Scientifica implantology

Clinical Oral Implant Research, 21 (10): 1085, 2010

During implant-supported prosthetic rehabilitation, the manoeuvres for replacing a provisional prosthesis with a final prosthesis can cause negative stress to the tissues around the implant, even if the switching platform method is applied. Based on this assumption, this 3-year prospective study, whose results were presented in the form of a Short Oral Presentation at the 2010 EAO Congress of Glasgow, evaluates how these two techniques infl uence bone levels (MBL): one abutment - one time (i.e. immediate use of the final prosthesis) compared to the traditional protocol of using a temporary prosthesis which is then replaced by a final prosthesis at a later date. For this purpose, 26 patients were selected with as many unitary sites in pre-molar areas that required the insertion of wide-diameter implants immediately after tooth extraction. Divided randomly into two groups, a provisional prosthesis with a smaller diameter than the implant platform was immediately inserted into the control group. This provisional prosthesis was constructed on a provisional titanium abutment, while the final prosthesis was implanted in patients belonging to the test group. The final prosthesis was inserted using the platform switching technique on a titanium abutment. In both cases, the crowns were not placed in occlusion. After 3 months, all the implants underwent final restoration, adopting the traditional technique of taking an imprint (therefore, of connecting and removing the abutments several times). Whereas pre-fabricated metallic caps were used in the test group, which allowed the final structure to be placed without having to remove the abutment. Standardised digital x-rays were taken at baseline (T0 = Time of implant placement), at final prosthetization (T1 = 3 months after placement) and at an 18-month follow-up (T2) and 36-month follow up (T3). The bone levels (MBL) were measured with computerised measurements applied to the x-ray images, thanks to the use of digital radiography subtraction of the bone tissue density around the implant. The MBL differences between the two groups were identifi ed with the Student’s t-test (P<0.05)
at the various follow-ups. The CG contained an average peri-implant bone reabsorption of 0.4 mm (SD = 0.15 mm) at T1, 0.38 mm (SD = 0.12 mm) at T2, and 0.53 mm (SD = 0.13 mm) at T3. The TG contained  an average peri-implant bone reabsorption of 0.59 mm (SD = 0.19 mm) at T1, 0.31 mm (SD = 0.11 mm) at T2 and 0.32 mm (SD = 0.16 mm) at T3. Therefore, a statistically signifi cant difference was only found at T1. At the same time of observation, a higher peri-implant bone density was recorded around the neck of the implant in the TG. The stability of the implant/abutment connection after adoption of minimally invasive prosthetic strategy (“platform switching” and “one abutment - one time”) could lead to greater preservation of the longitudinal hard tissues compared to traditional protocols.
In any case, even though the data is not encouraging, further clinical tests on a wider range of patients and more histological exams are needed in order to confi rm this hypothesis by analysing the biological mechanisms.

This clinical study highlights the greater stability of the crest bone levels by immediately positioning the final abutment in place of the provisional one.

Journal of Periodontology, 81:403-411, 2010

This study compared rehabilitations with the Platform Switching technique and with standard technique; at 36 months, the fi rst technique showed significantly better bone level maintenance than the second. An analysis of the peri-implant microbiota did not reveal differences in the two cases, thus indicating that the operating principle of platform switching is not attributable to the microbiological profi le.

The International Journal of Oral and Maxillofacial Implants, 24:920-926, 2009

This study compared the behaviour of crestal bone at 24 months around Outlink² implants (external hexagonal connection), rehabilitated with traditional prosthetic protocol, and around platform switched Ankylos implants (conometric connection). The survival of the implants was 100% and bone reabsorption did not present statistically signifi cant differences in the two cases.

Clinical Oral Implant Research, 20(9):873-874, 2009

This study evaluated the correlation between crestal bone remodelling and the presence of metalloproteinase in the peri-implant sulcus in rehabilitated sites with different fixture/abutment mismatching. The width of the mismatching infl uences the extent of the crestal bone reabsorption in inversely proportional terms, but it does not affect the metalloproteinase.

International Journal of Prosthodontics, 22 (3):277-282, 2009

22 implants were placed immediately into fresh extraction sockets in the maxilla; 11 cases were treated with conventional prosthetic protocol and 11 with the Platform Switching technique. It was highlighted how this latter provides greater stability of the crestal module.

Clinical Oral Implant Research, 20 (4):414?420, 2009

This clinical study highlights that the rehabilitation of implants according to the switching platform concept allows better stability of the hard and soft tissues around the implant compared to rehabilitation with abutments of the same diameter.

