Periodontics Instrumentation Question And Answers

Periodontal Instrumentation

Classification Of Periodontal Instrument:

• Periodontal probes
• Explorers
• Scaling, root-planning and curettage instrument
• Sickle scalers

Read And Learn More: Periodontology Important Question And Answers

• Curettes
• Hoe, chisel, file scalers
• Ultrasonic and sonic instrument
• Periodontal endoscope
• Cleansing and polishing instrument

Question 1. Describe the parts of the periodontal instrument.
Answer:

The periodontal instrument has three parts, they are Handle, shank, and working end (blade).

Periodontal Instrument Handle

• This forms the terminal part of the instrument. It can vary in diameter for better comfort.
• The surface texture of the handle may be serrated and smooth in order to prevent slippage during instrumentation.
• Hollow handles are preferred over solid handles because they increase tactile sensitivity.

Periodontal Instrument Shank: It is an extension device of the instrument as the length increases, the working end can be placed closer to the working area of the tooth surfaces. The area of the shank has two parts:

• Functional shank: Functional shank from the working end to the last bend next to the instrument handle.
• Terminal shank: Terminal shank begins below the working end extend to the fist shank bend.

Type Of Periodontal Instrument  Shank

• Simple shank: The shank that bend in one plane used in the anterior quadrant of the tooth surface.
• Complex shank: The shank that bends in more than in one plane. Used in the posterior quadratant and in the sub-gingival instrumentation.

Periodontal Instrument Working End

• It is the functional part of the instrument and it designs and determines the area in use.
• The working end of the instrument is called the face of the instrument. The surface that is opposite to the face is the back of the instrument, the surface that are on either side of the face of instrument is called the lateral surface.
• This surface may be straight, curved, or parallel. The cutting edge is where the lateral surface and the face of the instrument meet.

Question 2. Write a note on hand scalers.
Answer:

Sickle Scalers

• Sickles scalers are instruments designed to remove gross supragingival calculus. The blades of scalers are triangular in cross-section with a pointed tip. The cutting edges may be straight or rounded.
• The arched shape of the instrument makes the tip strong so that it will not break of during use.
• Scalers are relatively rigid and heavy in construction and are designed for cleaving large deposits from the tooth surface.
• Their shape generally limits their use to supragingival regions. Positioning a scaler into the gingival crevice requires considerable tissue displacement and produces the potential that the instruments pointed end may go to the root surface or lacerate the soft tissue.
• The relatively long, straight working edge of a scaler does not adapt well to the concave region of the root surface, to thus limiting the effectiveness of the scaler in root planning.
• Sickle scalers with the same base design can be obtained with different blade sizes and shank types to adapt to specific areas. The U 15/30 and Ball sickles are large.
• The Jaquette sickles No. 1,2 and 3 have medium-sized blades. The Morse sickles has a very small, miniature blade. It is useful in the mandibular anterior area if there is little interproximal space.
• The relation of these instruments should be based on the area to be scaled. Sickles with straight shanks are designed for use on molars and premolars.
• There are two types of sickle scaler, anterior sickle scalers, and posterior or modified sickle scalers.
• Anterior sickle scalers are straight and hooked. The blade and shank of anterior sickles are in a straight line with the handle.
• The blades are at 90° to the shank and have two cutting edges that adapt to the tooth surface like curettes (45°–90° angle). Sickle scalers are used with pull strokes.
• Both straight and hooked sickles are good for removing supragingival calculus on the mandibular anterior tooth.
• The hooked sickle is helpful on the lingual surfaces of lingually averted teeth.
• Posterior sickles have the same blade design as anterior sickles but they have a modified shank, designed to adapt interproximally in the premolar and molar areas.
• The blades of some sickle scalers are extremely thin, sometimes as fine as 0.2–04 mm. They may be used for a push or a pull stroke.

