Mandibular Volume Research Articles

Morphologic quantification of the maxilla and the mandible with cone-beam computed tomography

The purpose of this pilot study was to use cone-beam computed tomography (CBCT) to determine the volumes of the maxilla and the mandible in subjects with skeletal Class I, Class II, and Class III malocclusions. Hypothesis 1 was that the volume (size) of a skeletal Class II maxilla is larger than those of Class I and Class III. Hypothesis 2 was that the volume of a skeletal Class III mandible is larger than those of Class I and Class II. Thirty women patients were classified into 3 groups according to their skeletal pattern: skeletal Class I (0 degrees < or =ANB <6 degrees ), Class II (ANB > or =6 degrees ) and Class III (ANB <0 degrees ). The volumes of the maxilla and the mandible were measured with CBCT. CB MercuRay (Hitachi Medico, Tokyo, Japan) and CB works software (CyberMed, Seoul, Korea) were used to process the images. There was a trend that skeletal Class III subjects might have significantly greater mandibular volume compared with Class II subjects (P = 0.089). The ratios of maxilla-to-mandible volumes between the skeletal Class II and Class III groups were significantly different (P = 0.005). Differences were observed in the ratios of maxillary and mandibular volumes across the 3 groups. Hypotheses 1 and 2 were rejected; there was no trend for Class III subjects to have larger mandibles (P = 0.089) compared with Class II subjects. The ratio of the maxilla and mandible volumes in skeletal Class III subjects was significantly larger (P = 0.005) compared with Class II subjects.

Soft tissue facial morphometry in subjects with Moebius syndrome

Moebius syndrome is a congenital facial palsy associated with the impairment of ocular abduction. The three-dimensional characteristics of the facial soft tissues of 12 male and 14 female subjects [3-52 yr of age (mean age + standard deviation: 17 + 14 yr)] were measured using a non-invasive, computerized system; facial volumes, areas, angles, and distances were computed and compared with those obtained in reference subjects of the same age and gender. When compared with reference subjects, patients with Moebius syndrome had a more prominent and hyperdivergent face in the sagittal plane, a smaller and more prominent upper facial third; a smaller middle facial width; a smaller nose; smaller mandibular volume, depth, corpus length, and ramus height; and a more posterior positioned mandible, with a less prominent chin. In conclusion, patients with Moebius syndrome had a tendency towards a skeletal Class II pattern. These morphological variations may be the combined effect of a general alteration of the motor and sensitive facial nerves, including the trigeminal nerve, and of a maldevelopment of the brainstem.

Quantitative analysis of the maxilla and the mandible in hyper‐ and hypodivergent skeletal class II pattern

To examine the volumetric (size) difference in the maxilla and the mandible of hyper- and hypodivergent skeletal patterns in Angle class II malocclusion. Descriptive retrospective study. The hypothesis is that a hypodivergent mandible has a larger size than a hyperdivergent mandible. Using cone-beam computed tomography, 20 subjects with Angle class II malocclusion were classified into two groups; 10 of 20 subjects formed a hyperdivergent group while the rest formed a hypodivergent group. Cone-beam computed tomography images were obtained and processed and 3D volume data was measured by one clinician. Dahlberg's technique was used to assess the measurement error and significant difference was set at p < 0.05. No significant differences were found between the volumes of the maxilla and mandible in both groups. Differences were observed in the ratio of mandibular/maxillary volumes. The hypodivergent group had a significantly larger (p = 0.014) ratio than the hyperdivergent group. Maxillary and mandibular volumes differ between hyper- and hypodivergent skeletal patterns.

Osteoradionecrosis (ORN) of the Mandible in Head/Neck Cancer Treated with Intensity Modulated Radiation Therapy (IMRT)

