Transcutaneous carbon dioxide suppresses skeletal muscle atrophy in a mouse model of oral squamous cell carcinoma.

Cancer cachexia causes skeletal muscle atrophy, impacting the treatment and prognosis of patients with advanced cancer, but no treatment has yet been established to control cancer cachexia. We demonstrated that transcutaneous application of carbon dioxide (CO2) could improve local blood flow and reduce skeletal muscle atrophy in a fracture model. However, the effects of transcutaneous application of CO2 in cancer-bearing conditions are not yet known. In this study, we calculated fat-free body mass (FFM), defined as the skeletal muscle mass, and evaluated the expression of muscle atrophy markers and uncoupling protein markers as well as the cross-sectional area (CSA) to investigate whether transcutaneous application of CO2 to skeletal muscle could suppress skeletal muscle atrophy in cancer-bearing mice. Human oral squamous cell carcinoma was transplanted subcutaneously into the upper dorsal region of nude mice, and 1 week later, CO2 gas was applied to the legs twice a week for 4 weeks and FFM was calculated by bioimpedance spectroscopy. After the experiment concluded, the quadriceps were extracted, and muscle atrophy markers (muscle atrophy F-box protein (MAFbx), muscle RING-finger protein 1 (MuRF-1)) and uncoupling protein markers (uncoupling protein 2 (UCP2) and uncoupling protein 3 (UCP3)) were evaluated by real-time polymerase chain reaction and immunohistochemical staining, and CSA by hematoxylin and eosin staining. The CO2-treated group exhibited significant mRNA and protein expression inhibition of the four markers. Furthermore, immunohistochemical staining showed decreased MAFbx, MuRF-1, UCP2, and UCP3 in the CO2-treated group. In fact, the CSA in hematoxylin and eosin staining and the FFM revealed significant suppression of skeletal muscle atrophy in the CO2-treated group. We suggest that transcutaneous application of CO2 to skeletal muscle suppresses skeletal muscle atrophy in a mouse model of oral squamous cell carcinoma.

Risk factors associated with prognosis of patients with medication-related osteonecrosis of the jaw.

OBJECTIVES: Medication-related osteonecrosis of the jaw (MRONJ) is a severe adverse effect of antiresorptive and/or antiangiogenic agents. As the treatment application for MRONJ is controversial, we aimed to identify the risk factors for poor prognosis and to help determine appropriate management. METHODS: This study included 119 patients. Relevant clinical data were obtained for all the patients. In computed tomography images, osteosclerosis, osteolysis, cortical perforation (buccal or lingual), periosteal reaction, and sequestration were evaluated. RESULTS: Multivariate analyses showed statistically significant associations between poor prognosis in patients with MRONJ and conservative treatment alone (hazard ratio [HR] 1.89), osteolysis (HR 4.67), and the absence of sequestration (HR 5.33). CONCLUSIONS: Conservative treatment alone without clear objectives needs to be avoided, and osteolytic change could be the criteria for surgical intervention. As the boundary between the lesion and vital bone is indistinct, we recommend extensive surgery in cases with unpredictable sequestration.

The Efficacy of Carbon Dioxide Paste in Alleviating Pain in Patients After Neck Dissection: Protocol for a Double-Blinded, Randomized Controlled Trial.

