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.

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.

Influence of occlusal appliances on the masticatory muscle function in individuals with sleep bruxism: A systematic review and meta-analysis.

This systematic review answers the question: "Does occlusal appliance use influence masticatory muscle function of dentate individuals with sleep bruxism?". The literature search included six databases, grey literature, and manual search for articles. Randomized and non-randomized clinical trials were included comparing muscle function of sleep bruxers before and after receiving occlusal appliances. Risk of bias was assessed with risk of bias assessment for randomized and non-randomized clinical trials tool. Twelve studies, three represent randomized clinical trials, were included. Risk of bias was considered low, moderate, or serious. Meta-analyses indicated that soft and hard appliances did not influence muscle activity and bite force of bruxers. Qualitative analysis showed that occlusal appliance use did not influence masticatory performance and muscle volume. However, it was effective in reducing tongue force. Certainty of evidence was considered very low for muscle activity when evaluated with hard appliances, and for bite force evaluated with both appliance materials. Low certainty of evidence was observed for muscle activity with soft appliances. Based on the findings of this meta-analysis, occlusal appliances do not affect masticatory muscle function of sleep bruxers. Regardless of appliance material, the activity of masseter and temporal, and bite force of sleep bruxers was not influenced.

Bite Force Mapping Based on Distributed Fiber Sensing Network Approach.

Bite force measurements are crucial in the realm of biomedical research, particularly in the areas of dentistry and orthodontic care. Various intraoral devices have been used to assess biting force, but each has limitations and drawbacks. Fiber optic sensors (FOSs) offer advantages such as electrical inertness, immunity to electromagnetic interference, and high sensitivity. Distributed fiber optic sensing allows an increase in the number of sensing points and can interrogate numerous reflections from scattering events within an optical fiber. We present four dental bites with heights of 6 mm, which enabled bilateral measurements. U-shaped sensors were prepared by embedding fibers into silicone by folding a single-mode fiber into four lines and multiplexing eight parallel nanoparticle-doped fibers. Dental bite models were created using two silicone materials (Sorta Clear 18 and Sorta Clear 40). The developed sensors were calibrated by applying weights up to 900 g, resulting in a linear response. Experiments were conducted to compare the efficacy of the dental bites. The collection of massive data was enabled by constructing a 2D map of the dental bites during multi-point sensing.

Oral health self-perception, maximum bite force and masticatory efficiency in patients with overdentures with different attachment systems-A crossover study.

BACKGROUND: The literature is unclear about how the different attachment systems for overdentures impact the maximum bite force, the masticatory efficiency and how this impact in the oral health self-perception in patients. OBJECTIVE: To evaluate the effect of two attachment systems (O-ring and Locator) for mandibular overdenture using single implant on quality of life, maximum bite force (BF) and masticatory efficiency (ME). METHODS: Twenty-eight completely edentulous denture wearers with a mandibular symphysis implant were randomly selected and allocated into two groups in a crossover study, considering O-ring and Locator attachment types. The quality of life and self-perception of oral health were assessed using the Oral Health Impact Profile (OHIP-Edent) and Geriatric Index of Determination of Oral Health (GOHAI) questionnaires, respectively. BF was measured using a gnathodynamometer and ME by chewing silicone cubes and almonds in different numbers of cycles. RESULTS: There was no difference between the attachment systems about self-perceived oral health and impact on quality of life (p > .05). The O-ring-type system obtained a significantly higher BF than the locator-type system (p = .04). Regardless of the food chewed, no statistically significant difference was observed with the type of attachment (p > .05). The ME was directly proportional to the masticatory cycles only for almonds (p < .01). CONCLUSIONS: Locator and O-ring inserts had a similar impact on patients' quality of life, self-perception of oral health and ME. Additionally, the O-ring system exhibited superior properties in the BF.

