Maximum Intercuspation Research Articles

Mandibular border movements: The two envelopes of motion.

The envelope of motion is a diagrammatic representation of the mandibular border movements. Classically, those movements are carried out eccentrically; starting from the position of maximal intercuspation, the mandible describes an excursion movement until reaching maximal mouth opening. Reverse movements would describe a different path, but up to now concentric development of mandibular border movements has not been considered. Literature states that beyond mandibular border movements limits, no movement is possible. Therefore, it is of great interest to compare both paths-both envelopes of motion-and define the actual limits of mandibular movement. The aim of this study was to compare the geometric characteristics of mandibular border movements carried out eccentrically and concentrically by healthy subjects. Sixteen individuals aged between 18 and 27years, molar class I and with no temporomandibular disorders, participated in the study. Eccentric and concentric mandibular movements were recorded using a 3D electromagnetic articulograph. Data were processed with computational scripts developed in MATLAB. Maximum mouth opening, trajectories, displacement ranges, polygon areas and chewing cycle area/ mandibular border movements area ratio were analysed. The frontal plane showed significant differences in all the parameters evaluated. Higher values were registered in the concentric area of the border movement envelope (P=.008) and in the trajectories on both sides. Statistical differences were observed in polygon areas (P=.006) in the sagittal plane and right ranges (P=.046) in the horizontal plane. Concentric mandibular movements revealed significant differences in three-dimensional trajectories in the frontal plane.

Orthodontic treatment of open bite involved in diffuse hypercementosis: A case report

BackgroundOpen bite is considered one of the most complicated malocclusions in orthodontic treatment. In this study, the authors successfully treated total open bite involved in hypercementosis using orthodontic miniscrews. Case DescriptionA woman aged 25 years 8 months had total open bite. Her occlusal contact at the maximum intercuspation was present at the right second molars. A panoramic radiograph showed diffuse hypercementosis. The titanium miniscrews were interradicullay implanted between the first and second molars, and intrusion force was applied for 14 months. After active treatment, the patient’s maxillary first molars showed about 1.6-millimeters of intrusion, resulting in counterclockwise mandibular rotation. Her acceptable occlusion was maintained after 1.0-year retention. Practical ImplicationsMiniscrews might be useful tool to improve malocclusion involved in diffuse hypercementosis though they are considered to be difficult to move and brought on ankylosis.

Predictive Model for Occlusal Vertical Dimension Determination and Digital Preservation with Three-Dimensional Facial Scanning

(1) Background: Occlusal vertical dimension (OVD) in the optimal maxillo–mandibular relationship is an important parameter to establish when complex dental rehabilitation has to be done. The optimal method to measure OVD is still a challenge in everyday practice. The aim of the present study was to test the reliability of the correlation between OVD and some anthropometric and cephalometric methods described in the literature. The validity of OVD registration using a facial scanner was also assessed. (2) Materials and Methods: 150 dentate participants, aged 20–25 years, were randomly selected using sealed envelopes. Anthropometric measurements between specific standard points were performed: Subnasion–Prementon (Sn–PM) and Subnasion–Gnation (Sn–Gn) in maximum intercuspation and in the rest mandibular position, right and left pupil to the corresponding chelion. The cephalometric measurements registered were the lower facial angle and the angle between mandibular and Frankfurt planes. The distance Sn–Gn in maximum intercuspation was compared to all other parameters. Facial scanning, with a mobile phone and installed dedicated application, was performed on ten subjects, randomly selected using the same method among the participants, and the obtained 3D files were analyzed. The digital measurements were compared, for validity, to the clinical measurements. Pearson’s correlation coefficient was used, for comparing clinical Sn–Gn in maximum intercuspation position to the other parameters. (3) Results: A strong agreement between all measured anthropometric parameters of the facial scan and clinical contact measurement method was registered. None of the measured parameters could predict the exact OVD. (4) Conclusions: In the limits of our study, the facial scanning could be used for predictable registration of OVD and the stored digital information could be preserved through life and use for oral rehabilitation. However, if OVD needs to be determined, several measurement methods, including cephalometric measurements, need to be used simultaneously to reach a final decision.

