ProTaper Next vs ProTaper Ultimate

Eight comparative full texts were read for this pair: one randomised trial, three shaping studies in extracted teeth, one retreatment study, and three bench studies of fatigue, torsion and bending. The two systems share the ProTaper variable-taper idea and an off-centred cross-section (rectangle for Next, parallelogram for Ultimate), and differ in alloy and heat treatment (M-Wire for Next; M-Wire, Gold and Blue by file for Ultimate), in motor settings (300 rpm for Next, 400 rpm at 4.0 to 5.2 Ncm for Ultimate) and in the Slider-first glide path of Ultimate.

The one clinical trial found no difference. In 28 necrotic mandibular premolars with asymptomatic apical periodontitis, preparation to Ultimate F3 or Next X3 reduced cultivable bacteria to the same degree, with the caveat that F3 carries a 9 % apical taper and X3 a 7 % taper, so the preparations were not identical (PMID 41169779).

On shaping, a micro-CT study of 50 mandibular premolars with 10 to 35 degrees of curvature found a smaller canal-volume increase and less dentin loss with Ultimate to F2 than with Next to X2, and a smaller uninstrumented area in the coronal third; in that study the Ultimate group used the Slider without a hand glide path while the Next group had one (PMID 40546860). In 50 mandibular first molars, Ultimate to F2 and Next to X2 left the same share of unprepared wall (17.1 % against 19.6 %) and the same volume increase, but Ultimate showed the highest transportation of five systems at the 6 mm level of the mesial canals (PMID 41964818). In 150 roots assessed by CBCT, with Ultimate stopped at F1 to match diameters, wear was similar, transportation stayed under 0.3 mm for both, Ultimate tended to transport toward the inner curve at 3 mm in moderately curved canals while Next tended outward, and Ultimate centred better than Next at 3 mm and 5 mm in severe curvatures (PMID 41744930).

Cyclic fatigue results point in opposite directions. At room temperature in a 60-degree canal with a 3.5 mm radius, Next X2 lasted 403 cycles against 294 for Ultimate F2, both at their own settings (PMID 35912033). At 35 °C in a 60-degree canal with a 5 mm radius, Ultimate F2 reached 727 cycles against 469 for Next X2 (PMID 41964818). The temperature, the radius and the year of manufacture all differ between the two series, so neither result overrides the other.

Torsion and bending are more consistent. At the ISO test point 3 mm from the tip, Next X2 broke at a higher maximum torque (1.81 Ncm against 1.45 Ncm) while Ultimate F2 twisted further before fracture (399 degrees against 282), and Ultimate F2 needed the highest bending torque of five systems in a 60-degree deflection (PMID 41964818). Measured at 6 mm instead, Ultimate F2 broke at the higher torque (2.66 against 2.40 Ncm), twisted further (505 against 255 degrees) and survived more torsional cycles at 90 % of its ultimate strength at both 22 °C and 37 °C; Next's torsional fatigue life rose at body temperature while Ultimate's did not change (PMID 41826551). In a six-system bench series at room temperature, Ultimate F2 required among the lowest bending loads and Next among the highest, Next showed the smallest angle of rotation, and Next's M-Wire was harder (425 HVN) than Ultimate's Gold and Blue wires; Ultimate was fully R-phase at 20 °C and mixed at body temperature, Next mixed at both (PMID 40141543).

In retreatment of 80 single-rooted premolars filled with AH Plus and gutta-percha, Next and Ultimate left the same amount of filling behind whether or not retreatment files came first and whatever the access design; no group removed everything, and residues ranged from 12 % to 30 % (PMID 39768860).