A Cephalometric Method To Determine The Occlusal Plane Curve Of Edentulous Patients

Objective Through analysis and compare the differences of cephalonmetrics in adult patients with normal occlusion and adult edentulous patients,establish each fixed point equation of occlusal plane curve in adult patients with normal occlusion,provide theoretical basis for clinical to determine occlusal plane curve of complete denture.Methods According to the inclusion and exclusion criteria,43 adult patients with normal occlusion and 25 adult edentulous patients were selected from June2019 to September 2021.The patients were divided into four groups:male normal occlusion group（20 men,average age 27.00±3.95 years）、female normal occlusion group（23 women,average age 27.30±4.17 years）、male edentulous group（12 men,average age 67.75±5.38 years）and female edentulous group（13 women,average age 65.77±1.92 years）.Making routine complete dentures which were completely adapted for 2-3 months and restored good morphology and function after adjusting for adult edentulous patients.In intercuspal position,bleidraht for adult patients with normal occlusion and lead shots for adult edentulous patients with a diameter of 0.3mm were fixed on the incisal edge of the anterior teeth and the buccal tip of the posterior teeth in maxillary,and everyone took a standard cephalometic roentgenogram.U1（anterior point）、U3（turning point）、U6m（key point）、U7d（posterior point）of the occlusal plane curve were located and the data were measured by cephalometric software.In the vertical line distance:Frankfort horizontal plane was regared as the standard plane,the distances from S（sella）、Ptm（pterygomaxillary fissure）、ANS（anterior nasal spine）、N（nasion）、U1、U3、U6m、U7d to Frankfort Plane were measured and named as S-FH、Ptm-FH、ANS-FH、N-FH、U1-FH、U3-FH、U6m-FH、U7d-FH,perpendicular foots were named as S’、Ptm’、ANS’、N’、U1’、U3’、U6m’、U7d’.In the horizontal line distance:The distances from S’、ANS’、N’、U1’、U3’、U6m’、U7d’to Ptm’were measured and named as Ptm’-S’、Ptm’-ANS’、Ptm’-N’、Ptm’-U1’、Ptm’-U3’、Ptm’-U6m’、Ptm’-U7d’.In the angle mesurement:OP₁-FH、OP₂-FH、OP₃-FH、OP₀-FH、Po-N-ANS、Ar-Go-Me、S-N-Pog、MP-FH、ANS-Go-Me.All data were input into the computer,and statistical software SPSS26.0 was used for statistical analysis of all measured data,α=0.05,P<0.05 considered that the difference was statistically significant.Indepent sample t test is used to analyze the gender differences and the class different,One-way ANOVA is used to analze the differences of OP₁-FH、OP₂-FH、OP₃-FH、OP₀-FH,Pearso correlation analysis method is used to analyze the correlation between two variables of the vertical line distance、the horizontal line distance and the angle measurement,the linear regression analysis is used to analyze two variables of the vertical line distance and the horizontal distance.Results1.The gender differences:In the vertical line distance,both normal occlusion group and edentulous group,there were statistically significant differences in U1-FH、U3-FH、U6m-FH、U7d-FH between male group and female group（P<0.05）,and the distances in male group were all larger than those in female group,while there were no statistically significant differences in other vertical line distance（P>0.05）;In the horizontal line distance,both normal occlusion group and edentulous group,there were statistically significant differences in Ptm’-ANS’、Ptm’-N’between male group and female group（P<0.05）,and the distances in male group were all larger than those in female group,while there were no statistically significant differences in other horizontal line distance（P>0.05）;In the angle measurement:both normal occlusion group and edentulous group,there were no statistically significant differences between male group and female group（P>0.05）.2.The class differences:In the vertical line distance,both male group and female group,there were no statistically significant differences between normal occlusion group and edentulous group（P>0.05）;In the horizontal line distance,both male group and female group,there were statistically significant differences in Ptm’-U6m’、Ptm’-U7d’between normal occlusion group and edentulous group（P<0.05）,and the distances in edentulous group were all larger than those in normal occlusion group,while there were no statistically significant differences in other horizontal line distance（P>0.05）;In the angle measurement:both male group and female group,there were statistically significant differences in OP₂-FH、OP₃-FH between normal occlusion group and edentulous group（P<0.05）,and the angle measurements in normal occlusion group were all larger than those in edentulous group,while there were no statistically significant differences in other angle measurement（P>0.05）.3.The differences of four cants of occlusion plane:both male normal occlusion group and female normal occlusion group,OP₁-FH<OP₀-FH<OP₂-FH<OP₃-FH,the differences between groups were statistically significant（P<0.05）;both male edentulous group and female edentulous group,the differences were statistically significant between groups among them（P>0.05）,OP₀-FH、OP₁-FH and OP₂-FH were all smaller than OP₃-FH,and the differences were statistically significant（P<0.05）.4.Both male normal occlusion group and female normal occlusion group,U1-FH、U3-FH、U6m-FH、U7d-FH were positively correlated with ANS-FH,while U1-FH、U3-FH、U6m-FH were negatively correlated with N-FH,and were most correlated with ANS-FH.Ptm’-U1’、Ptm’-U3’、Ptm’-U6m’、Ptm’-U7d’were positively correlated with Ptm’-ANS’.There was a positive correlation between OP₀-FH and MP-FH in male group.In female group,OP₀-FH was positively correlated with MP-FH and ANS-Go-Me.The vertical line distance regression equation adopted the relation with ANS-FH,and the horizontal line distance regression equation adopted the relation with Ptm’-ANS’.Male group:U1 in the vertical and horizontal line distance:Y=34.904+0.883X、Y=-50.545+1.935X;U3 in the vertical and horizontal line distance:Y=35.298+0.821X、Y=-33.654+1.434X;U6m in the vertical and horizontal line distance:Y=37.087+0.598X、Y=-31.979+1.306X;U7d in the vertical and horizontal line distance:Y=35.358+0.490X、Y=-37.707+0.863X.Female group:U1in the vertical and horizontal line distance:Y=33.060+0.868X、Y=-2.371+1.091X;U3 in the vertical and horizontal line distance:Y=35.283+0.737X、Y=-8.947+1.038X;U6m in the vertical and horizontal line distance:Y=36.065+0.519X、Y=-8.651+0.620X;U7d in the vertical and horizontal line distance:Y=36.012+0.305X、Y=-20.491+0.563X.Conclusion1.Taking Frankfort horizontal plane as the standard plane,in the vertical line distance,the occlusal plane curve of the adult male moved down relative to adult female.2.Compared with adult normal occlusion,the first molar and second molar were moved forward and the middle and posterior OP inclination were more gentle in the routine complete denture.3.About accurate positioning of the anterior point,turning point,key point and posterior point of the occlusal plane curve,the regression equation between U1-FH,U3-FH,U6m-FH,U7d-FH and ANS-FH could be used in the vertical line distance,and the regression equation between Ptm’-U1’,Ptm’-U3’,Ptm’-U6m’,Ptm’-U7d’and Ptm’-ANS’could be used in the horizontal line distance.