Ramus Frame Implant Revisited

A common problem with long-term edentulism is advanced osseous atrophy, especially in the mandible. Removable complete dentures are likely to be unstable and lack sufficient retention for adequate function.^1–4  The mandibular bone can be very thin and unable to accept endosseous implants for prosthetic support^1–4  (Figures 1 and 2). As the mandible resorbs, the osseous ridge crest moves medially and apically. The facial and lingual cortices approach each other. The symphysis may become prominent, and the genial tubercles can be at or above the ridge crest. Vertical dimension of occlusion can decrease, producing facial and functional detriments. In jaw overclosure, the position of the mandible can move closer to the maxilla and can lead to angular cheilitis, aesthetic compromises and decreased function.⁵ 

With the mandibular osseous crest now lingual to proper tooth position, prosthetic fabrication needs to be designed and engineered for esthetic and masticatory function. The remaining bone volume and location may be inadequate to accept cylindrical endosseous implants.⁶  Supportive cylindrical dental implants may not be placed in appropriate positions for proper prosthetic design. Neurovascular transposition or vertical augmentation of the atrophic ridge can be done, but these have a significant potential for serious complications and costs.

When the maxilla is restored with a removable complete denture, the opposing atrophic mandible will have diminished functional loading and decreased off axial loading that would complicate prosthetic rehabilitation.^1–4  A maxilla with a fixed prosthesis or natural tooth dentition may place a significant dynamic loading on a mandibular complete denture, and that would require a fixed retentive modality.

The ramus frame implant (RFI) is a modality that can offer an immediately loaded treatment solution for a severely atrophic mandible. The RFI is made from commercially pure grade 2 titanium. The frame has three points, or feet, of osseous insertion: left and right ascending ramus and the symphysis. RFI treatment precludes the need for inferior alveolar nerve transposition or osseous vertical or horizontal augmentation grafting, thus decreasing treatment time and cost for the patient.

The RFI was first introduced in 1970 by the brothers, Drs Ralph and Harold Roberts. The RFI takes advantage of osseous sites that still have sufficient bone remaining that will accept the three supportive components. The last published article on the RFI was published in 2013, so it is not considered out of date or “passé.”⁷  The RFI has been successfully used for over 46 years. The ramus frame, after loading, may induce bone apposition.⁷ 

Drs Ralph Roberts and Richard Hughes appeared before a Federal Drug Administration hearing in 2014. They provided evidence and testimony of the efficacy of the RFI and assisted in the reclassification of this implant into the same category as cylindrical screws.⁸ 

A specialized armamentarium is required to install an RFI (Pacific Implant, Buena Park, Calif):

• Two RA-3 posterior try-in instruments.

• Anterior try-in straight and bayonet seating instruments.

• Titanium-tipped pliers to adjust the frame to fit the bone sites.

• Union Broach surgical adjustment mallet.⁹ 

Treatment for the atrophic mandible requires preoperative planning. Osseous landmarks should be identified on a preoperative study cast. There are 3 “feet” on the RFI that are embedded bilaterally in the rami and one in the symphysis.⁹  Available bone volume can be evaluated by cone beam computerized tomography. An appropriate osseous height is 10 mm minimum. Posterior ridge width should be at least 5 mm to accept the ramus foot. The distal feet are placed bilaterally in the base of the ascending ramus—as far inferior as possible to utilize as much attached tissue as possible. The anterior plate is inserted into the symphysis.

Bilateral inferior alveolar nerve blocks are done. The anterior incision is placed on the ridge crest (Figure 3). Facial and lingual attached gingiva of 2 mm or greater is required; if less than 2 mm, the attached gingiva should be augmented.¹⁰  An augmentation is best done before the RFI is installed. A 35-mm incision is required for the anterior foot. The foot should be centered according to the anatomical midline to provide as much bone support as possible.

The mental foramina are located on preoperative radiographs and by palpation intraorally after careful dissection and exploration with the back end of a #5 explorer. Care should be taken not to encroach on the mental foramen; in the atrophic mandible, it may be located at the crest of the ridge. Vertical releasing incisions may be placed at the distal incision corners.

A high-speed surgical drill with surgical length 557 bur is used to prepare the osteotomy along the ridge crest to a depth of 7 to 8 mm⁹ (Figure 4). A template is used for depth and length assessment. The anterior osteotomy should be centered on the midline (Figure 5). The angulation of osteotomy can be vertical or lingually canted. The anterior foot superior edge is to be placed 2 mm below the osseous crest. After the osteotomy is completed, it can be modified to fit the template. Additionally, the osteotomy can be altered with the surgical drill until the foot is seated 2 mm below the ridge crest. There is an anterior try-in foot instrument to aid in appropriate placement (Figure 6). The anterior osteotomy is now ready for foot insertion. Attention is now turned to the ramus osteotomies.

