Before one embarks on surgically placing and restoring a dental endosseous implant, a thorough and rigorous treatment planning process has to be performed. A detailed history should be taken especially looking for the etiology of the tooth fracture or loss.
Pets that have habits that can lead to tooth abrasion and tooth fracture, or pets with underlying malocclusions, including tooth attrition, may not be suitable candidates for implants unless the underlying problem or habit can be modified or rectified. Pets with periodontitis may not be candidates for implants unless the periodontal disease is mild and is well controlled.
The monetary outlay for an implant motor and surgical kits can be prohibitive for practitioners interested in placing and restoring implants.
Other treatment options should be offered that may be more suitable or practical for the patient and the owner.
PHOTO COURTESY OF DRS. CAIAFA AND MELE
Placement of implant.
A prognosis should be given for each option. Other treatment options may include root canal therapy, extraction and possible bridging of the edentulous space or simply extraction and no further treatment. Ethical considerations when dealing with hypodontia in breeding or show animals also need to be considered.
Owners need to be made aware that a dog or cat with a missing tooth or teeth can still masticate without any difficulties. However in some cases where the edentulous space may contribute to a dental malocclusion, or through owner preference, a dental implant can be placed.
The owner will need to be informed of the cost of the implant surgery and prosthetic phase of treatment, including a number of anesthetic episodes as well as the ongoing commitment to quality homecare (absolutely essential) and continuing professional reviews of the implanted site.
The owner also needs to be made aware that at the present time, studies looking at the longevity of implant crowns in dogs or cats are lacking.
Only after taking into consideration all of the above can the clinician then embark on implant placement.
Implants on some occasions can be placed immediately post tooth extraction under the one anesthetic procedure (so-called immediate placement). A thorough assessment of the affected tooth should be carried out prior to extraction.
It is important that if granulation tissue is associated with the compromised tooth or tooth root, it be removed with curettes. Any frank or acute apical pathology will preclude an immediate implant placement.
Delayed surgery or delayed placement involves waiting for an extraction site to heal with no evidence of infection. Usually the clinician needs to wait about six to eight weeks. If the clinician waits too long, ridge alterations and bone loss will have occurred, which may make implant placement more difficult without further bone augmentation techniques.
STEP 1 Site Evaluation
The implant site needs to be thoroughly assessed prior to implant placement. This will include at the very least intraoral radiographs of the site plus an evaluation of the bucco-lingual bone width as well as the bone depth at the site. The choice of implant diameter and length is then made.
It is important that approximately 1mm of crestal bone remains at the buccal and lingual boundaries of the implant. Avoidance of vital structures such as roots of other teeth, nerves, blood vessels, nasal cavity, mandibular canal and sinuses is essential for accurate implant placement.
The prosthodontic component of the implant procedure will dictate the surgical placement of the implant. This may lead to correction of drill angulation during the procedure. A pharyngostomy endotracheal tube placement will assist when assessing occlusal concerns from the opposing arch.
STEP 2 Raising a Full Thickness Flap
Under sterile conditions, it is usually recommended that a full-thickness mucoperiosteal flap (on both the buccal and lingual sides) be raised for implant placement. This allows for visualization of the bony ridge contour as well as any bony deficits that may not have been seen on radiographs.
If the crestal bone is knife-edged, a high speed round bur can be used to flatten the ridge. On some occasions, a flapless approach can be performed especially with immediate implant placement post tooth extraction.
STEP 3 Drilling
An implant motor will be required for drilling (speeds <800 rpm are common) and implant placement. Pilot drills penetrate the crestal bone. The bone density can also be assessed while drilling. A series of water cooled twist drills are used to enlarge the osteotomy site (all based on the implant system that the clinician is using).
Depth gauges will assess drilling depth as well as indicate correct angulation of the implant. Intraoral radiographs are essential during the drilling to assess the correct placement of the implant.
STEP 4 Placement
Once the desired depth is reached, the implant is either screwed in by hand or with an implant motor (<15 rpm). Most implants these days are bone level threaded implants that sit flush with the crestal bone. Bone augmentationc and a barrier membraned if required can be placed at this point prior to closure.
PHOTO COURTESY OF DRS. CAIAFA AND MELE
Healing cap is placed.
STEP 5 Healing Cap Placement and Flap Closure
Healing caps can either be buried under the sutured flap or are transmucosal and the keratinised gingiva is contoured around the healing cap. A radiograph of the submerged implant is taken to assess correct placement.
It should be noted that the endosseous implant can maintain the crestal bone height once placed (i.e. it can act like a natural tooth root).
STEP 6 Uncovering the Implant
If the healing cap was buried beneath the flap, then a tissue punch can be used to uncover the implant and a new transmucosal or tissue conditioning cap is placed. An impression (using an impression transfer part and PVS impression material)e is taken of the implant fixture and this is sent to the dental laboratory. A bite registration an an impression of the opposing arch are also required.
STEP 7 Restorative Phase
Any type of prosthetic crown can be laboratory manufactured for implants. Porcelain fused to metal (PFM or VMK), metal crowns or zirconia crowns can be made. Usually the implant abutment (the connector between the implant and the crown) is made of the same material as the implant, namely titanium.
The operator will need to decide, based on the case and implant angulation, whether to manufacture a crown that is cement- or screw-retained.
After impression-taking and shade selection, for a non-metallic crown, the impressions are sent to the laboratory with the appropriate laboratory formula. The customized abutment/crown will probably take about two to three weeks to be manufactured.
STEP 8 Abutment/Crown Placements
The crown and abutment and screw(s) will arrive at your office. Before trying the abutment and crown in the mouth, they can be checked on the model, especially to make certain that there are no occlusal interferences or premature contacts with the opposing dentition.
The tissue-forming cap is removed, and the abutment is seated into the implant head and the abutment screw tightened down by hand. An intraoral radiograph is then taken to ensure correct seating of the abutment. If seated correctly, the abutment screw is torqued down with a torque wrench to the manufacturer’s recommendation (usually 35-40 NCm).
Once the abutment is in place, the crown can be placed over the abutment. Before cementing the crown (usually with resin cement) or tightening the screw if the crown is screw retained, the occlusion should be checked for any occlusal interference. Articulating paper will assist the operator with this procedure. If using a screw-retained crown, the access hole is sealed with a composite resin.g
STEP 9 Follow-up Visits
As for any complex dental case, appropriate follow up is essential. Re-evaluation appointments (authors advise six monthly rechecks) should include an assessment of the quality of homecare with no evidence of gingival inflammation or bleeding at the implant site.
Stability of the implant may be difficult to evaluate, but a comparison of periodontal probing depths with base measurements at the time of the crown restoration may be helpful.
Excerpt from Veterinary Practice News, April 2014 with permission from its publisher, Lumina Media. To subscribe to Veterinary Practice News, click here.