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Extracoronal Restorations in Pediatric Dentistry Wednesday 24-11-2010

Slide 2:Last lecture was about intracoronal restorations , today we will talk about 2 extracoronal restorations: Stainless steel crowns (S.S.C) , very commonly used in pediatric dentistry. (Used only for molars) Composite resin-strip crowns (used for anterior teeth). Slide 3:Other types of extracoronal restorations: Labial veneers : · direct: you make it straight forward in the clinic from composite. · indirect:you take an impression , fabricate it in the lab, & then cement it on the tooth. Onlays: · Composite is the simplest type · or from gold or cast metals. Slide 4:S.S.C are preformed restorations , they are ready made & come in kits from the company in different sizes , according to the average dimensions of the primary tooth. So size 2 , is the average size 2 for several teeth which have been measured & they take the average They are used for restorations in posterior primary teeth, & they can be also used for permanent molars.(other types that come in kits for permanent molars). Described by Engel in 1950,then by Humphrey in 1950. Metal in them is a mixture of iron, carbon,& chromium which improves corrosion resistance, it also got nickel that also helps resist corrosion & adds strength to the alloy. So it Doesn't corrode due to the chromium & nickel it contains. Slide 5:This is a S.S.C Slide 6:Morphology of primary molar differs from permanent tooth by having its greatest convexity at the cervical 1/3 of the crown. So you've got a very huge undercut at the cervical area of the primary tooth , because the greatest hight of contour of the primary tooth is slightly above the undercut, this undercut area is what we are going to benefit from in the retention of the crown.

Because The crown being made from stainless steel can expand & you push it , it will expand at the area of the highest contour , & then it will go back to its original form under the undercut, so you'll hear a click. In this way it is resistant to being dislodged of the tooth, *this is how the crown is retained on the tooth : from the undercut. Using the cement. Don't just rely on the undercut . NOTE: Never rely only on the adhesive properties of the material, always rely on having a retention form and the adhesive properties of the material. As in composite class II box restorations , it's always beneficial of having a very small dovetail , this adds to the retention plus the adhesive properties of composite , for better retention. The thin metal of S.S.C margin is flexible enough to spring into & be retained by this undercut area Enamel & dentine of primary molars are proportionally thinner than in permanent teeth & are susceptible to caries attack. This is important , because caries progresses much more quickly in primary teeth than in permanent teeth. if you have class II in a D & it starts at the same time at 6 , in the D it will affect the pulp much quicker, this means that the tooth gets destructed quickly , so you need to restore the tooth with something more durable like S.S.C. Primary pulp is also large with prominent pulp horns & situated close to the mesial surface of the tooth crown , this is also important because if caries starts in a tooth & progresses , it can easily reach the pulp, which mean that you might need pulp therapy. Remember when you look at your x-ray during the radiographic form , if you see deep caries we usually tell you it needs pulp therapy , because microorganism most probably have progressed into pulpal area. Any primary tooth that gets pulp therapy done will need a SSC afterward. you may say that you want to put composite or amalgam , but SSC is the best & most durable. Slide 7:The SSC for permanent molar is designed so that it closely resembles the anatomy of a 1st permanent molar tooth & it also obtains its retention mainly also from the cervical area. Slide 8:This is where the undercut situated cervically , so when you place your crown , it will spring at the area of highest contour "it will open'', then it will flex over the undercut area, then it will click. Slide 9:Indications of SSC in primary molars: 1) after pulp therapy (which is two procedures: pulpotomy & pulpectomy) 2) restorations of multisurface caries ( like if you have M.O lesion & another B lesion, or class II) , SSC here is more durable than amalgam.& for patients at high caries risk , especially under GA. because SSC are more durable & we don't want the patient to be under general anesthesia everyday, also most of the patients in the clinics have a lot of caries ''high risk patients'', so SSC here is better than intracoronal restorations.

