Anatomy of the Zeyco dental cartridge: A guide for healthcare professionals

Introduction

The objective of this guide is for healthcare professionals to learn about the operation and handling of dental cartridges, as well as the most common problems related to their use.
It is estimated that on average a dentist will administer around 1,500 local dental anesthesia cartridges per year, therefore, in addition to a thorough knowledge of the properties of the anesthetic solutions, it is equally important to know the design and operation of the cartridges containing them, in order to ensure the best results for the patient with each administration. (1)
Until before the invention of the dental cartridge, injectable anesthetics were prepared from powdered drugs that had to be mixed into a solution and then introduced into the syringe for administration. Due to the nature of the components of these formulations, which were prone to degradation, the preparation was always performed moments before each administration. Errors in the preparation of these mixtures were not uncommon and usually caused problems of overdose or adverse reactions in patients. (2)

It is interesting to note that an example of this type of error is reflected in the literature of the mystery genre. In Agatha Christie’s Death Visits the Dentist, the mythical detective Hercule Poirot must solve a case in which one of the main characters, the dentist Henry Morley, is suspected of causing the death of one of his patients due to an alleged error in the preparation of anesthesia. (3)

The introduction of dental cartridges at the end of World War I in 1917 represented one of the major advances in the safety of dental anesthesia. The inventor of the dental cartridge, Harvey S. Cook was a U.S. Army medic during the war. Cook had a vision to create an anesthesia delivery system that was faster and more efficient and could also be used while on the battlefield. This vision was inspired after watching soldiers use their rifles and how the empty shells were discarded after each shot. He later came up with the idea of cutting glass tubes and filling them with anesthetic solution so that prepackaged cartridges would be available for immediate use. Cook used pencil erasers as caps for the cartridges. This new system made it possible to replace the previous process of mixing powders into a solution and drawing it into a syringe each time anesthesia needed to be administered. Improvements to Cook’s invention would soon lead to the cartridge used today. (4) (5)

Dental cartridge definition

The dental cartridge is a glass or polypropylene cylinder containing the local anesthetic along with other ingredients.
The cartridges store 1.8 ml of solution. (6)

Components of the Zeyco dental cartridge

The dental cartridge is composed of four elements, a cylindrical tube made of glass or polypropylene, a mobile semipermeable elastomer plunger, an aluminum seal with an uncovered center and an elastomer semipermeable membrane (see Figure 1).

Figure 1. Zeyco dental cartridge’s components.
A. Glass or polypropylene cylindrical tube
B. Plunger
C. Cap
D.Membrane

Cylindrical tube

The cylindrical tube works as a container for the anesthetic solution and it’s the main component of the dental cartridge. It can be made out of glass (type I borosilicate glass) or polypropylene.

Plunger

The plunger is made out of semipermeable material, it is a gray bromobutyl, latex-free elastomer, grooved in three sections. It is placed at the end of the cartridge and receives a siliconized treatment to facilitate displacement while pressure is applied to move the suction syringe’s harpoon.

Cap

The cap is located at the opposite end of the plunger. The cap is made of aluminum and fits firmly around the neck of the cartridge, it has an exposed center and its function is to hold the membrane in place.

Membrane

The membrane is a semipermeable barrier made of latex-free bromobutyl. The penetrating end of the needle pierces the center of the membrane to take up the solution and this in turn acts as a seal to prevent the anesthetic from leaking around the needle.

Quality controls

In Zeyco, the Quality Assurance department analyzes every batch of the components composing the dental cartridge. The components used comply with all the specifications established on the United States Pharmacopeia (USP), the Pharmacopeia of the Mexican United States (FEUM from its acronym in Spanish), the international standard ISO 11499 of Dental Cartridges for Local Anesthetics, and the in-house controls.

This ensures that only materials that meet strict quality standards are used in the manufacturing process.

Some of the most important tests applied to the materials consist of infrared spectrophotometry to ensure the identification of the component according to the approved formula, microbiological and heavy metal detection tests to verify that there is no contamination and hermeticity and evaporation tests to confirm that the volume of the solution remains within specification throughout the shelf life of the product.

Considerations for handling the Zeyco dental cartridge

Proper handling of the dental cartridge is critical to provide safe and efficient anesthesia performance. The following are common handling considerations for dental cartridges.

Cleaning and sterilization of the cartridge before use

There is concern among dentists that the surface of the cartridge may be contaminated and measures are taken such as immersing the cartridge in disinfectant solutions or sterilizing it before use.

