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BDS 7135: Preformed metal crowns Aims: The aim of this lecture is to describe the indications and techniques for placing preformed metal crowns for primary molar teeth Subject Title Goes Here Objectives: On completion of this lecture, the student should be able to: -Describe the indications for...

BDS 7135: Preformed metal crowns Aims: The aim of this lecture is to describe the indications and techniques for placing preformed metal crowns for primary molar teeth Subject Title Goes Here Objectives: On completion of this lecture, the student should be able to: -Describe the indications for placing preformed metal crowns on primary molar teeth -Describe the Hall Technique and its appropriate use -Describe the conventional approach for preformed metal crowns and its appropriate use Chrome steel crowns, as introduced by Humphrey in 1950, are ready-made crowns that have proved to be serviceable restorations for children and adolescents and are now commonly called stainless steel crowns. Indications 1. Restorations for primary or young permanent teeth with extensive and/or multiple carious lesions 2. Restorations following Pulp Therapy (pulpotomy or pulpectomy) for primary or young permanent teeth when there is increased danger of fracture of the remaining coronal tooth structure as the teeth become brittle and weak. Indications (cont.) 3. Restorations for primary or permanent teeth with Developmental Defects that cannot be adequately restored with bonded restorations. In amelogenesis imperfecta, dentinogenesis imperfecta, MIH or enamel hypoplasia, the enamel is chipped or worn off exposing the underlying dentin, which may also lead to reduction in vertical height of the crown. Cast crown is avoided, considering the pulpal morphology and reduced tooth height. Care must be taken while placing a stainless steel crown as enamel Indications (cont.) 4. Restorations for fractured teeth 5. Restorations for primary teeth to be used as abutments for appliances 6. Children with special health care needs CSHCN: Oral hygiene maintenance is difficult, so stainless steel crowns are preferred to restore carious teeth than amalgam or composite restorations when Contraindications of stainless steel crowns 1- As a permanent restoration in permanent dentition. Stainless steel crowns are used as temporary crowns for permanent teeth because: a. The margins of the crowns cannot be made as accurate as other materials, which can be adapted for marginal excellence. b. They are not as durable for a long period as custom-made crowns. 2- Deciduous teeth that exhibit resorption of > ½ of the root length. 3- Very deep bite with severely reduced vertical crown dimension of the tooth. Classification of Crown (Based on shape) A. Untrimmed: They are long and usually require trimming B. Pretrimmed uncontoured: These crowns are short in length but are not contoured and so have parallel sides C. Precontoured: These crowns are contoured, these are the commonly used type. Contouring of the crown (when necessary) The pre-contoured and festooned crowns currently available often require very little, if any, modification before cementation. In case of untrimmed crowns that are cut using crown scissors, or in case of crown margin that are trimmed or contoured, the final step before cementation is to produce a beveled gingival margin that may be polished and that will be well tolerated by the gingival tissue. Usually there is no need to trim the crown margins, as all available crowns are pretrimmed precontoured. Final finishing to produce the smooth margin is done with stone and rubber wheel to remove scratches and obtain shine. Contouring of the crown (when necessary) A crown-contouring pliers with a ball-and-socket design is used at the cervical third (if loosely fitting, start at the middle third) of the buccal and lingual surfaces to help adapt the margins of the crown to the cervical portion of the tooth. The handles of the pliers are tipped toward the center of the crown, so that the metal is curved inward as the crown is moved toward the pliers from the opposite side. Contouring of the crown (when necessary) Crimping plier: to produce marked curvature in cervical region Ball and socket plier: used to get a bell shaped contouring Curved beak plier: used for general contouring and shaping. STEPS INVOLVED IN ADAPTATION OF THE PREFORMED STAINLESS STEEL CROWN *****Patient and parent preparation 1. Crown selection 2. Preoperative occlusal evaluation 3. L.A. administration 4. Rubber dam application 5. Placement of wedges 6. Tooth preparation • Occlusal reduction • Proximal reduction • Buccal and lingual reduction • Finishing 7. Trial fitting of the crown 8. Finishing the crown 9. Cementation 10. Post-cementation instructions STEPS INVOLVED IN ADAPTATION OF THE PREFORMED STAINLESS STEEL CROWN Silver tooth *****Patient and parent preparation Tiara Iron man tooth Crown selection A correctly selected crown should cover all the tooth preparation and provide resistance to removal. Contoured crown is superior because it most accurately reproduces the tooth morphology and requires least trimming and contouring. Crown selection (cont.) Mesiodistal Width of the Tooth: Preoperative mesiodistal width of the tooth to be crowned is measured with the callipers and matched with the stainless steel crown. WHY? In addition to improper fit and occlusion it should be also kept in mind that an over-contoured or over-sized crowns on 2nd deciduous molar can prevent normal eruption of the 1st permanent molars. Preoperative occlusal evaluation Comparing the occlusal level of the tooth to the occlusal level of the adjacent teeth as a reference to the amount of occlusal reduction. Also a probe can be placed