Dental Instruments are used to examine, clean, cut and restore teeth
Main types are:
Hand-held instruments
Rotary instruments
Auxilliary instruments
1) Hand instruments Examining the mouth and teeth
Scalers
Cutting teeth and removing caries
Placing and condensing restorative materials
Carving and finishing restorations
miscellaneous
Hand instrument designMost hand instruments are made of
stainless steel or carbon steel (incase of some cutting instruments) and Teflon-coated
Some chisels and scalers have tungsten carbide tips brazed to the cutting edge. This helps them retain their sharpness for much longer
For increased effectiveness, the working surface of the instrument must meet the surface at an angle
This facilitates in the access to awkward places where approach is impossible with a straight instrument
One, two or three bends in the shank of the instrument may be present to improve access by off setting the working tip
Instruments with the working tip in line
with the handle are most easy to use
Design of the handle is related to the purpose of the instrument
Light weight with small diameter handles used primarily for tactile and exploratory purposes. E.g. Probes
Heavier, with larger diameter handles are designed to transmit heavy pressure and which will be held for a longer time. E.g. scalers
Cutting instrument names Black classified all instruments by name
By 1) function e.g. scaler, excavator
By 2) manner of use e.g. hand condenser
By 3) design of the working end e.g. spoon excavator, sickle scaler
By 4) shape of the shank e.g. mon-angle, bin-angle, contra-angle
Combing all together, bin-angle spoon excavator
Cutting instrument Formulas Black also developed a numeric
formula to characterize the dimensions and angles of the working end
These help in identification and assistance in cataloging and ordering
Formulas are placed on the handle using a code of three or four numbers separated by dashes or spaces e.g. 10-8.5-8-14
1st number—indicates width of the blade or primary cutting edge in tenths of a millimeter (0.1) e.g. 10=1mm
2nd number—(of a four number code) indicates primary cutting edge angle…measured from a line parallel to the long axis of the instrument handle in clockwise centigrade
Angle expressed as a percent of 360 degrees e.g. 85% x 360 degrees = 306 degrees
Instrument is positioned so the number always exceeds 50
If edge is locally perpendicular to the blade then this number is normally omitted, resulting in a three-number code
3rd number (second number of a three-number code)—indicates blade length in millimeters e.g. 8=8mm
4th number—indicates blade angle, relative to the long axis of the handle in clockwise centigrade, e.g. 14 = 50 degrees
The instrument is positioned so that this number is always 50 or less
In some instances, an additional number is present along with the formula number on the handle
It is simply to assist the specific manufacturer in caloging and ordering
Using hand instruments
1) Pen grip Most frequently used
Middle and ring fingers used for support
Allows fine controlled movements with light or heavy touch
2) Palm grip
Instrument held between thumb and forefinger
Handle lies across the palm and clasped by remaining fingers
Thumb used for support
Greater control than with pen grip when using on maxillary teeth, providing heavier force over a limited range of movement
3) Finger grip Modification of palm grip
Of limited value
Used when palm grip fails to give correct line of access
REMEMBER ! All instrumentation must be
accompanied by finger or thumb support upon adjacent firm structures, commonly, crowns of the adjacent healthy teeth
Thumb and third or fourth fingers of the hand holding the instrument most commonly used for rest
Provides for accuracy in fine movements, and safety in forceful manipulations
INSTRUMENTS USED FOR EXAMINING THE MOUTH AND TEETH
1) MOUTH MIRRORS
• Vary in size
• Flat mirrors most commonly preferred and used
• Two main types are:-
A) Front-surface reflecting
• Produce a clearer image particularly at angles
• Most widely used
• Easily scratched
• Care required during cleaning and sterilization
B) Rear-surface reflecting
• Reflective surface beneath the glass so image seen through the thickness of glass twice
• Hence, produces a double image
• However, resistant to damage due to glass surface
• FUNCTIONS
• Retraction of tongue and cheek
• View areas not visible by direct vision
• Reflect operating light to dark areas
2) PROBES
• Mainly used for diagnoses with care taken by the operator
• Types and functions :-
• A) straight probe (actually bent)
• Checks the margin of restoration
• Examination of caries in dentine during cavity preperation
• Helpful if sharp
• B) Briault probe
• Sharp probe
• Easy access to enamel-dentine junction during cavity preparation
• For detection of subgingival calculus
• 3) periodontal probe
• Blunt with small ball at the end
• Marked with graduations to measure depth of periodontal pockets
• May measure the width of a tooth when a temporary crown is to be fitted
• Other types are:- CPITN and FURCATION
SCALERS
Used for removing supra and subgingival calculus and other deposits from teeth
Useful for removing temporary crowns
INSTRUMENTS FOR CUTTING TEETH AND REMOVING CARIES1) EXCAVATORS
Have discoid or ovoid blade
With margin bevelled to a sharp cutting edge
Functions:-
For removing soft dentine
Removing temporary fillings
For placing lining with its back surface (blade)
Sometimes for carving amalgam
2) CHISELS Straight and angled chisels are used
for splitting off unsupported enamel
Gingival margin trimmer is a double ended instrument with curved blades and a sloping cutting edge
Used to trim margins of small cavities adjacent to other teeth where access for rotary instruments is limited
3) HATCHETS AND HOES Similar to chisels in design and
function
Always angled or contra-angled
Hatchets—cutting edge is in the plane of the shank (like and exe)
Hoe—cutting edge lies in an axis at right angles to the shank
INSTRUMENTS USED FOR PLACING & CONDENSING RESTORATIVE MATERIAL1) PLASTIC INSTRUMENT
Stainless steel material for general use
Teflon coated or titanium nitride for composite use. Prevents sticking of the material & not scratched by composite filler particles
Flat blades—used for conveying and shaping materials which do not involve the use of particularly heavy pressure
Round ends—used for pushing materials into cavities and for shaping and burnishing
Heated for use with certain materials like wax
2) CONDENSERS OR PLUGGERS
Used for compressing and forming filling materials, particularly amalgam
Used with heavy pressure
Variety of shapes and sizes available for use in different situations
End may be smooth or indented
Smooth version preferred as indented may become clogged with old amalgam
3)CARVING AND FINISHING INTRUMENTS
Used for carving materials by cutting or scraping
Have sharp or semi-sharp blades of various shapes which is very important
Also important is their smoothness
MAINTAINING HAND INSTRUMENTS SHARPENING HAND INSTRUMENTS
Instruments will only cut properly if they are sharp
Steel instruments with bevelled edges, like chisels, can be sharpened on a small flat sharpening stone OR on a mounted stone in a hand piece
Light machine oil used as a lubricant
Instrument held to produce a 30-45 degree bevel
A fine edge initially cuts better but rapidly becomes better
Alternatively, fine abrasive disc can be used which are ideal for probes, excavators and scalers
Light pressure used with no lubricant
Over heating must be avoided
This removes metal rapidly and gives coarser finish to the edge, but has the advantage of speed
Tungsten carbide instruments retain their sharpness for much longer than steel instruments, but when they become blunt, they have to be returned to the manufacturer for sharpening
STERLIZING HAND INSTRUMENTS
Stainless steel, tungsten carbide and Teflon-coated instruments can be autoclaved
Carbon steel instruments, if autoclaved and left in a wet condition, will corrode
Hence, it is ideal to autoclave them in a post-vacuum autoclave
This leaves the contents dry at the end of the cycle
Top Related