hey everyone ryan here and welcome back to our operative dentistry series in this video we'll cover everything from hand instruments to hand pieces and burrs used in operative dentistry so put on your seat belts and let's get to it so the two main categories of dental hand instruments are non-cutting and cutting instruments this is certainly not a list of every dental instrument out there but the ones that are most commonly used and that'll come up on the board exam in the second half of the video we'll talk about hand pieces which fall into their own category so dental hand instruments have three main regions the handle which is represented here by the letter c is usually about six millimeters in diameter it can be eight sided like the one shown here or it can be round and sometimes it has a ribbed grip like you see here or it can be smooth and flat the shank is represented here by the letter b and the shake may have one or more bends in it you see one bend right here and then another right here and that allows the working end which we'll talk about in a second to be aligned with the long axis of the handle and so the working end is represented by the letter a and it should lie along the long axis of the instrument for the best balance and control so you can see and appreciate how that aligns up pretty well with the long axis of the rest of the instrument there and the working end either consists of a blade and a cutting edge or a nib and a face so the blade and cutting edge refers to terms for a cutting instrument nib and face for a non-cutting instrument so if we look at these diagrams up here the nib refers to the entire hook part of this dental explorer which is a non-cutting instrument the face refers to the little point or the explorer tine at the very end of the instrument that's the part that's contacting the tooth or the restorative material for cutting instruments we have different terminology the blade is the actual cutting part of the instrument so that's this entire portion right here and even more specifically the cutting edge is the tiny little edge the specific sharp part that contacts the tooth or the restorative material so the handle is what you hold the shank is for transition and the working end is what actually does the work so now we can talk about some specific non-cutting dental hand instruments so first we'll talk about the dental mirror this small angled mirror allows you to see areas of the mouth that otherwise be difficult or impossible to see for example the occlusal surfaces of the upper molars or lingual surfaces of the upper incisors would require you to have the patient sitting way back and you'd likely have to twist your neck somehow to get a clear view but the mirror makes this a lot easier we call this ability to look at oral structures using the mirror indirect vision as opposed to direct vision where your eyes can look at the tooth or structure of interest directly the dental explorer provides tactile sensitivity to detect if margins of restorations have good integrity with the surrounding tooth structure the margins of crowns fit well to the tooth and there are many other uses historically they've been used to detect carries but doing so too roughly can actually transition an incipient lesion to a cavitated legion like we talked about in the previous two videos so we have different variations of the explorer the shepherd's hook may be the most commonly used also a number also called the number 23 explorer this is the classic curved end again most commonly used today the back action explorer or the number 17 is this flatter shorter hook which is great for detecting uh inner proximal areas if you're detecting margins of restorations between teeth and also for detecting sub-gingival calculus lastly there is the number two or pigtail explorer which curves under and around and can be preferred by some providers for detecting crown and restoration margins again there are more out there but these are among the most common and commonly tested the periodontal probe is used to routinely measure pocket depths and they can be used to measure other things like the width of teeth the amount of overbite of a patient etc there are different versions of this as well the unc 15 probe measures up to 15 millimeters each mark here it's kind of small to see but each mark represents one millimeter and the bigger hash marks here represent four to five millimeters nine to ten and the final increment fourteen to fifteen the williams probe has little marks at one two three it skips four goes to five skips six and then seven eight nine ten and the marquee probe shows three millimeter increments zero to three is this first silver part then three to six is this thick hash six to nine nine to twelve etcetera the amalgam condenser is used to condense amalgam into the depths and corners of a cavity preparation to ensure that there are no voids in the material it can be also used for condensing composite in much the same way remember we're still talking about non-cutting instruments here so this part the working end of this instrument is going to be called the nib and it's the portion of the condensing instrument that does the work and the face is the actual end of the instrument that comes into contact with the restorative material being condensed this part is usually smooth but it can also be serrated the ball burnisher is one of my personal favorite it typically has two ends a small round end and a larger football shaped end and it's really great for burnishing and even carving the surface of an amalgam restoration before it completely sets to give it some contour and anatomy or it can be used in a similar way to smooth out the occlusal surface of a composite restoration before it's cured all right so that's a brief overview of some of the most common non-cutting instruments let's talk about some cutting dental hand instruments this time and we'll look at most of the in fact we'll look at all of the instruments listed here on this slide it's a bit of an over generalization here but this is generally what each of these categories of instruments applies to and works on and i find it help as a helpful memory tool for the board exam just to keep this in the back of your head so scalers are typically working to remove calculus from teeth excavators are typically used on removing carious dentin or at least working on dentin 2 structure chisels for removing unsupported and or friable