INTRODUCTION:
Intrusion of extruded maxillary second molar has always been a challenging situation in orthodontics. Extrusion of second molar/s is commonly seen when the opposing tooth is missing due to extraction or congenital absence. It leads to occlusal plane problems and occasionally buccal tilting of second molars. Sometimes it is also seenin cases of a complete ope bite, with occlusal contacts in second molar region only.
An attempt to level the extruded maxillary second molars by using fixed orthodontic appliance involving the second molars with a continuous arch wire leads to extrusion of teeth anterior to the second molars rather than its intrusion. It results in opening of mandibular plane angle, and downward and backward rotation of mandible. It is detrimental esp in cases of vertical growth pattern and skeletal class II cases.
Some clinicians tend to equilibrate the occlusal surface of extruded maxillary second molar to level it. It may be a method of choice in mild extrusion cases, but in other cases, the tooth may require intentional root canal treatment, reduction of crown and then placing jacket crown, thus jeopardising the long life of the tooth.
To solve this problem, we have successfully used a modified form of transpalatal arch (M-TPA) to apply isolated intrusive forces on the extruded maxillary second molar only. The anchorage is obtained by M-TPA and involving the other teeth in a continuous arch wire from first permanent molar of one side to other side.
FABRICATION OF M-TPA:
A double buccal tube having a headgear tube is used on the maxillary first molar bands and the bands are then taken in a pick-up impression, and a working cast is made in plaster of paris. M-TPA is made in 0.9 – 1.0 mm hard stainless steel round wire. Its distal ends are bent in the form of hooks adapted along the palatal curvature; approx 2 mm away from the palatal tissues, and extending around 6 – 8 mm from the free gingival margins. It is then soldered on thefirst molar bands taken in the pick-up impression, (FIGS.). Another hook of the same wire is made extending approx. 4 - 6 mm from free gingival margin avoiding the active vestibular depth on buccal side, which is adapted in relation to the extruded maxillary second molar on buccal side. It is inserted in the headgear tube from the distal opening and soldered there. It may be done for both the sides if required. This assembly is now cemented in place on the maxillary first molars with light cured glass ionomer cement.
These two hooks on M-TPA can now be used for engaging elastic or E-chain, crossing over the occlusal surface of extruded maxillary second molar, (FIGS.). The forces are now concentrated on extruded maxillary second molar only. The forces required can be achieved by adjusting the length of E-chain or size of the elastics. A lingual button or a Beggs’ bracket or other bracket can be bonded on the occlusal surface of extruded maxillary second molar to avoid slippage of the E-chain, which otherwise may lead to gingival trauma if it gets slipped in the proximal side of the extruded maxillary second molar. Elastics are to be changed everyday which require patient’s cooperation, so E-chain is a better option.
Adequate intrusion of extruded maxillary second molar can be achieved within 3 – 4 months. A palatally – directed force from the E-chain may also lead to correction of buccal inclination of the second molar. After intrusion ,the second molars can now be incorporated in the continuous arch wire with other teeth, by placing buccal tube in proper position. It will help in prevention of the relapse of the intrusion. However, a light intrusiove force must be continued on the corrected maxillary second molar with the help of E-chain as before to avoid relapse for at least 3 -4 months more.
CONCLUSION:
M-TPA is an inexpensive and effective appliance for intrusion of extruded maxillary second molars. It helps to apply isolated forces on the extruded maxillary second molar, without disturbing anchorage teeth and causing any ill – effects on the dentition.