Changes in tongue-palatal contact during swallowing in patients with skeletal mandibular prognathism after orthognathic surgery.

This study aimed to evaluate improvement of tongue-palatal contact patterns during swallowing after orthognathic surgery in mandibular prognathism patients. Thirty patients with mandibular prognathism treated by orthognathic surgery (average age of 27 years, 3 months) and 10 controls (average age 29 years, 6 months) participated in this study. Tongue-palatal contact patterns of patients before and three months after surgery were evaluated by electropalatography (EPG) as well as controls. Whole total of tongue-palatal contact at 0.3, 0.2, and 0.1 sec before complete tongue-palatal contact during swallowing were evaluated. The duration of swallowing phases was also examined. Complete contact of tongue-tip in the alveolar part of individual artificial EPG plate were shown at 0.3, 0.2, and 0.1 sec before complete tongue-palatal contact in the controls, although incomplete contact in the alveolar part were shown at 0.3 sec in mandibular prognathism patients. Whole total of tongue-palatal contact at 0.3 and 0.2 sec before complete tongue-palatal contact was significantly lower in the patients before surgery than in the controls (p<0.05). However, these values increased after surgery. The duration of oral and pharyngeal phase was significantly longer in the patients before surgery than in the controls and the patients after surgery (p<0.01). This study demonstrated that the tongue-palatal contact pattern improved and the duration of oral and pharyngeal phase was shortened in mandibular prognathism patients during swallowing after orthognathic surgery. It is suggested that changes in maxillofacial morphology by orthognathic surgery can induce normal tongue movement during swallowing. (The data underlying this study have been uploaded to figshare and are accessible using the following DOI: https://doi.org/10.6084/m9.figshare.14101616.v1).

Mandibular prognathism attenuates brain blood flow induced by chewing.

Mastication is closely related to brain function. Animal experiments have revealed that tooth loss has a negative influence on brain function. Clinical studies also suggest that normal occlusion is an essential factor for favorable brain function. Mandibular prognathism (MP) usually results in occlusal dysfunction. However, the relationship between MP and brain function remains unclear. In the present study, we examined the relationship between MP and brain function by measuring brain blood flow (BBF). Seventeen subjects with normal occlusion (NORM) and 25 patients with MP participated in this study. The number of occlusal contacts were counted. Electromyography of the masseter muscles during clenching was also recorded. BBF was measured with non-invasive functional near-infrared spectroscopy during calculation task and chewing task. The number of the occlusal contacts and masseter muscle activity were lower in MP compared with NORM. The calculation task increased BBF in both groups. The chewing task also increased BBF in the inferior frontal gyrus in both groups, although the increase in MP was smaller than in NORM. We discovered that patients with MP exhibited a smaller increase in BBF at the inferior frontal gyrus during chewing as compared with NORM. As such, MP would negatively affect brain function.

Computational analysis of airflow dynamics for predicting collapsible sites in the upper airways: a preliminary study.

The present study aimed to detail the relationship between the flow and structure characteristics of the upper airways and airway collapsibility in obstructive sleep apnea. Using a computational approach, we performed simulations of the flow and structure of the upper airways in two patients having different facial morphologies: retruding and protruding jaws, respectively. First, transient flow simulation was performed using a prescribed volume flow rate to observe flow characteristics within upper airways with an unsteady effect. In the retruding jaw, the maximum magnitude of velocity and pressure drop with velocity shear and vortical motion was observed at the oropharyngeal level. In contrast, in the protruding jaw, the overall magnitude of velocity and pressure was relatively small. To identify the cause of the pressure drop in the retruding jaw, pressure gradient components induced by flow were examined. Of note, vortical motion was highly associated with pressure drop. Structure simulation was performed to observe the deformation and collapsibility of soft tissue around the upper airways using the surface pressure obtained from the flow simulation. At peak flow rate, the soft tissue of the retruding jaw was highly expanded, and a collapse was observed at the oropharyngeal and epiglottis levels. NEW & NOTEWORTHY Aerodynamic characteristics have been reported to correlate with airway occlusion. However, a detailed mechanism of the phenomenon within the upper airways and its impact on airway collapsibility remain poorly understood. This study provides in silico results for aerodynamic characteristics, such as vortical structure, pressure drop, and exact location of the obstruction using a computational approach. Large deformation of soft tissue was observed in the retruding jaw, suggesting that it is responsible for obstructive sleep apnea.

