Implant-Retained Overdenture Diagnosis to Delivery

David A. Little, DDS

with David A. Little, DDS

Introduction

In the past, patients suffering from tooth loss faced many challenges and were considered dental cripples. The average bite force for dentate patients, 150 to 250 psi, was reduced to 50 psi when they became edentulous.1 After 15 or more years of wearing dentures, many patients' bite force and chewing efficiencies were reduced even further to 5.6 psi, making simple, functional tasks like eating very difficult. While the edentulous population is increasing, so too are treatment options for the edentulous patient. Today, osseointegrated implant-retained denture prostheses have eliminated many of the disadvantages associated with traditional dentures. The emotional impact of edentulism can be life altering, causing embarrassment, lack of self-esteem, a negative self-image, dissatisfaction with one's facial appearance and emotional insecurity culminating in social inhibition and difficulty establishing relationships.

The physical effects of tooth loss include decreased oral facial support due to the loss of hard and soft tissue;2 the look of premature aging in the facial region caused by bone resorption, a decrease in lip support and facial height; impaired phonetics and oral function; and pain.2 These physical issues contribute to the discomfort and ultimate instability of conventional removable denture prostheses by requiring the denture wearer to utilize the lip, tongue and cheek muscles to hold traditional dentures in place.3,4

Implant-retained dentures resolve many of these issues. For instance, patients experience a secure and stable fit, better comfort, improved biocompatibility, increased support and decreased bone loss when two to four implants are placed to support a full-arch prosthesis.3,5 In addition, improved material sciences have provided newly developed denture base technology and denture tooth materials that are stronger and more esthetic. Overall, this type of prosthesis allows patients to function normally in society and enables them to eat what they want, instead of only what they can. The preservation of bone that is noted around root-form implants also promotes long-term health and prosthetic stability.

This article describes a case in which a team approach was undertaken to meet the patient's expectations. By visualizing the case conceptually, then in wax and ultimately in the acrylic dentures, the team was able to deliver a highly esthetic and functional implant-retained prosthesis.

Case Report Diagnosis and Treatment Planning

A 54-year-old patient presented with ill-fitting upper and lower removable partial dentures (Figs. 1a, 1b). A comprehensive examination was performed, including a clinical exam, digital panoramic radiograph, full-mouth radiographs and clinical photographs. An oral cancer screening was then performed, which resulted in negative findings.

In treatment planning the implant-retained overdenture case, several factors were considered. To help the patient make a fully informed financial decision, it is best to present the patient with a single case fee for the different treatment modalities: a two-implant overdenture solution, a four-implant solution, a six-implant fixed solution, and so forth. In this case, a four-implant overdenture solution was chosen.

The treatment plan was accomplished in three phases. The first phase consisted of extracting the remaining teeth and placing transitional dentures. After healing, a lab-fabricated radiographic guide was used to show the positions of the teeth in the CT scan (Figs. 2a, 2b).

A cone beam computed tomography (CBCT) scan was taken, which is the authors' standard of care for any patient considering implant treatment. Using SimPlant® software (Materialise Dental; Glen Burnie, Md.), the case was treatment planned using a team approach. Via an online meeting, Glidewell Laboratories helped facilitate digital treatment planning for four implants in the mandible. Care was taken to place the implants in the best bone, taking into account the position of the teeth in their correct anatomical positions and leaving adequate space for the planned attachments. In this virtual environment, we are able to visualize the end result before commencing treatment (Figs. 3a-3e).

The second phase of treatment is placement of the implants. Four ANKYLOS® implants (DENTSPLY Friadent; Waltham, Mass.) were placed in the positions predetermined in the planning software. The surgical guide helps to ensure that the implants are parallel (Fig. 4). Healing abutments were placed, the transitional lower denture was relieved and a soft liner was used.

The third, restorative phase of treatment involved upper and lower denture fabrication and the placement of LOCATOR® Abutments (Zest Anchors; Escondido, Calif.) on top of the implants. LOCATOR Attachments (Zest Anchors) serve as the retentive devices for the mandibular implant-retained, soft tissue-supported overdenture. These attachments resist wear and maintain satisfactory retention for up to 56,000 cycles of function.

