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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 11  »  Supplementary routes to local anaesthesia
Supplementary routes to local anaesthesia
Intraosseous anaesthesia.

Intraosseous anaesthesia.
The use of intraosseous anaesthesia was described by Lilienthal in (1975) and this author notes the reluctance at that time of operators to use the method. Since that time, specialized delivery systems have been introduced and this may increase the acceptance of the technique (Leonard1995).

The method is as follows: the point of perforation is infiltrated with 0.2 mL local anaesthetic and 50-60 s allowed to pass to ensure gingival anaesthesia (Leonard 1995). This point should lie in attached gingiva and is determined by imagining two lines running at right angles to one another. The horizontal line runs along the buccal gingival margins of the teeth and the vertical line bisects the distal interdental papilla of the tooth of interest. The point of penetration is 2 mm apical to the intersection of these lines. If this point lies within the reflected mucosa, an area of attached gingiva coronal to this is chosen. While using the specialized equipment, the perforator (attached to a slow-speed handpiece) is advanced through the anaesthetized gingiva and bone until a characteristic ‘give’ indicating penetration through to the cancellous bone is experienced (Fig. 3). At this stage, the perforator is removed, the short (8 mm) 27 gauge needle is inserted through the perforation into the cancellous space and around 1.0 mL solution is delivered slowly (over a 2-min period). The technique anaesthetizes the tooth of interest and will also anaesthetize the teeth mesial and distal to that tooth in the majority of cases (Repogle et al. 1997). Problems may arise if the needle is too large for the perforation as variations in diameter have been noted (Leonard 1995). Similarly, if the approach is made through reflected rather than attached gingiva the perforation in the alveolus may be difficult to locate (Parente et al. 1998). Limitations to the technique include active periodontal disease, limited attached gingiva and little interradicular bone (Parente et al.1998).

Figure 3. The use of a perforator to gain access to the cancellous space at the initial stage of intraosseous anaesthesia (illustration reproduced by kind permission of Oxford University Press).

The use of a perforator to gain access to the cancellous space at the initial stage of intraosseous anaesthesia

Duration of anaesthesia.
The onset of intraosseous anaesthesia is rapid (Coggins et al.1996, Repogle et al.1997). Leonard (1995) noted that the onset of anaesthesia ranged from10to120 s. The success falls of rapidlyover1 h. Repogle et al. (1997) reported that 30 min after injection pulpal anaesthesia was present in 52% of subjects who had received 2% lidocaine with1:100 000 adrenaline as intraosseous anaesthesia for mandibular first molars. Coggins et al. (1996) reported that the decline in anaesthesia is more rapid with anterior teeth.

Factors governing success.
  1. Anaesthetic solution.
    As was the case with intraligamentary anaesthesia, the efficacy of intraosseous injections is poor in the absence of a vasoconstrictor. Repogle et al. (1997) reported less than 50% success in mandibular first molars when a plain 3% mepivacaine solution was injected compared to 74% success with lidocaine and adrenaline. In addition to increasing the success, the duration of anaesthesia was longer with the adrenaline-containing solution (Repogle et al.1997).
  2. Type of tooth.
    Again, as with intraligamentary injections, the efficacy of the intraosseous technique varies between teeth. Coggins et al. (1996) reported a 75% success rate with mandibular first molars compared to 93% success with maxillary first molars. These authors suggest that variations in success are owing to differences in the cancellous space between sites.
Advantages of intraosseous anaesthesia.
  1. Smaller doses are used than in conventional regional block anaesthesia.
  2. The amount of soft tissue anaesthesia produced is less than that caused by infiltration and regional block methods (Leonard1995).
  3. The method can overcome failure after conventional techniques. When used in combination with inferior alveolar nerve blocks the method increases the success rate for pulpal anaesthesia (Dunbar et al.1996). Similarly, supplemental anaesthesia via the intraosseous route has been shown to be effective in teeth with irreversible pulpitis where conventional methods have failed (Reisman et al. 1997, Nusstein et al. 1998, Parente et al. 1998). Reisman et al. (1997) showed that in pulpitic teeth where an initial inferior alveolar nerve block was successful in only 25% of cases an intraosseous injection increased success to 80%and a subsequent intraosseous injection increased success to 98%.
Disadvantages of intraosseous anesthesia.
  1. The method is technically more difficult than infiltration anaesthesia.
  2. Although not absolutely essential specialized equipment may be required.
  3. There is rapid entry of local anaesthetic and vasoconstrictor into the circulation. Systemic effects attributable to catecholamine entry into the circulation occur early after intraosseous injection (Lilienthal & Reynolds 1975). Many subjects report an increase in heart rate during intraosseous anaesthesia with adrenaline-containing solutions (Coggins et al.1996).
  4. Post-injection discomfort may occur. Repogle et al. (1997) reported a 5%incidence of postoperative swelling and exudate after intraosseous injections. Coggins et al. (1996) noted 3%of patients had slow-healing perforation sites. Two patients required antibiotics. However, all subjects had returned to normal at14 days.
  5. The method may damage teeth. The perforators used to drill the hole in bone can penetrate teeth. However, there is a tactile change detectable and strong pressure has to be used for this to occur (Coggins et al.1996).