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Three-dimensional dental arch and palatal form changes after extraction and nonextraction treatment. Part 2. Palatal volume and height
ORIGINAL ARTICLE
Three-dimensional dental arch and palatal form changes after extraction and nonextraction treatment. Part 2. Palatal volume and height Wolfgang Heiser, MD, DDS,a Andreas Niederwanger, MD,b Beatrix Bancher, MD, DDS,c Gabriele Bittermann, MD, DDS,d Nikolaus Neunteufel, MD, DDS,d and Siegfried Kulmer, MD, DDSe Innsbruck, Austria, and Neumarkt, Italy The purpose of this study was to investigate the changes in palatal volume and palatal height in patients treated with and without premolar extractions. Records were collected at pretreatment, at bracket removal, at the end of retention, and 5 years out of retention. Stone casts were mounted in a SAM 2 articulator with an anatomic face-bow and a central wax record, and measurements were made with a 3-dimensional digitizer. The hypothesis, that orthodontic treatment with premolar extractions changes the palatal form, was verified. Increases in palatal volume and height were demonstrated in the nonextraction group. The extraction group showed a decrease in palatal volume but could compensate for some loss by an increase in volume in the anterior segment. (Am J Orthod Dentofacial Orthop 2004; 126:82-90)
A
t birth, the growth of the maxilla is already accompanied by extension of the sinus maxillaris. The expansion of the maxilla is carried out by apposition and resorption in the area of the thin-walled structures over the roots of the premolars and molars. In contrast to the mandible, the maxilla can increase in width (because of the palatal suture) until the end of the growth period. The growth of the maxilla and the mandible become coordinated1 by the interdigitation of the molars and premolars, incipiently starting at the age of 16 months, when the first deciduous molars move into occlusal contact.1 The teeth take, as a reaction to the cusp fossa mechanism,2 a suitable occlusal position. If necessary, a buccolingual movement, especially in the maxilla, can also be found. As soon as a good intercuspation is obtained, the jaws find the same cusp-fossa relationship whenever the closing movement occurs. The typical occlusal morphology of the teeth and the correct indentation in an Angle Class I occlusion, especially of the first molars, play leading roles in the growth of the face. a
Private practice, Innsbruck, Austria. Clinical instructor, Department of Internal Medicine, University of Innsbruck. c Private practice, Neumarkt, Italy. d Clinical instructor, Universita¨tsklinik fu¨r Zahn-, Mund- und Kieferheilkunde, Innsbruck, Austria. e Chairman, Department of Preventive and Restorative Dentistry, Universita¨tsklinik fu¨r Zahn-, Mund- und Kieferheilkunde. Reprints requests to: DDr Wolfgang Heiser, Dr. Stumpftr. 73, Innsbruck A-6020, Austria; e-mail, [email protected]. Submitted, August 2002; revised and accepted, May 2003. 0889-5406/$30.00 Copyright © 2004 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2003.05.016 b
82
Because of these strong mutual influences, treatment can be successful only if the stomatognathic system is considered in the long term. The changes in tooth position as a result of orthodontic therapy should lead to changes in tongue posture and function.3-16 This should be reflected in a changed palatal volume and height. The purpose of this study was to evaluate 3-dimensionally the treatment and posttreatment changes during growth and treatment in the palatal heights and volumes of patients treated with and without extractions. MATERIAL AND METHODS
All patients had been treated in the private orthodontic practice of the first author (W.H.). The sample was described in part 1 of this study.17 The patients were drawn from (insert copy added to part 1); the only criterion for patient selection was good occlusion at bracket removal (ie, each subject met the 6 keys to normal occlusion18). Neither cephalometric characteristics nor postretention occlusion was considered in the sample selection. The groups were formed before the follow-up examination. The records were collected at 4 times: pretreatment, bracket removal, end of retention, and follow-up. The nonextraction group consisted originally of 25 Class II patients (19 girls, 6 boys; average age, 11 years 4 months) who were treated with fixed appliances (straightwire) without premolar extractions. The follow-up examination was carried out 6.3 years out of
American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 1
Fig 1. Trimmed silicone impression.
retention, and 22 patients (17 women, 5 men; average age, 20 years 7 months) returned for it. The mean irregularity index19 was 5.1 before orthodontic treatment. The average active treatment time was 1 year 9 months, and the average retention period was 1 year 3 months. The extraction group consisted originally of 24 patients (18 girls, 6 boys; average age, 13 years 7 months) who were treated with fixed appliances (straightwire) and premolar (first or second) extractions. Twenty patients (16 women, 4 men; average age, 21 years 10 months) were examined at follow-up. The mean irregularity index was 5.8 before orthodontic treatment. The average active treatment time was 1 year 9 months, and the average retention period was 1 year 10 months. The follow-up examination was carried out 4 years 8 months out of retention. Recording palatal volume and height
Accurate alginate mandibular and maxillary impressions were taken for each patient at pretreatment, bracket removal, the end of retention, and follow-up. The impressions were poured in stone, and the maxillary model was provided with a split-cast.20 With the aid of an anatomic face-bow, the maxillary model was mounted skull-related onto a semi-adjustable articulator (SAM 2, SAM Pra¨ zisionstechnik, Gauting, Germany). Then the mandibular model was mounted joint-related to the maxillary model according to a central wax record.21 In all cases, cephalometric and panoramic radiographs were taken. The records were made according to the rules of the Austrian Dental Society.22 From all maxillary stone casts, 2 silicone impres-
Heiser et al 83
Fig 2. U-shaped aluminum guide track with silicone impression. Inserted knife cuts along marked line.
Fig 3. Demarcations of silicone sections A through E.
sions were made. One was used to construct crosssections, and the other to obtain longitudinal sections. The method to evaluate the palatal volume was reported by Hammedinger.23 The silicone impression material was brought into the palatal cavity limited by the palate, the teeth, and the occlusal plane. The occlusal plane was found by pushing the plaster model filled with soft silicone material down to a glass plate until the glass plate touched the incisal edges of the maxillary central incisors and the mesiopalatal cusps of the first molars. Then the hardened silicone impression was taken from the model. The silicone impression was trimmed with a scalpel along the incisal edges of the central and lateral incisors to the cusps of the canines, to the various contact points and the palatal cusps of the premolars and molars (Fig 1). To make exact sections, a special cutting device
84 Heiser et al
Table I.
