Analysis Of Tooth Movement And Occlusion In Intruding Supraerupted Maxillary Molars Using Interim Removable Prosthesis

[Objective]To obtain sufficient vertical space for the mandibular edentulous area of the recruited subjects,which were repaired by interim removable prosthesis to intruding supraerupted maxillary molars by occlusal force.T-Scan test were performed to trace the changes of occlusal contact,and the masticatory efficiency was measured evaluate the chewing function of the subjects.Furthermore,by contrasting and analyzing the plaster model of preoperative,intraoperative and postoperative using Geomagic software to assess the movement of teeth.Making a preliminary research on the mechanisms of the occlusal reconstruction,molar intrusion,and the effect on stomatognathic system of the subjects who are treated with this methods.[Methods]8 subjects between 20 to 63 years old(mean age:37)visiting Nanjing Stomatological Hospital were recruited from May 2015 to December 2016.5 of them were female,and the other 2 were female.All the subjects have at least one mandibular posterior tooth loss with supraerupted antagonist(s)on either left or right.Reference FWS(the free-way spac,FWS)of the subjects to determine an increase of OVD(Occlusal Vertical Dimension,OVD),then record it using silicone bite registration material.Face bow were used in jaws relationship transferring and mounted onto an articulator for casts of the subjects.We send it to lab technician to make provisional removable prosthesis in the absence of grinding tooth tissue.It should increase the area of the rest as much as possible and guarantee for the denture stability for the design of denture framework.In order to make the occlusal force along the axial overeruption tooth movement,we adjusted occlusal relation between the denture and antagonist(s)and used red heat-curing resins for base,white for artificial teeth.The change in occlusal contact and masticatory efficiency were detected on the baseline,immediately,the second,the fourth week and every three months.Preparing impression and pouring die stone model at regular intervals,scaning it by the means of Dental Wings Dental 3D scanner and save it as.STL.The same researcher analyze the dimension of intrusion and eruption using Geomagic Qualify 2013 software.Using SPSS 19.0 software to make a statistical analysis.Nonparametric tests(wilcoxon rank sum test),correlation analysis were conducted,All statistical analyses were performed at the 95%confidence interval(a=0.05).[Results]1.Clinical outcome:the whole session need 3 to 10 months to obtain restorative space.The sudden placement of a provisional removable prosthesis between the posterior teeth caused some difficulties for the subjects both about lisping and chewing.The complaint did not last for long and speaking stopped after about 1-2 weeks.No pain was reported.2.T-scan tests:it revealed the change in occlusal contact conform to the following regular pattern:1)the last molar of the opposite side of the test tooth were the very first area and the premolar were the second to reconstruct contacts;2)The anterior teeth area and the premolar of the same side of test tooth gradually subsequently resumed contact.3.The masticatory efficiency test:masticatory efficiency of the subjects decreased significantly immediately after wearing provisional prosthesis,but it gradually improve as time goes on and significantly higher than that before the treatment.The quality of life of the patients was improved finally.4.In all participants there was a combined effect of intrusion of the test teeth and eruption of the residual posterior teeth.The intrustion was,on an average,0.78mm,range 0.2 to 2.46 mm,and the eruption was,on an average,0.35 mm,range 0.22 to 1.66 mm.Differences between intrusion and eruption is no statistically significant(p>0.05).In 63%of the subjects the amount of intrusion exceeded that of eruption while in 25%the opposite occurred.Only one subject had the same amount of eruption and intrusion.5.There was a negative correlation between the amount of intrusion,eruption and age.The change of tooth movement is the fastest in 20-39 year old subjects,the tendency is reduced in the 40-69 year old.No difference was observed between sexes.[Conclusions]1.Provisional prosthesis regained restorative space of mandibular edentulous area by intrusion of the supraerupted antagonist,and does not affect the masticatory function.2.The change of occlusal contact was temporary and conform to the following regular pattern:1)the last molar of the opposite side of the test tooth were the very first area recovered contact;2)The posterior teeth of contralateral side regained contact faster than ipsilateral side.3.There was a combined effect of intrusion of the test teeth and eruption of the others in the course of treatment,and the differences between intrusion and eruption is small.4.The fastest tooth movemwnt was found in the youngest age group(20-39 years),then the old group(40-69 years).