Download Pitchfork Analysis of Class II Correction using

10.5005/jp-journals-10021-1166
ORIGINAL ARTICLE
Meenu Goel et al
Pitchfork Analysis of Class II
Correction using Forsus FRD
1
Meenu Goel, 2Saurabh Sonar, 3Mudita Srivastav, 4Puneet Batra, 5Anurag Bhagat
ABSTRACT
Introduction: A paradigm shift in nonsurgical treatment modality, i.e. fixed functional appliances have been shown to correct the overjet and the
Class II molar relationship via a combination of skeletal and dental changes.
Aim: To evaluate the skeletal and dental changes using Forsus Fatigue Resistant Device (FRD) (3M Unitek Corp, Monrovia, California, USA) in
young adults during Class II correction.
Materials and methods: Lateral cephalograms of post leveling and aligning sample (T1) and post Forsus sample (T2) of 10 orthodontically
treated young adult patients (CVMI-CS5) with borderline skeletal Class II malocclusion (ANB = 3°-7°) due to mandibular retrognathism, requiring
skeletal mandibular sagittal correction were selected. The skeletal and dental treatment changes were analyzed using the Pitchfork analysis
(PFA).
Results: The PFA showed that the maxilla and mandible moved mesially by 0.3 and 3.2 mm, respectively; the average apical base change was
2.9 mm. The maxillary molar moved distally 0.5 mm, and the mandibular molar moved mesially 1.6 mm. Molar intercuspation changed by 5 mm.
The upper incisor moved palatally by 1.5 mm, and the lower incisor moved labially by 2.8 mm. Total overjet change was 6.2 mm.
Conclusion: The FRD protocol led to a successful correction of Class II malocclusion with more of skeletal than dental correction. However,
more parameters are required to assess the mandibular growth and remodeling of the glenoid fossa.
Keywords: Pitchfork analysis, Forsus FRD, Class II malocclusion.
How to cite this article: Goel M, Sonar S, Srivastav M, Batra P, Bhagat A. Pitchfork Analysis of Class II Correction using Forsus FRD. J Ind
Orthod Soc 2013;47(4):240-244.
INTRODUCTION
Class II malocclusion presents a major and common challenge
to orthodontists. Numerous orthodontic techniques and
appliances have been introduced to treat Class II
malocclusions, including intra-arch and interarch appliances,
extraoral appliances, selective extraction patterns, and surgical
repositioning of the jaws.
Class II skeletal malocclusions are commonly treated with
fixed appliance therapy or with a functional appliance followed
by a fixed appliance. Recent studies suggested that fixed
functional appliances can be effective in correcting Class II
skeletal abnormalities by promoting growth of the mandible
and remodeling of the glenoid fossa.1-3
It has been reported that the effectiveness of functional
therapy depends on both the treatment timing (skeletal maturity
1,3
Senior Lecturer, 2Professor, 4Professor and Head, 5Reader
Department of Orthodontics, Institute of Dental Studies and
Technologies, Ghaziabad, Uttar Pradesh, India
1-5
Corresponding Author: Meenu Goel, Senior Lecturer, Department of
Orthodontics, Institute of Dental Studies and Technologies, DelhiMeerut Road, Kadrabad, Modinagar, Ghaziabad, Uttar Pradesh, India
Phone: 9897353694, e-mail: [email protected]
Received on: 24/8/12
Accepted after Revision: 14/2/13
240
at the start of functional therapy) and the type of functional
appliance.4-6 According to several studies, mandibular growth
can extend beyond puberty, and minimal residual growth can
only be stimulated with fixed functional appliances.7-11 Ruf
and Pancherz,8-9 Konik et al,10 and Kinzinger and Diedrich11
stated that the treatment of late adolescents and young adults
with rigid fixed functional appliances, such as the Herbst or
functional mandibular advancement resulted in correction of
the Class II malocclusion with the skeletal and dental changes.
The present study was designed to evaluate the skeletal
and dental changes using Forsus Fatigue Resistant Device
(FRD) (3M Unitek Corp, Monrovia, California, USA) in young
adults during Class II correction.
MATERIALS AND METHODS
A post leveling and aligning sample (T1) of orthodontically
treated patients was selected from the Department of
Orthodontics of Institute of Dental Studies and Technologies
(IDST), Kadrabad, Modinagar, India. The criteria for patient
selection were:
• Young adult patients (CVMI-5)12 with borderline skeletal
Class II malocclusion (ANB = 3° to 7°) due to mandibular
retrognathism, requiring skeletal mandibular sagittal
correction. As the correlation values between Fishman
maturation prediction (FMP) method and cervical
vertebral maturation (CVM) method are moderately high.13
A distinctive advantage of the cervical maturity evaluation
JIOS
Pitchfork Analysis of Class II Correction using Forsus FRD
•
•
•
•
•
•
is that it does not imply extraradiation exposure for the
patient.