Cube weights
Cube no. Weight (g)
Table II.
American Journal of Orthodontics and Dentofacial Orthopedics July 2004
1 18.87
2 19.09
3 18.92
4 18.92
5 18.92
6 18.77
7 18.64
8 18.67
9 18.67
10 18.60
Weight of 6 specimens of silicone sections A to E, in grams
1 2 3 4 5 6 Standard deviation
A
B
C
D
E
Sum A-E
A⫹B⫹C⫹D⫹E weighed
3.77 3.71 4.05 3.66 3.78 3.58 4.32%
4.12 3.83 3.75 4.14 4.00 4.01 3.92%
4.99 5.17 5.02 5.62 5.36 5.10 4.22%
10.51 10.36 10.23 10.58 11.29 10.60 3.48%
8.20 8.72 9.52 9.01 8.59 8.27 5.67%
31.57 31.78 32.55 32.98 33.01 31.54 2.15%
31.59 31.79 32.57 33.01 33.02 31.56 2.14%
was developed, consisting of a U-shaped guide track (length, 15 cm; width, 8 cm; height, 4 cm) and a blade, which was guided by 0.5-mm incisions in the side walls of the track (Fig 2). Sectioning could thus be carried out exactly at the desired position, and cross-sections of each silicone impression could be made (Fig 3). To evaluate the tongue room supply on the palate, different silicone sections were made with the following demarcations: Cross section A. From the incisal edges 11/21 and 12/22 to the cusps of 13/23 and to contact points 14/13 and 23/24 (Federation Dentaire Internationale tooth numbers). Cross section B. From contact points 14/13 and 23/24 to the lingual cusps 14/24 and to contact points 15/14 and 24/25. Cross section C. From contact points 15/14 and 24/25 to the lingual cusps 15/25 and to contact points 16/15 and 25/26. Cross section D. From contact points 16/15 and 25/26 to the lingual cusps 16/26 and to contact points 17/16 and 26/27. Cross section E. From contact points 17/16 and 26/27 to the lingual cusps 17/27 and to contact points 18/17 and 27/28. The single cross sections were weighed, and, with the correlation index, the volume could be calculated. To find the correlation between weight and volume, the following method was used. An aluminum cubic form of known side lengths (a ⫽ 2.1 cm, b ⫽ 2.1 cm, c ⫽ 2.4 cm) was used to fabricate 10 silicone cubes of known volume (a ⫻ b ⫻ c ⫽ 10.58 cm3).
The cubes were weighed (Table I), and the weights could then be correlated to known volumes. The mean weight of the cubes was 18.81 g, and the formula for the correlation of weight to volume was as follows: 18.81 g ⫽ 10.58 cm3; 1 g ⫽ 0.56 cm3; 1.78 g ⫽ 1 cm3. Six silicone impressions were fabricated from a randomly selected maxillary stone cast, and each was cut into 5 cross sections (A-E). They were weighed, the results were noted, and the deviation in percentage was calculated (Table II). The possible deviation was found to be between 2.14% and 5.67%, or a maximum of 0.03 g. This is in accordance with the specified measurement precision of the electronic weighing machine. By independent t test, the 2 patient groups (nonextraction and extraction) were compared to identify statistically significant differences between pretreatment, bracket removal, end of retention, and follow-up (t test for independent samples). Changes between pretreatment, bracket removal, end of retention, and follow-up within the same group were analyzed by paired t test (t test for dependent samples). Statistically significant values were determined at P ⬍ .05, P ⬍ .01, and P ⬍ .001. RESULTS Palatal volume
The definitions for volume A, volume B⫹C, volume D, and volume E correspond to the cross sections A, B, C, D, and E (Fig 3). The various volumes and their changes in the different sections are reported in
Heiser et al 85
American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 1
Table III and illustrated in Figures 4 and 5. Volume was measured in cubic centimeters. For volume A, the nonextraction and extraction groups both showed steady increases over all observation periods. The extraction group showed a statistically significant (P ⬍ .001) increase from pretreatment to bracket removal, as did the nonextraction group (P ⬍ .05). The increase in volume A was much greater in the extraction group (0.59 cm3) than in the nonextraction group (0.20 cm3), according to the absolute values (Table III). Also significant (P ⬍ .001) was the increase of volume A from end of retention to follow-up in the nonextraction group. In the extraction group, volume B⫹C showed a significant (P ⬍ .001) decrease from pretreatment to bracket removal; this is the effect of premolar extraction. The extraction group showed a decrease in volume B⫹C from end of retention to follow-up, which was statistically significant (P ⬍ .05). This decrease compares with a slight increase in the nonextraction group, a behavior that was not found in any other section. In all other sections of both groups, there was no decrease but only an increase from end of retention to follow-up. Volumes D and E increased in both groups, but significantly (P ⬍ .05 and P ⬍ .001, respectively) only in the nonextraction group between end of retention and follow-up. Table III and Figure 4 show the volume A⫹B⫹C⫹D at the various evaluations times for the nonextraction group. The change in volume was statistically significant. The extraction group showed a different behavior (Table III, Fig 5): volume A⫹B⫹C⫹D decreased statistically significantly (P ⬍ .001) from pretreatment to bracket removal as an effect of premolar extraction. From bracket removal on, there was also a slight increase of volume A⫹B⫹C⫹D in the extraction group, but the increase was not statistically significant. The changes of volume A⫹B⫹C⫹D⫹E are almost identical to the changes in volume A⫹B⫹C⫹D for the nonextraction and extraction groups from bracket removal to follow-up (Table III, Figs 4 and 5). Palatal height
The silicone cross sections were photocopied at a ratio of 1:1. A line from the highest point at the palate raphe perpendicular to the occlusal plane was constructed, and the distance was measured with an electronic slide caliper. Table IV and Figures 6 and 7 illustrate the different palatal heights. Palatal heights A through E increased over all evaluation periods in the nonextraction group.
