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Dental Implants

Dental Implants

 

Replacing Back Teeth

Because missing front teeth are considered aesthetically and socially unacceptable, most people consider their replacement a higher priority than back (posterior) teeth normally hidden from sight. From a dental point of view, however, you should definitely consider their replacement, if not for cosmetic reasons, then for the loss of function created by their absence.

Besides their obvious role in chewing, the posterior teeth affect the overall bite and help ease some of the excessive pressure on the front teeth created by chewing. Dentists generally agree the loss of posterior teeth can lead to a wide array of consequences, especially involving the remaining teeth, gums, jaw muscles, ligaments and joints:

  • Decrease in chewing efficiency
  • Tipping, migration and rotation of remaining adjacent teeth
  • Eruption or extrusion of unopposed teeth
  • Excessive wear or erosion of remaining teeth
  • Loss of alveolar jaw bone and reduction of the residual boney ridges
  • Painful dysfunction of the temporomandibular joints (TMD) that unite the lower jaw with the skull

And, just because the site of the missing teeth is hidden from view doesn't mean there won't be changes to your appearance. For instance, the loss of the posterior teeth can cause a reduction in facial height that becomes increasingly noticeable over time.

Unfortunately, that's only the beginning of problems you may encounter from missing posterior teeth. Some of the above factors, particularly shifting or migration of teeth, can set off a chain reaction that weakens the overall dental system.

For instance, teeth normally move to maintain contact with adjacent and opposing teeth as natural wear slowly occurs over time (you won't notice this movement because of the equilibrium created by the teeth touching each other). When you lose a tooth, however, the remaining teeth tend to shift at an accelerated rate. This creates a force greater than normal along the tooth, causing abnormal displacement of the tooth in the jaw bone. If these teeth shift too much they may become worthless in the future.

Along the same lines, if the teeth erupt too much there may not be enough room to replace the missing teeth below them. Also, as a tooth moves, it changes the relationship of how the jaw bone is attached to the tooth. This change may leave the tooth more vulnerable to periodontal disease.

Obviously, then, replacement would help deter some of these consequences - but which method is best? Dentists now recognize implants as the best option for replacing missing teeth. They have some obvious benefits: as a free-standing restoration, adjacent teeth aren't usually affected by the preparation process and the replacements are easier to clean and can contribute to the support of the bite.

The most critical factor for implantation is that adequate bone height and volume exists where an implant will be placed. If not, a non-removable fixed bridge is the second best option, although there are a number of considerations to take into account.

First, teeth must be present on both sides of the missing teeth to create a fixed bridge - and you are actually asking two teeth to do the work of three. The adjacent teeth have to be drilled down for bridge placement, so there is a greater risk to the nerves - a future root canal treatment may be necessary. There is also a greater risk of trapped food under a bridge than around an implant restoration.

A third and least favorable option is a removable partial denture. Removable restorations can be difficult to wear and trap more food. Because they are moveable, they may put additional stress on the teeth that hold them in place, which could lead to loosening and loss of those teeth.

In summary, I think you can now see the importance of replacing missing teeth, seen or unseen. Excellent options in dental implants or bridgework are worth looking into and discussing with your dentist.

Osteoporosis & Dental Implants

Osteoporosis (from "osteo," meaning bone, and "porous," meaning sieve - or sponge-like) is a condition in which the bones lose calcium, becoming thinner and more prone to fracture. An ongoing process called bone remodeling, in which old areas of damaged bone are removed ("resorbed") and replaced with new structurally-intact bone, is normal for adults. Under ideal circumstances, these two processes - bone resorption and bone formation - are balanced. Living bones are not like the dry bones of skeletons you see in a museum, which are static and unchanging. Many things can change the balance between normal bone resorption and formation. In osteoporosis, the balance is tipped toward resorption, so more bone is removed than is replaced, resulting in a gradual decrease in the bone density over the years. In recent years, oral (taken by mouth) drugs in a class known as bisphosphonates have been widely used to treat osteoporosis. They act by slowing the excessive bone resorption, establishing a better balance between resorption and formation and increasing bone density.

