bimaxillary proclination or protrusion by almuzian

UNIVERSITY OF GLASGOW

BIMAXILLARY PROCLINATION

Mohammed Almuzian

1/1/2013

.

Table of Contents

ContentsDefinition..............................................................................................................................................2

Prevalence............................................................................................................................................2

Aetiology..............................................................................................................................................2

Skeletal factors

Soft tissue factors

Dental

Habit

Pathological

Classification......................................................................................................................................5

Features..............................................................................................................................................5

Aims for treatment of bimaxillary proclination..................................................................................7

Treatment...........................................................................................................................................8

I. Mild cases..............................................................................................................................8

II. Moderate cases.......................................................................................................................9

III. In severe cases..................................................................................................................11

Stability & Relapse..........................................................................................................................11

Equilibrium theory revisited: Factors influencing position of the teeth, Proffit, 1977......................12

Secondary factors.............................................................................................................................14

Summary of evidences.....................................................................................................................14

Mohammed Almuzian, University of Glasgow, 2013

Bimaxillary proclination or protrusion

Definition

Bimaxillary proclination: the teeth are proclined on normal bases

Bimaxillary protrusion or bialveolar protrusion occurs when both the

maxillary and mandibular incisor dentitions are forwards in relation to their

dental bases and the cranial base leading to soft tissue procumbent (Burden

1996). It is considered as subset of class I malocclusion.

Bimaxillary prognathism: the jaws/basal bones are forward relative to the

cranial base

Prevalence

Most common in Afro-Caribbeans (Farrow 1993)

It is also common among Arab groups and Asians (Hussein 2007)

It is less prevalent in white Caucasian populations (Keating 1985).

Aetiology

A. Skeletal factors

B. Soft tissue factors

Lip length

Adenoid & nasal blockage


Endogenous (primary) thrust

C. Dental

D. Habit

E. Pathological

In details:

1. Skeletal factors with underlying genetic relationship. Lamberton 1980

2. Soft tissue factors

I. Lip length, activity, morphology and position (Naini and Gill 2008): in

bimaxillary proclination cases, usually the lips are full, loose and everted, and

the tongue acts to mould the dental arches forward as they erupt. The effect of

abnormality of soft tissues at rest is more influential than that during function

(Profitt 1979).

II. Adenoid & nasal blockage

Soft tissues stretching theory of Solow & Tallgren 1976, showed that:

airway obstruction lead to some sort of neuromuscular feedback mechanism

where the patient can't breathe through nose, so adopt a head up posture with

extension, in so doing, you now stretch the superhyoid muscles, skin + fascia.

This in turn imparts a force on the mandible and in turn means that the

mandible adopts a downward posture ( LAFH + MM angle) this will allow

the tongue to drop and imparts less force on maxillary arch in the lateral

dimension which with the unopposed action of the cheeks pushes the dentition


into a narrower arch which leads to cross bite situation. At the same time the

tongue will be pushed forward to increase the phyryngeal space overcoming

the lip force and causing bimaxillary proclination.

Adenoids: It was proposed that the “Adenoids” were the most important “soft

tissue” responsible for the difficulty in breathing through your nose then the

adenoids enlarged causing chronic constriction in the nasopharyx followed by

the same pathway as “soft tissue stretch theory”. Aronson (1979). Vig (1985)

didn’t agree with this theory.

III. Occasionally the tongue is very large and is the primary cause of the

bimaxillary proclination, usually occurs with AOB. This is called endogenous

(primary) thrust. It is very rare & affects 1% of population. Usually associated

with lack of neuromuscular control e.g. Downs syndrome and characterized

by:

Usually associated with a lisp,

bimaxillary proclination,

Reverse COS in the lower and deep COS in the upper.

The diagnosis is therapeutic which means the high tendency to relapse after

treatment.

3. Dental

Due to way of incisors eruption in a forward direction.

Tooth size discrepancy has been associated (Burden 1996).

4. Habit like tongue thrust

5. Pathological conditions

Cancrum oris


Cerebral palsy

Haemangioma with swelling of the lips/tongue/cheeks produces a

“new” zone of balance.

Untreated cleft lip or palate swings forwards

Classification

From the dental perspective, the severity of the dentoalveolar protrusion is

best characterised by the interincisal angle.

125 degree 115 degree = mild

115 degree 105 degree = moderate

<105 degree = severe.

Features

A. Skeletal features, (Keating, 1985)

1. Short cranial base length

2. Long prognathic maxilla

3. Similar mandibular prognathsim and dimension to class I skeletal relationship.

(Keating, 1985).

