Obturator prostheses with intramucosal retention system in patients with maxillectomy.

PURPOSE: To evaluate the intramucosal retention system in patients' masticatory efficiency and quality of life in this case series. MATERIAL AND METHODS: A total of 3 individuals with maxillectomy were included for rehabilitation with a complete obturator prostheses with an intramucosal retention system (OPI). The complete obturator prostheses was made for 60 days, and electromyography assessments and bite force were applied before, after 30, 60, and 90 days of surgery and prostheses installation. The University of Washington Quality of Life Questionnaire (UW-QoL) and the Obturator Functional Scale (OFS) were also administered at baseline and in the same follow-up periods. The electromyography was evaluated on both sides of the masseter, temporalis, and buccinator muscles while chewing hard and soft food. The maximum bite force was recorded in the central incisors and both sides of the first molar region. RESULTS: Bite force values increased in the first molar region, and muscular electrical activity remained constant. Items related to the taste and swallowing of the UW-QOL impacted. Most OFS questionnaire data responses indicated that patients improved in swallowing liquid foods and appearance. CONCLUSIONS: The rehabilitative capacity improves masticatory efficiency and QoL in adults maxilectomized and rehabilitated with OPI analysis in the study. Further clinical studies should be encouraged to determine the effectiveness of this retentive system.

Gonial angle and late implant loss: A retrospective clinical study.

PURPOSE: Occlusal overload can cause late implant loss. However, whether the magnitude of the occlusal force is a risk factor for late implant loss remains unclear. Thus, this clinical study aimed to determine the relationship between the gonial angle (GoA), which is associated with the magnitude of occlusal force, and late implant loss. METHODS: All implants with fixed prostheses placed at the Niigata University Hospital between April 2006 and August 2019 were included in this retrospective study. The implants with and without late loss were compared. Relevant variables, including smoking habits, diabetes mellitus status, remaining dentition, implant length and diameter, prosthesis design, retention systems, splinting, and GoA were assessed. Log-rank test and Cox proportional hazards regression analysis were used to estimate the adjusted hazard ratio (aHR) and to calculate the corresponding 95% confidence intervals (CI) for late implant loss. RESULTS: A total of 919 patients (349 men and 570 women) with 2512 implants were included in this study. Cox proportional hazards regression analysis revealed that a 10° decrease in the GoA (aHR, 1.588; 95% CI, 1.115-1.766; P = 0.010), smoking habits (aHR, 3.909; 95% CI, 2.131-7.168; P < 0.001), and male sex (aHR, 2.584; 95% CI, 1.376-4.850; P = 0.003) were significantly associated with late implant loss. CONCLUSIONS: Within the limitations of this retrospective study of 2512 implants, smaller GoA, smoking habits, and male sex were risk factors for late implant loss.

Unravelling the Complexities of Bite Force Determinants in Paediatric Patients: A Literature Review.

The amount of maximum voluntary bite force (MVBF) is determined by the combined action of the jaw elevator muscles, which are altered jaw biomechanics and reflex processes. Bite force (BF) measurements can yield valuable information on the activity and function of the jaw muscles. The accuracy of biting force measurements depends on several variables, including age, gender, malocclusion, dental caries, dental prostheses and temporomandibular joint (TMJ). This information is essential for evaluating the development and function of the masticatory system, identifying potential abnormalities or impairments and guiding appropriate treatment interventions for paediatric patients. The aim of this article is to review the literature on the factors affecting bite force and the importance of these factors in assessing dental development and guiding interventions for paediatric patients with bite force-related issues. Additionally, establishing normative values for bite force in different age groups can aid in monitoring growth and detecting any deviations from expected patterns. Measuring bite force in paediatric patients is significant in comprehensive oral health assessment and management.

Laboratory Validation of a Novel Indigenously Developed Bite Force Measuring Device.

INTRODUCTION: It is critical to measure the maximum voluntary bite force of patients receiving restorative dentistry. A new device known as "BYTE" has been developed indigenously to measure bite force in humans. The purpose of this study is to evaluate the BYTE device's consistency and accuracy in a lab setting. METHODOLOGY: Testing and calibration were done in the laboratory. The calibration machine with load cell pressed the biting part of the device with various forces from 3 N to 444 N in 3 N increments for two to three seconds each. The recorded force value in Newton by the device was noted down. RESULTS: At numerous standard loads, the minimum accuracy error is 0.333 N, while the maximum is 1.667 N. It marginally underestimates the load with an average accuracy error of 0.833 N. CONCLUSION: The calibration report showed that the BYTE device is precise and reliable and can be used to measure maximum bite force.

