The Periodontics-Orthodontics relationship
1. Introduction:
Although orthodontics and periodontics remain two specialties in their own right today, the relationships that unite them, although studied for a long time, have only really appeared essential in the last few decades.
These two disciplines have periodontium in common. The first specialty allows teeth to be moved with their supporting tissue under certain conditions, the second helps to clean up and treat the environment.
Periodontal therapy aims to control inflammation and prevent reinfection. This is where orthodontic therapy comes in. Orthodontics, through induced dental movements, helps re-establish an anatomical and occlusal-functional framework that is favorable to good periodontal maintenance.
2. Histophysiology of tooth movement
2.1. Actors in dental movement
For Nefussi, the various participants in dental movement constitute the odontological functional entity (EFO) which is composed of the dental organ, the desmodont and the alveolar bone. During orthodontic movement, it is this entire unit that is reworked.
Tooth
Its root morphology determines the speed of movement. An important element is the cementum adaptation capacity. The cementum tissue actively participates, through its anchoring fibers, in the establishment and maintenance of the dental organ in a functional position.
Desmodont
The desmodont plays a major role in dental movement, its central anatomical position between the bone tissue and the cementum tissue and its compressibility rate higher than the other components of the odontological functional entity allow it to be defined as the active and regulatory element of dental movement.
Alveolar bone
It is the third component of the odontological functional entity. Cortical and spongy bones present a functional and structural difference.
The structural difference is based on the difference in bone density: 80 to 90% of cortical bone is occupied by bone tissue compared to 20 to 25% at the level of spongy tissue.
The functional organization includes:
• bone envelopes;
• bone cells (osteoclasts, osteoblasts and osteocytes).
The Periodontics-Orthodontics relationship
2.2. Physiological tooth movement
Bone remodeling is the mechanism by which bone tissue is constantly renewed. In the alveolar bone, this remodeling is responsible for ligament anchorage and its maintenance during physiological or induced tooth migration. In humans, physiological migration is mesial. All cellular events of bone remodeling take place at the interface between calcified tissues and soft tissues.
Face in resorption
Baron modified Frost’s concept of the activation-resorption-formation (ARF) cycle by adding a reversal phase to form the ARIF cycle. This cycle, which consists of a sequence of unchanging events, reflects the activity of the multicellular unit or
(BMU). The final product of the remodeling activity forms a bone structural unit or bone skeletal unit (BSU). Baron defines the notion of “balance” as the quantitative equilibrium between the phenomena of resorption and formation at the level of each bone multicellular unit (BMU) and the notion of “coupling” as the qualitative relationship between these two cellular activities.
Face in apposition
It is the seat of a progressive mineralization of the desmodont which transforms into fasciculated bone. This bone is then reworked by resorption and replaced by lamellar bone. An inversion line separates these two types of bone.
2.3. Induced tooth movement
Induced tooth movement is a biological response to the application of force through mechanical systems to the tooth or group of teeth.
2.3.1. Immediate mechanical effects
These immediate effects correspond to the hydropneumatic capacities of the desmodont and to the elastic deformations of the alveolar bone and the tooth. Thus, as soon as the force is applied, an immediate displacement can be observed. There is then compression of the desmodont on one face, called the pressure face.
On the other side, called tension, the desmodont is stretched. These two phenomena occur concomitantly. If the force stops, there follows a more or less rapid return to normal.
2.3.2. Short-term biological effects
Face under pressure
Tooth movement has two phases.
First phase: phase of shock. Due to vascular crushing, a tissue zone of variable extension. The collagen bundles are compressed. The ground substance and the cells located between these bundles are driven out.
After the immediate displacement linked to desmodontal compression, the movement will stop and can only resume after the elimination of this hyaline zone and colonization by new cells.
Second phase: bone remodeling phase. The destruction of the hyaline zone is carried out by cells from the lateral parts of the desmodont that have not been altered.
Face in tension
A desmodontal widening is observed quantitatively equal to the narrowing on the opposite side.
If the force is low, immediate osteoblastic apposition is observed.
If the force is high, an osteoclastic hyperreaction occurs initially followed by osteoblastic apposition.
Osteoblasts synthesize osteoid tissue that mineralizes and allows bone apposition. The desmodontal fiber bundles will be included in the newly formed bone.
