Influence of Implant Scanbody Wear on the Accuracy of Digital Impression for Complete-Arch: A Randomized In Vitro Trial

Accuracy of edentulous full-arch implant impression: An in vitro comparison between conventional impression, intraoral scan with and without splinting, and photogrammetry

OBJECTIVES

The purpose of this in vitro study was to compare the trueness and precision of complete arch implant impressions using conventional impression, intraoral scanning with and without splinting, and stereophotogrammetry.

MATERIALS AND METHODS

An edentulous model with six implants was used in this study. Four implant impression techniques were compared: the conventional impression (CI), intraoral scanning (IOS) without splinting, intraoral scanning with splinting (MIOS), and stereophotogrammetry (SPG). An industrial blue light scanner was used to generate the baseline scan from the model. The CI was captured with a laboratory scanner. The reference best-fit method was then applied in the computer-aided design (CAD) software to compute the three-dimensional, angular, and linear discrepancies among the four impression techniques. The root mean square (RMS) 3D discrepancies in trueness and precision between the four impression groups were analyzed with a Kruskal-Wallis test. Trueness and precision between single analogs were assessed using generalized estimating equations.

RESULTS

Significant differences in the overall trueness (p = .017) and precision (p < .001) were observed across four impression groups. The SPG group exhibited significantly smaller RMS 3D deviations than the CI, IOS, and MIOS groups (p < .05), with no significant difference detected among the latter three groups (p > .05).

CONCLUSIONS

Stereophotogrammetry showed superior trueness and precision, meeting misfit thresholds for implant-supported complete arch prostheses. Intraoral scanning, while accurate like conventional impressions, exhibited cross-arch angular and linear deviations. Adding a splint to the scan body did not improve intraoral scanning accuracy.

Influence of connected and nonconnected calibrated frameworks on the accuracy of complete arch implant scans obtained by using four intraoral scanners, a desktop scanner, and a photogrammetry system

STATEMENT OF PROBLEM

Different techniques have been proposed for increasing the accuracy of complete arch implant scans obtained by using intraoral scanners (IOSs), including a calibrated metal framework (IOSFix); however, its accuracy remains uncertain.

PURPOSE

The purpose of this in vitro study was to compare the accuracy of complete arch scans obtained with connecting and non-connecting the implant scan bodies (ISBs) recorded using intraoral scanners (IOSs), a laboratory scanner (LBS), and photogrammetry (PG).

MATERIAL AND METHODS

A cast with 6 implant abutment analogs was obtained. Six groups were created: TRIOS 4, i700, iTero, CS3800, LBS, and PG groups. The IOSs and LBS groups were divided into 3 subgroups: nonconnected ISBs (ISB), splinted ISBs (SSB), and calibrated framework (CF), (n=15). For the ISB subgroups, an ISB was positioned on each implant abutment analog. For the SSB subgroups, a printed framework was used to connect the ISBs. For the CF subgroups, a calibrated framework (IOSFix) was used to connect the ISBs. For the PG group, scans were captured using a PG (PIC Camera). Implant positions of the reference cast were measured using a coordinate measurement machine, and Euclidean distances were used as a reference to calculate the discrepancies using the same distances obtained on each experimental scan. Wilcoxon squares 2-way ANOVA and pairwise multiple comparisons were used to analyze trueness (α=.05). The Levene test was used to analyze precision (α=.05).

RESULTS

Linear and angular discrepancies were found among the groups (P<.001) and subgroups (P<.001). Linear (P=.008) and angular (P<.001) precision differences were found among the subgroups.

CONCLUSIONS

The digitizing method and technique impacted the trueness and precision of the implant scans. The photogrammetry and calibrated framework groups obtained the best accuracy. Except for TRIOS 4, the calibrated framework method improved the accuracy of the scans obtained by using the IOSs tested.

Influence of implant reference on the scanning accuracy of complete arch implant scans captured by using a photogrammetry system

STATEMENT OF PROBLEM

Photogrammetry has been reported to be a reliable digital alternative for recording implant positions; however, the factors that may impact the accuracy of photogrammetry techniques remain unknown.

