AUTHOR – Dr. Manoj kumar singh , m.d.s., Sr. Lecturer, Dept. of Periodontics, Guru Nanak Institute of Dental sciences & Research, Kolkata

Introduction

Every orthodontic patient is enthusiastic about the possibility of reducing their treatment time. Given this constant demand for shorter treatments, orthodontists from around the world have increasingly sought ways to boost orthodontic treatment efficiency. The search for this efficiency, i.e., new approaches to shorten treatment time without foregoing optimal results, has become a primary goal of orthodontics. Low friction and self-ligating bracket systems, robot preformed archwires, rapid canine retraction and alveolar corticotomies are examples of approaches that aim to reduce the time required for orthodontic therapy. Since the promise of a faster treatment holds considerable commercial appeal, orthodontists are faced with a major challenge: To critically shift through the available options by distinguishing genuine breakthroughs in alternative treatment approaches from others more financially oriented and not committed to improving service quality for our patients. Typical orthodontic treatment takes 18-36 months. The treatment time depends on the distances the teeth need to be moved, treatment goals, the type of techniques employed and the cooperation of the patient which is otherwise known as accelerated orthodontic treatment.
Various efforts made to increase the tooth movements¹.

1. Accelerated tooth velocity by pharmacological agents.
2. Acceleration of tooth velocity with physical stimuli.
3. Acceleration of tooth movement by surgical means.

a)  Accelerated tooth velocity by pharmacological agents.

The speed of tooth movement was found to be related to the force magnitudes, the level of cytokines in GCF , the IL-1 gene predisposition. The actual velocity of tooth movement may depend on the rate of bone turnover. It was modified pharmacologically by inducing either hypothyroidism or hyperthyroidism. Yamasaki et al (1980,1984)^2,3 injected prostaglandin E1 or PGE1 analog (misoprostol) in to the gingiva of moving tooth to significantly increase the velocity of tooth movement without enhancing root resorption. Relaxin reduced the level of PDL organization and mechanical strength, leading to increased tooth mobility (Madan et al., 2007 )⁴.

b ) Acceleration of tooth velocity with physical stimuli.

The tissue remodeling in orthodontics is mediated by a variety of cells, including fibroblasts, root and bone surface lining cells, endothelial , epithelial, and nerve cells ,as well as by different leukocytes, prompted clinical investigators to apply physical and chemical agents concomitant with orthodontic forces, in order to augment the effect of the mechanical forces. Local application of heat, minute electric currents, static magnetic field enhanced significantly the number and size of bone nodules, and content of calcium, alkaline phosphatase, and osteocalcin^5,6.

c ) Acceleration of tooth movement by surgical means.

When mechanical loads are applied to intact tissues in vivo or in vitro, the tissues usually become distorted. In the case of the skeleton, loads such as gravity prompt cells to arrange the architecture of the bony structural features in a way that would resist redundant loads (Wolf”s Law ).
The alveolar corticotomies and selective alveolar decortications (SAD) are most effective means to increase the orthodontic tooth movements.⁷ The other technique provides an increased net alveolar volume after orthodontic treatment. This is called the periodontally accelerated osteogenic orthodontics (PAOO) technique. It is a combination of a selective decortication facilitated orthodontic technique and alveolar augmentation. With this technique, one is no longer at the mercy of the preexisting alveolar volume, and teeth can be moved 2 to 3 times further in [1/3] to [1/4] the time required for traditional orthodontic therapy. It can be used to treat moderate to severe malocclusions in both adolescents and adults and can reduce the need for extractions. Except for severe Class III skeletal dysplasia, PAOO can replace some orthognathic surgery, and reduce the  morbidity rate.^8,9.

Rapid tooth movement following selective alveolar (jaw) bone decortication is well documented and results in treatment outcomes routinely produced in 6 to 9 months of active orthodontic care. The out-patient decortication surgery induces a transient osteopenia (bone healing) condition that favors "accelerated orthodontic treatment". The basis for the therapy is biological in nature and the biological changes are well documented. Uncompromised orthodontic treatment results are readily achievable utilizing orthodontic treatment in combination with selective alveolar decortication.

While dentists may treat some orthodontic conditions in very short time periods, for example, "braces in 6 months", this approach may not address all the features which could be treated in an extended orthodontic treatment program. The ideal use of "accelerated orthodontics" is to offer a patient a viable alternative to porcelain veneers when they want straight teeth but do not want to invest years in traditional orthodontics. The exception to this is when braces are used in combination with alveolar decortication to produce a rapid orthodontic outcome wherein the patient’s malocclusion is treated comprehensively.

