UNIVERSITY OF GLASGOW
BIMAXILLARY PROCLINATION
Mohammed Almuzian
1/1/2013
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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
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
Mohammed Almuzian, University of Glasgow, 2013
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
Mohammed Almuzian, University of Glasgow, 2013
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
Mohammed Almuzian, University of Glasgow, 2013
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
Mohammed Almuzian, University of Glasgow, 2013
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.
Mohammed Almuzian, University of Glasgow, 2013
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
Mohammed Almuzian, University of Glasgow, 2013
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.Mohammed Almuzian, University of Glasgow, 2013
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.
Mohammed Almuzian, University of Glasgow, 2013
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.
Mohammed Almuzian, University of Glasgow, 2013
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
Mohammed Almuzian, University of Glasgow, 2013
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.
Mohammed Almuzian, University of Glasgow, 2013
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
Mohammed Almuzian, University of Glasgow, 2013
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
Mohammed Almuzian, University of Glasgow, 2013
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.
Mohammed Almuzian, University of Glasgow, 2013
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.
Mohammed Almuzian, University of Glasgow, 2013