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Bioengineering (Basel, Switzerland) Mar 2024The purposes of this study are to establish and validate a finite element (FE) model using finite element analysis methods and to identify optimal loading conditions to...
The purposes of this study are to establish and validate a finite element (FE) model using finite element analysis methods and to identify optimal loading conditions to simulate masticatory movement. A three-dimensional FE model of the maxillary and mandibular cortical bone, cancellous bone, and gingiva was constructed based on edentulous cone-beam-computed tomography data. Dental computer-aided design software was used to design the denture base and artificial teeth to produce a complete denture. Mesh convergence was performed to derive the optimal mesh size, and validation was conducted through comparison with mechanical test results. The mandible was rotated step-by-step to induce movements similar to actual mastication. Results showed that there was less than a 6% difference between the mechanical test and the alveolar bone-complete denture. It opened 10° as set in the first stage, confirming that the mouth closed 7° in the second stage. Occlusal contact occurred between the upper and lower artificial teeth as the mouth closed the remaining angle of 3° in the third stage while activating the masseter muscle. These results indicate that the FE model and masticatory loading conditions developed in this study can be applied to analyze biomechanical effects according to the wearing of dentures with various design elements applied.
PubMed: 38671758
DOI: 10.3390/bioengineering11040336 -
The Journal of Prosthetic Dentistry Jun 2024More data are needed on the influence of preparation design on the fracture strength, failure type, repairability, and polymerization-induced cracks of molar teeth...
STATEMENT OF PROBLEM
More data are needed on the influence of preparation design on the fracture strength, failure type, repairability, and polymerization-induced cracks of molar teeth restored with direct composite resin restorations.
PURPOSE
This in vitro and finite element analysis study investigated the effect of different preparation designs on fracture strength, failure type, repairability, tooth deformation, and the formation of polymerization-induced cracks of compromised molars restored with direct composite resin restorations.
MATERIAL AND METHODS
Human molars (n=64) were randomly assigned to 4 different preparation designs: undermined inlay (UI), extended inlay (EI), restricted overlay (RO), and extended overlay (EO). The teeth were restored using direct composite resin and subjected to artificial thermomechanical aging in a mastication simulator, followed by load-to-failure testing. Three-dimensional (3D) finite element analysis was conducted to assess tooth deformation. Polymerization-induced cracks were evaluated using optical microscopy and transillumination. The fracture strength data were analyzed using a Kruskal-Wallis test, while the failure mode, repairability, and polymerization cracks were analyzed using the Fisher exact test (α=.05).
RESULTS
All specimens withstood thermomechanical aging, and no statistically significant difference in fracture strength was observed among the 4 preparation designs (P>.05). The finite element analysis showed differences in tooth deformation, but no correlation was observed with in vitro fracture resistance. The RO and EO groups presented significantly more destructive failures compared with the UI and EI groups (P<.01). The RO group had significantly fewer repairable failures than the UI and EI groups (P=.024). A correlation was found between higher frequencies of repairability and higher tooth deformation. A significant correlation between the increase in microfractures and preparation design was observed (P<.01), with the UI group exhibiting a higher increase in microfracture size compared with the EO group (P<.05).
CONCLUSIONS
No influence of preparation design on the fracture strength of compromised molars restored with direct composite resin restorations was evident in this study, but the failure mode of cusp coverage restorations was more destructive and often less repairable. The finite element analysis showed more tooth deformation in inlay preparations, with lower stresses within the root, leading to more reparable fractures. Since cusp coverage direct composite resin restorations fractured in a more destructive manner, this study suggests that even a tooth with undermined cusps should be restored without cusp coverage.
Topics: Composite Resins; Finite Element Analysis; Humans; Molar; Dental Restoration Failure; Dental Restoration, Permanent; Dental Stress Analysis; Tooth Fractures; In Vitro Techniques; Inlays; Materials Testing; Polymerization
PubMed: 38670907
DOI: 10.1016/j.prosdent.2024.03.039 -
Journal of Dental Research Jun 2024Alveolar bone, as tooth-supporting bone for mastication, is sensitive to occlusal force. However, the mechanism of alveolar bone loss after losing occlusal force remains...