Scalers Chisels

• They are straight or slightly bent instruments designed to dislodge relatively heavy masses of supra-gingival calculus from the tooth in confined spaces.
• The chisel has a small cutting edge and is pushed between the calculus and the tooth surface to cleave the attachment. It is relatively limited in use because of the problem inherent in their use with a push stroke.
• The chisel may be the only hand/mechanical instrument capable of gaining access to regions such as on the lingual aspect of the lower anterior teeth.
• The instrument is inserted from the facial surface, and a push stroke is engaged to dislodge the deposits.
• Some chisels may have extremely sharp corners that may nick the tooth surface and traumatize tissue. The operator should round these corners.
• With the refinement of curettes and advent of ultrasonic devices, chisels are used less frequently.
• It is a double-ended instrument with a curved shank at one end and a straight shankat the other, the blade are slightly curved and have a straight cutting edge beveled at 45°.
• The scaler is inserted from the facial surface. The slight curve of the blade makes it possible to stabilize it against the proximal surface, whereas the cutting edge engages the calculus without nicking the tooth.
• The instrument is activated with a push action while the side of the blade is held primarily against the tooth.

Hoe Scalers

• Hoe Scalers are used to remove heavy calculus. These are subgingival and supragingival scalers used for scaling of ledges or rings of calculus.
• The blade is bent at 99° angle, the cutting edge is formed by the angle of the flattened terminal with the inner aspect of the blade.
• The cutting edge is beveled at 45°. The blade is slightly bowed so that it can maintain contact at two points on a convex surface.
• The back of the blade is rounded, and the blade has been reduced to minimal thickness to permit access to the roots without interference from the adjacent tissues.

Hoe Scalers are Used in the Following Manner

• The blade is inserted to the base of the periodontal pocket so that it makes two-point contact with the tooth. Ths stabilizes the instrument and prevents nicking of the root.
• The instrument is activated with a firm pull stroke towards the crown, with every effort being made to preserve the two point contact with the tooth.
• The McCalls Hoe scalers No. 3, 4, 5, 6, 7, and 8 a set of six hoe scalers designed to provide access to all tooth surfaces. Each instrument has a different angle between the shank and the handle.
• Hoes may be single or double-ended and are designed to function either in the anterior or the posterior regions of the mouth.
• Anterior hoe have shorter and straighter shanks, and posterior hoes have longer and angled shanks.
• All hoes are best suited for facial and lingual surfaces and for proximal surface adjacent to edentulous areas. Hoes are best suited when tissue is easily displaced.
• Hoes are most useful in flat surfaces not accessible to curettes. The straight cutting edge limits the hoes ability to access root contours.
• Like the chisel, ultrasonics and rigid curettes have replaced the hoe in today’s armamentarium.

Scalers Files

• Files may be considered to be a series of small hoes. Like hoes, most fies are designed for removing supragingival and subgingival deposits when the gingiva is easily displaced.
• They are relatively small and provide excellent access to subgingival regions. The fie blade consists of multiple cutting edges that crush or fracture heavy and/or tenacious deposits.
• The shank design is like that of a hoe and therefore limits its adaptability to root form. It is used on facial and lingual surfaces like the hoe with a pull stroke.
• Files are currently seldom used for scaling and root planning because they gouge and roughen root surfaces.

Question 3. Describe curettes. Add a note on Gracey curettes.
Answer:

Curette

• This is the most versatile of hand/mechanical scaling and root planning instruments. Curettes have a curved working end with a round back.
• As the curette tip is rounded, forming a toe, it prevents inadvertent gouging of the root surface or soft tissue trauma during instrumentation.
• Curettes are generally smaller and thinner than the other scaling and root planning instruments.
• Their small size and rounded design allow the clinician to more easily maneuver the working end of the instrument into deep pockets or regions having difficult access.
• It is able to conform to the curvatures of the root more readily and with more safety than any other instrument. Except for the explorer, the curette has the greatest tactile sensitivity than any other subgingival instruments.
• In cross-section, the blade is semicircular with a convex base. The lateral border of the convex base forms a cutting edge with the face of a semicircular blade. There are cutting edges on both sides of the blade.
• A curette can be single ended or double-ended. Double-ended instruments have two working ends at either sides of the blade, one at either end of the instrument handle.
• The blades are mirror images of each other. Single-ended instruments have only one working end and is generally named after the designer and are matched in sets.
• The handle of the curette vary in size and shape. A larger and textured handle will enhance tactile sensitivity.
• Curettes have two cutting edges: An outside edge and an inner edge. The outer cutting edge can be used on facial, lingual, and mesial surfaces of posterior teeth and on all surfaces of anterior teeth.
• Here the instrument should be parallel to the tooth surface being scaled. The inside cutting edge is used on the distal surfaces of posterior teeth.
• Here the handle of the instrument should be perpendicular to the tooth surface being scaled.
• The curved blade and the rounded toe of the curette allow the blade to better adapt to the root surface, unlike the straight design and pointed tip of a sickle scaler, which can cause tissue laceration and trauma.