PURPOSE

The purpose of this in vitro study was to assess the influence of the implant reference on the accuracy of complete arch implant scans acquired by using a photogrammetry system.

MATERIAL AND METHODS

An edentulous cast with 6 implant abutment analogs (MultiUnit Abutment Plus Replica) was obtained and digitized by using a laboratory scanner (T710; Medit). A photogrammetry system (PIC System) was selected to obtain complete arch implant scans. An optical marker (PIC Transfer, HC MUA Metal; PIC Dental) was positioned on each implant abutment of the reference cast. Each optical marker code and position was determined in the photogrammetry software program. Three groups were created based on the implant reference selected before acquiring the photogrammetry scans: right first molar (IPR-3 group), left canine (IPR-11 group), and left first molar (IPR-14 group) (n=30). Euclidean linear and angular measurements were obtained on the digitized reference cast and used to compare the discrepancies with the same measurements obtained on each experimental scan. One-way ANOVA and the Tukey tests were used to analyze the trueness data. The Levene test was used to analyze the precision values (α=.05 for all tests).

RESULTS

One-way ANOVA revealed significant linear (P=.003) and angular (P=.009) trueness differences among the groups tested. Additionally, the Tukey test showed that the IPR-11 and IPR-14 groups had significantly different linear (P<.001) and angular trueness (P<.001). The Levene test showed no significant precision linear (P=.197) and angular (P=.235) discrepancies among the groups tested. The IPR-3 group obtained the highest trueness (P<.001) and precision (P<.001) values among the groups tested.

CONCLUSIONS

Implant reference impacted the accuracy of complete arch implant scans obtained by using the photogrammetry system tested. However, a trueness ±precision linear discrepancy of 6 ±3 µm and an angular discrepancy of 0.01 ±0.01 degrees were measured among the groups tested; therefore, the impact of the discrepancy measured should not be clinically significant.

Influence of scanbody design and intraoral scanner on the trueness of complete arch implant digital impressions: An in vitro study

This study aimed to compare the accuracy of full-arch digital implant impressions using seven different scanbodies and four intraoral scanners. A 3D-printed maxillary model with six implants and their respective multi-unit abutments was used for this study. Seven scanbodies (SB1, SB2, SB3, SB4, SB5, SB6, and SB7) and four intraoral scanners (Primescan®, Omnican®, Trios 3®, and Trios 4®) were assessed. Each combination group was scanned ten times and a dental lab scanner (D2000, 3Shape) was used as a reference. All scans were exported as STL files, imported into Convince software (3Shape) for alignment, and later into Blender software, where their 3D positions were analyzed using a Python script. The 3D deviation, angular deviation, and linear distance between implants #3 and #14 were also measured. Accuracy was measured in terms of "trueness" (scanbody 3D deviation between intraoral scan and desktop scan). Kruskal-Wallis followed by the Bonferroni correction was used to analyze the data (⍺ = .05). The study found statistically significant differences in digital impression accuracy among the scanners and scanbodies (p<0.001). When comparing different intraoral scanners, the Primescan system showed the smallest 3D deviation (median 110.59 μm) and differed statistically from the others, while Trios 4 (median 122.35 μm) and Trios 3 (median 130.62 μm) did not differ from each other (p = .284). No differences were found in the linear distance between implants #3 and #14 between Trios 4, Primescan, and Trios 3 systems. When comparing different scanbodies, the lowest median values for 3D deviation were obtained by SB2 (72.27μm) and SB7 (93.31μm), and they did not differ from each other (p = .116). The implant scanbody and intraoral scanner influenced the accuracy of digital impressions on completely edentulous arches.

Influence of implant scan body design (height, diameter, geometry, material, and retention system) on intraoral scanning accuracy: A systematic review

PURPOSE

To evaluate the influence of implant scan body (ISB) design (height, diameter, geometry, material, and retention system) on the accuracy of digital implant scans.

