The art of conversation

The art of conversation alongside the culture of apology”

Be upset with me, be upset, be angry… but don’t be angry! Don’t fall into yourself

Don’t hurt with the third and fourth person and others! When you calm down, come back so we can talk

Face to face, I listen patiently until you say and I say and I expect to be heard…

Let’s talk and the power of apology and the power of expressing feelings; Like oxygen in the air, flow through our culture and communication.

learning articlesIf the culture of dialogue and apology is institutionalized in our relations, it will definitely solve many existing problems and crises quickly.

Chlorhexidine, chemical composition, clinical application and its effect on the strength and durability of enamel and dentin bonding (part one)

Chlorhexidine is considered a strong substance to destroy resistant bacteria and fungi in dentistry.

In 1940, in pursuit of obtaining an effective drug for malaria, scientists found a group of substances called bisbiganide, among which chlorhexidine was marketed in England in 1954 as a wound antiseptic, skin cleaning and disinfection before surgery. Released.
Then, this substance was introduced in the 1970s as an anti-microbial oral plaque substance, and its use in dentistry increased after that. Today, chlorhexidine is considered the strongest antimicrobial mouthwash in dentistry. A comparison of the performance of mouthwashes in aerobic and anaerobic environments has shown that chlorhexidine is still the best mouthwash. In a research that was conducted with the aim of investigating the antimicrobial effect of cinnamol herbal mouthwash and Irsha antiseptic mouthwash and comparing them with chlorhexidine as a standard sample in laboratory conditions, it showed that chlorhexidine is still the best mouthwash.Chemical composition: Chemical formula of chlorhexidine gluconate C22H30Cl2N10 is. The active ingredients in the chemical composition of chlorhexidine mouthwashes are:

Thymol, eucalyptol, hextidine, methyl salicylate, menthol, chlorhexidine gluconate, benzalkonium chloride, cetylpyridinium chloride, methyl paraben, hydrogen peroxide, diphen bromide, enzymes and sometimes fluoride and calcium. Water is also a component that keeps the above components together. Sweeteners such as sorbitol, sucralose, sodium saccharin and xylitol, which have an antibacterial effect, may also be added. Sometimes alcohol is added up to 20% as a carrier of flavoring agents; In addition, alcohol also exerts its antibacterial properties. Of course, alcohol can cause dryness and dehydration of the oral environment and exert its carcinogenic effects in case of frequent consumption. Many new chlorhexidine mouthwashes do not contain alcohol.

A preservative such as sodium benzoate is added to most mouthwashes to keep the mouthwash fresh after the lid is opened.

Many mouthwashes have an acidic pH. In people who have acid reflux or have digestive problems, it is recommended to use mouthwashes with neutral pH.

Chlorhexidine is a bisbiguanide compound with a similar molecule, which is highly cationic. Chlorhexidine is a bacteriostatic drug and bacteriocide. This substance is a strong antiseptic against Gram-negative and Gram-positive bacteria. The important point is that chlorhexidine can also affect the lipid and protein membrane of Gram-negative bacteria.

Chlorhexidine exists in three forms: digluconate, acetate and hydrochloride, of which two forms, digluconate and acetate, are soluble in water. One of the advantages of chlorhexidine is its strong connection and adhesion to most areas of the mouth, which causes this substance to be released gradually and slowly after adhesion, and in a period of time, it constantly provides an antimicrobial environment in the mouth.
Approximately 30% of consumed chlorhexidine remains on the surface of the mouth and its buffer release varies depending on the pH of the mouth. The reason for the stickiness of chlorhexidine is attributed to its cationic property, which causes it to bind to the anionic groups present in glycoproteins and phosphoproteins on the surface of the mucous membrane and oral pellicle. The effect of chlorhexidine is not limited to a specific species and is effective on a wide range of gram-positive and negative bacteria, as well as some fungi and some viruses, including the virus that causes AIDS and hepatitis.
Due to its cationic property, its skin and mucous absorption from the digestive system is minimal. In animal experiments, toxic and carcinogenic effects have not been seen in this substance.
Most researchers are of the opinion that the mechanism of action of chlorhexidine is related to the strong tendency of this substance to adhere and bind strongly to the membrane of bacteria and tear the cell membrane. After the chlorhexidine molecule binds to the bacterial membrane, the permeability of the said membrane increases and due to the disruption of the osmotic balance on both sides of the cell wall, some of the intracellular contents with low molecular weight leave the cell. This phenomenon occurs in the presence of low amounts of chlorhexidine, while in higher amounts, this substance is deposited in the cystoplasm.

Available commercial forms:

Chlorhexidine is available in the form of mouthwash, varnish, gel or in chewing gum. Its gel is recommended for people with high caries risk; In this way, it is used once a week with a toothbrush. The concentration of chlorhexidine gel is 1%.

Chlorhexidine varnish is also available. Acceptable concentrations of chlorhexidine in varnish are 0.1-0.2%. Fluoride varnish remains on the teeth for at least 24 hours. For this reason, its effect is more than other methods, and on the other hand, it causes the teeth to look ugly, which will last up to 24 hours. Another disadvantage of fluoride varnishes is its bitter taste.

Chlorhexidine mouthwash is available under the trade names Pridex, Priochip Towelette, Periogard, Perisol, Spectrum-4, and Oral rinse. In England it is available as Corsodyl or Chlorhex. In Germany it is known as Chlohexamed and in Australia it is named Sevacol. In some countries, it is known by its medicinal name, chlorhexidine. In Iran, chlorhexidine, which is available to the public in pharmacies, is 0.2% chlorhexidine; Of course, recently 0.12% chlorhexidine has also been introduced, which according to the manufacturer’s claim, its side effects such as discoloration of teeth are much less than similar types (with higher concentrations). Chlorhexidine mouthwash is not recommended for children under 6 years old.

Chlorhexidine, which is available in dental offices, is pure and does not contain additives necessary to create a mouthwash. Chlorhexidine 0.12% (Ultra dent) is provided to disinfect the cavity before restoration. Chlorhexidine 2% (FGM) is also available in the dental market, which, due to its high concentration, has very strong bactericidal and bacteriostatic effects, which can be used to wash the canals or disinfect the cavity before restoration. Of course, due to its high concentration, it has a burning effect on the mucous membrane, and for this reason, it is not recommended to use it as a mouthwash.

A new mouthwash named Epimax has entered the market. This mouthwash contains 0.12% chlorhexidine and 0.05% sodium fluoride and does not contain any alcohol.

It should be noted that the highest concentration of chlorhexidine available is 4%, which is used to disinfect the surgical environment. Its 2% concentration is used to disinfect hands. Its concentration of 2% and 4% can inhibit bacteria, fungi, yeasts and viruses.

