Unilateral, isometric bite force in 8-68-year-old women and men related to occlusal factors

Effects of healthy aging on tongue-jaw kinematics during feeding behavior in rhesus macaques

Several age-related oral health problems have been associated with neurodegenerative diseases such as Alzheimer's Disease (AD), yet how oromotor dysfunction in healthy aging differ from those found in pathological aging is still unknown. This is partly because changes in the cortical and biomechanical ("neuromechanical") control of oromotor behavior in healthy aging are poorly understood. To this end, we investigated the natural feeding behavior of young and aged rhesus macaques (Macaca mulatta) to understand the age-related differences in tongue and jaw kinematics. We tracked tongue and jaw movements in 3D using high-resolution biplanar videoradiography and X-ray Reconstruction of Moving Morphology (XROMM). Older subjects exhibited a reduced stereotypy in tongue movements during chews and a greater lag in tongue movements relative to jaw movements compared to younger subjects. Overall, our findings reveal age-related changes in tongue and jaw kinematics, which may indicate impaired tongue-jaw coordination. Our results have important implications for the discovery of potential neuromechanical biomarkers for early diagnosis of AD.

Oro-facial function and quality of life in children and adolescents with large horizontal maxillary overjet-A case-control study

BACKGROUND

Large horizontal maxillary overjet (overjet) is associated with reduced bite force (BF) and number of contacts, which influence the chewing effectivity (CE). Oral health, oro-facial function (OF) and malocclusion have great impact on psychological well-being and quality of life (QoL).

OBJECTIVES

The aims of the study were to examine OF, temporomandibular disorders (TMD), BF, CE, QoL and well-being in children and adolescents with large overjet.

METHODS

The study was a case-control study including healthy children with large overjet in the study group compared to a control group of healthy children with neutral occlusion, all 9-14 years old. OF was examined by use of Nordic Orofacial Test-Screening (NOT-S), Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and registration of morphological and functional occlusion. QoL and well-being were examined using KIDSCREEN-10 and Strengths and Difficulties Questionnaire.

RESULTS

The study and control groups included 37 and 32 participants, respectively. Significantly increased NOT-S score (p < .001) and reduced BF (p = .011), numbers of contacts (p < .001) and CE (p = .005) were found in the study group. BF, numbers of contacts and CE were negatively associated with erupting canines and premolars. No significant difference was found in age, gender, dental eruption, TMD diagnosis or QoL between the groups. Significantly increased emotional symptoms (p = .007), hyperactivity (p = .043) and total difficulties score (p = .009) were found in the study group.

CONCLUSION

The study group showed higher NOT-S score and reduced BF, number of contacts and CE. No difference in QoL were found between the groups, although reduced well-being and increased emotional symptoms, hyperactivity and total difficulties were found in the study group.

Short-term and long-term effects of unilateral external carotid artery ligation on orofacial functions in rats

The external carotid artery (ECA) plays a major role in supplying blood to the head and neck. Although impeded blood flow in the ECA is expected to affect orofacial functions, few studies have shown how blood flow obstruction in the ECA contributes to impairment of these functions, including chewing and swallowing. This study was performed to investigate the effects of ECA ligation (ECAL) on immediate and long-term changes in masticatory and swallowing functions as well as the jaw-opening reflex evoked in the digastric muscle. The experiments were carried out using male Sprague-Dawley rats. In the acute experiment, the digastric reflex evoked by low-threshold electrical stimulation of the inferior alveolar nerve and the swallow reflex, identified by digastric and thyrohyoid electromyographic (EMG) bursts, were compared between before and 1 h after ECAL. The chronic experiment was conducted on freely moving rats. EMGs of the masseter, digastric, and thyrohyoid muscles were chronically recorded. The long-term effects of ECAL on behavior and muscle histology were compared between rats with an intact ECA and rats with ECAL. In the acute experiment, the peak amplitude of the digastric reflex on the ECAL side was significantly decreased 1 h after ECAL. In the chronic experiment, although most parameters of the masticatory and swallowing EMGs were not significantly different between the groups, the results suggest wide variation of the effect of ECAL on the muscles. Blood supply compensation from collaterals of the internal carotid artery may be permanent in some animals.NEW & NOTEWORTHY The inhibitory effect of unilateral external carotid artery ligation (ECAL) on the ipsilateral digastric reflex was small but evident. Most parameters of masticatory and swallowing muscle activity were not significantly different after ECAL. Wide variation was noted in the effect of ECAL on the ipsilateral muscle activity. Blood supply compensation from collaterals of the internal carotid artery may occur in response to the impaired blood flow.

Development of a test bench for biomechanical simulation-a preliminary study of mandibular forces

Purpose: The aim of this study is to develop a test bench, which integrates different complexity levels and enables in that way a flexible and dynamic testing for mid and long term intervals as well as testing of maximum loads till implant failure of different osteosynthesis systems on the mandible. Material and Methods: For this purpose, an analysis of the state of the art regarding existing test benches was combined with interviews of clinical experts to acquire a list of requirements. Based on these requirements a design for a modular test bench was developed. During the implementation of the test stand, functional tests were continuously carried out and improvements made. Depending on the level of complexity, the test bench can be used either as an incorporated variant or as a standalone solution. In order to verify the performance and the degree of fulfilment of the requirements of these two variants of the test bench, preliminary studies were carried out for all levels of complexity. In these preliminary studies, commercially available osteosynthesis and reconstruction plates were investigated for their biomechanical behaviour and compared with data from the literature. Results: In total, fourteen test runs were performed for the different levels of complexity. Firstly, five test runs were executed to test the simplified load scenario in the incorporated variant of the test bench. High forces could be transmitted without failure of the miniplates. Secondly a quasi-static test scenario was examined using the incorporated variant with simplified load insertion. Five experiments with a number of cycles between 40,896 and 100,000 cycles were carried out. In one case the quasi-static testing resulted in a fracture of the tested reconstruction plate with a failure mode similar to the clinical observations of failure. The last four test runs were carried out using the standalone variant of the test bench simulating complex load patterns via the insertion of forces through imitated muscles. During the test runs joint forces were measured and the amplitude and vector of the resulting joint forces were calculated for both temporomandibular joints. Differences in the force transmission depending on the implant system in comparison to the zero sample could be observed. Conclusion: The presented modular test bench showed to be applicable for examination of the biomechanical behavior of the mandible. It is characterized by the adjustability of the complexity regarding the load patterns and enables the subsequent integration of further sensor technologies. Follow-up studies are necessary to further qualify and optimize the test bench.

Bolus rheology of texture adjusted food-Effect of age

Swallowing disorders, or dysphagia, affect a large part of the population due to factors such as degenerative diseases, medication side effects or simply age-related impairment of physiological oropharyngeal function. The management of dysphagia is mainly handles through texture-modified foods of progressively softer, smoother, moister textures, depending on the severity of the disorder. Rheological and physiological-related properties of boluses were determined for a group of five older persons (average age, 74) for a set of texture-modified foods: bread, cheese and tomato and the combination into a sandwich. The softest class was gel food, after which came a smooth timbale; both were compared to boluses of regular food. The subjects chewed until ready to swallow, at which point the bolus was expectorated and measured regarding saliva content, linear viscoelasticity and shear viscosity. The results were compared to those of a previously studied younger group (average age, 38). The general physiological status of the subjects was determined by hand and tongue strength, diadochokinesis and one-legged standing and showed that all subjects were as healthy and fit as the younger group. Age-related properties such as one-legged standing with closed eyes and salivary flow plus bolus saliva content were lower for the older group, but the average chews-until-swallow was surprisingly also lower. Consequently, bolus modulus and viscosity were higher than for the younger group. Overall, the intended texture modification was reflected in bolus rheological and physiological-related properties. Bolus modulus, viscosity, saliva content and chews-until-swallowed all decreased from regular food to timbale food to gel food.

