Intraoral scanning v conventional impressions – patient related outcomes

dental impression

The move towards digital workflows in dentistry is increasing. While computer-aided design and computer-aided manufacture (CAD-CAM) have been around for more than 20 years improvements in the accuracy of intra-oral scanning and new technologies are impacting on patients and clinicians. Potential benefits for intra-oral scanning include shortened clinical times, improved patient satisfaction and reduction in adverse effects.

The aim of this review was to compare patient-related outcomes of intraoral scanning and conventional impression methods.


A protocol was registered with the PROSPERO database. Searches were conducted in the Medline/PubMed, Cochrane Library, Latin American and Caribbean Health Sciences Literature, Brazilian Library of Dentistry, Scopus, Web of Science, abstracts of the annual meetings of the International Association for Dental Research and its regional divisions (2000-2019), System for Information on Grey Literature in Europe, ProQuest and Capes databases and the Current Controlled Trials, International Clinical Trials Registry Platform,, Brazilian Register of Clinical Trials, and EU Clinical Trials Registers. Clinical trials comparing digital scanning and conventional impression procedure in the restorative and prosthetic treatments of adults were considered.

Two reviewers independently selected studies with three reviewers extracting data. Two reviewers independently assessed study quality using the Cochrane risk of bias tool (RoB2) for randomised controlled trials (RCTs)  and the Newcastle- Ottawa scale  (NOS) was used for nonrandomized clinical trials (NRCTs). Primary outcomes were patient preference and satisfaction, with discomfort, nausea, unpleasant taste, breathing difficulty, pain, and anxiety as secondary outcomes. Mean difference (MD) and 95% confidence interval (CI) were calculated for each outcome and random-effects meta-analyses conducted.  The Grading of Recommendations: Assessment, Development, and Evaluation (GRADE) approach was used to assess the certainty of the evidence.


  • 13 studies (10 cross-over studies, 2 split mouth, 1 parallel) were included.
  • 3 studies were conducted in Switzerland, 2 the Netherlands and Italy and one each in Belgium, China, Denmark, Sweden, Thailand and Turkey.
  • 7 studies evaluated implant-supported single crowns, 4 tooth-supported single crowns, 1 tooth-supported 3- unit fixed partial dentures, and 1 tooth-supported single crowns and fixed partial dentures of up to 6 units.
  • 9 of the 13 studies were RCTs and were rated as being at unclear risk of bias. The 4 NRCTs were assessed as being at low risk of bias.
  • 11 studies contributed to the meta-analyses.
  • Meta-analyses showed a superiority for digital scanning over conventional impressions for, patient preference, less discomfort, absence of nausea, unpleasant taste and breathing difficulty but not for anxiety or pain (see table below).
Outcome No. of studies Mean difference (95%CI)
Patient preference 9 15.02 (8.33 to 21.73)
Discomfort 2 -44.92 (-59.66 to -30.17)
Nausea – absence 4 32.87 (24.15 to 41.58)
Nausea- occurrence 2 -25.42 (-85.08 to 35.24)
Absence of unpleasant taste 4 23.93 (9.95 to 37.91)
Absence of breathing difficulty 2 34.00 (25.80 to 42.20)
Anxiety 2 13.90 (-0.93 to 28.73)
Pain 2 13.21 (-12.66 to 39.09)
  • The certainty of evidence was graded as moderate to low.


The authors concluded: –

Intraoral scanning is a suitable alternative to conventional impression procedures, promoting less discomfort for patients sensitive to taste, nausea, and breathing difficulty than when conventional impression making techniques are used.


The authors registered their protocol on the PROSPERO and searched a wide range of databases. They included 13 studies of which 9 were RCTs, none of the RCTs were at low risk of bias although blinding the operator and patients to the interventions is impractical although most of the RCTS lacked details about the randomisation method and allocation concealment.  The meta-analyses demonstrated a patient preference for intraoral scanning over conventional impressions with a mead difference of 15.02 (95%CI; 8.33 to 21.73) although the prediction interval is wide (-6.61 to 36.65). Meta-analyses were also conducted for a number of secondary outcomes suggesting superiority for digital impressions, However, these analyses included only a small number of studies so should be interpreted cautiously. As highlighted by the authors there was a lack of standardisation in recording of outcomes across the studies making overall comparisons difficult, so the use of a common outcomes set would be helpful for future comparisons.


Primary Paper

de Paris Matos T, Wambier LM, Favoreto MW, Rezende CEE, Reis A, Loguercio AD, Gonzaga CC. Patient-related outcomes of conventional impression making versus intraoral scanning for prosthetic rehabilitation: A systematic review and meta-analysis. J Prosthet Dent. 2023 Jul;130(1):19-27. doi: 10.1016/j.prosdent.2021.08.022. Epub 2021 Oct 28. PMID: 34756424.

Review protocol on PROSPERO

Other references

Dental Elf – 8th Jan 2021

Digital or conventional workflow for single implant crown impressions?

Dental Elf – 16th Feb 2018

Digital impressions- faster or slower than conventional procedures?

Picture Credits

Photo by Quang Tri NGUYEN on Unsplash



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