Клінічно-лабораторний аналіз результатів реєстрації максимальної інтеркуспідації у пацієнтів із частковими дефектами зубних рядів залежно від використання різних реєстраційних матеріалів

Introduction. In general, it is equally important in dentistry to be able to examine the occlusion and to register it, store and transmit information from oral cavity. The aim of the study. Clinical and laboratory analysis of inter-maxillary relationship formation efficiency in patients with partial defects of dentition in the position of maximum intercuspation of jaws by means of different bite registration materials selected. Materials and methods. Examination of 10 patients (5 women, 5 men) aged 27 to 59 years was conducted. Upon receipt of teeth impressions of both jaws, and fabrication of their cast models, intermaxillary relationship in the position of maximum intercuspation (MIC) of the jaws with the help of selected registration materials (Consiflex (Ukraine), metallized wax (Germany), Futar D (Germany)) was determined. Results. During clinical examination of 10 patients it was found that when using Futar D registration material, biometric deviation of markers (BDM) index in the region of teeth 16-46 was (0.03±0.03) mm, 26-36 - (0.035±0.03) mm (p-value more than 0.75). At the same time, BDM index in the region of teeth 13-44 reached (0.05±0.03) mm, and teeth 23-34 demonstrated values (0.04±0.03) mm (p-value more than 0.5). Studies in the region of teeth 21-31 established BDM value within (0.01±0.03) mm. Application of Consiflex as a registration material demonstrated that BDM index in the region of molars on the right was (0.065±0.04) mm, on the left it reached (0.05±0.05) mm (p-value more than 0.49). According to the results of the study conducted, this index in the region of upper incisors - lower premolars on the right reached (0.08±0.03) mm, being (0.07±0.03) mm (p-value more than 0.53) between these pairs of teeth-antagonists on the left side. BDM index in the region of teeth 21-31 was determined in the range of (0.03±0.05) mm. Application of metallized wax as a registration material demonstrated that BDM index in the region of molars on the right was (0.085±0.02) mm, on the left it reached (0.07±0.03) mm (p-value more than 0.28). According to the results of the study conducted, this index in the region of upper incisors - lower premolars on the right reached (0.10±0.03) mm, being (0.08±0.03) mm (p-value more than 0.21) between these pairs of teeth-antagonists on the left side. BDM index in the region of teeth 21-31 was determined in the range of (0.04±0.05) mm. During laboratory study of cast models of 10 patients in the MIC position, it was found that when using Futar D registration material, BDM index in the region of teeth 16-46 was (0.03±0.03) mm, teeth 26-36 - (0.35±0.03) mm (p-value more than 0.75). At the same time, this index in the region of teeth 13-44 was (0.055±0.04) mm, teeth 23-34 - (0.045±0.04) mm (p-value more than 0.59), respectively. In the region of teeth 21-31, its value reached (0.01±0.03) mm. Application of Consiflex demonstrated that BDM index on cast models in the region of molars on the right was (0.07±0.05) mm, on the left it reached (0.55±0.055) mm (p-value more than 0.53). According to the results of the studies, this index in the region of upper incisors - lower premolars on the right reached (0.09±0.04) mm, being (0.08±0.04) mm (p-value more than 0.59) between these pairs of teeth-antagonists on the left side. BDM index in the region of teeth 21-31 was determined in the range of (0.03±0.05) mm. Application of metallized wax as a registration material demonstrated that BDM index on cast models in the region of molars on the right was (0.095±0.03) mm, on the left it reached (0.08±0.03) mm (p-value more than 0.23). According to the results of studies, this index in the region of upper incisors - lower premolars on the right reached (0.11±0.03) mm, being (0.09±0.04) mm (p > 0.23) between these pairs of teeth-antagonists on the left side. BDM index in the region of teeth 21-31 reached (0.045±0.05) mm. Conclusions. Application of Futar D demonstrates lower optimum (0.00-0.08 mm) of differences between biometric deviation of markers indices, suggesting better complementarity during maximum intercuspation registration of this material in comparison with Consiflex (0.00-0.11 mm) and metallized wax (0.00-0.13 mm).

Influence of Occlusal Splint on Mandibular Movements in Patients with Bruxism: a Comparative Pilot Study.

