The accuracy of impressions is a crucial factor in the fabrication of implant-supported prostheses, as it directly influences the fit, function, and longevity of the final restoration. A precise impression ensures an accurate transfer of intraoral conditions to the laboratory, thereby minimizing errors in prosthetic fabrication and enhancing clinical outcomes (1). Traditionally, conventional impression techniques using elastomeric materials such as polyvinyl siloxane (PVS) and polyether have been widely used. However, these techniques are susceptible to dimensional changes, material deformation, and operator-dependent variability, which may compromise the accuracy of the final prosthesis (2,3).

With advancements in digital dentistry, intraoral scanning has emerged as an alternative to conventional impression techniques. Digital impressions eliminate the need for impression materials, trays, and laboratory model fabrication, thereby reducing potential sources of error (4). Studies have demonstrated that digital impressions can achieve high precision and reproducibility, especially in cases involving multiple implants (5). Additionally, digital workflows provide enhanced patient comfort, reduced chairside time, and immediate visualization of the scan, allowing for real-time adjustments if necessary (6).

Despite these advantages, concerns remain regarding the accuracy of digital impressions in complex cases, particularly in full-arch implant prostheses, where the accuracy of intraoral scanners may be influenced by factors such as scanning strategy, angulation, and the number of implants (7). Moreover, differences in software algorithms, scanner resolution, and operator expertise may impact the reliability of digital scans when compared to conventional methods (8).

This study aims to evaluate and compare the accuracy of digital and conventional impressions in implant-supported prostheses by analyzing marginal discrepancy, internal fit, and occlusal accuracy. The findings of this research may contribute to the growing body of evidence supporting the clinical applicability of digital impressions in implant prosthodontics.

Study Design and Sample Selection

This in vitro study was conducted to compare the accuracy of digital and conventional impressions for implant-supported prostheses. A total of 40 patients requiring single implant-supported crowns in the posterior region were selected and randomly assigned into two equal groups (n = 20 each). Group A underwent digital impressions using an intraoral scanner, while Group B received conventional impressions with polyvinyl siloxane (PVS) material. All procedures were performed by a single experienced clinician to minimize operator variability.

Impression Techniques

Digital Impression (Group A)

For digital impressions, an intraoral scanner (e.g., Medit i700, Trios 4, or CEREC Primescan) was used following the manufacturer’s scanning protocol. The scanning process included a systematic approach to ensure complete arch capture. The final digital files were exported in STL format and analyzed using a specialized software for accuracy assessment.

Conventional Impression (Group B)

For conventional impressions, polyvinyl siloxane (PVS) impression material (light and heavy body) was used with a dual-phase putty-wash technique. Impressions were made using a rigid custom tray, ensuring proper border extension. After setting, impressions were poured with Type IV dental stone to fabricate master casts.

Accuracy Assessment

The accuracy of impressions was evaluated based on three parameters:

1. Marginal Discrepancy – Measured using a coordinate measuring machine (CMM) to assess the gap at the implant-prosthesis interface.
2. Internal Fit – Assessed using a micro-CT scan, measuring the internal adaptation of the prosthesis to the abutment.
3. Occlusal Accuracy – Evaluated by 3D superimposition analysis of digital scans with the definitive prosthesis to determine deviations in occlusion.

Statistical Analysis

Data were analyzed using SPSS software (version 26.0). Descriptive statistics, including mean and standard deviation, were calculated for all accuracy parameters. An independent t-test was performed to compare differences between the two groups, with statistical significance set at p < 0.05.

Marginal Discrepancy

The marginal discrepancy was significantly lower in the digital impression group compared to the conventional impression group. The mean marginal discrepancy was 35.2 ± 4.6 µm for digital impressions and 48.5 ± 5.2 µm for conventional impressions, with a statistically significant difference (p = 0.003) (Table 1).

Internal Fit Accuracy

The internal fit accuracy was also superior in the digital impression group, with a mean internal gap of 42.3 ± 3.8 µm, whereas the conventional impression group exhibited a higher internal gap of 55.7 ± 4.1 µm. The difference was statistically significant (p = 0.001) (Table 2).

Occlusal Accuracy

The occlusal accuracy assessment showed that the digital impression group had a mean occlusal discrepancy of 23.4 ± 2.5 µm, which was significantly lower than the 37.6 ± 3.2 µm observed in the conventional impression group (p = 0.002) (Table 3).

Table 1: Marginal Discrepancy

Table 2: Internal Fit Accuracy

Table 3: Occlusal Accuracy

The accuracy of implant impressions is a crucial factor in ensuring the proper fit and longevity of implant-supported prostheses. This study compared digital and conventional impression techniques and found that digital impressions provided superior accuracy in terms of marginal adaptation, internal fit, and occlusal precision. These findings align with previous research, which has shown that digital impression systems can reduce errors associated with material deformation and operator handling, resulting in improved prosthetic outcomes (1,2).

Marginal discrepancy is an important factor influencing the success of implant prostheses, as excessive gaps can lead to bacterial colonization, peri-implantitis, and mechanical complications. In this study, the mean marginal discrepancy was significantly lower in the digital impression group compared to the conventional impression group (35.2 ± 4.6 µm vs. 48.5 ± 5.2 µm, p = 0.003). Similar results have been reported in previous studies, where digital impression techniques demonstrated better marginal adaptation due to the elimination of impression material shrinkage and expansion (3,4). However, some studies have indicated that conventional impressions may still be preferable in cases requiring multiple implant restorations, as intraoral scanners may struggle with full-arch accuracy (5).

