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Efficacy of a Smart Injector for Dental Anaesthesia. A split- mouth study

This split-mouth study involving 30 volunteers demonstrates that the Smart Dental Injector significantly reduces pain perception and accelerates anesthesia onset compared to traditional syringes, without altering the duration of the anesthetic effect.

Original authors: Ali Rokia, Mouetaz Kheirallah

Published 2026-06-30

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Ali Rokia, Mouetaz Kheirallah

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you're at the dentist, and the most dreaded part of the visit is about to happen: the injection of local anesthesia. For many, the fear isn't the drilling; it's the "poke."

This research paper is like a head-to-head race between two different ways of delivering that "poke." On one side, you have the Old Guard: the traditional metal syringe that dentists have used for decades. On the other side, you have the New Tech: a "Smart Dental Injector," which is essentially a high-tech, computerized pen that controls the injection.

The researchers wanted to see if the fancy new pen could beat the old metal syringe in three specific categories:

How fast does the numbness kick in? (Onset time)
How long does the numbness last? (Duration)
How much does it hurt? (Pain perception)

Here is the breakdown of their findings, translated into plain English:

The Setup: A Split-Mouth Race

To make the test fair, they didn't just compare two different groups of people. They used a "split-mouth" design. Think of it like a taste test where you eat a slice of apple on your left side and a slice of pear on your right side, then decide which you liked better.

They took 30 volunteers and gave them a nerve block (a shot to numb the lower jaw) on both sides of their mouth.

Left Side: Got the shot from the Smart Injector.
Right Side: Got the shot from the Traditional Syringe.

This ensured that every person acted as their own control, eliminating differences in how sensitive different people's nerves might be.

The Results: The Three Contests

1. The Speed Contest (Onset Time)

The Claim: The Smart Injector was statistically faster.
The Reality: It was faster, but only by a hair's breadth.

The Old Syringe: Took about 148 seconds (just under 2.5 minutes) to numb the tooth.
The Smart Pen: Took about 143 seconds.
The Verdict: The Smart Pen won by 5 seconds. While the math says this is a "win," the authors admit that in the real world, saving 5 seconds isn't a game-changer. It's like a runner winning a marathon by 0.01 seconds; technically first, but practically the same.

2. The Endurance Contest (Duration)

The Claim: Did the Smart Injector make the numbness last longer?
The Reality: No difference at all.

Both methods numbed the tooth for roughly 108 to 112 minutes.
The Verdict: The Smart Pen didn't make the numbness last any longer or shorter. It was a tie.

3. The Pain Contest (The Big Winner)

The Claim: This is where the Smart Injector absolutely crushed the competition.
The Reality: The Smart Injector made the experience significantly less painful.

The Old Syringe: Patients reported feeling a moderate amount of pain (averaging around 13 on a scale where 100 is the worst pain imaginable). The pain levels were also very unpredictable; some people felt almost nothing, while others felt a lot.
The Smart Pen: Patients reported feeling very little pain (averaging around 5).
The Verdict: The Smart Injector reduced the perceived pain by 61.7%.

Why Did the Smart Pen Win the Pain Contest?

The paper explains that the traditional syringe relies on the dentist's hand. If the dentist pushes too hard or too fast, it hurts. It's like trying to pour water from a bucket; if you tip it too quickly, it splashes everywhere.

The Smart Injector, however, is like a high-precision garden hose with a pressure regulator. It uses a computer to push the anesthetic fluid at a perfectly constant speed and pressure. Because the flow is smooth and steady, it doesn't stretch the tissue as violently as a manual push, resulting in much less pain.

The Bottom Line

The study concludes that the Smart Dental Injector is a promising tool, but not because it works faster or lasts longer. Its superpower is comfort.

Speed? It's a tie (with a tiny, meaningless edge to the Smart Pen).
Duration? It's a tie.
Pain? The Smart Pen is the clear champion, cutting the pain by more than half.

In short: If you want the numbness to start a few seconds sooner, the Smart Pen might help a tiny bit. But if you want to avoid the "ouch" of the injection, the Smart Pen is the clear winner.