Retrospective review of the incidence and patterns of ORN in head/neck cancer patients treated with IMRT at a single institution. We combined our institutional databases of head/neck cancer patients who underwent IMRT from 9/99 to 5/07 (n = 218). The sites were: nasopharynx (n = 25), paranasal sinuses (n = 35), oral cavity (n = 36), oropharynx (n = 41), larynx/hypopharynx (n = 31), and thyroid gland (n = 50). The T-stages were: T1, 9% (n = 19); T2, 28% (n = 61); T3, 19% (n = 42); T4, 41% (n = 89). Seven patients were not staged. Fifty-four percent of patients (n = 118) underwent surgery prior to RT and 57% (n = 125) had chemotherapy as a component of their initial treatment. Six patients (3%) had mandibular invasion prior to treatment. All patients underwent a comprehensive dental examination at our institution and were given instructions on post-RT dental care/fluoride treatment. Patients that were expected to receive a significant dose to the oral cavity were also fitted with a mouth guard prior to treatment. Pre-RT extractions were performed in 15% of patients (n = 33). The median prescription dose was 69.96 Gy. The median Dmax, mean dose, D05, and D95 doses were 66.89 Gy (range, 24.71-77.69 Gy); 37.46 Gy (range, 3.36-65.30 Gy), 60.09 Gy (range, 16.76-73.32 Gy), and 15.99 Gy (range, .29-56.85 Gy), respectively. The mean mandibular volume receiving IMRT was 73 cc (range, 8-163 cc). Median doses to the left and right parotid gland were 25.61 Gy (range, .90-65.95 Gy) and 25.54 Gy (range, .53-59.07 Gy), respectively. With a median follow-up of 28 months (range, 1-101 months), 2 patients, both with oral cavity primaries, (stages T2N2 and T2N1) experienced ORN. The first patient had ORN 31 months after IMRT. He underwent a sequestrectomy and had healed well at last follow-up. The second patient had ORN 32 months after IMRT. He underwent surgical debridement and also healed fully at last follow-up. In addition to surgery, these patients also underwent post-operative concurrent chemoradiotherapy. Neither patient had mandibular invasion prior to treatment. The mandibular and parotid parameters in these 2 patients were: Dmax, 68.28/71.83 Gy, mean dose 53.35/58.12 Gy, D05 64.64/70.17 Gy, D95 14.98/28.30 Gy, volume 66.8/87 cc, left parotid 25.99/24.73 Gy, and right parotid 23.95/25.30 Gy, respectively. ORN is rare after treatment of head/neck cancer with IMRT. However, the incidence was 6% in oral cavity cancer. Due to the delayed onset of this complication more patients may experience ORN with longer follow-up. Patients that experienced ORN had mandibular parameters that were higher than the median values. All patients should be followed with rigorous dental care and mandibular dose constraints should be applied.

Lack of Osteoradionecrosis of the Mandible After Intensity-Modulated Radiotherapy for Head and Neck Cancer: Likely Contributions of Both Dental Care and Improved Dose Distributions

To assess the prevalence and dosimetric and clinical predictors of mandibular osteoradionecrosis (ORN) in patients with head and neck cancer who underwent a pretherapy dental evaluation and prophylactic treatment according to a uniform policy and were treated with intensity-modulated radiotherapy (IMRT). Between 1996 and 2005, all patients with head-and-neck cancer treated with parotid gland-sparing IMRT in prospective studies underwent a dental examination and prophylactic treatment according to a uniform policy that included extractions of high-risk, periodontally involved, and nonrestorable teeth in parts of the mandible expected to receive high radiation doses, fluoride supplements, and the placement of guards aiming to reduce electron backscatter off metal teeth restorations. The IMRT plans included dose constraints for the maximal mandibular doses and reduced mean parotid gland and noninvolved oral cavity doses. A retrospective analysis of Grade 2 or worse (clinical) ORN was performed. A total of 176 patients had a minimal follow-up of 6 months. Of these, 31 (17%) had undergone teeth extractions before RT and 13 (7%) after RT. Of the 176 patients, 75% and 50% had received >or=65 Gy and >or=70 Gy to >or=1% of the mandibular volume, respectively. Falloff across the mandible characterized the dose distributions: the average gradient (in the axial plane containing the maximal mandibular dose) was 11 Gy (range, 1-27 Gy; median, 8 Gy). At a median follow-up of 34 months, no cases of ORN had developed (95% confidence interval, 0-2%). The use of a strict prophylactic dental care policy and IMRT resulted in no case of clinical ORN. In addition to the dosimetric advantages offered by IMRT, meticulous dental prophylactic care is likely an essential factor in reducing ORN risk.