BACKGROUND: Head and neck cancers that cause severe aesthetic and functional disorders normally metastasize to the cervical lymph nodes. Patients with cervical lymph node metastasis are undergoing neck dissection. Shoulder complaints are common after neck dissection, with patients reporting symptoms such as pain, weakness, shoulder droop, and disability. However, no safe and effective treatment is available for this condition at present. We will conduct a double-blinded, randomized controlled trial to evaluate the efficacy of carbon dioxide (CO2) paste in relieving pain in patients after neck dissection. OBJECTIVE: This will be the first clinical study to compare the efficacy of CO2 paste with placebo in relieving postoperative pain in patients who underwent neck dissection. METHODS: We will perform this trial at the Kobe University Hospital in Japan. Patients will be randomized 1:1 into the CO2 paste and control groups. Patients in the CO2 paste group will have the CO2 paste applied to the cervical surface skin for 10 minutes once per day for 14 consecutive days. The primary end point of the study is a change in the visual analog scale (VAS) scores of neck pain from baseline on day 1 (preapplication) to the end of drug application (day 15). Secondary end points include changes in the following parameters from baseline on day 1 to the end of drug application (day 15) or the study (day 29): neck pain VAS score (days 1-29), grip strength (days 1-15 and 1-29), VAS scores for subjective symptoms (the feeling of strangulation, numbness, swelling, and warmth in the neck and shoulder region) for days 1-15 and 1-29, whether the VAS score improved more than 30% (days 1-15), the arm abduction test (days 1-15 and 1-29), shoulder range of motion (abduction and flexion) for days 1-15 and 1-29, occurrence of skin disorders, and occurrence of serious side effects. Periodic monitoring will be conducted for participants during the trial. This study was approved by the certified review board of Kobe University. RESULTS: The intervention commenced in May 2021 and will continue until March 2024. The collected data will provide information on the efficacy of the CO2 paste treatment. The primary end point will be compared using the Wilcoxon test, with the 1-sided significance level set at 5%. Each evaluation item will be summarized. Secondary efficacy end points will be analyzed to provide additional insights into the primary analysis. Findings based on the treatment effects are expected to be submitted for publication in 2025. CONCLUSIONS: This trial will provide exploratory evidence of the efficacy and safety of CO2 paste in relieving pain in patients after neck dissection. TRIAL REGISTRATION: Japan Registry of Clinical Trials (jRCT) identifier: jRCTs051210028; https://jrct.niph.go.jp/en-latest-detail/jRCTs051210028. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/50500.

Relationship of Mitochondrial-Related Protein Expression with the Differentiation, Metastasis, and Poor Prognosis of Oral Squamous Cell Carcinoma.

Mitochondrial dysfunction and respiratory function changes have been consistently associated with the initiation and progression of cancer. The purpose of this study was to retrospectively investigate the expression of mitochondrial tumor-suppressor and DNA-repair proteins in patients with oral squamous cell carcinoma (OSCC) and to evaluate the relationship between their expression and prognosis. We enrolled 197 patients with OSCC who underwent surgical resection between August 2013 and October 2018. Clinical, pathological, and epidemiological data were retrospectively collected from hospital records. The expression of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), mitochondrial transcription factor A, mitochondrial tumor suppressor gene 1, silent information regulator 3, and 8-hydroxyguanine DNA glycosylase was investigated using immunochemistry. The 3-year disease-specific survival (DSS) rates of patients showing positive expression of all selected proteins were significantly higher than those of patients showing a lack of expression. Multivariate analysis revealed that the expression of PGC-1α (hazard ratio, 4.684) and vascular invasion (hazard ratio, 5.690) can predict the DSS rate (p < 0.001). Low PGC-1α expression and vascular invasion are potential clinically effective predictors of the prognosis of OSCC.

Transcutaneous carbon dioxide application suppresses the expression of cancer-associated fibroblasts markers in oral squamous cell carcinoma xenograft mouse model.

Oral squamous cell carcinoma (OSCC) is the most common head and neck cancer. Cancer-associated fibroblasts (CAFs) are the main stromal cells in the tumor microenvironment (TME). As CAFs promote tumor progression and hypoxia in the TME, regulating the conversion of normal fibroblasts (NFs) into CAFs is essential for improving the prognosis of patients with OSCC. We have previously reported the antitumor effects of transcutaneous carbon dioxide (CO2) application in OSCC. However, the effects of reducing hypoxia in the TME remain unclear. In this study, we investigated whether CO2 administration improves the TME by evaluating CAFs marker expression. Human OSCC cells (HSC-3) and normal human dermal fibroblasts (NHDF) were coinjected subcutaneously into the dorsal region of mice. CO2 gas was applied twice a week for 3 weeks. The tumors were harvested six times after transcutaneous CO2 application. The expression of CAFs markers (α-SMA, FAP, PDPN, and TGF-ß) were evaluated by using real-time polymerase chain reaction and immunohistochemical staining. The expression of α-SMA, FAP, PDPN, and TGF-ß was significantly increased over time after co-injection. In the CO2-treated group, tumor growth was significantly suppressed after treatment initiation. In addition, the mRNA expression of these markers was significantly inhibited. Furthermore, immunohistochemical staining revealed a significant decrease in the protein expression of all CAFs markers in the CO2-treated group. We confirmed that transcutaneous CO2 application suppressed CAFs marker expression and tumor growth in OSCC xenograft mouse model.

Local application of a transcutaneous carbon dioxide paste prevents excessive scarring and promotes muscle regeneration in a bupivacaine-induced rat model of muscle injury.