ObjectiveThe objective of this pilot study was to examine the impact of occlusal splint treatment on mandibular border movements and the condyle position in subjects with bruxism.Materials and methodsThe study included 9 subjects diagnosed with bruxism (mean age 28.7) and 9 subjects in the control group (mean age 30.5). All subjects were adults, eugnathic, and with a dentoalveolar Angle Class I, without prosthetic restorations, previous or current orthodontic treatments, a systemic disease or previous surgical interventions in the temporomandibular joint. All experimental and control group subjects were provided with a standardized relaxation occlusal splint, which they wore for 8 weeks. During this time, an initial and three additional measurements of incisal opening (IO), left condyle opening (OLC), right condyle opening (ORC), left laterotrusion (LLI) and right laterotrusion (LRI) (after 2, 4 and 8 weeks) were performed using an Arcus Digamma II (Kavo) ultrasound device for mandibular movements recording. Using the same instrument, the condylar position during protrusion, left and right laterotrusion, and in the centric relation position (CR) was analyzed initially and after 8 weeks using the maximum intercuspation as reference point. Continuous variables were described using basic statistical parameters, and the statistical significance of differences between the variables was checked by the t-test and χ2 test (p <0.05).ResultsThe values of IO, OLC, ORC, LLI and LRI ​​increased after 8 weeks of wearing, with the highest increase for OLC, by 13.8%. No statistically significant difference (p <0.05) was found for any changes in movements. Changes in the condyle position during all movements and those in the CR were higher in the experimental group for 10 out of 14 measured parameters compared to the control group. A statistically significant difference was established for 5 out of 14 measured parameters after the occlusal splint treatment.ConclusionsThe results of this pilot study have proven the influence of the occlusal splint treatment on mandibular border movements in subjects with bruxism by increasing the range of movements. Also the changes of the condyle position in subjects with bruxism were greater compared to those in healthy subjects.

Occlusion Heightened by Metal Crown Cementation is Aggressive for Periodontal Tissues.

To investigate the effect of experimental traumatic occlusion (ETO) induced by metal crowns on alveolar bone loss. Metal crowns were custom-made for the lower first molars with occlusal discrepancy of 0.4 and 0.7 mm from the maximum intercuspation. Thirty-six animals were randomly divided into three groups (n = 12 animals per group): 0.4-mm hyperocclusion group, 0.7-mm hyperocclusion group and the sham group (no metal crown). Twenty-eight days after crown cementation, the animals were euthanized and gingival tissue was collected to assess cytokine levels of IL-17, IL-6, and TNF-α using enzyme-linked immunosorbent assay (ELISA). Mandibles were stained with 1% methylene blue and alveolar bone levels were quantified. Western blotting was used to quantify the expression of receptor activator of nuclear factor κ B (RANK), and its ligand (RANKL), secreted osteoclastogenic factor of activated T cells (SOFAT) and TNF-α-converting enzyme (TACE). Also, mandibles were histologically processed and stained with hematoxylin and eosin, from which the presence of osteoclast-like cells, multinucleated cells containing ≥3 nuclei was counted at 100× magnification. The data were analyzed using one-way ANOVA and Tukey tests. Experimental occlusal trauma for 28 consecutive days significantly increased alveolar bone loss and multinucleated cell counts (p < 0.05). RANK, RANKL, SOFAT, TACE, IL-6, and TNF-α were significantly higher in gingival tissues of ETO groups (p < 0.05). IL-17 titers were unchanged among the groups (p > 0.05). Experimental traumatic occlusion activates and sustains bone resorption pathways in the periodontium inducing alveolar bone resorption. As the intensity of occlusal trauma increased, alternative osteoclastic pathways were activated, such as TACE and SOFAT.

