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General Anesthesia as It May Interest the General Practitioner, with Special Consideration of Nitrous Oxide-Oxygen and Ethyl Chloride*
Jacobs— General Anesthesia dren sh ow in g m ottled enamel w ere na tive born. T w e n t y o f the patients used city w ater. Patient 1 really first brou gh t m y at tention to m ottled enamel because o f her interesting history. She w as the daughter o f a physician. H e r father and fam ily dentist recognized the condition as m ottled enamel at the age o f 12. T h e father took her to several clinics in d if ferent cities. She w as given treatment over a period o f about three years o f ultraviolet rays and a strictly supervised diet high in calcium and w ith an abun dance o f cod liver oil. She w as 16 years o f age w hen brou gh t to m y attention, and, according to her father and her form er dentist, the condition o f m ottled enamel w as m uch im proved. A t the pres ent time, the enamel is on ly slightly rough and I have classified it according to D ean as very m ild o r even question
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able. Som ething brought about an im provem ent. C ou ld it have been the care fu lly supervised diet and treatm ent? M o s t o f the w orst cases o f m ottled enamel w ere associated w ith high and prolon ged fever, such as is found in diphtheria and scarlet fever. C ou ld these high tem peratures have had any part in affecting the form ation o f the teeth and in the depositing o f calcium ? T h e rem aining fou r patients w ho are trying some treatm ent in an endeavor for im provem ent have not had sufficient time as yet to show any results. O f course, it is quite probable that they w ill not derive any benefit or sh ow im prove ment. T h e r e seems to be no significance in the type o f early feed in g ; i.e., as to w hether the patient w as bottle fed or breast fed. 222 East Commercial Street.
GENERAL AN ESTH ESIA AS IT M A Y INTEREST T H E GEN E RA L P R A C T IT IO N E R , W IT H SPECIAL C O N SID E R A T IO N OF N IT R O U S O X ID E -O X Y G E N A N D E TH Y L CH LORIDE* B y M A X H . J A C O B S , M .D ., D .M .D ., B oston , Mass.
H A T the dentist is becom ing m ore interested in general anesthesia is manifested in three w ay s: 1. T h ere has been an increase in the sale o f the m odern gas apparatus, in spite o f the eco nom ic depression. 2. T h e r e has been a trem endous increase in the num ber of general practitioners taking postgraduate training in general anesthesia. 3. T h e re is a ready m arket fo r discarded gas
T
machines. T h is has been brou gh t about because *Read before the Massachusetts Dental So ciety, Boston, Mass., M ay 1, 1936. Jour. A .D .A ., Vol. 23, September, 1936
( 1 ) many patients are dem anding a gen eral anesthetic, having been inform ed that, under its effect, there is no mental or physical p a in ; ( 2 ) there are definite indications in the dental office fo r gen eral anesthesia, and ( 3 ) m uch has been w ritten recently on the new er anesthetics administered intravenously, rectally or orally. A s a result, m any dentists have been forced to include nitrous oxide-oxygen in their anesthetic arm am entarium . In so doing, they have encountered many dis couraging conditions.
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It is the purpose o f this paper to dis cuss these conditions through a series o f questions from general practitioners and to offer suggestions that m ay help elim inate or reduce the problem s involved. T h e m ore com m on o f these questions are: 1. H o w and w h ere can I procure training in general anesthesia? 2. W h y do I encounter difficulties du ring the in duction o f nitrous oxide-oxygen ? 3. W h y is vom iting so com m on during gen eral anesthesia? 4. W h e n shall I give nitrous oxide-oxygen to a patient? 5. Shall I use carbon d iox id e? 6. Shall I em ploy m edication before administering nitrous oxide-oxygen ? 7. Shall I give gas to children ? 8. Is the use o f ethyl ch lor ide dangerous and have there been any changes in its use? 9. Is there an indica tion fo r the n ew er anesthetics in the den tal office?
H o w and where can I procure training in general anesthesia? T h e re are three sources from w hich one m ay procu re training in general an esthesia: the dental school, the hospital and private instruction. W it h fe w exceptions, the dental schools o f this cou n try have not yet recog nized the ardent need for intensive train ing o f their students in general anes thesia. A s a result, graduates have ab sorbed w hat little they have observed and have attem pted the administration o f a general anesthetic unsuccessfully. T h is accounts fo r the num ber o f dis carded gas apparatus. Som e graduates have supplem ented their school k n ow l edge w ith the com m ercial salesman’s in struction. T h ese men, also, have been unsuccessful. It seems that graduates often cannot turn to their A lm a M a te r fo r further study, because the num ber o f dental schools offerin g postgraduate courses in general anesthesia is lim ited. H ospitals, under com petent super vision, are the ideal source fo r training.
U n fortun ately, tw o facts militate against this: 1. D en tal anesthesia differs from that o f general surgery, the form er be ing practically nasal adm inistration and the latter through the m outh and nose, w hich are com pletely covered at all times. 2. H ospital anesthetists can neither spend the time n or secure the cases; nor can they properly take care o f the num ber o f dentists w h o m ight avail themselves o f the opportunity o f such training. T h e r e remain, therefore, the private teachers, m any o f w hom are sufficiently com petent to teach not on ly the fu nda mentals o f anesthesia, but also every phase o f it. T h ese instructors have failed to recognize one im portant fa c t: T h e re are certain persons w h o, no m atter h ow m uch training in general anesthesia they m ay have had, or h ow great their theo retical kn ow led ge may be, can never be com e good dental anesthetists. T h e y lack w hat is term ed the “ anesthetic sense.” T h ese persons are continually taking courses, but the m ore anesthetics they ad minister, the m ore difficulties they en counter. T h e y m ust be discouraged from adm inistering nitrous oxide-oxygen and lim it themselves entirely to local anes thesia o r call in an expert anesthetist.
