***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: PURPOSE The present study evaluated implant and peri-implant outcomes as well as prosthodontic  maintenance efforts for implant/bar-supported m and ibular prostheses with different prosthesis anchorage systems . MATERIAL S AND METHODS Seventy-six patients who received two or four interforaminal implants  were assigned to one of three different bar design s and subsequently to different prosthesis supporting systems . Forty-nine patients received implants and a mucosa-supported implant-retained overdenture ( OD ) with an ovoid bar ( two implants ; design 1 ) or multiple ovoid bars ( four implants ; design 2 ) . Twenty-seven patients received four implants and a rigid implant-supported prosthesis ( ISP ) with a milled bar ( design 3 ) . Implant survival , peri-implant parameters ( marginal bone resorption , pocket depth , and plaque , bleeding , gingival , and calculus indices ) , and postinsertion prosthodontic maintenance were followed over a 5-year period and compared among the different retention modalities . At the most recent follow-up examination , subjective patient satisfaction was additionally evaluated using a simplified scoring system ( ranging from 1 = not satisfactory to 5 = excellent ) . RESULTS Implant survival rates ( 100 % ) and all peri-implant parameters evaluated showed no differences among the three design s used for implant prosthesis anchorage . Prosthodontic maintenance did not differ between the different ODs ( OD design 1 : average of 1.04 maintenance visits/year/patient ; OD design 2 : 1.2 maintenance visits/year/patient ) , but it was significantly lower for the dentures that were rigidly stabilized with milled bars ( ISP : 0.37 maintenance visits/year/patient ) . A high subjective satisfaction rate ( range : 4.5 to 5.0 ) was registered at the final examination , without any differences among the design s used . CONCLUSIONS Rigid anchorage with milled bars on four-implant prostheses combined with a metal-reinforced framework showed a lower extent of prosthodontic maintenance issues than round bars on two- or four-implant overdentures with resilient denture stabilization . Nevertheless , implants and peri-implant structures were not negatively affected by either resilient or rigid anchorage mechanisms This study is a two-center clinical trial with the aim to assess the treatment effects of  implant-retained m and ibular overdentures versus conventional complete dentures .  Treatment had been assigned according to a balanced allocation method . The following criteria were used to enhance the comparability of the treatment groups : age , gender , the edentulous period of the m and ible , the number of previously made m and ibular dentures , the number of years having worn the present m and ibular denture and the symphyseal bone height . 151 patients with severely resorbed m and ibles participated in the study , they were treated at two centers . Ninety-one patients received an implant-retained m and ibular overdenture ( IRO ) and 60 patients a conventional complete denture ( CD ) .  Since some patients refused the allocated treatment the " Intention To Treat " principle was applied . This implies that patients are evaluated in the originally allocated treatment group regardless of the actual treatment they received . Patient 's experiences were evaluated before treatment and 1 yr after insertion of the new dentures . Results before treatment showed that both treatment groups were comparable : they were dissatisfied with their m and ibular denture and they could hardly chew tough or hard foods . One year after insertion of the new dentures the IRO-group was satisfied with their m and ibular denture , whereas only one third of the CD-group was satisfied . With respect to the chewing ability the IRO-group scored significantly better than the CD-group(P<0.0001 ) PURPOSE The aim of this research was to determine the long-term prosthodontic maintenance requirements of m and ibular two-implant overdentures using different loading protocol s and attachment systems . MATERIAL S AND METHODS A total of 106 participants were allocated r and omly to one of  four  different implant systems ( Steri-Oss , Southern , Straumann , or Branemark ) . Three different loading protocol s ( 2 , 6 , and 12 weeks ) were used with six different ball abutment patrices and their respective matrices ( Steri-Oss rubber , Straumann gold , Straumann titanium , Branemark gold , Southern plastic , and Southern gold/platinum ) . Prosthodontic maintenance events were documented prospect ively from baseline until the 8-year recall according to predefined categories . RESULTS After 6 years , 90 participants attended recall and , thereafter , 68 participants were followed for 8 years . No significant differences were found between the number of prosthodontic