Skip Navigation


The European Journal of Orthodontics Advance Access originally published online on October 11, 2006
The European Journal of Orthodontics 2007 29(1):26-30; doi:10.1093/ejo/cji069
This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
29/1/26    most recent
cji069v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Marini, I.
Right arrow Articles by Salemi, G.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Marini, I.
Right arrow Articles by Salemi, G.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2006. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oxfordjournals.org.

A photogrammetric technique for the analysis of palatal three-dimensional changes during rapid maxillary expansion

Ida Marini*, Giulio Alessandri Bonetti*, Vladimiro Achilli** and Giuseppe Salemi**

* Department of Periodontology, School of Dentistry, University of Bologna
** Department of Architecture, Urban Planning and Surveying, Faculty of Engineering, University of Padua, Italy

Address for correspondence Dr. Ida Marini, Via S. Angela Merici, 60, I-25123 Brescia, Italy, E-mail: idmarini{at}tin.it


   Summary
Top
 Summary
Introduction
 Subjects and methods
 Results
 Discussion
 Conclusion
 ACKNOWLEDGMENTS
 References
 
The aim of this study was to assess, by a digital photogrammetric technique, the relative dimensional changes before and after rapid maxillary expansion (RME). The transverse diameters and volumetric variations of the palate were measured by photogrammetry on study casts taken at three different phases of therapy: at the beginning of treatment (T1), on removal of the rapid expander, after expansion and retention for three months (T2), and six months after appliance removal (T3).

The sample consisted of 30 children, (age range 7–8 years), all with a crossbite; 15 were angle Class I, six Class II and nine Class III. They were treated with an acrylic splint expander with two turns per day until the maxillary molar palatal cusps were in contact with the mandibular molar buccal cusps. The RME device was used as a passive retainer for three months, after which it was removed. During the following six months, no retention was used and no orthodontic treatment was undertaken.

The findings demonstrated a significant relapse (P < 0.001) in the dental transverse diameter in all patients six months after appliance removal, although the palatal volume remained stable.


   Introduction
Top
 Summary
 Introduction
Subjects and methods
 Results
 Discussion
 Conclusion
 ACKNOWLEDGMENTS
 References
 
Rapid maxillary expansion (RME) as a means to correct a deficiency of the transverse dimension of the maxilla has recently become more routine (Haas, 1980Go; McNamara and Brudon, 2001Go).

Although the skeletal and dental effects of this therapy have been demonstrated (Haas, 1970Go; Isaacson et al., 1964Go; Zimring and Isaacson, 1965Go; Wertz, 1970Go; Wertz and Dreskin, 1977Go; Melsen and Melsen, 1982Go) there seems to be no agreement among researchers on the real efficiency or long-term stability of RME (Haas, 1980Go; Stockfish, 1969; Timms, 1976Go; Brust and McNamara, 1995Go; Adkins et al., 1990Go; Franchi et al., 1998Go; Cameron et al., 2002Go). The studies were limited by the difficulty in separating the effects of RME from those of subsequent orthodontic treatment; differences in time and the type of retention after RME removal must also be taken into account. Furthermore, treatment stability was evaluated with callipers and compasses, etc, which register measurements in only one plane and therefore do not provide precise three-dimensional (3D) measurements.

The aim of this study was to investigate the effect of RME on 3D change of the palatal vault by evaluating the changes in palatal shape and volume immediately after expansion and six months after completion and removal of the appliance.


   Subjects and methods
Top
 Summary
 Introduction
 Subjects and methods
Results
 Discussion
 Conclusion
 ACKNOWLEDGMENTS
 References
 
The sample consisted of 30 Caucasian children in the mixed dentition stage, (14 boys, 16 girls; age range 7 to 8 years, mean 7.5 years). All subjects had crossbites (12 unilateral, 14 bilateral) due to a narrow maxilla; 15 were Angle Class I, six Class II and nine Class III. Sixteen had a normal anterior bite, three a deep bite, and 11 an open bite.

An acrylic splint expander was bonded in each patient. The Hyrax screw was activated one-quarter turn (0.25 mm) twice a day until the maxillary molar palatal cusps were in contact with the lower mandibular buccal cusps. After expansion, the appliance was left in situ for three months and then removed. During the following six months, no retention or additional orthodontic treatment was carried out.

Impressions were taken and casts were made at the start of the treatment (T1), immediately after RME removal (T2), and six months after RME removal, (nine months since the beginning of the study) (T3).

