Dental Implants

Indications for implants
Contraindications
What are the age limits?
Inadequate bone
Types of implants
Surgical guides
Treatment time and stages
Patient recovery
Abutment selection
Immediate implants
Immediate/early restorations
Implant in smile zone
Indexing/impression techniques
Placement of final prosthesis
Healing abutment too tight

Indications for implants
Dental implants are now the standard-of-care for tooth replacement. Dental implants are indicated for replacement of single or multiple missing teeth and rehabilitation of completely edentulous patients. They are also indicated in partially edentulous patients with adjacent teeth planned for full coverage restorations. This is not a rationale for offering a conventional bridge.

Contraindications
Dental implants are contraindicated in children and young adults who have not completed their growth phase. They are also contraindicated in patients with very poor and uncontrolled diabetes, patients with severe immune compromise, and those who have received IV bisphosphonate therapy.
Implants may be placed safely, but with caution in smokers and in patients with a history of irradiation or chemotherapy. Patients who have taken oral bisphosphonates may safely and predictably receive dental implants, only with proper informed consent. At the time of this writing (March 2010), it is recommended that patients stop oral bisphosphonate for at least three months prior to extractions or dental implants.

What are the age limits?
Implants may be placed in young adults who have completed their growth phase. There are no upper age limits for implants, as they are equally successful in older patients, even with osteoporosis. Life expectancy and overall health should be considered when deciding on implants in much older patients. For many, implants improve quality of life and are worth considering even if only for a few years.

Inadequate bone
Patients with inadequate bone, whether horizontally or vertically, may have bone grafting to augment and develop adequate sites for implants. Bone augmentation procedures include onlay bone graft, sinus lift bone augmentation, split thickness approach, or distraction osteogenesis. These techniques are routine and quite predictable when performed properly by a trained specialist with appropriate instrumentation and materials. Dental implants can often be placed in four to six months after grafting. We specialize in tissue engineering and implant site development, and Dr. Kazemi has extensive experience in this area.

Types of implants
We place Zimmer, 3i, and nobelactive implants. We carry both tapered and parallel walled implants, chosen as appropriate for each site. All of our implants are internal hex. We provide impression posts for Zimmer implants.

Surgical guides
Surgical guides are a must for every implant case. We can fabricate guides for sites involving one or two missing teeth. When three or more teeth are missing, we request a surgical guide from the restorative dentist. Unique surgi-guides can also be fabricated when computer assisted implant planning is done with Simplant. In this case, we will review the 3-D computer work-up with you and arrange for fabrication of the surgical guides. Acceptable surgical guides must have the following features:

  • Guides are made based on a wax-up and proper occlusion with mounted models.
  • Guides should be made of clear acrylic material, and should be stable with positive occlusal coverage on teeth adjacent to the edentulous site. VACUSHELLS OR SUCKDOWN MATERIALS ARE NOT ACCEPTABLE AS SURGICAL GUIDES.
  • The precise implant angle and position is determined by a 2.3 mm metal sleeve placed in the acrylic or just a simple preparation. This preparation must be precise and must allow only one path of insertion for the surgical drill.


Treatment time and stages
Implants placed in D1 or D2 bone (mandible and anterior maxilla) can often be placed in a single stage with healing abutment and allowed to heal for two to three months before impression. Implants in D3 or D4 (posterior maxilla and occasionally posterior mandible) may be placed as a two-stage procedure and allowed to heal for four to six months before exposure and preparation for impression. Implants requiring uncovering and placement of healing abutments should be allowed to heal for at least six weeks before impression. Implants placed in grafted bone, or grafted at the time of placement, are allowed to heal for five to six months. Other factors that can affect the healing time include implant type, surface characteristics, stability at the time of placement, and patient physiology and healing potential.

Patient recovery
Recovery from implant surgery can be remarkably quick. There is minimal discomfort and in absence of bone grafting, there may be no swelling. Most patients can return to normal activities by the following day. Any transitional prosthesis can be worn immediately.

Abutment selection
Custom abutments are recommended in every patient. We do not recommend pre-fabricated stock abutments as they do not provide proper form and emergence. Ceramic abutments may be considered based on aesthetic requirements in the smile zone. In selected patients, we can perform the impression and provide you with Atlantis abutments. Atlantis abutments are custom CAD designed abutments. We place the custom abutment on day of exposure with a custom provisional restoration. You will be given a duplicate abutment that you can send to your lab for fabrication of the final restoration. The final restoration is cemented to the custom abutment already on the implant.

