Influence of implant neck surface and placement depth on crestal bone changes and soft tissue dimensions around platform-switched implants: A histologic study in dogs.

OBJECTIVES: To analyse bone remodelling and peri-implant soft tissues around platform-switching implants with and without a machined collar placed at different levels in relation to bone crest. MATERIAL AND METHODS: All mandibular premolars and the first molars were extracted in five dogs. At 6 months, six implants with and without a machined neck (MACH and GBAE implants, respectively) were randomly inserted in each hemimandible positioning the implant-abutment interface in either a supracrestal (+1.5 mm), equicrestal, or subcrestal (-1.5 mm) position. After 6 months, animals were killed for histomorphometric analysis. RESULTS: When net bone loss (primary outcome variable) was compared between MACH and GBAE groups, the multivariable regression analysis revealed no significant differences between implants inserted at the same vertical position. The dimensions of the peri-implant mucosa were greater in MACH implants compared with GBAE implants; however, these differences failed to reach statistical significance. Regarding the number of inflammatory cells and collagen fibre orientation, no statistically significant differences were found between MACH and GBAE groups. CONCLUSIONS: The surface treatment of the implant neck does not seem to have an influence on net bone loss, and there were no statistically significant differences in the peri-implant soft tissues between platform-switching implants with and without a machined neck.

Influence of subcrestal implant placement compared with equicrestal position on the peri-implant hard and soft tissues around platform-switched implants: a systematic review and meta-analysis.

AIM: The aim of this article is to systematically review the effect of subcrestal implant placement compared with equicrestal position on hard and soft tissues around dental implants with platform switch. MATERIAL AND METHODS: A manual and electronic search (National Library of Medicine and Cochrane Central Register of Controlled Trials) was performed for animal and human studies published up to December 2016. Primary outcome variable was marginal bone level (MBL) and secondary outcomes were crestal bone level (CBL), soft tissue dimensions (barrier epithelium, connective tissue, and peri-implant mucosa), and changes in the position of soft tissue margin. For primary and secondary outcomes, data reporting mean values and standard deviations of each study were extracted and weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated. RESULTS: A total of 14 publications were included (7 human studies and 7 animal investigations). The results from the meta-analyses have shown that subcrestal implants, when compared with implants placed in an equicrestal position, exhibited less MBL changes (human studies: WMD = - 0.18 mm; 95% CI = - 1.31 to 0.95; P = 0.75; animal studies: WMD = - 0.45 mm; 95% CI = - 0.66 to - 0.24; P < 0.001). Furthermore, the CBL was located at a more coronal position in subcrestal implants with respect to the implant shoulder (WMD = - 1.09 mm; 95% CI = - 1.43 to - 0.75; P < 0.001). The dimensions of the peri-implant mucosa seem to be affected by the positioning of the microgap and were greater at implants placed in a subcrestal position than those inserted equicrestally (WMD = 0.60 mm; 95% CI = 0.26 to 0.95; P < 0.001). While the length of the barrier epithelium was significantly greater in implants placed in a subcrestal position (WMD = 0.39 mm; 95% CI = 0.19 to 0.58; P < 0.001), no statistical significant differences were observed between equicrestal and subcrestal implant positioning for the connective tissue length (WMD = 0.17 mm; 95% CI = - 0.03 to 0.36; P = 0.10). CONCLUSION: This systematic review suggests that PS implants placed in a subcrestal position have less MBL changes when compared with implants placed equicrestally. Furthermore, the location of the microgap seems to have an influence on the dimensions of peri-implant soft tissues. Clinical relevance When compared with PS placed in an equicrestal position, subcrestal implant positioning demonstrated less peri-implant bone remodeling.

Influence of Implant Neck Surface and Placement Depth on Crestal Bone Changes Around Platform-Switched Implants: A Clinical and Radiographic Study in Dogs.

BACKGROUND: The aim of this animal study is to analyze bone remodeling around platform-switching (PS) implants with and without a machined (MACH) collar placed at different levels in relation to the crestal bone in a canine model. METHODS: All mandibular premolars and first molars were extracted in five dogs. After 6 months, grit-blasted acid-etched (GBAE) PS implants with and without a MACH neck were randomly inserted in each hemimandible, positioning the implant-abutment interface in either a supracrestal (+1.5 mm), equicrestal, or subcrestal (-1.5 mm) position, and healing abutments were connected. Implant abutments were dis/reconnected at 12, 14, 16, and 18 weeks after implant placement. After 6 months of healing, animals were sacrificed. Clinical parameters and periapical radiographs were registered on the day of implant placement, at 2 months, at every abutment dis/reconnection, and at sacrifice. Crestal bone changes were calculated and defined as the primary outcome variable. RESULTS: When crestal bone changes from implant placement to 6 months were compared between MACH and GBAE groups, no significant differences were encountered except for implants placed in an equicrestal position (P = 0.04). However, multivariable regression analysis revealed no significant differences between MACH and GBAE implants placed in a supracrestal (ß = -0.08; P = 0.45), equicrestal (ß = -0.05; P = 0.50), or subcrestal (ß = -0.13; P = 0.19) position. CONCLUSION: Surface treatment of the implant neck had no significant influence on crestal bone changes around PS implants with and without a MACH collar.

