Posterior Direct Composite Restoration

Prepared By Azheen Mohamad

References Sturdevant's Art and science of operative dentistry.2013 Mosby Elsevier . Sixth

Edition chapter 10 pep 254

Contemporary esthetic dentistry .2012 Mosby Elsevier. first Edition chapter 10 .pep 244

Tooth colored restorative ,principle and techniques . 2012 Albers .ninth edition

https://www.dentalaegis.com/special-issues/2010/06/limiting-postoperative-sensitivity-in-composite-restorations-part-ii

http://www.powershow.com/product/presentations/

http://www.dentaleconomics.com/articles/print/volume-103/issue-7/features/posterior-composites-choosing-and-using-them-well.html

IntroductionWhen esthetic dentistry began its evolution, the posterior teethwere considered unimportant. As patient expectations haveincreased, more focus has been placed on the estheticcontribution of posterior teeth With the mechanics ofmandibular function, as humans speak, laugh, and exhibit thebehaviors considered human, the incisal edges of the loweranterior teeth and the occlusal surfaces of the posterior teethare critical .

DEFINITION composite resin is three dimensional combination of two or

more chemically different materials with a distinct interface between them.in combination, the properties are superior to those of individual components.

Composites are indicated for Class 1, class 2 and class 5 defects on premolars and molars. Ideally, an isthmus width of less than one third the intercuspal distance is required.

This requirement is balanced against forces created on remaining tooth structure and composite material. Forces are analyzed by direction, frequency, duration and intensity. High force occurs with low angle cases, in molar areas, with strong muscles, point contacts and parafunctional forces such as grinding and biting finger nails.

Composite is strongest in compressive strength and weakest in shear, tensile and modulus of elasticity strengths.

Failure of a restoration occurs if composite fractures, tooth fractures, composite debonds from tooth structure or micro-leakage and subsequent caries occurs. A common area of failure is direct point contact by sharp opposing cusps.

DIRECT POSTERIOR COMPOSITES

Tooth preparation requires adequate access to remove caries, removal of caries, elimination of weak tooth structure that could fracture, beveling of enamel to maximize enamel bond strength, and extension into defective areas such as stained grooves and decalcified areas.

Matrix systems are placed to contain materials within the tooth and form proper interproximal contours and contacts

Enamel and dentin bonding is completed. Composite shrinks when cured so large areas must be layered to minimize negative forces.

Generally, any area thicker than two millimeters requires layering. In addition, cavity preparation produces multiple wall defects.

Composite curing when touching multiple walls creates dramatic stress and should be avoided.

Composite built in layers replicate tooth structure by placing dentin layers first and then enamel layers.

Final contouring with hand instruments is ideal to minimize the trauma of shaping with burs.

Matrix systems are removed and refined shaping and occlusal adjustment done with a 245 bur and a flame shaped finishing bur. Interproximal buccal and lingual areas are trimmed of excess with a flame shaped finishing bur.

Final polish is achieved with polishing cups, points, sandpaper disks, and polishing paste.

Polymerization Shrinkage

Composite materials shrink while polymerizing. This is

referred to as polymerization shrinkage. This phenomenon

cannot be avoided, and important clinical procedural techniques must be incorporated to help offset the potential problems associated with a material pulling away from the preparation walls as it polymerizes. Careful control of the amount and insertion point of the material and appropriate use of an adhesive on the prepared tooth structure to improve bonding reduce these problems.

There are several mechanisms of composite wearincluding adhesive wear, abrasive wear, fatigue, and chemical wear:_

Adhesive wear is created by extremely small contacts and therefore extremely high forces, of two opposing surfaces. When small forces release, material is removed. All surfaces have microscopic roughness which is where extremely small contacts occur between opposing surfaces.

Abrasive wear is when a rough material gouges out material on an opposing surface. A harder surface gouges a softer surface. Materials are not uniform so hard materials in a soft matrix, such as filler in resin, gouge resin and opposing surfaces.