This study was based on biostereometric analysis of the casts at each of the phases using a digital photogrammetric technique (Krauss, 1993Go; Berkowitz and Pruzansky, 1968Go). This approach, based on the model creation of an object from two homologous photographic acquisitions, allowed 3D reproduction, accurate dimensional measurements, and a precise evaluation of shape. The operative phases of a digital photogrammetric survey are: (1) digital photographic acquisition, (2) optical 3D model creation, and (3) graphic rendering.

Digital photogrammetry acquisition of a dental cast allows the definition of a 3D model with the characteristics of the starting object, where the height differences among all visible points can be estimated. The resulting 3D digital cast is metrically accurate and allows measurement of areas, volumes and angles. The digital camera used was a Digital Nikon DCS (Nikon Corporation, Tokyo, Japan), with a 29.5 mm focus at 700 mm distance. The image resolution was 1524 x 1012 pixel/cm with a 12-bit colour range.

The final part of the study was carried out using modified stereovision software (Stereo View 300, Leica Geosystems AG, Heerbrugg, Switzerland). Special glasses were connected to an infrared system to evaluate the Z dimension. The transverse diameter in the 30 subjects also evaluated, whereas the volumetric variations were computed for a subset of 15 subjects. The following transverse diameters were measured: the distances between the first permanent molars (16–26), the second primary molars (55–65), the first primary molars (54–64), and the primary canines (53–63).

The points selected to calculate the diameters on the plaster models were the upper part of the most lingual points at the gingival margins of the teeth (Adkins et al., 1990Go).

The contour of the reference surface for the palatal volume was obtained by connecting the extremes of the transversal diameters, the rear distal of the permanent molars, and the upper part of the gingival margins of the incisors (Figure 1).


Figure 1
View larger version (154K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 1 The reference surface of the palatal volume obtained by connecting the extremes of the transverse diameters, the rear distal of the permanent molars, and the upper part of the gingival margins of the incisors.

 
The reference surface for evaluating the palatal volume was obtained by using a Delaunay triangulation scheme connecting the points. The base area was delineated by the gingival margins and by the segment connecting the distal aspect of the last permanent molars. The palatal volume was then defined as the volume between the reference surface and the palatal surface and was calculated as the sum of small solid parallelepipeds, each having an area of 0.25 mm2. The height was equal to the distance between the reference and palatal surfaces.

A regular grid of the palatal vault, with 1 mm steps, was then generated. The grid was automatically obtained by the software, using a matching function based on the break lines.

The palatal vault surface was obtained using a Delaunay triangulation, and the palatal volume computed (Figure 2). The base area was divided into 0.5 x 0.5 mm sub-areas and the distance between the reference and the palatal surfaces measured to determine the centre of each area. The absolute orientation of the model was metrically accurate to 0.5 mm, with respect to the selected fixed points on the grid.


Figure 2
View larger version (53K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 2 The palatal vault surface obtained using a Delaunay triangulation.

 

Statistical analysis

Statistical analysis was carried out using F and ANOVA tests for each of the five variables. For each data series a sphericity test using the Mauchly criterion was also performed to check the appropriateness of an unadjusted univariate F test for the within-subject effects (Glantz, 2003Go). Furthermore, multiple comparisons were performed to evaluate the differences between T2 and T1, T3 and T1, and T3 and T2.


   Results
Top
 Summary
 Introduction
 Subjects and methods
 Results
Discussion
 Conclusion
 ACKNOWLEDGMENTS
 References
 
The recordings at T1, T2 and T3 showed the variations in palatal transverse diameter and provide information relating to the palatal surface depth at those times (Figure 3).


Figure 3
View larger version (51K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 3 Depth of the palatal surface represented by false colour contour lines at (a) the beginning of treatment (T1), (b) the end of expansion (T2) and (c) six months after removal of the rapid maxillary expansion appliance (T3) shown at the same scale. Dark blue = 0 mm; red = 18 mm and upwards.

 
The results concerning the transverse diameters are shown in Table 1 and the data from the descriptive statistics in Tables 2 and 3. All tests confirmed the hypothesis that the measurements at T2 and T3 were significantly different from those at the start of treatment. The confidence interval also appeared to be small, the narrowest interval of change being found for the second primary molars (between 2.8 and 7.3 per cent), and the largest interval for the variable volumes (between 2.2 and 12 per cent); in this case the omission of one ‘unusual’ case lowered the interval to between 2.3 and 8.3 per cent. The same finding was confirmed for the variables second primary molars and volume.


View this table:
[in this window]
[in a new window]

  		Table 1 Crossbite, Angle classification and transverse diameter for each patient.

