Oral and Maxillofacial Aspects of Diving Medicine

Transcription

1 MILITARY MEDICINE, 169, 2:137, 2004 Oral and Maxillofacial Aspects of Diving Medicine Guarantor: LT Matthew T. Brandt, DC USNR Contributor: LT Matthew T. Brandt, DC USNR Sport diving has witnessed explosive growth in the past decade, as 8.5 million people are certified in the United States alone. Even though scuba diving is a relatively safe sport, there are serious risks that all divers must consider. Beyond the better-known sequelae such as decompression sickness, middle ear dysfunction, and potential central nervous system effects, scuba diving also carries inherent risk to the maxillofacial region. Atypical facial pain, temporomandibular joint dysfunction, sinus barotraumas, and barodontalgia have all been reported by dentists and physicians treating military, commercial, and sport divers. Additionally, clinicians must address anatomic concerns for would-be divers, including cleft lip and palate, edentulism, or patients with pre-existing temporomandibular dysfunction, midfacial trauma, or craniomaxillofacial surgery. Health care professionals should have a thorough understanding of the implications of scuba diving for consultation and recommendation regarding diving fitness and the treatment of adverse effects of scuba diving to the maxillofacial region. Introduction he invention of the self-contained underwater breathing apparatus (SCUBA) in 1948 enabled numerous sport enthusi- T asts to venture into the depths of the ocean. It is now estimated that scuba diving is one of the fastest growing sports as 8.5 million people in the United States and 15 million people around the world are currently certified in scuba diving. Along with this explosive growth has been a resulting increase in the number of diving accidents and injuries. Any sport carries risk and scuba diving is not without exception. The majority of diving injuries can result from the potential toxic effects of the inhaled gas, the mechanical effects from changes in ambient pressure, decompression sickness (DCS), equipment noncompatibility or malfunction, or anatomic characteristics that predispose divers to increased risk of injury. In addition to the well-known complications such as DCS, middle ear dysfunction, and potential central nervous system effects, maxillofacial sequelae such as atypical facial pain, temporomandibular dysfunction, sinus barotrauma, and cranial nerve injury have been reported by health care providers treating sport and commercial divers. Many injured divers seeking care at emergent facilities will require consultation for the examination and treatment of the oral cavity, temporomandibular joint, and the paranasal sinuses. This study provides a comprehensive review on the pathophysiology of scuba diving as it relates to dentistry and diving medicine and provides recommendations for the examination and treatment of maxillofacial injury from scuba diving. Division of Oral and Maxillofacial Surgery, University of Kentucky, D-512 Chandler Medical Center, College of Dentistry, Lexington, KY This manuscript was received for review in January The revised manuscript was accepted for publication in May Reprint & Copyright by Association of Military Surgeons of U.S., Barotrauma Physiology To accurately diagnose and treat oral and maxillofacial complications associated with scuba diving, it is important for clinicians to have a solid background in diving medicine and physiology. 1 The majority of diving pathology is related to the result of barotrauma or tissue damage resulting from changes in the volume of gas (air) spaces due to the changes in ambient pressure. 2,3 Pressure is the amount of force applied per unit area. 2 Pressure units commonly found in diving include pounds per square inch (psi), kilograms per square centimeters (kg/cm 2 ), atmospheres (atm), and millimeters of mercury (mm Hg). Atmospheric pressure is the amount of force or pressure exerted by the earth s atmosphere. At sea level, it is equal to 14.7 psi, 760 mm Hg, 1.03 kg/cm 2, or 1 atm. This becomes the standard 1 atm or absolute pressure (1 ATA). 2,4 Because pressure changes in water are linear, ambient pressure increases by 1 atm for each 33 feet of sea water depth (10.23 m) or 34 feet of fresh water depth (10.54 m). Thus, the pressure at 33 feet of fresh water is 2 ATA, at 66 feet is 3 ATA, and so forth. 2,4 Divers balance this increased pressure on descent by breathing air delivered at a new ambient pressure and by equalizing the pressure in all gas-containing body cavities to ambient pressure. 4 Boyle s law states that at a constant temperature, the volume of a gas (air) varies inversely with the pressure. Thus, as a diver descends to a depth of 33 feet of fresh water or 34 feet of fresh water, his or her lung volume is compressed to one-half of its original volume. This volume will expand to its original volume as the diver ascends or decompresses. 