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Dental implants

Dental implants

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What is a dental implant?

  • A dental implant is an artificial root that is anchored into the jawbone to create a resistant and durable anchorage used to support a dental prosthesis that replaces one or several teeth.
  • The dental implant serves as an intermediary between the jawbone and the dental prosthesis. As a shock absorber, it enables the transfer of the masticatory forces to the bone in which it is anchored.
  • The missing teeth could have been extracted for different reasons (cavity, damage, fracture) or were simply congenitally (genetically) missing. The implant is inserted into the bone, like a screw, and provides support for the visible part of the tooth: the crown.
  • The implant can support fixed prostheses that cannot be removed by the patient like a single tooth (crown) or several teeth linked together (bridge).
  • Several implants can also support removable prostheses (dentures) or complete prostheses to restore an entire mouth.
  • Orthodontists do not install dental implants; this procedure is done by a general dentist, a periodontist, a maxillofacial surgeon or any other specialist in dentistry.
Comparison between a natural tooth and a dental implant.

Dental implants characteristics

Dental implants present a surface that encourage osseointegration.

Dental implants present different textures and designs that encourage osseointegration, an essential element for them to be solid and stable.

 

Indications and case selection

Not everybody is a good candidate for dental implants. The patient’s periodontium must be of good quality for the installation of implants. This implies:

Contraindications to the installation of dental implants include:

Interdisciplinary approach

It is important to realize that dental implants are just one prosthetic solution available for partially toothless patients. Just like any restorative solution, they present certain benefits and disadvantages.
Each patient’s ideal solution will have to be evaluated globally with all the dental practitioners involved (general dentist, periodontist, maxillofacial surgeon, prosthodontist, etc.).

When orthodontics is required to prepare the dentition and the occlusion for dental implants, the orthodontist will work together with the various specialists to give the teeth an optimal position, allowing them to offer the best prosthetic solution to their patient afterward.

To see examples of interdisciplinary cases with dental implants.

Success

Significant progress was made in dental implantology since the early 1980s.
Literature now reports success rates from 95 to 98%.
Several implants that were installed more than 20 years ago do not present any problems. It is believed that osseointegrated implants can remain untouched for life. However, studies report a lifetime of at least 10 years in average.
Important: the crowns, the bridges or the prostheses supported by an implant will have to be replaced after some time, like any other dental prosthesis.

Preventing bone loss

  • When a tooth is extracted, a certain bone loss will inevitably occur.
  • This loss will progressively worsen throughout the years; the height and width of the bone mass may have to be increased to allow the installation of an implant.
  • The sooner an implant is installed after the loss of a tooth, the better are the chances of maintaining the bone volume.
  • Dental implants prevent the bone loss by allowing the masticatory forces to be distributed in the alveolar bone around the implant. The jawbone reacts to these forces by increasing the bone density, which makes it more resistant, solid and functional.

Installation techniques

The installation of dental implants and bone augmentation (grafting) procedures are performed by either a general dentist having received proper training on implants, a periodontist or a maxillofacial surgeon.

New periodontal techniques to regenerate tissues contribute to the increase of the success rate of implants when periodontal tissues show certain deficiencies.

Once the diagnosis is made and the feasibility of the installation of implants is confirmed, several techniques can be used to install dental implants.

These procedures are usually performed under local anesthesia. An incision is made in the gum tissue, a drill bit is then used to make a hole where the titanium screw (implant) will be inserted.

Dental implant dentistry orthodontics Sherbrooke

Two-step technique
Implants are installed into the bone, covered by gingiva and left as is from 3 to 6 months to enable the adaptation of bone around the implant (osseointegration) and healing.
After this delay, implants are uncovered (removal of the gum tissue covering them), a screw is put in place and if everything is stable in the bone, the prosthesis may then be made.

One-step technique
After the installation, the implants are not covered with gingiva, leaving the neck out of the bone. The prosthesis will be made once the osseointegration is obtained (3-6 months).

“Immediate” technique
In certain cases, it is possible for the practitioner to install an implant immediately following the extraction of a tooth by positioning it in the dental alveolus.
A period during which healing and osseointegration occur is nevertheless necessary as with the other techniques.

 

Example of the use of an immediate dental implant. (A) The root of the fractured tooth is considered useless to support a new crown. (B) Therefore, the root was extracted and replaced by an implant with a pillar inserted into the bone alveolus where the root was located. (C) Afterward, a crown is fixated onto the pillar and matches the shape and color of the adjacent teeth for maximized esthetics (D). (Courtesy, Dre K. Archambault)

Example of the use of an immediate dental implant. (A) The root of the fractured tooth is considered useless to support a new crown. (B) Therefore, the root was extracted and replaced by an implant with a pillar inserted into the bone alveolus where the root was located. (C) Afterward, a crown is fixated onto the pillar and matches the shape and color of the adjacent teeth for maximized esthetics (D). (Courtesy, Dre K. Archambault)

 

 

When are dental implants installed?

Installing one or several dental implants often requires the intervention of several practitioners and good planning and communication between all players is essential.

After orthodontics

Financial considerations

Before or after an orthodontic treatment

Temporary anchorage mini-screws

The introduction of temporary anchorage mini-screws or implants in orthodontics offers new mechanical possibilities for cases with missing teeth in a way that it is now less frequent to use “permanent” dental implants during an orthodontic treatment. To learn more on anchorage miniscrews and see examples on how they are used.

Orthodontics with dental implants

As described previously, it is usually preferable to install dental implants after an orthodontic treatment. However, sometimes a patient who already has a dental implant would like to envision orthodontic corrections to improve his/her occlusion. This is usually possible, but can introduce certain limits to the orthodontic treatment. Thus, since it is impossible to move a dental implant by any orthodontic movement, this can prevent the correction of certain dental malpositions. An implant cannot be moved forward, moved backward, moved downward or brought out of the bone to be “moved upward”, so the tooth replaced by the implant will need to keep the same position as the one at the beginning of the treatment.