Soft tissue facial volumes and shape in skeletal Class III patients before and after orthognathic surgery treatment

To obtain the best surgical results in orthognathic surgery, treatment planning and the evaluation of results should be performed on measurable three-dimensional reproductions of the face of the patients, and compared to reference subjects. Seven women aged 18-35 years, all with a skeletal Class III and mandibular asymmetry, were assessed both before (on average, 2 months) and after (on average, 10.7 months) surgical intervention (mandibular reduction by sagittal split osteotomy and LeFort I maxillary advancement). The three-dimensional coordinates of 50 soft tissue facial landmarks (face, eyes, nose, mouth and lips, ears) were collected with a noninvasive, electromagnetic digitizer; facial volumes were estimated, and compared to reference values collected in 87 healthy women of the same age and ethnic group. Inter-individual modifications in facial shape were also assessed. Before surgery the patients had smaller faces than the reference women, with larger lower lips and noses. A large within-group variability was found. Surgical treatment significantly reduced total facial volume and mandibular volume, increased total and upper lip volumes (Student's t test, p<0.05), and made all values more homogenous within the group. Shape differences were significantly larger before than after surgery. On average, right side gonion was the landmark that moved the most, closely followed by menton, while the tragi and ala nasi moved the least. The three-dimensional approach used in this study enabled quantitative evaluation of the final soft tissue results of surgery, without submitting the patients to invasive procedures.

Bilateral mandibular distraction for patients with compromised airway analyzed by three-dimensional CT

The purpose of this study was to present the method of mandibular distraction osteogenesis in order to improve airway to respiratory distressed patients due to significant mandibular deficiency, and to present the quantitative volumetric evaluation of mandible and upper airway using three-dimensional-CT (3D-CT) before and after distraction. This study involved 12 patients aged 12 months to seven years with various complaints of Obstructive Sleep Apnea (OSA) such as noisy breathing during sleep, waking episodes, pauses in respiration and daytime somnolence. Some of them were considered tracheostomy candidates. All the patients underwent bilateral mandibular distraction under general anesthesia. 3D-CT of face and neck was performed before and after distraction and a quantitative volumetric evaluation of mandibular volume and airway volume was performed. The results reveal successful mandibular advancement with increase of mandibular volume by an average of 28.24% and increase of upper airway volume with a mean of 71.92%. Moreover, there were improved apnea index and oxygen saturation and elimination of OSA symptoms. In conclusion, the results demonstrate that following distraction osteogenesis of hypoplastic mandible the volume of the mandible and upper airway increases, eliminating symptoms of OSA and preventing tracheostomy.

Treatment of pediatric obstructive sleep apnea by mandibular distraction

Obstructive sleep apnea (OSA) in pediatric populations is often associated with congenital craniofacial malformations, as Pierre Robin syndrome, hemifacial microsomia, resulting in decreased pharyngeal airway, which, in severe cases, leads to tracheostomy dependence. A total of fourteen children were treated, six patients had tracheostomies placed and another eight patients were considered tracheostomy candidates. The mean age of the patients was four years old, ranging from 9 months to 7 years. The patients that are without tracheostomy are respiratory distressed and have various complaints of OSA, as noisy breathing during sleep, waking episodes, pauses in respiration, daytime somnolence and are considered tracheostomy candidates. OSA, due to congenital malformations, was treated by mandibular distraction osteogenesis. Mandibular distraction osteogenesis was performed bilaterally in the mandibular body using two extraoral distraction devices. After a latency period of four days, a gradual distraction in a rate of 1 mm/day was performed followed by consolidation period of eight weeks. The expansion of mandibular framework was analyzed using bony cephalometric landmarks and 3D CT. The size of the pharyngeal airway preoperatively and post-treatment was evaluated by measurements of lateral (sagittal) and axial width and by 3D CT. The results demonstrate average mandibular elongation of 34mm on each side, and an increase in mandibular volume and pharyngeal airway. To date, all six patients are decannulated and in the other eight patients there is improved airway with improvement of signs and symptoms of OSA and elimination of oxygen requirement. Then, continuous treatment of the palate and the velopharyngeal sphincter was possible without impairing the airway.

Relationship between Masticatory Ability and Shape of Denture-supporting Area of Complete Denture Wearers

Purpose : The purpose of this study was to examine the characteristics of the shape of a denture-supporting area and their relationship to masticatory ability. The correlation among the shape of the denture-supporting area, maximum biting force, and the masticatory ability of the wearers of maxillary and mandibular complete dentures was investigated.Materials and Methods : Duplicate casts were made from the master casts of 28 complete denture wearers. The surface area (S) and projected area (P) of the maxillary and mandibular denture-supporting areas were measured ; the volume (V) was measured using a duplicate of the mucosal surface of the denture base made with the duplicate cast. In addition, V/P, S/P, and V/S were calculated from the factors of V, S, and P. The correlation among these measurements and ratings, the maximum biting force and the masticatory ability of the subjects were analyzed using Pearson's correlation coefficient.Results : Maximum biting force significantly correlated with mandibular volume (V), surface area (S), projected area (P), and V/S, which indicates the average height of the residual ridge. No significant correlation was observed between the shape of the denture-supporting area of the maxilla and the maximum biting force. Masticatory ability significantly correlated only with the mandibular surface area (S).Conclusion : The height and surface area of the mandibular denture-supporting area can help predict the recovery of function in complete denture wearers before treatment.