Effect of botulinum toxin type A on muscular temporomandibular disorder: A systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Botulinum toxin type A (BTX-A) is increasingly used to manage painful temporomandibular disorders (TMD). However, the effect of BTX-A on muscular TMD remains unclear. OBJECTIVE: To assess the efficacy, safety and optimal dose of BTX-A for treating TMD. METHODS: We conducted systematic literature searches in MEDLINE, Embase, Web of Science, ClinicalTrials.gov and Cochrane Library until March 2023. We extracted data from randomized controlled trials (RCTs) that evaluated the efficacy and safety of BTX-A in treating muscular TMD. We performed a meta-analysis using a random-effects model. RESULTS: Fifteen RCTs involving 504 participants met the inclusion criteria. BTX-A was significantly more effective than placebo in reducing pain intensity, as measured on a 0-10 scale, at 1 month (MD [95% CI] = -1.92 [-2.87, -0.98], p < .0001) and 6 months (MD [95% CI] -2.08, [-3.19 to -0.98]; p = .0002). A higher dosage of BTX-A (60-100 U bilaterally) was associated with a greater reduction in pain at 6 months (MD [95% CI] = -2.98 [-3.52, -2.44]; p < .001). BTX-A also resulted in decreased masseter muscle intensity (µV) (MD [95% CI] = -44.43 [-71.33, -17.53]; p = .001) at 1 month and occlusal force (kg) at 3 months (MD [95% CI] = -30.29 [-48.22 to -12.37]; p = .0009). There was no significant difference in adverse events between BTX-A and placebo. CONCLUSIONS: BTX-A is a safe and effective treatment for reducing pain and improving temporomandibular muscle and joint function in muscular TMD patients. A bilateral dose of 60-100 U might be an optimal choice for treating muscular TMD pain.

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.

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.

A randomized controlled trial assessing denture adhesive efficacy on denture retention across 13 hours.

PURPOSE: To compare the effects of two denture adhesive formulations on the bite force required to dislodge a maxillary denture in adult participants during a 13-h test period. MATERIALS AND METHODS: Twenty-two participants with a fair-to-poor fitting maxillary denture opposed by natural dentition or a stable mandibular denture were enrolled in this single-center, randomized, double-blind, two-treatment, 4-period crossover study. Participants were randomly assigned a product usage sequence so that each participant used each product twice during the 4-day test period. The test product was a denture cream adhesive formulated with an optimized calcium/zinc partial salt of polyvinyl methyl ether/maleic acid (Fixodent Ultra technology); the control product was a cream adhesive formulated with a calcium/zinc partial salt of polyvinyl methyl ether/maleic acid (Fixodent Original technology). On each study day, bite force at dislodgement was measured with a gnathodynamometer at baseline, representing the "no adhesive" score. Then, after standardized product application to the participant's existing maxillary denture by site staff, bite force measurements were retaken at 1, 3, 5, 7, 9, 11, and 13 h. The change from baseline and the 13-h area under the bite-force-change-from-baseline curve were analyzed via an analysis of variance. RESULTS: Twenty-one participants completed all test periods; one additional participant completed three test periods so 22 participants were included in the analysis. There were 15 females and 7 males with a mean age of 70 years. The mean 13-h area under the bite-force-change-from-baseline curve was 8% greater (p = 0.010) for the test adhesive (114.3 lb) than for the control adhesive (105.9 lb). Both adhesives showed a statistically significant increase in bite force (p < 0.001) at each time point compared to no adhesive. CONCLUSIONS: The optimized calcium/zinc partial salt of polyvinyl methyl ether/maleic acid test adhesive provided superior maxillary denture retention relative to that of the control adhesive across 13 h. Both adhesives increased bite force at dislodgement compared to no adhesive.

Rheumatoid Arthritis and Osteoarthritis in Adult Women: A Functional Approach to the Stomatognathic System.

