The document discusses a study that evaluated root canal preparation in flattened root canals of mandibular incisors treated with either rotary instruments or the Self-Adjusting File (SAF) using micro-computed tomography analysis. Forty teeth were instrumented, half with rotary files and half with SAF. The SAF resulted in a more homogeneous preparation of the root canal walls compared to rotary instruments, particularly in the coronal third of the canal where it achieved significantly higher increases in volume and area as well as a higher percentage of prepared walls. The SAF was able to better prepare flattened root canals compared to rotary instrumentation.

1. Thank you very much. It is an honor to be here with you today. I would like to thank
SkyScan for this invitation and to the University of São Paulo in the person of Prof.
Manoel for the oportunity to be here.
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2. A tooth is basically made up of two parts: the crown and the root. Different tissues
make up each tooth. The enamel, the dentin, that supports the enamel, and the pulp
that is a soft tissue located within a tooth, in a place called pulp cavity that is divided
into root canal and pulp chamber.
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3. Root canal treatment is a dental procedure which is undertaken to treat the infected
pulp of a tooth. The ultimate goal of root canal preparation is to remove the inner
layer of the dentin while allowing an irrigant solution to reach the entire length of the
root canal.
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4. To achieved this goal, different shaping techniques and instruments are available.
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5. In the last 15 years, root canal preparation with rotary instruments has become
popular.
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6. Although many technical advances have been made in endodontics, canal
preparation is still adversely influenced by the highly variable anatomy, especially in
oval, flat, or curved root canals
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7. In flattened canals, rotary files have failed to perform adequate cleaning and shaping
leaving untouched fins or recesses on the buccal and/or lingual aspects of the bore
created by the instrument.
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8. Recently, The Self-Adjusting File has been devised with the purpose of sidestepping
some of the limitations of rotary instruments.
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9. The SAF is a hollow file designed as a compressible pointed cylinder composed of a
thin nickel-titanium lattice. During its operation, the file is designed to adapt itself
three-dimensionally to the shape of the root canal.
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10. The purpose of this study was to evaluate the root canal preparation in flattened root
canals of mandibular incisors treated with either rotary or SAF, using three-
dimensional µCT analysis.
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11. Forty single-rooted human mandibular incisor teeth were used. Before experimental
procedure, each specimen was vertically positioned on a metal holder in the centre
of the stage and scanned in a desktop X-ray microfocus CT scanner SkyScan 1174v2
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12. Then, half of the sample was instrumented using rotary intruments and the other half
using Self Adjusting File
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13. Then, all sample was re-scanned using the same initial parameters.
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14. Images were reconstructed from the apex to the level of the cementoenamel
junction (NRecon v1.6.1.5; SkyScan) providing axial cross sections of the inner
structure of the samples. For each tooth, evaluation was done for the full canal length
in approximately 400 slices per specimen
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15. CTAn v1.10.1.0 software (Skyscan) was used for three-dimensional analysis of volume
and surface area. Increases of all analyzed parameters were calculated by subtracting
the scores for the treated canals from those recorded for the untreated counterparts
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16. OnDemand 3D software (Cybermed Inc., Irvine, CA, USA) was used for the analysis of
the fifteen superimposed cross-sections images of each specimen (n=300 per group)
regarding the percentage of instrumented and non-instrumented walls. The root
canal preparation was classified into two categories: (a) cross-section in which the
whole perimeter or almost all perimeter was treated (80% or more of the perimeter
treated) and (b) cross-section in which most of the perimeter was untreated (20% or
less of the perimeter treated).
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17. OnDemand 3D software (Cybermed Inc., Irvine, CA, USA) was used for the analysis of
the fifteen superimposed cross-sections images of each specimen (n=300 per group)
regarding the percentage of instrumented and non-instrumented walls. The root
canal preparation was classified into two categories: (a) cross-section in which the
whole perimeter or almost all perimeter was treated (80% or more of the perimeter
treated) and (b) cross-section in which most of the perimeter was untreated (20% or
less of the perimeter treated).
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18. OnDemand 3D software (Cybermed Inc., Irvine, CA, USA) was used for the analysis of
the fifteen superimposed cross-sections images of each specimen (n=300 per group)
regarding the percentage of instrumented and non-instrumented walls. The root
canal preparation was classified into two categories: (a) cross-section in which the
whole perimeter or almost all perimeter was treated (80% or more of the perimeter
treated) and (b) cross-section in which most of the perimeter was untreated (20% or
less of the perimeter treated).
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19. CTVol software (Skyscan) was used for three-dimensional visualization and qualitative
evaluation of the pre- and post-instrumented canals. Color-coded root canal models
(green indicates preoperative, red postoperative canal surfaces) enabled qualitative
comparison of the matched root canals before and after shaping.
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20. Despite the mean increase of the canal volume was significantly higher with SAF (1.47
± 0.67 mm3) than rotary instrumentation (2.32 ± 1.0 mm3) (P = .04), the same was not
observed with the surface area (P > .05). Within group, volume and surface area
showed significant statistical difference between pre- and postoperative results (P <
.05).
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21. The percentage of mechanically untreated canal walls at coronal, middle and apical
third, calculated by using superimposed µCT data sets, were 8%, 35%, and 15% for
SAF group and 38%, 56%, and 25% for rotary group. There was statistically significant
difference between the instrumented and the non-instrumented walls between
groups at coronal and middle thirds
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22. Cross sections and tridimensional analysis showed that the use of SAF resulted in a
more homogenous preparation of the root canal walls compared to rotary
instruments.
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25. It can be concluded that in the coronal third of the canal, mean increases of area and
volume of the root canal, as well as the percentage of prepared walls, were
significantly higher with SAF than rotary instrumentation. By using SAF instrument,
flat-oval-shaped canals of mandibular incisors were homogenously and
circumferentially prepared.
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