General Dentistry

Subcutaneous, orbital, and mediastinal emphysema secondary to theuse of an air-ahrasive device

William H. Liebenbei^*/Bruce J. Crawford**

Abstract Subcutaneous emphysema can occur wfietiever compressed air is employedintraorally A case is presented of subcutaneous, orbital, and media.stinalemphysema subsequent to the use of an air-abrasive device. The case is believedto be the first reported case of an air-abrasive~reiated etnphysema and is presentedas a cautionary report. (Quintessence Int 1997:28:31-38.)

Introduction

The term empliysema originates from the ancientGreek and means "to blow in,"' In spite of theextensive use of compressed air in the delivery ofambulatory nonsurgicai dental procedures, the inci-dence of emp h y se matous complications in dentistry isremarkably low, A recent review of the literaturesuggests that many cases may, in fact, go unnoticed orumeported or simply misdiagnosed,- Most reports inthe literature reveal that dentists, primary care physi-cians, and emergency room physicians are unfamiliarwith empbysematous complications.

The employment of extraordinarily high-pressurizedmicroscopic abrasive powder in the newly reemergedair-abrasive technology has the potential to increasethe morbidity of emphysematous complications. Theobjectives of this article are to highlight this iatrogenicpotential and to draw the profession's attention towardtbe need for vigilance during the use of air-abrasivedevices.

" Private Practice, North Vancouver, British Columbia, Canada.

** Associate Professor, Department of Anatomy, Faculty of Medicine,UniversityofBritish Columbia, Vancouver, British Columbia, Canada.

ReptTTit requests: Dr William H. Liebenberg, Suite 201, 3609 WestviewDrive, North Vancouver, British Columbia, V7N 4M2 Canada.

Case report

A 16-ycar-old patient, in excellent health, presentedfor restorative treatment in the maxillary left posteriorsextant, Radiographic exatnination revealed a cavi-tated occlusai lesion on the first molar. Minimalcarious involvement was noted on tbe second molar,while the premolars displayed elaborate but caries-freefissures.

Restorative procedure

Subsequent to the administration of local anesthesia, aretainer was applied to the first molar, and the workingfield was isolated with dental dam through to thepremolars. Although the second molar was to beincluded in the operative effort, incomplete eruptionprecluded its use as an anchor.

The first molar was restored with a resin compositerestoration. An air-abrasive device was used to removestains and organic debris from the remaining fissuresofthe first molar and the premolars in preparation forsealant application. The isolated teeth were sealed withan opaque fissure sealant. The dental dam was removedto facilitate restoration ofthe second molar.

An air-abrasive cavity preparation system, with theair pressure set at 120 psi and the powder fiow rate athigh, was chosen as the ideal conservative means ofdebriding tbe minimal carious lesion of the second

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Fig 1 Subcutaneous left facial andorbifal air emphysema subsequenf tothe careless use of an sir-abrasivedevice. The swelling was sudden and ofa ballooning nature, concurrent with Ihebrief application of compressed air intothe area of dislolingual gingival sulcus.

Fig 2 Inlraoral view of the site of application cf oom-pressed air ¡arrow), 72 hours later Note the slightlyerythematous margin of the previously air-dissected ging-ival tissues. The tooth precluded application of a dental damretainer; consequently the choice of air abrasion wasinappropriate.

moiar in preparation for a preventive resin treatmentoption.

The 0.015-inch tip of the handpiece was inadver-tently (without ihe protection of dental dam) appliedto the area of the distolingual gingival sulcus. Thepatient moaned in discomfort as an immediate "bal-looning" ofthe patient's left facial and periorbital areawas noted. The procedure was immediately aborted,

Immediate clinical picture

The patient, in mild distress, reported moderatediscomfort across the swollen and erythematous por-tion of her face (Fig 1 ), Physical examination revealedoutright asymmetry ofthe face, complete left ptosis,and crepitus on palpation from Ihe outer canthus oftheleft eye, inferiorly along the posterior border of theramus, to the angle ofthe mandible, A diagnosis ofsubcutaneous facial and orbital emphysema secondaryto the inappropriate application of compressed air tothe gingival tissues was made (Fig 2). The patient wasassured that recovery would be uneventful and that theswelling would be expected to subside within 7 days.

