Dr Dheeraj S Bijlani, Dr Swapnali Mhatre, Dr Reema Srichand, Dr Mridula Joshi, Dr Gunjan Jain
Associate Professor & PG Guide
Professor & Head
Department of Prosthodontics, Crown & Bridge,
Bharti Vidyapeeth Deemed University, Dental College & Hospital, Navi Mumbai.
Purpose : This scoping review aimed to identify and summarize the available literature related to accuracy of digital versus conventional, full arch impression techniques for angulated implants as the literature shows contrasting evidence about the effect of implant angulation on accuracy of master casts.
Methods and Material : This scoping review was conducted based on the Arksey and O”Malley methodological framework. The PICO criteria were established based on the research question. PubMed database was electronically searched for articles published in English language between 1st January 2000 and 31st August 2020 using various combinations of MeSH terms and key words.
Results : A total of 5 studies were selected for the review, based on the predefined inclusion and exclusion criteria. Plotting charts were made for comparison of different Intra Oral Scanners. Intra Oral Scanners were found to be significantly more accurate than conventional techniques when compared for parallel implants. For angulated implants, results of 2 studies favored Intra Oral Scanners and 2 favored the Conventional impressions, while the 5th study found them to have comparable accuracies.
Conclusion : Digital impressions offer various advantages over conventional procedures, but the techniques still have to be improved in order to fully substitute conventional ones. Further In vivo studies are needed to investigate the accuracy of IOS to ensure clinically acceptable results.
Keywords : Dental Implants, Dental Impression Technique, Implant impressions, Digital Impressions, Intraoral Scanners, Angulated Implants.
Citations : Bijlani D, Mhatre S, Srichand R, Joshi M, Jain G. Accuracy of Digital Impressions with Intraoral Scanners in Angulated Implants- A Scoping Review. . J Prosthodont Dent Mater 2021;2(1):3-10.
The accuracy of implant impression-making procedures is one of the most critical factors that significantly impacts the quality and fit of implant restorations. Digital Dental Technology for fabrication of dental restorations including computer-aided design/computer-assisted manufacturing (CAD/CAM) has been in development since the 1980s and its rapid expansion and incorporation into the field of dentistry has been documented since the beginning of 1990s.2 The fabrication of a framework for multiple implants requires highly precise clinical and laboratory procedures. Conventional procedures have been applied for years in routine dental practice and are widely discussed in the literature. However, every step of the conventional workflow generates a certain amount of error, which can either be accumulated or compensated for, yet cannot be fully automated.
Benefits of the digital impressions over conventional ones have been presented as: (1) patient friendly (2) reduced distortion of impression materials (3) 3-D view of the preparation (4) better time management.2 Digital impressions for implant rehabilitations, would allow for: pre-visualization of (1) Available restorative space (2) depth of interface and (3) emergence profile, before starting fabrication process.
The introduction of digital technologies in dentistry has enhanced the capability to examine, diagnose, and treat dental patients by improving the accuracy of each step. However, it is still unknown whether conventional procedures can be completely substituted by using computer-aided impression-making technologies. In recent years, the application of computer aided impression-making technologies has gained significant interest. Digital impressions were found to be favorable because of, a time efficient workflow, the potential to correct the entire impression without the need to repeat the whole procedure and to avoid the unpleasant taste of impression materials.
Implant angulation is another factor which has been reported to have a significant effect on the accuracy of master casts. Studies using experimental casts containing four or five implants have better accuracy with straight implants as compared to angulated implants. In contrast, earlier studies using 2-3 implants found the accuracy of impressions to be unaffected by the angulation of implants.
Hence this review was aimed at comparing the accuracy of digital impressions with intraoral scanners and conventional techniques for angulated implants in full arch impressions.
This review was conducted based on the Arksey and O’Malley methodological framework (2005) (Figure 1)
Figure 1: Arksey and O’Malley methodological framework for conducting a scoping review.
Stage 1: Identifying the research question.
