Since the advent of self-contained underwater breathing apparatus (SCUBA) in the middle of the 20th century, many of the known in-flight oral phenomena caused by atmospheric pressure changes have been described in association with diving as well.
Owing to the overwhelming popularity of scuba diving, general dental practitioners should be prepared to address complications arising as a result of diving and to provide patients with accurate information, much of which currently comes from Australia and New Zealand. However, due to a paucity of data from diving related conditions, many conventions of barometric effects on oral tissues are derived from in-flight observations, mostly in the military setting.1 The aim of this article was to introduce the concepts of diving medicine and dentistry to the dentist, and to supply the dental practitioner with some diagnostic tools as well as treatment guidelines.
Head and face barotrauma
According to Boyle’s Law, the volume of gas at constant temperature varies inversely with the surrounding pressure. The changes in gas volume inside the body’s rigid cavities, associated with the changing atmospheric pressure, can cause several adverse effects, which are referred to as barotrauma.2 Barotrauma can occur during diving, flying, or hyperbaric oxygen therapy.
Head and face barotrauma include the entities of barotitis, barosinusitis, barotrauma-related headache, dental barotrauma and barodontalgia. The first three entities are briefly discussed here (with reference to other texts),1,3 and the latter two will be discussed extensively.
Barotitis-media (also known as middle ear barotrauma and ear squeeze) is an acute or chronic traumatic inflammation in the middle ear space produced by a pressure differential between the air in the tympanic cavity and that of the surrounding atmosphere.4 The symptoms of barotitis-media range from ear discomfort to intense earache, tinnitus, vertigo with nausea, and hearing loss.2 Upper respiratory tract infection may impair the equalizing function of the Eustachian tube, thus predisposing the individual to barotrauma, and may be a (temporary) contraindication for diving.4 A potential complication is facial palsy secondary to middle ear barotrauma (also called facial baroparesis), caused when elevated pressure from the middle ear is transmitted to the facial canal via dehiscence within its course along the medial wall of the middle ear or via the fenestra of the chorda tympani, resulting in ischaemic neurapraxia of the facial nerve. This phenomenon usually occurs only on a single episode, even in those who have been recurrently exposed to similar barometric conditions.5 The condition is unilateral, occurring during or soon after diving ascent, with the possible involvement of facial expression muscles and taste sensation from the anterior tongue. Spontaneous resolution usually occurs within a short time (minutes to hours), as blood flow rapidly resumes when pressure in the middle ear becomes less than capillary closing pressure.6
Several reports have claimed that a relationship exists between dental malocclusion and Eustachian tube dysfunction.7 A dental splint was offered as a preventive and/or therapeutic measure for barotitis-media.8,9 Currently, barotitis-media is usually not considered an indication for a dental splint.
Barosinusitis (also known as sinus barotrauma and sinus squeeze) is an acute or chronic inflammation of one or more of the paranasal sinuses, produced by the development of a pressure difference (usually negative) between the air in the sinus cavity and that of the surrounding atmosphere.4 The pressure gradient created results in a vacuum, which may cause mucosal oedema, serosanguinous exudate and submucosal haematoma. These ailments may consequently cause pain, sometimes abrupt and severe, and possibly epistaxis. Palsy may occur as a result of ischaemic neurapraxia of branches of the trigeminal nerve in the maxillary sinus. The incidence of barosinusitis during diving descent is about double that during ascent.
