1. Hyperbaric oxygen therapy (HBOT) involves breathing pure oxygen in a pressurized chamber, which increases the amount of oxygen that dissolves in the patient's plasma and tissues. This promotes healing and reduces recovery time. 2. HBOT works by increasing oxygen tension in tissues through several physiological effects, including increased angiogenesis and fibroblast proliferation. The increased oxygen aids neutrophils in fighting infection and promotes tissue regrowth. 3. HBOT is used to treat osteoradionecrosis, refractory osteomyelitis, and compromised bone healing after radiation therapy for dental implants through its effects on increasing oxygen delivery and stimulating cell growth in hypoxic tissues.

2. 1
Introduction
Hyperbaric oxygen therapy (HBOT) facilitates the transfer of oxygen to the
tissues of the human body. By doing so, it promotes healing of wounds and
minimizes the typical recovery time for patients. (1)
At this juncture, strictly within
dental medicine, HBOT indicates the distribution of comprehensive oxygen at
pressures greater than 1.4 atmosphere absolute (ATA), often in a series of
treatments. (2)
This treatment requires the patient to stand within a hyperbaric
chamber with pressure greater than ambient. It has many uses such as patient care,
and wound care within standard medicine and dental medicine. (3)
HBOT exploits numerous physiological principles of how gases and oxygen react
under specific adjustments of pressure. There is a direct relationship between the
concentration of oxygen in solution and the diffusion gradient. The increase in
concentration of oxygen in solution results in the increase of the diffusion
gradient for the delivery into deeper tissue, thus being the basis for HBOT. In
HBOT, the oxygen level is amplified, which highly increases the oxygen tension
in the tissues. When the treatment is concluded, the oxygen tension decreases
allowing for an inundation of neutrophils. Neutrophils are a type of white blood
cells which specifically aid in fighting off infection and tissue regrowth.
Conclusively, the increase in dissolved oxygen generated by HBOT has potential
to alter tissue responses to disease and injury. (4)
Mechanism of action
The effects caused by hyperbaric oxygen on the body can be divided into primary
or direct effects like increased oxygen tension and diffusion in the tissue;
secondary or immediate effects like vasoconstriction, angiogenesis, fibroblast
proliferation and increased leukocyte oxidative killing. (5)
These effects are based
on the gas laws, physiological and biochemical effects of hyper oxygenation.
Henry’s Law states that the amount of gas which is dissolved in a liquid or tissue
is proportional to the partial pressure of that gas which is in contact with liquid

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or tissue. (6)
In hyperbaric oxygen therapy, the increased amounts of oxygen
which is supplied, increases the oxygen tension in the tissues, thus explaining the
effects of hyperoxia in hypoxic tissues.
When the oxygen tension decreases, there is influx of neutrophils. The activated
neutrophils consume enormous amount of oxygen, leading to further decrease in
oxygen levels in the hypoxic tissues. Very low levels of oxygen can cause tissue
injuries. Hyperbaric oxygen therapy reverses the hypoxic tissue injuries by
increasing the oxygen concentration, thereby helping the neutrophils by
supplying oxygen and accelerating the healing process. (7,8)
Hyper oxygenation
causes vasoconstriction in the normal tissues.
Equipment
HBO therapy is administered in a hyperbaric chamber. (9)
They are of two types:
Monoplace chambers: It is transparent, made up of acrylic, can accommodate a
single patient and the patient does not require a mask. Primary advantage: Cost
and space requirements. Fig.1
Multiplace chambers: Usually of steel (some may be made up of aluminum),
can accommodate more than two people and is pressurized with air, while the
patients breathe O2 from a tight fitting mask/circuit. Advantage: Is suitable for
critically ill patients requiring ventilation, monitoring and constant attendance.
Pressure and duration: It depends upon the indication. It ranges from 2 to 6 ATA
for 2-6 h. Decompression sickness/gas embolism may require prolonged,
continuous saturation protocols. Emergency indications for HBO therapy
generally require only 2-3 separate chamber treatments. Fig.2
Fig.2 Multiplace chambersFig.1 Monoplace chambers

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Practical aspects of care in a chamber
● Fire safety: Maintaining electrical components outside the chamber. Passing
cables through insulated pass throughs.
● Electrical defibrillation: In a hyperbaric chamber defibrillation is controversial,
because of the possibility of poor skin contact, arcing and risk of fire. Large metal
environment may predispose attendants to shock. Chambers needs to be
decompressed prior to use of a defibrillator. (10)
Cellular and biochemical benefits of hyperbaric oxygen
• Promotes angiogenesis and wound healing
• Kills certain anaerobes
• Prevents growth of species such as Pseudomonas
• Prevents production of clostridial alpha-toxin
• Restores neutrophil mediated bacterial killing in previously hypoxic tissues
• Reduces leucocyte adhesion in reperfusion injury preventing the release of
proteases and free radicals which cause vasoconstriction and cellular damage. (10)
1. Osteoradionecrosis
Osteoradionecrosis of the mandible is a significant complication of radiation
therapy for head and neck cancer. In this condition, bone within radiation field
becomes devitalized and exposed through overlying skin or mucosa, persisting as
a nonhealing wound for 3 months or more. In 1983, Marx proposed the first
staging system for ORN that also served as a treatment protocol. This protocol
advocated that patients whose disease progressed following conservative therapy
(HBO, local wound care, and debridement) were advanced to a radical resection
with a staged reconstruction utilizing a nonvascularized bone graft. The purpose
of HBO is to increase the blood-tissue oxygen gradient, which enhances the
diffusion of oxygen into hypoxic tissues. The increased oxygen supply stimulates
Hyperbaric oxygen therapy in dentistry is used in:

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fibroblast proliferation, angiogenesis, and collagen formation. In addition,
Increased oxygen tension is bactericidal and bacteriostatic. The use of HBO in
early and intermediate ORN remains important because the benefit seems clear
based on numerous retrospective studies. The morbidity of HBO is minimal
including transient myopia, middle ear barotrauma and seizures. Absolute
contraindications for HBO include optic neuritis, history of chronic obstructive
pulmonary disease or congenital pulmonary blebs. (11)
2. Periodontal disease
The effect of hyperbaric oxygen on aggressive periodontitis and subgingival
anaerobes in Chinese patients, documented the effect of hyperbaric oxygen
therapy. This assessment was done by measuring plaque index, gingival index,
probing depth and attachment loss, two years after hyperbaric oxygen therapy
was indicated. It was concluded in this study, that HBO could inhibit the growth
of subgingival obligate anaerobes, facultative anaerobes and Bacteroides
melaninogenicus, thus promoting healing of peridontium, which could help in the
treatment of aggressive periodontitis. (12)
The use of hyperbaric oxygen as a adjunct to scaling and root planning in patients
with generalized chronic periodontitis, is found to improve the clinical parameters
like probing depth and attachment level, thus indicating the beneficial effects of
hyperbaric oxygen on the periodontium. (13)
In a study, hyperbaric oxygen was found to stimulate the proliferation of
osteoblastic cells in vitro, in presence of 10% foetal calf serum (FCS) and an
inhibitory effect was observed in presence of 2% (FCS). (14)
3. Refractory Osteomyelitis
The jaw bone osteomyelitis represents about one third of all diagnosed cases of
osteomyelitis. This is due to the presence of the teeth which are often the source
of infection. The main complication in osteomyelitis is the presence of a barrier
between the host and the infection. This barrier can be suppuration, necrotic bone,

6. 5
but it can limit the action of the host’s immune system. In refractory
osteomyelitis, antibiotics which are used to destroy the microorganisms in the
soft tissues around the sites of infections and surgery are used for the macroscopic
removal of necrotic bone. But hyperbaric oxygen therapy aims at the improval of
the host response and at making the environment more favourable for the action
of the inflammatory cells. In a study which was done on the treatment of chronic
refractory osteomyelitis, 11 out of 14 patients were successively treated with
hyperbaric oxygen therapy without any complications. (15)
4. Implants in irradiated bone
Dental implants offer an alternative for tooth replacement. Dental implants are
directly inserted into the bone which replaces the missing teeth. The adjacent
bone around the implant should fuse well into the implant surface by forming new
bone. But in an individual who has already undergone radiation therapy, the
implant is likely to fail, because the bone formation is compromised after
radiation. In an experimental study done on implants inserted into irradiated bone,
to assess the effects of hyperbaric oxygen therapy on the capacity of bone
formation, hyperbaric oxygen therapy was found to stimulate effective bone
formation. According to histomorphometric studies done on effects of bone
reactions on titanium implants, it was found that the woven bone was not replaced
by lamellar bone in irradiated patients. (16)
Contraindications of HBO
The various contraindications of hyperbaric oxygen therapy are:
Absolute contraindications: Untreated tension pneumothorax
Relative contraindications: Upper restrictive tract infections / Emphysema with
carbon dioxide retentions / Asymptomatic pulmonary lesions which are seen on
chest X- ray / History of thoracic or ear surgery / Uncontrolled hyperthermia /
Pregnancy / Claustrophobia / Seizure disorder. (17)

7. 6
Complication
Though hyperbaric oxygen therapy has widespread applications, complications
in the usage do occur. In hyperbaric oxygen therapy, there are pressure
equalization problems which predominantly affect the middle ear and the nasal
sinus, which cause barotraumatic lesions. In a study which was done to analyze
the side effects of hyperbaric oxygen therapy, oxygen toxicity and ocular
disturbances were reported.
Non-emergent patients who are treated routinely with hyperbaric oxygen, with
oxygen being administered via a head hood, have a potential risk of CNS oxygen
toxicity which is three fold greater than is normally quoted. But the complications
which were observed were transient and they were limited mostly within the
duration of the treatment. (18)
Conclusion
HBO provides the most benefit in tissues with vessels which have good blood
flow. The anatomical structure of the mouth with its rich vascular beds is an
advantage to benefit from the treatment, which supports the intent to use this
therapy in dentistry. HBO proved its worth as an adjuvant therapy in multiple
dental indications. HBO application also proved its preventive worth in case of
tooth extraction at the site after irradiation. Tissue devastation after the head and
neck tumors treatment requires functional and aesthetic reconstruction. Success
of implants retention in the given site is significantly higher after HBO
application. As an adjuvant therapy, HBO proved its worth in treatment of
refractory osteomyelitis. HBO inhibits the growth of anaerobes in gingival
pockets which is probably the cause of the effect in the treatment of aggressive
periodontitis. Studies evaluating the positive effect of HBO in dentistry mostly
recommend it as an adjuvant therapy. Despite promissing results of experimental
works, the use of HBO in dentistry still has room for improvement. The effect
objectification for its more extensive use will require further studies. (19)

8. 7
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