In postoperative patients with head and neck cancer, scar tissue formation may interfere with the healing process, resulting in incomplete functional recovery and a reduced quality of life. Percutaneous application of carbon dioxide (CO2 ) has been reported to improve hypoxia, stimulate angiogenesis, and promote fracture repair and muscle damage. However, gaseous CO2 cannot be applied to the head and neck regions. Previously, we developed a paste that holds non-gaseous CO2 in a carrier and can be administered transdermally. Here, we investigated whether this paste could prevent excessive scarring and promote muscle regeneration using a bupivacaine-induced rat model of muscle injury. Forty-eight Sprague Dawley rats were randomly assigned to either a control group or a CO2 group. Both groups underwent surgery to induce muscle injury, but the control group received no treatment, whereas the CO2 group received the CO2 paste daily after surgery. Then, samples of the experimental sites were taken on days 3, 7, 14, and 21 post-surgery to examine the following: (1) inflammatory (interleukin [IL]-1ß, IL-6), and transforming growth factor (TGF)-ß and myogenic (MyoD and myogenin) gene expression by polymerase chain reaction, (2) muscle regeneration with haematoxylin and eosin staining, and (3) MyoD and myogenin protein expression using immunohistochemical staining. Rats in the CO2 group showed higher MyoD and myogenin expression and lower IL-1ß, IL-6, and TGF-ß expression than the control rats. In addition, treated rats showed evidence of accelerated muscle regeneration. Our study demonstrated that the CO2 paste prevents excessive scarring and accelerates muscle regeneration. This action may be exerted through the induction of an artificial Bohr effect, which leads to the upregulation of MyoD and myogenin, and the downregulation of IL-1ß, IL-6, and TGF-ß. The paste is inexpensive and non-invasive. Thus, it may be the treatment of choice for patients with muscle damage.

Detection of bone marrow edema in differential diagnoses of odontogenic cysts using dual-energy computed tomography.

PURPOSE: In this study, we prospectively investigated the relationship between bone marrow edema (BME) and odontogenic cysts and explored the possibility of using dual-energy computed tomography (DECT) as an auxiliary tool for the diagnosis of odontogenic cysts. METHODS: This cross-sectional study included 73 patients who underwent the DECT scan and surgery for odontogenic cysts or odontogenic tumors. The virtual noncalcium (VNCa) computed tomography (CT) values and CT values were measured at several sites. The predictor variable was diagnosis, and the other variables included age, sex, and sites. The primary outcome was VNCa CT value. Variables were tested using the chi-square test or the Kruskal-Wallis test. The VNCa CT and CT values were tested using the Scheffe test for multiple comparisons. All variables were analyzed as independent variables affecting the VNCa CT values around the lesion in the multiple regression analysis. RESULT: There were 35 men and 38 women. The mean patient age was 50.0 ± 19.5 years (range: 8-86). The VNCa CT values (- 6.2 ± 34.3) around the lesion in patients with RCs were significantly higher than those in patients with dentigerous cysts (- 44.4 ± 28.6) and odontogenic keratocysts (- 67.3 ± 19.5). In multiple regression analysis, the VNCa CT values around the lesion showed a significant positive correlation with histological results (regression coefficient: - 0.605, P < 0.001). CONCLUSION: The presence of BME is associated with radicular cysts, and DECT can be used as an auxiliary tool for radicular cyst diagnosis.

Exploratory clinical trial to evaluate the efficacy and safety of carbon dioxide paste in healthy people.

INTRODUCTION: Scarring and pain are postoperative complications in patients after head and neck cancer treatment; however, there is no effective treatment. These complications are affected by local blood flow disorders, and it is well known that the transcutaneous application of carbon dioxide (CO2) improves local blood flow. Previously, we have shown that the transcutaneous application of carbon dioxide causes absorption of CO2 and increase the oxygen (O2) pressure in the treated tissue; it is expected that the application of CO2 may reduce scarring and pain caused by cancer treatment. We newly introduced the CO2 paste as a new CO2 application method, which does not need to use CO2 gas directly. In this study, we aimed to apply of CO2 paste to healthy people and to investigate its usefulness, safety and feasibility by analysing the increase in blood flow and frequency of adverse events. METHODS: We applied carbon dioxide paste to skin over the sternocleidomastoid and gastrocnemius muscles of eight healthy volunteers. The changes in blood flow before and after the CO2 paste application using dynamic MRI, and changes in the vital signs were evaluated. RESULTS: In the neck area and middle layer of the lower leg, the signal intensity (SI) significantly increased 60 seconds after application. In the surface layer of the lower leg, the SI was significantly increased 60 and 300 seconds after paste application. Although mild heat was noted after the paste application, no obvious adverse events occurred. CONCLUSION: We demonstrated the increase in SI by dynamic MRI at the site of the carbon dioxide paste application, which indicates the paste application is effective in improving the blood flow.

