CHAPTER 16 Intramucosal Insert Surgery and Prosthodontics
The intramucosal insert armamentarium consists of a base-preparing bur that prepares the denture with holes designed to receive the inserts; a surgical trephine to create the mucosal receptor sites; surgical indicator styli, which transfer the sites from denture to tissue; and the inserts themselves. Eight to 14 inserts must be used. Additional requirements include a scalpel with a BP No. 11 blade, pressure indicator paste (PIP), indelible pencil, college pliers, paintbrush, and autopolymerizing resin.
Inserts must be placed at least 1 cm apart. Insert bases are set in exact continuity with adjacent denture base material (neither too deep nor too shallow) and at absolute right angles to the tissue-borne denture surface at each site. Inserts need not be parallel to each other. In fact, it is best if they are not parallel, because this offers additional (interhead) clasping.
Proper patient selection is a requisite for success. This technique benefits only those who gag or have a lack of retention; it is not meant for patients who reject dentures because they “burn,” are “too tight,” or cause pressure.
Intramucosal inserts may be used for full upper dentures or unilateral partial dentures in either jaw. They are useful for patients who have problems with retention of a maxillary full denture. They are not for patients who claim that their dentures are too tight or for those who say their tissues burn from denture wearing. However, if the patient gags from denture wearing, these inserts can help by shortening postdam areas. However, U-shaped, or palateless, dentures work only for short periods; they slowly lose their retention as the healed receptor sites fill in with secondary-intention epithelium, which gradually reduces denture retention.
The technique must be followed carefully, and the inserts must be set into the denture base exactly flush with and perpendicular to the acrylic. If they are placed too deeply, they will fail to develop retention. If placement is too shallow, the protruding bases may cause ischemia and necrosis of the opposing mucosa, with subsequent chronic inflammation or loss of receptor sites.
Eight to 14 sites are selected on the surface of the maxillary mucosa, depending on the design of the insert head. The newer (Park) flatheads develop superior retentive qualities and succeed with as few as eight inserts. The traditional inserts, which are more of a rounded arrowhead shape, function best with 14 devices.
The tissues are dried, and then a Kerr Dycal applicator tipped with pressure indicator paste (Fig. 16-1) is used to mark the spots, which should be evenly placed at the crest. The first mark is made 5 mm lateral to the midline. The second mark is made in the center of the tuberosity, and the third is made halfway between them. The distance between these three marks is divided, and marks four and five are placed at the midway points. Repetition on the opposite side of the arch locates the first 10 marks. This is more than sufficient for the Park-type heads. For the earlier designs, the eleventh mark is placed 1 cm palatally from the ridge crest and midway between marks three and four. The twelfth mark is placed midway between marks four and five in line with the eleventh mark. These steps are repeated on the opposite side to locate the thirteenth and fourteenth marks. The surgeon should check the radiographs for low-dipping antra and should avoid the regions of major foramina and nerve bundles.
The denture is dried and seated directly upward, and the patient is guided into firm centric closure. When the denture is removed, the white marks will have transferred to it from the opposing tissues (Fig. 16-2). At the site of each white spot on the denture, the base-preparing bur is used to make an opening at an absolute right angle to the acrylic at each of the marks (Fig. 16-3). The bur is sunk precisely to the depth of the cutting blade to create holes into which the intramucosal insert bases will find flawless housing, exactly level with the acrylic.
FIGURE 16-3. A, The base preparation is used to make an opening at each location marked by the pressure indicator paste. These apertures are drilled at right angles to the acrylic and to the full depth of the bur’s blade. B, The 14 insert recesses have been completed with the base-preparing bur.
A 30-gauge, short anesthetic needle is used to infiltrate a single drop of lidocaine 2% and 50,000 epinephrine into each of the 8 to 14 white marks in the tissues, assuming that these drugs are not contraindicated for the patient (Fig. 16-4).
A single arrowhead surgical indicator stylus is placed in each of the holes in the denture (Fig. 16-5), and each is tipped with a moistened, purple, indelible pencil. If the chosen system does not supply indicator styli, a somewhat less exacting technique can be used. The intramucosal inserts are processed into place with self-curing acrylic and tipped with indelible pencil to transfer their locations to surgical sites in the mucosa. Again, the denture is seated aggressively in a directly vertical maneuver so that each of the arrowheads or indelible pencil marks transfers to the tissues exactly opposite the site of its denture hole. The denture is removed with care after a gauze throat curtain has been placed to catch any loosened styli.
FIGURE 16-5. A, Surgical indicator styli have bases of a slightly smaller diameter than the inserts themselves. They are characterized by sharp, arrowhead-shaped tips. B, A surgical indicator stylus occupies each of the apertures.
