fix the bite block with biting force without biting firmly. The registrations were scanned with a document scanner in incident and transmitted light; a calibration strip was used to determine the transparency threshold of a layer thickness of 20 μm, below and equal to which the transparent zone was considered as a contact or contact area. The Greifswald Digital Analyzing System 2 (GEDAS 2) software was used to determine the number and location of occlusal contact areas tooth by tooth. To define the localization of the contacts, a cross with two concentric circles symmetric to the longitudinal fissure was superimposed on the occlusal surface; this resulted in four inner and four outer quadrants. Thus, the number of pixels in occlusal contact areas per inner and outer quadrant could be determined. The image resolution was 300 dpi. On average (median), the premolars had two occlusal contacts each, the posterior teeth had four to five, and tooth 46 had six contacts. The right and left teeth did not differ in the frequency of occlusal contacts in the Mann-Whitney U test for independent samples. In the maxillary premolars, frequent contact areas were primarily located mesially on the inner and outer slopes of the palatal cusp. In the maxillary molars, the palatal slope of the distopalatal cusp and the inner slopes of the mesiopalatal and distopalatal cusps were frequently affected. On the mandibular premolars, the inner slopes of the buccal cusps and the buccal slope of the distobuccal cusp were particularly frequently addressed; in teeth 35 and 45, the buccal slope of the mesiobuccal cusp was also somewhat more frequently addressed. Teeth 36 and 46 frequently had contact areas on the buccal slope of the distobuccal cusp as well as on the inner slopes of the distal cusps (distobuccal and distolingual), whereas teeth 37 and 47 tended to behave similarly. Epidemiologically, the focus of the frequent contact areas on the respective supporting cusps of the maxillary and mandibular posterior teeth and a distribution of contacts stabilizing the tooth in its position in the dental arch through the interlocking were confirmed. It makes sense to take this into account when designing occlusal surfaces in the posterior region.

Digital Quantification of Occlusal Contacts: A Methodological Study

OBJECTIVE

To compare the reliability of digital occlusal contacts quantification and the validity of digital occlusal contacts quantification with traditional methods used for occlusal contact determination.

SUBJECTS AND METHODS

Thirty participants, all of whom were students at the Sahlgrenska Academy, University of Gothenburg in Gothenburg, Sweden, were included in the study. Three different methods were used to evaluate occlusal contacts: (I) a digital examination of the patients' casts, using the Ortho 3D Models (O3DM) software and measuring the total occlusal contact area in square millimeters (DE); (II) an examination involving the measurement of the total number of occlusal contacts on stone casts mounted in an articulator (AE); and (III) a clinical examination with the measurement of the total number of occlusal contacts with 8 μm-thick articulating foil (CE).

RESULTS

The repeated digital measurements (same casts scanned multiple times) showed a significant correlation of 0.85 (p < 0.01), which shows a diagnostic consistency. Furthermore, there was a significant correlation between the results obtained with the DE method and the AE of 0.41 (p < 0.05), and between those acquired with the AE method and the CE of 0.37 (p < 0.05). However, no significant correlation was found between the DE method and the CE method with a correlation coefficient of 0.10 (p > 0.05).

CONCLUSIONS

Digital casts can be used for quantification of the total occlusal contact area (in mm²) owing to the high reliability of repeated measurements and the strong validity of the method compared to traditionally employed stone cast measurements.

Comparative Study of Occlusal Contact Marking Indicators

BACKGROUND

A variety of indicators to register occlusal contacts are used in the daily dental practice. One of the most frequently used qualitative occlusal indicators is the articulating paper. Its reliability is often disputed because this indicator could produce false positive results or fail to register any occlusal contacts.

AIM

To compare the number and size of the recorded contacts on a tooth surface obtained with articulating paper and foil.

MATERIALS AND METHODS

Typodonts of upper and lower jaw with intact dental arches Frasaco A-3Z were fixed in a Girbach arcon articulator. Articulating contacts were marked with 12-micron Bausch articulating foil and 200-micron Bausch articulating paper under the same load. For each study a new sheet of the occlusal indicators was used, and 10 repetitions were made for each one. After every marking, the lower jaw was dismounted from the articulator and the distribution of the markings was videographed using a camera. The number of occlusal contacts was entered in a table. We analysed the markings on the first maxillary and first mandibular molars.

RESULTS

We found that fewer and bigger contacts were recorded using the 200-micron articulating paper in comparison with the contacts obtained using the foil.

CONCLUSIONS

The type of occlusal contact indicator has an effect on the number and the size of the occlusal contact markings.