Implant positioning when replacing the four maxillary incisors: a platform-switched treatment option.

Patients do not view dental implants as an object of desire but seek a way to replace teeth that will be as cost-effective and minimally traumatic as possible. Nowadays, anterior fixed partial dentures can provide an esthetic result that is difficult to distinguish from the natural dentition. Consequently, any implant-supported prosthesis will be compared to the esthetic and functional standards set by conventional tooth-supported restorations. The restoration of the four maxillary incisors by means of an implant-supported prosthesis is one of the most challenging situations in implant dentistry. The questions of how many implants should be placed and where they should be positioned are especially important for achieving a superior end result. This article proposes and describes the placement of two platform-switched implants in the central incisor positions as a means of achieving the correct biomechanical behavior of the prosthesis, along with the best possible esthetic results.

Biomechanical repercussions of bone resorption related to biologic width: a finite element analysis of three implant-abutment configurations.

Most biomechanical studies of implant-supported restorations have not taken into account the biologic changes that occur following exposure of the implants to the oral environment. Therefore, the present finite element analysis study was designed to compare the biomechanical response of three types of implant-abutment configurations both before and after establishment of a new biologic width. The three functional units studied were: a 5-mm implant platform connected with an external hexagon to a 5-mm-diameter abutment (type 1), a 5-mm implant platform connected with an external hexagon to a 4.1-mm-diameter abutment (type 2), and a 4.8-mm implant platform connected with an internal hexagon to a 4.1-mm-diameter abutment (type 3). The type 3 design, which combined platform switching with an internal connection, exhibited the smallest distortions in stress distribution after bone modeling, and the stress was distributed over the entire contact surface most smoothly and uniformly. Bone resorption following creation of the biologic width changes the biomechanical behavior of a restoration. In this study, the two implant-abutment designs featuring a smaller-diameter abutment on a larger-diameter implant platform achieved better results than the implant featuring the same-diameter implant platform and abutment, even though their initial bio?mechanical load potential was lower. (Int J Periodontics Restorative Dent 2009;29:479-487.).

The effect of interimplant distance on the height of the interimplant bone crest when using platform-switched implants.

A distance of more than 3 mm between two adjacent standard implants has been shown to preserve the interproximal bone peak, resulting in only 0.45 mm of resorption. The purpose of this study was to determine whether use of the platform-switching technique would change the bone resorption patterns between adjacent implants placed less than 3 mm apart. Radiographic studies of bone resorption around 41 pairs of implants placed less than 3 mm apart in 37 patients were carried out. Mean vertical bone resorption was 0.62 mm, and the mean horizontal component was 0.60 mm. The bone peak that extended coronally beyond an imaginary line connecting the two implant-abutment interfaces was measured, and the mean bone height preservation above this interimplant line was 0.24 mm.

Benefits of an implant platform modification technique to reduce crestal bone resorption.

PURPOSE: The alveolar bone resorption that occurs around a 2-piece implant following abutment attachment is a well-documented observation. Several investigators propose that crestal bone loss is a response to the invasion of the biologic width by secondary bacterial colonization and micromovements at the implant-abutment interface. This study proposes the creation of a difference between the diameter of the implant platform and diameter of the abutment (implant platform modification), shifting the implant-abutment interface medially to minimize invasion of the biologic width. MATERIAL AND METHODS: We present a series of 30 control cases and 30 study cases using the platform-modification technique. Interproximal bone resorption on the medial and distal of each implant was assessed using digital radiography at 1, 4, and 6 months after abutment attachment. RESULTS: The mean value of bone resorption observed in the mesial measurement for the control group was 2.53 mm, whereas for those patients included in the study group, it was 0.76 mm. The mean value of bone resorption observed in the distal measurement for patients in the control group was 2.56 mm, whereas for those included in the study group, it was 0.77 mm. CONCLUSIONS: All patients in the study group had a significant reduction of bone loss in comparison to the control group (P < 0.0005).