Radiation dose distribution in the teeth, maxilla, and mandible of patients with oropharyngeal and nasopharyngeal tumors who were treated with intensity-modulated radiotherapy

Ultrasonic activation of the endodontic sealer enhances its intratubular penetration and bond strength to irradiated root dentin

To evaluate the effect of ultrasonic activation of the endodontic sealer on its intratubular penetration and bond strength to irradiated root dentin. Forty human teeth were distributed into 4 groups (n = 10), according to the radiation therapy (RT) exposure-70 Gy-and ultrasonic activation (UA) of the endodontic sealer: RT/UA-irradiated teeth and sealer UA; RT/no-UA-irradiated teeth and no sealer UA; no-RT/UA-non-irradiated teeth and sealer UA and no-RT/no-UA-non-irradiated teeth and no sealer UA. Push-out bond strength test was performed in a Universal Testing Machine. Failure modes and adhesive interface were analyzed under Scanning Electron Microscopy. The data were statistically compared (two-way-ANOVA and posthoc Games-Howell test; Fisher's exact test - α = 5%). The different experimental conditions (radiation and UA) and the root third had a significant effect on push-out bond strength, and the interaction of these factors was significant (p < 0.05). UA of the sealer significantly increased its bond strength to both irradiated and non-irradiated dentin (p < 0.05). The irradiated groups mostly presented adhesive-type failure of the sealer (p < 0.01). Regardless of the irradiation, the ultrasonically activated groups showed a more homogeneous adhesive interface, with the presence of sealer tags in greater density and depth. Ultrasonic activation enhanced the intratubular penetration and the bond strength of the endodontic sealer to irradiated dentin. The impact of ultrasonic activation of the endodontic sealer on teeth undergoing radiotherapy is a gap in the scientific literature that needs to be bridged.

Ultrasonic activation of adhesive systems increases bond strength and intratubular penetration of resin cement in root dentin subjected to radiation therapy

OBJECTIVE

This study aimed to evaluate the effect of ultrasonic activation of etch-and-rinse and self-etch adhesive systems on the bond strength of resin cement to irradiated root dentin.

MATERIALS AND METHODS

Eighty human maxillary anterior teeth were distributed into 8 groups (n = 10), according to the type of adhesive system used (etch-and-rinse and self-etch), the ultrasonic activation of the adhesive systems, and the dentin condition (irradiated or non-irradiated - 70 Gy). Endodontic treatment was performed followed by fiberglass post-space preparation. After fiberglass posts' luting, the roots were transversely sectioned on dentin discs and submitted to the push-out bond strength test (0.5 mm/min). The fractured specimens were analyzed under a stereomicroscope and Scanning Electron Microscope (SEM) for failure mode classification. One of the dentin discs was analyzed under SEM to evaluate the characteristics of the adhesive interface.

RESULTS

Irradiated specimens had lower bond strength than non-irradiated specimens (P < 0.0001). Ultrasonic activation of both adhesive systems increased the bond strength of the resin cement to irradiated dentin (P < 0.0001). Radiotherapy significantly affected the failure mode in the middle (P = 0.024) and apical thirds (P = 0.032) (adhesive failure).

CONCLUSION

Non-irradiated specimens had a more homogeneous adhesive interface. When ultrasonically activated, both adhesive systems showed a greater number of resinous tags, regardless of the dentin condition.

CLINICAL RELEVANCE

Ultrasonic activation of adhesive systems is a feasible strategy to enhance fiberglass posts retention in oncological patients.

Assessing push-out bond strength in re-irradiated teeth: Universal resin cement performance in self-etch and self-adhesive modes

OBJECTIVES

To investigate the effect of cumulative doses of radiation on the pushout bond strength (BS) of a universal resin cement used in the self-etch (SE) and self-adhesive (SA) modes to the intraradicular dentin.

MATERIALS AND METHODS

Forty-eight human teeth were distributed into three groups (n = 16) according to the radiation therapy dose (RT): NoRT (no-radiotherapy), 70RT (70 Gy), and 70 + 70RT (70 Gy + 70 Gy). The teeth were redistributed into two subgroups (n = 8), according to the adhesive mode: SE (NoRT-SE, 70RT-SE, and 70 + 70RT-SE) and SA (NoRT-SA, 70RT-SA, and 70 + 70RT-SA). Data were statistically compared after BS test (ANOVA, Tukey's post hoc test, and Fisher's exact test).

RESULTS

In the SA mode, BS was significantly higher in nonirradiated teeth compared with 70RT and 70 + 70RT (p < 0.0001). There were no significant differences between SE and SA modes in nonirradiated teeth (p = 0.14). In the 70RT group, SE mode increased BS compared with SA mode (p < 0.0001). Most specimens had adhesive and mixed failures in SA and SE modes, respectively.