The two basic forms of curettes are the universal curettes and area-specific curettes.

1. Universal Curette

• • As the name implies they are used in all quadrants of the mouth. The instrument has a small functional shank used in the cervical 1/3 of the root surface.
  • They can be a single-ended instrument or a double-ended instrument.

Characteristics of the Instrument

1. Working end: Curved upwards
2. Cutting edge: Straight or parallel to one another
3. Relationship to the shank: 90° to the lower shank
4. No. of cutting edge: Two cutting edge per working end
5. Cross section: Semicircular in cross-section
6. Functional shank: Rigid or flexible small function shank.

• Instrument Application:
  • A single-ended curette is used in all the area of the mouth.
  • Use on the crown and root surface – enamel and cementum.
  • Instrument Example: Barnhart curettes No.1-2 and 5-6, Columbian curettes No. 13-14, 2R-2L and 4R-4L.
• Universal curettes have cutting edges that can be inserted into most areas of dentition.
• Altering the finger rest, fulcrum and hand position of the operator does this. The face of the blade of every universal curette is at a 90° angle to the lower shank when seen in cross-section from the tip.
• The blade of the universal curette is curved in one direction from the head of the blade to the toe.

2. Area-Specific Curettes

• As the name implies they are used mostly according to certain area of the mouth specified.
• The instrument has a long functional shank that can be used in the apical and middle 1/3 of the roots.
• They are single-ended instrument or double-ended instrument.
• Area specific curettes have specialized shape that helps it to closely adapt to a particular tooth surface in a particular region of the mouth.
• They are manufactured as complete sets so that all surfaces of all teeth throughout the mouth can be accessed using the set.
• Of the area-specific curettes the most popular type is the Gracey curettes. These are relatively small and delicate instruments.
• They have their cutting blade set at a 60 to 70° angle to the lower shank. This allows the outside edge of the instrument to be used in a pull or push stroke.
• These curettes and their modifications are probably the best instruments for subgingival scaling and root planning because they provide the best adaptation to complex root anatomy.

Double-ended Gracey curettes can be paired in the following manner:

• Anterior teeth: Gracey 1–2, 3–4
• Anterior and bicuspid teeth: Gracey 5–6
• Posterior teeth, buccal and lingual surfaces: Gracey 7–8, 9–10
• Posterior teeth, mesial surfaces: Gracey 11–12
• Posterior teeth, distal surfaces: Gracey 13–14

Single-ended Gracey curettes comprise a set of 14 instruments: The modifiations of Gracey curettes are:

1. Gracey 15–16
2. Gracey 17–18.

1. Gracey 15–16 curette: This is a modification of the standard Gracey 11–12. It has a Gracey 11–12 blade, Gracey 13–14 shank. The shank is acutely angled. It is used for posterior mesial surfaces.

2. Gracey 17–18 curette: This is a modification of Gracey 13–14. The shank has a more accentuated angle and is 3 mm longer. It can be assessed to all posterior distal surfaces.

Extended shank curettes (afterlife curettes):

• This is a modification of the standard Gracey curette.
• Here the blade is thinned and the shank has a larger diameter, is tapered, and is 3 mm longer. It is available is a rigid and finishing design. In the after-fie curettes all the numbers of the standard
• Gracey curettes are available except for No. 9–10. The rigid design is used for tenacious calculus removal. Th finishing after curettes can be used for light scaling or deplaning.

Mini-bladed Instruments

• Mini Five Curettes
  • This is a modification of after 5 curettes. Here the terminal shank is longer when compared with standard Gracey.
  • The blade is half the length of Gracey and an after-fie curette. It can be used in deep, narrow pockets, furcations, developmental depressions, line angles, deep tight pockets, and on facial and lingual surfaces. These are used with vertical strokes.

Question 4. Describe the principles of scaling and root planning.
Answer:

Principles of Scaling and Root Planning

• The objective of scaling and root planning is to remove plaque and calculus deposited on the root surface so as to facilitate the resolution of gingival inflammation and obtain a gain in clinical attachment by providing a biocompatible root surface that can be re-colonized by the cells of the periodontium.
• Scaling is the process by which plaque and calculus are removed from both supragingival and subgingival tooth surfaces.
• Root planning is the process by which residual embedded calculus and portions of cementum are removed from the roots to produce a smooth, hard clean surface.