DEVELOPMENT OF AN IN VIVO ULTRASOUND PROTOCOL TO STUDY THE MUSCULOAPONEUROTIC ARCHITECTURE OF THE MASSETER DURING MANDIBULAR PROTRUSION AND LATERAL EXCURSION

Background Temporomandibular disorders (TMDs) affect 5% to 12% of the population and lead to disability and pain. It has been suggested that architectural changes occur in the masseter muscle (MM) in TMDs. However, studies on normal in vivo MM architecture are scarce. Previously, our laboratory examined MM architectural changes during maximum intercuspation. Objective This work is an extension of our earlier studies in that it incorporates border jaw movements. It is hypothesized that a prototype in vivo ultrasonography protocol that will detect MM architectural changes during mandibular protrusion and lateral excursion can be developed. Materials and Methods The study was on the development of a prototype in vivo ultrasonography protocol based on cadaveric data. Results A protocol was successfully developed by identifying optimal probe positions and sites to visualize the MM laminae in mandibular protrusion and lateral excursion. The development involved correlation of anatomic specimens with in vivo ultrasonography, which enabled quantification and comparison of fiber bundle length, muscle thickness, and aponeurotic height. Discussion A novel ultrasonography protocol that will facilitate better understanding of normal MM morphology during mandibular protrusion and lateral excursion was developed. In the future, this protocol could be used as a basis to study MM changes in TMDs. Temporomandibular disorders (TMDs) affect 5% to 12% of the population and lead to disability and pain. It has been suggested that architectural changes occur in the masseter muscle (MM) in TMDs. However, studies on normal in vivo MM architecture are scarce. Previously, our laboratory examined MM architectural changes during maximum intercuspation. This work is an extension of our earlier studies in that it incorporates border jaw movements. It is hypothesized that a prototype in vivo ultrasonography protocol that will detect MM architectural changes during mandibular protrusion and lateral excursion can be developed. The study was on the development of a prototype in vivo ultrasonography protocol based on cadaveric data. A protocol was successfully developed by identifying optimal probe positions and sites to visualize the MM laminae in mandibular protrusion and lateral excursion. The development involved correlation of anatomic specimens with in vivo ultrasonography, which enabled quantification and comparison of fiber bundle length, muscle thickness, and aponeurotic height. A novel ultrasonography protocol that will facilitate better understanding of normal MM morphology during mandibular protrusion and lateral excursion was developed. In the future, this protocol could be used as a basis to study MM changes in TMDs.

Biofotogrametric and electromyographic analysis in different position in women with temporomandibular disorder.

Introduction: The relationship established between TMJ (Temporomandibular Joint), cranium and cervical spine requires the synchrony of these structures for the proper performance of stomatognathic functions and muscle balance in this region. Objective: Evaluate the craniocervical posture and the electrical activity of masticatory and cervical muscles in sitting and standing positions in patients with TMD, correlating these variables. Method: The participants were 21 women, with mean age 28 ± 5.33 years and severe TMD. The participants were evaluated by electromyography of the masseter, anterior temporal and sternocleidomastoid (SCM) and upper trapezius muscles, bilaterally, in standing and sitting position. The body posture was evaluated by biophotogrammetry, with analysis of the Head Horizontal Alignment (HHA) and Acromion Horizontal Alignment (AHA) in frontal view and the Head Vertical Alignment (HVA) and Head Horizontal Alignment related to seventh cervical vertebra (HHAc7) in lateral view. Results: The electrical activity of masticatory muscles during resting did not differ between the different evaluated positions. During maximum intercuspation, the electrical activity was significantly lower in the left masseter (p=0.016), higher in the left anterior temporal muscle (p=0.046) and higher in the right (p=0.005) and left (p=0.015) upper trapezius muscles, in standing position when compared to sitting position. The photogrammetric values found were within the normal range. There was a significant and moderate negative correlation between the left SCM muscle and the right (r=0.386) and left (r=0.428) HHAc7 angle. Conclusions: Muscular electrical activity was modified with the change between sitting and standing positions, with an increase in cervical muscle recruitment and asynchrony of the masticatory muscles. Thus, it can be inferred that there is a postural destabilization with possible head anteriorization during maximum intercuspation, reinforcing the relation of synergy between the masticatory and cervical muscles.

Effects of Occlusal Scheme on All-on-Four Abutments, Screws, and Prostheses: A Three-Dimensional Finite Element Study.