CONCLUSIONS

The universal resin cement in the SE mode had greater BS to the irradiated dentin. When teeth were re-irradiated, the universal resin cement had similar performance in terms of BS, regardless of the adhesive approach.

CLINICAL SIGNIFICANCE

There is no research establishing a correlation between radiotherapy and its impact on the BS of a universal resin cement used in SE and SA modes to intraradicular dentin.

Effect of the timing of primary endodontic treatment and dosage of radiation therapy on the filling material removal

This study investigated the effect of the timing of primary endodontic treatment and dosage of radiotherapy on the remaining filling material (RFM) during endodontic reintervention. 60 single-rooted human mandibular premolars were distributed into five groups (n = 12), according to the timing and dosage of radiation (55Gy or 70Gy): NegativeCG-non-irradiated teeth; Endo-pre-RT55/70-obturation before irradiation (55Gy or 70Gy); Endo-post-RT55/70-obturation and reintervention after irradiation (55Gy or 70Gy). Roots were cleaved and analysed under stereomicroscope and Scanning Electron Microscope to quantify (%) the RFM. Experimental groups had a significantly greater amount (p < 0.05) of RFM in the middle and apical thirds than the control group, except for Endo-pre-RT55 in the middle third (p < 0.0001). The apical third had greater amount of RFM (p < 0.05). Radiation therapy, before and after primary endodontic treatment, increased the amount of RFM, regardless of the dose delivered. When necessary, reintervention preferably must be performed before radiation therapy.

Site-specific radiation dosage and implant survival in oral cancer patients: A cohort study

OBJECTIVES

We assessed the radiation dosages (Dmean ) on implant regions to identify the threshold for implant loss in patients with an intraoral malignancy treated with dental implants to support a mandibular denture during ablative surgery before volumetric-modulated arc therapy (VMAT).

MATERIALS AND METHODS

Data was collected prospectively from 28 patients treated surgically for an intraoral malignancy, followed by postoperative radiotherapy (VMAT) and analyzed retrospectively. Patients received 2 implants in the native mandible during ablative surgery. Implant-specific Dmean values were retrieved from the patients' files. Radiographic bone loss was measured 1 year after implant placement and during the last follow-up appointment. Implant survival was analyzed with the Kaplan-Meier method. Univariate logistic regression and Cox-regression analyses were performed to investigate the effect of increasing implant-specific radiation dosages on implant loss.

RESULTS

Five out of 56 placed implants were lost during follow-up (median 36.0 months, IQR 39.0). Radiographically, peri-implant bone loss occurred in implants with a Dmean  > 40 Gy. Implant loss occurred only in implants with a Dmean  > 50 Gy.

CONCLUSION

An implant-specific Dmean higher than 50 Gy is related to more peri-implant bone loss and, eventually, implant loss.

The use of liquid formulation pentoxifylline and vitamin E in both established and as a prophylaxis for dental extractions "at risk" of osteoradionecrosis

BACKGROUND

Osteoradionecrosis (ORN) of the jaws remains one of the most debilitating complications of radiotherapy (RT) in patients with head and neck cancer (HNC). Liquid pentoxifylline and vitamin E (PVe) presents an alternative formulation to tablets for patients with dysphagia or enteric feeding.

OBJECTIVE

This study aimed to assess the clinical outcomes of using a liquid formulation of PVe for both established ORN and as a prophylaxis to avoid its occurrence after dental extractions. A secondary objective was to determine patient-reported side effects in relation to the liquid formulation of PVe.

STUDY DESIGN

The clinical records of 111 patients with HNC who were prescribed liquid PVe were reviewed retrospectively (66 with established ORN and 45 as prophylaxis before an invasive dental procedure).

RESULTS

In established ORN, 44% healed, and 41% were stable. In the prophylaxis group, 96% of surgical sites healed completely, with 4% (n = 2) developing ORN. Most patients (89%) were able to tolerate liquid PVe. Of the 11% (n = 12) who could not tolerate this regime, the most commonly reported side effect was gastric irritation (n = 5/12), whereas no more than 1 patient reported dizziness, malaise, and bleeding.

CONCLUSIONS

This retrospective review suggests that liquid PVe is efficacious for both established ORN and as a prophylaxis. Side effects reported were similar to those recognized for the tablet formulation.

