Master's Thesis

Classification of Clinical Dental Attributes from 3D Scans

Final Thesis 16.67 MB Appendix 3.21 MB

Author of thesis: Ing. Juraj Dedič

Acad. year: 2025/2026

Supervisor: Ing. Tibor Kubík

Reviewer: doc. Ing. Michal Španěl, Ph.D.

Abstract:

This master's thesis addresses the classification of clinical dental attributes from 3D intraoral scans. An experimental case-level point-cloud dataset is prepared from 3D dental models and paired with the provided clinical labels for five attributes: dentition type, dental crowding, malocclusion class, overbite, and overjet. The work compares PointTransformerV3, PointMamba, and PointNet++ in a multi-task formulation and evaluates them using accuracy, macro-F1, and per-class metrics. The strongest reported PointTransformerV3 test checkpoint reaches 76.6% average accuracy and 0.635 macro-F1. The thesis also includes visual explainability analysis using GradCAM, input-gradient saliency, and PCA feature colouring mapped back onto the original 3D mesh surfaces.

Keywords:

3D intraoral scans, point clouds, dental attribute classification, orthodontics, malocclusion, dental crowding, multi-task learning, Point Transformer V3, explainable artificial intelligence

Date of defence

24.06.2026

Result of the defence

Defended (thesis was successfully defended)

znamkaBznamka

Grading

B

Process of defence

Student nejprve prezentoval výsledky, kterých dosáhl v rámci své práce. Komise se poté seznámila s hodnocením vedoucího a posudkem oponenta práce. Student následně odpověděl na otázky oponenta a na další otázky přítomných. Komise se na základě posudku oponenta, hodnocení vedoucího, přednesené prezentace a odpovědí studenta na položené otázky rozhodla práci hodnotit stupněm B.

Topics for thesis defence

  1. Is the point cloud scale normalisation to a unit sphere proper? Is it also used in other works like Borghi et al. [2]? Can it negatively affect the model's ability to classify dentition ("baby" teeth vs "adult" teeth) or crowding (spacing measured in mm)?
  2. How do you select samples for a training batch? Is the selection fully random, or do you apply any strategy to balance classes?
  3. Is my understanding correct that, in the single-task formulation, you trained a backbone model with a single classification head separately? Have you considered training all “single-task heads” with a shared backbone, with only one head trained at a time as you switch tasks?
  4. Figure 6.4 - How do you interpret that aggregate GradCAM exhibits differences between left and right jaw parts? This asymmetry is most visible in the malocclusion and dentition classification.
  5. Zkoušel jste provádět "flipping"?

Language of thesis

English

Faculty

Department

Study programme

Information Technology and Artificial Intelligence (MITAI)

Specialization

Computer Vision (NVIZ)

Composition of Committee

prof. Ing. Adam Herout, Ph.D. (předseda)
prof. Ing. Martin Čadík, Ph.D. (místopředseda)
doc. RNDr. Milan Češka, Ph.D. (člen)
prof. Dr. Ing. Pavel Zemčík, dr. h. c. (člen)
Ing. David Bařina, Ph.D. (člen)
Ing. Tomáš Milet, Ph.D. (člen)

Supervisor’s report
Ing. Tibor Kubík

The student demonstrated that he is capable of training and systematically evaluating existing 3D machine learning models in a complex setting such as the medical domain. His results provide interesting incremental findings for the actively researched field of 3D dental shape analysis. He also showed a good level of independence.

Evaluation criteria Verbal classification
Informace k zadání

The analysis of orthodontic anomalies in 3D dental scans is a challenging task with clear practical relevance. An automatic classification model could assist clinicians in better understanding planned cases and could also provide useful structured information for other algorithms during 3D digital planning. The difficulty of the task comes from two main aspects: the non-trivial application of deep learning methods to 3D shapes, and the common challenges of medical datasets, such as limited data availability and class imbalance.

The goal of the thesis was to experimentally evaluate several general-purpose frameworks for 3D shape classification and compare their performance under different settings. An additional goal was to explore the explainability of the predictions, so that clinicians could obtain visual feedback indicating which parts of the 3D model contributed to the model’s decision. Mr. Dedič fulfilled the assignment, and I am satisfied with the achieved results.

Aktivita při dokončování

The work was completed ahead of schedule. My minor comments on the text were incorporated into the final version of the technical report.

Publikační činnost, ocenění

Not known.

Práce s literaturou

The student was given an initial set of scientific articles covering recent deep learning frameworks for 3D shape analysis. He explored several alternatives to the methods originally suggested. This led, for example, to experiments with models such as PointMamba, which methodologically complemented the other evaluated approaches well.

