Page 10 - ADITI 2018 Newsletter - Volume 2
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Orthodontic brackets : Manufacturing been used for manufacturing of Orthodontic brackets.
processes A broad range of raw materials such as metals and
alloys (austenitic and martensite stainless steels,
The word Orthodontics is derived from a Greek word commercially pure titanium and titanium alloys,
orthros meaning straight and odontos meaning cobalt-chromium alloys etc.), ceramic, and plastics
teeth.The main goal of this treatment procedure is to are used. Metallic brackets which are made of
improve oral functions, aesthetics and general dental stainless steel are the most commonly used in
health for the patients. Orthodontic braces were not orthodontic therapy and are manufactured by three
invented until the early 1800's but desire for straight main processing methods: casting, injection molding
teeth could also be seen during that period. and milling, which may be used in combination.
Archaeologists discovered many mummified remains
in and around Egypt. It was also found that some Investment casting:
teeth of deceased had gold wires wrapped around the Advantages
teeth for space closure. ·The Investment Casting process has its advantages
in that it is suitable to make parts with complex
The first official use of the word “braces” was in the designs, whereas other processes are either too long
early 1900's. During this time the dentist use to wrap and costly or there are no flash or parting lines.
metal strips around each tooth. The strip would then Otherwise, investment casting's simpler technology
be connected to a wire to apply force for teeth and dimensional accuracy is better than the other
straightening. In 1970's dental adhesives were processes.
introduced which stuck braces directly to the teeth. In ·Biggest advantage of investment casting is that it is
addition to the dental adhesive, tie wires and elastic possible to produce a very wide variety of products
ligatures were often used to keep the braces tight and across different industries. This versatility is a definite
in place. Holding the archwire to the bracket was quite plus over other casting method that either have
time consuming and this lead to the development of difficulty producing some designs or cannot produce
self-ligating brackets. Self-ligating brackets have an them at all. Also, many different metals and alloys can
additional advantage of reducing force acting on the be used in investment casting.
teeth and thus are more comfortable to the patients.
Disadvantages:
In orthodontic treatment pressure is applied to the ·Large machinery is required for this process, and
teeth through an archwire which is inserted onto the when extremely high-volume manufacturing is
slot of a bracket bonded to enamel, which is the desired, the associated costs and longer cycle times
outermost layer of a tooth (Fig.1). Brackets are to be can make investment casting a less-suitable option
bonded to enamel and for that purpose is equipped depending on one's needs and deadlines.
with a mesh, a network of grooves which provides ·Although investment casting saves on cost in a
interlocking of metallic surface with the adhesive variety of ways, prep work can be labor-intensive
used to retain them onto the enamel surface. compared to other methods. The preparation of the
wax patterns and shell molds require much time and
Fig 1. Orthodontic braces with arch wires fixed on teeth effort to ensure a quality product.
The surface of bracket which contacts the wire should The first process in investment casting is producing
be stiff to resist any deformation while the base of the the wax pattern of an orthodontic bracket. Injection
bracket that contacts the enamel should be machines are used that inject the wax into the mold.
deformable to allow easy removal of brackets after Then, the wax pattern of the orthodontic bracket
completion of treatment. A wide array of methods has assembly is shaped into the tree form. The next step
is to build a ceramic shell around the wax tree. This
shell will eventually become the mold that the metal is
poured in. The tree form is then dipped into ceramic
slurry and allowed to harden (Fig 2.). After the
ceramic slurry hardens, the ceramic slurry has a
thickness in the region of 10 mm. The ceramic mold is
