I recently had a new patient (Patient B) come in for a consultation in regards to “fixing her rocking”, upper 4 Mini Implants over-denture. The patient said that her previous dentist was not able to fix the problem and she was recommended to me by a friend who had a similar problem for which I was able to remedy.
Initial inspection of the under surface aspect of the rocking denture revealed only two, properly imbedded metal “female” basket housings. There were also two gouged out areas where two other two baskets formerly resided within the denture. In the final processing of an implant over denture, the female basket component is imbedded within the denture and designed to receive the “male” counter which is usually the “ball” component of the Mini Implant (see photograph above). Consider the ball aspect as an extension of the implant. This ball aspect of the Mini Implant protrudes thru the gingiva, and is responsible for engaging the imbedded denture basket and thereby creating the “snap” you hear upon insertion of the over denture. Because all Mini Implants are of narrow diameter, they must be manufactured as one solid fixture. They would be inherently too weak and unable to resist forces of chew during mastication if they were not one piece. They would snap like a toothpick. A Mini Implant is not like a traditional implant where you have component parts and abutment choices (see previous blog on implants for description of What Is An Implant).
Immediately, I thought to myself, easy fix with just a simple chair-side cold cure. Add two new basket attachments where she had lost the two, twenty minute appointment, go to lunch. I keep baskets on hand inventory for such an emergency. Everybody happy.
Boy, was I wrong!
Upon further inspection during the intra-oral examination, I realized that, unfortunately, her over denture had never and would never work properly.
The 4 mini implants were originally placed in divergent directions. As a result of implant placement and choice of the implant ( a one-piece fixture ), the denture had No One Path of Insertion or Withdrawal. It just could never engage all the ball fixtures. In defense of the doctor. The one piece nature of the Mini Implant offers no room for error in surgical placement. All implants MUST BE Parallel. The female basket may offer a slight degree of variance for the slightest bit of angulation error. The dentist had good intentions to help this patient via the advantage of implant stability. He lacked the surgical skill in pre-implant placement; specifically bone augmentation. He had not anticipated the prosthetic hurdles created by his in experience. This was truly a very difficult case because the patient had minimal bone quantity and poor quality to start with. The implants were also placed too close to each other and too far anteriorly in the maxilla (upper jaw) where the bone naturally becomes very narrow and flares upward dramatically. Her denture never engaged her implants. Subsequently, the metal balls of the Mini Implants were responsible for smacking and cracking the acrylic. Ultimately the metal baskets became dislodged from the denture. The fit of all components when they come together in a snap on denture must be passive. A passive fit leads to less lateral loads on the implant fixture. Lateral loads are disastrous on a dental implant.
It is of my opinion that, lateral loading onto excessively angled placed implants, in poor quality bone, with compromised bone volume with inadequate implant diameter led to this catastrophic failure for patient and dentist.
A rocking denture does not mean a failing implant case. There are many reasons for a rocking denture other than failing implants. Patients can lose weight or change medications resulting in physical changes of their oral tissues. Metal housings can pop out due to manufacturing flaws by the laboratory, “O” rings wear out, denture acrylic cracks, things can just break yet, the implants can be just fine, do not despair.
There are many important difference to remember in type of rehabilitations there are. A subtle and very significant difference with an Implant Over Denture Prosthetic versus a totally Fixed Implant Prosthetic is chewing power.
An acrylic implant Over Denture engages the implant’s male part, however, the denture is still 100% tissue supported. Gum tissue is compressible. The oral tissue carries the chewing load. The implants only keep things in place from shifting. The acylic denture does not drop or slide. You will bite and chew 100% more efficiently than the non implant denture person. You’ll be fine with 95% of the foods out there with confidence of knowing they will not fall out when you sneeze or laugh.(This has been reported to me by previous non implant denture wearers). You can not bite nearly as hard as the fully implant supported prosthesis on 6-8 implants. This is the real deal. Hardcore chewing power. Totally implant supported with no tisue compression discomfort. Your brain magically knows thu the wonders of muscle physiology. You can break rocks with your prosthesis(not advised). This is not a denture snap on option.
A bit of Trivia: The hardest food in the human diet is a raw carrot.
The previously case failed for this patient for numerous reasons:
1-The Mini Implants placed were just too narrow. It is my clinical experience that mini implants in the maxilla have a very high failure rate; more so than a regular traditional diameter implant. I only utilize mini implants for the mandible ONLY (mandible jaw) because the quality of the lower jaw bone is much better than the quality of the upper jaw bone.
In General in terms for categorizing Quality of Bone: The Best Quality bone is in the lower anterior mandible. The Poorest quality of bone is in the upper posterior maxilla (upper jaw bone).
As a Rule: If the implant Diameter is increased by 1mm (in a 10mm long implant) you will have increased the surface area of the implant 25%. That much more surface will be available to osseointegrate.
2-The Mini Implants were too short. The more length the more surface area to stick to the bone. That’s better than shorter implants. As mentioned previously, the dentist attempted to fit the implant for bone available. There are several options to overcome this issue; not to mention for this discussion.
3-The Mini-Implants were too close to each other. Think of this simple analogy. A table has a better foundation when the legs are spaced further away from each other as opposed to next to each other. Better spread of the implants leads to a better stable over denture
4-The angulation of the Mini Implants were less than Ideal, NOT parallel. This was a function of bone architecture available to the dentist upon surgery.
5-Lack of Preparation. A 3-D (CBCT) analysis preoperatively providing visualization of bone morphology PRIOR to picking up the scalpel would have demonstrated the degree of difficulty ahead for surgeon and patient. I personally refer out to dentists in my area frequently for the most challenging cases that require super I.V. Sedation or more advanced surgical care.
Don’t get me wrong…………I love Mini-Implants. When used appropriately in the anterior mandible, they are fantastic! Many of my elderly patients benefit from this life changing approach of stabilizing their lower denture. I only use 2.8 mm x 14.0 mm Mini Implants and place a minimum of two and as many as five to deliver a “snap on” lower denture . It’s tremendous. Every implant patient I treat must have a preoperative CBCT so that I can anticipate complications and plan appropriately to avoid any surgical or prosthetic nightmares.
Treatment rendered for this patient B: Removal of all 4 Mini Implants with simultaneously bone grafting to implant removal the sites and bilateral Sinus Lift procedures. She now has a ton of available bone waiting for implant placement this upcoming month.
Some of My Cases:
Dr. Emilio & Associates, Always Accepts New Patients. He especially exceeds at treating same day emergencies patients suffering from tooth ache pains.
His goal is to keep his patients’ Teeth and Gums Healthy For Life.
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