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Ahmad / Zaripah / Adam / Aws H. Alidata should be used to determine the load that mustapplied during dynamic tests. Further more, whendynamic investigations are performed, specimens canbe first subjected to thermocycling to imitate aging ofmaterials, mocking the clinical functions over time. 12Static Mechanical Test (Fracture Resistance Test)The choice of appropriate restorations should beinfluenced by both physical properties and aesthetics.The aims of restoration are: to compensate the missingtooth structure, to reinforce the tooth and to provide aneffective isolation between the root canal system andthe oral environment 13, 14 . Coronal leakage may lead tobacterial contamination; it is well documented that, theprognosis of an endodontic treatment is significantlyincreased by accurate coronal restoration or seal 15,16 . Clinicians often experience the clinical fractureof endodontically treated teeth 17 . Most of thesefractures are the result of the loss of tooth structuredue to carious lesions and/or cavity preparation 18 .Furthermore the interfaces of restorative materialswith different module of elasticity represent the weakpoint of a restorative system which may be lead tothe failure in restoration 19, 20 . Many studies havebeen conducted to measure the mechanical fractureresistance of pulpless teeth 13, 21-29 . These studieshave been conducted to evaluate the mechanicalresistance to fracture in many teeth especially onmaxillary premolars 25, 26, 29 , as a high incidence offracture for this group of teeth has been reported 30 .Some of these studies focused on the materials andtechniques used to reinforce the tooth-restorationcomplex 31 . While other studies have been tried todetermine the best technique and combination ofmaterials to be used to reinforce the tooth restorationcomplex 13, 16, 32 . In all mechanical resistance to fracturetests of endodontically treated teeth share commonfeatures such as load form, load application area, loadfrequency, load jig characteristics, load speed, loadintensity, angle of load application, and simulation ofsupporting tissues 25-29, 33-37 .Load form (Static or Dynamic)The selection of load form depend the aim of thestudy and other convenient factors, like time and costs.The use of static load permits to simplify the studyunderstanding and requires universal testing machineswhich they are easier to use and less expensivethan fatigue and thermo-mechanical (dynamic) cyclingtest workstations. Static load tests allow investigatingthe mechanical properties of a material to evaluatestiffness, toughness, or static strength to differentkind of loads 38, 39 . While dynamic load tests allow toanalyze the mechanical performances of materials orrestorative systems during function over time 37, 40 .Load application areaIt is one of the principal factors to achievereliable laboratory results and this area changes inrelation to tooth anatomy and type of tooth to betested 9, 23, 41 . When anterior teeth are tested 41-43 ,particularly maxillary incisors, and the load has beenalways applied on the palatal aspect in an area 2 to 3mm below the incisal edge. This was due to the roleof incisors, designed to bear non axial loads ratherthan axial forces. While When the posterior teethis investigated 5, 44 , especially maxillary premolars,the load has been applied in areas ranging from thecenter of the occlusal surface to the supporting cusps.Furthermore the position of the loading site mayinfluence the failure mode, particularly when the postspresent 5 .Load frequencyThis has been considered only in dynamic testssuch as fatigue tests and thermomechanical cyclinganalyses 28, 37, 45, 51 . 1.3 Hz was selected as thefrequency that the specimens have been loaded, basedon the masticatory function investigating speed ofmandibular movements during functions.Load jig kindsDifferent types of jigs have been used; thewidth of these jigs had been selected accordingto tooth anatomy, occlusal morphology and/orrestoration type. Usually rounded tips have beenchosen to homogeneously apply loads 5, 9, 32, 36 ; on thecontrary, sharp tips are well known to develop stressconcentration areas. On the other hand, differentmaterials have been used to perform load application,just like ceramics 42 and steel 32, 33 .Load speedSpeed of load application should simulate oralfunctions just like chewing. High speed would causenot homogenoeus stress arising in both tooth tissuesand restorative materials, whereas low speed wouldnot represent the real oral functions. On such basis,specimens have been loaded at a speed ranging from0.5 to 2 mm/min 26, 34, 46,47, 49 . As in static investigations,specimens have always been loaded from 0 Newtontill fracture occurred, in order to record data aboutthe maximum fracture resistance 9, 52 . In most fatigueanalyses an arbitrary load of 30 Newton has beenapplied to assess the mechanical resistance to fractureof endodontically treated teeth 28, 37, 51 .Angle of load applicationIn clinical oral function teeth are subjectedto different loading condition due to their functionand location within dental arch. Such as, posteriorteeth are responsible for heavy grinding forces whileanterior teeth for tearing forces. It has been welldocumented that fracture resistance of teeth depends13Malaysian Dental Journal Jan-Jun 2011 Vol 32 No 1
