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It's always best to include the rules of the item in question:
These thick brass and leather gauntlets allow the wearer to tear through bone and muscle like paper.
Once per day, as part of a melee attack, the wearer can activate the gauntlets to inflict a horrific injury on an opponent. If the attack hits, the target must make a DC 14 Will save. If the save fails, the gauntlets reduce the target's Strength, Dexterity, or Constitution (wearer’s choice) by –6. This penalty cannot reduce the target's ability score below 1. The injury heals over time, reducing the penalty by 1 for each day that passes since the time of the injury, and is immediately removed by heal, regenerate, restoration, or any magic that can break a curse.
The item text just states that it must be part of a melee attack, and as it's a wondrous item instead of a specific weapon, it has nothing that suggests it must be made with the gauntlets.
The dagger is fine.