enamel and the other category typically these are going to be used for modifying the restoration of some sort others basically a category i threw together of a couple instruments that we'll mention at the end of this section of the video all right we can now introduce a formula that describes the dimensions of the working end of most cutting instruments i see this come up on the board exams quite frequently so let's spend some time unpacking and really understanding this concept so the formula consists of four numbers the first number corresponds to the width of the blade in tenths of a millimeter so a number ten a number of ten means that the blade is one millimeter wide so if we're looking at the width of the blade we're talking about this dimension right in here so again a number of 10 for this number refers to one millimeter width of the blade which is quite common and also is the case for the instrument pictured here so we'll write 10 down here for the first number the second number refers to the angle of the cutting edge to the long axis of the blade so this one is a little bit more involved the cutting edge is here the actual part that's contacting the tooth or restorative material and the long axis of the blade runs up here i apologize for not a perfect straight line there but you can see what i'm going for there so the angle between these two lines is a perfect 90 degrees in this case so for this we would just write 90 for our second number that's the angle between the blade and the cutting edge but if and only if this is 90 degrees we can actually omit the second number from the formula and that's because 90 is the most common most of these instruments are going to have a blade that is perpendicular to its cutting edge so we don't we can omit that number and we just assume that that angle is 90 degrees otherwise we have to list what that angle is all right let's move to the third number this simply corresponds to the length of the blade so that's going to be this dimension right in here and so it's simply simply listing the length of the blade in millimeters so this one's nice and easy the blade happens to be seven millimeters long so the third number we just write seven and finally the fourth number we get a little bit more complicated again and the fourth number corresponds to the angle of the blade relative to the long axis of the handle so remember the second number was the angle of the cutting edge to the long axis of the blade now this is the angle of the blade to the long axis of the handle or the entire instrument so because there's a lot more variation in this number it can literally be anywhere between 0 and 360 degrees so this one is reported not as an angle but as a percentage of 360 degrees so if this number were 10 let's say that would signify 10 percent of 360 degrees which means the blade would be 36 degrees off axis this instrument's four fourth number happens to be 14 which would correspond to 14 percent of 360 degrees which is about 50 degrees so the angle that this blade takes relative to the long axis of the handle which runs this way this angle right in here happens to be 50 degrees so we don't write 50 we write 14 which represents 14 of 360 degrees so if you can remember what each of these numbers just kind of generally represents that will be enormously helpful on the board exam and the idea behind all of this is that if you know the formula of a cutting instrument you can visualize and identify what kind of hand instrument it's describing and the board exam will sometimes even refer to the specific formulas so i'll include them in the slides for each of the following instruments we discuss but if you got nothing else out of this slide just remember the kind of this part of the descriptions and that will be enough to net you at least one or two questions when they ask about what a specific number of the formula refers to and here's just another way of looking at it and we just broke this down a bit more simply so let's start with the dental scalers and we'll actually start with an exception the scalars that are used to remove calculus are one of the few cutting instruments that don't have that four digit formula in fact they follow a different numbering system entirely that we discuss more in depth in the periodontics series if you're interested in that so scalars usually are sided and each working end has two cutting edges to it and they adapt closely to the two surface and remove calculus from the crown or the root surface there are universal types that can be used anywhere in the mouth and then specific types like gracie instruments that are designed for specific teeth and areas in the mouth down here we have another categorization sickle scalers are scalars that have sharp points at the end of their blades and they are used for calculus above the gum line or super gingival calculus so that you don't accidentally shred the gum tissue if you drive that sharp point subgingivally curettes on the other hand not pictured here have rounded edges and are used for calculus below the gum line because you have less risk of damaging the soft tissue spoon excavators are used for gentle and controlled carries removal their formula is 11.5714 and now you know what all that is talking about the second number is omitted because the cutting edge is perpendicular to the blade as it is in most instruments some operators like using small controlled movements with the spoon excavator to scrape carius denton with the spoon-shaped paddles of this excavator and this is most useful for very soft infected dentin removal the black spoon is just a larger more robust version of the spoon excavator it can be also used to burnish metal like a toefl meyer matrix band or the margin of a gold crown with the rounded back of this black spoon working end you can notice how this first number is larger 15 referring to the blade width being 1.5 millimeters as opposed to a little bit less in the spoon excavator the enamel hatchet is a double-ended cutting instrument used for planing walls of enamel and the bevel on one end of the instrument planes the facial wall and the bevel on the other end of the instrument planes the lingual wall here's a close-up view of what that process might look like in part of the cavity preparation process the bin angle chisel is also a double-ended cutting instrument used for planting walls of enamel it's called bin angle because there are two angles in the