From practitioner to practitioner - ZZI 02/2017

Long-term analysis of bone stability with a platform-switched and flat-connection implant system – radiological analysis

José Eduardo Maté Sánchez de Val1, Ronny Gläser2

Background: Dental implants have proven to be a predictable treatment for replacing missing teeth; with an extensive literature base and numerous studies supporting the safety of treatment. They have been introduced modifications protocols and implants to improve osseointegration; including surface topography, implant design, implant anatomy, connection, load time and load type. In all, the survival rates of long-term implant analysis are set at high values above 95 %.

Aim: The aim was to analyze from radiological analysis the stability of bone surrounding implants and complete the follow-up with long-term results.

Materials and methods: Standardized radiographs were taken at the implant placement day and at the moment of the restoration of the prosthesis, recall 1 year and long-term (7 years) by means of a one-position paralleling system. 60 implants (blueSKY, bredent medical GmbH Co. KG, Senden, Germany) have been inserted and after a subgingival healing period of 3 to 6 months have been restored with cemented metal ceramic and Zirconia single crowns. Radiological analysis was performed with image J software Wayne Rasbarnd, USA. Distances between platform to first bone contact were recorded.

Results: No implants were lost during the study period; no abnormal inflammation phenomena were observed that were not due to a peri-implant cicatrization process. The measured distance values between the implant platform and the first contact with the peri-implant bone have been recorded. For the initial moment of implant placement, an average distance of 0.23 ± 0.02 mm was found with a variation at 0.20 ± 0.04 at the time of connection of the prosthesis, and 0.31 ± 0.11 at the 1-year review. After 7 years the bone level has been found at 0.68 ± 0.03 mm from the platform to the first contact.

Conclusions: With the limitations of a clinical study in humans, it can be established that the combination of a platform switch technique with an adequate implant design and adequate attachments allows stabilization of the peri-implant tissues, minimizing the apical migration of the bone during a period of time analyzed in the long term, independent from the kind of connection.

Keywords: bone implant interactions; radiology; imaging; prosthodontics

Cited as: Sánchez de Val JEM, Gläser R: Long-term analysis of bone stability with a platform-switched and flat-connection implant system – radiological analysis. Z Zahnärztl Implantol 2017; 33: 143-151

DOI 10.3238/ZZI.2017.0143–0151


Postoperative reduction in crestal bone dimensions around implants is a normal consequence of two-stage placement protocols. In both cases, if the implant is placed at the same time of extraction, and if the implants are placed deferred, dimensional variations occur that begin in the horizontal direction and finally proceed to the vertical direction.

Different procedures have been developed to minimize these dimensional variations of the bone, including: preservation prior to implant, overcorrection of peri- implant bone volumes, variations in implant design, and variations in implant-abutment interfaces.

Regarding implant procedures, it has been demonstrated that the change of platform or platform switch is an effective method to achieve greater stability in the peri-implant tissues, both in soft tissue and peri-implant bone tissue. The technique consists in creating a discrepancy between the diameter of the implant and the diameter of the abutment, which is smaller, in order to achieve a sealing zone that avoids bacterial colonization, invasion of external agents and therefore minimizes bone loss after implant placement [2].

The term platform switching refers to the use of a smaller diameter abutment on a larger diameter implant collar. Such a connection shifts the perimeter of the implant-abutment junction (IAJ) inwardly towards the central axis of the implant. Lazzara and Porter hypothesized that such an inward movement of the IAJ also shifts the inflammatory cell infiltrate inwardly and away from the crestal bone [10]. This limits bone resorption around the coronal aspect of the implant [5].

A direct relationship between preservation of peri-implant bone tissue and preservation of soft tissue has been observed. Bone stability values are one of the indicators of implant success. Albrektsson defined a successful implant in terms of bone preservation as one that lost no more than 1.5 mm in the first year and no more than 0.2 mm after the second year of placement [1].

The causes of peri-implant marginal bone loss have been studied, determining as causal agents: the variation of the peri-implant biological space, bone remodelling, and the modification caused by the different disconnections of the prosthesis as a consequence of the usual placement protocol. Bone resorption is thought to be caused by biological width re-establishment following chronic bacterial inflammation of the implant-abutment connection [3].

The concept of platform scwitch will allow to control some of these factors, minimizing the changes caused by the modification of the peri-implant space.

The peri-implant biological width is characteristic, so that radiological and histological assessments suggest that a process of remodeling is established from the moment of implant placement and will be modified by the following procedures. Vertical repositioning of hard and soft tissues occurs when an implant is exposed to the oral environment and a matching-diameter restorative component is attached [8].

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