on the operating tooth so that the probe extends and touches the cusps of the two adjacent teeth. This helps in later evaluation of the reduction and crown fit. Local anesthesia administration Local anesthesia reduces the discomfort to the patient during tooth reduction and crown fitting. Rubber dam application It prevents slipping of crown during preparation and trial fitting into the throat accidentally and also provides isolation if tooth has to undergo pulp therapy. Placement of wedges They are placed in the interproximal space which act as tooth separators and also protects the underlying soft tissues. Tooth Preparation Tooth Preparation Occlusal Reduction around Wheel-shaped, tapered fissure or flame shaped diamond stone can be used. The occlusal reduction of approximately 1-1.5 mm following the anatomy of the occlusal surface. The general contour of the occlusal surface is followed, and approximately 1 mm of clearance with the opposing teeth is required. Initial placement of 1 mm depth grooves in the occlusal surface followed by removal of remaining portion according to cuspal inclines makes the reduction easier and accurate. Sharp line angles should be rounded. Tooth Preparation (cont.) Proximal Reduction The fine tapered fissure bur is used to avoid trauma to soft tissues and adjacent teeth. Attention should be paid to avoid injuring the adjacent tooth The bur is moved in a buccolingual direction 1-2 mm away from the adjacent tooth, until the contact area clears gingivally and buccolingually. Also matrix band can be used for protection of adjacent tooth during proximal reduction. The preparation should have no finish line. The gingival margin of the preparation on the proximal surface should have no ledge or shoulder. Tooth Preparation (cont.) Buccal and Lingual Reduction It is usually not necessary to reduce the buccal or lingual surfaces; in fact, it is desirable to have an undercut on these surfaces to aid in the retention of the contoured crown. However, it may be necessary in most cases to reduce the distinct buccal bulge, particularly on the first primary molar as well as slight buccal and lingual surface reduction. Finishing All the line angles must be rounded. The buccoproximal and linguproximal line angles should be rounded. The occlusobuccal and occlusolingual line angles are rounded by holding the bur at a 30-45˚ angle to the occlusal surface and sweeping it in a mesiodistal direction. Fitting of the crown The crown should be replaced on the preparation to see that it snaps securely into place. The crown should fit the preparation snugly and extend under the free margin of the gingival tissue. The occlusion should be checked at this stage to make sure that the crown is not opening the bite or causing a shifting of the mandible into an undesirable relationship with the opposing teeth. Cementation Cementation Usually, seating of a crown on a mandibular molar is best done by first fitting the lingual side and then rotating it buccally. In the upper arch it is easier to fit the buccal side first, but that is variable according to the case. The tooth is cleaned from debris or blood, isolated with cotton and dried. The crown is 1/2- 2/3 filled with cement and seated on the tooth along the predetermined path of insertion. Glass ionomer is used usually, however, zinc polycarboxylate and zinc phosphate can be used. The patient requested to bite gently on the crown to ensure it is being forced to place. The end of a tongue depressor trimmed to the mesiodistal size of the crown or the back side of a tweezer or a cotton roll, is placed between the crown and opposing tooth and the patient is asked to occlude gently. When the cement has been half set, the occlusion is rechecked and excess cement is removed using scaler from the buccal and lingual aspects and floss can be used for Post-cementation Instructions Instructions should be given for maintaining oral hygiene and patient should be recalled once every 6 months for evaluation. The patient and parent are informed that slight discomfort may be encountered during the first few days after crown placement, and this is normal due to the crown placement, and that the child shouldn’t manipulate the crown margins. Tooth Preparation MODIFICATIONS OF STAINLESS STEEL CROWN A. When more than one stainless steel crown has to be prepared, additional factors are to be remembered: i. Occlusal reduction of one tooth should be done completely before starting the second tooth. If done together there is a tendency to over reduce. ii. Contact point between adjacent teeth should be broken producing 1.5 mm space at the gingival level. iii. Both crowns should be adjusted and prepared for cementation simultaneously. Cementation sequence of the crowns should be the same as during trial fitting. MODIFICATIONS OF STAINLESS STEEL CROWN B. Drifting of tooth and space loss: The crown required to fit a tilted tooth buccolingually will be too wide mesiodistally and crown selected to fit mesiodistally will be too small buccolingually. MODIFICATIONS OF STAINLESS STEEL CROWN B. Drifting of tooth and space loss: In such a case the crown is taken and mesiodistal width is adjusted by using Howe utility plier. Alternate method when there is space loss is by using the crown of diagonally opposite arch. The Hall Technique The Hall Technique is considered a quick non-invasive method for managing carious primary molars where decay is sealed under preformed metal crowns (PMCs) without local anaesthesia, without tooth preparation, without any caries removal. Background The technique is named after Dr Norna Hall, a general dental practitioner from Scotland, who developed and used the technique for over 15 years until she retired in 2006. A retrospective analysis of