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Table of Contents   
ORIGINAL RESEARCH  
Year : 2012  |  Volume : 23  |  Issue : 6  |  Page : 774-777
Mandibular bone changes induced by head and neck radiotherapy


Department of Oral Radiology, Shiraz University of Medical Sciences, Shiraz, Iran

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Date of Submission09-Jun-2011
Date of Decision01-Nov-2011
Date of Acceptance28-Nov-2011
Date of Web Publication3-May-2013
 

   Abstract 

Context: The mandible is inevitably affected by radiation during radiotherapy of head and neck cancers. Surveys have shown that most of the emphasis has been on osteoradionecrosis (ORN), while the other bony changes occurring in this area have been largely ignored.
Aims: In this study we examine the radiologic changes in the mandible of irradiated patients using panoramic radiography and compare it with the mandible in non-irradiated cases.
Materials and Methods: Mandibular bone changes of 48 patients who had received therapeutic radiation for head and neck cancer were assessed. We measured the width of the cortex and the width of the mandibular canal on panoramic radiographs and assessed the changes by comparison with the mandibular bones of non-irradiated subjects. Clinical evaluations were performed for assessing maximum jaw opening, masticatory muscle tenderness, and presence of mucosal ulcers and/or exposed bone in the oral cavity.
Statistical analysis: Paired t-test, Chi-square test, and Mann-Whitney test were used for statistical analysis. P < 0.05 was taken to indicate statistical significance.
Results: There was no evidence of mucosal ulceration or exposed bone in irradiated patients. There was significant relationship between the number of years after radiotherapy and the degree of limitation of mouth opening (P = 0.000). Receipt of concurrent chemotherapy did not seem to have any additive effect on the width of mandibular canal or the thickness of the mandibular cortex.
Conclusion: Reduction in the width of the mandibular cortex and dimensions of the inferior alveolar canal could be considered as one of the effects of head and neck radiotherapy.

Keywords: Bone changes, panoramic, radiotherapy

How to cite this article:
Khojastepour L, Bronoosh P, Zeinalzade M. Mandibular bone changes induced by head and neck radiotherapy. Indian J Dent Res 2012;23:774-7

How to cite this URL:
Khojastepour L, Bronoosh P, Zeinalzade M. Mandibular bone changes induced by head and neck radiotherapy. Indian J Dent Res [serial online] 2012 [cited 2020 Nov 28];23:774-7. Available from: https://www.ijdr.in/text.asp?2012/23/6/774/111258
Radiotherapy (RT) for treatment of head and neck cancer produces a wide range of side effects in patients, including decreased salivary secretion, xerostomia, opportunistic infection, radiation caries, dysphagia, local discomfort, and limitation of mouth opening. [1]

Osteoradionecrosis (ORN) is a potentially devastating complication of radiotherapy in head and neck cancer. According to the literature, ORN is diagnosed when exposed irradiated bone fails to heal over a period of 3 months. It can be the acute/immediate or delayed effect of radiation therapy It can be the short- or long-term effect of radiation therapy It can be the acute/immediate or delayed effect of radiation therapy on bone and the surrounding soft tissue. Although incidence rates vary, most reports cite an incidence of 5%-15% for ORN in irradiated patients. [2]

Over the past 80 years a number of theories about the pathogenesis of ORN have been proposed, with consequent implications for its treatment. Until recently, tissue hypoxia was accepted as the primary cause of ORN and this led to the use of hyperbaric oxygen (HBO) for both treatment as well as prevention of the complications of RT in the head and neck. A new theory that has been put forward proposes that damage to bone is caused by radiation-induced fibrosis. According to this theory, cells in the bone are damaged as a result of acute inflammation and free radicals, and there is chronic activation of fibroblasts by a series of growth factors. [3]

Complications due to RT are related to the dose and frequency of the radiation as well as the site exposed to radiation. The number of complications increases with the volume of tissue that is irradiated. Intraosseous lesions are relatively radioresistant. Complications also increase as the dose increases; Using dose fractionation, -exposing the patient to lower doses over a longer period- reduces the rate of side effects. Patient-related variables, such as preirradiation bone surgery, bad oral hygiene, alcohol and tobacco abuse, and dental extraction after RT, have all been reported to increase complications. [1],[4]

Trismus, or limited mouth opening, is usually seen at 3-6 months after the end of RT, and it remains a major problem for the rest of the patient's life. The prevalence of trismus after head and neck RT ranges from 5% to 38%. [5]

Panoramic radiography has been used widely to screen for mandibular bone changes as the modality is freely available and involves low doses of radiation.

The major part of the mandible is inevitably affected by the radiation during RT of head and neck cancers and therefore this retrospective cross-sectional study was done using panoramic radiography to determine the effect of RT on mandibular bone. We also wanted to evaluate the radiation effects on soft tissue.


