Free excerpt - SAC Classification in Implant Dentistry

A. DAWSON, W. MARTIN, W. D. POLIDO

3.7.1.3 VOLUME AND CHARACTERISTICS OF THE EDENTULOUS RIDGE

Subject to the extent of dimensional changes following loss of the natural tooth or teeth, the volume and contours of the edentulous ridge may represent a greater or lesser prostho- dontic challenge for creation of an ideal restoration anatomy (Figure 70). The assessment focuses on whether prosthetic replacement of soft tissue volume or other adjunctive ther- apy such as a bone grafting is needed. If there is no need, the situation is deemed low risk. If the volume and characteris- tics are inadequate and require adjunctive therapy, it is re- garded as having high risk. 3.7.2 Occlusal factors The biophysical response to occlusal force is different for implants and teeth, as teeth are connected to the surround- ing alveolar bone via the periodontal ligament. Dental im- plants, by contrast, are in contact with the bone directly by osseointegration. As a consequence, natural teeth are sub- ject to a mean axial displacement of approximately 25– 100 µm, while dental implants get displaced by only 3–5 µm (Kim et al, 2005; Schulte, 1995). This affects capacity for movement and sensory feedback of implants and has been shown to impact risk of—predominantly—hardware com- plications (Salvi & Brägger, 2009). To adjust and reevaluate the occlusion with implant-supported reconstructions is therefore of fundamental importance, as the absence of the periodontal ligament significantly detracts from their load-sharing ability, occlusal force adaptation, and mecha- noperception (Kim et al, 2005). Occlusal considerations are addressed by the ITI in its Academy Learning Module “Occlusion on fixed implant prostheses” (Stilwell, 2015).

Fig 70. An atrophic maxilla opposing natural dentition, requiring augmen- tation procedures for an implant-supported restoration.

ITI Learning Module Occlusion on Fixed Implant Prostheses by Charlotte Stilwell.

The characteristics of the patient’s occlusal scheme and the extent of involvement of implant prostheses in the scheme affect the degree of difficulty of implant restoration. The presence of occlusal parafunction with greater and unpre- dictable occlusal forces will further elevate risk. The modi- fying considerations of three occlusal factors are found in Table 10.

Table 10 Occlusal factors.

Occlusal factors

Risk or degree of difficulty

Low

Medium

High

Site factors

Occlusal scheme

User-defined occlusal scheme achievable

User-defined occlusal scheme not achievable Implant restoration is involved with guidance

Involvement in occlusion

Minimal or no involvement

Occlusal parafunction

Absent

Present

The SAC Classification in Implant Dentistry

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