MATERIAL AND METHODS

A literature search was completed in five databases: PubMed/Medline, Scopus, Embase, World of Science, and Cochrane. A manual search was also conducted. Studies reporting the evaluation of ISB design on the accuracy of digital scans obtained by using IOSs were included. Two investigators evaluated the studies independently by applying the Joanna Briggs Institute critical appraisal. A third examiner was consulted to resolve any lack of consensus. Articles were classified based on the ISB features of height, geometry, material, and retention system.

RESULTS

Twenty articles were included. Among the reviewed studies, 11 investigations analyzed the influence of different ISB geometries, 1 study assessed the impact of ISB diameter, 4 studies investigated the effect of ISB splinting, 2 articles evaluated ISB height, and 2 studies focused on the effect of ISB material on scan accuracy. In addition, 8 studies involved ISBs fabricated with different materials (1- and 2-piece polyetheretherketone and 1-piece titanium ISBs), and all of the reviewed articles tested screw-retained ISBs, except for 3 in vitro studies.

CONCLUSIONS

The findings did not enable concrete conclusions regarding the optimal ISB design, whether there is a relationship between IOS technology and a specific ISB design, or the clinical condition that maximizes intraoral scanning accuracy. Research efforts are needed to identify the optimal ISB design and its possible relationship with the IOS selected for acquiring intraoral digital implant scans.

Intraoral digital implant scans: Parameters to improve accuracy

PURPOSE

To report the means to maximize the predictability and accuracy of intraoral digital implant scans through the evaluation of operator and patient-related factors.

MATERIALS AND METHODS

A search of published articles related to factors that can decrease the scanning accuracy of intraoral digital implant scans was completed in four data sources:MEDLINE, EMBASE, EBSCO, and Web of Science. All studies related to variables that can influence the accuracy of intraoral digital implant scans obtained by using intraoral scanners (IOSs) were considered. These variables included ambient lighting, scanning pattern, implant scan body (ISB) design, techniques for splinting ISBs, arch location, implant position, and inter-implant distance.

RESULTS

Among operator-related factors, ambient lighting conditions, scanning pattern, and ISB design (material, geometry, and retention design) can impact the accuracy of intraoral digital implant scans. The optimal ISB for maximizing IOS accuracy is unclear; however, polymer ISB can wear with multiple reuse and sterilization methods. Among patient-related factors, additional variables should be considered, namely arch (maxillary vs. mandibular arch), implant position in the arch, inter-implant distance, implant depth, and angulation.

CONCLUSIONS

Ambient lighting conditions should be established based on the IOS selected to optimize the accuracy of intraoral digital implant scans. The optimal scanning pattern may vary based on the IOS, clinical situation, and the number of implants. The optimal ISB design may vary depending on the IOS used. Metallic implant scan bodies are preferred over polymer ISB designs to minimize wear due to multiple use and sterilization distortion. Among patient-related factors, additional variables should be considered namely the arch scanned, implant position in the arch, inter-implant distance, implant depth, and angulation. The impact of these factors may vary depending on the IOS selected.

Characteristics of intraoral scan bodies and their influence on impression accuracy: A systematic review

OBJECTIVE

The aim of this systematic review was to evaluate the influence of the characteristics of intraoral scan bodies (ISBs) on the accuracy of intraoral scanning.

MATERIALS AND METHODS

An electronic search was conducted through PubMed (MEDLINE), Scopus and Cochrane Library, up to March 2023. The literature search intended to retrieve all relevant clinical and in vitro studies about the effect that the various properties of ISBs may have on the accuracy (trueness and precision) of intraoral scanning. Only publications in English language were selected with animal studies, case reports, case series, technique presentation articles and expert opinions being excluded.

RESULTS

A total of 28 studies met the inclusion criteria and were included in this systematic review. They were published between 2019 and 2023 and were all in vitro studies. Among the parameters described, the scan body material, position, geometry, height, diameter, and fixation torque were evaluated. The most common materials used for ISBs were polyetheretherketone (PEEK) and titanium alloys. The diameter and position of ISBs seemed to affect the trueness of implant impressions. Subgingival implant position and decreased ISB height affected negatively the trueness of scanning. Geometrical characteristics of ISBs also affect the implant impression accuracy, especially the bevel location and the types of designing modifications.

