http://elearn.uobabylon.edu.iq

https://publons.com/researcher/1437059/ameer-hamdi-hakeem-alameedee/

http://staff.uobabylon.edu.iq/site.aspx?id=876

http://livedna.net/?dna=964.23578

Direct Aesthetic

adhesive Restorations Lect. 4

2019-2018

األستاذ المساعد الدكتور

امير حمدي العميدي

دكتوراه اختصاص طب االسنان التجميلي و الترميمي

Global concerns regarding mercury in the environment are the primary driver for the discontinuation of dental

amalgam. Identified as one of the top five mercury added products, dental amalgam is ranked fifth behind

batteries, measuring devices, electrical switches and relays, and mercury-containing light bulbs.

Restoring posterior teeth with resin-based composite materials continues to gain popularity among clinicians,

and the demand for such aesthetic restorations is increasing. Manufacturers are working aggressively to

improve resin composite materials by modifying components to decrease polymerization shrinkage, to improve

mechanical and physical properties, and to enhance handling characteristics. The two main causes of

posterior composite restoration failure are secondary caries and fracture (restoration or tooth).

Clinical performance of composite versus dental amalgam restorations

Resin composite is the most common alternative to dental amalgam ,but numerous studies report that

composite restorations have more recurrent caries, higher failure rates, and increased frequency of

replacement.

Factors can influence the clinical success of class II composite restorations:

• patient characteristics.

• tooth preparation.

• matrix utilization.

• composite composition–dentin bonding.

Cavity designs for composite cavity preparation:

Conventional:

-Similar to that of cavity preparation for amalgam restoration.

-A uniform depth of the cavity with 90° cavosurface margin is required

Indications:

1. Moderate to large class I and class II restorations.

2. Preparation is located on root surfaces.

3. Old amalgam restoration being replaced.

Cavity designs for composite cavity preparation:

Beveled conventional:

1. Similar to conventional cavity design.

2. Have some beveled enamel margins.

Indications:

1. Composite is used to replace existing restoration (class III, IV, V).

2. Restore large area rarely used for posterior composite restorations.

Cavity designs for composite cavity preparation:

Modified:

2. No specified wall configuration.

3. No Specified pulpal or axial depth.

4. All parameters determined by extent of caries.

5. Conserve tooth and obtain retention (Micro-Mechanical).

6. Scooped out appearance

Indications:

1. small, cavitated, carious lesion surrounded by enamel.

2. correcting enamel defects.

The “tunnel” technique:

has been used to remove proximal caries while leaving the marginal ridge intact; the most conservative

proximal restorative technique available.

Minibox or “slot” preparations:

When only Proximal surface is faulty and no lesion on occlusal surface. These preparation designs have

been described as minimally invasive and relatively successful with a reported 70% success rate over an

average of 7 years. surface is faulty and no lesion on occlusal surface.

Traditional preparation designs:

Which involve access through the carious marginal ridge and the removal of infected occlusal enamel

and dentin, may be required.

Esthetics 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.

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

restoration.

Bulk cure versus incremental cure:

Incremental filling techniques have long been recommended due to the polymerization shrinkage associated

with dental composites. Reducing the volume of composite that is polymerized at each stage of the restorative

procedure minimizes shrinkage and maximizes the conversion of monomers to polymer. This is achieved, in

part, by decreasing the attenuation of the curing light.

-Recent studies report that incremental filling produces lower shrinkage stress whencompared to bulk filling

techniques.

-Bulk cure: Currently, manufacturers are striving to produce resin based composite systems that have less

polymerization shrinkage (,2%) and, more importantly, reduced polymerization shrinkage stress. Strategies to

improve shrinkage include utilizing new low-shrinking monomers or those with an increased molecular weight.

As the low-shrinking composite resins improve, incremental filling and curing of posterior composites may no

longer be recommended.

Bulk cure versus incremental cure:

However, until the long-term clinical success of the lower shrinking composite resin systems is confirmed,

using an incremental filling technique in deep cavity preparations is recommended.

