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1
Dr. Mohammed Alruby
Fenestration
And
Dehiscence
Prepared by
Dr. Mohammed Alruby

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Dr. Mohammed Alruby
Fenestration
Dehiscence: lack of cortical bone at the level of dental root, at least 4mm apical to the margin of
interproximal bone, the measurement was per found by graduated probe.
Or: lowering the crestal bone margin to expose root surface.
Fenestration: 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.
Or: is isolated areas in which the root is denuded of bone and the root surface is covered
only by periosteum and overlying gingiva.
Fenestration is a term derived from Latin ward fenestra, meaning window, describe area of
alveolar process devoid of bone, creating a window exposing the root surface.
Gingival recession: is the apical movement of the marginal soft tissue surrounding the tooth
exposing root surface.
According to some studies that irreversible recession can be caused by fixed appliances for 1.3%
to 10.0% of treated cases.
We can use CBCT to measure the labial and lingual thickness of the bone related to roots.
ABT: apical buccal thickness. MBT: middle buccal thickness. CBT: cervical buccal thickness.
ALT: apical lingual thickness. MLT; middle lingual thickness. CLT: cervical lingual thickness.
== naturally occurring alveolar bone dehiscence and fenestration are common finding in different
type of malocclusion especially in anterior region of class III.
== fenestration and dehiscence may lead to gingival recession and additional bone loss during
orthodontic treatment in addition to large amount of labial inclination such as decompensation in
class III malocclusion may pose a greater risk of periodontal complication such as:
Alveolar dehiscence, fenestration, gingival recession.
Clinically gingival recession, is always accompanied by alveolar bone dehiscence whether
underlying bone dehiscence is developed before or parallel to gingival recession.
N:B- gingival recession; is described as exposure of root surface by an apical shift in the position
of gingiva.
Factors affect recession increase:
1- Difficulty of plaque control due to fixed appliances
2- Proclination of teeth.

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Dr. Mohammed Alruby
3- Coronally attached Frenum.
4- Muscle attachment.
5- Abnormal tooth position.
6- Overhanging restoration or crowns.
7- Fenestration and dehiscence.
** Classification of fenestration according to their apicocoronal location in relation to root length
to:
1- At the level of the apical third of the dental root 48% all in maxilla.
2- At the level of the middle third of dental root 28% in maxilla and mandible.
3- At the level of the coronal third of the dental root 19% all in mandible.
4- Extending from the apical to the middle third of the dental root 4.3% of them located in
maxilla.
** Etiology of dehiscence:
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 the tooth may erupt in buccal position compared to the crown creating the
dehiscence, especially in the mandibular incisors.
3- Frenum attachment; they can place another pressure on the bone in certain areas to
eventually cause recession of the bone.
4- Patients habits: use of smokeless tobacco products cause defect on the location of use.
** Dehiscence or fenestration can cause facial or dental pain which is spontaneous and may be
initiated by touching the mucosa over the involved tooth.
** Factors affect occurrence of fenestration and dehiscence during orthodontic treatment:
1- The direction of movement.
2- The frequency and magnitude of orthodontic force.
3- The volume and anatomic integrity of periodontal tissues.
Diagnosis:
Visualization of labial, buccal and lingual plates was not possible because of image
superimposition associated with conventional radiographs and because the gingival covering
interfered with clinical analysis. Dehiscence also escape routine radiographic diagnosis because
of the overlapping images of the surrounding bony tissues.
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.
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.

