Chitubox for dentistry: slicing, supports and parameters

A correctly modelled file may yield a deficient part. Between the STL and the physical object lies a set of decisions — orientation, supports, exposure — whose bearing on the outcome is comparable to that of the modelling itself.

Function of the slicing system

Chitubox sections the file into horizontal layers and generates, for each, the image the display will project. It likewise determines support placement and the exposure time of each layer.

It does not, therefore, constitute an intermediate formality: a substantial proportion of the final result is decided at this stage.

Import and dimensional verification

Once the file has been imported, dimensions should be verified before any other procedure. A unit error at export manifests at this stage as an evident dimensional discrepancy.

It should likewise be verified that the part lies entirely within the build volume and that no isolated fragments persist.

Orientation

This constitutes the decision of greatest bearing. It determines the location of support scarring, the cross-sectional area of each layer and the distribution of peel forces.

Principles

• Inclination. Horizontal placement maximises cross-sectional area, and peel force is proportional to that area. Inclination reduces the area per layer and produces progressive peel.
• Critical surfaces oriented away from supports. The aspect requiring surface quality should remain free of contacts.
• Preservation of seating surfaces. Scarring in the marginal zone or on the internal surface compromises adaptation.
• Elimination of islands. Regions commencing without continuity from the preceding layer require mandatory support; reorientation may eliminate them.

By appliance type

• Crowns and provisional restorations: inclined, with the internal surface preserved.
• Occlusal splints: inclined, with supports on the external aspect.
• Models and biomodels: admit flatter placement and hollowing for resin economy.
• Surgical guides: orientation preserving in full the support surfaces and sleeve housings.

Supports

Automatic generation constitutes a starting point requiring systematic review.

Components

• Contact tip: excessively fine, it fractures during the process; excessively thick, it leaves deep scarring.
• Body: must possess sufficient rigidity to prevent vibration.
• Base: fixation to the platform.

Review following automatic generation

1. Inspection through full rotation to identify unsupported overhanging regions.
2. Removal of supports on critical surfaces by individual selection.
3. Manual addition at fine edges and isolated extremities.
4. Density verification: deficiency produces deformation; excess impedes removal and marks the surface.

Layer parameters

• Layer height. Thinner layers increase definition and process time. Appliances with seating surfaces require fine layers; models admit greater thicknesses.
• Bottom layers and their exposure. Initial layers receive prolonged exposure to ensure adhesion. They constitute the first parameter to review in the event of detachment.
• Normal exposure. The parameter of greatest sensitivity. Excess increases dimensions and occludes fine detail; deficiency produces brittle layers and delamination.

Preview

Prior to export, the layer-by-layer visualisation should be traversed, identifying:

• Layers commencing without support.
• Regions disappearing between layers, indicative of insufficient thickness.
• Adhesion area of the first layer.

Post-processing

Washing, drying, support removal, post-curing and finishing constitute integral phases of manufacture. An appliance with deficient post-curing exhibits inferior mechanical properties irrespective of modelling quality.