The Study Of Changes In The Temporomandibular Joint Space And Condyle Before And After Orthognathic Surgery In Patients With Skeletal Class Ⅲ Malformation With Mandibular Deviation

Background and Objective: The Skeletal Class Ⅲ malocclusion with mandibular deviation deformity has an abnormal relationship between the maxilla and mandible that is very obvious.The occlusion is seriously disturbed,which affects daily life and physical health.The obvious facial deviation will also have a significant psychological impact.The clinical manifestations of temporomandibular joint(TMJ)snapping,pain,joint disc displacement,and abnormal movement can be found in a significant number of patients with mandibular deviation,with a high likelihood(84.6 percent)that the aforementioned symptoms will manifest on the deviated side(DS).Mandibular deviation brought on by isolated unilateral condylar hypoplasia is very challenging to treat.Timely combined orthodontic and orthognathic therapy is required to prevent the aforementioned TMJ abnormalities and symptoms in these patients,and ongoing TMJ monitoring should not be disregarded while treating these patients.This study gathered 20 patients who received combined orthodontic-orthognathic treatment for Skeletal Class Ⅲ malocclusion with mandibular deviation.We then used 3D reconstruction and volumetric reconstruction to determine the TMJ space volume and condylar morphological parameters at various time points.To examine the effects of orthognathic surgery,try to discern distinctions based on the severity of the deviation and analyze and synthesize change patterns and trends.Method: 1.Menton point deviation(MD),which is the degree of deviation,was noted and measured in 20 patients with Skeletal Class Ⅲ malformation and mandibular deviation.Ten patients were assigned to each of the two groups,A(mild deviation group)and B(severe deviation group),based on the amount of deviation: 4·mm≤ MD<10·mm for group A and MD ≥10·mm for group B.2.Data from craniofacial spiral CT(Computed Tomography)scans taken preoperative(T0),two weeks postoperative(T1),six months postoperative(T2)were gathered and imported into Proplan CMF(2.09,Belgium)for the three-dimensional reconstruction of the TMJ fossa and condyle model.3.The condylar volume(V)and surface area(S)during T0 and T2 periods were read in Proplan CMF,and the morphometric index(MI)= condylar volume/surface area was determined.Condylar models from before and six months after surgery were imported into Geomagic Studio 2021(USA)for fitting analysis.4.The TMJ model was imported into 3-Matic Medical 13.0(USA)to read the volumetric characteristics for each of the T0,T1,and T2 periods and volumetrically reconstruct the joint space and partition it according to the relevant plane.Result: 1.A statistically significant difference(P<0.05)existed between the postoperative TMJ space volume in group A and the preoperative overall,anterolateral,and anteroinferior space volume;the same difference also existed between the postoperative TMJ space volume in the non-deviated side(NDS)and the preoperative posterolateral,posteroinferior space volume.2.In group B,the postoperative TMJ space volume was statistically significant(P<0.05)compared to the preoperative total and anteroinferior space volume in the DS;the difference between the total volume of the T1 stage on the NDS and the total volume of the T0 stage was statistically relevant(P<0.05).3.Between groups A and B on the DS,there was a significant difference in the volume of the anterolateral and posterolateral TMJ spaces during the T1-T0 period(P< 0.05),with the difference in the anterolateral space being more relevant(P=0.002).The differences in the overall and subdivisional TMJ space volume changes between groups A and B during the T2-T1 period were statistically relevant(P<0.05),with differences in the changes in the posterolateral space being statistically relevant(P=0.002).The rest of the differences were not statistically relevant.4.The volume and surface area of condyles on the DS and NDS was reduced in group A at T2(P<0.05).Condylar volume,surface area,and MI in T0 and T2 phases in each group: the NDS was larger than the DS,and the difference between the two sides in group A was smaller than that in group B(P<0.05).5.The values of each index of condylar morphology in group A were greater than those in group B,and the difference on the DS was statistically relevant(P<0.05).The magnitude of condylar change in the T2-T0 period was different,and there was a statistically relevant difference in the magnitude of change in volume and surface area on the DS between the two groups(P<0.05).The fitted chromatographic analysis graphs of the condyles in the T2-T0 period in groups A and B showed that the tendency of the condylar surface osseous alteration was consistent with the numerical analysis results.Conclusion: Patients with Skeletal Class Ⅲ malocclusion and mandibular deviation,where there are differences in condylar morphology between the DS and NDS but essentially the same volume of the TMJ space,can benefit from orthognathic surgery by having their occlusion and facial aesthetic issues effectively resolved.In this group of patients,orthognathic surgery increased the amount of TMJ space,and the change was correlated with the degree of deviation as the length of time postoperatively increased.At two weeks after surgery,the direction of condylar movement and rotation was unaffected by the degree of mandibular deviation,but the degree of change was correlated with the degree of deviation,the larger of which.The downward and posterolateral rotation of the condyle in the early postoperative phase was more prominent and continued longer the more severe the degree of deviation.The condylar volume,surface area,and MI on the skewed side were smaller than those on the NDS;the decrease in condylar indices on the DS and the increase in the difference between the DS and NDS led to an increase in the degree of deviation.Six months after surgery,patients with mild deviation experienced a decrease in condylar volume and surface area as well as a significant change in condylar morphology,while patients with severe deviation experienced a prolonged active period of condylar remodeling.The proper removal of intraoperative bone barriers is essential in clinical activity.Such patients should be followed up after surgery for at least six months,and in cases of significant deviation,for a year or longer.Regular follow-up is necessary to prevent postoperative recurrence of jaw deformity.