the outcomes for the teeth she treated in this way was published in the British Dental Journal in 2006. This showed the technique to have outcomes comparable to conventional restorative techniques. Steps of Hall Technique essing the tooth shape, contact areas and the occlusio Protecting the airway Size of the crown The smallest size which covers all the cusps and will seat properly and completely cover all the tooth surfaces. Loading the crown with cement Fitting the crown and seating Final clearance of cement, check occlusion A modification of the Hall technique, where minimal caries removal is combined with minimal reduction of the tooth and then the crown can be fitted. For decades, all carious tooth tissue should be removed before restoring the tooth; how can leaving caries in the tooth be acceptable? Plaque can loose its cariogenic potential if its environment is altered, cariogenic bacteria will not continue to flourish. Effective sealing from the oral environment can cause the necessary environmental change, resulting in plaque losing its cariogenic potential for as long as the seal is maintained. The Hall Technique is one method of achieving that seal for primary The Hall Technique in clinical practice Case selection It is important to note that: -Hall crowns are not a universal answer to managing all carious primary molars. The Hall Technique will not suit every tooth, every child or every clinician. -As with every treatment decision, clinicians should use their own clinical judgement in deciding which method is appropriate for their patient and within their own clinical capabilities to deliver, with consent being obtained from the patient, and parent, before delivering that treatment. For example in this case, Hall crowns can be suitable for this moderately advanced Class I lesion where the extent of the cavity would make it difficult to obtain a good seal with an adhesive restorative material. ontra indications for fitting Hall crowns include: rreversible pulpal involvement linical signs or symptoms of irreversible pulpitis, or dental abscess. adiographic signs or symptoms of dental abscess. on-physiological mobility. A patient at risk from bacterial endocarditis. In such situations, the tooth should managed with a conventional restoration which would include complete caries rem nsufficient sound tissue left to retain the crown Parent or child unhappy with crown aesthetics. Buccal sinus associated with maxillary second primary molar . Mandibular first primary molar (84) has bone resorption in the furcation area, indicative of a dental abscess. Maxillary second primary molar (55) with extensive cavity, that has been painful, keeping the child awake at night. This is indicative of an irreversible pulpitis, or even an abscess developing. Mandibular first primary molar (84) was painful, but is currently symptomless, with non-physiological mobility. This, with the DO cavity, xray and history, indicates a dental This mandibular first primary molar ( 84) has a large distooccusal cavity. There is history of spontaneous unprovoked pain. The tooth should have pulp therapy if a crown is to be placed. Mandibular second primary molar (75) has a large occlusomesial cavity which clearly involves the pulp chamber. The tooth should be managed with pulp therapy (decision was taken after x-ray). Mandibular second primary molar (75) has pulp polyp associated with the mesial root, there is clearly a sinus associated with a non-vital distal root, and the tooth should be managed by extraction (decision was taken after x- When is there no need to fit Hall crowns? Examples Maxillary and mandibular first primary molars (54 & 84) although cavitated, are clearly going to be shed soon, so are unlikely to cause Mesial cavity in mandibular second primary molar (75) is accessible, and can be managed with caries removal, sealing the cavity with an adhesive restorative material, avoiding both the aesthetics and bite The cavitated occlusal lesion on this mandibular second primary molar (85) should be managed with caries removal and restoration, and sealing the occlusal surface with an adhesive restorative material. Clinicians should continue to monitor all primary molars managed with Hall crowns for signs or symptoms of pulpal disease at every recall visit, just as they should for all carious primary teeth managed with conventional restorations. Aims: The aim of this lecture is to describe the indications and techniques for placing preformed metal crowns for primary molar teeth Subject Title Goes Here Objectives: On completion of this lecture, the student should be able to: -Describe the indications for placing preformed metal crowns on primary molar teeth -Describe the Hall Technique and its appropriate use -Describe the conventional approach for preformed metal crowns and its appropriate use References: • Arathi Rao. Principles and Practice of Pedodontics, 2 nd edition. Jaypee Brothers Medical Publishers (P) Ltd • Dean, J.A., Avery, D.R. and McDonald, R.E., 2010. McDonald and Avery Dentistry for the Child and Adolescent 10th edition, 2010. Elsevier Health Sciences. • Reading material: • Students are advised to review any relevant teaching provided in the first year. In addition they are advised to read relevant sections of the following texts: • The Hall Technique, Dundee University, https://dentistry.dundee.ac.uk/files/3M_93C%20HallTechGuide2191110.pdf • Prevention and Management of Dental Caries in Children, Scottish Dental Clinical Effectiveness Programmehttp://www.sdcep.org.uk/published-guidance/caries-in-children/ • Welbury R et al; Paediatric Dentistry; 5 th Edition, Oxford Press • Koch G et al; Pediatric Dentistry - a Clinical Approach; 3 rd Edition, Wiley Blackwell Thank you Subject Title Goes Here