Source and preparation method

← Complete molar collection

12 complete human molars, 29 roots and 40 canals with 41 preparation courses. Crown, chamber, roots, native masks and source files are preserved. The 72 µm native data cannot recover every fine terminal passage or histological constriction.

Illustrative apical completion

Stephen authorised separately labelled apical completions on 19 October 2026, with normal canal anatomy retained as the constraint. The native scans are unchanged. Terminal extensions follow each existing course, taper with noncircular sections and blend into it; they do not introduce extra branches or joins. Individual extensions, targets, controls and native evidence are recorded with each canal. Some reconstructed terminal courses span several millimetres. Further native apical fragments guide the continuation where present; intervening gaps and the selected internal landmarks remain illustrative. These regions must not be interpreted as observed specimen anatomy.

The model uses an explicitly selected internal teaching endpoint just inside a selected illustrative external portal. It is not a recovered minor foramen. Targets are measured along the curved passage, generally 0.15 mm inside the portal and 0.28 mm for ACTA 0002 Root A canal 2. These are model-specific authoring choices, not clinical working-length guidance. Every offered file in a canal reaches that same point.

ACTA0115 MB2 also has a separately recorded illustrative coronal connection, based on the user’s approach annotations. See the sizing and entry review for its source limitation.

Files and motion

Existing MicroPath 17/.03 and ET .04 source assemblies are reused without altering their source vertices. ET25 is the previously approved solid artwork; ET20, ET30 and ET35 are the existing explicitly nominal teaching derivatives, not size-specific certified manufacturer CAD. No larger ET size has been invented. Each canal offers a reviewed prefix of the available sequence, finishing at 25, 30 or 35. See the canal-by-canal sizing review and research. ACTA 0002 Root A canal 2 stops at ET25 because the sampled ET30/35 envelopes crossed the outer root at the selected target.

Motion uses a smooth fixed route with axial rotation applied before bending. The protected shank and handle remain a rigid assembly. Broad free spaces do not force a sharp deviation. Short voxel-scale blips are suppressed using Stephen’s approximate 0.5 mm modelling preference; this is not a validated NiTi mechanics law. The construction does not solve material forces, fatigue or clinical transportation.

The rotational geometric cutting envelope uses source-derived active profiles from 0.05 mm behind the distal tip through the recorded active length. The small distal cap and the protected assembly do not cut. This revision’s declared teaching interval follows inspection of the saved source-tip detail; it is not a manufacturer certification of cutting behaviour. Its evidence is retained in Research/CUTTING-INTERVAL-REVIEW.json.

Visible preparation and quantities

Persistent ISO wall colour identifies the stage that actually shapes a surface. Untouched native recesses stay coral. Withdrawal does not restore removed material. Switching canals preserves completed preparation. A matched section shows original canal, dentine and actual modelled additions at the same coordinates.

Removal is calculated from the cumulative visited cutter envelope against the initial teaching hard tissue, including separately authored apical passages. Per-file additional stock is sampled at 0.025 mm and whole-tooth totals use a union of aligned voxel IDs to avoid double counting overlapping canals. The displayed time is compressed teaching playback, 16 seconds per file. Geometric contact/removal is not evidence of clinical cleaning or disinfection.

Review and saved files

Each canal has route, target, source and instrument hashes, native oblique evidence, sampled protected-cap and outer-root checks. Final prepared tooth solids are closed. The review includes exact 10° exterior and canal-relation rotations for every root, exit-facing views and cutaways. Numeric checks do not certify clinical anatomy. Remaining fine source branches and constrictions stay unresolved.

Each tooth folder includes an editable Blender final-geometry scene, the complete source file-motion inspection rig, separate stock meshes, native-derived fields and its viewer. The Blender final wall geometry is static inspection geometry; the browser is the time-resolved progressive preparation viewer.

Sources

• ACTA DIRECT dataset · CC BY 4.0.
• ACTA DIRECT paper and acquisition description.
• The Root Canal Anatomy Project · realistic anatomies. Morphology and before/after comparison; no reference anatomy copied.
• Micro-CT constriction study and terminal morphology variability. Neither establishes an endpoint in these specimens.

Biological contour revision

The ACTA0115 MB2 coronal connection and two ACTA0062 terminal regions have been rebuilt from the user-selected course and specimen-native section contours. Their variable noncircular shapes blend into retained native walls. Generic uniform-radius connectors are rejected. The three missing regions remain labelled illustrative; original scans and native masks are preserved.

ACTA 0115 · native contour continuity

The unprepared Model 13 apical reconstructions were revised on 20 October 2026 after review of their shape and surface transitions. Changing asymmetric native section contours and local calibre variation replace the smooth taper. Extended overlaps blend into the retained native canal; terminal additions avoid unsupported bulbs or collars. The original 72 µm scan, external root, selected endpoints and MB2 entry course are preserved. These missing regions remain illustrative.

ACTA 0062 · fourth canal

Model 10 now includes the fine fourth course omitted by the earlier single-level component cutoff. All four canals have individual preparation buttons. The fourth uses MicroPath17/.03 → ET20/.04 → ET25/.04. Its native trace disappears before the root surface; the separately authored terminal continuation and internal target remain illustrative. Native scans, the other three selected courses and source instruments are preserved. The presentation is roots upwards, as requested.

Coronal entry · Model 6

The Root B file approach was refitted on 20 October 2026 from 3.45 mm of the native coronal course. Its straight external assembly follows that entrance tangent through the chamber and blends into the deeper canal. File motion, contact, stock and cusp stop were regenerated together. Native canal geometry, terminal passages and apical targets are preserved. This is a teaching construction under Stephen’s first-3–4-mm rule.

Model 12 · fine inner branch

Root A canal 2 follows the fine inner limb identified in the marked views. Its entry follows the dominant course across the first 3.45 mm of native canal. It shares a native isthmus with Root A canal 1. The offered sequence is MicroPath 17/.03 → ET 20/.04 → ET 25/.04. The missing terminal passage is an explicitly illustrative continuation guided by changing native sections. All four preparations remain selectable.

Model 7 · two passes in one broad canal

Select Root A canal 1, then choose Pass 1 (red path) or Pass 2 (green path). Each uses MicroPath17/.03 → ET20/.04 → ET25/.04 → ET30/.04. Red and green identify the paths only. The original ribbon-shaped canal is preserved. Both passes share its apical target; their cumulative preparation and shared canal total remain visible without double counting. Complete both passes to finish this canal.

Model 9 · green-marked native limb

Root B canal 2 follows a fine native limb that converges into the existing terminal region. It uses MicroPath17/.03 → ET20/.04 → ET25/.04. The starting scan and irregular walls are preserved; no extra apical connector was added. The two earlier preparation courses remain available.