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A Comparison of Micro-hardness and Marginal Adaptation of Re

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mohamed abouelnaga

on 11 May 2014

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Transcript of A Comparison of Micro-hardness and Marginal Adaptation of Re

A Comparison of Micro-hardness and Marginal Adaptation of Resin Based Class II Composite Resins Restorations Placed Using Layer versus Bulk Techniques
M.Abouelnaga
Special thanks to all my committee members
Purpose of Study
Hypothesis
1- Conventional composites used in layering technique have better gingival marginal adaptation compared to bulk fill composites restored in one increment.
2- Conventional composites used in layering technique have higher micro-hardness than the conventional composites used in one increment.
3- Bulk fill composites used in layering technique have better marginal adaptation compared to the bulk fills used in bulk fill technique.
4- Bulk fill composites used in a layering technique have a higher micro-hardness compared to the bulk fills used in bulk fill technique.
Materials and Methods
Controlled variables (Independent figures)
- Size of Class II proximal boxes restored with composite resin
- Bulk filling technique using two nanohybrid filled composite resins (TetricEvo-Ceram Bulk fill and Tetric Ceram conventional composite from Ivoclar Vivadent)
- Layering technique using both a conventional composite resin (Tetric Ceram) and (TetricEvo-Ceram Bulk Fill from IvoclarVivadent)
- Adhesive System (Syntac three-step total etch system from IvoclarVivadent)
- Light curing time and intensity( LED Bluephase G2 light cure of 12000 mW/cm2 from Ivoclar Vivadent)

Methodology (Dependent Variables)
- Knoop Hardness testing (KHN) at different levels to determine degree of polymerization
- Microscopic determination of percentage of intact gingival margins compared to non-intact margins to determine amount of gap formation

Experimental Groups
- Group 1 – proximal box filled in two increments with conventional composite. (positive control)

- Group 2 – proximal box filled in one increment with conventional composite (negative control)

- Group 3 – proximal box filled in two increments with bulk fill composite (experimental group)

- Group 4 – proximal box filled in one increment with bulk fill composite (experimental group)


Tooth Preparation
- Fully erupted extracted molar teeth will be selected for the experiment.

- Number of teeth per group will be determined depending on the pilot study.

- Teeth will be cleaned from soft tissue and debris with a slurry of pumice and water and a # 12 scalpel blade and stored in artificial saliva (AS) with 5000 ppm chloramine solution at 4 Celsius for 1 week to prevent bacterial growth, then transferred to AS without chloramine T.

- Proximal and occlusal surfaces will be lightly polished to smoothen surfaces using the 600, 1200 and 2000 grit sand paper .

-Teeth will be stored in (AS) chloramine solution 4 Celsius until they are required for cavity preparation (reference A.Moorthy et al, 2012)

- The occlusal surfaces and proximal surfaces of the teeth will be flattened using a grinder (all margins in dentine.
Cavity Design
- Proximal boxes will be prepared on the flattened mesial and distal parts of each tooth.

- The proximal box basic outline will be prepared using a high speed hand piece with a 330 bur. The basic prepared cavities will have dimensions of 3 mm long, 1mm deep and 3 mm wide.

- The SONICSYS will be used to refine and standardize the cavities toa 1.7 mm depth,4mm length, and 3.50mm width using the approx diamond. Cavities will be checked for their standardization using a digital caliper.

- Cavities will be cleaned using air-water stream


Matrixing of the preparation
-Two teeth will be mounted in contact with each other in a vinyl polysiloxaneputty material (Exaflex, GC America, IL, USA) to simulate clinical situation.

- One tooth will have a preparation while the other tooth will only be flattened without a preparation.

- Putty will be left to set for 2 minutes

- A straight metal matrix band (WaterPik, USA) will be placed between both teeth to ensure an accurate confinement of restorative material adaptation.

- A c-clamp will be placed over the putty material on the mesial and distal of both teeth to tighten both teeth together. The c-clamp will be placed on the putty not on the teeth as the clamp adapts better on the putty, then the putty pushes the teeth tight.