The patient did not remark on any chest pain orbreathing-associated discomfort. The patient was ad-vised to avoid maneuvers that could further increaseintraoral pressure.

Nine-hour trtediastinal emphysema

The patient was admitted to the emergency departmentofa general hospital shortly before midnight that sameevening, cotnplaining of chest pain overlying thecardiac area and shortness of breath. Aside from thedental episode, the medical history was noncontribu-tory. Physical examination revealed that the patientwas afebrile but thai the subcutaneous emphysema hadnow tracked to the mediastinal tissues (Figs 3 and 4).Auscultation of the chest demonstrated inspiratorycrepitus,

Radiographic examination confirmed the presenceof mediastinal air (Figs 5 and 6), The patient wasmonitored for a few hours, reassured of recovery, andcautioned to return promptly if any fever or worseningof the symptoms developed.

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Fig 3 Diagram of the path of thecompressed air subsequent to its in-traoral application From ttie retropha-ryngeal space, the air tracks down theright and left carotid sheathes to sur-round the heart.

Fig 4 Drawing of a cross section through the level ot theC2 vertebrae showing the putative course of the air from themaxillary left second molar beneath the mucosa, betweenthe tonsilar bed and the superior constnctot on the medialside and between the tonsilar bed and the medial pterygoidon the lateral aspect, to the retropharyngeal space Theretropharyngeal space lies between the superior constrictorand the prevertebral fascia.

Fig 5 (ieñ) An te ropo s te ri or radio-graph of the thorax tai<en 9 hoursafter the initial event. This pro]ec-tion reveals that the majority of theair in the mediastinum follows thecourse of the carotid sheaths onboth the left and right sides (arrowslabeled 1).

Fig 6 (nghl) Lateral view of the thor-ax taken at the same time as Fig 5.Air can be seen in the mediastinumsurrounding the bronchi (arrowslabeled 2) and between thesternum and the heart (arrowslabeled 3). It is not possible todetermine whether the air is withinor outside the pericardial sac.

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Fig 7 Appearance o; th<j pd!iu/it 5 days after the initialepisode, Crepitus was barely palpable, vision was restored,and the swelling had diminished considerably.

Fig 8 Appearance of the patient al 7 days after theepisode. Her vision was back to normal, and her recoverywas complete Note the dramatic change from this normalview to the emphysematous episode depicted in Fig 1. Theseverityot the episode can only be fully apprécia ted when itis realized that this change was virtually instantaneous.

Recover)-

The patient continued to improve and recovered fromthe incident without any ñirther setbacks. At 24 hours,the swelling had subsided by 50%. At 5 days, recoverywas 90% complete ( Fig 7 ). The patient reported slightresidual soreness of the structures of the neck andthorax. At 7 days, the patient's vision was back tonormal, and her recovery was complete (Fig 8). Todate, at 1-year recall, no further adverse sequela havebeen noted.

Discussion

Diagnosis

A sudden facial swelling occurring during a dentalprocedure involving pressurized air is characteristic ofan emphysematic reaction. Although the diagnosis ofemphysema in this patient was straightforward, giventhe ballooning nature ofthe swelling on application ofthe air-abrasive device, an initial diagnosis of anallergic reaction to the injection of local anestheticmust always be considered when rapid onset of edemaoccurs at a site of drug administration. An anaphylac-tic reaction is a sudden, intense, allergic reaction,mediated by the immune system's release of histamineand other factors from the circulatory mast cells. Thispossibility must be foremost in a clinician's mind whenrapid edema occurs.^

The pathognomonic finding of emphysema is thecrackling sensation (crepitus) on palpation of thesubcutaneous tissues. Crepitus is not always immedi-ately evident, however, and may appear after a numberof hours.'' Although the onset of swelling is usuaUyimmediate, it may be delayed and progression mayoccur over several hours.' Mediastinal air emphysemais suggested when the patient complains of dyspneaand chest or back pain.

