Fenestration and dehiscence

How does the orthodontist
avoid fenestration and
dehiscence ?
Prepared by: Ahmed S. Baattiah
Supervisor: Prof. Maher Fouda
Mansoura University
Faculty of Dentistry
Orthodontics Department

Note :
Remember:
EDITORIAL 1980 The C V Mosby Co.

 Dehiscence was registered as lack of cortical bone at the level of a dental
root, at least 4 mm apical to the margin of the inter-proximal bone. (The
measurements were performed with a graduated periodontal probe)
 Fenestration was identified as a localized defect in the alveolar bone that
exposed the root surface, usually the apical or the medium third, but did not
involve the alveolar margin
Schematic representation of what is considered
a dehiscence (a) and a fenestration (b).
Romanian Journal of Morphology and Embryology 2009, 50(3):391–397

Fenestrations were classified based on their apicocoronal location in
relation to root length, into four categories:
 At the level of the apical third of the dental root (48.5%) all in maxilla
 At the level of the middle third of the dental root (28%) in maxilla &mandible
 At the level of the coronal third of the dental root 19% all in mandible
 Extending from the apical to the middle third of the dental root (4.3%) all of them
located in the maxilla
fenestration fenestration
Fenestration (apical
to middle third )fenestrationDehiscence

1) Ectopically positioned teeth which are outside of the bony limits of
the alveolus are often lacking the normal amount of bone on
the overlying facial surface.
2) Roots of a tooth may erupt in a more buccal position compared to the
crown creating a dehiscence, especially on mandibular incisors.
3) Frenum attachments are another cause for dehiscenses. They can place
enough pressure on the bone in certain areas to eventually cause recession of the
bone.
4) Patient habits are a frequent cause of dehiscences. The use of smokeless
tobacco products causes defects in the location of use
Saint Louis University-Ising thesis
 Facial or dental pain can be caused by a fenestration or dehiscence of a
tooth root. The pain may be spontaneous, or it can be initiated by
touching the mucosa over the involved tooth.
The etiology of dehiscences can be
attributed to many causes:

 To avoid these problems, the alveolar morphology must
be determined before orthodontic treatment through
imaging.
The occurrence of dehiscence and fenestration during
orthodontic treatment depends on several factors, such as :
 The direction of movement
 The frequency and magnitude of orthodontic force
 The volume and anatomic integrity of periodontal tissues.

IMAGING 2D
2D
 visualization of labial/buccal and lingual bone plates was not possible
because of image superimposition associated with conventional
radiographs, and because the gingival covering interfered with
clinical Analysis.
(Angle Orthodontist, Vol 82, No 1, 2012)
 Dehiscences also escape routine radiographic diagnosis because of
the overlapping images of the surrounding bony tissues.
(Int. J. Morphol.,33(1):361-368, 2015.)

 CBCT images can show bone dehiscence and fenestration by
means of high definition and sensitivity.
 The voxel size of 0.25 mm could have contributed to poor image
resolution when compared using a dimension of 0.125 mm. However,
the smaller voxel size has greater radiation exposure compared with
0.25 mm. This technical parameter choice must be balanced between
the clinical objectives of the examination and the exposure dose, since
the higher image resolution implies a higher dose of radiation.
(Am J Orthod Dentofacial Orthop 2010;138:133)
 The main advantage of CBCT is the ability to evaluate the real
anatomy without superimposition of the neighboring structures
IMAGING 3D
3D
 The analysis of dehiscence and fenestration also depends on
the high-resolution image, which is related to small voxel size in the
CBCT

The potential dehiscence and fenestration (white arrow) A and B show a 4.8-mm
dehiscence; C and D show a 4.3-mm fenestration on the CBCT scan
Am J Orthod Dentofacial Orthop 2015;147:313-23)
Dehiscence
Dehiscence
fenestration
fenestration

Presence of dehiscence
Other way to confirm present of dehiscence by CBCT
If you doubt about presence of
dehiscence
Dehiscenc

 Take view of dehiscence from panoramic x-ray
from CBCT , and measure the mesial-distal
height from CEJ to alveolar crest.
 Take a cross section view from CBCT , and
measure the height of Buccolingual from
CEJ to alveolar crest

Height of dehiscence (DH) = (HBL – HMD).
IF DH > 0 indicated the existence of an alveolar bone
dehiscence,
whereas DH ≤ 0 indicated a false-positive result of the 3D view.
Dehiscenc
(Int. J. Morphol.,33(1):361-368, 2015.)

Fenestrations are most commonly seen in the maxilla, especially in the
first molar and canine region. Dehiscences are found predominantly in
the lower anterior region especially on buccal surfaces.
The majority of fenestrations were found in the maxilla (around first
premolars), the maxillary first premolars are located in an area that
becomes narrower upwards.
The majority of dehiscences were found in the mandible (around central
incisors), the bone becomes thinner from the posterior to the anterior region.
Angle Orthodontist, Vol 82, No 5, 2012

 It is of clinical importance to note that labial root torque to upright
maxillary incisors may produce alveolar bone fenestrations and/or
dehiscences
Wainwright(1973) retracted root apices that had penetrated the cortical
bone plate back to their original position and found that, during the
subsequent four month retention period, osteogenesis occurred on the
buccal surface of the cortical plate.
European Journal of Orthodtnuia'5 (1983) 105-114
 Crowded and misaligned teeth are possible risk factors for bone
dehiscences and fenestrations. Inadequate bone support during
orthodontic movement may have deleterious effects on teeth and the
periodontium, causing buccal and lingual bone plate resorption.