shank we can locate one here and one here and that's to allow for the proper orientation of the blade for optimal control and balance when using this instrument it's similar to the enamel hatchet and function but this blade happens to be perpendicular to the blade of the enamel hatchet so it enables use in the other side of the mouth or in areas that an enamel hatchet simply cannot access so if we compare this directly with the enamel hatchet you can see how this blade you can kind of see the face of that blade whereas this one is parallel to the screen or perpendicular to the screen i should say so that you can notice that those two blades are perpendicular to each other the gingival margin trimmer is similar to the enamel hatchet except this instrument is designed for planting enamel at the gingival floor of a preparation rather than the facial and lingual walls like the two instruments we just talked about and don't worry we'll talk much more about the anatomy of a cavity preparation including the external and internal walls in the next video in this series so the cutting edge of this instrument is most importantly not perpendicular to the long axis of the blade so this is one of the times when there will be a second number in this four digit formula for the distinct two versions of this gingival marginal tremor so the distal margin trimmer is has a number a second number that's greater than 90 which is for a gingival floor on the distal side of a tooth the mesial gingival margin trimmer has a number less than 90 which is for the gingival floor on the mesial side of a tooth so just remember for the distal you're going to see a number greater than 90. for the mesial version of this instrument you're going to see a second number less than 90. the main difference and benefit of the gingival margin trimmer over the enamel hatchet is that angle of the cutting edge which allows for for you to properly bevel the gingival floor and again we can talk about more of that in the rest of the series so you can appreciate how this enamel hatchet again that cutting edge is perpendicular to the long axis of the blade whereas that is not the case if we were to follow that long axis to the blade this cutting edge is not perpendicular and nor is this one and this is showing the two different variations of this instrument depending on which side of the tooth you're working on all right next we have the discoid cleoid carver which is yet another double-ended instrument it typically has a rounded handle and it's used for a carving and contouring amalgam the cleoid end refers to the claw-like end for carving grooves into the amalgam and the discoid end is this circular disc-like end for carving pits and fossa in the amalgam the holland back carver is a double-ended round handle instrument used for placing carving and contouring amalgam the two ends on either side of the instrument are oriented 90 degrees to one another all right so that's enough about hand instruments let's talk about how to hold them so a normal pen grasp involves holding a dental instrument with your index finger and your thumb and the instrument would rest on the middle finger supporting it your ring finger is used as a finger rest on a nearby steady surface to keep this hand stabilized however the board examiners and most dental providers today prefer the modified pen grasp which adds the middle finger to grabbing the instrument and so the instrument would then rest on the ring finger behind it this provides additional control for fine motor function and then you use both your ring finger and your pinky finger together for a stable finger rest a firm finger rest is necessary for stabilization of your hand so in the case the patient moves it around you essentially move with them because those fingers are directly and stably supported on one of their oral structures so you can rest on adjacent teeth or the maxilla which are the most stable structures the mandible is stable if the patient is biting on a bite block but otherwise they can freely open or close and again you will move with them if that's the case also maintaining a short working radius is important and that means that you grab the instrument more towards the working end so that your fulcrum is nearer to the working end for more control and more accuracy all right let's talk about rotary instruments now so we have the low speed or slow speed handpiece which operates at less than 12 000 rpms rpms are revolutions per minute and even though it's the slowest of these handpiece varieties 12 000 rpm is still pretty quick that's 200 spins per second and so it can easily injure yourself or the patient if you're not careful the low speed handpiece is used for cleaning and polishing teeth with a profi cup for finishing and polishing a restoration with a polishing cup or brush and perhaps most important for the board exam for carries excavation the board examiners love to ask about this that a large round bur in a slow speed handpiece is the best way to carefully remove affected dentin near the pulp here is the slow speed motor this is the latch type contra angle slow speed attachment for carries excavation and polishing and this here is the straight attachment for the profi cup for hygiene cleanings the high speed handpiece is used for tooth preparation whether that be for caries removal for crowns removing old restorations and many other procedures that require quote unquote drilling teeth they usually have a fiber optic light and an air water spray built into the unit the medium speed handpiece is not routinely used but it can be used for the same applications as the high speed though not quite as efficient and notice how the high speed operates at greater than 200 000 rpm so you can imagine how quick that burr that's going to be inside that handpiece is going to be rotating the medium speed operates between these two thresholds for low and high speed the rheostat is this foot pedal that's used to control all of these handpiece varieties often with variable speed depending on how hard you push down on this foot pedal the switch right here turns the water on and off when you're using a high speed hand piece so burs that you load into the hand pieces have their own anatomy of course more terminology but there's an overlapping term with hand instruments that can be kind of confusing so let's break this down real quick a bur consists of a shank which does not serve the same purpose as the