Between the extraction and the nonextraction groups (Table IV), different behaviors in height A and height C can be seen. A slight decrease occurred in height A from end of retention to follow-up in the extraction group, compared with a slight increase in the nonextraction group; both were statistically significant. Again, whereas the extraction group showed a slight insignificant decrease from end of retention to follow-up in height C, the nonextraction group showed a significant (P ⬍ .001) increase. The behaviors of heights D and E were similar for both groups: steady increases over all observation periods. These changes in height correspond to the changes in volume (compare Figs 4 and 5 with Figs 6 and 7). DISCUSSION
The different findings regarding changes in palatal volume in the nonextraction and extraction groups between pretreatment and bracket removal reflect the premolar extractions. This was expected. The nonextraction group showed statistically significant increases in volume over all evaluation periods. This principle could also be found in the palatal heights of the nonextraction group. The changes in palatal heights and volumes in the extraction group paint a more complex picture, and the changes from end of retention to follow-up seem to be important. The extraction and nonextraction groups show different behaviors in volume B⫹C and height C. Whereas a slight decrease from end of retention to follow-up could be recorded for the extraction group, the nonextraction group showed an increase. Also for height A, a curious behavior was seen: an increase in the nonextraction group and a decrease in the extraction group. Whereas volume A increased by a statistically significant amount in the nonextraction group between end of retention and follow-up, it increased only slightly in the extraction group. Volume A and volume B⫹C in the extraction group seem to reflect the 3-dimensional changes that occur as a product of arch width, arch depth, and palatal height alterations. The same tendency can be found in volume A⫹B⫹C⫹D between end of retention and follow-up. Whereas the nonextraction group exhibited a statistically significant large increase of 0.49 cm3 in volume A⫹B⫹C⫹D, the extraction group showed only a slight increase of 0.04 cm3, which was not statistically significant. The large increase in height A in the extraction group between pretreatment and bracket removal must be mentioned again. Volume A reflects this, of
86 Heiser et al
Table III.
American Journal of Orthodontics and Dentofacial Orthopedics July 2004
Volumes (cm3) at pretreatment, bracket removal, end of retention, and follow-up Palatal volumes Vol A
Pretreatment (T1)
Bracket removal (T2)
End of retention (T3)
Follow up (T4)
Mean SD Significance, nonextraction vs extraction Mean SD Significance, nonextraction vs extraction Significance, T1 vs T2 Mean SD Significance, nonextraction vs extraction Significance, T2 vs T3 Mean SD Significance, nonextraction vs extraction Significance, T3 vs T4
Vol B⫹C
Nonextraction
Extraction
Nonextraction
Extraction
1.82 0.41
1.97 0.31
5.28 0.91
5.29 1.30
NS
2.02 0.42
NS
2.56 0.55
5.34 0.79
**
3.03 0.67 ***
*
***
NS
***
2.07 0.41
2.56 0.48
5.39 0.77
3.07 0.58
**
***
NS
NS
NS
NS
2.25 0.52
2.61 0.48
5.51 0.91
2.93 0.53
*
***
***
NS
NS
*
*.01 ⬍ P ⬍ .05; **.001 ⬍ P ⬍ .01; ***P ⬍ .001; NS, nonsignificant.
Fig 4. Volumes (in cubic centimeters) in nonextraction group. VOLA, volume of section A; VOLB⫹C, volume of section B⫹C; VOLD, volume of section D; VOLE, volume of section E; VOLABCD, sum of volumes of sections A through D; VOLABCDE, sum of volumes of sections A through E.
course, but whether the height A and volume A increases are only the effect of altered tooth position
Fig 5. Volumes (in cubic centimeters) in extraction group.
(retruded central incisors and distalized canines) is not clear. The cause for the varying behavior between nonextraction and extraction groups over the total observation time might have been the different ages
Heiser et al 87
American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 1
Table III.
Continued Palatal volumes Vol D
Vol E
Vol A⫹B⫹C⫹D
Vol A⫹B⫹C⫹D⫹E
Nonextraction
Extraction
Nonextraction
Extraction
Nonextraction
Extraction
Nonextraction
Extraction
4.32 0.65
5.49 0.87
3.25 0.55
4.47 0.78
11.42 2.75
13.01 1.43
14.67 2.75
17.99 0.61
***
5.33 0.63
NS
5.78 0.57
3.90 0.64
NS
*
4.65 0.64
12.69 1.45
**
NS
11.37 1.25
16.59 1.81
*
16.05 1.74 NS
***
NS
NS
NS
***
***
***
NS
5.49 0.58
5.83 0.62
4.11 0.60
4.85 0.80
12.95 1.46
11.46 1.22
17.06 2.03
16.15 2.12
NS
*
**
NS
NS
NS
NS
NS
*
NS
**
NS
5.68 0.63
5.96 0.69
4.60 0.76
5.24 0.75
13.44 1.78
11.50 1.33
17.96 2.40
16.74 1.78
NS
*
*
NS
***
**
NS
of the 2 patient groups at the evaluation periods, or it could also be a late effect of the different treatment modes. It is not clear what this all means with respect to tongue posture and function and what the clinical implications are. Does the lesser increase of palatal volume in the extraction group between bracket removal and follow-up mean that we could expect more transversal support of the tongue to the maxillary arch, with a resulting smaller relapse tendency? The smaller relapse tendency of area B⫹C in the maxillary arch (see part 117) of the extraction group could be a sign for this. The questions arising from these results are the following: 1. Is the increase of palatal volume due to the eruption of teeth or to the remodeling (growth) of the palate, or both? In both patient groups, the arch area decreased (see part 117) from bracket removal to end of retention; this indicates that the volume increase was not the result of arch widening.
**
NS
NS
*
NS
2. Does the palate change its form during growth or treatment? 3. Do different treatment modalities influence the palatal form? These questions should be clarified by evaluating changes of the palatal form in part 3 of this article. Generally, all palatal heights and volumes increased in the nonextraction group over the observation periods. Heights D and E, as well as volumes D and E, increased in the extraction group over the observation periods. In contrast to the nonextraction group, height A in the extraction group decreased from end of retention to follow-up. Volume A rose only slightly. CONCLUSIONS
This study investigated the changes of palatal volume and height in patients treated with edgewise orthodontic appliances, with or without premolar extractions. The results were as follows:
88 Heiser et al
Table IV.
