Local injective anaesthesia is very common in most clinical procedures in dentistry, in adults as well as in paediatric subjects, and it has a key role in the management of dental anxiety. The primary clinical objective is to obtain complete and long-lasting pulpal anaesthesia at the lowest biological cost; in other words, to reduce the pain associated with the injection as much as possible.
Speaking of a procedure that any professional performs several times a day, the most straightforward basic operational indications will also be the most valid and repeatable. A recommendation, in this almost “scholastic” sense, is certainly to administer the anaesthetic solution slowly. As a concept, we could speak of “slow anaesthesia”.
When a pre-treatment with topical anaesthesia is performed, to reduce the discomfort related to the penetration of the needle, an exposure of at least 1 minute is required.
When approaching a first or second upper molar, therefore, to perform infiltration anaesthesia, the injection of a cartridge of anaesthetic, in turn, takes at least 1 minute to increase the success rate and, at the same time, decrease the data of pain. The clinician may prefer a two-step technique.
60 seconds per cartridge is also the speed required by a multirooted mandibular tooth. In other words, this is the minimum time to perform the common lower alveolar block technique. Haste is an important and confusing factor in this procedure, which already has a high failure rate (20-25%). This procedure requires at least 10 minutes of waiting, and, only after this latency, the lack of the symptom of numbness of the lower lip will force the dentist to a second administration. This period is twice as long as what is required at the level of the multirooted maxillary teeth which, have a period of latency; a positive cold test after 5 minutes, however, does not require a second administration. After another 3-5 minutes of waiting in most cases, the test will be denied, thus indicating the achievement of the minimum effect required.
In the final analysis, there are technologies developed explicitly on the concept of slow anaesthesia. This is the case, for example, of the computer-controlled local anaesthetic delivery (CCLAD); as suggested by the term, it is the software that manages the speed of administration, which is kept low and, at the same time, constant. It is clear that an instrument of this type has a higher sensitivity than the human one; indicatively, the speed of the cartridge per minute (1.8 mL/min) is set as the fast rate of the instrument, which reaches a slow rate of 0.5 mL/min, or about four minutes for an entire vial tube.