QUESTIONS & ANSW ERS
th e solution toward th e nerve tru n k is sug gested, and an incom plete block o f th e nerve may occur unless th e anesthetic agent or th e concentration of th e solution is strong enough to compensate fo r th is discrepancy.—Edward J. Driscoll, DDS, Oral M edicine and Surgery Branch, Na tio n a l In s titu te o f Dental Research, Na tio n a l In stitu te s o f Health, Bethesda, Md 20014.
Fissures Readers are invited to su b m it questions to The Journal's Questions and Answers section. Answers provided by experts are sent to questioners in advance of publication. Questions should relate to the a rt and science of dentistry.
A n esth esia
Q. A successful mandibular nerve block has been performed both on the inferior alveolar and the long buc cal nerves with the patient under lo cal anesthesia, and normal anesthesia of the lower quadrant has been achieved. There is a minor periapical abscess on one of the lower premolar teeth in the same quadrant. Why will the patient feel pain in this abscessed tooth when it is ex tracted although the nerve trunks to the tooth have been successfully blocked at a point about 2 inches away? Although a low pH in a region of infection can neutralize the local anesthesia, this is a situation in which the local anesthesia has been placed at a point some distance from the lo calized periapical abscess. What ac counts for this? A.
There is no lite ra tu re or te x t refer ence w hich precisely answers th is inter esting, c lin ic a l question. Incom plete anes thesia a fte r a nerve block occurred rather fre q u e n tly when procaine was the only lo
cal anesthetic available. Since stronger so lutions o f procaine (4% ) and stronger drugs (lidocaine) have been used, incom plete anesthesia rarely occurs. T his is true even in the te st o f local anesthesia fo r dental purposes, ie, removal of an in flam ed pulp. If a nerve block is successful, there is a com plete break in th e a ffe re n t pathways, and th e pa tie nt can feel no pain; there fore, in th e situ a tio n described, there m ust be e ith e r an incom plete block or pain is carried by pathways other than the f ifth nerve, fo r example, by the cuta neous branches of cervical sensory nerves. Although both explanations áre possible, the fir s t would probably occur. In an in com plete block, when th e solution has been placed at some distance from the c ritic a l anatom ic region and has only in filtra te d th e region, it is possible to see signs o f fifth nerve anesthesia on th e lip, tongue, and gingiva w ith o u t obtaining c lin ic a l anesthesia. In the second explana tio n , th e outerm ost fibers, but not all the centerm ost fibers, o f th e nerve tru n k are anesthetized. When the solution has been placed in the exact anatom ic region, the signs of anesthesia are instantaneous. However, when 3 to 5 m in ute s or more elapse be fore th e signs appear, an in filtra tio n of
Q. I have a female patient about 25 years of age with pronounced Assur ing of long duration at the corner of the mouth. Her physician has not been able to cure this condition. She has complete dentures but, because her bite is closed, I am constructing new dentures. What other treatment for these fissures should I consider? ----- L A W R E N C E V. P E T E R S O N , D D S , Ait kin, Minn. 56431. A.
Vitam in B com plex d eficiency and perleche should be considered in relation to fissu ring a t th e corners o f th e mouth. A lthough rib ofla vin is th e sp e cific v ita m in B fa cto r associated w ith fissuring, human beings usually do not show single B com plex fa cto r deficiencies. One would also expect other oral signs such as g lo ssitis w ith atrophy o f th e pa p illa e and redness and cheilosis. Thera p eutic doses of vita m in B com plex given over several weeks should be used if die ta ry analysis indicates such deficiency. Perleche may be associated w ith lock ing the lips or w ith saliva accum ulating at th e corners of th e mouth. This condi tio n is an in fe ctio n w ith Candida albicans and bacteria. Fungicides should be ap plied locally. Loss of interdental dim ensions is prob ably an im p orta n t fa cto r in your patient, and th is fa cto r should be corrected. If th e fissu rin g persists, th e vita m in d e fi ciency or perleche should be considered since there may be more than one cause fo r th e fissu ring .—H. B.G. Robinson, DDS, Dean, U niversity o f M issouri at Kansas City, Dental School, Kansas City, Mo.