Development of integrated jaw-neck motor function in children at 6, 10 and 13 years of age compared to adults: A kinematic longitudinal study

BACKGROUND

The functional integration of the jaw and neck motor systems, of great importance to everyday oral activities, is established in early childhood. Detailed characterisation of this developmental progress is largely unknown.

OBJECTIVE

To establish developmental changes in jaw-neck motor function in children over the ages 6-13 years compared to adults.

METHODS

Jaw and head movement kinematics during jaw opening-closing and chewing were longitudinally recorded in 20 Swedish children (8 girls) at 6 (6.3 ± 0.4), 10 (10.3 ± 0.3) and 13 (13.5 ± 0.7) years of age and 20 adults (9 women, 28.2 ± 6.7). Movement amplitudes, jaw movement cycle time (CT), coefficient of variation (CV) and head/jaw ratio for amplitudes were analysed. Linear mixed effect analysis and Welch's t-test were used.

RESULTS

Children showed pronounced movement variability and longer CT at 6 and 10 years old during opening and chewing (p < .001). Compared to adults, 6-year-olds showed higher head/jaw ratios (p < .02) and longer CT (p < .001) during opening and chewing, and higher CV-head (p < .001) during chewing. Whereas 10-year-olds showed larger jaw and head amplitudes (p < .02) and longer CT (p < .001) during opening, and longer CT (p < .001) and higher CV-head (p < .001) during chewing. For 13-year-olds, longer CT (p < .001) during chewing was found.

CONCLUSION

Children showed pronounced movement variability and longer movement cycle time at 6-10 years and developmental progress in jaw-neck integration from 6 to 13 years, with 13-year-olds displaying adult-like movements. These results add new detailed understanding to the typical development of integrated jaw-neck motor function.

Application in the analysis of the occlusal force of free-end missing tooth implant restoration with T-SCAN III

Introduction: The occlusal force of the teeth in the dental arch and the remaining adjacent natural teeth will change after implant restoration with a free-end missing tooth. This study intends to use the T-SCAN III scanner to collect dynamic quantitative data before and after the restoration of free-end implants and to explore the application of the T-SCAN III in redistributing the occlusal force of free-end implants.

Methods: In this study, 24 patients with free-end implant restoration were selected, and their occlusion was tested before, immediately after, and 3 months after implant restoration.

Results: In all 24 cases, the bite force of the first natural tooth adjacent to the implanted tooth after restoration changed from 19.12% ± 9.48%–12.93% ± 11.47% (p &lt; 0.01). For additional data analysis, all cases were further subdivided by single implant and fixed bridge restorations. In 17 cases, there was a successful follow-up after 3 months. The percentage of the total bite force of dental arch with implant increased from 41.92% ± 10.78%–53.06% ± 10.71% (p &lt; 0.01).

Discussion: This study shows that the free-end implant restoration protects the remaining natural teeth, and the patient’s missing dental arch bite force improves within 3 months of implant restoration.

Occlusal contacts and treatment with the Invisalign appliance: a retrospective analysis of predicted vs achieved outcomes

OBJECTIVES

To quantify the predicted occlusal contact outcomes compared with the clinically achieved occlusal contacts following treatment using the Invisalign aligner appliance.

MATERIALS AND METHODS

The occlusal contacts of 33 adult patients presenting with a Class I mild-to-moderate malocclusion (spacing <4 mm or crowding of <6 mm) and treated using the Invisalign appliance were measured at the initial, predicted, and achieved stages of treatment by the metrology software Geomagic Control X. Assessed measurements were related to individual teeth and anterior, posterior, and overall contacts.

RESULTS

The mean (standard deviation) difference between the achieved occlusal contact was significantly less than that predicted for overall occlusal contact and posterior occlusal contact (P < .0025). The achieved posterior occlusal contact was also less than pretreatment initial posterior occlusal contact. There was no difference in anterior occlusal contact between the predicted and achieved outcomes (P > .05). The central and lateral incisors displayed no statistically significant difference between the predicted and achieved occlusal contact. The patients with prescribed overcorrection demonstrated a statistically significant difference in predicted occlusal contact compared with those with nonprescribed overcorrection (P ≤ .0025), but no statistically significant difference in achieved occlusal contact.

CONCLUSIONS

Treatment by the Invisalign appliance in Class I mild-to-moderate malocclusion resulted in a decrease in posterior occlusal contact. Further research is required to account for the deficiencies between the predicted and achieved clinical outcome related to occlusal contact and to determine the corrective changes required in the treatment protocols.

Association of Non-carious Cervical Lesions with Oral Hygiene Aspects and Occlusal Force

AIM

The purpose of this case-control (CT) study was to investigate the association between the presence of non-carious cervical lesions (NCCLs) with occlusal force and other potential risk factors.

MATERIALS AND METHODS

Thirty-nine participants with NCCLs [cases (CS)] and 39 with no NCCLs [control (CT)] attending the dental clinic of the Faculdades Integradas São Pedro (FAESA), located in Brazil, were enrolled in this study. Information was collected through anamnesis, clinical examination, and a questionnaire addressing aspects related to tooth brushing, dentifrice, and mouthwash use. In clinical examination, patients were submitted to four measurements of occlusal force in the maxillary first premolars and maxillary first molars, using a strain gauge sensor of medium intensity, the Flexiforce (Tekscan, South Boston, Massachusetts, United States of America). The sensor was calibrated for the unit of measurement in Newtons (N). Data were analyzed using a student's t-test and multiple logistic regression, e with a significance level of 5%.

RESULTS

There was no statistically significant difference between the case and CT groups regarding the bite force in the four measured regions. Logistic regression identified sex as a factor significantly associated with NCCLs (p = 0.020). The odds ratio showed the female sex had more chance (OR = 6.082; CI = 1.332-27.765) of having NCCLs.

CONCLUSION

It is concluded that females presented a higher risk factor for NCCLs than men. In contrast, there was no association of occlusal force, as well as aspects related to brushing and deleterious habits.

CLINICAL SIGNIFICANCE

Females have a higher risk factor for non-carious lesions than men.

Common eating habit patterns are associated with a high maximum occlusal force and pre-eating cardiac vagal tone

Background

Masticatory function is associated with nervous function, including autonomic nervous function, and both functions are influenced by human habits. In a previous preliminary study of 53 young women, we found that eating habit patterns were associated with occlusal force as an indicator of masticatory function. Therefore, we hypothesized that relationships exist between occlusal force, the autonomic nervous system, and eating habit patterns.

Methods

To test our hypothesis, we analyzed the relationship between heart rate variability measured before and after lunch in 53 young women, and measured and surveyed maximum occlusal force and eating habit patterns, respectively, in these participants.

Results

High occlusal force was associated with an increased high-frequency (HF) component (vagal tone index) of the heart rate variability index immediately before lunch (standardized regression coefficient (β) = 0.417, P = 0.002). Each of the eating habit items surveyed in a questionnaire showed a similar tendency for the HF component immediately before lunch and maximum occlusal force; in particular, "Habit of eating breakfast" and "Number of meals per day" were significantly associated with both variables. Additionally, total eating habit scores related to higher maximum occlusal force were associated with an increase in the HF component immediately before lunch (β = 0.514, P < 0.001). The maximum occlusal force and the pre-eating HF component values were stratified by total eating habit scores (into low, medium, high categories), and the high scores were significantly higher than the medium or low scores.

