Wong Direct Restoration 2012
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Identify and describe the features that provide retention form for class I, class V, and occlusolingual preparations.
- Amalgam retention form involves
- 1) mechanical locking of the inserted amalgam into surface irregularities of the preparation (even though the desired texture of the preparation wall is smooth” to allow good adaption of the amalgam to the tooth
- 2) preparation of vertical walls (especially facial and lingual walls) that converge occlusally
- 3) special retention features such as locks, grooves, coves, slots, pins steps, or amalgampins that are placed during the final stage of tooth preparation, and 4) bonding of the amalgam to the tooth (optional).
- a. Retention form is part of Internal Form: holds restoration in place
- i. Class I: buccal and lingual walls converge occlusially; convergent walls retain restorative material (90-100 degree cavosurface angle desired)
- ii. Class V: occlusal and gingival retention grooves in dentin from a ¼ round burr (.25 mm)
- iii. Occlusolingual Preparations: Convergent occlusal walls in occlusal outline with grooves in mesial & distal walls of box of lingual preparation. Retention grooves get deeper gingivally
Define and describe outline form and identify the specific features, with criteria, that address it in the class I occlusal cavity preparation. (pp. 300-304)
- Outline form is the general shape and size of the preparation, including all of the various features of the prep.
- Outline form itself refers to the general contours of the prep. This means that the outline should be smooth-flowing without ledges and catches. The isthmus must be located on the central groove of the tooth. Outline form also involves the proper placement of the fishtail (around distal cusp) and the dovetail (parallel to marginal ridge).
- In class one occlusal preparation, this applies to the following criteria of outline SIZE:
- (a) Isthmus: 0.8-1.0 mm
- (b) Groove extensions: 1.0-1.5. These extend into primary grooves (grooves that separate the cusps)
- (c) Dovetail: 0.25-0.5 mm on each the buccal and lingual. This should furthermore be parallel the marginal ridge
- (d) Fishtail: 0.8-1.0. These should follow the primary grooves that outline the distal cusp of the mandibular molars
Define and describe resistance form and identify the specific features, with criteria, that address it in the class I occlusal cavity preparation. (pp. 304-306)
- Resistance form refers to the ability of the filled prepation to withstand the occlusal force associated with mastication and normal use.
- The criteria are listed as follows.
- (a) A pulpal wall depth of 1.5-1.9 mm. (for adequate thickness given compressive and tensile properties of restorative material)
- (b) Pulpal wall (or floor) parallel to occlusal surface (may be tilted in some premolars)
- (c) The pulpal floor should be smooth, flat and even throughout the prep – this helps the tooth resist occlusal loading by virtue of being at right angles to those forces of mastication.
- (d) Resist the extension of the external walls (keep as small as possible) to allow strong cusp and ridge areas to remain with sufficient dentin support.
- (e) The dovetail segments should be divergent to eliminate the possibility of undermined enamel
- (f) Dovetail placement should be at least 1 mm from edge of marginal ridge in order to not undermine the integrity of this ridge
- (g) To have slight rounding of internal line angles to reduce stress concentrations in the tooth structure.
Describe the proper technique of condensing amalgam into a cavity preparation that maximizes the physical and mechanical properties of the final restoration. (pp. 721-724)
- It must
- 1) be placed into a tooth preparation that provides for a 90-degree or greater restoration angle at the cavosurface margin (because of limited edge strength)
- 2) have a minimum thickness of .75 to 2mm (because of lack of compressive strength) and
- 3) be placed into a prepared undercut form in the tooh in order to be mechanically retained (because of its lack of bonding to the tooth).
- It is important to properly condense the amalgam into the tooth preparation. Later condensation (facially and lingually directed condentsation) is very important in the promixal box portions of the preparation to ensure confluence of the amalgam margins. As a general rule, smaller amalgam condenser are used first. This allows the amalgam to be properly condensed into the internal line angles and secondary retention features. Subsequently, larger condensers are used. Once the amalgam is placed to slight excess with condensers, it should pre-carve burnished with a large egg-shaped burnisher to finalize the condensation, remove excess mercury, and intitiate the carving process.
Describe the proper technique for contouring and finishing the amalgam restoration after condensation. (p. 724)
- The amalgam material selected for the resoration has a specific setting time.
- Occlusal areas-
- A discoid-cleoid instrument is used to carve the occlusal surface of an amalgam restoration. The rounded end (discoid) is positioned on the unprepared enamel adjactent to the amalgam margin and pulled parallel to the margin. This removes any excess at the margin while not allowing the marginal amalgam to be overcarved. The pointed end (cleoid) can be used to define the primary grooves, pits, and cuspal inclines. However, an amalgam restoration is not carved with deep, acute grooves or pits because that may leave the adjacent amalgam materal more subject to fracture. Once the pit and groove anatomy is initiated with the cleoid end, the instrument is switched and the discoid end is used to smooth out the anatomic form. Also it may be beneficial to be certain that the mesial and distal pits are carved to be inferioir to the marginal ridge height, thus helping prevent food from being wedged into the occlusal embrasure.
