Reports on the ADI Team Congress 2011
Thursday 14 - Friday 15 April
Manchester Central Convention Complex
Petersfield, Manchester M2 3GX
Long-term experience of dental implants - clinical development and biological response
Speaker: Professor Torsten Jemt DDS Odont Dr/PhD – Sweden
Reported by Catherine Drysdale
Prof Branemark made two major contributions to implant dentistry. The first was that he showed that osseointegration of dental implants did work and secondly, Prof Branemark presented his clinical experience in published articles in a systematic way. He presented clinical studies at 10 years, 15 years and 20 years of follow-up. The Branemark concept has been to build up clinical experience based on a strict follow-up protocol reporting on clinical outcomes. This protocol includes a 1 year, 5 year and 15 year follow-up. Thereafter the follow-up is every 5 years.
This is the 25 year anniversary of the Branemark clinic and during that time 9000 patients have been treated with a total of 36,000 dental implant placements. In 1965 the first dental implants are placed in an edentulous mandible to provide a four implant retained fixed restoration. 11 years after the placement the radiograph shows up to 4 mm of bone loss around the implants and associated soft tissue information which we now describe as peri-implantitis. After 25 years in function the follow-up radiograph shows that the progression of bone loss has slowed down and after 35 years in function the bone loss has levelled out into a stable situation. He showed a similar case in an edentulous maxilla where in the early stages of follow-up there is dramatic bone loss of rent implants. After 13 years in function the bone loss is seen to level out and the follow-up after 37 years confirmed continued good function and a good prognosis to the restoration.
Prof Jemt posed the question “what is the meaning and importance of bone loss around implants”?
When the first single tooth dental implant was placed in 1982, the treatment became focused on technique, stability of the screw and aesthetics of the abutments. There was a standardised protocol for single tooth implants which is called the Cera One. The clinical outcomes of these patients were reported in many publications over an 18 year period. In the early 1990s the first customised abutments were seen such as Ti Adapt and Cer Adapt. By the mid-1990s CADCAM designed abutments became available and this is now the design technique of choice for all single tooth and partially dentate abutments. Prof Jemt’s experience is with now 27 years follow-up of single implants, these restorations remain stable with little recession and soft tissue complications and show predictable long-term function. Cases of infrapositioning may indicate that the implant was placed in a growing patient or placed in a patient with an unstable occlusion. His research followed up single implants in the anterior approach all over 15 to 20 years. More males than females were created to be completely stable after 15 to 20 years 60% of single tooth implants are stable with no infra positioning after 15 to 20 years. However, 40% had more obvious signs of infrapositioning with a stronger trend for this in female patients. Of interest, there appears to be a risk of infra positioning in a long-faced patient compared with square-faced patients.
Prof Jemt described the many changes today in the implant protocols compared with those of the 1970’s for example healing times, bone grafting, implant surfaces, internal connections etc. He posed the question have these protocols resulted in improvements or do we have more complications as a result? The original treatment protocol is based on biocompatibility, predictability and long-term function. Today, the protocol is focused more on speech and aesthetics for example immediate placement, immediate loading and optimal aesthetics.
Prof Jemt then discussed the issue of one-stage versus two-stage surgery. To state that this was based on claims of stability at the surgical site and secondarily Osseointegration. This establishes improved stability of the implant whilst in one-stage certainly the protocol relies on mechanical stability alone i.e. the clinician is not connecting the prosthesis to an osseointegrated implant. Many larger studies have concluded that the two-stages technique is more favourable. However many small studies show no difference but this is likely to be related to the design of the studies. Prof Jemt believes that it is safer to place implants using a two-stage procedure.
In the early 1990s, the internal connection was introduced to address the problems with loosening abutment screws with external hex implants. Initially in single tooth implants and then of partial and edentulous patients. An additional change in the protocol is the quality of the titanium. Dental implants were originally Grade I and now clinicians routinely use a poorer grade of titanium including Grade V which is an alloy. The internal connection requires a lower grade of titanium because it is stronger at the implant head thereby reducing the risk of fracture. Effect of this may be to introduce a higher risk of corrosion the implant area which could result in inflammation and consequently bone loss. This could be related to a higher incidence of peri-implantitis. He has found a very low incidence of implant fracture with the external hex design (1%).
Prof Jemt described other more recent changes to the implant treatment protocol such as the introduction of the CADCAM technique which results in improved prosthetic technique, shorter and fewer appointments but on follow-up, there is no difference in the complications of screw loosening, bone loss etc between the CADCAM and the original cast framework. In the last 20 years we have focused more on aesthetic approach rather than the biologic. The original protocol focused very much on access for cleaning but this became aesthetically unacceptable and protocol was therefore changed in the late 1980s for shorter abutments with closer positioning to gingival soft tissues and less visible titanium.
Prof Jemt then discussed the issue of implant surface and questioned whether the medium roughened surface was attributed to increased implant survival. We should look to clinical evidence to establish this and not base treatment principles on animal study results. Studies show only a 2% difference in implant survival of medium rough versus turned surfaces.
With barely placement of implants that is evidence of increased bone loss at five-year follow-up with no significant difference in marginal bone loss of current versus medium rough implants there is evidence that turned implant surfaces are more resistant to inflammation than roughened. There are implants with smooth coronal and successive increased roughness towards the atypical. They may therefore be a link of roughened implant surface to later bone loss and inflammation. Medium rough implants there for half better and quicker osseointegration and 2% improved survival at the early stage but there may be a link to bone loss and infection at a later stage. On the 1.6% of Prof Jemt patients per year have surgical treatment for peri-implantitis and 0.25% of implants are removed per year.
Questions from the floor to Prof Jemt were based mainly on the influence of roughened surface and turned surface implants on the bone and soft tissue in particular in relation to the incidence of peri-implantitis.