Dental Tribune India Issue

Clinical Dentaltribune|July-September, 20108 5. Specialized Rotary Instruments Designed for Retreatment Atpresent,3manufacturershave introduced the specially desig- ned instruments along with their set of NiTi rotary instruments as retreatment instruments. A. ProTaper Universal Retreat- ment Kit (Dentsply Maillefer) The ProTaper Universal retreat- ment kit consists of three instru- ments which are identified as: D1 File: is a 30/0.09 NiTi file (marked with one white ring) of 16mminlengthusedforremoval of filling material from the coro- nal third of the root canal. D2 File: is a 25/0.08 NiTi file (marked with two white rings) of 18mminlengthusedforremoval of filling material from the mid- dle third of the root canal. D3 File: is a 20/0.07 NiTi file (marked with three white rings) of 22 mm in length used for removal of filling material from the apical third of the root canal. All instruments have a non- workingroundtiptofollowcanal path for effective removal of the obturating material without modifying the original curvature or shape of the root canal. B. R-Endo (Micro-Mega) R-Endo instruments are made up from a round blank, and their cross-section is characterized by three equally spaced cutting edges. The instruments neither have radial lands nor active tip. These instruments are recom- mended to be used at a speed of 300-400 rpm along with gutta- percha solvent. The R-Endo re- treatment kit, consists of a series of six files named as Rm, Re, R1, R2, R3 and Rs. Rm File: isastainlesssteel25/.04 hand instrument with a 17 mm length and a 12 mm working tip. The file is used in a quarter- turn motion and to dig or break the hard layer of filling material. This instrument allows the cen- tring and alignment of the next instrument. Re File: is a 25/.12 NiTi file with a 15 mm working length and 10 mmcuttingtip.Itisusedforelim- inating the possible interference or dentine overhang, and flaring the access space in order to in- crease the solvent quantity. The shortlengthofthisinstrumental- lows removal of only 2-3 mm of filling material from the orifice level of the root canal. R1 File: is a 25/.08 NiTi file with a 15 mm working length and 8 mm cutting tip. This file is designed for removal of filling material from the coronal-third. R2 File: is a 25/.06 NiTi file with a 19 mm working length and 12 mm cutting tip. This file is designed for removal of filling material from the middle-third of the root canal. R3 File: is a 25/.04 NiTi file with a 23 mm working length and 16 mm cutting tip. This is to be used in the last for removal of filling material from the apical-third of the root canal. Rs File: is a 30/.04 NiTi file with a 15 mm working length & 10mm cutting tip. This instrument is designed to be used in cases that require further enlargement of apical diameter of the root canal. C. Mtwo Retreatment Kit (Sweden and Martina) The Mtwo instruments have an S-shaped cross-section, an incr- easing pitch length in the apical– coronal direction. The Mtwo retreatment kit consists of only two instruments with cutting tips, i.e., Mtwo R 15/.05 and Mtwo R 25/.05, designed to reach the apex. They also have the advantage of shaping the root canal in an under-prepared tooth, simultaneously. During the use of all retreat- ment files, the file penetration is carried out by exerting very slight apical pressure. The in- struments should be withdrawn frequently, to inspect & remove the debris from its flutes, before continuing. In case of resistance felt during rotation, hand files should be used to confirm canal permeability. These files remove gutta-percha effectively by ther- mosoftening the gutta-percha with frictional heat. They can be used in the com- bination with gutta-percha, solvents to soften and remove the obturation material. 6. Heat Transfer Devices A. Heat Carrier Tips The number of heat transfer devices like the System B, Endo- tec, EndoTwinn, E&Q Master, Touch’N Heat, DownPak, etc. is available for the warm vertical technique of obturation. The heat generated on the tip can be used for softening of the gutta- percha mass, thereby, aiding in retrieval of the mass. These devices are more effective in well prepared canals. Alternatively, the hand spre- aders can also be used in the similar manner, however, the amount of heat transferred to these instruments is not consis- tent and they retain the heat for a longer period of time as well. B. Ultrasonic Tips Ultrasonic tips available for ultra- sonic condensation of gutta-per- cha or specialized re-treatment tips can be used for gutta-percha removal. These tips work on the sameprincipleastheheatcarrier devices, by softening the gutta- percha and finer tips of these instrumentsmaybeused to work around the curvatures. 7. Soft Tissue Lasers The studies, conducted on effec- tiveness of the Nd: YAG laser for removal of gutta-percha, have shown that it is capable of soften- ing gutta-percha. The addition of solvents have not shown any improvement in their efficiency in terms of time required for removal of gutta-percha from the canal walls.7 The use of Nd: YAG laser at lower settings (100 mJ, 15 Hz, 1.5 W) produces fairly clean root canals, but an incom- pleteeliminationofgutta-percha from dentinal walls occurs. At increased power levels (100 mJ, 20 Hz, 2 W), the laser seems to be moreeffectiveonthecanalwalls, cleaning them better. Conclusion The major factors associated with the endodontic failure are the persistent microbial infec- tion in the root canal system and /or in the peri-radicular area. It is important to remove as much sealer and gutta-percha as possi- ble during retreatment, to un- cover remnants of necrotic tis- sue or bacteria that might set as the antigenic source. The new technologies, such as loupes and surgical micro- scopes, enable the clinician to have better visual access while treating difficult cases. Nonethe- less, complete removal of gutta- percha from the canal wall is still a difficult task. Also, the comple- xity of the root canal system further complicates the process of retreatment, requiring a dif- ferent approach to tackle the problem in each case. Every re- treatment case should be treated as a fresh case and should be deal with accordingly in order to provide a predictable degree of success for the endodontic therapy. DT Current concepts in gutta-percha removal for re-treatment Second and final part by Dr Roheet Khatavkar & Dr Vivek Hegde Fig. 3: ProTaper Universal retreatment files D1, D2 and D3 from DentsplyMaillefer. Fig. 5: Mtwo NITI retreatment files Fig.6b:200µmfiberactivatedinthecanal for gutta-percha removal (under 16X magnification). Dr Roheet Khatavkar is a post- graduate student in the depart- ment of conservative dentistry and endodontics at M A Rangoon- wala Dental College, Pune, India. Dr Roheet can be contacted at drkhatavkar @gmail.com. Dr Vivek Hegde is professor and head of the department of conser- vative dentistry and endodontics at M A Rangoonwala Dental College, Pune, India. He can be contacted at drvivekhegde@rediffmail.com. About the authors Fig.4:R-EndorotaryandInGeT(IntegratedGearTechnology)retreatmentfilesfromMicro-Mega. Fig. 6a: Nd:YAG laser from Fotona with 200 µm fiber has also been tried for gutta- percharemoval.