The effect of hyperbaric oxygen on irradiated oral tissues: transmucosal oxygen tension measurements

The impact of hyperbaric oxygen therapy on late irradiation injury in oral microcirculation

BACKGROUND

Late side effects of radiotherapy in patients with head and neck cancer (HNCPs) result in decreased tissue vascularity, a compromised healing capacity and spontaneous breakdown of tissue. The aim of this study was to examine the in vivo effect of hyperbaric oxygen therapy (HBOT) on the microcirculation in irradiated oral tissue.

METHODS

Using a handheld microscope, the effect of HBOT on oral mucosal microcirculation parameters was measured in 34 previously irradiated HNCPs prior to HBOT and at 4 weeks and 6 months posttreatment.

RESULTS

A significant increase in mean buccal vessel density and decrease in buccal vessel diameter was found 6 months after HBOT compared to baseline, 22 ± 11 versus 25 ± 7 cpll/mm² (p < 0.05) and 20 ± 4 versus 16 ± 5 μm (p < 0.05), respectively.

CONCLUSION

Our results indicate that oral microcirculation histopathology associated with irradiation is able to respond to HBOT by redirecting oral microcirculation parameters towards values consistent with healthy tissue.

Focused ultrasound ablation of a large canine oral tumor achieves efficient tumor remission: a case report

Purpose: Oral cancers are one of the commonly diagnosed tumors worldwide in human and veterinary patients. Most oral cancers are surgically resected; however, obtaining an adequate margin of safety in patients without compromising their quality of life is often challenging. Herein, we investigated the ability of non-invasive focused ultrasound (FUS) to thermally ablate a biopsy confirmed canine oral cancer. Materials and Methods: A male canine patient with a large neurilemmoma (schwannoma) mass on the left maxilla, with evidence of thinning and loss of alveolar bone and pressure necrosis, was treated with FUS ablation instead of the traditional maxillectomy procedure. FUS ablations were performed in three sessions over three weeks. Tumor remission was determined with computed tomography and histopathological examination of the treated site. Additionally, the anti-tumor immune effects of FUS were assessed by flow cytometry analysis of blood and tumor samples. Results: Complete tumor remission was noted at the treated site. Treatment related adverse events were primarily thermal burns of the buccal mucosa, which were managed with periodic hyperbaric oxygen therapy and surgical coverage of the underlying exposed bones with gingival flaps. Enhanced proliferation of adaptive immunity cells (e.g., T-cells) was observed in tumor and blood samples. Conclusion: Our limited investigation in a canine oral cancer patient suggests that FUS may avoid the need for large-scale resection of bony tissues, thus potentially improving quality of life.

Metabolomic Alteration of Oral Keratinocytes and Fibroblasts in Hypoxia

The oxygen concentration in normal human tissue under physiologic conditions is lower than the atmospheric oxygen concentration. The more hypoxic condition has been observed in the cells with wound healing and cancer. Somatic stem cells reside in a hypoxic microenvironment in vivo and prefer hypoxic culture conditions in vitro. Oral mucosa contains tissue-specific stem cells, which is an excellent tissue source for regenerative medicine. For clinical usage, maintaining the stem cell in cultured cells is important. We previously reported that hypoxic culture conditions maintained primary oral keratinocytes in an undifferentiated and quiescent state and enhanced their clonogenicity. However, the metabolic mechanism of these cells is unclear. Stem cell biological and pathological findings have shown that metabolic reprogramming is important in hypoxic culture conditions, but there has been no report on oral mucosal keratinocytes and fibroblasts. Herein, we conducted metabolomic analyses of oral mucosal keratinocytes and fibroblasts under hypoxic conditions. Hypoxic oral keratinocytes and fibroblasts showed a drastic change of metabolite concentrations in urea cycle metabolites and polyamine pathways. The changes of metabolic profiles in glycolysis and the pentose phosphate pathway under hypoxic conditions in the oral keratinocytes were consistent with those of other somatic stem cells. The metabolic profiles in oral fibroblasts showed only little changes in any pathway under hypoxia except for a significant increase in the antioxidant 2-oxoglutaric acid. This report firstly provides the holistic changes of various metabolic pathways of hypoxic cultured oral keratinocytes and fibroblasts.

