DTUK13

May 17-23, 2010United Kingdom Edition If tertiary dentin were perceived of as “irritational dentin” or dys- trophic calcification considered “decay”, the chamber outline could be used to blueprint an in- lay configuration for the access design that literally replicates the “virgin” tooth (Fig 7). Removal of the existing res- toration in its entirety and/or preliminary preparation of the coronal tooth structure for the subsequent full coverage restora- tion will identify decay, fractures, unsupported tooth structure and expose the anatomy of the under- lying root trunk periphery which assists in discovery of the spatial orientation and morphology of the roots. The pulp chamber ceil- ing and pulp stones can be peeled away with a football diamond bur to grossly identify the primary orifices. Micro-etching (Danville Materials, San Ramon CA) the floor of the chamber, perhaps the most underused of all access tools, is invaluable in the expo- sure of fusion lines and grooves in order to identify accessory ori- fices. Troughing with ultrasonic tips of any design is used solely to trace fusion lines, not effect gross removal. The use of ultrasonics to “jackhammer” pulp stones is sim- ply too risky as one approaches the floor of the chamber, particu- larly if there are no water ports on the tips. Orifice lengthening and widening enables straight line glide path to the apical third. The strategic objective is not to impede the file, stainless steel or nickel-titanium rotary along the axial walls with minimal dentin removal (Fig 8a, 8b). It is equally as important to produce a high quality coronal restoration at the time of seal- ing the root canal system (21, 22) . Despite research supporting the effectiveness of coronal barriers and the need for their immediate placement as a component of the completion phase of root canal treatment, a universally accepted protocol does not exist. Schwarts and Fransman have described a clinical strategy for coronal sealing of the endodontic access preparation that lists the follow- ing considerations in the proto- col; use bonded materials (4th generation (three step) resin adhesive systems are preferred because they provide a better bond than the adhesives that re- quire fewer steps), the “etch and rinse” adhesives are preferred to “self etching” adhesive systems if a eugenol containing sealer or temporary material is used, “self etching” adhesives should not be used with self-cure or dual-cure restorative composites, when restoring access cavities, the best esthetics and highest initial strength are obtained with an incremental fill technique with composite resin, a more effi- cient technique which provides acceptable esthetics is to bulk fill with a glass ionomer mate- rial to within two mm to three mm of the cavo-surface mar- gin, followed by two increments of light-cure composite and if retention of a crown or bridge abutment is a concern after root canal treatment, post placement increases retention to greater than the original state (23) (Fig 9). Irrigation The complex anatomy of the root canal space presents a daunting challenge to the clinician who must debride and disinfect the corridors of sepsis with abso- luteness to achieve a successful treatment outcome (see Fig 10). In addition, the absence of a cell- mediated defense (phagocytosis, a functional host response) in necrotic teeth means the micro- organisms residual in tubuli, cul de sacs and arborisations are mainly affected by the redox potential (reduction potential reflects the oxidation-reduction state of the environment – aero- bic microflora can only be active at a positive Eh, whereas strict anaerobes can only be active at negative Eh values) and avail- ability of nutrients in the various parts of the root canal (24) . While our knowledge of persistent bacteria, disinfecting agents and the chemical milieu of the necrotic root canal has greatly increased, there is no doubt that more innovative basic and clini- cal research is needed to opti- mise the use of existing methods and materials and develop new ones in order to prevent and/or treat apical periodontitis. Varying degrees of sterility of the root canal space are achieved by mechanistic removal, the chemical reactivity and fluid dynamics of irrigants and their introduction to the canal space; Midi Premium • piezo scaler and curing light included • 2 handpiece outlets with fibre optics • pneumatic unit based on standard DCI parts • comfortable chair with seamless, artificial leather upholstery • 4 basic movements and 4 programmable settings • porcelain spittoon bowl • only 7% VAT 27 Woodcock Close Birmingham, B31 5EH mobile voicemail fax e-mail office@profi-dental.co.uk RRP £2,210 HIGH SPEED HIGH SPEED TURBINES non-optic £649 RRP £1,170 3x TKD THALIA® push button, single spray, non-return valve, direct connection to Midwest 4-hole HIGH SPEED TURBINES WITH LED ILLUMINATION Cominox autoclaves TKD Handpieces WWW.PROFI-DENTAL.CO.UK RRP £4,550 6l autoclave with fast 10-min B-type cycle, perfect for implantology, printer SterilClave 6 B £3,820 RRP £3,150 great value 18l autoclave for everyday sterilisation, integrated printer SterilClave 18 S £2,640 RRP £5,600 large 24l, B-type autoclave for busy practices, integrated printer SterilClave 24 B £4,690 £1,199 3x TKD THERA®L 40SE illumination 25,000 lux, titanium finish, ceramic bearings, triple spray, non-return valve, compatible with Kavo® Multiflex®, 2 year guarantee 1x TKD GYROFLEX® LED RRP £2,210 Simple and reliable unit with generous specification. £7,990 SPECIAL OFFER - SPRING 2010 DENTAL CHAIRS AUTOCLAVES SUCTION PUMPS X-RAY UNITS HANDPIECES WASHER DISINFECTORS COMPRESSORS SURGERYPLANNING 07981075157 08450044388 08719442257 page 21DTà Fig 8a – Dystrophic calcification confounds even the most experienced clinician. The key to identification of the orifices is to regress the inner space using the continuum, cusp tip, pulp horn, canal orifice. In lieu of an ultrasonic tip which tends to chop the stone and scatter debris, gross removal is best done with a diamond bur in a high speed handpiece. The fine removal of residue can be done with a multi-fluted carbide bur to trace the fusion lines. Fig 8b – Keeping the chamber wet with alcohol improves optics and highlights colour differential. The most important tool for orifice identification in addition to dyes is a micro-etcher. The satin finish produced highlights the disparity between the natural tooth structure of the floor and the secondary and tertiary dentin of the calcified orifice. Fig 9 – Micro-etching ensures the removal of oils and debris as well as eliminating the residue in fusion lines and fissures. Routine dentin bonding is then performed. The com- posite chosen in this instance is Permaflo® Purple (UPI, South Jordan, UT) which enables differentiation of restoration and tooth structure should re-entry be necessary.