In the very large majority of dental operations nitrous oxide is to be preferred to ether and chloroform, and possesses the great advantage over them of being practically safe. In addition, the administration of nitrous oxide occupies a shorter period, and the recovery is rapid and complete. Within the last few years, combinations of nitrous oxide with oxygen and with air have been introduced by Dr. Hewitt and Mr. Rowell respectively, and both combinations possess advantages over nitrous oxide used alone.
The advantages of nitrous oxide and oxygen over nitrous oxide alone are:—
(1) The anæsthesia is quieter.
(2) The mucous membranes of the mouth do not swell to the same extent, and the operator therefore gains a clearer view of the tooth.
(3) The period of anæsthesia is lengthened, perhaps by only a few seconds, but the quieter condition of the patient assists indirectly in prolonging the period for operating.
The advantages of nitrous oxide with air over nitrous oxide alone are somewhat similar to those of nitrous oxide and oxygen, though less marked.
For operations requiring a long anæsthesia, such as the extraction of a difficult third molar, ether should be used, the administration being commenced with nitrous oxide. In such cases many operators prefer to use chloroform, but the regular employment of this agent in dental surgery is to be severely condemned, and the cases are rare indeed in which its use is called for. A most careful inquiry into this important subject has been made by Dr. Hewitt, and the results of his work were communicated in an exhaustive paper published in the Journal of the British Dental Association for November, 1895, which is well worthy the perusal of all those who are in the habit of administering chloroform.
Whenever a general anæsthetic is given for the removal of teeth, two people should always be present, one to confine his attention solely to the administration of the anæsthetic, the other to the removal of the tooth, as it is impossible for one person to operate and at the same time to observe the condition of the patient during the anæsthetic period. This rule should be strictly adhered to.
For extraction under nitrous oxide, and also to a great extent under ether, the positions of the patients should differ but little if at all from those already advocated, with this exception, it is advisable not to have the head too far back. Before the administration of the anæsthetic is commenced, any removable artificial teeth that may be in the mouth should be taken out; the operator should decide exactly what he intends to do; at the same time it is well not to attempt too much and to avoid pricking the gum during the examination of any roots that it may be necessary to extract. The prop should be placed on sound firm teeth in such a position that the operator can work without being hindered by it, and a final view of the mouth should be taken. Where several teeth have to be extracted at one sitting, their order of removal should be decided upon before the operation is commenced, and if any particular tooth is causing pain, it should be extracted first. The order of removal should also as far as possible be arranged so that changes of instruments are reduced to a minimum. As a rule, lower teeth should be extracted before upper teeth, because if the latter are removed first, the blood may pass down and so obscure the lower ones. Roots should be removed before whole teeth for the same reason. Each tooth or root must be cleared from the mouth before any attempt is made to remove another except in cases where the gum is thoroughly adherent; under this condition the tooth or root may be left and freed from the gum when the patient has recovered. With teeth which have a liability to slip out from between the blades of the forceps, it is well as a precaution to keep a finger of the left hand behind the blades to prevent the tooth passing backwards should it slip out.