EVOLUTION OF CORTICOTOMY ASSISTED TOOTH MOVEMENT

The technique of distraction osteogenesis was applied first in orthopaedic surgery for long-bone lengthening and was subsequently utilized in the treatment of cranio-facial microsomia and bony defects. Both corticotomy and osteotomy are used for bone separation prior to distraction. Preservation of intermedullary blood supply and periosteum at corticotomy / osteotomy site is essential as osteogenic potential for bone regeneration derived from the periosteum.
The first reports on surgical approaches to correct poorly positioned teeth are assigned to L. C. Brian, in 1892, and G. Cunningham, in 1893. The former reported such cases at the Meeting of the American Dental Society of Europe and the latter presented the possibility of immediate correction of irregular teeth during the Dental Conference in Chicago that year. Some fifty-odd years later, in 1959, Köle¹⁰ used a combination of interradicular corticotomies and supra-apical osteotomies to speed up tooth movement. This treatment approach never gained widespread acceptance, probably due to the association of horizontal subapical osteotomies, which posed considerable risks to the periodontium and tooth pulp vitality.¹⁰ Furthermore, the use of removable orthodontic appliances provided poor control of tooth movement, which inevitably compromised orthodontic treatment outcome. In 1975, Düker¹¹ performed the first animal study replicating the technique described by Köle.¹⁰ A few years later, subapical osteotomies were replaced by cuts limited to the cortical portion of the alveolar bone. Hence the first description of a surgical attempt to enhance orthodontic treatment using only corticotomies, there by reducing the risks inherent in the previous approach. Furthermore, the use of fixed orthodontic appliances increased the control and efficiency afforded by this therapeutic combination.¹² Nevertheless, the use of ACS as an aid to orthodontic therapy remained limited. Since 2001, however, there have been renewed attempts at popularizing this therapeutic approach.

INDICATION

• Increased alveolar volume and enhanced periodontium ( I e., correction of dehiscences and fenestration.)
• accelerated treatment.(I e , 3 to 4 times more rapid active orthodontic treatment)
• greater stability of clinical outcomes and less relapse.
• Enhanced scope of malocclusion treatment  (I e – avoiding orthognathic surgery and treatment in selected cases )
• Enhancement of patients profile when indicated.
• Rapid recovery of impacted teeth (i. e, canines )

CONTRAINDICATION

• Active periodontal disease.
• Osteoporosis or other bone disease.
• Long term use of medication (anti-inflammatory,immunosuppressive or steroid)
• Long term use of bisphosphonate.

MECHANISM OF ACTION

In orthodontics, osteotomies or corticotomies have been combined with tooth movement to facilitate difficult tooth movements, reshape the alveolar arch, and accelerate tooth movement (Wilcko et al., 200113; Yen et al., 2001, 2003 ¹⁴). Selective buccal and lingual decortication of alveolar bone has been used to accelerate orthodontic tooth movement (Wilcko et al., 2001¹³). The theory behind accelerated tooth movement is that the corticotomy induces a response in the alveolar bone that can demineralize the bone around the dental roots. Once the bone has demineralized, there is a three- to four-month window of opportunity to move teeth rapidly through the demineralized bone matrix before the alveolar bone remineralizes. The bone response is called “regional acceleratory phenomenon” or RAP, a term initially coined to describe rare cases of fracture healing (Frost, 1989a,b)^15,16. The term “regional” refers to the demineralization of both the cut site and adjacent bone (Bogoch et al., 1993)¹⁷. The term “acceleratory” refers to an exaggerated or intensified bone response in cuts that extend to the marrow. For both normal and accelerated tooth movement, RAP may be an important prodromal action to effective tooth movement. It is postulated that osteoclast and osteoblast cell populations shift in number, resulting in an osteopenic effect (Bogoch et al., 1993)¹⁷. Corticotomy-assisted tooth movement is associated with a lack of hyalinization and early tartrate resistant alkaline phosphatase staining (Iino et al., 2007). Regional accelerated phenomenon is different from distraction osteogenesis, which has been described as an orthopedic technique for lengthening limbs (Ilizarov, 1988)¹⁸. Currently, there are many craniofacial applications, including some that use interdental incisions to create distraction sites (Liou et al., 2000¹⁹; Kisniscu et al., 2002²⁰; Iseri et al., 2005²¹; Yen et al., 2005²²; Sukurica et al., 2007²³). Ilizarov, who developed the tension stress principles of distraction osteogenesis, believed that a corticotomy was the ideal method for creating a distraction site (Ilizarov, 1989²⁴), because the bone marrow is intact during distraction procedures. While important for limb lengthening, it is unclear whether the alveolar bone responds to cortical incisions in the same manner as does long bone.