 

View this table:
[in this window]
[in a new window]

  		Table 2 Multiple comparison between phases T2–T1, T3–T1, and T3–T2 for molars, canines and volume.

 

View this table:
[in this window]
[in a new window]

  		Table 3 Multiple comparison between F test results for molars, canines and volume.

 
The rapid expansion procedure had a percentage variation at the permanent molar, second primary molar, and first primary molar of between 10 and 20 per cent in 18 patients. In eight cases this was higher than 20 per cent, and in only one case was it lower than 10 per cent.

For the primary canine there was a low percentage variation of 10 per cent in all the patients.


   Discussion
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
Conclusion
 ACKNOWLEDGMENTS
 References
 
Although experimental research has been carried out to verify the long-term stability of RME (Haas, 1980Go; Stockfisch, 1969Go; Timms, 1976Go; Brust and McNamara, 1995Go; Cameron et al., 2002Go) all the studies had limitations. Some of them were essentially case reports, while others included non-homogeneous samples and had significant differences in retention time. The main limitation was in the differentiation of the effects of RME from the differences in time and retention type after RME. Studies including long-term controls compared post-expansion parameters with those following the completion of orthodontic therapy; the data cannot therefore be considered as a reflection of the effects of expansion alone, but of the entire orthodontic therapy plus growth (Haas, 1980Go; Stockfisch, 1969Go; Timms, 1976Go; Brust and McNamara, 1995Go; Adkins et al., 1990Go; Krebs, 1964Go).

Methodological errors were discussed by Brust and McNamara (1995)Go who compared data obtained from large homogeneous samples using RME with those of a control group. This evaluation was made on dental casts at the beginning of expansion, immediately after expansion, at the time of first premolar eruption, and immediately before final comprehensive orthodontic treatment. Unfortunately evaluation of relapse is difficult since retention (with a stabilization device) was used for a significant time after RME. In fact, after expansion, the device was left in place for five months, followed by the application of a palatal plate for an indefinite period of time and, furthermore, the insertion of a transpalatal bar before the loss of the primary second molars. In contrast, the subjects in the present study did not receive any additional orthodontic treatment after removal of the RME device. Palatal expansion was carried out as interceptive orthodontic therapy, hence it was possible to stop treatment and await exfoliation of the primary teeth before starting comprehensive orthodontic therapy. Although the sample was small it was homogeneous for age, dentition, type of appliance, clinical procedure and time of retention.

A standard control group was not used because in this age range there is no demonstrated change in transpalatal arch width (Spillane and McNamara, 1989Go; Ngan et al., 1996Go; McNamara, 1999Go).

Analysis of data relative to palatal widths indicated a higher percentage of relapse in this preliminary study compared with that in the literature. The percentage relapse has been reported variously as 0 (Haas, 1980Go), 10–15 (Brust and McNamara, 1995Go), and 25–30 (Stockfish, 1969) per cent. Only Timms (1976)Go reported a percentage relapse similar to that found in the present study. All these investigations were limited because of the difficulty in separating the effects of the orthodontic treatment that all the patients underwent from the RME phase. In the present study patients were treated with RME only.

RME seems to be more stable in the anterior than in the posterior region. The greater increase in the transverse dimension of the anterior maxilla could be caused by the retention period of RME. Three months are necessary to allow normal histology of the suture to be re-established (Starnbach and Cleall, 1964Go; Cleall et al., 1965Go).

Analysis of the data relative to palatal volume showed a different trend to that of width. In fact, in all subjects there was some (non-significant) relapse in the post-retention phase. There may be a correlation between the differences in the post-retention phase.

Further research on a larger number of patients is in progress to validate the present findings.


   Conclusion
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
 Conclusion
ACKNOWLEDGMENTS
 References
 
The findings of this investigation show the effects of RME in patients who underwent treatment without any subsequent retention or fixed appliances. In all patients there was an increase in palatal volume and a change was observed in the morphology of the palate. The palatal vault became more symmetrically harmonious, wider, and less deeply arched in all subjects.


   ACKNOWLEDGMENTS
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
 Conclusion
 ACKNOWLEDGMENTS
References
 
The authors would like to thank Dr Paolo Antonelli for his help with the statistical analysis, and Dr Eve Marie Box for editing the manuscript.


