Assessing the feasibility and accuracy of digitizing edentulous jaws

doi:10.14219/jada.archive.2013.0209

The Journal of the American Dental Association

Volume 144, Issue 8, August 2013, Pages 914-920

https://doi.org/10.14219/jada.archive.2013.0209 Get rights and content

ABSTRACT

Background

Despite the accuracy of intraoral scanners (IOSs) in producing single-unit scans and the possibility of generating complete dentures digitally, little is known about their feasibility and accuracy in digitizing edentulous jaws. The purpose of this in vitro investigation was to evaluate the feasibility and accuracy of digitizing edentulous jaw models with IOSs.

Methods

The authors used an industrial laser scanner (reference scanner) and four IOSs to digitize two representative edentulous jaw models. They loaded the data sets obtained into three-dimensional evaluation software, superimposed the data sets and compared them for accuracy. The authors used a one-way analysis of variance to compute differences within groups (precision), as well as to compare values with those of the reference scanner (trueness) (statistical significance, P < .05).

Results. Mean trueness values ranged from 44.1 to 591.8 micrometers. Data analysis yielded statistically significant differences in trueness between all scanners (P < .05). Mean precision values ranged from 21.6 to 698.0 μm. The study results showed statistically significant differences in precision between all scanners (P < .05), except for the CEREC AC Bluecam (Sirona, Bensheim, Germany) and the Zfx IntraScan (manufactured by MHT Italy, Negrar, Italy/ MHT Optic Research, Niederhasli, Switzerland; distributed by Zfx, Dachau, Germany) (P > .05).

Conclusions

Digitizing edentulous jaw models with the use of IOSs appears to be feasible, although the accuracy of the scanners differs significantly. The results of this study showed that only one scanner was sufficiently accurate to warrant further intraoral investigations. Further enhancements are necessary to recommend these IOSs for this particular indication.

Practical Implications. On the basis of the results of this study, the authors cannot recommend these four IOSs for digitization of edentulous jaws in vivo.

Section snippets

METHODS

We used the following four IOSs in this study:

▄
CEREC AC Bluecam, CEREC 3D Service Pack V3.85 (Sirona, Bensheim, Germany);
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Lava Chairside Oral Scanner C.O.S., Lava software 3.0 (3M ESPE, St. Paul, Minn.);
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iTero, software version 4.0 (Align Technology, San Jose, Calif.);
▄
Zfx IntraScan, software version 0.9 RC33 2.8 (manufactured by MHT Italy, Negrar, Italy/ MHT Optic Research, Niederhasli, Switzerland; distributed by Zfx, Dachau, Germany).

In addition, we used a tabletop reference scanner

RESULTS

The superimposition of the reference scanner data sets revealed no statistically significant differences either between the data sets obtained before the scans with the IOSs (R₁ through R₅—the precision measurement of the reference scanner) or for the evaluation of the final scan (R₁ and R₆—evaluation of reliability of the reference scanner). The mean (SD) deviation was 5.2 (2.1) μm between R₁ through R₅ and 4.6 (2.2) μm between R₁ and R₆.

Although digitization of edentulous jaw models was

DISCUSSION

To our knowledge, this is the first study in which the feasibility and accuracy of digitization of edentulous jaws with IOSs have been evaluated. Researchers in previous studies focused on the accuracy of abutment scans.7, 8, 9, 10 In addition, no information is available in the published literature about the accuracy of conventional impressions and plaster models of edentulous jaws. The available literature focuses on 3-D measurements11, 12 and linear measurements¹³,14, 15, 16, 17, 18, 19, 20

CONCLUSION

Although the results of our study show that digitization of edentulous jaw models was feasible with the use of four IOSs, the high levels of inaccuracy lead us to conclude that enhancements are needed before we can recommend use of these scanners for digitization of edentulous jaws in vivo.▪

