Comparative Distalization Effects of Jones Jig and Pendulum

Comparative distalization effects of Jones jig and pendulum appliances by Mayara Paim Patel,a Guilherme Janson,b Jos Fernando Bauru, Brazil

Comparative distalization effects of Jones jig and pendulum applianceMohammad SaoodPG orthodontics

Mayara Paim Patel,a Guilherme Janson,b Jos Fernando Bauru, BrazilINTRODUCTIONNonextraction treatment for Class II malocclusion often requires distal movement of the maxillary molars.Generally correction of this malocclusion involves application of an external force via headgear to the maxillary molars, which mainly needs patients compliance.Intraoral devices and techniques for maxillary molar distal movement. Magnets have been used since 1978 for molar distalization, followed by several other appliances with the same purpose such as, the pendulum, and the Jones jig. The Jones jig and the pendulum are noncompliance appliances for molar distalization.

Some authors found that:

Pendulum produced greater molar distalization than the Jones jig. Molar tipping from the pendulum can be reduced when molar uprighting bends are incorporated in it.

The amounts of anchorage loss of the premolars were similar for both appliances.

AIMTo compare the dentoalveolar effects of treatment with Jones jig and pendulum appliances for molar distalization in Class II malocclusion patients.MATERIAL AND METHODSThe sample comprised 40 subjects (19 boys, 21 girls) who were prospectively treated at the Department of Orthodontics, Bauru Dental School, University of So Paulo, Brazil. Inclusion criteria

Class II malocclusion, All permanent teeth up to the first molars erupted at pretreatment No severe mandibular crowding No previous orthodontic treatment. Lateral cephalograms of each patient were obtained before and after molar distalization. The sample was divided into 2 groups.Group 1Group 1 comprised 20 subjects (11 boys, 9 girls) at a mean initial age of 13.17 years (SD, 1.52; range, 10.83-16.24 years), treated with the Jones jig . Four patients had a full-cusp Class II molar relationship; 8 had a one half-cusp Class II molar relationship; 1 had a three quarters Class II molar relationship, 7 had a one quarter-cusp Class II molar relationship. The coil spring was activated 5 mm every 4 weeks to deliver 100 g of force. A Nance button was also used as anchorage. The mean molar distalization time was 0.91 years (SD, 0.35; range, 0.50-1.95 years).Group 2Group 2 comprised 20 subjects (8 boys, 12 girls) at a mean initial age of 13.98 years (SD, 1.72; range, 11.33-17.26 years), treated with the pendulum Six patients had a full-cusp Class II molar relationship;8 had a one half-cusp Class II molar relationship5 had a three quarters Class II molar relationship 1 had a one quarter-cusp Class II molar relationship. All subjects in this group had the second molars erupted. pendulum springs were activated parallel to the palatal midline,with a mean force of about 250 g,The mean molar distalization time was 1.18 years(SD, 0.28; range, 0.68-1.79 years).In both groups, the appliances were used until the maxillary first molars were distalized to a Class I relationship.

Pretreatment and postdistalization cephalometric radiographs were taken of each patientLandmark were identifications by 1 investigator and then digitized.The cephalometric measurements of the maxillary incisors, premolars, and first molars are described.

The centroid is the midpoint on a horizontal line from the greatest mesial and distal convexity of the 2-dimensional outline of the molars and the premolars.

A month after the first measurements, 40 randomly selected cephalograms (20 pretreatment, 20 postdistalization) were retraced and remeasured by the same examiner. Statistical analysesClass II molar relationship severity and the number of patients with erupted maxillary second molars between the groups were compared with chi-square and Fisher exact tests.

Intergroup comparisons of pretreatment age, treatment time, pretreatment variables, and treatment changes were performed with t tests, and the results were considered significant at P