However, it is important to highlight that the Zeyco dental cartridges are packaged inside pre-cut, individual blisters, which protects them from cross contamination. Additionally, studies show that bacterial cultures obtained from the cartridge after removing it from its packaging usually do not cause any growth. In this regard, it is not necessary to take additional steps to clean the cartridge prior to use, and even practices such as immersing a cartridge in disinfectant solutions or subjecting it to sterilization are discouraged. The semipermeable nature of dental cartridge components may allow disinfectant solutions to diffuse into the cartridge and thus contaminate or alter the properties of the anesthetic solution.

On the other hand, autoclaving a cartridge for sterilization would damage the cartridge components and also cause epinephrine to degrade as it is a thermolabile substance.

If there is any carelessness in handling the dental cartridge and there is a concern that it is contaminated, it can be cleaned with a swab soaked in 91% isopropanol (isopropyl alcohol) or 70% ethanol (ethyl alcohol). (5)

Storage conditions

Zeyco dental cartridges should always be stored protected from light in their original packaging and kept at a temperature not exceeding 30° C (86° F). Although Zeyco dental cartridges are presented in pre-cut blister packs, they should not be stored outside the carton as light may degrade the contents of the solution. In other words, it is recommended to store the cartridges in their original container, inside the blister and inside the carton until they are to be administered.

Heating the cartridge

It is neither necessary nor recommended to use cartridge heaters. Overheating the solution may cause patient discomfort and faster degradation of the epinephrine. Studies have shown that heating the solution to 27°C or higher causes patients to feel burning during administration. In addition, the degradation of epinephrine shortens the duration of the anesthetic effect, which may cause even more discomfort for the patient. (5)

Cooling the cartridge

It is not advisable to refrigerate or freeze dental cartridges. The mechanical effect of cooling or freezing could cause the liquid inside to expand, causing leakage or material integrity problems. If this occurs, the solution may become unsterile and unsafe to use for injection. (5)

Aspects of the Zeyco dental cartridge integrity

During the manufacturing process, small air bubbles of 1 to 2 mm in diameter may be trapped in the dental cartridge. Bubbles of this size are not a risk or quality issue and the anesthetic can be used.

On the other hand, the cartridge should be discarded if larger bubbles (greater than 2 mm) are observed, sometimes accompanied by a plunger protruding from the cartridge.

According to ISO 11499 Dental Cartridges for Local Anesthetics, the correct way to determine if the cartridge should be discarded due to the presence of a large or out-of-specification bubble is to hold the cartridge vertically with the cap facing up, tap it lightly on a horizontal surface to dislodge the bubbles adhering to the side walls and finally observe it from a horizontal angle. If the bubble protrudes (i.e. is visible below the edge of the cartridge cap), the cartridge should not be used (see Figure 2). (7) (8)

Figure 2. Air bubbles.
A. Normal dental cartridge without air bubbles or with small air bubbles that do not protrude from the bottom of the cap.
B. Dental cartridge with a large air bubble protruding from the cap.

Figure 3. Aspect of the membrane.
A. Appearance of a bulging or protruding membrane of the casing.
B. Appearance of a sunken membrane.

Aspect of the membrane

Some cartridges may have a sunken or bulging membrane appearance, which is merely a cosmetic detail that does not affect the sterility of the solution or the integrity of the cartridge and is due to the effect of the filling process during the fitting and adjustment of the cap (see Figure 3).

Solution leakage

Leakage from the end of the cap usually happens if the needle and cartridge have not been prepared correctly and if the needle puncture in the membrane is not centered, i.e. it is ovoid and eccentric; this causes part of the solution to leak between the needle and the membrane when the piston is pressed. The risk of leakage can also increase when the syringe is manipulated during injection, as it can cause the needle to move in the membrane and create tears in the membrane.

A damaged plunger can also allow the anesthetic solution to leak from the cartridge. A dental syringe harpoon that has not been centered on the piston can increase the risk of solution leakage during injection; moreover, this same risk is increased by the use of defective or poor-quality syringes.

Protruding plunger

The plunger should be fully inserted into the cartridge. If the plunger protrudes and is accompanied by a large air bubble, this indicates that the cartridge was exposed to freezing or heating which caused the liquid inside to expand (see Figure 4).

On the other hand, if the plunger protrudes but there is no air bubble, it is because the cartridge was immersed in a disinfectant solution and the solution was able to diffuse into the cartridge.

In both cases, the cartridge should be discarded as the anesthetic solution is contaminated.