Fatigue causes wear. Constant repeated force causes substructure deterioration and eventual loss of surface material.

Chemical wear occurs when environmental materials such s saliva, acids or like affect a surface.

COMPOSITE WEAR

Significance of Gap FormationThe gap formation that usually occurs when the composite

restoration is extended onto the root surface may not have any long-term clinical effects. With the two vectors of the defect being primarily resin or composite, recurrent caries may not be a problem. How long the exposed hybridized resin layer on the root stays intact is unknown, however, and if it deteriorates in a short time, the area is exposed to risk for caries. Use of an RMGI liner material may reduce the effect of gap formation by rendering the surrounding tooth structure more resistant to recurrent caries.

Dental composite is composed of a resin matrix and filler materials. The resin filler interface is important for most physical properties.

There are three causes of stress on this interface including:i. resin shrinkage pulls on fillers, filler modulus of elasticity is

higher than resin, and filler thermo coefficient of expansion allows resin to expand more with heat.

ii. When fracture occurs, a crack propagates and strikes a filler particle. Resin pulls away from filler particle surfaces during failure. This type of failure is more difficult with larger particles as surface area is greater. A macrofill composite is stronger than a microfill composite.

iii. Coupling agents are used to improve adherence of resin to filler surfaces.

COMPOSITE FRACTURE

1) Class-I, II, III, IV, V & VI restorations.

2) Foundations or core buildups.

3) Sealant & Preventive resin restorations.

4) Esthetic enhancement procedures.

5) Luting.

6) Temporary restorations.

7) Periodontal splinting.

INDICATIONS of composite

1) Inability to isolate the site.

2) Excessive masticatory forces.

3) Restorations extending to the root surfaces.

4) high caries incidence and poor oral hygiene.

CONTRAINDICATIONS

Advantage

The advantages of composite as a Class I and II direct restorative

material relative to other restorative materials are:

1. Esthetics

2. Conservative tooth structure removal

3. Easier, less complex tooth preparation

4. Insulation

5. Decreased microleakage

6. Increased short-term strength of remaining tooth

Structure.

Disadvantages

The disadvantages of Class I and II direct composite restorations

are as follows:

1. Polymerization shrinkage effects

2. Lower fracture toughness than most indirect

restorations

3. More technique-sensitive than amalgam restorations

and some indirect restorations

4. Possible greater localized occlusal wear.

5. Unknown biocompatibility of some components

(bisphenol A [BPA])

Composite Variants Packable

Flowable

Packable Composites Marketed for posterior use

increase in viscositybetter proximal contacts

handle like amalgam

Subtle alteration of fillershape

size

particle distribution

Similar resin chemistry and filler volume

Proximal Contact Studies Packables similar to hybrids

diameter and tightness

Best contacts

sectional matrix system

Flowable CompositesClinical applications:-

• preventive resin restorations

• small Class 5

• provisional repair

• composite repair

• liners

Advanced composite for direct posterior restoration

Bulk Fill Composite

Advanced composite technology allows for directly placed posterior restorations with bulk-fill resin-bonded composite in a single increment. Engineered with a smooth and creamy consistency, bulk-fill composite (eg, Tetric EvoCeram® Bulk Fill, Ivoclar Vivadent , can achieve high marginal adaptation to the floor and walls of cavity preparations, eliminating the need for a flowable liner. The patented shrinkage stress reliever technology increases marginal integrity and decreases polymerization shrinkage due to a low shrinkage stress of 1.13 MPa and a low shrinkage volume of 1.9%.Good marginal integrity and low polymerization shrinkage can result in a decreased probability of tooth deformation, postoperative sensitivity,microleakage, and secondary caries.

1) Local anaesthesia.

2) Preparation of the operating site.

3) Shade selection

4) Isolation of the operating site.

5) Tooth preparation.

6) preliminary steps of enamel and dentin bonding.

7) Matrix placement.

8) Inserting the composite.

9) Contouring the composite.

10) polishing the composite.

