Evaluation of pharyngeal airway space changes after bimaxillary orthognathic surgery with a 3-dimensional simulation and modeling program.

INTRODUCTION: The aims of this study were to use 3-dimensional simulation and modeling programs to evaluate the effects of bimaxillary orthognathic surgical correction of Class III malocclusions on pharyngeal airway space volume, and to compare them with the changes in obstructive sleep apnea measurements from polysomnography. METHODS: Twenty-five male patients (mean age, 21.6 years) with mandibular prognathism were treated with bilateral sagittal split osteotomy and LeFort I advancement. Polysomnography and computed tomography were performed before surgery and 1.4 ± 0.2 years after surgery. All computed tomography data were transferred to a computer, and the pharyngeal airway space was segmented using SimPlant OMS (Materialise Medical, Leuven, Belgium) programs. The pretreatment and posttreatment pharyngeal airway space determinants in volumetric, linear distance, and cross-sectional measurements, and polysomnography changes were compared with the paired samples t test. Pearson correlation was used to analyze the association between the computed tomography and polysomnography measurements. RESULTS: The results indicated that setback procedures produce anteroposterior narrowing of the pharyngeal airway space at the oropharyngeal and hypopharyngeal levels and the middle and inferior pharyngeal volumes (P <0.05). In contrast, advancement of the maxilla causes widening of the airway in the nasopharyngeal and retropalatal dimensions and increases the superior pharyngeal volume (P <0.05). Distinctively, bimaxillary orthognathic surgery induces significant increases in the total airway volume and the transverse dimensions of all airway areas (P <0.05). Significant correlations were found between the measurements on the computed tomography scans and crucial polysomnography parameters. CONCLUSIONS: Bimaxillary orthognathic surgery for correction of Class III malocclusion caused an increase of the total airway volume and improvement of polysomnography parameters. A proposed treatment plan can be modified according to the risk of potential airway compromise or even to improve it with 3-dimensional imaging techniques and polysomnography.

Reconstruction with a patient-specific titanium implant after a wide anterior chest wall resection.

The reconstruction of full-thickness chest wall defects is a challenging problem for thoracic surgeons, particularly after a wide resection of the chest wall that includes the sternum. The location and the size of the defect play a major role when selecting the method of reconstruction, while acceptable cosmetic and functional results remain the primary goal. Improvements in preoperative imaging techniques and reconstruction materials have an important role when planning and performing a wide chest wall resection with a low morbidity rate. In this report, we describe the reconstruction of a wide anterior chest wall defect with a patient-specific custom-made titanium implant. An infected mammary tumour recurrence in a 62-year old female, located at the anterior chest wall including the sternum, was resected, followed by a large custom-made titanium implant. Latissimus dorsi flap and split-thickness graft were also used for covering the implant successfully. A titanium custom-made chest wall implant could be a viable alternative for patients who had large chest wall tumours.

Annealing of Co-Cr dental alloy: effects on nanostructure and Rockwell hardness.

PURPOSE: The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS: Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring 4 × 2 × 2 mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukey's HSD test was used for post hoc analysis. P values of <.05 were accepted as statistically significant. RESULTS: The general nanostructures of the samples were composed of small spherical entities stacked atop one another in dendritic form. All groups also displayed different hardness values depending on the manufacturing technique. The annealing procedure and environment directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness (48.16 ± 3.02 HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness (27.40 ± 3.98 HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 Å). CONCLUSION: After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic substructures. The dentists should be familiar with the materials that are used in clinic for prosthodontics treatments.

Relationship between Class III malocclusion and hyoid bone displacement during swallowing: a cine-magnetic resonance imaging study.

OBJECTIVE: The displacement of the hyoid bone (HB) is a critical biomechanical component of the swallowing function. The aim of this study was to evaluate the swallowing-induced vertical and horizontal displacements of the HB in subjects with 2 different magnitudes of skeletal Class III malocclusion, by means of real-time, balanced turbo-field-echo (B-TFE) cine-magnetic resonance imaging. METHODS: The study population comprised 19 patients with mild skeletal Class III malocclusion, 16 with severe skeletal Class III malocclusion, and 20 with a skeletal Class I relationship. Before the commencement of the study, all subjects underwent cephalometric analysis to identify the nature of skeletal malformations. B-TFE images were obtained for the 4 consecutive stages of deglutition as each patient swallowed 10 mL of water, and the vertical and horizontal displacements of the HB were measured at each stage. RESULTS: At all stages of swallowing, the vertical position of the HB in the severe Class III malocclusion group was significantly lower than those in the mild Class III and Class I malocclusion groups. Similarly, the horizontal displacement of the HB was found to be significantly associated with the severity of malocclusion, i.e., the degree of Class III malocclusion, while the amount of anterior displacement of the HB decreased with an increase in the severity of the Class III deformity. CONCLUSIONS: Our findings indicate the existence of a relationship between the magnitude of Class III malocclusion and HB displacement during swallowing.

