dental implant - supported overdentures have been documented to be a predictable and successful option to treat edentulous patients [ 1 , 2 ] . currently , with the evolution of implant surfaces , osseointegration of implants is less of a challenge . however , the stability and health of the peri - implant soft tissue is necessary for the success and the long - term maintenance of dental implants . two millimeters wide band of keratinized tissue has been considered clinically desirable to provide a soft tissue seal around natural teeth . however , controversy still remains over the necessity for a band of keratinized tissue around dental implants [ 69 ] . the role of dental plaque in the etiology of peri - implant diseases is well documented in the literature [ 10 , 11 ] . the absence of periodontal ligament , supracrestal fibers attachment around dental implants may make peri - implant tissue more susceptible to an inflammatory process caused by plaque accumulation . several studies have reported increased gingival and plaque index scores , mucosal recession , and marginal bone resorption in areas around implants with less than 2  mm of keratinized tissue [ 4 , 8 , 1316 ] . conversely , some authors have claimed that , with adequate plaque control , peri - implant tissues can be maintained in a healthy state with a minimum amount of keratinized tissue [ 69 ] . however , patient discomfort has been reported to be associated with insufficient keratinized tissue in implant - supported overdentures . in many cases , performing oral hygiene was reported to be painful as a result to the absence of the keratinized tissue surrounding the implant . moreover , discomfort has been related to mechanical irritation due to the mobility of the nonkeratinized tissue under function [ 17 , 18 ] . in 1999 , kaptein et al . investigated the peri - implant tissue health of loaded implants . there was a significantly higher gingival index and probing depth in overdenture versus fixed prosthesis cases . it has been reported that implants supporting overdentures had more risk for bone loss , based on poorer peri - implant tissue health . investigated the association between the width of the keratinized tissue and the health status of the soft tissue around implants supporting overdentures . they concluded that the absence of adequate keratinized tissue was associated with a higher plaque accumulation , gingival inflammation , bleeding on probing , and mucosal recession . to date , there are a limited number of studies that discuss peri - implant tissue health and the presence of keratinized tissue around implants supporting overdentures [ 1719 ] . these studies conclude that the presence of keratinized tissue around implant - supported overdentures is a factor effecting bone maintenance and soft tissue health around those implants [ 17 , 18 ] . various surgical procedures have been developed to preserve and/or reconstruct keratinized tissue around dental implants [ 2024 ] . these techniques , including apically positioned flaps , pedicle grafts , free gingival grafts , and connective tissue grafts , can be performed prior to implant placement , during the second stage surgery or after delivery of the final prosthesis . allogenic and xenogenic soft tissue grafts have also been used as other options for increasing peri - implant keratinized tissue [ 2427 ] . the purpose of this retrospective case series was to describe and compare different surgical techniques that can be utilized to augment the keratinized soft tissue around dental implant - supported overdentures . this data set was extracted as deidentified information from the routine treatment of patients at the ashman department of periodontology and implant dentistry at new york university college of dentistry . this study is in compliance with the health insurance portability and accountability act ( hipaa ) requirements . eight edentulous cases were selected from the i d to be included in this retrospective study . patients were treated for lack of keratinized tissue prior to implant placement , during the second stage surgery or after delivery of the prosthesis . the population consisted of 2 females and 6 males , with a mean age of 65 years ( range : 54 to 83 ) . in 7 out of 8 , patients who underwent implant surgery and were restored with a maxillary and/or mandibular implant - supported overdenture.patients wearing a maxillary and/or mandibular implant - supported overdenture.clinical symptoms of discomfort or difficulty to perform oral hygiene due to insufficient keratinized tissue around implant - supported overdentures . insufficient was defined as < 2  mm of keratinized gingiva.patients who underwent a surgical procedure to increase keratinized tissue around implant - supported overdentures . patients who underwent implant surgery and were restored with a maxillary and/or mandibular implant - supported overdenture . clinical symptoms of discomfort or difficulty to perform oral hygiene due to insufficient keratinized tissue around implant - supported overdentures . patients who underwent a surgical procedure to increase keratinized tissue around implant - supported overdentures . presence of systemic diseases that influence bone or soft tissue metabolism.smoking habit of more than a pack a day , and unwillingness to stop.radiotherapy to head / neck region in the past 12 months prior to surgery.chemotherapy in the past 12 months prior to surgery.unwillingness to commit to a long - term maintenance program after treatment . preoperative measurement of the width of keratinized tissue , in the area of the planned implants , or around already placed implants , measured in millimeters using a periodontal probe from the free soft tissue margin to the