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

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Restorative Technique placement of the Adhesive:

When 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 in vital teeth, the operator may elect to use

a base material prior to placing the adhesive and the composite:

-If the remaining dentin thickness (RDT) is between 0.5 and 1.5 mm, a resin-modified glass ionomer (RMGI)

base is used.

-if the RDT is less than 0.5 mm, a calcium hydroxide liner should be applied to the deepest aspect of the

preparation, then protected with an RMGI base prior 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.

Enamel Bonding Agents

- Diluted Bis-GMA or TEG-DMA resins.

- Hydrophobic….. Bond only to dry enamel surfaces

- New formulations have hydrophilic resins (HEMA) to be used for both enamel and dentin bonding

Dentin Bonding Agents (DBA) should Have both hydrophilic and hydrophobic resin

components.

-The hydrophilic part is to displace the dentinal fluids and wet the surface.

-The hydrophobic part is responsible for bonding to composite filling materials.

Creating perfect direct composite restorations has been for long time a strict

challenge due to many materials’ limitations impacting either shade integration or surface

quality, and possibly color stability. Next to technological drawbacks, a certain complexity

and lack of predictability in clinical application was inherent to the technique and made it

elitist for a long time.

Shading and layering concepts then progressively evolved from a simplistic, non histo-

anatomical, bilaminar technique to a multi-layering approach (3 to 4 or more layers), One of

the most achieved concepts is polychromatic layering which makes use of a variable

number of layers (basically opacious dentin, chromatic enamel and translucent/opalescent

enamel), driven by the natural tooth optical composition.

In parallel with this evolution, a simplified, shading system was developed with a reduced

number of layers (basically dentin & enamel layer, plus effect shades if required) known as

the natural layering concept, aiming to the same optimal esthetic integration and natural color

reproduction/emulation. The latest improvements appear all driven by the same view of

improved reliability and clinical simplification.

several modern composites are equal to or better than some porcelain systems,

featuring enhanced optical properties and aesthetics; it is today up to the operator, acting

as an artist and scientist, to exploit the full potential of direct bonding and correlate them

with natural tooth tissues to create better function and aesthetics without any bio-

mechanical impairment, which may prove elusive with indirect ceramic restorations. E

Essential to the successful use of composites for direct free-hand dentistry:

1. Knowledge of tooth anatomy.

2. Color and materials’ optical and physical properties enables dentists to achieve high-end.

3. Long lasting aesthetics.

4. Promoting tissue conservation.

5. Constraining treatment costs.

6. Depends on the operator’s understanding.

7. knowledge of their intrinsic properties and his or her ability to master related clinical protocols.

Layering of composite restorations for aesthetic purposes, started with the development of light-

curing technology and the launch of comprehensive, optically structured composite systems. The

increasing demand of patients for a better aesthetic integration of their direct restorations.

Composite systems can be classified according to the number of layers usually

applied together with their specific optical parameters:

1. It includes mono-layer systems.

2. Bi-laminar systems (aiming or not to emulate natural tooth anatomy and colour).

3. Tri-layer systems showing a few variations (ie.: opaque dentins – dentins – enamels or

dentins – chromatic enamels – incisal shades).

4. Hue and opacity.

5. Opalescence and fluorescence properties, as well as filler technology, will impact the final

aesthetic integration, underlining.

6. The need for a proper understanding and integration of this material’s various properties.

Bilaminar ‘non histo-anatomical’:

It comprised one set of body masses, usually following the Vita Classic shading

system, offering different hues (A to D) in varying chroma levels (1 to 4, according to the

shade group). Body shades exhibited an intermediate opacity (between natural dentin

and enamel values); a few ‘opaque’ and ‘incisal’ masses usually completed the overall

system. This concept was based on a monolaminar chromatic build-up of the restoration

with one incisal/translucent shade on the surface to emulate translucency and possibly

opalescence as well. Most of those composite systems were making use of the porcelain

VITA shade guide. While being a simple layering approach, the restoration aesthetic

quality was overall restrained by an oversimplified, non histoanatomical shading

approach.

