Download Efficacy of Nickel-Titanium Palatal Expanders

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10.5005/jp-journals-10021-1044
ORIGINAL ARTICLE
Efficacy of Nickel-Titanium Palatal Expanders
Efficacy of Nickel-Titanium Palatal Expanders
1
Rahul Paul, 2Tapasya Juneja Kapoor, 3Varun Malhotra, 4US Krishna Nayak, 5Shruti Bhatt
ABSTRACT
Objective: Timely treatment of narrow maxilla by means of maxillary expansion during the primary or transitional dentition is recommended
to reestablish optimal function in order to normalize dental, skeletal and neuromuscular growth. The aim of this study was to assess the
amount of orthodontic and orthopedic expansion achieved in the maxilla and to evaluate cephalometrically the various postural changes in
the maxilla and mandible with the use of nickel-titanium palatal expander.
Materials and methods: A total of ten subjects, five males and five females were selected from a survey conducted on 2000 children in age
range of 7 to 15 years, belonging to various schools. Their study cast, cephalograms and occlusal radiographs were used for the study.
Maxillary intermolar width, maxillary intercanine width and mandibular intermolar width were measured on study cast using Vernier caliper.
Certain measurements were done on the cephalogram and occlusal radiograph.
The data obtained out of various measurements made on study casts, frontal, lateral cephalograms and occlusal radiographs at the
pretreatment, postexpansion and postretention stages were statistically analyzed. All the observations were made by two observers. The
interexaminer variability was calculated using t-test. The mean and standard deviations were calculated and student's t-test (paired) was
applied to determine the amount of change, variability of change and significance of change, respectively.
Results: A constant force exerted by nickel-titanium palatal expander had orthopedic effects in growing age group indicated by statistically
increase in the maxillary width. The ratio of relative orthodontic to orthopedic effect with this appliance was 6:1. Consequent to maxillary
expansion, there occurred a significant downward movement of the maxillae and downward and backward rotation of the mandible. There
was opening of midpalatal suture during active phase followed by suture remineralization during the retention period.
Conclusion: To conclude, a Ni-Ti expander brings about expansion by a combination of orthodontic and orthopedic effects by an increase
in maxillary intermolar, maxillary intercanine and mandibular intercanine widths as also the opening of the midpalatal suture.
Keywords: Nickel-titanium expander, Maxillary expansions, Maxillary width.
How to cite this article: Paul R, Kapoor TJ, Malhotra V, Nayak USK, Bhatt S. Efficacy of Nickel-Titanium Palatal Expanders. J Ind Orthod
Soc 2011;45(4):243-250.
INTRODUCTION
The narrow maxilla is one of the common problems encountered
in orthodontics which may manifest as posterior crossbite.
Timely treatment of such transverse discrepancies, by means
of maxillary expansion during the primary or transitional
dentition is recommended to reestablish optimal function in
order to normalize dental, skeletal and neuromuscular growth.
The primary aim of maxillary expansion is to coordinate the
maxillary and mandibular dental bases by increasing the arch
width and thus eliminate interarch width discrepancies. This
can be accomplished by means of rapid or slow maxillary
expanders.
