Rubber-Dam is a small stretchable sheet of rubber that dentists use to isolate teeth that dentist are working on and keep them dry. Rubber Dam also prevents debris falling into the throat.

How it is placed

To place Rubber Dam in mouth, a hole is made into it keeping the teeth-size and its location in mind. Then one or more small metal clamps are put on the teeth and then Rubber Dam is attached to the clamps. Then remaining rubber-dam is stretched using a small metal frame which keeps it stretched and out of the way, covering entire part of mouth.

Benefits of using Rubber Dam

Moisture presents a problem in the performance of many dental operations. Dryness of the operative field is essential to the success of restorations and endodontic procedures. The use of the rubber dam is the best method of maintaining a dry field. Rubber dam equipment is listed and illustrated in figure below.

Rubber dam equipment.

Problems of using Rubber Dam

Not every patient is able to use a rubber dam. People with strong gag reflexes often have a difficult time wearing a rubber dam because the tongue is not able to penetrate through the rubber dam. People that suffer from claustrophobia may also have a difficult time wearing a rubber dam, for similar reasons. In the case of a gag reflex or claustrophobia, a small hole may be cut into the rubber dam to allow the tongue to penetrate through the rubber dam.

Rubber Dam Clamps

Following Rubber Dam Clamps are most commonly used.

• Ivory Punch
• Lightweight Rubber Dam Forceps
• Rubber Dam Frame 6″
• Stainless Steel Frame
• Stainless Steel Clamps Tray
• Stainless Steel Tray with Lid
• 40 Pcs Rubber Dam Clamps

Rubber Dam Punchers

Rubber Dam Punchers are the instruments used to make hole in Rubber Dam sheet. Ivory Punch and Lightweight Ivory Forceps are the two most commonly used instruments to make punches in the Rubber Dam sheet.

Further Reading & Resources

• Wikipedia – Rubber Dam Instruments
• Medical Tools Rubber Dam Kit
• Buy Ivory Punch Rubber Dam Puncher
• Dental-Forceps Rubber Dam Instruments

a. Stout A Root Elevator. This elevator’s nib is flat on one side and rounded on the other. The nib has straight tapering walls and a rounded end (figure 3-11).

Figure 3-11. Stout A elevator.

b. Straight Root Elevator Number. 34-S: This elevator is straight and shaped like a gouge (figure 3-12). In cross-section its nib is crescent-shaped. It is one of the most commonly used elevators.

Figure 3-12. Straight elevator number 34-S.

c. Straight Elevator Number 301. This elevator is similar in shape to but smaller than number 34-S (figure 3-13).

Figure 3-13. Straight elevator number 301.

d. Apical Fragment Root Elevators. These are used to remove apical root fragments (figures 3-14 and 3-15).

Figure 3-14. Miller root elevators numbers 73 and 74.

What happens during the tooth extraction process

The root portion of a tooth is firmly encased in bone (its socket) and it is tightly bound into place in this socket by a ligament. During the extraction process the dentist needs to expand the socket (widen and enlarge it) and separate the tooth from its ligament to a point where the tooth is loose and free to come out.

The bone of the jaw is compressible to some degree. That means if a dentist can apply firm pressure to a tooth, forcing it against one of the sides of its socket, the bone in that area will become compressed. The net result is that the socket becomes slightly enlarged. After repeated application of pressure to a tooth, from many different directions, the entire socket becomes larger. The ligament that holds the tooth in place will become detached from the tooth too. Finally at some point, enough space will have been created and the ligament separated from the tooth enough that the tooth will come out.

Dentists have a variety of tools they use to manipulate and apply pressure to teeth. Some of them are specialized pliers termed “extraction forceps.” Dentists also use levers that are called “elevators” (they look somewhat similar to small screwdrivers). Usually a dentist will use an elevator first. These tools are intended to wedge between the tooth and the bone surrounding it. The force the dentist applies to the elevator in turn places pressure on the tooth. This action on the tooth helps to expand its socket and separate its ligament. It’s somewhat common that a tooth can be extracted with just the use of an elevator.

