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Utilizing Digital Dentistry and CAD/CAM Prosthetics to Optimize Treatment Outcomes – Part 1: Orthodontic Pre-Implant Therapy

Perry E. Jones, DDS, MAGD

article by Perry E. Jones, DDS, MAGD

Digital dentistry and CAD/CAM prosthetics and appliances can be utilized during every phase of implant treatment, producing results that are predictable, precise and esthetic. This case presentation — the first in a comprehensive three-part series examining the advantages of these tools — will demonstrate how orthodontic treatment can be used prior to surgical intervention to reposition teeth, correct the occlusion and establish the restorative space needed for the eventual implant restoration.

In this series of articles, we follow a patient through a multidisciplinary treatment plan, from pre-implant orthodontic treatment, to implant placement, to delivery of the final restoration. The first article will focus on tooth movement with Invisalign® (Align Technology; San Jose, Calif.). Part 2 will explore virtual treatment planning, guided surgical implant placement and immediate provisionalization. Part 3 will focus on the final restoration, illustrating the exceptional function and esthetics that can be achieved with a multidisciplinary approach to digital dentistry.

It is crucial to account for the design of the final prosthesis when determining where to place implants. In situations where malocclusion or poorly positioned teeth are present, creating a functional, esthetic prosthetic design can become a challenge. As detailed in the sections that follow, Invisalign treatment offers a straightforward, patient-friendly means of tooth movement, and is just one example of how CAD/CAM prosthetics are helping implant practitioners achieve ideal, reproducible results.

Clinical Examination

A healthy 60-year-old patient presented with a noncontributory medical history (Fig. 1). The patient’s chief complaint pertained to her maxillary anterior fixed bridge, which had come loose and was on the verge of falling out (Figs. 2a, 2b). She was also concerned about her worn-down, crowded anterior teeth, especially her malpositioned lower incisors (Fig. 3). Examination revealed multiple posterior crowns and restorations (Figs. 4a, 4b).

The patient reported that her ill-fitting, failing maxillary bridge was delivered as a temporary solution by her previous dentist after she lost one of her canine teeth that was supporting the original restoration. The 6-unit bridge was essentially a wire-reinforced acrylic appliance that was anchored only by the remaining canine and central incisor (Fig. 5). The patient stated that she was seeking dental implants to replace her unstable bridge.

Overall, the patient’s periodontal health was within normal limits. Minimal depth probings of 2–3 mm were recorded with little or no bleeding. Her oral hygiene appeared satisfactory, and radiographic evaluation revealed minimal loss of crestal bone density. Although the panoramic radiograph confirmed a hopeless state of the maxillary canine and central incisor, there was sufficient bone for an implant restoration (Fig. 6). Accumulation of slight supragingival calculus was noted. There appeared to be no abnormal anatomic concerns.

Evaluation revealed an apparently healthy TMJ with no pain on palpation, a full range of motion and no joint pain or noise. The patient confirmed a history of bruxing, clenching and grinding. Significant occlusal wear was observed on the posterior as well as the anterior teeth. Supereruption of the mandibular anterior teeth along with a concave Curve of Spee presented a deep vertical appearance of overbite. Compromised intercuspation was observed as a result of the patient’s Class II malocclusion.

To address the dental problems and concerns of the patient, a thorough assessment was conducted to evaluate both restorative and tooth movement options. While the patient was indicated for implant treatment, her mandibular anterior dentition needed to be straightened and lowered by approximately 2 mm in order to create the vertical clearance needed for the restoration.

Tooth movement with Invisalign clear aligners was the first step of a comprehensive, prosthetically driven treatment plan. Intrusion and rotation of anterior teeth are strengths of Invisalign treatment.1 In this case, the clear aligners helped position the lower incisors in the proper vertical position, correct the patient’s occlusion, and reduce the functional forces exerted by the eventual implant restoration onto the opposing dentition, preventing future wear of the patient’s teeth. After completion of orthodontic treatment, the incisal edges of the lower teeth were restored with composite.

Instead of depending on orthodontic bands and brackets, this approach to treatment allows the patient to wear a removable, comfortable, virtually invisible appliance to create the tooth movement necessary to set up an ideal restorative outcome.

