A method and apparatus for searching data to locate a portion identified by a search query. In one particular exemplary embodiment, the technique may be realized as a method for improving the quality of transmitted digital signals in a multi-level signaling system wherein digital signals representing more than one bit of information may be transmitted at more than two signal levels on a single transmission medium. The thick first and second ends are adapted to provide a bearing surface for the clamping screws of a matrix band retainer, while the thin central portion provides a snug fit and tight contact with the tooth. , the lighting LEDs, and the UV-LEDs, are fixed on a circuit board evenly and mixedly in a certain way, and a separator is also provided on the circuit board.