Table 2 Summary of studies evaluated trueness of IOSs by CMM with CI. CI, conventional impression; DI, digital impression; IOS, intraoral scanner; RMS, root mean square √((x² + y² + z²)/3); RSS, root sum square ( √(x² + y² + z²))

Ajioka et al. 2016 [14]

COS

UPMC 550-CARAT (CMM)

Open tray, non-splinted

IIDD & IIAD

1 experienced

Partially edentulous mandible with 2 implants (#35,36)

IIDD between implant #35 and #36

Calculation: RSS

DI: 64.5 ± 19.0 μm

CI: 22.5 ± 12.4 μm

5-mm height abutment

COS: 0.42 ± 0.18°

CI: 0.14 ± 0.01°

7-mm height abutment

COS: 0.20 ± 0.20°

CI: 0.15 ± 0.12°

Longer abutment reduces angle error in DI.

Chia et al. 2017 [31]

TRIOS

Global Silver Performance 7.10.7 (CMM)

Open tray

Linear and angle deviation

Not mentioned

Partially edentulous mandible with 2 implants (#44, #46) 0, 10, and 20° of buccolingual inter-implant angulation

Linear error in distance from reference point

Calculation: RSS

DI:

0°: 31 ± 14.2 μm

10°: 45 ± 3.4 μm

20°: 42 ± 9.9 μm

CI:

0°: 18 ± 8.4 μm

10°: 33 ± 15.8 μm

20°: 36 ± 6.5 μm

Angule error towards x-axis in each inter-implant angle; DI: 0°: 0.041 ± 0.032°

10°: 0.55 ± 0.27°

20°: 0.80 ± 0.27°

CI: 0°: 0.07 ± 0.06°

10°: 0.28 ± 0.30°

20°: 0.55 ± 0.06°

Angule error towards y-axis in each inter-implant angle; DI: 0°: 0.10 ± 0.07°

10°: 0.11 ± 0.06°

20°: 0.08 ± 0.06°

CI: 0°: 0.20 ± 0.13°

10°: 0.11 ± 0.08°

20°: 0.17 ± 0.13°

Bigger inter-implant angles tend to cause linear and angle error strain.

Alikhasi et al. 2018 [19]

TRIOS

DEA Mistral (CMM)

ATOS Core 80 (CMM)

Open tray, non-splinted closed tray

IIDD & IIAD

1 experienced

Fully edentulous maxilla with 4 implants (#13, #15, #23, #25)

#15, #25: distally 45° tilted

Calculation: RSS DI + internal connection; straight implant:188 ± 134 μm,/tilted implant:162 ± 103 μm

DI+external connection; straight implant:195 ± 158 μm/tilted implant:165 ± 134 μm

CI (open tray) + internal connection; straight implant: 280 ± 142 μm/tilted implant:389 ± 228 μm

CI (open tray) + external connection; straight implant:711 ± 286 μm/tilted implant:364 ± 231 μm

CI (closed tray)+internal connection; straight implant:885 ± 389 μm/tilted implant:721 ± 384 μm

CI (closed tray)+external connection; straight implant: 797 ± 351 μm/tilted implant:442 ± 226 μm

Angle errors in each impression method and implant connection type:

DI+internal connection; straight implant: 0.59 ± 0.72°/tilted implant:0.36 ± 0.37°

DI + external connection; straight implant: 0.59 ± 0.72°/tilted implant:0.37 ± 0.38°

CI (open tray) +internal connection; straight implant: 2.29 ± 1.33°/tilted implant: 4.77 ± 2.20°

CI (open tray)+external connection; straight implant: 1.00 ± 0.45°/tilted implant:1.10 ± 0.39°

CI (closed tray)+internal connection; straight implant: 4.10 ± 2.73°/tilted implant: 9.37 ± 6.90°

CI (closed tray)+external connection; straight implant: 4.85 ± 1.46°/tilted implant:2.06 ± 0.97°

Trueness of impression: DI > CI with open-tray > CI with closed tray

Connection type and implant angulation did not affect the trueness in DI.

Menini et al. 2018 [39]

TDS

Crista Apex S (CMM)

Open tray, non-splinted

Open tray, splinted

Closed tray

IIDD

3 experienced

Fully edentulous jaw with 4 implants

DI: 15 ± 11 to 19 ± 15 μm

CI: 22 ± 23 to 63 ± 59 μm

DI showed better trueness than CI.