The extent of unnecessary tooth loss due to extractions prior to radiotherapy based on radiation field and dose in patients with head and neck cancer

BACKGROUND AND PURPOSE

Prior to radiotherapy (RT), teeth with poor prognosis that pose a risk for post-RT osteoradionecrosis (ORN) are removed. To allow enough time for adequate wound healing prior to RT, decisions are made based on the estimated radiation dose. This study aimed to gain insight into (1) the overall number of teeth extracted and (2) the patient and tumor characteristics associated with the number of redundantly extracted teeth.

MATERIALS AND METHODS

Patients with head and neck cancer (HNC), treated with RT between 2015 and 2019, were included in this cross-sectional study. For each extracted tooth the radiation dose was calculated retrospectively. The cut-off point for valid extraction was set at ≥ 40 Gy in accordance with the national protocol. Potential factors for doses ≥ 40 Gy were identified, including age, sex, tumor location, tumor (T) and nodal stage (N), overall tumor stage and number of teeth extracted.

RESULTS

A total of 1759 teeth were removed from 358 patients. Of these 1759 teeth, 1274 (74%) appeared to have been removed redundantly, based on the mean dose (Dmean) of < 40 Gy. Using the maximum dose (Dmax) of < 40 Gy, 1080 teeth (61%) appeared to have been removed redundantly. Tumor location and N-classification emerged as the most important associative variables in the multivariable regression analysis.

CONCLUSION

To our knowledge this is the first study to provide insight into the amount of teeth redundantly extracted prior to RT and represents a step forward in de-escalating the damage to the masticatory system prior to RT.

Effect of the timing of radiation therapy on the push-out strength of resin cement to root dentine

This study investigated the effect of radiation timing on the bond strength of resin cement to intraradicular dentine. Fifty human teeth were distributed into 5 groups (n = 10): Control (nonirradiated teeth), Before-RCT (teeth irradiated before root canal treatment), After-CH (teeth irradiated after canal preparation and placement of calcium hydroxide intracanal dressing), After-RCT (teeth irradiated after completion of root canal treatment) and After-FPL (teeth irradiated after luting of a glass fibre post). Each tooth received 70 Gy irradiation. The roots were sectioned for push-out strength testing. After-RCT and After-FPL groups had significantly lower push-out strength than the control at the middle third (p < 0.05). Control and After-CH groups had a higher percentage of cohesive dentine failure. Radiotherapy after root canal obturation and post luting adversely affected the adhesiveness of resin cement to intraradicular dentine. Teeth irradiated before root canal treatment and after placement of calcium hydroxide had the best performance.

Planned dose of intensity modulated proton beam therapy versus volumetric modulated arch therapy to tooth-bearing regions

BACKGROUND

Intensity modulated proton beam therapy (IMPT) for head and neck cancer offers dosimetric benefits for the organs at risk when compared to photon-based volumetric modulated arch therapy (VMAT). However, limited data exists about the potential benefits of IMPT for tooth-bearing regions. The aim of this study was to compare the IMPT and VMAT radiation dosimetrics of the tooth-bearing regions in head and neck cancer patients. Also, we aimed to identify prognostic factors for a cumulative radiation dose of ≥40 Gy on the tooth-bearing areas, which is considered the threshold dose for prophylactic dental extractions.

METHODS

A total of 121 head and neck cancer patients were included in this retrospective analysis of prospectively collected data. We compared the average Dmean values of IMPT versus VMAT of multiple tooth-bearing regions in the same patients. Multivariate logistic regression analysis was performed for receiving a cumulative radiation dose of ≥40 Gy to the tooth-bearing regions (primary endpoint) in both VMAT and IMPT.

RESULTS

A lower Dmean was seen after applying IMPT to the tooth-bearing tumour regions (p < 0.001). Regarding VMAT, oral cavity tumours, T3-T4 tumours, molar regions in the mandible, and regions ipsilateral to the tumour were risk factors for receiving a cumulative radiation dose of ≥40 Gy.

CONCLUSIONS

IMPT significantly reduces the radiation dose to the tooth-bearing regions.

Systematic dosimetric evaluation of risk of osteoradionecrosis (DERO): First results of dose reporting for preventing teeth osteoradionecrosis after head and neck irradiation

PURPOSE

OsteoRadioNecrosis (ORN) is a late complication of radiation for head and neck cancer. Predicting ORN is a major challenge. We developed DERO (Dosimetric Evaluation of Risk of ORN), a semi-automatic tool which reports doses delivered to tooth-bearing sectors, to guide post-therapeutic dental care. We present the method and the first results of a 125-patient prospective cohort.