Describe the proper location on a 6” X 6” rubber dam for the hole to be punched for the posterior anchor tooth on an ideal rubber dam application when treating tooth #20. (pp. 469-470)
- When treating tooth number 19, the anchor tooth will be the third molar (tooth #17, 2 distal to the treated tooth) and it will be extended to the contralateral first premolar (tooth #28).
- To determine proper location of the anchor punch you must dived the dam into 3 vertical sections (each 2” width) Left, middle, and right. The proper punch if the anchor tooth were #20, the hole is placed toward the superior border and also toward the center of the dam.
Describe the recommended operator chair positions and patient positions when treating tooth #19. (pp. 449-451)
- Below are the list of positions and their recommended uses for a right handed operator. This is according to the right-arm approach, which lines up the angle
- Right-Front, 7:00mandibular anterior teeth, maxillary anterior teeth, and mandibular posterior teeth (especially on the right side)
- Right Position, 9:00facial surfaces of the max and mand right posterior teeth and occlusal surfaces of the mand right posterior teeth
- Right Rear, 11:00Most commonly used position, and most parts of the mouth are viewed and accessible. Lingual and occlusal surface of maxillary teeth viewed thru mouth mirror. Direct vision used on mandibular teeth, especially on the left side.
- Direct Rear, 12:00Limited application; lingual surfaces of mand anterior teeth
- For tooth #19, which is a mandibular posterior tooth on the left side, the 11:00 position is recommended. The patient may have his/her head tilted slightly toward the operator, with height of operating field at approximate elbow height of the operator,
- For lefties: the above positions are 5, 3, 1, 12 with all the “rights” switched to “lefts” and vice-versa
Describe the proper application of the Barton matrix in the restoration of an occlusolingual cavity preparation on tooth #14. (pp. 735-736)
- a. Purpose: support the lingual portion of the restoration during condensation; prevent “land-sliding” during condensation
- b. Universal Tofflemire Retainer is used on the buccal side (so that the matrix band is flush on the lingual side where you are doing the restoration
- c. Wide end of pinched matrix band toward occlusal
- d. Guide slots of Tofflemire Retainer open toward gingiva
- e. Insert wide end into guide slots
- f. Tighten rotating spindle to lock band
- g. Twist set screw to adjust band circumference; place around tooth #14 with Universal Tofflemire Retainer on buccal side.
- h. Create a shim from a piece of matrix band; place between the band already in place and the prepared lingual tooth surface. Place gingival edge of the shim slightly gingival to the gingival edge of the band to help secure the band segment
- i. Soften Greenstick compound with flame; while holding a wooden wedge with pliers, cover it with the softened Greenstick Compound; immediately wedge this between the sham and matrix band; use a burnisher to press the compound gingivally; this pushes the sham firmly against the lingual cavosurface margin of #14
Describe: caries of pit and fissure origin; caries of smooth surface origin; root surface caries; primary versus secondary caries.
- a. Caries of pit and fissure origin—form in the regions of pits and fissures usually resulting from the imperfect coalescence of the developmental enamel lobes. When these areas are exposed to carious conditions, caries usually develops. Often asymptomatic until forces of mastication fracture the unsupported enamel. Caries penetrates a small area in a pit/fissure and remains small until the DEJ. “Two cones” with bases together (apices at point of origin and towards pulp).
- b. Caries of smooth surface origin—occurs in a smooth area of enamel surface that is habitually unclean (covered with plaque). Base of enamel cone on the enamel surface. Dentin cone same as pit and fissure caries. So apex of enamel cone contacts base of dentin cone
- c. Root surface caries—may occur on exposed tooth root that is habitually covered with plaque. Prevalent in the elderly. More rapid that other forms of caries
- d. Primary caries—original carious lesion of the tooth. May be pit and fissure, smooth surface, or root surface origin
- e. Secondary caries-occurs at the junction of a restoration and the tooth and may progress under the restoration…. “recurrent caries” and indicates microleakage.
Describe the six classes of tooth preparations. (pp. 295-297)
- a. Class I: All Pit and fissure restorations: Occlusal surface of posterior teeth, occlusal two thirds of the facial and lingual surfaces of molars, and the lingual surfaces of maxillary anterior teeth
- b. Class II: defects that affect one or both of the proximal surfaces of the posterior teeth
- c. Class III: Proximal surfaces of anterior teeth that do not involve the incisal angle
- d. Class IV: Proximal surfaces of anterior teeth that do involve the incisal edge
- e. Class V: Restorations on the gingival third of the facial or lingual surfaces of all teeth (except pit-and fissure lesions);
- f. Class VI: affect cusp tips of posterior teeth or the incisal edges of anterior teeth
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