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ePaper created 2016-04-19, 11:44:05 | version 1.38.0
tooth extractions trends & applications | 29 ortho 1 2016 aided by tracing the inferior dental canal (IDC) to the mandibular foramen in the preoperative panoramic radiograph. The teeth of such in divid uals may also havelongerandmorecurvedrootsandbeembedded inhighlydense,compactalveolarbone,andthussec- tioningoftheteethmayberequiredtoeasetheresis- tance.Racialdifferencesshouldalsobetakenintoac- count, as extractions of teeth from individuals of Afro-Caribbean descent tend to be more challenging owing to the hardness of their bone and divergence of roots in their molars. The resistance of hard tissue should be expected, particularlyifmaxillarysecondandthirdmolarsarebe- ing extracted, as the potential for fracture of both the buccal plate and the tuberosity is relatively common when excessive force is applied with dental forceps. Fractureofthetuberositymayproduceirregularsharp bonyboundaries,significantsoft-tissuelacerationand potentially an oroantral fistula. If such risk factors are identified, tooth sectioning should be followed by ele- vationofrootswithdentalluxatomesinsteadoftradi- tional elevators or forceps, which are known to deliver muchhigherforcetothealveolarbone. The indications for the extraction of impacted lower third molars (LM3) have been the subject of long-standingdebate.Surgicalproceduresfortheex- tractionofuneruptedLM3areassociatedwithsignif- icant morbidity. This includes pain, swelling and the possibilityoftemporaryorpermanentnervedamage, resulting in altered sensation of the lip, chin, gingiva or tongue. Damage to the inferior dental nerve (IDN) isawell-knowncomplicationofsurgicalextractionof deeplyimpactedLM3.Itshouldbeacknowledgedthat this is not simply a loss of sensation; the damaged nerve can be responsible for a number of abnormal sensations, including sharp pain and abnormal re- sponse to stimuli, such as the perception of a light touch as a sharp stab. This can have a significant im- pact on quality of life for many patients. InjurytotheIDNmayoccurfromcompressionofthe nerve, either indirectly by forces transmitted by the rootandsurroundingboneduringelevationordirectly by surgical instruments, such as elevators. The nerve may also become transected by rotary instruments or during extraction of a tooth whose roots are notched orperforatedbytheIDN.TheriskfactorsforIDNinjury during extraction of LM3 are shown in Table I. Preoperative radiographic in vestigations may in- cludeintra-oralimages,suchasocclusalradiographs; panoramic views of the jaws; and conventional CT or CBCT scans. It should be noted that risk-predicting signs in radiographs only indicate that there is an in- creased risk of nerve damage associated with the ex- traction of the corresponding third molar. However, they cannot actually prevent the nerve injury if the tooth is to be extracted. The effective strategies that mayavoidorminimisetheriskofinjurytotheIDNcan be collectively categorised into two main sets. The firstisthepreoperativeworkup,whichshouldinclude critical assessment of the need to extract the third molar, clinical examination and radiographic investi- gation, and the second is intra-operative measures, includingproperselectionoflocalanaestheticagent, the injection technique, modification of the surgical procedure and measures to reduce the degree of po- tential injury to the nerve. Most literature published in the last decade has given us sufficient evidence to suggest a significant riskofdamagetoboththeinferiordentalandthelin- gual nerve owing to the nerve block procedure. This injury may be related to the pharmacological properties of the agent itself or the injection tech- nique. Studies have shown that the lingual nerve is affectedapproximatelytwiceasoftenastheIDN,and one reason for this may be the fascicular pattern in theregionwheretheinjectionisgiven.Italsoappears that about half of patients feel an electric shock sen- sation during injection. There is a higher incidence of reports of nerve in- jury after the use of articaine and prilocaine. Al- though the reason for this remains unknown, it has beensuggestedthatthismaybebecausetheyare4 % solutions, whereas the other commonly used local anaestheticshavelowerconcentrations.Othersasso- ciate the damage with the neurotoxicity potential of 4 % articaine and 3–4 % prilocaine. Hence, it is rec- Risk factors for IDN injury during LM3 extraction Overall risk factors for IDN injury Radiographic signs of increased risk of IDN injury Full bony impactions Apices of the LM3 located inferior to the lower border of the IDC Horizontal impactions Darkening of the root Use of burs for extraction Abrupt narrowing of the root Radiographic risk markers Interruption and loss of the white line representing the IDC Clinical observation of the bundle during surgery Displacement of the IDC by the roots Excessive bleeding into the socket during surgery Abrupt narrowing of one or both of the white lines Patient´s age Representing the IDC most of dentists and surgeons 12016