Our teeth are arranged in form of an arch commonly resembling U or V shape. Throughout life, our teeth move forward towards the midline which is called as physiological drift. This is a very common phenomenon.
Mesial drift can be defined as the tendency of teeth to move in a mesial direction within the arch with an aim to maintain interproximal contact between teeth.
While chewing, the teeth rub against each other on the sides at the contact points, resulting in interproximal wear off and that space which is created is filled by mesial/ forward movement of the teeth to re-establish contact.
Mesial drift can be because of physiological, pathological or induced reasons (for e.g.: in case of orthodontic tooth movement to obtained desired results during treatment).
Classification of Mesial Drift by Angle:
Mesial drifting is multifactorial and causes collapse of dental arch. And this collapse indicates one of the following:-
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Mesial Drift of buccal teeth in relation to their alveolar process
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Mesial Drift in relation to maxillary and mandibular denture bases.
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Mesial Drift in relation to Cranium. Such cases are usually called as bimaxillary protrusion.
Here in this article we will be discussing mainly the mesial drift of buccal teeth in relation to their alveolar process.
Which teeth move in mesial direction and in distal direction in the arch?
Kronfeld’s theory states that there are neutral areas located in the following:
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Between the bicuspids in the maxilla
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Just mesial to the 1st molars in the mandible.
Based on that theory, the following conclusion can be drawn:
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Teeth anterior to the neutral area have a tendency to drift distally
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Teeth posterior to the neutral area have a tendency to drift mesially.
Rationale for mesial drifting:-
Following factors are considered to be contributing towards teeth drifting mesially-
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Heredity
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Premature loss of primary teeth and inadequate space maintenance.
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Contraction of trans-septal fibers-
Transseptal fibres draw neighbouring teeth together and maintain them in contact. They are also capable of adaptation. Contraction of these fibers plays a major role in the interproximal teeth contact.
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Adaptability of the bone tissue-
Bone is a very adaptable tissue because of its ability of resorption and apposition. The pressure side on the periodontal ligament causes resorption and pull on the fibers causes apposition. Therefore as the contact wears off the tooth tend to move in mesial direction to maintain contact.
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Anterior component of the occlusal force-
Most of the teeth have mesial inclination. When the teeth are clenched, an anteriorly directed force is created from the summation of the intercuspal planes causing mesial migration of teeth. If the opposing teeth are missing, there is absence of biting force thus the mesial migration is slowed down. The forces can also be enhanced or reversed by selectively grinding the cusps resulting in the slowing of the mesial migration.
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Pressure from the soft tissues:
Pressure generated by the musculature of the check and tongue, does influence the tooth position even if it does not cause the tooth movement. Though not significant role, it does play a minor role in mesial drifting.
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The rate of physiological drift of teeth depends upon the health, dietary factors, and age. It usually varies from 0.05 to 0.7mm per year.
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Extractions of teeth due to dental decay.
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Extractions of teeth for strategic mesial drifting for treatment needs.
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Eruption of 3rd molars can put a forward push pressure on teeth leading to mesial migration.
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Presence of pathologies like cysts or tumours can push the teeth in mesial direction causing pathological mesial movement of teeth.
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Dental trauma, facial fractures and avulsions.
How to stop mesial drift from causing crowding in children?
Children usually lose their deciduous/milk teeth starting approximately age 6 years, this loss of primary teeth creates a space for their permanent successor to erupt, but sometimes when a tooth is lost early, the tooth present behind the lost tooth (posteriorly) slowly starts tipping into and obliterating the space created that causes crowding in children and alteration of bite plane in adults or in permanent teeth.
Preventive orthodontics and paediatric dentistry are branches of dentistry which deals with maintenance of space created due to premature loss of primary teeth and treatment of the space loss to make sure the permanent successor erupts into its position.
It is important that parents bring it to the notice of dentist about the early loss of teeth and other teeth filling up the space, as soon as they notice it. Preventive measures can be taken to maintain space. Remember prevention is better than cure.
In the mixed dentition stage, space maintainers can be used to preserve the space for the successor to erupt. Appliances can be removable or fixed, can be chosen based on the needs of the patient.
Space maintainers (in case where primary teeth have been lost and adequate space is present) are:
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Band and Loop ( Crown and loop)
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Distal Shoe ( before eruption of permanent molar)
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Lower Lingual arch
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Nance palatal appliance
Space regainers (localized space loss) indicated when space loss is less than 3mm:-
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Removable appliance with finger springs to tip teeth distally
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Activated lingual arch ( for mandibular arch)
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Lip bumpers (for mandibular arch)
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Some fixed appliances to regain space followed by space maintainers to keep the space until the successor is erupted.
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In some cases head gears can also be used( for maxillary arch )
All this must be followed by the use of space maintainers until the successor takes its dedicated space.
Mesial drifting in permanent dentition or in adult teeth:-
In permanent dentition, in younger as well as older patients there are good chances of mesial drifting of posterior teeth owing to the presence of space due to many physiological, pathological and induced/ generated factors. With advancing age, the mandible continues to grow and to accommodate that growth, teeth also drifts slightly mesially. There are many other causes for teeth shifting in space mesial to its location.