Shade matching performance of normal and color vision-deficient dental professionals with standard daylight and tungsten illuminants.

STATEMENT OF PROBLEM: The lighting conditions of the environment and visual deficiencies such as red-green color vision deficiency affect the clinical shade matching performance of dental professionals. PURPOSE: The purpose of this study was to evaluate the shade matching performance of normal and color vision-deficient dental professionals with standard daylight and tungsten illuminants. MATERIAL AND METHODS: Two sets of porcelain disc replicas of 16 shade guide tabs (VITA Lumin) were manufactured to exact L*a*b* values by using a colorimeter. Then these twin porcelain discs (13 mm x 2.4 mm) were mixed up and placed into a color-matching cabinet that standardized the lighting conditions for the observation tests. Normal and red-green color vision-deficient dental professionals were asked to match the 32 porcelain discs using standard artificial daylight D65 (high color temperature) and tungsten filament lamp light (T) (low color temperature) illuminants. The results were analyzed by repeated-measures ANOVA and paired and independent samples t tests for the differences between dental professionals and differences between the illuminants (alpha=.05). RESULTS: Regarding the sum of the correct shade match scores of all observations with both illuminants, the difference between normal vision and red-green color vision-deficient dental professional groups was not statistically significant (F=4.132; P=.054). However, the correct shade match scores of each group were significantly different for each illuminant (P<.005). The correct shade matching scores of normal color vision dental professionals were significantly higher with D65 illuminant (t=7.004; P<.001). Color matching scores of red-green color vision-deficient dental professionals (approximately 5.7 more pairs than with D65) were significantly higher with T illuminant (t=5.977; P<.001). CONCLUSIONS.: Within the limitations of this study, the shade matching performance of dental professionals was affected by color vision deficiency and the color temperature of the illuminant. The color vision-deficient group was notably unsuccessful with the D65 illuminant in shade matching. In contrast, there was a significant increase in the shade matching performance of the color vision-deficient group with T illuminant. The lower color temperature illuminant dramatically decreased the normal color vision groups' correct shade matching score.

Effects of hyperbaric oxygen during experimental tooth movement.

OBJECTIVE: To determine the effects of hyperbaric oxygen (HBO) on bone remodeling during orthodontic tooth movement. MATERIALS AND METHODS: Twenty-four male, adult Sprague Dawley rats were randomly divided into two groups. HBO was administered in the first group, and the second group served as a control. The mandibular first molars were moved mesially by means of Ni-Ti closed coil springs in all groups. RESULTS: Results were evaluated histomorphometrically and the parameters of trabecular bone volume (BV/TV), trabecular bone number (Tr.N), and trabecular separation (Tr.Sep) were evaluated at the interradicular bone area of the mandibular first molars. Increases in BV/TV and Tr.N and decreases in Tr.Sep revealed the osteoblastic activity of HBO. HBO application caused an increase in bone apposition and osteoblastic activity or a decrease in osteoclastic activity. CONCLUSIONS: HBO enhanced the bone formation during experimental tooth movement. Therefore, the findings of this study support our hypothesis that osteoblastic activity might be modulated by changes in the environmental oxygen tension.

Esthetic rehabilitation of bilateral geminated teeth: a case report.

Geminated teeth are the consequences of developmental anomalies leading to the eruption of joined elements. According to current definitions, gemination occurs when one tooth bud tries to divide, while fusion occurs if two buds unite. Clinical experience shows, however that diagnosis can be complicated due to superimposed anomalies. This report describes a unique case of bilateral gemination of permanent maxillary central incisors. The esthetic rehabilitation of the geminated incisors accomplished utilizing all ceramic crowns. It is important that in these types of cases, reaching to the available esthetics and avoiding the complication of caries and periodontal problems with prosthetic application is satisfactory.

Vertical distraction osteogenesis of fibular bone flap in reconstructed mandible.

Excellent functional and aesthetic results can be achieved in mandibular reconstructions with using free fibular bone flap. However, the vertical deficiency between the reconstructed segment and the occlusal plane made dental rehabilitation impossible in some cases. We encountered this problem in our 3 patients who had mandibular reconstruction with fibular flap due to extensive bone defect result from gunshot injury. To overcome this segmental vertical distraction of the reconstructed mandible was performed. Fibular bone segments (40-70 mm) were distracted with using extraoral distraction device after a latency period of 5-7 days. The rate of distraction was 1 mm/day, and the rhythm was 4 times (4 x 0.25 mm). Distraction was continued until the desired height was achieved, and the distractor left in place for 12 weeks for bony consolidation. No minor or major complications were encountered. The increase of vertical height was between 9 and 13 mm, and it was stable during the follow-up period (7-22 months). Following the vertical distraction and vestibuloplasty operations, the dental restoration of the patients was performed with mandibular removable partial dentures.