how many implants are neededThe old joke in dental school regarding dentures was you should charge $4,000 dollars for the upper one and don't charge them for the lower. That way when they come back and complain about the lower you can say, “What did you expect, you got it for free?” The truth is, very few patients are happy with their lower complete dentures. In surveys, 80 percent of patients are not happy with the fit or function of their lower prosthesis.

With implants however, 80 percent of respondents are happy with their lower prosthesis. The question is: How many implants are needed for a mandibular overdenture? This depends on the chief complaint of the patient. The two reasons most people dislike their lower denture is either lack of retention or pain on biting.

The most common problem with the lower dentures is retention of the denture during speech or mastication. This is due to lack of a bony ridge and/or no retentive seal since their denture is a horseshoe shape. The tongue retains the lower denture. When the tongue moves so does the denture. Luckily if this is their chief complaint then placement of two implants in the canine to the first premolar area will relieve most of the issues with retaining the denture. The implants need enough separation and anterior-posterior spread to prevent tipping that can cause the retentive rings of the denture to release their hold.

The more complicated case is when the patient complains of a burning or sharp pain on biting. Typically they will point to the area where the premolars used to be. The cause of their discomfort is the mental foramen. As the ridge resorbs, the bone over the mental foramen goes away and eventually leads to the mental foramen passively migrating to the top of the ridge. With the mental nerve now sitting directly under the denture there is pressure on the nerve every time the patient bites down. The pain is similar to when you hit your funny bone, which we all know is not that funny.

This is a case where just retaining the denture is not enough. You have to be able to keep the pressure off the nerve when the patient masticates. This is when you’ll need four implants to retain the lower denture and help keep pressure off the tissue. There is some debate as to whether or not a bar is needed to accomplish this. The bar can extend over the mental foramen area or bridge over it and allow the denture to be completely supported by the implants. This is the difference between an implant retained denture and an implant supported denture.

Without question the bar will take care of the problem; however, the difficult thing for some patients is the expense of the bar. If the implants can be placed close enough to the mental foramen then by nature of having the implant there the pressure on the nerve upon biting will be relieved. The challenge in these cases is finding the bone to work with. The whole problem stems from resorption, so finding enough bone can be challenging. A CBCT scan is a must in these cases along with a guide to make sure placement is ideal.

Darin O'Bryan, D.D.S. www.onemorereasontosmile.com


Comments

Sean Mooring
July 31st, 2012
I am happy to see more information on implant assisted removable prosthetics coming from Spear Education. For a lot us, dentures are the most common full mouth rehabilitations we see. I would suggest that the mandibular overdenture with only two implants be placed in the lateral incisor areas rather than the canine or premolar area. This helps prevent an A-P rock and allows the patient to securely bite into food with their front teeth. We see longer lasting male attachments and higher patient satisfaction with only two implants in the lateral positions. It also makes it easy to upgrade to four implants and a fixed hybrid denture later if the patient desires. I like to use the sitting analogy. You can sit on a chair and rock on two legs, but a three legged stool is a little more stable. However, four on the floor is the most stable way to kick up your feet and relax. So how stable do your want your teeth to be? Most people understand the difference. I look forward to hearing how others approach these cases.
Kevin Huff, DDS
July 31st, 2012
I also have found that two implants in the lateral incisors work best for the same reasons. I have three other suggestions: 1. Always remind patients of the risk for combination syndrome. Adding implants creates a similar situation to natural teeth. 2. I also have found that using 0 degree mandibular teeth against lingualized 10 degree maxillary teeth adds to patient comfort and function rather than using intercuspation. 3. I have used many retainer mechanisms over the years, and I have found that simple o-rings tend to outperform other attachments for the 2-implant scenario.
Douglas Benting
August 10th, 2012
The article was great & I enjoy reading the comments as the dental implant retained or supported prostheses have changed the quality of life for many of our patients and it is energizing to see the patient through the process. A couple of thoughts, I feel that the number of dental implants really depends on the mandibular arch form. Specifically, a 'U' shaped arch would work great with two implants in the lateral incisor position for an implant retained restoration which would allow for the option in the future to add two more in the premolar area for an implant supported restoraiton (either fixed hybrid or removable overdenture). A 'V' shaped arch on the other hand creates a situation where a third dental implant in the midline would improve the stability in the form of an indirect retainer for an implant retained overdenture. In a situation with a 'V' shaped arch, I might also consider 5 dental implants for a fixed hybrid prosthesis or an implant supported overdenture. I look forward to reading more comments!
George Duello
August 22nd, 2012
This is an interesting question. The best reference for this is the approach that is advocated by Carl Misch, Chapter 14-Treatment Options for Mandibular Overdenture-An Organized Approach in Dental Implant Prosthetics, Elsevier-Mosby, 2005. I concur with his recommendations that have been a staple of my decisions regarding over denture even though I am not a Misch graduate. My first thought is why even consider over dentures. For most patients it is cost and for most dentists it is usually cost. I will debate costs, short and long term, vs. the value of fixed implant prosthesis on the lower which is part of a larger and longer lecture. In the US the cost of milled frameworks and overdenture attachments is now higher in most commercial labs than a fixed bar hybrid prosthesis. I would rather lower my cost to the patient to move them to a fixed option rather than removable even though in my opinion the fixed appliance has more value and should command a higher fee. We spend a great deal of time allowing the patient to make informed decisions-good, better, and best options for implant prosthesis on the mandible and maxilla with upgradable options for all treatment plans. Too many times the patient is backed into a corner with a treatment and can't be upgraded.
Zuhirah Rasul
December 26th, 2012
I would like to t hank all who have participated in this forum, from an individual who has to make a decision from ill fitting upper lower prothesis and wanting replacements that fill well and comfortable and esthetically looks as natural as possible. I was unaware until I found this website that there was an alternative to removable upper and lower dentures. I would be interested in locations in Cleveland, Ohio area and min to max costs for this area. Again many thanks for this information, it is very valuable.
Darin O'Bryan
December 26th, 2012
I don't know anyone in the Cleveland area off the top of my head. I can certainly look into it or someone on here may very well be in that area or know of someone.
J. Mather
June 29th, 2014
Great observations and advice! I was fortunate enough to have a general Dentist who knew my limited finances and sent me to a dental school where the cost was minimal, fantastic students and I obtained wonderful results! Chemo therapy can not only cause hair loss, but little publicized it can destroy gums. This has given me my healthy life back.