Rheumatoid arthritis and osteoarthritis both affect the articular cartilage, and are characterized by signs and symptoms that can affect the functions of the human body. This cross-sectional observational study evaluated electromyographic activity in the masseter and temporalis muscles, molar bite force, and mandibular mobility in adult women with rheumatoid arthritis or osteoarthritis. A total of 42 women were distributed into 3 groups: rheumatoid arthritis group (ARG, n=14); osteoarthritis group (OAG, n=14); and a healthy control group (CG, n=14). Electromyography was used to evaluate mandibular tasks at rest, right and left laterality, protrusion, and dental clenching during maximum voluntary contraction, with and without parafilm, and a dynamometer was used to analyse the right and left molar bite forces. A digital caliper was used to measure the range of mandibular movement for maximum mouth opening, right and left laterality, and protrusion. Statistical analyses were performed, including analysis of variance and Tukey's test (P<0.05). Electromyography showed no significant differences between the groups when evaluating the masticatory muscles during the mandibular tasks. Significant difference was observed between the ARG and CG, however, in the maximum right (P=0.007) and left (P=0.02) molar bite forces. Significant difference was observed in the maximum mouth opening of the ARG and OAG groups compared with that of the CG (P=0.009), suggesting that adult women with rheumatoid arthritis or osteoarthritis experience functional alterations in the stomatognathic system, particularly in molar bite force and maximum mouth opening.

Temporary Hydrostatic Splint Therapy and Its Effects on Occlusal Forces.

Background and objectives: This study analyzed and compared the distribution patterns of occlusal forces using T-Scan III before and after the hydrostatic temporary oral splint (Aqualizer Ultra) therapy in healthy subjects and subjects with temporomandibular disorders (TMDs). Materials and Methods: Fifty-one subjects were divided into groups based on anamnesis and responses to the Fonseca questionnaire. The first group, non-TMDs group (n = 19), and the second group, TMDs group (n = 32), had mild-to-severe TMDs, as identified by the Fonseca questionnaire. The non-TMDs group had an average age of 25.4 years (SD = 4.8, range 20-38) with 15 females (78.95%) and 4 males (21.05%). The TMDs group had an average age of 27.4 years (SD = 7.0, range 22-53) with 25 females (78.125%) and 7 males (21.875%). T-Scan III device was used for occlusal analysis before and after hydrostatic splint usage. Results: Significant differences were observed in the TMDs group for anterior and posterior right percentages of forces before and after hydrostatic splint usage. The analysis of force distribution per sector before and after hydrostatic splint therapy showed no significant differences in the non-TMDs group. Analysis of force distributions in the entire study population before and after hydrostatic splint therapy showed significant differences in the anterior and posterior right regions. Occlusal force increased by 32-56% in the front region and decreased in the posterior area after hydrostatic splint usage. Conclusions: Hydrostatic splint therapy is recommended as a part of full-mouth rehabilitation treatment for all patients regardless of the severity of TMDs.

Form-function relationships underlie rapid dietary changes in a lizard.

Macroevolutionary changes such as variation in habitat use or diet are often associated with convergent, adaptive changes in morphology. However, it is still unclear how small-scale morphological variation at the population level can drive shifts in ecology such as observed at a macroevolutionary scale. Here, we address this question by investigating how variation in cranial form and feeding mechanics relate to rapid changes in diet in an insular lizard (Podarcis siculus) after experimental introduction into a new environment. We first quantified differences in the skull shape and jaw muscle architecture between the source and introduced population using three-dimensional geometric morphometrics and dissections. Next, we tested the impact of the observed variation in morphology on the mechanical performance of the masticatory system using computer-based biomechanical simulation techniques. Our results show that small differences in shape, combined with variation in muscle architecture, can result in significant differences in performance allowing access to novel trophic resources. The confrontation of these data with the already described macroevolutionary relationships between cranial form and function in these insular lizards provides insights into how selection can, over relatively short time scales, drive major changes in ecology through its impact on mechanical performance.

Oral function in completely edentulous patients rehabilitated with implant-supported dental prostheses: A systematic review and meta-analysis.