Effects of Occlusal Contact on Maxillary Alveolar Bone Morphology in Patients with and without Anterior Open Bite: A Cross-Sectional Study.

Background/Objectives: Anterior open bite (AOB) is characterized by the absence of occlusal contact between the maxillary and mandibular anterior teeth, while the posterior teeth are in contact when occluded. Here, we aimed to clarify the difference in maxillary alveolar bone morphology in adult patients with and without AOB. Methods: This cross-sectional study was conducted on 50 adults aged 18-39 years: 25 patients without AOB (control group; 13 males and 12 females; age: mean ± standard deviation [SD], 22.2 ± 4.5 years) and 25 patients with AOB (9 males and 16 females; age: 24.2 ± 6.4 years). Using cone-beam computed tomography images, the height of the maxillary alveolar bone crest in the anterior and posterior teeth and thickness of the alveolar cortical bone on the labial and palatal sides were measured and compared between the two groups. An independent t-test and Pearson's correlation analysis were used to examine statistical significance (p < 0.05). Results: The AOB group showed a significantly longer (p = 0.016) posterior alveolar crest and thinner cortical bone on the buccal (p < 0.001) and lingual (p = 0.009) sides of the anterior region and the buccal (p = 0.006) sides of the posterior region than the control group did. Moreover, a significant negative correlation (p = 0.046; r = -0.403) was observed between bite force and cortical bone thickness on the buccal side of the posterior region in the AOB group. Conclusions: It is suggested that the absence of occlusal contact in the anterior area influences the alveolar bone morphology of the maxilla.

Functional adaptation of the infant craniofacial system to mechanical loadings arising from masticatory forces.

The morphology and biomechanics of infant crania undergo significant changes between the pre- and post-weaning phases due to increasing loading of the masticatory system. The aims of this study were to characterize the changes in muscle forces, bite forces and the pattern of mechanical strain and stress arising from the aforementioned forces across crania in the first 48 months of life using imaging and finite element methods. A total of 51 head computed tomography scans of normal individuals were collected and analysed from a larger database of 217 individuals. The estimated mean muscle forces of temporalis, masseter and medial pterygoid increase from 30.9 to 87.0 N, 25.6 to 69.6 N and 23.1 to 58.9 N, respectively (0-48 months). Maximum bite force increases from 90.5 to 184.2 N (3-48 months). There is a change in the pattern of strain and stress from the calvaria to the face during postnatal development. Overall, this study highlights the changes in the mechanics of the craniofacial system during normal development. It further raises questions as to how and what level of changes in the mechanical forces during the development can alter the morphology of the craniofacial system.

Craniometric Characteristics of Selected Carnivora Species Kept in Captivity in Relation to Bite Force and Bending Strength of the Upper Canines.

The aim of this study was to analyse the bite forces of seven species from three carnivore families: Canidae, Felidae, and Ursidae. The material consisted of complete, dry crania and mandibles. A total of 33 measurements were taken on each skull, mandible, temporomandibular joint, and teeth. The area of the temporalis and masseter muscles was calculated, as was the length of the arms of the forces acting on them. Based on the results, the bite force was calculated using a mathematical lever model. This study compared the estimated areas of the masticatory muscles and the bending strength of the upper canines among seven species. A strong correlation was found between cranial size and bite force. The results confirmed the hypothesis that the weight of the animal and the size of the skull have a significant effect on the bite force.

Comparative Study on the Duration and Efficacy of Various Botulinum Toxin Type A Injections for Reducing Masseteric Muscle Bite Force and Treating Facial Wrinkles.