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Dr. Mohammed Alruby
RME and fenestration:
During rapid maxillary expansion, heavy orthodontic forces are transmitted to the maxilla
through the teeth and unfavorable changes may occur in the anchor teeth and their supporting
tissue including:
= Buccal crown tipping
= Root resorption
= Reduction of the buccal bone thickness
= Marginal bone loss
 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.
 Rapid maxillary expansion has been reported to produce bone fenestration and / or
dehiscence in the buccal aspect of the maxillary teeth.
 An example of treatment changes: the palatal cortical bone thickness increased after active
expansion and decreased at the end of retention.
Relationship between heavy force and alveolar bone loss (fenestration and dehiscence):
Orthodontic force will result in alteration of regulating alveolar bone function as well as
its cell. The alteration 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:
1- Damaged of periodontal tissue in the pressure region, the adjacent bone will be necrotic with
undermining resorption.
2- Injury by the principle fiber rupture of the periodontal ligament and a part of alveolar bone
will be necrotic due to vessels injury.
The pressure which is exceeded than the blood pressure will make the capillary blood vessels
of periodontal ligament collapse, which can inhibit the blood supply.
== 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 loss and it is still debatable.
== alveolar bone resorption might cause by: too far tooth movement
Narrow alveolar bone and symphysis.
== compensation of remolding bone is not matched with the number of tooth movement so there
is many dehiscence and fenestration found at the end of orthodontic treatment.
The amount of degree to return tooth to the original position:
Calculated by;
== determine the value of the angle between the long axis of the tooth and perpendicular line to
the occlusal plane assessed through CBCT
== sum of the value + 10 -15 degree = (the play between wire and bracket)
N:B = Class II malocclusion group had greater prevalence of fenestration than Class III and Class
I
= More fenestration occurs in maxilla but dehiscence in mandible.
= Most fenestration in maxilla at 1st
molars and premolars, but dehiscence seen greater in
mandibular incisors.

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Dr. Mohammed Alruby
= in normal divergent face: the biting force is twice than hypodivergant but hypodivergant is
still more biting force than normal face.
** Factors that cause resorption at cervical region of the roots, (external cervical resorption,
ECR):
1- Dental trauma.
2- Orthodontic treatment.
3- Intra-coronal bleeding.
4- Periodontal therapy.
5- Surgical procedure.
6- Idiopathic etiology.
** Heithersay Classification: of external cervical resorption.
1- Small invasion resorption lesion near to cervical area with shallow penetration dentine.
2- Well defined resorptive lesion that has penetrated close to coronal pulp chamber but show
little or no extension into radicular dentine.
3- Deeper invasion of dentine by resorping tissue not only involve the coronal dentine but
extended at least to the coronal third of the root.
4- Large invasive resorptive process that has extended beyond the coronal third of the root
canal.
External cervical resorption: is an aggressive and insidious type of external resorption which can
result in significant loss of tooth structure.
Treatment objective for managing external cervical resorption:
1- Arrested resorptive process.
2- Restore damaged root surface.
3- Prevention further resorption.
4- Improve esthetic of teeth (in case where resorption has led to pink spot).
Heithersay recommend:
1- Topical application of 90% aqueous solution of trichlor acetic acid: result in coagulation
necrosis of ECR resorptive tissue with no damage to adjacent periodontal tissue.
2- Curettage.
3- Restoration with Ionomer cement.
Endodontic treatment might be necessary with some Class 2 or 3 lesion success rate.

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Dr. Mohammed Alruby
1, 2 100%
3 78%
4 12,5%
N: B== Andreasen classification of tooth resorption:
External: surface, inflammatory, replacement.
Internal: inflammatory, replacement.
Mucosal fenestration:
Describes the situation where the apex of tooth is exposed to the oral environment following
breakdown of overlying bone and alveolar mucosa.
Mucosal fenestration was first reported by Mendener Q R 1946.
Mucosal fenestration may be attributed to:
1- Mal-positioning teeth.
2- Thin alveolar cortex.
3- Prominent morphology of root apex.
4- Sever per radicular inflammation with bone destruction.
Mucosal fenestration is most commonly seen in the mandibular or maxillary anterior region
especially in labial aspect because tooth angulation placing root apex in labial position.
Treatment procedure:
 Root canal treatment and root canal resection.
 Full thickness muco-gingival flap with guided tissue regeneration and bone grafting.
(= full thickness muco-gingival flap was raised by two vertical incisions, one at mesial side and
other at the distal side.
= ultrasonic root end preparation was performed and the root end cavity was filled with super-
EBA cement- bone graft freeze dried is placed on the bony defect and covered by connective tissue
graft that may take from the inner surface of the alveolar mucosa on the hard palate. The graft is
carefully trimmed and covered the whole defect. The donor side is covered by hemostatic gel foam
and sutured.
= the whole bony healing may be take from 6 months to 1 year).
 Dehiscence and fenestration are all governed by the anatomy and shape of the overlying
alveolar bone on the root as well as the alignment of the root in the alveolus.
 Dehiscence is commonly seen in clinical practice, whereas gingival fenestration is rare.
 To overcome the problem of fenestration, prior to orthodontic treatment, the evaluation of
the bone structure and anatomy of the tooth is necessary so that a stable position is achieved
after treatment.
With my best wishes------