The principles of instrumentation using scalers are as follows:

Accessibility: Positioning of Patient and Operator

• Good access to the area of operation facilitates thoroughness of instrumentation. This is determined by position of the clinician and patient.
• For good access the patient should be in a supine position and close to the resting elbow of the clinician. The clinician’s position should provide the best access to the operating area.

Visibility, Illumination, and Retraction

• The area of operation should be well-illuminated to avoid tissue injury. The tongue and cheek should be retracted with the help of mouth mirror to improve visibility.
• Operator can have direct visibility or indirect visibility by seeing reflection of the site on the mouth mirror.

Sharpness of Instrument

• A sharp instrument is more effective and has better tactile sensitivity when compared to a blunt instrument.
• The cutting edge of a sharp instrument does not reflect light.

Maintaining A Clear Field

• The operating area should not be obscured by saliva, blood, or debris as it will interfere with visibility during instrumentation.
• Adequate suction or gauze should be used to remove excess saliva or blood to obtain a clean operating area.

Instrument Stabilization

• Instrument stabilization is important for effective instrumentation and prevents tissue injury.
• The factors that provide stability are instrument grasp and finger rest.
• The types of grasps include pen grasp, modified pen grasp, and palm and thumb grasp. The most stable instrument grasp is the modified pen grasp which creates a tripod effect enhancing control of the instrument.
• Palm and thumb grasp is used during heavy, tenacious calculus removal and sharpening of instruments.
• Finger rest aids in stabilizing the instrument by providing a fulcrum to activate the instrument.
• The fourth figure is most often used as figure rest. Finger rests can be either intraoral or extraoral.
• Variations of intraoral finger rests are conventional (finger is placed on the tooth adjacent to the operating area), cross-arch, opposite arch, and figer on the finger.
• Extraoral fulcrums may be either palm up or palm down.

Instrumentation Activation

• Adaptation: Only the lower third (1–2 mm) of the working end should be in contact with the tooth surface.
• Angulation: The optimal angulation between the tooth and the face of scalers should be between 45 and 90°.
• Lateral pressure: Once the scaler is positioned on the tooth surface pressure is applied against the tooth surface to remove calculus from the tooth surface.
• Strokes: The basic strokes used during instrumentation are the exploratory stroke, scaling stroke, and root planing stroke. These strokes use a pull motion in either a vertical, oblique, or horizontal direction.

Question 5. Describe the power-driven instruments used in periodontal therapy.
Answer:

Power-Driven Instruments: Power-driven scalers can be classified into three groups based on the basic design ideology of the equipment. These are:

1. Sonic scalers
2. Magnetostrictive scalers
3. Piezoelectric scalers

• All the above types of scalers work with slightly different methodologies and hence have varying degrees of efficiency.
• A clinician should be aware of the different characteristics of these scalers to be able to decide and choose the most suitable equipment.
• Magnetostrictive and piezoelectric units are composed of the following:

1. An electric power generator that delivers energy in the form of high-frequency vibrations to a handpiece.
2. A handpiece
3. Electric and water outlets
4. A foot control.

• Both types of units have interchangeable tips. Piezoelectric ultrasonic units are less common than magnetostrictive ultrasonic units but tend to provide safety for use on patients with cardiac pacemaker devices.
• With a magnetostrictive handpiece, energy is carried from the power generator through strips that encircle the handpiece.
• The insert is composed of many magneto strips that convert the electrical energy in the handpiece to mechanical energy in the form of rigid vibrations.
• The vibrations may vary from 20,000 to 29,000 cycles per second. This causes the tip of the instrument to alternatively increase or decrease, thus the tip moves approximately 1/1000 of an inch in a back and forth, circular, or figure 8 motion.
• It is the tip motion that disrupts the calculus deposits. In magnetostrictive units, the pattern of vibration of the tip is elliptical, which means that all sides of the tip are active and will work when adapted to the tooth. In piezoelectric it is linear.