Physical examination will commoniy reveal Ham-man's sign—a friction rub synchronous with theheartbeat, heard on cardiac auscultation and sugges-tive of air in the pericarditmi.^ Recommended diag-nostic radiologie studies include plain radiographs ofthe chest and neck ( anteroposterior and lateralviews),' The lateral chest radiograph is often morehelpiul than the anteroposterior view because pneu-momediastinum is usually diagnosed by the demon-stration of air in the mediastinum, seen as retrostemalradioiucency.^

Treatment

Treatment for subcutaneous emphysema and each ofIts sequela should be in accordance with the severity ofthe problem. In mUd cases, simple observation andreassurance of resolution is the only treatment neces-sary because the complication normally runs a benigncourse. Measures to prevent transient increases in

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intraoral pressure, as occur with coughing, sneezing,and nose blowing, are taken; these measures includethe use of cough suppressants and decongestants.^Prophylactic antibiotic treatment, previously routinelyrecommended, is tiow beitig questioned followingHeyman and Babayofs comprehensive review,- al-though they noted that the practice should not bediscouraged and certainly would appear to be wise inthe event that aluminum oxide particles accompany theemphysematous episode. Surgical evacuation of air haspreviously been reported with temporary and incom-plete resolution.'"

As with all medicodental complications, it isimportant to fully communicate to the patient thenature of the swelling and the expected course.Although discomfort is generally slight when emphy-sema is limited to subcutaneous tissues, fltrther deeperfascial trackitig can require the administration ofanalgesics. Application of moist heat to the area ofswelling may be helpftil.* Hospitalization should beconsidered in the presence of infection, or when thereis respiratory obstruction, extreme arrxiety. and debili-tating discomfort.

Although peripheral to this discussion, the effect ofnitrous oxide is mentioned for its exacerbating poten-tial. If emphysema is detected at any stage during anoperative procedure, the use of nitrous oxide should bediscontinued because the gas will diffuse into the airspaces and increase the volume of trapped air."

Probable course ofthe air through the neck and thorax

The visceral spaces of the neck, retropharyngeal,vascular, and pretrachea! spaces are in direct com-munication with the mediastinal spaces ofthe thorax. '-Subcutaneous emphysema gaining access to the inter-stices of these connective tissue areas in the head andneck may follow tbe fascial planes, much as aninfectious process would,'^ In this patient, the air,introduced distolingually at the gingival margin proxi-mal to the second maxillary molar, dissected backwardalong the connective tissue plane between the gingivaand the hard palate, then between the bed ofthe tonsiland the superior constrictor on the medial aspect andbetween the bed ofthe tonsil and the medial pterygoidmuscle on the lateral aspect. This would then allow itaccess to the retropharyngeal space (a potential space,filled with areolar connective tissue, located betweenthe superior constrictor and the prevertebral fascia)and caudally into the carotid sheaths, which are justmedial and posterior to this region. The fact that therewas even more air adjacent to the right carotid sheath

than the left one (see Fig 5). where the technique wasperformed, suggests that the air crossed the midline,probably through the retropharyngeal space. This mayhave been a result of the extraordinarily high airpressure that was employed.

Although the sheath is thick in the carotid region,which would tend to keep the air out of the sheathitself, it is thinner near the internal jugular veins. Entrythrough the sheath could have been gained at thispoint. It was not possible, from the radiographs alone,to determine whether the air associated with thecarotid sheath was actually within this structure or justsurrounding it, although it seems likely that the airwould have remained outside the sheatb.

It was difTtcult to tell if the air surrounding the heartwas between the sternum and the pericardial cavity orwithin it (see Fig 6). If the air remained outside thecarotid sheath, the anatomy ofthis area would suggestthat it lay outside the pericardial sac. because thecarotid shealh fuses with the pericardium and theconnective tissue ofthe great vessels at this point andwould not allow the air access to the sac.

The fact that a pneumomediastinum was presentsuggests that the majority of the air lay outside thepericardial sac. If all or some ofthe air gained access tothe inside ofthe carotid sheath, it may also have gainedentry to the pericardial cavity alongside the greatvessels.

Emphysema and air-abrasive technology

Air-abrasive technology is based on the principle ofkinetic energy. Essentially, energy is related to mass inmotion. In 1945 Black,'"* in the introduction to thistechnology, wrote; "The air-abrasive process employsfor its action a very fine—almost pinpoint—stream ofcompressed air into which a suitably finely dividedabrasive agent has been introduced." As an alternativeto the slow-speed, beh-driven handpieces, this tech-nology enjoyed a brief period of popularity. The firstair-turbine handpiece. introduced in the late 1950s,soon overshadowed the early air-abrasive instru-ments,'^ and air-abrasive technology soon lost favoramong clinicians and manufacturers alike.

