Bibliographic reviews

Med Oral Patol Oral Cir Bucal. 2011 Sep 1;16 (6):e852-6

The aim of this study was to evaluate the biomechanics of the implant-post system in the case of a traditional and switching platform configuration by means of a finite element analysis. With the proper precautions, it can be affirmed that this technology allows bringing the biomechanical events back to a digital model, analysing the distribution of the stress and evaluating any biological repercussions. The higher the definition (number of nodes and elements), the closer to reality the analysis.
In this case, a 3D finite element analysis was conducted after constructing a mesh with 60,000 elements and 100,000 nodes. To make the analysis conditions as real as possible, special attention was placed on the bone definition. This involved drawing both the cortical and medullary component with the different biophysical characteristics (Young module).
Three different implant-post configurations were evaluated:
1. Implant with a diameter of 3.8 mm and corresponding post (Standard control model)
2. Implant with a diameter of 5.5 mm and corresponding post (increased control model)
3. Implant with a diameter of 5.5 mm and 3.8 mm post (experimental model with switching platform configuration).
A Global implant manufactured by Sweden & Martina was used.
In accordance with the literature and the ISO standards which standardise the experimentation conditions, vertical (axial) loads of 130N and horizontal loads of 90N were applied on the crown portion of the post. With these load conditions, the Von Mises stress index was evaluated and the minimum and maximum values were recorded for each implant-post configuration.
At the end of the experimentation, the Von Mises stress levels recorded on the standard configuration induced by the load varied from 150 MPa to 58 Pa (at an implant level) and from 150 Mpa to 52 MPa (at an abutment level); in the configuration of the increased model, the stress levels varied from 45 MPa to 55 Pa (implant) and from 70 MPa to 55 MPa (abutment); in the switching platform configuration, the stress levels measured varied from 190 MPa to 64 Pa (implant) and from 85 MPa to 42 MPa (post). The maximum stress levels transmitted by the implant-post system to the cortical and trabecular bone were respectively 67 Pa and 52 MPa (standard configuration); 54 Pa and 27 MPa (increased configuration) and 64 Pa and 42 MPa (switching platform). An evaluation of the stress levels on the body of the fixture
allowed highlighting a substantial reduction in stress in the threading region, correlated to a diameter difference between the implant and post in the switching platform configuration. In conclusion, it can be affirmed that the switching platform configuration not only leads to a relative reduction in the stress levels compared to standard configurations (both standard and increased), but also to a significant movement in the stress area from the bone to the implant platform, thus potentially generating less overloading of the bone crest.

This mechanical finite element study evaluated the different distribution of the stress levels between implants with a small and large diameter restored with traditional protocol, comparing them with implants restored with reduced abutments according to the switching platform concept. The results demonstrated that the switching platform configuration not only leads to a relative reduction in the stress levels compared to standard narrow and large configurations, but also to a significant movement of the stress area, potentially resulting in less overloading of the bone crest.

Clinical Oral Implant Research, Early View First Published online on 2011, November 2nd

The switching platform technique with a mismatching of 0.85 mm can maintain the bone level of the buccal crest better than a traditionally loaded implant.

International Journal of Oral and Maxillofacial Implants, 2011 May-Jun;26(3):618-30

The authors examined the immunohistochemical relationship between the quality of the receiving bone and peri-implant bone reabsorption at 36 months in sites treated with standard protocol versus switching platform protocol. An individual tendency for reabsorption was observed. The individual bone structure and quality at a local level seemed to be correlated to the level of reabsorption, which was also influenced by the presence of biglycans and the tumour necrosis factor-alpha.

Journal of Clinical Periodontology, 2011; 38: 86?94

This histological study in humans analysed the characteristics of soft tissues around the implant at 48 months, and compared implants rehabilitated with the switching platform concept to the traditional prosthetic protocol. The results showed that the switching platform protocol does not alter the soft tissues and that bone peaks are maintained.

Clinical Oral Implant Research 22, 2011; 438?444

This study demonstrated that implants restored according to the switching platform concept with mismatching of 0.25 mm maintained the same level of bone crest as traditional implants if the smooth part of the neck of traditional implants is left to emerge from the bone.

NumeriUno, 1: 6-7, 2008

PLATFORM SWITCHING AND IMMEDIATE SINGLE TOOTH LOADING IN THE AESTHETIC ZONE

Today’s aesthetic requirements force dentists to use immediate rehabilitation procedures in cases of tooth extraction in the front-upper sectors. In these cases, implant treatment is now a valid alternative to traditional fi xed prosthesis because it does not require the preparation of the teeth next to the edentulous site, therefore resulting in greater preservation. Furthermore, immediate loading protocols have contradicted the Brånemark dogma, which requires a 6-month submerged healing period for
implants inserted in type D3 or D4 bone (upper front sectors). Numerous studies have shown that immediate loading has a long-term effi cacy in single-tooth replacement, which forms the basis of the clinical case presented in this article. The report illustrates the implant therapy of a vertical fracture with traumatic aetiology of an element at the same time as the micro-invasive extraction of the tooth, performed by trying to protect the vestibular cortex as much as possible and the mesial and distal bone peaks. For a better aesthetic result, the implant tunnel for inserting the Ø 5.50 mm and 1.13 mm Global prosthesis was prepared, sinking it 3 mm into the basal bone with a torque of 42 Ncm and fi lling the jumping distance with bovine bone matrix mixed with collagen. The alternate use of drills and osteotomes allowed maintaining the vestibular lump preventing the creation of fenestrations or bone defects.
Within 24 hours, a prosthetization was performed with a provisional crown with direct technique using the Platform Switching restoration concept, screwing a fi nal post with a diameter of 3.8 mm to the implant. The patient was re-evaluated after 12 months to check the healing state of the soft tissues and the bone. Clinical and radiographic controls showed no evidence of gingival recession or aesthetic difficulties. The height of the papillae and of the vestibular and oral gingival margin remained constant. Instead, there was an increase in the distal papillae between the mounting of the final prosthesis and the 12-month follow up. The periodontal parameters showed that there was no bleeding on probing and the probing was always below 3 mm. The radiography showed minimal bone reabsorption even
after the 12-month follow up. The ZirTi surface along the entire length of the implant and the coronal micro-grooving seemed to affect the bone maintenance. Therefore, the aesthetic result was as expected and remained constant over time. The elementary surgical and prosthetic technique made it easy to reproduce the method. The micromechanical qualities (ZirTi surface) and the macromechanical qualities of the Global implant make it resistant to micro-movements, which are detrimental for the long-term stability of the bone-implant interface, making it possible to load the fi nal prosthesis after 2 months of insertion. The early interception of the fracture, the presence of a thick gingival biotype, the morphology of the implant platform, the use of the platform-switching concept and the use of a fi nal abutment on the fi rst day of loading are all extremely important conditions for maintaining the bone and gingival architecture in the long term and, consequently, the aesthetics.

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.