 Hello everyone, welcome back to another session in dentistry and more. Today's topic in conservative dentistry is pin retained amalgam restoration so usually Amalgam restoration we've been using the amalgam for many decades, but in recent time we have better products As restorative material because amalgam has many disadvantages. One is its color. It is not at all aesthetic and it is Requiring a minimum 1.5 mm thickness. So if it is less than 1.5 mm The strength will be marginally decreased. So it cannot be much recommended on class 2 cavities So if it is properly done on an ideal class 1 with proper 90 degree bud joint It may last or it will last for many years But if we are planning to do amalgam restoration on a weekly structure tooth or a grossly decayed tooth We need to give additional Retin T features So in that case one of the Feature is pin retained Amalgam restoration that is we are keeping pins within the restoration or within the dentine To provide the amalgam restoration more retention Because the tooth is in a compromised state because we are not able to provide proper walls So the retention provided by pin would be sufficient So that is what we are going to learn in today's session that is pin retained amalgam restoration The pin retained amalgam restoration is defined as any restoration requiring the placement of one or more pins in the dentine To provide adequate resistance and retention forms It is used whenever adequate resistance and retention form cannot be established with slots, locks, undercuts So this is the basic retin T features we give to the normal amalgam restoration So still it is not sufficient in those cases we can opt pins for the additional retention and resistance So it is nothing but placement of one or more pins to get the additional retention and resistance So it is commonly indicated for tooth with extensive carisofracture or it can also be used with cast restoration And the main advantages are the one thing is the conservation of tooth structure Then it saves time when compared to the cast restoration and it is economic And obviously it provides a better resistance and retention Whereas the disadvantages one is dental micro fracture or grazing So dental micro fracture grazing may happen because of the pressure which exerts by the pin to dentin And there will be micro leakage around the pin and it might decrease the strength of amalgam So there will be micro leakage and it might decrease the strength of amalgam And there can be chances of perforation of the pulp or external tooth surface So these are the disadvantages Now let us move on to the cavity preparation So the cavity preparation of these mutilated teeth through Excavation of carious dentin and removal of all undermined enamel So we need to keep the dentin floor must be sound and the rims of the preparation And the damaged area is then squared to resemble a shoulder finish line So we need to make it squared finish line Then the outline of the cavity is extend on to smooth and sound tooth structure Not on the undermined enamel Okay it should be on the sound tooth structure, the walls The cavity outline And we should make every effort to conserve the remaining tooth structure And there should be additional undercut can be given in the cavity walls So if this is a crucial cavity, so this is ideal Class 1 Okay So additional undercuts can be done in cavity walls Additional undercuts can be given So undercuts can be given Then the cavity depth is detected to determine the type of base should be used Now let us move on to the pins Okay So we have basically three types of pin The first one is cemented pin which is also known as mercilipins Which is larger than other pins and it uses sink first feed cement For the cementation It has got 3mm into the dentine and 2mm outside The second one is friction locked or tapping pins Which is smaller, which is actually retained by the resilience of dentine Because it has got friction There is no cement is placed here It has got the resilience of dentine is keeping it in its position So maybe it has increased retentive features and the cemented one But the problem is with the time when dentine relax There is chance of loosening of this pin So that is cemented and friction locked pins Now we have the self threaded pins It has got threads So threads in the pin So this is almost equal in dentine and outside there is 3mm and 3mm This is 2mm and 2mm It is self threaded pins It is available in different size It threads the threads which is present on the surface which engages the dentine It depends on the elasticity of the dentine Which is the most retentive one And there is less chance of corrosion But it create horizontal and vertical stress And it cause the dentinal crease lines Now we move to the TMS system There is ThreadMate system pins So we have pictures here Regular one It has got 0.031 inch diameter Then minimum It has got 0.024 diameter Then Minikin 0.019 inch diameter And Minuta which is 0.017 inch diameter So you can see the picture here So this TMS system available in double shear That is 2 pins in 1 And gold plated one stainless steel or titanium alloy Which we can insert it manually Or by using low speed Last type hand piece What are the factors which affects the retention of pin in dentine and amalgam So the first one is type of pin The type of pin So in type of pin We have self threading So this is the most retentive one Self threaded is the most retentive one And then we have friction Friction lock So it should be like this Friction lock And the least one is cemented one So this is the order of retention Most retentive is self threaded Then friction locked and cemented pins Second thing is surface characteristics In surface characteristics The number and depth of the elevation on the pin That is the serration or thread It depends on the retention So the self threaded pin has got more threaded surface It is giving greatest retention Then the orientation and number Orientation Orientation and number So if we have a non parallel pins It gives more retention So non parallel pins If the pins are like this It gives more retention And bending of pin is not desirable It should be straight So if bending is there It will interfere with condensation of amalgam And it results in weaker pin And also create fracture in dentine And if we have more number