This system proved appropriate where occlusal clearance became an issue. The LOCATOR Attachments come in a variety of retention strengths, from extra light to heavy (Figs. 5a-5b). This type of prosthesis allowed for excellent retention and stability for this patient.

To select the proper abutment height, the healing abutments were removed and a periodontal probe was used to measure from the head of each implant to the gingival crest. The attachments are best positioned supragingivally to allow for good tissue adaptation and easy maintenance (Figs. 6a-6d).

A conventional impression was made by seating impression copings onto the implants (Fig. 7). One of the most critical steps in the prosthetic procedure is to make a very accurate impression (Figs. 8a-8c).

The key to a successful overdenture is a well-made denture. The dental laboratory team accomplished the necessary fabrication steps prior to the next appointment. First, the impressions were boxed, poured and trimmed appropriately. Then, stabilized record bases with wax rims were fabricated.

During the subsequent visit, the record bases and wax rims were first tried in to ensure proper fit and comfort. Necessary adjustments were made for form and function, and the wax rims were contoured to achieve proper lip support, phonetics and occlusal plane. Once satisfied, a jaw relation was taken and vertical dimension of occlusion established at the position previously marked on the patient's nose and chin with her existing transitional dentures in place. A bite registration material was applied between the indexed wax rims and allowed to set at the proper position. The properly oriented casts were then sent to the dental laboratory team for use in setting the teeth.

Once the casts were mounted on an articulator, the teeth were set in the wax rims and returned to the office. At the try-in appointment, the proper position of the teeth was verified for form and function, then returned to the laboratory for processing on the final cast. Once laboratory processing was accomplished, the finished dentures were returned for delivery.

Delivery of the Esthetic Dentures

The dentures were tried in to evaluate for proper fit, comfort and occlusion. With minor adjustments, the mandibular denture was secured. An intraoral pick-up of the retaining element was necessary, and the intaglio surface of the mandibular denture was modified to accommodate the LOCATOR Attachments (Figs. 9a, 9b). Lingual vent holes were also placed to aid in the pick-up. Another option would have been to have the LOCATOR Denture Caps processed into the overdenture.

Auto-polymerizing acrylic was mixed and placed in the modified areas of the mandibular denture. The denture was positioned over the abutment-retained LOCATOR Attachments, and the patient was instructed to close and hold in full centric occlusion to allow for complete cure of the acrylic material. After approximately seven minutes, the denture was retrieved and inspected for complete pick-up. Excess acrylic was trimmed to remove any sharp edges.

Finally, the mandibular denture was checked in situ for fit, and the occlusion verified. The denture was accepted by the patient, and she was scheduled to return in one week for a post-delivery check.

Conclusion

Through the use of dental implants and overdenture prostheses, patients now have options beyond the conventional dentures of the past. By utilizing a team approach and advancements in technologies, material sciences and implant techniques, dentists can provide edentulous patients with the best in artificial dentition, while treating the patient as a whole (Figs. 10a-10d). Implant-retained, soft tissue-supported overdentures can drastically improve the quality of life for patients who otherwise might be considered dental cripples.

References

  1. Geckili O, Bilhan H, Mumcu E, Dayan C, Yabul A, Tuncer N. Comparison of patient satisfaction, quality of life, and bite force between elderly edentulous patients wearing mandibular two implant-supported overdentures and conventional complete dentures after 4 years. Spec Care Dentist. 2012 Jul-Aug;32(4):136-41.
  2. Henry K. Q&A on the future of implants. Dental Equipment and Materials. 2006 Sept/Oct.
  3. Rossein KD. Alternative treatment plans: implant-supported mandibular dentures. Inside Dentistry. 2006;2(6):42-3.
  4. DiMatteo A. Dentures and implants: bringing them together for a win- ning combination. Inside Dentistry. 2009;5(1):97-104.
  5. Agliardi E, Panigatti S, Clericò M, Villa C, Malò P. Immediate rehabilitation of the edentulous jaws with full fixed prostheses supported by four implants: interim results of a single cohort prospective study. Clin Oral Implants Res. 2010 May;12(5):459-65.