Conclusions

Occlusal force and the pre-eating cardiac vagal response of individuals were characterized by their common eating habit patterns, indicating that eating habits may be simultaneously associated with the development of masticatory function, nervous system development, and cardiovascular rhythm. Although further research is needed to investigate these relationships in detail, our findings provide insights that will inform the study of physical functions, neurodevelopment, habitual behaviors, and health in humans.

A Low-Cost Wireless Bite Force Measurement Device

Assessing maximum voluntary bite force is important to characterize the functional state of the masticatory system. Due to several factors affecting the estimation of the maximum bite force, a unique solution combining desirable features such as reliability, accuracy, precision, usability, and comfort is not available. The aim of the present study was to develop a low-cost bite force measurement device allowing for subject-specific customization, comfortable bite force expression, and reliable force estimation over time. The device was realized using an inexpensive load cell, two 3D printed ergonomic forks hosting reusable subject-specific silicone molds, a read-out system based on a low-cost microcontroller, and a wireless link to a personal computer. A simple model was used to estimate bite force taking into account individual morphology and device placement in the mouth. Measurement reliability, accuracy, and precision were assessed on a calibration dataset. A validation procedure on healthy participants was performed to assess the repeatability of the measurements over multiple repetitions and sessions. A 2% precision and 2% accuracy were achieved on measurements of forces in the physiological range of adult bite forces. Multiple recordings on healthy participants demonstrated good repeatability (coefficient of variation 11%) with no significant effect of repetition and session. The novel device provides an affordable and reliable solution for assessing maximum bite force that can be easily used to perform clinical evaluations in single sessions or in longitudinal studies.

Bite Force, Occlusal Contact and Pain in Orthodontic Patients during Fixed-Appliance Treatment

Previously, bite force, occlusal contact and pain were investigated in orthodontic patients with moderate-to-severe malocclusion, but not in patients with minor malocclusion. The purpose of this study was to investigate changes in bite force, teeth in occlusal contact and pain in orthodontic patients with minor crowding before orthodontic treatment (T0), after bonding (T1), during treatment (T2), post-treatment (T3) and during retention (T4). In total, 27 patients (21 females, 6 males, median age 15.3 years) with neutral occlusion and normal craniofacial morphology were treated with non-extractions and fixed appliances. Differences in the registered data were analysed by a mixed linear model with repeated measures. Bite force and teeth in occlusal contact significantly decreased between T0 and T1 (p < 0.0001, respectively) and between T0 and T2 (p < 0.01, respectively). Bite force and teeth in occlusal contact significantly increased between T1 and T4 (p < 0.05, p < 0.0001, p < 0.001, respectively) and between T2 and T4 (p < 0.05, p < 0.0001, p < 0.01, respectively). No significant difference in pain was found. The results indicate that bite force and teeth in occlusal contact significantly decreased during treatment and reached baseline level at retention. The findings may prove valuable for informing orthodontic patients with minor malocclusion.

Anterior occlusion in shortened dental arches

Objectives

The aim of this study was to examine the occlusion of anterior teeth in individuals with shortened dental arch (SDA).

Material and methods

In a case–control clinical study, 41 individuals with SDA and 41 individuals with complete dental arch (CDA) participated. The CDA control group was matched for age and gender. Testing for occlusal contacts of anterior maxillary teeth was conducted by biting on foil strips (8 µm) with subjectively normal bite force (NBF) and maximal bite force (MBF). The data was analyzed on individual and tooth levels.

Results

The median rates of anterior maxillary teeth with occlusal contacts were 0.67 (NBF) and 0.83 (MBF) in the SDA group and 0.50 (NBF) and 0.83 (MBF) in the CDA group. Within both groups, the contact rates were significantly higher in MBF. The group difference with NBF was significant. A generalized linear model showed that the odds of an anterior maxillary tooth to have an occlusal contact were greater in the SDA both for NBF with an odds ratio (OR) 2.277 and MBF with an OR 1.691.

Conclusions

The findings suggest effective compensatory mechanisms relative to the occlusal function in individuals with SDA.

Clinical relevance

The study delivers further evidence regarding the SDA concept as a viable option in the management of posterior tooth loss.

Sexual dimorphism of the mandibular conformational changes in aging human adults: A multislice computed tomographic study by geometric morphometrics

The aging process has an impact on mandibular bone morphology and can therefore affect shape sexual dimorphism. Understanding the effect of senescence on mandibular shape changes is particularly important to correctly estimate the sex of an individual and predict age-related conformational modifications. The purpose of this study was to assess age-related changes in mandibular shape and sexual dimorphism. The study sample comprised 160 Multi Slice Computed Tomography examinations of individuals aged 40 to 79 years. Geometric morphometric analysis of fourteen osteometric landmarks was used to examine sexual dimorphism and patterns of mandibular shape variation with age. Results showed that mandibular sexual dimorphism of shape remained significant with aging. Conformational changes occurred between 50 and 70 years and were different for male and female individuals. Females presented earlier and more marked age-related shape changes than males. These observations suggest that mandibular senescence is a sexually dimorphic process since its onset, rate, and the areas subjected to conformational changes differ from male to female individuals. Senescence-related changes present substantial variability, and further investigation is required to determine precisely the age that marks their onset.

Masticatory Force in Relation with Age in Subjects with Full Permanent Dentition: A Cross-Sectional Study

Masticatory performance is directly correlated with masticatory muscle work to grind and cut the food. Chewing efficacy is decisive to eating a variety of foods needed maintain general health status at all ages. Older people have oral problems that get worse with age. Elders have more pathologies such as periodontal diseases, caries, tooth loss and inadequate dental prostheses than younger subjects. Objectives: to investigate the correlation between masticatory bite force (MBF) and body mass index (BMI) vs. aging and sex. Methods: This study was performed on 426 subjects (213 females plus 213 male) assigned into five different groups by age. Group “A” aged from 20 to 35 years; group “B” aged 45–59 years; group “C” aged 60–69 years; group “D” aged 70–79 years; and group “E” aged more than 79 years. Results: There were not statistically significant differences in right-side MBF versus left-side MBF. The differences between sex were statistically significant with a stronger bite in males than females (p < 0.05). At the same time, younger subjects had a stronger bite than elders (p < 0.05). In group “E”, more corpulent subjects (BMI > 25) had an MBF higher than less corpulent subjects (BMI < 25, p < 0.05). The analysis of mean MBF showed a statistically significant difference within all groups stratified by BMI with mean values inversely proportional with age (p < 0.001). Conclusion: The results in our study confirm data from many scientific papers. The importance of the present paper was to correlate data between and within a large sample with a wide range of ages. Our sample subjects had a 31%–33% decrease in MBF from group “A” to group “E” group, but they all had full permanent dentation and they preserved a valid MBF.

Digital Radiographic Study of Gonial angle in Forensic Odontology in a Tertiary Care Centre: A Descriptive Cross-sectional Study

Introduction:

Gonial angle measurements serve as an important parameter of the craniofacial complex and are usually studied on lateral cephalograms, but recently panoramic radiographs have also been used. The aim of this study is to measure the gonial angle using orthopantomogram and lateral cephalogram based on age, gender, ethnicity, and skeletal malocclusion in a tertiary care hospital.

Methods:

This is a descriptive cross-sectional study comprising 350 selected radiographs of apparently healthy individuals collected for a period of one year, from the Department of Oral Radiology of a tertiary care centre of Nepal. Gonial angle measurements were recorded from digital panoramic radiograph (both right and left side) and lateral cephalogram. Data was collected in terms of age, gender, ethnicity, and skeletal malocclusion and then statistically analysed using the Statistical Package for the Social Sciences version 20.

