IOI was developed to deliver dental anesthetic for maximum clinical effect with minimal side effects. The benefits of using the IOI technique are evident to patients since they do not have their lips and tongues anesthetized, and dentists can rely on predictable, profound anesthesia at the targeted tooth with instant effect. With the IOI technique having such desirable characteristics, the following question needs to be asked: "Why is IOI a lesser-known and -used technique compared with block and infiltration injections?" As I explore the historical use of intraosseous anesthesia, or IOA, I will show that the IOI is a reliable backup technique for dentists when an inferior alveolar nerve block fails. The expansion of IOI’s role in dentistry reveals that it is a primary solo technique, as well as a supplemental procedure used as a last resort.

The IOI technique traditionally was a two-step procedure used to deliver anesthetic into the cancellous bone near the apex of the targeted tooth. The first step was to drill a small hole through the soft tissue and cortical bone to a depth of 5 to 8 millimeters. The second step involved finding the hole with the same long axis orientation and inserting a nearly matched diameter needle to the same depth. Anesthetic solution was manually injected into the cancellous bone, and the sensory nerves of the tooth were anesthetized.

This technique’s lack of popularity was due to the reluctance of dentists to drill into cortical bone and the difficulty of inserting the needle precisely into the drilled hole with a tight fit. These two factors combined to make IOI a reserve technique that was used only when traditional nerve block and infiltration anesthetic techniques failed clinically. Instrumentation consisted of a round bur or a 0.45-mm motorized endodontic reamer and a standard 27-gauge short needle. The volume of anesthetic deposited was 0.5 to 1.5 cubic centimeters, but due to the lack of an intimate fit between the needle and the hole, the effective amount deposited was halved due to leakage at the infusion site. The predominant anesthetics used were lignocaine (1:80,000 epinephrine) and lidocaine (1:100,000 epinephrine).

As dentists and patients experienced the versatility and effectiveness of IOA, the IOI technique grew from its status as a last-resort technique to a first-use technique used to achieve local anesthesia. The popularity of IOA expanded as patients experienced the benefits of immediate deep anesthesia without lip and tongue anesthesia. Magnes,² Bourke,³ Cannell and Cannon,⁴ Lilienthal⁵ and Pearce⁶ published subjective reports about thousands of patients who were treated successfully using IOI as the primary anesthetic technique for restorations, crowns, extractions and select endodontic therapy. The volume of anesthetic used was 0.5 to 1.5 cc, yielding a duration of anesthesia of 30 to 60 minutes. The predominant anesthetics used were lignocaine (1:80,000 epinephrine), mepivacaine 3 percent, and prilocaine 4 percent and lidocaine 2 percent (1:100,000 epinephrine).

The mental barrier that most dentists must cross before using the intraosseous injection technique is that of intentionally creating a small hole in healthy bone and tissue.

In the evolution of IOI, specific instrumentation for the two-step technique was developed to replace the adaptation of common needles and drills for the procedure. The Stabident system⁷ (Fairfax Dental, Miami) is a beveled, solid-core perforator that is driven by a latch-type slow-speed handpiece to make an access hole through the soft tissue and cortical bone. The perforator then is withdrawn, and a 27-gauge extra-short needle is fitted on a standard syringe. The second step is to find the hole, orient the needle to the same long axis of the hole, insert the needle to depth and manually inject the desired volume of the selected anesthetic into the trabecular bone. Anesthesia is immediate, and the dentist can begin the procedure promptly. The Stabident system has received the ADA Seal of Acceptance from the ADA Council on Scientific Affairs.

The X-tip (X-tip Technologies, Lakewood, N.J.) has a rotating perforator with a removable stylette that is kept in place during drilling. The stylette is withdrawn, leaving a tube in the interradicular cancellous bone. A 27-gauge short needle on a standard syringe is inserted into the tube, and anesthetic is infused manually using thumb pressure. The advantage of using this device is improved visualization of the infusion site hole to insert the secondary needle.