Barotrauma-related headache of 15–20 minute duration was reported during ascending and descending.10 In an Israeli study, Potasman et al.11 reported flight-associated headaches in 5.7% of air-travellers, rated as 6 on a 1-to-10 severity scale (with 10 the most severe pain). Distribution between unilateral and bilateral headache was almost equal, and about one-fifth of these headaches were diagnosed as migraine. Indeed, weather (e.g. rain, high humidity, bright sunshine) and barometric changes (e.g. on-ground low barometer reading and falling barometer) are often considered as major headache triggers by migraineur patients.12
Barometric-induced otitis-media, sinusitis or headache can be manifested as pain to the oral region (indirect barodontalgia).13 Thus, they should appear in the differential diagnosis of dental pain that is evoked during diving. Since otalgia while diving is the most common complaint of scuba divers and almost every diver suffers from it,14 the dental practitioner must rule out an extraoral origin when diagnosing oral pain. This must be taken into consideration especially in higher risk patients (e.g. recent upper respiratory infection or corrected cleft palate with Eustachian tube dysfunction). Moreover, other diving-associated headache conditions must be ruled out. These include tension-type headache due to muscle strain and rigidity, and a manifestation of carbon dioxide toxicity, which is a common diving related condition caused by hypoventilation (e.g. infrequent and shallow breaths).15 Headache may also be a manifestation of decompression sickness (DCS), in which rapid ascent with rapid decompression allows the discharge of dissolved nitrogen and the creation of gas bubbles with potentially severe consequences in various body organs (e.g. joint pain, skin rash, itching, dizziness, nausea, vomiting, tinnitus and fatigue).15,16
In non self-resolving cases of facial baroparesis, the clinician should rule out DCS, and then treat by steroid administration. However, despite the common wisdom among diving medicine practitioners ‘when in doubt – recompress’, treatment for DCS by recompression/hyperbaric chamber while there is Eustachian tube dysfunction (which is the true causative for the baroparesis) may worsen symptoms.
Dental barotrauma can manifest as tooth fracture, restoration fracture (both will be referred as dental fracture), and reduced retention of dental restoration. Other than need for dental treatment, potential consequences include aspiration or swallowing of the dislodged restoration or dental fragment,17 and pain, which may lead to incapacitation while diving and premature discontinuation of the planned dive.3
The term barodontocrexis (barometric-induced ‘tooth explosion’, Greek) describes the phenomenon of dental fracture.3,18 Most of the reports regarding dental fractures under barometric changes considered in-flight conditions and were published several decades ago.3 Dental barotrauma occurs while ascending; upon surfacing after completing the dive, the diver may report that a tooth broke or has shattered.19 Dental barotrauma can appear with or without pain20 similar to dental fracture occurring at ground level.
In a 10-year longitudinal study that was conducted in the German navy, there was a four-fold increase in missing teeth and a 10-fold increase in crown placement among navy divers, who were constantly exposed to barometric changes (200–300 annual hours of underwater diving), in comparison to an almost three-fold increase in missing teeth and a five-fold increase in crown placement among submariners who usually served under normal pressure conditions.21 These authors concluded that increased exposure to barometric stress was associated with elevated dental deterioration.22 In a recent survey among 125 Australian divers, Jagger et al.23 reported one diver who experienced tooth shattering and two divers who experienced restoration displacement during diving. The authors concluded that dental barotrauma was uncommon and was reported by less than 1% of the divers.23 However, since no data of time length of participants’ diving experience was reported, no further conclusions can be made from these results.
Calder and Ramsey18 reported on an in vitro decompression study on extracted teeth. They applied a pressure drop of 1035 kPa (approximating a common diving pressure) to ground atmosphere pressure within two minutes on 86 extracted teeth. Five of the teeth studied were damaged. All the damaged teeth had either poor-quality amalgam restorations with undesired clearance between the tooth and the amalgam or secondary caries under the restoration. The 81 non-damaged teeth included unrestored teeth with carious lesions. The authors concluded that the main predisposing factor for tooth fracture was leaking restoration rather than caries.
The predisposing factors that appeared repeatedly in dental barotrauma reports were pre-existing leaked restoration and/or occult remaining/recurrent caries lesions underneath restoration in the affected tooth prior to exposure to the barometric changes. Although the destructive potential of arrested or remaining carious lesions in daily life is minimal, it seems that these lesions may not be as innocent in a pressure-changed environment. Nevertheless, recently Gunepin et al. reported a unique case of fracture of previously intact molar during flight.24
Pressure changes in micro air bubbles in the cement layer underneath crowns can lead to a significant reduction of the prosthetic device’s retention and even to dislodgement, especially if the crown was cemented with zinc phosphate cement.25,26 Lyons et al. studied the effect of cycling environmental pressure changes (up to 3 atm) on the retention of crowns to extracted teeth. The crowns that were cemented with either zinc phosphate cement or glass-ionomer cement had significantly reduced retention (in approximately 90% and 50% of cases, respectively), whereas crowns that were cemented with resin cement did not have reduced retention after pressure cycling.25 This may be attributed to porosities generated during the preparation of zinc phosphate cement and glass-ionomer cement, and the expansion and contraction of these microbubbles upon pressure changes cause weakening of the cement. Indeed, microleakage was detected in the zinc phosphate and glass-ionomer cements after pressure cycling, whereas no microleakage was detected in the resin cement,26 probably owing to dentinal tubule obstruction by resin tags or cement flexibility.27 In the aforementioned survey of 125 Australian divers, no diver reported loosening of a crown or bridge occurring during diving.23
Although reduced barometric pressure can impair the retention of full removable dentures (especially maxillary dentures),3 this consequence has only been observed in flight conditions.