MATERIAL AND METHODS

Dosimetric data of patients treated with IMRT for head and neck cancer were prospectively segmented to the DERO algorithm. Four arches corresponding to 8-tooth sectors were semi-automatically generated. Thirty-two cylindrical Regions Of Interest (ROI) corresponding to each tooth and surrounding periodontium were created by linear interpolation. Mean doses (Dmean) of ROI were extracted and included in a database, along with data about primary tumor site, laterality and dose values from organs at risk. Dmean to tooth sectors were computed for molar sectors, (teeth X5 to X8) and anterior sectors (teeth X1 to X4). An individual dose map was generated and delivered to patients and dentists.

RESULTS

Dosimetric data from 125 patients treated with Tomotherapy® were prospectively collected and analyzed: 9 parotid tumors (PA), 41 Sub-Hyoid tumors (larynx, hypopharynx) (SH), 43 Oropharynx tumors (OR), 32 Oral Cavity tumors (OC). Irradiation was unilateral for 100% of PA tumors (9), 12% of OR tumors (5) and 47% of OC tumors (15). For unilateral cervical irradiation, Dmean in ipsilateral molar sectors was 54Gy for OC tumors, 45Gy for OR tumors, 20Gy for PA tumors. For Oral Cavity bilateral irradiation, Dmean was high in all tooth sectors, 49 to 55Gy. For SH tumors, Dmean in molar sectors was 27Gy. A dose gradient of 10 to 20Gy was observed between molar and anterior sectors whether radiation was uni or bilateral.

CONCLUSION

Mandibular molar sectors of Oropharynx and Oral Cavity tumors were exposed to high Dmean of 40 to 50Gy. On the other hand, tooth sectors received lower doses for SH radiation. The DERO tool guide post-radiation dental care with a personalized dosimetric cartography to patient. With data update and patient follow-up, we will be able to determine ORN risk after head and neck radiation.

The dose limits of teeth protection for patients with nasopharyngeal carcinoma undergoing radiotherapy based on the early oral health-related quality of life

Radiation-related teeth damage is a common complication in nasopharyngeal carcinoma (NPC) patients undergoing radiotherapy (RT) that seriously affects their oral health-related quality of life (OHRQoL). However, few studies have focused on protecting teeth function. This study aimed to calculate dental dose limits based on OHRQoL. Analysis was performed on 96 NPC patients who received RT (all received routine pre-radiotherapy dental interventions in our department). Based on the General Oral Health Assessment Index (GOHAI), OHRQoL was assigned into poor (<46) and good condition groups (≥46). The binary logistic regression analysis model was used for single-factor and multivariate analyses to identify the independent factors affecting OHRQoL. The cut-off value of dose received by teeth was obtained by drawing a receiver operating characteristic curve. NPC patients experienced a decline in OHRQoL following RT (P < 0.05). Univariate analysis of GOHAI revealed that the average dose of maxillary anterior teeth, the average dose received by the oral cavity, tumor volume (GTVnx), and liking of the sweet food all affected GOHAI (P < 0.05). Multivariate analysis indicated that the average dose of maxillary anterior teeth and liking sweet food were independent factors that influenced the OHRQoL of NPC patients with RT. When the average dose received by maxillary anterior teeth is greater than 28.78 Gy, and there is a tendency in sweet food, the OHRQoL will deteriorate. NPC patients who received RT had a better OHRQoL if the average dose to maxillary anterior teeth was limited to less than 28.78 Gy and the intake of high-sugar foods was reduced.

The clinical effect of radiotherapy on pulpal microvasculature: a systematic review

Introduction/objectives Radiotherapy (RT) has a detrimental effect on the histomorphology of oral tissues. Patients undergoing RT are at risk of developing macrovascular and microvascular changes, which can lead to significant clinical consequences. Despite advances in RT delivery systems, radiation injury remains a modern-day clinical problem. The aim of this systematic review is to investigate the available evidence regarding the impact of RT to the dental pulp and the clinical manifestations of these effects.Data and sources A multi-database search (PubMed, Medline, Embase and CINAHL) was performed to identify related papers published from inception until November 2021. An additional manual search was performed to identify further articles. The data extracted from relevant papers were analysed according to the outcomes selected in this review.Study selection The search generated seven articles eligible for analysis with a total of 2,709 teeth included. RT dose exposure ranged from 30-71.2 Gray with a common finding that RT decreases the number of teeth responding to pulp sensibility testing.Conclusions Knowledge related to the impact of RT on dental pulp is limited and based on weak evidence and a low-level quality of studies. Future studies should incorporate exact RT doses to the teeth and use replicable pulpal testing methods. Understanding the pulpal status post-RT remains an important consideration as dental extractions should be avoided in this cohort due to the risk of osteoradionecrosis.