NOTE : most of the students write in the treatment plan , class II restorations, which is meaningless ! you have to write what you want to do. Some may write class II amalgam restoration , the dr. would rather you to use SSC in these high caries risk patients. 3) primary teeth with developemental defects '' enamel hypoplasia, enamel hypomeneralization '' where the tooth structure is very week & tooth wear . 4) Where an amalgam is likely to fail (e.g: proximal box extends beyond the anatomic line angles) ; large classII , it's better to place a crown. 5) Fractured teeth 6) teeth with extensive wear. 7) abutment for space maintainer. Slide 10:There are no straight forward contraindications for SSC in primary teeth . Duggal 1989 listed one exclusive criterion for fitting a primary molar crown; he said if you can not fit a crown then it's probably contraindicated, & this is rarely ever happens. An inability to fit one due to amount of tooth tissue remaining & the ability of the patient to cooperate with the treatment. So this is when, if you don't have enough tooth structure for the crown to be retained, this is the only contraindication!& this is rare, it can happen when you have an MOD , & a lot of loss of tooth structure mesiodistally , this crown have been reduced a lot , & the shapes of SSC in the kit will not fit, the d was rectangular & now because of mesial & distal loss now it's like a square. if you go to the kit , it usually has deep formed crowns according to the morphology of a normal tooth, so in this case the retention will be minimized. The other contraindication is when the patient is not cooperating, but usually we can manage to put a crown. It has also been recommended that teeth approaching exfoliation within 6 to 12 months should not be fitted with a preformed metal crown.

Slide 11:Indications in permanent teeth: usually parents ask whether they should come back when the tooth you've placed a SSC is exfoliating or not. they shouldn't , because the SSC is cemented to the tooth , & it will fall with the tooth when it exfoliate. in permanent teeth the SSC is not placed as a permanent restoration'' interim restoration'' it is placed until the patient grows older & then you can put a cast metal or PFM crown, It's a temporary restoration that will maintain the structure of the tooth. In the primary it's permanent until the tooth exfoliate. interim restoration of a broken-down or traumatized tooth until the construction of a permanent restoration can be carried out.

Why don't we use a PFM crown to a 7 Y.O child's molar ''6'' with multiple caries on B, M & D surfaces? · · Very high pulp horns . in order to place a PFM crown you need to remove a lot of tooth structure '' about 2mm'' , most probably you'll expose the pulp , this is harmful for a thin primary tooth. The 6's erupts at the age of 6, but the roots still growing in a 7 Y.O child , the tooth is erupted in the mouth , but it's not fully erupted , it never reaches the full eruption stage until the age of 18-20, it will still erupt even in a small millimeters. If you place a PFM and the gingival margin looks excellent at this stage , after few months you'll find that it is short cause the tooth erupted a little more. Also because the patient is still growing, there might be mesial drift of the crown , or the distal edge of the crown might prevent the 7 from erupting. So at the stage when the patient is still growing you don't put something permanent. The PFM cost is way much higher than the SSC cost , so the parents shouldn't spend that much of money on something that is still not permanent. when financial considerations are a concern as an interim, permanent preformed metal crowns are useful as a medium term , economical restorations. there might be some cases where the patient is 18-20 Y.O and had pulp therapy done to their 6's & for economical reasons ,cause they couldn't afford a PFM crown, they had to place a SSC, & that's better than leaving the tooth without a crown. teeth with developmental defects this is a great indication for placing a SSC , they are beneficial for restoring the occlusal height & reducing the sensitivity caused by wear of tissue in enamel & dentine dysplasia in young patients .


~Developmental defects: enamel hypoplaisa. enamel hypomeniralization. dentinogenisis imperfect. amelogenesis imperfect. vitamin D dependent rickets. vitamin D resistant rickets. dentine dysplasia. turner tooth. all these are structural anomalies, where the tooth structure is weakened with severe tooth wear , the patient is 7 Y.O & half of the crown is worn out, Also they get a lot of sensitivity & pain in their tooth, so these are very important indications for placing crowns in permanent teeth disabled patients with poor oral hygiene; patients with physical or intellectual disabilities, so we place something more durable, SSC more durable than composite or amalgam, so that we won't have to go back & do the restoration if it fails , we rarely , if ever have to redo or replace a crown, or fix something wrong with it, but the restoration might be high or needs polishing or it might fracture or get recurrent caries, but in the crown you don't have these problems. Slide 12:Other considerations: · caries risk for high caries risk patients



restoration longevity (when the restoration needed more than 2 years , or when the patient less than 6 years, evidence suggests that it's best to place a SSC. the tooth will stay long in the patient mouth so you need something more durable. cost effectiveness , class II amalgam is less expensive compared to SSC , but more likely to fail .