American Journal of Orthodontics and Dentofacial Orthopedics July 2004
Palatal heights (mm) at pretreatment, bracket removal, end of retention, and follow-up Palatal heights Height A
Pretreatment (T1)
Bracket removal (T2)
End of removal (T3)
Follow-up (T4)
Mean SD Significance, nonextraction vs extraction Mean SD Significance, nonextraction vs extraction Significance, T1 vs T2 Mean SD Significance, nonextraction vs extraction Significance, T2 vs T3 Mean SD Significance, nonextraction vs extraction Significance, T3 vs T4
Height B
Nonextraction
Extraction
Nonextraction
Extraction
11.42 1.42
11.88 2.39
16.51 1.74
17.87 2.05
NS
11.82 1.60
*
15.13 2.10
16.98 1.64
NS
***
***
12.36 1.91
15.61 1.81
17.42 2.06
*
*
NS
12.57 1.73
15.32 1.93
17.78 2.10
NS
NS
***
***
***
NS
*.01 ⬍ P ⬍ .05; **.001 ⬍ P ⬍ .01; ***P ⬍ .001; NS, nonsignificant.
Fig 6. Palatal heights (in millimeters) of silicone sections at various evaluation times in nonextraction group.
1. Palatal height increased over the observation periods in nonextraction and extraction patients; the exception was height A, which did not increase in the extraction group between end of retention and follow-up.
Fig 7. Palatal heights (in millimeters) of silicone sections at various evaluation times in extraction group. Height C at bracket removal is also compared with height B at pretreatment, because of mesial movement of second premolars and, with them, height C. Height has increased.
2. Palatal volume increased over the observation time in the nonextraction group.
Heiser et al 89
American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 1
Table IV.
Continued Palatal heights Height C
Height D
Height E
Nonextraction
Extraction
Nonextraction
Extraction
Nonextraction
Extraction
17.92 1.70
19.50 1.43
15.77 2.03
18.60 1.39
15.58 2.18
17.37 1.27
**
18.60 1.62
***
20.03 1.44
17.39 2.09
***
NS
19.92 1.33
15.92 2.44
***
17.78 2.16 NS
***
NS
***
NS
NS
NS
19.25 1.77
20.43 1.31
18.19 1.86
20.23 2.14
16.28 2.53
18.07 3.35
*
**
NS
*
NS
**
NS
**
NS
19.84 1.84
20.36 1.64
19.32 1.69
21.26 1.76
17.42 1.83
19.86 2.55
NS
***
**
NS
***
3. Palatal volume decreased as a consequence of premolar extraction, but at least some of the volume loss due to premolar extraction is regained by the large increase in volume A between pretreatment and bracket removal. We thank Dr Kent Floreani, Sault Sainte Marie, Ontario, Canada, for reading and correcting the manuscript. REFERENCES 1. Van der Linden FPGM. Gesichtswachstum und faziale Orthopa¨ die. Berlin: Quintessenz Verlag; 1984. 2. Van der Linden FPGM. Gebissentwicklung. Berlin: Quintessenz Verlag; 1983. 3. Brodie A. Consideration of musculature in diagnosis, treatment and retention. Am J Orthod 1952;38:823-35. 4. Mason RM, Proffit WR. The tongue thrust controversy: background and recommendations. J Speech Hear Disord 1974;39: 115-32. 5. Garliner D. Myofunktionelle Therapie in der Praxis. Gesto¨ rtes Schluckverhalten, gesto¨ rte Gesichtsmuskulatur und die Folgen— ¨ bersetDiagnose, Planung und Durchfu¨ hrung der Behandlung. U zung H. Hahn. Mu¨ nchen: Verlag Zahna¨ rztlich-medizinisches Schrifttum; 1982.
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6. Bolten MA. Myofunktionelle Therapie. ZWR 1985;94:210-3. 7. Arnold GE. Die Sprache und ihre Str¨ungen. In: Luchsinger R, Arnold GE, editors. Handbuch der Stimm- und Sprachheilkunde. Vienna, New York: Springer Verlag; 1970. ¨ ber das Mundatmungs-Syndrom und seine 8. Bahnemann F. U Bedeutung in der Zahn-, Mund- und Kieferheilkunde. Berlin: Quintessenz Verlags; 1981. p. 1-7. 9. Fletscher SG, Casteel RL, Bradley DP. Tongue-thrust swallow, speech articulation and age. J Speech Hear Disord 1961;26: 201-8. 10. Hahn V. Myofunktionelle Therapie. Ein Beitrag zur interdisziplina¨ ren Fundierung aus der Sicht der Sprachbehindertenpa¨ dagogik. Mu¨ nchen: Profil Verlag; 1988. 11. Hanson ML, Andrianopoulus MV. Tongue thrust and malocclusion: a longitudinal study. Int J Orthod 1982;20:9-18. 12. Hanson ML. Some suggestions for more effective therapy for tongue thrust. J Speech Hear Disord 1967;32:75-9. 13. Hanson ML. Tongue thrust: another look at the evidence part I. Int J Orthod 1975;1:105-13. 14. Hoffmann JA, Hoffmann RL. Tongue-thrust and deglutition: some anatomical, physiological and neurological consideration. J Speech Hear Disord 1965;30:105-20. 15. Palmer JM. Tongue thrusting: a clinical hypothesis. J Speech Hear Disord 1962;27:323-33. 16. Straub WJ. Malfunction of the tongue. Am J Orthod 1960;46: 404-24. 17. Heiser, W, Niederwanger A, Bancher B, Bittermann G, Neun-
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American Journal of Orthodontics and Dentofacial Orthopedics July 2004
teufel N, Kulmer S. Three-dimensional dental arch and palatal form changes after extraction and nonextraction treatment. Part 1. Arch length and area. Am J Orthod Dentofacial Orthop 2004. In press. 18. Andrews LW. Six keys to normal occlusion. Am J Orthod 1972;62:296-309. 19. Little RM. The Irregularity Index: A quantitative score of mandibular anterior alignment. Am J Orthod 1975;68:554-63.
20. Lauritzen A. Occlusal relationship: the split-cast method for articulator techniques. J Prosthet Dent 1964;14:256. 21. Wirth CG. Interocclusal centric relation records for articular mounted casts. Dent Clin North Am 1971;15:627-40. 22. Kulmer S. Grundlagen der Rehabilitation des parodontal reduz¨ sterr Z Stomat 1980;77:9-15. ierten Gebisses. O 23. Hammedinger D. Volumetrische Erfassung des Zungenraumes. Medizinische [thesis]. Innsbruck: Innsbruck University; 1993.