W h y do I encounter difficulties during the administration o f nitrous oxideoxygen? T h e answer to this question may be divided into tw o p a rts: mechanical short com ings and an incorrect classification o f patients. M y observations o f general practi tioners adm inistering nitrous oxideoxygen to patients have been interesting and have disclosed many m echanical diffi culties. A m o n g these are defects in gas machines because o f dry, cracked rubber, open joints and leaking v alves; the use o f too large o r too sm all a nasal inhaler o r in correctly placed throat cu rta in s; an
Jacobs— General Anesthesia incorrect position o f the head, causing respiratory embarrassment, and faulty m anipulation o f the hands and fingers during operation. T o correct these mechanical faults is an easy m atter. T h e rubber tubing and rubber bag must be frequently moistened. N o t on ly does this increase the durability, but it also aids in preventing explosions, for m ixtures o f nitrous oxide-oxygen have been kn ow n to explode in too dry an atmosphere or where there is too much static. O p en joints and leaking valves alter m ixture percentages. A large nasal in haler permits an ingress o f air. A small one may im pinge on the nares, shutting o ff nasal respiration. . A throat pack or curtain incorrectly placed is one o f the most com m on means o f disturbing an otherw ise sm ooth induc tion. It must not perm it an ingress o f air and must be inserted w hen the gag reflex is obliterated. I f it is inserted sooner, gagging, retching or vom iting
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D ifficulties are also encountered dur ing the adm inistration o f nitrous oxideoxygen because o f incorrect classifica tion o f patients. The sooner general practitioners recognize the fa ct that not all patients are susceptible to nitrous oxide, the sooner w ill m any difficulties be elim inated. H yposusceptible patients may be taken care o f in hospitals, but it is a different matter in the dental office. A l coholics, athletes, patients suffering from hyperthyroidism an d drug addicts can best be anesthetized w ith nitrous oxideoxygen by experts, w h o, m any times, in spite o f their experience, have to resort to ether o r some oth er anesthetic. T h e re are nonsusceptible patients even am ong the n orm al. A small, frail w om an m ay becom e a terror under the influence o f nitrous oxide, and a robust ou tdoor w ork er m a y prove very m ild. T h e ability to p rop erly classify patients is an im portant fa c to r in the successful use o f nitrous ox ide-oxygen anesthesia.
results. T h e greatest factor in the success o f an anesthesia is an open airw ay. T h e o c
W h y are nausea and vomiting so com mon during nitrous oxide-oxygen anes thesia?
ciput, shoulders and back should form a straight line. A V-shaped space between the head and shoulders causes a muscu lar im pingem ent on the larynx o r trachea,
T h e m ore com m on causes o f nausea and vom itin g are ( 1 ) the presence o f food in the stom a ch ; ( 2 ) too ligh t anes thesia; ( 3 ) too deep anesthesia, and (4 ) sw a llow in g o f b lo o d or mucus. Nausea and v om itin g m ay be con trolled b y : 1. H a v in g the stomach empty. Instead o f giving gas to any patient w h o enters the office at any time, an appoint m ent should be m ade at least tw o or three hours after a meal. 2. E m ploying oxygen is a stim ulant. I f one w ere to breathe oxygen fo r a period o f time, he w o u ld becom e d iz z y and nauseated, apnea ensuing. T o o light anesthesia w ith too large a percentage o f oxygen in the gas m ixture, results in prolonged stimu lation o f the nausea and vom iting centers. 3. A v o id in g too deep anesthesia,
w ith embarrassment o f respiration and cyanosis. T h is may, o f course, be avoided by the use o f intranasal or intratracheal catheters; w hich has no practical value in a dental office. T h e operator him self is m any times responsible for lack o f a sm ooth main tenance stage during general anesthesia. W it h his hands or fingers, he m ay shut o ff the glottis by pushing the tongue backw ards o r cover the glottis w ith the throat pack. T h e patient becomes cya notic. T h e assistant, n otin g this, employs straight oxygen, disrupting the gas per centages w hich evidently w ere indicated.
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w hich results in a toxic irritation o f the vom iting centers. T h is is generally as sociated w ith jactitation, w hich may be the foreru n n er o f v om itin g during the anesthesia. 4 . A v o id in g sw a llow in g o f blood d u rin g the recovery stage o f gas anesthesia. O perative w oun ds should be kept covered w ith gauze under pressure until all reflexes have returned. T h e re are some patients w h o very easily becom e nauseated. T h e patient w h o can not travel by boat because o f sea sickness is in this class. Such a patient must be in form ed o f the possibility o f nausea a n d vom itin g du ring o r after nitrous oxide-oxy g en anesthesia.
W h en shall I give nitrous oxide-oxygen to a patient? In the discussion o f this question, it must be u nderstood that the general prac titioner is the one to be considered. I believe th at nitrous oxide is indicated in acute, subacute and chronic infections in w hich infiltration o r condu ction anes thesia m a y spread existing infection. E xtrem ely nervous persons, w h o suffer m entally and in w h om it is best to cut all association paths to the brain as quickly as possible, are better o ff w ith a general anesthetic, if susceptible to the anesthetic. N itrou s oxide-oxygen is indi cated in the general practitioner’s office fo r patients w h o have certain types o f heart disease in w hich an anginal attack may be precipitated psychologically, or through the use o f some vasoconstrictor.
Shall I employ medication before ad ministering nitrous oxide-oxygen? T h is depends upon tw o th in gs: ( 1 ) the in dividu al reaction to the prem edi cating agen t, and ( 2 ) w hether the pa tient is accom panied to the office by some one w h o w ill make certain that he returns h om e safely. In d iv id u al reaction varies, depending on the type o f prem edicating agent used. T h ose in com m on use today are nerve
sedatives, narcotics and barbiturates. T h e tw o form er ones are gradually being re placed by the last, and herein lies a story. T h e barbiturates m ay cause delirium and restlessness in some patients or pro lon ged som nolence in others. P en to barbital sod iu m ,(n em b u ta l) has been the most effective barbiturate in m y practice. Its effects are not so prolon ged as those o f other barbiturates and it does not have the so-called “ hangover,” if given in a 1-| grain dose fo r premedication. F o r prolon ged operations, prem edi cating agents are indicated. T h e ir use cuts d ow n the am ount o f anesthetic nec essary, permits a larger percentage o f oxygen and helps, to som e extent, to quiet the overstim ulated type o f patient. O n the other hand, prem edication in the dental office fo r short operations is unwise, especially if the patient is to re turn hom e alone.