Alveolar bone, as tooth-supporting bone for mastication, is sensitive to occlusal force. However, the mechanism of alveolar bone loss after losing occlusal force remains unclear. Here, we performed single-cell RNA sequencing of nonhematopoietic (CD45) cells in mouse alveolar bone after removing the occlusal force. Mesenchymal stromal cells (MSCs) and endothelial cell (EC) subsets were significantly decreased in frequency, as confirmed by immunofluorescence and flow cytometry. The osteogenic and proangiogenic abilities of MSCs were impaired, and the expression of mechanotransducers () and () in MSCs decreased. Conditional deletion of and from LepR cells, which are enriched in MSCs that are important for adult bone homeostasis, significantly decreased alveolar bone mass and resisted any further changes in bone mass induced by occlusal force changes. Interestingly, mice showed a decrease in CD31 endomucin (Emcn) endothelium, and the expression of some EC-derived signals acting on osteoblastic cells was inhibited in alveolar bone. Mechanistically, conditional deletion of and in LepR cells inhibited the secretion of pleiotrophin (Ptn), which impaired the proangiogenic capacity of LepR cells. Knockdown in MSC-derived Ptn repressed human umbilical vein EC tube formation in vitro. More important, administration of recombinant PTN locally recovered the frequency of CD31Emcn endothelium and rescued the low bone mass phenotype of mice. Taken together, these findings suggest that occlusal force governs MSC-regulated endothelium to maintain alveolar bone homeostasis through the Yap/Taz/Ptn axis, providing a reference for further understanding of the relationship between dysfunction and bone homeostasis.
Topics: Animals; Mice; Homeostasis; Mesenchymal Stem Cells; YAP-Signaling Proteins; Bite Force; Adaptor Proteins, Signal Transducing; Endothelial Cells; Osteogenesis; Alveolar Bone Loss; X-Ray Microtomography; Flow Cytometry; Transcriptional Coactivator with PDZ-Binding Motif Proteins; Neovascularization, Physiologic
PubMed: 38665065
DOI: 10.1177/00220345241236120 -
The Journal of Prosthetic Dentistry Apr 2024Preserving and restoring oral functions, especially mastication and swallowing, is important to the quality of life of patients being treated for head and neck tumors....
STATEMENT OF PROBLEM
Preserving and restoring oral functions, especially mastication and swallowing, is important to the quality of life of patients being treated for head and neck tumors. Studies that help predict maximum occlusal force and tongue pressure during prosthetic treatment, necessary for providing comprehensive, appropriate treatment and encouraging patient adherence and confidence are lacking.
PURPOSE
The purpose of this clinical study was to develop a decision tree model for predicting maximum occlusal force and tongue pressure in patients diagnosed with head and neck tumors that could help both experienced and less experienced prosthodontists and oral surgeons optimize the treatment plan and support patient compliance and their quality of life.
MATERIAL AND METHODS
A total of 80 patients who had been treated for head and neck tumors were enrolled in the study. Their maximum occlusal force was measured using a pressure-sensitive film and tongue pressure using a tongue pressure measurement device. Data, including basic characteristics, were transferred to a comma separated values file, which was then imported into a statistical software package to produce a decision tree. The classification and regression tree method was used to construct a predictive model.
RESULTS
The number of occlusal contacts associated with not wearing a prosthesis, flap reconstruction, radiotherapy, chemotherapy, the number of teeth present, age, tumor stage, and tumor type were found to be associated with maximum occlusal force, with a prediction accuracy of 96.3%, area under the receiver operating characteristic curve of 0.99, sensitivity of 97%, and specificity of 94%. The number of occlusal contacts associated with wearing and not wearing a prosthesis, tumor stage, age, radiotherapy, and surgery type were found to be associated with tongue pressure, with a prediction accuracy of 96.3%, area under the receiver operating characteristic curve of 0.97, sensitivity of 97%, and specificity of 93%.
CONCLUSIONS
The decision tree model can be an effective tool for the prediction of maximum occlusal force and tongue pressure in patients diagnosed with head and neck tumors, helping both experienced and less experienced prosthodontists and oral surgeons to provide early, appropriate, and necessary treatment before starting prosthetic treatment and helping patients with treatment compliance and communication with medical staff.
PubMed: 38664182
DOI: 10.1016/j.prosdent.2024.03.025 -
MethodsX Jun 2024In the literature, there is consistent evidence related to the influence of chewing on brain functions, either from experimental models or in humans. In the case of...