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Three-dimensional dental arch and palatal form changes after extraction and nonextraction treatment. Part 2. Palatal volume and height Wolfgang Heiser, MD, DDS,a Andreas Niederwanger, MD,b Beatrix Bancher, MD, DDS,c Gabriele Bittermann, MD, DDS,d Nikolaus Neunteufel, MD, DDS,d and Siegfried Kulmer, MD, DDSe Innsbruck, Austria, and Neumarkt, Italy The purpose of this study was to investigate the changes in palatal volume and palatal height in patients treated with and without premolar extractions. Records were collected at pretreatment, at bracket removal, at the end of retention, and 5 years out of retention. Stone casts were mounted in a SAM 2 articulator with an anatomic face-bow and a central wax record, and measurements were made with a 3-dimensional digitizer. The hypothesis, that orthodontic treatment with premolar extractions changes the palatal form, was verified. Increases in palatal volume and height were demonstrated in the nonextraction group. The extraction group showed a decrease in palatal volume but could compensate for some loss by an increase in volume in the anterior segment. (Am J Orthod Dentofacial Orthop 2004; 126:82-90)
A
t birth, the growth of the maxilla is already accompanied by extension of the sinus maxillaris. The expansion of the maxilla is carried out by apposition and resorption in the area of the thin-walled structures over the roots of the premolars and molars. In contrast to the mandible, the maxilla can increase in width (because of the palatal suture) until the end of the growth period. The growth of the maxilla and the mandible become coordinated1 by the interdigitation of the molars and premolars, incipiently starting at the age of 16 months, when the first deciduous molars move into occlusal contact.1 The teeth take, as a reaction to the cusp fossa mechanism,2 a suitable occlusal position. If necessary, a buccolingual movement, especially in the maxilla, can also be found. As soon as a good intercuspation is obtained, the jaws find the same cusp-fossa relationship whenever the closing movement occurs. The typical occlusal morphology of the teeth and the correct indentation in an Angle Class I occlusion, especially of the first molars, play leading roles in the growth of the face. a
Private practice, Innsbruck, Austria. Clinical instructor, Department of Internal Medicine, University of Innsbruck. c Private practice, Neumarkt, Italy. d Clinical instructor, Universita¨tsklinik fu¨r Zahn-, Mund- und Kieferheilkunde, Innsbruck, Austria. e Chairman, Department of Preventive and Restorative Dentistry, Universita¨tsklinik fu¨r Zahn-, Mund- und Kieferheilkunde. Reprints requests to: DDr Wolfgang Heiser, Dr. Stumpftr. 73, Innsbruck A-6020, Austria; e-mail, [email protected]. Submitted, August 2002; revised and accepted, May 2003. 0889-5406/$30.00 Copyright © 2004 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2003.05.016 b
82
Because of these strong mutual influences, treatment can be successful only if the stomatognathic system is considered in the long term. The changes in tooth position as a result of orthodontic therapy should lead to changes in tongue posture and function.3-16 This should be reflected in a changed palatal volume and height. The purpose of this study was to evaluate 3-dimensionally the treatment and posttreatment changes during growth and treatment in the palatal heights and volumes of patients treated with and without extractions. MATERIAL AND METHODS
All patients had been treated in the private orthodontic practice of the first author (W.H.). The sample was described in part 1 of this study.17 The patients were drawn from (insert copy added to part 1); the only criterion for patient selection was good occlusion at bracket removal (ie, each subject met the 6 keys to normal occlusion18). Neither cephalometric characteristics nor postretention occlusion was considered in the sample selection. The groups were formed before the follow-up examination. The records were collected at 4 times: pretreatment, bracket removal, end of retention, and follow-up. The nonextraction group consisted originally of 25 Class II patients (19 girls, 6 boys; average age, 11 years 4 months) who were treated with fixed appliances (straightwire) without premolar extractions. The follow-up examination was carried out 6.3 years out of
American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 1
Fig 1. Trimmed silicone impression.
retention, and 22 patients (17 women, 5 men; average age, 20 years 7 months) returned for it. The mean irregularity index19 was 5.1 before orthodontic treatment. The average active treatment time was 1 year 9 months, and the average retention period was 1 year 3 months. The extraction group consisted originally of 24 patients (18 girls, 6 boys; average age, 13 years 7 months) who were treated with fixed appliances (straightwire) and premolar (first or second) extractions. Twenty patients (16 women, 4 men; average age, 21 years 10 months) were examined at follow-up. The mean irregularity index was 5.8 before orthodontic treatment. The average active treatment time was 1 year 9 months, and the average retention period was 1 year 10 months. The follow-up examination was carried out 4 years 8 months out of retention. Recording palatal volume and height
Accurate alginate mandibular and maxillary impressions were taken for each patient at pretreatment, bracket removal, the end of retention, and follow-up. The impressions were poured in stone, and the maxillary model was provided with a split-cast.20 With the aid of an anatomic face-bow, the maxillary model was mounted skull-related onto a semi-adjustable articulator (SAM 2, SAM Pra¨ zisionstechnik, Gauting, Germany). Then the mandibular model was mounted joint-related to the maxillary model according to a central wax record.21 In all cases, cephalometric and panoramic radiographs were taken. The records were made according to the rules of the Austrian Dental Society.22 From all maxillary stone casts, 2 silicone impres-
Heiser et al 83
Fig 2. U-shaped aluminum guide track with silicone impression. Inserted knife cuts along marked line.
Fig 3. Demarcations of silicone sections A through E.
sions were made. One was used to construct crosssections, and the other to obtain longitudinal sections. The method to evaluate the palatal volume was reported by Hammedinger.23 The silicone impression material was brought into the palatal cavity limited by the palate, the teeth, and the occlusal plane. The occlusal plane was found by pushing the plaster model filled with soft silicone material down to a glass plate until the glass plate touched the incisal edges of the maxillary central incisors and the mesiopalatal cusps of the first molars. Then the hardened silicone impression was taken from the model. The silicone impression was trimmed with a scalpel along the incisal edges of the central and lateral incisors to the cusps of the canines, to the various contact points and the palatal cusps of the premolars and molars (Fig 1). To make exact sections, a special cutting device
84 Heiser et al
Table I.
Cube weights
Cube no. Weight (g)
Table II.