mucogingival junction . all the measurements were performed by the same investigator.antibiotic premedication : 2  g amoxicillin 1 hour prior to surgery or 600  mg clindamycin in case of penicillin allergy.infiltrative local anesthesia using lidocaine hcl 2% containing epinephrine 1  :  100,000 or carbocaine 3% without epinephrine in cases where a vasoconstrictor was contraindicated.one of the following techniques was utilized to increase the amount of keratinized tissue : apically positioned flap , pedicle graft , connective tissue graft , or free gingival graft . the technique was selected depending on the time the surgery was performed and operator preferences ( table 1).postsurgically , the patient was instructed to not wear their prosthesis for 3 weeks.postoperative antibiotics ( amoxicillin 500  mg tid or clindamycin 150  mg qid ) and analgesics ( ibuprophen 600  mg q 46  hrs ) were prescribed for a week.postoperative care instructions were given , including use of clorhexidine gluconate 0.12% rinses 3 times a day and soft diet , for two weeks.postoperative measurement of the width of keratinized tissue taken 1 month and 3 months after the surgery , using a periodontal probe and measured from the free gingival margin to the mucogingival junction in the area where the preoperative measurement was taken and where the surgical technique was performed . preoperative measurement of the width of keratinized tissue , in the area of the planned implants , or around already placed implants , measured in millimeters using a periodontal probe from the free soft tissue margin to the mucogingival junction . antibiotic premedication : 2  g amoxicillin 1 hour prior to surgery or 600  mg clindamycin in case of penicillin allergy . infiltrative local anesthesia using lidocaine hcl 2% containing epinephrine 1  :  100,000 or carbocaine 3% without epinephrine in cases where a vasoconstrictor was contraindicated . one of the following techniques was utilized to increase the amount of keratinized tissue : apically positioned flap , pedicle graft , connective tissue graft , or free gingival graft . the technique was selected depending on the time the surgery was performed and operator preferences ( table 1 ) . postoperative antibiotics ( amoxicillin 500  mg tid or clindamycin 150  mg qid ) and analgesics ( ibuprophen 600  mg q 46  hrs ) were prescribed for a week . postoperative care instructions were given , including use of clorhexidine gluconate 0.12% rinses 3 times a day and soft diet , for two weeks . postoperative measurement of the width of keratinized tissue taken 1 month and 3 months after the surgery , using a periodontal probe and measured from the free gingival margin to the mucogingival junction in the area where the preoperative measurement was taken and where the surgical technique was performed . over time , clinicians have used different surgical techniques to increase the width of keratinized tissue around natural teeth . understanding these techniques would help the clinician to decide which one to use in specific circumstances . in this study , all 8 patients in this study were wearing a complete maxillary and/or mandibular denture for at least a year before the time of the surgery . one of the following surgical techniques was utilized to increase the amount of keratinized tissue : apically positioned flap ( apf ) , pedicle graft ( pg ) , connective tissue graft ( ctg ) , or free gingival graft ( fgg ) . in seven out of the eight cases , the augmentation procedure was performed on three cases with the implants already restored with the final prosthesis . four cases had the procedure done as part of the second stage implant surgery . however , in one case the augmentation utilized before the implants were placed . when planning for implant - supported overdentures , a preoperative assessment of the amount of keratinized tissue is an important step . when necessary , augmentation of keratinized mucosa should be done prior to implant placement . in case 1 , an apically positioned flap was performed one month before the stage 1 surgery to allow adequate soft tissue closure ( figure 1 ) . the initial measurement of the band of keratinized tissue in sites # 22 and # 27 was 3 and 4  mm , respectively . a single horizontal beveled incision was made into the attached gingiva ( figure 1(b ) ) . the mesiodistal extension of the incision was made from # 21 to # 28 , making it possible to elevate a partial thickness flap which was apically repositioned by suturing the flap to the periosteum with vicryl 4.0 ( polyglactin 910 ) ( figure 1(c ) ) . as a result of this procedure , a 5  mm increase in the width of keratinized tissue was obtained at both sites ( figure 1(d ) ) . when a surgery to increase the width of keratinized tissue is performed during implant placement , the incision should be designed to maintain the amount of keratinized tissue . this incision design will allow the implant to be surrounded by at least 2  mm of keratinized tissue all around . a second stage surgery is a good opportunity to increase the width of keratinized tissue ( figures 2(a ) , 2(b ) , 2(c ) , and 2(d ) ) . this approach was utilized in cases 2 , 3 , and 4 . in three patients , an apically repositioned flap was used as described in case 1 , which resulted in a mean increase in the width of keratinized tissue of 3.1  mm . case 5 was also treated as part of the second stage surgery utilizing pedicle flap with a mean increase of 2.8  mm . the pedicle flap technique is an approach similar to an apically repositioned flap and should be used when there is adequate keratinized tissue adjacent to the implant . a beveled horizontal incision of approximately 6  mm was made distal to the implant , with a small vertical incision