articol-gibelli-2017
ORTHODONTICS
QUANTIFICATION OF DENTAL MOVEMENTS IN ORTHODONTIC FOLLOW-UP:
Education
A NOVEL APPROACH BASED ON REGISTRATION OF 3D MODELS OF DENTAL CASTS
Daniele Maria Gibelli1a*, Valentina Pucciarelli1b, Luca Pisoni1c, Francesca M.E. Rusconi1d,
Gianluca Martino Tartaglia1e, Chiarella Sforza1f
1
LAFAS, Laboratory of the Functional Anatomy of the Stomatognathic Apparatus
Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
a
MD, PhD
b
BSc
c
DDS, PhD
d
MD
e
DDS, PhD
f
MD, Head
Received: February 28, 2017
Revised: March 21, 2017
Accepted: April 02, 2017
Published: April 03, 2017
Academic Editor: Mariana Păcurar, DDS, PhD, Professor and Head, University of Medicine and Pharmacy Târgu Mureș, Târgu Mureș, Romania
Cite this article:
Gibelli DM, Pucciarelli V, Pisoni L, Rusconi MEF, Tartaglia GM, Sforza C. Quantification of dental movements in orthodontic follow-up:
a novel approach based on registration of 3D models of dental casts. Stoma Edu J. 2017;4(1):53-59.
ABSTRACT DOI: 10.25241/stomaeduj.2017.4(1).art.5
Introduction: The assessment of dental displacement achieved by orthodontic procedures is important
as it allows operators to verify their clinical treatment and provide adequate adjustments. Modern 3D
image acquisition and elaboration systems may represent a valid method for the three-dimensional
assessment of dental movement.
A novel protocol for the 3D assessment of success of orthodontic therapy is proposed, based on
registration of surfaces.
Methdology: Pairs of casts of the upper dental arch, taken at two different time periods during the
therapy, were chosen for three patients who underwent an orthodontic treatment. Dental casts were
scanned by a 3D laser scanner: for each patient, the two 3D models were then registered according to
the least distance at the area including palatal rugae. The chromatic map of changes within the dental
arch and the RMS (Root Mean Square) point-to-point distance between the dental profiles from the two
models were obtained, and compared with the same data from a control group including five adult
individuals who did not undergo orthodontic therapy. Inter- and intra-observer errors were evaluated
as well.
Results: The novel procedure proved to be repeatable and gave a detailed description of those dental
areas most affected by orthodontic therapy: RMS values seem to be related with the weight of dental
modifications and are far higher than the same parameters computed in the control group.
Conclusion: Further studies are needed in order to explore the possible correlation of RMS value with
clinical parameters linked to the improvement of dental function and aesthetics due to orthodontic
therapy.
Keywords: orthodontics, dental anatomy, laser scanner, RMS (root mean square).
1. Introduction During the past century orthodontic techniques
Orthodontics represents one of the most have been developed in order to obtain more
sensitive fields of research in dentistry, where controlled and faster movement of dental
the technological developments and treatment elements: the main tasks are the improvement
modalities are constantly applied in order of dental occlusion and function, anatomical
to ameliorate anatomical and functional stability and facial aesthetics.1 However, an
characteristics of the dental and facial profile.1 important issue concerns the assessment of
*Corresponding author:
Dr. Daniele Maria Gibelli, MD, PhD, Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Via Mangiagalli 31, I-20133, Milano, Italy
Tel: +39-02-50315399, Fax: +39-02-50315724, e-mail: daniele.gibelli@unimi.it
Stomatology Edu Journal 53
QUANTIFICATION OF DENTAL MOVEMENTS IN ORTHODONTIC FOLLOW-UP:
A NOVEL APPROACH BASED ON REGISTRATION OF 3D MODELS OF DENTAL CASTS
Education
Figure 1. 3D model of a dental cast and selection of Figure 2. Example of registration according to area of
area including palatal rugae. palatal rugae: in white the earlier cast, in light blue the
more recent one.
