Ross Cutts presents a case using CADCAM for multiple implants
Up until recently, providing large multiple unit implant frameworks has been an extremely costly, technique sensitive and protracted process.
Two traditional approaches are available for implant abutment and framework construction, namely, stock abutments and the lost wax/casting approach. Stock abutments are provided by all the implant suppliers and are milled in a similar way to an implant fixture. Since stock abutments are industrially produced in well-controlled conditions, they exhibit superior durability and fit accuracy than cast abutments (figure 1 – Stock Straumann aesthetic anterior bone level abutment).
One of the problems with stock abutments, is the finish line is located according to average values which might not necessarily coincide with the existing mucosal contour. The cylindrical emergence profile of stock abutments means for an aesthetic outcome the margins have to be placed more deeply, which in turn hinders cement removal.
To counter this limitation we have used cast abutments. In the dental laboratory, the abutment or framework is fully contoured by wax or resin and conventionally cast. The numerous steps involved and temperature fluctuations have been described as the cause of compromised marginal fit. The longer the span the more distortion is possible. To eliminate this we can incorporate additional fit modifying techniques such as sectioning and soldering, laser welding or spark erosion (figure 2 -Traditional framework sectioned and rejoined with pattern resin in preparation for laser welding framework).
Even a relatively simple 2 implant supported 3 tooth bridge can be a multiple appointment procedure – impressions followed by abutment and framework try in with possible sectioning and soldering of the framework followed by and fitting the final bridge. The Lost wax technique of manufacturing frameworks was a tried and tested method over many years and numerous clinicians have been quoted as saying “if it isn’t broken don’t fix it” – so why are we now looking at Computer Aided Design and Computer Aided Manufacturing (CADCAM) – quite simply to improve the design and creation of our dental prosthesis.
Since the mid-1980s, CADCAM has been used in Dentistry – mostly in combination with chair side intraoral scanning to provide a one visit restorative solution. However the accuracy until recently has always been variable – dependent upon a multitude of factors and definitely user sensitive.
Straumann’s partnership with Createch provides a wide range of CADCAM structure solutions for implant-borne dental prostheses for a variety of indications but importantly underlined by Straumann’s Guarantee of clinical accuracy of components.
It is also important to understand that utilising CADCAM technology doesn’t involve capital investment for the implant clinician. Laboratories simply need to send the model to Createch Medical for measurement and design, the proposed design is then reviewed and approved by the lab, and within approximately 7 days the fully milled restoration is returned to the lab for finishing.