Lec
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- Words: 1,941
- Pages: 48
10/14/08
1
Pre-treatment ( cont.) Adhesive resin (bonding agent)
Consists of viscous hydrophobic monomer (Bis-GMA or UDMA) diluted with monomers of higher hydrophilicity and lower viscosity, such as HEMA. The major role of low viscosity adhesive resin is the stabilization of the hybrid layer and formation of resin tags and copolymerize with the composite resin.
10/14/08
2
The smear layer is removed and dentinal tubules are opened
10/14/08
C= composite, H= hybrid layer, D= dentin 3
10/14/08
Hybrid layer, the resin tags penetrating the cut dentinal tubules.
4
Be aware:
Hybrid layer is the structure formed in dental hard tissues ( E,D, C.) by demineralization of the surface and subsurface, followed by infiltration of monomers and subsequent polymerization. Adhesive resins (unfilled or semi-filled) can be light and / or autocuring. Autocuring type exhibit slow polymerization. For light – curing bonding agents, it is recommended that the adhesive resin be polymerized prior to the application of the restorative resin.
10/14/08
5
In this way : Adhesive resin is not displaced. Adequate light intensity is available to sufficiently cure and stabilize the resin- tooth bond to counteract polymerization shrinkage of the resin composite.
10/14/08
6
(A) Prepared cavity. (B) The smear layer is dissolved. (C) The acid and the dissolved smear layer are washed away using a water- air spray. (D) Formation of hybrid layer. 10/14/08
7
10/14/08
8
Nanoleakage: (nano sized porosities within the hybrid layer) The causes for such defect may be:
10/14/08
incomplete resin infiltration inadequate polymerization of primer before application of bonding resin. Polymerization shrinkage of maturing primer resin. These defects may cause bond failures. More recent primers, include a chemical or photopolymerization initiator so that these monomers can be polymerized in situ.
9
Bonding agent
Because O2 inhibits resin polymerization, an O2 inhibited layer of about 15µm will always be formed on top of the adhesive resin, even after light curing . This O2 inhibited layer offers sufficient double methyl methacrylate (MMA) bonds for copolymerization of the adhesive resin with the restorative resin.
10/14/08
10
Bonding agent
Brush thinning is preferred over air thinning of the adhesive resin film to prevent the film thickness from being reduced to such an extent that the air-inhibited layer permeates the resin, resulting in low bond strength. A sufficiently thick resin layer may absorb, by elastic accommodations, the stress induced by polymerization contraction of resin composite.
10/14/08
11
10/14/08
12
Dentin bonding systems originated with 3-component designs – conditioner (etchant), primer, and bonding agents. While this produced a very consistent result, there was more and more interest in reducing the number of components to shorten the clinical procedure. The transition to 2-components and now 1-component has covered about 8 years.
10/14/08
13
Self-Etching Adh
E + nP + B E + nBonding PB or nEP +Systems B EPB Re-Designing Self-Etching Primer
US Companies
1=
2=
10/14/08
Japanese Companies
ETCHANT PRIMER BONDING AGENT ???
=1
=2
14
Bonding systems that utilized phosphoric acid are called (total etch) and are represented by the standard 3-component and the first 2-component types. Other bonding systems rely on acid monomers to accomplish the same thing (self-etching primers and selfetching adhesives).
10/14/08
15
One of the interesting accusations of 1-component systems is that they are so hydrophilic that they allow water in the dentin to penetrate through to their surfaces if left very long before the composite is placed – thereby defeating the bonding step. This is still being investigated.
10/14/08
16
Most recent innovations are directed toward a simplified application technique of adhesive systems: Total–etch technique: which means simultaneous acid etching of enamel and dentin. Be aware: It is not desirable to dry the enamel excessively when the total – etch technique is used, because this would desiccate the exposed dentin postoperative sensitivity and impair the bond to dentin.
10/14/08
17
In total etch technique, we are dealing with the problem of handling these two different substrates (E and D). We need an effective etching pattern in enamel, but we have to treat the dentin carefully with weaker etchants to avoid chemical harm to the collagen fibers. In this case, the application of the etching gel should start in enamel and expanded up to 30 sec. then the acid should be applied to dentin for another 15 sec.
10/14/08
18
Self-etching primers or condiprimer (slightly acidic primer) that was an aqueous solution of 20% of phenyl-p in 30% HEMA for bonding to enamel and dentin simultaneously. It is applied and dispersed with air without rinsing, the dissolved calcium phosphates are entrapped in the bonding resin layer. The combination of etching & priming steps: Reduce the working time, Eliminate the washing out of the acidic gel and, Eliminate the risk of collagen collapse.