The different effects of intraoral vertical ramus osteotomy (IVRO) and sagittal split ramus osteotomy (SSRO) on mandibular border movement.

OBJECTIVES: This study investigated the different effects of intraoral vertical ramus osteotomy (IVRO) and sagittal split ramus osteotomy (SSRO) on mandibular border movement. METHODS: The participants included 22 patients receiving IVRO and 22 patients receiving SSRO who were treated at Okayama University Hospital. Their mandibular border movement was evaluated in three dimensions with 6° of freedom using an optical recording system. RESULTS: A strong correlation between condylar and lower incisor movement was observed during maximum jaw protrusion and laterotrusion. Significant improvements in condylar and lower incisor movement were detected after orthognathic surgery during maximum jaw protrusion and laterotrusion in the IVRO group and during maximum jaw protrusion in the SSRO group. DISCUSSION: IVRO likely achieves greater improvement in jaw movement than SSRO. Therefore, the application of IVRO could be considered in the treatment of patients with jaw deformities featuring temporomandibular joint problems.

Physiological positioning strategy alters condylar position after mandibular ramus sagittal split osteotomies for mandibular prognathism.

OBJECTIVE: The aim of this study was to elucidate the physiological position of the proximal segment for postoperative jaw movement in patients with mandibular prognathism. METHODS: Twenty-two patients with mandibular prognathism were treated by orthognathic surgery using bilateral mandibular sagittal split ramus osteotomies (SSRO) with a physiological positioning strategy. The skeletal stability was assessed, and the movement of the proximal segment was evaluated by cephalography and computed tomography performed preoperatively, immediately postoperatively, and one year postoperatively. RESULTS: The patients were divided into two groups: the stable group (SNB relapse <1.5°) and the relapse group (SNB relapse ≥1.5°). In the stable group at one year postoperatively, the average SNB relapse was only 0.29° (7%), the condylar head had moved posteriorly by 0.75 mm, and the proximal segment had rotated counterclockwise by 1.2°. CONCLUSION: This new physiological positioning strategy improves the position of the condyle compared with the preoperative position in patients with mandibular prognathism.

Tongue-palatal contact changes in patients with skeletal mandibular prognathism after sagittal split ramus osteotomy: an electropalatography study.

The purpose of this study was to investigate the changes in tongue-palatal contact patterns using electropalatography (EPG) before and after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. Nine clients who underwent SSRO for mandibular setback and seven control subjects were participated in this study. Tongue-palatal contact patterns for /t/, /s/ and /k/ production were investigated using EPG before surgery and 3 months after surgery. The mean value of whole total of palate contact (WT) in the maximum contact frame was examined before and after SSRO. The correlation quantity between the change of center of gravity (COG) value and the amount of mandibular setback was also evaluated. The mean value of WT for /t/ and /s/ significantly increased after SSRO, and the EPG pattern became normal. However, a remarkable change in WT for /k/ was not observed, and the mean value was significantly larger in the SSRO group before and after surgery than in the control group. A negative correlation between COG variation and the amount of mandibular setback for /t/ and positive correlation for /s/ was observed. This study demonstrated that tongue-palatal contact patterns for /t/ and /s/ articulation improved clearly after SSRO. There was a significant correlation between COG variation and the amount of mandibular setback. However, no significant change was detected through perceptual assessment before and after SSRO. Further investigation is needed to determine whether these results will change over time.

Computational fluid dynamics study of the pharyngeal airway space before and after mandibular setback surgery in patients with mandibular prognathism.