Presence of permanent dentition up to 2nd molars.
Pretreatment permanent dentition with a minimum of half
the cusp width of Class II molar relation.
Increased overjet, not less than 5 mm.
Positive pretreatment visual treatment objective (VTO).
Treatment completed without any permanent teeth
extracted (excluding third molars).
Good quality pretreatment and post-treatment
cephalometric radiographs.
A total of 10 subjects were included in this trial after
consultation with the statistician. The patients underwent
functional appliance phase over a period of minimum 6 months.
Patients were treated with 0.022 MBT preadjusted edgewise
appliance. Before insertion of Forsus FRD the maxillary and
mandibular dental arches were stabilized with the help of
0.0193" × 0.0253" stainless steel wire, torque of 10° was
introduced in the lower anterior segment and the wires were
cinched back distal to molars. A Guerin lock was also placed
distal to the canine bracket. Forsus FRD spring was placed in
maxillary first molar head gear tube and distal to the mandibular
Figs 1A to C: (A) Pretreatment after leveling and aligning, (B) forsus FRD spring for mandibular advancement,
(C) post-treatment after mandibular advancement
Fig. 2A: Pitchfork superimposition 1. The superimposition is on the nasal
line, palatal curvature and anterior contour of key ridge. All measurements
are carried out parallel to the mean functional occlusal plane (MFOP).
Maxilla is measured at the SE-points, ABCH at the D-points, and upper
molar change at the mesial contact points and incisor-change at the
incisal edges
Fig. 2B: Pitchfork superimposition 2. The tracings are displaced along
the MFOP until the D-points are lying on a common perpendicular line to
MFOP. Again all the measurements are undertaken parallel to MFOP.
Lower molar change is measured at the mesial contact points and incisor
change at the incisal edges
Fig. 2C: Pitchfork superimposition 3. The tracings are displaced again
until the mesial contact points of the upper molars are lying on a common
perpendicular line to MFOP. The molar intercuspation change is measured
at the mesial contact points of the lower molars
Fig. 2D: Pitchfork superimposition 4. The tracings are displaced again
until the incisal edges of the upper incisors are lying on a common
perpendicular line to MFOP. The overjet change is measured at the incisal
edges of the lower incisors
The Journal of Indian Orthodontic Society, October-December 2013;47(4):240-244
241
Meenu Goel et al
both groups. The upper and lower incisors were moved
mesially. Overjet was improved in all patients. The study
showed a decrease of saddle angle by 1.0° ± 0.6°.
DISCUSSION
Fig. 3: Diagram of pitchfork analysis (maxilla+ mandible = ABCH;
ABCH + U6 + L6 = 6/6; ABCH + U1+ L1 = 1/1)
canine. The stepwise advancement of the mandible was done
with initial advancement of 4 to 5 mm, followed by
incremental advancement of 2 mm after 2 months, if required.
This was maintained for a period of minimum of 6 months
(Figs 1A to C).
The pretreatment and post-treatment cephalometric
radiographs were hand-traced on acetate paper. In order to
describe the sagittal treatment changes that occurred, the
radiographs were analyzed using the pitchfork analysis
(PFA).14 The PFA accounts for and summarizes sagittal
mandibular and maxillary molar movements, sagittal maxillary
and mandibular advancement relative to the cranial base, and
the combination of all of these movements in correcting the
molar relationship.
Distal maxillary skeletal and dental movements and mesial
mandibular skeletal and dental movements, which aid in Class II
correction, were assigned positive values. Movements that
worsen Class II relations were assigned negative values. Incisor
movements that affect overjet were also measured and
summarized. All measurements were made at the level of the
functional occlusal plane, which was drawn through the
occlusal contact points of the molars and premolars.
RESULTS
The tracings were superimposed as described by Johnston14
(Figs 2A to D). All measurements are described positive if
they contribute to Class II correction and negative if they
aggravate Class II relationship.
The PFA showed that the maxilla and mandible moved
mesially by 0.3 and 3.2 mm, respectively; the average apical
base change was 2.9 mm. The maxillary molar moved distally
0.5 mm, and the mandibular molar moved mesially 1.6 mm.
Molar intercuspation changed by 5 mm. The upper incisor
moved palatally by 1.5 mm, and the lower incisor moved
labially by 2.8 mm. Total overjet change was 6.2 mm (Table 1
and Fig. 3).
