cons sheet # 3 - by Ruba Jassar

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cons sheet # 3 - by Ruba Jassar

Post by Shadi Jarrar on 8/10/2010, 5:23 pm

بسم الله الرحمن الرحيم

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بسم الله الرحمن الرحيم
Instruments Used In Operative Dentistry
Cons Lec 3
Mon, 4/10
Dr. Sahar Taha
*** please check the slides esp. the figures while studying this sheet.
*** most of this lecture was reading the slides literally so only explanations and notes will be written.

- We have great variety of instruments but we’ll only cover the major ones
- The main part of operative dentistry that’s developed continuously is its instruments, while the science itself doesn’t change.
- In general, dental instruments are categorized into:
 Hand instruments: used by hand with no electricity, and includes cutting & non-cutting.
 Powered instruments
Hand Instruments
- G.V Black was the one who invented the classification of dental instruments that’s used till now.
- Hand cutting instruments are mainly made of:
 Carbon steel >>> has advantages over stainless steel since it’s harder and cuts more efficiently but the problem is that it’s hard to sterilize, so if u don’t sterilize it in a good manner it will ruin
 Stainless steel >>> it maintains its brightness but the problem is that it loses the sharpness of cutting edge more rapidly than carbon steel.
- Nowadays, modifications in manufacturing carbon steel are done using carbide inserts which is carbon bounded to or coupled with another material such as tungsten >>> Tungsten Carbide
- Tungsten Carbide is also hard plus that it’s easier to sterilize and keep bright
- Hand instruments are classified using name or numeric formula
- Design of hand instruments>>> regard their use, most are composed of 3 parts:
 HANDLE: the middle part that u grab by ur palm, it connects and supports the other parts
 SHANK: connects handle to distal end of instrument. Can be sraight or have small angle in it
 BLADE or NIB: blade in cutting instruments coz it’s sharp and nib in non-cutting ones

- The handle has different shapes >>> round, cylindrical, and sometimes polygonal.
- The shank can be made in several shapes too with different angles>>> according to Black’s classification depending on the number of bents: (see the figures in the slide)
 Straight
 Mon-angle
 Bin-angle
 Triple-angle
 Quadrangle
- Why do we need bents in the shanks?
• Recall that when we talked about the structure of teeth before we mentioned that they have different surfaces (buccal, lingual…) and some hidden areas, so in order to reach all surfaces and areas of all teeth in the mouth we can’t use straight instruments only. Thus, we need angulated instruments with bents to gain access of all surfaces.
• To maintain balance of the instrument>>> for an instrument to be balanced during cutting or during using it, 2 things must be proven in it:
1- Its shank must have bents
2- Its cutting edge must be in line with long axis or maximum 2-3 mm away from it (see the slide)>>> the tool on right has its cutting edge at long axis so it will balance, while the left one is away by 4 or 5 mm so it’ll imbalance>>>> i.e: orientation during work thus unability to control it.
So a tool must balance and work at straight line with no orientation

*** Operative cutting instrument formula:
- When u use any tool note that each has 4 digits at its sides, these numbers mean: (from left to right)
 1st digit: width of the blade in 1/10 mm
 2nd digit: angulation of cutting edge
 3rd digit: length of blade in mm
 4th digit: angulation of blade
- Note: cutting edge is the most distal part of the blade and it’s the part responsible for cutting
- Note: angles are measured by degrees and clockwise
- Imp. Note: when cutting edge is perpindicular to the blade, the 2nd digit will be ommited and that’s why we see only 3 digits on some tools.

*** Hand Non-cutting Instruments:
1- Instruments for examination >>> the basic set that’s used to examin any patient before starting, composed of:
 Mirror
 Explorer
 Cotton pliers or tweezers
 Periodontal probe
(read the slides because the Dr was just reading + the following notes)
- Recall that caries are soft, so when u feel softness on tooth surface using explorer this is an indication that there’s caries>>> this is the meaning of assessing integrity of surfacess
- Once u start cleaning the cavity u should remove the soft dentin, so to be shure that u removed all of it check using the probe (explorer) >>> assess hardness
- Periodontal probe has graduated mm markings >>> 1st band = 3mm, 2nd band = 3mm sooo we can measure 6mm, then 3rd is 3mm…… and so on (see the fig. to observe the bands)>>> each probe has its own markings so u have to check
- Periodontal pockets>>> recall that tooth is surrounded by gingiva, in btw tooth and gingiva there’s the gingival sulcus. Sometimes this sulcus increases due to periodontal diseases so we measure the depth using periodontal probe