Clinical Treatment

After a discussion of alternatives, benefits and potential complications, the patient agreed to a treatment plan that combined orthodontics, implant placement with immediate provisionalization, and CAD/CAM prosthetics to produce a highly esthetic outcome. The pre-implant phase of treatment consisted of tooth movement with Invisalign aligners in the lower arch and removal of the patient’s remaining maxillary anterior teeth. After successful repositioning of the opposing mandibular teeth and healing of the extraction sites, four maxillary implants were placed using a surgical guide, followed by the immediate delivery of a prefabricated BioTemps® provisional implant bridge. The edentulous span was then restored with a 6-unit screw-retained BruxZir® Full-Strength Solid Zirconia bridge, completing a clinical workflow that utilized the full potential of prosthetically driven treatment planning.

Part 1: Invisalign Treatment Planning

Vinyl polysiloxane impressions were taken and submitted to Invisalign along with photos, radiographs and instructions concerning the tooth movement needed to create the vertical space and correct the occlusion for the planned implant restoration. Based on this information, a treatment plan was developed using ClinCheck® software (Align Technology), a CAD/CAM program used to visualize and plan the repositioning of teeth. Following practitioner approval, the design file generated by the software was used to fabricate a series of aligners, which then were worn by the patient to create tooth movement in precise accordance with the treatment plan.

There were several objectives to the orthodontic treatment plan for the mandibular anterior dentition. The lower canines and incisors exhibited significant attrition, likely due to occlusal forces. Over time, as the incisal edges were worn, the anterior teeth had extruded such that the vertical appearance of overbite deepened to 60–75 percent (Fig. 7). During treatment, the anterior teeth tend to nestle into the V-shaped plastic “glove” of the aligner. The aligner is pinned to the posterior teeth and a preset flex is added to the appliance. As the aligner is worn, the flex effect causes an intrusion force that intrudes the target anterior teeth.2

As part of the treatment, tooth-colored composite resin forms that control tooth movement were attached to the teeth to precisely fit the reservoirs of the planned series of plastic aligners (Figs. 8a, 8b). These included optimized attachments in the areas of the right and left lateral canines to help control rotation during the intrusion movements. Conventional beveled retention attachments were placed on both the left and right mandibular bicuspids. It is not uncommon to see unwanted posterior reciprocal intrusion with anterior intrusion movements. To help reduce this effect, rectangular attachments were placed on the mandibular right and left second bicuspids and first molars. An Invisalign feature called Power Ridges™ (Align Technology) was added to the lower left lateral incisor. This feature uses a labial dimple in the aligner to create a movement force that adds root torque in the lingual direction of the buccal-lingual plane of resistance (Fig. 9).

The primary purpose of the anterior incisor intrusion movement was to reposition the extruded mandibular anterior teeth to create the vertical space needed for both the planned maxillary screw-retained implant bridge and the composite restoration of the incisal edges and cusp tips. The treatment also moved the lower anterior teeth into optimum position to occlude properly with the eventual implant restoration, while leveling the gingival heights of contour, the Curve of Spee and the occlusal plane.

The treatment plan for resolving lower anterior crowding was to use interproximal reduction (IPR) to maintain the overall position of the teeth in the arch form with no expansion or procline movements (Fig. 10). IPR was desired so that the lower incisors would maintain position in the “neutral zone” of oral musculature and tongue forces. The planned IPR value of 0.5 mm per contact is consistent with published data for the anterior.3 The use of the IPR crowding resolution modality also helps maintain the symmetry of the arch form, reduce black triangle formation and improve proximal contact anatomy.

In the maxillary arch, where tooth movement was not needed, the treatment plan included extraction of the remaining hopeless anterior teeth, which were eventually replaced by the anterior implant bridge. Because the maxilla exhibited an anatomically correct ovoid shape and there were no significant rotations or movements desired for the remaining posterior teeth, the treatment plan called for preserving the original form of the upper arch and the positions of the remaining maxillary dentition. The goal was to maintain the edentulous span of the six anterior teeth, canine to canine. Thus, a thermoplastic pontic appliance was fabricated in-office. This included the use of composite resin to fill the span of the missing six anterior teeth (Figs. 11a, 11b).4 The plan to maintain the maxillary arch and prevent any tooth movements was verified using the ClinCheck software (Fig. 12).