STEPS IN COMPOSITE RESTORATION

Tooth Preparation

As a general rule, similar to the tooth preparation for direct

anterior restorations, the tooth preparation for direct posterior

composites involves (1) creating access to the faulty Structure. (2) removal of faulty structures (caries, defective

restoration and base material, if present). (3) creating convenience form for the restoration. Retention is obtained by bonding. When placing most posterior composites, it is not necessary to incorporate mechanical retention features in the tooth preparation.

Small to Moderate Class I DirectComposite RestorationsSmall to moderate Class I direct composite restorations may

use minimally invasive tooth preparations and do not require

typical resistance and retention form features. Instead, theseconservative preparations typically use more flared cavosurface

forms without uniform or flat pulpal or axial walls. These

preparations are less specific in form, having a scooped-out

appearance. They are prepared with a small round or elongated

pear diamond or bur with round features. The initial

pulpal depth is approximately 0.2 mm inside the DEJ but may

not be uniform (i.e., the pulpal floor is not flat throughout its

length).

Small to Moderate Class I DirectComposite Restorations

Moderate to Large Class I DirectComposite Restorations

Moderate to large Class I direct composite restorations,especially when used for larger caries lesions or to replaceexisting defective amalgam restorations, will typically featureflat walls that are perpendicular to occlusal forces, as well asstrong tooth and restoration marginal configurations. All ofthese features help resist potential fracture in less conservativetooth preparations. However, the preparation should never beexcessively extended beyond removal of faulty structures tojustify resistance and retention forms, as this will weaken thetooth structure and can ultimately lead to failure of the toothrestoration unit. If the occlusal portion of the restoration isexpected to be extensive, elongated pearl cutting instrumentswith round features are preferred because they result in strong,90-degree cavosurface margins. However, this box-like form

preparation may increase the negative effects of theconfiguration factor (C-factor). (See the section on inserting andlight activating the composite for other considerations regardingthe C-factor for Class I direct composite restorations.) Theobjective of the tooth preparation is to remove all of the caries orfault as conservatively as possible. Because the composite isbonded to the tooth structure, other less involved, or at-risk,areas can be sealed as part of the conservative preparationtechniques. Sealants may be combined with the Class I compositeRestoration.

Small Class II Direct Composite Restorations

Small Class II direct composite restorations are often used for

primary caries lesions, that is, initial restorations. A small

round or elongated pearl diamond or bur with round features

may be used for this preparation to scoop out the carious or

faulty material from the occlusal and proximal surfaces. The

pulpal and axial depths are dictated only by the depth of the

lesion and are not uniform. The proximal extensions likewise

are dictated only by the extent of the lesion but may requireextended occlusally , facially, and gingivally enough to remove the lesion. The axial depth is determined by the extent of the lesion. The occlusal, facial, and gingival cavosurface margins are 90 degrees or greater. Care should be taken not to undermine the marginal ridge during the preparation.

Moderate to Large Class II DirectComposite Restorations

the tooth preparation for moderate to large class ii directcomposite restorations has features that resemble a more traditionalclass ii amalgam tooth preparation and include anocclusal step and a proximal box.

OCCLUSAL STEP:_The occlusal portion of the Class II preparation is preparedsimilarly as described for the Class I preparation. The primarydifferences are related to technique of incorporating the faultyproximal surface. Pre-operatively, the proposed facial andlingual proximal extensions should be visualized . Initial occlusalextension toward the involved proximal surface should gothrough the marginal ridge area at initial pulpal floor depth,exposing the DEJ. The DEJ serves as a guide for preparing theproximal box portion of the preparation.