4. Divergent facial plane, skeletal Class II and Increased FMPA

5. Increased ANB.

B. Soft tissue


1. Convex facial form.

2. Acute NLA & LMA.

3. Reduced lip length.

4. Lips incompetency.

5. Low lower lip line and high upper lip line (Keating, 1985).

6. Holdaway angle was increased with prominent lips.

7. Receded chin.

C. Dental

1. Dental bimaxillary proclination with reduced II angle (Keating, 1985)

2. Proclined LLS compensates for ANB difference

3. Larger dental arch length with resultant spacing and diastema

4. Normal or increased OJ

5. Variable molar relationship but usually normal.

6. Reduced OB or AOB

7. Large teeth compared to normal population (McCann and Burden 1996).

Keeping in mind that Keene (1979) reported that tooth size for the overall

maxillary and mandibular dentition among black people was on average 8.4%

larger than for whites.

8. May have other superimposed malocclusion traits.


NB: However the cephalometric values should be considered for each race.

For example Ajayi, (2005) found a different values for normal Nigerian

population which considered as a bimaxillary protrusion values if it is applied

on Caucasian. His findings were summarized into:

Compared with the norms for other ethnic groups, Igbo (one of the native

Nigerian population) children have a prognathic relationship of the maxilla

and the mandible to the anterior cranial base of about one SD of the Caucasian

norms.

The children also exhibited prominent bimaxillary proclination with

procumbent and protrusive maxillary and mandibular incisors of about one SD

of the Caucasian norms.

Steep Frankfort-mandibular plane angle of about one SD of the Caucasian

norms.

Aims for treatment of bimaxillary proclination

1. Normal aims for any orthodontic treatment including:

Relieve of crowding

Alignment and levelling

Close diastema and spacing

Normal OJ and OB

Correct incisor relationship

Normalization of buccal occlusion


Maintain a stable result

2. Other facial aims including;

Improving facial aesthetics i.e. flatten profile. The aesthetic preference

of the majority of lay and even clinicians are for a straighter profile (Marques,

2011, Morar 2011)

Enabling lip competence

Treatment

Always start with lower incisor retraction to provide space for ULS retraction.

I. Mild cases

Better to accept because

Aging can mask the protrusion by down and forward growth of the nose and

chin

The high risk of relapse.

II. Moderate cases

A. Space provision

IPS ; Germeç 2008 showed that both extraction and ARS combined with

nonextraction therapies are effective treatment alternatives for Class I

borderline patients with good facial profile and moderate dental crowding

Enmass retraction with or without &s extraction

Extraction in both arches usually first premolars.


http://www.ncbi.nlm.nih.gov/pubmed?term=Germe%C3%A7%20D%5BAuthor%5D&cauthor=true&cauthor_uid=18405818

If the condition is class 2 then it might be treated with extraction in the

upper alone.

B. Type of anchorage:

TADs or conventional anchorage? Upadhyay in 2008 RCT compare

treatment of bimaxillary protrusion with extraction of 4 premolars using

conventional anchorage or TAD with Enmass retraction and found that

i. TAD is better anchorage and the reduction of protrusion was high in TAD

group

ii. Also the TADs group showed a reduction in the VH due to intrusive effect of

the TADs.

iii. Also the soft-tissue response was variable, facial convexity angle, nasolabial

angle, and lower lip protrusion showed greater changes in TAD group.

TADs or TPA? Liu 2009 compared the use of TPA and TADs in he found

that

i. A better dental, skeletal and soft tissue changes could be achieved

by minicrew implants especially in hyperdivergent patients.

ii. Skeletal anchorage should be routinely recommended in patients with

bialveolar dental protrusion.

TADs or HG?

Junqing in 2008 showed again a better result by TADs in comparison with

HG.


http://www.ncbi.nlm.nih.gov/pubmed?term=Liu%20YH%5BAuthor%5D&cauthor=true&cauthor_uid=19602104

C. Elastic

Avoidance of intermaxillary elastic is recommended to overcome the

extrusive effect of the elastic that result in clockwise rotation of the mandible

and compromising the OB. Koyama 2011

D. AOB

If AOB is present, the modalities to treat AOB can be with combined (high

pull HG, TADs, Teuscher appliance if the condition is class II).

E. Appliance system

Lew 1989 recommended the use of Begg appliance in treating these problems

& reported that Begg appliance with extraction of 4 premolars resulted in:

i. Reduce the protrusion and improve the soft tissue profile.

ii. The nasolabial angle became more obtuse increasing from 80.7° to 90.7°.

iii. The upper lip and lower lip lengthened by 1.9 mm and 1.2 mm, respectively.

iv. The lower lip to 'E' line reduced from 7.5 mm to 3.7 mm.

v. The upper lip to upper incisor retraction was 1:2.2 while the lower lip to lower

incisor retraction was 1:1.4.

vi. Results show that the upper incisors were retracted by 5.6 mm ± 0.8 mm and

the lower incisors by 4.4 ± 0.8 mm on the average.

vii. Tip edge brackets or Begg bracket allow tipping and help in reducing

proclination easily.


In order to avoid the opening of the bite, it is better to swap lower canine

bracket or it is possible to use tip edge bracket on the canine only.

III. In severe cases

Orthognathic surgery is required to correct significant skeletal problems

(Jacob, 1983) using subapical osteotomies with extraction and with or without

Genioplasty.

