RESTORATIVE
1. Liners indications, types, advantages of GIC liner. How GI bond to tooth structure? Chemical bonding. GIC in locks?
Liners are thin layer of material used to provide a barrier to protect dentin. Contribute electrical insulation, thermal protection, and pulpal treatment.
Indicated under metallic restorations (not well bonded to tooth structure) and under tooth coloured materials if tooth prep is too close to the pulp.
Types: Solution liners (varnishes, 2-5 um), Suspension liners (thicker, 20-25 um), cements liners (thickest for pulpal medication and thermal protection, 0.2-1 mm).
Bases (cement bases, 1-2 mm) provide thermal protection, mechanical support for the restoration.
Liners and bases may be combined in a single preparation.
Moderate depth: ZOE, currently RMGI. Deepest portion, calcium hydroxide when microscopic pulp exposure to encourage dentinal bridging (reparative dentine). ZOE and CH cannot be used together, strong exothermic reaction.
Zinc phosphate cement and resin-reinforced ZOE cement were widely used before. Then Polycarboxylate cement; and then light cured resin modified GI or compomers, provide chemical adhesion, good mechanical strength, fluoride release, well-controlled setting and rapid achievement of strength (ADVANTAGES)
Before in a deep restoration: calcium hydroxide liner, then a base for mechanical support and stress distribution, then varnish. Currently, light-cured calcium hydroxide and GI material.
For indirect restoration, mechanical undercuts or bonding of base material to prepared dentin.
In a shallow tooth excavation, 1.5-2 mm of remaining dentin thickness, not need for pulpal protection.
In moderate deep liner of ZOE or calcium hydroxide for amalgam, Calcium hydroxide for composites (eugenol inhibits polymerization)
If pulp exposure, calcium hydroxide, spherical amalgam recommended as it requires less condensation pressure. If extensive dentin lost cement base over calcium hydroxide liner. Sealer or bonding agent and then the restoration.
A liner should not extend closer than 1 mm to a slot or pin.
Summary of pulpal protection procedures (Medicament/liner/sealer)
Shallow excavation (RDT > 2 mm) / Moderate excavation (RDT 0.5-2 mm) / Deep excavation (RDT < 0.5 mm)Amalgam / No/no/sealer / No/base/sealer / CH/base/sealer
Composite / No/no/DBS / No/no/DBS / CH/no/DBS
Gold inlays and onlays / No/no/cement / No/base/cement / CH/base/cement
Ceramic, PR, FRP / No/no/DBS, CC / No/no/DBS, CC / CH/no/DBS, CC
Pulpal protection includes pulpal medication, dentin sealing, thermal insulation, electrical insulation, and mechanical protection.
Sealer: Gluma or Hurriseal; Base: Vitremer or Durelon cement; Cement: luting cement (e.g. RMGIC). CC: composite cement (e.g. Rely X luting cement); CH: Dycal liner; DBS: dentin bonding system; FRP: fiber reinforced prosthesis; PR: processed resin; RDT: remaining dentin thickness.
2. What do you use for etching and make a drawing of the etched area.
Acid etching (or conditioning) dissolves the smear layer (residual organic and inorganic components whenever a tooth is prepared with a bur or other instrument) and produces microscopic relief with undercuts on the surface to create an opportunity for mechanical bonding.
Acid etching transforms the smooth enamel into a very irregular surface and increases it surface free energy. Phosphoric acid gel 30%-40%.
Total etch technique, simultaneous application of an acid to enamel and dentin, current strategy.
Self etching primers: etching and priming of dentin and enamel, not rinsed off.
Porcelain and processed composites veneers are etched with 10% hydrofluoric acid for 2 minutes.
Etching enamel affects both the prism core and prism periphery. Etching dentin affects the intertubular and peritubular dentin, enlarging the tubular openings, removing much of the surface of hydroxyapatite, and leaving an interconnected network of collagen fibrils. The acid (liquid or gel) 32%-37% phosphoric acid is gently applied to the appropriate surface to be bonded, keeping the excess to a maximun 0.5 mm past the anticipated extend of the restoration.
For Fissure sealants etch for 30 seconds, wash for 30 sec, dry for 15 sec, cure sealant for 60 seconds.
For abrasion lesion, cleanse dentine with dentine conditioner, polyacrylic acid for 15 seconds, wash, mix GIC, apply, put matrix, leave for 4 min, apply bond, and cure for 40 seconds.
3. Differences between matrices, advantages, disadvantages?
A matrix is placed when a proximal surface is to be restored.
