Influence of abutment tooth geometry on the accuracy of conventional and digital methods of obtaining dental impressions

Influence of Tooth Preparation Design and Scan Angulations on the Accuracy of Two Intraoral Digital Scanners: An in Vitro Study Based on 3‐Dimensional Comparisons

“…The complex geometry together with the presence of the adjacent teeth significantly reduced the accuracy of the TRU compared to the TRI. This likely explains the contradictory finding of this study as compared to the one done by Mejīa et al 31 , where they stated that the geometry (taper) did not affect the scanning accuracy.…”

Marginal and Internal Fit of CAD/CAM Crowns Fabricated Over Reverse Tapered Preparations

“…Four studies conducted before cementation found that angulation did not influence the marginal fit, whereas Iwai et al and Beuer et al (cemented restorations), reported that tooth preparations with a TOC angle below 6° had statistically significant marginal discrepancies. This can be explained by the possible distortion of the 3D model of abutments with a TOC angle less than 6°, as it was demonstrated that desktop scanners could not accurately reproduce low TOC angles . In contrast, intraoral scanners can record low TOC angles, although to date, only one study evaluated and showed that the fit of crowns with a low TOC angle (4°) fabricated from direct digital impressions were not affected by the preparation convergence angle.…”

“…This can be explained by the possible distortion of the 3D model of abutments with a TOC angle less than 6°, as it was demonstrated that desktop scanners could not accurately reproduce low TOC angles. 6,7 In contrast, intraoral scanners can record low TOC angles, although to date, only one study 26 evaluated and showed that the fit of crowns with a low TOC angle (4°) fabricated from direct digital impressions were not affected by the preparation convergence angle. More laboratory and clinical studies are needed in this regard to draw robust conclusions.…”

“…As a general principle, undercuts (negative angles) should be avoided during tooth preparation or blocked out to a great extent before making a conventional impression so as to prevent distortion of the impression when it is removed from the mouth; however, negative angles neither restrict the making of intraoral digital impressions nor are detrimental to their accuracy because multiple scans from many different directions are required to digitize the abutment tooth. Additionally, if an undercut is recorded at the first stage of a fully digital workflow, the clinician can either remove more dental structure (overprepare) to obtain a tapered preparation or, whenever possible, take advantage of the algorithms from the CAD software to overcome them (i.e., digitally blocking out undercuts or changing the path of insertion of the crown).…”

Workflow description of additively manufactured clear silicone indexes for injected provisional restorations: A novel technique

“…5,6 Different studies have analyzed the relationship between technology employed by an IOS system and the accuracy of its acquisition procedure. [7][8][9][10][11][12][13][14][15][16][17] Factors that could impact the accuracy of a digital impression performed by IOS 18 have also been studied, namely handling and learning curve, 19,20 calibration, 21 scanning protocol, [22][23][24] AMbient light scanning conditions, 25 surface characteristics, [26][27][28][29] mobile tissue, 30 reflective restorations, and/or presence of saliva. 19,[31][32][33] Digital impression techniques are a clinically acceptable alternative to conventional impression methods in fabrication of tooth and implant-supported crowns and short fixed dental prostheses (FDPs).…”