Search Results (149)

Objectives: To quantitatively assess masticatory function with instrumental measures in a group of patients suffering from temporomandibular joint (TMJ) arthralgia, and to compare the results with symptom-free controls. Methods: Data of bite force, variance-of-hue-based (VOH) chewing efficiency, chewing frequency, the bilateral pressure pain threshold (PPT) of the temporalis and masseter muscles, and mandibular range of motion (RoM) were collected in a sample of TMJ arthralgia patients (n = 14) and controls (n = 19). The diagnosis of arthralgia was obtained following the DC/TMD protocol. Comparison between the groups was conducted using independent samples t-tests (level of significance α = 0.05). Associations within the arthralgia group were assessed using Pearson’s correlation coefficient. Results: In comparison to the controls, arthralgia patients showed significantly restricted pain-free and maximum unassisted mouth opening (p < 0.001, p = 0.022 respectively) as well as a significant decrease in both bite force (p < 0.001) and chewing frequency (p = 0.01). The average chewing efficiency for the arthralgia group was 0.14 ± 0.08 VOH. The PPT for both masseter muscles did not show significant differences in comparison to the control group. Conclusions: In patients with TMJ arthralgia, functional markers such as RoM, bite force, and chewing frequency exhibited significant limitations compared to the control group. The employment of instrumental measurements in the documentation of symptoms in clinical practice provides an objective basis for the assessment of functional limitations. Hence, we recommend integrating them into the longitudinal patients’ observation during therapy. Full article

This in vitro study evaluated the fracture resistance of CAD/CAM-fabricated lithium disilicate and 3D-printed resin crowns with varying occlusal thicknesses (0.5, 1.0, and 1.5 mm) following thermomechanical aging. Sixty extracted human molars were assigned to six experimental groups (n = 10), categorized by crown material and occlusal thickness. The crowns were fabricated using CAD/CAM technology in accordance with the manufacturer’s protocol. All specimens underwent thermomechanical aging, which consisted of thermocycling between 5 and 50 °C (5500 cycles) combined with mechanical loading of 50 N at 1.6 Hz for 75,000 cycles. The fracture loads were measured using a universal testing machine, and the failure modes were assessed using scanning electron microscopy. Statistical evaluation was performed using two-way analysis of variance with Tukey’s post hoc test (α = 0.05). Both the material type and occlusal thickness had a statistically significant effect on fracture resistance (p < 0.001). Lithium disilicate crowns exhibited higher fracture loads than 3D-printed resin crowns independent of occlusal thickness. Although the fracture resistance of 3D-printed resin crowns was lower, specimens with occlusal thicknesses ≥1.0 mm exhibited fracture loads exceeding average physiological masticatory forces, suggesting that 3D-printed resin crowns may represent a clinically acceptable option for conservative posterior restorations. In contrast, crowns with an occlusal thickness of 0.5 mm demonstrated fracture resistance values below the reported functional masticatory loads. Additionally, the proportion of repairable fractures increased with increasing occlusal thickness for both materials. Overall, the findings suggest that an occlusal thickness of at least 1.0 mm may represent a reliable threshold for posterior restorations, whereas a thickness of 0.5 mm may be insufficient to withstand functional occlusal loads in molar regions. Full article

Background: Oral frailty is an emerging determinant of late-life disability. While objective functional measures have been proposed as key indicators, their combined role in predicting frailty among physically active older adults remains unclear. Therefore, this study aimed to investigate the association between the presence of oral frailty and lip pressure, bite force, and denture use. Methods: This cross-sectional study included 192 participants aged 60 years or older from Brazil (n = 131) and Portugal (n = 61), all physically active and with ≥20 natural or rehabilitated teeth. Data were collected through a questionnaire on sociodemographic data and the Oral Frailty Index-8. The clinical assessment included lip pressure, bite force, and denture use. Multiple logistic regression identified independent predictors; model fit and discrimination were examined using the Hosmer–Lemeshow test and ROC curve. Results: Participants were mainly female (83.3%), mean age ≈72 years; 76% used dentures and frailty prevalence was ≈49%. Higher lip pressure (OR = 0.986, 95% CI = [0.973–0.999]) and higher bite force (OR = 0.925, 95% CI = [0.885–0.967) were independently protective, whereas denture use (OR = 6.898, 95% CI = [2.994–15.895]) markedly increased oral frailty odds. The model showed good discrimination (AUC 0.779). Conclusions: Even small increases in lip pressure and bite force reduced the likelihood of frailty, while denture use identified individuals at substantially higher risk. These findings highlight orofacial muscle strength and masticatory capacity as core components of oral frailty and support incorporating lip pressure and bite force testing into multidimensional frailty assessment and targeted rehabilitation. Full article