Shall I give gas to children? O pin ion s vary as to this. Some experts believe that children under 6 years o f age should not be given nitrous oxide because o f instability o f the nervous system and the possibility o f status lymphaticus. M y experience has been different. In looking over the records at the Forsyth D en ta l Infirm ary, I fou n d that in 2,7 04 nitrous oxide cases fo r extractions up to Jan. 31, 1936, there w ere no u ntow ard results. In 14,397 nitrous oxide-oxygenether administration fo r tonsillectom y and adenoidectom y, there w as no anesthetic fatality. T h e value o f nitrous oxide and oxygen in children is best determ ined by the fact that approxim ately fifty tonsillectom ies w ere perform ed under straight nitrous oxide and oxygen, 50 per cent being given sodium amytal before anesthesia. T h ese operations w ere perform ed successfully w ith ou t a fatality in spite o f the m ost adverse anesthetic conditions. It must be realized that the postnasal spaces in these
Jacobs— General Anesthesia children w ere filled w ith obstructive adenoids and that the throats w ere blocked w ith hypertrophied and diseased tonsils. T h e ages o f the children in all cases ranged from 2^ to 13 years. In 17,151 children given nitrous oxideoxygen fo r extractions or tonsillectom ies or as an induction to ether, there has been no anesthetic fatality or u ntow ard result. F or a num ber o f years, children w ere examined by the roentgen rays fo r en larged thymuses. W h e n a suspicious suprasternal shadow w as fou n d, the child w as given roentgen therapy before operation. F or the last eight or nine years, w e have n ot em ployed the roentgen rays on children, but have proceeded to anesthetize and operate on them. T h e re sults have been no different. T h e thing to guard against in children is psychic shock. T h e ir confidence m ust be gained and they m ust n ot be “ scared to death.” In m y opinion, nitrous oxide-oxygen is a safe anesthetic fo r children.
Shall I use carbon dioxide? L et us study the physiology o f carbon dioxide and the indications fo r its use in the dental office. C arbon dioxide ex ists in solution in the b lood to the extent o f about 3.5 to 5.5 per cent. Its presence is essential to respiration, stim ulating the respiratory centers in the m edulla and con trollin g the depth o f respiration. A s carbon dioxide is w ith draw n from the circulation, the respiratory centers are depressed and respiration becomes shal low . W h e n all carbon dioxide has been exhausted, the centers becom e paralyzed and respiration ceases. T h e cessation o f respiration as a result o f the absence o f carbon dioxide is k n ow n as acapnia. I f one w ere to remain in an atmosphere o f pure oxygen fo r several m inutes, he w ou ld becom e som ewhat nauseated, un dergo vertigo and then cease breathing. In an atmosphere supersaturated w ith
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oxygen, insufficient carbon dioxide is perm itted to form , respiratory depression resulting. Cessation o f respiration as a result o f too m uch oxygen is know n as apnea. W e find, therefore, that breathing m ay cease as a result o f too little carbon di oxide (acapnia) or too m uch oxygen (a p n ea ). T r u e apnea is due to acapnia. (H o w e ll.) T h is is one o f the reasons that under prolon ged ether anesthesia a patient w ill stop breathing, although the color is good and the pulse is w ithin norm al limits. O ccasion ally, this occurs in nitrous oxide-oxygen anesthesia. A patient may undergo extrem e em otional excitement resulting in such rapid breathing that the carbon dioxide is elim inated and the carbon dioxide content o f the blood is low ered, respiration becom ing shallow o r ceasing. T h e operations perform ed by the gen eral dental practitioner are usually short. R arely does a patient becom e apneic or acapniac. I f a prem edicating agent is used, especially m orphine, respiratory depression, w ith shallow breathing, may occu r. H ere, the use o f carbon dioxide is indicated to increase the depth o f respira tion. C arbon dioxide administration does n ot increase the rate o f respiration. C arbon dioxide may be administered in one o f three w a y s: ( 1 ) rebreathing; ( 2 ) adm inistration o f pure carbon di oxide through a tank, and ( 3 ) adminis tration o f carbo-oxygen. Rebreathing is accom plished by shut ting o ff both the air valve and the ex haling valve in the nasal inhaler, per m itting the exhaled air to enter the m ix ing cham ber and thus be rebreathed. T h e exhaled air contains the products o f gaseous metabolism and consists o f carbon dioxide and other impurities. T h is means that occasionally the exhaling valve m ust be opened to perm it the es
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cape o f the impurities and rebreathing started again. F rom 3 to 5 per cent pure carbon di oxide may be given directly through a tank. C a rbo-oxygen , a m ixture o f 95 per cent oxygen and 5 per cent carbon dioxide, may be used in place o f pure oxygen or pure carbon dioxide, and the necessity o f rebreathing be elim inated. C arbon dioxide is a valuable adju nct to nitrous oxide-oxygen, and though it need not be used fo r short operations, its use w ill stimulate respiration in those persons w h o are naturally shallow breathers o r those w h o have been given prem edication. It is also o f some value in the overstim ulated type o f patient. T h e increase in the depth o f respiration increases the rate o f absorption o f nitrous oxide, decreasing the length o f or elim inating the excitem ent stage.
Is the use of ethyl chloride dangerous? In the D ental Cosmos , September, 1930, I reported 123,210 cases o f ethyl chloride administrations by inhalation to children ranging from 3 to 14 years o f age, at the Forsyth D en ta l Infirm ary, fo r extraction o f deciduous teeth and other m inor surgery. In T h e J o u r n a l, June, 1933, I re ported 26 ,388 additional cases, m aking a total at that time o f 149,598 ethyl ch lor ide administrations. I am n o w ready to report on 4 4 ,7 9 6 m ore cases, m aking a total o f 194,304 up to Jan. 31, 1936. A series approxim ating 2 0 0,00 0 cases is sufficiently large to furnish definite in form ation. L et us analyze this series and find the danger, if any, in the adminis tration o f ethyl chloride. In 1915, w hen w e first started to use ethyl chloride fo r extraction o f decidu ous teeth, it w as em ployed in large enough quantity to produce prim ary an esthesia. W e w ere able to extract six, eight o r m ore teeth in a period o f a few
minutes. Several minutes was required fo r the patient to recover. T h is w as fo l low ed, in a large num ber o f cases, by prolon ged nausea or vom iting. T h e r e is no record o f a death or inability o f the patient to return to school or to his home. In 1923, w e began to reduce the am ount o f ethyl chloride, producin g a state o f deep analgesia rather than pri m ary anesthesia. T h e num ber o f cases o f nausea and vom iting decreased. W e fou nd that practically the same am ount o f operating cou ld be accomplished, and there w as a shorter recovery period. A s the years elapsed, the am ount o f ethyl chloride used per patient has been reduced to such an extent that rarely does an induction period last over forty to fifty seconds. T h e operating time has, o f course, been shortened, the extractions being lim ited to tw o or three teeth. R arely is there nausea o r vom iting and the recovery period is a m atter o f sec onds. Analgesia on ly is produced and no attem pt is made to produce anesthesia. Since 1932, w e have noted an interest ing phenom enon. T h ose patients oper ated on before the analgesic stage has been reached have squirm ed and some times cried or otherwise manifested signs o f pain. Investigation has proved that, ten m inutes after recovery, the child has no recollection o f the teeth having been extracted. In v iew o f these findings, I am n ow w ork in g on a technic w hereby the child can hear me talk and reacts to sugges tion, in having the tem porary teeth re m oved and yet experiences no pain dur ing the procedure. T h is technic w ill be reported as soon as a sufficient num ber o f patients have been operated on sucessfu lly to w arrant its description.
