It could be hypothesised that attachments, which provide more retention against  dislodgement forces, will be associated with more favourable parameters of oral function.. This in vivo study is designed to provide data regarding retention force and chewing efficiency at insertion,  after 3 and 6 months of function  with the use of  bar clip (group1)&telescopic  attachments(group 2) in mandibular overdenture treatment. Six healthy male  completely edentulous  patients will be selected from the outpatient clinic of Prosthodontic Department, Faculty of dentistry, Mansoura University, Egypt. Each patient  will receive three dental implants in the 2 in the canine region of the mandible bilateraaly  and one in the midline and two suprastructure modalities (bar and telescopic attachments ).  The retention force of the attachments at insertion , after 3 and six months was measured in a standardized way. The amount of retention  that was related to the attachment were evaluated. The difference in retention force at insertion , after 3 and 6 months observed for bar-clip attachments. Decrease of bar-clip  retention  from at insertion to 3& 6 months at bar attachment (from 20.07 to 9.1 and 6.5 , respectively). Slight  differences in retention force at insertion, after 3and 6 months were observed for telescopic attachments.(mean retention 8.5).chewing efficiency at insertion , 3 and 6 months was measured in s standardize way. The  mean chewing efficiency illustrates statistically significant higher mean among bar attachment than telescopic attachment at insertion , after 3 and 6 months. Chewing efficiency illustrates increased mean by increasing number of cycles.
Purpose:The aim of this within patient study was to evaluate the effect of linear distribution of implant supported mandibular over denture using bar and telescopic attachments on the retention and chewing efficiency.
Methods:Six male patients ofSix healthy male patients ranged between 48-60 years old were included in the study. For each patientrecieveda conventional complete denture before  implant surgery was performed in the midline and two canine areas. After healing period, the conventional  denture was converted into implant supported overdentureattached to three implants  and checked forretention  at insertion and 3 and 6 months later  by forcemeter and masticatory efficiency was evaluated at insertion 3 and 6 months later  by two-colored chewing gum.Repeated Measures ANOVA test was used to compare more than 2 studied periods with post Hoc test Tukey test. Two & three Way ANOVA tests were used to assess the effect of combination of 2 or 3 independent factors on continuous parametric outcome (retention and chewing efficiency ).
 
Results: Mean retention illustrates statistically significant higher value among Bar attachment than telescopic at insertion (20.07 and 8.5) , while there is statistically significant lower value among bar than telescopic attachment(6.5 and 8.83). Repeated Measures ANOVA illustrates statistically significant decrease of retention  from at insertion to 3& 6 months at bar attachment (from 20.07 to 9.1 and 6.5 , respectively). Mean chewing efficiency illustrates statistically significant higher mean among bar attachment than telescopic attachment at insertion , after 3 and 6 months. Chewing efficiency illustrates increased mean by increasing number of cycles.