Dr. Rios, what is the challenge for the bone when teeth are moved in the context of orthodontic treatment?
Dr. Rios: Orthodontic tooth movement has two different effects on the bone. On the compression side, we see a catabolic effect, leading to bone resorption. And on the tension side, new bone is formed, so we see an anabolic effect. Depending on several factors—such as the magnitude of the force, direction of tooth movement and the local anatomy—these effects can be physiologic, or they can increase the vulnerability of the surrounding tissue.1
Does tooth movement influence soft tissue as well?
Dr. Rios: Yes. Often, gingival recessions are the more tangible signs for the underlying cause, which is bone loss.
Do problems often occur? If so, which and when?
Dr. Rios: 20-35 percent of patients develop gingival recessions after orthodontic treatment.1 The incidence of bony dehiscence and gingival recession is higher in teeth surrounded by thin periodontal phenotypes.2 Lower incisors and upper or lower canines are especially prone to soft tissue breakdown. The problems mostly start years after the treatment.1 So, for the patient the cause is not apparent.
Surgically accelerated orthodontics is a relatively new treatment option. What does it mean?
Dr. Rios: It’s not really a new treatment option, but it is definitely more in demand now. Surgically accelerated orthodontics includes dentoalveolar bone decortication. This accelerates tooth movement in a certain time frame after an injury.3
There are many different treatments that fall under this category. The decortication can, for example, be combined with bone or soft tissue augmentation, and it can be done in a minimally-invasive way or with flap elevation.
What is the effect of the decortication?
Dr. Rios: On the one hand, it is obviously a mechanical effect. The bone is slightly damaged and a tooth can be moved easier in this damaged zone. But there is also a biochemical effect. Damaging the cortical layer induces the release of pro-inflammatory cytokines such as interleukin 1-beta along with other molecular mediators. These molecules cause a transient osteopenia. During this “window of opportunity” tooth movement is accelerated.3
What is the advantage compared to conventional orthodontic treatment?
Dr. Rios: Most adult patients undergoing orthodontic treatment want a quick solution. And with this option, treatment time can be reduced significantly, by about 50 percent.4 Patients also report less pain.5
And the combination of dentoalveolar bone decortication and bone augmentation with a bone substitute—known as surgically facilitated orthodontic treatment or periodontally accelerated osteogenic orthodontics—can create additional space for tooth movement and maintain the thickness of the buccal bone after mandibular decompensation. This can be highly beneficial for the overall treatment plan and avoid unnecessary tooth extractions.
Finally, surgically accelerated orthodontics should reduce the level of orthodontic relapse.
So, the risk of iatrogenic sequelae is lower compared to non-surgical orthodontic treatment?
Dr. Rios: Yes, just recently a Best Evidence Review from the American Academy of Periodontology concluded that surgically accelerated orthodontics enhances post-orthodontic stability of the mandibular anterior teeth. But long-term tissue loss after orthodontic treatment has not yet been fully investigated. What we can say today is that orthodontic treatment in general might add to the susceptibility of the tissue and that understanding both treatments better will make them both safer.
You did a study on the combination of surgically accelerated orthodontics and phenotype modification therapy. What did you want to find out?
Dr. Rios: The study included 40 patients in need of orthodontic treatment.5 They were divided into four groups. First: control group with conventional orthodontics, second: orthodontics plus piezocision, third: orthodontics plus piezocision plus collagen matrix and fourth: orthodontics plus collagen matrix without piezocision. So, on the one hand, we compared conventional orthodontic treatment with surgically accelerated orthodontic treatment. On the other hand, we investigated whether combining decortication with a collagen matrix on the periosteum has a positive effect.
A. Pre-operative clinical situation of a patient under orthodontic treatment, B. vertical and inter-radicular gingival incisions are performed on the buccal aspect of the mandibular arch, starting 2-3 mm below the interdental papilla with enough depth to allow the piezotome to reach the alveolar bone, C. a tunnel is created, and the collagen matrix is pulled into the tunnel, D. the sutures for the collagen matrix are located in the inter-proximal / interradicular space and engage at least have of the material
Dr. Rios: Our idea is that the spongy layer of the collagen matrix serves as a reservoir for the pro-inflammatory cytokines that are produced in the bone because of the corticotomy. Collagen is known to have this capability. By storing the cytokines and releasing them over a longer period, Geistlich Mucograft® may extend the window of opportunity in which tooth movement is facilitated.
On the other hand, the denser layer of the matrix should protect the buccal periodontium from invasion of soft tissue fibroblasts. It’s beneficial to separate these two tissues for a while so that the new osteoblasts are not suppressed by faster growing soft tissue fibroblasts.
Did you see this effect?
Dr. Rios: We could see a positive effect on vestibular bone height and gingival thickness and certainly a positive effect on treatment time.5 The latter was in the collagen matrix group even shorter than in the surgically accelerated orthodontics group without collagen matrix. We would expect further improvements in buccal bone thickness in the two collagen-matrix groups over time. But we don’t have the results yet.
What does this mean for clinical practice? Do you advise protecting the bone with a collagen matrix in the context of orthodontic treatment?
Dr. Rios: Absolutely. And I think it is important that periodontists and orthodontists together develop protective strategies to ensure a healthy periodontal phenotype in the long run. This includes standard treatment goals to minimize an increase in tissue vulnerability through orthodontic treatment. It also requires a change of mindset from correcting defects to protecting tissues.