Failure rate for amalgam is 4 times that of SSC over 5 years.

Slide 13:The advantages of SSC: extreme durability & longevity relatively inexpensive subject to minimal technique sensitivity during placement ; you don't have to worry about the moisture control , or the multiple steps required , you don't have to worry about this when you place a crown. offers the advantage of full coronal coverage; in case of M.O composite restoration ,you restore the mesial side, probably later you might get a distal caries, so you need to do another restoration. So you remove the caries & you build up the tooth using GIC , then you put the crown on the top. Slide 14:Disadvantages , the risks associated with SSC: periodontal concern: if you place the crown in a wrong way or if the patient has poor oral hygiene of course you'll get periodontal problems, & if you cement the crown & the cement pops out if the cervical margin , if you don't clean this area properly , you'll have residues of the cement remain there & cause gingival inflammation. nickel allergy: Ni used to be 70% of the metal in the past, now it's less.some people are allergic to Ni but it's rare (1%) due to contact dermatitis. esthetics: some parents dislike the appearance of the SSC,but this is rare. especially the D's because they are close & they can show when the patient smile. slide 15:Success Rate: rarely need to be replaced replacement rate in primary teeth: amalgam class II: 15% of class II's will need to be replaced. SSC: 3% of SSC you might replace. The ratio is 5 times more. Slide 16:Methods of placement:

Armamentarium: what instruments needed next to you when you want to put a crown. scissors crimping pliers adams plier burs: tapered diamond, flame-shaped bur, stone/rubber bur for polishing. Usually we use diamond burs, we don't use the stainless steel burs. Slide 17:These are the scissors , their tip is slightly curved, these are used for cutting the margins of the crown sometimes to enlarge it a little bit . if you have a size 3 crown , you try it & it's small , then you try a size 4 & it's big . so for this patient the tooth is something between 3 & 4, in the kit there is no 3.5, so what we do is we take size 3 & we cut 1 mm from its margin & it becomes 3.5. Slide 18:After this we use the crimping pliers , we use it on the margins of the crown to bend it inward. the cervical area of the crown is converged & when you cut the margin will change so you use your pliers to bend it inward so that it can fit to the tooth. Slide 19:So we use a crimping or contouring plier to do this . Slide 20:So we need local anesthesia , rubber dam , gauze, during trial. restore the tooth with glass ionomer where applicable , you remove your caries, do pulpotomy & put IRM so the tooth is ready for a crown. reduce the occlusal surface by about 1.5 mm. cut interproximal contacts, use tapered bur held convergent to long axis of tooth. Sometimes the lower D has a primate spaces on the distal of the canine on the lower , so actually the mesial side of the lower D is already open, so you don't need to open the contact in this case. So we only remove 1.5 mm from the occlusal , and we open interproximal contacts , we don't do anything buccally or lingually as in porcelain or cast metal crowns, because we need the buccal & lingual bulge for the undercut area, it will hold the crown in place. try the SSC & measure the mesio-distal width. crown should sit no more than 1mm subgingivally, so it must be in the upper 1mm of the free gingiva, so it never reaches the junctional epithelium ,cause there will be pocket formation. cement with GIC or polycarboxylate cement. Wipe excess cement, place Vaseline around margins during the setting period. Slide 21:This is an example of a patient who had local anesthesia ,rubber dam , pulpotomy procedure