Background/Objectives: The performance of the adhesive system used for bonding fundamentally influences the success of fixed orthodontic treatment. To withstand masticatory forces and prevent bracket debonding, it is critical to achieve optimal shear bond strength (SBS), improving treatment time. The aim of this study was to compare the shear bond strength and adhesive remnant index (ARI) of orthodontic brackets bonded using LED light-curing units with intensities of 3200 mW/cm² at two different exposure times, evaluated after 24 h and 14 days. Methods: Eighty extracted permanent premolars were randomly divided into four experimental groups. Brackets were bonded using Transbond XT adhesive and cured with a VALO™ Ortho Cordless unit (3200 mW/cm²) for 3 or 6 s. SBS was measured using a universal testing machine, and the ARI was assessed under a stereomicroscope at 40× magnification. Results: Increased light intensity and longer curing time significantly improved SBS values. The highest bond strengths were observed in groups cured with 3200 mW/cm² for 6 s, after 14 days. ARI scores showed that longer curing reduced adhesive remnants on the enamel. Statistical analysis confirmed significant differences among groups. Conclusions: Therefore, clinicians may achieve better bonding performance and easier enamel clean-up by using high-intensity lights with adequate curing duration. Full article

Dental implantation affects masticatory bite and muscle forces. The temporomandibular joint (TMJ) bears a substantial amount of these masticatory forces. Thus, the objective of the current study was to investigate whether dental implantation alters the human mandibular condyle. Among 556 images, 54 and 22 CBCT scans were successfully identified from 27 patients (10 males and 17 females; 54.93 ± 19.46 years) in the control group and 11 patients (3 males and 8 females; 51.32 ± 13.13 years) in the implant group, respectively. In the control group, CBCT images were obtained longitudinally at the time of implantation and after the post-implantation healing period, both prior to crown placement. In the implant group, CBCT images were obtained at the time of crown placement on a single-tooth implant and after the functional loading period following crown placement. Left and right mandibular condyles were digitally isolated from the images. The bone mineral density (BMD) parameters and morphological changes were assessed using frequency plots of BMD and TMJ osteoarthritis (OA) counts, respectively. In the control group, BMD values were not significantly different between the first and second scans. In contrast, the implant group showed a significant decrease in BMD values, along with a marginal increase in TMJ OA counts after the functional loading period. The TMJ OA counts were highest in the anterior regions, followed by the middle and posterior regions. Most regions showed significantly reduced BMD values, except the antero-lateral and antero-central regions. The current findings give an insight that dental implantation may alter the morphology and BMD of human mandibular condyles. The TMJ OA counts increased, while BMD decreased during the functional loading period of more than 3 months following implantation. Masticatory loading associated with the dental implant likely increases the load on the TMJ, which could stimulate new bone formation to balance the load distribution on the mandibular condyle. Full article

Objectives: The aim of this study was to compare the stiffness-related mechanical response and peak von Mises stress distribution of low-profile 2.4 mm mandibular reconstruction systems (a conventional reconstruction plate, a 3D grid-type plate, and a customized plate) in a virtual atrophic mandible model with a 5 cm segmental defect. Materials and Methods: A CT-based three-dimensional mandible model was created and instrumented with three plate configurations (G1–G3). Linear static finite element analyses were performed under a 300-N masticatory load combined with literature-based muscle force vectors. Peak von Mises stresses were recorded for plates and screws, and the locations of maximum stress concentration were identified. Results: Peak plate stress was highest in the conventional reconstruction plate (G1: 695.5 MPa), followed by the 3D grid-type plate (G2: 595.6 MPa), and lowest in the customized plate (G3: 185.2 MPa). The peak screw stress was 692.9 MPa (G1), 898.0 MPa (G2), and 595.6 MPa (G3). The 3D grid-type plate increased construct stiffness but shifted stress concentration toward the mandibular angle and adjacent screws, whereas the customized plate reduced the peak plate stress and limited the extent of the high-stress region across the defect. Conclusions: Within the limitations of a linear static FEA (stiffness/stress distribution rather than failure load or fatigue resistance), the customized plate (G3) demonstrated the most favorable biomechanical performance (lowest peak plate stress). The 3D grid-type plate (G2) reduced peak plate stress compared with the conventional design (G1) but produced the highest peak screw stress. Practical considerations such as manufacturing lead time and resource requirements may favor off-the-shelf plates; however, a formal cost or operative-time analysis was not performed. Full article