Dosimetric Comparison between Volumetric Modulated Arc Therapy (VMAT) and Intensity-Modulated Radiotherapy (IMRT) for Dental Structures of Head and Neck Cancer Patients

Background

This retrospective study aimed to evaluate the radiation dose delivered to dental structures in intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) without dental dose constraints, compare the dosimetry differences of dental structures between the two radiation techniques, and determine whether dental structures should be one of the organs at risk for IMRT and VMAT plans according to the dosimetric analysis.

Materials and Methods

A total of 138 head and neck cancer patients (nasopharyngeal, oral cavity, pharyngeal, hypopharynx, and larynx), who underwent IMRT (69 patients) or VMAT (69 patients) from March 2016 to March 2021 in our hospital, were included to assess the dosimetry difference between two radiotherapy techniques for dental structures.

Results

The radiation dose delivered by IMRT and the mean maximum doses delivered by VMAT to the maxillary teeth of nasopharyngeal cancer patients were significantly higher than the dose received by the mandibular teeth. In contrast, the mandibular teeth of oral cavity cancer, oropharynx cancer, and laryngeal cancer received higher radiation doses than maxillary teeth. Except for mandibular teeth of oral cancer patients, the molars received significantly high-dose radiation than premolars and/or incisors in both radiotherapy techniques. No significant difference was observed between IMRT and VMAT in the dosimetric comparison of dental structures, except that oral cavity cancer patients treated with VMAT received a significantly higher mean average dose than those treated with IMRT. When PTV included level Ib, the radiation doses of the mandibular teeth delivered by both radiotherapy techniques were significantly higher than that in PTV when level Ib was excluded.

Conclusion

Without dental dose constraints, no major difference was observed between IMRT and VMAT plans in tooth dose distribution. We suggest that dental structures should be delineated as part of the organ at risk (OAR) when IMRT and VMAT are planned. Meanwhile, attention should be paid to dental structures that might have a high-dose area according to the specific tumor location.

Should the HPV positive oropharyngeal cancer patient be considered for a two-stage dental assessment for their radiation treatment?

Patients due to commence head and neck radiation treatment are expected to undergo a dental assessment and be deemed 'dentally fit'. Though this intervention is welcomed by the dental fraternity it is not without its challenges especially in human papilloma virus (HPV) related oropharyngeal cancer (OPC) which has seen a phenomenal rise over the past decade. This perspective piece presents these challenges and proposes a potential adaption of the dental assessment for HPV OPC patients though not necessarily exclusive to this tumour sub-site.

Prophylactic pentoxifylline and vitamin E use for dental extractions in irradiated patients with head and neck cancer

OBJECTIVE

Osteoradionecrosis (ORN) of the jaw is preceded by dental extractions in up to 10% of cases. We present a case series of post-radiotherapy patients undergoing dental extractions who have received the prophylactic antifibrotic agents pentoxifylline and vitamin E (PVe) to prevent ORN.

STUDY DESIGN

A retrospective review was conducted of 219 patients with head and neck cancer (HNC) undergoing 1079 dental extractions between 2009 and 2020. Data regarding oncological treatment, prophylactic drug regimen, dental history, and clinical outcome was collected.

RESULTS

Twelve patients developed ORN at 17 extraction sites (ORN rates, 1.6% and 5.5% at tooth level and patient level, respectively). PVe regimen compliance significantly decreased ORN rates at the patient level (3.4% vs 11.5%; P < .03) and the tooth level (1.0% vs 3.5%; P < .01) compared with no PVe. Regimen compliance significantly reduced ORN rates in patients with oropharyngeal cancer (P < .01); in those with mandibular (P < .005) molar (P < .003), and flapless extractions (P < .04); in patients with radiation regions >40 Gy (P < .0009); and in those who underwent primary closure (P < .03). Machine learning analysis identified almost all these factors as influential at a tooth level for ORN.

CONCLUSIONS

PVe regimen compliance decreased dental extraction ORN rates more than the literature base rates of 7% at the patient level and 2% at the tooth level. Given its success in managing existing ORN, PVe could be extended prophylactically for dental extractions in irradiated patients with head and neck cancer.

Dentoalveolar radiation dose following IMRT in oropharyngeal cancer-An observational study

OBJECTIVES

This observational study aims to determine individual dental doses in oropharyngeal cancer (OPC) patients managed by intensity modulated radiation treatment (IMRT).

MATERIALS AND METHODS

OPC patients treated with IMRT had each tooth individually contoured on post-IMRT CT scans. The mean, maximum and minimum doses were calculated per tooth-based upon patient and tumor demographics (tumor size and nodal status).

