Abstract: Objective To observe the clinical effects of three methods protecting molar teeth during root canal treatment.Methods We applied the orthodontic band,resin fullcrown and steelwire cerclage to protect molar teeth before root canal treatment.Compare the protective effects on molar teeth,looseness,dislocation,and breakage of protective device as well as irritative symptoms at gingivae caused by the three methods.Results The resin fullcrown group and orthodontic band group had obvious difference with steelwire cerclage group in protective effects on molar teeth and irritative symptoms at gingivae as well as looseness,dislocation,and breakage of protective device,while resin fullcrown group and orthodontic band group had no obvious difference with each other.Conclusions Applying resin fullcrown or orthodontic band to molar teeth before root canal treatment can obviously protect molar teeth,avoid crown fracture, and induce less adverse effects than applying steel wire cerclage.