Retrospective Clinical Study Of Odontogenic Keratocysts

Part Ⅰ.Recurrence and Prognostic Factors of Odontogenic KeratocystsPurpose: To describe epidemiological features of 565 Chinese patients with odontogenic keratocysts(OKC,)to investigate possible prognostic factors related to recurrence,and to analyze features of recurrent OKC(r OKC).Material and Methods: A retrospective chart review of 663 cases of OKC treated between 2003 and 2015 was undertaken.The probability of recurrence related to prognostic factors including large size,cortical perforation combined with involved teeth in the lumen of the cyst,inflammation,sites of the involved lesion,sex,and daughter cyst variables were analyzed.The subsequent relapse of each OKC was compared.Results: Patients ranged in age from 7 to 81 years(mean age,28.4 years)and,of those affected,66.9% were male and 33.1% were female.Mandibular OKC occurred in 63.01% and 36.99% occurred in the maxilla,80.53% of patients had non-r OKC,10.44% r OKC,and 9.03% had multiple OKC lesions.Enucleation with preservation of the teeth involved in the cyst combined with cortical perforation was statistically associated with high recurrence rate,as were daughter cysts.The average time(in years)to relapse decreased from the first relapse of OKC to the third relapse,and the difference was significant(P<.05).Conclusions: Preservation of the involved teeth combined with cortical perforation appeared to be a potential prognostic factor associated with high recurrence.The follow-up evaluation period for r OKC with ≥ 2 previous treatments should be shorter than for first-time r OKC.The decreasing average duration(years postoperatively)to relapse was related to the number of r OKCs,and r OKC type.Part Ⅱ: Management of Mandibular Odontogenic Keratocyst by Resection ApproachPurpose: The present study reported the clinical outcomes of 35 patients with mandibular odontogenic keratocysts(OKCs)following treatment by radical resection and immediate defect reconstruction.Material and methods: Amongst 565 patients with OKCs that were treated between April 2003 and May 2015,35 patients underwent segmental or marginal mandibulectomy.The use of radical resection was based on clinical and/or radiographic evidence of size,cortical perforation and subsequent soft tissue involvement,and on the history of previous recurrence of the same lesion.Recurrence,justifications of the main major factor for resection,and functional and cosmetic results of the patients following mandibular reconstruction were systematically evaluated.Results: There were 26 OKCs in the mandibular molar-ramus region,eight in the mandibular anterior-premolar region and one in the mandibular molar-ramus and anterior premolar regions.Among the 35 patients,20 had primary OKCs and 15 had recurrent OKCs.A total of 31 patients underwent segmental mandibulectomy,of which 28 were immediately reconstructed with a vascularized flap,whereas four patients underwent marginal mandibulectomy.The functional and cosmetic outcomes of patients were evaluated as satisfactory.The length of the follow-up period ranged from 2 to 17 years following operation(average,5.82 years).Recurrence was identified in one patient who had been treated with marginal mandibulectomy.Conclusion: The findings from the present study suggested that radical resection may be recommended for patients with OKCs and locally aggressive features.Immediate mandibular reconstruction with a vascularized flap may be a crucial part of this aggressive treatment method that may reduce OKCs-associated morbidity.Part Ⅲ: Recurrence of Primary Multiple Odontogenic KeratocystsPurpose: Optimal treatment of odontogenic keratocysts(OKC)remains a matter of debate in the literature.This study aimed to estimate the post-surgical recurrence rates of multiple odontogenic keratocysts(MOKCs)in Chinese patients.Materials and Methods: A retrospective cohort study of histologically confirmed MOKCs treated between 2003 and 2017 using enucleation,marsupialization alone,enucleation and peripheral ostectomy or marsupialization followed by secondary enucleation was performed.Patients who had MOKCs and underwent follow-up for ≥12 months,underwent panoramic radiography and radiographys of the chest and skull at the first visit and were treated by the same team using the same treatment protocol were included in the study.Patients were excluded if the lesion had been treated previously,they had a solitary OKC,or their records were not available for review.Treatment methods,recurrence rate,and time to recurrence were evaluated.The Kaplan-Meier method was used to estimate survival rate and,median time to recurrence;univariates analysis was used to identify the risk factors associated with recurrence.Significant differences were determined at an alpha level of 5%.Results: The sample included 81 patients with MOKCs;21(25.6%)were males and 60(74.07%)females,ranging in age from 7 to 63(18.4±4;mean ± SD)years.The overall recurrence rate was 26.63%,with an overall recurrence-free interval of 26.85 months.The average length of follow-up was 55.68 months.No association was found between the treatment method and the risk of recurrence(P=.178).Although time to recurrence was not affected by any of the study variables,the average time to recurrence of MOKCs involving the maxilla was shorter compared to that of MOKCs involving the mandible.Conclusions: The surgical treatment method does not influence the risk of recurrence in patients with MOKCs,and time to recurrence was not associated with any of the study variables.Part Ⅳ: Behaviors and Features of Recurrent Multiple Odontogenic KeratocystsPurpose: To analyse the clinical features of recurrent multiple odontogenic keratocysts(r MOKCs)treated in young patients.Materials and Methods: Records of patients with r MOKCs treated between 2003 and 2018 using enucleation and marsupialization were identified.Eligibility criterion was r MOKCs treated by the same surgical team.Patients with a follow-up of < 1 year and treatment received at other hospitals were excluded.Clinical features and time to the event were evaluated;differences in clinical features were analysed using t-tests,ANOVA,or chi-squared test.Recurrence analysis was conducted using the Kaplan-Meier method.Statistical significance was set at 5%.Results: Of the 67 r MOKCs included,38 affected the maxilla and 29 affected the mandible.The mean patient age was 26±4.6 years.Thirty-seven cysts occurred in females and 30 in males.Twenty-seven r MOKCs recurred once,13 recurred twice,10 recurred thrice.Finally,9,5,and 3 r MOKCs recurred 4,5,and 6 times respectively.The average time to event for r MOKC1 to r MOKC6 was 27.33±4.6,20.77±1.2,15.1±2.4,10.77±6.1,8.8±3.3 and 6±2.0 months respectively.The number of r MOKCs and the average time to the event decreased significantly from the r MOKC1 to r MOKC6(P=.001 and.031).Patient’s age of ≤ 30 years correlated with high recurrence rates for r MOKC1,r MOKC2,r MOKC3,and r MOKC4(P=.002).Conclusion: Multiple cysts may recur several times and always present with a shorter time to the event in each r MOKC type.Younger patients(≤ 30 years)are at a greater risk of r MOKC recurrence.