Dental Impressions: The Continued Expansion of Digital Technologies

Intraoral scanners (IOSs) offer a digital approach, capturing direct optical impressions by projecting a light source onto the area of interest of the oral tissues.^4-6 Sensors capture images that are processed by software to generate point clouds. Consequently, the software triangulates these points to create a 3D surface model or mesh.^5,7 Digital impressions offer advantages in speed, efficiency, and the ability to store information indefinitely. Current studies suggest that with a proper technique, IOS accuracy is comparable to conventional impressions for single and short-span restorations.^6-13 However, traditional methods may still offer superior accuracy for longer spans, angled implants, and full-arch fixed dentures.^9,13,14

According to Kaitatzidou et al, in terms of accuracy (trueness and precision) and marginal and internal adaptation, digital scanning and conventional impression techniques for crowns and fixed partial dentures, implant-supported fixed restorations, and both tooth- and implant-supported restorations showed no statistically significant differences.¹⁵ Conversely, in an in vivo study, conventional impression materials and digital impression systems differed significantly in terms of complete-arch precision.¹⁶ Highly accurate conventional impression materials provide significantly higher precision than current digital impression systems. Nevertheless, challenges remain in edentulous areas. A systematic review that included data from 10 laboratory studies and eight clinical studies found that IOSs can achieve accuracy comparable to conventional impressions when capturing denture-bearing soft tissues, especially in cases where the ridges are firm and have attached mucosa.¹⁷

Digital impression systems offer several benefits over their analog counterparts, including increased patient comfort, improved workflow, reduced chairside time, immediate 3D pre-visualization of tooth preparations, tooth shade analysis, and potential cost and time effectiveness. IOS is less invasive and more comfortable for patients, especially those with strong gag reflexes or profuse salivation. Furthermore, digital impressions can be immediately inspected, and areas that have not been captured adequately can be rescanned without having to remake the entire impression.^4,11,12,18 Communication with patients and the laboratory has become easier due to the transfer of digital data, and there is no need for storage, thereby reducing time, shipping costs, and the risk of damage to the physical models during transportation.¹⁹ Also, digital impressions reduce the risk of human error.²⁰

Yet, studies show that IOSs do not capture subgingival margins well, especially if covered with blood, saliva, or tissue.^9,10,21Effective contamination control and soft-tissue management are crucial for successful optical scans. Undercuts also pose a particular challenge, as conventional impressions can flow into these areas and better reproduce finish lines of subgingival preparations due to applied physical pressure.^9,12 However, advancements in IOS technology are continuously addressing these limitations.

Expanding Applications and Future Directions

The integration of CAD/CAM is becoming increasingly essential in modern dental practice, offering efficiency in treatment planning and communication, thus helping to reduce chairtime. Like analog protocols and techniques, the treatment outcomes of CAD/CAM methods vary and are directly related to the experience and skill level of the clinician and/or technician involved. Additionally, several factors, such as the location of the finish line, moisture control, gingival retraction, and the scanning technique used, can affect the accuracy of digital impressions.¹⁹

Due to the shortcomings of the IOS technique in creating edentulous dental implant impressions, researchers have proposed the use of artificial markers or geometric devices to improve its accuracy. Alternative scan methods like photogrammetry (eg, Aoralscan Elite, Shining 3Ddental; ICam, IMetric 4D) could provide superior accuracy for precise 3D intraoral capturing of dental implants.^22-24 This technique is used to determine the geometric characteristics of objects and their 3D spatial orientation by capturing digital images according to a specific protocol. It also enables the virtual transfer of a patient's dental implant location to computer-aided design software.²⁵ Nevertheless, these devices pose some challenges, as they struggle to accurately capture soft-tissue images, require primary impressions for fabrication, and increase the duration and complexity of the IOS process.²⁶ Such systems only record the positions of the implants in the patient's mouth. Additional procedures, such as superimposing an intraoral scan or using a digitized conventional cast, are needed to obtain further information about the soft tissue in the oral cavity.²⁵