[Clinical study on the accuracy of occlusal contacts on digital model]

Objective: To explore the accuracy of occlusal contacts on digital model made by intraoral scanner. Methods: Twenty healthy subjects [6 males, 14 females, (24.4±1.4) years old] with intact dentition were randomly recruited from postgraduate students in Capital Medical University School of Stomatology who volunteered to participate in this study. For each participant, the 2nd and 3rd quadrant of natural dentition was scanned. A diagnostic test design was performed. The occlusal contacts of the maximal intercuspal position (MIP) were extracted with the transillumination of silicone interocclusal records, and the extraction threshold was set as ≤50 μm. Intraoral scanning system was used to scan in MIP and generate occlusal contacts on digital model. Five groups were designed as test groups according to included tooth position: group 1 (buccal scanning ranged from tooth 21 to 23), group 2 (buccal scanning ranged from tooth 23 to 26), group 3 (buccal scanning ranged from tooth 24 to 26), group 4 (buccal scanning ranged from tooth 25 to 26), group 5 (buccal scanning ranged from tooth 21 to 26). Five groups occlusal contacts on digital model were generated respectively. According to the relevant literature, the upper occlusal surface was divided into 28 partitions, and the accuracy of occlusal contacts on digital model was calculated with the transillumination of silicone interocclusal records as the reference standard. Subgroup analysis was performed according to anterior teeth area, premolars area and molars area. Results: The accuracy of occlusal contacts on digital models of the half dentition in five buccal scanning positions were: group 1 (86.8%), group 2 (92.0%), group 3 (90.7%), group 4 (91.1%), group 5 (90.4%), and the accuracy of occlusal contacts in group 1 was significantly lower than those in the other four groups (P<0.05). The accuracy of anterior teeth area were 85.6%-93.9%; the accuracy of premolar area were 92.5%-94.4%; the accuracy of molar area were 77.3%-93.6%, group 1 was significantly lower than those in the group 4 in molars area (P<0.05), the accuracy of anterior area was statistically less than premolars area and molars area in group 1 (P<0.05). There was no statistical difference in pairwise comparison between the three sections (P>0.05). Conclusions: The digital models scanned intraoral methods provide accurate, quantitative measures of occlusal contacts when transillumination contacts are the reference standard.

Comparison between conventional and computerised methods in the assessment of an occlusal scheme

PURPOSE

In the definition of an occlusal scheme, clinicians should choose between conventional and computerised methods based on a careful appraise of the advantages and limitations. This study aims to assess the correlation between the two approaches in a clinical setting.

METHODS

Twenty-four patients were included to compare different methods of occlusal contacts assessment on the posterior surfaces of flat mandibular appliances. In supine position, they were asked to clench with maximum strength, in the maximum intercuspation position with a 24 μm articulating paper positioned between the teeth and the appliance surface. An extra-oral photograph of the marks was taken (total N = 2082). They were visually classified based on a pre-defined scale (ie, conventional assessment) and with ImageJ analysis software (ie, photographic software assessment). Additionally, a computerised occlusal analysis was performed (ie, computerised assessment). Correlation analysis of the data achieved with conventional, photographic and computerised assessments was performed.

RESULTS

Correlation between conventional and computerised assessments was weak (r = .265), whilst it was moderate between conventional and photographic assessments (r = .633), as well as between photographic and computerised assessments (r = .476).

CONCLUSIONS

This investigation showed a weak-to-moderate correlation between different methods (ie, conventional, photographic and computerised) to assess occlusal marks. None of the three can actually be considered the standard of reference, but based on their specific features, it can bet suggested that the conventional method may be enough for most clinical purposes, unless otherwise proven.

Digital evaluation of occlusal forces: comparison between healthy subjects and TMD patients

Aim

Continuous technological innovation has provided the clinicians to access to a computerized device that can analyse the different characteristics of occlusal contacts. The purpose of this research was to use this device to study the occlusal forces comparing healthy subjects and TMD patients.

Materials and methods

The study was conducted by following specific criteria to select participants; the sample was divided into two homogeneous groups: control group (CG) comprising healthy subjects, and dysfunctional group (DG) comprising TMD patients. The occlusal force analysis was performed using the computerized system T-Scan III V 5.20 T. The data were analysed with statistical methods.

Results

The most significant differences emerged between the groups in the average occlusal load distribution and in the location of the centre of occlusal forces (COF). In particular, compared with the CG and the functional standard, reductions in the molar field forces on the second and first molars of 27% and 6.9%, respectively, were observed in the DG. The COF was located in the most forward position in TMD patients compared with healthy subjects.

Conclusions

Although the differences in the distribution of the occlusal forces and the location of the occlusal centre of gravity were significant, the relationship between occlusal contacts and TMD remains to be fully clarified. Further research is needed to investigate whether studying occlusal force distributions in both healthy subjects and TMD patients.