The growth of implant dentistry

02 October 2012
Volume 28 · Issue 9

Craig Parker explores the latest techniques and materials available.

The global dental implantology market was valued at approximately $6.8bn in 2011 and is estimated to grow by an average of 9.3 per cent per year from 2011 to 2016. This is not surprising considering the many perceived benefits of dental implants. Europe is currently the largest market for dental implants at 41 per cent and much of the predicted growth is due to increasing demand from Asian and South American nations. However the UK is one of the European countries with the greatest potential for an increase in the use of dental implants and the number of implants placed per 10,000 people in the UK is currently significantly lower than many comparable European nations.

The increased use of dental implants can be put down to many factors, especially the introduction of more minimally invasive surgical techniques, shorter treatment times and a wider knowledge and acceptance amongst the profession and general public of the benefits of dental implants. Indeed it is now almost universally accepted that dental implants are the treatment of choice for the replacement of the missing tooth.

Survival rates of dental implants are relatively high although not as high as many believe and it is essential when advising our patients and gaining informed consent that we understand the issues. When reviewed by the International Team for Implantology (ITI) the cumulative survival rate of oral implants supporting fixed partial dentures was 95.4 per cent after five years of function and 92.8 per cent after 10 years of function. Survival of single fixtures is higher; however we need to be a little cautious when interpreting these figures because there is a widespread misunderstanding, even amongst professionals, regarding the difference between 'survival' and 'success' of dental implants.

Implants can survive in the mouth but can fail for biological (for example soft-tissue loss) or technical (for example restoration or screw fracture) reasons. Depending on the success criteria evaluated failures can be as high as 50 per cent. When dental implant and conventional treatments are compared success rates are actually fairly similar.

Digital workflow

One of the latest drivers in the growth of implant dentistry is the integration of computer technology; it is now used extensively in implantology and can significantly enhance the process of treatment provision through the various stages of diagnosis and treatment planning through to the execution of surgery and the laboratory design and manufacture of restorations. This concept of 'digital workflow' is likely to have a significant impact in most dental specialities and dental implantology in particular. The main areas of relevance are Cone Beam Computed Tomography (CBCT), computer guided surgery, Digital impressions and Computer-Aided Design and Computer-Aided Manufacture (CAD-CAM).

CBCT

Cone Beam Computed Tomography (CBCT) produces an image of the maxillofacial structures made of up of thousands of 3D pixels called 'voxels'. The scan is produced from a cone-shaped beam that makes a single rotation of the patient, which takes 24 seconds. The radiation dose is normally less than 100 micro-sieverts, a fraction of annual background radiation dose or a conventional CT scan, both of which have over 20 times the exposure. At a further-reduced radiation dose, small-field scans are also available which have a view that is cylindrical in shape, 38mm high and 50mm in diameter. The information from either large or small-field scans is stored as a DICOM file which can be imported into various commercially available software programmes for use in treatment planning.

In order to dramatically improve diagnostic yield it is good practice to fit the patient with a radio-opaque scan-prosthesis. This is a radiographic template constructed from a diagnostic wax-up of the planned, restored dentition. This enables the dentist to use the treatment planning software to visualise the ideal restoration position and plan potential implant placement options relative to the quality and quality of available bone; also taking into account the various anatomical considerations including in particular the maxillary sinuses, mental and inferior-dental nerves and the sub-lingual fossa and artery. If bone grafting is required the extent of the required graft can be evaluated prior to surgery and the donor site assessed and chosen accordingly.

Computer-guided surgery

Following planning of the ideal dental implant placement protocol, the information generated by the treatment planning software can be used to construct a surgical guide. This stent incorporates sleeves designed to carry inserts and burs to enable implant surgery and placement according to the virtually, pre-planned, design. Computer-guided surgery can often be carried out without flaps, reducing the operative time and post-operative discomfort and swelling associated with surgical incisions, raising the mucoperiosteum and provision of sutures. The latest techniques will consistently achieve accurate 3D implant placement to within +/-0.8mm facilitating treatment in challenging anatomical situations. Pre-planning of implant position also enables accurate provisional restorations to be provided by the laboratory for immediate loading if so required.

Digital impressions

Digital impressions are taken by an intra-oral scanner that combines multiple images of the site to be restored, the opposing arch and a bite registration in order to create a 3D computer generated rendering of the patient. The dental implant has a scan-body attached to assist in information capture. The image is emailed directly to the laboratory that then liaises with a central, industrial milling centre to digitally produce the final restoration using a CAD-CAM process. Digital impressions can significantly improve patient comfort and eliminate the potential inaccuracies associated with taking, storing, transporting and casting of conventional impressions.

CAD-CAM

Advanced dental laboratories are now using CAD-CAM (Computer Aided Design and Computer Aided Manufacture) to produce restorations, even from conventional impressions. Conventionally, the laboratory process involves the waxing-up of restorations, abutments or superstructures on stone dies. Wax patterns would previously be invested and cast in the traditional way and then the restoration finished accordingly. Alternatively in the CAD-CAM process the stone die is scanned and the restoration designed digitally. The laboratory then emails the prescription to the central, industrial, production centre where the restoration is manufactured, often using a milling process. The restoration is returned to the laboratory for finishing. The reduction in analogue procedures increases reliability and accuracy of fit of final restorations. It has also facilitated the increased use of alternative, milled, materials that can have cost or aesthetic benefits, including cobalt-chromium or zirconia. The laboratory can use CAD-CAM to produce the full range of restorations from single abutments to full-arch reconstructions.

Dental implantology is likely to continue to rapidly develop in the foreseeable future and increase in penetration particularly in the UK. The utilisation of computer technology in various stages of treatment and the potential implementation of a 'digital workflow' with its many benefits to patient and clinician is likely to add to this impetus.

References available on request.