Technical Summary: Efficacy of a Smart Injector for Dental Anaesthesia

Problem Statement
Traditional metallic syringes used in dental practice lack precise control over fluid flow rates and rely on manual force, which can lead to inconsistent injection speeds and increased patient discomfort. While various devices have been developed to mitigate injection pain—such as external cooling, vibration, and needleless jet methods—the direct comparison between modern electronic "smart" injectors and conventional syringes regarding onset time, duration of action, and pain perception remains under-researched. The primary clinical challenge addressed is the reduction of patient anxiety and pain associated with local anaesthetic delivery without compromising the efficacy of the anaesthesia itself.

Methodology
The study employed a randomized, double-blinded, split-mouth crossover design involving 30 healthy volunteers (11 males, 19 females; mean age ~23–24 years) from the Faculty of Dentistry at Al-Andalus University for Medical Sciences.

Intervention: Each participant received bilateral intraoral mental nerve blocks. One side received 1.8 mL of 2% plain lidocaine via a wireless smart electronic injector (Anesthesia Pen X), while the contralateral side received the same volume via a conventional carpule syringe with a 30G needle.
Controls: No topical anaesthetic was used to avoid confounding pain perception results. Participants were blinded to the device type, and the assessor was blinded to the results.
Measurements:
- Onset Time: Measured in seconds using an electric pulp tester on the lower first premolar, starting immediately post-injection and continuing at 60-second intervals until no response was recorded.
- Duration: Measured from administration until the return of pulp sensitivity, assessed every 3 minutes.
- Pain Perception: Evaluated using a 100 mm Visual Analog Scale (VAS).
Statistical Analysis: Data distribution was assessed via the Shapiro-Wilk test (showing abnormal distribution), leading to the use of the Wilcoxon signed-rank test for comparisons.

Key Results
The study yielded three primary findings regarding the performance of the Smart Dental Injector (SDI) versus the traditional injector:

Pain Perception: The SDI demonstrated a statistically significant reduction in pain. The mean pain score for the smart injector was 4.93% (±3.71), compared to 12.87% (±13.78) for the traditional injector. This represents a 61.7% reduction in perceived pain ( $p < 0.001$ ). The traditional group also exhibited much wider data dispersion (range 1–70%) compared to the smart group (range 1–15%).
Onset Time: The smart injector achieved a statistically faster onset of anaesthesia ( $p = 0.002$ ). The mean onset time was 143 seconds for the SDI versus 148 seconds for the traditional method. However, the authors note that the absolute difference of 5.2 seconds is clinically insignificant.
Duration of Anaesthesia: There was no statistically significant difference in the duration of the anesthetic effect between the two groups ( $p = 0.381$ ). The mean duration was 108.43 minutes for the SDI and 112.17 minutes for the traditional injector.

Key Contributions

Quantitative Validation: The study provides empirical evidence that electronic control of fluid dynamics significantly reduces pain perception during dental injections, validating the theoretical advantage of constant pressure and flow rate.
Split-Mouth Design: By utilizing a split-mouth design on the same patient, the study effectively controlled for individual physiological variations in pain threshold and anaesthetic metabolism.
Clinical Differentiation: The research distinguishes between statistical significance and clinical relevance, acknowledging that while the SDI is statistically faster in onset, its primary clinical value lies in patient comfort rather than speed or duration extension.

Significance and Claims
The paper concludes that the Smart Dental Injector is a viable and promising alternative to conventional syringes, primarily due to its ability to eliminate human error in fluid dynamics, thereby reducing dosing inaccuracy and injection pain. The authors assert that the device's competitive advantage is not in accelerating the onset or prolonging the duration of anaesthesia, but in providing a more comfortable and less painful treatment experience.

The study claims that the SDI's capacity to deliver anaesthetic solutions at a constant pressure, volume, and rate directly correlates with the observed 61.7% reduction in pain. Consequently, the device is presented as a tool to minimize factors related to patient anxiety, making the anaesthetic experience less unpleasant without altering the pharmacological efficacy of the lidocaine. The authors modestly suggest that while the device is effective, further studies are needed to evaluate the impact of age, gender, and physiological factors on pain perception.