Analysis of mandibular dose distribution in radiotherapy for oropharyngeal cancer: dosimetric and clinical results in 18 patients.

The relationship between the radiation dose and the risk of the osteoradionecrosis is well known. However, the dose to the mandible is not routinely assessed in the radiotherapy for head and neck cancer. The aim of our study was to analyze the mandibular dose distribution in the patients administered curative radiotherapy for squamous cell carcinoma of the oropharynx. Moreover, the clinical results have been analyzed. We examined the clinical records and treatment plans in 18 patients treated with bifractionated radiotherapy for stage II-IV oropharyngeal cancer. In 17 patients, the total radiotherapy dose prescribed in the International Committee of Radiation Units and Measurements (ICRU) reference point was 74.4 Gy administered in 62 fractions (1.2 Gy twice daily with 6h interfraction interval) and one patient received a dose of 75.6 Gy. The whole dose to the mandibular-orophryngeal region was delivered with 6 MV photons. The mandible was contoured manually on computed tomographic scans and the point doses at the both mandibular condyles, ascending ramus, mental symphysis, molar and retromolar regions were assessed. Moreover, the cumulative dose-volume histograms (DHVs) were evaluated. The median follow-up period for alive patients is 30 months (range, 21-44+ months). Tumor remission was observed in 17 patients: in 11 cases, complete remission was achieved and in six cases, only partial remission was possible. One patient was lost to follow-up before the first response evaluation. The median survival for all patients is 22 months (range, 3-44+ months). Ten patients are alive and seven died. In six cases, the cause of death was head and neck tumor and in one died due to pancreatic cancer (second primary). No late bone post-radiation complication was seen. The highest radiotherapy doses were observed in the retromolar regions. The mean percentage doses at the right and left retromolar regions were 101.3+/-3.8% (range, 90.2-109.1%) and 101.7+/-2.5% (range, 95.2-105.8%), respectively. Lower doses were seen in ascending ramus (the mean percentage doses at right and left ascending ramus were 97.3+/-8.5% and 97.8+/-7.6%, respectively), the molar regions (the mean percentage doses at right and left molar regions were 86.0+/-13.5% and 88.1+/-12.9%, respectively), and at the mandibular condyles (the mean percentage doses at the right and left mandibular condyles were 72.6+/-18% and 77.0+/-16.5%, respectively). The volume of the mandible ranged from 60.1 to 110.1cm(3) (a mean of of 82.3 cm(3)). In all patients, the maximum dose absorbed in the mandible was higher than the dose prescribed in the ICRU point and the mean maximum dose absorbed in the mandible was 105.7+/-2.1% (range, 102.4-110.6%). The percentage of mandibular volume receiving a dose higher than prescribed was 28.6+/-14.9% (range 10.2-58.1%). The area underlying the DVH curve, the maximum mandibular doses and the retromolar doses did not appear to statistically depend on use of wedge or mandibular volume. Radiotherapy for oropharyngeal cancer is associated with high doses to the retromolar mandibular regions (the dose can be higher than prescribed in the ICRU reference point), ascending ramus and molar regions. Lower doses are absorbed at the condyles and mental symphysis. The single dose point (for example, the ICRU reference point) could be not used as a representative for the mandibular dose. In our small series of patients treated with hyperfractionated irradiation, these dose heterogeneities were not correlated to the patient- and treatment-related factors and are not related to the increased risk of late bone complications. The clinical relevance of mandibular dose distribution remains to be established in larger series of patients treated with conventionally and unconventionally fractionated irradiation.

Effect of distraction osteogenesis of the mandible on upper airway volume and resistance in children with micrognathia.