An ideal occlusal scheme plays an important role in a good prognosis of All-on-Four applications, as it does for other implant therapies, because of the potential impact of occlusal loads on implant prosthetic components. The aim of the present 3D finite element analysis (FEA) study was to investigate the stresses on abutments, screws, and prostheses that are generated by occlusal loads via different occlusal schemes in the All-on-Four concept. 3D models of the maxilla, mandible, implants, implant substructures, and prostheses were designed according to the All-on-Four concept. Forces were applied from the occlusal contact points formed in maximum intercuspation and eccentric movements in canine guidance occlusion (CGO), group function occlusion (GFO), and lingualized occlusion (LO). The von Mises stress values for abutment and screws and deformation values for prostheses were obtained, and results were evaluated comparatively. It was observed that the stresses on screws and abutments were more evenly distributed in GFO. Maximum deformation values for prosthesis were observed in the CFO model for lateral movement both in the maxilla and mandible. Within the limits of the present study, GFO may be suggested to reduce stresses on screws, abutments, and prostheses in the All-on-Four concept.

A digital approach to the evaluation of mandibular position by using a virtual articulator

The purpose of this technique report was to describe a fully digital technique to evaluate the mandibular position both in centric relation occlusion (CRO) and maximal intercuspation position (MIP). The procedure transfers data relative to the position of the maxillary and mandibular dentition to a virtual articulator based on a single cone beam computed tomography (CBCT) image. A CBCT scan of the patient was obtained in CRO, and the maxillary and mandibular casts were scanned both in CRO and MIP with an intraoral scanner. The model CRO scan data were registered on the dental part of the CBCT image by using a virtual articulator program, and a virtual facebow transfer process and mounting was performed. The virtual articulator was positioned in the right and left condyle medial pole and right orbitale. The mandibular position was evaluated in CRO and MIP by superimposing the data of the mandible position in both CRO and MIP. A quantitative 3D measurement was obtained by using the grid function. Based on this protocol, it is possible to use a fully digital approach to transfer the position of a patient’s maxillary dentition to a virtual articulator based on the data from a single CBCT scan and intraoral scans. This technique eliminates the traditional facebow transfer and mounting process and complicated laboratory procedures for evaluating mandibular positional changes in CRO and MIP.

Accuracy of Vertical Dimension Augmentation Using Different Digital Methods Compared to a Clinical Situation-A Pilot Study.

To test the accuracies of different methods of digital vertical dimension augmentation (VDA) by comparison with a clinical situation. Bite registrations with approximately 5 mm of VDA were made in the incisor regions of 10 subjects (mean VDA 4.5 mm). The conventional maxillary and mandibular stone casts in maximum intercuspation (MICP) and VDA bite registrations were digitized for all subjects using a laboratory scanner (control group). Lateral portraits were taken of all subjects to locate the position of the condylar axis. Four different digital VDA methods were compared to the control group: 100% rotation of the mandible referring to the lateral picture (100RL); 85% rotation and 15% translation referring to the lateral picture (85R15TL); 100% rotation in normal mounting mode of the Trios virtual articulator (100R); and jaw-motion analysis (JMA) equipment. The amount of VDA for each experimental group was compared to the control group. The augmented distances between the central incisors and the second molars were measured using 3D analyzing software. The ratio of the augmented distances between the posterior and anterior regions (P/A ratio) was calculated. One-way analysis of variance and multiple comparisons via least significant difference test were carried out to determine statistical significance. The P/A ratio of each group was as follows: Control = 0.61; 100RL = 0.55; 85R15TL = 0.61; 100R = 0.53; JMA = 0.52. Significant differences were observed for control vs JMA and for 85R15TL vs JMA (P < .05). The addition of translational movement was the primary factor for increasing the accuracy of digital VDA, with the lateral picture being a secondary factor. VDA using a virtual articulator with 100% rotation induces an error when compared to the clinical situation. When a clinician performs digital VDA, the setting of 85% rotation and 15% translation produces results closer to the real clinical condition.

The Influence of Dental Occlusion on Spectrophotometric Tooth Color Determinations

