Horizontal Scan Bodies Gave Full-Arch IOS Its Best Chance
Azevedo and colleagues show that six-implant complete-arch digital impressions become markedly truer and more consistent when horizontal scan bodies replace a conventional vertical design, with Primescan the standout performer and iTero plus a vertical PEEK body the least convincing pairing.
Horizontal bodies steady the scan
Source Paper
Effect of Horizontal and Vertical Intraoral Scan Bodies on the Trueness of Complete-Arch Digital Implant Impressions: A Comparative In Vitro Study With Six Implants
The intraoral scanner is a slightly vain device. Give it a tidy single crown and a few obedient landmarks and it behaves like a prodigy; ask it to map six implants across an edentulous mandible and it begins looking for excuses. In “Effect of Horizontal and Vertical Intraoral Scan Bodies on the Trueness of Complete-Arch Digital Implant Impressions: A Comparative In Vitro Study With Six Implants,” Luís Azevedo and colleagues show that the excuses are not all in the software. Horizontal scan bodies produced truer and more consistent complete-arch digital implant impressions than the vertical reference design, and the best pairing in this model was with Primescan.
That matters because the profession has spent years treating the scan body as a minor accessory, a sort of geometric extra, when it is plainly part of the acquisition system. In a long, stitch-heavy walk across a feature-poor arch, the shape of the thing being recognised starts to matter quickly.
The Data Anchor
This in vitro study used an edentulous mandibular definitive cast with six multi-unit analogues placed at the first molar, first premolar, and lateral incisor positions. Four horizontal intraoral scan body systems were compared with one vertical reference design: H-NB, H-NS, H-M6, H-SF, and V-EA. The horizontal systems varied in design and material, while the vertical reference was a single-piece PEEK scan body. Two experienced operators scanned each set-up 10 times with four scanners: iTero Element 5D, Primescan, TRIOS 3, and TRIOS 4, yielding 400 digital impressions in total.
Trueness was assessed as root-mean-square deviation after CAD-library alignment and metrology superimposition against a high-accuracy desktop-scanned reference cast. The point was not whether the scan looked pretty; it was whether the implant positions landed where they were supposed to.
Key Findings
- Horizontal scan bodies outperformed the vertical reference overall. When ISBs were compared irrespective of scanner, V-EA showed significantly poorer trueness than all horizontal designs (P < .001).
- The best and worst pairings were not close. H-NS used with Primescan delivered the highest trueness at 12 [3] μm, while the vertical V-EA paired with iTero Element 5D produced the lowest trueness at 77 [28] μm.
- Primescan was the steadiest scanner in the room. Across conditions it consistently produced the lowest RMS values, while iTero was the weakest performer overall and TRIOS 4 showed more variability than TRIOS 3.
- Operator inconsistency was mainly a vertical-scan-body problem. The notable operator effect appeared with V-EA plus iTero; the horizontal designs stayed comparatively stable across both operators.
- One horizontal design was especially dependable. H-M6 maintained high trueness across IOS devices, which suggests some geometries are simply easier for stitching algorithms to live with.
- Limitations matter here. This was an in vitro mandibular model, not a saliva-filled mouth; only two operators were tested, and RMS analysis gives an overall deviation rather than implant-specific vector errors.
💡 The Clinical Bottom Line
If you are determined to use intraoral scanning for a complete-arch implant case, treat the scan body as part of the scanning system, not as neutral hardware. Horizontal designs appear to give the software more to hold on to, and in this model that translated into cleaner, more consistent full-arch records, particularly with Primescan.
This does not settle the full-arch impression argument; photogrammetry remains a formidable benchmark, and clinical validation still has work to do. But it does sharpen the next decision. The question is no longer merely which scanner you own. It is which scanner, paired with which scan body, asks the fewest favours of the stitching algorithm. Some combinations cooperate beautifully; others behave like strangers obliged to share a very small lift.
Dr Samuel Rosehill is a general dentist with a prosthodontic focus, practising at Ethical Dental in Coffs Harbour, NSW. He holds a BDSc (Hons) from the University of Queensland, an MBA, an MMktg, and an MClinDent in Fixed & Removable Prosthodontics (Distinction) from King’s College London.
Clinical Relevance
If you are recording a complete-arch implant case with an intraoral scanner, scan body geometry is not an afterthought. In this six-implant model, horizontal scan bodies produced more consistent and truer scans than the vertical reference design, and the strongest performance came from pairing them with Primescan. Clinicians using IOS for full-arch work should think in terms of scanner-scan-body systems rather than assuming one scan body will behave the same way on every device.
Disclosure: The author has no financial conflicts of interest related to the products or topics discussed in this review. This is an independent summary prepared for educational purposes.
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