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Odontogenic tuinors should he defined :I Y i 1 1 neopl:isnis originating from epi thelin with the potentiality to differenti:lte into odontogenic epithelia, i.e. producing or inducing dental structures or ( 2 ) neoplasms originating froni the connecti\ e tissue o f the I)eriotlontal iiienihr:ine, which differs in some respects froin connective tissue in other p:irts of the hody4. ILIost otiontogenic neoplasin.; iniit:ite w i n e stage or other in the norninl developiiient of teeth and especi:illg the inductive effect of anielohl :I s t s on t 17 e ;id j :ic e n t in e senr 11 y 111 :I 1 c el 1 s to d iff ere n ti :I t e into odontob1:ists :ind also the inductive effect of the dentin ~11)on the :meloblnsts to forin enamel. Therefore, :in :ittempt inay he iiiade to classitg these tuinors iiiainlg :iccording to enihryologic princ i p 1 e s . P I < EVI0 r s CIA AS s I F IC AT ION s One of the first :itteiiipLs t o c1:issify tnniors originating fronl dentnl tissues was ni:ide hy Broctr in 1867'. He based his classification upon the stage of developnient which the tooth in question hntl reached when :1bnorii1:11 growth commenced. In 1887 Bl (in tl-Sir t ton 2 1) r 01) o sed :i r 1 a s sil ic :it i o n hi set1 upon t h e n :I t u re 'This study I Y~S supported by ii grant from the 1)anisli State Research Fountlntioii. Acta Odontol Scand Downloaded from informahealthcare.com by Mcgill University on 11/18/14 For personal use only. Acta Odontol Scand Downloaded from informahealthcare.com by Mcgill University on 11/18/14 For personal use only.

Abstract— Focal epithelial hyperplasia of the oral mucosa was found in 19.4% of 460 inhabitants of an Eskimo population in south‐west Greenland (Nanortalik). The condition was found in all age groups examined, the youngest person with focal epithelial hyperplasia being 2 years old, the oldest 70 years old. There was a statistically significant higher prevalence (33.1%) in the age group above 30 years old than in the age group below 30 years old (14.3%). No significant difference in prevalence could be found between women (17.3%) and men (21.8%). None of 26 Danish Caucasians examined had focal epithelial hyperplasia. The predilection of locations of the focal epithelial hyperplasias was quite different from that previously published. More than 50 % of the lesions were located to tongue; next in frequency were labial mucosa of lower lip, buccal mucosa, commissures, upper lip, and gingiva. None was found in the palate. In many cases the lesions appeared in more than one location in the same patient.

Rhodamine B was first used as a stain for cornification b y Adortinofti 1924, who presented two methods for eleidine and keratogenc substances i n which the dye was used together with either monophenylrosanilin o r Victoria blue. I n 1968, Liisberg published a method for demonstrating-cornified tissue which mas claimcd to he extremcly specific. Rhodamine H was uscd a t pH 3,6 after blocking of basophilic suhstances by toluidine blue.The present authors tried Liisberg's method on formalin fixed, paraffin embedded sections of oral mucosa and Iwratocysts, b u t found that they stained rather faintly and not absolntcly specifically. -4s rhodamine B has becn used as a fluorchrome for many years (Harms 1965), it w a s decided t o t r y to enhance the sensitivity of the method hy means of fluorescence microscopy.Formalin fixed, paraffin embedded sections of biopsies from oral lcucoplakias, Iteratocysts, oral lichen planus and oral carcinomas, containing lteratinizcd layers as evidenced i n haemalum-eosin stainings w c r e used as test ohjects. I n addition scrapings from the palatal and buccal mucosa were staincd after fixation i n 96 per cent ethyl alcohol.T h e rhodaminc H mas Gurr's "Michrome no. 407", and t h e toluidine hlue was "Toluidinblau nach Hoyer". Sections were mounted i n Eultitt. Fluorcsccnce microscopical examination was made with a Leitz Orthoplan microscope fitted with a n Osram HHO 200 W lamp. A 5 m m BG 12 filter was nscd for cxcitation and a Leitz K530 filter as a harrier.In all sections examincd the sensitivity of thc rhodaminc B method was significantly enhanced by fluorcsccnt blue light. The kcratinized laycrs showed an intense: brilliant yellow, secondary fluorescence ( Fig. 1 A + B). A distinct fluorescence was seen cven i n areas whcre the Iteratinizcd layer was very thin and the staining very difficult to evaluate in white light ( Fig. 2 A + B). Unstained sites showcd a greenish fluorescence, a sharp contrast between lteratinizcd and unlicratinized sites therefore being readily obtained. Unfortunately, striatcd muscle tissue, collagen fibres, and erythrocytes arc often partly stained hy rhodamine 13, the reaction being seen clearly b y white light. These limitations of t h e method do not, however, influencc the interpretations of the kcratinization of the epithelium.Leucoplakias with orthokeratinized epithelium showed an intcnse rhodaminc Epositive reaction confined to the lteratinized layers, with a distinct border adjacent to the granular layer. The reaction was more sharply demarcatemd and more uniform i n fluorescent light t h a n in white light. Some of thc prickle cells showed a weak cytoplasmic reaction i n fluorescent light which was hardly recognizable i n white light.Leucoplakias having a paralteratinizcd epithelium and a stratum granulosnm exhibited, in visible light a n irregularly rhodamine B-positive kcratinized laycr with negative pylinotic nuclei, and i n fluorcsccnt light, a regularly positive sharply demarcated keratinized laycr with negative nuclei.Incomplete paralteratosi...