A variation of the IOI technique is to use an externally reinforced 30-gauge intraosseous needle in a syringe and manually twist the needle through the cortical plate. A European variation involves a similar technique in which the needle and syringe together are rotated into position by a motor and then the anesthetic is injected manually.

	FACTORS AFFECTING THE SUCCESS OF INTRAOSSEOUS ANESTHESIA

TOP ABSTRACT FACTORS AFFECTING THE SUCCESS... NEW INTRAOSSEOUS ANESTHESIA... SUMMARY REFERENCES

 
Infusion site selection. Preoperative radiographs of the projected infusion site need to be taken to assess bone density, interradicular space and root length (Figure 1). With the two-step IOI technique, infusion sites require the presence of attached gingiva to ensure that the hole in the soft tissue is aligned with the hole in the bone. The presence of anatomical anomalies such as tori at the proposed site would preclude the dentist from using this technique effectively.

View larger version (119K): [in this window] [in a new window]   Figure 1. Radiograph of potential intraosseous injection site in the maxilla.

Preparing the infusion site for needle penetration involves placing topical anesthetic (20 percent benzocaine gel) on the soft tissue papilla. An intraligamentary injection with a separate manual-pressure syringe will anesthetize the crestal interproximal bone and papilla to facilitate a comfortable intraosseous perforation and infusion.

Patient comfort. During IOI, needle insertion, perforation and anesthetic injection have resulted in low perceived pain ratings, with 85 to 90 percent of the patients reporting mild or no pain during and after the procedure.^8,9 Quarnstrom¹⁰ compared onset of anesthesia time for block (7.0 minutes), infiltration (3.7 minutes) and IOI (0.6 minutes) techniques. All patients were pleased that primary IOI did not interfere with lip and tongue sensation compared with the block and infiltration techniques. Patients’ ability to return to their regular daily routines immediately postoperatively with oral tissues that feel normal can increase the perceived value of this technique for dentists and patients. Secondary IOI usage enhances the mandibular nerve block for deep pulpal anesthesia that is especially desired during pulpal extirpation and endodontic therapy.

Anesthetic selection. Using an amide anesthetic with a vasoconstrictor in the delivery of IOA merits special consideration by dentists. Because the highly vascular network of the jaw causes rapid absorption of the anesthetic and the space at the infusion site is confined, vasoconstrictors in anesthetics have a magnified effect and will produce tachycardia in most patients.¹¹ Epinephrine and levonordefrin produce an increased heart rate that can be unsettling to apprehensive patients. The epinephrine-induced "fight or flight" tachycardia is a primal physical state that can be managed with a realistic discussion with the patient preoperatively, but dentists should never ignore the response. My advice is to inform before you perform.

Replogle and colleagues¹² reported an average increased heart rate of 28 beats per minute in patients receiving 1.8 cc of lidocaine with 1:100,000 epinephrine; other vasoconstrictors had similar responses. A literature review by Brown⁹ has reported an increase in heart rate (46–100 percent of the time) of patients receiving IOI of epinephrine-containing solutions and their equivalents. Replogle and colleagues¹² found that 3 percent mepivacaine did not increase patients’ heart rate. Therefore, when considering the effect of IOA on heart rate, a 3 percent mepivacaine anesthetic has an advantage over epinephrine-compounded anesthetics, though it has a shorter duration of anesthesia.^13,14

Smith and Pashley¹⁵ observed that an IOI containing epinephrine created a cardiovascular reaction similar to that of an intravenous injection. Because of the tachycardia in patients infused with epinephrine and like-compounded anesthetics, dentists should use 3 percent mepivacaine for short procedures and for patients with heart conditions instead of lidocaine 2 percent with 1:100,000 epinephrine.

After receiving IOIs using epinephrine-containing anesthetics, some patients may overreact to the tachycardic effects and say, "My heart is beating very fast. I do not feel well." Although these effects are transient and usually pass in two to three minutes, some patients subsequently will refuse to have anesthetics containing epinephrine administered to them or will say they are allergic to it. Patients with high blood pressure, cardiac dysrhythmias or severe cardiac disease are at increased risk and should be infused with anesthetics without vasoconstrictors or solutions containing a minimal amount of epinephrine. Patients taking tricyclic antidepressants should not be infused with epinephrine or like solutions due to an exaggerated response.¹⁶ Anesthetics with reduced epinephrine are bupivacaine 0.5 percent with 1:200,000 epinephrine, prilocaine 4 percent with 1:200,000 epinephrine and etidocaine 0.5 percent with 1:200,000 epinephrine.