OBJECTIVE: Botulinum toxin serotype A (BoNT/A) is widely used for minimal invasive aesthetic treatments. Different brands of BoNT/A exhibit structural variations. The aim of this study was to compare the duration and efficacy of various BoNT/A brands available in Thailand for reducing bite force and treating wrinkles. METHODS: Fifty participants were randomly assigned to one of five groups, with each group receiving a different BoNT/A brand, namely, incobotulinumtoxinA (IncoA), onabotulinumtoxinA (OnaA), abobotulinumtoxinA (AboA), letibotulinumtoxinA (LetiA), and prabotulinumtoxinA (PraboA). BoNT/A was administered to the masseter muscle and the upper face. Bite force was measured before injection and at 2, 4, 8, 12, 16, 20, and 24 weeks post-injection. Evaluation scores for wrinkle improvement were assessed after the treatment. RESULTS: The most significant reduction in bite force occurred between 2 and 4 weeks post-injection. PraboA demonstrated the most substantial reduction in bite force, while IncoA had the least effect. However, the percentage of bite force reduction did not exhibit statistical significance between BoNT/A types. Additionally, the reduction in bite force for all BoNT/A types was reversed at 4 months post-injection. More than half of the participants experienced improvement beyond 16 weeks. CONCLUSIONS: The structural differences among BoNT/A brands did not significantly affect the longevity and efficacy of bite force reduction and wrinkle treatment. TRIAL REGISTRATION: ClinicalTrials.gov identifier: TCTR20211205001 (registered 4 Dec 2021).

A Preliminary Report of Maximum Voluntary Bite Force of Young Indian Population.

Introduction: The measurement of bite force is increasingly gaining importance in dentistry. This preliminary report evaluates the maximum voluntary bite force (MVBF) of young healthy individuals with normal occlusion and correlates the effect of age and gender with the maximum bite force (MBF). Materials and Methods: 405 participants in the age group of 18 to 40 years were selected from the outpatient department meeting inclusion and exclusion criteria. MVBF was measured with the help of a digital device called "Byte" at incisors, right first molar, and left first molar region. Results: There was a strong correlation between age with bite force. Bite force increased with age. Males had more bite force than females. The posterior region had higher bite force than the anterior region. Conclusion: Measurement of bite force is very important for every patient undergoing restorative treatment. The "Byte" device was found to be very efficient.

An Innovative Technique for Assessment of Bone Change, Bite Force, and Retention of the Single-Implant-Supported Mandibular Overdenture: A Clinical Study.

This study is the first study to incorporate a novel approach to single-implant-retained mandibular overdenture with a bar attachment on a single implant in the symphysis region. The use of a single-implant-retained bar overdenture significantly improved patients' chewing efficiency, indicating enhanced overdenture retention and stability. Materials and Methods: Ten maxillary and mandibular completely edentulous patients were enrolled in the study. A complete denture was fabricated for them. On completion, bite force, retention force, and bone change were recorded. Bite force was recorded with the strain gauge, retention force with the force measurement gauge, and bone changes with radiographs. Conclusion: Single-implant-supported bar mandibular overdenture (SISBOD) can be a suitable standard economic option for edentulous mandible and can greatly improve the quality of life of patients.

Association between oral health status and occlusal bite force in young adults.

Background/purpose: Oral health is related to general health and a person's overall well-being. The aim of the present study was to explore the association between oral health status and bite force among young adults. Materials and methods: Maximum bite force (MBF) was measured using Dental Prescale II in conjunction with a pressure-sensitive film and bite force analyzer in 40 young adults aged 20 to 40. Supragingival dental plaque was collected and cultured. Plaque weight, pH, and colony counts were assessed. The decayed, missing, and filled teeth index (DMFT) and body mass index (BMI) were recorded. Results: Bite force was negatively correlated with the number of missing teeth and the sum of missing and filled teeth. When the filled-to-remaining-teeth ratio (F/R ratio) was less than 8%, the bite force was significantly higher compared to an F/R ratio of 8-25%. Additionally, the amount of total bacteria was positively correlated with total bite force, and the quantity of Streptococcus mutans (S. mutans) along with total bacteria was positively correlated with bite force in the molar region (∗P < 0.05). The molar region predominantly contributed to bite force. Conclusion: Elevated levels of cariogenic bacteria may increase the risk of tooth loss, subsequently leading to reduced bite force. This reduction in bite force can further impact the efficiency of chewing function and, consequently, the quality of life. An F/R ratio above 8% could be easily calculated clinically and could serve as a guide to identify patients, particularly young adults, at risk of reduced bite force.

Finite Element Analysis of Fixed Orthodontic Retainers.

