José Eduardo Maté Sánchez de Val*, Ronny Gläser*²
Long-term analysis of bone stability with a platform-switched and flat-connection implant system – radiological analysis
Why should you read this article?
Long-term observation of the bone level around single-tooth implants which were placed in a
private practice in Germany and in Spain.
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 %.
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.
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.
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
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
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 implantabutment 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 .
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 . This limits bone resorption around the coronal aspect of the implant .
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 .
The causes of peri-implant marginal bone loss have been studied, determining as causal agents: the variation of the periimplant
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 .
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-dia meter restorative component is attached . It has been suggested that this biologic process resulting in loss of crestal bone height may be altered when the outer edge of the implant-abutment interface is horizontally repositioned inwardly and away from the outer edge of the implant platform. This prosthetic concept has been introduced as “platform switching”, and radiographic follow-up has demonstrated a smaller than expected vertical change in the crestal bone height around implants .
Many studies show that the displacement of the zone of inflammation that produces the change of platform is a major cause for the better conservation of bone obtained with this technique [6, 12]. Radiological assessment of stability levels and standardized radiological technique is a standard protocol in different clinical assessment studies . It is important to check the procedure to avoid variations arising from the technique; as well as a good protocol of measurement based on computer systems that allow to calibrate the measurements and obtain reliable and reproducible results.
In the literature platform-switch is associated with implants with conical internal connection. The objective of this research was to evaluate from radiological long-term analysis the stability of peri-implant bone tissues in the case of implants with a flat connection treated using a platform change protocol.
Material and methods
At 2 dental practices in Senden, Germany and Alicante, Spain, a total 60 implants (blueSKY, bredent medical, Senden, Germany)
have been inserted and after a subgingival healing period of 3 to 6 months they have been restored with cemented metal ceramic and full ceramic single crowns.
The patient selection was carried out independently from sex and age. Exclusion criteria were nicotine abuse, bruxism, lack of compliance, general disease and continuous medication. All patients had a minimum of 1 to 1,5 mm bone around the implant during surgical procedure.
All implants were placed in healed bone according to the placement and drilling protocol recommended by the manufacturer.
In all cases, an incision was made at full thickness using a scalpel 15c, total removal of the flap, placement of the implants and replacement of the tissue and suture to achieve the primary closure without exposure of the implant during the healing time.
The suture used was 3 or 4 zeros silk and the closure was performed by single stitches. Removal of the suture was performed one week after the first intervention. During the first week the patient performed localized hygiene using CHX 0.12 % and soft brushing. No previous antibiotic treatment was prescribed.
After a period of integration recommended by the manufacturer, the reentry was carried out for the preparation of the prosthesis according to a conventional protocol of action in 3 phases: healing abutments, impression and placement of the prosthesis.
All of the prostheses used were metal ceramic or fully ceramic unitary crowns, for which suitable platform change attachments were used (Esthetic abutment, bredent medical GmbH & Co. KG, Senden, Germany) (Fig. 1).
Figure 1: Clinical and prosthetic protocol. X-ray analysis and clinical situation with abutment (a) and with final restoration (b) at different times:
implant insertion (I), the insertion of the prosthetics (P) and the first recall after 12 months (R) and after 7 years (R2)
Standardized radiological records were taken by means of bitewing holder KWIK-BITE (Hawe Neos) for the different areas in the mouth. Radiological analysis was performed with imaging software by Wayne Rasbarnd, USA. Distances between platform to first bone contact were recorded on the day of the implant insertion (I), the insertion of the prosthetics (P) and the first recall after 12 months (R) and after 7 years (R2). Additionally, to the use of bite wing holder an precise calibration of each measurement was carried out using the technical data of the implant manufacturer, e.g. implant length, length of the machined area, distance of the threads to correct amplifications caused by the X-ray technique. The reference points for all measurements were the edge of the
implant shoulder and the first radiological visible bone implant contact point.
The documented bone resorption around each implant was calculated by subtraction of the measured bone levels at the different treatment times. If different values for mesial and distal bone resorption were found, then always the higher value was used. All measurements, evaluations and calibrations as well as the surgical and prosthetic procedures were done by the first author (Fig. 2).
The statistical analysis was carried out with SPSS-software.
The significance of the results was proved with ONEWAY ANOVA analysis on p < 0.01 or p < 0.05 for the different implant
systems according to Bonferroni.