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Fit and retention of complete denture bases: Part II – conventional impressions versus digital scans: A clinical controlled crossover study
2024, Journal of Prosthetic Dentistry
Although the intraoral scanning of edentulous ridges is feasible, clinical evidence that the resulting denture retention is equivalent to that achieved with conventional impressions is lacking.
The purpose of this clinical study was to determine the retention of complete denture bases fabricated from digital intraoral scans versus conventional impressions by using border molding and posterior palatal seal compression.
Twenty volunteers with an edentulous maxilla were recruited. An intraoral scan of the maxilla and a conventionally border-molded impression with a custom tray were made. The conventional impression was poured; the definitive cast was scanned. Three-dimensionally (3D) printed (PB1) and milled bases (MB1) were fabricated based on the scan of the definitive cast. Based on the intraoral scan, a 3D printed (PB2) and a milled base (MB2) were fabricated. On each base, a platform with a hook consisting of a central notch orienting the force against the post dam (PD) and 2 lateral notches orienting the forces against the left (LT) and right (RT) tuberosities was set in the center of the outer surface of the base. A traction dynamometer was inserted in the hook and oriented into the corresponding notch by applying force until dislodgement. All bases were subsequently stored in artificial saliva for 2 weeks and scanned. Retention testing was repeated by using the same procedure. To evaluate trueness and to visualize the differences on a color map, the scan of the definitive cast and the intraoral scans were matched and compared in 3 dimensions. The Wilcoxon tests were used to compare the retention of the different bases (95% confidence interval, α=.05).
Nineteen participants with a mean ±standard deviation age of 64.1 ±14.7 years completed the 4 study sessions. The retention of printed bases (PD: 16.08 ±15.28 N; LT: 14.98 ±14.72 N; RT: 11.28 ±9.57 N) and milled bases (PD:14.52 ±17.07 N; RT: 11.99 ±12.10 N; LT: 13.55 ±15.53 N) fabricated from conventional impressions presented significantly higher retentive forces than those printed (PD: 6.21 ±4.72 N; RT:5.12 ±2.78 N; LT: 4.45 ±2.77 N) and milled (PD: 6.58 ±4.92 N; RT: 4.65 ±2.63 N; LT: 5.02 ±3.58 N) from the intraoral scans (P<.05). The differences were significant in all directions of dislodgement, as well as after storage in artificial saliva for 2 weeks. Comparison of the 3D distances between the intraoral scan and the definitive cast revealed a mean deviation of 0.45 ±0.11 mm.
Conventional impressions of the edentulous maxilla, including the clinical steps of border molding and posterior palatal seal compression, provide better retention than digital intraoral scans with both milled and 3D printed denture bases.
THE ACCURACY OF INTRAORAL SCAN IN OBTAINING DIGITAL IMPRESSIONS OF EDENTULOUS ARCHES: A SYSTEMATIC REVIEW
2024, Journal of Evidence-Based Dental Practice
Accuracy is a crucial factor when assessing the quality of digital impressions. This systematic review aims to assess the accuracy of intraoral scan (IOS) in obtaining digital impressions of edentulous jaws.
This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the International Prospective Register of Systematic Reviews (PROSPERO ID: CRD42022382983). A thorough retrieval of 7 electronic databases was undertaken, encompassing MEDLINE (PubMed), Web of Science, EMBASE, Scopus, Cochrane Library, Virtual Health Library, and Open gray, through September 11, 2023. A snowball search was performed by tracing the reference lists of the included studies. The Population, Intervention, Comparison, and Outcome (PICO) question of this systematic review was: “What is the accuracy of intraoral scan in obtaining digital impressions of edentulous arches?” The Modified Methodological Index for Nonrandomized Studies (MINORS) was employed to assess the risk of bias.
Among the studies retrieved from databases and manual search, a total of 25 studies were selected for inclusion in this systematic review, including 9 in vivo and 16 in vitro studies. Twenty-one of the included studies utilized the 3D deviation analysis method, while 4 studies employed the linear or angular deviation analysis method. The accuracy results of in vitro studies indicated a trueness range of 20-600 μm and a precision range of 2-700 μm. Results of in vivo studies indicated a trueness range of 40-1380 μm, while the precision results were not reported.
According to the results of this study, direct digital impressions by IOS cannot replace the conventional impressions of completely edentulous arches in vivo. Edentulous digital impressions by IOS demonstrated poor accuracy in peripheral areas with mobile tissues, such as the soft palate, vestibular sulcus, and sublingual area.
Impact of the superimposition reference area on intraoral scanning accuracy in a partially dentate maxilla
2024, Journal of Prosthetic Dentistry
The alignment of 3-dimensional (3D) files involves selecting a reference area before performing a local best fit alignment during the digital scan superimposition and is essential for comparing digital scans. Scan alignment relies on both reference area location and the alignment algorithm. However, a consensus on the impact of different reference areas on intraoral scanning accuracy is lacking.
The purpose of this in vitro study was to assess the impact of 3 superimposition reference areas on the accuracy of 3 intraoral scanners for a partially dentate maxilla.
A Kennedy class II resin cast was scanned using 3 intraoral scanners (Primescan, TRIOS 3, and Emerald) outputting 30 digital scans (10 per scanner). Test scans from intraoral scanners were subsequently compared with a reference digital standard tessellation language file generated by a laboratory scanner with validated accuracy. The files were superimposed using best fit alignment for each intraoral scanner using 3 different superimposition reference areas (whole region of interest, palate, and all teeth). Accuracy was assessed by using a 3D analysis program (Geomagic Control X; 3D systems) for each scanner at 4 preselected areas. Test and reference scan differences were depicted on color maps and quantified via root mean square deviations. Differences were analyzed using regression analysis with the post hoc student t test and Bonferroni correction (α=.05).
