Influence of composite resin volume and C-factor on the polymerization shrinkage stress

Abstract

<p>Objective: Composite polymerization shrinkage<br />stress is an inherent process of chemical and light<br />composite resin activation. Consequently, this fact has<br />been associated to potential clinical problems. The<br />aim of the present in vitro study was to evaluate the<br />volume and C-factor influence on chemical and lightcuring<br />composite resin polymerization shrinkage<br />stress, using a non-rigid method that thereby provides<br />lower stress values, causing a minimal deflection in<br />load cell. Materials and Methods: The contraction<br />forces of the Z-250 and Concise composite resins<br />during polymerization were recorded in an UTM in<br />two experiments. In the first experiment, the Z-250<br />composite was inserted beetwen two rectangular<br />steel plates (6.0 x 2.0 mm), varyng the resin volumes<br />and C-factors, in a single increment, polymerized for<br />20 s and the forces generated were recorded for 120<br />s. In the second experiment, a pair of rectangular steel<br />plates (3x2mm) and two square steel plates (2x2mm),<br />with varied heights (2; 3 mm, respectively), were<br />used to determine the C-factor (0.6; 0.3) influence.<br />Results: The polymerized Z-250 results showed that<br />the volume variations, independent of the C-factor,<br />had a direct influence on the shrinkage stress,<br />different from the Concise, which was influenced by<br />the C-factor. Conclusion: The present study showed<br />that a higher volume of composite resins determines<br />an increase in the shrinkage stress of light-curing<br />composites.</p><p><strong>Keywords</strong></p><p>C-factor. Composite resin. Polymerization. Shrinkage<br />stress.</p>

Effect of thickness on shrinkage stress and bottom‐to‐top hardness ratio of conventional and bulk‐fill composites

“…The shrinkage stress was measured from load cell deformation (10,28,30). The specimens evaluated consisted of the relevant composite inserted between two rectangular steel bases (6 mm × 2 mm) arranged parallel to one another at a distance (composite thickness) of either 2 mm or 4 mm.…”

“…For this reason, new composites have been developed to counter shrinkage stress as a cause of a series of clinical complications (2). When contraction forces overcome the bond strength of the composite to the dental rates of shrinkage stress, since the material's volume defines the number of monomers available for cross-links (7,10). It has been reported that larger volumes of composite tend to generate greater stress (7,10); therefore, the incremental technique is the most used in the clinical practice (2,11,12), with material increments of up to 2 mm of thickness being lightcured before more material is added.…”

“…When contraction forces overcome the bond strength of the composite to the dental rates of shrinkage stress, since the material's volume defines the number of monomers available for cross-links (7,10). It has been reported that larger volumes of composite tend to generate greater stress (7,10); therefore, the incremental technique is the most used in the clinical practice (2,11,12), with material increments of up to 2 mm of thickness being lightcured before more material is added. As consequence, cusp deflection is minimized, since less final volumetric shrinkage of the restorative material is involved (1,13).…”

Аналіз Успішності Функціонування Композитних Реставрацій В Умовах Різних Параметрів Конфігурації Порожнини

“…У дослідженні M. F. Witzel et al (2005) не вдалось підтвердити статистично значиму роль показників С-фактора чи об'єму композита в якості критеріїв прогнозування розвитку конкретних рівнів напруги при усадці матеріалу в ході полімеризації, хоча регресійний аналіз і підтвердив наявність лінійної кореляції між показниками стресу та рівнями С-фактора [17]. Проте у пізнішому дослідженні R. F. Mondelli et al (2016) було встановлено, що показники об'єму реставрацій незалежно від рівнів С-фактора порожнини, напряму впливають на параметри напруг, що розвиваються при усадці матеріалу [18]. У досліджен-ні R. Braga et al (2006) авторам вдалось встановити наявність корелятивного зв'язку між рівнем мікропідтікання у ділянці композитних реставрацій та об'ємом останніх (r=0,724, p<0,0001), однак ідентичних залежностей між рівнем мікропідтікання та показниками С-фактора зареєструвати не вдалось (r=0,048, p=0,6120) [19].…”

Influence of a hydrophobic monomer on the physical and mechanical properties of experimental surface sealants

“…5 The shrinkage stress has been associated to potential clinical problems such as marginal failure, recurrent caries, and dental fracture. 6,7 Therefore, alternative polishing materials, including surface sealant agents, have been developed to fill surface defects and irregularities, prevent microleakage, and improve marginal seal. 8 However, the effectiveness of sealants is quite controversial.…”