2- Restorative hand instruments >>> used for teeth restoration
 Amalgam carrier
 condenser
(read the slides because the Dr was just reading + the following notes)
- Note that the amalgam carrier has one end that looks like blender, so u place the amalgam inside the tool and mix it using this end so it’ll exit from the other end.
- Condenser is used to condense amalgam….. WHY DO WE NEED TO CONDENSE THESE MATERIALS??
 To decrease ( ) phase >>>>>> CHECK IT LATER N$ALLAH
 Maintain mechanical properties of amalgam restoration by proper condensation
- Condensers have many shapes (round, oval….) and what we use depends on the shape of prepared cavity
- Larger condensers need more force to condense restorative material in cavity ( size, force) >>> this has to do with surface area according to Newton’s law.

3- Carving instruments >>> they’re used to carve the amalgam and smoothing it coz it mustn’t be left flt or out of shape
 Discoid-cleiod carver (one end looks like a disc>>>discoid, one end has pointed tip>>>cleiod)
 Hollenback carver
- Hollenback has more uses, not only for occlusal like Discoid-cleiod but also buccal, lingual….
- It’s better in axial carving than occlusal carving so for fine anatomical occlusal use Discoid-cleiod

4- Burnisher

5- Plastic instruments>>> specific for resin materials (composites, glass ionomer)
• Why do we use different tools with composites than with amalgam?
 Coz metalic tools are subjected to discoloration bcoz of composites since composites contain quartz as inorganic filler which is very hard so it makes scratches on metalic surfaces resulting in discoloration
 Composite is too sticky to metalic surfaces so must look for something that’s less or non-sticky

*** Hand cutting instruments
Hand cutting instruments are rarely used nowadays coz we use powered instruments that cut more easily and more efficiently.
1- Chisel
• Bevel: straight line or cut
• Chisels in fig. from Lt to Rt>>> bin, mon, almost straight, straight
2- Hatchet
• Looks like chisel but its cutting edge is in palne of handle and it’s used for cutting unsupported enamel
3- Gingival margin trimer
• Used for caries class2 and not used for class 5
• Looks like hatchet but curved blade rather than straight and cutting edge isn’t at right angle with long axis
4- Spoon excavator

*** Rotatory (powered) instruments
1- Dental handpiece >>> major improvement of modern dentistry
• Angled (contrangled)
 High speed
 Low speed
• Straight
2- Dental burs
>>> read the terminology from the slides
Dental handpiece
- High speed with low torque>>> u shouldn’t exert large force or pressure on it coz it tends to rotate easily and pressure will imbalance it.
- One complete unit>>> comes in one piece not in several pieces that u have to put togather
- Slow speed with high torque>>> gripping power should be more than high speed handpiece
- Although high speed cuts ore efficiently but low speed enables us to feel tooth structure and what we’re doing more clearly, that’s why it’s used for polishing and finishing
- High speed handpiece + friction grip bur
- Low speed handpiece + latch-type bur
- Straight handpiece has very limited applications in operative dentistry, mainly used in labs
Dental burs
- Made of different shapes, sizes, materials… but all have 3 parts: shank, head, and neck
- Note that it differs from hand instruments in hving neck instead of handle
- Classification of shanks
• Long shank: straight and long, used with straight handpieces in the lab
• Latch-type: note that this shank has one end with specific shape (see b in the slide) so u need to rotate it when placing it in handpiece (which is contra angle slow)
• Friction grip: called so becoz it is the friction that holds the bur inside the hanpiece unlike the latch-type where it’s hold by interlock. In general, it’s uesd with high speed but new low speed can hold them as well.
- Main classification of burs depends on head coz it can be made of different shapes, sizes… while shank and neck are almost same.
- The upper classification was according to shank, now this is according to head:
• Cutting>>> used in 1st procedures or at begining of cutting. It has 6 blades with distances in between
• Finishing>>> used in finishing steps (اللمسات الأخيرة) to smoothen walls of cavities. It has 12 blades or more and are close to each other
• Diamond
• Discs
• Finishing and polishing stones
- In general ther’s no universal numbering for burs (like 4 digits formula of hand instrument) each manufacturer has his own naming system but WHO tries to alssify them according to shapes and sizes
- U don’t need to know the sizes written in slides
- Straight fissure cross cut enables cutting axial walls since it has sharp sides
- Flared walls: walls are opening more toward surface

Done by: Ruba M. Jassar
Shadi Jarrar
مشرف عام

عدد المساهمات : 997
النشاط : 12
تاريخ التسجيل : 2009-08-28
العمر : 27
الموقع : Amman-Jordan

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