Factors Associated with Treatment Outcomes and Pathological Features in Patients with Osteoradionecrosis: A Retrospective Study.

A standard treatment for osteoradionecrosis (ORN) has not yet been established because of the diversity. Therefore, identifying the risk factors for a poor prognosis is essential. This study retrospectively investigated the factors associated with the prognosis of ORN in 68 patients. Relevant clinical data of all patients were obtained. Of the patients, 16 who underwent extensive surgery underwent histopathological analysis. The necrotic changes of the anterior and posterior margins in the cortical and cancellous bones were investigated. Multivariate analyses showed statistically significant associations between poor prognosis in patients with ORN and high radiation dose (hazard ratio [HR] 1.15), orocutaneous fistula (HR 2.93), and absence of sequestration (HR 2.49). Histopathological analysis showed a viable anterior margin of the middle portion of the cortical bone for all recovered cases; in contrast, most cases (75%) with a poor prognosis showed necrotic changes. The anterior margin of the cancellous bone was viable and resilient to high irradiation, regardless of the prognosis. These results suggest that patients with orocutaneous fistula should receive early surgical intervention, even if the affected area is limited or asymptomatic. In extensive surgery, a sufficient safety margin of necrotic bone, particularly in the anterior region, is required to improve the prognosis.

Success of dental implants in patients with large bone defect and analysis of risk factors for implant failure: a non-randomized retrospective cohort study.

OBJECTIVES: This study aimed to retrospectively investigate the success and survival rates of dental implants used for dentomaxillary prostheses at our hospital and the risk factors associated with large bone defects. MATERIALS AND METHODS: A total of 138 external joint system implants used for dentomaxillary prostheses in 40 patients with large bone defects were included in this study. The alveolar bone at the site of implant insertion was evaluated using panoramic radiography and computed tomography. Various risk factors (demographic characteristics, dental status, and operative factors such as the employment of alveolar bone augmentation, the site, the length, and diameter of implants) for implant failure and complete implant loss were investigated using univariate and multivariate analyses. The associations between the variables and the success and survival rates of dental implants were analyzed using the multivariate Cox proportional hazard models. RESULTS: The 10-year overall success and survival rates were 81.3% and 88.4% in this study. Multivariable analysis showed that the male sex (HR 6.22), shorter implants (≤ 8.5 mm) (HR 5.21), and bone augmentation (HR 2.58) were independent predictors of success rate. Bone augmentation (HR 5.14) and narrow implants (≤ 3.3 mm) (HR 3.86) were independent predictors of the survival rate. CONCLUSION: Male sex, shorter or narrow implants, and bone augmentation were independent risk factors for dental implants used in dentomaxillary prostheses in patients with large bone defects. CLINICAL RELEVANCE: Clinicians should consider these risk factors and pay close attention to the management of these patients.

Local Application of Transcutaneous Carbon Dioxide Paste Decreases Inflammation and Accelerates Wound Healing.

INTRODUCTION:  Delayed wound healing after surgery lowers the long-term quality of a patient's life and leads to discomfort and pain. However, treatments for wound healing are often difficult and have not yet been fully established. In this study, we investigated the effect of a special paste that can be administered transdermally and holds a non-gaseous carbon dioxide (CO2) source in its carrier, which can be applied to the head and neck region for wound healing in a rat skin defect model. METHODS: Forty-eight Sprague Dawley rats were randomized into control and CO2 groups. We punched a 6.2-mm wound on the back of each rat. The control rats were left untreated, whereas rats in the CO2 group were treated with the CO2 paste every day after surgery. We evaluated wound healing 3, 7, 14, and 21 days after wounding by analyzing the diameter of the wound, gene expression of inflammatory markers vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-ß, hypoxia-inducible factor (HIF)-1α, interleukin (IL)-1ß, and IL-6 using quantitative real-time polymerase chain reaction, hematoxylin and eosin, and immunohistochemical staining patterns. RESULTS: Rats in the CO2 group showed accelerated wound healing compared to those in the control group. Furthermore, VEGF and TGF-ß were overexpressed, whereas HIF-1α, IL-1ß, and IL-6 were downregulated in the rats treated with CO2. Immunohistochemical analysis also revealed similar patterns of expression. CONCLUSION: Taken together, the CO2 paste promoted wound healing by regulating the hypoxic environment, reducing inflammation, and accelerating angiogenesis.