at the distal end part of the first incision . a partial thickness flap was then elevated and the pedicle flap sutured apically ( figures 3(a ) , 3(b ) , and 3(c ) ) . in some cases , a lack of keratinized tissue is evident after the insertion of the final prosthesis , causing discomfort and restricting oral hygiene performance . moreover , since implant - supported overdentures are a removable prosthesis , patients often experience pain when taking the overdenture on and off . in this retrospective case series , three patients had surgery to increase the amount of keratinized tissue around 6 implants supporting overdentures , either by utilizing free gingival grafts or connective tissue grafts . preference was giving to connective tissue graft when the patient had high vault palate , which allows harvesting a good amount tissue and reduces the risk of endangering the greater palatine artery . in case 6 , an autogenous free gingival graft was harvested from the palatal premolar area , around # 12 , 13 , and then sutured to the periosteal recipient bed of # 11 and # 13 ( figures 4(a ) , 4(b ) , and 4(c ) ) . after healing and maturation of the soft tissue an increase of 3 and 2  mm was obtained , respectively , ( figure 4(d ) ) . cases 7 and 8 were treated with connective tissue grafts harvested from the premolar area of the palate . at the same time , the recipient site was prepared ; a vertical incision mesial to the implant was made and a partial thickness flap was then elevated , creating a tunnel where the connective tissue graft was inserted and sutured . one of them ( case 7 ) resulted in no increase of keratinized tissue as a result of significant decrease of the vestibular depth following the excessive amount of alveolar bone resorption . in case 8 , the healing was accompanied with nonkeratinized soft tissue growth over the implant which made it very difficult both to perform oral hygiene and to insert the overdenture . a customized healing abutment was designed to control the excessive growth , and two more implants were placed , converting the overdenture prosthesis . the apically repositioned flap is a relatively simple procedure that provides a good esthetic outcome , as the newly formed tissue is indistinguishable from the surrounding mucosa . the main limitation of this technique is the need for at least 0.5  mm millimeters of keratinized tissue preoperatively . in cases where less than 0.5  mm of keratinized tissue is present preoperatively , moreover , discrepancies in color and texture with the surrounding mucosa oftentimes result in a compromised esthetic outcome . after one year , it has been reported that in the case of a free gingival graft , shrinkage of 38 to 45% occurs in relation to the thickness of the graft . although the augmentation was not successful in one case , this technique can still be an option to augment the keratinized tissue around implants restorations . there was average of 1.5  mm increase in the width of the keratinized tissue . however , the author believes that the stability of the graft is very important for this technique to be successful . this technique was less invasive and resulted in up to 3  mm increase in the keratinized tissue . this technique can be very useful in unilateral single implant cases where only small areas of narrow keratinized tissue need to be augmented . the amount of keratinized tissue should be taken into consideration when planning for implant - supported overdentures . when the initial amount is considered insufficient , an apical repositioning flap is an effective approach to increase the width of keratinized tissue prior to the implant placement if 0.5  mm of keratinized tissue was preoperatively available . during the second stage surgery , lingualized incision designs and pedicle grafts are a less invasive alternative to increase a limited zone of keratinized mucosa . although free gingival graft or connective tissue graft could also be utilized but around implants , they can impose some challenges to the clinician during the surgery or throughout the healing . when patients experience discomfort after insertion of the final prosthesis due to a lack of keratinized mucosa , free gingival or connective tissue grafts are a feasible alternative . in some cases , a change of design of the prosthesis could be performed , placing more implants and converting from overdenture to a fixed restoration .
purpose . 
 the purpose of this retrospective case series is to describe and compare different surgical techniques that can be utilized to augment the keratinized soft tissue around implant - supported overdentures . 
 materials and methods . 
 the data set was extracted as deidentified information from the routine treatment of patients at the ashman department of periodontology and implant dentistry at new york university college of dentistry . 
 eight edentulous patients were selected to be included in this study . 
 patients were treated for lack of keratinized tissue prior to implant placement , during the second stage surgery , and after delivery of the final prosthesis . 
 results . 
 all 8 patients in this study were wearing a complete maxillary and/or mandibular denture for at least a year before the time of the surgery . 
 one of the following surgical techniques was utilized to increase the amount of keratinized tissue : apically positioned flap ( apf ) , pedicle graft ( pg ) , connective tissue graft ( ctg ) , or free gingival graft ( fgg ) . 
 conclusions . 
 the amount of keratinized tissue should be taken into consideration when planning for implant - supported overdentures . 
 the apical repositioning flap is an effective approach to increase the width of keratinized tissue prior to the implant placement .