Differential intrusion of maxilla/maxillary segments with clockwise rotation

of the occlusal plane is a useful technique for treatment of anterior open bite

and creation of a consonant smile arc (Chu 2009).

Le Fort I osteotomy with setback sometimes provides an alternative to

segmental maxillary osteotomies but it is difficult to performed clinically.

A protocol of Cochrane review by Fleming et al 2012 is under process.

Stability & Relapse

1) Keating 1986 showed that II angle showed almost 30% relapse.

2) Long-term stability is unpredictable, depends on lip adapting to incisor

retraction, i.e. lower lip becoming competent

3) Permanent fixed retainer supported with VFR in both archs

4) Buccal intercuspation is crucial

5) The aims for a good stability at the end of treatment should be:

Interincisal angle and lower edge centroid should be normalized


Lower lip should cover one third of upper incisor

6) If the tongue is very large, then surgical reduction can be justified

Equilibrium theory revisited: Factors influencing position of the teeth,

Proffit, 1977.

Definition of equilibrium: it is said to exist when a body at rest is

subjected to forces in various directions, but is not accelerated. Proffit

feels malocclusion is interplay between innate genetic factors and

external environmental factors.

Primary factors in equilibrium

1. Intrinsic forces from tongue & lips

Tongue and lip is High force for Short duration & Low importance

Tongue pressure is always measured at a higher value than the lip

pressure. Therefore other factors must be involved.

2. Extrinsic forces: habits, orthodontic appliances.

Orthodontics deliberately disturbs the force equilibrium on the teeth.

Swallowing & speech is high force for short duration and low

importance

Rest is low force for long duration and high importance

Light forces over a long time will move teeth.

Duration is far more important than the force.


With regards to AOB patients - most people feel that the tongue

activity during swallowing may be the cause of AOB. Studies

(WALLEN) show that pressures on the teeth during swallowing from

the tongue are significantly lower in patients with AOB than the

normals. Hence this does not support the theory that tongue pressure

is the cause of an AOB during swallowing. More likely to be an result

than the cause.

3. Forces from dental occlusion.

Force from occlusion is high force for short duration and low

importance

May be of importance in the vertical development of the occlusion.

It is an adaptive mechanisim, example is when the maxilla is

surgically impacted the mandible will rotate closed and a new rest

position will be established. Proprioceptive fibres in the PDL play

apart in mandibular rest position.

4. Forces from the periodontal ligament:

Pd ligament is very low for long duration and high importance

Teeth erupt into the mouth to keep up with an increase in vertical

dimension of the face

Also when the opposing tooth is removed the now unopposed tooth will

still continue to erupt.

Eruption force is between 2 - 10 grams


Secondary factors

Postural relationships: Solow & Tallgren 1978 showed relationship

between the craniocervical angulation and both facial proportion and

dentoavleolar proportions. The further the head is carried forward on the

neck the more the face is to be vertically long. This leads to a lowering of

the tongue, upper dental arch contraction and over eruption of the

posterior teeth and the development of an AOB. Same is seemed in

patients with a muscle weakness.

Summary of evidences

Definition (Burden 1996)

Prevalence it is less prevalent in white Caucasian populations (Keating

1985).

Aetiology, Skeletal factors with underlying genetic relationship.

Lamberton 1980,

Aetiology Soft tissue factors Lip length, activity, morphology and

position (Naini and Gill 2008)

Aetiology The effect of abnormality of soft tissues at rest is more

influential than that during function (Profitt 1977).

Aetiology Adenoid & nasal blockage, Solow & Tallgren 1976, Aronson

(1979). Vig (1985) didn’t agree with this theory.

Aetiology Dental Tooth size discrepancy has been associated (Burden


1996).

Features, Skeletal features, (Keating, 1985), Similar mandibular

prognathism and dimension to class I skeletal relationship. (Keating,

1985).

Features Low lip line (Keating, 1985).

Features Ajayi, (2005) found a different values for normal Nigerian

population which considered as a bimaxillary protrusion values if it is

applied on Caucasian.

Aims of treatment Improving facial aesthetics i.e. flatten profile. The

aesthetic preference of the majority of lay and even clinicians are for a

straighter profile (Marques, 2011, Morar 2011 )

Treatment, IPS ; Germeç 2008 ,

Treatment TADs or conventional anchorage. Upadhyay in 2008 ,

Treatment TADs or TPA. Liu 2009

Treatment Junqing in 2008 TADs or HG.

Appliance system, Lew 1989 recommended the use of Begg appliance

in treating these problems & reported that Begg appliance with

extraction of 4 premolars

In severe cases Orthognathic surgery is required to correct significant

skeletal problems (Jacob, 1983) using subapical osteotomies with

extraction and with or without Genioplasty.


A protocol of Cochrane review by Fleming et al 2012 is under process.

Stability & Relapse, Keating 1986 showed that II angle showed almost

30% relapse.


bimaxillary proclination or protrusion by almuzian

Health & Medicine