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1. Identify and describe the principles in each of the four steps in initial tooth preparation. (pp. 300-308)
- Step 1: Outline form and initial depth
- This means placing the preparation margins in the positions they will occupy in the final prep (except for finishing steps) and preparing the initial full depth.
- The Principles
- (1) All friable or weakened enamel should be removed
- (2) All faults should be included
- (3) all margins should be placed in good position to allow for good finishing of the margins of the restoration. This differs between pit and fissure compared to smooth surface preps.
- Step 2: Primary Resistance Form
- This step should provide protection against fracture along the tooth’s long axis.
- Principles
- (1) Box shape with relatively flat floor perpendicular to long axis of the tooth
- (2) Restrict the extension of the external walls (allows for strong cusp and ridge areas)
- (3) Have slight rounding (coving) of internal line angles (ie. transition from groove extension to the isthmus)
- (4) Cap weak cusps
- (5) Provide enough thickness for the restorative material to prevent its own fracture under load
- (6) Bond material to tooth structure when appropriate
- Step 3: Primary Retention Form
- Principles (for Class I amalgam restorations—these vary by material)
- (1) External tooth walls the converge occlusally (buccal and lingual walls)
- (2) Cavosurface angle where facial and lingual walls meet the marginal ridge is 90 deg
- Step 4: Convenience Form
- Shape and size that allows for adequate observation, accessibility and ease of operation in restoring the tooth
- Principles: self explanatory
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2. Define outline form and identify the specific features, with criteria, that address it in the class I occlusal cavity preparation. (Lecture presentations)
- 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: 0.9-1.3 mm (the RGS 6 should NOT be able to fit in the isthmus)
- (b) Groove extensions: 0.9-1.3. 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
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3. Define resistance form and identify the specific features, with criteria, that address it in the class I occlusal cavity preparation. (Lecture presentations)
- Resistance form refers to the ability of the filled prepation wto 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
- (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
- (d) The dovetail segements should be divergent to eliminate the possibility of undermined enamel
- (e) Dovetail placement should be at least 1 mm from edge of marginal ridge in order to not undermine the integrity of this ridge
- Other Aspects of the prep
- Retention Form: This is the ability af the filling material to stay in the preparation
- (a) Convergent buccal and lingual walls thoughout the prep.
- (b) On a lingual “box” prep, proper placement of retention grooves
- Convenience Form
- (a) The smallest condenser we have is 0.8 mm, therefore all parts of the prep must have this as a minimum width.
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4. Describe the proper technique of condensing amalgam into a cavity preparation that maximizes the physical and mechanical properties of the final restoration. (721-724)
- (1) Properly mix the amalgam (should a homogenous, slightly reflective mass)
- (2) Have mental image of the outline form and general characteristic of the preparation to aid in locating cavosurface margins
- (3) Amalgam should be inserted incrementally and condensed with overlapping strokes
- (4) Tooth prep should be overpacked to ensure well-condensed marginal amalgam that is not mercury-rich
- (5) Precarve burnishing with larger burnisher will help with final condensation
- (6) In general, move from smaller condensers to larger condensers
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5. Describe the proper technique for contouring and finishing the amalgam restoration after condensation. (724)
- (1) With care, carving may begin immediately after condensation.
- (2) The recommended instruments are sharp cleiod-discoids of suitable size.
- (3) Start with the larger cleioid-discoid first (nos 3-6), followed by the smaller (nos 4-5)
- (4) ALL carving should be done with edge of instrument perpendicular to the margins as instrument is moved parallel to the margins
- (5) Part of the edge of the instrument should rest on unprepared tooth to use as a guide to prevent over carving!!!
- (6) Mesial and distal fossae should be carved slightly deeper than proximal marginal ridges
- (7) The finished margin should be regular and in the same form as the initial preparation (remember mental image)
- (8) Post carve burnishing can produce smoother satin (not shiny) appearance but is only to be used with high-copper amalgams
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6. 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 #19. (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). The proper punch if the anchor tooth were #19 is halfway between the top and bottom edges, right between the left and center vertical thirds, For the third molar, you must move this anchor position towards the inferior border and toward the center of the rubber dam.
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7. Describe the recommended operator chair positions and patient positions when treating tooth #19. (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 goofy lefties: the above positions are 5, 3, 1, 12 with all the “rights” switched to “lefts” and vice-versa
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6. 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)
- REFER TO LECTURE 5 AND THE RUBBER DAM TEMPLATE-#18/#31
- When treating tooth number 20, the anchor tooth will be the second molar (tooth #18, 2 distal to the treated tooth) and it will be extended to the contralateral first premolar (tooth #28).
- To determine the proper location of the anchor punch you must first divide the dam into 3 vertical sections (each 2” wide) and into two horizontal sections (each 3” wide). When a rubber dam is applied to the mandibular teeth the first hole punched is for the posterior anchor tooth that is to receive the retainer. In this case, again, it would be #18. To determine the proper location, you must be aware that there needs to be enough rubber dam material on the superior border to cover the upper lip. Therefore, you punch the first hole for tooth #18 at 1/4” below the right intersection and 1/4” toward the center. The last hole punched is for the contralateral first premolar, which is tooth #28.
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