In the literature, there is consistent evidence related to the influence of chewing on brain functions, either from experimental models or in humans. In the case of humans, most results are restricted to functional tests, lacking cellular or molecular evidence. In the described method, the possibility of using experimental models is presented, as well as the mimicry of deprivation and rehabilitation of masticatory activity and without stress impact. By opting for the use of mash feed, instead of extracting or implanting an intraoral device, alternations between restriction and rehabilitation of mastication were imposed on murine models. The animals completed various temporal windows, with aging also representing a potential factor for translational dementia associations. Additionally, animals were segregated into environments characterized as either standard, simulating a sedentary lifestyle, or enriched, rich in sensorimotor and visuospatial stimulation. Thus, it was possible to study the influence of changes in masticatory activity, associated with aging and environmental enrichment, on cells from subregions of the hippocampus, as well as on performance in tests of learning and spatial memory.•Animal model for masticatory activity alteration;•Masticatory deprivation and rehabilitation, and•Models to study the interaction among masticatory activity, aging and enrichment environment.
PubMed: 38660048
DOI: 10.1016/j.mex.2024.102701 -
Cureus Mar 2024Facial muscles, particularly those involved in mastication, play a pivotal role in the chewing process. Despite their influence on chewing, these muscles undergo...
BACKGROUND
Facial muscles, particularly those involved in mastication, play a pivotal role in the chewing process. Despite their influence on chewing, these muscles undergo alterations during mastication. Examining the relationship between chewed substances and muscle activity can provide insights into various pathological processes and aid in the development of therapeutic chewing techniques.
AIM
This study aimed to evaluate the impact of different commercially available chewing gums on the activity of key masticatory muscles.
METHOD
Twenty-two participants were recruited for the study. They were instructed to chew four commercially available gums: group 1 comprised sugar gum with a strong flavor; group 2 included gum containing sorbitol; group 3 consisted of gum containing xylitol; and group 4 provided sugar gum with a mild flavor. Electromyogram (EMG) recordings were utilized to assess muscle activity. Various aspects of muscle activity, including chewing time, maximum muscle potential, and coordination between different muscles, were evaluated. Data tabulation and analysis were performed using IBM SPSS software version 23.0 (IBM Corp., Armonk, NY).
RESULT
Analysis revealed that in terms of temporalis symmetry, group 2 exhibited the highest mean deviation, while for masseter symmetry, group 3 demonstrated the highest mean deviation. The total deviation for the temporalis and masseter muscles was 72.16% and 65.55%, respectively, indicating greater symmetry in the temporalis muscle. Additionally, group 3 displayed the highest mean deviation in both left and right-sided synergic activity of the muscles. The total deviation for the right and left sides was 64.34% and 65.67%, respectively.
CONCLUSION
The findings suggest that sugar-free chewing gums elicit increased muscle activity compared to sugar-containing chewing gums. Furthermore, the utilization of calorie-free chewing gums with a firm texture was associated with better-coordinated muscle activity. These results provide valuable insights into the effects of different chewing gums on masticatory muscle function and coordination, which may have implications for therapeutic interventions and oral health management.
PubMed: 38659520
DOI: 10.7759/cureus.56849 -
BMC Oral Health Apr 2024Up to 25% of the tooth extraction after root canal treatment could be attributed to the vertical root fracture (VRF). The treatment choice for teeth with VRF would...
BACKGROUND
Up to 25% of the tooth extraction after root canal treatment could be attributed to the vertical root fracture (VRF). The treatment choice for teeth with VRF would mostly be the extraction despite some repairing methods were also reported. The repairing treatment result of VRF would mostly depend on the fixation strength and the bioactivity of the repairing materials, especially for the posterior teeth with high masticating stresses. This case report designed a novel surgical treatment approach for the VRF of posterior teeth.
METHODS
a maxillary premolar with buccal-palatal complete VRF was treated with a new dual-layered repairing approach using adhesive resin + iRoot BP Plus bioceramic cement to fill the modified fracture line with retention forms through the intentional replantation.
RESULTS
At the 24-month review, the tooth showed desirable periodontal healing and normal function.
CONCLUSIONS
This case report indicated that the dual-layered repairing approach might be effective for saving the posterior teeth with VRF. Nevertheless, further clinical trials are needed for its long-term result.
Topics: Humans; Tooth Fractures; Tooth Root; Bicuspid; Male; Female; Tooth Replantation; Root Canal Therapy
PubMed: 38658927
DOI: 10.1186/s12903-024-04268-9 -
JDR Clinical and Translational Research Apr 2024Oral frailty leads to poor nutritional status, which, in turn, leads to frailty. This cross-sectional study aimed to determine regional differences in the prevalence of...