1
Professor and Head, 2Professor, 3Reader, 4Principal and Head, 5Intern
1,2,3,5
Department of Orthodontics, Inderprastha Dental College and
Hospital, Ghaziabad, Uttar Pradesh, India
4
Department of Orthodontics, AB Shetty Memorial Institute of Dental
Sciences, Deralakatte, Mangalore, Karnataka, India
Corresponding Author: Rahul Paul, Professor and Head, Department
of Orthodontics, Inderprastha Dental College and Hospital, Sahibabad
Ghaziabad, Uttar Pradesh, India, e-mail: [email protected]
Received on: 8/8/11
Accepted after Revision: 10/12/11
Rapid maxillary expansion produces mainly an orthopedic
response as heavy forces, in the range of 3 to 10 pounds are
generated daily. Such heavy forces can cause disruptive changes
within the sutures and bring about root resorption of the teeth.1,2
Slow maxillary expansion produces more physiologic response
of the midpalatal suture as the suture is opened at the same rate
at which it is repaired. It produces less tissue resistance in the
suture and allows better bone formation. Both these factors
help to minimize the postexpansion relapse.3
Dr Wnadell V Arndt4 of USA, in 1993, developed a preprogramed, tendon looped, semifixed, nickel-titanium palatal
expander, which produces light continuous forces producing
slow maxillary expansion (Figs 1 and 2). It is available in eight
sizes and exerts forces in the range of 180 to 300 gm. NiTi
alloy is stronger, flexible and exerts longer range of action than
stainless steel. It has a transition temperature of 94°F, when
chilled, it becomes more flexible, when up, the metal stiffens
and shape memory is restored and the appliance begins to exert
a light continuous force on the teeth and palatal suture. Arndt
used this expander on several cases of unilateral as well as
bilateral posterior crossbites and demonstrated his results by
means of study casts only. No attempts were made to determine
the relative amount of orthopedic vs orthodontic expansion
produced by the appliance. Moreover, various expected/
probable spatial, functional changes, posture of maxilla,
The Journal of Indian Orthodontic Society, October-December 2011;45(4):243-250
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Rahul Paul et al
Fig. 1: Nickel-titanium palatal expander assembly
Fig 3A: Measurement of maxillary intermolar width
Fig. 2: Nickel-titanium palatal expander fitted on maxillary arch
Fig. 3B: Measurement of maxillary intercanine width
mandible, degree of bite opening, change in the size of nasal
cavity and effect on the mandibular arch width remained
undocumented. The aim of this study was to fill-up the vacuum
of knowledge by assessing the amount of orthodontic and
orthopedic expansion achieved in the maxilla and to evaluate
cephalometrically the various postural changes in the maxilla
and mandible with the use of nickel-titanium palatal expander.
MATERIALS AND METHODS
The present study was conducted at the Department of
Orthodontics and Dentofacial Orthopedics, AB Shetty
Memorial Institute of Dental Sciences, Derlakatte, Mangalore
after obtaining ethical clearance.4 Ten subjects, five males and
five females,4 were selected from a survey conducted on 2000
children, in age range of 7 to 15 years, belonging to various
schools of Mangalore city. Prior informed consent was obtained
from the parents of the subjects. Subjects having unilateral or
bilateral posterior crossbite were selected for the study. Case
selection was made after evaluation of study casts, frontal and
lateral cephalograms, standard occlusal radiographs of the
maxilla and intraoral and extraoral photographs. Subjects having
gross periodontal disease, extensive caries, congenitally missing
teeth, anterior open bite and with previous history of orthodontic
treatment were excluded. Maxillary intermolar width, maxillary
intercanine width and mandibular intermolar width, were
measured on study cast using Vernier caliper.
The following measurements were made on the study cast
as described by Frank and Engel,5 using Vernier caliper, having
an accuracy of 0.5 mm (Figs 3A to C):
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Fig. 3C: Measurement of mandibular intermolar width
Maxillary intermolar width: The distance between the tip of
the distobuccal cusp of maxillary first molars across the arch
(Fig. 3A).
Maxillary intercanine width: The distance between the cusp
tips of the maxillary canine of each side (Fig. 3B).
The mandibular intermolar width: The distance between the
tip of the distobuccal cusp of the mandibular first molars across
the arch (Fig. 3C).
These measurements were made by two observers. The
reliability for accuracy of the measurements was checked by
applying student’s t-test for paired observations. The
interobserver difference was found to be nonsignificant
statistically. Therefore, the observations recorded by the main
observer were taken.
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Efficacy of Nickel-Titanium Palatal Expanders
CEPHALOGRAMS
Posteroanterior and lateral cephalograms were recorded with
teeth in centric occlusion and with similar exposure parameters.
All the cephalometric measurements were recorded up to
0.5 mm/0.5 degree.
THE FOLLOWING CEPHALOMETRIC LANDMARKS
WERE RECORDED ON EACH OF THE
CEPHALOGRAMS AND USED FOR THE STUDY
Landmarks as defined by Rickets6
1. A6 (upper molar): A point on the occlusal plane located
perpendicular to the buccal surface of crown of the upper
permanent first molar.
