9: Root Form Implant Surgery: Generic

CHAPTER 9 Root Form Implant Surgery: Generic

ARMAMENTARIUM

Before undertaking the placement of any type of root form implant, the practitioner should read this section in its entirety. It lists the introductory techniques of insertion for all types of root forms. In addition, recommendations are found in the tables of Chapter 4 for the selection of a wide variety of implant designs. The techniques for placement of the specific proprietary designs are presented in chapters 10 and 11.

This chapter first presents the generic, step-by-step technique for insertion of root form implants. The illustrations and explanatory notes demonstrate the procedure in a sequence that starts with gingival incision and ends at a point that satisfies the introductory requirements for all systems. The final osteotomies and techniques for specific implant insertions are described in the following sections. If the instructions in this chapter are followed, a “generic” root form implant can be inserted and uncovered. That is, these steps are identical for most root form systems.

After acquiring an understanding of each maneuver, the reader should refer to Chapter 4. Its charts describe most of today’s implant varieties, their general grouping, material and design characteristics, surface finishes, methods of primary retention (during the integration period), and basic restorative options. Several systems offer implants with diameters of 3, 3.25, and 3.3 mm (small diameter). Especially in the maxillae, such implants often may be inserted after a 3-mm diameter drill is used without the formality of tapping, enlarging, or countersinking.

The diameters of drills should be increased in increments of 0.5 mm only (Brookdale Generic System). Bone density is a determining factor, as are internal irrigation, drill speed, torque, and bur sharpness. The smaller each graduation of bur size, the less heat and trauma are generated to the host site and the more accurate the osteotomy.

Not all systems supply all drill sizes. Different manufacturers supply a variety of sizes that may be selected to complete an entire generic set. For example, Nobel Biocare does not manufacture burs or a console that supplies internal irrigation; Calcitek recommends a round starter bur (the rosette); and Brasseler supplies graduated-diameter, internally irrigated spade drills.

Unless a computed tomography (CT) scan is available, the actual bone dimensions are known only at the time of flap reflection, and they dictate where the implants can be placed and what sizes should be chosen. However, the surgeon will find it significantly beneficial to use a surgical guide or template, so that the ideal locations for all implants are presented clearly where bone dimensions can accommodate them.

CAVEATS

In all endosteal implant procedures, the dental surgeon must take care not to impair vital structures. The use of infiltration anesthesia in the mandible helps guide drilling depths when the mandibular canal is approached, because the patient will report lip tingling. Slow drilling keeps intraosseous temperatures at safe levels. Saline irrigants can be chilled preoperatively to aid temperature control.

Implant placement must be planned with impeccable care; drills must be directed accurately, which can be aided by the use of paralleling pins and intraoperative radiographs.

Perforations of the cortical plates must be avoided. Systems that supply backup (or larger) implant diameters are valuable in case an oversized osteotomy is made (see Chapter 28 for specifics).

Burs and drills should be marked with the number of times used and discarded when they become dull.

Bone drills should be pumped vertically, rather than in an arc, to introduce copious irrigant and to encourage straight osteotomies.

Pressure should not be used when osteotomies are prepared; rather the drills should be allowed to find their own way. In systems that require bone tapping, use of a ratchet wrench by hand is preferable. Avoid this step completely if the bone is compliant enough to allow the implant to tap itself to place (e.g., Nobel Biocare, Biomet-3i, Zimmer). This level of pliability is found most frequently in the maxillae.

In the planning stages, a surgical template should be prepared for implant placement (see Chapter 4 and this chapter). However, the surgeon should keep in mind that sometimes, even the most careful planning does not yield satisfactory results because the bony ridge is not found directly below the soft tissues. The surgeon must be versatile enough to alter the positions and angles of the implants at the time of surgery.

Root form selection procedures (see Chapter 4) should be reviewed for the manufacturers’ recommended drilling speeds for different implant systems.

Particularly in the maxillae, but also in less dense mandibles, some of the preparatory steps may be eliminated (i.e., tapping, or threading, the bone and use of the final sizing drill and the countersink drill). In this less dense bone, the implant can seat itself and thread and countersink the host site bone.