American Journal of Orthodontics and Dentofacial Orthopedics July 2004
1 18.87
2 19.09
3 18.92
4 18.92
5 18.92
6 18.77
7 18.64
8 18.67
9 18.67
10 18.60
Weight of 6 specimens of silicone sections A to E, in grams
1 2 3 4 5 6 Standard deviation
A
B
C
D
E
Sum A-E
A⫹B⫹C⫹D⫹E weighed
3.77 3.71 4.05 3.66 3.78 3.58 4.32%
4.12 3.83 3.75 4.14 4.00 4.01 3.92%
4.99 5.17 5.02 5.62 5.36 5.10 4.22%
10.51 10.36 10.23 10.58 11.29 10.60 3.48%
8.20 8.72 9.52 9.01 8.59 8.27 5.67%
31.57 31.78 32.55 32.98 33.01 31.54 2.15%
31.59 31.79 32.57 33.01 33.02 31.56 2.14%
was developed, consisting of a U-shaped guide track (length, 15 cm; width, 8 cm; height, 4 cm) and a blade, which was guided by 0.5-mm incisions in the side walls of the track (Fig 2). Sectioning could thus be carried out exactly at the desired position, and cross-sections of each silicone impression could be made (Fig 3). To evaluate the tongue room supply on the palate, different silicone sections were made with the following demarcations: Cross section A. From the incisal edges 11/21 and 12/22 to the cusps of 13/23 and to contact points 14/13 and 23/24 (Federation Dentaire Internationale tooth numbers). Cross section B. From contact points 14/13 and 23/24 to the lingual cusps 14/24 and to contact points 15/14 and 24/25. Cross section C. From contact points 15/14 and 24/25 to the lingual cusps 15/25 and to contact points 16/15 and 25/26. Cross section D. From contact points 16/15 and 25/26 to the lingual cusps 16/26 and to contact points 17/16 and 26/27. Cross section E. From contact points 17/16 and 26/27 to the lingual cusps 17/27 and to contact points 18/17 and 27/28. The single cross sections were weighed, and, with the correlation index, the volume could be calculated. To find the correlation between weight and volume, the following method was used. An aluminum cubic form of known side lengths (a ⫽ 2.1 cm, b ⫽ 2.1 cm, c ⫽ 2.4 cm) was used to fabricate 10 silicone cubes of known volume (a ⫻ b ⫻ c ⫽ 10.58 cm3).
The cubes were weighed (Table I), and the weights could then be correlated to known volumes. The mean weight of the cubes was 18.81 g, and the formula for the correlation of weight to volume was as follows: 18.81 g ⫽ 10.58 cm3; 1 g ⫽ 0.56 cm3; 1.78 g ⫽ 1 cm3. Six silicone impressions were fabricated from a randomly selected maxillary stone cast, and each was cut into 5 cross sections (A-E). They were weighed, the results were noted, and the deviation in percentage was calculated (Table II). The possible deviation was found to be between 2.14% and 5.67%, or a maximum of 0.03 g. This is in accordance with the specified measurement precision of the electronic weighing machine. By independent t test, the 2 patient groups (nonextraction and extraction) were compared to identify statistically significant differences between pretreatment, bracket removal, end of retention, and follow-up (t test for independent samples). Changes between pretreatment, bracket removal, end of retention, and follow-up within the same group were analyzed by paired t test (t test for dependent samples). Statistically significant values were determined at P ⬍ .05, P ⬍ .01, and P ⬍ .001. RESULTS Palatal volume
The definitions for volume A, volume B⫹C, volume D, and volume E correspond to the cross sections A, B, C, D, and E (Fig 3). The various volumes and their changes in the different sections are reported in
Heiser et al 85
American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 1
Table III and illustrated in Figures 4 and 5. Volume was measured in cubic centimeters. For volume A, the nonextraction and extraction groups both showed steady increases over all observation periods. The extraction group showed a statistically significant (P ⬍ .001) increase from pretreatment to bracket removal, as did the nonextraction group (P ⬍ .05). The increase in volume A was much greater in the extraction group (0.59 cm3) than in the nonextraction group (0.20 cm3), according to the absolute values (Table III). Also significant (P ⬍ .001) was the increase of volume A from end of retention to follow-up in the nonextraction group. In the extraction group, volume B⫹C showed a significant (P ⬍ .001) decrease from pretreatment to bracket removal; this is the effect of premolar extraction. The extraction group showed a decrease in volume B⫹C from end of retention to follow-up, which was statistically significant (P ⬍ .05). This decrease compares with a slight increase in the nonextraction group, a behavior that was not found in any other section. In all other sections of both groups, there was no decrease but only an increase from end of retention to follow-up. Volumes D and E increased in both groups, but significantly (P ⬍ .05 and P ⬍ .001, respectively) only in the nonextraction group between end of retention and follow-up. Table III and Figure 4 show the volume A⫹B⫹C⫹D at the various evaluations times for the nonextraction group. The change in volume was statistically significant. The extraction group showed a different behavior (Table III, Fig 5): volume A⫹B⫹C⫹D decreased statistically significantly (P ⬍ .001) from pretreatment to bracket removal as an effect of premolar extraction. From bracket removal on, there was also a slight increase of volume A⫹B⫹C⫹D in the extraction group, but the increase was not statistically significant. The changes of volume A⫹B⫹C⫹D⫹E are almost identical to the changes in volume A⫹B⫹C⫹D for the nonextraction and extraction groups from bracket removal to follow-up (Table III, Figs 4 and 5). Palatal height
The silicone cross sections were photocopied at a ratio of 1:1. A line from the highest point at the palate raphe perpendicular to the occlusal plane was constructed, and the distance was measured with an electronic slide caliper. Table IV and Figures 6 and 7 illustrate the different palatal heights. Palatal heights A through E increased over all evaluation periods in the nonextraction group.