The pulpal floor is prepared with the instrument to a depththat is approximately 0.2 mm inside the DEJ. The instrumentis moved to include caries and all defects facially or linguallyor both, as it transverses the central groove. Every effort shouldbe made, however, to keep the faciolingual width of the preparationas narrow as possible. The initial depth is maintainedduring the mesiodistal movement, but follows the rise and fallof the underlying DEJ

PROXIMAL BOXTypically, caries develops on a proximal surface immediately

gingival to the proximal contact. The extent of the caries lesion

and amount of old restorative material are two factors that

dictate the facial, lingual, and gingival extensions of the proximalbox of the preparation. Although it is not required to

extend the proximal box beyond contact with the adjacent

tooth (i.e., provide clearance with the adjacent tooth), it may

simplify the preparation, matrix placement, and contouring

procedures. If all of the defect can be removed without extendingthe proximal preparation beyond the contact, however, therestoration of the proximal contact with the composite issimplified.

After the operator cleans the teeth, administers local anesthetic, selects the shade of composite, and isolates the area, a wedge is placed in the gingival embrasure .Early wedging helps in the separation of teeth, to compensate later for the thickness of the matrix band, fulfilling one of several requirements for a good proximal contact for the composite restoration. The placement of a bitine ring preoperatively can achieve the same goal. The lack of pressure against the matrix during placement of composite compared with pressure of amalgam during its condensation dictates the need not only for increased separation by early wedging but also the need for operator alertness to verify matrix contact with the adjacent tooth before composite placement. The wedge also depresses and protects the rubber dam and gingival tissue when the proximal area is prepared. An additional, further tightening (insertion) of the wedge during tooth preparation may be helpful. The presence of the wedge during the composite in these areas. Beveled composite margins also may be more difficult to finish.

Mesio-occlusal (MO) Class II tooth preparation for posterior composite restoration in the maxillary first premolar. A, Esthetic problem is caused by caries and existing amalgam restoration. B, In this patient, the mesial marginal ridge is not a centric holding area. C, Early wedging after rubber dam placement. D, An elongated pear bur or diamond is used for initial tooth preparations on both premolars. E, After extensive caries is excavated, a calcium hydroxide liner and a resin-modified glass ionomer (RMGI) base are inserted. F, Preparations are completed, if necessary, by roughening the prepared tooth structure with diamond instrument.

Bevels are rarely used on any of the proximal box walls because of thedifficulty in restoring these areas, particularly when using inherently viscouspackable composites. Bevels also are not recommended along the gingivalmargins of the proximal box; however, it is still necessary to remove anyunsupported enamel rods along the margins because of the gingivalorientation of the enamel rods. For most Class II preparations, this marginalready is approaching the cementoenamel junction (CEJ), and the enamel isthin.

Factors can influence the clinical success of class II composite restorations

patient characteristics

tooth preparation

matrix utilization

composite composition–dentin bonding

*Patient selection The popularity and demand for resin-based

posterior restorations.

societal focus on aesthetics.

restorations placed in patients with high caries risk have restoration failure rates two times than those of patients with low caries risk.

the practitioner must give careful consideration to the caries status of the patient and adjust recommendations for restorative materials accordingly.

*Tooth preparation

resins are utilized to maximize aesthetics and minimize the loss of tooth structure during preparation.

Due to the location of the caries and thus the need to restore proximal surfaces in class II restorations, a number of tooth preparation designs have been advocated:_

The “tunnel” technique

Minibox or “slot” preparations

These preparation designs have been described as minimally invasive and relatively successful with a reported 70% success rate over an average of 7 years.

traditional preparation designs

traditional preparation designs, which involve access through the carious marginal ridge and the removal of infected occlusal enamel and dentin, may be required.

aesthetics deemed restoration

that clinicians should utilize posterior resin composites in areas where aesthetics is

deemed essential and should maintain as much tooth structure as possible.

aesthetics deemed restoration

the aesthetic results obtained when replacing a proximal amalgam restoration with a resin-based composite restoration.

Matrix Application

One of the most important steps

in restoring Class II preparations

with direct composites is the selection and proper placement

of the matrix. In contrast to amalgam, which can be condensed to improvethe proximal contact, Class II composites are almost totally dependent onthe contour and position of the matrix for establishing appropriate proximalcontacts.

