10: Root Form Implant Surgery: Proprietary I

CHAPTER 10 Root Form Implant Surgery: Proprietary I

The generic steps leading to the definitive procedures described in this section can be found in Chapter 9. Not all the systems described in this chapter begin after the use of the 3-mm spade drill. For example, for small-diameter implants, the sequence must stop at the 2.5- or 2.7-mm drill. If the surgeon uses the 3-mm spade drill for these systems, the host sites will be too wide. Therefore, the dental surgeon must read each section carefully before beginning.

Although this chapter may not mention all the implant sizes available, Table 4-2 lists dimensions for each type and style. For the practitioner who does not want to use the generic system, as described in Chapter 9, to begin the osteotomy for the chosen implant system, the illustrations begin their instructive patterns with the full spectrum of drills, starting with the smallest diameter offered by the specific manufacturer.

EXTERNAL HEX, THREADED IMPLANTS

The abutments for external hex, threaded implants have an antirotational design in the form of an external hexagon that protrudes from the top of the device (Fig. 10-1, A).

image image

FIGURE 10-1. A, The external hexagon is the second most commonly used form of antirotational design. B, The internal hexagon is the most frequently used antirotational design.

Manufacturer System
BioHorizons

External system

Imtec
Hexed-Head
Keystone
Restore
Nobel Biocare
Mk III, Mk IV, Brånemark system, NobelSpeedy Groovy, NobelSpeedy Shorty
Osteomed
Hextrac
Zimmer Dental
Swede-Vent
Park Dental Research
Star/Vent
Sargon
Immediate load implant
Biomet-3i
Standard system, Microminiplant, Miniplant

INTERNAL HEX THREADED IMPLANTS (Fig. 10-1, B)

Manufacturer System
Zimmer Dental

Screw-Vent, Micro-Vent
Friatec
Frialit (two step)
Nobel Biocare
NobelSpeedy Replace

PRESS-FIT IMPLANTS

Manufacturer System
Zimmer Dental

Spline-Cylinder
Innova
Endopore
Lifecore
Restore

SPLINE AND SIMILAR IMPLANTS

Manufacturer System
Zimmer Dental

Spline
Park Dental Research
StarimageLock

MORSE TAPER

Manufacturer System
Astra Tech

Implant with screw fixation
ITI
Implant with screw fixation, Standard Plus
Bicon
Implant with screw fixation

NOBEL BIOCARE

Although most implant systems are quite similar, they are packaged differently. For example, Noble Biocare is available in a scored glass tube that snaps in half on finger pressure. Biomet-3i comes in a blister pack that includes the surgical cover screw. Some of the designs are manufactured as self-tapping implants in wide and small diameters. Various coatings (e.g., hydroxyapatite [HA], titanium oxide [TiO2], and titanium plasma spray [TPS]) also are available for some implants. The directions for placement are similar for each system (e.g., Osteotite, NobelActive, Advent), but the instruments have different names. In the directions that follow, Nobel Biocare’s Brånemark instrument names are used. These implants are available in diameters ranging from 3.25 to 6 mm and in varying lengths (5.5 to 18 mm) for most applications, even up to a 52.5-mm length, which is used as an extraoral implant to be inserted into the Zygoma. Insertion techniques vary slightly according to the size of the implant.

Joining the Procedure in Progress

The generic process (see Chapter 9) will have been performed up to this point; that is, the 3-mm twist drill will have been used to its final depth. The procedure then follows these steps.