10/14/08
19
However, the self-etching primer solution also has some disadvantages, e.g. The solution must be refreshed continuously because its liquid formulation cannot be controlled where it is placed, and Often the residual smear layer remained in between adhesive material and dentin. Also, the effectiveness of self-etching primer system on properly etching the enamel was less predictable than the 10/14/08 result obtained with phosphoric acid
20
One – bottle adhesives
The function of the primer and that of the adhesive resin were combined into one liquid that is applied after etching enamel and dentin simultaneously with phosphoric acid.
10/14/08
21
Packing of composite resin restoration:
Bulk – packing Incremental packing
Direct application with a carpule system
10/14/08
22
Bulk-packing:
Applied in one increment. It is suitable for chemically curable composites: because the degree of polymerization is not affected by the bulk of the restoration, and conversion occurs throughout the whole mix at the same time and to the same degree. It may be employed with light curd composites in small cavities. This technique makes no compensation for polymerization shrinkage.
10/14/08
23
Bulk-packing:
10/14/08
The mixed material may be transported and pressed into the preparation using a gold-plated or Teflon-tipped plastic instrument or by using injection technique that prevent air–entrapment. The matrix is then tightened around the restoration and held for 3min avoiding moisture contamination.
24
Incremental packing
Involve packing of the restoration in successive small increments (no thicker than 2mm), each is pressed into place and is light cured for 20-40 sec. Be-aware: The initial increments must be thin to copolymerize adequately to the bonding resin. This technique Partly compensate for polymerization shrinkage (reduce but does not eliminate the problem)
10/14/08
25
Carving:
Gold – plated or Teflon – tipped carving instruments are used to overcome composite stickiness. Be aware: Bonding agent is a better lubricant for preventing composite resin from sticking to the plastic instrument. Care must be taken to maintain the carving in a direction towards the margins to avoid disturbing peripheral apposition of enamel surface. The VLC systems allow the dentist unlimited working time for carving and reproduction of lost tooth form and contour.
10/14/08
26
Contouring a composite surface with a particular composite spatula
The surface of composite can be processed with fine brushes before polymerization.
10/14/08
27
Polymerization:
10/14/08
Three different induction systems for polymerization of resin-based restorative may be employed, namely VL curable, the chemical cure and the combined dual-cure systems.
28
Advantage 0f VLC: 1- Command first polymerization
10/14/08
The working time with this system is under full control of the restorative dentist. This provides the time he needs for contouring and reproduction of correct anatomy. This will decrease the amount of finishing required. Furthermore, quick polymerization prevents possibilities for moisture contamination. 29
Advantage of VLC: 2- No air inclusion
10/14/08
V.L.C. composites are non-mixable single component systems. Therefore, there would be no chance for air-inclusion that inhibits polymerization and causes: Development of soft spots. Loss of surface hardness. Decrease in density. Discoloration tendency. 30
Advantage of VLC: 3-Controled polymerization shrinkage:
10/14/08
Polymerizing VLC composites shrink towards the curing light i.e. away from the interface with substrate enamel and dentin surfaces. This results in gapping which invites leakage. Therefore, reflecting plastic wedges are placed at the gingival end of class II to overcome this problem.
31
10/14/08
32
Advantage of VLC 4- Longer shelf time 5- Superior color stability:
10/14/08
These systems utilize the more stable and color-fast aliphatic tertiary amines for activation of polymerization.
33
Advantage of VLC: 6- Improved wear resistance
10/14/08
The surface of VLC restorations will be in direct proximity to the light source, and thus will exhibit maximum conversion with improvement in wear resistances.
34
Disadvantages of VLC:
10/14/08
1- Depth-dependent cure:The degree of conversion of VLC composites is depth-dependent. However, incremental condensation serves to overcome such problem. 2- Eye hazards.
35
CURING LIGHT TYPES • Quartz-Tungsten-Halogen (QTH) Lights > Continuous output -- normal intensity > Continuous output -- high intensity > Staged output (stepped, ramped, …)
• Plasma Arc Curing (PAC) Lights • Argon-Laser Curing (Laser) Lights • Light-Emitting Diode (LED) Lights
10/14/08
QTH
PAC
Laser
LED
36
Characteristics of Light
Visible light
Most composites sensitive
400-700 nm 400-520 nm (blue)
Photo-initiator in resin
absorbs photon energy combines with activator
creating free radicals
10/14/08
amine initiates polymerization
37
Be aware:
Degree of conversion depending on:
The energy intensity of the light higher more conversion.