Treatment and Outcome

There are three factors considered critical to tooth movement: space, force and time. The first two factors were addressed in the aligner design and virtual movements illustrated in the treatment plan. The third factor requires patient compliance and minimum activation time. Published data places minimum activation time for proper tooth movement with Invisalign aligners at 22 hours per day and 300 total hours between each aligner change.5 This minimum threshold essentially requires 24/7 wear except for when the aligner is removed to eat or brush and floss. The 300 hours between changing aligners translates to two weeks.

After extracting the patient’s remaining maxillary canine and central incisor, the maxillary thermoplastic pontic appliance was seated as well as the first in a series of mandibular Invisalign aligners (Fig. 13). This allowed healing of the extraction sites and execution of the tooth movement treatment plan to occur simultaneously. The aligner attachments were closely observed at monitoring visits to ensure proper seating in the aligner attachment reservoirs (Figs. 14a, 14b).

Orthodontic treatment produced the desired tooth movements. The ClinCheck predictions for anterior intrusion estimated a reduction of the anterior vertical appearance of overbite from 75 percent to a more reasonable 25 percent (Figs. 15a, 15b). The posttreatment intraoral images illustrate clinical results that mirror the virtual plan, including successful intrusion of the mandibular incisors (Figs. 16a, 16b). The desired rotation of the anterior dentition needed to resolve the crowding issue and correct the occlusion was also achieved (Figs. 17a, 17b).

The maxillary arch form was maintained as planned during treatment, as the thermoplastic pontic appliance preserved the width of the anterior space from the mesial of the right bicuspid to the mesial of the left bicuspid. This later aided implant and restoration planning, as the patient continued to wear the thermoplastic pontic appliance until the time of surgery, ensuring the upper arch was not altered. The implants could thus be placed without fear of tooth movement causing fit issues with the surgical guide.

Conclusion

Tooth movement was a critical component of this complex case and the first of several restorative-driven techniques employed to achieve an ideal outcome. As will be demonstrated in the next two articles of this series, the predictable tooth movement achieved by the Invisalign treatment was essential in creating the space needed for the implant restoration while correcting the patient’s occlusal and orthodontic problems. By paving the way for an esthetic, functional and well-fitting implant prosthesis while protecting the patient’s natural dentition from further wear, this approach can contribute to a lifetime of excellent dental health.

Part 2 Preview

The next article of this three-part series will explore how the digital world of intraoral scanning, virtual treatment planning, guided surgery and immediate CAD/CAM provisional bridges is helping restorative-driven implant treatment reach its full potential (Figs. 18a, 18b). The maxillary implant restoration is created in a 100 percent digital workflow, without conventional stone models. Stay tuned as we illustrate the higher levels of accuracy and the precise prosthetic outcomes that can be achieved using digital technology and CAD/CAM prosthetics.

Figures 18a, 18b: In a continuation of the restorative-driven treatment plan, the next article will spotlight the virtual planning and guided surgical placement of the maxillary implants followed by the immediate delivery of a CAD/CAM-produced provisional implant bridge.

References

  1. Djeu G, Shelton C, Maganzini A. Outcome assessment of Invisalign and traditional orthodontic treatment compared with the American Board of Orthodontics objective grading system. Am J Orthod Dentofacial Orthop. 2005 Sep;128(3):292-8.
  2. Kravitz ND, Kusnoto B, BeGole E, Obrez A, Agran B. How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign. Am J Orthod Dentofacial Orthop. 2009 Jan;135(1):27-35.
  3. Hudson AL. A study of the effects of mesio-distal reduction of mandibular anterior teeth. Am J Orthod. 1956;42:615-24.
  4. Jones PE. The thermoplastic pontic appliance. J Am Acad Cosmet Orthod. 2015 Winter;4(4):14-20.
  5. Baldwin DK, King G, Ramsay DS, Huang G, Bollen AM. Activation time and material stiffness of sequential removable orthodontic appliances. Part 3: premolar extraction patients. Am J Orthod Dentofacial Orthop. 2008 Jun;133(6):837-45.
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