2,4 However, when divers inspire compressed air from the regulator at ambient water pressure, the volume of air remains the same as it was on the surface. 2,4 Scuba divers will have to expire one total lung volume of air to account for this re-expansion. 2,4 Barotrauma results when divers fail to equalize the pressure within aircontaining spaces either during descent (compression) or ascent (decompression). 2 Barodontalgia Barodontalgia refers to dental pain resulting from environmental pressure changes. This symptom was originally known as aerodontalgia or flyer s tooth, and was used almost exclusively in describing the pain experienced by pilots in unpressurized cockpits during the early 1940s. 4 7 Although uncommon, incapacitation of pilots and divers from this pain has stimulated continued research into barotrauma to the dentition, which has been reported to occur in aviators from an altitude of 3,000 m (0.75 atm) and in divers at 10 m (1 atm). 5 Certain generalities have been accepted to assist in the diagnosis of barotraumas; posterior teeth are more frequently involved than anterior teeth, maxillary teeth are more frequently involved than mandibular teeth, and restored teeth are more likely to be involved than those that are unrestored. 5 However, 137

2 138 Oral and Maxillofacial Aspects of Diving opinions differ regarding the precise mechanism for pain production in barodontalgia. Previous studies have supported theories involving trapped gases, low temperature, pulpal embolism, prolonged vasoconstriction, dentinal tubule permeability, impacted teeth, recent extractions, recent restorations, the effect of pressurized oxygen, recurrent caries at restorative margins, periodontal disease, and microleakage of restorations Although the precise mechanism has not been determined, the most significant factor throughout the literature is exposure to altered atmospheric pressure coupled with the pathological condition of the pulpal tissues. Based on clinical and radiographic evaluation and a review of the symptomatology, Ferjentsik and Aker 12 proposed a classification system for barodontalgia (Table I). Proper diagnosis of barodontalgia must first rule out sinus barotrauma, which should be included in the initial differential diagnosis. This type of barotrauma is discussed later in this study. Once barodontalgia and its specific type have been properly diagnosed, treatment is aimed at the removal of caries, diseased pulp, or extraction of teeth that cannot be restored or maintained periodontally. Odontocrexis Odontocrexis refers to the physical disruption of teeth during diver descent or ascent. Anecdotal reports of teeth shattering or fracturing during diving have been supported by in vitro investigations. 1 Calder and Ramzey 21 found that teeth with inferior quality restorations suffered significant tooth damage on decompression when compared with unrestored teeth either with or without caries. Fracture of porcelain bonded to metal due to air trapped at the porcelain/metal interface has been reported in divers as well as fracture of teeth undergoing endodontic therapy. 12,13 Atmospheric changes may also be responsible for a significant reduction in crown retention due to negative pressure effects on microbubbles in dental cements. In a recent study, Lyons and Rodda 5 cycled teeth to 3 atm in a simulated diving experience to study the microleakage of three different cements and the retention of full cast crowns. Their results suggest that the occurrence of microleakge and the reduction in the retention of crowns luted with zinc phosphate and glass ionomer cements after environmental pressure cycling may present clinically as barodontalgia before crown debonding. 5 Weakened cement secondary to porosities introduced during mixing, microcracks resulting from volumetric contraction, or internal stress may have led to the physical disruption of the cement, thereby allowing microleakage and subsequent crown loss. 5 Resin cements were unaffected, possibly as a result of dentinal tubule obstruction by resin tags or cement flexibility and, thus, have been advocated for use in patients who anticipate exposure to marked variation in atmospheric pressure, such as scuba diving, soon after crown or restoration cementation. 5 Cranial Nerve Injury Neurological sequelae of sinus barotrauma include cerebral emphysema, blindness, pneumocephalus, and cranial nerve involvement. 