Weight loss is an indicator of nutritional disorders, is associated with increased morbidity and mortality, and is more likely to be experienced by individuals with fewer teeth. In this study, we examined the relationship between 1-year body weight changes and variations in various oral function tests. In total, we examined 104 individuals aged 45–84 years (70 men and 34 women) who underwent health check-ups at our hospital in 2023 and 2024. Several oral function tests were performed, and changes over a 1-year period were compared using the Wilcoxon signed-rank test. The rate of change in oral function was compared between individuals who lost ≥5% of their body weight in 1 year and those who did not; no significant differences in body weight and oral function were observed between 2023 and 2024, and no significant differences in the rates of change in oral function or weight loss were observed based on sex and age. The rates of change in occlusal force and masticatory function were significantly correlated with weight loss rates, while no differences were observed in terms of sex or age between those who lost ≥5% of their body weight in 1 year and those who did not; the only significant difference was in occlusal force: weight loss was correlated with occlusal force over 1 year, with individuals who lost ≥5% of their body weight exhibiting significantly lower occlusal force, a risk factor for nutritional disorders. Full article

Background/Objectives: Oral function impairment negatively impacts nutrition, health, and quality of life in older adults. While retaining ≥20 natural teeth is often recommended for maintaining oral function, its validity is uncertain, particularly for those who adapt to tooth loss with dentures. This study aimed to determine the minimum number of remaining functional teeth necessary to prevent oral hypofunction in older adults, focusing on two diagnostic criteria: decreased masticatory function and reduced occlusal force. Methods: A total of 154 participants (≥60 years) were included. Oral examination assessed the number of remaining functional teeth. To assess masticatory function, masticatory performance was objectively measured using a visual scoring method of gummy jelly, and occlusal force was quantified with pressure-sensitive film. Pearson’s correlation analyzed relationships among variables, while receiver operating characteristic (ROC) analysis identified optimal tooth number cut-offs for detecting decreased masticatory function (score ≤ 2) and reduced occlusal force (<500 N). Results: Significant positive correlations were found between the number of remaining functional teeth and both masticatory performance (r = 0.591, p < 0.001) and occlusal force (r = 0.453, p < 0.001). ROC indicated that 17 teeth was the optimal threshold for identifying both decreased masticatory performance and reduced occlusal force, with sensitivities of 0.79 and 0.72 and specificities of 0.93 and 0.88, respectively. Conclusions: Retention of 17 or more remaining functional teeth may be sufficient to maintain adequate masticatory performance and occlusal force. These findings serves as a preliminary guide for treatment planning and targeted interventions focused on preserving tooth retention and improving oral function in aging populations. Full article

Background: The bond strength of orthodontic tubes to the enamel surface is essential for maintaining appliance stability, especially due to high masticatory forces on molars. Strong adhesion reduces the need for rebonding, shortening treatment time. This study aimed to evaluate the impact of tube base size and enamel sandblasting on bond strength in vitro. Methods: Eighty extracted permanent molar teeth were used for this study, divided into four groups of 20 samples each: M—small base tubes (non-sandblasted enamel), SM—small base tubes (sandblasted enamel), T—large base tubes (non-sandblasted enamel), and ST—large base tubes (sandblasted enamel). Shear bond strength was measured using the Mecmesim Multitesters 2.5-I device. Statistical analysis was conducted using IBM SPSS 27.0 software, applying ANOVA and Tukey’s post hoc test. Results: The highest bond strength (N) was recorded in the ST group, 85.51 ± 25.04 N, and the lowest in the M group, 50.23 ± 19.76 N. In terms of MPa, the SM group had the highest average value, 11.31 ± 3.57 MPa, while the T group had the lowest, 4.89 ± 1.33 MPa. ANOVA showed a statistically significant effect of tube base size on bond strength (p < 0.001), while sandblasting had no significant effect (p > 0.05). Conclusions: Larger base orthodontic tubes demonstrate stronger adhesion to enamel and are recommended for molars. Sandblasting the enamel does not significantly impact bond strength. Full article