Bacterial Colonization of the Condyle in Patients with Advanced Mandibular Osteoradionecrosis: Analysis of Hemimandibulectomy Specimens.

Advanced mandibular osteoradionecrosis (ORN) sometimes requires extended resection (e.g., hemimandibulectomy). Bacterial infection contributes to ORN pathogenesis. To control infection and determine the extent of debridement required, an understanding of bacterial spread within sites of mandibular ORN is important. The current study used a histopathological approach to assess bacterial colonization in the mandibular condyle and elucidate possible paths of bacterial spread towards the mandibular condyle. Four hemimandibulectomy specimens were selected. Areas of bone destruction were macroscopically assessed and confirmed using hematoxylin and eosin staining. Bacterial presence within mandibular condyle was confirmed with Gram staining. Bone exposure was observed in the molar area in all specimens. Macroscopic bone destruction was apparent especially near the medial side of the cortical wall. Gram staining revealed bacterial colonization of the mandibular condyle in three of the four specimens. In conclusion, bacteria tended to spread posteriorly and through the medial side of the mandibular cortical wall. In patients with advanced ORN, the potential for bacterial colonization of the mandibular condyle should be considered during treatment.

Transcutaneous Carbon Dioxide Decreases Immunosuppressive Factors in Squamous Cell Carcinoma In Vivo.

INTRODUCTION: In recent years, the tumour immunosuppressive mechanism has attracted attention as a cause of tumour chemoresistance. Although chemoresistance and immunosuppression of tumours have been reported to be associated with a hypoxic environment, effective treatments to improve hypoxia in tumours have not yet been established. We have previously applied carbon dioxide (CO2) to squamous cell carcinoma and have shown that improvement in local oxygenation has an antitumour effect. However, the effects of local CO2 administration on tumour immunosuppression, chemoresistance, and combination with chemotherapy are unknown. In this study, we investigated the effects of local CO2 administration on squamous cell carcinoma and the effects of combined use with chemotherapy, focusing on the effects on tumour immunosuppressive factors. METHODS: Human oral squamous cell carcinoma (HSC-3) was transplanted subcutaneously into the back of a nude mouse, and CO2 and cisplatin were administered. After administration twice a week for a total of 4 times, tumours were collected and the expression of tumour immunosuppressive factors (PD-L1, PD-L2, and galectin-9) was evaluated using real-time polymerase chain reaction and immunostaining. RESULTS: Compared with the control group, a significant decrease in the mRNA expression of PD-L1 was observed in both, CO2-treated and combination groups. Similarly, the expression of PD-L2 and galectin-9 decreased in the CO2-treated and combination groups. Furthermore, immunostaining also showed a significant decrease in the protein expression of tumour immunosuppressive factors in the CO2-treated and combination groups. CONCLUSION: It was confirmed that the tumour immunosuppressive factors decreased due to local CO2 administration to the mouse model. CO2 administration has the potential to improve the hypoxic environment in tumours, and combined use with chemotherapy may also improve tumour immunosuppression.

A Case Report of Tongue Lymphoepithelial Carcinoma with a Histological Diagnostic Dilemma.

Most head and neck lymphoepithelial carcinomas (LECs) arise in the nasopharynx and harbor Epstein-Barr virus (EBV). LEC is also a rare subtype of the oral squamous cell carcinoma (SCC). Morphologically, LEC is defined as resembling non-keratinizing nasopharyngeal carcinoma, undifferentiated subtype. The histological features and pathogenesis of oral LEC are not established. We describe a case of tongue LEC with histopathological diagnostic difficulties. A 72-year-old Japanese female presented with a whitish change on her left-side tongue. The diagnosis was atypical epithelium; neoplastic change could not be ruled out by a biopsy. Although the lesion was monitored at our hospital per her request, invasive carcinoma was detected 11 months later. Microscopically, conventional SCC was observed with the characteristic features as LEC confined to the deep part of the lesion. We briefly discuss this unusual histological finding and make a novel proposal for distinguishing oral LEC from LECs in other regions based on these histological findings.

The prospective evaluation and risk factors of dysphagia after surgery in patients with oral cancer.