This procedure is based on the registration of
3D models of casts performed at different times
and registration of surfaces according to the least
point-to-point distance between the respective
surfaces including palatal rugae. Displacement of
molars was then assessed according to possible
movements of their center of mass as calculated
by the software.8 The authors state that the use
of laser scanner provides accurate and reliable
measurements of dental displacement and
might be a valid alternative to cephalometric
radiographs.8 However, the potential advantages
which may derive from 3D-3D superimposition
techniques have still to be explored: for example,
Figure 3. Example of chromatic map according
the previously cited study took only the center
to point-to-point distance between the two 3D
of mass of the tooth into consideration, whereas
models: blue areas are more vestibularized,
techniques of registration may give information
whereas red and yellow areas are less
on the displacement of the entire surface of the
vestibularized in the last cast than in the first one.
dental crown, with a more anatomically adherent
dental displacement due to orthodontic devices evaluation of dental arch modifications. In addition,
for verifying the success of therapy and provide the assessment of the translation of dental center
adequate corrections. Most of these procedures of mass does not take into consideration the entire
are based on X-ray examinations (OPG or range of movements which may affect the 3D dental
cephalometric radiographs.1-3 In the last years surface, such as rotation. A possible alternative is
modern 3D image acquisition systems, already given by modern 3D image elaboration software,
applied to the study of facial modifications caused which are able to provide the registration of 3D
by dental displacement,4 have been used also to surfaces and metrical parameters useful to assess
detect the characteristics of dental movements. the discordance between two models, expressed
The main advantage concerns the chance of in terms of point-to-point mean and RMS (Root
performing a three-dimensional assessment Mean Square) distance. In addition, the same
of dental morphology, more informative than procedure can generate a chromatic sheet able to
the traditional radiological methods which are immediately highlight areas affected by possible
mainly based on the analysis of displacement modifications.9,10 These procedures may represent
of single landmarks or dental two-dimensional a novel point of view for the assessment of dental
profile. In addition metrical measurements taken movements in orthodontic procedures.
on digital models have been widely tested and The present article aims at exposing a protocol for
proved to be reliable, with a high concordance 3D-3D registration of three-dimensional models
with measurements taken directly on the plaster of dental casts for the quantification of dental
models.5-7 However, surprisingly very few studies displacements, based on the calculation of point-
have tested 3D image acquisition systems so to-point distance between two surfaces. This may
far for assessment of orthodontic therapies: an provide additional information for evaluating the
example was provided by Thiruvenkatachari et success of therapy and orthodontic procedures.
al. who first developed a protocol for 3D-3D
superimposition of three-dimensional models of 2. Materials and methods
dental casts acquired through a laser scanner.8 Casts of the upper dental were chosen from three
patients aged from 10 to 15 years who underwent
54 Stoma Edu J. 2017;4(1):53-59. http://www.stomaeduj.com
QUANTIFICATION OF DENTAL MOVEMENTS IN ORTHODONTIC FOLLOW-UP:
A NOVEL APPROACH BASED ON REGISTRATION OF 3D MODELS OF DENTAL CASTS
Education
Figure 4. First patient: on the left, the 3D model from the first cast, showing a malposition of both canines; on the
right, the 3D model from the second cast, after one year and the removal of the second premolar on the right side
and the first on the left side, and consequent realignment of canines.
Figure 5. first patient, chromatic map of modifications of dental surfaces from the left side between the two casts
(on the left vestibular surface, on the right lingual surface): blue areas are more vestibularized in the last cast, vice
versa for the red and yellow areas. Green areas (including the first and second molar) remained unchanged.
an orthodontic treatment in a private dental office: RoI. Mean values consider together positive and
all the patients were IOTN (index of orthodontics negative movements, whereas RMS values are all
treatment needs) ≤3.11 At least two dental casts positive, and can provide a complete evaluation
were available for each patient, taken at different of the variations between two dental scans.
time periods during the therapy. The casts were Together with these quantitative parameters,
scanned by a 3D laser scanner (iSeries, Dental a chromatic map of surface modifications of
Wings©, Montreal, Canada). According to the dental element extracted from the more recent
manufacter, the precision of the instrument is 15 dental cast is provided, with areas coloured in
μm. The 3D models were then elaborated through blue, green and red: the blue areas are more
VAM© software (Canfield Scientific, Inc., Fairfield, vestibularized in the last cast than in the earlier
NJ): first the palatal area including palatal rugae one, whereas the red areas are less vestibularized.
was manually selected in both surfaces (Fig. 1); Green areas do not show modifications between
then the software was requested to automatically the two casts (Fig. 3). To test the method on
register the two models in order to reach the a control group, the same procedure was
minimum point-to-point distance between the applied on the dental arch models of five
selected areas (Fig. 2). Once the registration adult patients aged over 18 years who had
between the two surfaces was reached, the longitudinal records taken but where no dental
dental arch (dental crown surfaces) was manually movements or modifications were expected.