The efficacy of retainers is a pivotal concern in orthodontic care. This study examined the biomechanical behaviour of retainers, particularly the influence of retainer stiffness and tooth resilience on force transmission and stress distribution. To do this, a finite element model was created of the lower jaw from the left to the right canine with a retainer attached on the oral side. Three levels of tooth resilience and variable retainer bending stiffness (influenced by retainer type, retainer diameter, and retainer material) were simulated. Applying axial or oblique (45° tilt) loads on a central incisor, the force transmission increased from 2% to 65% with increasing tooth resilience and retainer stiffness. Additionally, a smaller retainer diameter reduced the uniformity of the stress distribution in the bonding interfaces, causing concentrated stress peaks within a small field of the bonding area. An increase in retainer stiffness and in tooth resilience as well as a more oblique load direction all lead to higher overall stress in the adhesive bonding area associated with a higher risk of retainer bonding failure. Therefore, it might be recommended to avoid the use of retainers that are excessively stiff, especially in cases with high tooth resilience.

Pain-free bite force in a healthy population: Within-session test-retest reliability in different sitting positions.

BACKGROUND: Pain-free bite force (PFBF) is a promising measure to evaluate bite function in temporomandibular disorders (TMDs), yet the reliability of the measure is unknown. OBJECTIVES: Establish the (1) within-session test-retest reliability of PFBF in a healthy population for a single and mean of three trials in supported and unsupported sitting; (2) standard error of measurement (SEM) and minimal detectable change (MDC). METHODS: Thirty healthy participants (n = 15 female, mean [SD] age = 34.4 [11.0] years) completed two sessions (30-60 min apart) comprising three PFBF trials on each side, in both supported and unsupported sitting, to provide data for 60 (30 participants × two sides) test-retest assessments. Test-retest reliability for the first trial and mean of three trials in each position were determined using intraclass correlation coefficients (ICCs), before calculating the corresponding SEM and MDC for males (M) and females (F) respectively. RESULTS: Within-session reliability was considered excellent for a single trial in supported sitting (ICC = 0.85; SEM M/F = 99/84 N; MDC M/F = 275/232 N) and unsupported sitting (ICC = 0.91; SEM M/F = 72/59 N, MDC M/F = 200/163 N), and for a mean of three trials in supported sitting (ICC = 0.89; SEM M/F = 66/79 N, MDC M/F = 182/220 N) and unsupported sitting (ICC = 0.92; SEM M/F = 64/59 N, MDC M/F = 177/164 N). CONCLUSION: Single and a mean of three trials in supported and unsupported sitting appear reliable methods to measure PFBF in a healthy population. Testing PFBF using a mean of three trials in unsupported sitting appears superior over other methods though due to higher test-retest reliability, and lower SEM and MDC. Future studies should examine the reliability of PFBF in TMD populations.

Effect of gum-chewing exercise on maintaining and improving oral function in older adults: A pilot randomized controlled trial.

Background/purpose: Gum chewing has been found to improve oral function. Nevertheless, few randomized controlled trials have investigated the effects of gum-chewing exercises on oral function in older adults. This study aimed to examine the effect of gum-chewing exercises on oral function in older adults. Materials and methods: This was a single-blind, randomized controlled trial, conducted from November 2021 to January 2022. A total of 130 participants were divided randomly into the intervention and control groups. The intervention group was told to chew experimental gums for one month, while the control group was instructed to chew experimental tablets for one month. Maximum bite force, occlusal contact areas, oral dryness, tongue pressure, tongue and lip functions (number of times each of the following syllables is pronounced per second:/pa/,/ta/, and/ka/), masticatory function, subjective masticatory function, and gum-chewing time were measured at baseline and one month following intervention to assess outcomes. Results: One month following the intervention, tongue pressure was significantly higher in the intervention group than in the control group (P = 0.027). In the within-group comparisons, maximum bite force (P < 0.001), unstimulated saliva flow (P < 0.001), tongue and lip functions (/pa/: P < 0.001;/ta/: P < 0.001;/ka/: P < 0.001), color scale value (P = 0.019), and ΔE value (P = 0.024) were significantly increased in the intervention group. Conclusion: The results suggest that gum-chewing exercises can improve oral functions in older adults, although additional increases in masticatory load may be necessary to establish a more effective oral function training method using gum-chewing exercises in older adults.

