Cons- Sheet 13 Mahmoud Massalha - Alakyaz Assadourian

This lecture is about Class 5 Cavities:

We will repeat the same three cavity preparation methods; the conventional, beveled conventional and modified – however with few modifications.

- Quick Revision:a. The materials that we can use for restoration of a class 3 :

Composite, Glass ionomer - very rarely, Amalgam - for a lower canine (It’s not absolutely contraindicated)

b. The only material that we can use for restoration of a class 4 is composite.

- For a class 5; composite, glass ionomer and amalgam cavities are valid.Therefore, the conventional cavity of a class 5 is very useful when we are doing an amalgam restoration – which we still do especially for (mainly) lower and (occasionally) upper posteriors.We can also apply glass ionomer or composite.

Class 5 cavity def: according to G.V Black, is the cavity that occurs on the cervical area buccally or lingually of anterior or posterior teeth, not involving grooves or pits.

→ Keep in mind that cavities which start in pits or grooves (in the buccal or lingual extensions of molars) are class 1 cavities – and NOT class 5.

- Quick Revision:a. Class 3 is carious in origin.b. Class 4 could be carious in origin, or due to trauma

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- For a Class 5, the lesion could be carious or non-carious.

→ We will have a full lecture about the various types of non-carious lesions, however

we must know that they include:

1. Abrasion: the mechanical loss of tooth structure, without the presence of caries, which happens in weak areas where enamel is thin – exactly at the cervical area.

2. Erosion: which is due to either extrinsic or intrinsic acids;

√ Intrinsic acids from acid regurgitation – such as in pregnant ladies or anorexia nervosa patients, who develop class 5 cavities in the cervical area on inner aspect of upper anterior teeth.

√ Taking good history and determining the location of the lesion are good diagnostic tools to know what is the lesion.

3. Abfraction: caused by flexural forces, usually from cyclic loading; where the enamel, especially at the cemento-enamel junction (CEJ), undergoes a pattern of destruction by separating the enamel rods causing non-carious lesions. (The Dr. didn’t mention the definition, she only mentioned Abfraction)

❶

Class 5 Carious lesion(notice color)

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❷ Class 5 Non-carious Lesion

→most probably due to abrasion(forceful tooth brushing )causing cervical lesions where enamel is thinnest

(leading to loss of enamel followed by loss of dentine)

(When placing the probe no soft dentine is felt because this is a non-carious lesion)

- As mentioned earlier; composite, glass ionomer and amalgam – hybrid or micro-fill can be used for restoration of class 5 cavities:

Composite → is commonly used

has superior esthetics and superior physical properties

Glass Ionomer → has moderate esthetics due to incomplete shade matching with

natural teeth and moderate physical properties since its wear

resistance property is weaker than both amalgam and composite

Amalgam → has very good physical properties but no esthetics

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❸

Class 5 restoration with GI

(Notice opaque and whitish color)

→ We will frequently use it in the lab

❹

Class 5 restoration with Amalgam

How to classify Amalgam or Tooth-colored (Composite and GI) restorations?

(In other words, what are the indications or contraindications for using amalgam?)

→ i.e; in a posterior tooth, any of the restorative materials can be used, however

there are specific cases in which only one of the materials is indicated.

(Explained Below)

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- The indications for using Amalgam:

1. Difficult Moisture Control – the only absolute and most important indication

Ex: When there is a sub-gingival cavity, no good fluid isolation can be achieved leading to a failed composite restoration.

→ This doesn’t mean that we don’t need any isolation for amalgam restorations. However, it is less critical, therefore when it is difficult to control the isolation we should only and only use amalgam.

2. Limited Access and Visibility – composite does not only need good isolation, but also good technical skills because it includes multiple steps. However, amalgam is easier to place which is why it is indicated whenever access or visibility are limited.

3. With Partial Removable Denture Abutment – the clasps of the removable dentures hold on to the undercuts of teeth; since composite is less wear resistant, it might be more susceptible to wearing with time than amalgam. But, this is not an absolute indication.

4. Non-esthetic areas – such as posterior teeth and sometimes even lingual surfaces of anterior teeth.

5. Large cavities – since amalgam bonds to tooth structure purely mechanically, it is important to offer opposing walls for good retention of the amalgam restoration.

Note: Composite binds to tooth structure micromechanically.