Adults are self-motivated, so the treatment and follow ups become comparatively easy. For a dentist, Judgement and deductions based on analysis of the forces of occlusion and also on facial type are the reliable means to diagnose.
If a successful end result is to be obtained, it is essential that the axial inclination of the lower anteriors must be kept normal. Appliance adjustment must focus on distal movement of posterior teeth to gain space necessary for blocked out teeth. In permanent dentition, once the space is gained and a balanced occlusion is attained, the space can be filled up by implants followed by removable or fixed prosthesis such as crowns and bridges as per the need.
Note:-
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Maxillary molars tend to migrate mesially more readily than mandibular molars, because bone resorption and apposition in maxilla takes place at a faster rate than in mandible owing to rich blood supply in maxilla. There are distinct differences in the mode of mesial movement between maxillary and mandibular molars, differences caused by variations in crown shape, number of roots and occlusal relationships.
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Mesial drifting of 1st permanent molars involves 3 separate kinds of tooth movements- mesial crown tipping, rotation and translation.
Mesial drifting in Osteoporosis patients and Diabetic patients:-
It is very important to bring it to the notice of the dentist that the adult patient is suffering from osteoporosis, hypertension and diabetes.
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It is contraindicated to do orthodontic tooth movement in osteoporosis if it is untreated.
In osteoporosis patients undergoing bisphosphonate therapy, it is advisable to take the physicians consultation before trying to regain the lost space due to mesial drifting.
Usually, the mobility of teeth is reduced if patient is on bisphosphonate therapy making the orthodontic treatment more difficult and therefore bisphosphonates are called as bone hardening drugs. Plus the chances of relapse are very high. So passive retainers that do not exert pressure on bone should be used for extended period of time. Also healing of bone is impaired these cases. One of the very serious side effects of bisphosphonate therapy is osteoradionecrosis of the jaw. All this must be taken into consideration before planning an active orthodontic treatment for regaining space in case of obliterated space due to mesially drifted teeth.
In cases of juvenile osteoporosis, strategic extraction of teeth should be avoided for orthodontic purposes.
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Diabetes is a serious disease which must be given a high priority while planning any dental treatment. Whether it is Type 1 or Type 2 Diabetes, it is essential to get laboratory reports for blood glucose levels especially HbA1C (glycated haemoglobin) If the person has Diabetes, the healing capacity is impaired which means the bone remodelling is slowed down. Also the patient is prone for more oral infections. In these cases along with blood glucose it is also necessary to ask for platelet count. Before start of any treatment the blood glucose level must be under control and should remain in control throughout the treatment period.
Note:
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It is advisable not to consume excess alcohol during the orthodontic treatment because excess alcohol consumption impairs the osteoblastic activity of bone cells and increase the osteoclastic activity resulting in more bone loss and decreased bone remodelling. Although this is still under research, remember prevention is better than cure.
Consequences of Mesial Drifting of teeth:
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Most obvious consequences are obliterating the space and blocking out the permanent dentition from erupting in its dedicated position in mixed dentition.
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Other consequences such as
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improper alveolar ridge heights,
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impacted successor teeth
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changes in occlusion
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Change in bite plane of an individual and decreased chewing ability.
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development of oral Para-functional habits,
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pain in temporomandibular joint,
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temporomandibular joint dysfunctions
Can be clearly seen if mesial drift is left untreated.
Due to disturbed bite plane, the patient often feels decreased efficacy and muscle stress in jaws while eating. This alters the temporo-mandibular joint (TMJ) function of the patient. Most noticeable symptom would be pain and clicking sound during movement in the joint. Minor changes in the occlusion often goes unnoticed by the patient as the joint tries to adapt to the changes, but in the long run the joint apparatus stops functioning normally and can lead to TMJ dysfunction (TMJD). If not taken care in early stages, this condition worsens and eventually might require surgical intervention to make the joint functional again.
Damage to the teeth and surrounding structures due to mesial drift:
In an attempt to tip mesially, the tooth exerts pressure on the bone towards the missing tooth and also causes the pull on the trans-septal fibers on the distal side, if there is an adjacent distal tooth present, which causes the distal tooth also to follow the mesially tipped tooth.
In some cases it is observed that it accelerates the process of bone resorption in that localised area as it causes the damage to the minute periodontal and osseous vasculature.
In some cases it is observed that, there is increased tooth mobility due to the damaging effects on supporting periodontal apparatus.
Conclusion:
Physiological mesial drift is a continuous natural process that occurs during the course of life of the teeth. Mesial drift (as a result of all the reasons discussed in the article) as such needs attention and must be addressed in timely manner to avoid further complications. The regular dental check-up should neither be missed nor postponed. The developing dentition must be keenly noted by the dentist and if required the necessary intervention should be performed timely to avoid the mesial drifting in young permanent teeth. Space maintenance should be taken care of and space should be filled to avoid relapses. It is necessary to use retainers. The earlier we diagnose the case the better it is, not just easier to treat but also the treatment cost is much affordable than what will be required in later stages. Above all, it is important to educate patients so that they continue to have patience and co-operates at every level to achieve the desired results.
Dr. Triveni Padale
B.D.S, India
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