Aktivita během řešení, konzultace, komunikace

The student consulted the work several times. The meetings usually focused on presenting the completed parts of the work and validating the next steps. The student was prepared for the meetings.

A higher frequency of consultations might have led to even more interesting results, as the student clearly has strong potential. Nevertheless, the collaboration was smooth, and the agreed direction of the work was followed.

Points proposed by supervisor: 80

Grade proposed by supervisor: B

Mr Dedič presents a respectable amount of high-quality work and experiments conducted with the latest models for 3D point cloud classification. He achieved good results, close to state-of-the-art on dental attribute classification tasks. His experimental design and technical solution demonstrate attention to detail and a strong theoretical understanding of the field. If he had taken one more small step forward and implemented some of the ideas mentioned as future work, such as labelling upper and lower jaw points or SSL pre-training using large, unannotated IOS datasets, my rating would be excellent.

Evaluation criteria Verbal classification Points
Rozsah splnění požadavků zadání

Evaluation level: zadání splněno

All required points of the assignment were met exhaustively. The student compared three state-of-the-art models for classifying 3D point clouds, performed an extensive ablation study to optimise their tuning and interpret the properties of various variants from the perspective of the selected classification tasks, and attempted to visually interpret the results using three XAI methods.

Rozsah technické zprávy

Evaluation level: je v obvyklém rozmezí

The scope of the overview of state-of-the-art methods is ideal. It clearly highlights the main differences between the methods and avoids unnecessary details. The most extensive part of the technical report is the author's own work: the definition of classification tasks, the experimental design, and, especially, a very detailed evaluation of all experiments.

Prezentační úroveň technické zprávy

The technical report is well written, and it is clear what the author experimented with and how. As a reader, I would appreciate a few changes:

  • Chapter 5 mixes specific implementation details and crucial experimental design. I would find it more understandable to formulate experimental questions (Chapter 5.7) right at the beginning in a separate chapter together with the overall overviews of ​​the solution (Figures 5.1-5.4).
  • The number of experiments is impressive; however, the sections devoted to the ablation study are difficult to read, making it hard to keep track of crucial findings. It would be appropriate to summarise only the most interesting findings in the report (i.e. the resulting hyperparameter settings and pipeline setup) and put detailed tables and comments in the appendix. It is unnecessary to list numbers in tables and repeat them in the text.
70
Formální úprava technické zprávy

The typographical and linguistic aspects of the work are very good. The text contains nice figures. Occasionally, it would be useful to structure the text into bullet points.

85
Práce s literaturou

The study literature is broad, covering the necessary knowledge and state-of-the-art approaches. The author draws heavily on scientific papers.

95
Realizační výstup

The technical and programming solution is high-level, and the careful design is evident. This is a relatively large Python project; the code repository is well-structured, all code is commented, and the training pipeline is designed so the author can easily experiment with different backbones.

90
Využitelnost výsledků

The work extends the results of other authors and provides additional insights into the accuracy of dental attribute classification using state-of-the-art point cloud models. An interesting aspect of the work is the use of various XAI techniques to interpret model behaviour, an area that remains underexplored in 3D shape analysis. It will be possible to build on the results in the future.

Náročnost zadání

Evaluation level: obtížnější zadání

I consider the topic of 3D shape analysis using deep learning, and in this case, explainable artificial intelligence (XAI) techniques, to be more difficult. Working with 3D data is specific and more demanding in terms of dataset preparation and output visualisation. For a task such as the classification of clinical dental intraoral scans, it does not allow the use of pre-trained models, as is the case with image data analysis.

Topics for thesis defence:
  1. Is the point cloud scale normalisation to a unit sphere proper? Is it also used in other works like Borghi et al. [2]? Can it negatively affect the model's ability to classify dentition ("baby" teeth vs "adult" teeth) or crowding (spacing measured in mm)?
  2. Is my understanding correct that, in the single-task formulation, you trained a backbone model with a single classification head separately? Have you considered training all “single-task heads” with a shared backbone, with only one head trained at a time as you switch tasks?
  3. How do you select samples for a training batch? Is the selection fully random, or do you apply any strategy to balance classes?
  4. Figure 6.4 - How do you interpret that aggregate GradCAM exhibits differences between left and right jaw parts? This asymmetry is most visible in the malocclusion and dentition classification.
Points proposed by reviewer: 85

Grade proposed by reviewer: B

Responsibility: Mgr. et Mgr. Hana Odstrčilová