Sonic Scalers

• Sonic scalers are driven by compressed air and create vibratory energies from pressure.
• Sonic scaler handpieces will generally fit onto the regular rotor handpieces. They generally work at frequencies ranging from 1500 to 7000 kHz depending upon the handpiece and the pressure of the compressed air.
• These scalers have a wide range of amplitude which is up to 1.5 mm from the center and the tip generally moves in an orbital fashion.
• Sonic scalers are susceptible to hand-pressure damping, which limits the amount of energy that can be applied to the tooth surface and thereby lessens the efficiency of the scaler.
• Sonic scalers do not even exhibit a phenomenon known as cavitation. On a comparison level with the other two kinds of scalers, the sonics are not as efficient in removal of calculus.
• In spite of the not-so-great effiencyat the removal of calculus, these units are capable of removing more than 100 um of cementum during routine debridement.
• The average width of the cementum is about 150 um and most of this layer can be lost if extreme care is not taken while scaling with these units.
• The sonic instruments should be used only on supragingival areas and never in areas of recession or exposed root surfaces.
• A few of the commonly available sonic scalers are available from JR Rand corp, Kavo, kinetic instruments, Medidenta and Star Dental.
• All these scaler handpieces or at least the tips are autoclavable. Almost all of them operate at a vibratory frequency of6000 MHz.
• The scalers generally have up to 3 tips in different shapes for accessing various sites in the oral cavity. These scalers have been in use now for close to 20 years.

Magnetostrictive Scalers

• This class of scalers can easily lay claim as the first kind of ultrasonic device to be made for power-driven scaling.
• These instruments work on the principle of conversion of electrical energy to magnetic energy to vibratory energy.
• The vibration of the tips of these scalers is elliptical in nature which enhances the application of energy to the tooth for debridement.
• Magnetostrictive scalers have a base unit and metal inserts of different tip shapes and sizes. The base unit processes the electrical energy and applies it to the inserts.
• The insert has a stack of metal plates at the base which is inserted into the socket of the base unit. The other end of the insert is the actual working tip.
• The stack is made up of metal strips sandwiched together. When the electrical signal is turned on, a low-voltage mechanical signal is generated in the handpiece, creating a magnetic field of fluctuating intensity.
• The metal stack acts like an attenuated antenna that picks up the magnetic field and causes a rapid vibration which is in turn transferred to the tip which shatters the calculus as soon as it comes in contact with the tip.
• These units generally operate at a frequency of 25,000 to 30,000 Hz. The tips of these instruments have four working surfaces and these four surfaces are active at different speeds with energy dissipation decreasing in descending order from the tip end, front surface, and the sides.
• The tips of magnetostrictive scalers have large amplitude of stroke which also results in a higher power. As the power or amplitude increases the patient comfort decreases.
• The tips are available in a variety of ranges and the thick tips can be used on higher power settings, but the thin tips should be preferably used only with a very low power setting.
• The larger tips make it pretty difficult to access furcation areas and hence Dentsply has introduced a slim line series of tips to be able to access such areas.
• Of all the classes of power scalers, these generate the maximum amount of heat. Close to 60% of the electrical energy is lost in the form of heat energy.
• A result of this great amount of heat production is the necessity of a copious amount of water for the purpose of cooling the tip.
• A positive fall out of the copious water is the cavitation and irrigation of the pocket during the debridement.
• Cavitation is the phenomenon by which numerous bubbles eventually collapse, producing shock waves in the liquid causing the cavitation with a flshing action.
• This cavitation has been known to demonstrate cell-wall rupture, which results in removing deposited bacterial endotoxin from the root surface.
• Units are available in which the water can be replaced by a medicated solution to be delivered into the pocket while debridement from an attached reservoir.
• A negative effect is the aerosol that is produced requiring high-speed suction units and controlled asepsis.