During treatment, the mandible and maxilla moved
mesially, with the mandible moving more than the maxilla in
242
The goal of functional appliance therapy is to encourage or to
redirect the growth in a favorable direction. Several functional
appliances are presented in the literature for the correction
of Class II division 1 malocclusion. The major differences in
the effects between various orthopedic appliances are mainly
related to the technique of fabrication, construction bites, and
hours of wear. Removable appliances are considered
uncomfortable and unesthetic by many patients and require
patient compliance. Consequently, a primary advantage of fixed
functional appliances is independence from the need for
patient cooperation.
The present study has evaluated the dental and skeletal
effects using PFA in young adults treated with Forsus FRD.
The PFA enables a clear distinction between skeletal and dental
changes in the sagittal dimension to describe therapeutic
effects caused by treatment strategies on orthodontic Class II
patients. Measurement data are usually recorded in the form
of diagrams that give the appearance of pitchforks. The
diagrams provide differential insight and permit informative
comparisons.14
The results showed that the molar relationships of patients
treated were corrected primarily due to mandibular growth
changes. Anterior mandibular displacement accounted for
3.2 mm or approximately 64% of the 5 mm molar correction.
Mesial mandibular molar movements accounted for 32% of
the total correction. In contrast, treatment changes in the
maxilla worked against the molar corrections, with anterior
maxillary skeletal movement of 6% and distal dental
movements of 10%.
Many previous studies also reported restriction in the
forward growth of maxilla by twin-block, 15-19 by other
mandibular protraction appliances,20 and also by many other
functional appliances.15,17,21 However, few studies reported
no restraint effect in the forward movement of maxilla by the
removable22,23 and fixed functional appliances.24,25 Thus, the
design of the appliance was not a major factor in the headgear
effect of functional appliance therapy.
Table 1: Comparison of pretreatment and post-treatment variables
and treatment changes in the and Forsus FRD groups
Variable
Maxilla (mm)
Mandibular (mm)
ABCH (mm)
U6
L6
U6/L6
U1
L1
U1/L1
Mean
–0.3
3.2
2.9
0.5
1.6
5.0
1.5
2.8
6.2
SD
0.48
1.31
1.59
0.84
0.84
1.56
0.70
1.39
2.89
JIOS
Pitchfork Analysis of Class II Correction using Forsus FRD
A net reduction of 6.2 mm was recorded for the overjet,
while a net improvement of 5 mm was obtained for the molar
relationship which accounts for the Class II correction. Lower
incisor moved labially by 2.8 mm which contributed to 45.2%
of overjet correction. Upper incisor moved palatally by
1.5 mm thus contributed to 8% of overjet reduction.
A general overview of the effects of Class II treatment
with Forsus FRD leads to the consideration that skeletally one
of the main outcomes of this protocol consists of a significant
change in the sagittal position of the mandible. This mandibular
advancement can be because of remodeling of the glenoid fossa
or mandibular growth. The saddle angle was evaluated to assess
the skeletal changes which showed a decrease of 1.0° ± 0.6°.
According to Rabie et al26 the Indian hedgehog gene is the
mechanotransduction mediator in the condyle. The expression
of Indian hedgehog elicited by mechanical loading of the
mandibular joint promoted mesenchymal cell proliferation and
initiated a cascade of cellular and molecular responses that
led to condylar growth. Indian hedgehog, a member of the
vertebrate hedgehog morphogen family, was reported to be
key morphogen during skeletal development and regeneration.
On the other hand, the skeletal outcomes of the FRD protocol
with regard to the maxilla appeared to be rather limited. The
lack of a significant effect of the FRD on the sagittal position
of the maxilla might be correlated with the short duration of
active treatment and the normal growth of maxilla.
Retroclination of the maxillary incisors (U1) and
proclination of mandibular incisors (L1) are a widely accepted
consensus with various functional appliances.27 In present
study, the upper incisors tipped palatally by 1.5 mm. The palatal
movement of the U1 was due to the reciprocal force that acted
distally on the maxillary dental arch. The mandibular incisors
tipped labially by 2.8 mm in present study. This could be due
to the mesial force on the L1 induced by the forward posture
of the mandible. This finding is in accordance with the effects
of other functional appliances.25 Various researches28-34
showing skeletal and dental changes with different functional
appliances are tabulated in Table 2.