Children with craniofacial anomalies often have compromise of the upper airway, a condition with potential for morbidity and mortality. In children with microretrognathia, the diminutive size and retruded position of the mandible reduces the size of the oropharynx, thereby predisposing to glossoptosis and airway obstruction. Although several authors have reported successful use of mandibular distraction osteogenesis to alleviate this type of upper airway obstruction, the physiologic relationship between changes in mandibular shape, size, and position and upper airway dynamics remains undefined. The purpose of this study was to develop methodologies to quantitatively evaluate upper airway dynamics in children with micrognathia both before and after mandibular distraction osteogenesis. The patient population consisted of four children with micrognathia who had successfully undergone upper airway stabilization by bilateral mandibular distraction osteogenesis. The data used were digitally archived computed tomographic scan data from high-resolution, thin-slice head computed tomographic scans obtained before and after mandibular distraction. Upper airway evaluation was performed in two ways: static and dynamic. Static analysis consisted of computer quantification of predistraction and postdistraction mandibular and upper airway volumes using Analyze imaging software. Dynamic analysis consisted of fabrication of rigid stereolithographic hollow cast models of the upper airway produced from computed tomographic scan data. Models were used for characterization of upper airway resistance and flow patterns as related to respiration. After distraction osteogenesis, mandibular total volume increased 32, 32, 18, and 25 percent (mean, 27 percent) and upper airway volume increased by 20, 31, 23, and 71 percent (mean, 37 percent). A significant decrease in flow resistance, both inspiratory and expiratory, was observed in the patient with the greatest upper airway volume increase (71 percent) after distraction. After distraction, the inspiratory resistance was diminished by 51 percent and the expiratory resistance diminished by 85 percent. However, the three patients with more modest upper airway volume increases of 20 to 31 percent demonstrated no statistically significant change in flow resistance after distraction. Results of this study support the conclusion that distraction osteogenesis of the micrognathic mandible increases the volume of the upper airway, roughly paralleling the increase in mandibular volume. In the biomechanical airway model studied, upper airway volume expansion has been shown to be able to decrease the flow resistance over the length of the airway, presumably secondary to an increase in the average cross-sectional area. The artificial rigidity of the stereolithographic "airway" compared with the elasticity of the human upper airway may account for the insensitivity of this model to smaller but clinically significant airway changes.

The effect of muscle transplantation after unilateral partial facial paralysis on craniofacial growth and development: relationship between muscle and nerve histomorphometric findings.

Muscle transplantation has become an indispensable tool to restore the smile in patients with long-standing or congenital facial paralysis. However, little is known of the effect of this surgical intervention on craniofacial growth and development or of the adaptation of the transplant to its recipient site under circumstances of growth. The present study investigates these phenomena in the rabbit model. Twelve-day-old New Zealand White rabbits were randomly assigned to three experimental groups. The control group was used to study normal craniofacial growth and development (n = 15). In the nerve ablation group, unilateral paralysis of the buccal branches of the facial nerve was surgically induced (n = 15). In the transplant group, the surgically induced unilateral paralysis of the buccal branches was immediately followed by a neuromuscular graft (n = 12). All animals were operated on at the age of 12 days, and follow-up evaluations were performed at the ages of 2 months and 6 months. Computerized dorsoventral roentgencephalometric and computed tomography investigations were performed at both ages. Nerve and muscle histomorphometric measurements were performed at the age of 6 months to relate the quality of nerve and muscle regeneration to the growth parameters. The roentgencephalometric measurements revealed that analogous disturbed parameters were present in the nerve ablation and the transplant groups. However, in the transplant group, an additional significant effect of time between 2 and 6 months was seen for some parameters. This resulted in significant differences between the nerve ablation and transplant groups at 6 months for these parameters. Computed tomography measurements showed no significant differences in maxillary or mandibular volume in the transplant group compared with the control or nerve ablation groups. However, a significantly diminished increase in bone volume existed in the transplant group for the time period between 2 and 6 months in comparison with the control and nerve ablation groups. Muscle histomorphometric findings revealed a significant change in muscle fiber composition in the graft compared with the normal latissimus dorsi muscle; this was due to a major decrease in type IIB fibers, with an increase in type I and type IIA fibers. Compared with the normal zygomaticoauricular muscle, the amount of type I fibers was significantly increased. No fiber atrophy was found. Macroscopically, the transplanted muscle failed to increase its length during growth. Nerve histomorphometric findings demonstrated a normal amount of nerve fibers; however, they had significantly decreased diameters and reduced myelin areas. The nerve histomorphometric parameters were related to the muscle histomorphometric findings, which in turn were related to craniofacial growth disturbances. These findings suggested that the main growth differences between the transplant group and the control group may have been due to altered nerve function influencing muscle function. Scar tissue formation and the development of more intense muscle activity later are suggested as the causes of the additional effect of time between 2 and 6 months for the several parameters in the transplant group. Reasons for the failure of complete conversion of the graft to a fast muscle and the failure of the transplant to elongate during growth are discussed.