Figure 4. Protruding plunger.

Figure 5. Solution between the plunger grooves.
A. Appearance of a plunger with solution between the membranes, it can be seen that the solution has leaked into the space between the last two grooves. This is a quality defect.
B. Appearance of a normal plunger where there is no liquid between any of the groove spaces.

Solution between the plunger grooves

The presence of solution between the plunger grooves is an indication that the integrity of the closure system is compromised and therefore there is a possibility that the solution is contaminated and its administration would put the patient’s health at risk. The Parenteral Drug Association (PDA) considers this problem as a quality defect, therefore cartridges with this defect should be discarded (see Figure 5). (9).

Aspect of the solution

All glass and polypropylene dental cartridges are transparent so that the contents of the anesthetic solution can be visualized before each injection. If the solution is found to be cloudy or contains particles, or has changed color, the cartridge should be discarded.

Cartridge breakage

Broken or cracked cartridges should be discarded.

Damaged cap

A cap that shows damage, is corroded or rusted, or appears dented is an indication to discard the cartridge. The hermetic seal that the cap creates when it fits over the neck of the tube may be compromised and affect the sterility of the anesthetic solution (see Figure 6).

Figure 6. Damaged cap.

Sticky plunger

A plunger that does not slide properly through the cartridge cylinder could be caused by the syringe harpoon not being properly engaged in the plunger. Another possible cause, although rarer, is that the plunger is not homogeneously siliconized.

Frequently asked questions about dental cartridges

Should I sterilize dental cartridges before use?
No, heat damages cartridge materials.

Is it safe to refrigerate, freeze or heat the dental anesthesia cartridges?
No, extreme temperature changes will damage the dental cartridge components.

Should the cartridges be submerged in disinfectant solution?
No, only if there is any carelessness in handling the dental cartridge and there is concern that it is contaminated, it can be cleaned with a swab soaked in 91% isopropanol (isopropyl alcohol) or 70% ethanol (ethyl alcohol).

How should the cartridges be stored?
Protected from the light inside their original package and kept at a temperature no higher than 30°C.

Is it safe to use cartridges with air bubbles?
It depends, the dental cartridge should be observed vertically with the cap upwards, it should be tapped lightly on a horizontal surface to detach the bubbles adhered to the side walls and finally observed from a horizontal angle. If the bubbles are small, 1 to 2 mm and are hidden by the cap, they do not represent any risk and it is safe to use the anesthetic. On the other hand, if larger bubbles (more than 2 mm) are observed showing below the cap, the cartridge should be discarded.

Can I use a cartridge with a protruding or sunken membrane?
Yes, this is a cosmetic detail caused by the cap placement and fit.

What to do if the dental cartridge has leakage?
The dental cartridge must be discarded, it is important to check that the syringe harpoon is not bent and is centered when the plunger is pierced.

If the plunger is protruding, is it safe to use it?
No, the cartridge must be discarded since there is no guarantee that the solution is still sterile.

What should I do if I notice that there is solution between the cartridge plunger grooves?
The cartridge should be discarded. The presence of liquid between the plunger grooves is an indication of a quality defect and there is a risk that the solution is not sterile.

Can the solution be used if it’s cloudy, has particles or color change?
No, it is not safe to administer the solution if its aspect is not clear and transparent.

Can the cartridge be used if the cartridge is cracked?
No, the cartridge must be discarded if it is cracked or broken.

Can the cartridge be used if the cap is damaged?
No, if the cap is dented, has oxide or corrosion, it is possible that hermeticity is lost and it is not safe to administer the solution.

What should I do if the plunger is sticky or does not slide correctly along the cylinder?
Verify that the syringe’s harpoon is correctly hooked through the center of the plunger.

What are the ingredients of the anesthetic solution contained in Zeyco dental cartridges?
The composition of the solution in the dental cartridge varies according to the distinguishing designation (e.g. Turbocaína, F.D., Dentocaín Simple). In general, they all contain one active ingredient, which causes the anesthetic effect. Sodium chloride as isotonic agent and water for injections as vehicle. There are formulations that also contain epinephrine as an additional active ingredient, to these presentations sodium metabisulfite is also added as a preservative and EDTA as a stabilizing agent. All the ingredients used to manufacture Zeyco brand dental anesthetics are suitable for human consumption due to their safety, quality and efficacy, and are guaranteed by strict quality controls and the authorization granted by COFEPRIS to each of our medicines.