But we've noticed something different in the bone of the jaws. In rare cases, a long-term user of a bisphosphonate drug may develop a complication called osteonecrosis ("osteo," - bone, "necrosis," - death), in which isolated areas of the jaw bone lose their vitality and die. For such an individual, tooth removal or any kind of oral surgery involving the jaw bone must be carried out with care. Expert opinion recommends that bisphosphonate treatment be stopped for three months or more prior to surgery, if possible.

The cause of osteonecrosis is not well understood, but it appears that the people at greatest risk are those with underlying cancers who have received relatively high-dose, intravenous ("intra," - within, "venous" - vein) bisphosphonate treatment, typically given every month over an extended time. The risk of osteonecrosis with relatively low-dose, oral treatment - as is used for the prevention and treatment of osteoporosis - has not been firmly established, but appears to be much smaller.

How Implants are Placed and Restored

The following page goes through a complete case. There are some mildly graphic surgical images ahead, however the emphasis is more on the reconstruction.

The patient in this case is a teenager with two congenitally missing lateral incisors, as you can see in the pictures below:

His restorative options were a Removable Partial Denture, a fixed Bridge or two dental implants. The patient chose the implant option.

Below you can see the patient during surgery. Two Root Form Implants (screw-type) are placed in the edentulous sites. The two x-rays show before and after images.

dental implant placed dental implant placed
 
pan of implants pan of implant

After the implants were placed, the tissues were sutured back together again. The sutures were removed approximately ten days after the surgery. Four weeks after the surgery the patient presented for a post-operative check-up. Below, you can see images of the surgical sites four weeks after surgery.

 

The implants were left undisturbed for approximately six months, after which they were uncovered. The Uncovery procedure involves a small exposure of the head of the implant and placement of either a Healing Abutment or a Temporary Crown. Both are designed to train your gum tissues to grow around the future prosthesis in a collar-like fashion. The temporary crowns are usually the better choice in an esthetic area, such as in this case, since they are able to shape the gum tissues into the nice, scalloped appearance, which makes the entire restoration look more natural and blend in better. The healing abutments are designed to stick out of our gums after they are placed, which would make them esthetically not so pleasing in this case, as you can see below.

 

Here you can see two images with healing abutments in place (not very esthetic).

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These two images show the temporary crowns to be exchanged for the healing abutments.

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This shows the patient with the temporary crowns in place.

The Temporary Crowns were left in place for approximately eight weeks. This is the amount of time it usually takes for tissues to mature or get trained, before final impressions can be taken for the permanent prostheses or crowns.

 

These two pictures show the healthy tissue condition, after the temporary crowns had been in place for 8 weeks (and the patient had bleached his teeth somewhat).

Once the tissues are in satisfactory condition, a final impression is taken with the help of specialized transfer impression pins, as you can see below to the left (the transfer pins connect to implant analogs, which will record the position of the implants in the stone cast). The impression is then poured into stone with the appropriate implant analogs in place (below to the right). The analogs (arrows) are metal components duplicating the exact position and neck morphology of the implant fixture as it is in the patient's mouth.

 

The laboratory technician will then make custom abutments (red arrow in the left image below), which are attached to the implant fixtures in the mouth via screws (green arrow in the left image below). The crowns (blue arrow in the same picture) are then cemented over the custom abutments. Below to the right you can see the custom abutments inserted. At this point, the screws, connecting them to the implants will be torqued to a pre-determined torque value, in order to achieve the correct pre-load value of the screw. This step is very important, because it will prevent future loosening of the screws.

 

Once the abutments are torqued in, the screw access is sealed off and the porcelain crowns are cemented onto the abutments, much like crowns are cemented onto natural teeth. Below you can see two views of the restored lateral incisors.

 

Again, please keep in mind that this is only one example of how a condition like the one above can be restored. There are always several solutions to a given problem in implant related reconstruction.