   Materials and Methods Top


Fifty-four patients with a diagnosis of head and neck malignancy that had been treated with RT at the RT Service of Namazi Hospital were selected for this study. Pretherapy dental examination findings and treatment information were available for all patients. Prior to RT, the periodontal condition was evaluated, and teeth with mobility, significant pocketing, furcation involvement, or advanced recession were extracted.

To be included in this study the subject had to satisfy the following inclusion criteria:

  • The patient must have had the mandible in the irradiated field
  • More than 1 year had passed from RT, with no evidence of remnant tumor or tumor recurrence
  • RT was received alone or in conjunction with chemotherapy
  • All cases benefited from preventive oral hygiene protocols, then recieved high-voltage radiation
  • The prescribed target doses were 50-60 Gy, with 2-2.2 Gy/fraction.
Six patients had received RT for breast cancer and therefore the absorbed dose was different in the left and right sides. Thus, we had 96 regions in the case group.

The control group was selected among the patients attending the radiology department of Shiraz Dental School. These subjects were matched for age and gender and had no known bony diseases.

During the clinical examination, maximum jaw opening, masticatory muscles tenderness, paresthesia, and presence of mucosal ulcers and/or exposed bone in the oral cavity were recorded by an oral medicine dentist. All patients underwent panoramic radiography (ProMax ® , Planmeca, Finland) in the standard position. Radiographs were digitized at 300 dpi (Microtek ® i800). Mandibular cortex width and the width of the mandibular canal in panoramic radiography were calculated for both groups using AutoCAD ® software (2009) with precision of 0.00. The width of the mandibular canal was measured where the bisecting line of gonial angle crosses borders of the canal. [Figure 1]. The width of the cortex was measured along a vertical line from the inferior border of the mental foramen to the mandibular cortex [Figure 2]. The paired t-test, Chi-square test, and Mann-Whitney test were used for statistical analysis. P<.05 was assumed to indicate statistical significance.
Figure 1: Canal thickness measured where the bisect of gonial angle crosses the inferior border of canal.

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Figure 2: Cortex thickness measuring along a vertical line from the inferior border of the mental foramen to the inferior border of the mandible.

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   Results Top


The mean age of the patients was 46.87 (14-70)years;. Males constituted 67.7% of the subjects and females 32.3%.

Among the patients 27.3% were edentulous, 34.6% were partially dentate, and 38.1% had all their natural teeth.

Twenty-three patients reported trismus. Other clinical complications due to head and neck RT were xerostomia (51.2%), mucositis (11.2%), complete loss or reduction in taste (38%), oral candidiasis (8.8%), and pain (5.6%). None of the subjects had paresthesia. The Chi-square test showed that there was a significant relationship between the number of years after RT and the complaint of limitation of mouth opening (P=.000). However, other complaints did not differ statistically between two groups by passing years. The width of the mandibular canal and the thickness of the cortex, as well as the amount of maximum jaw opening, were significantly lower in patients exposed to RT as compared to controls [Table 1] and [Table 2]. The amount of maximum jaw opening showed a significant decrease with increasing years following RT [Table 3]. Administered of chemotherapy along with RT did not have any significant effect on the width of the mandibular canal or cortex [Table 4]. Mucositis showed a significant increase with increasing number of RT sessions.
Table 1: Comparison of mandibular canal and cortex width in both groups

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Table 2: Comparison of maximum jaw opening in case and control groups

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Table 3: Comparison of maximum jaw opening with increasing years following radiotherapy

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Table 4: Comparison of treatment type on width of canal and cortex

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   Discussion Top


The incidence of ORN following RT of head and neck cancer has declined in recent decades. [6] The reduction in incidence of ORN has occurred despite increasing intensity of therapy in recent years, such as altered fractionation and concurrent-chemoradiation, RT, which are generally characterized by increase in acute side effects and occasionally by increased rates of late sequelae. ORN is a late sequel and some cases may require long follow-up; however, the large majority of events have been reported to occur within the first few years after the completion of treatment. The risk of a second episode of ORN after management of an initial episode is low. [4],[7] So, in this study complications a 1-year following RT were compared to long-term follow-ups.

No case of exposed bone or mucosal ulcer was detected in this study. The reduction in the rates of ORN may be attributed to more conformal dose distributions, which spared parts of the mandible that receive high doses with conventional techniques. However, it is not easy to assert whether it is dosimetric improvements or better dental care that was most important in preventing bony exposure in our patients.

Significant decrease in the width of the mandibular canal and thickness of the cortex was seen in irradiated cases, and this can be considered as an indicator of bony changes following RT. However, there was no significant difference in these changes between one year following RT and long follow ups. Thus, it seems that, as for ORN, the risk of these bony changes is highest during the first year post irradiation.

In this study significant difference in the width of mandibular cortex was detected in the region of the mental foramen between the two groups. It was also noted that concurrent chemotherapy did not have any significant additive effect on cortex width.