BACKGROUND: This prospective study investigated the change of swallowing ability using the Swallowing Ability Scale System (SASS) and swallowing-related quality of life (QOL) by Performance Status Scale for Head and Neck Cancer patients (PSS-H&N). This study also investigated the risk factors for postoperative dysphagia in patients who received reconstructive surgery for oral cancer. SUBJECTS AND METHODS: This study included 64 patients (33 men and 31 women) who underwent radical surgery with neck dissection and reconstructive surgery for oral cancers between July 2014 and February 2018. We evaluated risk factors for poor swallowing ability after treatment, including demographic factors, preoperative factors and perioperative factors, with univariate and multivariate analyses. The change of swallowing ability by the SASS and swallowing-related QOL by PSS-H&N were evaluated prospectively prior to the initiation of surgery within 1 week and at 1 and 3 months after treatment. RESULTS: Advanced T stage (T3, 4) (odds ratio (OR) = 79.71), bilateral neck dissection (OR = 20.66) and the resection of unilateral or bilateral suprahyoid muscles (OR = 17.00) were associated with poor swallowing ability after treatment. The scores for time for food intake and Eating in Public were associated with decrease of QOL in the poor group. CONCLUSIONS: We propose that clinicians consider the risk factors identified in this study and pay close attention to the management of oral cancer patients with reconstructive surgery.

Red LED Light Is Influenced by IL-6 to Promote the Migration Ability of Oral Squamous Cell Carcinoma Cell Line.

AIM: The purpose of this study was to search for the influence of red LED light of oral squamous cell carcinoma cells (OSCC) Material & Methods: HSC-3 was irradiated with red LED light (630 nm/3 J). Proliferative capacity was analyzed using WST-1. Transwell migration assay, real-time PCR, and ELISA method were also used to analyze migratory ability. CONCLUSIONS: HSC-3 cells irradiated with red LED light showed increased migration ability. Interestingly, we clarified that the expression of Interleukin-6 (IL-6), which promotes the migratory ability of cancer cells, is induced.

Dental Rehabilitation for Free Fibula Flap-Reconstructed Mandible with Scar Contracture: A Technical Note.

Dental rehabilitation with osseointegrated implants in reconstructed mandibles is a common procedure, but the technique still requires improvement, especially in its reliability and technical simplification. We herein report dental rehabilitation of a free fibula-reconstructed mandible with scar contracture. A vestibuloplasty technique with application of a polyglycolic acid (PGA) sheet is described. The implants were inserted into a viable fibula flap with severe scar contracture of the overlying epithelium resulting from vascular instability in skin paddle. Only the fibula periosteum was sutured after implant insertion; exposed surfaces were covered with a combination of PGA sheet and fibrin sealant. The area with PGA sheet coverage gradually healed with moderate contracture. The epithelium around the almost implants became immobilized. The implant-supported removable partial denture with custom titanium bar was acceptable. Dental rehabilitation is possible for reconstructed mandibles with severe scar contracture. Application of a PGA sheet may be useful for vestibuloplasty in patients with reconstructed mandibles.

Clinical Evaluation of CO2 Laser Vaporization Therapy for Oral Lichen Planus: A Single-Arm Intervention Study.

Objective: The purpose of this study is to evaluate the efficacy of CO2 laser vaporization therapy for oral lichen planus (OLP) refractory to conservative treatments. Methods: The study group comprised 16 patients with clinically and histologically diagnosed OLP. They underwent conservative treatment for 3 months using an adrenal cortex hormone ointment and azulene sulfonate sodium hydrate gargle. Patients who showed no improvement with conservative treatment underwent CO2 laser vaporization therapy (3 W, continuous-wave mode). The assessment was performed using the numerical rating scale (NRS) as a subjective indicator and the Thongprasom sign score (TSS) as an objective indicator of OLP. These two scales were recorded during examinations performed before treatment and then at 7 days, 1, 3, and 6 months, and 1 year after irradiation. Differences between preirradiation and each point of time after irradiation were tested by Wilcoxon's signed-rank tests. Results: Laser irradiation was administered to 9 patients with 11 sites. The NRS score and TSS decreased at all 11 sites (100%) and 10 sites (90.9%) at 1 year after irradiation compared with preirradiation scores. The NRS score and TSS were statistically lower (p < 0.05) at 1 and 3 months (short-term) and 6 months and 1 year (mid-long-term) after irradiation than the preirradiation scores. There were no patients with malignant transformation during the study period. Conclusions: These single-arm clinical trial results show the efficacy of CO2 laser vaporization therapy for OLP refractory to conservative treatment.