Hyperbaric oxygen treatment did not significantly affect radiation injury in the mandibular area of rats

OBJECTIVE

Hyperbaric oxygen therapy (HBOT) has been used to enhance microcirculation and thereby oxygen tension in tissues. The present study aimed to investigate the effect of HBOT on radiation injury in the mandibular area of rats.

STUDY DESIGN

The left mandibles of rats were irradiated by external radiotherapy (15 Gy every other week for a total of 75 Gy). Four HBOT strategies were used: 2 prophylactic groups receiving HBOT either between each radiation treatment or immediately following terminated radiation treatment, and 2 therapeutic groups receiving HBOT after the latent period of 6 weeks after irradiation either every day (standard HBOT protocol) or 3 days a week for 6 weeks. Tissue samples of the irradiated area were taken from skin, the salivary gland, and the mandible. All tissues were stained with hematoxylin and eosin for morphologic examination. Furthermore, skin samples were stained with CD31 for blood vessel analysis.

RESULTS

There was no change in blood vessel density or morphology between controls and HBOT tissues after radiation. The dentin of 2 of the 5 rats that received HBOT either normalized or was not affected by irradiation.

CONCLUSIONS

HBOT did not affect radiation injury of the mandibular area in rats within 12 weeks after irradiation.

Hyperbaric Oxygen Therapy for Wound Dehiscence After Intraoral Bone Grafting in the Nonirradiated Patient: A Case Series

PURPOSE

In maxillofacial surgery, hyperbaric oxygen treatment is used almost exclusively as adjunctive therapy for osteoradionecrosis of the mandible in irradiated patients. It also is used to prevent the occurrence of osteoradionecrosis in the irradiated patient when dental surgery is indicated. Theoretically, hyperbaric oxygen therapy should benefit the nonirradiated patient in maxillofacial surgery (eg, patients with persistent intraoral wound dehiscences after bone grafting).

MATERIALS AND METHODS

Six nonirradiated patients underwent hyperbaric oxygen therapy because of compromised wound healing after intraoral bone grafting of the maxilla as a preimplant procedure. All patients were treated 7 to 26 times with hyperbaric oxygen therapy at 2.5 ATA.

RESULTS

All patients healed uneventfully. In retrospect, almost all patients had a history of chronic maxillary sinusitis or trauma to the operated area.

CONCLUSION

Hyperbaric oxygen therapy seems to be an effective adjunctive therapy in the treatment of nonirradiated patients with compromised intraoral maxillary bone graft healing. Chronic maxillary sinus problems or a history of trauma could predispose to wound dehiscence after bone grafting.

Hypoxia induces an undifferentiated phenotype of oral keratinocytes in vitro

The aim of this study was to determine the effects of hypoxia on the proliferating potential and phenotype of primary human oral keratinocytes cultured at ambient oxygen tension (20%) or at different levels of hypoxia (2 and 0.5% O2). The effects of oxygen tensions on cellular metabolic activity, cell proliferation, clonogenicity and proliferation heterogeneity were measured. Cell cycle profiles were analyzed by a fluorescent-activated cell sorter, and p21(WAF1/CIP1) expression in the G0/G1 phase was also concomitantly quantitated. The expression levels of cell cycle regulatory proteins were examined by immunoblotting, and the cellular senescence was assessed by senescence-associated β-galactosidase staining. Basal and suprabasal keratinocyte phenotypes were determined by the expression levels of 14-3-3σ, p75(NTR) and α6 integrin. Despite having a lower metabolism, the proliferation rate and clonogenic potential were remarkably enhanced in hypoxic cells. The significantly higher percentage of cells in the G0/G1 phase under hypoxia and the expression patterns of cell cycle regulatory proteins in hypoxic cells were indicative of a state of cell cycle arrest in hypoxia. Furthermore, a decrease in the expression of p21(WAF1/CIP1) and p16(INK4A) and fewer β-galactosidase-positive cells suggested a quiescent phenotype rather than a senescent one in hypoxic cells. Compared with normoxic cells, the differential expression patterns of keratinocyte phenotypic markers suggest that hypoxic cells that generate minimal reactive oxygen species, suppress the mammalian target of rapamycin activity and express hypoxia-inducible factor-1α favor a basal cell phenotype. Thus, regardless of the predisposition to the state of cell cycle arrest, hypoxic conditions can maintain oral keratinocytes in vitro in an undifferentiated and quiescent state.