Objectives: provide proper contact, provide proper contour, confine the restorative material, and reduce the amount of excess material. Helps protect adjacent tooth from being damaged (placed on the adjacent tooth for this reason).Helpful ensuring marginal adaptation and strength of the restoration.
For a matrix to be effective, it should be: easy to apply and remove, extend beyond the gingival margin, extend above the marginal ridge height and resist deformation during material insertion.
Universal (tofflemire), compound-supported, precontoured, automatrix system and Squeland.
Universal (tofflemire) ideally indicated when 3 surfaces of a posterior tooth have been prepared. Can be placed on the facial or lingual aspect. Matrix bands of various occluso-gingival widths are available. Still does not meet the ideal retainer and band. The conventional, flat tofflemire band must be shaped (burnished) to achieve proper contour and contact. The uncontoured bands are available in 2 thicknesses. Precontoured bands are simpler to use, less chair time, little adjustment after positioning. Tofflemire retainer helps to hold the cotton roll in place for moisture control. Pre wedging will compensate for the thickness of the band, ensuring proper contact.
Compound supporting cooper band matrix: rarely used, more rigid, provides better contact and contour, virtually trouble free during proper removal, and requires very little proximal carving after the matrix removal, only one thickness.
Precontoured matrix strips: ready for application to the tooth, suitable for mandibular premolars and distal of upper canines; with the bitine ring.
Automatrix: 4 types of bands, use for extensive class II, especially when replacing cusps. The auto-lock loop can be positioned either on the facial or lingual surface, the bands are not precontoured. Convenience, improved visibility because of absence of a retainer.
Clear polyester matrices are other type, come precontoured to use with the tofflemire, are thicker, not recommender for large posterior composites restoration, cannot be contoured, don’t provide resistance to condensation.
4. Crack tooth syndrome, symptoms, diagnosis, treatment
Diagnosed by history, using fracfinder (force is directed to one cusp), pain upon pressure release, pain to cold and hot foods, probing with an explorer, sings and symptoms, staining and transillumination.
Consist of an incomplete fracture of a posterior tooth with vital pulp; the fracture involves enamel and dentin. Symptoms include pain on chewing, referred pain and sensitivity to thermal changes. The most common symptom is sharp pain that occurs upon release of chewing pressure. Most cracks run mesiodistally. Most common are molars of older patients, teeth with class I restorations or that are unrestored but have an opposing plunger cusp occluding centrically against a marginal ridge. Mandibular molars, maxillary molars and maxillary premolars.
The ideal treatment consists of applying a stainless steal band to the tooth, with cessation of symptoms confirming the diagnosis, review after 2-4 weeks, followed by a full coverage restoration. Urgent care is reduction of its occlusal contacts, remove any placed restoration and dress with sedative dressing. Definitive treatment is full occlusal coverage to preserve pulpal vitality. If sensitivity to temperature changes has not ceased, endodontic therapy has to be considered. The prognosis for a vertical root fracture extending apically from the alveolar crest is poor and tooth extraction is indicated.
5. Reasons cusp breaks in MOD amalgams.
Insufficient resistance form when preparing the tooth cavity. When the facial or lingual extension exceeds 2/3 the distance from a primary groove to the cusp tip, reduction of the cusp for amalgam is required to provide adequate resistance form.
Inadequate tooth preparation, insufficient bulk of amalgam
6. Difference between pin and slot? When do you use slots and when pins?
Pins in dentine to provide adequate resistance and retention form.
Slot is a retention groove in dentin whose length is in a horizontal plane. May be used in conjunction with pin retention, or as an alternative to it.
Pins are used whenever adequate resistance and retention forms cannot be establish with slots, locks, or undercuts only. In canines lingual dovetail is an alternative to pin retention.
They both has advantages and disadvantages, slot remove more teeth structure, while pins have the risk of perforation pulp chamber, periodontal ligament, and must have enough space for the use of pins.
Pin retention is used more frequently in preparations with few or not vertical walls. Slots are indicated in short clinical crowns and in cusps that have been reduced to 2-3 mm for amalgam.
7. What should be the dimensions of retentive slots prepared in an extensive amalgam cavity?
Slots: 0.6 mm deep, 0.5 mm width, 1 mm or more in length and 0.5 to 1 mm inside dentino-enamel junction. Prepared along the gingival floor, axial to the DEJ.
Slots are placed on the facial, lingual, mesial and distal aspects of the preparation. May be continuous or segmented.
8. Additional retention complex amalgam
Insufficient remaining tooth structure-pin, slots, undercuts, amalgam bonding techniques to enhance retention and resistance form.
Coves may be used to provide additional retention form in a preparation that utilizes pins or slots.
