November/December 2008, Volume 4, Issue 10
Published by AEGIS Communications
Completing Arch Intercuspation with Dental Implants After Incomplete Adult Orthodontic Treatment
Richard L. Brown, Jr, DDS; Robert B. Kerstein, DMD
The number of adults undertaking fixed orthodontic treatment has grown significantly in recent years. Improved appliance esthetics, treatment mechanics, and social acceptability are some of the contributing factors involved in this increase.1 However, there are significant differences in adult and adolescent orthodontic treatment, as well as differences in successful completion of adult orthodontic treatment. Often, treatment outcomes in adults are compromised somewhat because of various limiting factors related to the practitioner, the patients, the selected orthodontic appliances, and the underlying biology.2
Orthodontic treatment planning depends on determining specific treatment objectives before beginning treatment. Selecting specific treatment objectives aids in the selection of appropriate mechanotherapy for each patient. In adult patients, this is particularly important. With the exception of orthognathic surgery, orthodontic treatment in adults must rely exclusively on tooth movement because no skeletal growth potential exists. Therefore, the orthodontic movements must be achieved with greater precision.3
Additionally, orthodontic treatment of partially edentulous patients is difficult, especially if a significant number of teeth are missing. With loss of teeth, adjacent or opposing teeth usually tip, drift, or supraerupt, leaving spaces that may not be optimal for replacement of missing teeth. Orthodontic correction of these spatial relationships will aid prosthetic replacement of the missing teeth, function, hygiene, and esthetics.4 The initial placement of dental implants may need to be for orthodontic anchorage. Then, after tooth movement is complete, the same implants can be used for implant-retained crowns.5 The success rates of implant longevity indicate that using dental implants in many clinical scenarios is a predictable long-term tooth replacement therapy.6,7
Orthodontic treatment that precedes prosthodontic treatment facilitates tooth preparation, path of insertion, optimum oral hygiene, and a better pontic and abutment design, while occlusal forces can be directed against the long axes of the teeth for a more predictable prognosis.8 However, when orthodontic treatment of the adult is unsuccessful or incomplete, it is possible and desirable to use implant prosthodontics to replace missing occlusal units without destruction of natural dentition.
This article details the use of osseointegrated implants with computer-aided design/computer-aided manufacture (CAD/CAM) custom abutments to replace missing occlusal units to finish an incomplete adult orthodontic treatment.
A 39-year-old woman presented for adult orthodontics with the chief complaint of crowded teeth and the desire to have a more attractive smile (Figure 1 and Figure 2). All of the upper posterior teeth exhibited significant palatal inclination, with the opposing lower posterior teeth inclined to the lingual. A number of retained deciduous teeth created a unique orthodontic challenge because of their size, their probability of ankylosis, and their potential for root resorption during tooth movement. These potential complications warranted the extraction of the primary mandibular second molars, Nos. 20 and 29; however, no socket preservation was attempted at the time of the extraction because successful closure of the spaces was expected to be achieved orthodontically.
