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Computer-guided Surgery for Dental Implants

The placement of dental implants is greatly aided by the use of a computer fabricated surgical guide.  Placing an implant in just the right spot is a big factor in whether or not the implant will succeed on the long term.

What are dental implants?

Dental implants are metal posts (titanium) that are surgically placed into the jawbone beneath the gums.  Once in place and healed, the dentist can mount teeth on top of them.

How do they work?

Because dental implants fuse to your jawbone, they provide a stable support for artificial teeth.  These can be single teeth, multiple single teeth, bridges, and dentures.  Unlike conventional dentures or partial dentures, implant supported ones will not allow dentures or partial dentures to slip or shift in your mouth.  This secure fit helps dentures, partials, bridges, and single teeth that are attached to dental implants feel more natural than conventional ones.

Do implants always work?

Recent studies on the clinical success of dental have indicated a high implant survival rate.  However, there exist surgical and prosthetic complications related to improper diagnosis and implant placement that do lead to implant failure.  An excerpt from a dental implant textbook states, “Complications related to malpositioned implants…continue to be seen in implant dentistry and are perhaps one of the most common types of implant complications”.  This means that the positioning of a dental implant is real important if you expect it to last a long time.

 

How are implants placed?

Dental implants are placed into the jawbone using special twist drills that create a cylindrical hole into which an implant is placed.  This can be done either freehand or guided.

Freehand Surgery

Freehanded placement, as the name implies, is done by the dentist using his or her eyes and hands along with models and radiographs to position the drills in just the right spot.  Usually, the gums are cut and flapped open so the jawbone can be seen directly.  As you might imagine, this will result in greater trauma and post-operative pain.  But with freehand surgery, it’s often necessary.  The dentist then estimates the proper distance from adjacent teeth as well as from the jawbone walls.  This is the LOCATION.  Next, the dentist must align the drill properly.  He or she must look from a least two different angles to line the drill up properly relative to the adjacent teeth and the opposite arch of teeth.  This is the ANGULATION.  Finally, the implant must be placed at the correct depth.  The top of the implant is usually placed exactly at the top of the jawbone while the end of the implant is usually at the same length as the neighbor teeth and must not go into the sinus in the upper or the nerve channel on the lower.  This is the DEPTH.

While getting an implant to be parallel to adjacent teeth is not that difficult with single tooth implants, the difficulty increases significantly when multiple implants are placed and there are no adjacent teeth.  Another difficulty arises when the available bone is real thin or of poor quality leaving a very small margin of error for correct placement.

Guided Surgery

Guided surgery involves the fabrication of a plastic template that fits over the teeth or if there are no teeth, sits over and attaches to the jaw.  There are channels in the guide into which the drills are placed.  These holes are precisely manufactured so that the drill can go in only one way.

This takes care of location and angulation.  It’s programmed in.  The depth can be controlled by using drills with depth stops that will not allow the dentist to drill too deep.  But how is the guide fabricated?  It’s done using computers and 3D printers!  We start with a 3D x-ray called a conebeam.  That shows us the teeth and bone.

Next, we get a computer scan of the mouth.  It’s a digital impression.  This is done by using what looks like a video camera.  The camera fits into the mouth and scans all the teeth perfectly.

Now, using special software we can put the x-ray and the scan together.

The scan is in color and the x-ray is underneath.  As you can see, the implant placement can be planned virtually as well as the crown that will attach to it.  This is planning with the end in mind.  No surprises!  From here we can design the surgical guide.  This is done virtually using special software.

In the above picture, the scan is teal and the planned guide is magenta.  The channel for the drills is brown.  Data for the guide can now be sent to a 3D printer where it will be fabricated in plastic.

Advantages and Disadvantages

Advantages of freehand surgery include:

  1. Reduced prep time allowing for same day surgery if needed.
  2. Reduced cost.

Limitations of freehand surgery:

  1. The dentist is required to make clinical judgments on implant placement based on visualizing the clinical situation from the information provided by the casts and radiographs.
  2. Placement of the implants usually requires significantly more time than with the guided technique, since the dentist must think and plan while placing the implants.
  3. Paralleling numerous implants is more difficult using the freehand technique.
  4. The technique is not as predictable as adequately accomplished guided placement.
  5. Freehand surgery is more stressful for the dentist
  6. More invasive. Meaning, there’s more cutting and trauma.
  7. Often slower healing than guided surgery.

Advantages of guided surgery include:

  1. If all the preplanning is done correctly, Implant placement is almost foolproof, accurate, fast, nonthreatening to the clinician, and predictable.
  2. The implant placement is planned with location of the crown or denture in mind. The prosthetics are more likely to look and function
  3. Less stressful.
  4. Faster procedure than freehand.
  5. It’s often less invasive. Meaning, there can be less cutting of the gums and related trauma.
  6. Often quicker healing time.
  7. Often decreased post-operative infections.

Disadvantages of guided surgery include:

  1. Preparation time for the procedure is longer and may include multiple appointments.
  2. Increased cost

Summary

Dental implants have help millions of people replace missing teeth to a great level of satisfaction.  Both guided and freehand techniques have their place in in modern implant practice.  The circumstances of each case and the situation of the patient ultimately dictate which approach to use.  The cost-benefit analysis when deciding between the two techniques ought to include an assessment of the quality and quantity of available bone, the number and location of implants planned, health of the patient, desire for quicker procedure time, desire for decreased pain, and preparation time.  Quicker procedure, healing, and decreased pain are powerful advantages to guided surgery.  Unless an implant must be place right away or the added costs are too much, guided surgery seems to be the preferred choice.

Author Info

Gerald Torgeson

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