The Periodontics-Orthodontics relationship
2.3.3. Long-term biological effects
After this initial period, a phase of cellular adaptation appears during which the rate of bone remodeling is increased.
2.3.4. Concept of optimal force
To maintain tooth movement, osteoclasis must be maintained, i.e., a sufficient level of force to remain above the cellular threshold and fully utilize the reserve of specialized cells already produced. Intermittent forces remain effective if the periods of interruption are less than the latency time for cellular dedifferentiation.
2.3.4. How to produce this optimal force?
To have a physiological tooth movement, the mechanical system must deliver very light forces while maintaining sufficient intensity so that the movement is not interrupted. This is done by using small diameter springs and wires, leveling loops for a low load/flexion ratio. And get closer to the center of resistance of the tooth.
2.3.5. Direct effects of induced tooth movement on the periodontium
Version movement
Uncontrolled version. This movement is characterized by a displacement of the crown in one direction and the apex in the opposite direction, it is obtained by the application of a force on a tooth at the coronal level; the version can be mesiodistal or vestibulolingual. This simple force at a distance from the center of resistance creates a moment conducive to the displacements in the opposite direction of the crown and the apex.
Controlled straightening. This movement is a version characterized by a controlled displacement of the apex and the free edge.
The therapeutic version on reduced periodontium must be conducted with caution. Indeed, in the presence of a decrease in alveolar height which shifts the center of resistance in the apical direction, we observe, for a given force, a much greater moment.
Egression movement
This movement moves the tooth in the direction of its eruption, along the long axis of the tooth. The potential for extrusion of a tooth can go as far as orthodontic avulsion.
As the epithelial attachment moves with the tooth in the occlusal direction, there is an increase in the height of attached gingiva, since the mucogingival junction remains constant, and a decrease in the thickness of the alveolar septa.
Slow egression of a tooth, in the presence of a healthy periodontium, is the method of choice recommended in the event of a vertical bone defect. By involving the bone and soft tissues, it corrects the pockets by filling the bone defects and causing the attachment system to migrate gingivally. In return, occlusal grinding of the egressed tooth is often necessary.
In fact, therapeutic egression allows the tooth to be “pulled out” of the lesion by dragging the bottom of the lesion towards the crestal level corresponding to the neighboring teeth. The lesion is thus “removed”, but the support of the tooth is reduced.
Orthodontic egression is also suitable for the treatment of mesial angular lesions of protruding molars and for that of certain infrabony lesions linked to periodontitis.
Orthodontic egression can thus help with periodontics in different cases:
• cases of included teeth, infraclusion or even presenting a loss of subgingival dental substance, which could harm periodontal integrity: caries, fractures, erosions, endodontic perforations;
• treatment of infrabony periodontal defects;
• improvement of aesthetic defects related to the periodontium:
– defects in harmony and gingival contour of the anterior teeth;
-prevention of unsightly collapse after extraction;
-creation of taste buds.
The Periodontics-Orthodontics relationship
Ingression movement
The intrusion movement is the movement of the tooth in the opposite direction of eruption, along the major axis. It is a non-physiological movement, therefore difficult to achieve, which requires a multi-bracket appliance and significant anchoring. This is the movement that requires the lowest forces.
The changes obtained by this movement obey the same laws as those obtained by egression. Thus, the epithelial attachment follows the intruding tooth, the mucogingival line remains constant, therefore the height of attached gingiva decreases.
Movement of gression or translation
This movement is characterized by the displacement of the apex and the crown in the same direction and by the same distance, i.e. a movement of the tooth parallel to its major axis.
It is achieved by applying a force to a tooth, or group of teeth, whose line of action passes through the center of resistance of the tooth, or group of teeth. It is very difficult to realize orthodontic systems producing such forces.
It allows:
Closure of avulsion spaces. Mesiodistal orthodontic displacement will restore arch continuity and ensure parallelism of the roots.
Arrangement of alveolar ridges by lateral gression in cases of edentulism and atrophied ridges following old avulsions.
Rotational movement
This movement is characterized by a displacement of the tooth on itself around an axis which passes either through its major axis (this is axial rotation), or through an axis which is parallel to it (this is marginal rotation). The rotation is caused by a torque: double gression
vestibulolingual.