The outcomes reported in the current study refer to the
end of comprehensive Class II treatment. However, it should
be noted that more than half of the patients in the FRD group
completed their treatment protocols at very advanced post
pubertal stages in skeletal maturation (CS5 or CS6). The
amount of craniofacial growth occurring after those stages is
very limited in Class II subjects, and, more importantly, growth
differences between Class II and normal occlusion subjects
Table 2: Studies of different functional appliances
Functional appliance
Modified twin block28
Herbst appliance29-32
Jasper Jumper33
Eureka Spring34
Amount of
skeletal change
70%
60%
40%
10%
Amount of
dental change
30%
40%
60%
90%
after late puberty are insignificant. When orthodontic therapy
of Class II malocclusion is completed at late puberty, close
to completion of active craniofacial growth, relapse tendency
due to a re-establishment of Class II growth characteristics is
expected to occur less often.
As there are many factors involved in the correction of
disproportionate jaw relationships, therefore above-mentioned
findings should be interpreted with caution. Further studies
including more parameters and larger sample size are required
and the results of a long term follow-up are essential to address
issues of stability.
CONCLUSION
•
•
•
•
The FRD protocol led to a successful correction of Class II
malocclusion.
The protocol had a greater skeletal effect on the mandibular
structures by advancing the mandible and mesial movement
of mandibular molars.
The appliance was not efficient in restricting the forward
growth of the maxilla.
At the dentoalveolar level, a large amount of mesial
movement of the lower incisors and first molars occurred.
REFERENCES
1. McNamara JA Jr, Carlson DS. Quantitative analysis of
temporomandibular joint adaptation to protrusive function. Am J
Orthod 1979 Dec;76(6):593-611.
2. Woodside DG, Metaxas A, Altuna G. The influence of functional
appliance therapy on glenoid fossa remodelling. Am J Orthod
Dentofacial Orthop 1987 Sep;92(3):181-198.
3. Paulsen HU, Karle A, Bakke M, Heskind A. CT scanning and
radiographic analysis of temporomandibular joints and
cephalometric analysis in a case of Herbst treatment in late
puberty. Eur J Orthod 1995 Jun; 17(3):165-175.
4. Malmgren O, Omblus J, Hagg U, Pancherz H. Treatment with an
orthopedic appliance system in relation to treatment intensity and
growth periods. A study of initial effects. Am J Orthod Dentofacial
Orthop 1987 Feb;91(2):143-151.
5. Hagg U, Pancherz H. Dentofacial orthopaedics in relation to
chronological age, growth period and skeletal development. An
analysis of 72 male patients with Class II division 1 malocclusion
treated with the Herbst appliance. Eur J Orthod 1988
Aug;10(3):169-176.
6. Cozza P, Baccetti T, Franchi L, De Toffol L, McNamara JA.
Mandibular changes produced by functional appliances in Class II
malocclusion: a systematic review. Am J Orthod Dentofacial
Orthop 2006 May;129(5):599.e1-12.
7. Pancherz H, Littmann C. Morphology and position of mandible in
Herbst treatment. Cephalometric analysis of changes to end of
growth period. Inf Orthod Kieferorthop 1989;21(4):493-513.
8. Ruf S, Pancherz H. Dentoskeletal effects and facial profile changes
in young adults treated with the Herbst appliance. Angle Orthod
1999 Jun;69(3):239-246.
9. Ruf S, Pancherz H. Herbst/multibracket appliance treatment of
Class II division 1 malocclusions in early and late adulthood. A
prospective cephalometric study of consecutively treated subjects.
Eur J Orthod 2006 Aug; 28(4):352-360.
10. Konik M, Pancherz H, Hansen K. The mechanism of Class II
correction in late Herbst treatment. Am J Orthod Dentofacial
Orthop 1997 Jul;112(1):87-91.
The Journal of Indian Orthodontic Society, October-December 2013;47(4):240-244
243
Meenu Goel et al
11. Kinzinger G, Diedrich P. Skeletal effects in Class II treatment
with the functional mandibular advancer (FMA). J Orofac Orthop
2005 Nov;66(6):469-490.
12. Baccetti T, Franchi L, McNamara Jr JA. The cervical vertebral
maturation (CVM) method for the assessment of optimal treatment
timing in dentofacial orthopedics. Semin Orthod 2005
Sep;11(3):119-129.
13. Flores C, Burgessb CA, Champneyc M, Jensend RJ, Pitchere
MR, Majorf PW. Correlation of skeletal maturation stages
determined by cervical vertebrae and hand-wrist evaluations.
Angle Orthod 2006 Jan;76(1):1-5.
14. Johnston LE Jr. Balancing the books on orthodontic treatment: an
integrated analysis of change. Br J Orthod 1996 May;23(2):93102.