	NEW INTRAOSSEOUS ANESTHESIA DELIVERY SYSTEM

TOP ABSTRACT FACTORS AFFECTING THE SUCCESS... NEW INTRAOSSEOUS ANESTHESIA... SUMMARY REFERENCES

 
The IntraFlow (IntraVantage, Plymouth, Minn.) is a dedicated IOA delivery system that was developed to make IOI an easier technique for dentists to use (Figure 2). It is attached to a standard four-hole air hose on a treatment room delivery unit and is controlled by the foot rheostat. It is a specially modified slow-speed hand-piece that consists of four main parts:

View larger version (35K): [in this window] [in a new window]   Figure 2. The IntraFlow (IntraVantage, Plymouth, Minn.) dental anesthesia system. Image of the IntraFlow dental anesthesia system reproduced with the permission of IntraVantage, Plymouth, Minn.

– a needle/drill that makes the perforation through the bone and infuses the anesthetic;

– a transfuser that acts as a conduit from the anesthetic cartridge to the needle/drill;

– a latch tip/clutch that drives and governs the rotation of the needle/drill;

– a motor/infusion drive that powers the rotation of the needle/drill and, while holding the anesthetic cartridge in place, powers the infusion plunger.

The single-use needle/drill is a 24-gauge dual-beveled needle that has an elongated channel for the anesthetic to exit (Figure 3). The spade-shaped needle tip has cutting edges on the sides. A plastic housing that encircles the needle/drill fits into the miniature latch head on the latch tip/clutch and drives the rotation. The open rear is where the anesthetic enters the needle/drill from the conduit.

View larger version (82K): [in this window] [in a new window]   Figure 3. IntraFlow (IntraVantage, Plymouth, Minn.) beveled needle/drill. Image of the IntraFlow dental anesthesia system reproduced with the permission of Intra-Vantage, Plymouth, Minn.

The latch tip/clutch is a miniature latch tip head that has been mated to a clutch assembly (Figure 4). The clutch, operated by the dentist’s middle finger, disengages the rotation of the needle/drill once it has perforated the cortical bone and reached the targeted cancellous bone. Anesthetic solution is infused without the needle/drill rotating.

View larger version (48K): [in this window] [in a new window]   Figure 4. IntraFlow (IntraVantage, Plymouth, Minn.) latch tip/clutch assembly. Image of the IntraFlow dental anesthesia system reproduced with the permission of Intra-Vantage, Plymouth, Minn.

	SUMMARY

TOP ABSTRACT FACTORS AFFECTING THE SUCCESS... NEW INTRAOSSEOUS ANESTHESIA... SUMMARY REFERENCES

 
IOI has been a minor anesthetic delivery technique that has experienced cyclical popularity in dentistry. Supplemental IOI enhances block nerve anesthesia in the mandible for deep pulpal anesthesia. Some dentists use the IOI technique extensively as a primary technique to bring about anesthesia. Most dentists are aware of IOI but choose not to use it routinely because they are more comfortable with traditional infiltration and block techniques.

This trend is changing as education, research and instrumentation reduce the cognitive and emotional barriers in the dentists’ and patients’ perceptions of the local anesthesia experience. Patients’ emotions surrounding injections are some of the most powerful feelings that dentists routinely encounter in daily dentistry. IOI is a technique that can add to the dentist’s skills in treating patients with comfort and efficiency.

View larger version (129K): [in this window] [in a new window]   Dr. Kleber is a general dentist in full-time private practice in Coronado, Calif., and in El Cajon, Calif. Address reprint requests to Dr. Kleber at 1315 Ynez Place, Coronado, Calif. 92118, e-mail "ckleber1{at}san.rr.com".