shank for hand instruments so the shank here is the part of the bur that is inserted into the head of the handpiece so that's the part that's going inside this area of the handpiece the neck is the part which transitions to the head which is the actual cutting part of the instrument that does the work the first of these is a high speed bur the second of these is a latch type slow speed bur so burs or created and we had two main categories of these diamond burs historically called diamond instruments and not burrs but we're going to call them and collapse them into the greater category of burs because that's what the ada and manufacturers have done so let's talk about the carbide burs first they're made of tungsten carbide and this is what they look like they come in a variety of sizes and shapes and because of their material and design they are better for end cutting so they're better for cutting at their ends like for punch cuts to start a preparation they also create a smooth preparation wall they're good for amalgam removal and for creating retentive features they also tend to produce less heat the diamond burrs on the other hand are are better for side cutting although you can use either of these for end and side cutting of course but if we're being technical and talking about things that the board examiners like to ask they are better for side cutting and are therefore preferable for preparations bevels and enameloplasty due to the greater hardness of diamond and the more effective cutting overall but as a downside it generates more heat and they are way more expensive interestingly for carbide burrs the amount of blades corresponds to its function so if we start with six blades that is a typical cutting bur but if we go up to 12 blades that is a finishing bur so it's going to cut less but it's going to cut smoother so it's great for finishing a restoration getting towards that polishing final state if we add even more blades to the mix we're getting into fine and ultra fine finishing burrs so you can think of it like this the more blades that you have the less to structure each of those blades is going to be digging in so more blades means a smoother cut and less blades is more aggressive and more cutting efficient for diamonds similar policy but the finer the grit of the diamond the less aggressive the burr will be the coarser the grit of the diamond the more aggressive it will be so let's talk about some specific burrs commonly tested on the board exam and i mean these come up all the time the 245 burr pictured here on the left is three millimeters long and point eight millimeters in diameter i wish i had some kind of memory trick for you but i promise you memorize this if you can it will certainly show up on test day so three millimeters long this part here point eight millimeters in diameter it's described as being pear-shaped or inverted cone sometimes it's called an inverted cone design and it has these rounded corners along the bottom and sort of tapers up towards the sh towards the neck of the instrument the 330 burr pictured on the right is half the length of the 245 so it's only 1.5 millimeters long but it's the same diameter it's sort of an optical illusion here but this is actually the same diameter it's still 0.8 millimeters in diameter and it's the same shape pear-shaped or inverted cone the smaller size is helpful for pediatric preparations so it's an often a go-to for your primary tooth cavity preps and lastly we have the 169 elbow another commonly chosen one this is a tapered fissured design it tapers down this way as you go towards the neck of the instrument and it's preferred for this thin thin tip of the burr that's used for creating retentive features secondary retentive features and we can talk more about slot design in the next video so 245 330 most commonly tested 169l sometimes gets tested for its unique shape and lastly some hazards that we need to talk about for these rotary instruments i mentioned even the slow speeds are operating at relatively quick speeds and so you can easily damage tissue if you're not careful so some things to keep in mind the pulp is at risk due to the vibration caused by the instrument heat generated particularly from diamond instruments and desiccation so it's always important if you're operating at high speeds you're generating a lot of heat we want to rely on that air and water spray from the handpiece and also making sure that everything is well isolated so that we don't slip and damage soft tissue the lips the tongue and the cheek are all examples of nearby soft tissue so using cotton roll isolation rubber dam isolation using firm finger rests operating with your fulcrum near to the working end of a hand instrument all of those are great practices to eliminate potential hazards also we have to protect our eyes we use glasses with side shields protect our ears we have potential hearing loss which depends on the intensity of the loudness the frequency of the sound the duration of the noise and the susceptibility of the individual these hand pieces can get quite loud and if you're using them all through the day monday to friday you're going to be i'm experiencing quite a lot of uh duration of noise so that's something to keep in mind as well and of course inhalation risk these things i'm sure we're going to get some changes in our ppe after this coronavirus pandemic but as far as the board exam is concerned for now things they like to know for you to know about is that the rubber dam protects the patient from inhalation and masks protect the personnel including the doctor and the staff alright so that's it for this video on instrumentation i know there's a lot of stuff to cover but hopefully you found it helpful and enjoyed listening so thank you so much for watching guys please like this video if you enjoyed it and subscribe to this channel for much more on operative and all things dentistry if you're interested in supporting this channel and what i do please check out my patreon page thank you to michael raja reb boyd riawadwa jonathan muff david jaden isabella caldis ali bensteer badir hefnawi and all my patrons out there for their support you can unlock extra content like access to my video slides if you want to take notes on them and additional practice questions and explanations for the board exam so go check that out the link is in the description below thanks again for watching everyone i'll see you in the next video