OBJECTIVES: This review evaluated the effects of rehabilitation with implant-supported prostheses on the oral function of completely edentulous adults. MATERIALS AND METHODS: Systematic literature searches were performed to identify records reporting on oral function in completely edentulous adults rehabilitated with implant-supported prostheses. Meta-analyses were performed on various outcomes including bite force, masticatory performance, muscle activity, mandibular movement/chewing pattern, and salivary flow. RESULTS: 5507 records were identified. Thirty studies qualified for data extraction and analysis. The kappa (𝛋) for the search and identification strategy ranged between 0.50 and 1.00. Meta-analysis was performed grouping the studies by outcomes and split by time points of 6-12 months, 12-36 months, and >36 months after implant therapy. The meta-analyses revealed a significant improvement in oral function of completely edentulous adults after rehabilitation with implant-supported prostheses at 6-12 months (Z = -4.895, p < .001; 95% CI: -0.703, -0.301; τ2 = .609; Q = 114.953, df = 17, p < .001; I2 = 85.2%), at 12-36 months (Z = -4.886, p < .001; 95% CI: -0.580, -0.248; τ2 = .908; Q = 280.611, df = 35, p < .001; I2 = 87.5%) and at more than 36 months (Z = -9.108, p < .001; 95% CI: -1.472, -0.951; τ2 = .019; Q = 7.918, df = 7, p = .340; I2 = 11.6%). The included studies demonstrated a low to moderate risk of bias. CONCLUSIONS: This systematic review concluded that the oral function of completely edentate adults significantly improved with implant-supported/retained prostheses, even when only one jaw received implant therapy. Therefore, implant therapy should be promoted for edentulous adults to alleviate the shortcomings of conventional complete removable dental prostheses.

Short-term effect of material type and thickness of occlusal splints on maximum bite force and sleep quality in patients with sleep bruxism: a randomized controlled clinical trial.

OBJECTIVE: To evaluate the short-term effects of hard and soft splints of different thicknesses on maximum bite force (MBF) and sleep quality (SQ) in participants with sleep bruxism (SB). METHODS: One-hundred-fifteen patients were randomly allocated to five groups: Groups H2(Hard splint-2 mm), H3(Hard splint-3 mm), S2(Soft splint-2 mm), S3(Soft splint-3 mm), and C (control). Outcomes were MBF (assessed with a digital gnathodynamometer) and SQ (assessed with the Pittsburgh Sleep Quality Index). Measurements were performed at T0 (before the splints), T1 (1-month follow-up), and T2 (2-months follow-up). Data were analyzed using one-way analysis of variance(ANOVA), Tukey's HSD, and chi-square tests (alpha = 0.05). RESULTS: At T1, the highest MBF values were observed in group H3 (658.01 ± 22.6 N), while the lowest in group S2 (585.45 ± 8.68 N). For T2, the highest values were obtained in H3 group (676.85 ± 21.9 N), and the lowest in group S2 (565.65 ± 10.9 N) (p < 0.05).For SQ, groups S2 and S3 revealed the lowest PSQI values at T1 (9.1; 9.6) and T2 (9; 9.5) (p < 0.001). CONCLUSIONS: The short-term use of both 2 and 3-mm thick soft splints resulted in a decrease in MBF. Improvement in SQ in patients using soft splints was observed in the 1st month and was maintained in the 2nd month. CLINICAL RELEVANCE: This study provides insights on short-term clinical effects as regards to increased sleep quality and regulated maximum bite force as a function of splint material type and the thickness of the splint.

Impact of pivoting bite tip on bite force measurement tests.

OBJECTIVE: Present a gnathodynamometer design that increases patient comfort, precision, and/or ease for the operator during bite force tests. MATERIALS AND METHODS: A bite tip capable of pivoting 180° was tested on senior dental students in a double-blind trial. The tests were performed in teeth 11 and 16 with the bite tip on the long axis of the clamp and at an angle of 90° to the clamp. The sample was composed of 24 students, 13 males and 11 females, randomly divided into two groups: the operator group (OP), which was composed of 12 students, 7 males and 5 females, and the test group (TI), which was composed of 12 students, 6 males and 6 females. The operator and participants were asked to evaluate comfort and precision/ease in positioning the bite tip by attributing scores from 0 (total discomfort) to 10 (total comfort) during the test. RESULTS: No difference was noted in tooth 11 (P > 0.05). In tooth 16, there was a statistically significant improvement (P < 0.01) for the participants tested and the operator using the pivoting bite tip. CONCLUSIONS: The pivoting bite tip showed no difference in the comfort of the participants and operator precision when testing incisors; however, the tip showed a difference for both conditions in the molar region. The gnathodynamometer geometry showed good results in participant comfort and operator precision when used in bite force tests of the incisors and molars. Further investigations are needed to confirm whether these improvements influence the mean value and maximum bite force measurement. CLINICAL RELEVANCE: Bite force measurement is a method for obtaining important data to check the functional conditions of the stomatognathic system. With the aging of the world population, it has become important to check the quality of life during aging. The pivoting bite tip improves the comfort and precision of bite tests for the participants tested and for the operator, respectively.