The dentist should carry out preventive measures and periodically examine his or her patients who dive and search for occult pathologies, such as leaked restorations and secondary caries lesions.
For prevention of dislodgement and aspiration, patients should be advised not to dive while having provisional restorations or temporary cement in the mouth. Resin cement should be used when treating patients who are subjected to pressure changes. Since dislodged partial removable prostheses could be accidentally aspirated during diving (with one reported case of resulting death),19 these devices should be removed before diving, unless they are securely retained. Retention by adequate osteointegrated dental implants is probably the best resolution for edentulous divers. Alternatively, a ‘custom edentulous mouthpiece’ which combines a mouthpiece with a prosthesis, may be offered.28
Barodontalgia is an intraoral pain evoked by a change in barometric pressure, in an otherwise asymptomatic oral cavity. In a diving environment, this pain is commonly called tooth squeeze. Although rare, in-diving or in-flight barodontalgia has been recognized as a potential cause of diver or aircrew-member vertigo and sudden incapacitation, thus could jeopardize the safety of diving or flight, respectively.19,29 Barodontalgia is a symptom rather than a pathologic condition itself and in most cases reflects a flare-up of pre-existing subclinical oral disease. Most of the common oral pathologies have been reported as possible sources of barodontalgia,30,31 with faulty dental restorations and dental caries without pulp involvement (29.2%), necrotic pulp/periradicular inflammation (27.8%), vital pulp pathology (13.9%) and recent dental treatment (postoperative barodontalgia, 11.1%) being the most common. Barosinusitis was reported in 9.7% of cases.32 Barodontalgia due to barotrauma is unique because it arises during diving, rather than acts as a flare-up of a pre-existing condition. Barodontalgia is classified as direct (dental induced) and indirect (non-dental induced) pain. The currently accepted classification of direct barodontalgia consists of four classes according to pulp/periradicular condition and symptoms (Table 1). Currently, there is no consensus about the mechanism underlying barodontalgia.
|I||Irreversible pulpitis||Sharp transient (momentary) pain on ascent|
|II||Reversible pulpitis||Dull throbbing pain on ascent|
|III||Necrotic pulp||Dull throbbing pain on descent|
|IV||Periradicular pathology||Severe persistent pain (on ascent/descent)|
Barodontalgia has been experienced on one or more occasions by 9.2% to 21.6% of American and Australian civilian divers (Table 2).23,33 Barodontalgia was most prevalent in the third decade of life and demonstrated no gender preference. An additional 16.8% and 27.2% of divers suffered from ‘jaw pain’ and ‘sinus pain’, respectively.23 An incidence of 17.3% was reported among (male) military divers.34 Weighted incidence among divers was 11.9%, similar to that in aircrews (11.0%).32
|Population||American and Australian civilian divers33||Saudi-Arabian and Kuwaiti military divers34||Australian civilian divers23||Weighted average|
Pain appears at a water depth of 33 feet and deeper,30 usually at a depth of 60 to 80 feet.34 Upper teeth are more commonly affected than lower teeth23 (in contrast to flight, in which upper and lower teeth are affected equally) and the vast majority of the episodes occurred upon descent34 (Table 3), which may indicate a greater role of the maxillary sinuses in the aetiology of in-diving barodontalgia.
|Population||Saudi-Arabian and Kuwaiti military divers34||Australian civilian divers23|
Periodic examination, including periapical radiographs and vitality tests, is suggested for the prevention of barodontalgia in divers, with special attention to apical pathology, faulty restorations and secondary caries lesions.