Despite the best efforts of the orthodontist, complete treatment success was not achieved because the tooth movement alone could not adequately close the created edentulous spaces. Two 6-mm wide (mesiodistal dimension) edentulous sites remained (Figure 3 and Figure 4), requiring an alteration in the case treatment goals from space closure to creating ideal spacing for the replacement of teeth Nos. 20 and 29 with two endosseous implants after ridge osseous augmentation. The 6-mm edentulous spaces were too small to place 4.3-mm implants into site Nos. 20 and 29 successfully, necessitating that the final phase of tooth movement spread the edentulous spaces to a width of 7.5 mm to have the implants reside 1.5 mm from adjacent teeth.9,10
When the 7.5-mm space was obtained, a combination of an autogenous block graft taken from the mandibular ramus and a cancellous allograft (Puros® Allograft, Zimmer Dental, Carlsbad, CA) was used to augment the edentulous sites. After ridge augmentation maturation, 4 months posttreatment, two 4.3-mm x 10-mm NobelReplace™ Tapered Groovy endosseous implants (Nobel Biocare USA, LLC, Yorba Linda, CA) were inserted, healing abutments were placed (5.3 mm x 3 mm, Nobel Biocare USA, LLC), and the tissue was allowed to heal for 6 weeks (Figure 5 and Figure 6). At the same time, Snappy Abutments™ (Nobel Biocare, Gothenburg, Sweden) were placed and a vinyl polysiloxane impression was made (Exafast, GC America, Inc, Alsip, IL). Next, an occlusal registration (Occlufast® Rock, Zhermack, Inc, Eatontown, NJ) and opposing impression (Kromopan® 100, Kromopan USA Inc, Morton Grove, IL) were made so that the fabrication of laboratory-processed provisionals (Pro-Temp, Keating Dental Arts, Irvine, CA) could be accomplished. The provisionals shaped the sulcular area during the remainder of the integration period.
After 4 months of healing time, the implants were uncovered and impressed, and optimal abutments were designed to fit the edentulous spaces and provide proper support for the final restorations and interproximal tissues (Figure 7a and Figure 7b). CAD/CAM custom zirconia abutments were then milled and installed (Atlantis™, AstraTech Inc, Waltham, MA) (Figure 8 and Figure 9). Finally, two all-ceramic zirconia-based crowns (Procera®, Nobel Biocare USA, LLC) were placed to restore the intercuspation of the arches (Figure 10 and Figure 11). The result was a more attractive final smile for the patient (Figure 12).
Unsuccessful adult orthodontics can result from any one of many limiting factors. The inability to move teeth into every available edentulous area can occur, requiring tooth replacement to be accomplished with alternative approaches to the orthodontic treatment plan. Today, instead of using conventional fixed bridgework, which is destructive to the natural dentition, clinicians may use dental implants to replace missing occlusal units.
The advantages of using implants over fixed bridgework are: (1) preservation of natural tooth structure; (2) avoidance of potential pulpal trauma and endodontics; (3) avoidance of poor periodontal health at the cervical margin of bridge abutments; and (4) better hygiene access to single-unit restorations over multiunit splinted restorations. Lastly, the success rates of implant longevity are very high and indicate that placing implants as opposed to fixed bridgework provides predictable long-term occlusal unit replacement therapy.6,7 The disadvantages of implant placement are any required bone augmentation steps, and the surgical complications associated with bone grafting and implant placement, which include soft- and hard-tissue infection and implant rejection.
CAD/CAM zirconia implant abutments offer patients a strong and esthetic alternative to metal abutments. Cyclic loading and compressive strength studies have shown zirconia to be a durable abutment material when subjected to human occlusal forces,11,12 while providing better esthetics than metal abutments because of improved tissue color at the gingival margin of the restored implant.13 Zirconia abutments, when restored with all-ceramic crowns, offer orthodontic patients optimal esthetic replacement units over conventional metal-ceramic restorations.14
Using implants for orthodontic anchorage can aid tooth movement. However, when unsuccessful orthodontic treatment of adult patients compromises the desired final occlusal result, dental implants also can be used to replace any remaining missing occlusal units. Implants have been shown to be a viable treatment alternative to using conventional fixed bridgework. This approach minimizes tooth damage and limits the possibility of pulpal trauma and endodontic therapy while successfully restoring the necessary missing occlusal units.
Special thanks to Bob Brandon, CDT, Keating Dental Arts, for the fabrication of the all-ceramic crowns for the case presented, and to Dan Patterson, DDS, Tulsa, Oklahoma, for performing the surgical procedures.
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About the Author
Richard L. Brown, Jr, DDS
Esthetic and Family Dentistry
Smiles by Design, PC
Robert B. Kerstein, DMD
Private Practice limited to
Prosthodontics and Occlusion