Changes in masticatory performance during the retention period following 4-premolar extraction and non-extraction orthodontic treatment.

OBJECTIVES: To evaluate changes in masticatory performance (MP) during the retention period after extraction and non-extraction treatment and compare it with MP in individuals with normal occlusion. MATERIALS AND METHODS: Adult patients who had completed orthodontic fixed appliance treatment comprised the extraction and non-extraction treatment groups, and those with normal occlusion comprised the control group. Their mixing ability (MA), maximum bite force (MBF), and occlusal contact area (OCA) were recorded immediately after the fixed appliance was removed and at 1 month, 6 months, and 1 year post-treatment. The MA was measured via the two-color chewing gum MA test using ViewGum software, and the MBF and OCA were measured using Dental Prescale II system. RESULTS: MA immediately after orthodontic treatment was lower than that in the normal group but showed a time-dependent gradual increase during a 1-year retention period (P < 0.01). The MA at 1 month post-treatment was not significantly different between the three groups (P > 0.05). The MA revealed a significant correlation with the MBF and OCA (P < 0.01). CONCLUSIONS: The MP immediately after orthodontic treatment was lower than that in the normal group but increased gradually, with levels comparable to those of the normal occlusion group at 1 month post-treatment. Further, extraction did not affect the recovery of the MP after orthodontic treatment. CLINICAL RELEVANCE: No other study has evaluated the changes in MP during the retention period after orthodontic treatment. The findings show that compared with MBF and OCA, the patients' MP improved faster to levels found in normal occlusion.

Handgrip force and bite force in dentulous and edentulous individuals.

BACKGROUND: The literature is unclear about bite force (BF) and handgrip force (HF) in a specific group of different ages and dentate conditions, or even a predictive model for each specific group, using BF and HF as factors. OBJECTIVE: To establish the correlation between HF and BF in female participants with distinct ages and dentate conditions; also create a predictive model of BF as a function of HF. METHODS: Participants were divided into three groups (GI: young natural dentate women, n = 65; GII: adult natural dentate women, n = 67; and GIII: edentulous women users of bimaxillary complete dentures, n = 67) and subjected to an HF measurement test using a digital dynamometer. Subsequently, BF was measured using a digital gnathodynamometer in the molar region. Pearson correlation coefficient (r) and multivariate analysis of variance (α = 0.05) were performed, and simple linear regression was used to obtain a model to predict BF from HF for each group separately (α = 0.05). RESULTS: All groups presented moderate and strong correlations among the variables (GI: r = 0.838; GII: r = 0.714; GIII: r = 0.646). A significant difference in BF was observed (GI > GII > GIII; p < .05). GIII presented a significantly lower HF than the other groups (p < .05). Besides, three equations predicting BF, using HF, were obtained for use in young/adult dentate and edentulous women. CONCLUSION: All groups found a positive and significant correlation between BF, HF and groups. HF can be a simple and efficient method for predicting BF using the predictive models developed for women with good health.

Associations between temporomandibular disorders, pain, jaw and masticatory function in dentofacial deformity patients: A cross-sectional study.