The adhesive revolution, with its protocol of conser-vative and less structtired cavity preparation, togetherwith the desire for more conservative and patient-friendiy treatment modalities, bas sparked a reemer-gence of air-abrasive technology.'^ Although thisnewly revived technology incorporates a number ofsophisticated and impressive technologic advances, a!lthe devices are essentially powerful sandblasters. As

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such, the technology, stripped ofthe bells and whistles,is crude, and clinicians need to be reminded that theintraorai application of compressed air is potentiallyhazardous.

All the technique manuals mention the obligatoryuse of dental dam; however, there is a noticeable lackof dentiti dam within the presentations of authors,lecturers, promoters, advertising displays, and bro-chures. This marketing proclivity lends credence to thesafety of application in the absence of dental dam.

The air pressures employed are in some cases twicethose delivered to a high-speed handpiece (up to 160psi). Although there have been reporis of subcuta-neous emphysema following the intraorai use of anair-water syringe," we, as a prolession are generallycomfortable utilizing compressed air from this source.The pressure delivered by an air-abrasive device isreadily grasped when a medium-sized latex glove isinflated; it takes a mere 3-second burst of an air-abrasive device set at 120 psi to inflate a glove. Someproduct brochures exult in their maximal air pressurereadings and equate "higher pressure = faster cuttingwith less mess,"'^ It has recently been suggested thatadhesive bond strengths with air abrasion at 160 psi aresimilar to those obtained with acid-etching alone, '''•-'̂ Itseems inevitable that ñiture modules will be releasedwith pressures that exceed even the current median120 psi.

The morbidity associated with emphysema is pro-portionate to the amount and pressure of air deliveredto the soft tissues. It air is forced into the tissues,recovery is generally uneventful, even when the air isspread via fascial tissue planes to other anatomic sites,such as the mediastinum or thorax. However, althoughthere are many reports of dental emphysema, therehave been no documented cases associated with airabrasion. One can only but speculate as to the scenarioshould, for example, a gram of aluminum oxideparticles be blasted into tbe postseptal or retrobuibarorbital space. In this case, although the application ofair was careless, aluminum oxide particles were notdelivered with the compressed air.

Causative factor

Although the senior author fully acknowledges hiscareless application, the following "explanation" isincluded as a cautionary narrative for clinicians.

All the available units, with the exception of one,utilize an electromechanical two-stage foot control.The first contact position ofthe foot switch activatesthe air fiow (without aluminum oxide particles).Aluminum oxide and air can only be delivered when

the foot switch is depressed fully to the second stage.This iwo-stage mechanism prevents the inadvertentdelivery of powder, should the foot switch be acciden-tally depressed, (Incidentally tbis is a fairly commonoccurrence in modern operatories, where a number ofunrelated foot controls are situated side by side,)

Additional built-in protective designs reside in thecontrol panel, where a standby/ready touch pad allowsactivation following the appropriate selection of fiow,pressure, and nozzle-size parameters. However, in theauthors' opinion, a design fault allows tbe delivery ofcompressed air even if the powder rate bas not beenselected. Consequently, in the case reported, a powderrate was not selected, the tip of the handpiece wasplaced proximal to the minimally carious occlusa!lesion, and the foot switch was depressed to the secondposilion (to activate air and abrasive pariicles). Airwas delivered, but no tooth abrasion was noted, so thefoot switch was then lifted to the first position and thecontrol panel was checked. It was during this proce-dure that tbe tip ofthe handpiece was inadvertentlymoved off the occlusal surface ofthe tooth adjacent tothe distolingual gingival tissues. Air continued to bedelivered at 120 psi, dissecting the tissues and causingthe sudden emphysematous episode.

The manufacturers' motivation for permitting airflow without powder has been to permit cleaning ofthecavity preparation. A newly released air-abrasivedevice does away with the two-stage foot control butincludes an additional 1,5-second continuous air fiowafter the foot control has been deactivated. This ispotentially hazardous, because operators tend to liftthe handpiece oif the tooth surface as the abrasive fiowis terminated.

Clinicians must be cognizant ofthe fact that the airpressure (up to 120 psi) is still being delivered oncethe foot pedal is deactivated. The bandpiece nozzlemust be kept away from soft tissue at all times.