Is there an indication for the use of the newer anesthetics in the dental office? The
n ew er anesthetics are o f three
kinds: inhalation, rectal and intravenous.
Jacobs— General Anesthesia T h e inhalation anesthetics are ethylene, cyclopropane and divin yl oxide (vineth en e). Ethylene has been in use since 1923. Its explosibility is w e ll k n ow n . In order to use this gas safely, certain rules m ust be fo llo w e d . T h e hum idity o f the room must be high. T h e floor o f the operating room should be covered by a grounded m etal plate. T h e gas apparatus m ust be grounded, as w ell as the dental chair. M . H ille l Feldm an, o f N e w Y o r k , uses ethylene routinely w ith ou t these precau tions and has had no accident. H e be lieves this is due to the fa ct that the gas he em ploys is w ater w ashed. H e uses a G w a th m ey apparatus. It is o f interest to note that a num ber o f clinics and hos pitals have ethylene.
discontinued
the
use
of
C yclopropan e is also a dangerous gas because o f its intense explosibility. T h is is unfortunate, since 80 to 90 per cent oxygen can be given w ith the gas. R e laxation under its influence is marked and recovery is rapid. It m ay be used instead o f ethyl chloride in dental surgery, but its cost is m uch greater. A great deal w ill have to be kn ow n about its physio log ic action and contraindications before its use in the dental office can be co n sidered. T rib rom eth y la lcoh ol (av ertin ) is ad ministered rectally. It is a basal anes thetic, and w henever I have used it in hospital practice, nitrous oxide o r ether had to be used in supplement. It has no place in the dental office, first because o f the m ode o f adm inistration and, secondly, because o f the questionable recovery time. Som e patients may sleep fo r sev eral hours and must be under constant supervision during this time. T h is is too m uch to expect in a busy dental practice, and fo r short dental operations there are m ore advantageous anesthetics. T h e intravenous anesthetics are so
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dium amytal, evipan and thionembutal. Sodium am ytal is also a basal anes thetic. W h e n it is given intravenously in large enough dosage to produce com plete anesthesia, its m ortality rate has been high. U sed as a basal anesthetic, supplemented by nitrous oxide o r oxygen, its use has been curtailed o w in g to a de gree o f delirium in certain patients in the recovery stage. Evipan, a barbituric acid derivative, also an intravenous anesthetic, has been fou n d to be m ore satisfactory in hospital practice. R ecovery from its effect is sup posed to occu r w ithin fifteen o r tw enty minutes after its adm inistration. I have seen the recovery stage last over a period o f several hours. In one case, recovery w as not com plete fo r tw en ty -fou r hours. I f the dental office is n ot equipped to take care o f such a patient, no intravenous anesthetic is indicated. T h ion em bu ta l, w hich w ill be put on the m arket as sodium pentothal, given intravenously, is the m ost rapid acting o f this type o f anesthetic. I recently had occasion to rem ove an upper impacted third m olar under thionem butal. A s soon as a fe w drops o f the solution had been injected, the patient w as com pletely anesthetized. T h e pupils w ere w idely di lated and the pupilary reflex gone. O n injection o f a fe w m ore drops, relax ation w as so com plete that the tongue had to be held from closing the glottis. T h e anesthesia lasted fo r eight minutes, the pupils becom ing sm aller and the pupilary reflex returning as the patient recovered. A t the present time, it is a too rapid acting anesthetic to be used in a dental office, if a difficult extraction is to be perform ed. T h e re is no indication fo r the use o f any intravenous anesthetic in the office of the general dental practitioner. Asepsis must be com plete to avoid super ficial or blood infection. T h e chance o f
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an air embolus in inexperienced hands is forever present. I f intravenous anesthesia is used, a recovery room , w ith an as
the body. T h e possibility o f ether pneu m onia o r lu n g abscess must be consid ered. I f an operation is lon g enough or
sistant in constant service, must be p ro
severe enough to ju stify the use o f ether, the patient should be hospitalized. E thyl chloride is too dangerous a drug to gain com plete anesthesia. T h e m ortal ity is too high. A s an analgesic fo r ch il
vided. CONCLUSION
F o r general anesthesia in the dental office, nitrous oxide-oxygen is by fa r the m ost satisfactory o f the anesthetics. I n du ction and recovery are rapid. A l though the m argin o f safety is n arrow , nitrous oxide can be readily displaced by oxygen, since it form s a physical m ixture w ith the blood. F ran k W . R ou n ds has often stated, and ju stly so, that nitrous oxide-oxygen is practically the only anesthetic fo r w h ich w e have a specific a n tid ote; that is, oxygen. E ther affords the w idest m argin o f safety. T h e induction and recovery periods are slow . T h e dentist has neither the legal n or the m oral right to send a patient out o f the office after ether anes thesia, until it has been elim inated from
dren in m inor dental surgery, it is not o n ly safe, but also expedient. T h e dental profession has given to the w o r ld tw o anesthetics in nitrous oxide and ether that have stood the test o f tim e. O th er anesthetics have com e and gone. I f the safety o f the patient is to be considered, the n ew er anesthetics m ust be left to those m ost qualified in the field o f experim ental research. O u t o f the midst o f the present chaos, some anesthetic w ill at som e time or other stand out because o f its safety and effi cacy. U n til then, let us adhere to the o ld adage, “ Be not the first by w h om the n ew is tried, nor yet the last to lay the old aside.” 311 Commonwealth Avenue.
GENTLE M EAN S F O R R E D U C IN G FR A C T U R E B y C A R L F. M O R G E N T H A L E R , D .D .S ., H am m on d , Ind.