Results:

The mean gonial angle for panoramic right, left and lateral cephalogram was 122.490±7.570, 123.620±7.060, and 124.150±6.910, respectively. There was a decrease in the mean values of the gonial angle observed as age advances seen in all the radiographs. The gonial angle measured in Class III malocclusion was higher in all the radiographs, followed by Class II and Class I. Gonial angles obtained in females were higher than the males in all the radiographs. Finally, the Aryan population showed a higher gonial angle compared to the Mongolian population in all the radiographs.

Conclusions:

Panoramic radiograph (left side), could be considered as a reliable tool to measure the gonial angle.

Association between cognitive health and masticatory conditions: a descriptive study of the national database of the universal healthcare system in Japan

Cognitive health is subject to decline with increasing numbers of lost teeth which impacts mastication. This study is a descriptive data analysis of the association between masticatory and cognitive conditions using a large database. We obtained the dental and medical records from Japan's universal healthcare system (UHCS) from the national database in 2017. The data from 94% of the Japanese population aged 65 and over is included. It is inclusive of diagnostic codes for various types of cognitive impairment, as well as dental treatment records from 2012 to 2017. The cognitive impairment group was compared to those without a diagnosis of cognitive impairment. Crude odds ratio between loss of mastication with natural teeth (exposure) and cognitive impairments (outcome) were compared. Patients who have lost masticatory function are likely to have cognitive impairment with an odds ratio of 1.89 (p<0.0001) for early elderly (aged 65-75) and 1.33 (p<0.0001) for advanced elderly (over 75). Patients who are edentulous and function with complete dentures are likely to have cognitive impairment with an odds ratio of 2.38 (p<0.0001) and 1.38 (p<0.0001), respectively. The data shows a convincing and significant result of an association between cognitive health and oral health, related to masticatory conditions.

Comparison of Bite Force and the Influencing Factors Pre- and Post-cementation of Stainless Steel Crown in Children Using T-Scan

Background

In children, stainless steel crowns (SSCs) have become an invaluable restorative option for grossly decayed primary teeth. The crowns are manufactured in different sizes with preformed anatomy which requires trimming or contouring as a necessary step to fit an individual tooth. Initially, this may produce variation in the occlusal contact points yet may not result in pain or discomfort. Little research exists regarding bite force equilibration measurements in children after placing SSC, and its influencing factors such as age and gender.

Aim and objective

To evaluate and compare the measurements of bite force pre- and post-cementation of SSC using the conventional technique at maximal intercuspal position (MIP) on primary molars at different time intervals and whether age and gender influence bite force measurements.

Design

Bite force and occlusal contacts during occlusion were made using T-Scan III. Twenty children scheduled for treatment who needed SSCs were included. T-Scan measurements of the bite force and occlusal contacts of the maxilla and mandibular teeth were recorded and analyzed before and immediately after cementation of SSC later 4 weeks during the follow-up period. These measurements were correlated with age and gender influence.

Results

There was no significant result in the percentage of bite force on the crowned tooth (placement of SSC) at different time intervals. Prematurities were present in all the groups but a significant reduction was seen on the crowned tooth from baseline to 1-month follow-up (p = 0.03). Also, a statistically significant increase in the bite force was seen in >7 years of age (p = 0.006) and no statistical significance among the gender.

Conclusion

Following the standard tooth preparation, the SSC will continue to appear clinically acceptable for many years. Our study children showed an adaptable masticatory system irrespective of age and gender during growth and development.

How to cite this article

Aishwarya N, Nagarathna C, Poovani S, et al. Comparison of Bite Force and the Influencing Factors Pre- and Post-cementation of Stainless Steel Crown in Children Using T-Scan. Int J Clin Pediatr Dent 2021;14(1):46-50.

Mechanical performance of Anatomic-Functional-Geometry dental treatments: A computational study

In this paper the biomechanical response of a novel dental preparation technique, referred to as the Anatomic-Functional-Geometry treatment (AFG), is investigated through a 3D nonlinear finite-element modelling approach. A comparative investigation against a standard technique employed in dental clinical practice is carried out, by simulating typical experimental mechanical tests and physiological functional conditions. Failure mechanisms of treated tooth models are investigated through a progressive damage formulation implemented via a displacement-driven incremental approach. Computational results clearly show that AFG-treated teeth, as a consequence of a more conservative morphological preparation of the tooth, are characterized by more effective crown-dentin loading transfer mechanisms, higher fracture strength levels and more homogeneous stress patterns than the standard-treated ones, thereby opening towards widespread clinical application.

Manifestation of stress and anxiety in the stomatognathic system of undergraduate dentistry students

Objective

To assess the relationship between psychoemotional state and signs of oral cavity occlusal and nonocclusal parafunctions, together with masseter muscle tone, in undergraduate dentistry students.

Methods

The study population comprised first and fifth grade dentistry students who were investigated using psychological and health questionnaires, and stomatological examination with electromyography of the masseter muscles. Differences in variables between first and fifth grade students were analysed using Student’s t-test or χ²-test and Pearson’s correlation coefficient was used to analyse associations between variables.

Results

A total of 113 students (52 first-grade, mean age 20 years; and 61 fifth-grade, mean age 23.6 years) were included. Older age was associated with lower level of perceived stress and anxiety. Moreover, a significant positive relationship was observed between level of perceived stress and anxiety and tone of both masseter muscles.

Conclusions

Increased psychoemotional burden and increased rates of experienced anxiety were associated with growth of masseter muscle tone in this study population.

Effect of food hardness on chewing behavior in children

Objective

To investigate the effects of food hardness on chewing behavior in children compared with adults.

Materials and methods

Healthy children (3–17 years) were equally divided into five groups based on their dental eruption stages. Each participant ate soft and hard viscoelastic test food models (3 each), while the three-dimensional jaw movements and electromyographic (EMG) activity of the bilateral masseter muscles were recorded. The data from the children were compared with a control group of healthy adults (18–35 years). The data were analyzed with nonparametric tests.

Results

There was no significant difference in the number of chewing cycles and the duration of the chewing sequence between children groups and adults. Children with primary dentition (3–5 years) showed shorter lateral jaw movement and higher muscle activity at the end of the chewing sequence, compared with adults. Further, children’s age-groups (3–14 years) failed to adapt their jaw muscle activity to food hardness. However, at the late-permanent dentition stage (15–17 years), children were capable of performing adult-like chewing behavior.

Conclusions

Overall, it seems that children as young as 3-year-old are quite competent in performing basic chewing function similar to adults. Yet, there are differences in the anticipation or adaption of jaw muscle activity and jaw kinematics to food hardness.

Clinical relevance

The study may have clinical implication in the diagnosis and management of children with chewing impairment associated with dental malocclusions and other orofacial dysfunctions.

The ontogeny of maximum bite force in humans

Ontogenetic changes in the human masticatory complex suggest that bite force, a key measure of chewing performance, increases throughout growth and development. Current published bite force values for humans exist for molar and incisal biting, but few studies measure bite forces across all tooth types, or measure bite force potentials in subjects of different ages. In the absence of live data, models of bite force such as the Constrained Lever Model (CLM), are employed to predict bite force at different bite points for adults, but it is unclear whether such a model can accurately predict bite force potentials for juveniles or subadults. This study compares theoretically derived bite forces and live bite force data, and places these within an ontogenetic context in humans. Specifically, we test whether (1) patterns of maximum bite force increase along the tooth row throughout ontogeny, (2) bite force patterns estimated using the CLM match patterns observed from live bite force data, and (3) changes in bite forces along the tooth row and throughout ontogeny are associated with concomitant changes in adductor muscle leverage. Our findings show that maximum bite forces increase throughout ontogeny and change along the tooth row, with the highest forces occurring at the posterior dentition. These findings adhere to the expectations under the CLM and validate the model's utility in predicting bite force values throughout development. Furthermore, adductor muscle leverage values reflect this pattern, with the greatest leverage values occurring at the posterior dentition throughout ontogeny. The CLM informs our study of mammalian chewing mechanics by providing a model of how morphological changes of the masticatory apparatus during ontogeny affect bite force distribution along the tooth row. Furthermore, the decreased bite force magnitudes observed in juveniles and subadults compared with adults suggest that differences in juvenile and subadult diets may partially be due to differences in bite force production potentials.

