Y-TZP CERAMICS ( yttria stabilised tetragonal zirconia polcrystals )

Y-TZP ( yttria stabilized tetragonal zirconia polycrystals )  is  composed of many very small particles (tetragonal crystallites metastable at room temperature <0.5 micrometer,) without any glassy phase at the crystallite border and. In the stress field of propagating cracks the matrix pressure on the tetragonal particles of Y-TZP is reduced by tensile stresses and a tetragonal to monoclinic  phase transformation occurs by a diffusionless shear process at near sonic velocities, similar to those of the martensite formation in quenched steel. The resulting volume expansion (3-5%) and the shear stresses formed in the particles affect martensitic transformation and pressure tensions on the matrix, opposing the opening of the crack and increasing the energy necessary for further crack growth.

Because of its high strength and resistance to crack propagation this can be used as a material of choice for posterior F.P.D s  

REF : Dental Materials (2004) 20, 655-662

VEHICLES FOR CALCIUM HYDROXIDE

Vehicles for calcium hydroxide may be classified as Aqueous, Viscous, Oily

Aqueous -- water , saline, ringers solution, anesthetic solution.

Viscous – glycerin ,   propylene glycol.

Oily – silicone oil, olive oil , oleic oil , linoleic oil.

                                              REF:IEJ,32,1999

OBTURA ( THERMOPLASTICISED OBTURATION )

Recent advances in technology have led to development many gutta-percha obturating systems. One of the thermoplasticized gutta-percha injection system is Obtura II. This system may stand alone or be used along with standard obturation techniques. Many practitioners use the Obtura gun during classic warm vertical obturation to “BACKFILL” root canal systems after the “down- pack” of the master cone. The temperature range of the gutta percha is 165° to 200°C when injected into the canal space. The recommended technique for backfilling involves application of gutta percha in 4- to 5-mm increments, followed by uniform compaction with pluggers .

REF: JOE ,2009

MICROSEAL SYSTEM ( MC SPADDEN TECHNIQUE )

In 1979, McSpadden introduced a thermomechanical compaction technique. In this technique a rotating condenser creates frictional heat inside the root canal and plasticizes a cone of gutta-percha, which is forced laterally and apically to obturate the root canal space. The condenser, which has an appearance similar to an inverted Hedstrom file, but with the blades directed toward the blunt-tipped end is fixed in a latch type slow-speed contra angle, placed into the root canal as far apically as possible and rotated at the minimum recommended speed of 8000 rpm. Gentle apical pressure is applied to carry the condenser 1 mm short of the working length after the gutta-percha become plastic. At this length, the condenser is slowly removed while rotation is maintained.

                                             REF: JOE ,31, 4,  2005

TAURODONTISM ( endodontic management )

Taurodontism is a developmental disorder resulting in change in the shape of a tooth. Usually occurs in multirooted teeth. An enlarged body and pulp chamber, as well as apical displacement of the pulpal floor, are characteristic features. The term taurodontism was coined by Sir Arthur Keith to describe the “bull-like” condition in teeth , in which the tall root trunk encloses a high pulp chamber and short roots

Endodontic treatment  involves conventional cleaning and shaping and obturating the canal  using thermoplasticized compaction techniques like SYSTEM B AND OBTURA.

                                                            REF : JOE,2003

REVO-S ( only 3 instruments to clean and shape the root canal )

  Revo-S NiTi instrument system (Micro-Mega), which includes three shaping instruments; the shaping and cleaning instrument (SC) number 1 (SC1) is a #25/.06 taper rotary used to enlarge the coronal two thirds of the canal. SC2 is a #25/. 04 taper instrument used to the working length, and universal shaper (SU) is a #25/.06 taper also used to the working length.

Design

Asymmetrical cross section with three cutting edges.

Positive rake angle .

No radial land.

                                                                       REF: JOE ,37, 7,  2011

THERMAFIL (THERMOPLASTICISED OBTURATION )

One of the methods of obturation using warmed gutta-percha is the Thermafil endodontic obturator device (Dentsply Maillefer, Switzerland). Thermafil obturators are made of plastic cores coated with alpha-phase gutta-percha . This form of gutta-percha is considered to have better flow characteristics when molten than beta-phase gutta-percha, from which conventional gutta-percha cones are made. After heating in a thermafill heater, the gutta-percha surrounding the Thermafil carrier becomes plasticized, and the obturator is inserted into the prepared canal. The carrier remains in the root canal as a part of the obturation.

                                                   REF:JOE 28,2002