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Conservative treatment characterization

Tooth restoration by composite material is highly used for dental problems such as fractures that have brought the tooth to break or as a result of the treatment of caries. The restorative procedure involves placement of composite layer by layer followed by photopolymerization that turns the malleable polymer material in a hard material that binds to the remaining portion of the tooth.

Despite the ability of the dentist the photopolymerization procedure because of the shrinkage of the polymer can induce the formation of voids in the composite and at the interface between dentin and composite itself.

RestorativeLab is a software package designed to obtain information about photopolymerization process and highlight differences pre-and post-treatment within the native 3D tooth structure.

Pre – post structures overlapping

The first μCT acquisition (coloured in violet) shows the incisive tooth after preparation of a cavity to simulate the caries removal. The second acquisition (coloured in gold) was obtained as a result of the composite material application after the photopolymerization process.

If the two structures are not coincident the orientation of one of the two has to be changed, to obtain the best overlapping between the pre and post structure.

Characterization of conservative treatment

The structure, before application of adhesive composite (top row), is represented in white. The bottom row shows the overlapping between the native tooth, with cavity, and the tooth after conservative treatment. The adhesive composite is in green and red zones are part of the volume within the native structure, that changed during the shrinking of the composite.

Direct comparison of pre and post structures is used to distinguish among four different cases.

  • The voxels in black belong to native tooth in both pre- and post- structure
  • The voxels in white belong to the empty space again in both structure
  • The dark grey voxels correspond to the empty space in the pre-structure that was filled by the material.
  • The light grey voxels outlines zones where the native tooth in the pre- structure become empty space in the post treatment structure. This occurrence suggests that void spaces, or defects, are created by the application of the composite material and are somehow related to the shrinking of the polymer.

The images provide the evidence of the presence of an internal crack after application of the adhesive material. Voids inside the composite or at the interface between dentin and composite are white. There are some new voids near the interface (light grey) caused by dentin fragments which were pried following the composite adhesion and photopolymerization.