Osteoradionecrosis of the mandible: through a radiologist's eyes

Head and neck malignancies constitute a major cause of morbidity and mortality all over the world. Radiotherapy plays a pivotal role in the management of these tumours; however, it has associated complications, with mandibular osteoradionecrosis (ORN) being one of the gravest orofacial complications. Early diagnosis, extent evaluation, and detection of complications of ORN are imperative for instituting an appropriate management protocol. ORN can closely mimic tumour recurrence, the differentiation of which has obvious clinical implications. The purpose of the present review is to acquaint the radiologist with the imaging features of mandibular ORN and the ways to differentiate ORN from tumour recurrence.

Can tissue spectrophotometry and laser Doppler flowmetry help to identify patients at risk for wound healing disorders after neck dissection?

OBJECTIVE

Microcirculation and oxygen supply in cervical skin were measured with an optical, noninvasive method in patients with or without radiotherapy before neck dissection. The course of wound healing was monitored after the surgical procedure to identify predictive factors for postoperative wound healing disorders.

STUDY DESIGN

Tissue spectrophotometry and laser Doppler flowmetry were used to determine capillary oxygen saturation, hemoglobin concentration, blood flow, and blood velocity at 2-mm and 8-mm depths in the cervical skin of 91 patients before neck dissection in a maxillofacial unit of a university hospital in Munich, Germany. Parameters were evaluated for differences between patients with irradiation (24) and without (67) and patients with wound healing disorders (25) and without (66) (univariate or multivariate statistical analyses).

RESULTS

Velocity at 2 mm was lower in irradiated skin (P = .016). Flow at 2 mm was higher in patients with wound healing disorders (P = .018).

CONCLUSIONS

High flow values could help to identify patients at risk for cervical wound healing disorders.

Dental status, dental rehabilitation procedures, demographic and oncological data as potential risk factors for infected osteoradionecrosis of the lower jaw after radiotherapy for oral neoplasms: a retrospective evaluation

Purpose

Retrospective evaluation of the dental status of patients with oral cancer before radiotherapy, the extent of dental rehabilitation procedures, demographic and radiotherapy data as potential risk factors for development of infected osteoradionecrosis of the lower jaw.

Methods

A total of 90 patients who had undergone radiotherapy for oral cancer were included into this retrospective evaluation. None of them had distant metastases. After tumour surgery the patients were referred to an oral and maxillofacial surgeon for dental examination and the necessary dental rehabilitation procedures inclusive potential tooth extraction combined with primary soft tissue closure. Adjuvant radiotherapy was started after complete healing of the gingiva (> 7 days after potential extraction). The majority of patients (n = 74) was treated with conventionally fractionated radiotherapy with total doses ranging from 50-70Gy whereas further 16 patients received hyperfractionated radiotherapy up to 72Gy. The records of the clinical data were reviewed. Furthermore, questionnaires were mailed to the patients’ general practitioners and dentists in order to get more data concerning tumour status and osteoradionecrosis during follow-up.

Results

The patients’ dental status before radiotherapy was generally poor. On average 10 teeth were present, six of them were regarded to remain conservable. Extensive dental rehabilitation procedures included a mean of 3.7 tooth extractions. Chronic periodontitis with severe attachment loss was found in 40%, dental biofilm in 56%. An infected osteoradionecrosis (IORN) grade II according to (Schwartz et al., Am J Clin Oncol 25:168-171, 2002) was diagnosed in 11 of the 90 patients (12%), mostly within the first 4 years after radiotherapy. We could not find significant prognostic factors for the occurrence of IORN, but a trendwise correlation with impaired dental status, rehabilitation procedures, fraction size and tumour outcome.