Between the extraction and the nonextraction groups (Table IV), different behaviors in height A and height C can be seen. A slight decrease occurred in height A from end of retention to follow-up in the extraction group, compared with a slight increase in the nonextraction group; both were statistically significant. Again, whereas the extraction group showed a slight insignificant decrease from end of retention to follow-up in height C, the nonextraction group showed a significant (P ⬍ .001) increase. The behaviors of heights D and E were similar for both groups: steady increases over all observation periods. These changes in height correspond to the changes in volume (compare Figs 4 and 5 with Figs 6 and 7). DISCUSSION
The different findings regarding changes in palatal volume in the nonextraction and extraction groups between pretreatment and bracket removal reflect the premolar extractions. This was expected. The nonextraction group showed statistically significant increases in volume over all evaluation periods. This principle could also be found in the palatal heights of the nonextraction group. The changes in palatal heights and volumes in the extraction group paint a more complex picture, and the changes from end of retention to follow-up seem to be important. The extraction and nonextraction groups show different behaviors in volume B⫹C and height C. Whereas a slight decrease from end of retention to follow-up could be recorded for the extraction group, the nonextraction group showed an increase. Also for height A, a curious behavior was seen: an increase in the nonextraction group and a decrease in the extraction group. Whereas volume A increased by a statistically significant amount in the nonextraction group between end of retention and follow-up, it increased only slightly in the extraction group. Volume A and volume B⫹C in the extraction group seem to reflect the 3-dimensional changes that occur as a product of arch width, arch depth, and palatal height alterations. The same tendency can be found in volume A⫹B⫹C⫹D between end of retention and follow-up. Whereas the nonextraction group exhibited a statistically significant large increase of 0.49 cm3 in volume A⫹B⫹C⫹D, the extraction group showed only a slight increase of 0.04 cm3, which was not statistically significant. The large increase in height A in the extraction group between pretreatment and bracket removal must be mentioned again. Volume A reflects this, of
86 Heiser et al
Table III.
American Journal of Orthodontics and Dentofacial Orthopedics July 2004
Volumes (cm3) at pretreatment, bracket removal, end of retention, and follow-up Palatal volumes Vol A
Pretreatment (T1)
Bracket removal (T2)
End of retention (T3)
Follow up (T4)
Mean SD Significance, nonextraction vs extraction Mean SD Significance, nonextraction vs extraction Significance, T1 vs T2 Mean SD Significance, nonextraction vs extraction Significance, T2 vs T3 Mean SD Significance, nonextraction vs extraction Significance, T3 vs T4
Vol B⫹C
Nonextraction
Extraction
Nonextraction
Extraction
1.82 0.41
1.97 0.31
5.28 0.91
5.29 1.30
NS
2.02 0.42
NS
2.56 0.55
5.34 0.79
**
3.03 0.67 ***
*
***
NS
***
2.07 0.41
2.56 0.48
5.39 0.77
3.07 0.58
**
***
NS
NS
NS
NS
2.25 0.52
2.61 0.48
5.51 0.91
2.93 0.53
*
***
***
NS
NS
*
*.01 ⬍ P ⬍ .05; **.001 ⬍ P ⬍ .01; ***P ⬍ .001; NS, nonsignificant.
Fig 4. Volumes (in cubic centimeters) in nonextraction group. VOLA, volume of section A; VOLB⫹C, volume of section B⫹C; VOLD, volume of section D; VOLE, volume of section E; VOLABCD, sum of volumes of sections A through D; VOLABCDE, sum of volumes of sections A through E.
course, but whether the height A and volume A increases are only the effect of altered tooth position
Fig 5. Volumes (in cubic centimeters) in extraction group.
(retruded central incisors and distalized canines) is not clear. The cause for the varying behavior between nonextraction and extraction groups over the total observation time might have been the different ages
Heiser et al 87
American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 1
Table III.
Continued Palatal volumes Vol D
Vol E
Vol A⫹B⫹C⫹D
Vol A⫹B⫹C⫹D⫹E
Nonextraction
Extraction
Nonextraction
Extraction
Nonextraction
Extraction
Nonextraction
Extraction
4.32 0.65
5.49 0.87
3.25 0.55
4.47 0.78
11.42 2.75
13.01 1.43
14.67 2.75
17.99 0.61
***
5.33 0.63
NS
5.78 0.57
3.90 0.64
NS
*
4.65 0.64
12.69 1.45
**
NS
11.37 1.25
16.59 1.81
*
16.05 1.74 NS
***
NS
NS
NS
***
***
***
NS
5.49 0.58
5.83 0.62
4.11 0.60
4.85 0.80
12.95 1.46
11.46 1.22
17.06 2.03
16.15 2.12
NS
*
**
NS
NS
NS
NS
NS
*
NS
**
NS
5.68 0.63
5.96 0.69
4.60 0.76
5.24 0.75
13.44 1.78
11.50 1.33
17.96 2.40
16.74 1.78
NS
*
*
NS
***
**
NS
of the 2 patient groups at the evaluation periods, or it could also be a late effect of the different treatment modes. It is not clear what this all means with respect to tongue posture and function and what the clinical implications are. Does the lesser increase of palatal volume in the extraction group between bracket removal and follow-up mean that we could expect more transversal support of the tongue to the maxillary arch, with a resulting smaller relapse tendency? The smaller relapse tendency of area B⫹C in the maxillary arch (see part 117) of the extraction group could be a sign for this. The questions arising from these results are the following: 1. Is the increase of palatal volume due to the eruption of teeth or to the remodeling (growth) of the palate, or both? In both patient groups, the arch area decreased (see part 117) from bracket removal to end of retention; this indicates that the volume increase was not the result of arch widening.
**
NS
NS
*
NS
2. Does the palate change its form during growth or treatment? 3. Do different treatment modalities influence the palatal form? These questions should be clarified by evaluating changes of the palatal form in part 3 of this article. Generally, all palatal heights and volumes increased in the nonextraction group over the observation periods. Heights D and E, as well as volumes D and E, increased in the extraction group over the observation periods. In contrast to the nonextraction group, height A in the extraction group decreased from end of retention to follow-up. Volume A rose only slightly. CONCLUSIONS
This study investigated the changes of palatal volume and height in patients treated with edgewise orthodontic appliances, with or without premolar extractions. The results were as follows:
88 Heiser et al
Table IV.