Higher air pressures a change in prognosis?

Cervicofacial, retropharyngeal, mediastinal, and thor-acic emphysematous complications originating in theoral cavity of dental patients are, for the most part,self-recovering, A reasonable concern for clinicians isthe danger of upper airway obstruction. Study ofthereported cases to date indicates that air dissectionpreferentially takes place along loose, low-resistancestructures and not the relatively tight subtnucosa oftheglottis and trachea. The operative air pressures in-volved in previously reported episodes have been inthe range of 40 to 80 psi, well below the 160 psi now

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suggested for adequate air-abrasive "etching" of toothstructure,-" The sudden ballooning response wit-nessed in the patient in the present case report bearstestimony to the potentially devastating sequela to theinappropriate use of devices with extraordinarily highair pressure, Tlie tissue dissection may not necessarilyfollow the path of least resistance, as it has with lowerpressures In the past. Air may accumulate in sites thatcould be life threatening, requiring drainage pro-cedures.

In addition, it is relevant to note that 45X of patientswith subcutaneous emphysema develop emphysema ofthe periorbital subcutaneous tissue,- This distributionand occurrence has previously been reported to beunrelated to the location or nature of the dentaltreatment,- The first report-̂ of partial blindnesssecondary to iatrogenic subcutaneous emphysema hashighlighted the seriousness of this complication,because the optic nerve has little regenerative poten-tial. The external compression ofthe eye can result intransient hypoperfusion of the central retinal arteryand its arteriolar branches. Higher air pressuresassociated with preseptal lid edema may lead tofractures of the periorbital sinuses and increasedcompression ofthe eye.

Prevention of air emphysema

Clinically, these air-abrasive devices are most suitablefor minimally carious, noninvasive preventative resin-type situations. Given the paucity of dental dam usewith extensive restorative procedures, it is unlikely thatdental dam will routinely accompany the employmentof this technology. Without dental dam, vision islimited, particularly in the maxilla, because the mirrorhas to be kept at a distance to prevent scouring ofthereflective surface from the action of the ricochetedaluminum oxide particles. Ideally, dental dam shouldbe a prerequisite for the selection of an air-abrasivemethod of cavity preparation, particularly if an ad-hesive restorative option is proposed. The followingcautionary guidelines are appropriate for all clinicalprocedures utilizing compressed air, given the extra-ordinarily high pressures that accompany air-abrasivetechnology:

1, The appropriate operative access should be estab-lished to permit complete visualization ofthe tip ofthe handpiece at all times,

2, Dental dam should be used whenever operable.3, Control panel selections should be completed

before the handpiece is positioned within theoperative field.

4, Correctly tightened matrix bands should be usedwhen interproximal tooth substance is cut, Atissue-displacing instrument (Zekrya, Maillefer.Caulk/Dentsply) designed for cervical retractionmakes for an ideal shield for treatment of Class Vlesions and defective gingivally located resin res-torations,

5, The handpiece must never be directed at softtissues, even for a brief period of time,

6, The compressed air (first stage ofthe foot control)must never be used to clean the cavity or workingfield,

7, The air-abrasive device must never be directed intothe floor of a cavity when the pulpal tissues aresuspected to be patent because an air embolusfatahty has been reported following the use ofpressurized air during an endodontic procedure,^'

Finally, manufacturers are encouraged to review theneed for air flow without powder designed in thetwo-stage foot control.

Conclusion

A case detailing the consequences of careless andinappropriate application of an air-abrasive device, hasbeen reported, It is hoped that the incident will serve tohighlight the iatrogenic potential and reirtforce themanufacturer's instructions regarding the correct andappropriate use of air-abrasive technology Although itwould be foolish to discontinue use of this serviceabletechnology, or any dental modality that introduces airinto the mouth, the potential for emphysema must beconsidered at all times when an instrument withpressurized air is used intraorally.

Application criteria must always be judiciouslyfollowed, particularly when devices with extra-ordinarily high air pressure are used. The reportedincident has been the only complication encounteredduring 24 months of routine use ofthe air-abrasivedevice.

AcknowledgmentsThe authors express appreciation to Dr Barry Irish for his radiographieinterprétai ion and to Ms Marsha Mabluve for the lilerary searehes.

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38

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