This is a seemingly easy move to achieve, but it is, in reality, very tricky and prone to repeat performance. Three elements seem essential to the mechanics:
• the shape of the root in section;
• the number of roots of the tooth;
• the location of the axis of rotation around which the tooth moves.
2.4. Histophysiological particularities of the adult periodontium
The movement is slow: the cortices are dense, the cellular supply is less, the speed of apposition and resorption reduced. The latency time (response time of the tissues to the forces exerted) is extended and can last several weeks.
Indirect resorptions are very important, which results in significant mobility.
Hyalinization is long: cellular and fibrillar turnover is slow, resulting in delayed movement and significant risks of bone destruction. A mechanical system must be adopted to avoid repeated hyalinizations.
Healing is slow: stabilization will have to be long-term, or even permanent in certain cases.
The Periodontics-Orthodontics relationship
3. The orthodontics-periodontics interrelationship
Orthodontics is used as a complementary therapy in periodontal treatment, it allows to create or recreate more favorable conditions for the removal of dental plaque, and to restore occlusion, aesthetics. According to Glickmann, the only contraindication to orthodontic treatment in patients with periodontal disease is the persistence of gingival inflammation. Age is not a contraindication, although it is generally established that bone remodeling processes occur more slowly in older patients.
3.1. General conditions
Orthodontic tooth movement must meet the following conditions:
• anatomical conditions: the periodontium must be complete and healthy;
• non-inflammatory conditions: scaling, resurfacing, pocket surgery;
• mechanical conditions: use of light and continuous forces.
3.2. Contribution of periodontics to orthodontics
Periodontics facilitates orthodontic treatment by preparing the tooth’s environment and the terrain on which it will move as well as stopping the progression of periodontal disease and preventing its recurrence.
- Patients with healthy periodontium :
- Before orthodontic treatment :
- Hygiene education and motivation building.
- The oral examination will inform us about the possible risks of the treatment envisaged.
- The need for surgical intervention if the orthodontic movement risks aggravating the periodontal pathology (insufficient attached gum).
- During or at the end of orthodontic treatment :
- Correction of gingival defects in extraction sites.
- Fibrotomies: Surgical section of the fibers surrounding the tooth that has undergone orthodontic rotation reduces the risk of relapse.
- Creation of a surgical flap for dental disinclusion.
- Occlusal adjustment: performing selective grinding at the end of orthodontic treatment will perfect the occlusal contacts obtained.
- Corticotomy.
- Creation of an implant anchor.
- Frenuectomy.
- Patients with weakened periodontium:
The suppression of inflammatory phenomena should always precede the initiation of orthodontic treatment.
- Patients with gingivitis : establishing rigorous hygiene combined with scaling will help to achieve healthy gum tissue.
- Patients with Periodontitis : It is imperative to clean and eliminate periodontal pockets before performing orthodontic treatment.
The Periodontics-Orthodontics relationship
3.3. Contribution of orthodontics to periodontics
3.3.1. Choosing the timing of orthodontic treatment :
In the presence of periodontal pockets, the rules governing alveolar remodeling during induced tooth movement are profoundly disrupted by the presence of inflammatory tissues. First of all, the inflammation must be suppressed (initial therapy).
Treatment of gingival recession before orthodontic treatment if the tooth will undergo vestibular displacement and after orthodontic treatment if the tooth will be egressed.
Orthodontic treatment should only begin after all signs of inflammation have been eliminated by initial periodontal therapy and surgery if necessary.
3.3.2. The role of orthodontic treatment
Orthodontic treatment can help periodontology in two ways:
- Direct action on the superficial and deep periodontium :
- Displacement of the epithelial attachment and bone with the tooth.
- Orthodontics and bone regeneration: the orthodontic egression movement allows the regeneration of bone volume and optimizes a bone regeneration technique.
- Indirect or preventive action: preventing the worsening of periodontal disease and its establishment.
- Restoring dental alignment:
- Hygiene.
- Restoring satisfactory dental alignment allows for improved hygiene conditions (improved self-cleaning).
- Repositioning the tooth in the bone: the tooth must be surrounded by sufficient bone thickness so that it can be moved away from the cortices as much as possible. The gression movements and the displacement of the roots make it possible to provide a satisfactory bone foundation.
