TEETH 



333 



TEETH 



pulp confers numerous obstacles. The 

 wise histologist or pathologist will save 

 valuable time by at once seeking advice 

 from experts in some dental research 

 laboratory. They possess experience 

 and instruments for grinding and sawing 

 both of which he lacks. Teeth of adults 

 can be prepared for examination in 2 

 principal ways : 



1. Without decalcification. Church- 

 ill and Appleton (McClung, p. 253) 

 recommend, in place of the usual grind- 

 ing method, a cutting technique used by 

 Johnston at Yale. After extraction fix 

 the tooth immediately in formalin. Then 

 dry and fix to wooden block by modelling 

 compound. Sections are then made by 

 the cutting wheels of a power lathe. If 

 necessary they are polished on a Belgian 

 stone, dehydrated in alcohol, cleared in 

 xylol and mounted in balsam. 



Ground sections of very brittle teeth 

 or teeth with supporting structures 

 intact may be ground after imbedding 

 in methyl methacrylate according to 

 Sognnaes, R. F., Anat. Rec, 1947, 99, 

 133-144. This method permits sawing 

 of such thin slices before grinding that 

 serial sections may be prepared. 



When one wishes to include the soft 

 as well as the hard parts Chase's tech- 

 nique of petrifaction is advised by 

 them. Fix as desired (say 10% forma- 

 lin) and wash as required. Transfer to 

 aq. gum arable or dextrin of syrupy 

 consistency. Freeze on freezing micro- 

 tome and cut slices with very fine saw 

 (jeweler's). Remove gum arable by 

 washing in water and stain with carmine 

 or hematoxylin. Dehydrate through 

 alcohols to 95%, | to several hours each 

 depending on size of slice. Acetone ^ 

 hr. or more. Cover with thin celloidin 

 in a container to depth twice or more 

 thickness of slice. Leave container 

 top open very slightly permitting evap- 

 oration until celloidin will scarcely flow 

 when container is steeply tilted. Trans- 

 fer with considerable celloidin to con- 

 tainer of heavy lead foil and further 

 evaporate until completely hardened. 

 Grind and polish both sides of slice in 

 presence of water. Remove celloidin 

 with acetone and acetone with xylol. 

 Mount in balsam. Sections obtained 

 by this and the Johnston technique can 

 be examined by direct illumination, 

 in the dark field, in ultraviolet light 

 (Walkhoff, O., Dental Cosmos, 1923, 

 65, 160-176), in polarized light (Andre- 

 sen, V. The Physiological and Artificial 

 Mineralization of Enamel. Oslo. Dancke, 

 1926) and by x-ray for which many 

 references are given (McClung, 381- 

 385). 



2. With decalcification. In the par- 



affin technique, advised by Churchill 

 and Appleton, clip ends of roots of a 

 freshly extracted tooth or drill hole. 

 Fix in 4% formalin. Dry with towel 

 and seal openings to pulp with celloidin. 

 Quickly dry. Decalcify in 10% hydro- 

 chloric acid C.P. 10 days or more testing 

 with needle. Running water, 24 hrs. 

 95% ale. ,24 hrs. Abs. ale, 5 hrs. Chlor- 

 oform, 1 hr. Equal parts chloroform 

 and 45°C. paraffin in glass stoppered 

 bottle on top of oven (oven 58°C.) over 

 night. 5 hr. each in following paraffins 

 (1) 42-46°C., (2) 52-56°C.and (3)58- 

 60°C. within oven. Imbed in a mix- 

 ture of 235 cc. 52-56°C. paraffin and 15 

 cc. beeswax. See Paraffin Sections. 



In the celloidin technique (Churchill 

 and Appleton) cut off apex of tooth or 

 drill a hole to pulp through crown. 

 Fix in 4% formalin, buffered to counter- 

 act acid, 45 hrs. for single teeth. (Wash 

 in water) change to 80% ale. 95% ale. 

 2 weeks -\- depending on size. Abs. 

 ale. 2 weeks +, abs. ale. (exposed to 

 anhydrous copper sulphate, see Alco- 

 hol) 2 weeks +. Equal parts abs. and 

 ether, 2 weeks +. Then 1 month or 

 more in |, 1, 2, 5, 7, 10, 12% celloidin 

 (parlodion). Orient and imbed in 12% 

 in stender dish. Make depth of cel- 

 loidin twice height of tissue. Place lid 

 of stender dish on tightly. Allow 

 bubbles to rise 24 hrs. If bubbles still 

 present move tissue gently so they can 

 escape. Put piece of paper between 

 lid and dish, 24 hrs. +. Evaporate to 

 consistency hard rubber, 7 days +. 

 80% ale. 48 hrs. or until beginning decal- 

 cification. Trim block leaving sufficient 

 celloidin about tissue to facilitate cut- 

 ting. 10% acetic or hydrochloric acid 

 in 70% ale. changing daily 3 weeks + 

 until needle penetrates easily. When 

 spaces appear in the celloidin drill holes 

 to reach them. Wash 24 hrs. in running 

 water; then same time in weak sol. 

 sodium bicarbonate. Wash 24 hrs. + 

 in water. 50, 70 and 80% ale. each 24 

 hrs. +. 95% and abs. ale, § hr. each. 

 Ale. ether, 0.5% and 12% celloidin 5-20 

 min. each. Harden in chloroform, 24 

 hrs. Leave in 80% until sections are 

 made, see Celloidin Sections. 



For small and developing teeth a wider 

 variety of methods is possible see Teeth 

 Developing. To classify examples of 

 all the methods available for old and 

 young teeth and associated structures 

 in a manner expected by the reader is 

 not feasible. In general however there 

 are methods that involve whole teeth 

 which come under Teeth (Blood Ves- 

 sels, Innervation, Lymphatics) and 

 their response to Alizarin Red staining 

 and exposure to Radioactive Phos- 