2. B6 (lower molar): A point on the occlusal plane located
perpendicular to the buccal surface of the crown of lower
permanent first molar.
3. Jugal process: The most lateral and inferior point on the
zygomaticomaxillary suture.
4. Po (anatomic porion): The most superior point at the
external auditory meatus.
5. CF (center of face): The point of intersection of pterygoid
root vertical to the Frankfort horizontal plane.
6. Pt (pterygoid): The junction of pterygomaxillary fissure and
the foramen rotundum.
7. DC: A point in the center of condylar neck along Ba-N
plane.
8. Xi: Geometric center of ramus.
9. PM (protrubence mentii): The point at which the shape of
symphysis changes from convex to concave.
10. Gn (cephalometric gnathion): A point at the intersection of
facial and mandibular plane.
11. Go (cephalometric gonion): A point at intersection of the
ramus and mandibular plane.
Fig. 4A: Cephalometric landmarks used on lateral cephalogram
Landmarks as defined by Rakosi7 (Fig. 4A)
1. Point A (subspinale): The deepest midline point in the
curved bony outline from the base to the alveolar process
of maxilla.
2. Or (orbitale): The lowermost point of the bony orbit in the
radiographs.
3. Ba (basion): The lowermost point on the anterior margin of
foramen magnum in the median plane.
4. ANS (anterior nasal spine): The tip of bony anterior nasal
spine in the median plane.
5. PNS (posterior nasal spine): A point where palatal plane
meets with the pterygomaxillary fissure.
6. N (nasion): The most anterior point of nasofrontal suture in
median plane.
7. POG (pogonion): The most anterior point on the bony chin.
CEPHALOMETRIC PLANES USED IN THE STUDY
The following cephalometric planes as defined by Rickets6 on
frontal cephalogram (Fig. 4B):
Fig. 4B: Cephalometric landmarks and planes used on
frontal cephalogram
1. Frontal occlusal plane: A plane joining the occlusion of
upper and lower molars on each side.
2. Frontal facial plane: Passing from the center of the bony
nasal cavity at right angles to the occlusal plane.
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Rahul Paul et al
Fig. 5: Cephalometric planes used for angular measurements on
lateral cephalogram
1.
2.
3.
4.
5.
6.
7.
8.
Fig. 6A: Lateral measurements on frontal cephalogram
The following cephalometric planes as defined by Rickets6
on lateral cephalogram (Fig. 5):
Frankfort horizontal plane: Extending from porion to
orbitale (using anatomic porion).
Facial plane: Extending from nasion to pogonion.
Mandibular plane: Extending from gonion to gnathion
(using cephalometric gonion and gnathion).
Pterygoid vertical plane: A vertical line drawn through the
distal radiographic outline of the pterygomaxillary fissure
and perpendicular to the Frankfort horizontal plane.
Basion-nasion plane: Extending from basion to nasion.
Facial axis: Extending from the point Pt to cephalometric
gnathion (Pt to Gn).
Condylar axis: Extending from DC to Xi point.
Corpus axis: Extending from Xi to PM.
Cephalometric Plane as defined by Rakosi7
Palatal plane: A plane joining ANS and PNS.
MEASUREMENTS MADE ON FRONTAL (P-A)
CEPHALOGRAM (FIG. 6A)
Linear Measurements (in mm)
1. Maxillary width: The distance between right and left jugal
process.
2. Maxillary intermolar width: The distance between points
A6 and 6A.
3. Maxillary intercanine width: The distance between cusp
and tips of maxillary canines.
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Fig. 6B: Linear and angular measurements of lateral cephalograms
4. Mandibular intermolar width: The distance between the
points B6 and 6B.
5. Nasal width: The greatest distance between the right and
left lateral bony walls of nasal cavity.
6. Average molar relation: The average of horizontal distance
between the buccal surface of maxillary and mandibular
first molars on the respective sides measured along the
occlusal plane.
