| Background: The clinical classifications of odontogenic cysts of the mandible include radicular,primordial and dentigerous cysts.Curettage is the primary choice for treating odontogenic cysts.Major complications resulting from cyst curettage include alterations in body temperature,local swelling,and nerve damage.Minor symptoms caused by injury to the inferior alveolar nerve or mental nerve are reversible,and may recover within a few days,while severe symptoms are longer lasting and may not recover for months.Presently,research into pain and numbness of the chin and lower lip caused by injury to the inferior alveolar or mental nerves mostly consists of case reports or subjective questionnaire-based reports.Objective neurophysiological experiments are relatively less common.Quantitative sensory testing(QST)is a significant tool in the diagnosis,classification,and study of disease mechanisms of sensory disorders.Therefore,the purpose of this study was to apply QST to quantitatively analyze the somatosensory effects associated with curettage of odontogenic cysts of the mandible.Objective: 1)To investigate the changes in mechanical detection threshold(MDT),mechanical pain threshold(MPT),two-point discrimination(TPD),pressure pain threshold(PPT),cold detection thresholds(CDT),warm detection threshold(WDT),cold pain threshold(CPT),and hot pain threshold(HPT)before and after the operation.2)To explore factors that influence pain thresholds(MPT,PPT,CPT,HPT),temperature detection thresholds(CDT,WDT)and mechanical tactile thresholds(MDT,TPD).Methods: NNT4.6 was used to analyze data obtained using cone beam computed tomography(CBCT)to identify the location of the mental foramen and measure the width of the defect of the mandibular canal wall.An international standard QST program was used to conduct a prospective study of patients with odontogenic cysts in the posterior mandibular region who were admitted to our hospital between March and November 2017.Test sites included the lower lip red midpoint and the body projection site of the mental foramen,in both the operative and healthy sides.The parameters obtained on the healthy side were used as controls.Preoperative,and 2 days,7 days,and 1 month postoperative somatosensory parameters were measured.All data were log transformed to obtain normal distribution.Paired-samples Student's t-tests were used to compare parameters at different times and sites.The relative rates of change(RC)of all parameters in the operative side were calculated,and the effects of sex,use of iodoform gauze,and defect of the mandibular canal wall were analyzed by one-way analysis of variance.Z-scores were used to evaluate changes in mental nerve function.Results: 1.Pain 1.1)MPT.The lip threshold on the operative side was increased on postoperative day 7 and month 1 compared to postoperative day 2(p = 0.032,0.022);the threshold was increased at postoperative month 1 compared to postoperative days 7(p = 0.029).The chin threshold on the operative side was lower on postoperative day 2 compared to before the operation(p = 0.020),and was increased on postoperative day 7 and postoperative month 1 compared to postoperative day 2(p = 0.007,0.012);the threshold was increased at postoperative month 1 compared to postoperative days 7(p = 0.035).1.2)PPT.The lip threshold on the operative side was lower on postoperative day 2 compared to before the operation(p < 0.001),and was increased on postoperative day 7 and postoperative month 1 compared to postoperative day 2(p = 0.006,< 0.001).The chin threshold on the operative side was lower on postoperative day 2 compared to before the operation(p = 0.001),and was increased on postoperative day 7 and postoperative month 1 compared to postoperative day 2(p = 0.036,< 0.001).The lip threshold was lower than that of the chin on the operative side before the operation,and at postoperative month 1(p = 0.001,0.001).Further,the lip threshold was lower than that of the chin in the healthy side before the operation and on postoperative day 2(p = 0.001,0.013).1.3)CPT.The lip threshold on the operative side was lower on postoperative day 7 compared to postoperative day 2(p = 0.011).The chin threshold was increased on postoperative day 2 and 7 compared to before the operation(p = 0.003,0.006),and was decreased at postoperative month 1 compared to postoperative day 7(p = 0.015).The lip threshold was higher than that of the chin on the operative side before the operation and on postoperative day 7(p = 0.001,0.005).The lip threshold was higher than that of the chin in the healthy side before