1. For dense bone, the 3.15-mm twist drill is used next. The surgeon must proceed with care, particularly if internal cooling is not available.
2. The compatible (3 mm) end of a paralleling pin is placed in the osteotomy to verify the angulation of the preparation.
3. The appropriate countersink is used at the top of the osteotomy. The short countersink is recommended for implants 10 mm long or shorter; the long countersink is used for implants longer than 10 mm.
4. The osteotomy is measured with the depth gauge, and any necessary corrections are made.
5. The handpiece connector is attached to the ultra-low-speed handpiece, and the console is set to its lowest speed.
6. Unless self-tapping implants are used or the bone is compliant, bone tapping is performed. The appropriate bone tap is snapped into the handpiece connector while it is stabilized in the fixture rack with the titanium-tipped hemostat. The bone taps and implants should not be handled with fingers, gloved or otherwise. The rack and forceps are used for mounting and removal. Some manufacturers (e.g., Camlog) prepare each implant with its own handpiece connector. Others (e.g., Straumann) prepare some of their implants with a handpiece connector and some require attachment of a connector at the time of surgery.
7. The low-speed handpiece (8 to 18 rpm) is used (along with copious saline irrigant) in a forward or clockwise direction to tap the bone.
8. When the tap arrives at a point 3 mm short of the full depth, the motor is stopped, and the tapping is completed with the handheld wheel or handheld ratchet wrench.
9. The bone tap is removed by turning the handheld wheel or ratchet wrench counterclockwise (reverse mode).
10. The outer container of the chosen implant is opened, and the implant is allowed to fall gently into the small, sterile, square container marked “T” (for titanium). Alternatively, titanium-tipped forceps can be used to transfer the implant to the proper-diameter hole in the surgical tray and, if the handpiece connector is not already attached, the screwdriver is used to attach it to the implant. If the handpiece connector has already been attached to the implant, the implant is carried to the proper hole in the surgical tray and stabilized with the notched-beak, curved hemostat forceps.
11. The ultra-low-speed handpiece rotates the implant into its prepared site at less than 20 rpm until the implant is 3 mm short of full seating. Although most motors usually stop when the implant is fully seated, the risk of stripping the bone threads does exist. For this reason, the safest method is to use the handheld wheel or, if necessary, the ratchet device to seat the implant for the last 3 mm. The handpiece is detached from the handpiece connector, leaving it attached to the implant. The ratchet handle is held as close to the implant as possible to enhance tactile sensitivity and to minimize excessive distracting movements, which the long handle can cause.
12. Tightening with the wheel or ratchet wrench ensures the implant’s stability. If the operative site has stripped internal bony threads, most systems offer backup implants of commensurate lengths. The backup implant should be introduced into the site directly, without pretapping.
13. The screwdriver backs off the fixation screw while the open-ended wrench is used to provide countertorque to the implant.
14. The wounds are irrigated, and the cover screw is then placed. A throat pack should always be in place when small instruments and fittings, such as cover screws, are used. Techniques for placing the cap screw include the following:

• A special cover screw screwdriver can be used. This screwdriver is mounted in a low-speed handpiece; the speed should not exceed 15 rpm, and the lowest torque (10 Ncm) should be used. Final tightening always should be done by hand with either the short or long screwdriver (Fig. 10-2).
• The flat-top cover screw can be seated with the hexagonal screwdriver.

15. The flap may now be sutured (see Chapter 6).
image

FIGURE 10-2. A, Nobel Biocare implant. B, According to the manufacturer’s recommended procedure, the surgeon begins by using the guide drill to half its diameter to penetrate the cortical plate at the proposed implant site. C, The 2-mm twist drill is used to the final implant depth. D, The counterbore is used to enlarge the coronal portion of the osteotomy in preparation for the 3.5-mm twist drill (E). F, Countersink drill. G, Depth gauge. H, Screw tap. I, The implant is inserted attached to the handpiece connector. J, The open-ended wrench stabilizes the handpiece connector while the fixation screw is removed from the implant. K, Cover screw inserter. L, Placement of the cover screw with the small hexagon screwdriver. M, The Nobel Biocare implant is seated so that its cover screw is flush with the crest of bone.

The uncovering procedure is described in Chapter 9. The appropriate healing collar or cuff or an abutment is placed, depending on the thickness of the tissue and its esthetic needs. Healing cuffs should protrude approximately 2 mm above the free gingival margin. Special abutments are used that are similar in contour and diameter to the anticipated restoration. These abutments are kept in position until the tissues have matured sufficiently to allow the impression procedures. Generally, this takes 2 weeks.

Brånemark System

Mk III TiUnite and Mk IV TiUnite

The Mk III TiUnite and Mk IV TiUnite are the original Brånemark designs. A 1.5-mm external hex is part of the restorative platform design.

TiUnite is Brånemark’s patented, enhanced titanium oxide (TiO2) layer. As are other TiO2 surfaces, it is osteoconductive, and its texture and porosity are ideal for bone apposition and for creating an enhanced environment for bone formation. The enlarged surface area and structure, which absorb blood proteins and aid in bone growth, are very similar to human cancellous bone.

Mk III (Narrow Platform, Regular Platform, and Wide Platform)

The Mk III implant is a universal, self-tapping implant that can be used for all conditions in which sufficient bone volume is available for an implant. (Refer to Chapters 2, 4, and 7 for bone volume criteria for root form implants.) Mk III implants are available in three diameters: narrow platform (NP), 3.3 mm; regular platform (RP), 3.75 and 4 mm; and wide platform (WP), 5 mm. Seven lengths are available: 7, 8.5, 10, 11.5, 13, 15, and 18 mm. The line also includes a 5.5-mm long implant (i.e., the NobelSpeedy Shorty), which has been approved for immediate function. The osteotomy sequence and protocol for this implant are similar to those for the NobelSpeedy Groovy implant.