Immediate implants
Immediate implant placement is a predictable procedure but must be performed with proper site and patient selection. It is predictable in the following conditions:

  • Single root extraction sites with a diameter small enough to provide at least 50% primary stability to the implant.
  • Four wall defects with no significant bony deficiencies.
  • No purulence or significant infections.
  • Immediate implants are not predictable in molars or multi-rooted premolars. Adjunctive bone grafting and/or soft tissue graft may be done with immediate implants as necessary.


Immediate/early restorations
Immediate or early restorations offer great benefits to patients and also allow development of proper tissue form and architecture. They are most predictable when done on multiple implants in a splinted fashion with no or very light occlusion. They can also be done on single implants with caution. For optimal success, the following criteria must be met:

  • Excellent primary stability of the implant as reported by the surgeon with torque resistance greater than 35 ncm.
  • The provisional restoration must be clear of occlusion.
  • The patient must remain compliant with a soft diet for at least six weeks.
  • The provisional cannot be removed or manipulated for six to eight weeks.
  • It is also possible to place an immediate fixed implant supported overdenture in fully edentulous patients with four to six implants, providing the implants are stable and splinted with a metal bar. The overdenture is screw-retained and should not be removed for at least six to eight weeks.


Implants in the smile zone
Implants in the aesthetic zone are among the most challenging type of treatments. Proper sequencing, site development, close collaboration, and timing are necessary for predictable results. Here are the important principles:

  • Site preservation grafting after extraction must always be considered.
  • Immediate implants should be considered only if the site is appropriate.
  • Site development with bone and soft tissue grafting is critical to achieving aesthetic results.
  • Surgical guides fabricated based on carefully waxed-up models are mandatory.
  • CT-guided planning should be considered in sites with multiple missing teeth.
  • If there is thin soft tissue, the implant may be submerged to develop additional keratinized gingiva. During uncovering, a palatal-based flap may be indicated to further augment labial soft tissue.
  • Following uncovering, implants must be provisionalized with highly anatomic and polished acrylic material.
  • Implants must remain in a provisional state for at least three months before final impression.
  • Ceramic abutments and crowns should be considered instead of titanium abutments, and porcelain-fused to metal restorations.
  • An index impression may be done at the time of implant placement to allow fabrication of a provisional restoration that can be placed later following uncovering.


Indexing/impression techniques
The most accurate impression technique is the direct open tray approach. The impression post is placed, verified with a Periapical X-ray, and screw access hole plugged with a cotton pellet. An access hole is placed in the tray over the location of the impression post. If the impression post is too short for access with stock trays, consider a custom tray. A medium body impression material is injected at the gingival margin while heavy body material is placed on the tray. The tray is placed in the mouth, carefully positioned so that the impression post is at the hole in the tray. Immediately remove the excess impression material from the top of the impression post to gain access to the screw and allow adequate time to set. Remove the cotton plug and unscrew the impression post. Remove the tray along with the impression post gently and verify for proper capture and stability of the post. Finally, place the healing abutment on the implant.
Indirect impression techniques are also effective, but must be done with caution and careful attention to accuracy.

Placement of final prosthesis
The final abutment is placed on the implant, and the screw is finger-tightened with a screw driver. A Periapical X-ray may be done to verify proper seating and accurate margins at the implant platform. The screw is then torqued to its proper measure using a torque wrench. This is usually 25 to 30 ncm, depending on the screw and implant type. Once torqued, place a cotton pellet or impression material over the access hole and place the prosthesis with very light temporary cement. A mixture of temp-bond and Vaseline may be adequate. It is often recommended to re-torque the screw in seven to 10 days to account for the metal relaxation index. At this time, you may place gutta percha in the access hole and seal it before cementation of the prosthesis. Use very small amounts of a temporary cement and make sure subgingival cement excess is thoroughly removed. Any entrapped cement can cause tissue irritation.

Healing abutment too tight
All healing abutments are placed ‘finger-tight’. However, if you find them too tight to remove with your fingers, follow this instruction: Place the screw driver in the healing abutment. Then use a hemostat and grab the serrated surface of the screw driver and and while holding the screwdriver stable with your finger, give it a counterclock wise turn. The healing abutment will be loose and then can be removed easily.