Changes in electric activity of masseter and anterior temporalis muscles before and after orthognathic surgery in skeletal class III patients.

OBJECTIVE: The purpose of this study was to evaluate, through clinical and electromyographic (EMG) assessments, the electric activity of masseter muscle and anterior temporalis muscles during clenching, before and after orthodontic treatment and mandibular setback, with or without LeFort I osteotomy, for correction of mandibular excess. STUDY DESIGN: Seventeen adult patients (10 males, 7 females, mean age: 22.5 ± 2.4 years) were recruited for this study. All patients received orthodontic treatment and surgical corrections. EMG recordings were obtained from 4 channels of the 8-channel electromyograph FREELY (DeGoetzen spa, Olgiate Olona, VA, Italy). RESULTS: A significant difference was found in the value of activity index at T0-T1 (33% T0, 1% T1) (P < .05), of asymmetry index at T0-T1 (21% T0, 4% T1) (P < .05), and of torque index at T0-T1 (24% T0, 5% T1) (P < .05). CONCLUSIONS: The evaluation of EMG activity after surgery may be considered a sign of good adaptation of the neuromuscular system to the new occlusal condition and a good method for detecting nonresponding patients who might require further treatment.

Three-dimensional cephalometry: a method for the identification and for the orientation of the skull after cone-bean computed tomographic scan.

The aims of this work were (1) to describe a method to identify new skeletal landmarks useful to define the reference system to orient the skull in a new position after cone-bean computed tomographic scan and (2) to demonstrate the reliability of this new method.Ten orthognathic patients (5 male, 5 female; mean [SD] age, 18.9 [1.2] years) underwent the cone-bean computed tomographic scan before surgery. Seven 3-dimensional skeletal measurements derived from 4 skeletal point of construction (C) (right, left, and median orbital C, and sella C) have been used for this study. Reliability has been calculated using Pearson correlation coefficient tests.Intraobserver reliability was 0.9999 for operator A (T1-T2) and 0.9999 for operator B (T1-T2); interobserver reliability was 0.9999 between the first (T1-T1) measurement and 0.9999 between the second (T2-T2).The original method is able to reduce the variability of landmark identification due to the variability of the human anatomy and the influence of the human error in cephalometric analysis. The innovation of this new method is the real possibility to use the anatomical structures in a 3-dimensional way, enhancing the reliability of the reference points.

Reverse cycle chewing before and after orthodontic-surgical correction in class III patients.

OBJECTIVE: The aim of this study was to investigate the prevalence of reverse-sequence chewing cycles in skeletal class III patients before and after orthodontic-surgical therapy to evaluate whether the occlusal and skeletal correction is followed by a functional improvement. STUDY DESIGN: Twenty skeletal class III patients (11 males and 9 females, 22.7 ± 3.0 years old) were recruited for this study. All patients received orthodontic and surgical treatment. Chewing cycles were recorded with a kinesiograph before (T0) and after (T1) therapy. RESULTS: A significant decrease in the number of reverse chewing cycles after surgical correction was exhibited in all recordings, when chewing either soft or hard boluses, on both the right and the left side. CONCLUSIONS: Evaluation of the prevalence of reverse chewing cycles could be considered an indicator of functional adaptation after therapy and a method for the early detection of nonresponding patients who may require further consideration using a different approach.

Assessment of the reliability and repeatability of landmarks using 3-D cephalometric software.

The aim of this study was to analyze the reliability and repeatability of identification landmarks using 3-D cephalometric software. Ten orthognathic patients were selected for this study and underwent the following protocol: 1. radiographic evaluation (CBCT technique); 2. stone casts; 3. photos; and 4. 3-D cephalometric evaluation. Twenty-one hard tissue landmarks and 14 cephalometric measurements were taken three times (T1, T2, and T3) on each patient, with an interval of one week by two experts in orthodontics (A, B). Standard deviation and Pearson's correlation coefficient were calculated to evaluate intra- and inter-observer repeatability. The results showed a strong correlation for both intra- and inter-observer Pearson's correlation coefficient (>0.7). The current preliminary study showed that the reliability and repeatability of the identification landmarks were very high if the 3-D cephalometric landmarks are defined correctly in the three planes of the space. Further evaluation is necessary to better define the 3-D cephalometric system.