Comparative studies on the accuracy of photogrammetry in implant-supported fixed complete-arch prostheses are limited, and the results are mixed. Some studies show superior accuracy compared to conventional and digital techniques.^23,24,26 However, other research suggests that photogrammetry may be less accurate due to the use of 3D-printed splints in conventional methods, which offer enhanced accuracy and different measurement methods.²⁵

As digital and imaging technologies advance rapidly, IOSs are set to play an increasingly important role in several dental fields, such as restorative dentistry, oral and maxillofacial surgery, orthodontics, diagnostics, and treatment planning. Several advantages of using IOSs for managing patients with cleft lip and palate have been reported, the most significant being their non-invasiveness, which makes them more patient-friendly than conventional impression techniques, particularly for pediatric patients, who may find traditional impressions uncomfortable or distressing.²⁷ IOSs can offer clinical accuracy and validity in assessing dentofacial and nasolabial morphology in cleft patients.

The use of intraoral scanners in orthodontics has been expanding in recent years due to their ability to perform full-arch scanning, facilitate indirect bonding, and digitally manufacture fixed orthodontic appliances. Moreover, IOS offers orthodontists a range of applications, including measuring arch width and length, tooth size, transverse dimensions, Bolton discrepancy, overjet, and overbite, all of which can be obtained with remarkable accuracy and efficiency.²⁸ Users can create a digital diagnostic setup and simulate proposed treatment plans, cultivating a stronger relationship between patients and orthodontists.

This technology also offers more advanced diagnostic tools for detecting pathologies and anomalies in the oral cavity, such as caries, dental wear, hygiene assessment, soft-tissue evaluation, tooth shade determination, and oral cancer, compared to traditional methods. A systematic review by Angelone et al found that the most promising field for diagnostic application is the evaluation of dental wear.⁷ Such IOSs use image superimposition software based on best-fit alignment and enable quantitative assessment of surface alterations. For caries detection, the most commonly used scanners incorporate technology for this purpose. The first scanner to offer integrated caries detection technology (TRIOS^® 4, 3Shape) features built-in fluorescent technology designed primarily for detecting caries on occlusal surfaces. Another option (iTero^™ Element 5D, Align Technology, Inc.) employs near-infrared light with a wavelength of 850 nm to highlight demineralized areas, allowing for the identification of interproximal caries. Additionally, other scanners are available on the market that include caries detection technology (eg, Emerald^® S, Planmeca).

Digital dentistry represents a transformative shift rather than just a passing trend. Today's open-platform interfaces allow integration with advanced imaging modalities such as cone-beam computed tomography (CBCT) and facial scans, significantly enhancing diagnosis, patient communication, monitoring, and treatment planning. When combined with these imaging technologies, accurate intraoral scanning data is essential for creating comprehensive treatment-planning platforms. For instance, the merging of IOS scans with facial scans enables digital smile design. At the same time, integration with CBCT data supports both static and dynamic navigation methods, which are crucial in procedures such as orthodontic mini-implant placement, endodontic access cavity preparation, dental implant insertion, and tooth autotransplantation.²⁹ Moreover, tailored software applications, often powered by artificial intelligence, provide numerous tools, including implant planning and orthodontic simulation.

Looking to the future, next-generation scanning devices promise to differentiate between hard and soft tissues, blood, and saliva, leading to faster, more accurate, and stress-free image acquisition. Radiation-free methods like ultrasonography and optical coherence tomography, widely used in medicine, also show promise in the dental field.²

Conclusion

Overall, the continuous evolution of impression techniques and digital technologies aims to provide improved experiences and outcomes for clinicians, laboratory technicians, and especially patients.

About the Author

Macarena Rivera, DMD, MSc
Assistant Professor, Department of Prosthodontics, University of Chile, Santiago, Chile; Adjunct Professor, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania; Private Practice, Santiago, Chile