Retreatment: Fractured Implants Due To Biomechanical Overload (Continued)

Inadequately engineered implant prostheses that lead to implant fracture are among the most difficult clinical conditions to manage. Understandably, implants are initially placed in the optimal bone sites, leaving the less desirable locations for the placement of new implants. The removal or retention of fractured implants also poses a dilemma. If the implants are removed, additional bone is lost in the process. And if the fractured implants are allowed to remain, they may become a source of irritation, inflammation or infection, and can seldom be used to provide any support for a new prosthetic rehabilitation.

The following clinical example demonstrates the complications and difficulty of retreatment when an inadequate number of implants is used to support a prosthesis that exceeds the biomechanical limits.

Next Column

See Graphics

PATIENT HISTORY

The patient is a very healthy 77-year-old retired general dentist. He has no known allergies to drugs or medications, has never smoked, and does not drink alcoholic beverages. The patient had been totally edentulous for the past 30 years and had been wearing the same denture that he had made for himself three decades ago. Because of continued severe atrophy of the mandible, the denture had poor stability and continuously migrated anteriorly (Fig 1). It inhibited his ability to chew and detrimentally affected his speech. Facial esthetics were also affected by the severe loss of vertical dimension.

Continues Below

Six years prior to our initial examination, a dental colleague and friend of the patient had placed three press fit cylinder implants in the greatest bone volume of the anterior mandible to function as retentive support for an overdenture. All three implants osseointegrated; however, the extreme mechanical overload eventually led to their fracture (Fig 2). At the time of our examination, the mucosal tissue surrounding the fractured implants was highly inflamed, hyperplasic and painful.

Radiographic evaluation was accomplished with panradiographs (Fig 3), lateral cephalometric films (Fig 4) and anterior-posterior cephalometric films (Fig 5). The three fractured implants visible on these radiographs used only half the available vertical height of bone in the symphasis area. The severe atrophy of the body of the mandible, especially in the area of the mental foramina, ranged from 5 to 8 mm in height. The inferior alveolar canal was partially deteriorated due to advanced atrophy of the alveolus, exposing the neurovascular bundle on the crest of the alveolar ridge.
next column

DIAGNOSIS
According to the American College of Prosthodontists classification of edentulous conditions, this dentist patient had a Class IV mandibular condition, with failed fractured implants in the symphysis region, and serious potential for pathologic fracture.

TREATMENT OPTIONS

Few options are available when considering the treatment of a Class IV severely atrophic totally edentulous mandible with fractured implants in the anterior. Vertical bone height is certainly a concern, even if a traditional removable denture prosthesis is the only available treatment. Bone grafting to increase the vertical height of the mandible could be considered. However, onlay bone grafting in the mandible has had poor treatment outcomes with the majority of the grafted bone resorbing in the first three years. This form of grafting is also contraindicated in light of the highly inflamed and hyperplasic mucosa around the fractured implants.
next column

Another option would be inferior border bone grafting using a cadaver mandible as a carrier for autogenous bone. This requires hospitalization and the associated morbidity of the hip as the donor site. Additionally, this protocol requires the graft to mature a minimum of one year prior to the placement of endosseous implants. Then the implants should be permitted to remain submerged and unloaded for an additional 8 to 10 months.

A third option would be the careful removal of the fractured implants and the placement of multiple short threaded implants, in conjunction with the lateral repositioning of portions of the neurovascular bundle.

TREATMENT

The patient elected to proceed with the third option after careful consideration of the above options and full realization of the potential for mandibular fracture. Written consent for treatment forms were reviewed and signed.
next page