The comparison between various methods of mandibular reconstruction based on finite element analysis.

The Mandible can be damaged by pathological factors, tumors, trauma, infection, and needs a surgical operation for reconstruction and restoring function. There are different methods for the reconstruction of mandible. Based on the surgical approach, primary reconstruction of mandible by reconstruction plate after resection is necessary for maintaining mandibular symmetric and esthetic of the lower third of the face. A finite element model of mandible and masticatory muscles was produced from a normal person (male with 35-year-old). The normal model was resected from the left sixth tooth to the second tooth. The pathological model was reconstructed in different conditions by macro plate. Different conditions were analyzed and compared based on bite force on right fifth tooth, stress developed on screws and macro plate. The finite element analysis results showed that maximum bite force and lower stress on screws were seen in the pathological model (condition 5) when one macro plate and six screws were inserted in the mid-body. The findings showed that the use of two macro plates causes lower stress on it than when we use one. Use of one macro plate and six screws is the best choice in mandibular immobilization which decrease the stress applied on bone and increase the bite force. Because of less stress developed on macro plates and screws, use of two macro plates or one macro plate in mid-body area are also preferred.

Changes in the pharyngeal airway after different orthognathic procedures for correction of class III dysplasia.

OBJECTIVE: This study was conducted to compare changes in pharyngeal airway after different orthognathic procedures in subjects with class III deformity. METHODS: The study included CBCT scans of 48 skeletal class III patients (29 females and 19 males, mean age 23.50 years) who underwent orthognathic surgery in conjunction with orthodontic treatment. The participants were divided into three groups of 16, as follows: Group 1, mandibular setback surgery; group 2, combined mandibular setback and maxillary advancement surgery; and group 3, maxillary advancement surgery. CBCT images were taken 1 day before surgery (T0), 1 day (T1), and 6 months (T2) later. The dimensions of the velopharynx, oropharynx, and hypopharynx were measured in CBCT images. RESULTS: In all groups, there was a significant decrease in airway variables immediately after surgery, with a significant reversal 6 months later (P < 0.05). In subjects who underwent maxillary advancement, the airway dimensions were significantly greater at T2 than the T0 time point (P < 0.05), whereas in the mandibular setback and bimaxillary surgery groups, the T2 values were lower than the baseline examination (P < 0.05). The alterations in airway variables were significantly different between the study groups (P < 0.05). CONCLUSIONS: The mandibular setback procedure caused the greatest reduction in the pharyngeal airway, followed by the bimaxillary surgery and maxillary advancement groups, with the latter exhibiting an actual increase in the pharyngeal airway dimensions. It is recommended to prefer a two-jaw operation instead of a mandibular setback alone for correction of the prognathic mandible in subjects with predisposing factors to the development of sleep-disordered breathing.

Evaluation of Zygomaticosphenoidal Angle in Patients With Unilateral Zygomaticomaxillary Complex Fracture.

ABSTRACT: This study aimed to assess the zygomaticosphenoidal (ZS) angle in patients with reducted unilateral zygomatico-maxillary complex (ZMC) fracture and compare it with the normal control group. This study was performed on CT images of 60 cases and 60 controls with a mean age of 35.1 ±â€Š14.6. The ZS angle was measured on axial images containing the equator of the eyeball. Moreover, the mean absolute difference value and asymmetry index were calculated. Chi-square test, independent-sample t test, 1-way ANOVA, paired-sample t test, and ROC curve analysis were applied. The mean ZS angle in the control group was 46.6°â€Š±â€Š3.5°. Considering laterality, the mean of ZS was not significant in the control group. However, after reduction of unilateral ZMC fracture, there was a significant difference between the mean ZS angle in right and left sides. The mean absolute difference between right and left ZS angles was significantly higher in the case group. A threshold number of 0.9° is established in the mean absolute difference value which is the difference between the right and left ZS angles in an individual for detecting asymmetry. The ZS angle can be a useful anatomical aid to guide surgeons in achieving facial symmetry in ZMC fractures.

A Long-Standing Giant Mandibular Ameloblastoma and its Management with Microvascular Free Fibular Graft: a Case Report.

Ameloblastoma is one of the most common benign epithelial odontogenic tumors of jaws. We report a case of long-standing slow-growing giant ameloblastoma involving almost all of mandibular bone. The solid multicystic lesion was excised, and the histopathological examination showed the follicular type of ameloblastoma. Furthermore, the defect was reconstructed with microvascular osteocutaneous free fibular graft.

Evaluation of bite force recovery in patients with maxillofacial fracture.

