Alexander Johnson’s scientific contributions

[This corrects the article e45 in vol. 45, PMID: 33294410.].

Objective: The aim of this study was to introduce a gelatin/bovine serum albumin (BSA) tissue standard, which provides dissolution properties identical to those of biological tissues. Further, the study evaluated whether the utilization of endodontic activating devices led to enhanced phantom dissolution rates. Materials and methods: Bovine pulp tissue was obtained to determine a benchmark of tissue dissolution. The surface area and mass of samples were held constant while the ratio of gelatin and BSA were varied, ranging from 7.5% to 10% gelatin and 5% BSA. Each sample was placed in an individual test tube that was filled with an appropriate sodium hypochlorite solution for 1, 3, and 5 minutes, and then removed from the solution, blotted dry, and weighed again. The remaining tissue was calculated as the percent of initial tissue to determine the tissue dissolution rate. A radiopaque agent (sodium diatrizoate) and a fluorescent dye (methylene blue) were added to the phantom to allow easy quantification of phantom dissolution in a canal block model when activated using ultrasonic (EndoUltra) or sonic (EndoActivator) energy. Results: The 9% gelatin + 5% BSA phantom showed statistically equivalent dissolution to bovine pulp tissue at all time intervals. Furthermore, the EndoUltra yielded significantly more phantom dissolution in the canal block than the EndoActivator or syringe irrigation. Conclusions: Our phantom is comparable to biological tissue in terms of tissue dissolution and could be utilized for in vitro tests due to its injectability and detectability.

Abstract Purpose Currently available oral cancer screening adjuncts have not enhanced clinical screening methods due to high false positives and negatives, highlighting the need for a molecularly specific technique for accurate screening of suspicious oral lesions. The purpose of this study was to evaluate the in vivo screening accuracy of an oral lesion identification system that evaluates aberrant glycosylation patterns using a fluorescently-labeled lectin (wheat germ agglutinin – fluorescein isothiocyanate; WGA-FITC). Methods The investigators designed and implemented a prospective cohort study at three institutions composed of patients with and without suspicious oral lesions. Oral cavities were screening via clinical examination and with the oral lesion identification system following a stepwise procedure which included the topical application and fluorescence visualization of a fluorescent nuclear stain and WGA-FITC. Tissue samples were obtained from all enrolled subjects for histopathological diagnosis and were used to calculate sensitivity and specificity metrics (primary outcome variable) irrespective of the oral lesion identification system result. Results The sample was composed of 97 subjects, with 86 subjects displaying 100 clinically suspicious lesions while 11 normal subjects were included as a control group. The use of the oral lesion identification system resulted in 100, 100, and 74% sensitivity for cancer, high-grade dysplasia, and low-grade dysplasia, respectively, and a specificity of 80%. Clinical diagnosis yielded similar sensitivity values of 84, 100, and 88% for cancer, high-grade dysplasia, and low-grade dysplasia, respectively, and a specificity of 76%. The use of the oral lesion identification system enhanced the visualization of lesion dimensionality and borders. Conclusions The results of this study suggest the oral lesion identification system was a beneficial adjunct to standard clinical examination, as the system provided sensitivity and specificity values similar to or greater than clinical diagnosis.

Objectives: To evaluate SmearOFF, 7% maleic acid (MA) and two different preparations of ethylenediaminetetraacetic acid (EDTA) in smear layer removal. Materials and methods: Fifty single-rooted teeth were separated into five groups, instrumented and irrigated as follows: (1) SmearOFF, (2) 7% MA, (3) 18% EDTA (pH 11.4), (4) 17% EDTA (pH 8.5) and (5) 0.9% saline. Teeth samples were blinded and examined by scanning electron microscopy with Image J software. Results: Eighteen percent EDTA was less efficient when compared to SmearOFF and MA at all thirds of the root canal system. There was no difference between SmearOFF and MA in the coronal and middle thirds. In the apical third, MA removed more smear layer. Seventeen percent EDTA was as efficient as SmearOFF and MA in coronal and middle third but not in the apical third. Eighteen percent EDTA removed smear layer less efficiently in the coronal and middle thirds than 17% EDTA; in the apical third, there was no difference observed. In the saline group, all specimens were heavily smeared. There was no significant difference between 18% EDTA and saline at all canal thirds. Conclusions: SmearOFF and 17% EDTA (pH 8.5) had better smear layer removal capability in the coronal and middle thirds of the root canal system. In the apical third, 7% MA was superior. 18% EDTA (pH 11.4) and saline had poor smear layer removal ability.

Objective: This study evaluated intracanal smear layer removal using syringe and needle irrigation (ie, conventional irrigation [CI]) with and without adjunctive activation using EndoActivator® or EndoUltra®. Materials and methods: Thirty-five premolars were divided into three experimental groups (n = 10) and a control (n = 5): (1) CI, (2) CI plus sonic activation (EndoActivator), (3) CI plus ultrasonic activation (EndoUltra), or (4) CI using saline. All teeth were prepared to a size #40 K file. Following irrigation, the teeth were split and imaged using scanning electron microscopy (SEM). SEM images were evaluated by: (1) blinded researchers who provided a smear layer score (1-5), and (2) a custom software algorithm that automatically and independently quantified the number of open tubules. Results: Use of both the EndoActivator and EndoUltra resulted in significantly cleaner smear layer scores at all canal thirds compared to CI (P < .001). The EndoUltra yielded significantly cleaner scores than the EndoActivator at the apical third (P < .001); however, no significant difference was evident in the middle and coronal thirds. The software analysis yielded the same conclusions as the smear layer scores except statistical significance was seen between the EndoUltra and EndoActivator at all canal thirds (P < .02). Of the adjunctive irrigant activators, the EndoUltra opened 94%, 117%, and 26% more tubules in the apex, middle, and coronal thirds, respectively, than the EndoActivator. Conclusions: The EndoUltra cleaned canals more effectively than the EndoActivator and CI.

Oral and pharyngeal cancers combined rank within the top ten most common malignancies in the world for men, with an estimated global incidence of oral cancer alone at approximately 275,000 [1]. Over 90 % of oral cancers affecting the lips, gingiva, tongue, buccal mucosa, floor of mouth and hard palate arise from the squamous epithelium and are thus termed oral squamous cell carcinomas (OSCCs) [2, 3]. Conversely, neoplasms originating from the epithelial lining of oropharynx are called oropharyngeal squamous cell carcinomas (OPSCCs) [1].

Background: Aberrant sialylation is accepted as a carcinogenic biomarker. In previous work, fluorescently labeled wheat germ agglutinin (WGA) distinguished between cancerous and normal oral biopsies. The purpose of this study was to investigate WGA-fluorescein isothiocyanate (FITC) as a point-of-care tool for detecting oral malignant and dysplastic lesions in vivo. Methods: Subject recruitment was divided into two groups: (1) the clinically normal oral mucosa group; or (2) the presence of clinically suspicious oral lesion(s) group. A WGA-FITC solution was topically applied to observable lesions or to half the subject's mouth (sagittal plane) if lesions were absent. Fluorescent molecular imaging was used to evaluate WGA-FITC localization. Results: Fluorescent imaging in 55 subjects demonstrated that WGA-FITC could detect histopathologically-confirmed cancerous and dysplastic lesions with high sensitivity (100% and 81%, respectively) and specificity (82%). Conclusion: This study supports in vivo fluorescent molecular imaging of WGA-FITC to visualize aberrant sialic acid expression associated with carcinogenesis. This technique resulted in the immediate chairside detection of oral cancerous and dysplastic lesions.