Common Errors that Occur During Digital Impression Procedures Using In-office CAD/CAM CEREC AC Systems

The intraoral scanner was invented to rectify quality deficiencies associated with manual production of traditional, hand-produced dental impressions and dental restorations¹. Yet, a study by Kim et al. addresses common errors made with in-office CAD/CAM CEREC AC systems that affect the accuracy of dental restorations. Clinicians need to be aware that correct chairside procedures and operation of intraoral scanners are required to provide their dental lab optimal digital impression results.

Kim et al. investigated five categories of errors arising from digital impressions that were created from an in-office CAD/CAM CEREC AC system. The most frequent errors they found were non-linear powder application, inappropriate oral cavity scanner positioning, and insufficient scanned data. Powder application is needed with CEREC Bluecam and requires both experience and skill from the clinician to apply it evenly. The study found that “if more or less than the ideal amount of powder is applied, the precision of the digital impression is compromised, and it is therefore difficult to expect an accurate reconstruction”¹. In addition, uneven distribution of powder application may be an issue when salivary contamination and other obstacles such as the tongue and patient discomfort are unavoidable factors¹.

The second most common error found was inappropriate scanner positioning which results in the partial loss of the digital impression. The manufacturer states the scanner must be placed so that the teeth are present in the middle of the screen, at 3mm to 4mm distance and at a 10 degree angle with the direction of the ray parallel to the long axis of the teeth¹. If the angle is too sharp, the ray will not reflect certain areas of the cavity walls and the clinician will lose part of the impression image.

The third most common error found was insufficient scanned data which is similar to the frequency of inappropriate scanner positioning errors. According to Kim et al., adequate information regarding both the abutment and adjacent teeth is required to obtain a precise and ideal design¹. When insufficient data is an issue in both of these regions, an incomplete reconstruction of the patient’s teeth will result in an ill-fitted dental restoration.

Even though these errors common, it is worth noting the practitioner can immediately evaluate and eliminate preparation errors by modifying the images via the “repair” menu in CEREC system software. However, the clinician needs to be aware of these common errors so he or she may correct them immediately before sending the digital impression to their dental lab. Since dental restorations are manufactured based on the captured digital impression, dental labs rely on the clinician to send an accurate impression in order to fabricate a well-fitted prosthetic for their patients.

  About the organization

Since 1991, Iverson Dental laboratories has provided their clinicians with higher quality dental lab products and exceptional dental lab solutions to guarantee their clinicians’ patients are fully content with their tailored restoration. Iverson dental labs strives to be a great dental resource for dentists by providing training on digital dentistry and new dental implant methods at their high-tech operatory and coaching facility. Iverson dental labs strongly believes in using high quality certified materials and authentic manufacturing elements to fabricate their dental restorations. Iverson also has a knowledgeable team of accredited dental technicians simply because clinical evidence has shown ample skills of the technician are critical for the prolonged success of a dental restoration.

Resources:

1.     Jae-Hong, K., Ki-Baek, K., Sa-Hak, K., Woong-Chul, K., Hae-Young, K., & Ji-Hwan, K. (2015). Quantitative evaluation of common errors in digital impression obtained by using an LED blue light in-office CAD/CAM system. Quintessence International, 1-7. Retrieved May 5, 2016, from http://www.ncbi.nlm.nih.gov/pubmed/25699295