Conclusion

The occurrence of IORN is an important long-term side effect of radiotherapy for oral cancers. From this data we only can conclude that a poor dental status, conventional fractionation and local tumour progression may enhance the risk of IORN which is in concordance with the literature.

Effect of hyperbaric oxygen treatment on oxygen tension and vascular capacity in irradiated skin and mucosa

The aim of this study was to evaluate the effect of hyperbaric oxygen therapy (HBOT) on vascular function and tissue oxygenation in irradiated facial skin and gingival mucosa. Twenty-two patients, aged 51-90 years, were randomly allocated to a treatment or control group. All had a history of radiotherapy (50-70 Gy) to the orofacial region 2-20 years previously. Skin and mucosal perfusion were recorded with laser Doppler flowmetry (LDF). Tissue oxygenation was recorded by transcutaneous oximetry (TcPO(2)). Measurements were taken before HBOT and 3 and 6 months after a mean of 28 HBOT sessions (partial pressure of oxygen of 240 kPa for 90 min). For control subjects, measurements were taken on two occasions 6 months apart. After HBOT, blood flow in mucosa and skin after heat provocation increased significantly (P < 0.05). TcPO(2) increased significantly in the irradiated cheek (P < 0.05), but not at reference points outside the field of radiation. There were no differences between the 3- and 6-month follow-ups. In the control group, no significant changes in LDF or TcPO(2) were observed. It is concluded that oxygenation and vascular capacity in irradiated facial skin and gingival mucosa are increased by HBOT. The effects persist for at least 6 months.

Osteoradionecrosis of the jaws--a current overview--Part 2: dental management and therapeutic options for treatment

PURPOSE

The aim of this paper is to explore the current theories about pretreatment assessment and dental management of patients receiving head and neck radiotherapy, and the therapeutic options to treat osteoradionecrosis of the jaws, based on the literature review.

DISCUSSION

Osteoradionecrosis is one of the most serious oral complications of head and neck cancer treatment. Osteoradionecrosis is a severe delayed radiation-induced injury, characterized by bone tissue necrosis and failure to heal. Osteoradionecrosis either stabilizes or gradually worsens and is notoriously difficult to manage. Because most cases occur in patients who were dentulous in the mandible at tumor onset, proper dental management is the single most important factor in prevention.

CONCLUSIONS

Complete dental clearance before treatment is no longer necessary. Controversy exists regarding the management of osteoradionecrosis of the maxillofacial skeleton because of the variability of this condition. The treatment of osteoradionecrosis has included local wound care, antibiotic therapy, surgical procedures, and the administration of hyperbaric oxygenation. Recently, new methods of treatment were introduced, according to the new theory about its pathophysiology.

Inhibition of transforming growth factor-beta, hypoxia-inducible factor-1alpha and vascular endothelial growth factor reduced late rectal injury induced by irradiation

Tumor hypoxia and angiogenesis associated with malignant progression have been studied widely. The efficacy of angiogenesis inhibition combined with radiotherapy has been demonstrated in cancer treatment. Here, we studied the effect of hypoxia and angiogenesis inhibition on radiation-induced late rectal injury. The rectum of C57BL/6N mice was irradiated locally with a single dose of 25 Gy. Radiation-induced histological changes were examined at 90 days after irradiation by hematoxylin-eosin (H.E.) staining and azan staining. Pimonidazole was administered and its distribution was assayed by immunohistochemistry staining. Expression of transforming growth factor beta1 (TGF-beta1), hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) was assessed on the fibrotic region using real-time PCR and immunohistochemistry. In addition, the effects of TGF-beta, VEGF and HIF-1alpha on radiation-induced injury were investigated by the administration of neutralizing antibody of TGF-beta, antibody of VEGF or YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole) which was developed as an agent for inhibiting HIF-1 expression after irradiation respectively. Fibrosis and uptake of pimonidazole were found 90 days after irradiation. The expression of TGF-beta1, HIF-1alpha and VEGF significantly increased with the formation of fibrosis induced by irradiation compared with unirradiated controls. In addition, treatment of neutralizing antibody of TGF-beta, antibody of VEGF or YC-1 reduced the development of radiation-induced injury. Our results suggested that radiation-induced hypoxia may play an important role in late rectal injury. Although the inhibition of HIF-1alpha and VEGF reduced the radiation induced late injury, the precise mechanism is still unclear.