The TRIOS 3 and Emerald produced positive deviations in the palatal color maps, whereas Primescan produced more uniform color maps, regardless of the superimposition strategy used. Primescan exhibited the best accuracy (trueness and precision) in both palatal and bounded edentulous areas, regardless of the superimposition reference area. The TRIOS 3 recorded the highest distal extension trueness (ranging from 42.9±7.7 µm to 65 ±19.5 µm), and Primescan achieved the highest precision (ranging from 28.5 ±9.8 µm to 48.9 ±16.9 µm), regardless of the superimposition area. Emerald demonstrated the highest teeth trueness (ranging from 31.6 ±6.8 µm to 69.6 ±11.5 µm), while Primescan produced the highest precision (ranging from 17.9 ±6.1 µm to 30.7 ±9.2 µm), regardless of the reference area used.
The chosen reference area for best fit alignment significantly influenced digital scan accuracy (P<.001). Primescan displayed the highest palatal and bounded edentulous area accuracy, with TRIOS 3 recording the highest distal extension trueness. Emerald recorded the highest teeth trueness and Primescan recorded the highest distal extension and tooth precision. All conclusions were independent of the superimposition strategy used.
Improving the accuracy of complete arch implant intraoral digital scans by using horizontal scan bodies with occlusal geometry: A dental technique
2024, Journal of Prosthetic Dentistry
A technique to improve the accuracy of complete arch implant intraoral digital scans and to obtain more accurate virtual casts with them is described. First, 2 complete arch intraoral digital scans were obtained with an intraoral scanner: a multiunit abutment digital scan and an implant digital scan with reusable horizontal intraoral scan bodies (ISBs) placed on the implants. These were previously created by combining the conventional ISBs compatible with the patient’s implants with extensional structures with occlusal geometry. Once the digital scans had been acquired, the position of the implants was obtained by superimposing a virtual design of the conventional ISB onto each horizontal ISB of the complete arch implant digital scan. Finally, the virtual cast was obtained by superimposing the complete arch multiunit abutment digital scan on the complete arch implant digital scan.
A comparison of the shear bond strength between denture teeth and denture base resins manufactured either conventionally or with a 3D printer
2023, Journal of Prosthetic Dentistry
Limited information is available on the shear bond strength (SBS) between denture teeth and denture base resins fabricated using a stereolithography (SLA) 3-dimensional (3D) printer.
The purpose of this in vitro study was to evaluate the SBS between denture teeth and the denture base resins produced with the conventional method and with a 3D printer.
Conventional or 3D printed denture teeth were included in the study. The denture base resins were manufactured either conventionally or with a 3D printer. Four subgroups were tested: conventional teeth-conventional base resin (CT-CB), conventional teeth-printed base resin (CT-PB), printed teeth-conventional base resin (PT-CB), and printed teeth-printed base resin (PT-PB). The maxillary molars were combined with Ø5×2.5-mm-cylindrical denture base resin. Shear bond testing was performed by applying a parallel force to the denture teeth-denture base resin interface by using a blade-edge chisel with a crosshead speed of 1 mm/min until failure occurred. SBS and elastic modulus (EM) were recorded. One-way ANOVA followed by the Dunnett T3 post hoc test was used for the statistical analysis (α=.05). The failure modes of the specimens were also analyzed.
A statistically significant difference (P<.05) was found between the evaluated groups for the SBS and EM values. PT-PB showed the highest SBS value (15.4 ±2.7 MPa), and CT-PB showed the lowest (0.9 ±0.7 MPa). The PT-CB group showed the highest EM value (62.74 ±20.80 GPa), and the CT-PB group showed the lowest (29.46 ±28.40 GPa). The CT-CB and CT-PB specimens showed mostly adhesive failure; none of the PT-PB specimens showed adhesive failure.
Three-dimensional printing led to a better bond between the denture teeth and the denture base resin compared with the conventional method. Although these findings need to be supported by clinical studies, the use of 3D printers is appropriate in the production of denture teeth and denture bases.
Evaluation of the accuracy of intraoral scanners for complete-arch scanning: A systematic review and network meta-analysis
2023, Journal of Dentistry
This network meta-analysis (NMA) aimed to compare the complete-arch scanning accuracy of different intraoral scanners (IOSs) to that of reference standard tessellation language (STL) files.
Studies comparing the trueness and precision of IOS STL files with those of reference STL scans for different arch types (dentate, edentulous, completely edentulous with implants, and partially edentulous with implants) were included in this study.
An electronic search of five databases restricted to the English Language was conducted in October 2021.
A total of 3,815 studies were identified, of which 114 were eligible for inclusion. After study selection and data extraction, pair-wise comparison and NMA were performed to define the accuracy of scanning for four arch subgroups using four outcomes (trueness and precision expressed as mean absolute deviation and root mean square values). Cochrane guidelines and the QUADAS-2 tool were used to assess the risk of bias. GRADE was used for certainty assessment.
Fifty-three articles were included in this NMA. Altogether, 26 IOSs were compared directly and indirectly in 10 network systems. The accuracy of IOSs scans were not significantly different from the reference scans for dentate arches (three IOSs), edentulous arches (three IOSs), and completely edentulous arches with implants (one IOS). The accuracy of the IOSs was significantly different from the reference scans for partially edentulous arches with implants. Significant accuracy differences were found between the IOSs, regardless of clinical scenarios.
The accuracy of complete-arch scanning by IOSs differs based on clinical scenarios.
Different IOSs should be used according to the complete arch type.

