• The Journal of Advanced Prosthodontics
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• v.8 no.5
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• pp.363-371
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• 2016

PURPOSE. On maxillofacial tumor patients, oral implant placement prior to postoperative radiotherapy can shorten the period of prosthetic reconstruction. There is still lack of research on effects of post-implant radiotherapy such as healing process or loading time, which is important for prosthodontic treatment planning. Therefore, this study evaluated the effects of post-implant local irradiation on the osseointegration of implants during different healing stages. MATERIALS AND METHODS. Custom-made implants were placed bilaterally on maxillary posterior edentulous area 4 weeks after extraction of the maxillary first molars in Forty-eight Sprague-Dawley rats. Experimental group (exp.) received radiation after implant surgery and the other group (control) didn't. Each group was divided into three sub-groups according to the healing time (2, 4, and 8 week) from implant placement. The exp. group 1, 2 received 15-Gy radiation 1 day after implant placement (immediate irradiation). The exp. group 3 received 15-Gy radiation 4 weeks after implant placement (delayed irradiation). RESULTS. The bone mineral density (BMD) was significantly lower in the immediate irradiation groups. BMD was similar in the delayed irradiation group and the control group. The irradiated groups exhibited a lower bone-to-implant contact ratio, although the difference was not statistically significant. The irradiated groups also exhibited a significantly lower bone volume and higher empty lacuna count than the control groups. No implant failure due to local irradiation was found in this study. CONCLUSION. Within the limits of this study, the timing of local irradiation critically influences the bone healing mechanism, which is related to loading time of prostheses.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.13 no.3
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• pp.265-277
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• 1991

In this study, the healing changes of the implanted bone and its surrounding tissues were examined on the histopathologic basis following implantation of the freeze - dried and radiation - sterilized allogeneic bone in Rectus abdominicus of the rat. This study was performed to see the tissue recations after implantation of the freeze - dried and radiation - sterilized allogeneic bone and whether osteogenesis or osteo - induction or osteo - conduction is happened. And the results were as follows : 1. The shape of the implanted allogeneic bone of the 1, 2 - week group specimen was similar to that of normal bone in light - microscopic finding and the atrophy of cellular organells was found in trans - mission electron - microscopic finding. 2. The implanted allogeneic bone was surrounded with the dense fibroconnective tissues, and infiltration of the chronic inflammatory cells gradually became increased. 3. Hyaline degeneration was observed in the surrounding tissue at the 3, 4, 6 - week group specimen. 4. Light - microscopically the resorption of implanted bone became prominent after 4 - week group and the necrosis of allogeneic bone implant became severe with loss of cell components in lacuna. 5. Electron - microscopically, the osteoclast - like cells ere fond after, 2 - week group. It is summarized that the osteo - conduction potential of the bone is remained just after implanting the freeze - dried and radiation - sterilized allogeneic bone on Rectus abdominicus of the rat, but gradually it disappeared with the gradual increse of chronic inflammatory reaction and osteoclastic activity. So it is suggested that the antigenicity of the freeze - dried and radiation - sterilized bone is remained and it has little osteo - conductive activity when it is implanted in the muscle.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.2
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• pp.168-173
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• 2006

The side effects of head and neck radiation therapy include mucositis, xerostomia, loss of taste, radiation caries, oral infection, osteoradionecrosis and trismus. When a patient is arranged to begin head & neck radiotherapy, oral pathologic lesions are examined and managed for the prevention of oral complications. The advanced odontogenic infection should be especially controlled before the radiotherapy and the patient must be instructed for proper oral prophylaxis. Generally the more conservative treatments, such as, scaling, restoration, endodontic treatment, are the care of choice and dental extraction is performed in advanced periapical and periodontal pathologic conditions. If the dental extraction should be done, the radiotherapy consequently will be delayed until there is epithelium covering the extraction socket, leaving no exposed bone. The cancer patient with severe emotional stress pray for the early radiation therapy, in spite of possibility of the recurrent odontogenic infectious lesions. So, the authors attempted to do the early radiation therapy by the conservative endodontic drainage and surgical incision & drainage without extraction of the infected teeth, and resulted in relatively good prognosis without the severe side effects of head and neck radiotherapy.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.1
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• pp.285-297
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• 1998

This report details a case of 8-year-old girl showing failure of odontogenesis after chemo-radiation therapy for the rhabdomyosarcoma at the age of 4. The observed results were as follows : 1. Past history revealed that she had received for a total radiation dose of 4430cGy, 29 fractions in 6 weeks and chemotherapy with vincristine, actinomycin D and cytoxan, followed as maintenance phase for 2 years. 2. The patient was symptom -free and appointed for the treatment of multiple dental caries. 3. Oral examination showed hypoplastic enamel on whole erupted permanent teeth and showed retarded eruption. 4. Conventional radiograms showed failure of root development including abrupt cessation of root formation and root agenesis, and microdontia, missing teeth, irregular enamel, dislocation of the impacted teeth. Additional finding showed good healing bone pattern on the left mandibular ramus and angle area. 5. Cephalometric analysis revealed failure of bite raising due to incomplete eruption of all the first molars and made it possible to suspect entrapped mandibular growth and then Class II tendency growth. 6. There was correlation between the time of chemo-radiation therapy and the damage of the teeth.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.3
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• pp.239-246
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• 2019

