Suggested Intra-oral Scan Image Acceptance Standards

Suggested Intra-oral Scan Image Acceptance Standards

Requirements for prep For Oral Scan

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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.

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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.

digital scan MS dental arts

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.

digital scan ms dental arts
digital scan ms dental arts

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.

digital scan ms dental arts

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.

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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.

Margin 

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.

Contact 

Ensure that the scan registers a clear and complete interproximal contact area.

Occlusion 

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.

Missing data 

Scan should be complete or a rescan will be necessary.

Distortion 

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.

 

Major mistakes made when taking dental impressions and how to avoid them

3D DENTAL SCANNER
3D DENTAL SCANNER

A top-notch dental imprint is essential because without one, the dental lab cannot create precise, well-fitting restorations. Potential dental impression mistakes should be found before sending the impression to the lab. Otherwise, if the impression is turned down, work can be delayed.

If the project moves forward, there is a higher chance that you will need to spend valuable chairside time correcting it or that it will need to be completely redone.

The most typical dental impression mistakes are as follows:

  1. Poor choice of tray.
  2. Unsatisfactory Impression Material blending
  3. Surface pollution.
  4. Margin detail is poor.
  5. Internal turbulence
  6. minuscule tears
  7. Making the Wrong First Impression.
  8. Making a hasty impression.
  9. Failure to Maintain Patient Stillness.
  1. Poor choice of tray.

The chosen tray must accurately record the required data without distortion. All of the teeth should be covered by it, but it shouldn’t touch the soft tissues. After making an impression, the tray shouldn’t be visible.

Full arch trays come in a variety of sizes. Trays’ arch shapes vary depending on the manufacturer, with some being more square and others being more rounded. Make sure the tray you choose is long enough to encompass the entire arch and wide enough to accommodate the tray comfortably. Metal trays can be altered and their posterior parts can be widened, but altering the anterior part of metal trays is more difficult. An alcohol torch can be used to heat plastic trays and modify them.

It’s best to keep a variety of dual-arch trays (triple trays) in stock because they come in different widths. As the patient bites into the empty tray to determine the size of a dual-arch tray, look at the other side of the arch. You’ll have a clear notion of how the occlusion ought to appear while capturing the impression thanks to this. Additionally, it enables the patient to feel what is required of them and will guarantee that they bite properly when taking the impression. Due to the fact that wax bites are frequently less stable during transportation, it is beneficial to offer a separate occlusal registration using rigid vinyl polysiloxane (VPS) material.

  1. Unsatisfactory Impression Material blending

When imprint material is properly blended, the colour is smooth and streak-free. With hand-mixed putty materials, streaking is more likely to occur, so hand-mixed ingredients should be promptly kneaded to ensure consistent colour. When using cartridge materials, bleed the cartridge before affixing the automix tip. This will guarantee that the catalyst and the base flow uniformly, preventing mixing problems. Since the tray material and wash are chemically formulated to cooperate, it is essential to use products from the same manufacturer. When the impression is poured up in the dental lab, using different materials could increase the chance that the wash material will separate from the tray VPS.

  1. Surface pollution.

An imprint material layer that is sticky and unset might result from surface contamination. It can be because adhesives, composites, or core build-up materials left a greasy film on the tooth preparation. Any of these could stop the material from properly setting. Retraction cables and solutions containing ferric sulphate or aluminium chloride can deliver sulphur to vulnerable regions, preventing the marginal VPS material’s setting reaction. The same effect can be achieved through glove contact, rolling the retraction cord in gloved fingers, or using a rubber dam. When putty is mixed by hand, latex can get into it.

After removing the rubber dam, properly dry the area and rinse it with water or mouthwash to prevent surface contamination. Make sure to thoroughly wash the preparation after applying hemostatic agents to get rid of any remaining debris and hemostatic agent. Additional hemostatic can be burnished into the gingival sulcus to stop further bleeding if gingival bleeding resumes. The preparation is air-dried and prepared for an impression once the bleeding has ceased. If the putty is mixed by hand, wash your hands while wearing gloves to get rid of any remaining surface powder and sulfides. If not, pick vinyl or powder-free gloves.

  1. Margin detail is poor.

One of the most important features of a dental impression is the margin. Without a precise marginal impression, issues like overhanging or open margins or a restoration that doesn’t fit properly are more possible. Inadequate retraction or areas where fluid has gathered restrict the impression material from flowing around the margin, which is the usual cause of voids at the margin.

The best method to deal with this issue is to use retraction cords with syringeable hemostatics. Utilizing a double retraction cord is one method. Another method involves preparing the gingival sulcus and inserting retraction pastes there. When achieving hemostasis, a diode laser can help widen the sulcus and enhance visibility of the prepared margin.

  1. Internal turbulence

Bubbles may appear in the imprint if moisture, such as blood, water, or saliva, becomes entrapped in the impression substance. These bubbles might impact the luting agent and increase the amount of space that needs to be filled. The interaction between the restoration and the tooth is weaker when the luting substance is thicker. Additionally, if the prosthetic material is too thin, there is a greater chance it may fail; this is crucial when utilising all-ceramic materials, in which case a minimum thickness is essential. Hemostasis is the key to resolving this issue.

  1. minuscule tears

When the wash material lacks sufficient tear strength, marginal tears may happen. Low viscosity material is more likely to tear in the sulcus and varies in strength according on the manufacturer. The wash material is thinner and more likely to tear when being removed when the sulcus is extremely deep. Additionally, if the impression is taken out before the wash material is set, there may be some minor ripping. If you need to rebuild an impression due to minimal tearing, make sure any leftovers are taken out of the sulcus and think about pulling back more tissue to make the sulcus wider. Additionally, using a more viscous wash substance could enhance the impression’s quality.

  1. Making the Wrong First Impression.

For the impression to be precise and predictable, the best impression material must be used. For your patient’s comfort, a sort setting time is typically preferred; nonetheless, it is crucial to understand the working time for the substance you have selected. The working time must be used to insert the impression. If it is already set up, it might not seat all the way and won’t record the necessary information. Selecting a material that is more hydrophilic will make it easier for it to adhere to the prepared tooth, particularly sub-gingivally and where fluid may be present.

  1. Making a hasty impression.

It is essential to take your time and double-check the facts (for example, packing the retraction cord). Make that the cable is properly packed and that the tissue has been sufficiently retracted. Rushing could prevent the chord from having enough time to sit, which would just serve to traumatise the area surrounding the sulcus.

  1. Failure to Maintain Patient Stillness.

If the patient moves or starts to gag, dental impressions may get distorted. Engaging in conversation with the patient can assist keep them motionless by keeping them busy and preventing them from noticing any pain. Remind the patient to breathe in and out through their nostrils frequently. They can ease their discomfort by wriggling their toes.

If you have any questions, our knowledgeable technical team can provide guidance on obtaining more consistent and high-quality impressions.

To arrange a meeting with our technical team, click here.