Piezoelectrical Scalers

• This class of scalers use a crystal system to transfer electrical energy directly to magnetic energy without any magnetic interface.
• The scalers have a Piezo ceramic drive mechanism that produces a horizontal tip movement in a back-and-forth stroke.
• The handpiece of this class of scalers is the most ergonomic in utility.
• The units have crystals within the handpiece that become distorted by the incoming electrical current to create vibratory energy which is translated to the insert tip.
• There is almost no loss of energy in this process and hence negligible heat production. These scalers are the first scalers to have the potential to work at frequencies of up to 45,000 Hz but generally are available at field frequencies of 32,000 Hz.
• Since these tips vibrate in a back-and-forth linear motion, only lateral surfaces are active.
• This requires a little bit of experience in adapting the tip surface properly so that the inactive areas are not pressed on the tooth surface.
• The scaler creates a vortex action in the periodontal pocket, allowing the cavitation to progress beyond the tip.
• The vibratory motion generates a clean tip motion without creating interfering vibrations at the lower powers.
• This avoids a hammering effect against the root surface while increasing patient comfort. The crystals expand and contract about 30000 times per second.
• The technique is so important that the more the lateral force used, the less effective is the instrument due to the decreased vibratory action.
• A practical idea is to use the tip more like a probe rather than a traditional hand scaler or curette. Newer tips are fiery and shaped more like a probe for easier utility.

Indications

• Efficiently removes supragingival plaque and calculus, stain, and some subgingival calculus. Removal of these deposits is quicker than with hand instruments, with less operator fatigue.
• Useful in early phases of treatment when the tissue is hemorrhagic.
• Used in periodontal surgery to enhance the speed and completeness of root debridement.
• Washed field also makes the instrument convenient for calculus removal during periodontal surgery.
• They are useful in the treatment of ANUG and pericoronitis.

Contraindications

• It is contraindicated in patients with older pacemakers because of the danger of interfering with the electrical mechanism of the pacemaker. Newer pacemakers with increased shielding may eliminate this concern.
• Patients with AIDS, tuberculosis, and hepatitis should be treated with great caution because of aerosol production in the treatment room. A thirty-fold increase of airborne micro-organisms in the treatment room is produced by ultrasonic scalers.
• In small children.

Limitations

• The working tips are bulky making them difficult to use in deep periodontal pockets.
• Tactile sensation is very limited because of the bulkiness of the tips.
• Water spray necessary to control heat production makes indirect vision with an intraoral mirror difficult.
• Noise production from the ultrasonic scaler is disliked by some patients.
• Others may experience root sensitivity.
• The vibrations have been shown to disrupt the tissue by lifting of the epithelium and dismembering the collagen in young, growing tissue.

The EVA System

• The most efficient and least traumatic instruments for correcting overhanging or over contoured proximal alloy and resin restorations are the motor-driven diamond fies of the EVA prophylaxis instrument.
• These fries, which come in symmetric pairs, are made of aluminum in the shape of a wedge protruding from a shaft. One side of the wedge is diamond coated and the other is smooth.
• Th fies can be mounted on a special dental handpiece attachment that generates reciprocating strokes of variable frequency.
• When the unit is activated inter proximally with the diamond-coated side of the fie touching the restoration and the smooth side adjacent to the papilla, the oscillating fie swiftly planes the contour of the restoration and reduces it to the desired shape.

Question 6. Describe the surgical instruments.
Answer:

Surgical cutting instruments may be classified into fixed-blade instruments and removable-blade instruments.

Removable Blade Instruments: This includes Bard Parker handle (BP) with Swan-Morton blade Nos. 11, 15,15c, and 12.

• Blade No. 11 is used for stab incisions
• Blade No. 15 and 15c is used for incisions for reflect the flip
• Blade No. 12 is used for pericoronal incision.

Fixed Blade Instruments

• Kirkland knives:
  • They are available as single-ended instruments or double-ended instrument.
  • The entire periphery of this is used for the cutting procedure. The knife is generally used in gingivectomy procedures.
• Interdental knife: They are sphere-shaped knife that has both ends as cutting edge. They are used in the interdental area. They are single-ended and double-ended instruments. For example, Orban’s knife, Buck’s knife, Waerhaug’s knife.
• Periosteal elevator:
  • They are used in the elevation of the flip and retraction of the flap after the primary incisions are made.
  • The healing of the periodontal wound is critical for the success of the operation. This depends upon the handling of the flip during-periodontal procedure.
  • For example, Goldman-fox No. 14, Glickman periosteal elevator.
  • Other surgical instruments include but are not restricted to artery forceps, needle holders, bone fies, and suturing materials.

Conclusion

• In conclusion, power-driven scaling technology far greatly outweighs routine hand scaling and it is a likely possibility that very soon the hand scalers will be universally consigned to the archives.
• This, however, does not apply to curettes and root planning as of today but even this tenet may well give way in a few year time.