Impression making is an important and critical step in the fabrication of implant prostheses as the accuracy of impression affects the passive fit of the restoration. The introduction of digital technologies in dentistry has improved the accuracy of examination, diagnosis, and treatments. However, it is still not clear whether conventional procedures can be completely substituted by digital ones. 5 Literature shows contrasting evidence about the effect of implant angulation on accuracy of master casts, with Conrad et al 9 demonstrating significant effect and Moreno et al 10 demonstrating no effect of angulation on accuracy of digital impressions. Further, different angulations have been found to have varying effects on the accuracy of digital impressions.
Thus the research question defined for this scoping review was, “How accurate are Digital Impressions with Intraoral Scanners as compared to conventional Impressions for Angulated Implants in Full Arch Impressions?”
The PICO criteria was established based on the research question as follows:
Figure 2: PICO criteria.
Stage 2: Identifying relevant studies
Electronic search of the PubMed database for articles published from 1st January 2000 to 31st August 2020 was conducted. The search was conducted using a combination of MeSH terms as well as other keywords related to the research question. MeSH terms: “Dental Implants”, “Dental Impression Technique”
Keywords: Implant impressions, Digital Impressions, Intraoral Scanners, and Angulated Implants.
These terms were used in different sequences and combinations to conduct the search.
Stage 3: Study Selection
Amongst the studies obtained from the search results, studies comparing the accuracy of full arch impressions with intraoral scanners and conventional impression techniques for straight and angulated implants were selected. The inclusion and exclusion criteria were formulated as follows:
Figure 3: Inclusion & Exclusion criteria.
Initial search yielded a total of 535 studies, which were then screened and shortlisted as per the inclusion and exclusion criteria. As the study is limited to a single database, duplicates were eliminated manually. Eventually 5 studies were selected for the scoping review. The flow chart of study selection is as follows
Figure 4: Flowchart of study selection.
Stage 4: Charting the data
The data was then extracted from the 5 selected studies and was entered into a Microsoft excel spreadsheet. The data items that were extracted and charted are shown in figure 5A & 5B
Figure 5A & 5B: Study characteristics.
Stage 5: Collating, summarizing and reporting the results
Amongst the 5 studies reviewed, Gintaute et al1, Lin et al11 & Ribeiro et al12, had different models / groups with different angulations of implants ranging from parallel to 450, while Amin et al13 had parallel and angulated implants in the same model and Marghalani et al14 had placed implants at a fixed angulation of 300. In the study by Amin et al and Lin et al. Straumann implants were used, while Ribeiro et al used Klockner implants, Gintaute et al used Osseotite implants and Marghalani et al used both Straumann and Nobel Biocare implants. Two of the studies i.e Gintaute et al and Ribeiro et al used the True Definition Intraoral scanner by 3M, Lin et al used the iTero scanner by cadent, Amin et al used Omnicam by CEREC and Marghalani et al used both True Definition and Omnicam scanners. Accuracy of the master casts was determined by comparing with the master model. Method of comparison used was Digital Superimposition by all studies except the study by Gintaute et al, who used a Co-ordinate Measuring Machine to measure 3-dimensional deviations.
On comparing the accuracy outcomes of angulated implant models, Gintaute et al and Ribeiro et al found the conventional impression techniques to be more accurate than the digital impressions. Studies by Amin et al and Marghalani et al had a single model with both parallel and angulated implants and found digital impressions to be more accurate. The study by Lin et al had 4 models with different angulations varying from parallel to 450, and they concluded that accuracy of conventional impressions were not affected by implant angulation, while for the digital techniques, they were less accurate at angulation upto 300, beyond which their accuracy matched that of conventional impressions.
The two studies by Amin et al and Marghalani et al, which compared 2 intraoral scanners, found True Definition scanner to be more accurate than the Omnicam scanner. In the study by Marghalani et al two different implant systems were used. The results revealed that for Nobel Biocare implants, True Definition scanner was the most accurate followed by Omnicam and conventional was the least accurate. For Straumann implants, True Definiton was most accurate followed by conventional impressions and Omnicam was least accurate. Conventional impressions had better accuracies with Straumann implants.