The purpose of this study was to investigate the relationship between the pressure drop in the pharyngeal airway space (ΔPPAS) and the minimum cross-sectional area (minCSA) of the pharyngeal airway before and after mandibular setback surgery using computational fluid dynamics, in order to prevent iatrogenic obstructive sleep apnoea. Eleven patients with mandibular prognathism underwent bilateral sagittal split osteotomy for mandibular setback. Three-dimensional models of the upper airway were reconstructed from preoperative and postoperative computed tomography images, and simulations were performed using computational fluid dynamics. ΔPPAS and the minCSA of the pharyngeal airway were calculated, and the relationship between them was evaluated by non-linear regression analysis. In all cases, the minCSA was found at the level of the velopharynx. After surgery, ΔPPAS increased significantly and the minCSA decreased significantly. The non-linear regression equation expressing the relationship between these variables was ΔPPAS=3.73×minCSA-2.06. When the minCSA was <1cm2, ΔPPAS increased greatly. The results of this study suggest that surgeons should consider bimaxillary orthognathic surgery rather than mandibular setback surgery to prevent the development of iatrogenic obstructive sleep apnoea when correcting a skeletal class III malocclusion.

Three-dimensional surgical simulation improves the planning for correction of facial prognathism and asymmetry: A qualitative and quantitative study.

Traditional planning method for orthognathic surgery has limitations of cephalometric analysis, especially for patients with asymmetry. The aim of this study was to assess surgical plan modification after 3-demensional (3D) simulation. The procedures were to perform traditional surgical planning, construction of 3D model for the initial surgical plan (P1), 3D model of altered surgical plan after simulation (P2), comparison between P1 and P2 models, surgical execution, and postoperative validation using superimposition and root-mean-square difference (RMSD) between postoperative 3D image and P2 simulation model. Surgical plan was modified after 3D simulation in 93% of the cases. Absolute linear changes of landmarks in mediolateral direction (x-axis) were significant and between 1.11 to 1.62 mm. The pitch, yaw, and roll rotation as well as ramus inclination correction also showed significant changes after the 3D planning. Yaw rotation of the maxillomandibular complex (1.88 ± 0.32°) and change of ramus inclination (3.37 ± 3.21°) were most frequently performed for correction of the facial asymmetry. Errors between the postsurgical image and 3D simulation were acceptable, with RMSD 0.63 ± 0.25 mm for the maxilla and 0.85 ± 0.41 mm for the mandible. The information from this study could be used to augment the clinical planning and surgical execution when a conventional approach is applied.

Tongue pressure production during swallowing in patients with mandibular prognathism.

UNLABELLED: Abnormalities of swallowing in patients with mandibular prognathism have not been evaluated quantitatively. The aim of this study was to compare tongue pressure production for bolus transfer between volunteers with normal occlusion and patients with mandibular prognathism. The control group had 10 female volunteers with normal occlusion, and the patient group had 10 women with mandibular prognathism. Tongue pressure was measured by a palatal sensor sheet at five sites on swallowing 4 mL of a tasteless and odourless jelly. RESULTS: The tongue pressure waveform differed between the control and patient groups. The incidence of a double-peak tongue pressure waveform was more frequent in the patient group. In both groups, the exertion of tongue pressure began at the anterior point of the sensor sheet, followed by the peripheral parts. Although the order of expression of tongue pressure was the same for the two groups, maximum tongue pressure at all parts of the sensor sheet was lower in the patient group than in the control group. Furthermore, swallowing time was longer in the patient group than in the control group at the peripheral parts of the palate. These results clearly show the difference in tongue pressure production during swallowing between patients with mandibular prognathism and volunteers with normal occlusion. The current findings suggest that maxillofacial morphology may affect tongue movement during swallowing.

The amount of mandibular setback influence on occlusal force following sagittal split ramus osteotomy.

PURPOSE: The purpose of this study was to examine the influence between the magnitude of setback in sagittal split ramus osteotomy (SSRO) and occlusal contact area and bite force without relapse after surgery. PATIENTS AND METHODS: Sixty female patients with a diagnosis of mandibular prognathism were divided into 3 groups according to the magnitude of setback: group 1 (≤5 mm), group 2 (>5 mm but <10 mm), and group 3 (≥10 mm). All patients underwent skeletal analysis by lateral and frontal cephalogrammetry and measured the occlusal contact area and bite force by the pressure-sensitive system (Dental Prescale, Dental Occlusion Pressuregraph FDP-705; Fuji Photo Film Co., Tokyo, Japan) preoperatively and postoperatively at 1 month, 3 months, 6 months, and 1 year. RESULTS: There were no significant differences in occlusal contact area and bite force between the 3 groups. Only group 3 showed a significant difference in occlusal contact area and bite force between the preoperative and 1-year measurements. CONCLUSION: The results indicate that the magnitude of setback did not influence the bite force or occlusal contact area in SSRO.

