Stickiness and Stringiness of Uncured Nano- and Nano-hybrid Composites

Objectives: � This study measured the stickiness of selected uncured resin-composites, comparing one nano-composite (NC) to four nano-hybrids (NH). �The tendency to string while handled was also examined. �This study also sought to obtain a correlation between measured stickiness parameters and the composite's tendency to string.

Methods: � Stickiness was analyzed utilizing a texture analyzer.� A stainless steel probe was pushed into composite at constant force for a given contact time, and withdrawn at a given rate.� During withdrawal, the maximum tensile force (Fmax) exerted on the probe and the Work (area under the force-distance curve) were measured.� Data (n=4/group) was collected at 37�C and two combinations of contact time and removal speed (1s and 8mm/s, or 20s and 1 mm/s).

Stringiness was assessed by handling each composite with a dental instrument, ranking them on a scale of 1 (least stringy) to 4 (most stringy).

Estelite^� Sigma Quick (ESQ), Filtek� Supreme Ultra (FSU), Gradia Direct X (GDX), Paradigm� Nano Hybrid (PNH), and TPH^�3 (TPH3) were examined.

Results: �

	Fmax(N) 1s, 8mm/s	Fmax(N) 20s, 1mm/s	Work(N�mm) 1s, 8mm/s	Work(N�mm) 20s, 1mm/s	Composite Type	Instrument Stringiness
FSU	1.6�0.3	1.1�0.2	0.8�0.2	0.7�0.2	NC	1
ESQ	6.49�0.08a	5.13�0.2b	14�2c	7.8�0.2d	NH	3
GDX	5.3�0.6a	3.0�0.3b	6.3�0.6c	3.1�0.6d	NH	3
PNH	2.1�0.4	1.36�0.06	1.2�0.3	1.15�0.15d	NH	2
TPH3	4.9�1.3a	4.1�0.5b	30�7c	8.4�0.2d	NH	4

Superscript indicates samples that were statistically different from FSU using the 2-sample t-test and p<0.05.

Work and Fmax were evaluated by linear regression for their correlation with instrument stringiness rating at either condition.� Work correlated best with stringiness, R²=71% for 1s and 8mm/s and R²=73% for 20s and 1mm/s.

Conclusions: � The texture analyzer measurement of Fmax and Work indicated that FSU was less than or equal to in stickiness for all composites examined.� This work aids the dental practitioner by quantifying composite stickiness.