Tan et al. 2019 [10]

TDS

TRIOS

Ceramill Map400 (lab scanner) inEos X5 (lab scanner)

D900 (lab scanner)

Open tray, Splinted

Linear and angle deviation

Not mentioned

Fully edentulous maxilla with 6 implants (#12, #14, #16, #22, #24, #26) 20 mm inter-implant distance

Calculation: RSS

TDS:

− 267 ± 85.4 to − 709 ± 66.8 μm

TRIOS:

13.3 ± 47.4 to 166.8 ± 78.0 μm

Ceramill Map400: − 4.8 ± 11.6 to 35.8 ± 31.9 μm

inEos X5:

11.1 ± 9.3 to 45.4 ± 20.2 μm

D900:

2.7 ± 32.6 to − 59.8 ± 40.0 μm

Angle deviation towards x-axis;

TDS:

− 0.06 ± 0.41 to − 2.25 ± 1.10°

TRIOS:

0.02 ± 0.21 to − 2.19 ± 0.45°

Ceramill Map400: − .04 ± 0.31 to − 2.35 ± 0.17°

inEos X5:

0.05 ± 0.04 to − 1.62 ± 0.54°

D900:

− .15 ± 0.18 to − 1.94 ± 0.67°

Angle deviation towards y-axis;

TDS:

− .14 ± 0.25 to 0.47 ± 0.32°

TRIOS: 0.11 ± 0.20 to − .93 ± 0.29°

Ceramill Map400: 0.03 ± 0.27 to − .74 ± 0.18°

inEos X5:

− .00 ± 0.16 to − .54 ± 0.16°

D900: 0.22 ± 0.35 to 0.47 ± 0.36°

Shorter inter-implant distance reduce linear error in DI. TDS showed the poorest trueness for all linear errors in both models.

Fully edentulous maxilla with 8 implants (#11, #13, #15, #17, #21, #23, #25, #27)

13-mm inter-implant distance

Calculation: RSS

TDS:

− 151.1 ± 32.8 to − 602.5 ± 70.0 μm

TRIOS:

− 9.1 ± 28.9 to 69.8 ± 109.2 μm

Ceramill Map400: 9.8 ± 15.7 to 50.2 ± 20.9 μm

inEos X5:

14.6 ± 7.5 to 66.4 ± 5.9 μm

D900:

− 4.2 ± 26.3 to − 34.7 ± 28.8 μm

Angle error towards x-axis;

TDS:

0.02 ± 0.16 to − .69 ± 0.57°

TRIOS:

− .11 ± 0.30 to 0.53 ± 0.33°

Ceramill Map400: 0.07 ± 0.14 to 0.60 ± 0.14°

inEos X5:

− .03 ± 0.07 to − .35 ± 0.11°

D900:

0.04 ± 0.12 to − .31 ± 0.32°

Angle error towards y-axis;

TDS:

0.08 ± 0.15 to − 1.05 ± 0.30°

TRIOS:

0.15 ± 0.19 to − .81 ± 0.33°

Ceramill Map400:

0.28 ± 0.24 to − .84 ± 0.30°

inEos X5:

0.02 ± 0.05 to − .88 ± 0.38°

D900: 0.04 ± 0.11 to − .71 ± 0.24°

Gintaute et al. 2018 [29]

TDS

Crysta-Apex (CMM)

Open tray, non-splinted

IIDD & IIAD

Not mentioned

Fully edentulous mandible with 2 straight implants (#32, #42)

18.5 ± 19.8 μm

0.04 ± 0.05°

DI and CI are comparable but DI can be applied for fully edentulous jaw with multiple implant cases. Although some statistically significant differences in errors between the impression methods and models, they were within clinically acceptable range.

Fully edentulous mandible with 4 straight implants (#32, #34, #42, #44)

9.5 ± 16.0 μm

0.17 ± 0.14°

Fully edentulous mandible with 2 straight implants (#32, #42) and 2 distally angulated implants (#34, #44)

35.8 ± 24.2 μm

0.22 ± 0.19°

Fully edentulous mandible with 6 straight implants (#32, #34,#36, #42, #44, #46)

31.1 ± 27.1 μm

0.24 ± 0.22°