In these situations, conventional anesthetic techniques such as infiltration anesthesia and inferior alveolar nerve block (IANB) may fail to provide complete pulpal anesthesia, leading to discomfort during treatment and increased clinical difficulty.
Recent evidence reviewed by the American Association of Endodontists (AAE) highlights the limitations of traditional mandibular anesthesia techniques in cases of inflamed pulps.
Studies have shown that the inferior alveolar nerve block alone achieves success rates ranging from only 14% to 39% in mandibular posterior teeth with irreversible pulpitis.
However, when supplemental anesthetic techniques are added, the success rate significantly increases to approximately 50–65%, demonstrating the critical role of supplemental injections in modern endodontic practice.
Why Do Conventional Blocks Fail in “Hot Teeth”?
Inflamed pulpal tissues present altered local physiology, including lower tissue pH, increased blood flow, and sensitized nociceptors.
These factors reduce the effectiveness of local anesthetics and make profound anesthesia more difficult to achieve.
As a result, clinicians often require additional anesthetic strategies to ensure patient comfort and successful treatment.
Periodontal Ligament (PDL) or Intraligamentary Injection
The periodontal ligament injection—also known as the intraligamentary injection—is one of the most widely used supplemental techniques in dentistry.
Interestingly, current evidence suggests that the anesthetic solution does not simply travel through the periodontal ligament itself.
Instead, the solution penetrates the cancellous bone through natural perforations, spreading into the marrow spaces and beneath the periosteum.
This mechanism explains the rapid onset and localized pulpal anesthesia achieved with this technique.
Clinical recommendations regarding needle bevel orientation vary among authors:
✔ Some suggest directing the bevel toward the alveolar bone to improve anesthetic diffusion.
✔ Others recommend initially facing the bevel toward the root surface to facilitate needle advancement, followed by rotation toward the bone to improve efficacy.
When used as a supplement to conventional IANB, periodontal ligament injections demonstrate an impressive success rate of approximately 78%.
Intraosseous Injection: Direct Access to Cancellous Bone
Intraosseous anesthesia involves the direct deposition of anesthetic solution into the cancellous bone adjacent to the tooth being treated.
Specialized delivery systems such as Stabident® and X-Tip® are commonly used for this purpose.
This technique has shown excellent clinical outcomes in difficult endodontic cases:
✔ Supplemental intraosseous injections following failed IANB achieved approximately 80% success with the first injection.
✔ Success rates increased up to 98% after a second intraosseous injection.
One of the major advantages of intraosseous anesthesia is its ability to provide profound anesthesia for approximately 60 minutes, making it especially valuable during endodontic procedures involving irreversible pulpitis.
Intrapulpal Injection: The Last Resort
Despite the effectiveness of supplemental techniques, approximately 5–10% of mandibular posterior teeth with irreversible pulpitis still fail to achieve profound anesthesia. In these cases, pain may persist when the pulp chamber is accessed.
This situation indicates the need for an intrapulpal injection.
Although this technique is often painful upon administration, it provides:
✔ Immediate onset of anesthesia
✔ Reliable pulpal control
✔ No need for specialized syringes or needles
For many clinicians, intrapulpal anesthesia remains the definitive solution when all other methods fail.
Clinical Importance of Supplemental Injections
Supplemental anesthetic techniques have become essential tools in contemporary endodontics.
Their use not only improves patient comfort but also increases treatment efficiency and clinician confidence when managing difficult anesthetic cases.
Understanding when and how to apply periodontal ligament, intraosseous, and intrapulpal injections can dramatically improve anesthetic success rates and reduce stress for both the patient and the dental professional.
As endodontic research continues to evolve, supplemental injections remain a cornerstone in the management of irreversible pulpitis and failed mandibular anesthesia.
📘 We invite the international dental community to read the complete article in PDF and explore the latest evidence and clinical recommendations regarding supplemental injections in dentistry.