During the restoration of a carious tooth, the clinician should carefully examine the cavity floor to rule out penetration to the pulp chamber and apply a protective cavity liner (e.g. glass-ionomer cement).30 When performing multi-visit endodontic treatment, the dentist must carefully place the temporary restoration and educate the diver to confirm that the restoration is intact before diving. In a pressure-changing environment, open unfilled root canals may cause subcutaneous emphysema, as well as leakage of the intracanal infected content to the periradicular tissues.35 During surgery in the posterior upper arch, especially when the sinus is augmented, the dentist must rule out the existence of oroantral communication, which can lead to sinusitis and potentially adverse consequences upon exposure to a pressure-changing environment. When oroantral communication is diagnosed, referral to an oral surgeon for its closure is indicated.36
Temporary diving restriction after dental and surgical procedures is still a powerful tool for prevention of postoperative barodontalgia.1 Patients should not dive within 24 hours of a restorative treatment requiring anaesthetic and within at least seven days of having surgery.22 In suspected or actual oroantral communication, diving should be restricted for at least two weeks.37 Until otherwise indicated, the cautious dentist may consider all sinus augmentation procedures as potentially inducing oroantral communication. Thus, the dentist may recommend a longer restriction of diving to prevent failure of the procedure and pain during diving. Before diving is allowed after extraction, implantation and/or sinus augmentation, it is reasonable that the patient be invited back to the office for verification of wound healing and an absence of signs or symptoms of sinus inflammation. The regulations of the Australian Defence Force’s Surgeon General37 dictates such a restriction from the time of diagnosing the need for endodontic treatment until the completion of treatment, when the patient has remained asymptomatic for 24 hours. In addition, in order to prevent pulp inflammation or necrosis and their potential barometric pressure-related consequences, this guideline contraindicates direct pulp capping in such patients, and indicates endodontic treatment in all caries management in which invasion to the pulp chamber is evident or suspected.37
Studies emphasized the challenge of obtaining a definitive diagnosis of the causative pathology of barodontalgia38,39 owing to the need for identifying the offending tooth, which could be any tooth with existing restoration or endodontic treatment (often clinically accepted) and/or adjacent anatomical structures (e.g. maxillary sinus), without the ability to reproduce the pain trigger factor (i.e. barometric pressure change) with ordinary dental facilities. According to one report, as many as 14.8% of cases eventually remained undiagnosed.31 Moreover, according to another report, despite post-event evaluation and treatment, recurrence of barodontalgia was reported in 25.0% of in-diving cases.34 As always, meticulous history taking and examination are the mainstay of diagnosis (Table 4). History of recent dental treatments, on-ground preceding symptoms, pain onset/cessation (on ascent or descent) and nature of the pain, are invaluable data. The clinician is advised to look for faulty restorations (including dislodged restorations over a vital pulp) and secondary (residual) caries lesions, to perform a vitality test and necessary periapical radiographs, and to rule out sinusitis or pain originating from the temporomandibular joint (TMJ) or masticatory muscles (discussed later).30
|Direct barodontalgia owing to pulp disease with or without periradicular involvement||Indirect barodontalgia|
|Cause||Pulp/periradicular disease.||Barosinusitis, barotitis media.|
|Appearance||During ascent.||During descending. Pain usually continues on ground.|
|Symptoms||Reversible pulpitis or necrotic pulp: beating dull pain.|
Irreversible pulpitis: sudden sharp penetrating pain.
Periradicular periodontitis: continuous strong pain, swelling.
|Toothache in upper premolar/molar region.|
|History||Recent dental treatment. Recent dental sensitivity (e.g. to cold drinks, percussion/eating).||Present acute upper respiratory infection. Past sinusitis.|
|Clinical findings||Extensive caries lesions or (faulty) restoration. Acute pain upon cold or percussion test.||Pain on sinus palpation. Pain upon a sharp change in the head position.|
|Radiological findings||Pulpal caries lesions and/or restoration close to pulp-horn. Periradicular radiolucency. Inadequate endodontic obturation.||Opacity (fluid) on the maxillary sinus image.|
The diving mouthpiece has obvious relevance to oral tissues and conditions. The scuba diver gets air from a compressed air tank, which is transmitted to the mouth via a regulator with a mouthpiece that is held by the teeth (usually the canines and premolars). An airtight seal has to be created between teeth and lips. Inability to hold the mouthpiece due to complete or partial edentulism is one of the contraindications for scuba diving.28 Basically, there are three mouthpiece designs: commercial, semi-customized and customized mouthpieces. Most mouthpieces are currently made from silicone or soft acrylic resins. There is an argument that clenching on the mouthpiece, which may be increased due to the emotional stress and cold environment often present while diving, may participate in deterioration of dental restorations,40 even though the mouthpiece is flexible.41
Robichaud and McNally22 suggested that air pushing by mouthpiece into post-surgical wound may induce intraoral pain, mimicking barodontalgia. Owing to the helium in scuba tanks and the resulting lower gas viscosity, air from the pressurized tanks can be forced in through carious lesions and defective margins of restorations as well.19,22
Potasman and Pick42 identified the diving mouthpiece as a possible vector for transmission of herpes simplex virus between mates, especially during underwater drills, in which the mouthpiece is exchanged frequently between participants to simulate emergency conditions.