The purpose of this study was to examine dental complications and to evaluate the effects of initial treatment age, treatment modalities, and treatment duration on the disorder after radiation and chemotherapy in pediatric cancer patients. For 93 children with clinical and radiographic data, the number of teeth, the morphology of teeth, the shape of the roots, and development status of the dentition were evaluated. Dental development disorders were found in 61.3% of the children. The mostly found abnormality was root deformity with the prevalence of 31.2%. In children submitted to the therapy before the age of 6, the number of missing teeth (p = 0.029) and microdontia (p = 0.003) were greater compared to the children who started to receive the treatment after the age of 6. The combination of radiation and chemotherapy showed significantly greater incidences of missing teeth (p = 0.030), microdontia (p = 0.046), and root deformity (p = 0.009) when compared with the sole application of chemotherapy. When the children were submitted to anticancer therapy for 18 months or longer duration, greater number of missing teeth (p = 0.032), microdontia (p = 0.011), root deformity (p = 0.025), and total number of teeth affected (p = 0.036) were observed compared with duration less than 18 months. The number of dental abnormalities increased when the children were treated at earlier ages, with combination of radiation and chemotherapy, and for longer period of time.

• Imaging Science in Dentistry
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• v.30 no.4
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• pp.275-279
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• 2000

Purpose: Radiation damage is produced and viable cell number is reduced. We need to know the type of cell death by the ionizing radiation and the amount and duration of cell cycle arrest. In this study, we want to identified the main cause of the cellular damage in the oral cancer cells and normal keratinocytes with clinically useful radiation dosage. Materials and Methods: Human gingival tissue specimens obtained from healthy volunteers were used for primary culture of the normal human oral keratinocytes (NHOK). Primary NHOK were prepared from separated epithelial tissue and maintained in keratinocyte growth medium containing 0.15 mM calcium and a supplementary growth factor bullet kit. Fadu and Hep-2 cell lines were obtained from KCLB. Cells were irradiated in a /sup 137/Cs γ-irradiator at the dose of 10 Gy. The dose rate was 5.38 Gy/min. The necrotic cell death was examined with Lactate Dehydrogenase (LDH) activity in the culture medium. Every 4 day after irradiation, LDH activities were read and compared control group. Cell cycle phase distribution and preG1-incidence after radiation were analyzed by flow cytometry using Propidium Iodine staining. Cell cycle analysis were carried out with a FAC Star plus flowcytometry (FACS, Becton Dickinson, USA) and DNA histograms were processed with CELLFIT software (Becton Dickinson, USA). Results: LDH activity increased in all of the experimental cells by the times. This pattern could be seen in the non-irradiated cells, and there was no difference between the non-irradiated cells and irradiated cells. We detected an induction of apoptosis after irradiation with a single dose of 10 Gy. The maximal rate of apoptosis ranged from 4.0% to 8.0% 4 days after irradiation. In all experimental cells, we detected G2/M arrest after irradiation with a single dose of 10 Gy. Yet there were differences in the number of G2/M arrested cells. The maximal rate of the G2/M ranges from 60.0% to 80.0% 24h after irradiation. There is no significant changes on the rate of the G0/G1 phase. Conclusion: Radiation sensitivity was not related with necrosis but cell cycle arrest and apoptosis. These data suggested that more arrested cell is correlated with more apoptosis.

• Imaging Science in Dentistry
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• v.45 no.4
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• pp.263-265
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• 2015

Cone-beam computed tomography (CBCT) is routinely recommended for dental diagnosis and treatment planning. CBCT exposes patients to less radiation than does conventional CT. Still, lack of proper education among dentists and specialists is resulting in improper referral for CBCT. In addition, aiming to generate high-quality images, operators may increase the radiation dose, which can expose the patient to unnecessary risk. This letter advocates appropriate radiation dosing during CBCT to the benefit of both patients and dentists, and supports moving from the concept of "as low as reasonably achievable" (ALARA) to "as low as diagnostically acceptable" (ALADA).