Hypoxia enhances the replication of oncolytic herpes simplex virus

Hypoxia contributes to the resistance of tumors to conventional therapies. We hypothesized that their replication in hypoxic environments like brain or oral mucosa would make oncolytic herpes simplex viruses (HSVs) such as G207 (which has undergone clinical trials) replicate to a greater extent in hypoxic tumors like glioblastoma. Hypoxic cultured U87 cells yielded 4% more wild-type HSV (P = 0.04) and 3.6-fold more G207 (P = 0.001) after 48 hours of infection when compared with normoxic cells. Real-time RT-PCR confirmed a fivefold hypoxia-induced U87 upregulation of GADD34 mRNA, a factor complementing the gamma34.5 gene deletion in G207. The viral yield under conditions of hypoxia, as against normoxia, in GADD34 siRNA-treated U87 cells was 65% of that in control siRNA-treated cells. Treating subcutaneous U87 tumors in athymic mice with erythropoietin lowered the tumoral hypoxic fraction from 57.5 to 24.5%. Tumoral hypoxia dropped to 2.5% during 4 hours/day of hyperbaric chamber treatment. Each tumor-oxygenating maneuver reduced the G207 yield fourfold (P = 0.0001). Oncolytic HSV G207 exhibited enhanced replication in hypoxic environments, partly on account of increased GADD34 expression in hypoxic cells. The unique tropism of oncolytic HSVs for hypoxic environments contrasts with the hypoxia-mediated impairment of standard (radiation, chemotherapy) and other experimental therapies, and enhances HSV's appeal and efficacy in treating tumors like glioblastoma.

Dental extractions and radiotherapy in head and neck oncology: review of the literature

Management of irradiated patients with cancer in the head and neck region represents a challenge for multidisciplinary teams. Radiotherapy promotes cellular and vascular decrease that results in a low response rate in the healing. Consequently, surgical procedures in irradiated tissues present high rates of complication. Osteoradionecrosis (ORN) is the most severe sequelae caused by radiotherapy. It is associated with previous extractions especially those carried out post-irradiation. The management of this side effect is difficult and can result in bone or soft tissue loss, affecting the quality of life. The literature regarding dental extractions performed before and after head and neck radiotherapy was evaluated, focusing on indications, criteria, surgical techniques and adjunctive therapies such as antibiotics and hyperbaric oxygen. Osteoradionecrosis can be minimized by oral evaluation and care prior to irradiation and healing time which allows tissue repair until the commencement of radiotherapy. In dental extractions realized after irradiation, minimal trauma, alveolectomy, primary alveolar closure and adjunctive therapies are recommended. Patients must be evaluated before radiation therapy and at that time all unrestorable teeth and/or teeth with periodontal problems must be extracted to reduce the post-radiotherapy exodontias that contribute to ORN. Once dental extractions become unavoidable after irradiation, additional care is needed.

Hypoxia can be detected in irradiated normal human tissue: a study using the hypoxic marker pimonidazole hydrochloride

Chronic tissue hypoxia may play a role in the pathogenesis of late radiation fibrosis. In order to investigate this hypothesis, the immunohistochemical distribution of pimonidazole hydrochloride (n = 14 patients) and carbonic anhydrase IX (CAIX) (n = 38 patients) was studied in samples of previously irradiated normal human tissue. One sample of irradiated breast tissue, which also showed marked histological features of radiation injury, stained positive for pimonidazole hydrochloride. No CAIX staining was seen in irradiated tissue other than some evidence of physiological hypoxia in the epidermis of two samples of irradiated skin; both were positive for pimonidazole and one was focally positive for CAIX. Pimonidazole hydrochloride staining of tissue with morphological changes of radiation injury could support a role for hypoxia in the pathogenesis of late normal tissue fibrosis in humans.