RESULTS

A total of 160 patients were included in this study. Escalating tumor size and nodal status led to an observed increase in Dmean doses to the dentition on the contralateral tumor side. A significant region in both jaws received >30 Gy in this tumor group.

CONCLUSION

Tumor demographics were observed to influence RT doses to the dentition and need to be considered when providing a pre-RT dental assessment. The observed dose of >30 Gy in large spans of the dentition and jaws highlights future risk of dental deterioration and ORN with long term survival.

Dental radiation dosimetric maps from intensity-modulated radiation therapy planning for head and neck cancers

BACKGROUND

The purpose of this study was to create dental radiation maps to calculate the mean dose to individual teeth, maxilla and mandible using intensity-modulated radiation therapy (IMRT).

METHODS

Eighteen common clinical settings were chosen. Radiation plans were extracted, and each tooth was contoured at its junction with the gingiva and labeled based on the Universal/American numbering system.

RESULTS

All patients were treated with prescribed doses of 50-70 Gy in 1.66-2 Gy/fraction. Patients receiving mean doses >50 Gy to the teeth, mandible, and maxilla included those with advanced tumors of the oral cavity and gross lymphadenopathy of level 1b.

CONCLUSION

We believe this to be the first study generating dosimetric maps of estimated doses to each tooth and each third of the mandible and the maxilla for common examples of head and neck cancer faced by radiation oncologists. Adoption of these dental maps may help improve clinical workflow efficiency.

Risk assessment of osteoradionecrosis associated with periodontitis using 18F-FDG PET/CT

PURPOSE

Osteoradionecrosis (ORN) is a serious complication after radiotherapy (RT), even in the era of intensity modulated radiation therapy (IMRT). The purpose of this study was to evaluate whether ¹⁸F-FDG PET/CT can predict ORN associated with periodontal disease in patients with oropharyngeal or oral cavity squamous cell carcinoma (OP/OC SCC) undergoing RT.

METHODS

One hundred and five OP/OC SCC patients treated with RT who underwent pretreatment ¹⁸F-FDG PET/CT between October 2007 and June 2016 were retrospectively reviewed. A post-treatment diagnosis of ORN was made clinically based on presence of exposed irradiated mandibular bone that failed to heal after a period of three months without persistent or recurrent tumor. The maximum standardized uptake value (SUVmax) of periodontal regions identified on PET/CT was measured for all patients. Image-based staging of periodontitis was also performed using American Academy of Periodontology staging system on CT.

RESULTS

Among 105 patients, 14 (13.3 %) developed ORN. The SUVmax of the periodontal region in patients with ORN (3.35 ± 1.23) was significantly higher than patients without ORN (1.92 ± 0.66) (P <  .01). The corresponding CT stage of periodontitis in patients with ORN was significantly higher (2.71±0.47) than patients without ORN (1.80±0.73) (P <  .01). ROC analysis revealed the cut-off values of developing ORN were 2.1 in SUVmax, and II in CT stage of periodontitis. The corresponding AUC was 0.86 and 0.82, respectively.

CONCLUSIONS

Pretreatment ¹⁸F-FDG PET/CT identification of periodontitis may be helpful to predict the future development of ORN in patients with OP/OC SCC undergoing RT.

The impact of intensity-modulated radiation treatment on dento-alveolar microvasculature in pharyngeal cancer implant patients

OBJECTIVES

Dental rehabilitation post-radiotherapy often requires the consideration of dental implants. However, these are tentatively prescribed due to the concern of hypovascularisation and possible osteoradionecrosis. Hence, the current study assessed the microvasculature of the dento-alveolar bone at implant sites taking into consideration the exact radiotherapy dose received to the region.

MATERIALS AND METHODS

Bone cores were taken from nine patients during implant treatment and compared to nine control patients. Specimens were stained using CD31 and digitalised using a high-resolution scanner for qualitative and quantitative assessment of the microvasculature. Monaco^® treatment planning system was used to volume the implant site providing mean dose (D_mean ) and maximum dose (D_max ).

RESULTS

A total of 23 bone cores were retrieved for analysis. The cohort had a D_mean of 38.4 Gy (59.6-24.3 Gy). Qualitative analysis identified a clear reduction in the miniscule terminal capillaries and high incidence of obliterated lumens with increasing radiotherapy. Microvasculature density of irradiated patients was markedly reduced (P = .0034) compared to the control group with an inverse correlation to RT doses (P < .0001). Specifically, doses up to 30 Gy appear to preserve sufficient vascularisation (~77% in comparison with control) and tissue architecture. By contrast, exposure to higher doses 40%-61% of the micro-vessels were lost.