of pins More number of pins It results More retention But problem is more Crazing and fracture chance Decreased amount of dentine available And decreased amalgam strength Next we have the diameter of pin So if we have greater diameter It will increase the retention Diameter Diameter is high Retention also will be high So the danger of perforation On pulp or external tool surface Is there when we increase the diameter And it interferes with condensation Of amalgam and adaptation to pins Then we have extension into dentine And amalgam Extension Into dentine amalgam So we have retention It does not increase when depth of the pin So if it is more than 2 mm in dentine It will fracture the dentine And if it is more than 2 mm in amalgam It will fracture the amalgam So the most ideal one is 2 is to 2 Because both the case If it is going high It is more than 2 mm There is chance of either amalgam or dentine So here we have amalgam So now regarding the pin placement and techniques So the number of pins So several factors must be considered When deciding the number of pins It is such as the amount of Structure amount of dentine available To receive the pin On amount of retention required And size of the pin So the number of pins The rule is one pin For missing axial line angle So this is the rule So one line angle That is axial line angle is missing We can use one pin Similarly more than one So excessive number of pins It will increase the chances of fracture of tooth And weaken the amalgam restoration Now the location of pin So several factors aid in determining The pin hole location So we need to have a very thorough knowledge Of normal pulp anatomy and external tooth contour The current radiograph of the tooth should be taken To understand the proper orientation Of the canal And patient's age also is a factor So occlusion clearance should be sufficient To provide 2 mm of amalgam over the pin And pin hole should be located Halfway between the pulp and DEJ And at least 1 mm of sound dentine Around circumference of the pin hole If this is the pin hole There should be 1 mm dentine That is 1 mm sound dentine should be there Around the pin hole And pin hole should be located Halfway between the pulp and DEJ That is 1 mm inside DEJ Pin hole should be located In areas where greater stress occurs That is the first thing That is regarding the distribution of occlusion force It should be at an area where the greatest stress is happening Then it should be located near the line angle of the tooth Or the marginal ridge or cusp tip That should be parallel to the adjacent external surface But not closer than 1 to 1.5 mm And it should be prepared on a flat surface If 3 or more pin holes are placed It should be located at different vertical levels on the tooth Not on the same plane It should be at different vertical levels One here, one here, one here Not on the same level And interpin distance depends upon the size of the pin And maximum interpin distance results in Lower the level of stress in dentine Now regarding the perforation Which may result from pin hole placement So over the prominent mesial concavity of maxillary first primolar So maxillary first primolar There is always a concavity on the mesial side So there are chances of external perforation And at the mid-lingual and mid-facial bifurcation Of mandibular first and second molar We should also be very cautious And at the mid-facial, mid-mesial and mid-distal Perforation of maxillary first and second molar All these locations we should be extremely cautious Not to perforate the tooth So in pin hole preparation The number 1 by 4 burr should be used to prepare a pilot hole It is to permit more accurate placement of the twist drill Then prevent the drill from crawling Once it has begun to rotate An optimal depth of pin hole into the dentine is 2 mm And this hole should be prepared on a flat surface And the drill perpendicular to it Plays the flat thin-bladed hand instrument into the crevice And against the external surface of tooth Which indicates the proper angulation of the drill So what are the causes of failure of pin-retained restoration? So we can have failures at various levels So if this is our pin-retained amalgam So we have amalgam here So occur at 5 different locations That is a fracture occurred at 5 different locations One is here This is a restoration fracture here That is a pin restoration separation At the interface between the pin and the restorative material So this is the amalgam restorative material This is the pin So between the interface Now we have third fracture here That is the pin fracture That is happening within the pin So the pin will be fractured Now we have the fourth fracture That is pin dentine separation At the interface between the pin and dentine So it will be here This is the pin and this is the dentine So there will be fracture here And finally this is the fifth one That is dentine fracture That is happening within the dentine So these are the 5 locations where the fracture can happen So problems that arise during the pin-retained restoration The first thing is the broken drills and pins That is a twist drill will break If it is stressed laterally And allowed to stop rotating before removing the pin-hole And if you use a dull drill Pin will break during the over-screwed In the hole If you are trying to over-screw the hole The chances of breakage of pin So loose pins Basically due to Loosen while shortening with a bur And pin-hole prepared is too large In these cases the pins might be loosened And next thing is penetration Into the pulpan perforation of external To surface We already discussed that Where we should be very cautious And then there are chances of lateral perforation And also apical to gingival attachment The placement will be apical to gingival attachment So these are the problems associated with pin-retained restoration So we discussed in detail about various types of pins Its placement and the cavity preparation Requirements And the failure details of all these pins And its advantages and disadvantages This is a commonly asked essay question In university paper So I hope you understood this concept Of pin-retained amalgam restoration Where we use pin to provide a better resistance And retention to the amalgam restoration So I'll come up with a new topic in the conservator industry Thank you