Ultradent Katalog

Modern adhesive bonding works well when we respect the characteristics of the materials used, the mechanisms that result in adhesion, and the manufacturer’s instructions.

BOND/ETCH Parameters that affect the quality of bonding Modern adhesive bonding works well when we respect the characteristics of the materials used, the mechanisms that result in adhesion, and the manufacturer’s instructions. Neil Jessop, Head of Research and Development at Ultradent Products, has summarized the most important variables that affect bonding: 1. Etching process: Etching dentin too long may result in etch patterns that extend too deep for the adhesive resins to reach the healthy tooth structure. Depths of about 2 to 2.5 µm are the limit; deeper etching creates voids that may result in a weak link or tooth sensitivity. What to do: Use an etchant with a limited penetration depth. Etching with Ultra-Etch is self-limited at an average depth of 1.9 µm, even when left longer than the recommended 15 seconds. Dentin consists of organic and inorganic material. Etching (shown in blue) results in exposure of the organic collagen fibers. An ideal etchant penetrates only as far as the subsequent bonding agent (yellow) can penetrate the tooth structure. 2. Dentin drying: With some adhesive systems, overdrying the dentin after etching may severely compromise bond values. The exposed collagen fibers tend to collapse, and consequently cannot be completely permeated by the bonding agent. “Overetching” dentin results in too deep exposure of collagen fibers. As a result, the subsequent bonding agent cannot fully permeate the fibers leaving a gap that may reduce bond strength and cause tooth sensitivity. What to do: After etching and rinsing dentin, use only brief, gentle air blasts to remove pools of water. Alternatively, blot dry with cotton pellets. If dentin is overdried, remoisten it with a moist cotton pellet. 3. Application time: Allowing too little time for application (rubbing, brushing in, agitating the agent) may result in inadequate penetration of the bonding agent (incomplete hybrid layer formation), and incomplete evaporation of the solvent. What to do: Softly rub the bonding agent into the surface. This is easily accomplished with the Ultradent Products brush tips. Make sure to adhere to the application times specified by the manufacturer (use timer or stopwatch). 4. Thinning and drying: Too much thinning of the adhesive layer results in formation of an oxygen inhibition layer that will prevent adequate polymerization. If the adhesive layer is too thick, there may still be solvent contained in it. What to do: Place a rich layer of bonding agent – the major part of the liquid is solvent that needs to evaporate. Dry with a gentle, yet sustained stream of air rather than short, strong blasts. Observe the manufacturer’s time prescriptions. 5. Light curing: Too short or improper light curing leaves the bonding resin only partly polymerized. What to do: Use high energy curing lights with at least 400 mW/cm2, or preferably over 800 mW/cm2. 6. Composite placement: Adequate adaptation of the composite against the adhesive layer is mandatory to eliminate air voids. What to do: Use a flowable composite, like UltraSeal XT plus or PermaFlo, as a first thin increment. This will smooth out irregularities in the cavity floor that are otherwise difficult to pack with a doughy composite. 7. Contamination: Contamination with blood, sulcular fluid, or saliva prior to or during the bonding procedure creates barriers that preclude proper adaptation and a reliable bond. What to do: Rule out blood and sulcular fluid prior to the procedure, using the Tissue Management System. Place rubber dam whenever possible. 8. Deteriorated product: Many restorations fail because the bonding agent used was expired or volatilized. What to do: Don’t use products past the expiration date and observe manufacturer’s storage instructions. If dispensing from a bottle make sure to cap it immediately after use or the solvent will evaporate and make the material improper for use before its expiration date. This is not an issue with a syringedispensed bonding agent. 52