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Efficacy of Nickel-Titanium Palatal Expanders
7. Average maxillomandibular relation: The average of the
left and right distances from the maxilla (jugal process) to
the frontal facial plane on the respective side.
MEASUREMENTS MADE ON LATERAL
CEPHALOGRAMS (FIG. 6B)
Linear Measurements (in mm)
1. Convexity at point A: The distance between N Pog to
Point A.
Angular Measurements (in degree)
1. Palatal plane angle: The angle between Frankfort horizontal
plane and palatal plane.
2. Maxillary depth: The angle between nasion-basion plane
and nasion point A plane.
3. Maxillary height: The angle between nasion CF plane and
CF-A plane.
4. Mandibular plane angle: The angle between Frankfort plane
and mandibular plane.
5. Facial axis: The angle between basion-nasion plane and
the plane from rotundum (PT) to gnathion.
6. Facial depth: The angle between facial plane and Frankfort
horizontal plane.
7. Lower face height: The angle between ANS Xi to Xi-PM
8. Mandibular arc angle: The angle between condylar axis
and corpus axis.
OCCLUSAL RADIOGRAPHS
Standard occlusal radiographs of maxilla for each individual
were taken pretreatment, postexpansion and postretention.
RESULTS
The total appliance wear time including a 12 weeks retention
period was 26.13 ± 1.26 weeks. The mean number of
Fig. 7: Study models showing postexpansion
(overexpansion) stage
adjustments required was 0.8 ± 0.42. In two of the cases on
one, the appliance became loose and therefore molar bands had
to be recemented in position. The desired amount of expansion
was achieved in 9.42 to 19.28 weeks with a mean of 14.13 ±
1.26 weeks. Palatal expansion was considered to be adequate
and successful when the occlusal slopes of maxillary lingual
cusps contacted the occlusal slopes of mandibular buccal cusps
(Fig. 7).
Phase I (Changes from Pretreatment to
Postexpansion Stage)
Changes exhibited in various parameters on the study cast, linear
and angular measurements on the cephalograms are presented
in Tables 1 to 3 respectively. There was a significant decrease
in the average maxillomandibular relation indicating correction
of posterior crossbite. No significant difference existed between
the increase in maxillary intermolar width when the study casts
(9.474-1.73 mm) and the frontal cephalograms (10.2 ±
1.87 mm) were compared.
Table 1: Linear dental changes observed on study casts during phase I (active expansion period)
Sl. No.
Parameters
1.
2.
3.
Maxillary intermolar width
Maxillary intercanine width
Mandibular intermolar width
Range (in mm)
7.5-12
2-5.7
0.5-2
Mean increase (mm)
9.47 ± 1.73
3.33 ± 1.11
0.45 ± 0.599
SE
t
0.548
0.350
0.189
p
17.28
9.51
2.38
0.001****
0.001****
0.05**
**** Highly significant at p < 0.001; ** Significant at p < 0.05
Table 2: Linear dental and skeletal changes observed on frontal cephalogram during phase I (active expansion period)
Sl. No.
1.
2.
3.
4.
5.
6.
7.