maintenance events and the loading protocol used . Steri-Oss rubber matrices had the highest mean number of maintenance events at 32.2 ± 14.5 events , followed by the Branemark gold matrices at 28.8 ± 12.6 events . The Southern plastic matrices had a significantly lower mean number of maintenance events ( 8.7 ± 4.2 ) when compared with all other groups . Over a 6-year period , the matrices with the best longevity were Straumann gold at 3.9 ± 2.1 years . Straumann gold matrices also lasted significantly longer than all other matrices ( P < .05 ) . Southern gold/platinum , Branemark gold , and Southern plastic matrices all lasted significantly longer than the Straumann titanium and Steri-Oss matrices ( P < .05 ) . The mean time to reline for overdentures was 3.37 ± 2.06 years ; remaking of overdentures peaked by year 7 , with a mean time to remake of 5.81 ± 2.04 years . CONCLUSION Early loading protocol s do not influence long-term prosthodontic maintenance requirements of unsplinted m and ibular two-implant overdentures . By contrast , attachment systems do influence prosthodontic maintenance , particularly with regard to the type of matrices used PURPOSE This prospect i ve study evaluated the prosthodontic maintenance requirements during the first year of service of m and ibular overdentures supported by two unsplinted implants  using three different implant systems . MATERIAL S AND METHODS Seventy-two patients r and omly allocated to three equal groups were each provided with a conventional complete maxillary denture and a m and ibular overdenture supported by two unsplinted implants .  A different implant system was used for each group ( Steri-Oss , ITI , or Southern Implants ) , and their prosthodontic maintenance requirements were compared , primarily for the patrix and matrix . Additional maintenance categories recorded included any type of overdenture fracture , reline or remake of the overdenture , and maintenance of the maxillary denture . RESULTS Sixty-eight percent of the patients , regardless of implant system , required prosthodontic maintenance in the first year , most commonly for the matrices . The Southern Implants matrices required less maintenance than those of Steri-Oss or ITI ( P < .05 ) . Additional overdenture maintenance was required by 28 % of patients , irrespective of implant system . When all categories of prosthodontic maintenance were combined , there were no differences between implant groups . Evaluation of overall prosthodontic success using six-field tables revealed statistically significant differences between the three implant systems , with more ITI and Steri-Oss patients than Southern Implants patients requiring overdenture retreatment ( repair ) . CONCLUSION During the first year of service , the matrix maintenance requirements of Southern Implants were significantly lower than those of the ITI or Steri-Oss groups ; this was reflected in the number of retreatment ( repair ) categories recorded . Although the three systems did not differ significantly for overall prosthodontic maintenance , both the Steri-Oss and the ITI titanium matrices showed problems of clinical significance PURPOSE Implant success , peri-implant conditions , and prosthodontic maintenance requirements were evaluated and compared for m and ibular overdentures supported by two implants and retained with ball or resilient telescopic crown attachments during a 5-year period . MATERIAL S AND METHODS Twenty-five patients with an edentulous m and ible each received two root-form dental implants in the m and ibular interforaminal ( canine ) region . The type of denture attachment was chosen r and omly ; 13 patients received ball attachments and 12 patients received resilient telescopic crowns .  Implant success and peri-implant conditions ( bone resorption , pocket depth , Plaque Index , Gingival Index , Bleeding Index ) as well as prosthodontic maintenance and patient satisfaction were evaluated annually during a 5-year follow-up period and compared with respect to the two retention modalities used . RESULTS Implant success , peri-implant conditions , and subjective patient satisfaction scores did not differ between the two retention modalities used . However , during the 5-year observation period , significantly more postinsertion complications/ interventions for maintenance purpose s were registered in the ball group ( 87 interventions , 61.1 % ) than in the telescopic crown group ( 53 interventions , 37.9 % ; P < .01 ) . Differences in prosthodontic maintenance efforts were most significant in the second and third years ( P < .05 ) of the follow-up period but were similar at the end of the study for both anchorage systems . CONCLUSION Both ball attachments and resilient telescopic crowns on isolated implants in the atrophic m and ible are viable treatment options for implant-supported overdentures . No implant losses , good peri-implant conditions , and general patient satisfaction were noted . Although the frequency of technical complications was initially higher with ball attachments than with resilient telescopic crowns over a 5-year period , similar frequencies of maintenance efforts may be anticipated for both retention modalities In this prospect i ve multicenter study , non-submerged ITI implants were followed in order to evaluate their long-term prognosis in fully edentulous jaws . A total of 1286 implants were inserted in 233 consecutive patients and , after a healing period of three to six months , the successfully integrated implants were restored with 163 overdentures and 95 fixed full-arch bridges . This prospect i ve study not only calculated the 10-year cumulative survival and success rates for the 1286 implants by life table analysis , but also evaluated the actual survival and success rates for 498 implants after at least five years of functional loading . In addition , cumulative success rates were calculated for implant subgroups according to implant length and location . Additional analyses were performed to evaluate the estimated and actual survival and success rates of the implants in relation to various prosthetic rehabilitation techniques . The 10-year cumulative survival and success rates were 95.9 % and 92.7 % , respectively . The actual 5-year survival and success rates of the first 498 implants that were inserted were 97.7 % and 95.0 % , respectively . The analysis of implant subgroups showed slightly more favourable cumulative success rates for 12 mm long implants ( 93 % ) , in comparison to 10 mm and 8 mm long implants ( 91.6 % and 89.6 % , respectively ) . The cumulative success rate for m and ibular implants ( approximately 94 % ) was also more favourable than that for maxillary implants ( approximately 91 % ) . Patients who were loaded with both maxillary and m and ibular prostheses maintained success rates well above 90 % ; while only implants that were inserted to support maxillary overdentures that were retained by Dolder bars showed a success rate below 90 % 86 patients , in 2 Sc and inavian centers , participated in a prospect i ve study of m and ibular edentulism , treated with overdentures supported by Bioceram sapphire implants .  Implant success and prosthesis stability as well as parameters for peri-implant health were evaluated . Masticatory function and complications were also documented . The study began in 1991 and clinical treatment of the last patients was completed in 1991 . The patients have been followed for at least 3 years , and up to 12 years . 4 patients were lost to follow-up . Of the initial 324 implants , 7 implants failed before prosthetic treatment . 3 patients lost 1 implant each within the 1st year , and 4 patients lost all 4 implants . 16 implants were lost between 36 and 42 months in function , due to lack of osseointegration and pain . The loss of implants could be attributable to an association , not statistically verified , between bone quality and anatomy , with heavy smoking as a risk factor . Based on the remaining implants , the cumulative implant success rates were 95.2 % , 91.3 % , 91.3 % , 91.3 % at 3 , 5 , 10 and 12 year follow-up respectively . The cumulative success rates for overdentures were 96.4 % , 92.8 % and 92.8 % respectively , for the same follow-up periods . Indices for the health of the peri-implant mucosa disclosed no serious inflammatory reactions in the surrounding soft tissues . Patient satisfaction with this form of oral rehabilitation was high in all but 2 patients who experienced discomfort This prospect i ve study has been design ed to compare the results of immediate and delayed loading of implant-retained m and ibular overdentures after a 2-year follow-up . Twenty patients have been r and omly divided into two groups . Group 1 patients ( test group ) received four ITI implants in the intraforaminal area of the m and ible . Octa abutments were immediately screwed on implants ; 2 days after surgery , the implants were rigidly connected with a U-shaped Dolder gold bar and loaded with an overdenture . Group 2 patients ( control group ) received , in the same area , the same type and number of implants , which were left to heal according to the st and ard protocol . At 3 - 4 months , Octa abutments were screwed on the implants and the same prosthetic procedure of the test group was applied . The minimum follow-up period lasted 2 years , with recall appointments at 2 weeks ,  
    Output:
    
Rehabilitations with 2 implants showed more complications and required more maintenance according to the connection type .
Given the limitations of this review , m and ibular overdentures with 4 implants showed better results with respect to survival and success rates , especially those with a bar connection .