Bilaminar ‘natural layering shading:

The use of a natural tooth as a model has been a logical evolution of direct

restorative materials, leading to an improved shading and layering concept logically

named after nature’s original model and source of inspiration. It indeed resulted from a

thorough study of true natural dentin and enamel optical properties, recognising the

variations in tissue quality related to tooth age and functional maturing. Related findings

have logically drawn the lines of this new concept Spectrophotometric measurements

(tristimulus L*a*b* color and opacity values) of natural teeth belonging to various VITA

shade.

the use of distinct dentine colors for a direct composite restorative system could be

avoided, providing that enamels would offer not only different value/opacity levels. Then

a new concept was born, allowing the emulation of practically all usual VITA shades by

using a proper combination of universal dentin shades of a single opacity level and

presenting a wide chroma range that extends beyond Vita Classic shades and multi-tint/

multi-translucency enamels (typical brands named after their development period: Miris

and Miris2.

Layering concepts evolved from a primitive approach to emulate natural dental anatomy

and optical properties to superior and reliable protocols to perfectly match tooth color and

its many dimensions.

We normally classify composite systems in relationship to the number of

recommended layers (1, 2, 3 or more, when cavity/decay’s size involves dentin

replacement or when more in detail color characteristics are obvious) and as well as

some selected optical properties, which allow for finer differentiation among brands. Next

to the number of layers to be applied,

A mono-layer/single shading concept is not considered appropriate for

restorations in the demanding smile area; a single composite layer would

actually be sub-optimal in regard to both polymerisation stress management,

as well as restoration optical integration.

The only indication would be for small cavities(Class III) with no

extension toward the facial surface or small class V restoration.

Color mock-ups were created for each tooth according to the

achromatic and chromatic enamel techniques to verify the

accuracy of the layering techniques.

A properly trimmed silicone matrix made on a waxed-up

model is key for establishing a three dimensional blueprint for

layering composite increments.

The lingual shelf must be an achromatic enamel no thicker

than 0.3 mm.

Once cured, the lingual shelves of both centrals denote amber-

whitish nuances that replicate the opalescence present in natural

enamel.

A fine-tipped dental instrument was

used to gently create the dentin mamelons.

If correctly selected and applied, artificial

dentins of different brands should provide

naturemimicking color and opacity.

Translucent effect enamels were used on both

teeth to create natural opalescence and deep

translucency around and in between the mamelons.

A Vita-based chromatic enamel was applied

beyond the bevel line and contoured to create a

seamless transition between the tooth structure and

composite.

The chromatic enamel was faded-out toward the

incisal third and cut back along the incisal and

proximal areas to allow room for value effect

enamels.

An achromatic enamel was placed over the

lobes to promote higher opacity and color value.

After refinement and curing, the higher value

achromatic enamel blended in, replicating optical

properties of natural enamel lobes.

To render the proximal lobes, a microfill shade

of the same optical characteristics as those of the

hybrid composite used on both central incisors.

A more translucent achromatic hybrid composite

enamel was chosen for the middle lobes of both central

incisors to allow more dentin show-through.

After application and light-curing of chromatic and

achromatic enamels, both centrals depict similar optical

characteristics.

To establish natural facial planes, the transitional line

angles were evaluated and the facial planes worked with

finishing discs to establish the primary anatomy.

The transitional line angles were worked and the

embrasures opened until symmetry was achieved.

Anatomy mapping was penciled in on the centrals to

aid in attaining proper tooth morphology during finishing.

Secondary anatomy was achieved with a flame-

shaped, fine diamond bur to reduce volume and

emphasize the proximal lobes.

Tertiary anatomy was completed with a diamond

bur at slow speed to create arch-like horizontal lines.

Worn blunt rubber rotaries were used to eliminate

undesired texture and to impart a smoother

appearance.

Specialized chamois and cotton wheels were used

in the polishing steps to produce an enamel-like gloss.

Felt disc and aluminum oxide paste finalized the

polishing, bringing the restorations to a smooth and glossy

surface.

The finished restorations presented identical color

and optical characteristics and were indistinguishable

from the surrounding dentition.

The optical properties of the dentin and enamel

composites selected for the buildups replicate the

lifelike qualities of natural tooth structures.