A Prospective Comparison of the Effects of the Twin Block Appliance and the Dynamax Appliance on the Skeletal and Dental Tissues

G.J MACK and R.T.LEE Royal London Hospital, U.K

The Royal London Hospital

AIMS

To compare the dental and skeletal effects of the Dynamax and the Twin block

To investigate the incidence of breakages and the compliance rates

SUBJECTS and METHODS

Inclusion Criteria• Caucasians• Overjet 7mm, Class II

molars • Males 12-14 years • Females 10-13 years• No relevant Medical History• No extractions

The Dynamax Appliance

Bass and Bass, JCO, 2003

The Twin Block Appliance

Gill and Lee, AJODO, 2005

Treatment Protocol

Start 3 and 6 months

9 months

12 months

Treatment Appliance Inserted

Dynamax activated

2 mm

Appliance Removed

Records Lat CephLaser Scan

HeightOJ

Laser Scan

HeightOJ

Laser Scan

HeightOJ

Lat CephLaser Scan

HeightOJ

Constructed Horizontal 7º to SN

N

ANS

Me Pog

Cephalometry

A-PointA-Point

RESULTS

Patients enrolled into Trial N=62

Males=28 Females=34

RESULTS

Patients enrolled into Trial N=62

Males=28 Females=34

Allocated to Twin block N=31

Males=14 Females=17

Allocated to Dynamax N=31

Males=14 Females=17

RESULTS

Patients enrolled into Trial N=62

Males=28 Females=34

Allocated to Twin block N=31

Males=14 =1 Females=17

Allocated to Dynamax N=31

Males=14 Females=17

Completed trial N=28

Males=13 Females=15

Completed trial N=28

Males=13 Females=15

RESULTS

Statural Height Dental Changes Skeletal Changes Compliance Breakages

Statural Height Changes 0-12 months

(P=0.88)

Dynamax Twin block

m= 57 mm

m= 67 mm

mill

imete

rs

0

50

100

150

RESULTS

Statural Height Dental Changes Skeletal Changes Compliance Breakages

Overjet Reduction 0-9 months

(P=0.20)

0

4

8

12

Dynamax Twin block

m= 5mm m= 6mm

mill

imete

rs

U1-Maxillary Plane(P=0.96)

m= -3.0ºm= -1.7º

Dynamax Twin block-12

-6

0

6

deg

rees

L1-Mandibular Plane(P=0.41)

m= 2.3º

m= 2.3º

Dynamax Twin block-5

0

5

10

deg

rees

RESULTS

Statural Height Dental Changes Skeletal Changes Compliance Breakages

A-Point to S-Vertical(P=0.77)

m= 0.4mmm= 0.1mm

-2

0

2

4

Dynamax Twin block

mill

imete

rs

Pogonion to S-Vertical(P=0.19)

m= 2.0mm m= 2.1mm

Dynamax Twin block-5

0

5

1

mill

imete

rs

Total Anterior Face Height (P=0.03)

m= 2.8mmm= 3.2mm

Dynamax Twin block

-2

0

2

4

6

8

mill

imete

rs

RESULTS

Statural Height Dental Changes Skeletal Changes Compliance Breakages

Compliance

Dynamax Twin Block

Not Completing Trial 3 3

Not Reducing Overjet by 10% after 6 months

1 1

Non Compliance Rate (%) 12 12

RESULTS

Statural Height Dental Changes Skeletal Changes Compliance Breakages

Appliance Breakages

Dynamax Twin Block

Upper Appliance

19 5

Lower Appliance

3 7

CONCLUSIONS

The dental changes were similar for both appliances

The antero-posterior skeletal changes, including mandibular advancement, were similar for both appliances

The vertical dimension increased to a lesser extent with the Dynamax

Both appliances were well tolerated More breakages occurred with the Dynamax