SURGICAL TEMPLATES

As surgeons gain more experience, they will find that the same template may be used for radiographic diagnosis (Chapter 4), for surgical placement, and even for uncovering the implants. Fabrication of the surgical template is a necessary step in the planning and placement of implants. Its design is based on the anatomic, prosthetic, and esthetic considerations. If (as discussed in Chapter 4) a diagnostic, 5-mm, ball-imbedded Omnivac template is available and each ball has been processed at a potential implant site, simply removing the balls allows the device to be used as an implant site locator. However, a template can be fabricated to be used specifically for intraoperative guidance.

A surgical template also can be fabricated with computer-aided design and manufacturing (CAD/CAM) using computed and cone beam volumetric tomography (CT/CBVT) virtual implant planning (i.e., Nobelguide from Nobel Biocare, and Sicat’s Siroguide from GalaxisImplant). The latter requires some proficiency in computer-guided surgery, and the related fabrication costs are much higher than the traditional Omnivac template.

Three types of templates can be made using either the Omnivac or CAD/CAM process: a template for single tooth replacement or edentulous spans between natural teeth; a free-end saddle template for edentulous areas; and a template for completely edentulous sites.

Template for Completely Edentulous Sites

For completely edentulous sites, a new denture is fabricated at least to the wax try-in stage. If an existing removable denture is being converted or an original full denture is to be used, it is relined with a chairside material, such as Viscogel. Next, the denture is flasked using Kentosil in a denture duplicator with petroleum jelly as a lubricant. The denture is removed, and clear acrylic resin is poured into its place. The flask is closed, and the acrylic resin is allowed to polymerize. When it is removed from the elastomer, it is a duplicate of the original denture in clear acrylic. The borders are trimmed and polished.

In the areas to be implanted, the lingual and occlusal aspects of the teeth are cut away with a bur in the form of a U-shaped trough; the incisal and facial surfaces are left intact. The fenestrated area denotes the sites where the implants are to be placed to satisfy the reconstructive and aesthetic needs of the case. Individual holes can be made, although this may prove too restrictive. The clear labial surfaces allow direct viewing during the preparation for osteotomies (Fig. 9-2). This not only ensures proper angulations, but also shows that the transepithelial abutments (TEAs) emerge from optimal areas, such as the cingula of incisors and the occlusal surfaces of molars.

These templates subsequently can be used to point out the site of each implant at the time of uncovering, which makes major reflection of the overlying gingivae unnecessary.

SURGICAL TECHNIQUES

An infiltration technique is used to anesthetize the patient. A crestal incision then is made directly to bone, with adequate relief at either end, and the mucoperiosteum is reflected, exposing the bony operative site (Fig. 9-3, A and B). At this point, the bone is assessed. If the ridge is too narrow (i.e., knife edged), the surgeon must determine whether it can be flattened to an acceptable width and still have sufficient depth to accommodate an implant. If so, side-cutting rongeur forceps are used, and then a small, round vulcanite bur or a fissure type with irrigation (Fig. 9-3, C). Final smoothing is done with a bone file (Fig. 9-3, D). If the narrow ridge cannot be corrected but is deep enough, the surgeon should consider ridge augmentation (see Chapter 8) or placement of a blade implant (see Chapter 12).

After the ridge has been prepared and measurements indicate that the width is adequate (i.e., at least 5.25 mm) (Fig. 9-3, E), the osteotomies are made. As an alternative, ridge-widening procedures may be undertaken (see Chapter 8). (The surgeon must keep in mind that implants must be spaced one full width apart.) A colored sleeve is placed on the shaft of each drill at the level of the planned depth of each osteotomy (yellow Disposaboots currently are used) (Fig. 9-4). The drill tip pierces the rounded end, and the sleeve is slid up the shaft to mark the proper length.

The sterilized, clear acrylic, Omnivac surgical template is placed in the patient’s mouth. The flanges are trimmed so that they will nestle comfortably beneath the reflected flaps of tissue; in this position, the flanges keep the flaps reflected. The template is stabilized with the host bone that appears directly beneath the U-shaped window. The starter bur (No. 2 round) is set in the center of each proposed implant site and rotated only into the cortex. Copious coolant is used, even though most starter burs are not equipped for internal irrigation. For each planned implant, a similar starter hole is made and then deepened just through the cortex (Fig. 9-5, A).

After the starter bur, the pilot drill is used. This drill, which is 1.6 mm in diamete/>

Jan 5, 2015 | Posted by in Implantology | Comments Off on 9: Root Form Implant Surgery: Generic
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