Hyperbaric oxygen does not accelerate latent in vivo prostate cancer: implications for the treatment of radiation-induced haemorrhagic cystitis

OBJECTIVE

To assess the effects of hyperbaric oxygen (HBO2; often used to treat haemorrhagic cystitis, a known side-effect after radiation therapy for prostate cancer and with the potential to induce tumour angiogenesis and stimulate latent recurrence) on indolent in vivo prostate cancer in a murine model.

MATERIALS AND METHODS

Human prostate LNCaP cells were injected into 60 severe combined-immunodeficient mice; of these 24 (40%) did not develop palpable tumours after 6 weeks. They were randomized to undergo 20 sessions of either HBO2 or normobaric air in standardized conditions, and observed for another 4 weeks before the histological assessment of any palpable tumours that developed. Analysis of developed LNCaP tumours included tumour volume, microvessel density, MIB-1, p53, p27 and racemase staining intensity.

RESULTS

HBO2 was associated with less prostate tumour progression than normobaric air (P = 0.26). During HBO2 therapy, 10 mice remained free of palpable tumours, compared with seven controls (P = 0.30). On evaluation during the 4 weeks after therapy, six mice treated with HBO2 remained free of palpable tumours, vs eight of the controls (P = 0.17). There was tumour invasion and necrosis in a two of six and four of the HBO2 group during and after therapy, respectively, vs five and seven of the controls. Tumour microvessel density, proliferative index, differentiation and apoptosis markers were similar in both groups.

CONCLUSIONS

HBO2 does not accelerate the growth of indolent prostate cancer in a murine model, suggesting that it does not increase the risk of residual prostate cancer reactivation when it is used to manage radiation-induced haemorrhagic cystitis in patients treated by pelvic radiotherapy for prostate cancer.

Hyperbaric oxygen therapy in the treatment of radio-induced lesions in normal tissues: a literature review

Late complications are one of the major factors limiting radiotherapy treatment, and their treatment is not codified. Hyperbaric oxygen (HBO) has been used in combination with radiotherapy for over half a century, either to maximise its effectiveness or in an attempt to treat late complications. In this latter case, retrospective trials and case reports are prevailing in literature. This prompted European Society for Therapeutic Radiotherapy and Oncology and European Committee for Hyperbaric Medicine to organise a consensus conference in October 2001, dealing with the HBO indications on radiotherapy for the treatment and prevention of late complications. This updated literature review is part of the documents the jury based its opinion on. A systematic search was done on literature from 1960 to 2004, by only taking into account the articles that appeared in peer review journals. Hyperbaric oxygen treatment involving complications to the head and neck, pelvis and nervous system, and the prevention of complications after surgery in irradiated tissues have been studied. Despite the small number of controlled trials, it may be indicated for the treatment of mandibular osteoradionecrosis in combination with surgery, haemorrhagic cystitis resistant to conventional treatments and the prevention of osteoradionecrosis after dental extraction, whose level of evidence seems to be the most significant though randomised trials are still necessary. The other treatment methods are also outlined for each location.

Dental extractions in the irradiated head and neck patient: a retrospective analysis of memorial sloan-kettering cancer center protocols, criteria, and end results

BACKGROUND

This study was designed to use our institutional experience with irradiated head and neck patients to evaluate 1) dental extraction incidence and sequelae; 2) those patients who developed osteoradionecrosis via extraction and the efficacy of hyperbaric oxygen therapy; and 3) guidelines for extraction protocols in this population. Materials and methods A group of 1,194 patients with a history of radiation to the head and neck, who were evaluated and treated in the Dental Service at Memorial Sloan-Kettering Cancer Center, were reviewed. The 187 who required dental extractions were analyzed using patient demographics, tumor location, staging, histopathology, radiation dosage, field, and timing, dental extraction indications, location, surgical methods, and sequelae.