The distance from the light source.
The exposure time.
10/14/08
38
Polymerization shrinkage and its clinical significance:
Autocured composite polymerizes toward the center of the mass, while VLC composite polymerizes toward the light source. Stresses arising from polymerization shrinkage may produce defects in the composite-tooth bond, leading to bond failure, marginal leakage associated with postoperative sensitivity and may produce discoloration of margin and/or current caries.
10/14/08
39
10/14/08
40
Polymerization shrinkage and its clinical significance:
There have been many efforts at reducing the polymerization shrinkage: Incremental condensation technique. The lamination (sandwish) technique with glassionomer cement. The use of resin inlay. Use of improved adhesive system Application of flowable composite over the hybridized dentin (as a liner).
10/14/08
41
Finishing and polishing
10/14/08
Chemically cured restorations may be finished 24 hours after polymerization to allow for more advanced conversion with development of maximum surface hardness. VLC composites are finished immediately following polymerization.
42
Sof-Lex finishing strips and polishing disc
Diamond-coated metal wedges To remove proximal overhangs 10/14/08
43
Final finish of gingival margin
10/14/08
44
Finishing and polishing
Scalpel blade can be used for trimming the margins. 10/14/08
Composite sealer seals microscopic defects arise during finishing and Polishing.
45
Finishing procedures include:
Removal of gross excess and marginal finish. Disc contouring. Paste polishing. A no.12 scalpel blade is useful for removal of gross excess from margins. Finishing can be performed with 12- bladed carbide burs, diamond points, abrasive discs (sof-Lex disc) and finishing strips (to smooth the gingival proximal surfaces). Polishing is done with a very fine abrasive polishing paste applied with a soft rubber tips. Finishing and polishing are completed in a moist field to prevent overheating of the restorations.
10/14/08
46
Finishing procedures
10/14/08
Glaze materials, sealers, non-filled resin, may be applied to composite surface and visible light cured to seal microscopic defects (which arise during finishing and polishing) and provide smooth surface. However, they are soft material that may abrade in 6 months.
47
10/14/08
THANK YOU
48
1
Pre-treatment ( cont.) Adhesive resin (bonding agent)
Consists of viscous hydrophobic monomer (Bis-GMA or UDMA) diluted with monomers of higher hydrophilicity and lower viscosity, such as HEMA. The major role of low viscosity adhesive resin is the stabilization of the hybrid layer and formation of resin tags and copolymerize with the composite resin.
10/14/08
2
The smear layer is removed and dentinal tubules are opened
10/14/08
C= composite, H= hybrid layer, D= dentin 3
10/14/08
Hybrid layer, the resin tags penetrating the cut dentinal tubules.
4
Be aware:
Hybrid layer is the structure formed in dental hard tissues ( E,D, C.) by demineralization of the surface and subsurface, followed by infiltration of monomers and subsequent polymerization. Adhesive resins (unfilled or semi-filled) can be light and / or autocuring. Autocuring type exhibit slow polymerization. For light – curing bonding agents, it is recommended that the adhesive resin be polymerized prior to the application of the restorative resin.
10/14/08
5
In this way : Adhesive resin is not displaced. Adequate light intensity is available to sufficiently cure and stabilize the resin- tooth bond to counteract polymerization shrinkage of the resin composite.
10/14/08
6
(A) Prepared cavity. (B) The smear layer is dissolved. (C) The acid and the dissolved smear layer are washed away using a water- air spray. (D) Formation of hybrid layer. 10/14/08
7
10/14/08
8
Nanoleakage: (nano sized porosities within the hybrid layer) The causes for such defect may be:
10/14/08
incomplete resin infiltration inadequate polymerization of primer before application of bonding resin. Polymerization shrinkage of maturing primer resin. These defects may cause bond failures. More recent primers, include a chemical or photopolymerization initiator so that these monomers can be polymerized in situ.
9
Bonding agent
Because O2 inhibits resin polymerization, an O2 inhibited layer of about 15µm will always be formed on top of the adhesive resin, even after light curing . This O2 inhibited layer offers sufficient double methyl methacrylate (MMA) bonds for copolymerization of the adhesive resin with the restorative resin.