CONCLUSION

Intensity-modulated radiotherapy doses above 30 Gy identified reduction in microvasculature which is a lower threshold than previously accepted. In pharyngeal cancer patients' doses to the jaw bones often exceed this threshold. Coupled with favourable survival in certain oropharyngeal and nasopharyngeal cancer, dental rehabilitation via implants provides a significant clinical challenge.

In vivo and in vitro radiotherapy increased dentin enzymatic activity

OBJECTIVES

The present study investigated the effects of in vitro and in-vivo radiotherapy on endogenous enzymatic activity in dentin using gelatin zymography and in-situ zymography.

METHODS

Gelatin zymographic assays were performed on protein extracts obtained from dentin powder of sound non-irradiated (NRT), in vitro irradiated (VTRT) and in vivo irradiated (VIRT) human teeth. Their proteolytic activities were quantified using band densitometric evaluation. For in-situ zymography, dentin specimens from NRT, VIRT and VTRT were covered with fluorescein-conjugated gelatin and examined with confocal laser-scanning microscopy. Fluorescence intensity emitted by the hydrolyzed fluorescein-conjugated gelatin was quantified and statistically analyzed. In-situ zymography data were statistically analyzed using Kruskal-Wallis ANOVA and Dunn's multiple comparison procedures (α = 0.05).

RESULTS

No difference between in vitro and in vivo radiotherapy treatment was found. Both VTRT and VIRT groups showed increase in MMP-9 expression when compared to NRT group. Significant increases (p < 0.05) in gelatinolytic activity (26 % for VTRT; 55 % for VIRT) were observed when compared to the NRT group.

CONCLUSION

Radiotherapy increase endogenous enzymatic activity in non-restored dentin.

Leukocyte- and platelet-rich fibrin as an adjuvant to the surgical approach for osteoradionecrosis: a case report

We present a case of osteoradionecrosis treated with leukocyte- and platelet-rich fibrin (LPRF) and surgery and followed up with clinical and tomographic investigations. A 65-year-old woman presented with pain in the posterior region of the right palate. Her medical history included cardiovascular disease and squamous cell carcinoma in the anterior region of the floor of the mouth that had been treated with intensity-modulated radiation therapy. Measurements of isodose curves showed a full dosage of 6,462.6 cGy in the anterior mandibular region, whereas that in the posterior region on the right side of the maxilla reached 5,708.1 cGy. Osteotomy was performed using rotary instruments, and debridement and placement of two LPRF membranes were also carried out. New gum tissue with no bone exposure was noted 14 days postoperatively. Tissue repair was complete, and the patient had no further complaints. During a 39-month follow-up period, the oral mucosa remained intact, and the patient was rehabilitated with a new upper denture. Since there is no consensus regarding the best protocol to treat osteoradionecrosis, LPRF might be an interesting adjuvant to a surgical approach. The use of LPRF is simple and reduces operational costs, time of handling, probability of technical failure, and associated morbidities for patients with osteoradionecrosis.

Predicting radiation dosimetric distribution in different regions of the jaw in patients receiving radiotherapy for squamous cell carcinoma of the tonsil

BACKGROUND

Radiotherapy (RT), the main treatment for patients with head and neck cancer, can lead to dental complications.

METHODS

We identified 244 patients with squamous cell carcinoma of the tonsil treated with RT from 2004 to 2013. For each patient, we contoured the 10 tooth-bearing regions and calculated the radiation dose (gray, Gy) to each region. From this data set, we built two predictive models to determine the expected maximum radiation dose, one for the non-molar regions and another for the molar regions.

RESULTS

For the non-molars, the final model included location, T-classification, and overall stage, with a median absolute prediction error of 7.0 Gy. For the molars, the final model included location, T-classification, overall stage, and treatment year, with a median absolute error of 6.0 Gy.

CONCLUSIONS

Our current model offers a good estimation of the maximum radiation dose delivered to different regions of the jaw; future work will independently validate these models.

How to improve root canal filling in teeth subjected to radiation therapy for cancer