15. Toth LR, McNamara JA Jr. Treatment effects produced by the
twin-block appliance and the FR-2 appliance of Frankel compared
with an untreated Class II sample. Am J Orthod Dentofacial
Orthop 1999 Dec;116(6):597-609.
16. Mills CM, McCulloch KJ. Post-treatment changes after successful
correction of Class II malocclusions with twin-block appliance.
Am J Orthod Dentofacial Orthop 2000 Jul;118(1):24-33.
17. Trenouth MJ. Proportional changes in cephalometric distance
during twin-block appliance therapy. Eur J Orthod 2002
Oct;24(5):485-491.
18. O’Brien K, Wright J, Conboy F, Sanjil Y, Mandall N, Chadwick
S, Connolly I, Cook P, Birnie D, Hammond M, et al. Effectiveness
of early orthodontic treatment with twin-block appliance: a
multicenter, randomized, controlled trial. Part 1: dental and skeletal
effects. Am J Orthod Dentofacial Orthop 2003 Sep;124(3):234243.
19. Jena AK, Duggal R, Parkash H. Skeletal and dentoalveolar effects
of twin-block and bionator appliances in the treatment of Class II
malocclusion: a comparative study. Am J Orthod Dentofacial
Orthop 2006 Nov;130(5):594-602.
20. Siqueira DF, de Almeira RR, Janson G, Branda˜o AG, Coelho
Filho CM. Dentoskeletal and soft-tissue changes with cervical
headgear and mandibular protraction appliance therapy in the
treatment of Class II malocclusions. Am J Orthod Dentofacial
Orthop 2007 Apr;131(4):447.e21-e30.
21. Vanlaecken R, Martin CA, Dischinger T, Razmus T, Ngan P.
Treatment effects of the edgewise-Herbst appliance: a
244
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
cephalometric and tomographic investigation. Am J Orthod
Dentofacial Orthop 2006 Nov;130(5):582-593.
Clark WJ. The twin-block technique. A functional orthopedic
appliance system. Am J Orthod 1988 Jan;93(1):1-18.
Illing HM, Morris DO, Lee RT. A prospective evaluation of Bass,
bionator and twin-block appliances. Part I: the hard tissues. Eur J
Orthod 1998 Oct;20(5):501-516.
Pangrazio-Kulbersh V, Berger J, Chermak DS, Kaczynski R, Simon
ES, Haerian A. Treatment effects of the mandibular anterior
repositioning appliance on patients with Class II malocclusion.
Am J Orthod Dentofacial Orthop 2003 Mar;123(3):286-295.
Valant JR, Sinclair PM. Treatment effects of the Herbst appliance.
Am J Orthod Dentofacial Orthop 1989 Feb;95(2):138-147.
Ng TC, Chiu KW, Rabie AB, Hagg U. Repeated mechanical
loading enhances the expression of Indian hedgehog in condylar
cartilage. Front Biosci 2006 Jan;11:943-948.
Jena AK, Duggal R. Treatment effects of twin-block and
mandibular protraction appliance-IV in the correction of Class II
malocclusion. Angle Orthod 2010 May;80(3):485-491.
DeVincenzo JP, Huffer RA, Winn MW. A study in human subjects
using a new device designed to mimic the protrusive functional
appliances used in monkeys. Am J Orthod Dentofacial Orthop
1987 Mar;91(3):213-224.
Pancherz H. The mechanism of Class II correction in Herbst
appliance treatment. A cephalometric investigation. Am J Orthod
1982 Aug;82(2):104-113.
Wieslander L. Intensive treatment of severe Class II malocclusions
with a headgear-Herbst appliance in the early mixed dentition.
Am J Orthod 1984 Jul;86(1):1-13.
Wieslander L. Long-term effect of treatment with the headgearHerbst appliance in the early mixed dentition. Stability or relapse?
Am J Orthod Dentofacial Orthop 1993 Oct;104(4):319-329.
Hansen K, Pancherz H, Hagg U. Long-term effects of the Herbst
appliance in relation to the treatment growth period: a cephalometric
study. Eur J Orthod 1991 Dec;13(6): 471-481.
Weiland FJ, Bantleon HP. Treatment of Class II malocclusions
with the Jasper Jumper appliance: a preliminary report. Am J
Orthod Dentofacial Orthop 1995 Oct;108(4):341-350.
Stromeyer EL, Caruso JM, DeVincenzo JP. A cephalometric study
of the Class II correction effects of the Eureka Spring. Angle
Orthod 2002 Jun;72(3):203-210.