The Etiology,Diagnosis And Clinical Treatment Of Sudden Open Bite

Objective:To explore the causes,diagnosis and clinical treatment of a group of sudden open bite of unknown causes,in order to provide basic clinical diagnosis and treatment of sudden open bite.Materials and Methods:From January 2017 to October 2019,the open bite patients in the department of oral and maxillofacial surgery of the Affiliated Hospital of Qingdao University were selected as the screening objects.Firstly,the patients were examined by conventional clinical examination of the oral and maxillofacial region,the cone beam computer tomography(CBCT),the magnetic resonance imaging of temporomandibular joint and the research model of upper and lower dentition were made.Through the above examination,the developmental malocclusion caused by congenital dysplasia,open bite caused by trauma such as condylar fracture,open bite caused by rickets,open bite caused by abnormal position of posterior molars,open bite caused by space occupying lesions,organic destruction of temporomandibular joint area and joint origin open bite patients,the patients’ whose dentition model without stable cusp crisscross are excluded.Through the above screening,a total of 13 patients with no other abnormalities and unknown reasons were selected as the study objects.Among them,11 cases were open bite in the anterior teeth area and 2 cases in the posterior teeth.During the treatment,the arch splints were fixed in the upper and lower dentition and the prefabricated silicone rubber pads were placed in the bilateral molar area to guide the restoration of intermaxillary staggered occlusion.The elastic intermaxillary traction was performed for 3 weeks.Three weeks later,remove the rubber band,check the occlusion and let the patient repeatedly the relationship of the occlusion after removing the rubber band.When observing 1-2 hours of patients with stable occlusion and no tendency to open bite,guide the patients to exercise the oral and maxillofacial system function.After two weeks of functional exercise of the oral and maxillofacial system,the splint of the maxillary and mandibular hooked arch can be removed if there is no abnormal occlusion,and the functional exercise can be continued for a long time.One year later,the treatment outcome will be followed up and recorded.At the time of before the treatment(T1),removing the dental arch splint(T2)and one-year follow-up(T3),the measurement values of overbite relationship,overjet relationship,the number of occlusal contact points and the subjective satisfaction of patients were used to evaluate the treatment outcome.Results:According to the clinical indicators before and after treatment and at the time of patients’ follow-up visit,all patients were relieved of open bite of unknown causes,restored normal occlusion and coverage relationship,and achieved extensive and close cusp crisscross.At T1,T2 and T3,the values of overbite were-2.9 ± 1.5mm,2.3 ± 0.9mm and 2.4 ± 0.8,respectively.There was a significant statistical difference between T2 and T1(p < 0.01);the T3 and T2 had no statistical difference(p > 0.05).At T1,T2 and T3,the overjet measurements were 3.3 ± 1.2mm,2.5 ± 0.8mm and 2.4 ± 0.7,respectively.Compared with T1,T2 had a significant statistical difference(p < 0.01);compared with T2,T3 had no statistical difference(p > 0.05).At T1,T2 and T3,the number of occlusal contact points was23.5±15.6,33.8±9.8,34.3±8.5,respectively.Compared with the T1,T2 had significant statistical difference in the number of occlusal contact points(p < 0.01);compared with the T2,T3 had no statistical difference in the number of occlusal contact points(p > 0.05).During one-year follow-up(T3),13 patients were satisfied with the treatment outcome(VAS ranged from 7 to 10,and the mean VAS was 8.36 ± 0.91).Conclusions:1.The method of elastic intermaxillary traction and functional exercise of oral system is effective and the long-term effect is stable for the above-mentioned unknown open bite patients.2.The primary cause of these patients may be the dysfunction of oral and maxillofacial muscles,which leads to the sudden loss of intermaxillary crisscross,which belongs to sudden open bite.The specific mechanism remains to be studied.3.For the etiology of primary open bite,the author found a new possible cause,namely myogenic open bite,which is caused by the dysfunction of oral and maxillofacial muscles.4.For the above-mentioned primary open bite patients with unknown causes,the author temporarily classified them as masticatory disorders in temporomandibular disorders,and the specific classification remains to be explored.