RESULTS

Almost 85% of the patients reviewed did not require extraction. Only 4 of those who underwent extractions at Memorial Sloan-Kettering Cancer Center developed osteoradionecrosis.

CONCLUSIONS

The use of multidisciplinary team communications and careful extraction selection by prognosis and symptomatology regardless of preexisting dental pathologies, atraumatic extraction procedures, and meticulous follow-up can lower both extraction and osteoradionecrosis rates.

Ultrasound stimulation of maxillofacial bone healing

A substantial part of the maxillofacial surgery practice deals with maxillofacial bone healing. In the past decades, low-intensity ultrasound treatment has been shown to reduce the healing time of fresh fractures of the extremities up to 38%, and to heal delayed and non-unions up to 90% and 83%, respectively. Based on the assumption that the process of bone healing in the bones of the extremities and maxillofacial skeleton is essentially the same, the potential of ultrasound to stimulate maxillofacial bone healing was investigated. Although limited evidence is available to support the susceptibility of maxillofacial bone to the ultrasound signal, ultrasound may be of value in the treatment of delayed unions, in callus maturation after distraction, and in the treatment of osteoradionecrosis.

Adjunctive hyperbaric oxygen in irradiated patients requiring dental extractions: outcomes and complications

PURPOSE

This study assessed complications of hyperbaric oxygen (HBO) therapy, potential predictors of poor outcome, and treatment outcomes in irradiated patients undergoing dental extractions.

PATIENTS AND METHODS

This was a prospective, descriptive study of 40 consecutive patients treated with HBO before and after dental extractions in an irradiated field. All patients had radiation caries; none had osteoradionecrosis (ORN). All were prescribed a protocol of 20 pre-extraction and 10 postextraction HBO treatments at 2.4 ATA for 90 minutes. Potential risk factors for poor healing and risk factors for complications were identified. All complications were recorded. Extraction site healing was evaluated at the conclusion of HBO therapy, at 1 month, and 1 year later.

RESULTS

There were no serious complications. There was no correlation between preidentified risk factors and poor healing. At 1 year, 98.5% of all extraction sites were healed. Patients who did not heal were an average of 8 years since radiation, compared with 3.3 years for those who healed (P <.001).

CONCLUSION

Use of HBO is associated with a very low incidence of ORN at 1-year follow-up. However, the time since radiation has a positive correlation with risk for ORN.

Prevention of radiation-induced mucositis

Radiation-induced mucositis is an important dose-limiting acute side effect associated with the treatment of tumors of the upper aerodigestive tract. The toxicity of radiation therapy increases with prior or concurrent administration of some chemotherapeutic agents. Pretreatment eradication of infection, maintenance of oral hygiene, and treatment breaks, as necessary, have been the mainstay of the therapeutic options for patients with radiation-induced mucositis. Recent research has begun to clarify the pathophysiology of radiation-induced mucositis. This suggests that new, more effective agents for both prevention and treatment may be forthcoming in the near future. Currently, no highly effective and widely accepted prevention or treatment exists.

Rehabilitation with dental implants of oral cancer patients

The aim of this study was to evaluate the risks and complications of rehabilitation with dental implants after tumour surgery and radiotherapy. After a disease-free survival of 18 months, 29 patients who had undergone oral cancer treatment were rehabilitated with dental implants. The complication rate of implants in irradiated, non-irradiated and grafted bone was analyzed at least 3 years after implant placement. In the healing period, 28.6% of the implants in irradiated bone and 8.4% in non-irradiated bone showed soft tissue complications. Of the implants, 26.7% in the irradiated and 14.7% in the non-irradiated mandibular bone were lost in the first 36 months after placement. Thirty-one point two percent of implants inserted in non-irradiated bone grafts were affected and did not osseointegrate. Of 109 inserted implants, 70 were suitable for prosthetic rehabilitation. There are high complication rates after implant placement in oral cancer patients. Irradiation adversely affects soft tissue healing. Osseointegration is frequently disturbed, especially when implants were placed in non-vascularized bone grafts.