Impression orthodontics

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<ul><li><p>ALGINATE IMPRESSIONMD. ISHTIAQ HASANFCPS TRAINEE</p></li><li><p>SEATING OF THE PATIENT The pt should be seated upright in a comfortable position with the head resting firmly on the head rest Chair height and position is adjusted to a comfortable working position for the dentist.</p></li><li><p>For maxillary impression:The pt is seated in a upright position.Gravity affect the position of the oral tissues. Since the major part of the appliance use in upright position , the impression is made in this position.If reclining position is used , then there is a danger of impression material flowing down the palate , causing discomfort or gagging , which can hamper impression procedure.Gagging is most easily controlled in the upright position.The operator stands behind and to the right side of patient.</p></li><li><p>Position for mandibular impression:The mandibular impression also made with upright position.Unlike maxillary impression , the operator stands infront and right side of the patient.</p></li><li><p>SELECTING THE STOCK TRAY:The tray is selected according to the size of the arches.There should be a space of at leat 6 mm between the sides of tray and mucosa.Posteriorly it should extend upto and cover the palatal seal area in the maxilla and the retromolar pad in the mandible.</p></li><li><p>PATIENT PREPAEATION:Trial helps to prepare the pt.Relax the ptPt is educated about the impression procedure Pt is asked to perform various movement required to mold the impression.Trial are performed with the tray in the mouth </p></li><li><p>MODIFICATION OF THE STOCK TRAY:The borders of the stock tray can be lined with a strip of boxing wax to create a rimlock that helps confine the material.An adhesive can be painted on the tray to help retain the alginate.In the case of deep palatal vault , alginate may not record the deeper portion. The palatal portion can be built up with wax.The tray can be extended when necessary with wax.</p></li><li><p>TAKING MAXILLARY IMPRESSION Alginate mixed and loaded in tray.Some material take in hand and applied on the palate to reduce air entrapment.The loaded tray insert into mouth , right post corner first , while retracting the left cheek and rotated into position over the ridge.Next the lip is retracted and labial frenum is used as guide to align the midline of the tray.</p></li><li><p>The tray is pressed upward and backward.The index fingure is placed in the first molar region.Using alternate pressure , the tray is pressed until the posterior part contact the post palatal seal area.After seating , the tray is supported by finger on the middle of the tray and a limited and gentle border molding is carried out.Care should be taken to minimize the flow of the material to the throat.</p></li><li><p>TAKING MANDIBULAR IMPRESSION: Mix alginate and loads in tray.Some alginate can be placed in the retromolar sulcus before inserting the loaded tray.One corner of the tray is inserted into mouth. Meanwhile opposite corner of the mouth is retracted with a mirror and the tray is rotated into position over the teeth.The pt is instructed to raise the tongue and position it slightly forward. This ensure that the tongue does not get trapped beneath lingual borders of tray.</p></li><li><p>COMMON MISTAKES:Improper tray position is very common. In upper impression ,tray Is brought too close to the labial surface and posteriorly the tray may deviate too much to either right or left side causing exposure of the tray.Large voids may be observed in different area of important. Frequently seen in palatal region .Gagging can occur if excess material has been loaded in the posterior part of tray.</p></li><li><p>Separation of tray is occationally seen. If this happen , repeat the imp. Tray retention can be increased by Having more number of holes Having rimlock Use tray adhesive</p></li><li><p>MIXING:Mixing ratio of powder and water is 15 gm of powder mixed with 40 ml of water.Correct ratio is important.</p></li><li><p>Spatulation:First mix slowly to make all he powder wet.Then mix vigorously by using a figure of 8 method.Mixing time is 1 min At the end of it, the mix must be smooth , homogenous and creamy.</p></li><li><p>REMOVAL OF THE TRAYRemove the tray with sudden pull. Permanent deformation is more in alginate. Permanent deformation is less if the set impression is removed from mouth quickly </p></li><li><p>After removal of the tray fom th mouth , rinse in cold running water.Shake of excess water and cast should be done as soon as possible , preferably within an hour .If it is not possible , cover it with wet cloth , put it in polythene bag and sealed it. This step is necessary to prevent synersis which may cause shrinksage.