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- Advantages of Amalgam:

a. Higher strength (more wear resistant – used with partial removable dentures)

b. Easy to manipulate and place (less technical skills needed and less visibility and accessibility)

c. Less sensitive to moisture (used when it is difficult to provide full isolation)

d. Cheaper

- The contra-indications for using Amalgam:

1. Non-esthetic – rarely used for anterior teeth restorations2. Less conservative – since we have to provide a cavity preparation of specific shape and

depth

Initial clinical procedures of class 5 cavity preparation:

1. Anesthesia

2. Occlusal Assessment – although class 5 cavities are cervical in location, high occlusal forces could be an initiator of Abfraction (a type of non-carious lesion) which cause tooth micro-flexure – and therefore occlusal assessment is always a must, because it can also lead to failure and falling of the restoration

3. Shade Selection – at the beginning of the clinic

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4. Surgical Exposure (Crown Lengthening) – sometimes class 5 cavities might be located on the root surface (sub-gingivally) with limited access to cavity preparation or placing restoration material where surgical exposure of this area by slightly cutting from the gingiva is needed in order to expose the cavity and place a good restoration.

5. Proper Tooth Isolation – an example is using rubber dam for composite restoration;

→ This helps:

a. Prevent moisture contamination; since moisture (blood, saliva, fluids) can negatively affect the:

► Physical Properties of all restoration materials (amalgam and composite and GI) ► Bonding of composite (in other words moisture will impair the bonding of composite material to tooth structure resulting in failure of the restoration)

b. Enhance asepsis

c. Facilitate access and visibility; for better cavity and restoration

→ Tooth isolation methods:

1. Rubber Dam and Clamp

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2. Cotton Roll and Gingival Retraction Cord

►The retraction cord definition: a thick cord that is gently inserted below the gum-line into the gingival sulcus which is primarily used to push the gum tissue away from the prepared margins of the tooth for better access and also better isolation due to less fluids coming from the sulcus and therefore better composite restoration preparation.

★Types of cavity preparation:

① Conventional:

→ When to use conventional cavity?

(a) When using amalgam (b) When the cavity is on the root surface (there is no enamel on the root to bevel it)

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- Quick Revision:

a. Any cavity on the root surface is prepared as conventional cavity to receive amalgam.

b. Any cavity extended from root to crown is prepared as a combined cavity; where the part on the root is prepared as conventional cavity and the part on the crown as beveled conventional due to the presence of enamel as the outer surface.

◆ Initial Cavity Preparation Steps:

→ What bur to use and How to use it?!

A tapered fissure bur or a diamond round bur of appropriate size

→ high speed at first followed by low speed.

- we can use only round bur with Class 3 and Class 4 cavities, however we can also use fissure bur with Class 5 because we have direct access to labial and lingual surfaces; where the fissure bur can be placed at 90 degrees to the tooth surface and the outline is drawn.

- if access inter-proximally or gingivally is limited, use a No.1 or a No.2 round diamond bur; in other words, start cavity preparation with a fissure bur on the lingual or labial areas, however when approximating the proximal surfaces change the bur to a round diamond bur to avoid endangering the adjacent tooth.

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- Drawing the outline form:

Direct the fissure bur 90 degrees to the tooth surface (the bur long axis perpendicular to the external tooth surface) during preparation of the entire outline resulting in 90 degrees cavosurface margin with a uniform depth of:

a. 0.75 mm – for conventional root cavityb. 0.2 mm inside the DEJ – for conventional coronal cavity (crown portion)

→ wherever there is enamel, the Dentinoenamel Junction is considered as a border or as a reference.

→ the depth gives you resistance and retention form → also, resistance is achieved by strength of restoration and preparation While retention is achieved by placement of retention grooves

- Important notes:

→ any infective dentine remaining on the axial wall is removed during the final stage of

the preparation

→ axial wall should follow the original contour of the facial surfaces; which is convex

outward mesiodistally and sometimes occlusogingivally

→ we need retentive grooves as auxiliary means of retention when the cavity is large

and the opposing walls are farther apart from each other and lost

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→ all the external walls of the conventional preparation are visible when viewed for

rotational position; which means that they are diverging outward

► while a class 1 amalgam cavity preparation is always converging outward; this is

due to the cervical position of the class 5 cavities where enamel orientation is

diverging outward, and the cavity preparation follows the same orientation.

◆ Final Cavity Preparation Steps:

- Remove the remaining infected dentine or any restorative material

- Apply liner if necessary

- Prepare grooves and coves (same as in class 3 and class 4)

→ Place the grooves axio-gingivally and axio-incisally on line-angles, with a number ¼ bur at a distance of 0.5 mm of the DEJ so that not to undermined the enamel junction

→The depth of the groove is 0.25 mm, with the angle bisecting the axial wall with the external wall and the lengthwise direction parallels the DEJ

Two grooves; axio-gingivally and axio-incisally

→ Coves are placed at the four corner point-angles when the wall is too close to the

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pulp that the shadow of the pulp is visible through the wall and there is a risk of

exposure if grooves were placed, considering the corners as safe and away-from-the-

pulp areas.

