Freezing agents can be employed much better for front than for back teeth, in fact it is found at times difficult to freeze the gums at all satisfactorily at the back of the mouth. CHAPTER V. Difficulties, Complications and Sequelæ of Extraction of the Teeth. Like all other surgical operations, the extraction of teeth is at times attended with certain difficulties, complications and sequelæ which for the sake of description will be considered under the following headings: (1) Difficulties, complications and sequelæ connected with the teeth themselves. (2) Difficulties, complications and sequelæ connected with the jaws. (3) Difficulties, complications and sequelæ connected with the soft parts. (4) Difficulties, complications and sequelæ arising during extraction under anæsthetics. (5) Miscellaneous complications, difficulties and sequelæ. (1) DIFFICULTIES, COMPLICATIONS AND SEQUELÆ CONNECTED WITH THE TEETH THEMSELVES. (_a_) =Undue Resistance of the tooth and= =alveolus.=--Considerable resistance to our efforts to remove a tooth at times occurs. This is naturally most often, though by no means always, met with in those of strong physique. Teeth isolated are always firmer than those in series; this is accounted for by a consolidation of the bone around them. Experience will act as a guide, and it is to a certain extent possible, after a little observation, to gather from the general appearance of a tooth if it will give more than normal trouble in removal. Should undue resistance be met with, steady attempts to move the tooth slightly in different directions should be made and persevered with; if this precaution is not taken and too much force is used in any one direction, fracture of the tooth or alveolus is sure to result. It may, perhaps, be found impossible to remove the tooth; when this is the case it is best to dismiss the patient and to make a fresh attempt two or three days later; the tooth will then probably be loose, as a result of the inflammation which has been set up by the previous attempt at extraction, and can be easily removed. The causes of undue resistance are:-- (i.) Abnormal density of the alveolar process. (ii.) Divergent and twisted roots. (iii.) Alteration in the shapes of the roots brought about by periodontal inflammation (exostosis). (_b_) =Fracture of the tooth.=--The principal causes of this accident are:-- (i.) The use of badly fitting forceps. (ii.) The use of unnecessary or wrongly applied force in attempting to loosen the tooth in its socket.