Proximal locks also are placed in the proximal box and in other locations where sufficient vertical tooth preparation requires.
These locks and coves should be prepared before preparing pinholes and inserting pins.
Types of pins
Self threading pins (most frequently used, most retentive), friction-locked (intermediate) and cemented (less retentive).
Pinhole depth 2 mm. Placing pins in a non paralleling manner increases their retention. Strength of amalgam restoration decreases.
Four sizes of pin available. Selection depending on the amount of missing tooth structure, amount of dentin available, the amount of retention desired and the size of the pins. When only 2-3 mm of the height of the cusp is missing, no pin is required.
X ray useful for placement. Occlusal clearance should be sufficient to provide 2 mm of amalgam over the pin. Should be positioned not closer than 0.5- 1 mm to the DEJ or should be positioned no closer than 1 -1.5 mm to the external surface of the tooth, whichever distance is greater. Should be parallel to the adjacent external surface of the tooth. Should be placed on a flat surface perpendicular to the direction of the pinhole. Fluted and furcal areas should be avoided (M of 1rst premolar, midL and midF of mandibular molar, midL, midF and midM and midD furcations of the maxillary molars). Avoid on D of mandibular molars and L of maxillary molars.
Prepare pinhole with drill tip in proper position and with handpiece rotating at low speed, apply pressure to the drill, prepare pinhole in 1 or 2 movements and remove the drill. All of the pin designs can be inserted with an appropriate hand wrench or a contrangle hand piece. 2 mm length is optimal.
Pin holes for cemented pins are 3-4 mm depth, cemented with any luting agent.
For foundations pinholes must be located farther from the external surface of the tooth.
Dentin bonding systems are recommended for extensive preparations, with deep excavations, capped cusps and in weak teeth.
9. Why would you place slots and grooves for retention instead of pins in an extensive cavity for amalgams?
Slots and locks, and deepened proximal box are enough for retention; plus dentin bonding systems.
10. Patient has gingival recession in 4s what is the cause?
Abrasion or/ and Abfraction.
Abrasion is the physical wear of a tooth caused by an external agent (toothbrush). Non-carious defect in tooth structure usually located at, or near, the cemento-enamel junction and generally on the buccal surface of teeth. Usually caused by abrasion due to excessive or incorrect toothbrush use.
Abfraction lesions due to flexure of teeth under excessive occlusal loading.
Teeth are not rigid structures. Teeth bend either laterally or axially during occlusal loading. This flexure produces the maximal strain in the cervical region, producing micro fractures in the thinnest region of enamel in the CEJ. Such fractures predispose enamel to loss when exposed to toothbrush abrasion and/or chemical erosion. Sometimes causes the loss of bonded class V restorations in preparation with no retention grooves.
Attrition is physical wear caused by movement of one tooth against another. It affects interproximal and occlusal surfaces. Increase with more abrasive diets and in bruxism.
Erosion is loss of tooth substance from non-bacterial chemical attack.
11. What material would you use to restore a minimal cavity?
Sealer and amalgam, Bonding and composite.
12. What should be the amount of reduction for a functional and non functional cusp for amalgam onlay?
When the Facio-lingual extension of the occlusal preparation exceeds 2/3 the distance between the facial and lingual cusp tip, reduction of the cusp(s) for amalgam is required for the development of adequate resistance form. The reduction should be 2 mm for functional cusps and 1.5 mm for non-functional cusp.
When reducing only one or two facial or lingual cusps, the cusp reduction should be extended just past the facial or lingual groove, creating a vertical wall against the adjacent unreduced cusp.
13. If the lesion has close proximity to the pulp, what would be the materials you would use to restore the cavity? Pulp protection, base, restorative material?
Calcium Hydroxide as pulp protector, GIC as base, Composite, amalgam, indirect restoration as restorative material.
14. Types of amalgam?
Amalgam alloy is silver-tin alloy, varying amounts of cooper and small amounts of zinc.
Low-cooper amalgam 2-5% or conventional amalgams: corrosion because formation of tin-mercury phase (gammas two).
High cooper amalgam12-30%: the increased cooper content prohibits the formation of the corrosive phase (gamma two) within the amalgam mass. Can be either spherical or admixed in composition.
Spherical amalgam: contains small, round alloy particles that are mixed with mercury to form the mass. Because the shape of the particles, the material is condensed into the tooth preparation with little condensation pressure. High early strength , suited for very large amalgam restorations (complex amalgam).
Admixed amalgam: contains irregular shaped and sized particles, sometimes combined with spherical shapes. Requires more condensation pressure assisting in displacing matrix bands to more easily generate proximal contacts.