Accuracy of Bone Measurements in the Vicinity of Titanium Implants in CBCT Data Sets: A Comparison of Radiological and Histological Findings in Minipigs.

PURPOSE: The aim of this animal study was the determination of accuracy of bone measurements in CBCT (cone-beam computed tomography) in close proximity to titanium implants. MATERIAL AND METHODS: Titanium implants were inserted in eight Göttingen minipigs. 60 implants were evaluated histologically in ground section specimen and radiologically in CBCT in regard to thickness of the buccal bone. With random intercept models, the difference of histologic measurements and CBCT measurements of bone thickness was calculated. RESULTS: The mean histological thickness of the buccal bone was 5.09 mm (CI 4.11-6.08 mm). The four raters measured slightly less bone in CBCT than it was found in histology. The random effect was not significant (p value 1.000). Therefore, the Intraclass Correlation Coefficient (ICC) was 98.65% (CI 100.00-96.99%). CONCLUSION: CBCT is an accurate technique to measure even thin bone structures in the vicinity of titanium implants.

Artefacts in multimodal imaging of titanium, zirconium and binary titanium-zirconium alloy dental implants: an in vitro study.

OBJECTIVES: To analyze and evaluate imaging artefacts induced by zirconium, titanium and titanium-zirconium alloy dental implants. METHODS: Zirconium, titanium and titanium-zirconium alloy implants were embedded in gelatin and MRI, CT and CBCT were performed. Standard protocols were used for each modality. For MRI, line-distance profiles were plotted to quantify the accuracy of size determination. For CT and CBCT, six shells surrounding the implant were defined every 0.5 cm from the implant surface and histogram parameters were determined for each shell. RESULTS: While titanium and titanium-zirconium alloy induced extensive signal voids in MRI owing to strong susceptibility, zirconium implants were clearly definable with only minor distortion artefacts. For titanium and titanium-zirconium alloy, the MR signal was attenuated up to 14.1 mm from the implant. In CT, titanium and titanium-zirconium alloy resulted in less streak artefacts in comparison with zirconium. In CBCT, titanium-zirconium alloy induced more severe artefacts than zirconium and titanium. CONCLUSIONS: MRI allows for an excellent image contrast and limited artefacts in patients with zirconium implants. CT and CBCT examinations are less affected by artefacts from titanium and titanium-zirconium alloy implants compared with MRI. The knowledge about differences of artefacts through different implant materials and image modalities might help support clinical decisions for the choice of implant material or imaging device in the clinical setting.

Performance of cone-beam computed tomography and multidetector computed tomography in diagnostic imaging of the midface: A comparative study on Phantom and cadaver head scans.

PURPOSE: To compare multidetector computed tomography (MDCT) and cone-beam computed tomography (CBCT) regarding radiation, resolution, image noise, and image quality. METHODS: CBCT and 256-MDCT were compared based on three scan protocols: Standard-dose (≈24 mGy), reduced-dose (≈9 mGy), and low-dose (≈4 mGy). MDCT images were acquired in standard- and high-resolution mode (HR-MDCT) and reconstructed using filtered back projection (FBP) and iterative reconstruction (IR). Spatial resolution in linepairs (lp) and objective image noise (OIN) were assessed using dedicated phantoms. Image quality was assessed in scans of 25 cadaver heads using a Likert scale. RESULTS: OIN was markedly higher in FBP-MDCT when compared to CBCT. IR lowered the OIN to comparable values in standard-mode MDCT only. CBCT provided a resolution of 13 lp/cm at standard-dose and 11 lp/cm at reduced-dose vs. 11 lp/cm and 10 lp/cm in HR-MDCT. Resolution of 10 lp/cm was observed for both devices using low-dose settings. Quality scores of MDCT and CBCT did not differ at standard-dose (CBCT, 3.4; MDCT, 3.3-3.5; p > 0.05). Using reduced- and low-dose protocols, CBCT was superior (reduced-dose, 3.2 vs. 2.8; low dose, 3.0 vs. 2.3; p < 0.001). CONCLUSION: Using the low-dose protocol, the assessed CBCT provided better objective and subjective image quality and equality in resolution. Similar image quality, but better resolution using CBCT was observed at higher exposure settings. KEY POINTS: • The assessed CBCT device provided better image quality at lower doses. • Objective and subjective image quality were comparable using higher exposure settings. • CBCT showed superior spatial resolution in standard-dose and reduced-dose settings. • Modern noise-reducing tools are used in CBCT devices currently. • MDCT should be preferred for assessment of soft-tissue injuries and oncologic imaging.