V E R C O M I N G m uscular antag onism is perhaps the m ost difficult problem arising in the reduction o f fractures o f the m andible. W it h o u t this problem , fracture reduction w o u ld be greatly simplified. It w ou ld be as easy as assembling the different parts o f a box that are to be nailed or glued to gether. T h e muscles o f mastication play a definite part in creating this resistance, a part w hich varies w ith the site and extent o f the in ju ry. O w in g to the posi
O
Jour. A .D .A ., Vol. 23, September, 1936
tion o f the muscle fibers, contraction or relaxation is always in the direction o f the lon g axis o f the muscle. A muscle in contracting is shortened and in relaxing is lengthened. It follo w s that the muscles w hich exert a d ow n w a rd pull on the m andible are those that are attached to the body o f this bone, and run in a d ow n w a rd direction, and that those muscles w hich exert an upw ard pull are the ones that are attached to the m an dible and run in an u pw ard direction.
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able. Som ething brought about an im provem ent. C ou ld it have been the care fu lly supervised diet and treatm ent? M o s t o f the w orst cases o f m ottled enamel w ere associated w ith high and prolon ged fever, such as is found in diphtheria and scarlet fever. C ou ld these high tem peratures have had any part in affecting the form ation o f the teeth and in the depositing o f calcium ? T h e rem aining fou r patients w ho are trying some treatm ent in an endeavor for im provem ent have not had sufficient time as yet to show any results. O f course, it is quite probable that they w ill not derive any benefit or sh ow im prove ment. T h e r e seems to be no significance in the type o f early feed in g ; i.e., as to w hether the patient w as bottle fed or breast fed. 222 East Commercial Street.
GENERAL AN ESTH ESIA AS IT M A Y INTEREST T H E GEN E RA L P R A C T IT IO N E R , W IT H SPECIAL C O N SID E R A T IO N OF N IT R O U S O X ID E -O X Y G E N A N D E TH Y L CH LORIDE* B y M A X H . J A C O B S , M .D ., D .M .D ., B oston , Mass.
H A T the dentist is becom ing m ore interested in general anesthesia is manifested in three w ay s: 1. T h ere has been an increase in the sale o f the m odern gas apparatus, in spite o f the eco nom ic depression. 2. T h e r e has been a trem endous increase in the num ber of general practitioners taking postgraduate training in general anesthesia. 3. T h e re is a ready m arket fo r discarded gas
T
machines. T h is has been brou gh t about because *Read before the Massachusetts Dental So ciety, Boston, Mass., M ay 1, 1936. Jour. A .D .A ., Vol. 23, September, 1936
( 1 ) many patients are dem anding a gen eral anesthetic, having been inform ed that, under its effect, there is no mental or physical p a in ; ( 2 ) there are definite indications in the dental office fo r gen eral anesthesia, and ( 3 ) m uch has been w ritten recently on the new er anesthetics administered intravenously, rectally or orally. A s a result, m any dentists have been forced to include nitrous oxide-oxygen in their anesthetic arm am entarium . In so doing, they have encountered many dis couraging conditions.
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It is the purpose o f this paper to dis cuss these conditions through a series o f questions from general practitioners and to offer suggestions that m ay help elim inate or reduce the problem s involved. T h e m ore com m on o f these questions are: 1. H o w and w h ere can I procure training in general anesthesia? 2. W h y do I encounter difficulties du ring the in duction o f nitrous oxide-oxygen ? 3. W h y is vom iting so com m on during gen eral anesthesia? 4. W h e n shall I give nitrous oxide-oxygen to a patient? 5. Shall I use carbon d iox id e? 6. Shall I em ploy m edication before administering nitrous oxide-oxygen ? 7. Shall I give gas to children ? 8. Is the use o f ethyl ch lor ide dangerous and have there been any changes in its use? 9. Is there an indica tion fo r the n ew er anesthetics in the den tal office?
H o w and where can I procure training in general anesthesia? T h e re are three sources from w hich one m ay procu re training in general an esthesia: the dental school, the hospital and private instruction. W it h fe w exceptions, the dental schools o f this cou n try have not yet recog nized the ardent need for intensive train ing o f their students in general anes thesia. A s a result, graduates have ab sorbed w hat little they have observed and have attem pted the administration o f a general anesthetic unsuccessfully. T h is accounts fo r the num ber o f dis carded gas apparatus. Som e graduates have supplem ented their school k n ow l edge w ith the com m ercial salesman’s in struction. T h ese men, also, have been unsuccessful. It seems that graduates often cannot turn to their A lm a M a te r fo r further study, because the num ber o f dental schools offerin g postgraduate courses in general anesthesia is lim ited. H ospitals, under com petent super vision, are the ideal source fo r training.
U n fortun ately, tw o facts militate against this: 1. D en tal anesthesia differs from that o f general surgery, the form er be ing practically nasal adm inistration and the latter through the m outh and nose, w hich are com pletely covered at all times. 2. H ospital anesthetists can neither spend the time n or secure the cases; nor can they properly take care o f the num ber o f dentists w h o m ight avail themselves o f the opportunity o f such training. T h e r e remain, therefore, the private teachers, m any o f w hom are sufficiently com petent to teach not on ly the fu nda mentals o f anesthesia, but also every phase o f it. T h ese instructors have failed to recognize one im portant fa c t: T h e re are certain persons w h o, no m atter h ow m uch training in general anesthesia they m ay have had, or h ow great their theo retical kn ow led ge may be, can never be com e good dental anesthetists. T h e y lack w hat is term ed the “ anesthetic sense.” T h ese persons are continually taking courses, but the m ore anesthetics they ad minister, the m ore difficulties they en counter. T h e y m ust be discouraged from adm inistering nitrous oxide-oxygen and lim it themselves entirely to local anes thesia o r call in an expert anesthetist.
W h y do I encounter difficulties during the administration o f nitrous oxideoxygen? T h e answer to this question may be divided into tw o p a rts: mechanical short com ings and an incorrect classification o f patients. M y observations o f general practi tioners adm inistering nitrous oxideoxygen to patients have been interesting and have disclosed many m echanical diffi culties. A m o n g these are defects in gas machines because o f dry, cracked rubber, open joints and leaking v alves; the use o f too large o r too sm all a nasal inhaler o r in correctly placed throat cu rta in s; an
Jacobs— General Anesthesia incorrect position o f the head, causing respiratory embarrassment, and faulty m anipulation o f the hands and fingers during operation. T o correct these mechanical faults is an easy m atter. T h e rubber tubing and rubber bag must be frequently moistened. N o t on ly does this increase the durability, but it also aids in preventing explosions, for m ixtures o f nitrous oxide-oxygen have been kn ow n to explode in too dry an atmosphere or where there is too much static. O p en joints and leaking valves alter m ixture percentages. A large nasal in haler permits an ingress o f air. A small one may im pinge on the nares, shutting o ff nasal respiration. . A throat pack or curtain incorrectly placed is one o f the most com m on means o f disturbing an otherw ise sm ooth induc tion. It must not perm it an ingress o f air and must be inserted w hen the gag reflex is obliterated. I f it is inserted sooner, gagging, retching or vom iting
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D ifficulties are also encountered dur ing the adm inistration o f nitrous oxideoxygen because o f incorrect classifica tion o f patients. The sooner general practitioners recognize the fa ct that not all patients are susceptible to nitrous oxide, the sooner w ill m any difficulties be elim inated. H yposusceptible patients may be taken care o f in hospitals, but it is a different matter in the dental office. A l coholics, athletes, patients suffering from hyperthyroidism an d drug addicts can best be anesthetized w ith nitrous oxideoxygen by experts, w h o, m any times, in spite o f their experience, have to resort to ether o r some oth er anesthetic. T h e re are nonsusceptible patients even am ong the n orm al. A small, frail w om an m ay becom e a terror under the influence o f nitrous oxide, and a robust ou tdoor w ork er m a y prove very m ild. T h e ability to p rop erly classify patients is an im portant fa c to r in the successful use o f nitrous ox ide-oxygen anesthesia.