Bonding Material Placement
- All preparations will be restored using a total etch bonding system (Syntac, three-step total etch system, IvoclarVivadent, USA) according to the manufacturer's instructions.
- Phosphoric acid gel will be applied first to the
prepared enamel and then to the dentin surfaces. The etchant
will be left on the teeth for 15 seconds.
- All etchant gel will be removed with a vigorous water spray
for at least 5 seconds.
- Any excess moisture will be removed leaving the dentin
surface with a slightly glossy wet appearance by gently
blotting the surface with a piece of cotton.(wet bonding).
(Xu C, Wang Y. J Adhes Dent. 2012 )
- Syntac Primer will be applied with the brush in the cavity
gently rubbed for a contact time of 15 seconds on the dentin.
- Excess Syntac Primer will be dispersed and dried thoroughly.
- Syntac Adhesive will be applied ,left for 10 seconds and thoroughly dried with an air syringe.
- Heliobond will be applied and and blown to a thin layer.
and light cured for 10 seconds with a curing light (Bluephase, IvoclarVivadent) with 1200 mw/cm2 intensity.

Restorative Material Placement

- Composite material will be dispensed out of the capsule in a 2mm length (measured by the periodontal probe) The composite will be cut using the gold Almore (Swiss dental safident) into two lengths.

- Incremental placement will involve two horizontal increments placed in 2mm thickness using a ball burnisher (Premier Dental Products, USA).

- A curing light (Bluephase, IvoclarVivadent) with a 1200 mw/cm2 will be used to cure each layer of the sample of 2mm in thickness for 10 seconds by placing the light tip perpendicularly after one second of initiation against the occlusal surface of the tooth. (RBT Price et al, 2005) The light curing tip will be placed in the same orientation and position for each restoration.

- After placement and light curing, the matrix band will be removed. (The adjacent tooth will be used again with other samples as it is used just as a control to make close contact with the tooth to be restored.)

- The restored proximal surfaces will be lightly polished to remove flash using the 600, 1200 and 2000 grit sand paper (Buehler company, IL, USA).

- A light microscope (Carl Zeiss, Germany) will be used with magnification of 10x/23 X 5x to check the initial quality of composite placed.

- Samples displaying technique errors such as large voids or major gaps at the margins of the samples will be discarded from the experiment.

Material Testing
- Samples will be kept in dark until time of testing
- Gingival gap percent will be measured by doing epoxy resin replicas (Buehler Company, IL, USA).
- Epoxy resin replica's
1- The teeth will be cleaned in 70% ethanol ultrasonic bath (2min), then rinsed with water and dried with air.
2- The first impression will be taken using Aquasil XLV Ultrafast Set, (Caulk, USA)
3- After a wait of 5 minutes the first impression will be discarded.
4- The second impression will be taken and left to set for 10 minutes
5- The impression will be stored for 24 hours
6- The epoxy resin (5 parts) with the epoxicure hardener (1 part) will be mixed for 2 minutes, and placed in a vacuum for ten minutes.
7- The resin will be placed inside the impression using a pipette and spread uniformly with air.
10-Once the impression is filled totally with resin; it will be left to set for 24 hours.

Gingival Gap Testing
- Teeth will be sectioned B-L to produce mesial and distal halves using the Isomet 1000 machine


- Sample replicas will be sputter coated (k550 Emitech sputter, Quorum Technologies Ltd, UK)
- Samples will be evaluated under SEM at a magnification of 200X. (Blunck U, Zaslansky P., 2011)

Hardness testing


- Using the remaining half KHN will be measured in three points from the occlusal surface at 1mm, 2mm and 3mm depth. At each point three measurements will be done and the average will be recorded.

- Measurements will be taken 15 minutes after exposure to the curing light in the center of the preparation bucco-lingually at the point of 0.85 mm (half of 1.7 the width of box M-D) measured with the digital caliper ( Corey Felix et al, 2006, A.L.F Silva et al, 2005)

- Hardness testing will be done byMicromet II (Buehler, IL. USA) using a 50gm load for 5s.

- Gingival marginal adaptation will be determined along the gingival margins (3.5 mm) and 0.2 mm high on the buccal and lingual margins externally (3.6 mm).