Cone-beam computed tomography: accuracy of three-dimensional cephalometry analysis and influence of patient scanning position.

The aim of this research was to analyze the influence of the position of the skull during cone-beam computed tomography (CBCT) scan and if the three-dimensional cephalometric measurements are influenced by skull orientation during CBCT scan.The study consisted of 5 CBCT scanning (KODAK 9500 Cone Beam 3D System unit) in 5 different positions of a dry skull. The data were imported in SIMPLANT OMS Software version 13.0. Fifteen three-dimensional cephalometric measurements were calculated; moreover, the mean, the SD, the maximum/minimum Δ, and the maximum/minimum Δ percentage were calculated. The statistical analysis was performed by an independent-samples t-test to evaluate differences between the 5 scans.No difference was found in all the three-dimensional analysis. Twelve of 15 measurements have a Δ greater than 1.5, and 7 of 15 measurements have a Δ greater than 2. Nine of 15 have a Δ percentage greater than 5%. The preliminary results suggest that the three-dimensional cephalometric analysis is influenced by patient scanning position.

Sensitivity of magnetic resonance imaging and computed axiography in the diagnosis of temporomandibular joint disorders in a selected patient population.

PURPOSE: The aim of this study was to compare sensitivity differences and interpretative agreement for magnetic resonance imaging (MRI) and computed axiography (CA) tracings in a patient population group with temporomandibular disorder (TMD). MATERIALS AND METHODS: A convenience sample of 173 patients (53 men, 120 women; mean age: 33.2 ± 2.6 years) diagnosed with TMD was selected for this study. Each patient underwent an evaluation as per the European Academy of Craniomandibular Disorders clinical form as well as MRI and CA. RESULTS: Use of the MRI results as the gold standard for the planned comparison led to the following observations: a CA sensitivity of 68% for joints without morphologic changes (so-called normal temporomandibular joints [TMJs]), sensitivity of 27% for those with disc displacement, and sensitivity of 8% for those with osteoarthritis. The kappa index, or agreement between the two examination methods, was weak for normal TMJs (0.16), acceptable for anterior disc displacement with reduction (0.28), little for anterior disc displacement without reduction (0.10), and very little for morphologic alterations (0.01). CONCLUSION: The sensitivity and agreement of the two examination methods was generally low. It was even worse when pathologic changes in the TMJ were more severe. MRI and CA are different examinations that could both be considered for severe TMD diagnosis.

Correction of severe tooth rotations using clear aligners: a case report.

BACKGROUND: The present adult patient case report shows the correction of a crossbite malocclusion and severe tooth rotations treated with the Invisalign system. METHODS: A 27-year-old female with a dental crossbite (24, 34), severe rotations of two lower incisors (more than 40 degrees) and malalignment of the upper and lower arches is described. The Invisalign system was treatment planned to correct the malocclusion. RESULTS: The treatment goals of crossbite, rotation and malalignment correction were achieved after 12 months of active aligner therapy. The overbite improved (2.5 mm before treatment, 1 mm at the end); the dental crossbite, the crowding and the severe tooth rotations (with a mean of 2 degrees of improvement per aligner) were corrected. CONCLUSIONS: After treatment, the dental alignment was considered excellent. The presented case indicates that the Invisalign system can be a useful appliance to correct a dental malocclusion involving severe rotations.

Reverse-sequencing chewing patterns evaluation in anterior versus posterior unilateral crossbite patients.

