Figure 1

Figure 1: The Hypo intraosseous injection system has a 32-mm 30-gauge needle compatible with standard breech-loading syringes.

Figure 2a

Figure 2a: The Stabident system’s perforator is a 27-gauge 0.43-mm diameter solid core wire imbedded into a plastic sheath designed to engage a standard latch angle.

Figure 2b

Figure 2b: The most apical extent of the attached gingival margins of adjacent teeth is used as a landmark for locating the appropriate perforation point.

Figure 2c

Figure 2c: After application of topical anesthetic and infiltration of local anesthetic into gingival mucosa, perforation is performed mesial or distal to the tooth.

Figure 2d

Figure 2d: After removal of the perforator, the injection needle is introduced to deliver local anesthetic into periradicular medullary bone.

Figure 3a

Figure 3a: The X-Tip system consists of a perforator assembly (solid-core needle with overlying guide sleeve and handle consisting of a stainless steel sheath and plastic hub) and 27-gauge 0.4-mm diameter ultrashort injection needle.

Figure 3b

Figure 3b: Guide sleeve and handle over perforator needle.

Figure 4

Figure 4: The Wand is a computer-controlled system consisting of pump unit, foot pedal, transfuser tubing, handpiece assembly, luer-lock needles and standard anesthetic cartridges.

Figure 5

Figure 5: N-Tralig PDL injection syringe shown with conventional needle and cartridge.

Figure 6a

Figure 6a: Syrijet Mark II jet-injection system: Syrijet syringe, standard dental anesthetic cartridge and plunger rod.

Figure 6b

Figure 6b: Oral tissues are dried and nozzle is rested gently against attached gingiva at right angles. Release of trigger delivers anesthetic.

Figure 6c

Figure 6c: Small residual hematoma and erythema of palatal tissues follows application of jet injection.

Table 1 Success rates for conventional inferior alveolar nerve block

Authors	Drugs used	Total no. of patients	No. of patients with successful anesthesia^a(% success)
Dunbar and others²	2% lidocaine, 1:100,000 epinephrine	40	17 (43)
Clark and others³	2% lidocaine, 1:100,000 epinephrine	30	22 (73)
Reitz and others⁴	2% lidocaine, 1:100,000 epinephrine	38	27 (71)
Gallatin and others⁵	3% mepivacaine plain	48	39 (81)
Guglielmo and others⁶	2% mepivacaine, 1:20,000 levonordefrin	40	32 (80)
Childers and others⁷	2% lidocaine, 1:100,000 epinephrine	40	25 (63)
Total		236	162 (69)

^aVital asymptomatic mandibular first molar teeth demonstrating no response to maximum electrical pulp testing output (80 readings) on 2 consecutive tests over 60 minutes in patients who received up to 3.6 mL of local anesthetic to achieve subjective lip numbness at baseline.

Table 2 Success rates for conventional inferior alveolar nerve block in patients with irreversible pulpitis^a

Author	Drugs used	Total no. of patients	No. of patients with successful anesthesia^b (% success)
Reisman and others⁸	3% mepivacaine plain	44	11 (25)
Nusstein and others⁹	2% lidocaine, 1:100,000 epinephrine	26	10 (38)
Total		70	21 (30)

^aIrreversible pulpitis defined as acute pain, positive response to electrical pulp testing and cold test, sensitivity to percussion and radiographic evidence of a widened periodontal ligament space.

^bSuccess defined as mandibular posterior teeth demonstrating no response to maximum electrical pulp testing output (80 readings) or no response to endodontic access 5 minutes after IANB in patients who received up to 3.6 mL of local anesthetic to achieve subjective lip numbness at baseline.

Table 3

Reasons for failure of conventional local anesthetic techniques

Armamentarium-related factors

Deflection of needle tip

Inappropriate bevel direction
Incorrect needle gauge

Patient-related factors

Anatomical

            Accessory innervation (e.g., mylohyoid nerve)
            Barriers to diffusion (e.g., zygomatic buttress)
            Cross-innervation
            Intravascular injection
            Variation in location of soft- and hard-tissue landmarks relative to mandibular canal
            Unpredictable spread of local anesthetic solution