CONCLUSIONS

The characteristics of the currently used ISBs vary widely and the available scientific evidence is not yet conclusive about the optimal design of ISB. The implant impression accuracy achieved by any of the studied parameters is encouraging. Clinical studies are however necessary for more concrete conclusions.

CLINICAL SIGNIFICANCE

ISBs play a vital role in the digital workflow and influence significantly the accuracy and fit of implant restorations. More clinical trials are needed in order to conclude to the optimal characteristics of ISBs which would further enhance the success of the restorations.

Accuracy of single-implant digital impression with various scanbody exposure levels at anterior and posterior regions

OBJECTIVES

This in vitro study aimed to evaluate the effect of the exposure heights of the scanbody on the accuracy of digital implant impressions at different positions.

METHODS

Four maxillary master models with one analog at the anterior and posterior region were fabricated by a 3-dimensional (3D) printer. The analogs were submerged from the gingival margin to ensure four exposure heights of the scanbody: 10, 8, 6, and 4 mm. . The master models were then scanned with D2000 dental laboratory scanner as the reference models. An intraoral scanner obtained ten test models for each group. After aligning the scanbody library file, the related files were imported into inspection software for superimposition by a local fit algorithm based on the adjacent teeth.

RESULTS

3D trueness was significantly decreased at 6 and 4 mm scanbody exposure at the anterior region. In comparison, a significant decrease was only seen at 4 mm scanbody exposure at the posterior region. 3D precision was significantly decreased at 4 mm scanbody exposure at both anterior and posterior regions.

CONCLUSION

The exposure height of the scanbody influenced the accuracy of the digital implant impression, according to the implant positions. Scanbody exposure of less than 6 mm at the anterior region and 4 mm scanbody exposure at the posterior region could lead to increased deviations, but still in the tolerance range.

CLINICAL SIGNIFICANCE

The scanbody exposure height less than 6 mm at the anterior region and 4 mm scanbody exposure height at the posterior region could lead to significantly increased deviations. Though these deviations may be still in the clinically acceptable range, caution should be taken.

Fabrication of a reverse-engineered custom scan body as a digital solution for recording implant position: A dental technique

A technique for the reverse engineering of the implant-abutment connection to fabricate a custom scan body is described. The implant-abutment connection was designed using the exocad software program, the scan body with screw channel was designed with the Blender software program, and the file was either 3-dimensionally printed in definitive tooth-colored resin with ceramic filler material or milled in polyetheretherketone (PEEK). This technique offers an accurate, cost-effective digital solution for implant optical scanning that can replace prefabricated scan bodies that may not be available for all implants. (J Prosthet Dent xxxx;xxx:xxx-xxx).

Influence of arch location and scanning pattern on the scanning accuracy, scanning time, and number of photograms of complete-arch intraoral digital implant scans

OBJECTIVES

To measure the influence of arch location and scanning pattern on the accuracy, scanning time, and number of photograms of complete-arch implant scans acquired using an intraoral scanner (IOS).

MATERIALS AND METHODS

A maxillary (maxillary group) and mandibular (mandibular group) model with 6 implant abutments on each cast was digitized using a desktop scanner (control scans). Six subgroups were created based on the scanning pattern used to acquire the scans using an IOS (Trios 4): occluso-buccal-lingual (OBL subgroup), occluso-linguo-buccal (OLB subgroup), bucco-linguo-occlusal (BLO subgroup), linguo-buccal-occlusal (LBO subgroup), zigzag (ZZ subgroup), and circumferential (C subgroup). The control scans were used as a reference to measure the discrepancy with the experimental scans calculating the root mean square error. Two-way ANOVA and the pairwise comparison Tukey tests were used to analyze the data (α = .05).

RESULTS

Significant discrepancies in trueness (p < .001), precision (p < .001), scanning time (p < .001), and number of photograms (p < .001) were found. The maxillary group obtained poorer trueness and precision values, higher scanning times, and a larger number of photograms than the mandibular group. The C subgroup obtained the best trueness and precision values, but was not significantly different from the OLB, BLO, and LBO subgroups. The ZZ subgroup obtained the worst trueness and precision values (p < .05). The C subgroup obtained the lowest scanning time and number of photograms (p < .05).