Figure 2: Linear measurement analysis from X-ray with Image J software; measurements at mesial (M) and distal (D)
Figure 3: Bone level evolution at time point analysis
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 were recorded. The values were recorded in mesial and distal direction for each phase of study, as well as the average between both for the comparison between the different periods of the study (Tab. 1). 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 was found at 0.68 ± 0.03 mm from the platform to the first contact (Tab. 2). The comparison between the different periods shows a great stability of the bone with small variations at the moment of the placement of the implant and after 7 years of evaluation, when it varied up to 0.68 ± 0.03 mm (Fig. 3).
Table 1: Bone level at different study moments. Measurement in mm.
Values expressed as mean and sd
Table 2: Comparison of bone level at I, P, R, R2 measurement in mm;
values expressed as mean and sd; significant differences p < 0.05
An adequate implant design, as well as a surface that is difficult to contaminate, are the main bases for the success of any implant system. Once the osseointegration and the stability are obtained that give an adequate system, the variations derived from the physiological evolution of the peri-implant tissue allow to be minimized by means of different techniques . Radiological assessment of peri-implant bone loss is an effective tool with proven reliability in obtaining reproducible results. Therefore
it is important that there is a standardized technique that is simple allowing to be performed by various operators and that is valid and reliable. It could be shown that analyzing different parts of the implant and calculating the mean of these is the best way to obtain reliable data [4, 7]. The success rate of the study is in line with those found in the bibliography concerning implant survival rates that are above 95 %, with the integration of all the implants analyzed during the study period and without anomalous responses interfering with the correct integration of the implants.
One of the techniques that has shown greater efficiency in improving the stability of the peri-implant bone tissue and therefore of the soft tissue is the platform switch. The main reason is that it distances the potential inflammatory problem of the area of the most obvious, which is the implant-attachment junction, inward; Creating a protection zone or chamber that will avoid the future bacterial colonization and the beginning of the apical migration of the inflammatory infiltrate .
Although these studies are based on the use of a cone-type morse connection, the positive effect of platform switching over flat type connections has been widely demonstrated. In the radiological assessment performed on implants with internal non-conical connection found that the concept of platform switching appears to limit crestal resorption and seems to preserve peri-implant bone levels . The moments where the greatest risk exists of this invasion of the peri-implant biological space and therefore the rupture of this anchor is in those in which the disconnection of the different attachments on the implant takes place; that is to say, with the healing abutments, the connection of the prosthesis and in those cases in which it was necessary to remove the definitive prosthesis. Thus the peaks of reabsorption can be seen as the moment of disconnection. It is for this reason that modern implantology is focusing on one-step protocols or one-abutment-one-time protocols, where disconnections are minimal and the final abutment will be placed in the initial moments. Likewise the use of the platform change technique seems to favour that the passage of forces from the crown to the bone is displaced towards the more axial area of the implant and therefore avoids undesired side loads. These tangential forces could lead to loss of bone of difficult control; Therefore, also from the biomechanical point of view, the change of platform would be justified. It is important that the attachment used allows a great stability in the connection with the implant, since these possible micromovements could lead to rupture of the anchorage and sealing of the peri-implant tissue and
therefore initiate a phenomenon of reabsorption by inflammatory infiltrate. The beneficial effect of platform change on peri-implant bone preservation is well documented in the literature, independent of the kind of connection; as has been seen in several studies where the change of platform has been applied to different types of connections. Yang et al. demonstrated that platform switching reduced strain surrounding the implant neck area in both EX and IN during loading, having a positive effect on peri-implant tissue . In the same way, Telleman et al. suggest the benefits of platform switch with internal hex connections on inter proximal bone preservation .
In the first year of follow-up, the amount of bone remodeling at the level of the alveolar crest was limited to 0.1 mm, which is also in line with published data [11, 14]. And at 7 years, the results conform with other authors like Lorenzoni who found variations of less than 0.7 mm . It seems to be evident that the platform change technique manages to minimize
reabsorption phenomena by means of of improving the anchoring of the peri-implant connective tissue and increasing the stability of the connections by decreasing the peri-implant micro movements.
With the limitations of an observational trial without a control group, it can be concluded that the combination of a platform change technique with an adequate implant design and adequate attachments allows for stabilization of the peri-implant tissues, minimizing
the apical migration of the bone during a long-term follow-up.
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Conflict of interest: The authors declare
that bredent provided support in the form of translation and forwarding by this article.
Figures 1–3: José Eduardo Maté Sánchez de Val
* Extraordinary Professor of Biomaterials Engineering and Co Director of the Chair of Biomaterials Engineering. Head of Postgraduate Program in Oral Surgery and Implantology. UCAM. University, Católica San Antonio de Murcia. Murcia. Spain
*² Joint dental practice, Senden, Germany
© Deutscher Ärzteverlag | zzi | Z Zahnärztl Impl | 2017; 33 (2)