It is well established that patients with a unilateral posterior crossbite exhibit reverse-sequencing chewing patterns when chewing on the affected side. The aim of the study was to compare the prevalence of reverse-sequencing chewing cycles in patients with anterior versus posterior unilateral crossbite during chewing soft and hard boluses. Eighty-six children (39 boys, 47 girls) were included in the study: 26 (10.4 ± 2.7 years) with unilateral anterior crossbite, 43 (10.2 ± 4.2 years) with unilateral posterior crossbite, and 17 (10.6 ± 2 years) with normal occlusion were selected for the study. Mandibular movements were measured with a kinesiograph (K7, Myotronics Inc. Tukwila). The kinematic signals were analyzed using custom-made software. The results showed a low prevalence of reverse-sequencing chewing cycles in patients with anterior crossbite, without any significant difference between sides and with the control group, with both soft (P = 0.33) and hard (P = 0.29) bolus. The patients with posterior unilateral crossbite showed a significant higher prevalence of reverse-sequencing chewing cycles during chewing on the crossbite side with respect to the non-crossbite side (P < 0.001) and to the control group (P < 0.001). Comparing the patients with anterior versus posterior unilateral crossbite, a significant difference (P < 0.001) in the prevalence of reverse chewing cycles was demonstrated during chewing on the posterior crossbite side only with both soft and hard bolus. In conclusion, patients with anterior versus posterior unilateral crossbite show different functional characteristics depending on which dental region is involved.

Clinical and instrumental evaluation of the temporomandibular joint before and after surgical correction of asymptomatic skeletal class III patients.

The purpose of this prospective study was to evaluate the temporomandibular joint (TMJ) morphology, the disk position, and the TMJ symptoms before and after surgical-orthodontic correction of skeletal class III malocclusion.Eleven adult patients were recruited to participate in this longitudinal study. Each patient received presurgical and postsurgical orthodontic treatment with fixed appliances. Six patients were corrected exclusively through mandibular setback, whereas 5 received combined mandibular setback and maxillary advancement. All patients were investigated before and 2 years after treatment through (1) clinical examination, (2) magnetic resonance imaging, and (3) Computerized axiography (CA).The incidence of clinical signs and symptoms was reduced 2 years after surgical-orthodontic treatment, the condyle-disk relationship and TMJ appearance at magnetic resonance imaging were unchanged, and CA showed a significant improvement of TMJ border movements.Mandibular setback surgery does not appear to alter the condyle-disk relationship, whereas correction of class III malocclusion seems to improve clinical and CA signs of TMJ function. Further controls and more long-term evaluation of these patients are necessary to assess the maintenance of these improvements in time.

Slow or rapid palatal expansion for early treatment of unilateral posterior crossbite? Evaluation of the reverse chewing cycles correction.

OBJECTIVES: It is well established that patients with a unilateral posterior crossbite, when chewing on the affected side, show an increased frequency of reverse chewing cycles. It was hypothesized that the correction of reverse cycles may be due to the characteristics of the therapy. The aim was to investigate the prevalence of reverse chewing patterns in children with unilateral posterior crossbite before and after treatment with Function Generating Bite (FGB). MATERIALS AND METHODS: Twenty children, (9 boys, 11 girls; age, mean ± SD, 7.5 ± 1.1), 10 with a right and 10 with a left posterior unilateral crossbite were selected. Mandibular movements during chewing soft and hard boluses were measured with a kinesiograph (K7 -I, Myotronics Inc. Tukwila, Washington, USA). RESULTS: The results showed a significant difference when comparing the percentage of reverse chewing patterns, before and after therapy with FGB, during chewing on the crossbite side both with soft and hard bolus (p<0.0001). No significant differences were observed during chewing on the non-crossbite side. DISCUSSION: The results of this study confirmed that FGB corrects both the dental and functional asymmetries. Knowing that the rapid palatal expansion does not correct the masticatory function, it is of clinical relevance, for the orthodontists, the knowledge and the understanding of the functional outcomes with different therapies. CONCLUSIONS: The type of treatment and the biomechanics of the appliance used are of great importance for the correction of the reverse chewing cycles and for rebalancing the functional asymmetry of children with unilateral posterior crossbite.

Hemispheric prevalence during chewing in normal right-handed and left-handed subjects: a functional magnetic resonance imaging preliminary study.

This study evaluated the activation of different cortical areas during nondeliberate chewing of soft and hard boluses in five right-handed and five left-handed subjects with normal occlusion, to determine different hemispheric prevalences. The study was conducted with a functional Magnetic Resonance Imaging (1.5 T Magnetom Vision - Siemens Medical, Germany) using a head coil. The results showed that the most frequently activated areas were Brodmann's areas four and six in the primary motor and premotor cortex, the insula and Broca's area and, overall, showed greater activity of the cortical mastication area (CMA) in the right hemisphere for right-handed and in the left hemisphere for left-handed subjects.