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Complex amalgam restoration

Slide no.2 Outline of the lecture: -Capping cusps with amalgam -Pin-retained amalgam restorations -Non-pin mechanical resistance and retention features -Amalgam foundations - The idea of this lecture is when we have a large tooth structure missing then we have to replace this tooth structure. - Here we are going to replace this tooth structure by a direct restoration which is amalgam when it's possible. - So we will learn how to do this, how to manage large complex amalgam restoration, what choices we have? 1-Pin-retained amalgam restoration 2-Non-pin mechanical resistance and retention feature I want you to know that we have now other choices of direct restorative materials like composite. - Before we couldn't use composite to cover a lot of occlusal surface of the tooth bec of the(sorry its not clear) , fracture problem, but now we can use it as a posterior restoration. But sometimes we return to amalgam as a choice. - Pin was used before more than now. Now the use of pin-retained amalgam is diminished bec the problems associated with the pin-retained. So it's very limited and in selected cases only, but it has a lot of short coming and disadvantages we will talk about them. Slide no.3 Indications: Why we do complex amalgam restorations? 1.Control restorations in teeth that have a questionable pulpal and/or periodontal prognosis. - So why we choose a direct restoration? In some cases bec questionable pulpal it means the pulp diagnosis is not definit. For example after we excavate the caries this tooth might ended up later on, we will give a chance for this tooth to return vitality, but it might ended up by RCT. So we are going to restore the tooth, am not going to give this tooth without restoration until we dissolve this problem either if its pulpal or periodontal. We want to restore these tooth so amalgam is our choice rather than of putting more expensive like a crown. - The second indication is : 2.Control restoration in teeth with acute and severe caries.


- If the patient is a caries high risk we have to control the disease by putting a provisional restoration, so amalgam can be used as a definite restoration and interim restoration instead of using expensive restoration like indirect restoration. 3.The third indication is: Definite final restorations or foundations. - It still used if the patient cannot afford the crown for example. So still we can build up the missing tooth structure with amalgam and it can be as a definite restoration. - Foundation means that after we remove a lot of tooth structure we are planning to do a crown for the tooth, for example, there should be a foundation so still we do amalgam and prepare the crown over the amalgam. So this is what we mean by amalgam complex restoration can be as a foundation for a crown, an abutment for fixed partial denture or onlay for example. - The missing tooth structure should be replaced by amalgam then we can do a definite restoration like a crown. Slide no.4 Factors to be considered: There should be some factors to be considered in our decision making. 1.The first factor is: Resistance and retention forms. Depends on the remaining tooth structure. As the missing tooth structure increase the resistance and retention decreas. - And the features that we can apply the secondry resistance and retention forms will also decrease. - So resistance and retention forms depend on remaining tooth structure after removal of the defect. 2. Status and prognosis of the tooth - If the status and prognosis of the tooth is questionable then we use a complex amalgam restoration. 3.Role of the tooth in the overall treatment plan. We talked about it as a foundation. - For example the tooth will be abutment for a bridge, this tooth has a rest for removable partial denture for example, or guiding plan for a removable partial denture. 4.Occlusion, esthetics and economics. - Occlusion is very important, sometimes we can correct occlusion by this restoration. The amalgam restoration sometimes is difficult to correct occlusion, we need more indirect restoration to correct better the occlusion and contour of the teeth. Or for example closing diastema. Its difficult to do it with a direct restoration we need more subesticated indirect restoration to do this. So this means that we can choose more indirect restoration than complex amalgam restoration. Esthetics: - Amalgam is not esthetic. If esthetic is considered for the patient then we have to choose another material. While we can do porcelain crown or cement onlay, another restoration for sure will be more esthetic than amalgam. -Economic:


Work on the opposite side, which we talked also before a minute which is the economic status for the patient. If the patient can afford or cant afford, the amalgam is cheeper than another materials. Its less expensive than composite, onlay ,and crowns. The economic status for the patient is important. 5.Age and health of the patient. - If the patient is old age, and has medical problems then we can restore the tooth with amalgam. Slide no.5 Contraindications: -If the patient has significant occlusal problems that cannot be corrected, for example: 1.Supraerruption: We need to reduce the crown of the tooth and put a crown . 2.Infraerruption 3.Diastema closure 4. Anatomical contour -If the area to be restored is esthetically important to the patient for sure it is contraindicated with amalgam complex restoration. Slide no.6 Advantages: 1-Conserve tooth structure. For sure that amalgam conserve tooth structure more than crown. Bec we need to remove tooth structure, in addition amalgam may be in occlusal surface or mesial surface walls or buccal wall only. While the crown will be on all the tooth surfaces. As a result its effect on adjacent tooth and periodontium will be more. 2-Appointment time: we can do composite / amalgam restoration within one visit while an indirect restoration needs a multible visits. 3-resistance and retention forms: usually when there are more remaining tooth structure we can add more resistance and retention forms for complex amalgam than in a simple crown for crown preparation. -economics: we already talked about. Slide no.7 Disadvantages: those disadvantiges are more related to a pin retained amalgam restorations. 1- dentinal microfractures : The pin is inserted into the dentine which provide support to the amalgam restoration later on. Part of the pin will be inside the dentin and the other part will be outside the dentine, so the first part which inside the dentine may cause microfractures. 2-microleakage around the pin,or even at the margins of amalgam restoration.