Understanding the dentist’s use of extraction forceps is more straightforward. The dentist will grasp the tooth with the forceps and then firmly and deliberately rock the tooth back and forth. They will also rotate the tooth as much as it will. The combination of these tooth movements expands the tooth’s socket and separates its ligament.

Tooth sensitivity is the discomforting feeling mostly of pain…

Tooth sensitivity is the discomforting feeling mostly of pain one a person experiences when they drink or eat something cold or hot, sweets, touch the tooth with other teeth or the tongue or even when you breathe in cool air. Doctors describe this feeling as Dentin Hypersensitivity or Root Sensitivity.
Tooth sensitivity occurs when the underlying layer of the tooth (Dentin) is exposed when the gum covering the tooth recedes and leaves the root of the tooth exposed to the factors that cause one to notice he/she has tooth Sensitivity.

Causes of Tooth Sensitivity

1. Acidic foods – Regular partake of acidic food erodes away the outer covering of the tooth (Enamel) leaving you susceptible to teeth sensitivity. The acidic foods should be taken in controlled amounts.

• Dental Forceps No. 150s
• Dental Forceps No. 151s

The Pediatric Forceps #150S is used to remove maxillary deciduous teeth and is a scaled down version of the #150. The #151S, a smaller version of the 151, is used to remove mandibular deciduous teeth.

There are three hawkbill-type forceps:

• The Mead Dental Forceps no.  MD3
• Dental Forceps No. 13
• Dental Forceps No. 22

The Mead #3 forceps are used on mandibular anteriors and bicuspids, the #13 forceps are used on mandibular first, second bicuspids, and the #22 forceps on mandibular first, second, and third molars. The beaks are perpendicular to the working action of the handles. This design gives the dentist a great deal of leverage with minimum effort. The major difference between these forceps is the width of the beaks, because they are used to remove different teeth.

There are several popular extraction forceps for the mandibular molars, including the

• Dental Forceps No.  15
• Dental Forceps No. 16 (No. 16 variants)
• Dental Forceps No. 17 (No. 17 variants)
• Dental Forceps No. 217
• Dental Forceps No. 222 (No. 222 variants)
• Dental Forceps No. 15

Dental Forceps No. 15

These  are used to remove mandibular first and second molars. The beaks have concave inner surfaces with pointed projection on the tips. These forceps work well in grasping the crown with the two projecting tips extending to the bifurcation between the two roots on mandibular third molars. The left handle on the Dental Forceps No. 15 has a finger rest.

Dental Forceps No. 16

Forceps #16 are used to remove mandibular molars. The #16 forceps are nicknamed mandibular cowhorns when they are open. The left handle on the #16 has a finger rest.

Dental Forceps No. 17

Forceps #17, like the #15 and #16 forceps, are used on lower first and second molars. The beaks of the #17 forceps are similar to the beaks of the #15 forceps; however, the handle of the #17 is straight.

Dental Forceps No. 217

Forceps #217 are used to remove mandibular second and third molars. The beaks have inner concave surfaces and pointed projections much like those of the #15 forceps. The handles have a slight curvature and resemble those of the #151 forceps.

Dental Forceps No. 222

Forceps #222 are used on mandibular third molars. The beaks on the #222 forceps are rounded with concave inner surfaces, and angle sharply from the handle.

This requires the immersion of the instruments in a chemical solution consisting of Copper Sulphate (CuSO4-5H20) 4g, Sulfuric Acid (H2SO4) 10g, and distilled water 90ml. The instruments should be thoroughly scrubbed with soap and water, followed by immersion in 95% Ethyl Alcohol. It should then be immersed in the Copper Sulphate solution for 6 minutes at room temperature. The Copper Sulphate solution will react with any free iron on the surface of the instruments, and plate out copper on them, any reddish discoloration of the surface indicates that the composition of the metal is not of a surgical grade.

The Boil Test requires that the instruments should be scrubbed using soap and warm water, rinsed thoroughly in hot water, then dipped in 95% Ethyl Alcohol. It should then be in boiling distilled water, in a glass or ceramic beaker for at least 30 minutes, and subsequently allowed to cool in the distilled water.The Military Specification requires that it be cooled in the distilled water for 24 hours, at which time it should be examined. ISO requires that the metal be removed from the distilled water after boiling for thirty minutes, then remain in air 2 hours prior to examination.