· Gums containing chlorhexidine:

Gum is accepted as a standard pharmaceutical form and its name was registered as a pharmaceutical system in 1991 in the European Commission. The medicinal form of chewing gum is of interest due to the reduction of the drug dose, the reduction of side effects, the controlled release of the drug in a relatively long time, the stimulation of salivary secretion and the creation of a buffering effect, and the ease and attractiveness of consumption, etc. Ainamo and Etemadzadeh showed that gum can be a good carrier for chlorhexidine. It has been shown that the anti-plaque properties of gums containing chlorhexidine are higher than those containing xylitol and sorbitol. Gums containing chlorhexidine and xylitol significantly reduce the amount of pathogenic bacteria streptococcus mutans and lactobacillus and yeasts in the oral cavity; But gums containing xylitol only reduce the amount of Streptococcus mutans. Chlorhexidine gum has anti-gingivitis properties and the amount of tooth discoloration caused by it is significantly less than chlorhexidine mouthwash. In some studies, consumer satisfaction with the taste of chlorhexidine gum has been reported to be weak; Therefore, it seems necessary to present a new formula in order to achieve the desired taste for public consumption at the community level. The study of Dr. Kalahi, Dr. Ghaliani and Dr. Varshusaz showed that gum can be a good carrier for chlorhexidine gluconate. In this system, the drug was released over a relatively long time and in a controlled manner, which is preferable to the mouthwash form that is used for only 30 seconds. The amount of drug released in chlorhexidine gums is equal to 20 mg per day, which is half of the mouthwash form (40 mg per day). The results of this study showed that chewing gum containing chlorhexidine gluconate can completely prevent the formation of dental plaque; In addition, it can reduce the amount of plaque.

The most important concern about using chlorhexidine gums is their safety. A review of the 20-year use of chlorhexidine shows that this substance has no carcinogenic effects in laboratory animals and its long-term oral use has not caused any changes in hematological and biochemical indicators in humans. Chlorhexidine is hardly absorbed from the skin, mucous membrane and digestive system and shows little toxicity. In addition, the amount of drug in each piece of gum is very small, so there does not seem to be any concern about swallowing the drug content of the gum.

Therefore, due to the safety and effectiveness and many benefits, including reducing the amount of medicine by half, reducing side effects, stimulating saliva secretion, increasing the buffering effect, long-term and controlled release of the drug, this type of gum can be used as an important component in promoting Oral and dental hygiene should be recommended to patients.

· Glass ionomers containing chlorhexidine:

In a study conducted in 2005, it was shown that the best concentration of chlorhexidine for glass ionomer is 1%. In this concentration, bacteria will be inhibited and will have the least impact on the physical properties and bond strength of glass ionomer; While higher concentrations decrease the tensile strength and compressive strength of glass ionomer. This concentration has no negative effect on the setting time of chlorhexidine.

Two chlorhexidine salts (chlorhexidine diacetate and chlorhexidine dichloride) are in powder form and can be added to glass ionomer powder.



Application of chlorhexidine to mix MTA

Although the direction of mixing MTA Physiological serum or anesthesia can be used, but the use of chlorhexidine gluconate 0.12%, antibacterial effects MTA strengthens. While MTA mixed with water also inhibits bacterial growth; But replacing chlorhexidine instead of water is more effective and can inhibit bacteria such as Actinomyces odontolyticus, Fusobacterium nucleatum, Streptococcus sanguinis, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans.

۲% chlorhexidine can be used instead of 0.12% chlorhexidine; However, the use of 0.2% chlorhexidine mouthwash is not recommended due to impurities such as alcohol.

Chlorhexidine and the reduction of caries-causing bacteria:

Various antibacterial agents such as antibiotics have been considered to reduce caries-causing bacteria. In the meantime ; In addition to fluoride, chlorhexidine has had a significant effect in reducing caries-causing bacteria. Chlorhexidine has an effective role in inhibiting bacterial plaque. Since chlorhexidine adheres very firmly to dental tissue and maintains its effect for hours, it is a very effective antibacterial drug. For this reason (reduction of oral bacteria), chlorhexidine is an effective drug to reduce or eliminate bad breath; Thus, in addition to reducing bacteria, chlorhexidine reduces the sulfur created by anaerobic bacteria.

This substance is prescribed as a 0.12% mouthwash for high-risk patients and for a short period of time. Chlorhexidine, which is used to protect teeth against decay, can also be in the form of varnish. The best and most effective type of varnish is the one applied by the dentist on the teeth. Chlorhexidine causes remineralization of primary caries lesions and by reducing the amount of mutans streptococci, it reduces the rate of caries growth. If chlorhexidine is used for about 2 weeks; Mutans streptococci remain below the caries-causing level for 12-26 weeks. It is recommended to use chlorhexidine continuously for 2 weeks in people with high caries risk or people with acute caries. After completing the treatment period in these people, weekly use is enough to keep mutans streptococci down. Using chlorhexidine mouthwash does not make the patient unnecessary to use toothbrush and dental floss.

Spectrum of effect: Chlorhexidine is active against a range of aerobic and anaerobic, Gram-positive and Gram-negative bacteria. This drug is also effective against chlamydia trachomatis, some fungi and some viruses, but it has no effect on mycobacteria. Chlorhexidine is effective against a wide range of aerobic gram-positive bacteria, including Streptococcus mutans pyogenes (group A beta-hemolytic streptococci), Streptococcus salivarius, and Streptococcus sanguis. Chlorhexidine also has an effect on Staphylococcus aureus, Streptococcus epidermidis, Streptococcus hemolyticus, Streptococcus hominis, and Streptococcus simulans.

Although some groups of Escherichia coli, Klebsiella, Salmonella and Pseudomonas are inactivated by chlorhexidine in vitro; But in vivo, a large group of these gram-negative bacteria respond to higher concentrations of chlorhexidine and are therefore practically resistant to this drug.

Anaerobic bacteria: Chlorhexidine is effective in vitro against some groups of Bacteroides, Clostridium difficile, and Selenomonas, but it has less effect on Vilonella. Subgingival tablets are effective against some pus-causing bacteria such as Porphyromonas gingivalis, Provetella intermedia, Forsytus, and Campylobacter rectus.

Fungi: In in vitro tests, chlorhexidine is effective against Candida albicans, Candida doublinensis, Candida glabrata, Candida Guillermondi, Candida kefir, Candida crusi, Candida leucine, and Candida tropicalis.

Viruses: It seems that chlorhexidine is effective against viruses that have lipid compounds in their outer coat or have an outer envelope. Although its clinical significance is unclear, there is evidence that chlorhexidine has in vitro activity against cytomegalovirus (CMV), human immunodeficiency virus (HIV), herpes simplex types 1 and 2 (HSV-1 and HSV-2). , influenza virus, parainfluenza virus, and variola virus are effective.

Resistance to chlorhexidine: apart from bacterial spores and some gram-negative bacteria that are naturally resistant to chlorhexidine, the development of acquired resistance to this drug in microorganisms that were sensitive to it has rarely been reported.

The use of chlorhexidine in periodontal diseases:

Chlorhexidine gluconate 0.12 topical solution is used as a mouthwash in the treatment of gingivitis. This mouthwash reduces the prevalence and severity of mucosal inflammation (mucositis) and other complications of immunosuppressive diseases and reduces the prevalence of hospital infections of the respiratory system. Chlorhexidine gluconate is used under the gums in the form of absorbable tablets as an adjunctive treatment for patients with periodontitis.

Gingivitis: 0.12 chlorhexidine gluconate topical solution is used in the treatment of gingivitis in adults. This topical oral solution is used between dental appointments as a professional application in the treatment of gingivitis. Also, chlorhexidine topical solution has been used as an adjunctive treatment in the treatment of acute necrotizing ulcerative gingivitis. The safety and effectiveness of chlorhexidine oral solution for this purpose has not yet been determined.

The logic of using chlorhexidine gluconate topical solution in the treatment of gingivitis is based on both the antibacterial effects of this drug and its anti-plaque effects. The remaining antimicrobial properties reported along with chlorhexidine have made it the drug of choice for plaque control and gingivitis treatment. The result of a study on adults without symptoms of periodontitis has shown that a single use of 0.2% chlorhexidine mouthwash reduces the number of bacteria in saliva for at least 7 hours and is more effective than other mouthwashes (for example, compared to: steel pyridinium chloride, phenolic rugenha, triclosan, zinc chloride).