Background: Shade matching is a significant treatment step and a challenge for the clinical team with potentially high costs for color correction. Currently, in the United States, the majority of private dental practitioners use visual color matching, but a recent study has reported a high rate of mistakes of subjective color determination among graduate dentists. Objective: The aim of this retrospective study is to analyze whether a change in the oral background due to dental occlusion can influence tooth color determination. Methods: Volunteer dental students underwent spectrophotometric color assessment using the SpectroShade device. Two measurements were carried out (with the individuals’ occlusion closed and with the occlusion open) on 43 upper central and 58 lateral incisors. Association between colorimetric variables L*, a*, b* and ΔE00 and tooth width, length and tobacco usage were examined. Results: Slight changes in the CIELAB values between closed and open occlusions were found for both the gingival and the central sections as for the overall tooth area, with mean ΔL*=-1.24, Δa*=-1.77, Δb*=-1.42 and ΔE00=1,84. A larger difference was detected in the incisal area, with mean ΔL*=-2.99, Δa*=-1.76, Δb*=-2.83 and ΔE00=3.65. Conclusion: In conclusion, our study showed that dental occlusion does not play a significant role in tooth color matching determinations, even though attention to avoid overbite due to a maximum intercuspation should be made.

Occlusal Analysis Using T-Scan in Patients With Condylar Fractures When Managed by Closed Method.

The aim of the study is to assess the occlusion in mandibular condyle fractures using T-Scan and analyze the data obtained. Twenty patients underwent non-surgical management for condylar fractures were treated with Erich arch bar and guiding elastics, and periodically subjected to T-Scan III evaluations. The data obtained was analyzed with the clinical evaluation conducted. There were 18 males and 2 females. Mean age of the patients was 25.4 ± 7.4 years. There were statistically no significant changes in Centre of Force values, in Bite Force at First Contact (P < 0.05) during the study period. There were significant differences in Maximum Bite Force between preoperative and postoperative values, preoperative and sixth-month values, postoperative and first-month values, first-month and sixth-month values. There were significant (P < 0.05) differences in Bite Force at Maximum Intercuspation between preoperative and third month, preoperative and sixth-month values, postoperative and sixth-month values, first-month and consequent follow-ups. Subjective evaluation of occlusion revealed significant differences (P < 0.05) between preoperative and 1-month, preoperative and postoperative, postoperative and 1-month values. All patients improved by the end of 6 months with regards to their mouth opening. The center of force does not alter significantly in post trauma period. Mouth opening improves significantly at the end of 6-month period post-operative. Improvement in maximum bite force and maximum intercuspation take place simultaneously. Mouth opening improved significantly. Subjective evaluation of occlusion does not change significantly after the third month evaluation. Longer follow-ups would help us in understanding when or if the bite forces equilibrate after a condylar trauma.

The Use of a Novel CAD-CAM Splint to Simplify Open Reduction and Internal Fixation of Mandibular Angle Fracture: A Technical Note

Mandibular angle fractures are frequently encountered as they constitute an area of weakness. Complications after open reduction and internal fixation (ORIF) of angle fractures commonly arise due to improper reduction and fixation methods that fail to counteract the dynamic muscle forces present in this region. Conventional reduction methods such as digital manipulation, intermaxillary fixation, towel clip traction, and wiring are associated with various limitations. This technical note highlights the fabrication and use of a computer-aided designing/computer-aided manufacturing-generated splint for ORIF of a superiorly displaced mandibular angle fracture. The splint consisted of 2 components: (1) a distal tooth-borne component to guide the teeth into maximum intercuspation and (2) a proximal bone-borne component to reduce the angle fracture. This composite splint facilitates simultaneous restoration of occlusion as well as reduction of mandibular angle fractures. The advantages of this technique include the following: (1) easy fabrication of splint, (2) easy and precise anatomical reduction of angle fracture, and (3) less operative time.

Changes in Electrical Activity of the Masseter Muscle and Masticatory Force after the Use of the Masseter Nerve as Donor in Facial Reanimation Surgery.

Introduction The masseter nerve has been used as a donor nerve for facial reanimation procedures due to the multiple advantages it offers; it has been generally considered that sacrifice of the masseter nerve does not alter the masticatory apparatus; however, there are no objective studies to support this claim. Objective To evaluate the impact that the use of the masseter nerve in dynamic facial reconstruction has on the electrical activity of the masseter muscle and on bite force. Materials and Methods An observational and prospective longitudinal study was performed measuring bite force and electrical activity of the masseter muscles before and 3 months after dynamic facial reconstructive surgery using the masseter nerve. An occlusal analyzer and surface electromyography were employed for measurements. Results The study included 15 patients with unilateral facial paralysis, with a mean age of 24.06 ± 23.43. Seven patients were subjected to a masseter–buccal branch nerve transfer, whereas in eight patients, the masseter nerve was used as a donor nerve for gracilis free functional muscle transfer. Electrical activity of the masseter muscle was significantly reduced after surgery in both occlusal positions: from 140.86 ± 65.94 to 109.68 ± 68.04 ( p = 0.01) in maximum intercuspation and from 123.68 ± 75.64 to 82.64 ± 66.56 ( p = 0.01) in the rest position. However, bite force did not show any reduction, changing from 22.07 ± 15.66 to 15.56 ± 7.91 ( p = 0.1) after the procedure. Conclusion Masseter nerve transfer causes a reduction in electromyographic signals of the masseter muscle; however, bite force is preserved and comparable to preoperative status.

