 Good morning, today we will cover the topic Anchorage in orthodontics introduction. The force used to move teeth in orthodontic therapy is derived from some anatomical areas which act as anchors. So anchors are basically anything a tooth, a group of teeth, a muscle or an anatomical structure which we use to move another tooth or a group of teeth. The resistance that the Anchorage area offers to unwanted tooth movements is called Anchorage. So what is the definition? Krebber has defined Anchorage in orthodontics as the nature and degree of resistance to displacement offered by an anatomic unit for the purpose of affecting tooth movement. According to Voight and Gardener, Anchorage is the site of delivery from which a force is exerted. Anchorage during orthodontic therapy is obtained from two sources, basically intraoral sources and extraoral sources. So what are the intraoral sources? Here the points marked A, B, C and D are the intraoral sources, A is a tooth, B is the alveolar bone, C is the basal bone and D is the muscle. And extraoral sources are marked by E, F, G and H, that is the occipital bone, the parietal bone, the frondle bone, the chin and the back of the neck. Intraoral sources of Anchorage, what are the intraoral sources? They are the teeth, the alveolar bone, the basal bone and the musculature. Coming to the teeth, whenever some teeth are moved orthodontically, the remaining teeth can act as Anchorage or resistance units. The Anchorage potential of teeth depends on a number of factors such as tooth surface area, root form, size and number of roots, root length, tooth inclination and ankle or tooth surface area. So the Anchorage depends on the size of the teeth, that is the root surface area of the teeth. The more the tooth surface area, the better will be the Anchorage. So in this diagram, the root surface area of the different teeth are shown. The anterior have with single rooted tooth will have lesser root surface area, that is a central incisor in the lower, has only 170 mm square of root surface area. So the incisors, basically the root surface area differs from 170 to 230 mm square. For the canines, it is 270 to 280 mm square. For the premolars, 240 to 260 mm square and for the molars, because they are multi rooted, they have the maximum root surface area and mostly that is the reason why they are used as Anchorage. So the root surface area differs from 450 to 535 mm square and the maximum root surface area is seen in the maxillary first molars. So more the roots surface area, better will be the Anchorage. Root form, so when you take a cross section of the roots, we can see the roots are in three different forms. One they will see as round roots, flat roots of triangular roots. So round roots are basically seen in bica spits and the palatal root of maxillary molars and they can resist horizontally directed forces in any direction. Whereas flat roots, they are seen in mandibular incisors and molars and the buckle roots of maxillary molars and they can resist movement in the meso distal direction. Whereas the triangular roots, they are seen in canine and maxillary central lateral incisors and they offer the maximum resistance to displacement compared to the round or the flat root form. So these are the cross sections that you see here, round, flat and triangular. Next on the size and number of root, so more the number of roots that is multi-rooted tooth as we explained before, there will be more large roots surface area and it will have the greater ability to withstand stress and resistance. Root length, the longer the root, the deeper it will be embedded into the bone and greater will be the resistance. Inclination of the tooth, the greater the resistance to displacement is offered when the force exerted to move the teeth is opposite to that of their axial inclination. Ankylose teeth, orthodontic movement of such teeth is not possible and they can therefore serve as excellent angles whenever possible. Then is the alveolar bone, alveolar bone can resist tooth movement up to a certain amount of force but after a certain limit it perpets tooth movement because there will be bone remodeling that will be happening. This is the basal bone, basal bone example are the areas like the heart palate and the lingual surface of mandible. So this you can see in cases of NAMS button, removal appliances and for functional appliances we see that the mucosa and the lingual surface of the mandible and the maxilla are used. Next is muscular anchorage, the muscular anchorage is basically when there are hypotonic muscles like the case of a hypotonic labial muscle we can use the lip umber to use that force as anchorage to distillize the mandibular molars. Extrural forces of anchorage are the cranium, the back of the neck and the facial bone. So cranium basically the occipital and the parietal anchorage that is how we use the head gear to restrict the maxillary growth and the back of the neck as in how we use in for the cervical head gear then the facial bones that is the frontal bone or the chin or the mandibular symphysis which we use in the case of face mask to protect the maxilla. Example of extraaural anchorage is an occipital head gear which takes anchorage from the cranium and a face mask which we use for the protraction of the maxilla it takes anchorage from the frontal