Maintenance and Complications – Implant supported prosthesis

Maintenance and complications of the implant supported prosthesis is something we all must be aware of and paying attention to as the recommendations are likely to continue to evolve with new materials and new research.

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How often should we remove the implant supported prosthesis?

“Removal of a fixed, screw-retained implant prosthesis for evaluation is not needed unless there are signs of peri-implantitis, a demonstrated inability to maintain adequate oral hygiene, or there are mechanical complications that require removal.” This is from the 2016 ACP position paper.

It is said by some that ideally the prosthesis will be removed once a year and have the screws replaced.  I disagree and do not do it unless I see a need. However, there has been some research to suggest a re-tightening at 5 years. The loose screws in that study correlate to misfit prosthesis and since the study is old is likely from metal that was cast and may not be an issue with milled bars.

“I don’t take the prosthesis off unless I have a reason to do so.  If I see thread exposure, inflammation, poor oral hygiene or any other reason.  Screw threads will cross thread, you will find sometimes that you have created a problem that you other wise would not have created.” Howard C.

When removing there are multiple screws to check and verify

The MUA screw to the implant should be verified by either

• Placed to 35Ncm (if that is the recommended torque angled in particular may not be) and left for 15 minutes then rechecked
• Placed to 35Ncm and have return in 1 week to recheck

The prosthetic screw is often 15Ncm which is approximately hand tight.

Prosthetic issues for implant supported prosthesis

Gummy Smile or VME – Make sure get enough bone reduction! 13-15mm  Use a clear duplicate denture guide at surgery time

Limited post space – Can hide with acrylic but makes less cleansable

Failure or implant – Mandible just replace and pick up if in temp.  For maxilla replace but leave out of temp and adjust temp to all on one less than what you had

Men, bruxer, opposing natural or implant supported restoration consider extra implants.

Complications of the implant supported denture acrylic

Due to the fact that until recently this was not a very popular procedure, there is not a lot of long term data on comparing the different types of materials that can be used.  To date this is one of the best studies, meta-analysis by Bozini 

• All studies were on acrylic
• Almost all were external hex implants
• Most were in mandible

Complications for acrylic (keeping in mind the 3 bullet points right above this)

• Fracture rates 1/3 at 5 years, 1/2 at 10 years, and 2/3 at 15 years
• Screw loosening for both around 5-10-15% at years 5-10-15
• Screw fracture abutment 2-4-6% and prosthetic 4-8-12% at 5-10-15 years
• Framework fracture 3-6-9% at 5-10-15 years
• Wear 17-31-44% at 5-10-15 years

They also report that resin veneer fractures were highest in the beginning of the clinical period; severe wear increased in the later stages of follow up. They noted that wear and veneer fractures were time related during the clinical course of the study. 1

Papaspyridakos 2012 JOMI found only about 9% are complication free at 10 years. Riemann JOMI 2019 finds that 40% have a complication in their study with an average of less than 2 years. This is pretty consistent with Chochlidakis JPros 2020 who found about half had a complication out of 107 prosthesis with an average age of 3 years.

Mayo clinic study with Salinas Dhima J Pros 2014

• 20 year survival 86% prosthesis
• 92% implant survival
• only 15% free of any event

If anterior teeth break out posterior support needs to be verified (could be reason for breakage) Kent Knoernschild

Some people will have no issues without ever removing it 28 years without removing this one and this woman who had her implants for over 30 years and the prosthesis broke at year 26. JPD 2018 Seong

Staining can be an issue and if severe enough then use the Tiger Multi Mini polishing paste.

Maintenance and Complications – all ceramic implant supported prosthesis

Teeth will break when doing a frame with individual teeth. Malo shows 44% of patients experience this in the first 5 years.

Fractures of frameworks certainly do happen but the quality of zirconia is almost certainly why this occurs as Bidra JPD 2018 shows a 99% success with Prettau

Maintenance and Complications – metal ceramic implant supported fixed prosthesis

The survival rates of both implants and prosthesis are very high (above 98% at 5 year). However, there will be both biological and technical complications at high rates. Only around 10% of prosthesis will be either biological or technical complication free at 10 year. Most issues are either broken/chipped porcelain or peri-implantitis. Papaspyridakos JPD 2019

Cement vs screw retained full arch implant prosthesis issues are covered on another page.