From Volume 40, Issue 7, September 2013 | Pages 555-563
In this, the third part of the series, aesthetic orthodontic treatment will be considered. The previous two articles have looked at invisible orthodontics with Invisalign and lingual brackets. This article will discuss the properties and use of aesthetic brackets, along with examples of orthodontic treatment cases using the aesthetic brackets.
Although fixed appliances have been used for many years, the brackets have been constructed from a metal stainless steel material. Although functionally the metal brackets provide excellent properties with low friction, good resilience to breakage and superior debonding qualities, the appearance of the brackets are anaesthetic. The metal bracket appearance, often referred to as ‘train-track’ braces, are often unappealing to patients, especially adults who may already be conscious of wearing braces. The introduction of aesthetic ceramic brackets in 1986 has allowed many adults to seek orthodontic treatment, reassured in the knowledge that the aesthetic brackets are less visible and more socially acceptable (Figure 1).
The majority of aesthetic brackets are ceramic, composed from an aluminium oxide material. Originally, plastic brackets constructed from acrylic and later polycarbonate were introduced to improve the aesthetics of fixed appliances.1 Problems with rigidity, strength and staining led to further development, including reinforcing the polycarbonate with ceramic. These brackets demonstrated improved mechanical properties but still maintained torque control problems. Full ceramic brackets, using aluminium oxide in various forms, provided a major improvement in aesthetic brackets, with improved strength resistance to wear and overall aesthetic appearance. A number of manufacturers now produce aesthetic ceramic brackets, each implying an advantage often relating to mechanical or improved aesthetic properties (Table 1).
| Bracket Name (Manufacturer) | Features of Bracket System | Debonding Technique |
|---|---|---|
| Monocrystalline Ceramic Brackets | ||
| Inspire ICE (Ormco) | Improved breakage resistance and torque strength |
Inspire ICE debonding instrument |
| Purity (Orthocare) | Ultra smooth with low friction sliding mechanics |
Flash removal then apply bracket removers under pad |
| Radiance (American Orthodontics) | Patented Quad-Matte base - strong bond in centre for retention but weaker on outside for easy debond |
No special extra tools required for debond |
| Spa Aesthetics (DB Ortho) | Accurate base contour for reliable fit |
SPA direct bond remover |
| Polycrystalline Ceramic Brackets | ||
| Contour (DB Ortho) | Base has surface comparable to mesh base on steel bracket | Flash removal then DB Band Slitter applied |
| Intrigue Silk (OrthoCare) | Pseudo-twin design increases strength |
Stealth debonding instrument recommended |
| InVu (TP Ortho) | Exclusive colour matching technology so bracket blends with individual teeth |
No special extra tools required |
| Tip-Edge Plus Ceramic (TP Ortho) | Aesthetic version of Tip-Edge Plus - horizontal tunnel permits uprighting and torquing from superelastic auxiliary archwire | No special extra tools required |
| 20/40 (American Orthodontics) | Reduced particle size - smaller more rounded bracket and slot corners |
No special extra tools required |
| Polycrystalline Ceramic Brackets with Metal Slot | ||
| Clarity (3M Unitek) | Metal-lined archwire slot - no metal-ceramic friction |
No special extra tools required |
| Desire (Orthocare) | Gold slot to decrease frictional resistance |
No special extra tools required |
| Virage (American Orthodontics) | Gold alloy slot insert (100% nickel free) for enhanced sliding |
No special extra tools required |
| Polycrystalline Ceramic Self-Ligating Brackets | ||
| Damon clear (Ormco) | Passive self-ligation system with SpinTek slide for fast and comfortable archwire changes |
Damon Clear Debonder |
| Clarity SL (3M Unitek) | Combines SmartClip technology with a ceramic bracket | Remove flash then use Unitek Self-Ligating |
Aluminium oxide has an extremely high hardness property,2 nine times harder than stainless steel or enamel.3 This can be a desirable property in that ceramic brackets can resist damage from patient trauma or during orthodontic adjustments, but may be considered as a disadvantage if they come in contact with enamel from an opposing tooth. Indeed, a major concern is enamel abrasion that can occur when occlusal contact is made from a ceramic bracket.
The tensile strength of aesthetic ceramic brackets is higher than stainless steel,4 which will reduce or resist structural failure. This strength, however, also causes the ceramic to be more brittle1 and this can lead to a higher bracket breakage clinically.
