The Study Of Three Different Measure Methods For The Efficacy Of The Maxillary Expansion-an Animal Experiment

Objectives: The objective of this comparative study was to provide somereference for establishing evaluation criteria of maxillary expansion in an animalmodel of arch expansion with different evaluation methods.Methods: Eight6-month male beagles were used in this study, given numbersand anesthesia, then the self-threading pins were required to be implanted on the palateas mark points. After taking silicone expressions and cone-beam computedtomography (CBCT) images, the beagles were divided into two groups for four each.The first group ones were sacrificed instantly and measured in direct autologousmethod, which served as the group one. And the second group ones had been takenmaxillary expansion with new magnetic expansion appliance. They were sacrificed in2weeks later after being taken CBCT images and expression. The distances measuredwere canine (C-C), fourth premolar (P-PM4), first molar (M-M1) distances, and thebasal bone width.Both the dental casts and direct autologous ones were measured inthe first group. And the CBCT images were applied to measure C-C,P-PM4，M-M1besides the orthopedic data including distances between self-threading pins andforamen palatinum majus trailing edge as well as incisive foramen trailing edge, andbuccolingual tipping of molars. Direct autologous method was used to measure withthe animals both in teeth and bone. The measurements of the second group were sameas the first group before maxillary expansion, but added the buccolingual inclinationof molars. The direct autologous measurement was failed because the beaglescouldn’t be sacrificed. The measurements of the second group after maxillaryexpansion were same as before maxillary expansion, the digitals of direct autologousmeasurement could be obtained after the beagles were sacrificed. The necessarydigitals were quantified by differences calculated in these three methods before andafter arch expansion.Results:1) Before maxillary expansion, there is no significant differencebetween these three methods except that teeth distances including P-PM4,M-M1in models method is different from direct autologous method and CBCT method. Nosignificant difference was found in bone among these three methods.2) After maxillary expansion, no significant difference was found betweenCBCT method and direct autologous method. The date in models method is differentsignificantly from CBCT method and direct autologous method.3) The significant difference was found in all date before and after magneticmaxillary expansion,4) In the comparison of differences calculation before and after maxillaryexpansion, the evaluation criteria of orthodontic expansion was significantly differentbetween CBCT method and models method; In CBCT method, the significantdifference was found in the evaluation criteria of orthopedic expansion includingpalatal macroporous trailing edge trailing edge width, interanterior palatine foramentrailing edge, interimplant analog width and basal bone width.5) In CBCT method, no significant difference of measurement of buccolingualtipping of molars was found in2methods.The repeatability of the2methods werehigh.Conclusion:1) CBCT method was superior to models method but similar to direct autologousmethod.2) In this research, there is no bone mark points can replace self-threading pinsto evaluate the effect of maxillary expansion.3) From CBCT exams, the repeatability of the two measurements ofbuccolingual tipping of molars was high.