Parameters
Maxillary width
Maxillary intermolar width
Maxillary intercanine width
Mandibular intermolar width
Nasal width
Average molar relation I
Average maxillomandibular relation
Range (in mm)
1-3
6-12
2-4.5
0.5-2
0.5-1
4-7
1-2
Mean increase
(mm)
1.6 ± 0.715
10.2 ± 1.87
3.45 ± 0.88
0.45 ± 0.599
0.25 ± 0.125
5.45 ± 0.942
–1.15 ± 0.527
SE
t
p
0.226
0.592
0.279
0.189
0.112
0.298
0.166
0.08
7.22
2.36
0.38
0.23
8.28
0.03
0.001****
0.001****
0.001****
0.05**
0.1*
0.001****
0.001****
****Highly significant at p < 0.001; **Significant at p < 0.05; *Significant at p < 0.1
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Rahul Paul et al
Table 3: Linear and angular changes observed on lateral cephalogram during phase I (active expansion period)
Sl. No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Parameters
Range (in mm)
Convexity at A
Palatal plane
Maxillary height
Maxillary depth
Mandibular plane angle
Facial axis
Facial depth
Lower facial height
Mandibular arc angle
Mean increase (mm)
0-1
0-0.5
1-2
0-1.5
0-16
0-1
1-2
0-1
0-1
0.3 ± 0.483
0.1 ± 0.21
0.8 ± 0.919
0.15 ± 0.474
0.5 ± 0.527
–0.5 ± 0.527
0.6 ± 0.615
0.4 ± 0.516
–0.4 ± 0.516
SE
t
0.153
0.660
0.290
0.150
0.166
0.166
0.195
0.163
0.163
p
1.96
1.49
2.75
1.0
3.01
3.01
3.07
2.45
2.45
NS
NS
0.05**
NS
0.02***
0.02***
0.02***
0.05**
0.02***
***Highly significant at p < 0.2; **Significant at p < 0.05; NS: Not significant
Table 4: Linear dental changes observed on study casts during phase II (Retention period)
Sl. No.
1.
2.
3.
Parameters
Range (in mm)
Maxillary intermolar width
Maxillary intercanine width
Mandibular intermolar width
0.1-0.2
0.1-0.3
0.5-1
Mean increase (mm)
SE
t
p
–0.05 ± 0.273
–0.07 ± 0.317
+ 0.50 ± 0.159
0.086
0.10
0.159
0.581
0.7
3.14
NS
NS
0.02***
***Significant at p < 0.05; NS: Not significant
Table 5: Linear dental and skeletal changes observed on frontal cephalogram during phase II (retention period)
Sl. No.
1.
2.
3.
4.
5.
6.
7.
Parameters
Range (in mm)
Maxillary width
Maxillary intermolar width
Maxillary intercanine width
Mandibular intermolar width
Nasal width
Average molarrelation
Average maxillomandibular relation
0-1
0.5-1
0.5-1
0.5-2
0-0.5
0-1
0-0.5
Mean increase (mm)
– 0.1
0.2 ± 0.349
– 0.15 ± 0.033
+ 0.45 ± 0.599
–0.05 ± 0.158
–0.02 ± 0.42
+0.1 ± 0.632
SE
t
p
0.1
0.111
0.107
0.189
0.05
0.133
0.20
1
1.8
1.4
2.38
1.0
1.5
0.5
NS
NS
NS
0.05**
NS
NS
NS
**Significant at p < 0.05; NS: Not significant
Table 6: Linear and angular changes observed on lateral cephalogram during phase II (retention period)
Parameters
Convexity at A
Palatal plane
Maxillary height
Maxillary depth
Mandibular plane angle
Facial axis
Facial depth
Lower facial height
Mandibular arc angle
Range (in mm)
0-1
0-1
0-1
0-0.5
0.5-1
0.5-1
0.5-1
0.5-1
0-1
Mean increase (mm)
–0.1 ± 0.316
–0.1 ± 0.21
–0.1 ± 0.21
–0.1 ± 0.21
+0.35 ± 0.47
–0.35 ± 0.474
–0.15 ± 0.33
–0.35 ± 0.412
+0.3 ± 0.463
SE
0.1
0.066
0.066
0.066
0.150
0.150
0.107
0.130
0.153
t
1
1.96
1.96
1.96
2.33
2.33
1.28
2.69
1.96
p
NS
NS
NS
NS
0.02***
0.02***
NS
0.05**
0.1*
*** Highly significant at p < 0.2; **Significant at p < 0.05; *Significant at p < 0.05; NS: Not significant
The relative orthodontic and orthopedic response produced
with nickel-titanium palatal expander, was a ratio of 6:1
indicating 16% of response obtained was skeletal.
Occlusal radiographs of maxilla showed radiographic
evidence of suture opening. The pattern of separation was greatest
anteriorly with a progressive decrease apparent posteriorly.
Phase II (Changes from Postexpansion to
Postretention)
Changes exhibited in various parameters on the study cast, linear
and angular measurements on the frontal and lateral
cephalograms are presented in Tables 4 to 6 respectively.