Three-dimensional analysis of postoperative returning movement of perioperative condylar displacement after bilateral sagittal split ramus osteotomy for mandibular setback with different fixation methods.

This study aimed to evaluate postoperative returning movement of perioperative condylar displacement after bilateral sagittal split ramus osteotomy (BSSRO) depending on a fixation method using three-dimensional (3D) analysis of computed tomography (CT). Twenty-five mandibular prognathic patients (50 condyles) who underwent orthognathic surgery with BSSRO were divided into three groups depending on the fixation method, which consisted of miniplate only (Group A), combined with single bicortical screw (Group B), or with more than one bicortical screw (Group C). CT data taken before, immediately after, and 3 to 6 months after surgery were analyzed. The condyle exhibited mainly lateral bodily displacement and inward and inferior rotation immediately after surgery. The amount of perioperative lateral displacement of the condyle increased according to the increasing number of fixation screws, but the mean displacements were not significantly different among the three groups. During the postoperative follow-up period, the amount of medial returning of the condyle was 102.2% of the intraoperative lateral displacement in Group A. In contrast, Group B and C exhibited partial returning movement by 71.3% and 38.9% of cases, respectively. In conclusion, stronger rigid internal fixation in orthognathic surgery using BSSRO is associated with reduced flexibility of postoperative functional adjustment of displaced condyle to the preoperative condylar position.

Acoustic analysis of vowel sounds before and after orthognathic surgery.

The purpose of this study was to compare the articular structures and vowel sounds of patients with mandibular prognathism before and after bilateral sagittal split ramus osteotomy (BSSRO). Eight patients who underwent BSSRO to correct mandibular prognathism were selected for inclusion in this study. All patients were asked to read short words (vowels), and these sounds were recorded. Every utterance was repeated twice in four different sessions before the operation and at 6 weeks, 3 months, and 6 months after the operation. The data were analysed using Praat (ver. 5.1.31), and the formant frequencies (F1, F2) of the eight vowels were extracted. PlotFormant (ver. 1.0) was used to draw formant diagrams. The F1 and F2 of front-low vowels were reduced after BSSRO, and the articulating positions of the patients shifted in a posterior-superior direction after the procedure. Additionally, the area of vowel articulation was dramatically reduced after BSSRO but increased slowly over time.

Lip closing force of Class III patients with mandibular prognathism: a case control study.

INTRODUCTION: To compare the lip closing force of patients with mandibular prognathism to that of patients without dentofacial anomalies. METHODS: The subject group included 62 female patients of Class III relationship with mandibular prognathism. The control group been comprised of 71 patients of Class I relationships without skeletal deformities. Maximum lip closing force and average lip closing force were measured using a Y-meter. Student's t-test was carried out to analyse the differences between the groups. Correlation and stepwise multiple linear regression analyses were performed to analyse the relationship between lip closing force and craniofacial morphology. RESULTS: The lower lip closing force of subjects with mandibular prognathism was significantly greater than that of patients in the control group (P < 0.001), while the upper lip closing force showed no difference (P > 0.05). The lower lip closing force of patients with mandibular prognathism was strongly correlated with IMPA (Lower Incisor - Mandibular Plane angle, P < 0.001) and FMA (Frankfort Plane-Mandibular Plane angle, P < 0.001). Multiple regression equations: (MaxLL) = 12.192 - 0.125 * (IMPA) + 0.082 (FMA); (AveLL) = 9.112 - 0.091 * (IMPA) + 0.054 (FMA). CONCLUSIONS: The lower lip closing force was markedly increased in Class III patients with mandibular prognathism and was strongly correlated with lower incisor position and mandibular plane angle.

Mandibular growth comparisons of Class I and Class II division 1 skeletofacial patterns.