American Journal of Orthodontics and Dentofacial Orthopedics July 2004
Palatal heights (mm) at pretreatment, bracket removal, end of retention, and follow-up Palatal heights Height A
Pretreatment (T1)
Bracket removal (T2)
End of removal (T3)
Follow-up (T4)
Mean SD Significance, nonextraction vs extraction Mean SD Significance, nonextraction vs extraction Significance, T1 vs T2 Mean SD Significance, nonextraction vs extraction Significance, T2 vs T3 Mean SD Significance, nonextraction vs extraction Significance, T3 vs T4
Height B
Nonextraction
Extraction
Nonextraction
Extraction
11.42 1.42
11.88 2.39
16.51 1.74
17.87 2.05
NS
11.82 1.60
*
15.13 2.10
16.98 1.64
NS
***
***
12.36 1.91
15.61 1.81
17.42 2.06
*
*
NS
12.57 1.73
15.32 1.93
17.78 2.10
NS
NS
***
***
***
NS
*.01 ⬍ P ⬍ .05; **.001 ⬍ P ⬍ .01; ***P ⬍ .001; NS, nonsignificant.
Fig 6. Palatal heights (in millimeters) of silicone sections at various evaluation times in nonextraction group.
1. Palatal height increased over the observation periods in nonextraction and extraction patients; the exception was height A, which did not increase in the extraction group between end of retention and follow-up.
Fig 7. Palatal heights (in millimeters) of silicone sections at various evaluation times in extraction group. Height C at bracket removal is also compared with height B at pretreatment, because of mesial movement of second premolars and, with them, height C. Height has increased.
2. Palatal volume increased over the observation time in the nonextraction group.
Heiser et al 89
American Journal of Orthodontics and Dentofacial Orthopedics Volume 126, Number 1
Table IV.
Continued Palatal heights Height C
Height D
Height E
Nonextraction
Extraction
Nonextraction
Extraction
Nonextraction
Extraction
17.92 1.70
19.50 1.43
15.77 2.03
18.60 1.39
15.58 2.18
17.37 1.27
**
18.60 1.62
***
20.03 1.44
17.39 2.09
***
NS
19.92 1.33
15.92 2.44
***
17.78 2.16 NS
***
NS
***
NS
NS
NS
19.25 1.77
20.43 1.31
18.19 1.86
20.23 2.14
16.28 2.53
18.07 3.35
*
**
NS
*
NS
**
NS
**
NS
19.84 1.84
20.36 1.64
19.32 1.69
21.26 1.76
17.42 1.83
19.86 2.55
NS
***
**
NS
***
3. Palatal volume decreased as a consequence of premolar extraction, but at least some of the volume loss due to premolar extraction is regained by the large increase in volume A between pretreatment and bracket removal. We thank Dr Kent Floreani, Sault Sainte Marie, Ontario, Canada, for reading and correcting the manuscript. REFERENCES 1. Van der Linden FPGM. Gesichtswachstum und faziale Orthopa¨ die. Berlin: Quintessenz Verlag; 1984. 2. Van der Linden FPGM. Gebissentwicklung. Berlin: Quintessenz Verlag; 1983. 3. Brodie A. Consideration of musculature in diagnosis, treatment and retention. Am J Orthod 1952;38:823-35. 4. Mason RM, Proffit WR. The tongue thrust controversy: background and recommendations. J Speech Hear Disord 1974;39: 115-32. 5. Garliner D. Myofunktionelle Therapie in der Praxis. Gesto¨ rtes Schluckverhalten, gesto¨ rte Gesichtsmuskulatur und die Folgen— ¨ bersetDiagnose, Planung und Durchfu¨ hrung der Behandlung. U zung H. Hahn. Mu¨ nchen: Verlag Zahna¨ rztlich-medizinisches Schrifttum; 1982.
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6. Bolten MA. Myofunktionelle Therapie. ZWR 1985;94:210-3. 7. Arnold GE. Die Sprache und ihre Str¨ungen. In: Luchsinger R, Arnold GE, editors. Handbuch der Stimm- und Sprachheilkunde. Vienna, New York: Springer Verlag; 1970. ¨ ber das Mundatmungs-Syndrom und seine 8. Bahnemann F. U Bedeutung in der Zahn-, Mund- und Kieferheilkunde. Berlin: Quintessenz Verlags; 1981. p. 1-7. 9. Fletscher SG, Casteel RL, Bradley DP. Tongue-thrust swallow, speech articulation and age. J Speech Hear Disord 1961;26: 201-8. 10. Hahn V. Myofunktionelle Therapie. Ein Beitrag zur interdisziplina¨ ren Fundierung aus der Sicht der Sprachbehindertenpa¨ dagogik. Mu¨ nchen: Profil Verlag; 1988. 11. Hanson ML, Andrianopoulus MV. Tongue thrust and malocclusion: a longitudinal study. Int J Orthod 1982;20:9-18. 12. Hanson ML. Some suggestions for more effective therapy for tongue thrust. J Speech Hear Disord 1967;32:75-9. 13. Hanson ML. Tongue thrust: another look at the evidence part I. Int J Orthod 1975;1:105-13. 14. Hoffmann JA, Hoffmann RL. Tongue-thrust and deglutition: some anatomical, physiological and neurological consideration. J Speech Hear Disord 1965;30:105-20. 15. Palmer JM. Tongue thrusting: a clinical hypothesis. J Speech Hear Disord 1962;27:323-33. 16. Straub WJ. Malfunction of the tongue. Am J Orthod 1960;46: 404-24. 17. Heiser, W, Niederwanger A, Bancher B, Bittermann G, Neun-
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American Journal of Orthodontics and Dentofacial Orthopedics July 2004
teufel N, Kulmer S. Three-dimensional dental arch and palatal form changes after extraction and nonextraction treatment. Part 1. Arch length and area. Am J Orthod Dentofacial Orthop 2004. In press. 18. Andrews LW. Six keys to normal occlusion. Am J Orthod 1972;62:296-309. 19. Little RM. The Irregularity Index: A quantitative score of mandibular anterior alignment. Am J Orthod 1975;68:554-63.
20. Lauritzen A. Occlusal relationship: the split-cast method for articulator techniques. J Prosthet Dent 1964;14:256. 21. Wirth CG. Interocclusal centric relation records for articular mounted casts. Dent Clin North Am 1971;15:627-40. 22. Kulmer S. Grundlagen der Rehabilitation des parodontal reduz¨ sterr Z Stomat 1980;77:9-15. ierten Gebisses. O 23. Hammedinger D. Volumetrische Erfassung des Zungenraumes. Medizinische [thesis]. Innsbruck: Innsbruck University; 1993.
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