The Mk III 3.3-mm NP implant is used when interproximal space is limited or minimal alveolar bone width is available to accommodate an RP implant. Narrow-diameter implants have less mechanical strength; therefore the surgeon must carefully evaluate the expected loads and the support the planned restoration will require to function.

The Mk III 3.75- and 4-mm diameter RP implants are used for the widest range of conditions. RP implants have an extensive selection of implant restorative components.

WP implants are used when the potential functional loads of the restoration and the available anatomy justify the use of a wider implant. Although the mechanical strength of implants has been improved considerably, bone quality and quantity remain patient-dependent variables. Both the amount and quality of bone can be limiting factors when the higher occlusal loads found in the posterior regions of the jaws are factors in the treatment.

Mk IV (Regular Platform and Wide Platform)

The Mk IV implant is a tapered implant intended for use in soft bone. The tapered design and double threads achieve and enhance initial implant stability in soft trabecular bone. The RP implants have a 4-mm diameter, and the WP implants have a 5-mm diameter. As with the Mk III implants, seven lengths are available (7, 8.5, 10, 11.5, 13, 15, and 18 mm). All drills and components are marked so that the implantologist can prepare the implant site to the correct depth and create a secure, predictable implant position. Twist drill preparation is deeper than the final position of an implant apex. Depending on the diameter of the twist drill, the apical part of the drill deepens the site about 1 mm.

NOTE

The graduations on the twist drills and depth gauge represent the height of the implant plus a cover screw (Fig. 10-3).

image

FIGURE 10-3. Straight-walled external hex. Sequence of the osteotomy from initial pilot twist drill to the cover screw.

(Courtesy Nobel Biocare, Yorba Linda, Calif.)

Osteotomy Procedure

Mk III ∅︀ 3.3-mm NP Implant

Fig. 10-4 presents the osteotomy sequence for a narrow-platform implant.

image image image image image image image image image image image

FIGURE 10-4. Osteotomy sequence for the narrow platform (NP) implant.

(Courtesy Nobel Biocare, Yorba Linda, Calif.)

Mk III ∅︀ 4-mm RP Implant

A 4-mm diameter RP implant can be used in soft bone or when initial stability cannot be achieved with a 3.75-mm diameter RP implant. In very dense bone, a Mk III Screw Tap may also be required. Drills of different diameters can be used, depending on the bone quality and implant diameter.

Mk III ∅︀ 3.75- and 4-mm RP Implants

The crestal preparation drill and final shaping drill for an RP implant are shown in Fig. 10-5.

image

FIGURE 10-5. Crestal preparation drill and final shaping drill for a regular platform (RP) implant.

(Courtesy Nobel Biocare, Yorba Linda, Calif.)

Mk III ∅︀ 5-mm WP Implant

The crestal preparation drill and final shaping drill for a WP implant are shown in Fig. 10-6.

image

FIGURE 10-6. Crestal preparation drill and final shaping drill for a wide body implant.

(Courtesy Nobel Biocare, Yorba Linda, Calif.)

Drilling Procedure

Mk IV ∅︀ 4-mm RP Implant. 

The Mk IV implant is recommended for use in predominantly soft bone (classes III and IV). The surgeon must pay particular attention to bone quality. Optimum results depend on selection of the appropriate drill diameter after the bone quality at each site has been evaluated. In principle, the osteotomy sequences are the same as for placement of a Mk III implant (Fig. 10-7).

image

FIGURE 10-7. Because of the softer quality of the bone, a bone-tapping drill is not required.

(Courtesy Nobel Biocare, Yorba Linda, Calif.)

Class IV (Very Soft) Bone. 

The process for drilling in very soft bone is as follows:

1. A standard drill kit is used.
2. In very soft bone, the implant is placed directly after the 2/3-mm pilot drill is used.
3. In the posterior maxilla, where a wider preparation is needed, a 3-mm drill is used. To improve apical implant stabilization in soft bone, the surgeon may elect not to extend the full length with the 3-mm twist drill.
4. Traditional countersinking should be avoided in very soft bone, so that better use can be made of the available thin crestal cortex.

NOTE

The implant platform may be left to the level of the alveolar crest for maximum compression and initial stability.

5. If the bone topography is irregular and/or of a different density around the implant head, the Mk IV RP counterbore can be used for access shaping to allow easier future abutment connection. If a good-quality cortex layer is available, the Mk IV RP counterbore should be used according to the standard protocol, at either high or low speed. The reference line on the Mk IV RP counterbore indicates the seating level of the implant platform.
6. If the osteotomy equipment has the capability, the implant should be inserted using progressively increasing insertion torque. Torque levels are based on bone quality and the resistance encountered, so that the bone threads are protected from stripping. In soft bone, the torque level should begin at 20 Ncm. The last turn is carefully hand-tightened to obtain a precise platform level position and to ensure that the resistance to insertion is positive and increasing.