- Margins will be evaluated and categorized in groups of Marginal Quality 1 : Margin intact , no gaps , Marginal Quality 2 : No gap but severe marginal irregularity, Marginal Quality 3 : Gap visible less than 2 millimicron. Marginal quality 4 : Gap visible more than 2 milli micron. (UweBlunck, Paul Zaslansky, J Adhes Dent 2011)

- The gingival marginal adaptation will be tested along the gingival margin internally (1.7 mm)after sectioning M-D in the center of the restoration and fabricating epoxy replicas as described previously previously using half of the complex only.
Pilot study planned
-All the steps will be followed exactly to compare both techniques of layering versus bulk fills

- Five restorations will be tested in each group of the four groups (sum of 20 restorations)

- Ten teeth will be tested each tooth having a restoration on the mesial and distal sides.

- Results of gingival adaptation and surface micro-hardness will be tabulated and statistical comparisons will be made using the ANOVA.


References
1) Laurie St-Pierre, Cathia Bergeron, Marcos A. Vargas,Deborah S. Cobb, Marcela Hernandez, Justine Kolker.
Effect of finishing and polishing direction on the marginal adaptation of resin based composite restorations in-vitro.J EsthetRestor Dent. 2013 Apr;25(2):125-38
2)Bechtold J, Dos Santos PJ, Anido-Anido A, Di Hipólito V, Alonso RC, D'Alpino PH. Hardness, polymerization depth.and internal adaptation of Class II silorane composite restorations as a function of polymerization protocol.Eur J Dent. 2012 Apr;6(2):133-40.
3)Xu C, Wang Y.
Collagen cross linking increases its biodegradation resistance in wet dentin bonding. J Adhes Dent. 2012 Feb;14(1):11-8
4)TchorzJP, DollR, WolkewitzM, HellwigE, HannigC. Microhardness of composite materialswith different organic phases in deep class II cavities: an in vitro study. Oper Dent. 2011 Sep-Oct;36(5):502-11.
5)D'Alpino PH, Bechtold J, dos Santos PJ, Alonso RC, Di Hipólito V, Silikas N, Rodrigues FP.
Methacrylate- and silorane-based composite restorations: hardness, depth of cure and interfacial gap formation as a function of the energy dose.Dent Mater. 2011 Nov;27(11):1162-9.
6) Blunck U, Zaslansky P.
Enamel margin integrity of Class I one-bottle all-in-one adhesives-based restorations.J Adhes Dent. 2011 Feb;13(1):23-9. doi: 10.3290/j.jad.a18445.

7) Camila Sabatini, Gerald Denehy, Murray Bouschlicher, Marcela Hernandez, Deborah Dawson.
Effect of pre-heated composites and flowable liners on class II gingival margin adaptation.OperDent. 2010Nov-Dec;35(6):663-71
8)KrämerN, ReineltC, RichterG, PetscheltA, FrankenbergerR.Nanohybrid vs. fine hybrid composite in Class II cavities: clinical results and margin analysis after four years.Dent Mater. 2009 Jun;25(6):750-9.
9)ParkJ, Chang J, Ferracane J, Lee IB.
Should composite be layered to reduce shrinkage stress: incremental or bulk filling? Dent Mater. 2008 Nov;24(11):1501-5.
10)KuijsRH, FennisWM, KreulenCM, BarinkM, VerdonschotN.
Does layering minimize shrinkage stresses in composite restorations?J Dent Res. 2003 Dec;82(12):967-71.
11) Dietrich T, Kraemer M, Lösche GM, Roulet J.
Marginal integrity of large compomer Class II restorations with cervical margins in dentine.J Dent. 2000 Aug;28(6):399-405.
12) De Wet FA, Exner HV, du Preez IC, Van Niekerk JP.
The effect of placement technique on marginal adaptation of posterior resins.Journal of the dental association of South Africa,March 1991, 46,171-175.

Courtesy of Islam Ali
The purpose of this study is to test the effect of resin- based composite type (RBC) (conventional RBC and a bulk fill RBC) and the method of placement (layering versus bulk filling) of the RBC gingival and internal marginal adaptation and micro-hardness of the RBC
SEM Sample Preparation
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