22 Cranial nerve injury, usually neuropraxia, causing sensory or motor deficits are extremely rare. The anatomic location of the maxillary branch or second division of the trigeminal nerve and the facial nerve predispose them to barotrauma since they travel within the bony walls of air-filled cavities. The maxillary branch of the trigeminal nerve enters the orbit via the infraorbital fissure and continues as the infraorbital nerve in the infraorbital groove in the orbital floor. A thin plate of bone and the Schneiderian membrane separates the nerve at this point from the maxillary sinus. The infraorbital nerve gives rise to the middle superior alveolar branch and the anterior superior alveolar branch, providing sensation to the conjunctiva and skin of the lower eyelid, the skin of the alar portion of the nose, and the skin and mucous membranes of the cheek and upper lip. Neuropraxia results from edema in exposed nerve sheaths secondary to negative pressure changes in the maxillary sinus. 20,23 Positive pressure changes may cause ischemic neuropraxias as venules draining the exposed nerve become obstructed. 20 Similarly, middle ear space overpressure can cause compression of the horizontal portion of the facial nerve as it TABLE I PROPOSED SYSTEM OF CLASSIFICATION OF BARODONTALIGIA 12 Class Chief Complaint Clinical Findings Diagnosis Treatment I Sharp momentary pain during ascent (decompression); asymptomatic on descent (compression) and afterward. Caries or restoration with inadequate base Tooth is vital Acute pulpitis Temporary restoration followed by permanent restoration. Endodontics if irreversible. II III IV Dull throbbing pain during ascent (decompression); asymptomatic on descent (compression) and afterward. Dull throbbing pain during descent (compression); asymptomatic on ascent (decompression) and afterward. Severe persistent pain after ascent (decompression); or descent (compression). Deep caries or restoration Tooth is vital/nonvital Caries or restoration Tooth is nonvital Caries or restoration Tooth is nonvital Chronic pulpitis Necrotic pulpitis Periapical abscess or cyst Root canal therapy or extraction of unrestorable tooth. Root canal therapy or extraction of unrestorable tooth. Root canal therapy and/or surgery or extraction of unrestorable tooth.

3 Oral and Maxillofacial Aspects of Diving courses along the medial portion of the middle ear in individuals with an anatomic variant of a dehiscent bony facial nerve canal. Farmer 24 suggests that middle ear overpressure during ascent may also result in gas bubbles entering a nondehiscent facial nerve canal via the canal of the chorda tympani nerve, resulting in facial nerve paresis. Divers experiencing cranial nerve neuropraxias may complain of unilateral parasthesia of the upper lip, teeth, and cheek. 20,23 These symptoms, along with facial nerve paresis in facial nerve neuropraxias, all have been reported to resolve spontaneously without recompression. Treatment should rule out neurological DCS and provide palliative care. Cases with concomitant chronic sinusitis should be treated appropriately. Paranasal Sinus Barotrauma Barotrauma to the paranasal sinuses is a known risk for all divers due to their repeated exposure to changes in barometric pressures It is the second most common complication of sport SCUBA diving after middle ear barotraumas. 2 Equalization of the paranasal sinuses requires normally functioning nasal passages and patent ostia. Obstructions, including deviated nasal septum, polyps, mucosal thickening, mucous plugs, or purulence, may lead to sinus barotraumas Paranasal sinus barotraumas occurring on descent, commonly referred to as sinus squeeze, often involves the frontal and maxillary sinuses as the pressure differential between the sinuses and ambient pressure increases. 31,32 In a review of 650 SCUBA divers, Roydhouse 9 found that 6.6% of all acute head and neck sequelae from barotrauma was sinus related. Fagan et al. 33 reported that most symptoms are from the frontal sinus barotraumas even though the maxillary sinus displays the most significant changes radiographically. The most common symptoms are severe pain over the affected sinus and limited epistaxis. 2 The sinus mucosa may become edematous and hemorrhagic Immediate treatment consists of ascending to a depth at which relief occurs and equalization is possible. 2 A dull ache may persist after equalization. Divers should be instructed not to resume diving until hematomas resolve, symptoms no longer persist, and concomitant sinus infections are appropriately treated. 32 Confirmation of treatment success should include both physical examination and radiographic evaluation. 31 Yanagawa et al. 31 confirmed that divers have a tendency toward paranasal sinus hypertrophy following repeated barotraumas as evidenced on computed tomography. Thus, acute mucosal hypertrophy secondary to sinus barotraumas may be difficult to discern without baseline radiographs or computed tomography. Additionally, asymptomatic mucosal thickening is common in the general population. 