a new device for absolute anchorage in orthodontics. ajodo 1995.

A NEW DEVICE FOR ABSOLUTE
ANCHORAGE IN
ORTHODONTICS
www.indiandentalacademy.com

INTRODUCTION
 A new device to provide anchorage for orthodontic
tooth movement.
 A thin titanium alloy (6A14V) disk (onplant),
textured and hydroxyl apatite coated on one side, with
a threaded hole on the opposite side to be inserted
subperiosteally with the HA-coated side against bone
for bio integration.
 Can be placed in patients in various states of dental
eruption avoiding the unerupted and erupted teeth.
 This article reviews a dog study demonstrating
unilateral tooth movement towards the "onplant" and
a monkey study mimicking its use to anchor the
molars for anterior retraction.

MATERIALS AND METHODS
Onplant device
 The surface of the onplant that lies against bone is
textured and coated with a 75 µm thick layer of
hydroxyl apatite.
 The surface facing soft tissue is smooth titanium alloy
with an internal threaded hole at its centre into
which abutments can be placed.
 The initial onplants were a thin (2 mm thick × 10
mm diameter) disk with a sharp 90° angle at the
periphery.
 This design was modified to a more tapered shape
because of the soft tissue dehiscence caused by the

Canine study (Dog study)
Four mongrel dogs
Purpose
 To determine the ability of the onplant, once biointegrated
to bone, to remain stable when subjected to orthodontic
forces.
Procedure
 General anaesthesia was induced with an intravenous
pentobarbital.
 A full thickness mucoperiosteal incision was made in the
anterior region of the palate, followed by formation of two
subperiosteal tunnels reaching the first molars.

 Tunnelling was used to place the incision away from the
onplant. In each dog two onplants were placed onto the palate.
 The tunnels were conservatively formed to prevent migration
of the onplants after they were placed into the desired position.
In addition, one onplant was placed over the lateral ramus for
mechanical testing in two dogs.
 After 10 weeks, which were allowed for healing, one of the
onplants was exposed by removing a circular patch of palatal
tissue directly over the onplant. The healing screw was
removed, and a ball-shaped abutment was placed into the
internally threaded hole within the onplant.
 A hole was then created through the maxillary first premolar
on the contralateral side of the maxilla.
 A spring was placed and attached to the ball abutment, and
was activated between the tooth and the abutment to exert 11
ounces of force.

 The springs were checked weekly and reactivated when
needed. Impressions were taken every month to compare
the initial position of the tooth and subsequent positions.
 All the dogs were killed after 5 months. The maxillae were
retrieved intact and fixed in 10% neutral buffered formalin.
 After 10 days of fixation, the onplants were carefully
resected with accompanying bone and processed for
histologic evaluation.
 The tissue blocks were embedded in plastic and 30 µm
thick sections cut with a Leitz microtome (Ernest Leitz
Wetzlar, GMBH, Germany), then stained with Alizarin red.

Monkey study
Purpose
To stimulate an intended use of the onplant to stabilize
molars during retraction of the anterior dentition to mimic
a situation commonly encountered in clinical orthodontics.
Procedure
 Five monkeys were used.
 One monkey served as a control, and the remaining four
had one onplant placed in the middle of the palate opposite
the maxillary second molar.
 The onplant was placed through an incision made
anteriorly to prevent placing the incision directly over the
onplant.
 Two onplants had sharp 90° peripheral edges and two had
tapered edges. After 12 weeks for healing, the onplants
were exposed and the abutments placed.

 Two of the monkeys had prosthetic abutments inserted into
the onplants that were transferred to a model for
fabrication of a cast gold transpalatal bar.
 It was screwed into the abutment in the onplant and
soldered to orthodontic bands to the first molar on one side
and the second molar on the other side (Fig).
 The other two monkeys had an abutment placed with a
small groove that allowed engagement of a transpalatal
wire. A 0.051-inch wire was bent to engage the grooved
abutment and was soldered to previously adapted
orthodontic bands (Fig).
 The fifth monkey had a palatal bar made from 0.051-inch
wire soldered to the molar teeth only (Fig).

 At the time of onplant placement, the monkeys' first and
second maxillary premolars were extracted bilaterally,
creating space between the maxillary first molars and the
canines.
 The bar or wire was connected to the first molar on one
side and the second molar on the opposite side.
 Bilateral stainless steel springs from the canines to the
first molars.
250 gm reciprocal force.
calibrated weekly to keep the forces constant.
 Impressions were taken preoperatively and every 2 months
until the conclusion of the study.

 The monkeys were killed after 6 months.
 At that time, two of the onplants were removed without
difficulty with an osteotome to examine the underlying
bone.
 The remaining three monkeys had the onplants left in
place for direct examination after defleshing.
 The heads of the five monkeys were defleshed to study the
movements of the teeth and underlying bone of the maxilla.

RESULTS
Canine study
 In one of the four dogs a large soft tissue dehiscence
developed over the sharp edge of the onplant in which an
infection resulted. This onplant did not integrate.
 The onplants of the remaining three dogs integrated and
were activated.
 According to the measurements of study models of the
maxilla, the onplants did not move in relation to the
incisors or the molars. However, the premolar attached to
the onplant moved toward the onplant in each animal.
 At the conclusion of the study, one tooth moved 4 mm and
the other two teeth had moved 8 mm (Fig). The soft tissue
around the onplant was normal in appearance, with slight
inflammation consistent with plaque accumulation.