In another study in adults without symptoms of periodontitis, 0.2% chlorhexidine mouthwash reduced the amount of dentogingival plaque more than other tested mouthwashes such as phenolic oils. Microbiological sampling of dental plaque after 6 months of using chlorhexidine gluconate topical solution has shown a 54-97% reduction in the number of some anaerobic bacteria.

The results of a large number of controlled studies in adults with gingivitis show that the use of 0.12% chlorhexidine oral solution twice a day for 6 weeks as a mouthwash reduces gingivitis, gum bleeding, and plaque compared to Placebo or mouthwashes containing other substances (such as phenolic oils, sanguinarine).

Dosage of chlorhexidine in gingivitis: The usual dose for adults is 0.12% chlorhexidine gluconate topical solution for use as a mouthwash, 15 ml twice a day for 30 seconds (morning and night after brushing).

Periodontitis: Chlorhexidine gluconate can be used under the gums in the form of absorbable tablets containing chlorhexidine as an adjunctive treatment along with scaling and root planning to reduce pocket depth in the treatment of adult periodontitis. Chlorhexidine gluconate is used subgingivally as part of maintenance periodontitis treatments that include good oral hygiene after removal of bacterial plaque by the dentist. The safety and usefulness of using chlorhexidine gluconate under the gums in periodontal pockets with abscesses has not been proven so far and is not recommended.

Application of chlorhexidine at home by the patient:

Among the used mouthwashes, chlorhexidine has been studied more than others and has been introduced as the gold standard.

In cases where brushing is not possible temporarily, chlorhexidine mouthwash can be used as a substitute for brushing; For example, when it is not possible to use a toothbrush after oral surgery or gum surgery due to the presence of wounds and stitches, the use of chlorhexidine is very effective. In this situation, the healing of wounds and oral injuries is accelerated by chemical control of microbial plaque; Or when two jaws are fixed to each other to treat jaw fractures and the person is unable to open the mouth and use a toothbrush. Of course, it should be remembered that normally mouthwash cannot be used as a substitute for a toothbrush in controlling microbial plaque and cleaning dental surfaces, but it is better to use mouthwash along with brushing and to complete it.

How to use
Among the factors that reduce the power of chlorhexidine, we can mention low pH, the presence of pus, protein and sugar environments. These environments reduce the binding and adhesion of this antimicrobial substance; Also, anionic substances such as sodium lauryl sulfate present in toothpaste can reduce the effect of chlorhexidine. Therefore, it is better to use chlorhexidine mouthwash half an hour after brushing your teeth to maintain its maximum antibacterial power.
Effective dosage
The effectiveness of this mouthwash depends on its dosage and not on its concentration.
The therapeutic dose of chlorhexidine mouthwash is 10 mg to 20 mg of mouthwash with a concentration of 0.2% to 0.12%. It is used twice a day (after breakfast and before going to bed), which is kept in the mouth for 30 to 60 seconds.

Side effects of using chlorhexidine mouthwash

Usually, the side effects associated with chlorhexidine are mild and usually do not need to stop the treatment. The most common reported side effect of chlorhexidine mouthwash; Staining of the teeth, cosmetic restorations, the back surface of the tongue and other oral surfaces and increasing the formation of mass and change in the sense of taste.

As mentioned, chlorhexidine causes a brown color to appear on the teeth and fillings of the same color as the teeth, oral mucosa and tongue. This is attributed to the binding of cationic groups of chlorhexidine to substances in the diet such as gallic acid and tannins, and its intensity depends on the amount of substance consumed and the time of its consumption. This discoloration is external and can be removed by tooth polishing. Another side effect of chlorhexidine, which is not very common, is mucosal injuries depending on the concentration of chlorhexidine.

Chlorhexidine has an unpleasant taste and can cause temporary changes in the sense of taste. Especially, this effect is related to the taste of salt, which makes the food tasteless, and this change depends on the concentration of chlorhexidine. The sense of taste that is most affected; Sweetness, followed by saltiness and sourness, and finally bitterness. Usually these changes are temporary. The reason for this change is the denaturation of the surface proteins located on the taste buds.

A few cases of unilateral or bilateral swelling of the parotid gland due to chlorhexidine consumption have been reported. By inhibiting the breakdown of glucose by bacteria, chlorhexidine prevents acid production and keeps the environment alkaline; This factor prepares the ground for the formation of supragingival masses.

Drug interactions: Chlorhexidine is incompatible with soaps and anionic cleaners.

Warnings: contact of the drug with eyes, middle ear and body cavities should be avoided.

Side effects: Irritation, dermatitis, or sensitivity to light may occur with chlorhexidine. Chlorhexidine 0.12% mouthwash, in addition to destroying some pathogenic streptococci, also destroys some of the natural microflora of the mouth, which is one of the undesirable features of this mouthwash.

Carcinogenicity: No mutagenic properties were observed in this drug in two in vivo studies on mammals. In several other studies, it was shown that chlorhexidine does not have genotoxic properties. The level of mutagenicity of mouthwashes available in the market has not been investigated so far.

Pregnancy: Studies on rats and rabbits have shown that chlorhexidine does not have adverse effects on the fetus.

Breastfeeding: The possibility of the drug entering breast milk has not yet been determined, and therefore subgingival tablets should be prescribed to breastfeeding mothers only when needed.

Recommended points:

۱- One should refrain from taking medicine.

۲- In case of irritation, dermatitis or sensitivity to light, the use of the drug should be stopped.

Summary and conclusion
Due to the limited side effects and the absence of toxic and systemic side effects and due to the significant antimicrobial effects of this mouthwash, today, the combination of chlorhexidine gluconate is widely used as a mouthwash and its use in short-term periods and especially at the same time as scaling And oral surgeries are increasingly recommended.

Dr. Kasri Tabarirestorative and beauty expert

Dr. Sahar Mirzabigi – dentist




Plasma is a different method in modern restorative dentistry (first part)


Plasma is a quasi-neutral gas of charged and neutral particles that presents its own collective behavior. In other words, it can be said that the word plasma refers to an ionized gas in which all or a significant part of its atoms have lost one or more electrons and turned into positive ions. In another definition, a highly ionized gas whose number of free electrons is almost equal to the number of positive ions is called plasma.

In general, materials are considered to be in three states: solid, liquid and gas. But in scientific discussions, a fourth state is usually assumed for matter. The natural formation of plasma at high temperatures has given it the title of the fourth state of matter. A very natural example of plasma is fire, so the Sun is an example of a large hot plasma.

Plasma gases:

It is often said that 99% of the matter in the world is in the plasma state; It means that it is in the form of electrified gas whose atoms are divided into positive ions and negative electrons. Although this estimate may not be very accurate, it is a reasonable estimate of the fact that inside the stars and their atmospheres, gas clouds and mostly hydrogen in the interstellar space are in the form of plasma. Near us, as we leave Earth’s atmosphere, we immediately encounter the plasma that includes the radiation belts and the solar wind.

In everyday life

In our daily life, we encounter some limited samples of plasma. The spark of lightning, the soft glow of the aurora borealis, the gases inside a fluorescent or neon lamp, and the brief ionization seen in the exhaust gases of a rocket. So it can be said that we live in a percentage of the universe where plasma is not found naturally.


