| Objective:The purpose of this study is to evaluate the effect of maxillary removable expansion appliance combined with maxillary lip bumper on the transverse and horizontal growth of maxillary arch,and we constructed a multiple regression analysis model between the increment of dental arch perimeter and the increment of dental arch length and width,so as to provide further dependence on the clinical use of the modified appliance.Methods:A total of 21 patients with discrepancies of dental quantity and osseous volume were included in this study,of whom 14 were included in the lip bumper group(lip bumper modified maxillary expansion group)and 7 in the no lip bumper group(removable maxillary expansion group),with a mean age of 7.9 years in both groups.Both groups were asked to wear expansions for 24 hours daily in addition to wash times,and the lip bumper group asked to wear contact between the upper and lower lips of children when wearing,wrapping the lip stop.Rotating the expanded arch helix by 90° in the direction of the arrow using an arch key or blunt tip probe every two days until the lingual tip of the maxillary posterior teeth opposing the buccal tip of the mandibular posterior teeth was scored as the end of the expanded arch.Patients were instructed to return monthly during treatment,check the patient’s expansion screw opening when return visiting,adjust the retaining device,and care should also be taken to adjust the lip bumper position when return visiting in the lip bumper group.A retention model of the patient’s upper and lower dentitions before treatment(T1 stage)and at the end of the expansion(T2 stage)was used for later measurement and analysis studies.The measurement items of the retention model included several indicators,such as the periodontal length of the dental arch,the width of the anterior,middle,and posterior dental arches,the width of the gingiva at the anterior and mid apical bases,the length of the anterior part of the dental arch,and the full length of the dental arch.Spss22.0 software was used to comparatively study the differences of the change of measurement indexes between the two groups before and after arch expansion,to analyze the effect of the two groups’ expansion on the dentition of the dental arch,and to analyze the relationship between the change of dental arch perimeter and the indexes such as length and width of dental arch in the lip bumper group using stepwise multiple regression.Of the above statistical analyses,P<0.05 was considered statistically different.Results:1.Time:The expansion time was greater in the lip bumper group than in the no lip bumper group,with statistically significant differences(P<0.05).2.Arch perimeter:There was no statistically significant difference in the increase in perimeter between the 2 groups for the lip bumper group and the no lip bumper group(P>0.05).Within group comparisons there was a significant increase(P<0.05)in the expansion of the dental arch perimeter in both groups.3.Width:The middle basal bone width increased more in the lip bumper group than in the no lip bumper group,and the differences were statistically significant(P<0.05),with no significant differences between the two groups for the remaining measures of width(P>0.05).For intragroup comparison,the width of the anterior,middle,and posterior teeth of the dental arch,the width of the gingiva at the anterior,middle,and posterior,and the width of the basal bone at the anterior and middle sections increased significantly in both groups before and after expansion(P<0.05).4.Arch length:The amount of increase in arch full-length was greater in the lip bumper group relative to the no lip bumper group,although the difference was not statistically significant(P>0.05),nor was the amount of increase in anterior length between the 2 groups(P>0.05).For intragroup comparison,the increase in the anterior length of the dental arch and the increase in the full length of the dental arch after expansion in the labial stage group were statistically significant(P<0.05);The increase in the anterior length of the dental arch after expansion was statistically significant(P<0.05)in the no lip block group,and the increase in the full length of the dental arch was not statistically significant(P>0.05).5.Dental inclination:The labial tipping degree of the deciduous canine after arch expansion was significantly greater(P<0.05)in the lip bumper group than in the no lip bumper group,and there was no significant difference in the buccal tipping degree between the two groups for the second primary molar and first molar(P>0.05).For intragroup comparison,the labial tipping group showed increased labial(buccal)tipping of the primary canine,second primary molar,and first molar(P<0.05);In the no lip bumper group,there were no significant differences in the increase of labial(buccal)tipping of primary canine and first molar before and after arch extension(P>0.05),but the buccal inclination of second deciduous molar increased significantly(P<0.05).6.Correlations analysis and Regression equation:The increasing amount of dental arch circumference in the labial block group was moderately positively correlated(P<0.05)with the increasing amount of anterior and middle dental arch width and total dental arch length,strongly correlated(P<0.05)with the increasing amount of posterior dental arch width,very weakly or not correlated with the increasing amount of anterior dental arch length,and was not statistically significant(P>0.05).The relationship between the increment of dental arch perimeter Y and the posterior arch increment X1,the full length increment X2 meets the following equation:Y=0.601X1+1.035X2-0.667.Conclusion1.Lip bumper modified maxillary expansion is more useful in the presence of malocclusion caused by insufficient labial tipping or base bone width of the maxillary deciduous cusps,such as functional class Ⅲ or class Ⅱ malocclusion caused by forced protrusion or retropulsion of the mandible due to insufficient intermaxillary width.2.There were no significant differences between removable maxillary expansion and lip bumper modified maxillary expansion in increasing arch circumference or arch length.Combined with the lip bumper modified maxillary expansion correction time is longer than the removable maxillary expansion,the clinical can be combined with the specific situation of children to choose the diffuser. |
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