results. T h e greatest factor in the success o f an anesthesia is an open airw ay. T h e o c
W h y are nausea and vomiting so com mon during nitrous oxide-oxygen anes thesia?
ciput, shoulders and back should form a straight line. A V-shaped space between the head and shoulders causes a muscu lar im pingem ent on the larynx o r trachea,
T h e m ore com m on causes o f nausea and vom itin g are ( 1 ) the presence o f food in the stom a ch ; ( 2 ) too ligh t anes thesia; ( 3 ) too deep anesthesia, and (4 ) sw a llow in g o f b lo o d or mucus. Nausea and v om itin g m ay be con trolled b y : 1. H a v in g the stomach empty. Instead o f giving gas to any patient w h o enters the office at any time, an appoint m ent should be m ade at least tw o or three hours after a meal. 2. E m ploying oxygen is a stim ulant. I f one w ere to breathe oxygen fo r a period o f time, he w o u ld becom e d iz z y and nauseated, apnea ensuing. T o o light anesthesia w ith too large a percentage o f oxygen in the gas m ixture, results in prolonged stimu lation o f the nausea and vom iting centers. 3. A v o id in g too deep anesthesia,
w ith embarrassment o f respiration and cyanosis. T h is may, o f course, be avoided by the use o f intranasal or intratracheal catheters; w hich has no practical value in a dental office. T h e operator him self is m any times responsible for lack o f a sm ooth main tenance stage during general anesthesia. W it h his hands or fingers, he m ay shut o ff the glottis by pushing the tongue backw ards o r cover the glottis w ith the throat pack. T h e patient becomes cya notic. T h e assistant, n otin g this, employs straight oxygen, disrupting the gas per centages w hich evidently w ere indicated.
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w hich results in a toxic irritation o f the vom iting centers. T h is is generally as sociated w ith jactitation, w hich may be the foreru n n er o f v om itin g during the anesthesia. 4 . A v o id in g sw a llow in g o f blood d u rin g the recovery stage o f gas anesthesia. O perative w oun ds should be kept covered w ith gauze under pressure until all reflexes have returned. T h e re are some patients w h o very easily becom e nauseated. T h e patient w h o can not travel by boat because o f sea sickness is in this class. Such a patient must be in form ed o f the possibility o f nausea a n d vom itin g du ring o r after nitrous oxide-oxy g en anesthesia.
W h en shall I give nitrous oxide-oxygen to a patient? In the discussion o f this question, it must be u nderstood that the general prac titioner is the one to be considered. I believe th at nitrous oxide is indicated in acute, subacute and chronic infections in w hich infiltration o r condu ction anes thesia m a y spread existing infection. E xtrem ely nervous persons, w h o suffer m entally and in w h om it is best to cut all association paths to the brain as quickly as possible, are better o ff w ith a general anesthetic, if susceptible to the anesthetic. N itrou s oxide-oxygen is indi cated in the general practitioner’s office fo r patients w h o have certain types o f heart disease in w hich an anginal attack may be precipitated psychologically, or through the use o f some vasoconstrictor.
Shall I employ medication before ad ministering nitrous oxide-oxygen? T h is depends upon tw o th in gs: ( 1 ) the in dividu al reaction to the prem edi cating agen t, and ( 2 ) w hether the pa tient is accom panied to the office by some one w h o w ill make certain that he returns h om e safely. In d iv id u al reaction varies, depending on the type o f prem edicating agent used. T h ose in com m on use today are nerve
sedatives, narcotics and barbiturates. T h e tw o form er ones are gradually being re placed by the last, and herein lies a story. T h e barbiturates m ay cause delirium and restlessness in some patients or pro lon ged som nolence in others. P en to barbital sod iu m ,(n em b u ta l) has been the most effective barbiturate in m y practice. Its effects are not so prolon ged as those o f other barbiturates and it does not have the so-called “ hangover,” if given in a 1-| grain dose fo r premedication. F o r prolon ged operations, prem edi cating agents are indicated. T h e ir use cuts d ow n the am ount o f anesthetic nec essary, permits a larger percentage o f oxygen and helps, to som e extent, to quiet the overstim ulated type o f patient. O n the other hand, prem edication in the dental office fo r short operations is unwise, especially if the patient is to re turn hom e alone.
Shall I give gas to children? O pin ion s vary as to this. Some experts believe that children under 6 years o f age should not be given nitrous oxide because o f instability o f the nervous system and the possibility o f status lymphaticus. M y experience has been different. In looking over the records at the Forsyth D en ta l Infirm ary, I fou n d that in 2,7 04 nitrous oxide cases fo r extractions up to Jan. 31, 1936, there w ere no u ntow ard results. In 14,397 nitrous oxide-oxygenether administration fo r tonsillectom y and adenoidectom y, there w as no anesthetic fatality. T h e value o f nitrous oxide and oxygen in children is best determ ined by the fact that approxim ately fifty tonsillectom ies w ere perform ed under straight nitrous oxide and oxygen, 50 per cent being given sodium amytal before anesthesia. T h ese operations w ere perform ed successfully w ith ou t a fatality in spite o f the m ost adverse anesthetic conditions. It must be realized that the postnasal spaces in these
Jacobs— General Anesthesia children w ere filled w ith obstructive adenoids and that the throats w ere blocked w ith hypertrophied and diseased tonsils. T h e ages o f the children in all cases ranged from 2^ to 13 years. In 17,151 children given nitrous oxideoxygen fo r extractions or tonsillectom ies or as an induction to ether, there has been no anesthetic fatality or u ntow ard result. F or a num ber o f years, children w ere examined by the roentgen rays fo r en larged thymuses. W h e n a suspicious suprasternal shadow w as fou n d, the child w as given roentgen therapy before operation. F or the last eight or nine years, w e have n ot em ployed the roentgen rays on children, but have proceeded to anesthetize and operate on them. T h e re sults have been no different. T h e thing to guard against in children is psychic shock. T h e ir confidence m ust be gained and they m ust n ot be “ scared to death.” In m y opinion, nitrous oxide-oxygen is a safe anesthetic fo r children.
