classification of cavity preparation

General Dentistry
Chapter 48

Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights

Chapter 48
Lesson 48.1


Learning Objectives





Define, spell, and pronounce the Key Terms.
Describe the process and principles of cavity
preparation.
Discuss the differences between assisting
with an amalgam and with a composite
restoration.


Introduction
Restorative and aesthetic dentistry is
focused on the general dental
needs of the patient.


Restorative Dentistry


Specific conditions that initiate a need for
restorative dental treatment are:





Initial or recurring decay.
Replacement of failed restorations.
Abrasion or the wearing away of tooth structure.
Erosion of tooth structure.


Esthetic Dentistry


Specific conditions requiring aesthetic dental
treatment:





Discoloration due to extrinsic or intrinsic staining
Anomalies due to developmental disturbances
Abnormal spacing between teeth
Trauma


Terminology in Cavity Preparation


Initial Cavity Preparation


Outline form




Resistance form




Shape and placement of cavity walls

Retention form




Design and initial depth of sound tooth structure

To resist displacement or removal

Convenience form


Provides accessibility in preparing and restoring
the tooth


Final Cavity Preparation






Removal of decayed dentin or old restorative
material
Insertion of resistance and retention with
the use of hand cutting instruments
and burs.
Placement of protective materials (liners,
bases, desensitizing, or bonding)


Patient Preparation for
Restorative Procedures






Inform the patient what to expect throughout
the procedure.
Position the patient correctly for the dentist
and the type of procedure.
Explain each step to the patient as the
procedure progresses.


Responsibilities of the Chairside
Assistant







Prepare the setup for the procedures.
Know and anticipate the dentist’s needs.
Provide moisture control.
Transfer dental instruments and accessories.
Mix and transfer dental materials.
Maintain patient comfort.


Steps in the Restorative Procedure














The dentist evaluates the tooth to be restored.
The dentist administers local anesthesia.
The assistant readies the chosen means of moisture control.
The dentist prepares the tooth.
The dentist determines the type of dental materials.
The assistant mixes and transfers the
dental materials.
The dentist burnishes, carves, or finishes the dental
material.
The dentist checks the occlusion of
the restoration.
The dentist finishes and polishes the restoration.

Class I Restorations




These restorations are used in class I lesions,
affecting the pits and fissures of the teeth.
The following surfaces are involved:





Occlusal pits and fissures of
premolars and molars
Buccal pits and fissures of
mandibular molars
Lingual pits and fissures of the maxillary molars
Lingual pits of maxillary incisors, most frequently
in the pit near
the cingulum

Fig. 48-5 Class I restorations.


Class II Restorations




A class II lesion is the extension of a class I
lesion into the proximal surfaces of premolars
and molars.
The following surfaces are involved:




Two-surface restoration of posterior teeth
Three-surface restoration of posterior teeth
Four-surface (or more) restoration of posterior
teeth


Fig. 48-7 Class II restorations.
(From Baum L, et al: Textbook of operative dentistry, ed 3, Philadelphia, 1995, Saunders.)
dentistry,


Class III and IV Restorations


Class III lesion




Affects the interproximal surface of incisors and
canines

Class IV lesion


Involves a larger surface area, including the incisal
edges and interproximal surface of incisors and
canines


Fig. 48-9 Class III composite restoration.


Fig. 48-10 Class IV composite restoration.


Class V Restorations


Class V restoration




Classified as a smooth-surface restoration.

Decayed lesions occur at:



Gingival third of the facial or lingual surfaces of
any tooth
Root of a tooth, near the cementoenamel junction


Fig. 48-13 A, Class V conventional tooth preparation. B,
Schematic representation illustrating tooth preparation.
(From Roberson T, et al: Textbook of operative dentistry, ed 4, Philadelphia, 2006, Elsevier.)
dentistry,


Chapter 48
Lesson 48.2


Learning Objectives








Discuss why retention pins would be selected
for a complex restorative procedure.
Describe the need for placement of an
intermediate restoration.
Describe the procedure of composite
veneers.
Describe tooth-whitening procedures and the
role of the dental assistant.


Complex Restorations




Such restorations are required when decay
has extended beyond the normal size or
shape.
Retention pins



Decay has extended into the cusp of a tooth and
undermined the enamel and dentin.
General understanding when using retention pins:
One pin is placed for each missing cusp.


Fig. 48-14 Retention (retentive) pins placed in tooth structure
to help retain and support a restoration.


Intermediate Restorations



Restoration placed for a short term.
Primary factors for placement




Health of the tooth
A wait to receive a permanent restoration
Financial reasons


Procedure 48-5 Placement of intermediate restorative material.


Direct Bonded Veneers


Veneer




Thin layer of tooth-colored material, applied to the
facial surface of a prepared tooth

Used to improve the appearance of teeth that
are:





Abraded
Eroded
Discolored with intrinsic stains
Darkened after endodontic treatment


Fig. 48-15 Veneers placed to reduce discoloration and cover stain.
(From Roberson T, et al: Sturdevant’s art and science of operative dentistry, ed 4, St Louis, 2002, Mosby.)
dentistry,


Fig. 48-16 Veneers placed to close diastema.
dentistry,


Tooth Whitening
Known as vital bleaching, tooth whitening
is a noninvasive method of lightening
dark or discolored teeth.


Indications for Using a Tooth
Whitener


Indications for Procedure




Extrinsic stains from foods, cigarette smoking,
coffee, or tea
Aged, discolored teeth
Intrinsic stains, such as mild tetracycline stains
and mild fluorosis


Fig. 48-17 Before-and-after photos of
tooth whitening used for extrinsic stains.


Fig. 48-18 Before-and-after photos
of tooth whitening used for intrinsic stains.
dentistry,


Whitening Products


Chemical makeup



Active ingredient
• Either carbamide peroxide or hydrogen peroxide
Gel base
• With one or a mixture of propylene glycol, glycerin, and
water



Thickener
• Carbopol


At-Home Tooth-Whitening Procedure


Material is placed in a thermoplastic custom
tray that the patient wears
for a designated period.





With the 10% to 16% carbamide peroxide gels, the
wear schedule is 1 hour twice a day for the first
week and once a day for the second week.
The 20% to 22% mixture is used for 1 hour a day
for 2 weeks.
Hydrogen peroxide is used for 15 to 30 minutes,
two or three times a day, for 2 weeks.


Tooth-Whitening Strips




Thin, flexible strips are coated with
an adhesive hydrogen peroxide whitening gel.
Application



The patient peels off the backing like a Band-Aid
and presses the strip to the facial anterior teeth.
The remaining portion of the strip is folded onto
the lingual surface.


Possible Complications to Tooth
Whitening


Thermal hypersensitivity




Patient may experience sensitivity to heat and cold
after removal of the tray and material. The use of
toothpaste for sensitive teeth is recommended.

Tissue irritation


Gingival tissue exposed to excess gel as a result
of improper tray fit may become irritated. Tell the
patient not to overfill the tray with material and to
remove any excess after seating the tray.


Dental Assistant’s Role in
Tooth-Whitening Procedure











Aid in recording the medical and dental
history.
Assist in making shade selection.
Take intraoral photographs before and after
whitening.
Take and pour up preliminary impressions for
the tray.
Fabricate and trim the tray.
Provide postoperative instructions.
Assist in weekly or biweekly clinical visits.

Patient Instructions for
Tooth-Whitening Procedure







Brush and floss before tray placement.
Place equal amounts of gel in tray.
Seat tray.
Do not eat or drink when wearing the tray.
Wear tray for the recommended time.
If the patient experiences any problems,
discontinue use and discuss with the dentist.


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