As it often happens, this discovery occurred by accident: in the early phases of their marketing, abutments of the same size were not available for wide-diameter implants used in the restoration of posterior zones. Due to this “sales” difficulty, the fi rst users were forced to prosthesize them with standard healing abutments. Radiological analysis of the response of the peri-implant tissues, as described by Lazzara (2006), showed that bone reabsorption was signifi cantly lower than with implants prosthesized with conventional techniques. The reasons for such a positive behaviour are explained by the separation of the implant/abutment gap
(i.e. the infi ltrated infl ammatory source) from the vital bone and therefore, from the distribution, even horizontal, of the biological width (biological cause).
Although it is a retrospective study of limited scientifi c importance, this article marks an important step. In fact, it demonstrates the longitudinal reliability of this type of prosthetic protocol. Subsequently, different other works have confi rmed the radiological results of the Lazzara study both in implants placed
on native bone and in extraction sockets. At the same time, it was demonstrated that even the soft tissues draw advantages from the use of smaller abutments.
In the same years, the interest of researchers has led to histologically testing the application of the Switching Platform concept both on an animal model and on a human model. Although some authors have demonstrated that there are no statistically signifi cant differences between the test and control groups with regard to the behaviour of the vestibular bone, most of the works confi rm that the Platform Switching allows minimising peri-implant marginal reabsorption. The histological analysis identifi ed another reason for the positive response of the tissues to the use of the switching platform: the creation of a resting base for the connective tissue (the implant platform not occupied by the abutment) allows stabilising the collagen fi bres which in turn minimises bone reabsorption (anatomic cause).
Some studies seem to demonstrate that the biological and anatomical reasons are also joined by biomechanical factors. An analysis of the fi nished elements has demonstrated the biomechanical rationale of the platform switching: the difference in diameter between the implant and stump (mismatching) allows reducing the mechanical stress transmitted to the marginal bone, diminishing its reabsorption pattern. In recent years, the attention of researchers has shifted to the long-term response of hard and soft tissues to the platform switching. Various studies have proven the stability of the tissues even after 5 years. As further confirmation of the safety of this prosthetic protocol even in the long term, a microbiological study with PCR probe demonstrated that after 4 years the sub-gingival microbiological
flora in implants treated with Switching Platform do not present any statistically signifi cant difference compared to conventionally prosthesized implants.
A recently published study demonstrated that implants with small abutments not only presented a smaller vertical extension but also a smaller horizontal extension of the biological width, thus allowing the use of an inter-implant distance under 3 mm as proposed in standard protocols. In the same period, a randomised controlled study demonstrated how the width of the mismatching is inversely proportional to the size of the peri-implant reabsorption, suggesting, conditions permitting, the
use of wide-diameter implants with small prosthetic components. Obviously, the Switching Platform concept was demonstrated as being just as valid in vertically
reconstructed sites or in sinus lifts where, together with the use of new generation hydroxyapatite, it seemed to allow early loading (3 months) of the implants.

Italian Dental Journal, 2012; 08: 24

SURGICAL AND PROSTHETIC SWITCHING PLATFORM

One of the primary objectives of modern implantology is to maintain the crestal bone, so as to improve the aesthetic result and reduce the risk of late peri-implantitis. In comparison with traditionally designed implants, switching platform implants reduce early crestal bone loss in proportion to the size of the switch.
Switching platform implants are divided into two groups: implants with surgical switching (implants with a specially widened neck) and implants with prosthetic switching (implants with a standard neck with prosthetic posts having a reduced diameter). Both types of switching have proved to be effective and, in order to maximize the obtainable switch, for some years we have been using a switching platform protocol which combines the use of implants with surgical switching (Sweden & Martina Premium 3.80 SP implants) prosthesized with posts with a reduced diameter (posts for Premium 3.30). The combination of surgical and prosthetic switching has proved to be a valid and predictable protocol for minimizing crestal bone loss.
The clinical case illustrated below concerns the insertion of a single immediate post-extraction implant with immediate loading. Prosthetization was carried out according to the protocol described above.

Clinical Oral Implant Research, 21:115-121, 2010

This study on 80 implants, divided into four groups and rehabilitated with fixture/abutment mismatching increasing from 0 trough 0.85 mm, established an inverse relationship between the extension of the Platform Switching and the dimensional loss of the coronal bone, connecting this data to the horizontal repositioning of the biological width, and to a different stress distribution on the peri-implant bone.

Dental Cadmos, 77(9): 31-39, 2009

Two groups of 20 patients received single implant in an edentulous site, which was rehabilitated in a second surgical procedure with a standard abutment (control group) and with the Switching Platform technique (test group). One year after the loading of the prosthesis, the test group showed a significantly lower loss of crestal bone compared to the control group.