Early aesthetic ceramic brackets, chemically bonded using a silane-coupling agent, demonstrated extremely high bond strengths that could cause enamel damage during debonding procedures. The initial challenge was to reduce this to a level that had sufficient bond strength to allow orthodontic mechanics but could be debonded safely with no enamel damage.5 Studies have assessed various chemical and mechanical bond techniques and suggest that the use of a mechanical interlock reduces enamel detachment but still maintains high strength, durability and retention similar to metal brackets.6
Ceramic brackets tend to have a rougher surface than stainless steel7 and this inevitably produces a greater coefficient of friction. In simulated clinical conditions, conventional ceramic brackets generated significantly higher friction than other brackets tested.8 Manufacturers have attempted to address this by placement of a metal slot in the bracket to allow improved sliding of archwires. Although the overall appearance of the bracket remains aesthetic, particularly image conscious patients may still be concerned with the appearance of the metal slot. A lab-based study,9 however, failed to demonstrate improved properties in resistance to sliding following the insertion of a metal slot.
Frictional resistance properties have been of major consideration in orthodontics over the last decade, with an increased interest in self-ligating brackets. These are considered to have optimal frictional properties and this has led to the introduction of ceramic self-ligating brackets (Figures 2 and 3). These usually contain a metal gate that can be dulled to improve the appearance. Of course, the need for maximum resistance to frictional forces is debatable, as many adult treatments are undertaken on a non-extraction basis that do not require large sliding mechanical movements suited to low friction brackets.
Although most orthodontists would favour the use of stainless steel brackets10 for reasons expressed above, the use of aesthetic brackets can be used in most clinical cases. Table 2 lists the ideal case for the use of aesthetic brackets. Their use tends to be restricted to adults who are seeking private orthodontic treatment, although there is no reason for not using on adolescents and children. Adult patients should be counselled that, although the brackets may be tooth-coloured, the elastics that hold the archwire in place could often stain during treatment, even though these are routinely replaced. Initially, orthodontists may place tooth-coloured archwires, which also provide an excellent aesthetic appearance, but usually a metal-appearance archwire is needed at the later stages of treatment.
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If oral hygiene is suspect, it may be preferable to consider metal brackets as much as possible in areas such as premolars and the lower arch, which make the detection and accumulation of plaque much more visible for cleaning.
Once the aesthetic brackets have been placed, a close inspection of the occlusion should be made. Any potential occlusal contact with the ceramic brackets should be identified and may require the placement of a bite-opening filling material placed on the posterior occlusal surfaces.
Owing to the high bond strength generally achieved with ceramic brackets, initial preparation of the tooth is straightforward. Cleaning with a pumice agent should be used to remove any surface debris and the enamel can be etched with a conventional system or using a self-etching primer. Normal curing techniques can be applied and reliable bond strengths can be routinely obtained. Bracket placement is more difficult than stainless steel brackets owing to the tooth-coloured appearance and less obvious bracket edges that act as a positional guide.
As discussed above, the aesthetic brackets can attain high bond strength and this can pose a particular difficulty in debonding. Previous suggested techniques have involved initial removal of excess flash around the bracket, ultra-sonic scaling and use of debonding agents. More recently, manufacturers have designed specific techniques for predictable debonding, such as the insertion of a ‘stress concentrator’ that fractures during mesio-distal squeezing (3M Clarity™).
The failure of the bracket/adhesive interface leaves residual adhesive on the tooth surface, which necessitates a longer clean-up procedure but reduces enamel detachment.
This 21-year-old patient attended with a Class III incisor relationship on a mild Class III skeletal pattern. The upper and lower arches were both severely crowded with a reverse overjet, displaced upper lateral incisors and anterior open bite (Figure 4). The patient was only prepared to wear aesthetic brackets because of her occupation, which involved contact with the public.
A treatment plan was formulated which involved removal of four premolar teeth and camouflage of the malocclusion to finish with a Class I molar and incisor relationship.
The case progressed well with placement of the upper arch initially with the lower arch bonded later and maintained in round stainless steel archwires (Figure 5). Space closure progressed rapidly and an overall good aesthetic result was obtained (Figure 6).
A 42-year-old lady presented with a Class II division I incisor relationship on a skeletal 1 base complicated by grossly lingually-tipped lower premolars (Figure 7). The patient had previously sought orthodontic treatment but was informed that no orthodontic treatment could correct her malocclusion. A fixed ceramic appliance was placed on the lower teeth and space created to allow uprighting of the tipped premolars (Figure 8).
The fixed appliance stage progressed uneventfully and space was created to align the premolars. A bonded retainer (Manchester positioner) was placed along with a removable night-time retainer. The bonded retainer was extended to include the occlusal surfaces of the premolars (Figure 9).
Aesthetic brackets have allowed a significant number of patients to undertake orthodontic treatment that would otherwise have been unable to do so. The appearance of the appliances is acceptable and mechanical properties have improved to ensure treatment goals can be achieved. The brackets clearly have some limitations and manufacturing research and development will continue in the pursuit of the ideal aesthetic bracket.