Early wedging and re-tightening of the wedge during tooth preparation aid inachieving sufficient separation of teeth to compensate for the thickness ofthe matrix band. Before placing the composite material, the matrix bandmust be in absolute contact with (touching) the adjacent contact area.

two basic types:

(1) metal matrices, which are straight or circumferential/ precontoured

(2) transparent matrices which are either straight or circumferential/ precontoured

The influence of matrix type

Despite the theory that transparent matrices will enhance polymerization at the gingival margin, the recent literature suggests that the choice of matrix does not influence the clinical success of class II posterior resins.

Restorative TechniquePlacement of the AdhesiveWhen using an etch-and-rinse adhesive,

over-drying the etched dentin can compromise dentin

bonding. Aqueous solutions containing glutaraldehyde

and 2-hydroxyethyl methacrylate (HEMA) can be used as a

re-wetting agent when using etch-and-rinse systems . The

bonding agent is applied to the entire preparation with a

Micro brush , in accordance with the manufacturer’s

instructions.

After application, the adhesive is polymerized with a

light-activation unit, as recommended by the manufacturer

When the final tooth preparation is judged to be near the pulp invital teeth, the operator may elect to use a base material prior toplacing the adhesive and the composite. If the remaining dentinthickness (RDT) is between 0.5 and 1.5 mm, a resin-modifiedglass ionomer (RMGI) base is used; if the RDT is less than 0.5mm, a calcium hydroxide liner should be applied to the deepestaspect of the preparation, then protected with an RMGI baseprior to adhesive placement.

enamel and dentin bonding The clinical success of enamel bonding with 37% phosphoric acid led clinicians to take the same approach to dentin bonding .however , the early dentin bonding systems resulted in low bond strength.

Enamel is 95% inorganic matter( hydroxy –apatite). 4% water, and 1% organic matter(a collagen substance called enamelin)by weight. Although enamel is naturally hydrophilic (readily absorbing water),hydrophobic(resist to absorbing water) bonding resins can wet and penetrate dried,etched enamel because of high surface energy of an etched surface.

Dentin , on the other hand, is just 70% hydroxy apatite,18% collagen ,and 12% water by weight.This collagen is normally inaccessible, owing to surrounding hydroxyapatite crystals. The only obvious “pores” available for resin to penetrate are the dentin tubules , because of fluid flow from the dentine tubules , dentin is more hydrophilic than enamel ,which makes bonding a hydrophobic resin in to the dentin substrate difficult.Dentine bonding is highly technique sensitive and can be highly variable. Deep dentin exhibits far more tubules than superficial dentin , but also shows lower bond strength partly because the tubules are more fluid filled near the pulp . dentin fluids can interfere with a resin-dentin bond.Bond strength to all dentin surfaces are consistently lower than to enamel, regardless of the material used or the presence or absence of pulpal pressure.

Insertion and Light-Activationof the CompositeA matrix is usually not necessary for Class I direct composite

restorations, even when facial and lingual surface grooves are

included. The composite should not be dispensed until it is

ready to use because it may begin to polymerize from the

ambient light in the operatory. Because of variations in materials,

each manufacturer’s specific instructions should be followed.

Composite insertion hand instruments or a compule may

be used to insert the composite material. The dispenser, for

example, a syringe or compule, must be kept covered when

not in use to prevent premature hardening of the material.

Small increments of composite material are added and successively

light-activated . It is important to place (and light-activate) the composite incrementally to maximize the polymerization depth of cure and possibly to reduce the negative effects of polymerization shrinkage.

Insertion and Light-Activationof the Composite

C- factorsthe term “configuration factor” or “c-factor” has been used to describe the ratioof bonded to unbonded surfaces in a tooth preparation and restoration. a typicalclass i tooth preparation will have a high c-factor of 5 (five bonded surfaces—pulpal, facial, lingual, mesial, and distal. one unbounded surface— occlusal). thehigher the c-factor of a tooth preparation, the higher the potential for compositepolymerization shrinkage stress, as the composite shrinkage deformation isrestricted by the bonded surfaces. Incremental insertion and light-activation ofthe composite may reduce the negative c-factor effects for class i compositerestorations.

the use of an rmgi liner or a flowable composite liner also may reduce theeffects of polymerization shrinkage stress because of their favorable elasticmodulus (more elastic material will more effectively absorb polymerizationstresses). when composite is placed over an rmgi material, this technique isoften referred to as a “sandwich” technique.

