Invisible Margins in Anterior Composites, Tips&Tricks
It has been a constant challange for clinicians to integrate completely different materials such as the tooth tissue and composite. With composite resins many times one tends to feel when restorations are done, that there is a visible interface between the restoration and the tooth tissue. A lot of clinicians also refer to it as the white line at the interface. This can be mild to rather prononced and cannot be accepted.
This could happen due to various reasons and at attempt to identify and overcome those has been shown in this case.
Img. 1 – Preoperative view shows a day old Class IV fracture due to trauma. It is noteworthy to see that the frature line is quite jagged and that means that the enamel prisms have fractured at various angles and levels. This changes the optical qualities of the intact enamel as it would have existed in that area of the tooth had the trauma not taken place.
Img. 2 – After fabricating the silicone key and before isolating the tooth it is imperative to choose the shade before the tooth gets dehydrated. The idea would be to use the minimal amount of layers needed for such a restoration and to employ the controlled body thickness technique.
Img. 3 – Rubber dam is placed for isolating the teeth
Img. 4 – TIP NO. 1: LONG BEVEL AND SMOOTH MARGINS A 40 micron diamond is used to smoothen out the jagged margins of the tooth and create a smooth bevel at least 2mm beyond the fracture line. This softens the edges and rounds off the fractured enamel prisms.
Img. 5 – The situation after the diamond bur has been used. When one is making the bevel it is best to be made in sun burst appearance so that the light reflection in the finished restoration is from a wavy line and not a straight line.
Img. 6 – A cermic polishing rubber is used to smoothen the margins further
Img. 7 – Soflex discs are then used to create a smooth margin at an angle once again to maintain the bevel
Img. 8 – This view shows a very smooth margin and the bevel rather clearly.
Img. 9 – The silicone key is tried and adjusted if need be to ensure that the incisal edge is just visible.
Img. 10 – A scraping done with an instrument helps to highlight on the silcone key the extent of the fracture line
Img. 11 – TIP NO. 2 : ETCH 2 mm BEYOND THE BEVELED MARGINS The tooth is etched and the adjacent teeth are protected with Teflon tape at this point in time. Selective etching is advised and in this case 37% Phosporic acid was used for 30 secs. on the enamel and 15 secs. on the dentine
Img. 12 – The etchant is rinsed off for at least 15 seconds. The dentine is kept moist for adequate bonding.
Img. 13 – Multiple coats of bonding agent are applied. (Single Bond , 3M Espe) and after 30 seconds air is blown to let the solvent evaporate and for thinning the bonding agent. It is applied on all the area that has been etched and not only on the fractured margin.
Img. 14 – The first layer of enamel is placed on the silicone key and is placed in the mouth there after. A3 Enamel was used in this case. (Filtek Supreme XT, 3M Espe)
Img. 15 – It is a good idea if you have a deep under cut to place a little bit of flowable composite at this point in time to seal the dentine and avoid air trap or voids with a heavier consistency material. The shade of the flow used should be close to the shade of the dentine. A3.5 Flow (Filtek Supreme 3M Espe) was used in this case
Img. 16 – The first layer or the palatal wall has been created
Img. 17 – A posterior sectional matrix is one of the best ways to adapt against and create a proximal wall where the enamel shade is used. A3 Enamel in this case. (3M Espe) A well placed wooden wedge secures the band in place and also causes seperation of the teeth to ultimately ensure a good contact between the teeth.
Img. 18 – After adaptation and creating the proximal wall one can remove the sectional matrix but keep the wedge in place. Some times when the wedge is removed it can lead to bleeding from the gingival tissue and there by contamination of the restoration being done.
Img. 19 – One bulk of Dentine shade is placed and with the right intrumentation it is ensured that there is adequate thickness for enamel. A3 Dentine (Filtek Supreme XT, 3M Espe)
Img. 20 – TIP No. 3: RAMP THE DENTINE MASS OF COMPOSITE After removing the excess dentine do not leave a sharp interface between the dentine and the enamel. Using appropriate brushes one can ramp up the dentine mass almost to the top very close to the enamel surface. This ensures light reflection and transmission from and through a gradient and does not appear as an abrupt colour shift in the final restoration.
Img. 21 – The dentine mass in then shaped to attain primary and sedondary anatomy as the goal of the restoration should be additive and not substractive
Img. 22 – A final single mass of enamel is placed. Intruments are used at this point to create some macroanatomy of the tooth.
Img. 23 – TIP No. 4: USE AN OXYGEN INHIBITOR TO ENSURE GOOD POLYMERIZATION OF THE TOP MOST LAYER It is often seen that when this step is missed patients come back with discoloured margins and in some case discoloured restoration quite soon after they have been done A 1 minute final curing through a water soluble fluid or gel ensures a lot better conversion and avoids marginal deterioration of the restoration at its interface with the tooth.
Img. 24 – The restoration after rinsing of the gel and without any finishing and polishing procedure.
Img. 25 – TIP No. 5: TEXTURE The final polishing is carried out using rubbers, silcone coated discs and giffy brushes using a diamond polishing paste, but what is very imporatant to keep in mind is to to have adequate macro and microtexture on the tooth surface. This can be created with the right diamond bur on a contrangle hand piece (Perioset Flame Bur) This results in the light reflection, refraction and scattering to happen close to the natural tooth here by making the interface difficult to decipher.
Img. 26 – The final restoration integrates with the tooth with no notacable interface between the two entities.
In order to make the margins of the restoration blend with the tooth it is suggested to smoothen out the rough fractured enamel prisms with a long wavy bevel, etch and bond beyond the bevel, ramping up the composite resin, final curing through an oxygen inhibited gel and creating appropriate texture.