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Asociación Mexicana de Ortopedia Maxilar A.C. |
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CEFALOMETRIA |
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Dr. Prof. Sabine Ruf |
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Asociación Mexicana de Ortopedia Maxilar A.C. |
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CEFALOMETRIA |
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Dr. Prof. Sabine Ruf |
Encuentro Internacional de Ortopedia Dentofacial Amom 2002 México-Alemania,
Pto. Vallarta 27 Nov.- 1 Dic
7 Reunión Anual de Ortopedia Maxilar.
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The Herps Appliance in Modern Orthodontics
Introduction, clinical procedues, complications
Based on the "bite jumping" idea introduced by Kingsley in 1877, Emil
Herbst developed his appliance in the early 1900s and presented it for the first
time at the International Dental Congress in Berlin in 1909.
Twenty-five years later, in 1934, Herbst wrote about his experiences with the
appliance in 3 articles.
After that time, very little was published about the subject until Pancherz
reintroduced the
treatment method in 1979.
Initially, Pancherz used the Herbst bite jumping mechanism as a scientific
tool in clinical-experimental orthodontic-orthopedic research. Through the years,
however, it became obvious that the appliance is most useful in the therapy
of severe Class II malocclusions. In comparison to conventional functional appliances
(eg. activator, bionator, Fränkel), the Herbst appliance has several clinical
advantages:
The appliances is fixed to the teeth, works continuously 24 hours a day, does
not interfere with speech, and requires no patient compliance to attain the
desired treatment effects.
Different clinical designs have been used since 1979 (simple banded anchorage
system,
extended banded achorage system, casted maximum anchorage system). The clinical
procedures required for Herbst appliance treatment will be explained step by
step for every appointment. In comparison to the banded Herbst appliance, the
cast splint appliance has many advantages: It has a precise fit on the teeth,
is strong and hygienic, and saves chair time because it is easy to insert and
causes few clinical problems (no broken bands). Due to the higher laboratory
costs of the cobaltchromium splints, acrylic splints have been advocated by
some clinicians. However, acrylic splints break more easily and are less hygienic.
Complications during Herbst treatment are seldom, generally minor and easy
to control.
All complications encountered during the last decades
as well as the way to manage them will be presented.
Treatment effects and possibilities Part I
In current dentofacial orthopedics, Herbst appliance therapy, followed by a
conventional multibracket appliance treatment phase, is a most efficient 2-step
approach in the management of severe Class II malocclusions. In the first step,
Class II correction is accomplished with the Herbst appliance
(6 to 8 months of treatment).
When the appliance is placed at the start of Herbst treatment, the mandible is usually advanced to an incisal edge-to-edge position and the condyles are positioned on the top of the articular eminence. During the course of therapy, however, the condyles return to their original fossa position.
This is accomplished by adaptive dental and skeletal changes: posterior movement
of the maxillary dentition and anterior movement of the mandibular dentition,
stimulation of sagittal condylar growth in a more
favorable direction, and remodeling of the glenoid fossa.
The Herbst/multibracket appliance approach makes it possible to treat severe
Class II malocclusions, which otherwise would have been very difficult, if not
impossible, to handle without extraction or orthognathic surgery. Our clinical-experimental
research throughout the years has shown that the Herbst appliance is most useful
in the Class II subjects and situations described below.
Class II, Division 1 malocclusions
This malocclusion is the main indication for Herbst therapy. In cases with a
narrow maxilla, it is advantageo us to combine the maxillary splint with a rapid
maxillary expander or a quad-helix.
In most Class II, Division 1 cases, an undesirable side effect of the Herbst
appliance is the proclination of the mandibular incisors. This effect is the
result of anchorage loss, due to the forces exerted by the telescope mechanism
on the anterior teeth. The incisor proclination is difficult to control independently
of the anchorage system used. However, no increased incidence of mandibular
anterior crowding could be found several years posttreatment despite a spontaneous
uprighting of the teeth after Herbst therapy.
Class II, Division 2 malocclusions
The Herbst appliance is also very effective in Class II, Division 2 cases. In
this type of malocclusion, the mandibular incisors (as well as the maxillary
incisors) have a retroclined position. Therefore, the mandibular anchorage loss
(proclination of the mandibular anterior teeth) during Herbst
treatment can be used advantageously to reduce the interincisal angle and to
create a stable anterior
occlusion. This would be a prerequisite for the prevention of a deep bite relapse.
Class II malocclusions with a hyperdivergent jaw base relationship are generally
considered to have an unfavorable growth pattern, making their treatment difficult.
As the Herbst appliance has been shown to increase condylar growth in the therapeutically
desired sagittal direction without resulting in a posterior (backward) rotation
of the mandible, high-angle Class II subjects are good candidates
for successful Herbst therapy.
Retrognathic facial profile
The excessive facial profile convexity characteristic of Class II malocclusions
is generally reduced by Herbst therapy. This effect is obvious both in subjects
treated during growth and those treated at the end of
growth. The most favorable soft tissue profile changes are seen in Class II
Malocclusions with a retrognathic chin, retruded lower lip, and protruded upper
lip.
Maxillary anterior crowding
Besides the orthopedic effect on the mandible, the Herbst appliance has a pronounced
high-pull headgear effect on the maxillary molars. During therapy, the molars
are distalized and significantly intruded.
The headgear effect is most useful in gaining anterior space and relieving crowding
in the maxillary
canine and incisor areas.
Treatment effects and possibilities Part II
Early vs. Late treatment For an efficient Class II correction removable funct
ional appliances depend upon simultaneous guidance of the vertical dentoalveolar
development and are thus only indicated in the mixed dentition.
The ideal treatment period for the Herbst appliance in terms of efficiency,
stability and minimal retention time is in the permanent dentition after the
pubertal peak of growth.
Class II adults treated with either the Herbst appliance or with mandibular
sagittal split osteotomy.
Comparable changes in sagittal maxillary/mandibular jaw base relationship and
skeletal profile convexity were seen in the 2 groups at the end of treatment
(after final tooth alignment with multibracket appliances. Furthermore, in comparison
to surgery, Herbst treatment implies lower costs and lower risks for the patient
without increasing total treatment time. Thus, with respect to age and growth
development, the following modified new concept for Class II therapy is proposed:
Growth adaptation in children, adolescents, postadolescents, and young adults
Camouflage orthodontics in older adults
Surgical correction in older adults
TMJ patients
Our short- and long-term TMJ research using tomography and MRI has shown no
adverse effects of H Uerbst treatment on the different hard and soft tissue
joint structures. However, many cases have demonstrated that Herbst therapy
results in a retrusion of the articular disc. This effect can be used in the
therapy of Class II malocclusions with milder forms of anterior disc displacement
to attain a
reduction of the disc malposition.
