| BackgroundWith the morbidity of head and neck cancer increasing,radiation therapy is one of the main treatments of head and neck malignant tumors.In the radiation treatment of head and neck cancer,not only the tumor tissue was exposed,but also the normal oral tissue surrounded by the tumor was affected.Patients often suffer from many oral complications,such as mucositis,xerostomia,pain,dysphagia,dental caries,osteoradionecrosis and so on.Objective(1)According to the head and neck cancer patient’s tumor types,locations and radiotherapy plan,different types of personalized oral positioning stents were designed and fabricated with technology of prosthodontics.The normal oral tissue such as tongue,parotid gland,floor of mouth,teeth,mandible,will be pushed away from the radiation target region,which is precise and stable position repeated in the course of radiotherapy.(2)Personalized oral positioning stents were applied in head and neck cancer patients with intensity modulated radiation therapy(IMRT),and evaluated the clinical effects of stents by comparing the maximum and average doses of normal oral tissues from patients who wearing stents with patients who did not wear.Materials and methods(1)Design and fabrication of oral positioning stent: The impressions of the maxillary and mandibular teeth were made by alginate impression material.According to patients’ ability to open the mouth,an occlusion was record at an open vertical dimension of occlusion position with modeling wax.It’s usually 15 to 20 mm,which is one-half to two-thirds of the patient’s maximal opening.Then mounting the cast and wax record were transferred on an appropriate articulator simultaneously and fabricating interocclusal rims to occupy both of the space between maxillary and mandibular casts.According to the types and locations of the head and neck tumors,the wax patterns of oral positioning stents were designed and fabricated.After the completion of wax pattern,then processing with flasking,dewaxing,packing with methyl methacrylate resin(MMA),it was commonly used as the base of removable partial denture or complete denture in prosthodontics,and conducted by heat-curing,polishing,patient attempting.(2)Clinical application of oral positioning stents: Patients with nasopharyngeal carcinoma were randomly divided into experiment group and control group.Personalized oral positioning stents were used for the experiment group patients.The patients in experiment group wear stents when undergoing computerized tomography(CT)and radiotherapy while the control group did not.The clinical data were collect,including age,gender,tumor stage,concurrent chemotherapy before radiotherapy.The incidence of oral adverse reactions was compared,such as oral mucositis,xerostomia between the two groups at the day before radiotherapy and third month after completion of radiotherapy.After the radiotherapy,the doses of clinical target volume(CTV)and the normal oral tissues were analyzed between the experiment group and the control group by using SPSS23.0 software.A p value of less than 0.05 was considered statistically significant.Result(1)Three kinds of personalized oral positioning stents were fabricated: mouth opening tongue-depressing stent,mouth opening tongue-deviating stent,mouth opening tongue-backward stent.The stents were able to push the oral normal tissue away from the high dose target area of radiotherapy,and maintain them on accurate and stable repeatable position.(2)According to the inclusion criteria,a total of 23 patients with intensity modulated radiotherapy were randomly divided into experiment group and control group.There were 11 patients in experiment group and 12 in the control group.There was no significant difference between the two groups in age,gender,tumor stage and concurrent chemotherapy.The dosimetric analysis indicates that there was no significant difference between two groups when comparing the maximum and mean dose to the clinical target volume(CTV).The mean irradiation dose of the left parotid in experiment group was significantly lower than control group(24.93±4.47 Gy vs 28.50±3.32 Gy,t=2.188,p=0.040).Corresponding values of the right parotid(25.65±4.68 Gy vs 29.40±3.14 Gy,t=2.275,p=0.034).The maximum and mean irradiation dose of the mandible in experiment group were significantly lower compared with control group(62.25±3.20 Gy vs 65.16±3.00 Gy,t=2.251,p=0.035),(33.49±2.37 Gy vs 38.60±3.89 Gy,t=3.755,p=0.001),respectively.(3)The two groups of patients have no mucositis and xerostomia before radiotherapy.After radiotherapy,the incidence of mucositis in the experiment group was significantly lower than the control group.There were 1 patient occurred grade 2 mucositis on soft palate and 8 patients with grade 1 mucositis on soft palate and posterior pharyngeal wall in the experiment group.However there were 4 patients with grade 3 mucositis,including 2 cases on the tongue and 2 cases on soft palate in the control group.Two groups of patients showed varying degrees of xerostomia after radiotherapy.The two groups of patients have no mucositis in 3 months after radiotherapy.4 patients in control group still in grade 2 xerostomia.ConclusionThe fabrication process of personalized oral positioning stent process is simple.The patients wearing stents underwent IMRT could enable a significant reduction of the radiation dose to surrounding oral normal tissues without compromising the dose distribution to the tumor target volume. |
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