   References
Top
 Summary
 Introduction
 Subjects and methods
 Results
 Discussion
 Conclusion
 ACKNOWLEDGMENTS
 References
 

    Adkins MD, Nanda RS, Currier GF. (1990) Arch perimeter changes on rapid palatal expansion. American Journal of Orthodontics and Dentofacial Orthopedics 97:194–199.[CrossRef][Web of Science][Medline]

    Berkowitz S and Pruzansky S. (1968) Stereophotogrammetry of serial casts of cleft palate. The Angle Orthodontist 38:136–149.[Web of Science][Medline]

    Brust EW and McNamara JA Jr. (1995) Arch dimensional changes concurrent with expansion in mixed dentition patients. In Trotman C and McNamara JA Jr (Eds.). Orthodontic treatment: outcome and effectiveness(Ann Arbor, Monograph No. 30, Craniofacial Growth Series, Center for Human Growth and Development, University of Michigan) pp. 201–212.

    Cameron CC, Franchi L, Baccetti T, McNamara JA Jr. (2002) Long-term effects of rapid maxillary expansion: a postero-anterior cephalometric evaluaton. American Journal of Orthodontics and Dentofacial Orthopedics 121:129–135.[CrossRef][Web of Science][Medline]

    Cleall JF, Bayne DI, Posen JM, Subtelny JD. (1965) Expansion of the midpalatal suture in the monkey. The Angle Orthodontist 35:23–35.[Medline]

    Franchi L, Baccetti T, McNamara JA Jr. (1998) Shape-coordinate analysis of skeletal changes induced by rapid maxillary expansion and facial mask therapy. American Journal of Orthodontics and Dentofacial Orthopedics 114:418–426.[CrossRef][Web of Science][Medline]

    Glantz SA. (2003) Statistica per Discipline Biomediche(McGraw-Hill, Milano) pp. 316–327.

    Haas AJ. (1970) Palatal expansion: just the beginning of dentofacial orthopedics. American Journal of Orthodontics 57:219–255.[CrossRef][Web of Science][Medline]

    Haas AJ. (1980) Long-term post-treatment evaluation of rapid palatal expansion. The Angle Orthodontist 50:189–217.[Web of Science][Medline]

    Isaacson RJ, Wood JL, Ingram AH. (1964) Forces produced by rapid maxillary expansion. I. Design of force measuring system. The Angle Orthodontist 34:131–142.

    Krauss K. (1993) (Verlag, Photogrammetrie. Bonn)301–312.

    Krebs A. (1964) Midpalatal suture expansion studied by the implant method over a seven-year period. Transactions of the European Orthodontic Society 131–142.

    McNamara JA Jr. (1999) Growth modification: what works, what doesn't, and why. (Ann Arbor, Monograph No. 35, Craniofacial Growth Series, Center for Human Growth and Development, University of Michigan)153–192.

    In McNamara JA Jr and Brudon WL (Eds.). The transverse dimension. In: Orthodontics and dentofacial orthopedics (2001) (Needham Press, Ann Arbour) pp. 104–108.

    Melsen B and Melsen F. (1982) The postnatal development of the palatomaxillary region studied on human autopsy material. American Journal of Orthodontics 82:329–342.[CrossRef][Web of Science][Medline]

    Ngan P, Hägg U, Yiu C, Merwin D, Wei SHY. (1996) Treatment response to maxillary expansion and protraction. European Journal of Orthodontics 18:151–168.[Abstract/Free Full Text]

    Spillane LM and McNamara JA Jr. (1989) Arch width development relative to initial trnspalatal width. Journal of Dental Research 68:374 (Abstract).

    Starnbach HK and Cleall JF. (1964) The effects of splitting the mid-palatal suture on the surrounding structures. American Journal of Orthodontics 50:923–924.[CrossRef]

    Stockfisch J. (1969) Rapid expansion of the maxilla – success and relapse. Transactions of the European Orthodontic Society 469–481.

    Timms DJ. (1976) Long-term follow-up of cases treated by rapid maxillary expansion. Transactions of the European Orthodontic Society 211–215.

    Wertz R. (1970) Skeletal and dental changes accompanying rapid midpalatal suture opening. American Journal of Orthodontics 58:41–66.[CrossRef][Web of Science][Medline]

    Wertz R and Dreskin M. (1977) Midpalatal suture opening: a normative study. American Journal of Orthodontics 71:367–381.[CrossRef][Web of Science][Medline]

    Zimring JF and Isaacson RJ. (1965) Forces produced by rapid maxillary expansion. III. Force present during retention. The Angle Orthodontist 35:178–186.[Medline]


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?



This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
29/1/26    most recent
cji069v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Marini, I.
Right arrow Articles by Salemi, G.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Marini, I.
Right arrow Articles by Salemi, G.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?