The Danish dentist Victor Haderup devised a variation of the Palmer notation where the (⏌⎿ ⏋⎾) symbols are replaced by plus/minus signs, which can either be placed in front or behind the number. A plus (+) indicates upper position while minus (−) indicates lower.
The modified Palmer notation by Victor Haderup uses plus (+) and minus (−) signs to represent upper and lower positions in a dental system, replacing the original symbols (⏌⎿ ⏋⎾).