Fenestration and dehiscence

How does the orthodontist avoid fenestration and dehiscence ?Prepared by: Ahmed S. BaattiahSupervisor: Prof. Maher Fouda

Mansoura UniversityFaculty 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 ofthe alveolus are often lacking the normal amount of bone onthe overlying facial surface.

2) Roots of a tooth may erupt in a more buccal position compared to thecrown 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 2D2D 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 3D3D

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)

DehiscenceDehiscence

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 moveto 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

Health & Medicine

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