| Ph.D. Candidate: Liu Jianhua, Supervisor: Professor Wu QiuliangDepartment of Oral and Maxillofacial Surgery, First Affiliated Hospital, College ofMedical Sciences, Zhejiang University, Hangzhou, P.R.ChinaINTRODUCTIONCarcinomas on the lower lip are usually resected. Because of the need for 0.7-1 cm surgical margins on either side of the carcinoma, even small lesions may be associated with large defects of the lip. Reconstructing these defects is often done by using local vascularized flaps, such as Gilles fan flaps, modified fan flaps, cross-lip or Abbe flaps, or even distant flaps from the scalp and forehead. However, the use of these flaps can shorten the lower lip, leaving a small mouth (sometimes too small to accept a spoon) that has to be widened in successive operations to restore normal function. In addition, some flaps are technically complex to create and manage, some require displacing large amounts of normal tissue, and most are not successful in obtaining aesthetically pleasing results when used to treat large defects. Thus, a relatively simple, less-destructive surgical technique, capable of reconstructing large lip defects and leaving a functional and aesthetically pleasing mouth, is desirable.Though the "Bernard Advancement Flap" and some variant that are based on a rectangle excision for lip cancer, are technically easy to manage for repairing large lip defects, yet are apparently subject to "dog-ear" deformities.Besides, for the two most frequently introduced cancer excision ways, rectangle and 'V shape excisions, there is still no convincing research conclusion to show readers that which way is better to save more normal lip tissues while the 0.7-1 cm surgical margins on either side of the carcinoma are ensured.Furthermore, there is no flap that can precisely forecast the postoperative appearance of patient, even though a variety of the flap designs for reconstructing large lip defects are available.This study describes a modified labial tissue sliding flap technique suitable for treating lower-lip defects of between one-third and four-fifths of the length of the mouth, geometry analysis of "V" shape and rectangle resection of lower lip tumor, mathematical deduction and computer analysis of "V" shape resection on lip tumor, survey of adult lips and its significance in designing labial tissue flaps for repairing lip defects, vascular corrosion casting of facial artery and its meaning in judging local flaps for lip defects, and establishing of computerized forecasting system for labial and buccal sliding flaps and its application on surgery designing in repair of labial defect. PART ONE1) Geometry Analysis of "V" Shape and Rectangle Resection of Lower Lip Tumor Abstract: Objective: To analyze quantitatively the tissue loss of different resection modes on lower lip tumor. Methods: Deducing the geometrical formulae of tissue loss from 3 resection modes and comparing their advantages and disadvantages. Results: The ratios of ideal, rectangle and "V" shape resection are (n R2 / 2 - n 1^/2) : (2 R2- Ji r2/2): [(R / Sin a, )x (R / Sin a2 > n rV2] respectively. Conclusion: The tissue loss of ideal resection is the lowest, while that of rectangle is next and that of "V" shape is the highest. The smaller the angle of "V" shape resection is, the higher the tissue loss is. The angle range of 45?-60?in "V" resection is recommended.2) Mathematical Deduction and Computer Analysis of "V" Shape Resection on Lip TumorAbstract: Objective: To analyze quantitatively the tissue loss of "V" shape resection mode on lip tumor, and to provide theoretical references for designing or modifying correlative reconstruction flaps. Methods: Deducing the mathematical formulae of tissue loss from "V" resection and programming the formulae by MatLab software, with one half of the angle degrees in "V" resection as independence (a) and the normal tissue loss as dependence (Y). Results: The relationship between independence and dependence wasY= h * [(R / Sin a1 ) * R / Sin a2 ) -...
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