Temperature in plasma

Like all gases, the temperature in plasma is determined by the average energies of plasma particles (neutral and charged) and their degree of freedom (translational, rotational, vibrational and related to electrical excitation). Therefore, plasmas show multiple temperatures. In the common method of plasma production in the laboratory, energy is first accumulated in the electric field by electrons during collision, and then it is transferred from electrons to heavy particles. Electrons receive energy from the electric field during the free path and during the collision with heavy particles and lose only a small part of that energy; Because electrons are lighter than ions (the lightest ion is approximately 1800 times heavier than an electron). For this reason, the temperature of electrons in plasma is initially higher than that of heavy particles, and the collision of electrons with heavy particles balances their temperature. Of course, there is not enough time or energy for temperature equilibrium and a cooling mechanism such as low pressure ventilators is required to prevent the gas from heating up.

Plasma thermally

Plasma is thermally divided into two groups: thermal (with high temperature) and non-thermal (with low temperature). Only non-thermal (low temperature) plasma is used in dentistry. In this system, the temperature is the same as the temperature of the ions and is almost equal to the ambient temperature or at most a few degrees higher. In this system, the amount of ionization is 2-3%.

Ionization and chemical processes in plasma

Ionization and chemical phases in plasma are determined by temperature (and indirectly by electric field). This type of quasi-equilibrium plasma is usually called thermal plasma, which is characterized by solar plasma in nature. Ionization and chemical processes in non-equilibrium plasmas are directly determined by electron temperature and are not sensitive to gas temperature. Non-equilibrium plasma is called non-thermal plasma.

Today, non-thermal plasma has found many applications in medicine. This kind of plasma is called non-thermal because the temperature of plasma and ions is in the range of room temperature, while the temperature of electrons is high. Plasma is used in biology and biomedicine to inactivate bacteria and tissue sterilization, blood coagulation, wound healing, treatment of corneal infections, cancer treatment and dentistry.


Plasma is a new method for whitening (Bleaching) the teeth:

The use of plasma to whiten teeth has been considered. The advantage of this method over the usual methods is that in this method of gel Bleaching It is not used and these are free radicals that can oxidize organic substances and whiten teeth; While in other methods, including the laser application technique, the use of Bleaching gel It is mandatory.

One of the methods that may be used in the usual teeth bleaching methods is the use of a high-intensity plasma arc device that comes with gel. In this method, due to the high concentration of the gel and the high intensity of the device, the possibility of tooth sensitivity is high; But the method discussed in this article is without bleaching gel and with the help of plasma gas. In this method, the effect of teeth whitening by (PMJ) plasma micro jet sent by direct current in atmospheric air pressure of 0.9% saline solution has been investigated.

Plasma device

The plasma device used in this article consists of two coaxial cylinders as electrodes, which are separated by a dielectric layer with a thickness of 0.5 mm.

The internal electrode is powered by a high voltage DC power supply while the internal electrode is used due to safety considerations. The gap or nozzle of the plasma device has a diameter of about 0.8 mm.

In this study, compressed air is used as the working gas and is amplified between the internal electrodes. The stable voltage of microjet plasma is in the range of 400-600 volts with an operating current of 20-35 mA.

For the purpose of this research, 30 normal healthy teeth from caries were selected from the extracted premolars for orthodontic reasons and kept in a 0.1% thymol solution. They were randomly divided into 3 groups: Group A, Group B, and Group C.


In group A, the tooth was subjected to air flow and saline solution for 20 minutes.

In group B, the teeth were subjected to plasma and saline solution for 20 minutes (a flow of A m 30). The tooth was placed at a distance of 10 mm from the external nozzle of the plasma microjet (PMJ) device. During this period, the temperature was measured by a thermal couple in the approximate range of 40 c. No whitening gel was used in this method.

In group c, the teeth were exposed to 35% H2O2 gel at room temperature for 20 minutes. On the surface of group A and B teeth, saline solution was used once every 30 s to prevent dehydration.

As it is clear in the pictures and graphs, the plasma method has brought better results.

Although its main mechanism is not fully understood, reactive oxygen groups (ROS) produced by the plasma system are essential for the plasma teeth whitening process.


It is believed that the formation of perhydroxyl ions (HO2) and OH is necessary. The effectiveness of PMJ in teeth whitening is due to the production of ROS (reactive oxygen groups) at the tooth-liquid-plasma interface, which is very similar to the mechanism of oxygen production in the teeth-whitening gel interface in traditional treatments.

A study showed that trace amounts of ozone can be found downstream of the PMJ. atomic oxygen and ozone produced at the place of water and plasma interaction; produces O2, OH. .OH, O2. and other mediators of ROS or active oxygen groups are mixed together.

The improved efficacy of PMJ combined with saline in tooth whitening is due to the following mechanisms:

  • (.OH ,O2,.O2…) ROS caused by water-plasma interactions that directly or indirectly react with pigment molecules on the tooth surface and break long carbon chain bonds, resulting in the whitening effect.
  • ROS produced at the liquid-plasma interface (reactive oxygen groups) is easier and more effective than H2O2 gel.
  • Despite its absence in plasma and aqueous environment, small amounts of nitric acid have been found. As a result, local pickling of the above acid on the surface of the tooth increases the efficiency of tooth whitening.

PMJ reacts with NacL in saline solution and produces bischlorine ions and radicals. However, because the concentration of NacL in the saline solution is very low (0.9%), only small amounts of chlorine base ions and radicals are produced; Therefore, they do not cause a significant whitening effect.

Enamel surface of treated teeth

The enamel surface of the teeth treated by PMJ and saline solution is slightly rougher compared to the control samples; But they are similar to teeth treated with H2O2 gel. Tooth whitening by H2O2 or carbamide peroxide causes slight changes in enamel surface morphology. that this amount of changes in morphology is acceptable.

In another research of plasma with H2O2 35% in one group and H2O2 35% was used alone in the other group. In the group that used plasma, the color change (ΔE) was significantly improved. In the plasma group, the temperature measured on the surface was about 37 degrees Celsius and no temperature increase was seen.

Plasma effect

In another study, the effect of plasma for Non Vital Bleaching of root canal teeth was evaluated. In this research, 20 discolored teeth were bleached with 30% hydrogen peroxide for 30 minutes, and 20 other teeth were treated with 30% hydrogen peroxide for 30 minutes along with plasma.

In both groups, the temperature was measured at 37 degrees; But the amount of bleaching in the plasma group was statistically significantly better than the first group. Although plasma itself produces free radicals, the presence of hydrogen peroxide produces more OH free radicals, which maximizes its effect. It should be noted that helium gas was used in this study.

Although non-thermal plasmas have few known harmful effects on humans, a number of safety concerns should be addressed in future studies; For example, ROS produced in this system has a key role in teeth whitening; But if its dose is not controlled correctly, they can be harmful to oral tissues and respiratory system.

Although plasma has been effective in teeth whitening, more studies are needed to evaluate its durability and stability.

This article is dedicated to Pir and Murshid and Muradam; Dr. Mustafa Chamran, who was not only one of the pioneers of plasma physics in the world; Rather, he was a master of morality and mysticism and he proved his authority over all free people and men of wisdom.

God, thank you for giving us the pleasure of getting to know your parents.


Dr. Kasri Tabari restorative and cosmetic specialist

Dr. Fariba Azojirestorative and beauty resident

Mustafa Aqiqi – Plasma engineer

Bonding to Zirconia

Bonding to Zirconia

The use of ceramics in dentistry has created a tremendous transformation; In the meantime, zirconia has found a special place due to its unique structural characteristics. Today, zirconia has replaced metal copings and has opened its place in implant systems.

