Craniocervical posture and hyoid bone position in children with mild and moderate asthma and mouth breathing

Introduction The objective of the present study was to assess the craniocervical posture and the positioning of the hyoid bone in children with asthma who are mouth breathers compared to non-asthma controls. Methods The study was conducted on 56 children, 28 of them with mild (n = 15) and moderate (n = 13) asthma (14 girls aged 10 79 +/- 1 31 years and 14 boys aged 9 79 +/- 1.12 years), matched for sex, height, weight and age with 28 non-asthma children who are not mouth breathers The sample size was calculated considering a confidence interval of 95% and a prevalence of 4% of asthma in Latin America. Eighteen variables were analyzed in two radiographs (latero-lateral teleradiography and lateral cervical spine radiography), both obtained with the head in a natural position The independent t-test was used to compare means values and the chi-square test to compare percentage values (p < 0 05) Intraclass correlation coefficient (ICC) was used to verify reliability. Results. The Craniovertebral Angle (CVA) was found to be significantly smaller in asthma than in control children (106.38 +/- 766 vs. 111 21 +/- 7.40. p = 0 02) and the frequency of asthma children with an absent or inverted hyoid triangle was found to be significantly higher compared to non-asthma children (36% vs 7%, p = 0.0001). The values of the inclination angles of the superior cervical spine in relation to the horizontal plane were significantly higher in moderate than in mild asthma children (CVT/Hor 85 10 +/- 725 vs. 90 92 +/- 6.69, p = 0 04 and C1/Hor. 80 93 +/- 5.56 vs 85 00 +/- 4 20, p = 0 04) Conclusions These findings revealed that asthma children presented higher head extension and a higher frequency of changes in hyoid bone position compared to non-asthma children and that greater the asthma severity greater the extension of the upper cervical spine. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

An in vitro study of non-axial forces upon the retention of an O-ring attachment

Objective The purpose of this study was to evaluate the retention force of an O-ring attachment system in different inclinations to the ideal path of insertion, using devices to compensate angulations. Material and methods Two implants were inserted into an aluminum base, and ball attachments were screwed to implants. Cylinders with O-rings were placed on ball attachments and connected to the test device using positioners to compensate implant angulations (0 degrees, 7 degrees, and 14 degrees). Plexiglass bases were used to simulate implant angulations. The base and the test device were positioned in a testing apparatus, which simulated insertion/removal of an overdenture. A total of 2900 cycles, simulating 2 years of overdenture use, were performed and 36 O-rings were tested. The force required for each cycle was recorded with computer software. Longitudinal sections of ball attachment-positioner-cylinder with O-rings of each angulation were obtained to analyze the relationship among them, and O-ring sections tested in each angulation were compared with an unused counterpart. A mixed linear model was used to analyze the data, and the comparison was performed by orthogonal contrasts (alpha=0.05). Results At 0 degrees, the retention force decreased significantly over time, and the retention force was significantly different in all comparisons, except from 12 to 18 months. When the implants were positioned at 7 degrees, the retention force was statistically different at 0 and 24 months. At 14 degrees, significant differences were found from 6 and 12 to 24 months. Conclusions Within the limitations of this study, it was concluded that O-rings for implant/attachments perpendicular to the occlusal plane were adequately retentive over the first year and that the retentive capacity of O-ring was affected by implant inclinations despite the proposed positioners. To cite this article:Rodrigues RCS, Faria ACL, Macedo AP, Sartori IAM, de Mattos MGC, Ribeiro RF. An in vitro study of non-axial forces upon the retention of an O-ring attachment.Clin. Oral Impl. Res. 20, 2009; 1314-1319.doi: 10.1111/j.1600-0501.2009.01742.x.