defined on the 3D model obtained from the Time elapsed between the two casts was 1.5 years
more recent cast, and a Region of Interest (RoI) on average. The same procedures of registration,
was obtained. The software was then requested RoI selection, and calculation of RMS values on the
to select the RoI and to calculate the point-to control group was repeated by the same operator
point mean distance and RMS value (Root Mean and by another observer: intra- and inter-observer
Square) of the two models within the selected differences were statistically assessed by Student’s
Stomatology Edu Journal 55
QUANTIFICATION OF DENTAL MOVEMENTS IN ORTHODONTIC FOLLOW-UP:
A NOVEL APPROACH BASED ON REGISTRATION OF 3D MODELS OF DENTAL CASTS
Table 1. Details of dental modifications between the two casts in the three analysed patients, and comparison of
Education correspondent RMS values with the control group.
Average point-
First cast Second cast RMS value
to-point distance
removal of two teeth
malposition of 3 teeth
Patient 1 adjustment of malposition 1.61 mm 1.07 mm
distal rotation of central incisors
realignment of central incisors
Patient 2 malposition of a tooth adjustment of malposition 1.13 mm 0.24 mm
distal rotation of central incisors correction of central incisors
Patient 3 0.98 mm 0.26 mm
right canine in eruption right canine erupted
Control 0.26 mm
- - 0.02 mm
group (SD: 0.06 mm)
Figure 6. Second patient: on the left, the 3D model from the first cast, showing a malposition of the left canine;
on the right, the 3D model from the second cast, after orthodontic therapy.
The technical error of measurement (TEM) was
respectively 6.1% for intra-observer error and
9.6% for inter-observer error.
The first analysed patient was a female aged 12
years. She had a malposition involving both the
canines and the second premolar on the right
side. The orthodontic treatment was based on the
removal of the second premolar on the right side
and the first on the left side and the application
of an orthodontic device, as shown by the second
cast performed after one year (Fig. 4).
The registration and calculation of point-to-point
distances between the two models highlights
Figure 7. Second patient. Chromatic map of the mesial rotation of the lateral incisors and
modifications of dental surfaces between the two realignment of the canine, whereas the molars did
casts: blue areas are more vestibularized in the second not show any appreciable modification (Fig. 5). In
cast, vice versa for the red and yellow areas. Green addition the method was able to verify the novel
areas remained unchanged. orientation of the second premolar; mean RMS
value between the dental profiles from the two 3D
t test (p<0.01). In addition the technical error of scans amounted up to 1.61 mm.
measurement (TEM) was evaluated. The second patient, a female aged 11 years,
showed a malposition of the left canine: the
3. Results application of an orthodontic device was able to
In the group of control subjects, on average produce an adjustment of the canine position, as
the RMS value was 0.26 mm (SD: 0.06). No shown by the second cast taken after four years
statistically significant differences were observed (Fig. 6).
between measurements taken by the same The procedures of registration were able to verify
operator or different observers (p>0.01). the vestibular translation of all dental elements,
56 Stoma Edu J. 2017;4(1):53-59. http://www.stomaeduj.com
QUANTIFICATION OF DENTAL MOVEMENTS IN ORTHODONTIC FOLLOW-UP:
A NOVEL APPROACH BASED ON REGISTRATION OF 3D MODELS OF DENTAL CASTS
Education
Figure 8. Third patient: on the left, the 3D model from the first cast, showing a malposition of the left
canine; on the right, the 3D model from the second cast, after orthodontic therapy.
Interestingly, RMS value increased with the entity
of dental displacement and number of involved
teeth, and was in every case significantly higher
than the same parameter shown by the control
group (Table 1).
4. Discussion
In the last century orthodontics has seen a
progressive update of technologies and clinical
procedures, with an amelioration of dental position,
functionality and aesthetics.1 On the other side, a
parallel issue concerns the assessment of dental
displacement powered by orthodontic therapy,
in order to verify the clinical success and provide
corrections. Surprisingly, although the constant
Figure 9. Third patient, chromatic map of
development of 3D image acquisition systems
modifications of dental surfaces between the two
casts: blue areas are more prominent in the last
has represented a crucial revolution in dentistry,
cast, vice versa for the red and yellow areas. Most their application to the field of orthodontics is still
of modifications can be observed on the left central at the beginning and most of their potentiality
incisor and the left canine. remains to be explored.8 An example is provided
by Thirvenkatachari et al. who proposed a
protocol for the registration of 3D surfaces and
but for the left canine which remained in the same calculation of displacement of the center of
position and was realigned within the dental mass of dental elements.8 This type of approach
arch (Fig. 7). In addition, the method was able to provides a metrical information but is not able
accurate describe the novel presence of brackets to predict the modifications of the entire dental
and wire in the second cast, correctly assessed in surfaces, especially where the movements do not
blue areas (more vestibularized in the second cast consider dental translation. Another important
than in the first one). The average RMS value was aspect concerns the morphological assessment of
1.13 mm. dental movements, which may give an additional
The third patient was an 11 year old girl, who was information for the evaluation of orthodontic
chosen in order to test the detectability of lesser therapies.