The introduction of zirconia frameworks has removed the limitations of design and application of all-ceramic restorations and has brought more success and credibility. Today, long-span and complex all-ceramic restorations are possible due to the unique and excellent mechanical properties of zirconia; On the other hand, the surface stability of zirconia has led to other problems; Because it is difficult to create a durable chemical or mechanical bond with it. Unlike glass-containing ceramic systems, which have a glass structure and can be etched with hydrofluoric acid and chemically bonded with silane, zirconia is not able to create a micromechanical and chemical bond. The bond strength reported to dental ceramics varies widely, making it difficult to assess their clinical significance. The minimum strength of the band required clinically is 10-13 Mpa.

Structure and physical and mechanical properties: Zirconia is used in many dental and medical cases due to its tissue compatibility. One of the most common all-ceramic blind materials is zirconia, whose bending strength is 1000 MPa; While feldspathic porcelains have a bending strength of 100-300 MPa. Zirconia and alumina are ceramics with metal oxide structure.

Zirconia has different crystal forms: 1- Monoclinic 2- Tetragonal 3- Cubic among which yttrium tetragonal zirconia polycrystal (Y-TZP) has good properties compared to other crystal forms. The tetragonal form alone is unstable and may change into other forms with low properties; For this reason, 5% of yttrium is added to zirconium oxide to obtain its stable form.

Zirconia has 2-3 times the strength of alumina, its stiffness is less and creates a smoother surface than alumina, and thus it has replaced alumina. Zirconia is chalky white in color and does not have any structure for etching and bonding.

The fracture strength and fracture toughness of zirconia originates from its suitable physical properties. The lack of stability of conventional ceramics in the long term is related to the development of cracks and kerogen stress caused by the water in the saliva, which reacts with the glass structure and leads to the decomposition of the glass structure. Zirconia blinds do not have glass and have a polycrystalline microstructure, so they show excellent long-term stability. The chemical stability of zirconia makes it a desirable material, especially in environments prone to kerogen. In addition, zirconia has a hard and dense surface, which makes it ideal for resistance to wear and contact damage, and in general, zirconia is introduced as a material of choice in cases where there are high functional needs., LAVA (3M ESPE), Procera LLZirkon (NobleBiocare) Cercon (Dentsply) are among the systems with zirconia base.

Band with zirconia


Resin or conventional cements (conventional):

Considering the fact that the most important factor in zirconia restorations is correct and basic cutting, but knowing the type of cement also has a significant impact on its long-term durability. Most reference books recommend the use of resin and ordinary cements such as glass ionomer as if there is not much difference between them; While recent studies have shown that resin cements are more effective and durable; For example, several studies have shown that glass ionomer is not effective and shows little bond strength. Glass ionomer has a small bond strength of about 4 MPa and is susceptible to water absorption.

A study also showed that the bond strength of glass ionomer with zirconia is equivalent to the bond of zirconia with self-adhesive resin systems.

Common resin cements (Conventional resin cement) or self-adhesive resin cements (adhesive resin cement):

Studies have shown that self-adhesive resin cements are not durable due to low physical and mechanical properties and can be hydrolyzed in humid environments; While ordinary resin cements, which are individually etched and bonded, have more and more stable bonds. One of the reasons for the stability of the zirconia bond is the suitable physical properties of the resin cement. Resin cements that have functional groups are often acidic and hydrophilic and can absorb water even after polymerization.

The degree of polymerization of resin cement is one of the most important factors of the bond of zirconia to dentin; Theoretically, a hydrophobic cement that polymerizes in the form of self-cure within 5 to 12 minutes is considered the best case, but to control the hardening time and to increase the amount of polymerization, dual-cure resin cements are used. Cement is an ideal resin that is well polymerized in self-cure and light-cure conditions, is not affected by aging, and sets in a suitable period of time. If Dual Cure cement self-cures and fully polymerizes within 6 minutes, it allows the interproximal areas to be pulled and cleaned; While there are cements that need 10 to 12 times to clean without disrupting the bonding.

Therefore, the choice of resin cement and the amount of restoration is important; In this way, the characteristics of self-adhesive cements in terms of viscosity, self-curing and hydrophilicity are different from ordinary resin cements and they are not recommended for lathes that do not have sufficient and suitable adhesion.

Phosphate monomers or silane?

Unlike normal ceramics that have a structure

They bond with silane, zirconia not only with silane

There is no reaction; It is also effective in reducing their bandwidth.

Phosphate and carboxylate monomers can interact with zirconium metal oxides

react; In the meantime, phosphate monomers such as MDP create a stronger bond

they do In addition, the use of resins containing phosphate monomers after

Thermocycling is more durable and shows less band reduction; At

While other bonding cements with zirconia, their bond strength decreases


Monomers MDP:

MDP monomers have been introduced as another chemical agent to increase the bonding properties of these ceramics; Because the MDP functional phosphate ester group combines directly with metal oxides. It is expected that the combination of air abrasion with alumina and MDP will create a stable bonding between the YPSZ ceramic surface and the adhesive resin. Instability of MDP bonding has been reported especially after aging, while higher bond strength of silica coating is provided in dry conditions.

One of the most widely used cement resins used in dentistry is Panavia F 2.0. This cement consists of a bifunctional monomer 10-methacryloxydecyl dihydrogen phosphate (MPD). A recent study showed that a modified application of Panavia improved the adhesion of this cement to zirconia; But in practice, when only the manufacturer’s instructions were followed (which did not suggest any preparation method), no adhesion was obtained.

The effect of sandblasting on increasing the bond with zirconia:

One of the common methods to increase surface roughness and micromechanical grip is sandblasting. Sandblasting increases the mechanical strength of zirconia in the short term, but increases the monoclinic phase at the same time. Aging is also one of the factors that increases the monoclinic phase. Due to the increase of surface stress and monoclinic phase (decrease of tetragonal phase) due to sandblasting or roughening, the use of this method is not recommended for the long-term stability of the zirconia band.

However, mechanical treatments on zirconia should be done with caution; Because it has been shown that thermal treatments, sandblasting and grinding can be effective on mechanical properties. In a study conducted by Sundh and Sjogren, it was shown that the effect of resistance to fracture of zirconia depended on the length of time the samples were exposed to sandblasting, among other factors. The possible reason is that the sandblasting or grinding treatment can stimulate compressive stresses or phase transformation on the surface, which increases the strength on the one hand, and at the same time can create other flaws and defects that reduce the strength. Gives.

Silica coating(Silicoating):

Covering the inner surface of zirconia with silica can effectively help in increasing the bond; For this purpose, various methods such as

Tribochemical coating and pyrochemical coating can be used.

Tribochemical silica coating method is usually performed in dental laboratories using aluminum oxide particles with a particle size of 110 µm and coated with silica. Airflow pressure causes the silica-coated aluminum oxide particles to be buried in the ceramic surface, making the silica-modified surface more chemically reactive to the resin. Laboratory air abrasion or chair side with aluminum particles coated with 110 and 30 micron silica (tribochemical silica coating) provides surface preparation for acid resistant ceramics. After this operation, the silica surface is covered with a layer of silane.

An alternative to airborne particle abrasion in the laboratory is the application of sand particles using air abrasion tools in the office. This process increases the working area and surface energy for the adhesion of resin cements and increases the micromechanical grip. Also, surface tension is reduced and optimal wetting is provided for silane or adhesive agents.