248
There was a significant increase in mandibular intermolar
width, thus showing that the increase in mandibular width tended
to follow suit the maxillary expansion.
Frontal cephalogram showed significant increase in
mandibular intermolar width whereas nonsignificant in all other
parameters. Lateral cephalogram (Table 6) showed significant
increase in mandibular plane angle, facial axis, lower face height
and mandibular arc angle and nonsignificant in other parameters
showing that the mandible tended to come back to its original
position.
Occlusal radiographs of maxilla showed recalcification of
midpalatal suture evidenced radiographically as radiopaque
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Efficacy of Nickel-Titanium Palatal Expanders
obliteration of suture on the termination of 12 weeks (3 months)
retention indicating that there was no evidence left to show that
the midpalatal suture opened up in phase I.
DISCUSSION
Maxillary expansion, by means of slow maxillary expansion
undoubtedly, has created a great impact on the contemporary
orthodontic thinking and therapy. In the present study, an
attempt has been made to analyze the effects of a newly
developed palatal expander, namely the nickel-titanium palatal
expander, producing slow maxillary expansion.
The mean increase in maxillary intermolar width, in present
study, was comparable to that reported by Wertz8 and twice as
much as reported by Hicks,9 Bell,10 Frank5 and Arndt. This
difference might be because of the amount of expansion needed
in different studies. In phase II, there was an insignificant
decrease in maxillary intermolar width and maxillary intercanine
width (indicating that the nickel-titanium palatal expander used
in the present study was rigid enough to hold the expanded
segments in place and worked as a fixed retainer) which are
contrary to the findings of Skeiller,11 Hicks9 and Kreb.12
The mean increase in the mandibular intermolar width, is
in conformity to that observed by Hicks but more as compared
to Bell and LeCompte.10 This difference could be attributed to
a shorter period used by Bell and LeCompte.10 Even in phase
II, mandibular intermolar width increase was significant and
similar to that reported by Wertz.8
The orthopedic changes, in respect of increase in maxillary
width and decrease in average maxillomandibular width in our
study, were comparatively higher than found by Frank and
Engel.5 The difference in appliance design could be the
attributable reason.
Increase in nasal width was observed during the active
expansion period which is in conformity with the findings
reported by Wertz,8 Frank5 and Haas.13 There was insignificant
relapse in phase II. There was no significant change in convexity
at point A, ANS and PNS position during the phase of expansion
while there was a significant increase in maxillary height
indicating downward movement of maxilla which is similar to
Wertz8 and Frank.5
In the present study, there was a significant increase in
mandibular plane angle (p < 0.02) and facial axis angle
(p < 0.02) indicating bite-opening associated with expansion
which is similar to Wertz,8 Hicks9 and Frank.5 Thus, indicating
significant downward movement of maxilla with no forward
movement.
The change in facial depth and mandibular arc angle was in
accordance with that of Wertz8 who reported that the mandible
in most of the cases rotated backward although the forward
rotation of the mandible was also seen in few cases.
There was a significant change in all the four parameters
viz, mandibular plane angle, facial axis angle, lower face height
and mandibular arc angle which indicated that the mandible
tended to return to its original posture during the retention phase.
These findings compare favorably with those by Wertz8 and
Haas,13 in their studies on rapid maxillary expansion.
Increase in transverse dimension of maxillary arch indicated
palatal suture opening. This is in accordance to findings
observed by Ferrario et al.14
Relative orthodontic and orthopedic changes observed were
similar to that found by Frank and Engel.5
Standard occlusal radiographs of maxillae showed the
pattern of palatal suture opening was greater anteriorly than
posteriorly, which is similar to that reported by Harberson and
Myers,15 Bell and LeCompte,10 Wertz8 and Haas.16 The reason
for this differential response could be the greater resistance to
skeletal opening offered by zygomatic buttress in the posterior
region. However, study casts and frontal cephalograms
demonstrated greater change posteriorly than anteriorly where
more of the orthodontic than orthopedic effect was observed.