3-decrease strength of amalgam,because when we insert a pin as you can see later there should ba a space between the pin and the tooth structure(between the pin and the the outer surface of the tooth) to be able to condense enough amalgam, if we don't have enough space then the strength of amalgam will be decrease because the space available for amalgam will be decreased, and as we know the amalgam should be in a certain thickness otherwise it will fracture. 4- resistance form: the form that prevent fracture of the tooth and the restoration.with pin retained amalgam restoration the resistance form increase for both: the amalgam and the tooth structure. 5- penetration and perforation: penetration may occur when we place the pin. When we insert the pin in the dentine penetration of the pulp may occur causing pulpal exposure or perforation in periodontal ligament. 6- For tooth anatomy also: in direct restoration will be much difficult to retain the tooth anatomy , it will be much easier for indirect restorations, because technician the lab will take his time while preparing the crown and ding the wax up to give us the original anatomy of the tooth while in the clinic you have limited working time and limited access to do the form and the sheet of the original anatomy. Slide no.8 The first thing we will talking about is: capping cusps with amalgam: We can cap the cusp with amalgam if it become thin or weak after removal of tooth structure. For ex. (page 2,slide#4) its an MOD cavity preparation in lower 6, we can restore it with amalgam without problems because we have enough thickness of tooth structure both buccally and lingualy and the isthmus width is ok also, lets say its ideal tooth with acceptable isthmus width but the situation will be different if this tooth structure amount of remaining cusps here reduced and the isthmus is wide and the remaining thickness of cusps decreased a lot in this situation we need to cap this cusps to prevent the fracture of this cusp in the future under masticatory load. -when to cap the cusps? If the facial or lingual extension exceeds 2/3 the distance from a primary groove toward the cusp tip. It means that if there is 2/3 of the distance b/t central groove and the cusp tip is missing then we need to do cusp capping.or if the width of the isthmus is 2/3 of the tooth so we need cusp capping. Or if we measure from cusp tip to the cusp tip 2/3 of this area is missing this means we need to cap the cusps. - adequate resistance form for the tooth structure : if we leave thinning cusp or undermined cusps it will be enamel unsupported by dentine so we need to cap the cusp because this cusp may fracture in the future under masticatory load. On the other hand you should put a sufficient resistance for the amalgam which means that we should reduce the cusp about 1.5-2 mm to ba able to put amalgam because minimum thickness of amalgam is 1.5 mm so provide resistance form for both the tooth and the amalgam restoration. -survival rate for capping cusps is about 72% after 15 years, so its 72% of the teeth maintaining a good amalgam restoration after 15 years, and its high persent.


Slide no.9 - how to do capping for a cusp? For ex. We decided to cap this cusp, it's a mesiolingual cusp of lower molar , we are going to cut the cusp by the side of the fissure bur, we do a depth cuts. We do depth cuts to know exactly how much we should reduce from the cusp. 2 mm from functional cusp and 1.5 mm from a non functional cusps. Functional cusps: are the upper palatal and lower buccal cusps . Non-functional cusps: are the upper labial and lower lingual cusps. - usually the load is more on fnx cusps so we need to reduce the fnx cusps 2 mm while non fnx cusps 1.5mm. we do first what we call depth cuts by the side of the fissure bur, the side of the fissure bur is about 1mm so we need to go more than the side of the fissure bur. So we do depth cuts then we reduce the cusps. This is amalgam restoration after reduction, here the reduction should be continious with the continuity of the cusp it should follow the curve of the cusp. -another very important thing that you should not finish on the lingual groove for example or buccal groove, we should extend behind buccal groove or lingual groove little pit to be able to finish the amalgam restoration after that. -for ex. If we want to cap 2 cusps here, those are the depth cuts (that give us how much we should reduce).We make depth cuts and connect b/t them.(page3 slide3). -why should we do depth cuts ? why we don't reduce the cusp directly without the depth cuts? Because they give us how much should we reduce from the cusp.its easier to make depth cuts on every single area on the cusp, then connect b/t them.(Like the pic. In page 3 slide3). So it's the guidance how much should we remove from the cusps. When you learn crowns and bridges you will make the same thing in occlusal reduction in crown preparation. -this is a cusp capping (page3), we remove this cusp and do auxiliary retention and resistance form in the retention groove, because by reducing the cusps we decrease the retention and increase resistance of the tooth, retention decreased because the vertical wall is missing (in retention we depend on 2 opposing vertical walls), so when we remove the cusps we increase the resistance but decrease the retention so we need more retentive feature or auxiliary retention like central groove. Slide no. 13 Now we will talk about: pin retained amalgam restoration: its using a pin in missing tooth structure to be able to condense amalgam against it, as I told you the use of the pin is limited nowadays because of the problems with pin retained amalgam restorations, but still sometimes use them because sometimes the only option is to use them. We have 3 types: 1- self-threading pins. 2- cemented pins. 3- friction-locked pins.