Nearly half of patients suffered from limitation of mouth opening. Trismus can be caused by tumor infiltration into the masticatory muscles and/or temporomandibular joint dysfunction (TMD). It also can be a result of RT treatment when the masticatory muscles or temporomandibular joint (TMJ) are in the field of radiation. A combination of both situations may occur. [5] During clinical examination we noticed that not only was maximum jaw opening significantly lower in irradiated patients than in control, but there was also a significant decrease with increasing years following RT.

Engelmeier and Whitmyer support the idea that the limitation in mouth opening may occur in the course of RT due to stiffening of the epidermal and dermal layers. [8],[9] Deficiency in mucosal lubrication causes pain and discomfort as well as significant soft tissue thickening. masticator muscle atrophy have been reported leading to difficulty in mouth opening. [1],[10]

In this study, 11.2% cases presented with mucositis and 51.2% with xerostomia. These conditions may also affect mouth opening capacity and therefore more detailed investigation, taking into consideration the contribution of these conditions, is necessary before we can have accurate figures of the prevalence of limitation in mouth opening following RT.

According to Jereczek-Fossa [4] radiological evaluation of the mandible is not routinely performed after irradiation for head and neck cancer and the majority of authors report only the ORN rate. So, the incidence of bone injury is probably underestimated in literature. Long-term evaluations of bone alteration in irradiated patients could provide more precise information on postradiotherapy changes.

Histomorphometric analyses of the proximal tibias of rat shows that increasing doses of radiation may influence bone thickness at the implant-bone contact. [11] In dental applications, lower radiation doses (<50 Gy) were significantly associated with improved implant survival compared with higher doses (>50 Gy). Since all patients in this study had received doses in the range of 50-60 Gy, we could not examine the effect of variations in RT doses. However, fibrotic changes in masticatory muscles may occur in irradiation dose range of 50-60 Gy.


   Conclusion Top


Reduction of width of mandibular cortex and dimensions of the inferior alveolar canal could be considered to be among the postirradiation effects on mandibular bone of head and neck RT. These changes may be a predictor of the risk of future ORN in irradiated subjects. Long-term follow-up is recommended to evaluate the clinical consequences of these radiologic changes.

 
   References Top

1.Grandi G, Silva ML, Streit C, Wagner JC. A mobilization regimen to prevent mandibular hypomobility in irradiated patients: An analysis and comparison of two techniques. Med Oral Patol Oral Cir Bucal 2007;12:E105-9.  Back to cited text no. 1
    
2.Gal TJ, Yueh B, Futran ND. Influence of Prior Hyperbaric Oxygen Therapy in Complications Following Microvascular Reconstruction for Advanced Osteoradionecrosis. Arch Otolaryngol Head Neck Surg 2003;129:72-6.  Back to cited text no. 2
    
3.Lyons A, Ghazali N. Osteoradionecrosis of the jaws: Current understanding of its pathophysiology and treatment. Br J Oral Maxillofac Surg 2008;46:653-60.  Back to cited text no. 3
    
4.Jereczek-Fossa BA, Orecchia R. Radiotherapy-induced mandibular bone complications. Cancer Treat Rev 2002;28:65-74.  Back to cited text no. 4
    
5.Dijkstra PU, Kalk WW, Roodemburg JL. Trismus in head and neck oncology: A systematic review. Oral Oncol 2004;40:879-89.  Back to cited text no. 5
    
6.Wahl MJ. Osteoradionecrosis prevention myths. Int J Radiat Oncol Biol Phys 2006;64:661-9.  Back to cited text no. 6
    
7.Reuther T, Schuster T, Mende U, Kubler A. Osteoradionecrosis of the jaws as a side effect of radiotherapy of head and neck tumour patients- A report of a thirty year retrospective review. Int J Oral Maxillofac Surg 2003;32:289-95.  Back to cited text no. 7
    
8.Engelmeier RL, King GE. Complications of head and neck radiation therapy and their management. J Prosthet Dent 1983;49:514-22.  Back to cited text no. 8
    
9.Whitmyer CC, Waskowski JC, Iffland HA. Radiotherapy and Oral Sequelae: Preventive and Management Protocols. J Dent Hygiene 1997;7:23-9.  Back to cited text no. 9
    
10.Chong J, Hinckley LK, Ginsberg LE. Masticator Space Abnormalities Associated with Mandibular Osteoradionecrosis: MR and CT Findings in Five Patients. AJNR Am J Neuroradiol 2000;21:175-8.  Back to cited text no. 10
    
11.Ihde S, Kopp S, Gundlach K, Konstantinovic VS. Effects of radiation therapy on craniofacial and dental implants: A review of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;107:56-65.  Back to cited text no. 11
    

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Correspondence Address:
Pegah Bronoosh
Department of Oral Radiology, Shiraz University of Medical Sciences, Shiraz
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.111258

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]

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