Internal fit is another critical parameter affecting prosthesis longevity. Poor internal adaptation can lead to stress concentration and increased mechanical failures. In this study, digital impressions resulted in a significantly lower internal gap compared to conventional impressions (42.3 ± 3.8 µm vs. 55.7 ± 4.1 µm, p = 0.001). This is consistent with prior research demonstrating that digital impressions provide more precise internal adaptation, particularly in single-unit restorations (6,7). Additionally, the absence of impression material distortions in digital workflows contributes to more consistent fit accuracy (8).

Occlusal accuracy is essential for achieving proper load distribution and preventing occlusal discrepancies that may lead to implant overload and prosthetic complications. Our findings revealed that occlusal accuracy was significantly better in the digital impression group (23.4 ± 2.5 µm vs. 37.6 ± 3.2 µm, p = 0.002). Previous studies have shown that digital scanning provides highly accurate occlusal data, which reduces the need for occlusal adjustments during prosthesis delivery (9,10). However, the accuracy of digital impressions can be affected by factors such as scanner resolution, scanning protocol, and the number of implants involved (11).

Although digital impressions have demonstrated superior accuracy, some limitations should be considered. Intraoral scanning requires operator expertise, and scanning errors can occur due to improper angulation or incomplete surface capture. Additionally, in cases involving full-arch implant restorations, conventional impressions may still provide better trueness and precision (12). Cost and learning curve are also important factors, as digital impression systems require significant initial investment and training (13).

Despite these limitations, the advantages of digital impressions, including enhanced accuracy, patient comfort, and reduced chairside time, make them a promising alternative to conventional methods. With continuous advancements in scanning technology, the reliability and efficiency of digital workflows are expected to improve further (14,15).

This study compared the accuracy of digital and conventional impressions in implant-supported prostheses and found that digital impressions offer superior marginal adaptation, internal fit, and occlusal precision. The results demonstrated significantly lower marginal discrepancy, improved internal fit, and enhanced occlusal accuracy in the digital impression group compared to the conventional impression group.

The advantages of digital impressions, including greater accuracy, reduced procedural errors, enhanced patient comfort, and streamlined workflows, make them a reliable alternative to conventional methods. However, limitations such as the need for operator expertise, potential scanning errors, and cost considerations should be taken into account.

As digital dentistry continues to advance, further research is needed to evaluate its effectiveness in complex cases, including full-arch implant rehabilitations. Overall, digital impressions present a promising approach for improving prosthetic accuracy and clinical outcomes in implant dentistry.

1. Papaspyridakos P, Chen CJ, Chuang SK, Weber HP, Gallucci GO. Accuracy of implant impressions for partially and completely edentulous patients: A systematic review. Int J Oral Maxillofac Implants. 2014;29(4):836-45.
2. Kim JH, Park JM, Kim M, Heo SJ, Shin IH, Kim M. Comparison of the accuracy of digital and conventional impressions in maxillary edentulous arches using an intraoral scanner. J Prosthet Dent. 2019;121(5):880-6.
3. Alikhasi M, Siadat H, Nasirpour A, Hasanzade M. Three-dimensional accuracy of digital and conventional impression techniques and their effect on the fit of CAD/CAM-fabricated fixed dental prostheses. J Prosthet Dent. 2017;118(4):536-42.
4. Mangano F, Gandolfi A, Luongo G, Logozzo S. Intraoral scanners in dentistry: A review of the current literature. BMC Oral Health. 2017;17(1):149.
5. Ahlholm P, Sipilä K, Vallittu P, Jakonen M, Kotiranta U. Digital versus conventional impressions in fixed prosthodontics: A review. J Prosthodont. 2018;27(1):35-41.
6. Joda T, Zarone F, Ferrari M. The complete digital workflow in fixed prosthodontics: A systematic review. BMC Oral Health. 2017;17(1):124.
7. Revilla-León M, Raney AM, Sohn S, Morton D, Kirsch CA, Özcan M. Digital workflows for full-arch implant-supported fixed prostheses: A review. J Prosthet Dent. 2020;125(4):545-51.
8. Güth JF, Keul C, Stimmelmayr M, Beuer F, Edelhoff D. Accuracy of digital models obtained by direct and indirect data capturing. Clin Oral Investig. 2016;20(4):1657-65.
9. Chochlidakis KM, Papaspyridakos P, Geminiani A, Chen CJ, Feng IJ, Ercoli C. Digital versus conventional impressions for fixed prosthodontics: A systematic review and meta-analysis. J Prosthet Dent. 2016;116(2):184-90.
10. Imburgia M, Logozzo S, Hauschild U, Veronesi G, Mangano C, Mangano FG. Accuracy of four intraoral scanners in oral implantology: A comparative in vitro study. BMC Oral Health. 2017;17(1):92.
11. Flügge TV, Schlager S, Nelson K, Nahles S, Metzger MC. Precision of dental implant digitization using intraoral scanners. Int J Prosthodont. 2016;29(3):277-83.
12. Abduo J, Elseyoufi M. Accuracy of intraoral scanners: A systematic review of influencing factors. Eur J Prosthodont Restor Dent. 2018;26(3):101-21.
13. Ender A, Attin T, Mehl A. In vivo precision of conventional and digital methods of obtaining complete-arch dental impressions. J Prosthet Dent. 2016;115(3):313-20.
14. Patzelt SB, Lamprinos C, Stampf S, Att W. The time efficiency of intraoral scanners: An in vivo comparative study. J Am Dent Assoc. 2014;145(6):542-51.
15. Giménez B, Özcan M, Martínez-Rus F, Pradíes G. Accuracy of a digital impression system based on active wavefront sampling technology for implants: Effect of clinically relevant parameters. Implant Dent. 2015;24(5):498-504.