dental displacements like pathological overjet The present protocol may represent a proposal
value. In detail, the central incisors were distally for an innovative analysis of dental movements:
rotated, whereas the right canine was still erupting registration is based on the morphology of palatal
with the exposition of the tip. In the second cast, rugae which are stable with time12,13 and have
after orthodontic therapy, the central incisors were been already used as reference point in 3D-3D
medially oriented, whereas the canine crown was superimposition of dental arches.14 The procedure
erupted and in correct occlusion. The second cast is repeatable and provides both morphological
was taken after four years. and metrical analyses of dental movements.
The registration procedure correctly assessed the The chromatic map of dental arches can give
change in orientation of the left central incisor: in information concerning the specific movement
addition, the eruption of the canine was detected of each dental element (rotation, translation or
as well (Fig. 9); RMS value was 0.98 mm. inclination), immediately readable by the operator.
Stomatology Edu Journal 57
QUANTIFICATION OF DENTAL MOVEMENTS IN ORTHODONTIC FOLLOW-UP:
A NOVEL APPROACH BASED ON REGISTRATION OF 3D MODELS OF DENTAL CASTS
On the other side, RMS value provides a reliable to the gain in dental function and aesthetics due to
Education indication concerning the differences between orthodontic therapy. This point is crucial, as it may
the two casts, which seems to be adherent to verify if RMS value in registration of 3D models
the importance of modifications suffered by of dental cases do represent a potentially useful
the patients. In addition, patients who were not clinical parameter for assessing the success of
treated from an orthodontic point of view, show therapy.
lower RMS parameters, and this suggests that the
metrical parameter is strictly linked to the general 5. Conclusions
modification of the 3D position of dental crowns. In conclusion, a novel protocol for the assessment
Some limits should be acknowledged: of dental displacement in orthodontic therapy is
first, modifications highlighted by the proposed: further studies on a large sample of
registration procedures consider also patients may provide additional information about
dental eruption, and therefore are the clinical advantages which may derive from its
partly explained by orthodontic therapy. application.
A possible improvement may consider the
elaboration of each dental element, in order to Acknowledgments
separately consider already erupted elements. The authors declare no conflict of interest related
Another important limit concerns the possible to this study. There are no conflicts of interest and
correlation of RMS with clinical parameters linked no financial interests to be disclosed.
References
1. Ghafari GG. Centennial inventory: the changing face 8. Thiruvenkatachari B, Al-Abdallah M, Akram NC, Sandler J,
of orthodontics. Am J Orthod Dentofacial Orthop. O’Brien K. Measuring 3-dimensional tooth movement with a
2015;148(5):732-739. doi: 10.1016/j.ajodo.2015.08.011. 3-dimensional surface laser scanner. Am J Orthod Dentofacial
[Full text links] [PubMed] Google Scholar (5) Scopus (3) Orthop.2009;135(4):480-485.doi:10.1016/j.ajodo.2007.03.040.
2. Bansal A, Prakash AT, Deepthi, Naik A. A noble, easy and [Full text links] [PubMed] Google Scholar (59) Scopus (25)
conceptual radiographic analysis to assess the type of 9. Gibelli D, De Angelis D, Poppa P, Sforza C, Cattaneo C.
tooth movement (molar distalization). J Clin Diagn Res. An assessment of how facial mimicry can change facial
2015;9(8):ZC22-25. doi: 10.7860/JCDR/2015/13123.6286. morphology: implications for identification. J Forensic
[Free PMC Article] [PubMed] Google Scholar (0) Sci. 2017;62(2):405-410. doi: 10.1111/1556-4029.13295.
3. Jabbal A, Cobourne M, Donaldson N, Bister D. [Full text links] [PubMed] Google Scholar (3) Scopus (0)
Assessing lower incisor inclination change: a 10. Gibelli D, De Angelis D, Poppa P, Sforza C, Cattaneo C. A view
comparison of four cephalometric methods. Eur J to the future: a novel approach for 3D-3D superimposition
Orthod. 2016;38(2):184-189. doi: 10.1093/ejo/cjv027 and quantification of differences for identification from
[Full text links] [Free PMC Article] [PubMed] Google Scholar (4) next-generation video surveillance systems. J Forensic
Scopus (1) Sci. 2017;62(2):457-461. doi: 10.1111/1556-4029.13290.
