CHAPTER 13 Ramus Frame and Ramus Blade Implant Surgery
The anterior foot of the ramus frame must be bent carefully so that it enters the symphysis evenly between the cortical plates and goes directly into the medullary bone; this discourages fracture of the labial cortical plate.
The RA-2 implant may be used to support an overdenture for patients with atrophied mandibles (Fig. 13-1). This implant originally was made of 316L surgical stainless steel, but more recently it has been made of grade 2 surgical titanium. The RA-2 is a one-piece, tripodal design implant and is available in only one size.
The patient is anesthetized with bilateral mandibular and long buccal blocks and local infiltration. A full-thickness incision then is made along the crest of the ridge in the anterior region of the mandible. The incision is started at the area just distal to the mental foramen and proceeds around to the opposite side. It will be approximately 25 mm long (Fig. 13-2).
The flaps are reflected lingually and labially, and an anterior vertical relieving incision is made just lateral to the labial frenulum to facilitate this procedure (Fig. 13-3). The bony site is explored for lingual and labial concavities, as well as for adequate height. The mental nerve should be protected; this is best ensured by exposing the superior halves of the foramina (see Chapter 8).
The anterior try-in template is placed at the crest of the ridge and used as a guide for making the osteotomy (Fig. 13-4). This cut is made with a 557L surgical bur in a high-speed handpiece in the same manner as for conventional blade or plate-form implants. First, sketching perforations are made with a No. 2 round bur. If they are well aligned, the 557L fissure bur is used to convert them into a continuous groove (Fig. 13-5). The osteotomy is deepened to 6 mm if the vertical bone height is 10 mm or less; if 10 to 20 mm of height is available, the osteotomy should be 8 mm deep. The osteotomy is canted labially, and its base is placed in a slightly more anterior position than at the crest. Angling the bur in an anterior direction keeps it parallel to the ideal host site in a midcortical posture.
FIGURE 13-4. After the flaps have been reflected, the template is held with its large, curved border over the bony ridge to outline the shape of the osteotomy for the anterior component (foot). The template must be bent to conform to the shape of the ridge.
FIGURE 13-5. Before a transcortical osteotomy is made, a small, saline-cooled, round bur in the high-speed handpiece is used to form its outline. The initial effort is made in the form of shallow perforations about 3 mm apart.
The anterior template now should be tried in. Its shape may require modification with the Roberts anterior bending pliers. This instrument adapts the template more closely to the shape of the osteotomy. When seating of the template is satisfactory, these same bending modifications are made to the implant.
A full-thickness incision is made, beginning at a point 10 mm above the retromolar pad and just lateral to it, or approximately at the level of the sigmoid notch. The incision is continued downward and forward from the anterior border of the ramus along the external oblique ridge. As the anterior incision is approached, the scalpel is directed medially to the crest of the ridge, so that the two incisions meet. This process is repeated on the contralateral side. The posterior flaps are reflected buccally to expose the external oblique ridges and lingually just to the mylohyoid ridge.
A point 18 mm distal to the end of the anterior osteotomy is measured and marked; this is the site where the posterior osteo-tomy begins (Fig. 13-6). It should be noted that the posterior try-in template has two marks on it, at 18 mm and at 30 mm.
FIGURE 13-6. An alveolar crestal incision is made into fixed gingivae in each ramus retromolar area and then carried forward to meet the anterior incisions. The ridge must be exposed from the ramus anteriorly to the mental foramen. The posterior (ramus) osteotomies are made most easily with a straight (Hall) handpiece or an obtusely angled Impactair, although a conventional handpiece can be used if the patient can open sufficiently. The osteotomies should be created by first making transcortical bur holes in a perforated pattern.
The posterior template is placed on the crest of the ridge with the 30-mm mark on the ramus at the posterior end of the projected osteotomy and the anterior mark at the 18-mm point. The template is placed at the angulation of the long axis of the ramus and 2 mm medial to the lateral cortical plate. It acts as a guide for the osteotomy, which should be as close to a straight line as is possible.
With a No. 1 round bur, a series of perforations is made just through the cortical plate. They should be 1.5 to 2 mm apart along this line, beginning at 30 mm and working forward to 18 mm (Fig. 13-7). The surgeon’s tactile sense indicates when the cortex has been perforated and the marrow cavity reached. The template must guide the placement of the dots. When they have been completed, the surgeon evaluates their alignment and accuracy and makes corrections, if necessary. A 701L surgical bur then is used to connect and deepen the dots. The resultant groove is completed when it reaches a depth of 6 mm, which is 1 mm deeper than the flutes of the bur.