Objective To investigate the different biomechanical effects of two types of palatal expanders and expansion sites on a bi-lateral complete cleft lip and palate(BCCLP)in mixed dentition with a finite element analysis(FEA).Methods The CBCT data of a patient with BCCLP were collected to construct a FEA model containing craniomaxillary suture structure.The fan-shaped and traditional Hyrax expanders were drawn and assembled into the FEA model in SolidWorks software according to the working conditions as follows:condition 1 and 2,the fan-shaped expander was placed at the anterior/posterior part of the palate respectively;condition 3 and 4,the Hyrax expander was placed at the anterior/posterior part of the palate respectively.A 5 N force in X axis direction was loaded at the apex of the expander coil spring.The stress distribution and initial displacement of craniomaxillary complex in four working conditions were compared.Results ①In working condition 1,2 and 3,the displacement of anterior part was larger than the posterior part of the dental arch.Under condition 4,the displacement of anterior,middle and posterior parts of dental arch were basically the same.②The maximum stress and displacement were observed at crowns in all working conditions.③There was a certain skeletal enlargement effect,which showed a gradually decreasing deformation trend from alveolar region to the upward region.Conclusion The expansion effect of fan-shaped expander is more suitable for BCCLP patients with extremely narrow anterior arch and normal posterior arch.For the tradi-tional Hyrax expander,the position has a great influence on expansion effect.It is showed that the dental support expander could pro-duce skeletal dilation effect in BCCLP patients during mixed dentition.

Objective To investigate the different biomechanical effects of two types of palatal expanders and expansion sites on a bi-lateral complete cleft lip and palate(BCCLP)in mixed dentition with a finite element analysis(FEA).Methods The CBCT data of a patient with BCCLP were collected to construct a FEA model containing craniomaxillary suture structure.The fan-shaped and traditional Hyrax expanders were drawn and assembled into the FEA model in SolidWorks software according to the working conditions as follows:condition 1 and 2,the fan-shaped expander was placed at the anterior/posterior part of the palate respectively;condition 3 and 4,the Hyrax expander was placed at the anterior/posterior part of the palate respectively.A 5 N force in X axis direction was loaded at the apex of the expander coil spring.The stress distribution and initial displacement of craniomaxillary complex in four working conditions were compared.Results ①In working condition 1,2 and 3,the displacement of anterior part was larger than the posterior part of the dental arch.Under condition 4,the displacement of anterior,middle and posterior parts of dental arch were basically the same.②The maximum stress and displacement were observed at crowns in all working conditions.③There was a certain skeletal enlargement effect,which showed a gradually decreasing deformation trend from alveolar region to the upward region.Conclusion The expansion effect of fan-shaped expander is more suitable for BCCLP patients with extremely narrow anterior arch and normal posterior arch.For the tradi-tional Hyrax expander,the position has a great influence on expansion effect.It is showed that the dental support expander could pro-duce skeletal dilation effect in BCCLP patients during mixed dentition.

Objective To analyze the effect of topical ointment combined with periodontal therapy on oral lichen planus(OLP).Methods Forty OLP patients were randomly assigned to 2 groups(n=20).The control group was treated with triamcinolone acetonide(TA)oral ointment,and the experimental group was treated with TA,Xipayi mouth-wash,and periodontal scaling.The therapeutic effect of the two groups was compared at 1,3,and 6 months after treatment.A questionnaire survey was performed before and after treatment,including self-rating anxiety scale(SAS),self-rating depression scale(SDS),and oral health impact scale(OHIP-14 Chinese version).The differences of periodontal index,therapeutic effect,and psychological quality of life between the two groups were analyzed.Results The efficacy of the experimental group was significantly better than that of the control group(P<0.05).After treatment,there were significant differences in the periodontal index and the scores of SAS,SDS,and OHIP-14 between the two groups(P<0.05).Treating with TA,Xipayi mouth-wash,and periodontal scaling could improve the therapeutic effect and psychological quality of life of patients by changing the oral microenvironment.Conclusion Topical application of ointment combined with periodontal therapy can improve the therapeutic effect and alleviate psychological barriers in OLP patients.