1- the most still use is elf-threading : we make a hall in dentine smaller than the pin size and that pin is twisted inside the hole (like scrow). 2-cemented pins: the pin hole bigger than the pin size and we use cement to cement the pin inside , it has the least retention. 3-friction-locked pins: we use packing motion, its similar to self threading but the difference here that its packing motion so increasing the stress in the dentine may cause microfractures more. Slide no. 14 The most one that we use is the self threading pins. Its 3 to 6 times more retentive than the cemented pins. We have many systems in the self threading pins but the most use is the thread mate system (TMS). To make a pin retained amalgam restoration we use special drill and special instruments to hold the pin also, but you will not make this restorations in the lab, you have just to know about it. Slide no.15 factors affecting the retention of the pin in dentine and amalgam: 1- the retention in self threating > friction- locked > cemented. 2-surface caractaristics: some types of pins have smooth surface and some types have some threading (like some serrations or threading) when there is serration or threading more this means that there is more retention. 3-orientation: horizontal is more retentive than vertical , more difficult to place and more dangerous to the pulp and to the periodontal ligament. -the number: as the number increase the retention increase , the resistance decrease and the risk to the pulp and periodontium increase. -the diameter: as the diameter increase the retention will increase, pulp risk increase like microfractures or cracks inside the dentin ,and periodontal ligament risk increase ( because the size increase). 4-extension into dentin and amalgam: as the extension into the dentin increase the retention also increase but the problem that it will danger the pulp and the periodontal ligament so the retention should be equal to the problem that arise from using the pin. -the most acceptable using of pin will be like the one in the figure (slide 15): its 2 mm inside the dentin and 2mm outside the dentin (in the amalgam). Slide no.16 -the pin size: the TMS has only 3 sizes: 1) manikin 2)minim 3) the third one is not used. -there is a drilling devise : its either by itself or its like a bur that we inserted in the slow hand piece, we drill a hole inside the dentine, until it reach a certain point it will break from this notch (in the figure). Every drill make a certain size of hall that should


be smaller than the pin, so each pin has a drilling machine and its color coded, for example green drilling with green pin, yellow drilling with yellow pin because the pin hole should be slightly smaller than the pin size to be inserted in. So first we use very slow speed hand piece or drilling with the system then insertion of the pin until it reach the prepared depth of the pin it will break by itself (its about 4 mm , part of it will be in the dentine, the other part will be in amalgam). Slide no.17 - number of pins: how much pins should we place? It depends on the missing tooth structure, the amount of dentine to place the pin in, the amount of retention required , the size of the pin. Should be space between 2 pins. So if the size of the pin increased this means we have a limited numbers of pins to place. One pin per missing axial line angle as a general role. Slide no. 18 -location: - Its very important to know the normal pulp anatomy and external tooth contour and the direction, and where is the pulp, Not to injer the periodontium. - A current radiograph should be available, position of the pulp. - a periodontal prop in order to know the orientation of drilling. - the patient age: we try to avoid it in young adult because of the high position of the pulp. Slide no. 19 Pin hole position: We have 2 line angles missing here (according to the pic ), so we use 2 pins, there position should be in dentine and away from tooth surface by about 1.5 mm (away from the external surface of the tooth) and about 1 mm inside the dentinoenamel jnx. and we should be able to condense amalgam around the pin after we place it, so there should ba a space around the pin hole for the amalgam . Slide no. 20 - we made pilot hole with small round bur in order to avoid slopping of the hand piece while drilling . -then twist drill at very slow speed and - insert the pin. We can use conventional latch type slow speed hand piece and TMS system hand wrenches. Sometime in some of the systems you can put it on the slow speed as a latch type and other systems like TMS they have hand wrenches (you can put it by hands) once you enter the pin in its place it will break to leave a part of the pin inside the dentine and other out to put amalgam around. Slide no. 21 bending and shortening pins: -sometimes we need to bend a pin if its too much away or its in the wrong direction for example. - or we can shortening the pin with the carbide bur high speed, just cut it while in bending you need a certain tools to bend it otherwise you will lose it.