Do different dental conditions influence the static plantar pressure and stabilometry in young adults?

BackgroundPosture is influenced by many factors and dental occlusion seems to have its role on postural stabilization. Our rationale to perform the study was to find out if there are differences of static plantar pressure and stabilometric parameters depending on different dental conditions.MethodsThe observational study consisted in plantar pressure assessment and stabilometric analysis of 95 right-handed healthy volunteer subjects (mean age 22.94 ± 2.52 years) by using the PoData system. Each subject followed four measurements with open eyes: mandibular postural position, maximum intercuspation, biting on cotton rolls and maximum mouth opening. Plantar pressure was recorded on 1st and 5th metatarsal heads and heel, and was expressed as percentage of weight distribution on each foot. The recorded centre of pressure (CoP) parameters were: CoP path length, 90%confidence ellipse area and maximum CoP speed. Statistical analysis used repeated-measures ANOVA with Bonferroni posthoc analysis and Friedman test.ResultsLoading on the left 5th metatarsal head was significantly higher in maximum mouth opening condition when compared to maximum intercuspation and to biting on cotton rolls. The left heel loading was significantly lower in the maximum mouth opening in comparison to maximum intercuspation. The CoP path length and maximum CoP speed were significantly higher in maximum mouth opening compared to the other three conditions. Confidence ellipse area had significantly lower values in maximum intercuspation and in the biting on cotton rolls conditions compared to the mandibular postural position, and in maximum intercuspation compared to maximum mouth opening.ConclusionIn young adults with an optimum functional occlusion the static plantar pressure is influenced by the maximum mouth opening. An improved postural stability was recorded in maximum intercuspation (a condition used during swallowing) in comparison to mandibular postural position (a condition that allows relaxation of the masticatory muscles after functional moments).

Masticatory Muscles Activity in Sport Climbers

Masticatory muscle activity during teeth clenching is associated with changes in many physiological parameters throughout the body. Clenching can improve muscle activity, force production, rate of force development, and joint fixation. Hence, teeth clenching and masticatory muscle activity can be important in competitive sports activities. Sport climbing is becoming increasingly popular and will be included for the first time in the Summer Olympic Games, Tokyo, 2020. However, masticatory muscle activity in sport climbers has not yet been studied. The aim of the presented study is to compare the bioelectrical activity of the masticatory muscles in sport climbers and non-climbers in order to determine the relationship between these muscles and climbing activity. 44 subjects without masticatory system disorders (16 women and 28 men, average age 26.3) were divided into two groups of 22 sport climbers (8 women, 14 men, climbing experience >4 years), while 22 people (8 women, 14 men, with no regular sports activity) were assigned to the control group. Electromyographic examination of temporalis anterior (TA) and masseter muscle (MM) was evaluated in three conditions: during resting mandibular position, during maximum intercuspation clenching, and during maximum voluntary clenching with cotton rolls between teeth. For statistical analysis, the W Shapiro-Wilk test and the Mann-Whitney U test were used. Sport climbers showed significantly higher bioelectrical activities of MM during maximum intercuspation clenching (238.45 μV vs. 83.87 μV, p = 0.002), and during maximum voluntary clenching with cotton rolls between teeth (300.01 μV vs. 101.38 μV, p = 0.001) compared to controls. The differences between groups in relation to the resting bioelectrical activity of the MM muscles, and TA muscles in all conditions were not statistically significant (p > 0.05). Higher bioelectrical activity of masseter muscles during clenching in climbers can be associated with this sports activity. However, the mechanism remains unknown and requires future research.