Why did Zeyco change its local anesthetics presentation to pre-cut blister packs?
Pre-cut blister packs offer several advantages over the old presentations (some may remember the jar-shaped plastic containers or unblistered boxes), the most important of which are to protect the cartridge, prevent contamination, reduce the risk of adulteration and reduce the environmental impact.

How does the pre-cut blister protect the dental cartridge?
The pre-cut blister configuration, as opposed to uncut blister packs or those in jars or boxes without blister packs, provides individual protection for each cartridge and prevents breakage or deterioration during transport, handling and storage, which is especially useful in university environments. It has been observed that the new blister significantly reduces waste, i.e., the user will always receive the product in good condition.

How is contamination of the cartridge in the pre-cut blister avoided?
It has been reported that contamination after dental procedures can spread up to 4 meters, with the potential to affect any supplies used on the patient. Having individual pre-cut blister packs prevents unnecessary exposure of cartridges to contaminants expelled by aerosols and splashes and prevents potential pathogens that pose a risk of infection to patients from coming into contact with the cartridge membrane. (9)

Can the risk of anesthetic adulteration be reduced with the pre-cut blister?
Yes, the nature of the cartridge components makes it difficult to tamper with or counterfeit, however, the additional security measure of the pre-cut blister makes any attempt to tamper with the cartridge even more difficult as it would be extremely complex for counterfeiters to replicate the blister sealing and pre-cutting system.

It seems that the pre-cut blister has more plastic than the old presentations, doesn’t this cause more contamination to be generated?
No, because the technology used in the manufacturing process is more efficient, the amount of plastic used in the pre-cut blister is less than that used in the production of the plastic jar and the non pre-cut blister. That said, the change to the new presentation is not merely for aesthetic reasons, but to improve the quality and safety of the product with the advantages mentioned above unique to the Zeyco brand, no other dental anesthetic in Mexico has the innovation of the pre-cut blister.

Conclusions

In conclusion, in order to guarantee the best results for the patient with each anesthetic injection, it is of utmost importance to know the components and functioning of the dental cartridge.

Proper handling and storage of the cartridge allows it to retain its properties for safe use. No additional processing, such as sterilization, heating or cooling, is necessary before using the cartridge.

Being able to properly identify the appearance and integrity of each cartridge component makes it easier to determine when to discard or when it is safe to use an anesthesia cartridge.

Any doubt or problem related to the cartridge should be reported to the manufacturer. In case you want to know more about the use, safety and efficacy of dental anesthetics, we suggest consulting the Local Anesthesia Manual by Zeyco. (6)

Bibliographical references

1. Decloux D, Ouanounou A. Local anaesthesia in dentistry: a review. Int Dent J. 2020 Sep 17;71(2):87–95. doi: 10.1111/idj.12615. Epub ahead of print. PMID: 32944974; PMCID: PMC9275172.

2. Giovannitti JA Jr, Rosenberg MB, Phero JC. Pharmacology of local anesthetics used in oral surgery. Oral Maxillofac Surg Clin North Am. 2013 Aug;25(3):453-65, vi. doi: 10.1016/j.coms.2013.03.003. Epub 2013 May 7. PMID: 23660127.

3. Christie A. La muerte Visita al dentista. Booket; 2005.

4. Nathan J, Asadourian L, Erlich MA. A Brief History of Local Anesthesia. Int J Head Neck Surg 2016; 7(1):29-32.

5. Malamed SF. Manual de Anestesia Local. 7a ed. Elsevier; 2020.

6. Martínez Menchaca HR. Manual de Anestesia Local. Zapopan, Jalisco: Aleaciones Dentales Zeyco, S.A. de C.V.; 2018.

7. ISO 11499:2014, Dentistry — Single-use cartridges for local anaesthetics.

8. The fundamentals of pain control in today’s dental practice [Internet]. Cdeworld.com. [citado el 7 de junio de 2024]. Disponible en: https://cdeworld.com/courses/22424-the-fundamentals-of-pain-control-in-today-s-dental- practice-local-anesthesia.

9. Holliday R, Allison JR, Currie CC, et al. Evaluating contaminated dental aerosol and splatter in an open plan clinic environment: Implications for the COVID-19 pandemic. J Dent. 2021 Feb;105:103565.

Anatomy of the Zeyco dental cartridge: A guide for healthcare professionals

Introduction

Dental cartridge definition

The dental cartridge is a glass or polypropylene cylinder containing the local anesthetic along with other ingredients.
The cartridges store 1.8 ml of solution. (6)