bone and the chin. Now what is the classification of anchorage? It was given by Moyers. It can be divided according to the manner of force application it can be simple anchorage, stationary anchorage and reciprocal anchorage. According to the jaws involved it can be intramacillary anchorage and intermaxillary anchorage. According to the site of anchorage it can be intraaural, extraaural and muscular and a extraaural that's a vical, occipital, cranial and the facial. According to the number of anchorage units it can be single or primary anchorage, compound anchorage and multiple or reinforced anchorage. The types of anchorage according to the manner of force application the first one is simple anchorage. So simple anchorage is obtained by engaging a greater number of teeth than are to be moved in the same than the large. That is you are trying to move a single tooth by using a number of teeth there. So it's a simple type of anchorage. The combined wood surface area of the anchorage unit should be double that of the teeth to be moved. In this case you can see this as an example of simple anchorage. You are just using a simple screw to buckly move the palatally placed teeth. The rest of the whole teeth in the arch they act as anchorage. We are using clasp for attention and the whole base plate is taking anchorage from the rest of the teeth. Similarly in the case of an insert spring here we are using it for the labial movement of an incisor. Next is the stationary anchorage and the application of force tends to displace the anchorage unit bodily in the plane of space in which the force is being applied. So the example here is the retraction of the anterior teeth. So when in fixed appliance therapy when we are using we use the buckled teeth as the and here even the second primolar is taken as the anchorage. So here the only the bodily movement of the anchorage teeth is allowed and there is no tipping. So this is staying as stationary even if at all it is moving it should only move bodily there shouldn't be tipping of the anchor teeth. Next is the reciprocal anchorage so when two teeth or two groups of teeth of equal anchorage value are made to move in the opposite direction. So here the two teeth which are to be moved they should move in the opposite direction. So the reciprocal forces are acting here. So here the first example is a finger spring. So the first left lateral incisor and the right lateral incisor both have to be moved to each other to close the diastema. Similarly here we can use elastics to close the middle diastema. Also in a posterior crossbite case we can use the elastic to correct the single tooth crossbite and there example is the coffin spring which is incorporated into the base plate. Here we can use it to push both the arches to open up in case of constricted arches. Now according to the site of anchorage again as we have discussed before it is intraoral anchorage, extraoral anchorage and muscular anchorage. So intraoral anchorage is where all the anchorage resistance units are situated within the oral cavity. The teeth to be moved and the anatomical area that offer the anchorage are all within the oral cavity. And the teeth, the palate, the lingual alveolar bone of the mandible. Extraoral anchorage is anchorage in which the resistance units are situated outside the oral cavity. So we are taking anchorage from outside the oral cavity. Example cervical area, the occipital bone, cranial bone and the facial bone. Next is a muscular anchorage. As we discussed earlier we are taking it from the hypotonic muscles. For example the lip. So the example is a lip umber which we use to distillize the molars. This is the example where we use occipital head gear, a face mask and a chin cup for anchorage and the lip umber is used to take the muscular anchorage. According to the laws involved, based on which law we are using, it is divided into intramaxillary anchorage and intermaxillary anchorage. So intramaxillary anchorage is where the units offering the resistance, that is the anchorage unit. They are situated in the same jaw or the same arch. These are called as intramaxillary anchorage. So example as this once we saw before, the where we incorporate the screw, the springs or the coughing spring, we are using it only in the one arch. Next is the intermaxillary anchorage. So the anchorage in which the resistance unit is situated in one jaw but the teeth to which we are moving is in the opposite jaw. It is also termed as baker's anchorage. So here example is class 2 and class 3 elastics where we, that is we are taking anchor unit from one arch but we are trying to move the teeth in the opposite arch. So this is class 2 elastics and this is class 3 elastics. Now according to the number of anchorage units, so we can take single or primary anchorage, compound anchorage or reinforced or multiple anchorage. So single anchorage is we are only taking a single tooth as an anchorage. Compound anchorage is more than one tooth with greater support is used to move the teeth as a support. Reinforced or multiple anchorage is we are using more than one type of resistance unit to use as anchorage. So how can we reinforce anchorage? What are the multiple methods? We can use extraural forces to augment anchorage like as we discussed in head gears and face mask. We can use extraural anchorage