RAPID PALATAL EXPANSION - PART 1 - MINERALIZATION PATTERN, OF THE MIDPALATAL SUTURE IN CATS

The mineralization pattern of the midpalatal suture after rapid palata l expansion was investigated in 10 treated and 2 control cats, in ligh t of the tendency or RPE to relapse. The rapid palatal expansion treat ment consisted of active (25 days), retention (60 days), and relapse ( 60 days) phases. Standardized occlusal radiographs were taken periodic ally and analyzed for suture width, suture optical density in anterior vs. posterior regions, and suture area measurements of radiopaque vs, radiolucent zones. Nine cats exhibited suture splitting. During the a ctive phase, the radiolucent zone (nonmineralized tissue) increased 12 -fold and the increase in optical density was 50% greater in the anter ior over the posterior suture region, demonstrating increased formatio n of loose connective tissue at the anterior region. During the retent ion period, the suture's radiopaque zone (mineralized tissue) increase d by 62%, the radiolucent zone declined (64%) and the suture width dec reased (65%) indicating reorganization of mineralized tissue. The decr ease in optical density (increased mineralization) was 2.5 times great er in the posterior over the anterior suture region, indicating that t he remineralization (closure) pattern of the expanded suture is analog ous to a zipper closed in a posteroanterior direction. During the rela pse phase, the reduction in total suture area (41%) and in the radiopa que zone (32%) indicates medial convergence of the maxillary horizonta l processes. From our findings we extrapolated that the retention of t he suture anterior region should be longer than the posterior region t o catch up the lag in rebuilding and maturation of the newly deposited hard tissue.