31 Paranasal sinus barotraumas on diver ascent, referred to as reverse sinus squeeze, can also occur if ostia are obstructed Although symptoms will parallel that of barotraumas on descent, cranial nerve neuropraxic injury, namely parasthesia, may occur. Treatment consists of diver descent to a depth of relief and slow ascension. 32 Palliative care is usually adequate. Brown et al. 34 showed that 75% of individuals benefit from medications before SCUBA diving. Decongestants, inhaled antiinflammatory agents, and/or antibiotics may be indicated before planned dives for prophylaxis and treatment of chronic sinus inflammation and infection. Face Mask Squeeze Unless divers expel gas through their nose into the mask on descent, negative pressure builds within this enclosed space. 32 The increasing pressure can result in eyelid edema and subconjunctival hemorrhage. 32 Treatment is symptomatic. Traumatic hyphema, a more serious injury, can occur if a diver becomes unconscious and descends to a much greater depth without retaining the ability to equalize the mask. 32 Diagnosis and treatment of this condition has been thoroughly discussed in the literature. 35 Decompression Sickness DCS occurs when gases, such as nitrogen, dissolve into body fluids and come out of solution as the partial pressure decreases on ascent. Divers must follow decompression tables on ascent to prevent DCS. Joint pain, or the bends, is the most common presentation of DCS (60% 75%). 32 Joints of the shoulder, knees, and elbows are commonly affected. No cases involving the sternum, spine, or cranium have been reported. 32 Dysbaric Osteonecrosis Dysbaric osteonecrosis of bone involves gas emboli obstruction of end vessels of the vascular supply ultimately leading to infarction. 36 Considered a late complication of DCS, dysbaric osteonecrosis is probably caused by repeated exposure to increased pressure, insufficient decompression on ascent, or inadequate treatment of decompression illness. 36 The concept of avascular necrosis (AVN) or aseptic necrosis is a well-known entity in orthopedic surgery. 37 It most commonly occurs in the anterolateral aspect of the femoral head. Systemic factors increasing the risk of AVN include alcoholism, gout, steroids, sickle cell disease, trauma, and Caisson s disease. 37 Factors that compromise intramedullary blood flow or venous outflow such as edema, fat accumulation, infection, hematoma, and nitrogen gas bubbles secondary to DCS can also compromise bone viability. 37 Although AVN secondary to dysbaric injury has been reported in the orthopedic literature affecting the shoulders, hips, and long-shafted bones, no report of dysbaric osteonecrosis of the mandible or maxilla has been documented. As AVN of the mandible, specifically the condylar head, is being studied further, principles of pathogenesis and treatment of AVN in other bones must be studied and reconciled to AVN of the mandible. 37 Atypical Facial Pain and Temporomandibular Dysfunction 139 Headache and facial muscle pain is common among divers as they are required to maintain the mouthpiece of the regulator in position to facilitate proper gas exchange These neoprene or silicone rubber mouthpieces are isometrically held in place by an interdental bite platform that fits into incisor and canine occlusion and have labial flanges to aid in lip seal To ac-

4 140 Oral and Maxillofacial Aspects of Diving complish proper position of the mouthpiece, the mandible, in most cases, must be postured anteriorly. This activity increases uneven loading of the temporomandibular joint (TMJ) by creating a lack of posterior support of the dentition Most recreational dives last at least 30 minutes, and most divers perform several dives in a day. The regulator and mouthpiece are also of significant weight and bulk to the anterior teeth. 38 This, along with the potential for gingiva and mucosa trauma from the mouthpiece flange, can lead to pain in the masticatory musculature and TMJ, termed diver s mouth syndrome. 40 Additionally, mandibular-deficient patients with a deep class II malocclusion may have an increased risk of pathological TMJ loading during the posturing required to maintain the mouthpiece. 17 For all divers, muscular fatigue is common, exacerbation of preexisting temporomandibular dysfuction (TMD) is probable, and divers without previous symptoms may develop symptoms characteristic of TMD TMJ pain from repeated mouthpiece use is commonly mistaken for the inability to equalize ear pressure. However, TMJ pain will persist even when the diver returns to the surface while ear pain usually subsides Treatment for diving-induced or diving-exacerbated TMD should follow normal TMD protocols of conservative therapy before any surgical intervention. Prevention or decrease of masticatory or TMJ pain during SCUBA diving includes the creation of a more ideal mouthpiece design. Newton reports that the preferred mouthpiece design should have bite platforms that include the premolar and molar dentition and be at least 4 mm of thickness. 