the operation and on postoperative day 2(p = 0.026,0.015).The RC of the chin threshold in males was lower than that in females on the operative side at postoperative month 1(p = 0.011).1.4)HPT.The lip threshold on the operative side was increased on postoperative day 2 compared to before the operation(p = 0.023),and was decreased on postoperative day 7 compared to postoperative day 2(p = 0.008).The chin threshold on the operative side was increased on postoperative day 2 compared to before the operation(p = 0.001),and was decreased on postoperative day 7 and postoperative month 1 compared to postoperative day 2(p = 0.027,0.031).The RC of the chin threshold in patients with mandibular canal defects was higher than that in those without the defect on the operative side at postoperative day 7(p = 0.043).2.Thermal sensory 2.1)CDT.The lip threshold on the operative side was lower on postoperative day 2 and 7 compared to before the operation(p = 0.004,0.002);the threshold was increased at postoperative month 1 compared to postoperative days 7(p = 0.002).The chin threshold on the operative side was higher on postoperative day 2 and 7 compared to before the operation(p = 0.023,0.007);the threshold was lower at postoperative month 1 than on postoperative day 7(p = 0.010).The lip threshold was higher than that of the chin on the operative side on postoperative day 2(p = 0.007).2.2)WDT.The lip threshold on the operative side was lower on postoperative days 2 and 7 compared to before the operation(p = 0.008,0.022),and was decreased on postoperative day 7 and postoperative month 1 compared to postoperative days 2(p = 0.045,0.035).The chin threshold was increased on postoperative day 2 and 7 and postoperative month 1 compared to before the operation(p = 0.003,0.023,0.003).3.Touch 3.1)MDT.The lip threshold on the operative side was lower on postoperative days 2 and 7 compared to before the operation(p = 0.001,0.011);the threshold was decreased at postoperative month 1 compared to postoperative days 2 and 7(p < 0.001,= 0.008).The chin threshold on the operative side was higher on postoperative day 2 compared to before the operation(p = 0.002).The lip threshold was higher than that of the chin on the operative side on postoperative days 2 and 7(p = 0.011,0.025).The RC of the lip and chin in patients with mandibular canal defects was higher than in those without the defects on the operative side on postoperative day 7(p = 0.035,0.007).3.2)TPD.The lip threshold on the operative side was lower on postoperative days 2 and 7 compared to before the operation(p = 0.011,0.006).The lip threshold was lower than that of the chin on the operative side before the operation and on postoperative days 2 and 7,as well as postoperative month 1(p < 0.001,0.001,0.001,0.001).The lip threshold was lower than that of the chin on the healthy side before the operation and on postoperative day 2(p < 0.001,0.001).Conclusions: This study found that some patients who had undergone curettage of mandibular cysts,especially those with mandibular canal defects,experienced abnormal sensation in the lower lip and chin.(1)The changes in MPT and CPT were not significantly different before and after the operation.The CPT of the lip was higher than that of the chin,while the PPT of the lip was lower than that of the chin.The change in CPT in the chin of males was less than that of females.Differences in chin HPT in patients with mandibular canal defects was more significant.The PPT and HPT of the chin was significantly different on postoperative day 2,and recovered within 7 days.(2)The CDT and WDT were significantly altered after the operation.The sensitivity of the lip was lowest 2 days after the operation,and chin sensitivity was lowest after 7 days.CDT and WDT gradually recovered within one month after surgery.(3)MDT changed significantly after the operation,and recovered more slowly.Severe nerve injury required about 6 months to return to normal.The TPD of the lip was lower than that of the chin,and postoperative TPD changes also occurred mainly in the lips and recovered around 1 month following the operation.In addition,due to the presence of angular stomatitis,the MDT,TPD,and CDT of the lower lip were all higher than those in the chin at the early postoperative time points.QST is a highly sensitive,reproducible,and reliable neurophysiological technique that can quantitatively determine sensation,and has important reference and research value in the assessment of somatosensory abnormalities after cyst curettage. |
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