Slide 22:then a Glass ionomer build up slide 23:then occlusal reduction & then interproximal removal with the bur, the mesial side of the D in the pic is already present , they didn't touch that side , it's the primate space. Slide 24:then the crown was fitted in its place. In order to cement it, fill the crown with cement & put it on top of the tooth. Slide 25:This is the preparation of the tooth , you remove 1.5 mm occlusaly & then open the contact & never touch the lingual or the buccal. Slide 26:if upon trial the SSC is small , the next size is big , then cutting of the margin of the smaller SSC & make it a little bit bigger. If the SSC is impinging on the gingiva , causing severe blanching , this means it has gone too deep into the gingival, so you cut a little bit of the margin to make it shorter. if 2 SSC are placed at the same time '' D & E for example ", start from distal to mesial '' fix it on E then D '' ,in some cases you can flatten the mesial & distal surfaces of the crown because they are flexible. Sometimes if you find the tooth has less mesiodital dimention because of caries , you can make the crown a little bit shorter in the mesiodistal dimention by using adams plier or a hawe plier. The adams plier is just placed on the mesial or distal width, the crown is usually on the proximal convex , so with the adams plier you make it straight, so in this way you make the mesiodistal dimention a little bit less (1-2mm). the howe plier is open & you place it on the mesial & distal curve & bend the crown ,it will become a little bit smaller. these things not all of you will do, we need them in certain cases. Slide 27:After you cut the margins of the SSC, crimping & polishing are required, polish it with the rubber slow speed bur or ringfol bur, we polish it: · so that it could be smooth & don't cause any injury to the gingival. · also the crown when comes from the company the margins are polished, so when you cut , the new margins are not polished, so they can leak nickel or chromium and cause allergy, staining & corrosion. This area is susceptible to corrosion , & by polishing it you prevent that. optimum adaptation of the SSC: crown length have to be optimum, shape of the crown margin have to be optimum. U have to know the shapes of the margins. ''the dr. read the table in the slide''

Frown means sad face


When you have a crown & you want to cut it with the scissors , follow these shapes '' in the table''. Slide 28:This is a conservative method to place a SSC , here this is a permanent tooth "6"which is hypoplastic & hypomeniralized & you wanted to place a SSC on it , we built it with GIC , & because we don't want to remove any of the enamel, we already conserved the tooth structure as much as possible we placed separators. Separators :rubber bands we use them in ortho. to place bands and fixed appliances, & we use them also in pediatric dentistry, we put them between the teeth & they will push the teeth a little bit to create a space between them, in this case you didn't use the bur to remove any tissue ,so you conserved your tooth structure , & to open a space the little bit to place your crown , after you remove them & place your crown , the space will close back, in this way we conserved the tooth structure , because this tooth might need a porcelain crown in the future & it's better for the prosthodontist to find enough tooth structure in order to prepare the tooth, but if we both did preparation , then this is a removal of a lot of the tooth structure , & also you make the tooth more prone to sensitivity & tooth wear & pulpal problems.

Slide 29:This is postoperatively, these Are permanent SSC placed on the 6's, this is because of structural developmental problems. Slide 30:Another example , this is amelogenesis imperfect , pre-operatively , D, E & 6 are destroyed Slide 31:these are the upper teeth, so this is a severe case , specially the E. Slide 32:This is post-operatively, so we placed SSC on all the teeth Slide 33:all the upper teeth were crowned. So this is a way to conserve these teeth , it enables the patient to masticate & will reduce the sensitivity & it will reduce the tooth wear because these teeth are very weak ,& it will maintain the vertical dimension of the tooth. so we conserved the tooth for a very long time. Slide 34:Composite resin strip crowns : By using a cellulose crown to restore anterior teeth.