The aim of this study was to measure the maximum voluntary bite force and recovery time in patients treated for different types of the maxillofacial fracture. Patients aged between 18 and 60 years, who received surgical treatment for a single isolated fracture of the maxillofacial structure, were included in this study. Healthy individuals without any maxillofacial abnormality were selected as the control group. Bite force (in kg) was measured at the first incisor tooth, bilaterally, prior to surgery and 2 weeks, 6 weeks, 3 months, and 6 months after surgery. Of 120 patients, 89 (74.17%) were male and 31 (25.83%) were female. Mean patient age (±SD) was 31.21 (±11.64) years. Bite forces relating to fractures of the zygomaticomaxillary complex (ZMC) with involvement of the arch and zygomaticofrontal suture reached normal levels after 6 weeks (from 3.89 (±1.11) to 10.82 (±1.29); p = 0.296 and from 4.20 (±0.93) to 10.70 (±1.70); p = 0.192, respectively). Bite force returned to normal after 3 months in fractures of the symphysis (from 2.05 (±0.97) to 12.18 (±0.77); p = 0.222), body (from 2.21 (±1.26) to 11.9 (±0.73); p = 0.750), angle (from 2.45 (±1.24) to 11.89 (±0.76); p = 0.769), condyle (from 2.45 (±1.27) to 11.25 (±0.82); p = 0.968), and ZMC with and without infraorbital rim involvement (from 3.83 (±0.93) to 11.92 (±0.84); p = 0.724 and from 3.7 (±1.21) to 12.03 (±0.82); p = 0.482, respectively). Patients with ZMC fracture involving the arch and zygomaticofrontal suture require fewer follow-ups in comparison with those with other maxillofacial fractures. Measurement of maximal bite force can help to evaluate dentofacial deformities before and after surgical treatment.

Marginal bone resorption of posterior mandible dental implants with different insertion methods.

BACKGROUND: To evaluated the marginal bone loss around dental implants by two insertion methods. METHODS: Eligible patients were divided into two groups; manual and mechanized groups. Peri-apical x-ray using a customized device to standardize the radiographs designed and used to take three periodical radiographs; after surgery, three months, and six months follow up. An independent t-test was used to compare the two groups regarding the average level of marginal bone loss (p < 0.05). RESULTS: After excluding dropouts, a total of 273 patients (120 males and 153 females, aged between 25 and 67 years old) were included in the study. The average marginal bone loss in the manual insertion method was 0.44 ± 0.84 mm, and 0.59 ± 0.20 mm, and for the mechanized method was 0.51 ± 0.20 mm and 0.67 ± 0.19 mm after three and six months, respectively. There was a significant difference in marginal bone loss after six months between the two groups(p < 0.001). However, no differences were observed after three months (p = 0.24). CONCLUSIONS: Under the condition of this study, both techniques were safe and resulted in an acceptable amount of bone resorption; however, in the manual method, the less marginal bone loss occurred after six months.

Does the Winter or Pell and Gregory Classification System Indicate the Apical Position of Impacted Mandibular Third Molars?

PURPOSE: The present study investigated the relationship of impacted mandibular third molars to the cortical plates and inferior alveolar canal (IAC) using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: The present study included CBCT images of 386 lower third molars in 226 patients, for whom the initial panoramic radiographs had revealed a close relationship between the third molars and IAC. The coronal images were prepared to determine the position of apex about the buccal and lingual cortexes and IAC. The impacted third molars were categorized using the Winter and the Pell and Gregory classifications. The relationship between the third molars and buccal/lingual cortexes and IAC was determined in the different classes of the Winter and the Pell and Gregory systems. RESULTS: The mesioangular position was more prevalent in the present sample. Most teeth were Class I concerning the ascending ramus and level C in depth. Generally, the impacted mandibular third molars showed a lingual position and were in contact or intersecting into the IAC. A significant association was found between the type of tooth impaction using the Winter and the Pell and Gregory classifications and the position of the third molar teeth concerning the cortical plates and IAC. CONCLUSIONS: The possibility of the buccal position of the tooth and the chance of an intersection of the apex into the IAC was greater in teeth that were mesioangular and were Class III concerning the ascending ramus and level C in depth. These data should be considered during the preoperative assessment of third molars to reduce postoperative complications.

Does oral clonidine premedication decrease bleeding during open rhinoplasty?

This uni-blind randomized clinical trial study investigated the effect of clonidine premedication on preoperative blood loss during open rhinoplasty. The subjects were randomly divided into 2 groups. The members of the first group received oral clonidine as a single dose (0.2 mg) 2 hours before the induction of general anesthesia, whereas the members of the second group received a placebo. All subjects underwent open rhinoplasty without septoplasty. One anesthetic protocol was followed for all subjects. Variable factors include the subjects' weight, age, sex, and blood pressure during the surgery as well as blood loss during rhinoplasty. Group 1 consisted of 22 women and 11 men, whereas group 2 was composed of 16 women and 17 men. The mean for blood loss amounted to 68.03 ± 22.49 mL for group 1 and 132.12 ± 78.53 mL for group 2. An assessment demonstrated a significant difference in blood loss between the 2 groups (P < 0.001.) Oral clonidine premedication thus may decrease preoperative bleeding during open rhinoplasty.