INTRODUCTION
Oral frailty leads to poor nutritional status, which, in turn, leads to frailty. This cross-sectional study aimed to determine regional differences in the prevalence of oral frailty and to identify factors associated with oral frailty using 3-level multilevel models.
METHODS
This study comprised 165,164 participants aged ≥65 y without long-term care requirements in the Japan Gerontological Evaluation Study. The dependent variable was oral frailty, which was calculated based on age, number of teeth, difficulty in eating tough foods, and choking. The individual-level independent variables included sociodemographics, present illness, social participation, frequency of meeting friends, and social capital. The local district-level independent variable was social capital ( = 1,008) derived from exploratory factor analyses. The municipality-level independent variable was population density ( = 62). Three-level multilevel Poisson regression analysis was performed to calculate the prevalence ratios (PRs).
RESULTS
The prevalence of oral frailty in municipalities ranged from 39.9% to 77.6%. Regarding district-level factors, higher civic participation was significantly associated with a lower probability of oral frailty. At the municipality level, the PR of the rural-agricultural area was 1.17 (95% confidence interval, 1.11-1.23) (reference: metropolitan).
CONCLUSION
These results highlight the usefulness of oral frailty prevention measures in encouraging social participation in rural areas.
KNOWLEDGE TRANSFER STATEMENT
The results of the present study showed regional differences in oral frailty. In particular, rural-agricultural areas show higher prevalence rates of oral frailty than those in metropolitan cities. Promoting measures of social participation among older adults may help prevent oral frailty in rural areas.
PubMed: 38654451
DOI: 10.1177/23800844241238648 -
Medical & Biological Engineering &... Apr 2024The aim of this study was to evaluate the bone tissue effects under dynamic loading using finite element analysis (FEA) for four angled abutments with different deviated...
The aim of this study was to evaluate the bone tissue effects under dynamic loading using finite element analysis (FEA) for four angled abutments with different deviated palatal lateral tilt angles. A three-dimensional model of the posterior maxillary region and an implant crown model were reconstructed and assembled with a three-dimensional model of the implant, angled abutment, and central screw to create a total of 10 three-dimensional finite element models tilted at , , , and in three groups, and the dynamic loads simulating oral mastication were loaded on the implant crown to analyze the equivalent stresses and strains in the peri-implant bone tissues. Under the dynamic loading, the cortical bone on the buccal side of the implant neck showed different degrees of stress concentration, and the cortical bone stress was much higher than the cancellous bone, and the strain concentration area of each model was located in the bone tissue around the implant neck and base. For the use of angular abutment, under the premise that the cortical bone stresses and strains of the 10 models meet the requirements for use, the peak stresses of 2.907 MPa, 3.018 MPa, and 2.164 MPa were achieved by using the angular abutment to achieve the tilt angles of , , and implantation, which is more advantageous compared with other models.
PubMed: 38653881
DOI: 10.1007/s11517-024-03081-4 -
Ecology and Evolution Apr 2024Morphological adaptation is the change in the form of an organism that benefits the individual in its current habitat. Mole-rats (family Bathyergidae), despite being...
Morphological adaptation is the change in the form of an organism that benefits the individual in its current habitat. Mole-rats (family Bathyergidae), despite being subterranean, are impacted by both local and broad-scale environmental conditions that occur above ground. Common mole-rats () present an ideal mammalian model system for the study of morphological variation in response to ecology, as this species is found along an aridity gradient and thus can be sampled from geographically non-overlapping populations of the same species along an environmental longitudinal cline. Using the mass of five internal organs, ten skeletal measurements and 3D morphometric analyses of skulls, we assessed the morphology of wild non-breeding individuals from five common mole-rat populations in South Africa. We found that the body mass and mean relative mass of the spleen and kidneys in arid populations was larger, and individuals from arid regions possessed shorter legs and larger inter-shoulder widths compared to individuals from mesic regions. Additionally, arid populations demonstrated greater skull depth, and shape change of features such as angular processes of the lower jaw than mesic individuals, indicating that these distinct geographic populations show differences corresponding to the aridity gradient, potentially in response to environmental factors such as the variation in food sources found between different habitats, in addition to different soil compositions found in the different regions. Arid populations potentially require a stronger jaw and neck musculature associated with mastication to chew xeric-adapted plants and to dig through hard soil types, whereas mesic populations excavate through soft, looser soil and may make use of their front limbs to aid the movement of soils when digging. Aridity influences the morphology of this species and could indicate the impact of environmental changes on speciation and mammalian skull morphology.
PubMed: 38651162
DOI: 10.1002/ece3.11301