Relationship between RME
and alveolar bone loss
 During rapid maxillary expansion (RME), heavy orthodontic forces are
transmitted to the maxilla through the teeth, and unfavorable changes may
occur in the anchor teeth and their supporting tissues, including buccal crown
tipping, root resorption, reduction of buccal bone thickness, and marginal
bone loss. kjod.2013.43.2.83
If extensive palatal tooth movement was done, the tooth root would be
contacted with palatal cortex of alveolar bone. Cortex would bend and
limited movement would occur. If contact occurred, further movement would
cause perforate of cortical plate followed by bone loss, root resorption and
relapse. Dent. J, Vol. 41. No. 1 January-March 2008
The presence of dehiscenceThe presence of fenestration

 RME has also been reported to produce alveolar bone fenestration
and/or dehiscence in the buccal aspects of the maxillary teeth.
kjod.2013.43.2.83
 Buccal crown tipping, reduction of buccal bone thickness, and
marginal bone loss had occurred within 3 months after RME.
kjod.2013.43.2.83
An example of treatment changes: the palatal cortical bone thickness
increased after active expansion and decreased at the end of retention.

Palatal cortical bone thickness
before expansion = 1.1mm
The palatal cortical bone thickness increased
after active expansion =1.4 mm, because the
orthodontic force will result in the alteration of
regulating alveolar bone function as well as its
cell. The alteration is including bone formation
on tension side and bone resorption on
pressure side
The palatal cortical bone thickness
decreased after expansion because of
relapse = 1.2 mm

Relationship between heavy force and alveolar
bone loss(dehiscence and fenestration)
Orthodontic force will result in the alteration of regulating alveolar bone function
as well as its cell. The alteration is including bone formation on
tension side and bone resorption on pressure side thus the tooth will move
to the new position.
Excessive force will cause the damage of periodontal tissue on pressure
region, the adjacent bone will be necrotic followed by undermining resorption.
Excessive force will cause injury by principle fibers rupture in periodontal
ligament, and a part of alveolar bone will be necrotic due to vessel injury.
The pressure which is exceeded than the blood pressure will make capillary
blood vessel in periodontal ligament collapse, which can inhibit
the blood supply.
Dent. J. Vol. 41. No. 1 January-March 2008: 21-24

In the area of limited movement, excessive force will cause the tooth
touching the cortical plate of alveolar bone, so, cortical bone resorption
and root penetration will appear. Tooth movement in limited area can
contribute alveolar bone loss and it is still debatable.
Alveolar bone resorption might be caused by too far tooth movement,
narrow alveolar bone and symphysis. Based on the studies done by
Vardimon , Sarikaya and Wehrbein it can be conclude :
that compensation of remodeling bone is not matched with the number of
tooth movement so there are many dehiscence and fenestration found at
the end of orthodontic treatment.
fenestration dehiscence

Axial (A) and coronal (B) CBCT sections demonstrating the proximity of the roots
of the first premolar to the buccal cortical plate. Note the fenestration defect
adjacent to the buccal root of the first premolar (arrows).
Fenestration defect
Fenestration defect

The ratio of cortical bone remodeling and tooth movement during maxillary
incisors retraction (Torque degree)
The well known axiom in moving the tooth is that the bone will follow the
trace of the moving tooth. If tooth movement occur due to orthodontic force,
the bone around the tooth socket will remodel in the same width with tooth
movement .
The ratio between remodeling bone and tooth movement is 1:1
Vardimon compared the ratio of maxillary incisors retraction with tipping
and torque movement. It was found that either tipping or torque
movement would not produce ratio 1:1
In tipping movement the ratio was 1:2, meant that if the apex of
central incisors moves 3 mm posteriorly, so A point would be retracted
1.5 mm.

 Many experts have an opinion that extensive incisors movement should
be avoided to prevent cortex distraction of lingual alveolar bone resulting
in tooth supporting tissue loss.

Bucco-lingual
inclination of a
maxillary first
premolar with a
fenestration that
involves the apical
third of the root.
The amount of degree to return the tooth to the original position
calculated by :
 Determine the value of the angle between the long axis of the tooth and a
perpendicular line to the occlusal plane assessed through CBCT.
 Sum this value + 10 -15 degree (the play between wire and bracket )

Bucco-lingual inclination of mandibular canines, both affected by
dehiscences.

Bucco-lingual inclination of a maxillary first molar with a fenestration that
involves almost the entire length of the root and of a mandibular first molar with
a fenestration placed in the middle third of the root

Finally
The position of roots and the condition of the periodontium
should be on your mind when you contemplate any long-term
treatment or even short-term procedures for adults.
EDITORIAL 1980 The C V Mosby Co.

CONCLUSION
 Palpation of the alveolar bone before you start to check for over
prominent roots.
 Depend only the CBCT images to identify the dehiscence and
fenestration.
 Don’t use heavy orthodontic forces During rapid maxillary
expansion (RME).
 Orthodontic Excessive force will cause Alveolar bone
resorption.
 Use little degree of torque.
 Don’t forget the position of roots and the condition of the
periodontium

Fenestration and dehiscence

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