Depending on the tooth replaced by the implant, this can impact the orthodontic treatment differently. For instance, if the tooth is located at the far back of the dental arch (the second molar), this may not affect the teeth located more anteriorly unless they need to be pushed backward toward the implant. However, if an upper incisor was replaced by a dental implant and if anterior teeth must be moved backward, this is a problem, because all the incisors could be moved backward except the one replaced by the implant, which would be unesthetic and not functional.

Therefore, it is possible to envision an orthodontic treatment when dental implants are present, but the treatment plan may have to be modified.

The following examples show cases where implants were in the mouth before the first orthodontic consultation. Although it is still possible to perform orthodontic corrections, dental implants prevent certain orthodontic movements that would have led to better results.

Dental implants installed prior to an orthodontic treatment

(A, B, C) Before this patient began the orthodontic treatment, 2 lower dental implants (indicated by the *) were installed in the mouth. Even though these implants replace premolars, they are a lot larger than a premolar. This excessive width will prevent the orthodontist from obtaining an ideal interdigitation with the upper teeth. However, these two implants do not prevent corrections to be made in the other areas of the mouth (in the upper arch and the anterior part of the mouth). Moreover, it would have probably been possible to close these spaces during the orthodontic treatment and avoid the need for implants after the orthodontic treatment.

 

Installation of a dental implant before an orthodontic treatment that prevents moving backward the teeth.

(A) Correcting this malocclusion would require a backward movement of the upper left teeth to obtain a better interdigitation (arrow). (B) The presence of a dental implant (indicated by a *) at the back of the dental arch will prevent the teeth from being moved backward, because the implant installed before the treatment cannot be moved. (C) Upper occlusal view of the crown on implant. If this person had consulted an orthodontist before installing the implant, the suggestion would have been to wait the end of the treatment and the backward movement of the teeth to install this implant. The final occlusion and function would only be better.

The role of orthodontics in dental implant planning

 

Position of dental implants in the alveolar bone

To properly resist masticatory forces and have a maximum lifetime, dental implants must be placed precisely in the alveolar bone of the jaws. The orthodontic corrections make it possible to optimally position the teeth adjacent to the sites where the dental implants will be installed to maximize the chances of success.

Anterior area

CC’s case: Anodontia of lateral incisors and inadequate position of the canines for the installation of the dental implants.

Maryland bridges that replace both upper lateral incisors. These bridges have been in place for more than 10 years.

Maryland bridges that replace both upper lateral incisors. This 32-year-old woman underwent an orthodontic treatment once when she was a teenager and now wishes to replace the Maryland bridges (indicated by the arrows) by crowns on dental implants. These bridges have been in place for more than 10 years.

 

Inadequate position of roots for the installation of dental implants

Use of CBCT scans to evaluate the position of the roots of the upper canines and lateral incisors to get ready for the installation of dental implants to replace the missing lateral incisors (yellow *). (A) The red dotted lines indicate the axis (inclination) of the teeth before the treatment and the blue dotted lines represent the ideal position that the lateral incisors should have to allow the installation of implants without interfering with the dental roots. (B) Slices to the fraction of millimeter allow a precise evaluation of the bone and roots. (C) Sagittal or side view. (D) Occlusal or axial view through the crowns and the roots showing the space and the bone between the teeth.

 

CP’s case: Anodontia of lateral incisors and inadequate position of the central incisors to install dental implants.

 

Inadequate position of roots for the installation of dental implants

Since the upper central incisors show too much tipping, they will prevent the installation of dental implants to replace the missing lateral incisors. (A) Before the treatment: the blue arrows indicate the missing lateral incisors. (B) These lateral incisors are replaced by prosthetic teeth bonded to the adjacent teeth. (C) A panoramic radiograph confirms the bad position of the central incisors. (D) Enlarged view of the radiograph and the implants added as a simulation. The blue dotted lines represent the ideal position that the central incisors should have. (E) This patient opted for lingual braces for esthetic reasons.

 

Orthodontic uprighting of dental roots to get a site ready for dental implants.

(A) Root parallelism and inadequate space between the roots during the orthodontic treatment. (B) After a few months, the roots are parallel and there is enough space to install dental implants in the toothless spaces.

Posterior area

To learn more on the uprighting of posterior teeth.

 

(A) Posterior teeth that tipped forward several years after a 46-year-old woman lost a molar. (B) The teeth were uprighted orthodontically by moving them backward (arrow). Once the space was obtained, another specialist (periodontist or surgeon) installed 2 implants to replace the missing molar. (C) Final result once the general dentist installed the crowns on the implants (arrows).

 

Use of fixed orthodontic appliances to maintain a space while waiting for a prosthetic replacement.

(A) This orthodontic treatment aimed at repositioning the lower teeth in order to replace the missing teeth with dental implants. The teeth were uprighted and the space was opened optimally to receive the implants. (B) At the end of the orthodontic treatment, the corrective appliances (braces) were removed except the ones beside the spaces where a section of wire (arrows) maintains the teeth on each side of the space so they do not move while waiting for the installation of the implants and the crowns. A regular fixed retention wire maintains the anterior teeth in place. (C) The implants were installed during the retention period. The lower left implant is indicated by the arrow. (D) Once the implants and the crowns are installed, it is no longer necessary to keep the sections of wire.

The importance of volumetric imaging in planning

Planning dental implants requires taking special radiographs allowing the surgeon to properly visualize in 3 dimensions the structures surrounding the site where the implant will be installed.

 

To learn more on Cone Beam Computed Tomography (CBCT) or 3D dental radiograph.

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