It's similar to plastic , they call it celluloid . Slide 35:imagine it like a plastic crown & it has a small handle to hold it & try it on the teeth, & the idea behind this is to fill it with composite, put it on the tooth , take the shape of the tooth , to build up fractured teeth, it has the morphology of incisor. They come in different sizes & shapes for centrals & laterals & canines, some manufacturers make it also for premolars . Slide 36:The success/clinical performance: The treated children under general anesthesia , very high failure rate of composite crown (30%), & composite resin strip crowns (51%) in comparison to SSC that has (8%) failure rate. 88% retention rate. Causes of failure: · loss of composite resin. · color matching: we didn't choose the correct shade. · adaptation: you have to adapt it in the correct mesio-distal & buccolingual angulations · poor retention · recurrent caries. procedure is very technique sensitive ''because it involve composite'' any lapses in patient selection , moisture control, hemorrhage control; if the gingiva is inflamed for example your procedure will not work, tooth preparation, adhesive application & composite resin placement can lead to failure. Slide 37:Indications for strip crowns: caries present on multiple surfaces the incisal edge is involved ''with caries'' there is extensive cervical decalcification ''initiation of caries'' pulp therapy is done for the tooth hypoplasia '' enamel hypoplasia'' slide 38:Contraindications: 1. Inability to control moisture or hemorrhage especially in poor oral hygiene & marginal gingivitis is present 2. Insufficient tooth structure remaining to hold the restoration, remember that composite adheres to enamel if you don't have enough enamel , your filling will not be retained, so if you have dentine exposed you have to place a liner which can be RM-GIC ''vitrebond'' & then you place you composite on top, to get better retention 3. If you have insufficient enamel , you won't have enough retention. 4. If you have deep bite , or anterior cross bite , it might affect the retention

5. Uncooperative behavior by the child. Slide 39:Advantages of strip crowns: they are the most esthetic restorative option for carious primary incisors. ease of repair if the crown chips & part of the composite is broken, you put some acid itch & bonding agent & repair it. Slide 40+41:Disadvantages are the same !go back to the slides & read them . Slide 42-46:Steps in placement : oral hygiene : * if you have a patient with poor oral hygiene ,you give him oral hygiene instructions. start them on chlorhexidine mouth rinse or gel until the gingiva becomes perfect, before you even start your treatment & they are responsible if it fails preparation: Crown pierced with sharp explorer at mesial or distal incisal angle, you make this hole so that when you put composite & put it on the tooth , any excess can escape ,you can remove it & then cure. Instead of coming out at the gingival margin which will cause injury to the gingiva when you remove it. do not damage proximal seams of the crown. following vent preparation place the rubber dam remove your caries & try on your crown & then remove it so caries removal: care not to damage any gingiva , it will case bleeding & make the procedure difficult then you place RM-GIC like vitrebond fill & cure each crown individually. if you get any bonding agent on the gingiva , remove it with the explorer. minimal filling is highly recommended, don't fill the crown up with composite totally, because tooth structure will need some space a sharp hand-held instruments recommended to peel off the crown, after curing you can remove it with the carver. Slide 48:This is a case of early childhood caries, this patient has caries on upper anterior teeth Slide 49:The caries were removed, it's multiple surface caries , on inciso-buccal ,mesial ,cervical & distal. Slide 50:-

A slight reduction proximally, cause we want to put 2 strip crowns next to each other , so we need some space between the teeth Slide 51:So this is the final restoration Slide 52:Trial of the crown , you place it on the tooth to see if it matches, it comes in different sizes Slide 53:This is the final restoration Slide 54:Another case with amelogenesis imperfect, the patient didn't have poor oral hygiene , what you see is plaque but not because he doesn't brush will ,because he has hypoplastic type of amelogenesis imperfect & in this type the tooth has a rough surface which retains plaque, no matter how much he brushes it's hard to remove this plaque. The other thing is that the steep is very sensitive , there is barely , if any, enamel there & dentine was exposed. Slide 55:So this is what we did with composite strip crowns, we did teeth # 1, 2 ,3. Here the result wasn't complete because the teeth were partially erupting , we waited another 6 months then we added more composite, because the tooth erupts more , the cervical area is more exposed, but this made his life easier: now he can brush better eat better no more sensitivity & extensive tooth wear the vertical dimension especially for molars is maintained. so you really restored function for the patient in this case &especially for growing children it's better for their nutrition & growing & to carry out their activities.



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