Mouthpiece-associated pharyngeal (gag) reflex during depth diving, when accompanied with stress (which is relatively common during diving), often causes the diver to perform a quick escape to surface level (a ‘panic ascent’). This manoeuvre may cause DCS.
Although there is a controversy in the literature, most authors agree that owing to mouthpiece usage there is an elevated prevalence of signs and symptoms of temporomandibular disorder (TMD) among divers, especially women. TMD symptoms were reported among 24% to 68% of divers, in comparison to about one-quarter of the general population.43–45 Pre-existing TMJ problems may be worsened by the use of a diving mouthpiece,44 but symptoms may appear even in previously symptom-free divers. TMD symptoms were more prevalent in diving in cold water than in warm water,45 probably because of the impairment of the lips’ contracting capability in the cold environment, thus enforcing over-effort of the masticatory muscles.19 Among New Zealand divers, TMD was the second most prevalent head and neck disorder and comprised 24% of these disorders (with ear pathology the most common disorder comprising 65%, and nasal and sinus disorders comprising only 10% of disorders).46 Diving related TMD symptoms, also called diver’s mouth syndrome (or regulator mouth), may include all the TMD symptoms (e.g. muscle pain, joint pain, internal derangement of TMJ-disc, headache) in various degrees, and may be limited to diving time or become chronic and constant. These symptoms are attributed to the protruded mandibular position and the biting force exercised on the anterior occlusion (usually canines and premolars) during diving. A semi-customized mouthpiece required less muscle activity for retention than commercial type,47 and fully customized mouthpieces are reported to cause the least mandibular displacement from the normal resting position, thus usage results in the least discomfort, muscle pain, fatigue and effort.41
To prevent post-surgical forcing of air into the tissues and dry socket, diving should be restricted for at least one week following oral surgery; prior to diving the dentist should confirm healing.
The dental team must educate the diver patient of the infectious potential of the mouthpiece and recommend using only a private one, and encourage maintenance by hygiene procedures after each use, similar to other removable oral devices. The diver should not dive in times of illness, for the concern of his or her mate. Dentists should be familiar with the signs and symptoms of primary herpetic gingivostomatitis.
Possible solutions for divers with prominent pharyngeal reflex include: avoidance of personal gagging contributing factors (e.g. anxiety, stress), desensitization training (repeated introduction of devices to the sensitive region), trimming the intraoral trigger parts in the mouthpiece, or use of the (more expensive) full face mask. Anti-gagging medications should not be taken before diving to avoid a possible hazardous effect.
Diving related TMD symptoms should be differentiated from barotitis symptoms. Despite the potential limitations in the construction process because of the number of stages involved, the greater expense and the possible reluctance of experienced divers to change from the standard commercial mouthpiece, Hobson and Newton recommended the fabrication of a custom mouthpiece for divers, with a bite platform at least 4 mm in thickness, especially for divers who experience diving-associated TMD symptoms.27,41 Scully and Cawson further recommended the extension of the mouthpiece’s interdental bite platform to cover the molars, in addition to the accepted canines and premolars, in order to balance the weight of the regulator and relieve the stress on the TMJ.28 Jagger et al. emphasized the safety aspects of the fabrication of the custom mouthpiece; the mouthpiece must be easily removed and compatible with the mate’s use in emergency (when air sharing by alternate breathing is needed), and the prepared custom mouthpiece should be pretested in a training pool before being used in open-water diving.19 However, if a custom mouthpiece is not an option, the diver should remember that there are design differences between manufacturers. Thus, when choosing his or her equipment, the diver should test out (in a trial dive) a number of mouthpieces in order to find the design with the least likelihood of causing joint symptoms; at least 15 minutes of diving followed by a rest period of 15 minutes, and adequate disinfection of devices between trials.41,48