Background. The upper airway volume is among the factors that affect orthodontic treatment plans. Cone-beam computed tomography (CBCT), as an accurate diagnostic modality, can help assess anatomical structures associated with the upper airway volume.Objectives. This study aimed to use CBCT to determine if there are differences in the upper airway volume between different sagittal and vertical skeletal patterns, considering the hyoid bone position, palatal depth, nasal septum deviation (NSD), and concha bullosa. Material and methods.From among 105 initial CBCT samples retrieved from the archive of a private radiology clinic in Tehran, Iran, 90 CBCT scans of 27 males and 63 females aged 17-65 years were considered in the study according to the inclusion criteria. The upper airway volume was assessed with regard to Angle's classification (using the A point-nasion-B point angle (ANB)), the vertical skeletal dimension (using the sella-nasion plane to mandibular plane angle (SN-MP)), the hyoid bone position, palatal depth, NSD, and concha bullosa, using CBCT and the NNT ® software. The one-way analysis of variance (ANOVA), Levene's test and the t test were used to analyze the data with the SPSS Statistics for Windows software, v. 17.0.Results. The upper airway volume was significantly smaller in long-face cases (p = 0.037). There was no significant correlation between the upper airway volume and Angle's classification, the hyoid bone position, palatal depth, NSD, and concha bullosa.Conclusions. The vertical skeletal dimension was the only parameter that was related to the upper airway volume. The results of this study can be considered while preparing orthodontic treatment plans.

Background: Extensive restorative treatments of anterior primary teeth are challenging in pediatric dentistry. Objective: This study aimed to compare the fracture resistance of three post types for restoring the anterior primary teeth. Methods: This in-vitro study was carried out on 90 extracted maxillary anterior primary teeth with intact roots. They were randomly allocated into six groups to be restored with conventional composite resin post, X-tra fill composite resin post, Tetric N Ceram composite resin post, prefabricated glass fiber post with conventional composite build-up, prefabricated glass fiber post with X-tra fill composite build-up, and prefabricated glass fiber post with Tetric N Ceram composite build up. The samples were polished and placed in acrylic resin blocks with 1 mm of part of cervical root being out, thermocycled (×5000) and tested for fracture resistance. Intra-class correlation test, Kruskal-Wallis test and one-way ANOVA were used for statistical analyses (α=0.05). Results: The mean fracture resistance was significantly different among the six groups. It was the highest in prefabricated glass fiber post with conventional composite build-up (418.64 N), prefabricated glass fiber post with X-tra fill composite build-up (403.63 N) and prefabricated glass fiber post with Tetric N Ceram composite build up (361.63 N); and the lowest in Tetric N Ceram group (280.65 N). The groups were significantly different concerning the fracture strength and fracture state. Conclusion: Since the anterior teeth restored with prefabricated glass fiber posts were far more fracture resistant, and prefabricated glass fiber posts can be promisingly used for the restoration of anterior primary teeth.

Background: Stainless steel crowns are proposed to restore severely decayed teeth in pediatric dentistry. Yet, their retention is still debatable. Objective: This study aimed to investigate whether dental tissue reconstruction before placement of stainless steel crown on pulpotomized first primary molar affects the retention of stainless steel crowns. Methods: This experimental in-vitro study was performed on 30 extracted first primary molars with carious occlusal and distal surfaces. Dental caries and the pulp chamber roof were respectively removed. The stainless steel crowns were placed after tooth preparation. The samples were randomly divided into two groups (n=15) i.e, ZoE core buildup, and ZoE liner. Stainless steel crowns were cemented with self-curing glass ionomer cement. The crown retention was tested with the Instron testing machine. The two groups were compared by using SPSS software through the t-test (α=0.05). Results: The mean crown retention in the liner group (291.45±43.196 N) was significantly higher than that of the core buildup group (202.00±63.515 N) (P=0.001). Conclusion: Based on the results of this study for restoring the teeth with extensive tissue loss by SSC, ZoE should be used as lining without a core on teeth.

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