It has been reported that the chairside version of the silicoater technology (silicoater MD, Heraeus-Kuzler) that can create acceptable adhesion by means of a portable tool (silane-Pen or PyrosilPen) and the use of a flame preparation approach. In this flame system, there is a reaction zone in which tetraethoxysilane is decomposed into pieces of organic silicon (SiOx-C). These fragments cover the surface of the substrate with an adhesive boundary layer through van der Waals forces. This very thin layer (approximately 0.1 µm) has quasi-glass characteristics and can be silanized with MPS silane. Like metal primers, this method was originally developed for the preparation of metals, but more recently it is also indicated for ceramics.

using metal primer :

To increase the bonding, it has recently been suggested that the use of metal primer after air abrasion acts as an adhesion enhancer. Most metal primers are in liquid form and include monomers in their structure for polymerization. In addition to repairing broken metal-ceramic fixed prostheses, metal primers are also indicated for conditioning and strengthening zirconia ceramics. The results with these materials are not always favorable; Because they create high bond strength in dry conditions, but there are negative reports about their hydrolytic stability.

Application of special primers:

Primers that meet the special needs of non-silicone oxides (zirconia and alumina) and metals and are useful for restorations that are formed and resistant to danger. Zirconia bonding agents create a soft bond with hydroxyl groups on the surface of zirconia. Reports indicate that the shear bond strength improves before thermocycling, but a significant decrease is observed after thermal cycles, which depends on the concentration of silane.

As a new approach to increase the strength of the zirconia-to-resin bond, selective infiltration etching (SIE) of zirconia-based materials has been introduced to create a holding surface where the adhesive resin can be infiltrated and locked. In one study, 5 types of engineered zirconia primers were used in combination with SIE in an attempt to improve bond. The results of this study showed that there is a significant difference in the bonding ability between these primers despite the fact that they were used on the same surface of zirconia. It was concluded that different primers can react differently with zirconia etched surfaces. This issue was probably due to the chemical differences between the tested active agents. Most commercial primers contain phosphate or phosphonate monomers that bond to zirconia; But they are different based on the formulation and acid level (which is important for compatibility with self-curing and dual-curing resin cements). Phosphate monomers form a covalent bond with the zirconia surface and have resin ends that can be copolymerized with resin cements.

Examples of primers are briefly introduced:

۱-Clearfil Ceramic Primer(Kurrary) : This primer contains MDP, silane and ethanol.

Its application method is to apply a layer with a brush and then gently rub it until the solvent evaporates and the reaction takes place.

۲- Metal/Zirconia primer(Ivoclar Vivadent) : This primer contains phosphonic acid acrylate, benzoyl peroxide, T-butyl alcohol and methyl isobutyl ketone.

Its application method is that one of it is applied and left for 180 seconds to fully react with the surface. This primer is provided to create a chemical bond with metals, zirconia and alumina.

۳- AZ-Primer(Shofu) : This primer contains phosphonic acid monomer and acetone. Its application method is that a uniform layer of it is applied and it remains on the surface for 10 seconds until it reacts completely.

۴- Z primer Plus(Bisco) : Z-primer plus is a special formula containing both functional phosphate and carboxylate monomers. The synergistic binding of these tested monomers results in a stronger bond with improved durability compared to other commercial primers. This primer contains phosphate monomer, carboxylic acid monomer and ethanol.

The method of its application is as follows: a layer is applied and a gentle poar is taken to evaporate the solvent. According to the manufacturer’s claim, Z-Primer Plus is the only commercial primer that does not need to be kept in the refrigerator.

Bisco Dental Products’ internal research has shown that Z-Primer Plus not only provides high bond strength to zirconia with various surface treatments (such as sandblasting or polishing), but is also compatible with dual-cure or light-cure cements.

Z-Primer Plus cannot be used for feldspathic ceramics, normal pressable porcelains and lithium disilicate type pressable porcelains.


Short and accurate sandblasting along with the use of special primers can prepare the zirconia surface. A very important point is that the surface of the dentin must be coated with dentin bonding without any etching. Studies have shown that leaving a smear layer on the dentine surface creates a better and more effective bond in these systems. It is recommended to use a resin with hydrophobic properties and dual cure.

Relying on a chemical bond alone results in a weak bond between the zirconia and the resin cement, which is responsible for rapid hydrolysis under moist conditions. Therefore, providing a mechanically receptive zirconia surface is a critical prerequisite for strong bonding.

Creating a strong bond with zirconia is only part of the problem. Its more critical aspect is maintaining this band under fatigue conditions and in the presence of saliva and thermal changes for a clinically acceptable period of time. Several studies have investigated the effect of accelerated artificial aging by using storage in water, thermocycling or fatigue, and a decrease in zirconia-resin bond strength has been observed.

In clinical conditions, fatigue is the dominant factor in causing failure, and the reduction of the expected bond will lead to marginal destruction and debonding of zirconia restorations bonded with resin. The analysis of broken samples shows interfacial failure, which shows that the zirconia-resin interface is the weakest. The connection is in the structure. This finding can be related to two important factors:

The first factor is the hydrolytic effect of water on adhesive joints. Active agents in zirconia experimental primers are silane coupling agent. They are characterized by their structural metamorphosis that the unactivated primary monomers are initially very hydrophobic, but during the activation period (hydrolysis) they change into hydrophilic silanol type monomers, which initiate oligomerization reactions, which are formed by the polymerization reaction with followed by zirconia and cement resin.

The second factor is the phenomenon of limitation by water, which can lead to the thickening of the cement layer and as a result of the bond destruction. Relatively hot water is absorbed in composite resin cements and heat treatment also leads to some post-polymerization of MDP-containing cements.

Therefore, in general, it seems that the long-term durability of the band with zirconia is a challenge in cosmetic dentistry that requires more studies and research. In addition, the long-term stability of the resin-zirconia bond is directly related to the chemistry of the materials used, including the primers. Further research is needed to develop more hydrophobic compounds that can resist the damaging effect of hydrolysis.

Dr. Kasri Tabari – restorative and cosmetic specialist

Dr. Sodeh Jabari-Resident and Aesthetics

Amalgam band and its importance in the treatment of amalgam restorations

Amalgam Bond

Introduction: Although tooth-colored restorations have found a special place in dentistry today, amalgam is still a loyal material for dentists. It seems that each of these two materials are very good and appropriate if they are used in their own place. As much as the comparison of physical and mechanical properties of amalgam and composite is significant; In the same way, comparing these two materials in terms of the superiority of one over the other lacks value and credibility; In many cases where proper isolation is not possible, the use of composite resin is equivalent to the failure of the treatment, and conversely, the use of amalgam restoration in exposed areas is not justified at all. Based on this, the correct use of each of these two is very important in its place. In this way, the use of amalgam band has a significant effect in improving the clinical behavior of amalgam, which will be briefly explained.

Advantages of amalgam band: Bonding new amalgam to old amalgam or amalgam band to dental tissue has always been discussed. These systems are provided for filling the tooth structure and amalgam band with enamel and dentin or the new amalgam band to the old amalgam. The main advantage of this system in many clinical cases is filling the dentin and improving the resistant shape, but the grip created by it is not noticeable with the macromechanical grip resulting from the cavity gripper.

