***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 To prospect ively evaluate peri-implant bone and soft tissue dimension changes around adjacent implants placed at different horizontal interimplant distances . MATERIAL S AND METHODS Thirty partially edentulous patients , who underwent rehabilitation with two adjacent implant-supported crowns as part of their treatment plan , were assigned to three groups based on their prosthetic needs . Patients in group A ( 10 patients , 20 implants ) were to have two implants placed at a 2-mm interimplant distance , patients in group B ( 10 patients , 20 implants ) were to have two implants placed at a 3-mm interimplant distance , and patients in group C ( 10 patients , 20 implants ) were to have two implants placed at an interimplant distance of > 4 mm according to their prosthetic needs . All patients received single-crown restorations after 3 months . Clinical examinations were performed at the time of crown placement ( T3 ) , and 6 months ( T6 ) , 12 months ( T12 ) , and 24 months ( T24 ) after implant placement . Peri-implant bone levels were assessed radiographically at the time of implant placement ( T0 ) , and at T3 , T12 , and T24 . RESULTS One patient from group C did not return for follow-up examinations after implant placement . The mean ( ± st and ard deviation ) horizontal interimplant distance was 1.97 ± 0.44 mm for implants in group A , 3.12 ± 0.15 mm for implants in group B , and 5.3 ± 0.64 mm for implants in group C. For group A , the mean marginal bone loss was 0.29 ± 0.51 mm at the T0-T3 interval , 0.31 ± 0.36 mm at the T0-T12 interval , and 0.27 ± 0.33 mm at the T0-T24 interval . For group B , the mean marginal bone loss was 0.16 ± 0.29 mm at the T0-T3 interval , 0.20 ± 0.28 mm at the T0-T12 interval , and 0.23 ± 0.28 mm at the T0-T24 interval . For group C , the mean marginal bone loss was 0.51 ± 0.84 mm at the T0-T3 interval , 0.45 ± 0.72 mm at the T0-T12 interval , and 0.44 ± 0.74 mm at the T0-T24 interval . For group A , the mean midproximal bone loss was 0.33 ± 0.50 mm at the T0-T3 interval , 0.45 ± 0.35 mm at the T0-T12 interval , and 0.40 ± 0.32 mm at the T0-T24 interval . For group B , the mean midproximal loss was 0.31 ± 0.37 mm at the T0-T3 interval , 0.32 ± 0.39 mm at the T0-T12 interval , and 0.33 ± 0.42 mm at the T0-T24 interval . For group C , the mean midproximal bone loss was 0.40 ± 0.44 mm at the T0-T3 interval and 0.41 ± 0.50 mm at both the T0-T12 and T0-T24 intervals . There were no statistically significant differences in marginal and midproximal bone crest loss between the different groups at any time point . CONCLUSION The study failed to support the hypothesis that horizontal interimplant distance has an effect on peri-implant bone and soft tissue dimension changes for implants with internal conical implant-abutment interface connection and platform-switching characteristics PURPOSE The aim of this pilot study was to determine what effect thin mucosal tissues can have on crestal bone stability around implants with platform switching . MATERIAL S AND METHODS Twelve 2-piece implants  , consisting of 6 implants with horizontally matching implant-abutment connection ( control ) and 6 implants with platform switching ( test )  were placed in 4 patients . The mean age of the patients was 43 years ( range , 37 to 56 yrs ) . Mucosal tissue thickness  at implant sites was measured to be 2 mm or less .  Implants  were restored with 5 splinted crowns and single 3-unit fixed partial denture . Intraoral radiographs were obtained and crestal bone changes were measured at implant placement and after a 1-year follow-up post-treatment . The statistical significance level was set to P less than .05 . RESULTS Bone loss around the test implants was 1.81 + /- 0.39 mm on the mesial site and 1.70 + /- 0.35 mm on the distal aspect . Control implants overcame marginal bone resorption equaling 1.60 + /- 0.46 mm on the mesial site and 1.76 + /- 0.45 mm on distal measurement . No statistically significant difference was found between control and test implants either mesially ( F([1,10 ] ) = 0.746 ; P = .408 ) or distally ( F([1,10 ] ) = 0.080 ; P = .783 ) . CONCLUSION Within the limitations of this pilot study it can be concluded that implants with platform switching did not preserve crestal bone better in comparison with implants with traditional implant-abutment connection if , at the time of implant placement , thin mucosal tissues were present AIM To evaluate the peri-implant tissues in patients with two adjacent implant crowns in the aesthetic zone , treated with either two adjacent implants with a scalloped platform or with a flat platform . MATERIAL AND METHODS Forty patients were r and omly allocated to : ( 1 ) a  " scalloped implant group " : 20 patients treated with two adjacent implants with a scalloped platform , and ( 2 ) a " flat implant group " : 20 patients treated with two adjacent implants with a flat platform .  Clinical and radiographic examinations were performed during a 1-year follow-up period to assess hard and soft tissue changes . RESULTS The scalloped implant group showed significantly more marginal bone loss ( scalloped : 2.7±1.4 mm , flat : 0.9±0.8 mm ) and more inter-implant bone crest loss ( scalloped : 1.8±1.4 , flat : 1.0±0.9 mm ) than the flat implant group . There was no significant difference between the groups with regard to the papilla index and patients ' satisfaction . CONCLUSION After 1 year of function , there was more bone loss around scalloped implants than around flat implants . With regard to the presence of papilla , there were no differences between the groups . With both applied implant design s , it is difficult to establish a predictable and harmonious aesthetic result , especially regarding the peri-implant mucosa . Patients were very satisfied with the aesthetic outcome of the adjacent implants irrespective of the treatment concept applied PURPOSE The aim of this clinical trial was to evaluate the influence of gingival tissue thickness on crestal bone loss around dental implants  after a 1-year follow-up . MATERIAL S AND METHODS Forty-six implants ( 23 test and 23 control ) were placed in 19 patients . The test implants were placed about 2 mm supracrestally , whereas the control implants were positioned at the bone level . Before implant placement , the tissue thickness at implant sites was measured with a periodontal probe . After healing , metal-ceramic cement-retained prostheses were constructed . According to tissue thickness , the test implants were divided into A ( thin ) and B ( thick ) groups . Intraoral radiographs were performed and crestal bone changes were measured at implant placement and after 1 year . RESULTS Mean bone loss around the test implants in group A ( thin mucosa ) was 1.61 + /- 0.24 mm ( SE ; range , 0.9 to 3.3 mm ) on the mesial and 1.28 + /- 0.167 mm ( range , 0.8 to 2.1 mm ) on the distal . Mean bone loss in test group B ( thick mucosa ) implants was 0.26 + /- 0.08 mm ( range , 0.2 to 0.9 mm ) on the mesial aspect and 0.09 + /- 0.05 mm ( range , 0.2 to 0.6 mm ) on the distal aspect . Mean bone loss around control implants was 1.8 + /- 0.164 mm ( range , 0.6 to 4.0 mm ) and 1.87 + /- 0.166 mm ( range , 0.0 to 4.1 mm ) on the mesial and distal aspects , respectively . Analysis of variance revealed a significant difference in terms of bone loss between test A ( thin ) and B ( thick ) groups on both the mesial and the distal . CONCLUSION Initial gingival tissue thickness at the crest may be considered as a significant influence on marginal bone stability around implants . If the tissue thickness is 2.0 mm or less , crestal bone loss up to 1.45 mm may occur , despite a supracrestal position of the implant-abutment interface 
    Output:
    
Based on the available evidence , it is not possible to define a precise threshold for the optimal horizontal distance between two adjacent implants