BACKGROUND AND OBJECTIVE: Patients with dentofacial deformity often present with impaired masticatory function, orofacial pain and temporomandibular disorders (TMD). This study investigates the relationship between TMD, pain, jaw and masticatory function at different stages of orthognathic surgical (OS) treatment. METHODS: A total of 120 OS patients were prospectively recruited and grouped as pre-orthodontic (group 1), pre-surgery (group 2), 4-month post-surgery (group 3), 24-month post-surgery (group 4), in addition to 30 controls (group 0). Outcomes were assessed using: Jaw Function Limitation Scale (JFLS), McGill pain questionnaire, DC/TMD instrument, voluntary maximum bite force (MVBF), and masticatory efficiency (ME) using two-coloured chewing gum. Data were analysed using structural equation modelling. RESULTS: The prevalence of non-painful TMD did not differ between groups (p = .827). However, the prevalence of painful TMD differed between groups (p = .001). Among the painful TMDs, the highest prevalence was observed for masseter myalgia in group 2 (p = .031), and importantly group 4 did not differ from group 0 (p = .948). The MPQ score was significantly higher in group 1 (p = .001) compared to group 0, and the JFLS score was significantly higher in groups 1, 2 and 3 compared to group 0. Notably, MPQ (p = .756) and JFLS (p = .572) scores in group 4 were not different from group 0. However, MVBF (p = .996) and ME (p = .991) did not differ between groups 1 and 4. The association of self-reported pain and jaw function with the masticatory function was observed in OS patients. CONCLUSION: OS was not associated with a negative impact on TMD. Jaw function and pain levels were similar to controls at the 24-month follow-up. The masticatory function was further affected by the surgery and seems to require a longer recovery time. Moreover, it was confirmed that pain and TMD were associated with limitations in jaw function and impacts on masticatory function.

Duration of bite force reduction following a single injection of botulinum toxin in the masseter muscle bilaterally: A one-year non-randomized trial.

BACKGROUND: Previous studies concerning the effect of botulinum toxin in masseter muscle have mainly reported effects observed through inspection of facial features or differences in pain levels. One systematic review of studies utilizing objective measurements reported that long-term muscular effect of botulinum neurotoxin injections into masseter muscle was inconclusive. OBJECTIVE: To evaluate the duration of reduced maximal voluntary bite force (MVBF) after botulinum toxin intervention. METHODS: The intervention group was comprised of individuals seeking aesthetic treatment for masseter reduction (n = 20), the reference group (n = 12) comprised of individuals with no intervention. Intervention through 25 units of Xeomin® (Merz Pharma GmbH & Co KGaA, Frankfurt am Main, Germany) botulinum neurotoxin type A injected into the masseter muscles bilaterally (totalling 50 units). A reference group did not receive any intervention. MVBF was measured in Newtons using a strain gauge meter at the incisors and first molars. MVBF was measured at baseline, at 4 weeks, 3 months, 6 months, and after 1 year. RESULTS: Both groups were similar in terms of bite force, sex and age at baseline. MVBF remained similar compared to baseline in the reference group. At 3 months, a significant reduction at all measurement points was observed in the intervention group; at 6 months, this reduction was no longer significant. CONCLUSION: A single intervention of 50 units of botulinum neurotoxin results in a reversible MVBF reduction of at least 3 months, although a visually discernable reduction may be more long-lasting.

Assessment of masticatory performance in patients undergoing orthognathic surgery: A systematic review and meta-analysis.

BACKGROUND: One of the main goals of orthognathic surgery is to improve the masticatory performance in patients with maxillofacial deformities. OBJECTIVE: The aim of this study was to evaluate the literature on assessing masticatory performance before, after orthognathic surgery and normal occlusion. METHODS: An electronic search was performed via Pubmed, Scopus, LILACs and Web of Science without any restrictions until June 2022. The articles assessing masticatory performance using a comminution assay, bite force or occlusal contact area in patients undergoing orthognathic surgery with or without comparing controls were included. The risk of bias of the selected articles was assessed using the appropriate tools according to the study design. RESULTS: Of the 2507 records identified, 21 studies were included in the qualitative evaluation and 17 studies in the meta-analysis. Nine articles were cohort studies, and the other eight were before-after studies. Moderate to high risks of bias were found among the articles. Comparing the values before and after surgery, the meta-analysis revealed a significant improvement in the bite force and occlusal contact area at 1- and 2-year post-surgery. However, regardless of the assessed parameters, the masticatory performance in patients with normal occlusion was significantly greater than those in patients undergoing orthognathic surgery at all evaluated time points. CONCLUSION: Although combined surgical orthodontic treatment can improve impaired masticatory function, assessed by the comminution method, bite force and occlusal contact area, the improvement may not reach that of normal occlusion.