Suggested Intra-oral Scan Image Acceptance Standards
Requirements for prep For Oral Scan
The occlusal discount of the prepped enamel ought to comply with the product parameters of the cloth decided on for the restoration.
Anterior Preps, incisal edge ≥ 1.5mm minimal discount, facial & lingual surface ≥ 1.0mm minimal discount, margin > 0.8mm. A shoulder or chamfer prep is recommended.
Posterior Preps, occlusal fossa ≥ 1.5mm of minimal discount, occlusal cusp ≥2mm minimal discount, axial surfaces > 1.0 -1.5mm, margin > 0.8mm discount. A shoulder or chamfer prep is recommended.
Ideally, there should be no undercuts on the prepped tooth. If undercuts are present; they should be either blocked out or removed. For bridges; the preps need to be parallel, with the equal route of insertion among abutments. Convergent or divergent preps can prevent the bridge from seating and may be rejected at the design phase; or will require further adjusting at the seat appointment.
The surface of prep tooth should be smooth. Sharp corners and edges should be avoided as they can cause ill-fitting restorations or fracture issues.
Prep a clear shoulder or deep chamfer margin, unless monolithic zirconia is being used. Use of gingival retraction or laser is highly recommended.
The margin line of the prepped teeth need to be smooth. A zig zag, or difficult margin line can motive in shape problems including open or quick margins.
Ensure there are no undercuts on the tooth prep. Ideally, for a bridge; there should be no interference or draw issues caused by an adjacent tooth being convergent or impinging on the prepped tooth. When necessary; the adjacent tooth may have to be adjusted, or the path of insertion altered.
Tip: Keep the regions being scanned absolutely dry. Be certain to have more cotton rolls.
Clean up saliva and any debris in the scan area, in order to have a clear and accurate scan image.
For anterior scans; the contra-lateral teeth must be registered in the scan to provide a design reference. This is crucial to achieve symmetry with the adjacent teeth.
Clean up any blood or debris to ensure the margin is easy to be read by the scanner
Tip: When scanning the arch, make sure contacts are included in arch scan, not with the prep scan.
The prep and margin should be clear. Use of gingival retraction cord, double gingival retraction cord, or laser is highly recommended for a successful scan image. If cord is used; it should be removed just prior to the scan.
Ensure that the scan registers a clear and complete interproximal contact area.
Have the patient close into normal centric during the occlusal relationship scan phase.
Scan the opposing occlusal surface, buccal & lingual surfaces completely. Register appropriate gingival tissue. The scan area should be the same as the working side.
If a number of teeth are missing; scan multiple occlusal contacts or scan the full arch in order to register an accurate occlusal relationship.
Tip: Make sure the wand is being used properly. If cord is used; it should be removed just prior to the scan.
Scan should be complete or a rescan will be necessary.
Scan should show clear, clean contrast with no fuzziness, pitting or debris on models.
Tip: Select the settings option and make sure the restorative box is selected. This will show any areas that have not been scanned and will allow you to re-scan those missed areas.
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