The aim of this study was to evaluate the influence of radiation therapy on root canal sealer push-out bond strength (BS) to dentin and the sealer/dentin interface after different final irrigation solutions (NaOCl, EDTA, and chitosan). Sixty-four maxillary canines were distributed into two groups (n=30): non-irradiated and irradiated with 60 Gy. Canals were prepared with Reciproc-R50 and subdivided (n=10) for final irrigation (NaOCl, EDTA, chitosan) and filled. Three dentin slices were obtained from each root third. The first slice of each third was selected for BS evaluation, and the failure mode was determined by stereomicroscopy. SEM analysis of the sealer-dentin interface was performed in the remaining slices. Two-way ANOVA and Tukey's tests (α=0.05) were used. Lower BS (P<0.0001) was obtained after irradiation (2.07±0.79 MPa), regardless of the final irrigation solution used. The NaOCl group (P<0.001) had the lowest BS in the irradiated (1.68±0.72) and non-irradiated (2.39±0.89) groups, whereas the EDTA (irradiated: 2.14±0.77 and non-irradiated: 3.92±1.54) and chitosan (irradiated: 2.37±0.73 and non-irradiated: 3.51±1.47) groups demonstrated a higher BS (P<0.05). The highest values were observed in the coronal third (3.17±1.38) when compared to the middle (2.74±1.36) and apical ones (2.09±0.97)(P<0.0001). There were more cohesive failures and more gaps in irradiated specimens, regardless of the final solution. The present study showed that radiation was associated with a decrease in BS, regardless of the final solution used, whereas chitosan increased BS in teeth subjected to radiation therapy.

Optimising volumetric arc radiotherapy for dental rehabilitation in oropharynx cancer - A retrospective dosimetry review and feasibility planning study

PURPOSE

To assess the dosimetry to dentally relevant substructures within the mandible/maxilla, establish the predictors of increased mean anterior mandible dose and assess the feasibility of rationale optimisation of dose to the anterior mandible (AM) volume to aid reconstructive dental surgery planning, where the AM is a critical structure.

MATERIALS AND METHODS

In a cohort of radically treated oropharynx cancer patients we conducted a retrospective dosimetry analysis of mandible/maxilla volumes, created using a published atlas. Comparisons of mean AM dose and clinical parameters between groups were tested using Wilcoxon rank-sum and Kruskal-Wallis tests. A multivariate linear regression model was created to assess independent predictors of increased mean AM dose. Patients with a mean AM dose over 37.5 Gy were included in feasibility planning study to test the hypothesis that it is possible to safely limit the dose whilst maintaining dose tolerances for other organs at risk.

RESULTS

57 patients were included. Median AM mean dose was 32.2 Gy (IQR 27.7-38.7). T stage, N stage and inclusion of Level 1B were significantly associated with increased mean AM dose. Only T stage (p = .0132) and Level Ib inclusion (p = .018) remained significant in the linear regression model. 88% of plans, all of which included Level Ib, were successfully re-optimised without breaching accepted constraints.

CONCLUSIONS

Oropharynx cancer patients with advanced T stage and who require Level Ib treatment receive increased mean AM dose, potentially limiting surgical dental rehabilitation options. The majority of patients can be optimised safely with appropriate AM contouring.

IMRT delivers lower radiation doses to dental structures than 3DRT in head and neck cancer patients

BACKGROUND

Radiotherapy (RT) is frequently used in the treatment of head and neck cancer, but different side-effects are frequently reported, including a higher frequency of radiation-related caries, what may be consequence of direct radiation to dental tissue. The intensity-modulated radiotherapy (IMRT) was developed to improve tumor control and decrease patient's morbidity by delivering radiation beams only to tumor shapes and sparing normal tissue. However, teeth are usually not included in IMRT plannings and the real efficacy of IMRT in the dental context has not been addressed. Therefore, the aim of this study is to assess whether IMRT delivers lower radiation doses to dental structures than conformal 3D radiotherapy (3DRT).

MATERIAL AND METHODS

Radiation dose delivery to dental structures of 80 patients treated for head and neck cancers (oral cavity, tongue, nasopharynx and oropharynx) with IMRT (40 patients) and 3DRT (40 patients) were assessed by individually contouring tooth crowns on patients' treatment plans. Clinicopathological data were retrieved from patients' medical files.

RESULTS

The average dose of radiation to teeth delivered by IMRT was significantly lower than with 3DRT (p = 0.007); however, only patients affected by nasopharynx and oral cavity cancers demonstrated significantly lower doses with IMRT (p = 0.012 and p = 0.011, respectively). Molars received more radiation with both 3DRT and IMRT, but the latter delivered significantly lower radiation in this group of teeth (p < 0.001), whereas no significant difference was found for the other dental groups. Maxillary teeth received lower doses than mandibular teeth, but only IMRT delivered significantly lower doses (p = 0.011 and p = 0.003). Ipsilateral teeth received higher doses than contralateral teeth with both techniques and IMRT delivered significantly lower radiation than 3DRT for contralateral dental structures (p < 0.001).

CONCLUSION

IMRT delivered lower radiation doses to teeth than 3DRT, but only for some groups of patients and teeth, suggesting that this decrease was more likely due to the protection of other high risk organs, and was not enough to remove teeth from the zone of high risk for radiogenic disturbance (>30Gy).