Slide no. 22 possible problems: 1- failure of pin retention: the restoration come out with the pin. In this case we have to find another retentive feature and repeat the amalgam restoration. 2-broken drills and broken pins: the drill may break inside the dentine, by the way if you want to prevent breaking the drill you should keep drilling inside when you entering and when you are coming out of the dentine. -for broken pins: we leave this area and try to find another area for place the pin. 3- loose pins: When the pin hole is larger than the pin. Then we try to avoid this pin hole and trying to do another pin hole in another location. 4- penetration into the pulp and perforation of the external tooth surface(periodontium). It's the most dangerous problem. We treat this case like the treatment of traumatic exposure of the pulp. Then we do direct pulp capping and try to restore the tooth. If its in the external tooth surface, it means that we penetrate the periodontium we do surgical procedure. For this we have a lot of problems associated with using the pins. So its very limited now, but we still sometimes use it in some situation. Slide no. 23 Non-pin retained amalgam restoration: Now we have some retentive features other than pin-retained, we call them non-pin retained, we depend on the auxiliary retention features on the tooth. Its just a cross section of the tooth but it doesn't mean that the tooth will be retentive to the amalgam. No way to be retentive to the amalgam in this situation. - Circumferential slot: Small inverted cone bur or with tapered fissure bur, just to know the shape of circumferential slot. Slide no. 24 Amalgam pins: This is the most commonly used We do a pin inside the tooth with the amalgam. - I prepare a hole in the dentine about 1.5-2 mm in depth -0.8mm to 1mm in width. - entrance of the amalgam pins cannals should be beveled, and then I condence the amalgam inside it. So it will form amalgam pin inside the dentin for retention. So that's why we call it amalgam pin we condence amalgam. Sometime I use even the probe or very small application to condence amalgam while I'm doing condensation. We do it by three thirty bur(its not clear 53:12) Slide no. 25 Peripheral shelves: Again this is just to illustrate how the peripheral shelves it looks like.


You can use it after capping a cusp like this, you can use it peripherally 2mm axial depth it means toward the pulp and 1mm cervical depth gingivally. Slide no.26 Pin retained vs non-pin retained amalgam restoration. - pin-retained is more frequently used in preparatiom with few or no vertical walls. Bec we cant utilize more auxiliary retentive features, so when we have more missing vertical walls we use pin-retained. - non-pin retained are indicated in short clinical crowns and in cusps that have been reduced 2 or 3mm for amalgam. We use non-pin retentive features. -more structure is removed preparing mechanical retention and resistance forms. Its related to non-pin retained then we can use retention features more. - mechanical retention and resistance forms are less likely to create microfeatures in the dentin and to perforate the tooth or penetrate into the pulp. This is the advantage of non-pin retained, its less likely to create cracks or stresses inside the dentin in contrast to pi-retained that more likely to cause microfractures in the dentin and these fractures reach the pulp may cause sensitivity, microgaps and may endanger the pulp. Slide no. 27 Amalgam foundation: - amalgam can be used as a foundation as we said earlier. It can be used as a foundation for a crown or abutment for a fixed partial denture. Amalgam is the most used material for a foundation bec its easy to use and stronger we prefer it more than composite as a foundation for a crown or a foundation for an abutment. - the preparation for amalgam foundation can be: 1. pin retention 2. slot retention 3. camber retention - we use it when the tooth is endodonticaly treated we can utilize the pulp chamber. bec the chamber will give us a space for retention like this. This is amalgam in the pulp chamber that inserted into the canals, the retention in the pulp chamber more in molars than premolars. Bec the chamber in molars bigger than premolars. In premolars sometimes we need post retained crowns or post retained abutment. We need to put a post inside the prepared canal for anterior teeth and premolars more. While in posterior teeth or multi rooted teeth we can utilize the pulp chamber. And it depends on the length of pulp chamber. We can aperture(57:04) here 4mm from the tooth surface to the furcation, if its 4mm its enough as a foundation. If its less than 2mm then we have to put post for example in one of the roots to provide more retention as a foundation. This is an example for amalgam foundation(pic) this is endodontically treated tooth, we can utilize the pulp chamber we can condense the amalgam in the pulp chamber then we can build up the amalgam.


As a general role each root canal treated tooth should be occlusally covered to prevent fracture of the tooth, either with amalgam or this can be a foundation for a crown or onlay. We can use the amalgam as an occlusal coverage like capping cusps or as a foundation for preparing onlay for example or a crown.

Wish you all the best in med exams Baraa eigbaiya Aiat khalilia



Microsoft Word - cons #3

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