Pathological

Local infection
Trismus
Pulpal inflammation

Psychological

Operator-related factors

Inexperience
Poor technique

Table 4 Comparison of various systems for adjunctive local anesthesia

Type of system	System components	Method	Comments
Hypo intraosseous injection system (Fig. 1)	32-mm 30-gauge needle compatible with standard breech-loading syringes; distal 6 mm of needle reinforced with retractable stainless steel sheath (to prevent needle deformation during penetration)	Needle is driven with manual pressure through interproximal interseptal bone or maxillary periapical cortical bone; anesthetic solution is then injected	Obviates need to reintroduce needle after perforation Effectiveness reduced in some situations (e.g., mandibular molar region) because of difficulty in penetrating thicker cortical bone
Stabident intraosseous injection system (Figs. 2a,2b,2c, 2d)	Single-use perforator (27-gauge, 0.43-mm diameter solid-core wire embedded into plastic sheath designed to engage standard latch angle) and injection needle (0.4-mm diameter hollow-bore bevelled or nonbevelled tipped instrument compatible with standard breech-loading syringes)	Most apical extent of attached gingival margins of adjacent teeth used as landmark for locating appropriate perforation point (cortical bone in mandibular molar region is thinnest within crestal third of alveolar process); after application of topical anesthetic and infiltration of local anesthetic into gingival mucosa, perforation is performed mesial or distal to tooth; after removal of perforator, injection needle is introduced to deliver local anesthetic into periradicular medullary bone
X-Tip intraosseous injection system (Figs. 3a and 3b)	Perforator assembly (solid-core needle with overlying guide sleeve and handle consisting of a stainless steel sheath and plastic hub) and 27-gauge 0.4‑mm diameter ultrashort injection needle	Guide sleeve and handle are positioned over perforator needle, which is used to pierce cortical bone, a process that simultaneously introduces the guide sleeve and detachable handle; perforator needle is retracted, and guide sleeve and handle are left in place to facilitate reintroduction of injector needle	Guide sleeve and handle marketed as a means to facilitate reintroduction of injector needle as well as to perform supplemental injections, if required
Wand anesthetic delivery system (Fig. 4)	Computer-controlled system consisting of pump unit, foot pedal, transfuser tubing, handpiece assembly, luer-lock needles and standard anesthetic cartridges	Topical anesthetic is applied, flow is initiated at slow rate, and needle is advanced slowly	Unit may be used for infiltration or nerve block anesthesia May be particularly suited for injection into PDL¹⁴
N-Tralig PDL injection system (Fig. 5)	Hand-held injector gun	Needle is inserted at a 30° angle from the long axis of the tooth and directed into proximal gingival sulcus to point of maximum penetration; needle tip is thus wedged between crestal bone and root surface in faciolingual midline¹⁵; 0.2 mL of anesthetic is injected under definitive, sustained back pressure; if back pressure is not attained initially, repositioning or insertion at a more apical location is suggested¹⁵	Bevel always directed away from root surface Finger or hemostat may be used to stabilize needle on insertion¹⁵ Injection under marked back pressure is associated with significantly better anesthetic success than injection without such pressure
Siryjet Mark II jet-injection system (Figs. 6a,6b, 6c)	Siryjet syringe, standard dental anesthetic cartridge and plunger rod	Syringe is loaded with anesthetic cartridge, and plunger rod is inserted; rubber nozzle hood is positioned, and syringe is cocked; volume of anesthetic to be dispensed is selected (0.05, 0.10, 0.15, or 0.20 mL); oral tissues are dried, and nozzle is rested gently against attached gingiva (at right angles); release of trigger delivers anesthetic; precise volume can be delivered rapidly under controlled pressure through nozzle penetrating the mucosa or skin (but not hard tissues) to a depth of 1.0-1.5 cm¹⁶	To avoid alarming patient, practitioner must discuss procedure with patient in advance, as there is a noticeable popping sound and brief mechanical pressure on activation of the system Small residual hematoma and erythema of palatal tissues follows application of jet injection
PDL = periodontal ligament.

Table 5 Success rates for conventional inferior alveolar nerve block with supplemental intraosseous injection

Author	Drugs used	Total no. of patients	No. of patients with successful anesthesia^a (% success)
Dunbar and others²	2% lidocaine, 1:100,000 epinephrine	40	36 (90)
Reitz and others⁴	0.9 mL 2% lidocaine, 1:100,000 epinephrine	38	36 (95)
Gallatin and others⁵	3% mepivacaine plain	48	48 (100)
Reitz and others¹⁷	0.9 mL 2% lidocaine, 1:100,000 epinephrine	36	34 (94)
Guglielmo and others⁶	2% lidocaine, 1:100,000 epinephrine	40	40 (100)
Guglielmo and others⁶	2% mepivacaine, 1:20,000 levonordefrin	40	40 (100)
Total		242	234 (97)

^aSuccess defined as mandibular first molars demonstrating no response to maximum electrical pulp testing output (80 readings) on 2 consecutive tests. Patients received up to 3.6 mL of local anesthetic to achieve subjective lip numbness at baseline 2 minutes before the tests.

Table 6 Success rates for conventional inferior alveolar nerve block with supplemental intraosseous injection in irreversible pulpitis^a

Author	Drugs used	Total no. of patients	No. of patients with successful anesthesia^b(% success)
Reisman and others⁸	3% mepivacaine plain	44	35 (80)
Nusstein and others⁹	2% lidocaine, 1:100,00 epinephrine	21	19 (90)
Total		65	54 (83)

^aIrreversible pulpitis defined as acute pain, positive response to electrical pulp testing and cold test, sensitivity to percussion and radiographic evidence of a widened periodontal ligament space.

^bSuccess defined as mandibular posterior teeth demonstrating no response to maximum electrical pulp testing output (80 readings) or no response to endodontic access 5 minutes after IANB and intraosseous injection. All patients received up to 3.6 mL of local anesthetic to achieve subjective lip numbness at baseline.