About half of the styli will remain lodged in the tissues, and the other half will come away with the denture (Fig. 16-6). The latter group leaves the tissues tattooed with punctate purple spots.
FIGURE 16-6. The denture is seated, and its position is checked for accuracy by having the patient close in centric. On removal of the denture, the styli remain embedded in the tissues, transferring the exact concentric relationship of each denture aperture to the tissue.
After the styli are removed, one by one, a round hole is cut into the tissues with the trephine, which should be forced through the tissues in a perpendicular direction. Its handle is pushed directly to bone and then rotated clockwise and counterclockwise several times (Fig. 16-7). Care must be taken not to press too hard in the premolar and molar areas, or the maxillary sinus may be penetrated. If this should happen, the site should be abandoned until it heals by secondary intention. (See Chapter 28 if healing by secondary intention fails to occur.) The trephine is removed, and its lumen is unplugged with the stylet; this should produce a small core of tissue. However, this core can be obtained only when the cutting end of the trephine is rotated against bone firmly enough to excise the tissue thoroughly. Each receptor site is created in the same fashion. Some brisk bleeding may occur, but tamponade solves this problem. Dramatic hemostasis also can be achieved by plugging a Racellet cotton pellet into the site.
FIGURE 16-7. A, The trephine, a sharpened 18-gauge needle with Luer-Lok handle, and a stylet are used to remove a plug of tissue of sufficient diameter to accommodate the cervix of each insert. B, The trephine is placed at each stylus mark and forced into the mucosa with firm finger pressure until it strikes bone. At this point, it is rotated against the bone, which excises a full-thickness plug of tissue. The stylet is used to empty the lumen of this tissue.
Eight to 14 holes have been created, each the diameter of an insert cervix. At this point, none is wide enough to accommodate the insert head. To allow entry of these larger components, a Bard-Parker (BP) No. 11 blade in a long handle is used to make a cruciform or X incision is made at each site. Two 3-mm incisions at right angles to each other with the trephined hole at the center complete this operation (Fig. 16-8).
The depth of each hole is measured with a periodontal probe or with an actual insert that has been soldered to a broken instrument handle so that the measurements can be recorded on an anatomic chart. If any of the sites is less than the full depth of the insert head and cervix (usually 2.2 mm, but as much as 2.5 mm, depending on the system), the bone that lies at the base of the surgical site must be deepened. A sterilized No. 6 round bur in a high-speed handpiece should penetrate the bone to the bur head’s full depth, which creates enough vertical depth to accommodate the head and cervix of the insert (Fig. 16-9). The patency of each X incision is checked one last time, and the patient is instructed to bite on a roll of saline-moistened surgical sponges.
FIGURE 16-9. A, With shallow mucosae (as demonstrated by a millimeter probe), a No. 6 round bur is used to deepen the bone. Care must be taken not to enter the maxillary sinus. B, Within 72 hours, the deepened receptor site becomes lined with secondary-intention epithelium.
The denture is washed and dried thoroughly, and a sable paintbrush is used to place a drop of monomer in the first receptor site (Fig. 16-10, A). This is followed with application of a thin slurry of acrylic powder and liquid into the retentive groove of the intramucosal insert base. The inserts are held at their necks with the beaks of locking college pliers forceps, and each is vibrated into its receptacle in the denture (Fig. 16-10, B and C). Care must be taken to ensure that its platform is perfectly level with the surrounding acrylic. Minimal amounts of acrylic should be used, to allow total seating of the insert base.
FIGURE 16-10. A, Pink autopolymerizing polymethyl methacrylate, applied with a paintbrush, is required to seal each two-tiered or textured (see Fig. 16-14) insert base into the denture. B and C, The inserts are held with the tips of pliers, and small amounts of acrylic are used to lute each into its assigned aperture. D, When placement of the intramucosal inserts is complete, the denture is seated and centric occlusion is confirmed.
The sponges are removed from the patient’s mouth, and the denture is seated. The inserts should move completely into place (Fig. 16-10, D). This can be verified if centric occlusion is correct and the postdam area is well seated. If this is not the case, each surgical site must be reassessed with a depth gauge as instructed previously, and those that need it must be deepened.
In theory, the procedure is now complete. However, practical experience has shown that the 14-day period after surgery, during which the denture must not be removed for even the shortest time, can be disappointing. Patients, particularly those who gag when uncomfortable, remove their dentures despite all warnings. To achieve the highest level of success, the denture must be ligated into place, which is done according to the following process.
First, the denture is removed. Moistened sponges are placed over the receptor sites, and a No. 4 round bur is used to drill three pairs of holes into the denture flanges. For the first pair, one hole is pla/>