These findings are also in conformity to that observed by Hicks,9
Bell and LeCompte10 and by Wertz.8 There was an evidence of
obliteration of midpalatal suture at the end of retention period,
which was in accordance with the findings by Ekstrom,17
Harberson and Myers15 and Bell and LeCompte,10 indicating
remineralization.
CONCLUSION
The nickel-titanium palatal expander brings about an increase
in maxillary as well as mandibular dental arch width as indicated
by increase in maxillary intermolar, maxillary intercanine,
mandibular intermolar width and the average molar relation. A
constant force exerted by the expander in the range of 250 to
300 gm had definite effects in growing age group as indicated
by a statistically significant increase in the maxillary width as
seen on frontal cephalogram. The ratio of relative orthodontic
to orthopedic effect with this appliance was approximately 6:1.
Consequent to maxillary expansion, there occurred a significant
downward movement of the maxillae and downward and
backward rotation of the mandible, except in the case where
forward rotation was observed. The posture attained by maxillae
was stable during the retention period while the mandible tended
to come forward to its original position. Radiographic evidence
of midpalatal suture opening during active phase was seen on
all the 10 cases, which was followed by suture remineralization
during the retention period. The passive expander proved to be
sufficiently rigid and 12 weeks of fixed retention period was
adequate for the retention of expanded maxillary segments
which was evidence by no relapse.
REFERENCES
1. Bell RA. Maxillary expansion in relation to rate of expansion
and patient’s age. Am J Orthod 1982;81:32-37.
2. Hass AJ. Palatal expansion: Just the beginning of dentofacial
orthopedics. Am J Orthod 1970;57:219-55.
3. Storey E. Tissue response to the movement of bones. Am J
Orthod 1973;64:229-47.
4. ARNDT WY. Nickel Titanium Palatal Expander. J Clin Orthod
1993;28:129-37.
The Journal of Indian Orthodontic Society, October-December 2011;45(4):243-250
249
Rahul Paul et al
5. Frank SW, Engel GA. The effects of maxillary quadhelix
appliance expansion on cephalometric measurements in growing
orthodontic patients. Am J Orthod 1982;81:378-89.
6. Ricketts RM. Perspective in the clinical application of
cephalometrics. Angle Orthod 1981;51:115-50.
7. Rakosi T. An atlas and manual of cephalometric radiography.
London Wolfe Medical Publications Ltd. 1982.
8. Wertz RA. Skeletal and dental changes accompanying rapid
midpalatal suture opening. Am J Orthod 1970;58:41-66.
9. Hicks EP. Slow maxillary expansion: A clinical study of the
skeletal versus dental response to low magnitude force. Am J
Orthod 1978;73:121-41.
10. Bell RA, LeCompte EJ. The effects of maxillary expansion using
a quad helix appliance during the deciduous and mixed dentition.
Am J Orthod 1981;79:152-61.
11. Skeiller V. Expansion of the mid palatal suture by removable
plates, analysed by the implant method. Trans Eur Orthod Soc
1964;143-57.
250
12. Krebs AA. Expansion of the mid palatal suture studied by the
implant method over a 7yr period. Trand Eur Orthod Soc
1964;40:131-42.
13. Haas AJ. Rapid expansion of maxillary dental arch and nasal
cavity by opening of the mid-palatal suture. Angle Orthod
1961;31:73-90.
14. Ferrario VF, Garattin G, Colombo A, Flippi V, Pozzoli S, Sforza
C. Quantitative effects of a nickel-titanium palatal expander on
skeletal and dental structure in the primary and mixed dentition:
A preliminary study. Eur J Orthod 2003;25:401-10.
15. Harberson VA, Myers DR. Midpalatal suture opening during
functional crossbite correction. Am J Orthod 1978;74:310-13.
16. Haas AJ. The treatment of maxillary deficiency by opening the
midpalatal suture. Angle Orthod 1965;35:200-17.
17. Ekstrom C, Henrikson CO, Jensen R. Mineralization in the
midpalatal suture orthodontic expansion. Am J Orthod 1977;71:
449-54.
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