In the interpretation of the test, the ISO draft states “The instrument shall be wiped with a dry cloth, and inspected for visible signs of corrosion. Any blemish not removed by vigorous hand rubbing with a cloth, shall be considered evidence of corrosion.

In addition, it also describes passivation as “the chemical treatment of a stainless steel with a mild oxidant, such as a nitric acid solution, for the purpose of enhancing the spontaneous formation of the protective passive film.”

In layman’s terms, the passivation process removes “free iron” contamination left behind
on the surface of the stainless steel as a result of machining and fabricating processes.
These contaminants are potential corrosion sites which, if not removed, result in premature corrosion and ultimately result in deterioration of the component. In addition, the PASSIVATION OF STAINLESS STEEL passivation process facilitates the formation of a very thin, transparent oxide film, which protects the stainless steel from “selective” oxidation (corrosion).

So what is passivation?

• Is it cleaning?
• Is it a protective coating?

In my opinion, it is a combination of both!

How is the Passivation Process Performed?

The process typically begins with a thorough cleaning cycle. It is intended to remove oils, greases, forming compounds, lubricants, coolants, cutting fluids, and other undesirable organic and metallic residue left behind as a result of fabrication and machining processes. General degreasing and cleaning can be accomplished by a variety of commonly accepted methods, including vapor degreasing, solvent cleaning, and alkaline soaking.

After removal of the organic and metallic residues, the parts are placed into the appropriate passivation solution. Although there are many variations of passivating solutions, the overwhelming choice is still the nitric acid based solutions. Recently, there has been substantial research performed to develop alternative processes and solutions that are more “environmentally friendly,” yet equally effective. Although alternative solutions containing citric acid and other types of proprietary chemistry are available, they have not been as widely accepted commercially as nitric acid based solutions.

The three major variables that must be considered and controlled for the passivation process selection are time, temperature, and concentration. Typical immersion times are between 20 minutes and 2 hours. Typical bath temperatures range between room temperature and 160°F. Nitric acid concentrations in the 20% to 50% by volume range are generally specified. Many specifications include the use of sodium dichromate in the passivation solution, or as a post passivation rinse, to aid in the formation of a chromic oxide film. Careful solution control, including water purity, ppm (parts per million) of metallic impurities, and chemical maintenance, is crucial for success.

The type of stainless steel being processed is the determining factor when selecting the most effective passivation process. Bath selection (time, temperature, and concentration) are all a function of the type of alloy being processed. A thorough knowledge of the material types and passivation processes is paramount to achieving the desired results. Conversely, improper bath and process selection and/or process control will produce unacceptable results, and in extreme cases, can lead to catastrophic failure, including extreme pitting, etching and/or totaldissolution of the entire component.

PASSIVATION OF STAINLESS STEEL

Equipment and Precautions

Passivation should only be performed by trained, experienced technicians familiar with

the potential hazards associated with the science. Safety practices must be fully understood when handling passivation chemicals. Special boots, gloves, aprons and other safety equipment must be utilized. Tanks, heaters and ventilation, as well as baskets and racks, must be appropriately engineered to perform the process. Iron or steel parts or equipment must never be introduced to the process, or the results can be devastating! Furthermore, in order to comply with EPA requirements, the necessary water and air permits and treatment capabilities must be in place. The days of the “mom-and-pop” shops performing passivation in a stone crock in the back corner of the shop are diminishing, due to safety and environmental concerns.

Specifications and Verification Testing

There are a few generally accepted industry specifications available for reference when

choosing a passivation process. They offer time, temperature, and concentration information, and subsequent testing requirements to validate the effectiveness of the process. Many large corporations have developed internal specifications to control their unique requirements regarding passivation and verification testing. Regardless of the situation, it is usually prudent to reference a proven procedure when requesting passivation. By referencing a specification, you don’t have to “reinvent the wheel,” and by taking advantage of the past experiences of others, both successes and failures, you can eliminate much of the guesswork that would otherwise accompany a new process.

