ROEN0210

08 I I special _ endo-implant algorithm have historically been key modalities in the attain- ment of this foundational goal. Friedman noted that “the patient weighing one ‘success’ rate against the other may erroneously assume their definitions to be comparable and select the treatment alternative that appearstobeofferingthebetterchanceof‘success.’”13 The conundrum with which researchers and clinicians alike wrestle increasingly includes the non-science of emotionaswell. This publication will address non-surgical and/or surgicalresolutionoffailingprimaryendodontictreat- mentoutcomesandthehistoricalandongoingefforts of the dental industry to engineer the biomimetic replacementofnaturalteethsuccessfullyandreplicate the structural predicates that comprise the substitu- tionalgorithmofbone,softtissueandtooth.Thereare many levels to the accrual of ‘best evidence dentistry’. Thepurposeofthispaperistoensurethatallvariables in the treatment planning equation of foundational dentistryareunderstoodandgivenequalweightinthe decision-makingprocessforcomprehensivecare. Wheneverpossible,thetreatmentchoiceshouldbe anattempttosalvageatoothusingamultidisciplinary team approach, putting aside preconceived notions andbiases.Financesshouldnotdictatetheadviceprof- fered.Furthermore,itisadvisabletoforegobeingclin- ically ‘conservative’. Treatment should not be initiated in the absence of a critical evaluation of the potential forallcontributingfactorstoequatetoapositiveout- come. When needed, care must be taken to carry out every diagnostic procedure available, even those of amoreinvasivenature(Fig.1).Beforearrivingatadefi- nitive diagnosis and treatment plan, the clinician should obtain consent from the patient to remove any restoration in order to analyse the residual tooth structure and assess the potential to carry out reliably predictabletreatment.Thepatientmustunderstandin detail,thefeasibilityofandmarginforsuccessofeach treatmentoptionpresented.14 There are few studies in the endodontic literature analysingthereasonsforextractionofendodontically treated teeth. Root-filled teeth are invariably prone to extraction due to non-restorable carious destruction and fracture of unprotected cusps. Tamse etal. found that mandibular first molars were extracted with greater frequency than maxillary first molars; the most significant causal difference was the incidence of vertical root fracture (VRF—1.8% maxillary molar, 9.8% mandibular molar).15 Teeth not crowned after obturation are lost with six times the frequency of thoserestoredwithfullcoveragerestorations.16 Procedural failure, iatrogenic perforation or strip- ping, idiopathic resorption, trauma and periodontal disease all contribute to a lesser degree. The major biological factor that influences endodontic treat- mentoutcomefailurewiththepossibilityofextraction appears to be the extent of microbiological insult to thepulpandperi-apicaltissue,asreflectedbytheperi- apical diagnosis and the magnitude of peri-apical pathosis(TableIandFigs.2a–c).17 Fig. 3_Two different retreated teeth; two different potential treatment out- comes. The root-canal system of both teeth has been re-engineered in its anatomic entirety; however, the treatment outcome after restoration for both is unlikely to be the same. Regenerative technologies incorpo- rating mesenchymal stem cells derived from dental tissues may one day obviate the concern. Fig. 4_Less porous, less hydrated and highly mineralised outer dentine (a); pulp canal space (b); more porous, more hydrated and less mineralised inner dentine (c); water in the dentinal tubules and pulp space is held in a confined environ- ment under hydrostatic pressure (d). Fig. 5_Primary causes of fracture include excessive structure loss, loss of free unbound water from the root-canal lumen and dentinal tubules, age-induced changes in the dentine and restorations and restorative procedures. Secondary causes of fracture include the effects of endodontic irrigants and medicaments on dentine, the effects of bacterial interaction with dentine substrate and bio-corrosion of metallic post-cores. roots2_2010 Fig. 3 Fig. 4 Fig. 5