More osteoclast and less PDL hyalinization near teeth that had been operated than near non surgically treated teeth. Alveolar bone surgery may also stimulate a variety  of cell types inside marrow cavities, including mesenchymal stem cells. These cells can function synergistically with neighbouring PDL and alveolar bone cells that have been activated by the orthodontic forces, and model and remodel the bone faster.  Understanding the role of osteoprogenitor cells is important because , as a tooth is moved through a surgical wound, healing recapitulates regional tissue ontogeny (Murphy 2006) ²⁵ and , with the addition of bone graft can actually increase the total bone mass of the novel alveolus phenotype while enhancing long term stability.

The best technique consist of punctate and linear decortication in areas of the alveolus where accelerated and stable tooth movement is desire. the bone is added ad hoc where augmentation is needed. As teeth are moved through a healing wound, with or without bone graft, the bone is stressed.  However, because the movement of teeth produces tensional stress in the bone , the maturation and eventual recalcification of the repair tissue is delayed as long as the bone “senses” tooth movement. The reaction is similar to bone fracture that requires immobilization to achieve full development. The healing callus  will be delayed in final calcification when subjected to tensional stress.

With simple orthodontic tooth movement there is no increase in bone volume, even 2 – 3 years later. However, when the teeth are moved thorough a combination of decorticated alveolar bone and certain kind of bone graft , new phenotypes may be engineered and net increase in bone volume is evident. The degree of bone decalcification is commensurate within the amount of therapeutic trauma but penetration is rarely deeper then 1-2 mm beyond the labial alveolar cortex. Where minimal tooth movement is needed, simple segmental surgery can be performed on as  few as three teeth or on either side of an extraction site and the pattern of decortications seems less important then the total surface area that is decorticated.The usual rate of orthodontic tooth movement by conventional biomechanical protocol is relatively slow (about 1mm / month) compare with the 1mm / week that is possible with surgical intervention, and movement approaching 1mm / day has been reported in some cases (Iseri et al  2005)²¹.

Moreover, the entire” bone morphing” possibilities promise to take dentofacial orthopedics to an entirely new level of science that has witnessed a volcanic eruption of scientific data over the last few decades under the rubric of “tissue engineering”. Clinical results can quite dramatically alter facial form without the risk and morbidity of hospital surgery.

CONCLUSION

The interdisciplinary approach is needed to reduce treatment time in orthodontic patients. Surgical intervention incorporates periodontal tissue engineering and regenerative surgery to expedite orthodontic tooth movement with reduced side effects like root resorption, tooth devitalization, relapse, inadequate basal bone.

FURTHER RESEARCH AREA

Alveolar corticotomies and associated soft tissue surgery create conditions that significantly increase tooth velocities and tooth movements when orthodontic forces are applied.  Performing a second corticotomy procedure after 4 weeks maintains the enhanced velocities of tooth movement for a longer duration. However, the differences in tooth movement do not appear to justify a second corticotomy at present arena.

BIBLIOGRAPHY

1. Davidovitch z , okamato y , gogen h , saito I , et al (1996) orthodontic forces stimulate alveolar bone marrow cells.
2. Yamasaki k, miura f, suda t, (1980) prostaglandin as a mediator of bone resorption induced by experimental tooth movement in rats, journal of dental research ,59,1635 – 42.
3. Yamasaki k, shibata y, imai s, tani y, et al (1984) clinical application of prostaglandin  E1(PGE1  ) upon orthodontic tooth movement. American journal of orthodontics, 85, 508 – 18.
4. Madan MS, Liu ZS, Gu GM, King GJ (2007) Effect of human relaxin on orthodontic tooth movement and periodontal ligaments in rats. American Journal of Orthodontics and Dentofacial Orthopedics, 131:8.e1 – 10.
5. Davidovitch Z, Steigman S, Finkelson MD, Yost RW, et al (1980) Immunohistochemical  evidence that electric currents increase periosteal cell cyclic nucleotide levels in feline alveolar bone in vivo. Archives of Oral Biology, 25,321-7.
6. Tengku BS, Joseph BK, Harbrow D, Taverne AAR et al. (2000) Effect of static magnetic field on orthodontic tooth movement  in the rat. European Journal of Orthodontics,22,473-85.
7. Ren A, Lv T, Kang N, Zaho B, et al . (2007) Rapid orthodontic tooth movement aided by alveolar surgery in beagles.American Journal of Orthodontic and Dentofacial Orthopedics,131,160.e1-10.
8. Gantes B, Rathbun E, Anholm M. Effects on the periodontium following corticotomy-facilitated orthodontics: case reports. J Periodontol. 1990;61:234–8.
9. Yaffe A, Fine N, Binderman I. Regional accelerated phenomenon in the mandible following mucoperiosteal flap surgery. J Periodontol. 1994;65:79–83.
10. Kole H. Surgical operation on the alveolar ridge to correct occlusal abnormalities. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1959;12:515–29.