View all citing articles on Scopus

Disclosure. None of the authors reported any disclosures.

The authors express their gratitude to Sirona, Bensheim, Germany; 3M ESPE, St. Paul, Minn.; Align Technologies, San Jose, Calif.; and Zfx, Dachau, Germany, for providing the intraoral scanners.

The authors thank MDT Siegbert Witkowski and MDT Wolf Woerner, Freiburg, Germany, for their assistance in data processing.

¹: Dr. Patzelt is a visiting scholar, Department of Periodontics, School of Dentistry, University of Maryland, Baltimore, and an assistant professor and a scientific associate, Department of Prosthodontics, School of Dentistry, University Hospital Freiburg, Freiburg, Germany. Address reprint requests to Dr. Patzelt, Department of Periodontics, School of Dentistry, University of Maryland, 650 W. Baltimore St., Baltimore, Md. 21201

²: Mr. Vonau is a doctoral candidate, Department of Prosthodontics, School of Dentistry, University Hospital Freiburg, Freiburg, Germany.

³: Dr. Stampf is a statistician, Department of Medical Biometry and Statistics, Institute of Medical Biometry and Medical Informatics, University Hospital Freiburg, Freiburg, Germany.

⁴: Dr. Att is an associate professor and director, Postgraduate Program, Department of Prosthodontics, School of Dentistry, University Hospital Freiburg, Freiburg, Germany.

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Digital TechnologyAssessing the feasibility and accuracy of digitizing edentulous jaws

ABSTRACT

Background

Methods

Conclusions

Section snippets

METHODS

RESULTS

DISCUSSION

CONCLUSION

JADA

JADA

J Prosthet Dent

Comput Methods Programs Biomed

J Prosthet Dent

Comput Biol Med

Dent Mater

Dent Mater

J Prosthet Dent

J Prosthet Dent

Biophys J

Image Vis Comput

Trial of a CAD/CAM system for fabricating complete dentures

Dent Mater J

Accuracy (trueness and precision) of measurement methods and results, part I: general principles and definitions (ISO 5725-1:1994)

Accuracy testing of a new intraoral 3D camera (in English, German)

Int J Comput Dent

Full arch scans: conventional versus digital impressions—an in-vitro study (in English, German)

Int J Comput Dent

Accuracy of intraoral data acquisition in comparison to the conventional impression (in English, German)

Int J Comput Dent

Effect of different impression techniques on the dimensional accuracy of impressions using various elastomeric impression materials: an in vitro study

J Contemp Dent Pract

Digital Technology
Assessing the feasibility and accuracy of digitizing edentulous jaws