The primary prescription for amalgam banding is when the remaining dental tissue is weakened and it may be possible to restore the overall resistant shape of the restored tooth by bonding the amalgam. Of course, Amalgam Band can be used routinely under all amalgam restorations, thus saving time by eliminating the need for a base.

During amalgam packing, the new layer creates a strong and reliable bond due to chemical reactions to the previous mass. However, if more than 5 minutes have passed since the time of mixing the amalgam, the new amalgam does not have a chemical bond with the previous amalgam, and other measures such as macromechanical, micromechanical (such as sandblasting) or chemical bonding combined with micromechanical bonding with the help of amalgam bond should be used. .

The use of amalgam band has the following advantages:

  • Reduction of marginal leakage and microleakage: Several studies have shown that the use of amalgam band reduces microleakage significantly. Regardless of the type of amalgam used, amalgam bond significantly reduces microleakage compared to varnish or cases where no liner is used.

۲- Strengthening the remaining dental structure and increasing resistance to fracture: In a study conducted at the University of Manitoba, 40 premolars and molars whose buccal or lingual cusp had failed were repaired with amalgam and with the help of amalgam band; After one year, no failure was observed.

In another study, bonding amalgam was shown to increase the buccal cusp strength of a MOD restoration spanning one-third of the buccolingual width by 39 to 61%. On the other hand, it has been shown that restoration of pulpotomy milk teeth with amalgam along with amalgam band increases their strength by 26%.

۳- Resistance to future acid attacks and subsequent reduction of secondary decay

۴Increase flood and decrease sensitivity after treatment: sensitivity after treatment in amalgam restorations is one of the problems that cause pain to patients after tooth restoration with amalgam. This problem is more observed in spherical amalgams that cause less flooding.

The presence of 2 mm of dentin on the pulp or equivalent material covering the pulp is one of the methods that can reduce the sensitivity after work. Using materials such as zinc phosphate, polycarboxylate, glass ionomer and zinc oxide as a base for amalgam restorations is a traditional method to protect the pulp against thermal, electrical and mechanical stimulation. The new method is to use amalgam band instead of base and liner. In this method, by flooding the dentine tubules and preventing the movement of liquid inside the dentine tubules, no pain or sensitivity is caused. It is worth mentioning ; The use of desensitizing dentin systems, which have the same role as varnish, is effective in reducing post-treatment sensitivities, but it does not replace amalgam bonding and does not include the benefits of amalgam bonding.

Even the use of amalgam band has been very effective in reducing the sensitivities of dental collars. In a study, it was shown that the use of amalgam band with bis4-META has a great effect in reducing sensitivity after treatment at the end of a 6-month period; So that 91% of the treated teeth did not show any sensitivity within 6 months.

۵- Conservative and low cutting and keeping more fabric

۶- Reducing the need for a PIN Slot ، Dovetail ، Hole and other mechanical measures that cause additional tooth grinding and increase the possibility of pulp exposure.

The only problem that may be caused by the use of amalgam band is that due to the penetration of resin into the amalgam, the mechanical properties of the amalgam may be affected, which is not important from a clinical point of view.

The reaction mechanism of amalgam bond systems:

The adhesion created by the amalgam bond is based on the micro-mechanical grip; In this way, the amalgam is packed inside the resin that is not fully cured or is being cured. Based on this, amalgam band can be self-curing or dual-curing. Of course, light cure bondings that are very thick are also known as amalgam bonding, an example of which is PQ Amalgam. In these systems, due to exposure to oxygen, the surface layer is not completely polymerized and its surface layer remains uncured, and thus the amalgam inside is packed and a micromechanical seal is created. Studies have shown that the use of light-cured or dual-cured bandages is more effective than self-curing bandages.

In the dual cure system, the amalgam is packed inside the self-cure component and creates a micromechanical grip. For this purpose, it is necessary to lay the bonding in thicker layers (10 to 50 microns) and condense the amalgam on the resin. Thicker layers of bonding agents can be obtained by adding thickening materials or by applying multiple layers (5 to 8 layers).

Bondings with a high amount of filler also create more adhesion than bondings with less filler. In some amalgam bond systems, such as Amalgam bond plus, a powder called HPA has been added, which increases the thickness of the bonding and thereby increases its adhesion. It seems that this material is a type of resin (methyl methacrylate) that can increase its strength in addition to increasing the thickness of bonding.

The important point in all cases is that the amalgam should be triturated at the same time as light cure or dual cure bondings and packed immediately to achieve maximum adhesion.

Chemical bond resulting from the application of amalgam bond:

In addition to micromechanical locking, in some systems, a chemical bond is created in the interface region. In these systems, there are monomers that are able to create chemical bonds with metal oxides, such as 4-META and MDP.

These monomers have two hydrophilic and hydrophobic ends, to bond with both tooth components (hydrophilic) and amalgam (hydrophobic). The most important monomer in this field is 4-META. Other monomers such as MDP can also create an acceptable bond. This monomer can have a significant effect in creating a chemical bond in addition to creating a micromechanical jam.

In a study, it was shown that the use of amalgam band in Class II composite restorations has a significant effect in reducing post-treatment sensitivities. It seems that the main factor of this decrease in sensitivity is 4-META monomer.

Since these bondings can create a chemical bond with the metal matrix tape, to prevent further problems during removal of the metal tape, such as breaking the marginal ridge, it is necessary to treat the surface of the metal tape with inlay wax or a lubricant such as Vaseline before working. be smeared

Adhesion to teeth and amalgam:

The adhesion mechanism in the amalgam bond system is investigated from two areas: 1- Band with teeth 2- Band with amalgam

  • Bonding with teeth: since all bonding steps are similar to the usual method; A suitable hybrid layer is created that creates a flood and reduces sensitivity after treatment.
  • Resin bond with amalgam: On the other hand, the amalgam enters the uncured resin and creates a micromechanical grip. The strength of adhesive systems for connecting amalgam to dentin is relatively low and has a bond strength of about 10 to 14 MPa. Although a good bond is established with the tooth, there is a weak micromechanical connection between bonding and amalgam, and most failures occur between amalgam and bonding.

Application of amalgam bond as self-etch and total etch:

Today, there are systems that can be used as self-etch and total etch. In both of these systems, an Activator is provided separately. In the self-etch method, after applying the primer, adhesive with Activator It is mixed and applied to the entire cavity at the same time; However, in the total etch method, after the application of etch acid, the adhesive is first applied alone and cured as in the usual method, and then the adhesive is applied again with Activator It is mixed and applied to the entire cavity at the same time. The reason is that in the Total H method, collagens are exposed, and it is necessary for the adhesive resin to completely penetrate them. Thus, if like the self-etch method, after etching; Adhesive and Activator mixed together, the polymerization reaction of the resin has started and due to the high viscosity of the adhesive resin, it is not possible to penetrate the entire length of the collagen fibers, which will subsequently lead to sensitivity and microleakage. In the self-etch method, due to the non-exposure of collagen fibers, there is no need to use a separate adhesive.

In the self-etch method, the sensitivity after treatment was less; While in the Total H system, due to the greater thickness, the bond strength is greater.

Amalgam Bond


The effect of bonding thickness on amalgam bond strength:

By increasing the thickness of the amalgam bond, the adhesion strength also increases. For this purpose, the use of several bonding layers increases the strength of the shear bond. Some systems, such as Amalgam bond plus, have increased the thickness by adding methyl methacrylate powder; They also increase the strength of the bond mass.