When comparing two different implant systems, the study by Marghalani et al revealed that when both implant systems were compared in regard to the conventional impression technique, the Straumann system had significantly better accuracy than the Nobel Biocare system. When both implant systems were compared in regard to the Omnicam scan technique, the Nobel Biocare system had significantly better accuracy than the Straumann system. When both implant systems were compared in regard to the True Definition scan technique, the Nobel Biocare system had accuracy similar to that of Straumann system.
With respect to parallel implants models among the selected studies, digital impressions with intraoral scanners were found to be more accurate as compared to the respective conventional impression techniques used in each study.
Scoping reviews allow researchers to analyze the research potential of a certain subject by categorizing the available literature. The research question then, can be further studied in detail with the help of Systematic reviews and Meta analyses. The motive behind conducting this current scoping review was to analyze the available literature and determine the necessity and possibility to conduct a systematic review in the near future.
The methodology used was based on the Arksey and O’malley methodological framework as it has been used most frequently in literature to conduct scoping reviews.11 Also, authors like Levac et al12 have reported the methodology to be an appropriate foundation for such scoping reviews.
The advent of digital technology for impressions has definitely paved the way for a highly precise and efficient digital work flow.13 As per the results of the included studies, digital impression techniques have consistently shown better accuracy for straight implants. For angulated implants, the results are divided with some reporting a comparable accuracy while others having found conventional techniques to be significantly better. There still remains some uncertainty over the accuracy of digital impressions for angulated implants and hence further research is needed on this topic14. With the evolution and improvement of IOS softwares and digital technologies, we can achieve more accurate impressions and wider applications of IOS. Recent studies have reported patients accepting and preferring Digital impressions over Conventional ones.
The limitations of this scoping review are that the search was restricted to a single database and limited MeSH terms and keywords were used, leading to a possibility of having left out some relevant literature. Inspite of the limitations, a decent amount of publications do seem to be reported in literature relevant to this topic which definitely warrants for a more elaborate systematic review and meta-analysis to be conducted on this subject. Also, this review included only In-vitro studies which warrants inclusion of a few In-vivo studies in future research.
Digital impressions offer various advantages over conventional procedures. Accuracy of Intra Oral Scanners depends on clinical factors like movements of the object, saliva, fogging of the optics, and other patient operator and device related limiting factors, angulation of implants, number of implants, type of IOS used.14 Digital implant impression techniques still have to be improved in order to fully substitute conventional ones. Further In vivo studies are needed to investigate the accuracy of IOS to ensure clinically acceptable results. A systematic review on this topic has been registered on PROSPERO (Registration Number CRD42020216423) and shall be soon completed with a broader search of databases and inclusion of a few in vivo studies.
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4. Ajioka H, Kihara H, Odaira C , Kobayashi T Kondo H. Examination of the Position Accuracy of Implant Abutments Reproduced by Intra-Oral Optical Impression. Journal.pone.0164048 October 5, 2016; 1-12.
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9. Conrad HJ, Pesun IJ, DeLong R, Hodges JS. Accuracy of two impression techniques with angulated implants. J Prosthet Dent. 2007 Jun; 97(6):349-56.
10. Moreno A, Gimenez B, Ozcan M, Pradies G. A clinical protocol for intraoral digital impression of screw retained CAD/CAM framework on multiple implants based on wavefront sampling technology. Implant Dent. 2013; 22:320-25.
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13. Serag M, Nassar TA, Avondoglio D, Weiner S. A Comparative Study of the Accuracy of Dies Made from Digital Intraoral Scanning vs. Elastic Impressions: An In Vitro Study. J Prosthodont 2018 Jan; 27 (1):88-93.
14. Rutkunas V, Geciauskaite A, Jegelevicius D & Vaitiekunas M Accuracy of digital implant impressions with intraoral scanners. Eur J Oral Implantol 2017;10 (Suppl1):101–20.
15. Gallardo, Y. R., Bohner, L., Tortamano, P., Pigozzo, M. N., Laganá, D. C., & Sesma, N. (2018). Patient outcomes and procedure working time for digital versus conventional impressions: A systematic review. The Journal of Prosthetic Dentistry, 119(2), 214–19.