or upper anterior incline plane. This is an upper anterior incline plane and this is a sweat deploy. Same as the upper anterior incline plane but with the incisal capping when it comes this called as a sweat deployance. Next is the use of transpalactyl arch or lingual arch. This is the most commonly used multiple ring anchorage example. Here we are using the molars as the anchorage but to reinforce the anchorage so that the molars doesn't move into the extraction space we use the transpalactyl arch or the lingual arch. So you have placement and removal of the implant. So before placing an implant you should take a radiograph of the site where you are placing the implant. You can take an IOPR and an OPG to know the inter-radicular bone. The inter-radicular bone should be a minimum of 2 mm which is an ideal amount for the placement of an implant. Then you should give a topical local anesthesia on the region. If you are using a self-tapping implant then you have to drill it with a twist drill at 600 rpm and you should cool it with sufficient saline or a coolant. As you are placing it if the patient is uncomfortable or talks about pain then you should remove it and reinsert it or you should find a new position. When we use the implant driver to insert the TAD after the TAD is placed we use a radiograph to see the correct positioning of the TAD. The picture here shows the implant driver that we use and we can use the same implant driver to remove the TAD under topical LA gel. Now when you place it there will be few complications. So what are the complications that can happen in the placement of the TAD? The first is the contact with the adjacent root. This is very common if you don't place it carefully. So crude peregrinal ligament can cause pain and discomfort to the patient. You can verify it with the radiograph and then reposition it. Breakage of an implant. It is very rare but if there is too much resistance when you are placing it you should remove and reposition it. But if it is broken then remove it. Damage to the anatomical structures. So the maxillary sinus may be approximated when placing it in the upper premolars Also it can cause damage to the nerve. Soft tissue overgrowth. Over the head of the implant there are chances that the soft tissue grows. It can cause irritation to the tissues. And it is difficult to place an attachment or a ligature over the head of this implant if there is a soft tissue overgrowth. So you should try and place it on the attached ginger. Where the soft tissue overgrowth is chances are less. Implant loosening is another complication. Because of poor bone quality or excessive force application or if it is approximated to the root surface then there are chances that the implant may be loosened. So it can be tightened but if it happens again remove and reposition it in a new place. Anchorage planning. This is very important in orthodontic treatment. So before starting the treatment you should always evaluate the anchorage demands and then plan well. So what are the factors affecting? The number of teeth being moved. If there are more teeth, number of teeth that is being moved then the demand on the anchorage is more. On the type of teeth. The more the anterior teeth there is less strain on the anchorage. Type of movement. Bodily movement means it needs more anchorage and there will be more strain on the anchorage unit. Duration. If there is a longer duration of treatment then the strain on the anchorage unit is more. Skeletal growth pattern. In vertical growth pattern or high angle cases there is more tendency for anchorage loss. So what is anchorage loss? It is the unwanted movement of the anchor teeth which we don't want. But in horizontal growth pattern because of stronger facial musculature the chances of anchorage loss is less. Occlusive interlock. If there is a good movement occlusive interlock if there is a good buccal occlusion it resists anchorage tooth to move. So good buccal occlusion helps in good anchorage planning. Now what is the classification of anchorage demand? This is in extraction cases it is divided into minimum anchorage moderate anchorage, maximum anchorage and absolute anchorage. So in cases like in minimum anchorage cases if this is the extraction space then more than half of the extraction space can be lost by the anterior teeth moving messily. This is a moderate anchorage case the anchor teeth can be permitted to move forward into half to one fourth of the extraction space means the anchor teeth can move half of the extraction space and the anterior teeth can move half of the extraction space distally. And in maximum anchorage case not more than one fourth of the extraction space will be lost forward that means the anchor teeth can move only up to one fourth of the extraction space. The rest of the extraction space should be closed by the retraction of the anterior teeth. This in severe proclination cases it is very important otherwise the retraction will not be complete the teeth will still look proclined. Absolute anchorage is when we use a TAD the entire extraction space is used for retraction of the anteriors we are not using the posterior for retraction there is no chance that the forward movement of the posterior teeth will happen and the entire extraction space can be closed using the anteriors. Thank you.