 See, there are the different types of drill, the basic one is hand drill, very oftenly what we are using everywhere, what is that specially in India, so specially for chronic subdural hematoma where you wanted to evacuate immediately, you have to use a drill, those time we used to drill the outer cortex for putting this clamps, now that is all thing over now self tapping system which has come that is all vanishing. So hand drill is very rarely we are using it, the other two is pneumatic and electrical drill that is all high speed drills. So there is no typical definition for what is the high speed drill or what is the limitation for that. So whether there are so many studies which are there what is high speed drill and why it is called low speed drill, see when you are drilling the thing there is a generation of heat that is transported into the bone. So when it is transported into the bone, so because of heat there is a necrosis of the bone, when you are drilling there may be micro fracture of the drilling site. So over a period when the heat when it is there may be immediate necrosis, I will show you the what are the experiments they have done, it is actually it is not the work of medical person, it is all engineering studies, you do not get a referral very often only in the medical literature. So this high speed drills usually in the dental they use 3600 to 7500 RMP rotation per minute, orthopedics 60 to 800 because they put only a holes, they are not clearing the body of the spine and all, later on I will come to for that also. And neurosurgery hours is the one we use high speed drill, but we do not bother about the bone, we are drilling it and we are removing it, whereas when you go for the spine that is very very important, where when you are putting the screw here it has to hold. So if you use the drill there what will happen there. This drilling is not the today's one, since ancient see when you go through literature especially Egypt in literature when they have studied this skull there is large junk holes in the skull. So especially that is Egyptian thing, the literature wise still it is there is the Egyptian, then Greek romance when they have studied this skull they have found this openings. Then from 19th and 20th century only that has become modernized, so bone still starting in 1850 for fracture long bones especially orthopedic paper they were using, then we have applied cranial part also. So when you are drilling, so how long you can drill and how much energy will be liberated. See there, see if you continuous drill without any water irrigation it will create 82 degrees of centigrade temperature, see 82 degrees is not a simple one, so it will cause neck crosses, immediate neck crosses of the bone, when you irrigate with the ringer lactate it will comes down to 42 degrees, when you further reduce cold water when you use it will come to 22, okay this is the one that is experimentally which is studied by engineering students. Then when you start doing with the intermittent drilling, see you give some time not a continuous one, when you do intermittent drilling, so the temperature without irrigation it will create 66 degrees centigrade, then with the saline it will come drop down to 35, then with a cold saline it will come to 21 degrees. See when you drill how the temperature will be dissipated, so by way of conduction by way of convection or by radiation, so when electric energy when it is going it will cause electromagnetic field that will pass on to the bone. See this is the way they have shown how internal irrigation and external irrigation, internal irrigation means there is a inside only there is a halo, so through that water will be passing through at the site of irrigation, external irrigation means what we are doing in routine practice it is all external irrigation. This is what are the types of drill bits if you use, how it causes damage to the bone, this is the one higher the speed this speed versus the time, why we are all interested in high speed drilling, when you use high speed drilling that time becomes less, so the temperature created during that time is less that means the bone contact with the temperature will be less that is why always high speed high speed. See when you go with the low speed you are in touch with the bone for a long period, so that tissue will be exposed to the temperature for a long period, there the chances of necrosis or more or damage to the cell apoptosis can cause or sometimes there will be a micro fracture when you put the screw into that it may get loose and over a period or it may pull out because of this necrosis of the bone. This is the one they have studied depending upon that they have given a very good curve temperature versus time see that more than 70 degrees is absolute that is contraindication which causes death of the cell, so when you go at the 45 or a 50 there will be no damage to the soft tissue, even neuronal tissue also they have studied at 45 degrees damage to the neuron will be very very negligible, this is the one what I have told this one. So when we drill the things see we put a water the water acts like a lubricant whereas in a machine and all these things they will put a oil to reduce the temperature, so here also when you are drilling it the dust which is formed it clogs around the drill bit through that also temperature can pass into the normal tissue, so always irrigate, so heavily you have to irrigate do not allow any dust to accumulate there, so accumulation which causes damage to the normal tissue, so they have studied in this graph you see nicely see when they are putting water see this is the water 0.5 that is in liters that is the temperature see when you put a more water see per minute so much of water you have to put into the drilling site, so there the temperature will be maintained at 40 degrees only, when you are drilling the trans particular why the failure rate and all these things may be because of this we do not know, so when you put a less water and the temperature it rises see the relation okay see the when the irrigation site if you water level is more then temperature transmission is very very less, when the water irrigation site is less see how temperature rises and we do not know what we say nothing is we are not done properly and all where we are done is the drilling problem, so the temperature created there is more than 70 degree centigrade that too it is not the far in it or anything specially vagus spasm when you are drilling around the nerve or a heart rate, so you should take care of very very care when you are drilling it, so even I was not knowing it when you are given a subject I was studying this engineering books, so this is the one what is the relation when you are doing it, what is the use of water say our resident may sleep off and I am drilling it, if you see a whole blockish things we may see then when you say poor poor water means what by that time we have called the injury when you are perforating a bone, when you are drilling the bone both are different perforating a hole you are making it, there the contact with the tissue is more, this is studied by a engineering students in operation theater and experiments even how they have studied also this is the one see how the things which is transmitted it is not a visual appreciation see how they have computed see how they have monitored the thing, this is the one why our instruments say one is hand control drill another one is foot control drill very often we have a foot control drill rather than some period they were supplying with hand control that is also is good very high speed 70,000 RMP, so once you touch it it will take out the tissue I think this is the one nature motor and that is the tip is the drill bits there are different types of bits which are available again they have studied in each bit what is the generation of heat and monitor and usually why when this soft tissue when it is comes why we have to use diamond drill why not cutting drill bits again the tissue around that damages they have studied that is the one temperature when you use this one regularly diamond drill and also cutting drill the temperature released from that it is little less that is around 45 degrees and all I and foot what is the coordination all three has to be there I hand and foot this is only hand control you are seeing it and you can control that but now they are not manufacturing what is that hand control before it was coming so when you are correlating also when we are doing endoscopy I hand and foot one person has to do all the things this is your drilling with the hand also you should be very good in coordination also and foot to control also all the three you should concentrate over what you are doing it now you are doing like this one more if you have a this is the clip they have control list so the area of occupation is more and visibility at the end will be less see the motor is size is big as you go down it is the tapering and at the tip level so here the size will be more so here it is very now straight forward and foot control and you may not be holding wall with your hand only like a pencil you will do