OBJECTIVE: To determine class and sex differences in mandibular growth and modeling. MATERIALS AND METHODS: A mixed-longitudinal sample of 130 untreated French-Canadian adolescents, 77 (45 boys and 32 girls) with Class I (normal or abnormal) occlusion and 53 (26 boys and 27 girls) with Class II division 1 malocclusion, was used. Based on eight landmarks, eight traditional measurements were used to compare the anteroposterior position of the maxilla and mandible, relationship between the jaws, and mandibular size. Mandibular superimpositions were used to compare the horizontal and vertical changes of condylion, gonion, and menton. RESULTS: While there were no differences in maxillary position based on the SNA angle, Class IIs had more retrognathic mandibles than did Class Is. Total mandibular length was greater in Class Is than in Class IIs at 15 years of age. Superior and total growth and modeling changes at condylion and gonion, respectively, were greater for Class Is than Class IIs. Boys were more prognathic than girls; they had larger mandibles and exhibited greater size increases and growth changes than girls did. CONCLUSIONS: There are both class and sex differences in mandibular growth and modeling.

Comparison of soft tissue cephalometric norms between Turkish and European-American adults.

One of the most important components of orthodontic diagnosis and treatment planning is the evaluation of the patient's soft tissue profile. The main purpose of this study was to develop soft-tissue cephalometric standards for Turkish men and women and compare them with the cephalometric standards of normal European-American white people. The sample included 96 Turkish adults (48 women, 48 men), aged 20 to 27 years. Turkish subjects have increased facial convexity associated with retruded mandible, more obtuse lower face-throat angle, increased nasolabial angle and upper lip protrusion, deeper mentolabial sulcus, and smaller interlabial gap compared with European-American white people. It is appropriate to consider these differences during routine diagnosis and treatment planning of a Turkish patient or an American patient of European ancestry. Turkish males reveal more obtuse mandibular prognathism and upper lip protrusion, and smaller nasolabial angle than females.

Do Class III patients have a different growth spurt than the general population?

INTRODUCTION: Understanding the timing and length of the growth spurt of Class III prognathic patients is fundamental to the strategy of interceptive orthopedic orthodontics as well as to the timing of orthognathic surgery. Consequently, this study was undertaken to determine whether there are any significant differences in the stature growth pattern of Class III subjects compared with non-Class III subjects and the general population. METHODS: Twelve-year longitudinal stature growth data were collected for 402 randomly selected adolescents in the general population, 55 Class III mandibular prognathic patients, and 37 non-Class III patients. The growth data were analyzed by using the traditional linear interpolation method and nonlinear growth functions. The 6 stature growth parameters were measured: age at takeoff, stature at takeoff, velocity at takeoff, age at peak height velocity, stature at peak height velocity, and velocity at peak height velocity. Comparisons in the stature growth parameters and 15 cephalometric variables among the general population, Class III subjects, and non-Class III subjects were made with multivariate analysis. RESULTS: Patients with Class III prognathism did not have different growth parameters compared with Class II subjects or the general population. CONCLUSIONS: This study does not allow meaningful conclusions with regard to the relationship of mandibular size and stature growth pattern. The application of nonlinear growth curves vs the traditional linear interpolation method was also discussed.

Masticatory efficiency in class II and class III dentofacial deformities.

Masticatory efficiency may be impaired in individuals with dentofacial deformities. The objective of the present study was to determine the condition of masticatory efficiency in individuals with dentofacial deformities. 30 patients with class II (DG-II) and 35 patients with class III (DG-III) dentofacial deformity participated in the study, all had an indication for orthognathic surgery. 30 volunteers (CG) with no alterations of facial morphology or dental occlusion and with no signs or symptoms of temporomandibular joint dysfunction also participated. Masticatory efficiency was analysed using a bead system (colorimetric method). Each individual chewed 4 beads, one at a time, over 20s measured with a chronometer. The groups were compared in terms of masticatory efficiency using analysis of variance (ANOVA), with the level of significance set at P<0.05. Masticatory efficiency was significantly greater in CG (P<0.05) than in DG-II and DG-III in all chewing tasks tested, with no significant difference between DG-II and DG-III (P>0.05). It was observed that the presence of class II and class III dentofacial deformity affected masticatory efficiency compared to CG, although there was no difference between DG-II and DG-III.