The potential advantages of this technique are:_

(1) the RMGI material bonds to the dentin without opening the dentinal tubules, reducing the potential for post-operative sensitivity

(2) the RMGI material, because of its bond to dentin and

potential for fluoride release (potential anti- cariogenicity),

provides a better seal when used in cases where the preparation

extends gingivally onto root structure.

(3) the favorable elastic modulus of the RMGI reduces the effects of

polymerization shrinkage stresses. These suggested advantages

are considered controversial, as no published research

based on longitudinal clinical trials evaluating the technique

is available.

Flowable composites also are advocated as liners under posterior composite restorations. The purported primary advantage is that they may reduce some of the negative effects of polymerization shrinkage because of their very favorable

elastic modulus.

When it is necessary to extend a composite restoration onto

the root surface, the use of an RMGI liner beneath the portion

of the restoration on the root surface may decrease microleakage, gap formation, and recurrent caries.

Contouring and Polishing of the Composite

If the composite is carefully placed and shaped before light

activation, as described in the previous section, additional

contouring with burs is substantially minimized. However,

in many cases, refined contouring may be needed, especially when occlusion adjustments are necessary.

The occlusal surface is shaped with a round or oval carbide finishing bur or similarly shaped finishing diamonds. Finishing is accomplished with appropriate polishing cups, points, or both after the occlusion is adjusted as necessary.

Contouring and polishing of Class I composite. A, Mandibular molar with

old amalgam restoration. B, Rubber dam isolation; old restoration is carefully removed to minimize increasing preparation size. C, Final tooth preparation. D, Incremental placement of composite.

E, Incremental placement of composite. F, Rubber dam is removed and occlusion checked. G, Buccal view, a finishing fluted bur is used to selectively adjust the occlusion. H, Polishing with brush and diamond paste. I, Completed restoration.

sensitivitypost-operative sensitivity used to go hand

in hand with the restoration of teeth.

this sensitivity is associated with the odontoblastic process and is mostcommonly caused by inappropriate use of the dentin bonding agent. the painranges from slight to acute. with amalgam, for example, sensitivity commonlyoccurs immediately after placement and lasts for a week to 10 days.

during the first several days after restoration a definite gap of several micronsexists between the walls of the preparation and the amalgam restoration,thereby allowing the transfer of fluids. the sensitivity associated with posteriorcomposites can last considerably longer and demonstrate appreciably greaterintensity.

the mechanism of sensitivity is somewhat complex. regardless of the cause, thepain can be directly related to the odontoblast itself. whatever creates anegative pressure on the odontoblastic process creates a pain response.Positive pressure has no effect; only negative pressure creates a response.

Postoperative Sensitivity and Restorative Imperatives

The extent of preparation should be dictated by the amount and location of soundtooth structure present, with the clinician taking care to confine tooth reduction tothe elimination of carious tooth structures and creating a cavity design sufficient towithstand the demands of the intraoral environment. Whenever possible,preparations should remain in the enamel.

Bevel enamel margins to conceal the margin, Leaving the enamel marginsroughened will enhance bond strength as well.

Good bonding to prevent micro leakage.

The cavity design should feature rounded internal line angles to improve stressdistribution upon placement of the restorative materials through amicromechanical adhesive approach.

Rubber dam isolation is recommended for proper moisture control at therestorative site as well as to prevent bacterial or salivary contamination and toreduce airborne debris.

Postoperative sensitivity causes patient discomfort that often predisposes him orher for re-treatment and additional office time. Consequently, the ability of modernadhesive dental approaches to eliminate this sequellae is a considerable benefit topatient and practitioner alike.