 Histologic examination of the loaded and unloaded
onplants revealed no significant differences between the
loaded and unloaded control onplants.
 In all instances, bone was found directly apposed to the HA
coating.
 In some regions, dense bone was found connecting the
palatal bone to the onplant.
 However, in most regions, trabecular-type bone was found
traversing the gap between the underlying palatal bone and
the onplant.
 The coating was intact, without evidence of resorption.
 Macrophages and osteoclasts were not seen.

Monkey study
 The soft tissue response was different between the sharp
and the tapered edge onplants.
 There was a small soft tissue dehiscence over the two sharp
edge onplants but no soft tissue dehiscence over the tapered
edge onplants (Fig).
 All onplants integrated.

 The anchored molars moved an average of 1.2 ± 0.2 mm
toward the central incisors.
 The nonanchored molars moved an average of 4.1 ± 1.4
mm toward the central incisors (p < 0.01).
 The canines on the anchored side moved an average of 1.9
± 0.6 mm away from the central incisors, and the canines
on the nonanchored side moved an average of 1.9 ± 0.7 mm
away from the central incisors (p > 0.01).
 The anchorage was slightly better by using a cast gold bar
than with the 0.051-inch wire.
 Apparently, the wire had space present after cementation of
the bands that resulted in small compensatory movements
and perhaps a small amount of rotation around the wire.

 When the animals were killed, an incision was made and
the palatal tissue stripped from the onplant revealing the
bone onplant interface.
 When the onplant was placed close to the vertical shelf of
the palate, the bone extended over the edge onto the
superior surface of the onplant (Fig).
 When the onplant was gently removed from the bone with
an osteotome, the palatal bone under the onplant revealed
a textured surface mirroring the textured surface of the
onplant (Fig).

DISCUSSION
 Anchorage - the resistive value of posterior teeth toward mesial movement.
 Reciprocal anchorage- posterior teeth will be allowed to move in
accordance with Newton's Third Law of ". . . equal and opposite reaction."
 Maximum anchorage - additional resistance
extraoral device such as headgear
12 to 18 ounces
worn less than 12 hours a day
dangerous during physical activity
patient compliance
 Gainesforth and Higley (1945) attempted to harness the stability of devices
implanted into the mandible or the maxilla. Vitallium screws were inserted
into a dog's ramus to secure a spring used to distallize a maxillary canine.
All the screws failed in 16 to 31 days.

 In 1969 Linkow (JCO 1970) reported the use of mandibular blade-
vent implants in a person to attach Class II elastics while retracting
maxillary incisors. He subsequently used the implants as bridge
abutments to complete the patient's treatment.
 Beginning with Roberts in 1988 a series of authors reported the
use of standard endosseous implants in the orthodontic treatment
of human beings.
 The implants were completely successful for providing absolute
anchorage for tooth movements.
 However, since only edentulous areas are suitable for "root form"
implants, the site selection and frequency of opportunity were
severely limited.
 The placement of implants into the ramus is a compromise since
other alternatives did not previously exist.

 Adolescent patients have unerupted teeth preventing placement of
an endosseous implant.
 If placed in a growing person exhibiting considerable vertical
alveolar growth, the integrated endosseous implant would behave
similar to an ankylosed tooth and become submerged.
 This onplant device can be used to anchor teeth during
orthodontics.
 The classic orthodontic philosophy that transpalatal bars by
themselves serve as anchors is refuted in the control monkey.
However, the anchorage from the transpalatal bar and the 0.051-
inch wire when coupled to the onplant was significant.

 From a practical point of view, the cast bar is bulky and forces the
orthodontist to detour from standard orthodontic practice. The
orthodontist does not usually use cast devices.
 In addition, the use of a screw for retention of the cast bar creates
a larger vertical profile of the transpalatal bar and thus would not
be well tolerated by the patient.
 The grooved abutment for the heavy 0.051-inch wire allows the
orthodontist to use conventional impressions picking up the
abutment and the bands on the teeth to solder the wire to the bands
in a routine manner.
 Then when the bands are cemented, the transpalatal wire should
engage the abutment easily. The thick wire should be more practical
and provide lower profile transpalatal bulk than the cast bar.

CONCLUSIONS
 The onplant is sufficiently anchored to the underlying
bone to withstand 11 ounces of continuous force. It is
sufficiently anchored by the HA-bone biointegrated
interface to resist up to 160 pounds of shear force.
 The onplant can provide absolute anchorage to move a
tooth toward it without moving the onplant.
 The onplant can provide sufficient anchorage to molars to
prevent anterior migration when in situations requiring
maximum anchorage.
 The onplant may have the potential to largely replace
headgear and provide orthodontists with complete control
of anchorage rather than relying on patient compliance.

THANK
YOU

a new device for absolute anchorage in orthodontics. ajodo 1995.

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a new device for absolute anchorage in orthodontics. ajodo 1995.