Three dimensional biometric guide in determining maxillary tooth position and arch form / Omar Farouq Tawfiq
In complete denture fabrication, when pre-extraction records are lacking, determining the denture teeth positions to where the natural predecessors occupied is essential yet challenging. Although several biometric guides were suggested to position teeth for dentures, none is providing three-di...
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Format: | Thesis |
Published: |
2020
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Online Access: | http://studentsrepo.um.edu.my/12909/4/omar.pdf http://studentsrepo.um.edu.my/12909/ |
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Summary: | In complete denture fabrication, when pre-extraction records are lacking,
determining the denture teeth positions to where the natural predecessors
occupied is essential yet challenging. Although several biometric guides were
suggested to position teeth for dentures, none is providing three-dimensional
(3D) positions of teeth that can be used in the recently developed computer
designed digital dentures. The aim of this study was to develop new biometric
guides to determine the original 3D positions of the maxillary teeth and dental
arch form individualised for each given dentate or edentulous maxillary cast
based on selected intraoral landmarks. The objectives were to investigate the
relationship between measurements of selected maxillary anatomical
landmarks, to verify the accuracy of the relationship equations in predicting
tooth position; to predict teeth positions for edentulous casts; to investigate the
dental-arch curves morphological relationship with HNR-curve and
predictability of dental arch for dentulous casts from HNR-curve.
Ninety-two Malaysian adults (20-35 years old) who had class I dental and
skeletal relationships, well-aligned teeth and minimal attritions were selected
for the study. Maxillary stone-casts were obtained, digitised and standardised.
The points’ 3D Cartesian-coordinates were converted into spherical�coordinates for statistical analyses. The dentate sample (n=92) was subdivided
randomly into control group (n=70) and dentate verification group (n=22). The
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control group was used to investigate linear regressions and functional circular
relationships to generate equations, while the verification group was used to
compare the coordinates of teeth predicted by the relationship equations with
the measured coordinates in each cast of the group using paired t-test. Dental
arch curves and hamular-notch rugae-point curve (HNR-curve) were fitted to
polynomial-fourth-degree equations and compared for shape-similarity using
Z-test (α = 0.05). Then artificial neural network (ANN) was used to generate
dental arch curves by HNR-curves for dentate casts, verify the prediction
accuracy of the method before application on edentulous casts. Thirty-four
maxillary edentulous casts were obtained, digitised, standardised and had the
triangular pyramid landmarks coordinates similar to the dentate casts registered
and used to predict teeth positions. The results showed high correlation
coefficients between the landmarks and teeth positions (0.5 ≤ r ≤ 0.9, p < 0.05).
Fifty-four regression and circular relationship equations were derived to predict
the teeth positions (0.89 ≤ R
2 ≤ 0.998). No significant differences were found
between the existing and predicted coordinates of teeth through the verification
group subjects (p > 0.05). When the arch forms were compared for similarity
with HNR-curve; Z-test values (SD) were 0.894(0.64), 0.705(0.51),
0.382(0.31) for buccal, middle and lingual dental arches respectively. Within
the limitations of this study, predicted teeth positions showed non-significant
difference with the natural teeth positions when verified in new dentate sample.
Furthermore, predicted teeth positions for edentulous sample showed statistical
equivalence with the range of the natural teeth positions in dentate sample.
Additionally, the predicted dental arch forms for verification dentate group
showed no significant difference with the original dental arches. Conclusively,
the maxillary teeth 3D-points together with the dental arch form may suggest
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acceptable guide for digital dental rehabilitation for edentulous patients using
the latest digital denture manufacturing technology based on stable intraoral
anatomical landmarks with strong coefficients.
Keywords: Complete denture, Biometric guides; dental arch form; 3D tooth
position; CAD/CAM complete denture. |
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