Читать книгу Peri-Implant Therapy for the Dental Hygienist - Susan S. Wingrove - Страница 19

Since there are multiple types of dental implant systems, hygienists need to be aware of the implant design, the patient presents with, in order to ensure safe and effective implant maintenance. The three main implant design types are transosteal, subperiosteal, and endosteal (endosseous) implants. They are classified according to their shape and how they interface with the bone.

Subperiosteal implants (Figure 1.11) are custom‐casted framework of surgical grade metal or alloy that lies on top of the jawbone. They are surgically placed onto the ridge of an edentulous patient, similar to how a saddle is placed on a horse, and underneath the gum membrane.

Figure 1.10 SEM ceramic (zirconia) implant surface.

Courtesy of PDT, Inc.

This was a treatment option for patients when there was not enough bone to place an endosteal implant. Most of the implant structure, as illustrated in Figure 1.11, is covered with the original ridge tissue, so only the posts and bar are exposed above the gingiva. Subperiosteal implants come in different designs: unilateral, bilateral, and circumferential posterior only. A custom‐designed superstructure denture or partial attaches to the posts for retention of this prosthesis. These implants were somewhat successful, but infection was common and it caused damage when they needed to be removed. Hygienists must be aware of this form of implants because they may encounter a patient with this form of implant design. Radiographs are going to be necessary to monitor this type of implants and it may be necessary to refer to a specialist if infection or pathology is observed.

A transosteal or staple implant (Figure 1.12) is an orthopedic device that is inserted through the inferior border of the mandible and is designed to function for an edentulous atrophic mandible. A titanium plate with five to seven parallel posts or dowels, two of which protrude through the mandible, function as abutments to attach a custom‐designed overdenture. The discovery by Brånemark of osseointegration made rigidly designed fixed implant restorations possible to provide firm anchorage. The original design allowed for stress‐directing attachments connected to transosteal pins to provide the stability for a removable overdenture. The implants for this procedure are costly and difficult to produce, so this procedure is not usually recommended. However, hygienists need to be aware of this design and monitor with radiographs. A referral to a specialist may be necessary if infection or pathology is observed.

Endosteal (within the bone) implants are generally made of titanium alloy and are designed to replace the root of one or more teeth. They are classified as blade‐ or root‐form, cylindrical/press‐fit or screw‐threaded, and come in many different sizes, lengths, and shapes. The blade‐form endosteal implant (Figure 1.13) is wide, flat metal plate or blade in cross section available in different heights and lengths, some with tapered sides. They may replace one to multiple teeth with a single blade and were used for narrow bones in maxillary or mandible, which had sufficient height to accommodate the implant placed. The blade‐shaped implants (see Figure 1.13) were surgically placed into the bone, then posts were attached to the blade, and an individual crown or bridgework affixed on the posts after a healing period.

Figure 1.11 Subperiosteal implant. Reprinted from Taylor and Laney (23), with permission from the author.

Figure 1.12 Transosteal implant.

Reprinted from Taylor and Laney (23), with permission from the author.

The root‐form implants (Figure 1.14) mimic the shape of natural root, threaded, smooth, or rough surface, with or without coating. They are stepped, parallel, or tapered, with or without grooves or vents and designed to join with multiple components to retain prosthesis. They can replace one to multiple teeth, are placed directly into the bone, and can be used in maxillary or mandibular arches. The bone must be of sufficient height, width, and length to accommodate the implant(s) placed. These implants are referred to as cylinder or press‐fit implants; screw‐retained implants also referred to as threaded implants or a combination of the two.

They are available in different widths, varying from 3.2 to 7 mm, and are available in different lengths, varying from 10 to 18 mm. The width and length are decided by the dentist, depending on the width and the height of the bone, the type of bone, and the number of teeth to be replaced. An implant‐supported abutment, often called a post, attaches to the surgically placed implant. Alternatively, one‐piece root‐form implants are also available that do not require placement of separate abutments. The two‐stage root‐form implants are placed in the bone, an abutment is attached to the implant, and the prosthesis is then placed. The final restoration or prosthesis is fabricated into a crown, bridge, or overdenture.

Figure 1.13 Blade‐form implants.

Courtesy of Dr. Frank Wingrove.

Figure 1.14 Endosteal root‐form implants.

Reprinted from Taylor and Laney (23), with permission from the author.

Looking to the future, we may see more endosteal implants made from ceramic (zirconia) or a combination of titanium and zirconia. Studies are being conducted due to its biocompatibility, tooth‐like color, mechanical properties, and low plaque affinity. It has the potential to become the alternative to titanium as the alloy of choice. More long‐term studies are being conducted on different rough surfaces with one‐piece ceramic (zirconia) dental implants, which to date, have an average of 95% success rate after 5 years (13). More specialized types of endosteal implants, to be aware of, are mini dental implants (MDIs) and zygoma implants.

Figure 1.15 Mini dental implants.

Courtesy of Glidewell.

MDIs (Figure 1.15) were introduced in the 1980s and accepted by the FDA as long‐term implant devices by 1999. They are very narrow (1.8–2.9 mm), some as thin as toothpicks, and can be temporary anchoring devices (TAD) or permanent MDIs used to stabilize a lower overdenture. They are solid, not hollow like traditional implants, and are made in one piece that includes the abutment. In most cases, mini implants are used in the lower jaw to stabilize a lower denture. They can also be used for temporary implants, replacement of smaller diameter teeth such as lower incisors, or in cases where a traditional implant is too large in diameter. They are generally placed as a single‐stage surgical process and are often loaded immediately.