Changes in the lip closing force of patients with class III malocclusion before and after orthognathic surgery.

The purpose of this study was to examine the changes in lip pressure before and after orthognathic surgery for skeletal class III patients. The subject groups were 32 female and 31 male patients diagnosed with mandibular prognathism and/or maxillary retrognathism who underwent orthognathic surgery. Control groups consisted of 20 women and 20 men with normal occlusion without dento-alveolar deformity. Maximum and minimum lip closing force was measured with Lip De Cum® for the control groups and subject groups preoperatively and 6 months postoperatively. The difference between the pre- and postoperative values of the groups was examined statistically. The maximum lip closing force in men was significantly larger than that in women in both the preoperative class III group (p=0.0330) and the control group (p=0.0097). The preoperative class III group was significantly smaller than the control group in maximum lip closing force in both men (p<0.0001) and women (p<0.0001). The postoperative maximum lip closing force was significantly larger than the preoperative value in both men (p=0.0037) and women (p=0.0273) in the Class III group. This study suggested that the maximum lip closing force increases after orthognathic surgery in Class III patients.

The influence of the closing and opening muscle groups of jaw condyle biomechanics after mandible bilateral sagittal split ramus osteotomy.

OBJECTIVE: To investigate the influence of the closing and opening muscle groups of the jaw on mandibular stability after mandibular bilateral sagittal split ramus osteotomy (BSSRO). MATERIALS AND METHODS: To establish finite element models of four conditions (the normal mandible, preoperative mandibular prognathism, postoperative (BSSRO) mandibular prognathism, and mandibular prognathism following virtual BSSRO), we imported Digital Imaging and Communications in Medicine (DICOM) data into three-dimensional reconstruction software. Finite element analysis software and statistical software were used for analysis of the condylar stress distribution as a function of condylar position during the actions of jaw closing and jaw opening muscle groups. RESULTS: The stress distribution of the normal mandibular bilateral condyle was statistically different from the normal mandibular condyle, indicating that bilateral structures are asymmetrical. There was a significant difference in stress distributions with condyle position between healthy control patients and patients prior to mandibular prognathism surgery (P<0.05). There was no significant difference in stress distributions between the normal mandible and the mandible following virtual surgery or real mandibular prognathism surgery. Additionally, there was no significant difference at 6 months after mandibular prognathism surgery (P>0.05). CONCLUSIONS: Bilateral structures of the normal mandible were asymmetrical. After mandibular bilateral sagittal split ramus osteotomy, variation of the force arms of closing and opening muscle groups of the jaw was one of the major factors influencing mandibular stability. Virtual surgery is a promising strategy for preoperative planning to improve surgical success and reduce complications.

Smoothness of chewing jaw movements in adults with mandibular prognathism.

Indices such as smoothness, movement time, peak velocity, and symmetry of the velocity profile have been shown to be effective in explaining the degree of skilfulness of human saccadic eye, limb, and jaw motions. We investigated whether adult subjects with mandibular prognathism show impaired smoothness of the masticatory jaw movements. Forty-nine adults with skeletal Class III malocclusions and 52 healthy adults with acceptably good occlusions were selected respectively as Test and Control subjects. Subjects of the Test Group were subdivided into two groups: Class III(closed) showed full occlusal contact between the upper and lower teeth at the habitual intercuspal position, whereas Class III(open) showed inability of occlusal contact between the upper and lower anterior teeth. Each subject was asked to chew a piece of chewing gum. The normalised jerk-cost (NJC), movement duration, and tangential velocity profile during jaw-closing movements were compared between groups. Test Groups showed greater NJC (P < 0·01) with longer movement duration (P < 0·01) and lower peak velocity (P < 0·01) than the Control Group did. Class III(closed) showed greater NJC (P < 0·01) with longer movement duration (P < 0·01) and lower peak velocity (P < 0·01) than Class III(open) did. Results show that the mandibular movements made by the Test Groups exhibit lower skilfulness than those made by the Control Group. The jaw movement skilfulness of the prognathic patients decreases most drastically with existence of malocclusal contact between upper and lower anterior teeth.