- Repositioning of the alveolar-dental complex: for stable results, the tooth and the surrounding alveolar bone should be located in the balance zone between the jugal, labial and lingual muscles.
This repositioning will avoid excessive muscular pressure and possible gum recession.
- The elimination of root proximities: root proximities play a role in the etiology of periodontopathies, they present difficulties for the periodontist in the treatment of lesions associated with such malpositions, justifying their elimination.
- Restoration of balanced occlusal function
- Restoration of balanced neuromuscular function: correction of vestibuloversion in class II division 1 malocclusion, for example, allows the teeth and their alveolar bone to be placed in the balance zone.
Orthodontics also allows the rehabilitation of oral functions, namely swallowing and oral breathing (responsible for gingival inflammation).
- Improvement of prosthetic restorations:
Orthodontics plays an important role in facilitating less iatrogenic prosthetic construction. Distal movement of a tooth in an edentulous state can allow the construction of a fixed prosthesis that would otherwise be impossible.
3.3.3. Iatrogenic effects of orthodontic treatment:
- Anatomical:
- Root resorption and bending, Hypercementosis .
- Lesions: coronal, gingival, pulpal.
- Alveolar bone necrosis.
- Desmodontal degeneration.
- Technical: (therapeutic)
- Periodontal aggression by orthodontic materials such as molar braces.
- Disruption of the anchorage resulting in dental mobility.
- Increase in the moment of force.
The Periodontics-Orthodontics relationship
4. Maintenance of ortho-periodontal results
Maintaining the results, a decisive step in the ortho-periodontal care of adult patients, is ensured during two phases: the creation of a retention
orthoperiodontal and periodontal maintenance. If the first can be considered as a step whose realization is punctual, the second will see the succession, at regular intervals, of steps ensuring the maintenance of a flora compatible with periodontal health.
4.1. Contentions
Retention is an integral part of orthodontic therapy, it can be temporary or permanent. The sustainability of orthoperiodontal results requires maintaining teeth with weakened periodontal support after restoring functional occlusion.
Its objectives are as follows:
• bond the teeth together to prevent recurrence of migration and maintain the orthodontic result obtained;
• respect interdental spaces and embrasures. The retainer must not hinder plaque control;
• ensure functional and masticatory comfort for the patient.
4.1.1. Restraint devices
- Direct method restraint techniques
Direct method retention has the advantage of being performed in one session. It is the solution to minor stabilization problems.
This method combines support splints using a glued metal grid (the Ellman grid is the most common), fiber composite (polyethylene fibers), Kevlar fiber or preformed rigid metal wires.
- Indirect method restraint techniques
They often require enamel preparation. Their use is justified by the greater precision of the devices.
Bonded cast splint. It is a metal structure that encompasses the lingual and proximal faces of the supporting teeth and can replace one or more teeth.
Fiber composite splint. The indirect production of this splint allows for better impregnation of the fiber with the composite , which increases the strength of the assembly.
Retention bridge. When the decay of the teeth to be contained is very significant, the retention must be part of a global prosthetic rehabilitation. The creation of a retention bridge has the advantage of replacing the missing teeth and containing the teeth with weakened support.
4.2. Periodontal maintenance
Periodontal maintenance consists of the control of bacterial dental plaque by the patient and the implementation of periodontal care by the practitioner. It is now widely accepted that the control of supragingival plaque by the patient, associated with the elimination of subgingival plaque and tartar by the practitioner are the two conditions for the stability of periodontal results. During the maintenance phase, the practitioner will have to avoid relapses or slow them down; he will therefore have to provide a diagnostic part aimed at searching for possible active sites and a therapeutic part by maintaining at the subgingival level a flora compatible with periodontal health.
The Periodontics-Orthodontics relationship
5. Conclusion
Orthodontics therefore plays an important role in the treatment of periodontal diseases.
This multidisciplinary approach requires:
• perfect cooperation and high motivation of the patient;
• close collaboration in the conduct of the treatment plan between orthodontist and periodontist, if only to obtain and maintain a healthy periodontium, free of inflammation, an essential prerequisite for orthodontic treatment in adult patients, until the end of the treatment;
• an adaptation of orthodontic treatment according to periodontal changes linked to the disease and age: use of light forces, plaque control and often permanent retention.