CONCLUSIONS

Arch location and scanning pattern influenced scanning accuracy, scanning time, and number of photograms of complete-arch implant scans.

Comparison of Virtual Intersection and Occlusal Contacts between Intraoral and Laboratory Scans: An In-Vivo Study

BACKGROUND

The inaccurate maxillomandibular relationship of virtual casts following alignment by the vestibular scan may result in intersection (intermesh penetration) between opposing dental arch surfaces. Intersection occurs at short interocclusal distances in the occlusal contact area (OCA) and may result in infra-occluded definitive restorations. The purpose of this clinical study was to compare initial (by the proprietary scanner software) and new alignments (by a standalone 3D software) of virtual casts regarding OCA and intersection failure. New alignments aimed to rectify intersections by refinement of occlusal contacts.

MATERIAL AND METHODS

The virtual casts of 30 patients following digital and conventional impression-taking were analyzed, which were acquired for single implant restoration in the posterior site. Digital impressions were performed by both IOS 1 (3M True Definition) and IOS 2 (TRIOS 3), either as complete- or partial-arch scans, respectively. Mounted gypsum casts were digitized as complete-arch by a laboratory scanner (LS) in enabled and disabled mode to avoid intersection [LS (+)/LS (-)]. All virtual casts were newly aligned by a 3D software. The difference of the OCA and the area of intersection were calculated for initial and new alignments, using interocclusal distance ranges of 0-100 μm, 0-10 μm or <0 μm (=intersection). The difference of the OCA was compared using a linear mixed model. The distribution of occlusal contact points per modality and alignment was assessed independently by three observers and estimated by inter- and intraclass correlation (ICC) coefficients.

RESULTS

Virtual casts following initial alignment demonstrated intersections irrespective of the modality. The mean area of the intersection was most for IOS 2 (79.23 mm²), followed by IOS 1 (48.28 mm²), LS (-) (2.77 mm²), and LS (+) (2.01 mm²) in partial-arch scans. Complete-arch scans demonstrated an area of intersection of 70.63 mm² for IOS 1 followed by 65.52 mm² (IOS 2), 6.13 mm² [LS (-)] and 2.76 mm² [LS (+)]. Newly aligned scans showed no intersections. The overall distribution of occlusal contact points demonstrated moderate reliability (ICC 0.63). Good reliability could be observed (ICC 0.9) for LS (-) scans.

CONCLUSIONS

Intersections in the area of occlusal contact points are a phenomenon restricted to virtual casts, which should be considered in CAD/CAM. Initial alignments of LS are less affected by this virtual phenomenon, and contact points may be more distinct according to their anatomic region compared to IOS. Furthermore, intersections can be rectified in a 3D software by adjustment of the maxillomandibular relationship.

A guide for maximizing the accuracy of intraoral digital scans: Part 2-Patient factors

OBJECTIVES

To describe the factors related to patient intraoral conditions that impact the scanning accuracy of intraoral scanners (IOSs). A new classification for these influencing factors is proposed to facilitate dental professionals' decision-making and maximize the accuracy and reliability of intraoral digital scans.

OVERVIEW

Variables related to intraoral conditions of the patient that can influence the scanning accuracy of IOSs include tooth type, presence of interdental spaces, arch width variations, palate characteristics, wetness, existing restorations, characteristics of the surface being digitized, edentulous areas, interimplant distance, position, angulation, and depth of existing implants, and implant scan body selection.

CONCLUSIONS

The knowledge and understanding of the patient's intraoral conditions that can impact the scanning accuracy of IOSs is a fundamental element for maximizing the accuracy of IOSs.

CLINICAL SIGNIFICANCE

The patient's intraoral conditions, or patient factors, can significantly impact intraoral scanning accuracy. Dental professionals must know and understand these influencing patient factors to maximize the accuracy of IOSs.