This in vitro study investigated the fracture resistance of three ceramic-reinforced polymer (CRP) crowns—Cerasmart^® 270 (CE; milled), VarseoSmile Crown Plus^® (VS; 3D-printed) and the newly developed Hassawat-01 (HS; 3D-printed)—luted with cements of different elastic moduli. The principal hypothesis was that neither the CRP type nor the modulus of cement would significantly affect fracture resistance. Ninety-nine mandibular first molar resin dies were restored with 1 mm thick CE, VS, or HS crowns (n = 33 each) and luted with Maxcem Elite^®, RelyX Unicem^®, or Ketac Cem^® (n = 11 per subgroup). Occlusal cement morphology was evaluated using Micro-CT. Fracture resistance was measured using a universal testing machine. Crowns luted with Maxcem or RelyX withstood forces >2000 N without visible failure. Ketac-luted crowns showed reduced fracture resistance. CE-Ketac fractured in 4 of 11 specimens. VS-Ketac exhibited cracks or complete fractures (1795.2 ± 156.7 N), whereas HS-Ketac showed only superficial cracking (1732.6 ± 127.3 N). CRP crowns luted with lower-modulus resin cements demonstrated superior fracture resistance compared with those luted with glass-ionomer. VS exhibited both cracking and occasional complete fractures, whereas HS exhibited only surface cracking. All materials withstood loads greater than typical masticatory forces, supporting HS as a promising alternative within the CRP. Full article

Background: Temporomandibular disorders (TMDs) are associated with altered masticatory muscle function and pain. Although electromyographic parameters have been extensively studied, the rate of force development (RFD) remains an underexplored biomarker in this context. Objective: Analyze the RFD differences in women diagnosed with and without TMD. As a secondary outcome, the masseter and temporalis muscle pre-activation values were compared between groups based on the biting force onset. Additionally, neuromuscular efficiency analysis was also performed. Methods: A retrospective analysis of 62 medical records (41 with TMD, 21 controls) was conducted. Electromyographic activity and bite force were measured during three 5-s maximal biting tasks using synchronized surface electromyography (sEMG) and a laboratory-grade load cell. RFD was computed from force–time curves. Muscle pre-activation was assessed based on sEMG activity immediately preceding contraction onset. Results: The TMD group showed a significantly smaller RFD (mean = 85.5 N/s) compared to controls (mean = 109.0 N/s; p = 0.03; Cohen’s d = 0.5). No significant differences were found in neuromuscular efficiency and pre-activation or post-activation levels of the masseter and temporalis muscles between groups. Conclusions: RFD distinguishes women with TMD from healthy controls and may represent a sensitive biomechanical marker of neuromuscular adaptation in TMD, although confirmatory studies are needed. The absence of neuromuscular efficiency and pre-activation differences suggests compensatory neuromuscular mechanisms. Further prospective studies are needed to validate these findings and explore clinical applications. Full article