42 Also, they suggest that mouthpieces should have extended labial flanges posteriorly to the molars to improve retention and seal and be fabricated to each diver s normal occlusal relationship, occlusovertical dimension, and freeway space. 40 Several reports document custom mouthpiece design and list companies that fabricate custom mouthpieces and stock mouthpieces that are constructed with the TMJ and masticatory muscles in mind The Edentulous and Partially Edentulous Diver Diving with complete or partial dentures is extremely dangerous and should be avoided at all costs. 43 Complete dentures and more commonly partial dentures due to their smaller size can become dislodged during a dive and pose an immediate threat for aspiration. Stein 43 reported on a recreational diver who, during diving class in a pool, was found at the bottom of the pool and later pronounced dead from asphyxia due to airway obstruction from a maxillary complete denture. Custom mouthpieces, albeit more expensive, can be fabricated to be retained by the edentulous arches so the risk of aspiration of a dislodged prosthesis is eliminated. Patients with implants do not have an increased risk, unless their fixed prosthesis is loose or not maintained properly. Because osseointegrated implants are solid, they are not at risk for volumetric expansion or contraction under Boyle s law. However, patients with fixed-removable prosthesis, such as a Hader bar-retained mandibular complete denture, should follow the guidelines for removable prosthesis because dislodgement is still possible. Diving with a Cleft Lip and/or Palate Divers with previously repaired cleft lip and/or palates can have difficulty with equalization of their middle ears and air management with the regulator and mouthpiece. 44 Specifically, would-be divers with surgically corrected palates may experience difficulty in breathing through the mouth only without taking in water through the nose. A short, hard palate may not allow a diver the ability to create an adequate seal between the nasophaynx and the larynx by elevating their tongue to the posterior aspect of the hard palate when attempting to breathe through the mouth only. Clinicians should also inquire whether patients with concomitant nasoalveolar clefts and or fistulas have sought surgical repair. A mobile premaxilla will compromise mouthpiece retention, and an unrepaired fistula can potentially compromise airway management with reflux. Additionally, some individuals may not be able to clear their ears with a typical Valsalva maneuver to equalize ear pressure. Such patients should have a thorough physical evaluation to determine the degree of eustachian tube and nasopharyngeal dysfunction as well as any possible choanal atresia before beginning diving instruction. Diving with Fixed Orthodontic Appliances Normal commercial mouthpieces prohibit use with most fixed orthodontic appliances. Jones and Graham 45 describe a method for custom fabrication of a mouthpiece made for a 15-year-old trainee diver who lost bonded brackets after attempting to use a normal mouthpiece. They found that three other trainees could also use this custom mouthpiece of simple design and fabrication as air sharing is a crucial safety procedure used in diving emergencies. 45 Absolute Contraindications to Dive There are few absolute contraindications to scuba diving with regard to the oral and maxillofacial region. Generally speaking, any osseous or soft tissue defect after surgery of the head and neck, which may prohibit adequate face mask or mouthpiece fitting should be thoroughly evaluated before diving. For example, an untreated depressed zygomaticomaxillary complex fracture may prevent the patient from achieving a watertight face mask seal. Additionally, osteomyelitis and osteoradionecrosis are absolute contraindications. These conditions may predispose divers to tissue emphysema during descent or ascent. 2 Divers should also not be at risk for aspiration of any severely mobile teeth secondary to advanced periodontal disease. Conclusion Professional divers, including military, civil engineering, scientific, law enforcement, and remunerated instructors for amateurs must adhere to specific medical and dental guidelines as set forth by the Occupational Safety and Health Administration and their governing agencies. Divers requiring medical certification or injured divers seeking care at emergent facilities may require specific treatment of the oral cavity, TMJ, and the paranasal sinuses. Health care professionals should have a working knowledge of oral and maxillofacial aspects of diving.

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