CLASS I MALOCCLUSION

CL I malocclusions include all those anomalies where the anteroposterior relationship is within normal limits.

AETIOLOGY

SKELETAL PATTERN: ! This is usually CL I, but it can also be CL

II or III with the incisor inclination compensating for the skeletal discrepancy. There may be transverse (i.e crossbites) or vertical sk discrepancies (i.e.AOB)

SOFT TISSUES: ! Soft tissues are usually favourable. The

exception is bimaxillary proclination where the lips are full and everted. This is a major factor in determining tooth position

DENTAL FACTORS ! In the majority of CL I malocclusions the

underlying problem will be one of tooth/arch size discrepancy, leading to crowding or less frequently spacing.

! Environmental or local factors can also contribute to crowding or spacing e.g. premature loss of deciduous/permanent teeth.

! Local factors also include displaced and impacted teeth, anomalies in number and size of teeth.

CROWDING

CROWDING

! Approx. 60% of caucasian children exhibit crowding.

! relief of crowding cannot be achieved by either expansion of the lower intercanine width or labial movement of the lower incisors.

! Crowding is relieved either by extractions or distal movement of the upper buccal segments which gives limited space.

In a CL I case with mild crowding (1 mm/quadrant)-accepted.

! In cases with moderate crowding (3-5 mm/quadrant)-extract 4’s.

! In severe crowding cases (>5mm/quadrant)-space maintenance +4’s

! After relief of crowding a degree of spontaneous tooth movement will occur. Greater under the following circumstances:

! growing child ! extractions carried out prior to the

eruption of adjacent teeth. ! where adjacent teeth are favourably

positioned to upright if space is made i.e. mesially inclined canines more favourable than distal ones

! no occlusal interferences with anticipated movement

! most spontaneous movement occurs in the first six months.

! Mild crowding cases can be accepted as premolar extractions will provide a large amount of excess space, the closure of which will require fixed appliances.

The alternative of extracting teeth at the back of the arch does nothing to relieve anterior crowding unless EOT is used.

SPACING

SPACING

Aetiology; 1) small teeth in relation to the size of

arches 2) teeth are missing 3) a combination of 1) and 2) ! Complete space closure may be difficult

and permanent retention is usually required. It may be necessary to concentrate the spaces posteriorly in the arch and fit bridges as necessary.

Management

! 1) Close space. ! 2) Open space and placement of a

denture/ bridge.

DISPLACED TEETH

Aetiology1) Abnormal position of tooth germs; canines and premolars most common.

Management involves a) Extraction of primary tooth and space

maintenance b) Exposure and application of

orthodontic traction c) Extraction if severely displaced

2) Crowding: lack of space for a permanent tooth to erupt. Those teeth that erupt last in segment, e.g. lateral incisors, upper canines, 2nd premolars, 3rdmolars are most commonly affected.

Management involves: a) Relief of crowding followed by active

tooth movement b) If severe it may be prudent to extract

the tooth

3) Retention of a deciduous tooth; management involves extracting the deciduous tooth as soon as possible

4) Secondary to the presence of a supernumerary tooth/teeth. Management: extract the supernumerary tooth and align.

5) Secondary to pathology e.g. a dentigerous cyst- least common.

BIMAXILLARY PROCLINATION

can occur in CL 1, CL II Div 1 or CL III mal. ! Term used to describe occlusions where both

the upper and lower incisors are proclined. ! This may be a feature of CL II Div 1 mal, but

quite often the incisor relationship is CL I which may be mistakenly diagnosed as CL II Div I because of a an increased overjet.

! Important to make the distinction as the overjet cannot be reduced in CL I cases unless the lower incisors are also retracted.

! The underlying aetiology is the soft tissue pattern.

Management involves retroclining both the upper and lower labial segments with fixed appliances.

! It is sometimes suggested that bimaxillary proclination should not be treated because of its instability. However sometimes the soft tissues can adapt to the new incisor positions. If the lips are incompetent but have a good muscle tone the chances of obtaining a stable result are good.

! Where the lips are competent or grossly incompetent the result is likely to be unstable and permanent retention will be required.

Thanks