Angle Corrected CAD/CAM screw retained single units are here

A new solution for screw retained implant crowns

In this blog update we are going to look at a new technology that allows us to bend the access holes in screw retained restorations.

Screw retained implant units have always been popular with our surgeons for many reasons but I think a main advantage is the lack of cementation needed at fit, which negates any associated risks of retained cement causing issues sub gingivally later on.

However the access hole can be a problem in certain situations where the emergence angle leaves the hole coming through the aesthetic facings of the crowns, which often then means we have to switch to an abutment and cement retained restoration.

As our regular followers will know we have a belief that CAD/CAM restorations really are the only way to go when designing and producing implant sub structures to ensure the best clinical results, but this did mean there was no solution to the access hole problem as these structures are milled from a solid block of material and therefore the burs had to have a line of sight the section of the element that was being milled.

For a while we have been able to offer angle correction on the access holes for multiple unit cases but nothing was available for single units in CAD/CAM due to the complexity of the milling strategies required.

Thanks to new milling strategies and partnerships it is now possible to offer angle corrected screw retained CAD/CAM crowns on most of the popular implant systems, even down to some narrow platforms such as this Nobel Biocare Replace NP fixture that we restored with Dr Pav Khaira
 

 Original design

 

Angle corrected design

The red tube illustrates the original access hole direction, which would have been coming through the buccal of the crown and the green shows where the access hole was corrected to come out of the centre of the occlusal surface of the crown.

Once we have approved the new correction design the abutment can be milled from chrome with the access hole now corrected to come out of the occlusal of the crown, rather than the buccal where it would have been previously.



By using this new technology we can now have screw retained units with the clinical benefits they bring, without the compromise to aesthetics or the very challenging prospect of the surgeon having to fill the hole and blend the composite to match the surrounding crown in an aesthetic area of the restoration.

This image of the final crown back on the model shows that we have been able to bring the access hole well clear of the buccal of the crown (we will post up final fitted pictures when the patient comes back in for a review with Dr Khaira)

Fitting an angle corrected screw retained crown

For the surgeon these are to be fitted following the same protocols as any other screw retained crown, the only exception is that they must have a specially designed screwdriver, which we will look at below.

Screwdriver

To fit these crowns you need a specially designed screwdriver that has a thin shank to allow the head of the driver to engage with the head of the screw but a large head which is similar in design to a rosehead bur, this allows the grooves to stay engaged with the hex in the head of the screw, even if the shank of the driver is angled back.




the engaging head of screwdriver in action




The benefits of using this new solution are :-


All the traditional benefits of screw retained restorations (easy retrievability, no risk of retained cement etc.)

No change to the restorative procedure (you simply need a new screwdriver)

Control of where the access hole will emerge from our restorations

Incredibly cost effective as there is no need for a separate abutment and cement retained crown

Consistency and cost efficiency of CAD/CAM technology


We have also covered the difference between cement and screw retained and the advantages of CAD/CAM technology over traditional lab cast methods in this previous article which we wrote for the dental site Dentinal Tubules, and may be useful if you are unfamiliar with these types of restorations

For more information you can visit our website page for angle corrected screw retained implant crowns, call sean on 10765 607347 or email sean@ambridgeceramics.com