Dental Clinical Articles
Posted: 9 February 2012
The short implant: A long time coming
If a short implant works in a difficult site, why would it not in an easy site? Dr Clive Debenham reviews the case for the short implant
The three separate and independent leaders in dental education, mentioned in the box at the bottom of this page, combine the forces (and voices) of an academic/teacher, a high-level ‘specialist’ private practitioner and a dedicated research worker.
Put their various works alongside each other and the case for the short implant becomes irresistible. I believe that the successful short implant will oust its longer brother in just the same way that the current long implant heralded the death of the bicortical fixture, originally said to be mandatory.
So what actually is a short implant? If you take the last 10 years of articles on ‘short implants’ and average out what authors consider to be short, the answer comes out as 7.9mm. A short implant can therefore, reasonably be defined as a fixture of 8mm or less in length.
When I first visited the Bicon institute in Boston in 1997, along with Dr Geoff Pullen, we were told in no uncertain terms that a 5x8mm (long) should be our default implant and nothing longer was required for any tooth in the dental arch. At that time, Bicon did manufacture 11 and 14mm implants and recommended the 11mm length, where the well size was 2mm and the implant diameter 4mm. However, Bicon has manufactured the ‘short’ 8mm implant ever since the company was founded in 1987, a time when 14-18mm implants were considered more than ‘de rigueur’.
But do short implants work? It is simple to list the advantages of a short implant, of which the two greatest are anatomical safety and the minimal need for bone augmentation. However, it is those words, ‘if it works…’ that are at the heart of the matter.
Growing popularity
Since 1997 Bicon has introduced the 6mm implant (Figure 1) and now the 5mm implant (Figure 2). While figures 1-6 illustrate this versatility in all corners of the mouth, these are the tough cases, even though most of these were placed by general practitioners.
At Bicon’s Implant Centre in Boston, Massachusetts, the 6mm short implant has become the default implant of choice. In 2001 they were placing 58.6% short implants of 8mm or less. By 2007 that figure had risen to 95.2%. A similar trend has been seen in Geoff Pullen’s practice in London: 55% of implants placed were 8mm or shorter in 2001 and by 2009 all but 5% of the implants were short.
Meanwhile, every manufacturer is busily working towards a short implant. Unfortunately, macroscopic design is crucial to long-term success and it is not just a matter of cutting off more from the apex of the existing implant design. This is a complex subject beyond the remit of this current article but will be addressed in a future article.
Many think that the real advantage of the short implant lies in its ability to address the difficult clinical question without the need for ancillary procedures. While this is undoubtedly true, the real advantage is that the short implant allows the general practitioner to place implants safely in simple sites using the oro-surgical skills he/she learned in dental school.
Implant ‘specialists’ are essential for advanced cases and always will be. However, they will never be able to provide all the implants the public require and therefore those with adequate levels of training will be just as necessary. As ever, case selection is crucial.
Site selection
So what is a simple site? It is anywhere there is an excess of bone relative to the length and width of the implant that is to be used and an absence of anatomical structures potentially liable to damage. The idea that just because you have 16mm of bone above the inferior dental canal, you will have to use 14mm of it, is redundant thinking. The current default implant for Bicon is 4.5x6mm. This implant would normally be sunk 2-3mm subcrestally (although, it could be placed crestally without impairing success). This means that the total maximum depth of the osteotomy site would be 9mm giving a safety margin of 7mm.
If placed crestally - and thereby impairing gingival aesthetics slightly - the safety would be a full centimetre! With regard to width, it would be unusual to find anything insufficient in a recent molar extraction site for instance.
Clearly the easiest starting site for a first implant is a lower first molar. You will not be going below the apices of the neighbouring teeth with pilot drill, reamer burs or fixture. How long after extraction should you leave a site to heal? Four to six weeks would be usual. Figure 7 illustrates the steps from tooth to implant.
The second likely spot for an early implant is the upper premolar region. Again, if there has been a recent extraction and there is nothing untoward or exceptional about the sinus, there will be an excess of bone. This is another good site for a 4.5x6mm implant.
You will notice that no anterior has been mentioned because there is a simple rule that says all anterior implants are complex. They are to be tackled only after sufficient experience has been achieved in the posterior regions of the mouth. Some anteriors are easier than others and some are extremely complex.
Are there any other simple sites? There is the implant for the overdenture and one of the most life-changing treatments for a patient is providing two lower canine implants for a full lower denture case. Is this easy to do? The more ridge there is, the easier the surgery is to do; although conversely, the prosthetic need may be less! These implants will be anterior to the mental foramen and - provided there is sufficient guiding anatomy and ridge width - these are simple cases. With a flat ridge they are extremely challenging.
Summary
To sum up, the short implant is here to stay. In no way is it inferior to the long implant and may well prove to be better. Adequate training, mentoring and good case selection will provide excellent implant dentistry for the majority of the population and not leave it as the preserve of the few and the rich. In one way or another, every GDP will have to become involved.
|
‘I totally agree with respect the use of shorter implants, but it just seems the evidence is not getting to those that should hear it!’ Professor Tara Renton, Professor of Oral Surgery, King’s College London Dental School. Email correspondence (2011) |
|
‘The survival of 6x5.7mm implants was comparable to that of implants 8mm or longer.’¹ Dr Ranier Urdaneta - Dr Urdaneta has collated all the research on short implants; measured bone levels over countless X-rays and has demonstrated bone gain over implants in the presence of favourable conditions, which are under the control of the clinician. Note that the date of the paper he referred to was 2005. Seven years on, there are still clinicians fervently denying that short implants work. Dr Urdaneta has spoken in London on two occasions. |
|
Go to www.bicon.com and click on videos. Type ‘Schaeffer’ into the search box and scroll down to ‘Short dental implants, does size really matter?’ ‘This 40-minute lecture on short implants from Dr Bill Schaeffer, a dedicated research worker, should be required viewing for all implantologists whichever system they may be using.' Dr Clive Debenham |
| Declaration of interest |
|---|
|
Geoff Pullen and Clive Debenham are directors of Bicon Marketing Ltd Tel: 01473 829299 www.bicon.co.uk |
For a full list of references or to ask a question/comment on this article, please leave a message below or send an email to: .(JavaScript must be enabled to view this email address)
Follow us
Like us
LinkedIn Connect
RSS Subscribe