Development of a bite force transducer for measuring maximum voluntary bite forces between individual opposing tooth surfaces

Bite forces are studied in order to understand a wide range of factors pertaining to the mastication system. Various strain gauge transducers have been employed to measure bite forces, with several descriptions of these available in the literature; unfortunately, many reports provide insufficient detail to enable accurate reproduction. The aim of this project was to develop a bite force transducer with the capability of measuring maximum voluntary bite forces between individual opposing tooth surfaces. Furthermore, in an attempt to address the issue of vague device descriptions in the available literature, a detailed account of the transducer development has been included. A novel strain gauge transducer was designed and built. Bite forces of forty individuals were measured to verify the capabilities and clinical application of the device.

A Cross-Sectional Study of Age-Related Changes in Oral Function in Healthy Japanese Individuals

BACKGROUND

Oral function deterioration is related to a variety of factors, including aging, decline in activities of daily living, malnutrition, and cognitive decline. This cross-sectional study examined the effects of aging on oral function in healthy individuals.

METHODS

A retrospective study was conducted on 175 healthy, independent patients aged 40-89 years, without dementia and with ≥20 teeth, who visited a local dental clinic in Japan. Patients were compared with 92 university students aged 20-29 years. The seven criteria proposed by the Japanese Society of Gerodontology to diagnose "oral hypofunction" were observed and statistically analyzed.

RESULTS

Compared with those in the control group, the degree of tongue coating was increased in the group aged over 80 years, occlusal force was decreased in the group aged 70-79 years, tongue motor function was decreased in the groups aged 60-69 years and older, and tongue pressure was decreased in the groups aged 70-79 years and older.

CONCLUSIONS

Healthy, independent individuals maintained several oral function criteria across aging, including oral mucosal wetness, occlusal force, lip motor function, masticatory function, and swallowing function. Tongue motor function and tongue pressure decreased with aging, indicating that these may be rehabilitation targets.

Relating oral physiology and anatomy of consumers varying in age, gender and ethnicity to food oral processing behavior

The aim of this study was to link parameters describing oral physiology and anatomy of consumers varying in age, gender and ethnicity to food oral processing behavior. Three groups of healthy consumers were compared: Dutch, Caucasian adults (18-30 yrs, n =32), Chinese, Asian adults (18-30 yrs, n =32) and Dutch, Caucasian older adults (65-85 yrs, n =32). Mastication performance, salivary flow rate (stimulated and unstimulated) and dental status were quantified to characterize oral physiology. Volume of oral cavity, tongue dimensions, facial anthropometry, height and weight were quantified to characterize anatomy. Oral processing behavior of three solid foods (carrot, cheese and sausage) was quantified by video recordings and eating rate (g/s), average consumption time (s), chews per bite (-) and average bite size (g) were determined. Dutch, Caucasian older adults had smaller volume of oral cavity, lower number of teeth and larger head width compared to Dutch, Caucasian adults. Chinese, Asian adults showed significantly higher mastication performance and larger head width compared to Dutch, Caucasian consumers, while dental status did not significantly differ between groups. Males had significantly larger volumes of oral cavity and larger head height and width compared to females. Dutch, Caucasian adults had a shorter average consumption time (s), less chews per bite and consumed the three foods with higher eating rate (g/s) compared to Dutch, Caucasian older adults. Chinese, Asian adults had a significantly longer average consumption time (s), more chews per bite, smaller average bite size (g) and lower eating rate (g/s) compared to Dutch, Caucasian adults. Twenty-one significant relationships were found between oral physiological and anatomical parameters and oral processing behavior. Body weight resulted in the largest β-values, indicating to be the anatomical parameter of largest influence on oral processing behavior. We conclude that only few oral physiological and anatomical parameters related with food oral processing behavior. We suggest that other factors, including cultural factors contribute to variation in food oral processing behavior between different consumer groups more than saliva flow, volume of oral cavity, mastication performance and dental status.

Sex estimation in Indians by digital analysis of the gonial angle on lateral cephalographs

OBJECTIVE

Sex estimation of skeletons is important in forensic reconstructive identification. The mandible is a durable component that is suitable to discriminate the sexes while lateral cephalometry is a standardised radiographic technique accepted as a tool in personal identification. Limited data is available for the mandibular/gonial angle as a parameter for sex assessment using lateral cephalometric radiographs. The aim of this study is to determine the gonial angle's accuracy in sexing Indians using a new digital method and statistical approach.

METHOD

The sample comprised of 304 digital lateral cephalometric radiographs (155 females and 149 males, age between 18-30 years) of Indian subjects. The mandibular/gonial angle was measured on these radiographs using Adobe Photoshop software using tools available therein. The obtained angles for the sexes were subjected to logistic regression analysis (LRA), which forms a composite of weighted independent variables using a multivariate strategy.

RESULTS

The average angle was 122.7° for females and 121.1°for males. LRA produced an accuracy rate of 56.3% in sex assessment, with females being more accurately identified (61.9%) than males (50.3%).

CONCLUSION

The study demonstrated significant univariate sexual dimorphism among males and females in this population. However, the sex prediction value of this approach was low and thus may not be useful in sex estimation involved in human identification of Indians.

Radiographic evaluation of remodeling of mandible in adult South Indian population: Implications in forensic science

INTRODUCTION

Panoramic X-ray is an imagiological examination produced by a technique that exhibits images of the facial structure present in the upper and lower dental arches, as well as the support structures in the diagnosis of problems that require a broad view of the oral-maxillofacial complex, such as the assessment of traumatisms, extensive lesions, dental development, tooth retention, and growth anomalies. Many morphological and anatomical changes are exhibited by the mandible with the advancement of age and changes in gender, as well as dentoalveolar condition of the patient, and it can be assessed with the help of such radiograph, thus playing an important role in personal identification in forensic dentistry.

AIMS

This study aimed to evaluate the changes in gonial angle (GA), antegonial angle (AGA), and antegonial depth (AGD) in adult mandible with regard to age, gender, and dental status using panoramic radiographs.

SETTINGS AND DESIGN

This cross-sectional retrospective study was done using hospital records.

SUBJECTS AND METHODS

A total of 100 panoramic radiographs were evaluated. The images were grouped into three age groups (40-70) of 10 years each. GA, AGA, and AGD were digitally measured from the radiographs.

STATISTICAL ANALYSIS USED

Descriptive statistics of the variables were expressed in percentage, frequencies, mean, and standard deviations. Statistical differences between the variables were explored using independent sample t-test and one-way ANOVA. The significant level was set as 0.05.

RESULTS

There were no significant changes in GA, AGA, and AGD with age and dental status of the patients. Males had significantly smaller GA and AGA than females. Understandably, AGD was significantly greater in males than females.

CONCLUSIONS

Remodeling changes of the mandible with respect to the age groups and dental status studied were minimal. However, gender-related differences in ante AGA, depth, and GA were significant, which can be used as a tool in forensic identification.