Although recently cancelled, the most commonly referenced industry specifications regarding passivation are Fed. Spec. QQ-P-35C, which is now superseded by ASTM A-967, and ASTM A-380. All three are well written, well defined documents which provide guidance on the entire process, from manufacturing to final testing requirements. If you’re not sure what you need, they can be referenced in full, or selectively. The testing requirements can be utilized or waived, depending upon the individual situation.

One of the most commonly specified verification tests is the copper sulfate test. Passivated parts are immersed in a copper sulfate solution for 6 minutes, rinsed, and visually examined. Any copper (pink) color indicates the presence of free iron, and the test is considered unacceptable. Other validation tests include a 2 hour Salt Spray or 24 hour high-humidity test. These tests are performed by placing passivated parts in a highly controlled chamber which creates an accelerated corrosive environment. After subjecting the test pieces to the corrosive atmosphere for the prescribed exposure periods, the parts are removed and evaluated. Although results can be somewhat subjective, ASTM B-117 is an excellent reference in determining acceptability. It is important to note that each of the test methods mentioned have different advantages and limitations. Care should be taken to select the appropriate test methods, based on alloy type and end use environment.

PASSIVATION OF STAINLESS STEEL

Machining and Heat Treating Techniques

Perhaps the most overlooked variable in the entire passivation equation is the negative impact of poor machining and heat treating practices. All too often, gross contamination introduced during manufacturing and/or thermal processes leads to unacceptable test results. The following practices will reduce gross contamination during manufacturing and increase the chances of successful passivation and test results:

Never use grinding wheels, sanding materials, or wire brushes made of iron, iron oxide, steel, zinc, or other undesirable materials that may cause contamination of the stainless steel surface.

The use of carbide or other non-metallic tooling is recommended whenever possible. Grinding wheels, sanding wheels, and wire brushes that have been previously used on other metals should not be used on stainless steel.

Use only clean, unused abrasives such as glass beads or iron-free silica or alumina sand for abrasive blasting. Never use steel shot or grit, or abrasives which have been used to blast other materials. Thorough cleaning prior to any thermal processing is critical! Stress relieving, annealing, drawing, or other hot-forming processes can actually draw surface contaminants deeper into the substrate, making them almost impossible to remove during passivation.

Care should be taken during all thermal processes to avoid the formation of discoloration (oxides). Passivation is not designed to remove discoloration, and will not penetrate heavy oxide layers. In extreme situations, additional pickling and descaling operations are required prior to passivation to remove the discoloration.

Controlled atmosphere ovens are highly recommended for all thermal processes to reduce airborne contamination and prevent oxides from developing.

PASSIVATION OF STAINLESS STEEL

Conclusions

So how do you get “the performance you’ve paid for” from high-dollar stainless steel alloys? It really boils down to a basic understanding that the passivation process is both an art and a science, a that machining, fabricating, and heat treating practices can substantially affect the corrosion resistance of the component. It’s a well known fact that passivation will enhance the corrosion resistance of stainless steels, but to realize the maximum performance from these high-tech alloys, all parties involved with manufacturing must understand their responsibility in maintaining the integrity of the material throughout the process.

About the Author:

Dan Englebert is the Vice-President, Technical Services at Imagineering Enterprises, Inc., a metal finishing and consulting firm located in South Bend, Indiana. TheQS- 9000/ISO 9002 certified company was founded in 1959 and is recognized globally as an Electroless Nickel Plating expert source. Imagineering is a member of the National Association of Metal Finishers (NAMF) and the Indiana Association of Metal Finishers (IAMF). Englebert is a member of the American Electroplaters and Surface Finishers Society (AESF) and the National Association of Corrosion Engineers (NACE).

References

1. ASTM A 380 – 96 Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems
ASTM Committee A-1 on Steel, Stainless Steel, and Related Alloys
ASTM Committee on Standards
100 Barr Harbor Drive
West Conshohocken, PA 19428
2. Fed. Spec. QQ-P-35C October 28, 1988
Passivation Treatments For Corrosion Resistant Steel
CANCELLED April 4, 1997
SUPERSEDED by ASTM A 967 – 96