Are Aligners with attachements really invisible?
14.11.2022How much stripping is safe?
In 1944, Ballard first described the process of enamel reduction to eliminate dental abnormalities responsible for crowding in the dental arch. It wasn’t until 40 years later that Sheridan would demonstrate enamel reduction using a high-speed air-rotar and ever since then, studies on the subject have been piling enormously. Much of what we know today about enamel reduction has been derived from decades of research and practice and its application in aligner therapy is a testament to that dedication.
Stripping, also known as interproximal enamel reduction is a process whereby the enamel thickness of a tooth is reduced mesiodistally, usually in an attempt to create a minimum space necessary to resolve crowding. Today, enamel reduction has become a common practice in the orthodontic office, especially because doing so, eliminates the need for tooth extractions.
The procedure ensures the reduction of 0.2 to 0.5 millimetres of tooth width. Anything more than that may not be recommended.
How much stripping is recommended?
The primary function of the tooth enamel is to protect the tooth from chemical, biological, and physical wear and tear. Understandably, stripping the tooth of a certain enamel thickness for orthodontics can be tricky and should only be used in appropriate conditions, indications, and when specific criteria exist.
To realize the right amount of enamel to remove for orthodontic treatment, we must consider theories put forth by several authors. Hudson et al., published tables that show the maximum amount of enamel that can be safely removed so that iatrogenic damage is kept at as low a level as possible.
Refer to the table (TABLE 1) below: reference [1]
TABLE 1
| 1* | 2* | 3* | 4* | 5* | 6** | |
| 1 mm | 0.15 | 0.15 | ||||
| 2 mm | 0.20 | 0.30 | ||||
| 2 mm | 0.25 | 0.25 | ||||
| 2 mm | 0.15 | 0.15 | 0.20 | |||
| 3 mm | 0.20 | 0.25 | 0.30 | |||
| 3 mm | 0.15 | 0.15 | 0.20 | 0.25 | ||
| 4 mm | 0.15 | 0.15 | 0.20 | 0.25 | ||
| 5 mm | 0.20 | 0.25 | 0.35 | 0.45 | ||
| 5 mm | 0.15 | 0.20 | 0.25 | 0.30 | 0.35 | |
| 6 mm | 0.20 | 0.20 | 0.30 | 0.40 | 0.40 | |
| 7 mm | 0.20 | 0.30 | 0.35 | 0.45 | 0.45 | |
| 8 mm | 0.20 | 0.30 | 0.35 | 0.45 | 0.45 | 0.50 |
*4 surfaces: mesial, distal, right and left
**2 surfaces: mesial, right and left
This table illustrates the quality of enamel that should be removed from both surfaces of each tooth, except the first molar (enamel is taken only from the mesial surface of the first molar).
But that’s not all. Another author, Fillion published his own theory. In his guide, he described the upper limits of enamel that can be removed safely. He presents that by using his guide, orthodontists can gain at most 8.6 mm of space in the mandible and 10.2 mm in the interproximal stripping of all the teeth from the mesial surface of one first molar to the mesial surface of the other.
Refer to the table (TABLE 2) below:
TABLE 2
| Central | Lateral | Canine | First premolar | Second premolar | First molar | Total per arch | ||||||||
| M | D | M | D | M | D | M | D | M | D | M | D | |||
| Upper arch | 0.3 | 0.3 | 0.3 | 0.3 | 0.3 | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 | 10.2 | |
| Reduction of tooth surface | 0.6 | 0.6 | 0.6 | 1.2 | 1.2 | 1.2 | ||||||||
| Lower arch | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 | 8.6 | ||
| Reduction of tooth surface | 0.4 | 0.4 | 0.4 | 0.9 | 1.2 | 1.2 | ||||||||
While these two tables are complementary, they are not to be used blindly. Experts urge orthodontists to not follow them blindly but must adapt the stripping to the anatomical conformation and periodontal status of each tooth in question. Before stripping, the width of the teeth should be measured in order to know in advance how much enamel should be removed. As the process goes on, they should then make use of callipers to see how much they are actually removing.