Aim:The aim of this study is to evaluate the effect of different cross-sections of bar connecting two implants on the retention of mandibular overdentures with Hader clip or lined with heat-cured resilient liner as a housing material. The retentive values after simulated 1.5 years of service were also recorded.Materials and Methods:Edentulous mandibular acrylic model was constructed with two dummy implants located in the canine region and connected with cast bar assembly. According to bar cross-section and anchoring method, four groups (n = 10) of identical overdentures were used as Hader bar/clip group (HCG), Hader bar/silicone liner female housing group (HSG), oval bar/silicone liner female housing group (OSG), and round bar/silicone liner female housing group (RSG). Each overdenture sample was subjected to simulated wear up to 2740 manual insertions/separations. The mean retentive forces were measured at the baseline and after every 500 insertions. The data were statistically analyzed using one-way analysis of variance.Results:The present study demonstrated that all bar cross-sections showed a significant difference at the baseline (P < 0.05), but HSG showed greater initial retention compared to HCG, OSG, and RSG. OSG showed a significant higher retention after 2740 insertions (simulated five insertions/day).Conclusions:Within the limitation of this in vitro study and for a similar period of service, heat-cured silicone female housing for Hader bar could maintain greater retention for two-implant-retained overdentures than provided by conventional plastic clip after 1.5 year. The oval bar recorded reasonable initial retention values and maintained these values for 1.5 years of service.
To evaluate the effect of mesiodistal tilting of the terminal implants on the stresses distribution around the implant, a three dimensional (3D) model is designed by simulating an edentulous mandible, restored with mandibular cantilever bar overdenture and retained by 3 interforaminal implants. All the parameters are fixed except for the tilt of the terminal implants. Vertical and oblique loads are applied on one side. The stress distribution around the implants in each situation was recorded and compared to correlate the stress magnitude to the implant tilt. The change in the implant tilt resulted in significant change of the stress distribution pattern around the implants where anticantilever tilting of the implant collar resulted in a more homogenous stress distribution, while tilting the collar towards the cantilever direction resulted in stress accentuation at the distal aspect. Tilting the implant collar can be beneficial in improving the stress distribution pattern around the implants in cantilever situations.
Objectives: The aim of this 2-years cross-over study was to radiographically compare the influence of palatal contouring of maxillary denture on oro-pharyngeal airway space.
Methods:The study was conducted on 20 healthy patients who were completely edentulous in the maxilla and mandible. All patients were randomly allocated in two equal groups to receive a mandibular denture opposed by a maxillary denture with either an arbitrary contoured palate (ACP) or a functional contoured palate (FCP) at the start of the study. The maxillary denture was exchanged after 1 year from insertion. The oropharyngeal volume (OPV) and minimum cross sectional area (CSA) were measured by using CBCT.
Results:After 12 months of denture insertion, the mean OPV was more with FCP (29.9±3.1cm 3 ) compared to ACP denture (24.9±2.2 cm 3 ), also the mean CSA was more with FCP denture (363.7±67.3mm 2 ) compared to ACP denture (286.5±65.8mm 2 ). There was a high positive correlation between OPV and CSA with FCP denture ( r=0.90) and ACP denture (r= 0.61).
Conclusion:Within this limited study, fabricating a complete denture with functionally contoured palatal surface may have a positive role in maintaining the oropharyngeal airway patency especially in old patients.(1598) -Khalek, et al.
Abdel
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