The ramus sites are prepared with incisions 5 mm superior and 2 mm lateral to the retromolar pad, then onto the crest of the alveolar ridge to connect with the anterior incision. This is done to maintain the retromolar pad. Create a full thickness buccal flap with releasing incisions. Releasing incisions along the ascending ramus and toward the vestibule will assist with visualization.

The ramus linear osteotomy is created with a high-speed surgical drill (Figure 7). The distal portion undermines the ascending ramus. The osteotomy should be 2 mm medial to the buccal osseous crest and as straight as possible (Figure 8). The distal portion of the osteotomy undermines the ascending ramus about 10 mm and is a key point: It acts as a locking pivot point for the frame when it is seated. The posterior try-in foot is used in a similar fashion as the anterior to determine osteotomy refinements (Figure 9). Once a ramus osteotomy is completed, proceed with a frame try-in (Figure 10). To insert the frame, the posterior feet are first maneuvered into the distal undercuts, then rotated down so that the anterior foot inserts into the anterior osteotomy. If the insertion is difficult and binds against the osteotomy, a notched bayonet instrument and mallet or a spring-loaded hammer can gently assist in the final seating. If necessary, the frame can be widened or constricted with manual pressure to change the spread of the frame. The anterior foot can also be bent to allow placement directly under or slightly lingual to the superstructure. After the frame has been seated and the feet are 2 mm subcrestal, a particulate bone graft material is placed in the osteotomy gap (Figure 11). A panoramic radiograph can be made to ensure appropriate seating (Figure 12). The soft tissue is primarily closed with a nonresorbable suture with horizontal mattress or interrupted technique. Healing takes place with the fully functional denture in place.

Once the RFI is inserted and suturing is completed, an immediate provisional denture can be tried-in the mouth⁹  (Figure 13). A mandibular complete denture is provided by the manufacturer (Pacific Implant). There is a wide groove to accept the RFI. The denture is tried-in and adjusted for appropriate seating and occlusion. It is then relined with cold cure acrylic, taking care to keep the acrylic from engaging with the RFI (Figure 14). Alternatively, after festooning, any existing mandibular denture can be relined with cold cure acrylic to fit the frame. Refinement of the occlusion is now done (Figure 15). New dentures may be fabricated 4 months after healing (Figure 16).

The RFI is an inexpensive, immediately loaded treatment that can be placed in an extremely atrophic mandible under local anesthesia. There is far less morbidity associated with RFI treatment than with harvesting autogenous bone for ridge augmentation grafting in screw-type implants or nerve transposition.^1–4  The RFI can successfully function for many years.⁵ 

After mandibular teeth are removed, there is osseous resorption that changes the characteristics of the mandible. This resorption depletes the alveolar bone and can involve the basal bone.^1–4  Thus, a removable mandibular complete denture will become unstable and unretentive. Root-form endosteal implants are not always able to be placed in an advanced atrophic mandible without bone augmentation.^1–4  Financial limitations may also preclude endosseous treatment. The cost of the RFI is significantly less than screw-type implants. The RFI is immediately loaded and totally supports and retains the denture, providing a broad distribution of forces.

The denture can also be retained with a Lew-Loc attachment⁷  (Dutton Dental Concepts, Inc, Bolivar, Ohio). This provides fixated retention and allows the patient to unlock and remove the denture for hygiene access.

As with any surgery, complications are possible. These include neural disruption, infection and failure to integrate.

Functioning RFIs have shown 4.4 mm to 13 mm bone apposition of the mandible after years of use.³  Eighty-three cases were followed over 5 to 24 years at 5-year intervals.³  Pre- and postoperative panoramic radiographs were taken at each succeeding 5-year follow-up. After years of function, there were significant increases in bone height, averaging 4.4 mm with P values of <.0003. The growth of bone was apparently influenced by the ramus frame, dominant chewing side, and severity of the presenting atrophy. The success rate of ramus frame implants may be as high as 97%.¹⁰ 

There is a percutaneous exposure of the RFI as it penetrates the oral mucosa. Adequately attached gingiva around the percutaneous struts is key for a satisfactory long-term outcome. Nonetheless, immovable mucosa may be acceptable. The patient's oral hygiene should be excellent to keep the oral bacteria load at a minimum. The epithelial attachment may be susceptible to bacterial attack that can lead to peri-implantitis and bone loss, so optimal oral hygiene is imperative.^12,13 

Recent computer-aided design and diagnostic radiology can provide significant treatment benefits such as stereolithography and simplified placement.⁴ 

The ramus frame modality is a proven method that continues to be a viable option for the severely atrophic mandible. It provides immediate support for a removable complete denture and avoids invasive augmentation procedures and associated morbidities. As with all surgical techniques, the astute clinician should be well educated and trained in implant dentistry and understand the patient anatomical and systemic conditions before treatment is instituted.

Abbreviation
 
• RFI

  ramus frame implant

The authors report no conflicts of interest.