Comparative Evaluation of Mechanical Properties and Wear Ability of Five CAD/CAM Dental Blocks

This study compares the mechanical properties and wear ability of five CAD/CAM (computer-aided design/computer-aided manufacturing) millable dental blocks. All the discs, including Amber Mill Hybrid, Vita Enamic, Katana Avencia, Lava Ultimate, and Amber Mill, were cut in dimensions of 1.2 mm in thickness and 12 mm in diameter, polished to a machined surface, and immersed in distilled water for seven days. Vickers hardness was measured and the indentations were observed using microscope. The discs were brushed under a 150 g load. Mean surface roughness (Ra) and topography were determined after 100,000 cycles. Finally the biaxial flexure strength of the discs was measured and the broken surfaces were observed using scanning electron microscopy (SEM). The data was subjected to Weibull analysis. All data were analyzed by one-way analysis (ANOVA). The results of Vickers hardness are shown as: Amber Mill > Vita Enamic > Amber Mill Hybrid > Lava Ultimate > Katana Avencia. Katana Avencia showed the highest volume percentage reduction and the roughest surface after toothbrushing. The biaxial flexural strength is shown as: Amber Mill > Katana Avencia > Lava Ultimate > Amber Mill Hybrid > Vita Enamic. All the tested materials exhibited varying degrees of mass loss and surface roughness. The properties of the composite materials are related to the filler content, filler volume, and polymerization methods.

Implant fracture failure rate and potential associated risk indicators: An up to 12-year retrospective study of implants in 5,124 patients

OBJECTIVES

This study investigated fracture rates and risk indicators for fractures in internal connection dental implants.

MATERIAL AND METHODS

We performed a retrospective analysis of 19,006 internal connection implants used in fixed restoration in 5,124 patients (4,570 males, 554 females) at the Dental Hospital of Veterans Health Service Medical Center between 2006 and 2015. Patients were followed through June 2018 (0.03-12.39 years post-installation). Clinical factors (age, sex, implant diameter, implant length, placement site, bone graft, fixture material, cervical feature, abutment connection, microthread, and platform switching) were recorded. Kaplan-Meier survival analysis identified risk indicators associated with an implant fracture. Cox regression models elucidated potential fracture risks.

RESULTS

One hundred and seventy-four implants fractured in 135 patients, for an incidence rate of 0.92% after an average of 4.95 ± 2.14 years of use. Kaplan-Meier estimates showed that the 3-, 5-, and 10-year survival rates of implants were 99.8%, 99.2%, and 97.7%, respectively. In the multivariable Cox regression model, the diameter, location, history of bone graft, and microthread presence were significantly correlated with implant fractures. Wide-diameter implants had a reduced fracture risk within 90 months, after which the diameter did not correlate with fractures. Implants placed in the anterior mandible had a lower fracture risk within 90 months; mandibular premolar implants corresponded with a lower risk after 90 months. Implants without a history of bone graft or microthreads were more likely to fracture throughout the follow-up time.

CONCLUSIONS

These results elucidate risk indicators for implant fractures and facilitate their reduction in clinical practice.

Comparative evaluation of the mechanical properties of CAD/CAM dental blocks

This study compares the mechanical properties of commercially available CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) millable dental blocks including Vita Enamic, Lava Ultimate, and MAZIC Duro. All the discs were cut in dimension of 1.2 mm in thickness and 12 mm in diameter, ground up to #1200 Sic papers and polished. The biaxial flexure strength of the ceramic discs was measured after thermocycling treatment and the broken surfaces were observed using scanning electron microscopy (SEM). The discs were brushed using a toothbrush testing machine under a 150 g load. Surface roughness and morphology were determined after toothbrushing cycles. Finally, the friction and wear behavior of the materials against an opposing tooth were studied using a reciprocating pin-on-plate test configuration. The vertical loss of dental cusp was measured, and the surface image was examined using field emission scanning electron microscopy (FE-SEM). The biaxial flexural strength data were subjected to Weibull analysis. To compare the significance between the groups, all data were analyzed by one-way analysis (ANOVA). The biaxial flexural strength of the Lava Ultimate and MAZIC Duro materials is significantly higher than that of Vita Enamic. In addition, Lava Ultimate and MAZIC Duro exhibited significantly smoother surfaces than that of Vita Enamic after toothbrushing. Lava Ultimate and MAZIC Duro also showed less wear to the opposing tooth than that of Vita Enamic. In addition, Lava Ultimate possesses more suitable mechanical properties than the Vita Enamic and Mazic Duro for use in oral clinical prosthesis.

Tongue exercise and ageing effects on morphological and biochemical properties of the posterior digastric and temporalis muscles in a Fischer 344 Brown Norway rat model

OBJECTIVE

This study sought to examin effects of age and tongue exercise on the posterior digastric (opener) and the temporalis (closer). We hypothesized 1) age would result in differing morphological (cross sectional area) and biochemical (myosin heavy chain isoform) components of these muscles; 2) tongue exercise would result in coactivation of these muscles inducing a decrease in age-related differences between age groups.

DESIGN

Young adult (9 months) and old (32 months) Fischer 344 Brown Norway rats were randomized into a tongue exercise or control group. Post-training, posterior digastric and temporalis muscles were harvested and analyzed using: 1) Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) to assess percent myosin heavy chain (MyHC) content; 2) Immunohistochemical staining to determine cross sectional area (CSA).

RESULTS

A larger proportion of slowly contracting MyHC isoforms in the posterior digastric and temporalis muscles were found in old. No significant main effects for age or exercise in fiber size were found in posterior digastric muscle. An interaction between age and exercise for temporalis cross sectional area indicated the old exercise group had smaller average cross sectional area than all other groups. CONCLUSIONS FINDINGS: suggest that: 1) Increasing age induces biochemical changes in muscles of the jaw, specifically showing an increase the proportion of slower contracting MyHC isoforms; 2) Increasing age and tongue exercise induce a reduction in muscle fiber cross sectional area in the temporalis muscle only. However, continued study of these cranial muscle systems is warranted to better understand these changes that occur with age and exercise.

Quantitative comparison of incisal tooth wear in patients receiving one-phase or two-phase treatment for skeletal Class III malocclusion with anterior crossbite

OBJECTIVES

The present study aimed to compare the amount of incisal tooth wear in the maxillary central incisors of patients with skeletal Class III malocclusion and anterior crossbite receiving one-phase or two-phase treatment. The hypothesis was that tooth wear would differ according to treatment modalities.

MATERIALS AND METHODS

Maxillary dental casts obtained before (T1) and after (T2) orthodontic treatment were divided into three groups. Group I consisted of casts from 21 patients (7 males, 14 females; mean age 9.8 years) who received two-phase treatment (maxillary protraction followed by fixed appliance therapy). Group II comprised casts from 37 patients who underwent orthodontic camouflage treatment for crossbite, subdivided according to age. Group IIa consisted of casts from 15 adolescents (8 males, 7 females; mean age 13.5 years), and group IIb consisted of casts from 22 adults (13 males, 9 females; mean age 24.5 years). Maxillary dental casts obtained at T1 and T2 were scanned. For each pair of digital images, T2 was superimposed on T1 using the best-fit method. Tooth wear was quantified and compared among groups.

RESULTS

Significantly less tooth wear was observed in group I compared to groups IIa and IIb, but no difference was found between groups IIa and IIb. Spearman correlation analysis revealed no significant correlation between tooth wear and age, treatment duration, or craniofacial morphology.

CONCLUSIONS

Despite the long duration of early treatment, it caused less wear of the maxillary central incisors than did orthodontic camouflage treatment.

Influence of anthropometry, TMD, and sex on molar bite force in adolescents with and without orthodontic needs

PURPOSE

Bite force has been studied as representative of functional indices of mastication and its value may have diagnostic significance in disorders of the musculoskeletal system of facial bones. This study aimed to evaluate bite force in adolescents with and without orthodontic needs considering presence of temporomandibular disorders (TMD) as well as anthropometry: craniofacial dimensions and body mass index (BMI).