Shall I use carbon dioxide? L et us study the physiology o f carbon dioxide and the indications fo r its use in the dental office. C arbon dioxide ex ists in solution in the b lood to the extent o f about 3.5 to 5.5 per cent. Its presence is essential to respiration, stim ulating the respiratory centers in the m edulla and con trollin g the depth o f respiration. A s carbon dioxide is w ith draw n from the circulation, the respiratory centers are depressed and respiration becomes shal low . W h e n all carbon dioxide has been exhausted, the centers becom e paralyzed and respiration ceases. T h e cessation o f respiration as a result o f the absence o f carbon dioxide is k n ow n as acapnia. I f one w ere to remain in an atmosphere o f pure oxygen fo r several m inutes, he w ou ld becom e som ewhat nauseated, un dergo vertigo and then cease breathing. In an atmosphere supersaturated w ith
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oxygen, insufficient carbon dioxide is perm itted to form , respiratory depression resulting. Cessation o f respiration as a result o f too m uch oxygen is know n as apnea. W e find, therefore, that breathing m ay cease as a result o f too little carbon di oxide (acapnia) or too m uch oxygen (a p n ea ). T r u e apnea is due to acapnia. (H o w e ll.) T h is is one o f the reasons that under prolon ged ether anesthesia a patient w ill stop breathing, although the color is good and the pulse is w ithin norm al limits. O ccasion ally, this occurs in nitrous oxide-oxygen anesthesia. A patient may undergo extrem e em otional excitement resulting in such rapid breathing that the carbon dioxide is elim inated and the carbon dioxide content o f the blood is low ered, respiration becom ing shallow o r ceasing. T h e operations perform ed by the gen eral dental practitioner are usually short. R arely does a patient becom e apneic or acapniac. I f a prem edicating agent is used, especially m orphine, respiratory depression, w ith shallow breathing, may occu r. H ere, the use o f carbon dioxide is indicated to increase the depth o f respira tion. C arbon dioxide administration does n ot increase the rate o f respiration. C arbon dioxide may be administered in one o f three w a y s: ( 1 ) rebreathing; ( 2 ) adm inistration o f pure carbon di oxide through a tank, and ( 3 ) adminis tration o f carbo-oxygen. Rebreathing is accom plished by shut ting o ff both the air valve and the ex haling valve in the nasal inhaler, per m itting the exhaled air to enter the m ix ing cham ber and thus be rebreathed. T h e exhaled air contains the products o f gaseous metabolism and consists o f carbon dioxide and other impurities. T h is means that occasionally the exhaling valve m ust be opened to perm it the es
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cape o f the impurities and rebreathing started again. F rom 3 to 5 per cent pure carbon di oxide may be given directly through a tank. C a rbo-oxygen , a m ixture o f 95 per cent oxygen and 5 per cent carbon dioxide, may be used in place o f pure oxygen or pure carbon dioxide, and the necessity o f rebreathing be elim inated. C arbon dioxide is a valuable adju nct to nitrous oxide-oxygen, and though it need not be used fo r short operations, its use w ill stimulate respiration in those persons w h o are naturally shallow breathers o r those w h o have been given prem edication. It is also o f some value in the overstim ulated type o f patient. T h e increase in the depth o f respiration increases the rate o f absorption o f nitrous oxide, decreasing the length o f or elim inating the excitem ent stage.
Is the use of ethyl chloride dangerous? In the D ental Cosmos , September, 1930, I reported 123,210 cases o f ethyl chloride administrations by inhalation to children ranging from 3 to 14 years o f age, at the Forsyth D en ta l Infirm ary, fo r extraction o f deciduous teeth and other m inor surgery. In T h e J o u r n a l, June, 1933, I re ported 26 ,388 additional cases, m aking a total at that time o f 149,598 ethyl ch lor ide administrations. I am n o w ready to report on 4 4 ,7 9 6 m ore cases, m aking a total o f 194,304 up to Jan. 31, 1936. A series approxim ating 2 0 0,00 0 cases is sufficiently large to furnish definite in form ation. L et us analyze this series and find the danger, if any, in the adminis tration o f ethyl chloride. In 1915, w hen w e first started to use ethyl chloride fo r extraction o f decidu ous teeth, it w as em ployed in large enough quantity to produce prim ary an esthesia. W e w ere able to extract six, eight o r m ore teeth in a period o f a few
minutes. Several minutes was required fo r the patient to recover. T h is w as fo l low ed, in a large num ber o f cases, by prolon ged nausea or vom iting. T h e r e is no record o f a death or inability o f the patient to return to school or to his home. In 1923, w e began to reduce the am ount o f ethyl chloride, producin g a state o f deep analgesia rather than pri m ary anesthesia. T h e num ber o f cases o f nausea and vom iting decreased. W e fou nd that practically the same am ount o f operating cou ld be accomplished, and there w as a shorter recovery period. A s the years elapsed, the am ount o f ethyl chloride used per patient has been reduced to such an extent that rarely does an induction period last over forty to fifty seconds. T h e operating time has, o f course, been shortened, the extractions being lim ited to tw o or three teeth. R arely is there nausea o r vom iting and the recovery period is a m atter o f sec onds. Analgesia on ly is produced and no attem pt is made to produce anesthesia. Since 1932, w e have noted an interest ing phenom enon. T h ose patients oper ated on before the analgesic stage has been reached have squirm ed and some times cried or otherwise manifested signs o f pain. Investigation has proved that, ten m inutes after recovery, the child has no recollection o f the teeth having been extracted. In v iew o f these findings, I am n ow w ork in g on a technic w hereby the child can hear me talk and reacts to sugges tion, in having the tem porary teeth re m oved and yet experiences no pain dur ing the procedure. T h is technic w ill be reported as soon as a sufficient num ber o f patients have been operated on sucessfu lly to w arrant its description.
