Temporomandibular joint growth changes in hyperdivergent and hypodivergent Herbst subjects. A long-term roentgenographic cephalometric study.

The aim of this long-term study was to assess the amount and direction of glenoid fossa displacement, condylar growth, and "effective" temporomandibular joint (TMJ) changes (= the sum of glenoid fossa displacement, condylar growth, and condylar position changes in the fossa) in 3 vertical facial-type groups of Class II Division 1 malocclusions treated with the Herbst appliance. A comparison was made between 38 normodivergent (ML/NSL= 26.5 degrees -36.5 degrees), 17 hypodivergent (ML/NSL or= 37 degrees ) subjects. Lateral headfilms from before, after, and 5 years after treatment were scrutinized. Glenoid fossa displacement, condylar growth, and "effective" TMJ changes were analyzed. Treatment changes: in all facial-type groups, the glenoid fossa was displaced anteriorly and inferiorly. No differences existed between the 3 groups. Condylar growth and "effective" TMJ changes were directed posteriorly and superiorly. The changes in posterior direction were more apparent in the hyperdivergent group than in the normodivergent and hypodivergent groups. Posttreatment changes: in all facial-type groups, the fossa was displaced posteriorly. No differences existed between the 3 groups. Condylar growth and "effective" TMJ changes were directed more vertically compared with the treatment changes. The changes in posterior direction were more pronounced in the hyperdivergent group than in the other 2 groups. It was found that the amount and direction of TMJ growth changes (fossa displacement, condylar growth, and "effective" TMJ changes) were only temporarily affected favorably in the sagittal direction by Herbst treatment. Condylar growth and "effective" TMJ changes were directed more posteriorly in hyperdivergent than in hypodivergent Herbst subjects. This was true for both treatment and posttreatment period changes.