The benefit of abdominal sonography and chest X-ray for staging oral squamous cell carcinomas in stages UICC I and II.

PURPOSE: The purpose of this study was to evaluate how often distant metastases occur in localized oral squamous cell carcinomas (OSCC). The investigators hypothesize that abdominal sonography and chest X-ray may not be necessary for initial staging of early oral squamous cell carcinoma in UICC stage I/II. MATERIAL AND METHODS: The investigators implemented a retrospective study. The study collective was composed of 124 patients with OSCC, who were treated in the department of oral and maxillofacial surgery during the years 2011-2015 at the University Medical Center Hamburg Eppendorf, Germany. We focused on age, gender, date of diagnosis, tumour stage (clinical and pathological), HPV status, occurrence of metastases, recurrences, date and frequency of staging and restaging (abdominal sonography, chest X-ray, CT Abdomen/Thorax, PET CT), follow up time and date of death. Descriptive and bivariate statistics were computed (chi-square test) and the P value was set at .05. RESULTS: 19 distant metastases were found in 13 out of 124 patients (10.48%). Of those 20 metastases 5 were found in the liver (26.32%), 11 in the lung (57.89%) and 4 in the bone (15.79%). Hepatic metastases co-occurred in every case with pulmonary metastases. In one case bone metastases occurred without the presence of pulmonary metastases. There was no significant correlation of metastasis rate to T stage. But distant metastases were solely found in node positive patients. This was significant for pulmonary metastases, not for liver metastases. Only one out of 11 pulmonary metastases was diagnosed by chest X-ray. CONCLUSION: Abdominal sonography and chest X-ray can be omitted as a standard procedure in staging of localized node negative oral squamous cell carcinoma. A thoracic CT including the liver should be performed in patients with suspected lymph nodes metastases in the neck on CT. A skeletal scintigraphy or alternatively a PET/PET-CT should be added if there are signs and symptoms suspicious for bone metastases.

Immunohistochemical analysis of p16 expression, HPV infection and its prognostic utility in oral squamous cell carcinoma.

OBJECTIVES: Functional inactivation of p16 is an early and frequent event in the carcinogenesis of tumours of the head and neck region. However, the prognostic relevance of p16 protein expression for these tumours has been controversial. This study aims to examine immunohistochemical expression of p16 and HP virus in a large number of oral carcinomas, and possible correlation with clinical features of the tumours and survival of the patients. METHODS: Two tissue microarrays composed of 222 oral carcinomas and 427 squamous cell carcinomas of the head and neck region were used for this study. Sections were stained immunohistochemically (anti-p16), and PCR analysis (HPV status) was carried out. Correlation of p16 expression/HPV status with features of tumours and with survival of the patients was analysed by means of Chi-squared test and using Kaplan-Meier analysis, respectively. RESULTS: p16 expression was found immunohistochemically in 74% of tumours, but was not significantly correlated with features of the tumours, but recurrence-free survival of the patients (P = 0.009) if located predominantly nuclear. On the other hand neither intensity of p16 expression (P = 0.41) nor HPV status (P = 0.82) had any effect on these two aspects. CONCLUSION: Immunohistochemical expression of p16 alone provides a limited tool for diagnosis and prognosis of carcinomas of the head and neck region. Immunohistochemical analysis of p16 depending on its intracellular location might serve as a surrogate marker for HPV infection.