(A cove is like a groove, placed for the same purpose which is retention, using the

same shape and speed of bur in the same direction with the only difference that coves

are placed in four point-angles but the grooves are placed in two line-angles)

► Grooves should not remove the dentine immediately supporting the enamel and that is

why the initial depth is turned into 0.5 mm inside the DEJ instead of 0.2 mm inside the

DEJ when we want to place a groove or a cove

► A Chisel or a hand instrument can be used for placing grooves when we lose control over

the hand-pieces; this is possible since grooves are placed in (softer than enamel) dentine.

Note: Bevels can’t be placed by using a chisel or a hand instrument since bevels are on

hard enamel.

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- Dentine pins added when the restorative material is amalgam, as auxiliary means of retention, however it is very risky to use them in class 5. (Dentine pins should not be used with composite restorative material)→ In a class 2, dentine pins can be easily added in specific locations In a class 4, dentine pins can be added (please see class 4 lecture) In class 3 and class 5, we better not use dentine pins

There is a picture in the book showing the retentive

pins in a class 5 cavity preparation, however

they are very close to the pulp and it is risky

and undesirable to do like-wise.

② Beveled Conventional:

→ Very similar to conventional,

however with an additional

bevel on the enamel surface

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- The bevel in a class 5 is placed mainly on the occlusal (incisal) area where the enamel is thicker because the enamel is too thin cervically and might be eliminated during preparation by accident.

- Indication for beveled conventional:

Moderate to large lesions which occur on the cervical part of the crown where the margins have enamel and composite is the restorative material; all these are conditions for preparation of a beveled conventional cavity.

- Initial cavity preparation includes outlining a 90 degrees cavosurface margin with an axial depth of 0.2 mm inside the DEJ – except when grooves are needed the depth is increased to 0.5 mm inside the DEJ

- Retention is achieved through bonding of composite to enamel and dentine

→ Retentive grooves are not necessary unless part of the cavity extends to the roots; where the part of the cavity that is on the root is prepared as conventional cavity with additional retentive grooves for better retention

- Advantages of beveled conventional compared to conventional:

a. Increased retention b. Decreased micro-leakage

→ a. and b. explanation: bonding strength in beveled conventional is higher and retention in better due to the increased surface area of enamel through placing the bevel (enamel has highest bonding)

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c. More conservative→ c. explanation: no grooves are to be placed, therefore more natural tooth structure is conserved through preparation

- Final cavity preparation includes:

1. Placing grooves IF necessary for added retention

2. Enamel bevel using a high speed, diamond, flame-shaped/very large round/fissure bur with a 45 degrees margin, 0.2-0.5 mm width (like class 3) – wider bevels placed at the incisal area (Class 4 bevels can be up to 2.0 mm in width)

► In case of having caries with surrounding decalcified area, a normal class 5 cavity is prepared at the site of caries and the bevel is extended to include the decalcified area only upon the patient’s request due to esthetic reason The decalcified (demineralized) area should not necessarily be removed because it is only an initial and reversible lesion which can be remineralized and is still hard and intact.

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③ Modified:

- A modified cavity is the most conservative and is defined as the cavity that needs no effort to prepare its walls where the lesion is scooped out resulting in a preparation form that has divergent configuration and an axial wall that is usually not uniform in depth without any retentive groves added

- Indications for modified cavity preparation:a. Small to moderate class 5 lesions on the crownb. Lesions that are entirely in enamel (very important)c. Non-carious lesions

- Use a round bur of an appropriate size- During the final tooth preparation stage a bevel is placed, friable enamel is removed

while undermined enamel could be kept

★ Revision to the definitions of the various types of non-carious lesions:

a. Abfraction

b. Erosion: resulted due to acid attack leaving a smooth surface with no sharp cavity

c. Enamel Hypoplasia: a congenital condition that might cause aberrant pits on enamel surface

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d. Abrasion: due to vigorous tooth brushing or using a hard tooth paste or a tooth brush

→ mostly it appears on the premolar area opposing to the hand that we are using; meaning that a right-handed patient will usually have abrasion on his/her upper left premolar, since it is the most controlled area by the patient where most force is applied during the brushing procedure – however this is not absolute.

► Non-carious lesions are always treated using modified cavity preparation unless it is extended to or placed on the root – root has specific criteria as mentioned earlier, whenever a cavity is on the root it must be treated using conventional cavity preparation

◆ An aberrant (unusual) pit caused by enamel hypoplasia that does not follow any specific classification is of course treated using modified conventional cavity preparation

Done by: Mahmoud Massalha and Alakyaz Assadourian Do not hesitate to ask us any question and forgive us for any unintended mistake

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