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Authors : Dr. Vagish Mehta , Dr. Vishwas Bhatia , Dr. Anju Aggarwal.


One of the most challenging situations that the dentist confront is control of hemorrhage; especially during deep cavity preparation, before making impressions or cementing of restorations. Selection of appropriate agent for a specific situation is of utmost importance. The present article gives an insight into the most common chemical agents used in dentistry, based on their components and mechanism of action.


Constraints of the lips, tongue, cheeks, challenges for access to visualize and manipulate instruments, as well as, the position of the teeth that are being treated relative to the gingival tissues, make oral cavity a different area to treat.

Moisture control is one of the essential part of any restorative dentistry procedure, direct or indirect. It has been reported that contamination of a prepared cavity has a harmful effect on the durability of direct resin composite bond to tooth structure, especially when subgingival finish lines exists1. Though the use of dental dam provides good control of the restoration area and access to the preparation, in many situations its use is precluded. Hence, alternative methods of controlling moisture and blood should be considered.

Historically, techniques for soft-tissue management and moisture control are classified into three main methods: Mechanical, chemical or surgical. Mechanical methods were the first methods introduced for moisture control, especially for fixed restorations during impression making1. Among them, gingival retraction cord is the most popular. unmoistened, plain cords are not be able to control hemorrhage effectively. For achieving greater sulcular displacement, a combination of mechanical and chemical methods, like retraction cords impregnated with hemostatic agents can be used. Mechanical retraction methods have shown improvements with the introduction of cordless retraction techniques like GingiTrac (centrix), which uses a heavy viscosity matrix combined with a light body retraction paste and Magic Foam Cord (Colten-Whaledent), a polyvinyl siloxane material, expanding the sulcus before impression making. The latter also provides hemostasis to some extent2.

Chemical methods include a variety of chemical solutions and gels acting as astringents or hemostatic agents. Surgical methods such as electrosurgery and laser are possible methods in serious haemmoragic conditions or when soft-tissue removal and displacement are also required. The combination of chemical and mechanical methods or chemomechanical methods is the most popular retraction technique today and is used by 80% of dentists.

Some current cordless retraction techniques combine chemical and mechanical methods and provide a non-invasive tissue management, like Expasyl (Kerr), a paste-like material containing aluminum chloride (AlCl3) syringed into the sulcus, acting both as a chemical hemostatic agent and retraction material (chemomechanical method). Even though it provides excellent hemostasis, the retraction is minimal. Favourable results, like effective bleeding control and less histologic damage than retraction cords, has been shown with Expasyl and Magic Foam Cord. Retraction cords impregnated with hemostatic agents like AlCl3 or ferric sulfate (Fe2(SO4)3) are such examples of chemico-mechanical method.


Chemically, active gingival retraction agents are categorized as Class I (vasoconstrictors, adrenergics) or Class II (hemostatic agents, astringents).

Vasoconstrictors like epinephrine do not coagulate, but act by constricting blood vessels and decreasing their size. However, use of racemic epinephrine-impregnated cords causes elevation of blood pressure and increase in heart rate and no benefits have been recognized over non-impregnated cords.
Table 1 List of common hemostatic agents, their compositions and mechanisms of action.2

Astringents, such as alum or aluminum potassium sulfate (KAl (SO4)2), AlCl3 and zinc chloride (ZnCl2), act by precipitating proteins on the superficial layer of mucosa and make it mechanically stronger. Astringents like ferric chloride and Fe2(SO4)3 are concentrated forms of astringents, which cause superficial and local coagulation2.

In general, frequently used hemostatic agents used in restorative dentistry are ferric (ferrous) sulfate and AlCl3. However, there are other agents such as KAl (SO4)2 and aluminum sulfate (Al2(SO4)3) and ZnCl2, which have slight differences in their mechanisms of action and efficiency.