In a study where amalgam band was used on bovine teeth; It was shown that the use of one layer of amalgam bond gives a bond equal to 1 MPa and two layers gives a bond of about 14-15 MPa. Of course, it should be noted that the high thickness of the amalgam band should not prevent its accumulation in the margins.

The effect of amalgam type on adhesion strength:

Based on the studies, it seems that spherical amalgams have more bond strength when used with amalgam bond on dentin or composite. On the other hand, as the amount of spherical particles increases, the strength of the bond also increases.

The effect of Amalgam Bond in creating the adhesion of new Amalgam to Old Amalgam or Composite:

In a study, it was shown that bonding amalgam increases the bond strength of new amalgam to composite or old amalgam. In this study, the surface of composite or old amalgam was sandblasted to increase the micromechanical grip.

The effect of sandblasting enamel and dentin before applying amalgam band:

The study of Nikaido and her colleagues showed that sandblasting the surface of the dentin before applying the amalgam bond does not have a significant effect on the bond strength, but sandblasting the enamel significantly reduces the strength of the amalgam bond.

Glass ionomer as amalgam bond:

Self-curing and light-curing glass ionomer can be considered as amalgam bonds. This means that the amalgam is packed inside the glass ionomer and is mechanically stuck inside. There is also a self-curing component in Glass Ionomer Light Cure, which amalgam must be condensed inside before it hardens completely. In self-curing glass ionomers, it should be ensured that the cement is hardened to 90% so that the integrity of the cement is not lost. On the other hand, if the cement reaches the edges of the cavity, it may be washed away or it may stick to the opposite teeth.

It has been shown in a study that if amalgam bond is used on glass ionomer modified with resin (optical glass ionomer), the bonding strength of amalgam with optical glass ionomer increases. However, by using amalgam bond, there is no need to use glass ionomer.

Use of hypoallergenic resin systems:

If only cavity flooding is considered, cavity fillers can be used. Since these materials are used to cover the exposed surfaces of the root to limit the flow of liquid inside the tubules and reduce the sensitivity of the dentin, they are also called Dentin desensitizer. An expensive list of these products may be labeled as dentin desensitizers, but they are not routinely used for dentin flooding under amalgam.

Prototypes like Gluma 2 were actually the primer of the bonding system. Other materials were also presented, which were actually initiator monomers or polymers dissolved in the solvent, which penetrated the carved surface and dried inside it, or turned into a thin layer of polymer upon hardening.

The performance of the thin desensitizing layer of ivory is similar to varnish, but their moisturizing properties are higher and they create a uniform layer (without pores). This layer actually moisturizes the enamel as well as the dentin, but it is still known as a dentin sealant.

Bonding agents, which are used under insulation restorations such as composite, replace conventional flooring and liners; unless we are very close to the pulp (less than 0.5 mm); In this case, a layer of calcium hydroxide should be placed as a liner.

Introducing some commercial samples of amalgam band:

۱- DenTASTIC Amalgam bonding kit(Pulp dent) : Pulp dent band amalgam system is designed based on amalgam penetration in self-curing resin cement. The method of its application is that first the surface of the tooth is etched and after removing the excess moisture; Its bond, which contains two bottles of adhesive primer A and B, is mixed together to form a dual cure. Due to its low thickness, bonding should be done in 3 layers. There should be no air gap between the layers, and only after the last layer is applied, a light gap is applied to remove the solvent. Since its bandage is dual-cured, its curing is selective; This means that the band can be cured or not cured.

Then the cement, which is called Resilute and consists of two pastes, is mixed in equal amounts and placed on the bonded surface in a thin layer. At the same time, the amalgam must be mixed so that it condenses immediately inside the cavity (delay in condensing the amalgam reduces the effect of the amalgam bond). In this way, the amalgam inside the resin cement becomes micromechanical and increases the shape and resistance of the cavity.

۲- Optibond solo plus(kerr) :

This system includes a fifth generation band with an Activator. Due to the high thickness of this system, it is sufficient to use its bandage as a dual cure. Based on this, first the tooth is etched and after removing excess moisture, its bonding is mixed with Activator to make it a dual cure. At the same time, the amalgam must be triturated in the amalgamator to condense immediately in the cavity. In cases where metal matrix tape is used; Before using the amalgam band, the metal band must be greased with Vaseline or any other lubricant. Otherwise, during the removal of the matrix tape, a fracture may occur in the marginal ridge due to the bond created.

Optibond solo plus also has a self-etch system. In this method, instead of etching the cavity, from the bottle containing acid and primer, which is called under the general name Primer; is used and other steps are the same as before. After placing the Primer in the cavity, its bonding is mixed with the Activator and applied to the entire cavity.

۳- Tg amalgam bond(Tg co):

This amalgam bond can also be used in two ways: self-etch and total etch. The method of working with it is exactly like Optibond solo plus; with the difference that its thickness is low and it should be applied in 2-3 layers; While the thickness of Optibond solo plus is high and one layer of it is enough.

۴- Panavia F2 (Kurrary) :

Panavia is a dual-cure adhesive resin that, in addition to creating a micromechanical bond, can also create a chemical bond due to the presence of a monomer such as MDP. According to the manufacturer’s instructions, the resin surface does not need to be cured and the amalgam can be packed directly on it.

۵Amalgam bond plus(parkell): In this system, in addition to the micromechanical bond, the chemical bond resulting from 4-META is also significant. Its chemical composition is:

۱۰% citric acid ، ۲% ferric chloride > HEMA، ۴-META in MMA and TBB activator و PMMA “high-performance additive”

۶- Scotch bond multi purpose plus(3M) :

It is a fourth generation band that has a separate catalyst. In the last step (after etching and priming), the adhesive is mixed with the catalyst and a dual cure bond is obtained. In this way, the amalgam is bonded by penetrating the self-cure component and some amounts of the light-cure component.

۷Nano bond (Pentron) :

This bonding is designed in such a way that it can be used as self-etch or total etch. In this system, an activator has been supplied separately. In the self-etch method, after applying the primer, the adhesive is mixed with the activator and applied to all the holes at the same time. In the total etch method, after applying the etch acid, the adhesive is mixed with the activator and applied to the entire cavity at the same time.

۸- All bond 2-Amalgambond plus(Bisco) :

This system can provide good and acceptable flooding due to having monomers for chemical bonding. In a study, it was shown that the use of amalgam bond or All bond 2 is effective for bonding amalgam or composite to enamel and dentin and there is no significant difference.

In another study, it was shown that neither amalgam bond nor All bond 2 had any change in bond strength over time.

Clinical application method:

In some cases due to economic reasons, lack of time, the possibility of weakening the remaining tissue and to prevent possible damage to the dental pulp; Instead of replacing the entire amalgam mass, it is decided to cover it with composite to create a suitable aesthetic for the patient.

In these cases, it is very important to create a macromechanical lock in the first degree and a micromechanical lock in the second degree. Therefore, with the help of a fine process bur, holes with a depth of more than 0.5 mm are created inside the amalgam. Then its surface is roughened with the help of a burr. In the next step, the surrounding enamel is polished and etched. Then bonding is mixed with activator and applied to the entire surface of enamel and amalgam at the same time. Then the amalgam surface is covered with opaquer or opaque tint and finally it is repaired with composite.

It should be noted that most of the time there is no ready and commercial amalgam bonding, but it is necessary to prepare a separate activator along with the bonding so that it can be mixed together and applied to the entire surface of the tooth at the same time.

Dr. Kasri Tabari – restorative and cosmetic specialist

Dr. Neda Khoi – Dentist