Welcome everyone to part 3 of our blog series discussing full arch. The focus of today's blog is on FP1 complications and Partial Extraction Therapy concepts.
As mentioned in our last blog, one challenge that exists in full arch implant therapy is the ongoing bone remodelling that occurs. Implants do not preserve bone, and bone is a dynamic structure that will continue to change throughout the patient's lifetime. Keeping this in mind what are some elements of treatment planning that we should keep in mind?
1-Implant Diameter: If possible, I prefer to use implants in the 3.5-4.0 mm diameter for full arch, and no larger in most cases(posterior maxilla may go wider due to soft bone density). In alot of these cases, you will find that even after bone reduction is performed, it can be a challenge to obtain the ideal minimum of 1mm (buccal) and 1mm(lingual) around the implant. This is the bare minimum of 3.5mm for implant diameter and 2mm giving a total of 5.5 of ridge dimension. Ideally we should be aiming for 7.5mm in ridge width. So a 3.5mm diameter implant has 2+2 (B-L) of bone around it for long term stability. In my hands, i prefer to use these smaller diameter implants if possible and go LONGER for stability instead.
2-Partial Extraction Therapy(PET): We briefly touched on this topic last time, and this is a unique concept which can be applied to single teeth replacement to full arch. The concept of PET can be used to reduce the risk of facio-lingual collapse after tooth loss and improve the preservation of alveolar bone height and blood supply.
"When the facial alveolar bone is <2 mm in thickness, partial extraction of the tooth root can help preserve thin facial bone by leaving a portion of the root connected to the facial bone via the PDL. This approach keeps the PDL vasculature in place and better preserves the ridge form by maintaining the bundle bone–PDL apparatus" (12. Gluckman H, Du Toit J, Salama M. The pontic-shield: partial extraction therapy for ridge preservation and pontic Site Development.Int J Periodontics Restorative Dent. 2016;36(3):417-423.)
Can this concept be applied to full arch? The answer is YES. if a case requires bone reduction to gain adequate prosthetic thickness or to hide the transition zone, PET can still be applied on the remaining teeth to maintain the bundle bone. If you recall the last blog, at the end I posted a case with adjacent implants in the lower mandible, and with the PDL apparatus and thick tissue to protect the area, it can be unavoidable consequence.
This is a separate topic on its own requiring a discussion on the success criteria and case selection necessary, but it does bring up an interesting view. We as dentists work so hard to remove every little fragment of a tooth during extraction, yet in medicine if someone has an unhealthy tissue (liver or parotid ) or skin growth, we do not go and remove the entire affected area but only the diseased tissue. Its time we look at a change in how we approach our cases to ensure that we do not face unavoidable long term consequences.
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