Al2(SO4)3 compounds (KAl(SO4)2 [Alum] and Al2(SO4)3)
  • Alum: In a 100% concentration it is slightly less effective in shrinking the gingival tissues than epinephrine and it shows good tissue recovery. Though its tissue retraction and hemostatic abilities are limited, it has been recommended for use as a substitute hemostatic agent for epinephrine as it is safer and has fewer systemic effects.
  • Al2(SO4)3 : It is effective in controlling hemorrhage and is biologically acceptable. A practical concern is that sulfate compounds can inhibit/retard the setting reaction of additional-reaction impression materials.


It is one of the commonly used astringents. It acts by constricting blood vessels and extracting fluid from tissues. The material is used in concentrations of 5-25% and has minimal systemic side-effects. AlCl3 is the least irritating among hemostatic agents used with retraction cords, but it disrupts the setting of polyvinyl siloxane impression materials. Rinsing thoroughly with water resolves its inhibitory effect.

Ferric subsulfate (Fe4(OH)2(SO4)5)

It is also known as “Mosel’s solution”. It has been used in gingival displacement and is slightly more useful than epinephrine for gingival displacement. Tissue recovery is decent and the recommended time of usage is 3 min. Literature suggests that ferric or ferrous salts are corrosive and injurious to soft-tissues and enamel and they stain the teeth. These properties are attributed to the high acidity (72%, pH <1) of the solution.2


It does not traumatize the tissue noticeably and healing is more rapid than with AlCl3. Solutions of Fe2(SO4)3 above 15% are very acidic and can cause significant tissue irritation and post-operative root sensitivity. It coagulates blood so quickly that it must be placed directly against the cut tissue. The recommended application time is 1-3 min.

The resulting tissue displacement is maintained for at-least 30 min. The tissue is temporarily discolored for 1 or 2 days. It disrupts the setting reaction of polyvinyl siloxanes. Therefore, all traces of the medicament should be rinsed off thoroughly from the tissue before taking an impression. Due to its iron content, Fe2(SO4)3 stains gingival tissues is yellow-brown to black colour for several days.


This material has been used in 8% and 40% concentration which results in permanent injury to the soft-tissue and bone, their use has not been recommended.

Tannic acid (20% and 100%)

Tannic acid shows good tissue recovery despite being less effective than epinephrine. The recommended time of application is 10 min. The hemostatic efficacy of tannic acid is minimal3.


Hemostatic agents are steadily more used as a method of easier fluid control in dental procedures. While some side-effects have been investigated during bonding and impression making, as well as tissue inflammation and cell viability4, it is established that proper use of these handy materials can reduce the negative effects, thus maximizing their advantages. Some unfavourable effects, can be compensated by decreasing the concentration or by using gel type formation marketed by manufacturers4.

Surface changes in enamel and dentin do not happen when lower concentrations and shorter application times of astringents are used, due to their low pH; A minimum amount of 0.3-0.5 mL is enough for a single tooth to stop bleeding. The minimum hard and soft-tissue damage is recorded in the normal 3-10 min. application time and if any inflammation occurs it would subside within 7-10 days after application4.


Among the widely used chemical agents for control of hemorrhage in restorative dentistry, the most common hemostatic agents are AlCl3 and Fe2 (SO4)3 in 15-25% concentrations and 3-10 min application times2. In order to achieve satisfactory outcomes during making impression or using bonding agents, common hemostatic agents suggested before or during etching, should be washed off properly and it is recommended that they can be used with etch-and-rinse adhesive systems.

  1. A review on common chemical hemostatic agents in restorative dentistry Pardis Tarighi and Maryam Khoroushi. Eur J Dent1996;75:18-32.
  2. Methods And Materials For Soft Tissue Management, Displacement-Retraction and Hemorrhage Control. Dr. Howard Strassler and Dr. Leendert (Len) Boksman. J Am Dent Assoc 2009;141:1541-3.
  3. Fundamentals of Fixed Prosthodontics Third Edition, Herbert T. Shillingburg, Jr, DDS Sumiya Hobo, DDS, MSD, PhD Lowell D. Whitsett, DDS.
  4. Contemporary Fixed Prosthodontics by Stephen F. Rosenstiel.

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