10/14/08
10
Bonding agent
Brush thinning is preferred over air thinning of the adhesive resin film to prevent the film thickness from being reduced to such an extent that the air-inhibited layer permeates the resin, resulting in low bond strength. A sufficiently thick resin layer may absorb, by elastic accommodations, the stress induced by polymerization contraction of resin composite.
10/14/08
11
10/14/08
12
Dentin bonding systems originated with 3-component designs – conditioner (etchant), primer, and bonding agents. While this produced a very consistent result, there was more and more interest in reducing the number of components to shorten the clinical procedure. The transition to 2-components and now 1-component has covered about 8 years.
10/14/08
13
Self-Etching Adh
E + nP + B E + nBonding PB or nEP +Systems B EPB Re-Designing Self-Etching Primer
US Companies
1=
2=
10/14/08
Japanese Companies
ETCHANT PRIMER BONDING AGENT ???
=1
=2
14
Bonding systems that utilized phosphoric acid are called (total etch) and are represented by the standard 3-component and the first 2-component types. Other bonding systems rely on acid monomers to accomplish the same thing (self-etching primers and selfetching adhesives).
10/14/08
15
One of the interesting accusations of 1-component systems is that they are so hydrophilic that they allow water in the dentin to penetrate through to their surfaces if left very long before the composite is placed – thereby defeating the bonding step. This is still being investigated.
10/14/08
16
Most recent innovations are directed toward a simplified application technique of adhesive systems: Total–etch technique: which means simultaneous acid etching of enamel and dentin. Be aware: It is not desirable to dry the enamel excessively when the total – etch technique is used, because this would desiccate the exposed dentin postoperative sensitivity and impair the bond to dentin.
10/14/08
17
In total etch technique, we are dealing with the problem of handling these two different substrates (E and D). We need an effective etching pattern in enamel, but we have to treat the dentin carefully with weaker etchants to avoid chemical harm to the collagen fibers. In this case, the application of the etching gel should start in enamel and expanded up to 30 sec. then the acid should be applied to dentin for another 15 sec.
10/14/08
18
Self-etching primers or condiprimer (slightly acidic primer) that was an aqueous solution of 20% of phenyl-p in 30% HEMA for bonding to enamel and dentin simultaneously. It is applied and dispersed with air without rinsing, the dissolved calcium phosphates are entrapped in the bonding resin layer. The combination of etching & priming steps: Reduce the working time, Eliminate the washing out of the acidic gel and, Eliminate the risk of collagen collapse.
10/14/08
19
However, the self-etching primer solution also has some disadvantages, e.g. The solution must be refreshed continuously because its liquid formulation cannot be controlled where it is placed, and Often the residual smear layer remained in between adhesive material and dentin. Also, the effectiveness of self-etching primer system on properly etching the enamel was less predictable than the 10/14/08 result obtained with phosphoric acid
20
One – bottle adhesives
The function of the primer and that of the adhesive resin were combined into one liquid that is applied after etching enamel and dentin simultaneously with phosphoric acid.
10/14/08
21
Packing of composite resin restoration:
Bulk – packing Incremental packing
Direct application with a carpule system
10/14/08
22
Bulk-packing:
Applied in one increment. It is suitable for chemically curable composites: because the degree of polymerization is not affected by the bulk of the restoration, and conversion occurs throughout the whole mix at the same time and to the same degree. It may be employed with light curd composites in small cavities. This technique makes no compensation for polymerization shrinkage.
10/14/08
23
Bulk-packing:
10/14/08
The mixed material may be transported and pressed into the preparation using a gold-plated or Teflon-tipped plastic instrument or by using injection technique that prevent air–entrapment. The matrix is then tightened around the restoration and held for 3min avoiding moisture contamination.
24
Incremental packing
Involve packing of the restoration in successive small increments (no thicker than 2mm), each is pressed into place and is light cured for 20-40 sec. Be-aware: The initial increments must be thin to copolymerize adequately to the bonding resin. This technique Partly compensate for polymerization shrinkage (reduce but does not eliminate the problem)
10/14/08
25
Carving:
Gold – plated or Teflon – tipped carving instruments are used to overcome composite stickiness. Be aware: Bonding agent is a better lubricant for preventing composite resin from sticking to the plastic instrument. Care must be taken to maintain the carving in a direction towards the margins to avoid disturbing peripheral apposition of enamel surface. The VLC systems allow the dentist unlimited working time for carving and reproduction of lost tooth form and contour.
10/14/08
26
Contouring a composite surface with a particular composite spatula
The surface of composite can be processed with fine brushes before polymerization.