Is there an indication for the use of the newer anesthetics in the dental office? The
n ew er anesthetics are o f three
kinds: inhalation, rectal and intravenous.
Jacobs— General Anesthesia T h e inhalation anesthetics are ethylene, cyclopropane and divin yl oxide (vineth en e). Ethylene has been in use since 1923. Its explosibility is w e ll k n ow n . In order to use this gas safely, certain rules m ust be fo llo w e d . T h e hum idity o f the room must be high. T h e floor o f the operating room should be covered by a grounded m etal plate. T h e gas apparatus m ust be grounded, as w ell as the dental chair. M . H ille l Feldm an, o f N e w Y o r k , uses ethylene routinely w ith ou t these precau tions and has had no accident. H e be lieves this is due to the fa ct that the gas he em ploys is w ater w ashed. H e uses a G w a th m ey apparatus. It is o f interest to note that a num ber o f clinics and hos pitals have ethylene.
discontinued
the
use
of
C yclopropan e is also a dangerous gas because o f its intense explosibility. T h is is unfortunate, since 80 to 90 per cent oxygen can be given w ith the gas. R e laxation under its influence is marked and recovery is rapid. It m ay be used instead o f ethyl chloride in dental surgery, but its cost is m uch greater. A great deal w ill have to be kn ow n about its physio log ic action and contraindications before its use in the dental office can be co n sidered. T rib rom eth y la lcoh ol (av ertin ) is ad ministered rectally. It is a basal anes thetic, and w henever I have used it in hospital practice, nitrous oxide o r ether had to be used in supplement. It has no place in the dental office, first because o f the m ode o f adm inistration and, secondly, because o f the questionable recovery time. Som e patients may sleep fo r sev eral hours and must be under constant supervision during this time. T h is is too m uch to expect in a busy dental practice, and fo r short dental operations there are m ore advantageous anesthetics. T h e intravenous anesthetics are so
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dium amytal, evipan and thionembutal. Sodium am ytal is also a basal anes thetic. W h e n it is given intravenously in large enough dosage to produce com plete anesthesia, its m ortality rate has been high. U sed as a basal anesthetic, supplemented by nitrous oxide o r oxygen, its use has been curtailed o w in g to a de gree o f delirium in certain patients in the recovery stage. Evipan, a barbituric acid derivative, also an intravenous anesthetic, has been fou n d to be m ore satisfactory in hospital practice. R ecovery from its effect is sup posed to occu r w ithin fifteen o r tw enty minutes after its adm inistration. I have seen the recovery stage last over a period o f several hours. In one case, recovery w as not com plete fo r tw en ty -fou r hours. I f the dental office is n ot equipped to take care o f such a patient, no intravenous anesthetic is indicated. T h ion em bu ta l, w hich w ill be put on the m arket as sodium pentothal, given intravenously, is the m ost rapid acting o f this type o f anesthetic. I recently had occasion to rem ove an upper impacted third m olar under thionem butal. A s soon as a fe w drops o f the solution had been injected, the patient w as com pletely anesthetized. T h e pupils w ere w idely di lated and the pupilary reflex gone. O n injection o f a fe w m ore drops, relax ation w as so com plete that the tongue had to be held from closing the glottis. T h e anesthesia lasted fo r eight minutes, the pupils becom ing sm aller and the pupilary reflex returning as the patient recovered. A t the present time, it is a too rapid acting anesthetic to be used in a dental office, if a difficult extraction is to be perform ed. T h e re is no indication fo r the use o f any intravenous anesthetic in the office of the general dental practitioner. Asepsis must be com plete to avoid super ficial or blood infection. T h e chance o f
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an air embolus in inexperienced hands is forever present. I f intravenous anesthesia is used, a recovery room , w ith an as
the body. T h e possibility o f ether pneu m onia o r lu n g abscess must be consid ered. I f an operation is lon g enough or
sistant in constant service, must be p ro
severe enough to ju stify the use o f ether, the patient should be hospitalized. E thyl chloride is too dangerous a drug to gain com plete anesthesia. T h e m ortal ity is too high. A s an analgesic fo r ch il
vided. CONCLUSION
F o r general anesthesia in the dental office, nitrous oxide-oxygen is by fa r the m ost satisfactory o f the anesthetics. I n du ction and recovery are rapid. A l though the m argin o f safety is n arrow , nitrous oxide can be readily displaced by oxygen, since it form s a physical m ixture w ith the blood. F ran k W . R ou n ds has often stated, and ju stly so, that nitrous oxide-oxygen is practically the only anesthetic fo r w h ich w e have a specific a n tid ote; that is, oxygen. E ther affords the w idest m argin o f safety. T h e induction and recovery periods are slow . T h e dentist has neither the legal n or the m oral right to send a patient out o f the office after ether anes thesia, until it has been elim inated from
dren in m inor dental surgery, it is not o n ly safe, but also expedient. T h e dental profession has given to the w o r ld tw o anesthetics in nitrous oxide and ether that have stood the test o f tim e. O th er anesthetics have com e and gone. I f the safety o f the patient is to be considered, the n ew er anesthetics m ust be left to those m ost qualified in the field o f experim ental research. O u t o f the midst o f the present chaos, some anesthetic w ill at som e time or other stand out because o f its safety and effi cacy. U n til then, let us adhere to the o ld adage, “ Be not the first by w h om the n ew is tried, nor yet the last to lay the old aside.” 311 Commonwealth Avenue.
GENTLE M EAN S F O R R E D U C IN G FR A C T U R E B y C A R L F. M O R G E N T H A L E R , D .D .S ., H am m on d , Ind.
V E R C O M I N G m uscular antag onism is perhaps the m ost difficult problem arising in the reduction o f fractures o f the m andible. W it h o u t this problem , fracture reduction w o u ld be greatly simplified. It w ou ld be as easy as assembling the different parts o f a box that are to be nailed or glued to gether. T h e muscles o f mastication play a definite part in creating this resistance, a part w hich varies w ith the site and extent o f the in ju ry. O w in g to the posi
O
Jour. A .D .A ., Vol. 23, September, 1936
tion o f the muscle fibers, contraction or relaxation is always in the direction o f the lon g axis o f the muscle. A muscle in contracting is shortened and in relaxing is lengthened. It follo w s that the muscles w hich exert a d ow n w a rd pull on the m andible are those that are attached to the body o f this bone, and run in a d ow n w a rd direction, and that those muscles w hich exert an upw ard pull are the ones that are attached to the m an dible and run in an u pw ard direction.