Deleterious effects of orthodontic force Copyright by Ortho Department, Yangon

1. DELETERIOUS EFFECTS OF
ORTHODONTIC FORCE.

2. Deleterious effects of orthodontic force.
Mobility and pain.
Effects on pulp.
Effects on root structure.
Effects on alveolar bone height.

3. Mobility and pain.
Mobility.
 Orthodontic tooth movement requires resorption-
depositon of alveolar bone and destruction-
reorganization of periodontal ligament.
 Therefore, a moderate degree of mobility will be
observed in every patient.
 However, extreme mobility indicates the use of
excessive force and should be avoided.

4.  Mobility is related to the magnitude of force.
 With heavy force, the greater the amount of hyalinization
and undermining resorption is expected and the greater
the mobility will be observed.
 The extremely mobile tooth should be placed out of
occlusion and the force should be temporarily
discontinued until the mobility decreased to moderate
levels.
 The excessive mobility will usually correct itself without
permanent damage.

5. Pain.
 Orthodontic tooth movement is associated with the
compression and tension of PDL cells which leads to
the liberation of substances responsible for pain.
 Therefore, the patient usually feels a mild aching
sensation several hours after the force application.
 The teeth are quite sensitive to pressure so that biting a
hard object usually hurts.
 With optimal force levels, pain usually last for only 2 to
4 days, and then disappear, until the next appliance
activation.

6.  However, with heavy force, pain develops almost
immediately, intense and usually requires medication.
 Pain is related to the development of ischemic areas in
the PDL that will undergo sterile necrosis.
 Inflammation at the apex and mild pulpitis that appear
soon after orthodontic force is applied is also
responsible for increased tenderness to pressure and
hypersensitivity.

7.  The use of light force is the best way to minimize pain.
 Pain associated with light force can be alleviated by
allowing the patient to chew eg. gum during the first
8 hours after activation.
 Drugs which act centrally rather than inhibiting the
prostaglandin synthesis (ibuprofen, imidazole,alaxin)
should be a better analgesics

8.  Pain from traumatic ulcers due to irritation from brackets,
hooks, springs are common especially in severely
crowded patients.
 Less commonly pain may be associated with allergic
reactions to the nickle in stainless steel bands and
brackets, latex in elastics and gloves and to monomer in
orthodontic resin.
 Pain, erythema and swelling of the mucosa may be
seen.
 Use of titanium or ceramic brackets may be substituted.

9. Effects on pulp.
 A mild transient inflammation reactions in the pulp at the
beginning of treatment may be expected with optimal
force levels.
 However if a tooth is subjected to heavy force, large
increment of tooth movement in undermining resorption
would cause disruption of an apical blood vessel and
loss of vitality.
 Excessive lingual tipping of incisors to such an extent
that the root apex is moved out of the alveolar cortex
would sever the apical blood vessel and cause loss of
tooth vitality.

10. Effects on root structure.
 When orthodontic force is applied, there is usually an
associated resorption of cementum of the root adjacent to
the hyalinized area.
 Repair of the damaged root restores its original contour.
However, with extensive resorption, there is permanent
loss of root structure with shortenning of root apex is
likely to occur.
 The use of heavy continuous orthodontic force commonly
leads to severe root resorption.

11.  Despite potential for repair most teeth undergo
generalized moderate resorption with some loss of root
length.
 This is unavoidable, occurs in majority of orthodontic
patients and is clinically insignificant.
 It usually occurs in patients whose duration of
treatment is longer and more severe in maxillary
incisors

12. Illustration of apical root resorption.

13. Radiographs showing of root resorption.

14.  Severe generalized resorption is prone to occur in
patients who already had root resorption before
orthodontic treatment.
 Patients with hormonal imbalance and metabolic
disorders, deficiency in thyroid hormone are likely to
develop severe resorption.
 Tooth with conical or slender root, dilaceration and
previous history of trauma predispose to severe
generalized resorption.

15.  Severe localized resorption (severe resorption of a
few teeth) is associated with the use of excessive
orthodontic force and prolonged duration of
orthodontic treatment.
 It is prone to occur in maxillary incisors especially if
the incisors are forced against the alveolar cortex as
in extreme lingual tipping.

16. Effects on alveolar bone height.
 Orthodontic tooth movement is associated with the loss
of alveolar bone height due to resorption at the tip of
the alveolar process.
 Crestal bone loss varies from 0.5 mm to 1 mm.
Increases with the use of heavy force and at extaction
sites.
 The position of teeth determines the position of the
alveolar bone. When teeth erupt or are moved, they
bring alveolar bone with them.

17.  Therefore orthodontic tooth movement can be used
to create alveolar bone at the site of congenitally
missing or extracted tooth.
 Tooth can be brought into the arch by orthodontic
extrusion together with its alveolar bone support.
 If a tooth is intruded the alveolar bone height stays at
the same level along the root.
 Therefore, bone support around the periodontically
involved tooth can be improved by intruding the teeth
and forcing roots deeper into the bone.