Class III (Soft to Moderately Soft) Bone. 

The process for drilling in soft to moderately soft bone is as follows:

1. A standard drill kit is used.
2. The sites are prepared for use of the 3.15-mm twist drill.
3. The Mk IV RP counterbore is used to prepare the cortical bone for the implant flange. The reference line on the Mk IV RP counterbore matches the seating level of the implant platform.
4. If the osteotomy equipment has the capability, the implant is inserted using progressively increasing insertion torque. Torque levels are based on bone quality and the resistance encountered, to further protect bone threads from stripping. The last turn is carefully hand-tightened to obtain a precise platform level position and to ensure that the resistance to insertion is positive and increasing.
5. If the implant does not seat completely, the insertion torque is increased to a maximum of 40 to 50 Ncm.

NOTE

Insertion with the hand wrench above 50 Ncm of torque is not recommended. Instead, the implant should be backed out and the site should be pretapped at low speed with the Mk IV Screw Tap, accompanied by copious irrigation. The implant then can be reinserted into the pretapped site.

Class I and Class II (Cortical) Bone. 

The Mk IV implant is not recommended for use when predominantly dense cortical bone is present. In some patients, 2 to 3 mm of dense cortical bone is found in the posterior mandible, with loose trabecular bone underneath. Even if the rest of the bone in the area is soft, seating the Mk IV implant may be difficult because the implant cannot compress the thick layer of cortical bone. In such cases, the Mk IV Screw Tap can be used through the cortical layer (Fig. 10-8).

image

FIGURE 10-8. Bone-tapping drill for dense cortical bone.

(Courtesy Nobel Biocare, Yorba Linda, Calif.)

Mk IV 5-mm WP Implant

The Mk IV 5-mm WP implant is inserted as shown in Fig. 10-9.

image

FIGURE 10-9. Mk IV wide body external hex implant.

(Courtesy Nobel Biocare, Yorba Linda, Calif.)

Zygoma Implant

The Zygoma implant is used in patients with severe alveolar atrophy in the posterior maxilla when augmentation procedures are not possible because of financial or medical considerations. These extremely long endosseous implants can be secured into the zygomatic processes. When inserted there, along with two to four strategically placed, standard implants in the anterior maxilla, a bar-overdenture (two Zygoma implants + two anterior implants) or a fixed-detachable or fixed prosthesis (two Zygoma implants + four anterior implants) can be fabricated and put into function.

Compared to a standard implant, the Zygoma implant has a greater tendency to bend under horizontal loads. This is related to two factors:

• The much longer length of these implants (30 to 52.5 mm)
• The limited bone support available in the maxillary alveolar crest under some circumstances

Consequently, Zygoma implants should be rigidly connected to stable conventional fixtures in the anterior maxilla. Based on clinical experience and biomechanical theoretical calculations, a full arch restoration in the maxilla with two Zygoma implants (one on each side) should be assisted by at least two stable, standard Brånemark implants in the anterior maxilla, or even better, by four standard implants (Fig. 10-10).

image

FIGURE 10-10. Two 35-mm long Zygoma implants, along with conventional Brånemark implants, were used in the anterior maxilla to support this fixed, cross-arch stabilized prosthesis.

(Courtesy Nobel Biocare, Yorba Linda, Calif.)

Bending moment forces are known to be the most unfavorable type, because they have the potential to jeopardize the long-term stability of an implant-supported restoration. To reduce bending moments, the distribution of forces should be optimized by:

• Cross-arch stabilization
• Reduced buccal lever arms
• Reduced cantilevers (mesial/distal and anterior/posterior)
• Balanced occlusion
• Reduced cuspal inclination

Zygoma implants are available in the TiUnite line and with a machined titanium surface. The surgeon must have experience in maxillofacial surgical techniques to perform the implantation procedure. (A d/>

Related posts:

  1. Suggested Readings
  2. Postoperative Instructions for the Patient
  3. 19: Crte Mince, Mini-Implant, Transitional, Temporary Anchorage Devices, and other Implant Surgical and Prosthodontic Procedures
  4. 16: Intramucosal Insert Surgery and Prosthodontics
  5. 3: Evaluation and Selection of the Implant Patient
  6. 6: Preparations for Implant Surgery

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Jan 5, 2015 | Posted by in Implantology | Comments Off on 10: Root Form Implant Surgery: Proprietary I

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