Linking shape conspicuous asymmetry with shape covariation patterns and performance in the insect head and mandibles.

Bilateral symmetry is widespread across animals, yet, among bilaterians, many cases of conspicuous asymmetries evolved. This means that bilaterally homologous structures on the left and right sides display divergent phenotypes. The evolution of such divergent phenotypes between otherwise similarly shaped structures can be thought to be favored by modularity, but this has rarely been studied in the context of left-right differences. Here, we provide an empirical example, using geometric morphometrics to assess patterns of asymmetry and covariation between landmark partitions in a grasshopper with conspicuously asymmetric mandibles. Our morphometric data confirm the presence of strictly directional conspicuous asymmetry in the mandibles and surrounding structures. Covariance patterns and tests hint at a strong integration between mandibles despite their divergent morphologies, and variational modularity with the head capsule. While mandibles have been selected to achieve a key-and-lock morphology by having interlocking shapes, the developmental modularity required to achieve this seems to be overwritten by developmental and/or functional integration, allowing the precise matching required for feeding. The consequent conflicting covariation patterns are reminiscent of the palimpsest model. Finally, the degree of directional asymmetry appears to be under selection, although we find no relationship between bite force and mandible shape or asymmetry.

Impact of clear aligner therapy on masticatory musculature and stomatognathic system: a systematic review conducted according to PRISMA guidelines and the Cochrane handbook for systematic reviews of interventions.

BACKGROUND: Clear aligner therapy has gained popularity as a minimally invasive orthodontic treatment option. However, its impact on the masticatory musculature and the stomatognathic system is an area of growing interest, as it involves the adjustment of occlusion and tooth movement. This systematic review aims to comprehensively assess and synthesise existing evidence regarding the influence of clear aligner therapy on the masticatory musculature and the stomatognathic system. METHODS: An exhaustive search was performed on electronic databases that adhered to PRISMA guidelines. Clinical studies that evaluated the impact of patients receiving aligner orthodontic treatment on the muscles of the mastication and stomatognathic systems were included. A standardised data extraction form was devised for relevant variables. Two reviewers extracted the data variables. ROB-2 was used for bias evaluation in the selected studies. RESULTS: A total of six studies met the inclusion criteria. The wearing of clear aligners significantly impacted the muscles of mastication. Muscle activity and discomfort showed a significant alteration in the initial days of appliance placement. but this observation was temporary, with no significant changes thereafter in subsequent follow-up. Bite force reduction was also noted. All the studies evaluated showed good methodological quality. CONCLUSION: The review found that aligned orthodontic treatment may have a variable impact on muscles of mastication, with a potential for initial exacerbation of symptoms followed by possible improvement. However, due to the limited number of studies and their heterogeneous nature, further robust research is recommended to fully understand the relationship between aligned orthodontic treatment and masticatory muscles.

Finite element analysis of Neanderthal and early Homo sapiens maxillary central incisor.

Neanderthal anterior teeth are very large and have a distinctive morphology characterized by robust 'shovel-shaped' crowns. These features are frequently seen as adaptive responses in dissipating heavy mechanical loads resulting from masticatory and non-masticatory activities. Although the long-standing debate surrounding this hypothesis has played a central role in paleoanthropology, is still unclear if Neanderthal anterior teeth can resist high mechanical loads or not. A novel way to answer this question is to use a multidisciplinary approach that considers together tooth architecture, dental wear and jaw movements. The aim of this study is to functionally reposition the teeth of Le Moustier 1 (a Neanderthal adolescent) and Qafzeh 9 (an early Homo sapiens adolescent) derived from wear facet mapping, occlusal fingerprint analysis and physical dental restoration methods. The restored dental arches are then used to perform finite element analysis on the left central maxillary incisor during edge-to-edge occlusion. The results show stress distribution differences between Le Moustier 1 and Qafzeh 9, with the former displaying higher tensile stress in enamel around the lingual fossa but lower concentration of stress in the lingual aspect of the root surface. These results seem to suggest that the presence of labial convexity, lingual tubercle and of a large root surface in Le Moustier 1 incisor helps in dissipating mechanical stress. The absence of these dental features in Qafzeh 9 is compensated by the presence of a thicker enamel, which helps in reducing the stress in the tooth crown.