Fracture Resistance Tests Validation: A Survey of Literature Reviewon the angle of applied load and axial forces are lessdetrimental than oblique forces 48 . Experimental loadangulation remains a controversial topic 32, 44, 45 .When anterior teeth are investigated 42, 45 , specificallymaxillary incisors, loads at 130° to the longitudinal axisof teeth have been widely described due to both theaverage value of interincisal angle and incisor guidancesuch teeth are devoted to. Conversely, in case of invitro assessments on posterior teeth 33, 34, 44 , forceswith an angulation ranging between 30° and 45° to thelongitudinal axis of teeth have been proposed.Simulation of supporting tissuesUsing rigid materials, such as acrylic resin, toembed extracted teeth during mechanical tests as theacrylic resin blocks will produce a ferrule effect and thatmay lead to misleading results of load values and modefailure of teeth 34, 49, 50 . Further more, the fracturestrength values of restored teeth without artificialligament were higher than those with simulatedligaments, Most of in vitro studies, specimens havebeen embedded in acrylic resin blocks and a self curingsilicone index has been used to simulate alveolar boneand periodontal ligament respectively 9, 45 .CONCLUSIONMechanical tests should be performed beforeclinical trials to be conducted on the restorativematerials. These tests must be designed and preformedin precise rolls to gain validity results for properunderstanding the mechanical properties of dentalrestoration complex and to prove the efficacy andsafety for the clinical implementation.REFERENCES1. Zarone F, Apicella D, Sorrentino R, Ferro V, AversaR, Apicella A. Influence of tooth preparationdesign on the stress distribution in maxillarycentral incisors restored by means of aluminaporcelain veneers: A 3d-finite element analysis.Dent Mater 2005;21: 1178-88.2. Zarone F, Epifania E, Leone G, Sorrentino R, FerrariM. Dynamometric assessment of the mechanicalresistance of porcelain veneers related totooth preparation: A comparison between twotechniques. The Journal of prosthetic dentistry2006;95: 354-63.3. Sorrentino R, Aversa R, Ferro V, Auriemma T,Zarone F, Ferrari M, et al. Three-dimensionalfinite element analysis of strain and stressdistributions in endodontically treated maxillarycentral incisors restored with different post, coreand crown materials. Dent Mater 2007;23: 983-93.4. Jokstad A, Bayne S, Blunck U, Tyas M, Wilson N.Quality of dental restorations. Fdi commissionproject 2-95. Int Dent J 2001;51: 117-58.5. Fokkinga WA, Le Bell AM, Kreulen CM, LassilaLV, Vallittu PK, Creugers NH. Ex vivo fractureresistance of direct resin composite completecrowns with and without posts on maxillarypremolars. International endodontic journal2005;38: 230-7.6. Hayashi M, Takahashi Y, Imazato S, Ebisu S.Fracture resistance of pulpless teeth restoredwith post-cores and crowns. Dent Mater 2006;22:477-85.7. Salameh Z, Sorrentino R, Papacchini F, Ounsi HF,Tashkandi E, Goracci C, et al. Fracture resistanceand failure patterns of endodontically treatedmandibular molars restored using resin compositewith or without translucent glass fiber posts.Journal of endodontics 2006;32: 752-5.8. Sabbagh J, Vreven J, Leloup G. Dynamic and staticmoduli of elasticity of resin-based materials. DentMater 2002;18: 64-71.9. Hayashi M, Sugeta A, Takahashi Y, Imazato S,Ebisu S. Static and fatigue fracture resistancesof pulpless teeth restored with post-cores. DentMater 2008;24: 1178-86.10. Goracci C, Tavares AU, Fabianelli A, MonticelliF, Raffaelli O, Cardoso PC, et al. The adhesionbetween fiber posts and root canal walls:Comparison between microtensile and push-outbond strength measurements. European journalof oral sciences 2004;112: 353-61.11. Kremeier K, Fasen L, Klaiber B, Hofmann N.Influence of endodontic post type (glass fiber,quartz fiber or gold) and luting material on pushoutbond strength to dentin in vitro. Dent Mater2008;24: 660-6.12. Dilmener FT, Sipahi C, Dalkiz M. Resistance ofthree new esthetic post-and-core systems tocompressive loading. The Journal of prostheticdentistry 2006;95: 130-6.Sedgley CM, Messer HH. Are endodonticallytreated teeth more brittle? Journal of endodontics1992;18: 332-5.13. Ferrari M, Vichi A, Garcia-Godoy F. Clinicalevaluation of fiber-reinforced epoxy resin postsand cast post and cores. Am J Dent 2000;13: 15B-18B.Malaysian Dental Journal Jan-Jun 2011 Vol 32 No 114
Page 2 and 3: Malaysian Dental Journal Editorial
Page 6: Delivery Time Of Orthodontic Applia
Page 9: Delivery Time Of Orthodontic Applia
Page 12: Loke / Tan30-40 appliances a year w
Page 17 and 18: Fracture Resistance Tests Validatio
Page 19 and 20: An Audit Of The Caseload And Waitin
Page 21 and 22: An Audit Of The Caseload And Waitin
Page 23 and 24: Prosthodontic Considerations In The
Page 29 and 30: The Loading And Unloading Propertie
Page 34 and 35: ThomasX axis -- forces in Newton. -
Page 43 and 44: Surgical Reconstruction Of The Lost
Page 45 and 46: Surgical Reconstruction Of The Lost
Page 47 and 48: Single Tooth Odontodysplasia- Case
Page 53: Distinguish yourselfGraduate study

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