Lower incisor tip, angulation, and in-out
Lower centrals and laterals have -6° torque and zero angulation. For more than 20 years, the authors have recommended and used the -6° lower incisor bracket and it continues to be the bracket of choice for most cases. The torque is based on Andrews’ research finding of -1°, with additional control due to the .019/.025 wire not being a precise fit in the slot. The bracket delivers an ideal relationship with the lower canines, provided bracket positioning is accurate. This avoids the need for wire bending.
Since the days of the SWA, the correct in-out has resulted in lower incisor brackets which appear rather ‘thick’. Some doctors who are new to the technique comment on this, but most find it is easily manageable with System 5.0 mechanics. Lower incisor brackets are fully interchangeable, left and right, and between centrals and laterals.
The +6° torque option
In some cases it is helpful to invert lower incisor brackets, giving +6° torque and zero angulation. This can avoid the need for wire bending, it may also help the mechanics in some Class III cases, or in case where there is a need to ‘burn’ lower anchorage without retroclining the lower incisors. If a single lower incisor is proclined, inverting the bracket can help to bring the root into bone, but this requires care. For further discussion see page 56 of ‘Fundamentals of Orthodontic Treatment Mechanics’.
After inversion, increased prominence of the bracket tie-wings can theoretically be a problem. However, this is seldom an issue because appropriate cases normally have a Class III incisor relationship with a reduced overbite.
The -1° torque lower incisor bracket
The authors started using the -6° torque prescription for lower incisors in the mid 1990s and it has consistently worked very well. Today it remains the ‘go-to’ preference for most cases.
However, it is important to bear in mind the anatomy of the alveolar bone, which can be narrow and challenging in the lower incisor region. For a small number of cases, the authors have found it useful to have a -1° torque and zero angulation bracket available.
It is helpful that System 5.0 has three torque options for the lower incisors. This gives great versatility when managing the lower anterior segment.
Lower incisor brackets. The in-out delivers an ideal relationship with the lower canines at the end of treatment, provided there has been correct bracket positioning and good mechanics. They are fully interchangeable, left and right, and between centrals and laterals.
These lower left incisor brackets have been inverted to give +6° torque and zero angulation.
The System 5.0 treatment method has three torque options for the lower incisors. This provides great versatility when managing the lower anteriors, and minimises wire bending. The -6° remains the ideal bracket in most cases.(Not to scale).