4. RosatiR,DeMenezesM,daSilvaAM,etal.Stereophotogrammetric [Full text links] [PubMed] Google Scholar (3)
evaluation of tooth-induced labial protrusion. J 11. Brook PH, Shaw WC. The development of an index of orthodontic
Prosthodont. 2014;23(5):347-352. doi: 10.1111/jopr.12135 treatment priority. Eur J Orthod. 1989;11(3):309-320.
[Full text links] [PubMed] Google Scholar (3) Scopus (3) [PubMed] Google Scholar (949) Scopus (481)
5. Kim J, Lagravere MO. Accuracy of Bolton analysis measured in 12. English WR, Summitt JB, Oesterle LJ, Brannon
laser scanned digital models compared with plaster models (gold RB, Morlang WM. Individuality of human palatal
standard) and cone-beam computer tomography images.Korean rugae. J Forensic Sci. 1988;33(3):718-726.
J Orthod. 2016;46(1):13-19. doi: 10.4041/kjod.2016.46.1.13. [PubMed] Google Scholar (153) Scopus (68)
[Full text links] [Free PMC Article] [PubMed] Google Scholar (9) 13. Lysell L. Plicae palatinae trasversae and papilla
6. Kusnoto B, Evans CA. Reliability of a 3D surface incisiva in man; a morphologic and genetic study.
laser scanner for orthodontic applications. Am J Acta Odontol Scand. 1955; (Suppl. 18):5-137.
Orthod Dentofacial Orthop 2002;122(4):342-348. [PubMed] Google Scholar (103)
[Full text links] [PubMed] Google Scholar (219) Scopus (131) 14. Jang I, Tanaka M, Koga Y, et al. A novel method for the
7. Hayashi K, Sachdeva AU, Saitoh S, et al. Assessment assessment of three-dimensional tooth movement
of the accuracy and reliability of new 3-dimensional during orthodontic treatment. Angle Orthod.
scanning device. Am J Orthod Dentofacial Orthop. 2009;79(3):447-453. doi: 10.2319/042308-225.1.
2013;144(4):619-625. doi: 10.1016/j.ajodo.2013.04.021. [Full text links] [PubMed] Google Scholar (59) Scopus (32)
[Full text links] [PubMed] Google Scholar (40) Scopus (15)
Daniele Maria GIBELLI
MD, PhD
Dipartimento di Scienze Biomediche per la Salute
Università degli Studi di Milano
Via Mangiagalli 31, I-20133, Milano, Italy
CV
Daniele Maria Gibelli is a researcher in Human Anatomy in Università degli Studi di Milano (Department of
Biomedical Sciences for Health). His fields of research are the morphological and metrical assessment of
anatomical characteristics of bones and teeth, including the anatomical dimorphism, their modification with
age, ethnic variability and the analysis of individualizing characteristics. He deals also with the analysis of
facial anatomy both in healthy and pathological conditions, for studies concerning the assessment of facial
symmetry, modifications with mimicry and anatomical uniqueness of facial structures.
58 Stoma Edu J. 2017;4(1):53-59. http://www.stomaeduj.com
QUANTIFICATION OF DENTAL MOVEMENTS IN ORTHODONTIC FOLLOW-UP:
A NOVEL APPROACH BASED ON REGISTRATION OF 3D MODELS OF DENTAL CASTS
Questions
Education
Which instruments can be used to obtain a 3D virtual model of dental arches?
q a. Laser scans;
q b. Ultrasounds;
q c. Conventional orthopantomographs;
q d. Bite wing radiographs.
Which kind of modifications can be assessed on 3D virtual model of dental arches?
q a. Dental root reabsorption;
q b. Parodontal alterations;
q c. Dental crown movements;
q d. Temporomandibular disorders.
In the current study we assessed
q a. Three edentulous patients;
q b. Seven patients with deciduous dentition;
q c. Two patients submitted to orthognathic surgery;
q d. Three adolescent patients.
In the current study, we superimposed 3D virtual models of dental arches using
q a. The vestibular surface of anterior teeth;
q b. The palatal area including palatal rugae;
q c. The lingual surface of mandibular incisors;
q d. The occlusal surface of maxillary first molars.
Stomatology Edu Journal 59