METHODS

A total of 80 subjects were screened (61 females, 19 males; 18 ± 3 years old). Unilateral molar bite force was measured using a digital dynamometer with a fork thickness of 12 mm. Direct anthropometry was used to quantify craniofacial measurements. Dental Health Component of the Index of Orthodontic Treatment Need (IOTN-DHC) and the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) were used to classify samples according to malocclusion and to TMD, respectively. Data were analyzed using normality tests, Mann-Whitney U test, and multiple linear regression analyses with stepwise backward elimination, controlling for the presence of malocclusion and TMD (p ≤ 0.05).

RESULTS

The cephalic index was greater in females with malocclusion and the longitudinal cranial diameter was reduced in females with malocclusion. BMI was not different between normal and malocclusion groups for either gender. Bite force was negatively related with vertical dimension of the face, and positively related with facial width and facial index. The model explained 32% of bite force variability, considering the sample size (coefficient of determination R ² = 0.324).

CONCLUSIONS

Even when orthodontic needs and TMD signs and symptoms are present, stronger bite force is still observed in males and in subjects with smaller anterior facial heights and wider facial widths.

The anterior component of occlusal force revisited: direct measurement and theoretical considerations

BACKGROUND

The anterior component of occlusal force (ACF), considered to result from the mesial inclination of teeth relative to the occlusal plane, has been estimated by indirectly measuring contact point tightness (CPT) through interproximal insertion of metal strips. ACF has been observed concurrently with a posterior component, whose theoretical origin is difficult to explain.

OBJECTIVES

Evaluate ACF by measuring CPT directly, and integrate current data to propose a theoretical basis for ACF.

MATERIALS AND METHODS

The sample comprised 14 females (age: 22.3±2.8) and 16 males (age: 20.8±2.5). Our device consisted of two force sensors: one for measuring maximum bite force (MBF) (overall thickness: 4mm), and one for measuring CPT directly (0.2mm thick), inserted between the lower first molar and second premolar. ACF was computed as the difference in CPT between the biting (at 75 per cent of MBF) and non-biting conditions.

RESULTS

Averages of MBF, CPT, and ACF were 666.67 [standard deviation (SD): 36.06], 6.74 (SD: 1.17), and 20.59 (SD: 4.60) N, respectively. ACF, CPT, and MBF were higher in males by approximately 28, 18 and 7 per cent, respectively. A positive correlation was observed between ACF and MBF (R (2): 0.64). CPT was also significantly correlated to MBF (R (2): 0.40). Biomechanical analysis indicates that previously offered explanations do not unriddle the concurrent increase of CPT at anterior and posterior contact points.

CONCLUSIONS

ACF was related to bite force by a logarithmic model. We speculate that CPT increases during biting through a combination of mesial tipping of teeth and mandibular bending.

Evaluation of the effects of modified bonded rapid maxillary expansion on occlusal force distribution: A pilot study

Objective:

To evaluate the effects of modified bonded rapid maxillary expansion (RME) on occlusal force distribution.

Materials and Methods:

The sample included 12 patients (7 girls and 5 boys; mean age: 13.1 years) at the permanent dentition stage with bilateral posterior cross-bite. The patients were treated with a modified bonded RME appliance, activated twice a day. The study was terminated when the palatal cusps of the maxillary posterior teeth were occluding with the buccal cusps of the mandibular posterior teeth. The postretention period was 3 months. The T-Scan III device was used to analyze the percentages of occlusal force distribution, and records were taken at the pretreatment (T1), the postreatment (T2), and the postretention (T3) periods. Wilcoxon signed rank test was used for statistical analyses.

Results:

Incisors were most frequently without contact, followed by canines. The highest forces were seen in the second and first molar regions. A significant decrease was seen in total occlusal force during treatment (T1–T2); however, during retention, the force returned to its initial value, and no significant differences were found (T1–T3). No differences were found between right and left sides and in occlusal forces of the teeth in all time periods.

Conclusion:

The use of modified bonded RME decreases the total occlusal forces during the treatment period, but it does returns to its initial value after the postretention period.

The evaluation of MCI, MI, PMI and GT on both genders with different age and dental status

OBJECTIVES

The aim of this study was to measure the mandibular cortical index (MCI), mental index (MI), panoramic mandibular index (PMI) and cortical bone thickness in the zone of the gonial angle (GT) in panoramic radiographies from a large sample of males and females and to determine how they relate to patients' age, gender and dental status.

METHODS

910 panoramic radiographs were obtained and grouped into age, dental status and gender. The MCI, MI, PMI and GT were analysed.

RESULTS

Remarkable differences were observed for MCI and GT regarding gender, age groups and dental status on both sides (p < 0.05). While age and dental status had an effect on the MI and PMI in females, dental status had an effect on the MI and PMI in males (p < 0.05). Also, gender had an effect on the MI and PMI (p < 0.05).

CONCLUSIONS

The effects of age and tooth loss are different in females and males. In females, the harmful effects of tooth loss and age are more prominent according to the PMI and MI measurements. The effects of age and tooth loss in the GT and MCI measurements are similar, and these indices can be accepted as more reliable in studies including both genders.

Understanding the gastrointestinal tract of the elderly to develop dietary solutions that prevent malnutrition

Although the prevalence of malnutrition in the old age is increasing worldwide a synthetic understanding of the impact of aging on the intake, digestion, and absorption of nutrients is still lacking. This review article aims at filling the gap in knowledge between the functional decline of the aging gastrointestinal tract (GIT) and the consequences of malnutrition on the health status of elderly. Changes in the aging GIT include the mechanical disintegration of food, gastrointestinal motor function, food transit, chemical food digestion, and functionality of the intestinal wall. These alterations progressively decrease the ability of the GIT to provide the aging organism with adequate levels of nutrients, what contributes to the development of malnutrition. Malnutrition, in turn, increases the risks for the development of a range of pathologies associated with most organ systems, in particular the nervous-, muscoskeletal-, cardiovascular-, immune-, and skin systems. In addition to psychological, economics, and societal factors, dietary solutions preventing malnutrition should thus propose dietary guidelines and food products that integrate knowledge on the functionality of the aging GIT and the nutritional status of the elderly. Achieving this goal will request the identification, validation, and correlative analysis of biomarkers of food intake, nutrient bioavailability, and malnutrition.

Identification of mastication organ muscle forces in the biocybernetic perspective

Purpose of the Paper. This paper is an attempt to mathematically describe the mastication organ muscle functioning, taking into consideration the impact of the central nervous system. Material. To conduct model tests, three types of craniums were prepared: short, normal, and long. The necessary numeric data, required to prepare the final calculation models of different craniofacial types, were used to identify muscle and occlusion forces generated by muscles in the area of incisors and molars. The mandible in model tests was treated as a nondeformable stiff form. Methods. The formal basis for the formulated research problem was reached using the laws and principles of mechanics and control theory. The proposed method treats muscles as “black boxes,” whose properties automatically adapt to the nature of the occlusion load. The identified values of occlusion forces referred to measurements made in clinical conditions. Results. The conducted verification demonstrated a very good consistency of model and clinical tests' results. The proposed method is an alternative approach to the so far applied methods of muscle force identification. Identification of muscle forces without taking into account the impact of the nervous system does not fully reflect the conditions of mastication organ muscle functioning.

Maximum bite force following unilateral fixed prosthetic treatment: a within-subject comparison to the dentate side

OBJECTIVES

We evaluated the maximum occlusal bite force (MBF) among individuals with fixed partial dentures compared to the opposite dentate side and determined the relationship between MBF and gender, age, and body mass index (BMI).