Factors influencing root resorption in retained mandibular second deciduous molars with congenital absence of second premolars: a cross-sectional study.

BACKGROUND: There are currently no studies that quantitatively compare the relationship of root resorption to the patient's systemic history or craniofacial and intraoral morphology, especially in relation to possible host factors. Thus, this study aimed to clarify the factors associated with root resorption in retained mandibular second deciduous molars with the congenital absence of second premolars and predict the prognosis of retained mandibular second deciduous molars. METHODS: A cohort of 5547 patients who visited the orthodontic clinic at Tokyo Medical and Dental University Dental Hospital between 2013 and 2022 was screened. Lateral cephalometric radiographs, panoramic radiographs, upper and lower dental models, and orthodontic treatment questionnaires were used as reference materials to apply the inclusion and exclusion criteria. Ultimately, 111 patients were included in the analyses. The patients were divided into two groups based on the root resorption levels of the retained mandibular second deciduous molars. Those with less root resorption were classified under the good condition (GC) group, whereas those with more root resorption were classified under the poor condition (PC) group. Demographic, clinical, and cephalometric parameters were compared between the groups. A multivariate logistic regression model was used to predict the probability of root resorption. RESULTS: The prevalence of congenitally missing mandibular second premolars with persistent mandibular second deciduous molars was 2.0%. In a total of 111 patients, eighty-three teeth (53.2%) were classified into the GC group, whereas 73 teeth (46.8%) were classified into the PC group. The Frankfort-mandibular plane angle (FMA) [odds ratio (OR): 0.87], Frankfort-mandibular incisor angle (FMIA) (OR: 0.93), overbite (OR: 1.38), adjacent interdental space (OR: 1.46), distance from occlusal plane (OR: 0.80), and caries treatment (OR: 7.05) were significantly associated with the root resorption of the retained mandibular second deciduous molars. CONCLUSIONS: Our findings suggest that skeletal morphology, oral morphological patterns, and history contribute to root resorption in retained mandibular second deciduous teeth with congenital absence of subsequent permanent teeth.

The comparison between various methods of mandibular reconstruction based on finite element analysis.

The Mandible can be damaged by pathological factors, tumors, trauma, infection, and needs a surgical operation for reconstruction and restoring function. There are different methods for the reconstruction of mandible. Based on the surgical approach, primary reconstruction of mandible by reconstruction plate after resection is necessary for maintaining mandibular symmetric and esthetic of the lower third of the face. A finite element model of mandible and masticatory muscles was produced from a normal person (male with 35-year-old). The normal model was resected from the left sixth tooth to the second tooth. The pathological model was reconstructed in different conditions by macro plate. Different conditions were analyzed and compared based on bite force on right fifth tooth, stress developed on screws and macro plate. The finite element analysis results showed that maximum bite force and lower stress on screws were seen in the pathological model (condition 5) when one macro plate and six screws were inserted in the mid-body. The findings showed that the use of two macro plates causes lower stress on it than when we use one. Use of one macro plate and six screws is the best choice in mandibular immobilization which decrease the stress applied on bone and increase the bite force. Because of less stress developed on macro plates and screws, use of two macro plates or one macro plate in mid-body area are also preferred.

Cranial muscle architecture in wild boar: Does captivity drive ontogenetic trajectories?

The jaw system in mammals is complex and different muscle morphotypes have been documented. Pigs are an interesting group of animals as they are omnivorous and have a bunodont crushing dentition. Moreover, they have interacted with humans for over 10,000 years and grow nearly two orders of magnitude in size. Despite being a model system for studies on cranial form and function, data on the growth of the jaw adductor muscles are scant. Moreover, whether captivity impacts the growth and architecture of the jaw adductors remains unknown. Based on dissection data of the jaw adductors of 45 animals ranging from less than 1 kg to almost 100 kg, we show that muscle masses, muscle fiber lengths, and cross-sectional areas scale as predicted for geometrically similar systems or with slight negative allometry. Only the fiber length of the lateral pterygoid muscle grew with slight positive allometry. Animals raised in captivity in stalls or in an enclosure were overall very similar to wild animals. However, some muscles were larger in captive animals. Interestingly, variation in bite force in captive animals was well predicted by the variation in the size of the superficial masseter muscle relative to the overall jaw adductor mass.