Frequency distribution of temporomandibular disorders according to occlusal factors: A cross-sectional study

Temporomandibular disorder (TMD) is a common condition affecting the temporomandibular joint and causes pain and discomfort. However, the role of factors contributing to this problem is still controversial. The purpose of this cross-sectional study was to determine the correlation of occlusal factors and parafunctional habits with TMD and The determination of TMD prevalence among patients referring to Isfahan Dental School in 2017. In this cross-sectional study, A total of 200 patients between 20 and 50 years were examined and questioned based on the Research Diagnostic Criteria for Temporomandibular Disorders assessment instrument. The association of occlusal factors (dental relationship, lateral occlusal scheme, horizontal differences between centric occlusion and Maximum intercuspation (MI), difference between MI and mandibular resting position) and parafunctional habits (bruxism/clenching and habits) with TMD was analyzed using Chi-square tests and independent sample t-test (α = 0.05). Binomial logistic regression analysis was performed with respect to confounding variables. The prevalence of TMD in the studied sample was 58.9%. Only bruxism showed a significant difference between TMD and non-TMD groups (P < 0.05). Other parafunctional and occlusal factors did not act as influential factors for TMD. Parafunction may play an important role in the initiation of TMD, although other habits and occlusal factors are considered as noninfluential factors. However, larger sample size and multicenter sampling are recommended for the future studies.

Comparison of two computerized occlusal analysis systems for indicating occlusal contacts.

PURPOSEThe purpose of this study was to compare the performance of Accura to that of the T-scan for indicating occlusal contacts.MATERIALS AND METHODSTwenty-four subjects were selected. Their maxillary dental casts were scanned with a model scanner. The Stereolithography files of the casts were positioned to align with the occlusal plane. Occlusal surfaces of every tooth were divided into three to six anatomic regions. T-scan and Accura recordings were made during two masticatory cycles. The T-scan and Accura images were captured at the maximum bite force and overlapped to the cast. Photographs of interocclusal records were used as the reference during overlap. The occlusal contacts were counted to compare the T-scan and Accura. McNemar's test was used for statistical significance and the corresponding P-values were calculated from a chi-square distribution with one degree of freedom. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Accura were calculated relative to the T-scan values as a control.RESULTSNo statistical differences (P>.05) were found between the T-scan and Accura methods. The accuracy of Accura was 75.8%, sensitivity was 82.1%, specificity was 60.1%, PPV was 82.9%, and NPV was 60.1%.CONCLUSIONAccura could be another possible option as a computerized occlusal analysis system for indicating occlusal contacts at maximum intercuspation.

Moorrees-like mesh diagram for Romanian patients - a pilot study.

Background and aimsIn 1976, Coenraad F.A. Moorrees completed a series of facial mesh diagrams to ease the orthodontic diagnosis and treatment of North-American patients. Subsequently, the system was adapted by different authors to other races and populations. The objective of this study is to provide a system of Moorrees-like mesh diagrams for the Romanian population, Caucasian race, which would help orthodontists, surgeons and prosthetists.Methods40 patients were introduced in the study, 20 males and 20 females, with ages between 12–33 years, permanent dentition and slight dental-maxillary abnormalities, class I and II Angle. For each patient, a lateral cephalometric radiograph was taken, with CRANEX 3D, head straight, maximum intercuspation. On tracing paper were drawn 35 anthropometric points and 3 planes, Frankfurt plane, as the horizontal landmark, a perpendicular line through nasion as the vertical landmark and the occlusal plane. From each point we measured the distance in millimeters to the horizontal landmark and to the vertical landmark, respectively. The obtained values were introduced into 40 tables, using Microsoft Office Excel 2007 and 3 arithmetic means were calculated, for males, for females and a general one, for children under 12 years old. The arithmetic means were transferred on millimetric paper and tracing paper, joining the obtained points and completing the templates.ResultsThree different Moorrees-like mesh diagrams were obtained, one for male, one for female and a mixt one for children under 12 years, Romanian patients, Caucasian race, respectively.ConclusionsMesh diagram comes in the support of a better perspective of the anatomical elements of the face and the facial growth, being a useful tool in predicting treatment. Computer based programs with Moorrees-like diagrams adapted to Romanian patients may be the object of further studies.