SUBJECTS AND METHODS

A total of 85 subjects (43 males and 42 females, age range 28-66 years) with fixed partial dentures on one side and dentate on the other side participated in the study. The MBF was measured at the first molar area on both sides using a digital hydraulic bite force gauge. The highest MBF value was recorded from three measurements of bite force at each side (with 45-second intervals between measurements).

RESULTS

The mean MBF was 596.2 ± 76.3 N at the dentate side and 580.9 ± 74.3 N at the fixed partial denture side. The difference was statistically significant (p < 0.05). The MBF values were greater in males as well as in taller and heavier participants. Nevertheless, the BMI had no relationship with MBF values (p >0.05).

CONCLUSIONS

Within the same subjects, the measured MBF values at the dentate side were higher than those at the fixed partial denture side. Females, lighter, and shorter participants had lower MBF values. Meanwhile, the BMI had no significant relationship to MBF values.

Adaptive properties of human cementum and cementum dentin junction with age

OBJECTIVES

The objective of this study was to evaluate age related changes in physical (structure/mechanical properties) and chemical (elemental/inorganic mineral content) properties of cementum layers interfacing dentin.

METHODS

Human mandibular molars (N=43) were collected and sorted by age (younger=19-39, middle=40-60, older=61-81 years). The structures of primary and secondary cementum (PC, SC) types were evaluated using light and atomic force microscopy (AFM) techniques. Chemical composition of cementum layers were characterized through gravimetric analysis by estimating ash weight and concentrations of Ca, Mn, and Zn trace elements in the analytes through inductively coupled plasma mass spectroscopy. The hardness of PC and SC was determined using microindentation and site-specific reduced elastic modulus properties were determined using nanoindentation techniques.

RESULTS

PC contained fibrous 1-3 µm wide hygroscopic radial PDL-inserts. SC illustrated PC-like structure adjacent to a multilayered architecture composing of regions that contained mineral dominant lamellae. The width of the cementum dentin junction (CDJ) decreased as measured from the cementum enamel junction (CEJ) to the tooth apex (49-21 µm), and significantly decreased with age (44-23 µm; p<0.05). The inorganic ratio defined as the ratio of post-burn to pre-burn weight increased with age within primary cementum (PC) and secondary cementum (SC). Cementum showed an increase in hardness with age (PC (0.40-0.46 GPa), SC (0.37-0.43 GPa)), while dentin showed a decreasing trend (coronal dentin (0.70-0.72 GPa); apical dentin (0.63-0.73 GPa)).

SIGNIFICANCE

The observed physicochemical changes are indicative of increased mineralization of cementum and CDJ over time. Changes in tissue properties of teeth can alter overall tooth biomechanics and in turn the entire bone-tooth complex including the periodontal ligament. This study provides baseline information about the changes in physicochemical properties of cementum with age, which can be identified as adaptive in nature.

Analysis of fracture resistance of endodontically treated teeth restored with different post and core system of variable diameters: an in vitro study

The restoration of endodontically treated teeth requires the fabrication of a post and core; to provide retention and support for the final crowns. The purpose of this study was to evaluate fracture resistance of endodontically treated teeth restored with prefabricated zirconia post (CP), milled zirconia post (MZ), pressable ceramic post (PC) and cast metal post (Ni-Cr) of 1.4 and 1.7 mm diameter. 48 freshly extracted human maxillary central incisors were used for this study. The teeth were distributed in four groups of 12 teeth each. From each group, 6 teeth were selected for 1.4 mm diameter post and rest of the 6 teeth, is selected for 1.7 mm diameter post. All teeth were restored with metal crowns. Each specimen from the group was subjected to "load to fracture" in universal testing machine at 130° angle and the maximum load at failure was recorded. Statistically significant difference was found between the failure load of the groups studied. In group I (Ni-Cr)-1.4 mm diameter post and core recorded a maximum fracture load of 534.83 ± 1.28 N and 1.7 mm diameter post and core showed 294.33 ± 1.02 N. In group II (PC)-1.4 mm diameter post and core recorded a maximum fracture load of 205.33 ± 1.61 N and 1.7 mm post and core showed 375.00 ± 1.57 N. In group III (CP)-1.4 mm diameter post and cores recorded a maximum fracture load of 313.00 ± 0.73 N and 1.7 mm post and core showed 638.67 ± 0.81 N. In group IV (MZ)-1.4 mm diameter post and cores recorded a maximum fracture load of 312.00 ± 0.86 N and 1.7 mm post and core showed 415.00 ± 0.89 N. Prefabricated zirconia post (1.7 mm) with pressable ceramic core (Cosmo post)-exhibited higher fracture resistance. Milled zirconia and prefabricated zirconia post-showed same value with 1.4 mm diameter post. Pressable ceramic post and core showed satisfactory result with 1.7 mm post, but showed lesser values with 1.4 mm diameter post.

Evaluation of occlusal contacts among different groups of malocclusion using 3D digital models

OBJECTIVES

(1) To evaluate the applicability of using 3D digital models in the assessment of the magnitude of occlusal contacts by measuring occlusal contact surface areas (OCSAs) and 3D mesh points in 'contact' (OCMPs) in a sample of orthodontic patients; (2) To detect any sex differences in the magnitude of occlusal contacts in all malocclusion groups; (3) To detect inter- group differences; (4) To assess possible correlations between occlusal contacts and other dental characteristics.

MATERIALS AND METHODS

Study casts of 120 malocclusion patients were selected and divided into 4 groups (class I division 1, class II division 1, class II division 2, class III) with equal numbers for both sexes. 3D digital models were produced using O3DM™ technology. Occlusal contacts were quantified using two methods of measuring.

RESULTS

(1) No significant sexual differences were detected for OCMPs (mesh points) and OCSAs (mm(2)) in all groups. (2) There were statistically significant differences among malocclusion groups for OCMPs and OCSAs (p < 0.001). Tukey's HSD post- hoc tests showed that class III patients had significantly less occlusal contacts than other malocclusion groups. (3) Stepwise multiple regression equations showed that overjet, lower arch width and overbite could explain approximately 19.5% of the total variance of OCSAs and OCMPs.

CONCLUSION

Sexual differences in occlusal contacts were not detected. Class I division 1 patients had the highest amount of occlusal contacts among all groups of malocclusion. Overjet, overbite and lower dental arch width were best predictors of occlusal contacts in the current sample.

Analysis of gonial angle in relation to age, gender, and dentition status by radiological and anthropometric methods

Background:

With development and function, the mandibular angle has shown changes in size and shape. A variation in mandibular angle with age, gender, and even the dental status has been observed, which is supported by radiographic and anthropometric studies.

Aims:

The aim of this study were to evaluate relationship between complete loss of teeth and changes in the gonial angle; the study further intends to evaluate any variation in gonial angle with age and gender. The study intends to assess the reliability and accuracy of age and gender determination using gonial angle as a parameter.

Materials and Methods:

A total of 185 subjects (91 males; 89 females) were included in the study and were divided into five groups on the basis of the chronological age. Physico-forensic anthropometry and lateral cephalometric methods were used to record the gonial angle.

Results:

The present study shows a definite decrease in the gonial angle with advancing age, but the intergroup analysis does not follow a significant pattern. The study showed no correlation of gonial angle with gender. However, the study observed a 6° increase in gonial angle for edentulous subjects.

Conclusion:

Gonial angle has been used as an adjuvant forensic parameter, but its reliability is questionable, as the mandible does not follow one characteristic pattern. Gonial angle does show changes with dentition status, which may be attributed to physiologic function of the mandible. However, when evidence is scanty, it can be used to direct the investigation.