***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: OBJECTIVES To ( i ) investigate the influence of different extensions of a laser microgrooved abutment zone on connective tissue attachment and ( ii ) assess the impact of a repeated abutment dis-/reconnection on soft- and hard-tissue healing . MATERIAL S AND METHODS Titanium implants were inserted epicrestally in the lower jaws of six dogs . Healing abutments with either partially ( LP ) or completely ( LC ) laser microgrooved margins or machined surface margins ( M ) were r and omly allocated either to a single (1 × )/repeated ( 2 × ) dis-/reconnection at 4 and 6 weeks ( test ) , respectively , or left undisturbed ( control ) . At 6 and 8 weeks , histomorphometrical ( e.g. most coronal level of bone in contact with the implant [ CBI ] , subepithelial connective tissue attachment [ STC ] ) and immunohistochemical ( Collagen Type-I [ CI ] ) parameters were assessed . RESULTS At control sites , LP/LC groups revealed lower mean CBL ( 8 weeks , 0.95 ± 0.51 vs. 0.54 ± 0.63 vs. 1.66 ± 1.26 mm ) , higher mean STC ( 8 weeks , 82.58 ± 24.32 % vs. 96.37 ± 5.12 % vs. 54.17 ± 8.09 % ) , but comparable CI antigen reactivity . A repeated abutment manipulation was associated with increased mean CBL ( 8 weeks , 1.53 ± 1.09 vs. 0.94 ± 0.17 vs. 1.06 ± 0.34 mm ) , decreased STC ( 8 weeks , 57.34 ± 43.06 % vs. 13.26 ± 19.04 % vs. 37.76 ± 37.08 % ) and CI values . CONCLUSIONS It was concluded that ( i ) LC > LP abutments enhanced subepithelial connective tissue attachment and preserved crestal bone levels , ( ii ) repeated abutment dis-/reconnection during the initial healing phase ( 4 - 6 weeks ) may be associated with increased soft- and hard-tissue changes and ( iii ) LP and LC should be considered using a one abutment , one time approach Previous research has demonstrated the effectiveness of laser-ablated microgrooves placed on implant collars to support direct connective tissue attachments to altered implant surfaces . Such a direct connective tissue attachment serves as a physiologic barrier to the apical migration of the junctional epithelium and prevents crestal bone resorption . The current prospect i ve pre clinical trial sought to evaluate bone and soft tissue healing patterns when laser-ablated microgrooves were placed on the abutment . A canine model was selected for comparison to previous investigations that examined the negative bone and soft tissue sequelae of the implant-abutment microgap . The results demonstrate significant improvement in peri-implant hard and soft tissue healing compared to traditional machined abutment surfaces BACKGROUND : If an implant with a rough surface is exposed to the oral cavity , it may accumulate greater amounts of plaque than a smooth surface , which may lead to severe problems with mucositis and peri-implantitis . The purpose of the present paper was to investigate the early inflammatory response to mucosa-penetrating abutments prepared with varying surface roughness . METHODS : Nine patients had all five of their original abutments exchanged to test abutments for a 4-week period . The test abutments were prepared with five different roughnesses . The surface roughness was measured with an optical profilometer . At the end of the test period , clinical evaluation was performed ; the health of the surrounding mucosa , the amount of accumulated plaque and marginal bleeding were registered . One biopsy was taken from each test abutment . Qualitative and quantitative histological evaluations were performed . RESULTS : There was a statistically significant difference between patients regarding the amount of accumulated plaque on the abutment surfaces and inflammatory cells , but no difference between the surface modifications in relation to plaque accumulation or number of inflammatory cells . CONCLUSION : No relation was found between inflammatory response and abutment surface roughness after an evaluation time of 4 weeks in a human test model The roughness of intraoral hard surfaces plays an important role in bacterial adhesion and colonization . Earlier studies have shown that rough surfaces accumulate up to 25 times more subgingival plaque than do smooth sites . In the present study , the influence of surface smoothing was studied . In six partially edentulous patients waiting for a fixed prosthesis supported by endosseous titanium implants , four titanium abutments with different surface roughness were r and omly placed . After 1 month of intraoral exposure , subgingival plaque sample s from each abutment were compared within each patient by means of differential phase-contrast microscopy . After 3 months , supragingival and subgingival plaque sample s were taken from all abutments for differential phase-contrast microscopy and culturing . Probing depth , recession , and bleeding upon probing were scored at the same visit . Differential phase-contrast microscopy showed that subgingivally , only the two roughest abutments harbored spirochetes after 1 month . After 3 months , subgingivally , the composition of the flora showed little variation on the different abutment types , although spirochetes were only noticed around the roughest abutments . Anaerobic culturing result ed in comparable amounts of colony-forming units for all abutment types , both supragingivally and subgingivally . Subgingivally , the microbiologic composition did not show major interabutment differences . Clinical ly , small differences in probing depth were observed . The roughest abutment showed some attachment gain ( 0.2 mm ) during 3 months , whereas all other abutments had an attachment loss ranging from 0.8 to greater than 1 mm . The results indicate that a reduction in surface roughness ( less than a roughness of 0.2 micron ) had no major effect on the microbiologic composition , supragingivally or subgingivally . These observations indicate the existence of a threshold roughness below which no further impact on the bacterial adhesion and /or colonization should be expected . However , clinical evaluation seems to indicate that a certain surface roughness is necessary for increased resistance to clinical probing OBJECTIVES To histologically evaluate and compare the performance of healing abutments with either hydrophobic or hydrophilic surface properties in humans . MATERIAL S AND METHODS According to a parallel-group design , titanium implants placed in the posterior m and ible and maxilla of 30 patients were r and omly assigned to either ( 1 ) hydrophobic machined ( M ) , ( 2 ) chemically modified hydrophilic ( mod ) acid etched ( MA ) titanium ( Ti ) ( modMA1 ) or ( 3 ) modMA Ti- Zirconium alloy ( modMA2 ) healing abutments and left to heal in a transmucosal position . At 8 weeks , the abutments and a limited soft tissue biopsy were harvested according to a st and ardized procedure and processed for histological analysis ( primary outcomes : percentage epithelial- ( EC ) and subepithelial connective tissue contact ( CTC ) to the abutment surface ) . RESULTS The surgical procedure was associated with an incomplete mucosal coverage of the study abutments in nine patients , and an unintentional submerged healing procedure in three patients . Per protocol analysis ( 18 patients ) has pointed to an improved quantitative EC [ modMA2 ( 53.45 ± 28.25 ) > modMA1 ( 32.25 ± 24.3 ) > M ( 23.15 ± 16.09 ) ] and CTC [ modMA2 ( 75.12 ± 43.22 ) > modMA1 ( 69.41 ± 46.74 ) > M ( 47.63 ± 19.28 ) ] ( % ) to modMA surfaced abutments . CONCLUSIONS It was concluded that modMA surfaces may have the potential to enhance soft tissue adhesion at the transmucosal aspect of titanium dental implants 
    Output:
    
The human histologic studies showed evidence of perpendicular insertion of human gingival fibroblasts into the treated abutment surface .
Laser-ablated , hydrophilic , and oxidized titanium surfaces result ed in this type of attachment .
Epithelial cells seem to slightly favor zirconia and polished titanium surfaces .
Improvements in the surface topography and macro design of dental abutments might improve biocompatibility and adherence to soft tissue ; however , manipulation of soft tissue and second-stage surgery could negate any advantages of the improved surfaces