The resins recommended have low viscosity. Especially after heating, which makes placement qualities similar to a flowable. This produces a coherent mass with little fuss.
These are high C-factor restorations.To reduce contraction stress deriving from the resin itself, estimate contraction stress roughly with this formula,(CS=PSxFM). Multiply polymerization shrinkage (%) by Flexural Modulus). If the numerical quotient is under 20, freedom from enamel crazing will be obtained clinically. A variety of other tests are applicable. Clinician’s Report,March 2010 http://www.cliniciansreport.org/products/dental-reports/oraverse-anesthesia-reversal-agent-resin-based-composites-march-2010-volume-3-issue-3.php indicates that “Stress Rate” may be a indicator. Unfortunately,resin “Stress rate”is not a published specification for point-of-sale resins. This handicaps GPs in making optimum clinical decisions.
Two resins which have performed well over a decade have been Tokuyama Estelite, in the A3,A3.5 and B4 shades.These restore teeth in the Vita A and Vita B range well. For teeth in the Vita C and Vita D range, 3M Espe Z-250 is preferable.The best universal shade of Z250 in this author’s opinion is D-3. The A shades are not esthetic. Like many older materials, Z-250 does not exhibit close shade adherence to its stated shade.Both of these resins are quite transparent, Where a more opaque result is wanted, Kuraray Majesty Aesthetic meets both teh esthetic and contraction criteria. Nuance, distributed by Discus Dental, is identical, as near as can be determined, to Kuraray Majesty Aesthetic.
As a rule of thumb, all materials placed in these preps should have the lowest contraction possible. Many resins exceed 2% contraction, combined with a Flexural Modulus of over 10GPa, produce visible enamel crazing. Unfortunately, this excludes the majority of resins available today for use in incisal restoration.Where
Estelite has excellent metamerism, and its wear properties have been excellent in trials by The Dental Advisor. CRA has also given it high ratings. It is a very pretty material which is more faithful to its stated Vita shade than is Z250. Because of its lower shrinkage, it is the material that I use for at least half of my attrition cases now. It is somewhat harder to condense into preparations than the Z-250. Its handling is only slightly influenced by heating, as it a very plastic resin in its own right.
Majesty Aesthetic is a little-known resin in North America, made by Kuraray Dental, a powerhouse in the plastics world.http://www.kuraraydental.com/ It is without vices and attractive in cooler,lighter shades where less translucency and warmth is required than what one finds in Z-250 or Estelite. Nuance Universal exhibits identical physical parameters.
Long-term clinical trials show that Z250 is a very hard- wearing resins, due to the very small filler particles. Estelite has larger filler particles but has also shown good wear in clinical trials.(See 9-year review by the Dental Advisor)
All these resins are very fast-curing materials.High curability ensures full polymerization and optimum clinical properties.