</p></li><li><p>DISINFECTION:At first , wash with running water.Then spraying sodium hypochloride or glutaraldihyde for 10 min.</p></li><li><p>SEQUENCE OF BORDER MOLDING:Manibular border molding</p><p>Anatomic region Tissue that influence How to active Labial flange i.Mentalis muscleii.Incisive labi inferiorisiii.Orbicularis oris i.Hand massage and manipulate the lip side to side motionii.Instruct the pt to evert the lower lip Labial frenum Labial frenum &amp; its associatd connective tissue fibres Lower lip is lifted outward , upward &amp; inward and then massage the lip with side to side motion. </p></li><li><p>Buccal frenumBuccal frenumThe cheek is lifted outward , upward , then inward &amp; the mold the cheek in antero-posterior direction.Massetric notchMasseter muscle Instruct the pt to close his jaw against downward pressure from the operator thumb in the region of molar. Distal extension areaPterigomanibular rapheRetromolar padAsk the pt to open his mouth wideLingual frrenum and sublingual flangeLingual frenum &amp; its intrinsic connective tissue fibresi.Pt is asked to wipe his lower lip side to side with the tongue tipii.Pt is asked to push his tongue forcefully against his front part of palate </p></li><li><p>Mylohyoid portion of lingual flangei.Mylohyoid muscleii.Mylohyoid ridge &amp; the medial body of mandible i.To mold lingual flange , instruct the pt to bring the tongue in contact with left cheek.ii.The left lingual flange is mold similarly by contacting the right buccal mucosa.iii.Pt is asked to protrude the tongue, this determine the length of the flange in this region BuccalExternal obligueManually manipulate the cheek with fingure pressure upon the denture border I an ant-post direction. </p></li><li><p>Maxillary border molding:</p><p>Buccal frenum &amp; buccal fangeBuccal frenum associated with connective tissue fibres of facial expressionIn the region of buccal frenum , the cheek is pulled , then outward , downward , inward and finally forward and backward. Labial frenum and labial flangeLabial flangeThe upper lip is lifted up ,then outward , downward and inward.Coonoid process areaCoronoid process, Fibres of temporal muscle attached to coronoid process </p></li><li><p>Mixing time: 60 secWorking time: 2 min </p></li><li><p>Synersis loss of water , as a result shrink.Due to synersis , material exudates some acidic substance come out on the surface of the material and this acidic substances are retarder to model material as plaster of paris.</p></li><li><p>Inbibition Absorb water and swell.</p></li><li><p>How to prevent synersis Pour immediatelyWash in running water to wash away acid &amp; saliva from surfaceIf need to keep long time , should cover with damp but not wet cottonUse fixers or hardening solution ( solution of k-lam , sol of NaCl , sol of KCl)</p></li><li><p>Can we use plain tray for alginate impression?</p><p>No, because Na-alginate act as a separating media and it cannot stick to plain tray.</p></li><li><p>How we take alginate impression with plain tray?</p><p>Plain tray need to be lined by sticky wax or lined with adhesive paste.</p></li><li><p>IMPRESSION WITH PT OF EXCESSIVE SALIVATION:Imp field keep dry by placing cotton rolls in upper buccal sulcus to block parotid duct , in floor of the mouth to control sub-mandibular and sub-maxillary duct which are remove before tray loads.Use saliva ejector Use anti-sialogue.</p></li><li><p>TAKING IMPRESSION OF HYPERACTIVE GAGGING PATIENT1.REDUCTION OF STIMULI:Avoid thick trayAvoid oversized tray specially post palatal regionAvoiding loading excess material specially post palatal areaPt sit upright leaning slightly forward with head tilted slightly downward ,sothat material cannot go to throat.Use fast setting alginateUse saliva ejector. 2.DISTRACTION TECHNIQUE:Talking &amp; engage pt to some topic of his special interestRessurance Distract pt by asking him to breath deeply through nosehypnosis</p></li><li><p>3.PROGRESSIEVE DESENSITIZATION:</p><p>Use in case of severe gaggersPt is introduced to minimal stimuli which he can tolerate. Gradually stimuli is increase until pt is able to tolerate impression procedure. As a example , pt is asked to practice with marble. Gradually the numbers of marble increase.Impression tray is handed over to the pt &amp; allowed to take home &amp; practice in front of mirror everyday.</p><p>4.MEDICINE:ANTIHISTAMINESEDATIVETRANQUILIZERANTIEMETICLA GELCNS DEPRESSANT</p></li></ul>