Background/Objectives: Parafunctional habits such as bruxism generate high occlusal forces that can significantly compromise the performance of dental restorations during orthodontic treatment. This ex vivo study aimed to evaluate the surface wear of Class II composite restorations and the integrity of clear aligners (CAs) under simulated parafunctional loading. Methods: Thirty-four posterior teeth restored with composite materials were subjected to either normal masticatory forces or high-intensity cyclic forces mimicking bruxism while being fitted with orthodontic aligners. The collected experimental data were analyzed using R (version 4.3) under the Jamovi project (version 2.5.3). Differences between groups were assessed using paired samples t-tests and Wilcoxon tests for paired samples, with robust t-tests applied when data normality could not be confirmed. Statistical significance was set at α = 0.05. Results: Parafunctional loading led to significantly greater surface degradation of restorations and increased aligner wear. Compared with functional forces, RMS errors were substantially higher under parafunctional forces (33.5 vs. 21.5 units; p < 0.001), indicating reduced positional accuracy. Aligner thickness decreased more under parafunctional conditions (0.0304 mm) than under normal function (0.0122 mm), with all comparisons showing high statistical significance and large effect sizes. Conclusions: Parafunctional forces were found to significantly increase surface wear in Class 2 resin composite restorations during clear aligner therapy. Simulated bruxism also compromised aligner integrity, indicating the need for more durable materials and tailored treatment strategies for patients with bruxing habits. These findings highlight the importance of selecting durable restorative and aligner materials for bruxer patients to ensure long-term treatment success. Full article

This study investigated bite force changes after botulinum toxin type A (BoNT-A) injection into different masticatory muscles. Thirty-five male participants were divided into three groups: masseter only (M), masseter and temporalis (MT), and masseter, temporalis, and medial pterygoid (MTP). Bite force was measured before and up to 6 months after injection with the Dental Prescale II system. Baseline values showed no significant group differences. Group M exhibited significant reduction at 1 and 2 weeks, with recovery within 1 month. Group MT showed a similar transient decrease, also recovering after 1 month. In contrast, Group MTP demonstrated a more pronounced and prolonged reduction, persisting up to 4 months before recovery. These results indicate that the extent and duration of BoNT-A effects depend on the number of muscles injected. Multi-muscle injections, including the medial pterygoid, provide more durable suppression. However, further research involving patient populations is needed to clarify whether multi-muscle injection strategies provide therapeutic benefits in clinical conditions such as temporomandibular disorders or oromandibular dystonia. Full article

Background/Objectives: Occlusal disturbances occurring during central occlusion, mandibular movements and mastication may contribute to the development of temporomandibular disorders (TMDs). To reduce the disclusion time (DT) in all mandibular contacts, a procedure known as enameloplasty can be applied. The aim of this study was to evaluate the effect of occlusion-correcting treatments on disclusion time reduction, determination of the center of force, and the distribution of masticatory forces on the right and left side, through digital occlusal analysis in patients with TMD. Methods: The single-centered, prospective study including 106 patients with TMD after 6 months of prosthetic treatment. Digital occlusal analysis was performed before and after the enameloplasty to assess occlusion time, disclusion time and symmetry of occlusal contacts. Results: Selective enameloplasty significantly reduced disclusion time in the whole study population (0.8 vs. 0.4 s; p < 0.001), with greater improvement observed in patients with inappropriate Center of Force (COF) and premature occlusal contacts. Conclusions: Digital occlusal analysis-guided selective enameloplasty effectively reduces disclusion time and can improve occlusal parameters in TMD patients. Full article

This study aims to evaluate the biomechanical behavior of titanium and carbon fiber-reinforced polyetheretherketone (CF-PEEK) dental implants under varying bone densities and loading conditions using finite element analysis (FEA). A single-tooth mandibular molar implant system was modeled, comprising titanium or CF-PEEK abutment and fixture, and surrounding bone structures with four configurations: (I) fully cortical bone, (II) 2 mm cortical layer with trabecular bone, (III) 1 mm cortical with high-density trabecular bone, and (IV) 1 mm cortical with low-density trabecular bone. Vertical and oblique static loads of 100 N were applied to simulate masticatory forces. FEA results revealed that titanium implants exhibited higher von Mises stress values in the implant and abutment under oblique loading, exceeding 400 MPa, while CF-PEEK components showed reduced stress but significantly higher strain levels. Cortical and trabecular bone surrounding CF-PEEK implants received more uniform stress distribution, potentially minimizing stress shielding effects. However, fatigue life analyses indicated that CF-PEEK abutment and screw components were more susceptible to mechanical failure under oblique loads, particularly in low-density bone models. In conclusion, CF-PEEK implants offer a more physiological load transfer to bone and reduced stress shielding compared to titanium. However, their structural reliability under complex loading, especially in low-quality bone conditions, requires careful consideration. These findings support the potential use of CF-PEEK in select clinical scenarios but highlight the need for further material and design optimization. Full article