10/14/08
27
Polymerization:
10/14/08
Three different induction systems for polymerization of resin-based restorative may be employed, namely VL curable, the chemical cure and the combined dual-cure systems.
28
Advantage 0f VLC: 1- Command first polymerization
10/14/08
The working time with this system is under full control of the restorative dentist. This provides the time he needs for contouring and reproduction of correct anatomy. This will decrease the amount of finishing required. Furthermore, quick polymerization prevents possibilities for moisture contamination. 29
Advantage of VLC: 2- No air inclusion
10/14/08
V.L.C. composites are non-mixable single component systems. Therefore, there would be no chance for air-inclusion that inhibits polymerization and causes: Development of soft spots. Loss of surface hardness. Decrease in density. Discoloration tendency. 30
Advantage of VLC: 3-Controled polymerization shrinkage:
10/14/08
Polymerizing VLC composites shrink towards the curing light i.e. away from the interface with substrate enamel and dentin surfaces. This results in gapping which invites leakage. Therefore, reflecting plastic wedges are placed at the gingival end of class II to overcome this problem.
31
10/14/08
32
Advantage of VLC 4- Longer shelf time 5- Superior color stability:
10/14/08
These systems utilize the more stable and color-fast aliphatic tertiary amines for activation of polymerization.
33
Advantage of VLC: 6- Improved wear resistance
10/14/08
The surface of VLC restorations will be in direct proximity to the light source, and thus will exhibit maximum conversion with improvement in wear resistances.
34
Disadvantages of VLC:
10/14/08
1- Depth-dependent cure:The degree of conversion of VLC composites is depth-dependent. However, incremental condensation serves to overcome such problem. 2- Eye hazards.
35
CURING LIGHT TYPES • Quartz-Tungsten-Halogen (QTH) Lights > Continuous output -- normal intensity > Continuous output -- high intensity > Staged output (stepped, ramped, …)
• Plasma Arc Curing (PAC) Lights • Argon-Laser Curing (Laser) Lights • Light-Emitting Diode (LED) Lights
10/14/08
QTH
PAC
Laser
LED
36
Characteristics of Light
Visible light
Most composites sensitive
400-700 nm 400-520 nm (blue)
Photo-initiator in resin
absorbs photon energy combines with activator
creating free radicals
10/14/08
amine initiates polymerization
37
Be aware:
Degree of conversion depending on:
The energy intensity of the light higher more conversion.
The distance from the light source.
The exposure time.
10/14/08
38
Polymerization shrinkage and its clinical significance:
Autocured composite polymerizes toward the center of the mass, while VLC composite polymerizes toward the light source. Stresses arising from polymerization shrinkage may produce defects in the composite-tooth bond, leading to bond failure, marginal leakage associated with postoperative sensitivity and may produce discoloration of margin and/or current caries.
10/14/08
39
10/14/08
40
Polymerization shrinkage and its clinical significance:
There have been many efforts at reducing the polymerization shrinkage: Incremental condensation technique. The lamination (sandwish) technique with glassionomer cement. The use of resin inlay. Use of improved adhesive system Application of flowable composite over the hybridized dentin (as a liner).
10/14/08
41
Finishing and polishing
10/14/08
Chemically cured restorations may be finished 24 hours after polymerization to allow for more advanced conversion with development of maximum surface hardness. VLC composites are finished immediately following polymerization.
42
Sof-Lex finishing strips and polishing disc
Diamond-coated metal wedges To remove proximal overhangs 10/14/08
43
Final finish of gingival margin
10/14/08
44
Finishing and polishing
Scalpel blade can be used for trimming the margins. 10/14/08
Composite sealer seals microscopic defects arise during finishing and Polishing.
45
Finishing procedures include:
Removal of gross excess and marginal finish. Disc contouring. Paste polishing. A no.12 scalpel blade is useful for removal of gross excess from margins. Finishing can be performed with 12- bladed carbide burs, diamond points, abrasive discs (sof-Lex disc) and finishing strips (to smooth the gingival proximal surfaces). Polishing is done with a very fine abrasive polishing paste applied with a soft rubber tips. Finishing and polishing are completed in a moist field to prevent overheating of the restorations.
10/14/08
46
Finishing procedures
10/14/08
Glaze materials, sealers, non-filled resin, may be applied to composite surface and visible light cured to seal microscopic defects (which arise during finishing and polishing) and provide smooth surface. However, they are soft material that may abrade in 6 months.
47
10/14/08
THANK YOU
48