• Journal of Korean society of Dental Hygiene
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• v.9 no.2
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• pp.111-124
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• 2009

This study analyzes through the review of literature and laws the exposure time, clinical frequency, and radiation exposure of intraoral and extraoral radiography as well as of panoramic radiography performed by dental hygienists in dental clinics, compares the dental radiology curriculums of radiological science and dental hygiene departments, and proposes the expansion of dental hygienists' radiography operations. The radiology curriculums were compared between the radiological science and dental hygiene departments of colleges. For new analysis by radiography for dental diagnosis, the exposure time, radiation absorbed dose, effective dose, and number of days of natural radiation were compared by the type of oral radiation films and radiographical techniques proposed by domestic and international studies. The exposure time of panoramic radiography is 15 seconds and it takes about two minutes for completion, whereas the exposure time of the standard radiography is 0.2~0.8 seconds and it takes 10 times longer for completion of the radiography of full mouth than the panoramic radiography. The standard radiography can cause distortions of radiation at severely curved parts of dental arch and palatopharyngeal reflex. However, panoramic radiography can be performed even for lock jaw patients, causes less inconvenience to patients and is much simpler than the standard radiography. The percentage of dental clinics where radiography is performed by dental hygienists was 92.0%, and the percentage of standard film radiography by dental hygienists was 98% whereas the percentage of panoramic radiography by dental hygienists was 92%. For the absorbed dose which is an indicator of radiation exposure, the When the effective dose which is an indicator of the danger of radiation exposure was converted to the number of days of natural radiation, it was 3.3 days for panoramic radiography, but 13.9 days for the full mouth standard radiography by bisecting angle technique which was 4.2 times longer than the panoramic radiography. There were two colleges that had a dental radiology course with two credits in the departments of radiological science. The credits for dental radiology courses in the department of dental hygiene ranged varied by college, ranging from 3 to 8; on average, the theory course was 2.2 credits and the practice course was 2.02 credits. To summarize the above results, the percentage of dental clinics where panoramic radiography is performed by dental hygienists under the guidance of dentists is high. Panoramic radiography has become an essential facility for dental clinics. It is faster than standard film radiography and less dangerous due to low radiation exposure. Panoramic radiography is a simple mechanical job that does not require training of oral radiography by radiotechnologist. Because panoramic radiography is one of major operations which must be performed at all times in dental clinics, it must be designated as intraoral technique rather than extraoral technique, or legalized for inclusion in the scope of operations of dental hygienists.

• Journal of radiological science and technology
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• v.42 no.6
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• pp.469-476
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• 2019

The purpose of this study examines the education, knowledge and behavior of radiation safety management among dental workers and compares the education, knowledge and behavior between dental hygienist group and other occupational groups. This study was conducted from November 2nd to November14th, 2019. The survey was conducted on dental workers(dental hygienists, nursing, assistants, coordinators, etc.) who worked in dental hospitals and clinics in Busan area. The tool of this study was modified and adapted to the clinical setting based on the questionnaire. Radiation safety education has 39 dental hygienists who had more education than non-dental hygienists (p=0.286). The most common types of radiation safety education were self-education which usually performed by dentistry, followed by conservative education and others. The average of radiation attitudes, knowledge and behaviors was higher in the dental hygienist group then in the non-dental hygienist group. On the item-specific behavior among employees, the question of 'the radiation should be shielded according to the menstrual cycle or pregnancy of the woman of childbearing' was significant (p<0.05). On the item-specific knowledge between occupations, the question of 'the intensity of X-rays decreases over distance' and 'the individual exposure can be measured by TLD badge or film badge' was significant (p<0.05). Taken together, these results indicate that the dental hygienist group is more concerned about radiation safety and that the dental hygienist group is receiving more radiation safety management training. However, if there is a low level of 'has experienced' in the presence or absence of safety management education, it is difficult to train radiation safety management in dentistry. Therefore, it is considered that dentists should be trained in radiation safety management periodically to pay attention to radiation safety accidents.

• Imaging Science in Dentistry
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• v.31 no.4
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• pp.227-233
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• 2001

Purpose: The purpose of this study was to investigate the apoptosis induction in tissues constituting the craniofacial region of growing rat by irradiation. Materials and Methods: The submandibular gland, brain, articular cartilage of condylar head, and calvarium were extracted from 20-day-old rats irradiated 10 Gy. Apoptosis of each tissue was examined by DNA fragmentation and estimated quantitatively using apoptotic index on TUNEL assay. Apoptotic index of each tissue was calculated by the equation for apoptotic cells/total cells × 1,000 on the images of confocal laser scanning microscopy. Apoptotic index was analyzed statistically according to the time lapse after irradiation on the tissues. Results : In the submandibular gland, apoptotic index was significantly increased from 6 hours after irradiation showing the highest value at 12 hours and decreased to the control level at 3 days after irradiation. In the brain, apoptotic index was abruptly reached to the maximum value at 6 hours after irradiation and decreased to the control level at 4 days after irradiation. Articular cartilage and calvarium showed no or little apoptotic signals. The results obtained by the apoptotic index accorded with that of DNA fragmentation. Conclusion : Radiation was closely related with the apoptosis of submandibular gland and brain but, not related with the apoptosis of the articular cartilage of condylar head and calvarium. The changes induced by radiation of the hard tissues would not be explained by apoptosis.