A Retrospective Analysis of 129 Ameloblastoma Cases: Clinical and Demographical Trends from a Single Institution

Ameloblastomas are benign neoplasms of the jaw, but frequently require extensive surgery. The aim of the study was to analyze the demographic and clinicopathological features of ameloblastoma cases at a single Oral and Maxillofacial Surgery group in the United States.

STUDY DESIGN

A retrospective chart review of patients evaluated for ameloblastoma between 2010 and 2020 at a single tertiary care center. Age, race, sex, tumor size, tumor location, and histological subtypes were recorded.

RESULTS

A total of 129 cases of ameloblastoma were recorded with a mean patient age of 42 ± 18.6 years (range 9-91 years old), male to female ratio 1.08:1. Ameloblastoma presenting in the mandible outnumbered maxilla in primary (118 to 8, respectively) and recurrent cases (8 to 1, respectively). There was a higher prevalence of ameloblastoma in Black patients (61.3%) with mean age of Black patients occurring at 40.5 years and the mean age of White patients occurring at 47.8 years and mean tumor size trended larger in the Black patients (15.7 cm2) compared to White patients (11.8 cm2).

CONCLUSION

Data suggests a strong influence of racial factors on the incidence of ameloblastoma, with regards to size, Black patients with ameloblastoma trended higher and more data is needed to clearly elucidate any relationship between the tumor size and race, as other factors may influence the size (such as time to discovery).

Abstract 4554: Head and neck cancer HuBiogel-embedded microtumor assay system for therapeutic efficacy testing of patient tumor specimens

Head and neck (HN) cancer recurrence is common, and selecting effective salvage systemic therapy remains difficult, particularly for oral cavity cancers. Developing a rapid, robust and predictive therapeutic testing system could support clinical decision-making and improve patient outcomes. We developed a Patient Therapy Evaluation System (PTES) that employs a three-dimensional (3D) fully human microtumor drug testing assay using tissue specimens collected during surgery of HN cancers. Remnant fresh tumor tissue from patients is dissociated into single-cell suspension that is embedded using a novel HuBiogel-cell encapsulation technology (3D microtumors). This high-throughput assay platform allows morphologic, functional, and molecular evaluations in parallel by real-time imaging, cell proliferation, and biomarker protocols. Microtumor viability, growth profiles, and drug screening data are captured at multiple time points up to 14 days. Our initial cohort included 57 patient specimens (53 squamous cell carcinomas, 1 verrucous carcinoma, 1 osteosarcoma, 1 ameloblastoma, and 1 non-cancerous lichenoid mucositis). HuBiogel-embedded tumor cells formed numerous multicellular colonies exhibiting distinct organization and growth patterns in 14-day microtumor cultures. Interestingly, epithelial, stromal and stem-cell like populations were preserved in HN microtumor models based on marker expression. Treatment with single (cisplatin, 5FU, docetaxel) drugs and their combinations resulted in tumor inhibitory responses (IC50) evaluated by CellTiter-Glo assay, and residual surviving cells were also recorded by Calcein-AM staining of 3D Microtumors. While patient-derived HN microtumors were produced with high success rates, factors associated with lower microtumor yield included smaller tumor specimens and low viability after dissociation. In conclusion, our new all human microtumor assay models replicating phenotypic, functional, and molecular properties ex vivo provide a potential theranostic tool for rapidly predicting drug sensitivity and improving treatment strategy for HN cancer patients.

Citation Format: Christopher D. Willey, Yedeh P. Ying, Anthony B. Morlandt, Hope M. Amm, Patricia H. Hicks, Joshua C. Anderson, Andee M. Beierle, Carissa M. Thomas, Jason M. Warram, Jingsong Chen, Jeffrey A. Thomas, Katie Banko, Raj K. Singh. Head and neck cancer HuBiogel-embedded microtumor assay system for therapeutic efficacy testing of patient tumor specimens. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4554.

Neurotrophin Pathway Receptors NGFR and TrkA Control Perineural Invasion, Metastasis, and Pain in Oral Cancer

Oral squamous cell carcinoma (OSCC) patients suffer from poor survival due to metastasis or locoregional recurrence, processes that are both facilitated by perineural invasion (PNI). OSCC has higher rates of PNI than other cancer subtypes, with PNI present in 80% of tumors. Despite the impact of PNI on oral cancer prognosis and pain, little is known about the genes that drive PNI, which in turn drive pain, invasion, and metastasis. In this study, clinical data, preclinical, and in vitro models are leveraged to elucidate the role of neurotrophins in OSCC metastasis, PNI, and pain. The expression data in OSCC patients with metastasis, PNI, or pain demonstrate dysregulation of neurotrophin genes. TrkA and nerve growth factor receptor (NGFR) are focused, two receptors that are activated by NGF, a neurotrophin expressed at high levels in OSCC. It is demonstrated that targeted knockdown of these two receptors inhibits proliferation and invasion in an in vitro and preclinical model of OSCC, and metastasis, PNI, and pain. It is further determined that TrkA knockdown alone inhibits thermal hyperalgesia, whereas NGFR knockdown alone inhibits mechanical allodynia. Collectively the results highlight the ability of OSCC to co-opt different components of the neurotrophin pathway in metastasis, PNI, and pain.

Adverse events secondary to cetuximab therapy in head & neck cancer therapy and risk factors for serious outcomes

OBJECTIVES

The objective of this study is to illustrate the adverse events secondary to cetuximab therapy for head and neck cancer and elucidate risk factors for serious outcomes.

MATERIALS AND METHODS

This retrospective study was conducted using the FDA Adverse Event Reporting System (FAERS). The predictor variables were patient characteristics, country of treatment, and adverse events. The outcome variable was the rate of serious outcomes. Multivariate logistic regression was created to identify all significant risk factors of the outcome. P < 0.05 was considered statistically significant.

RESULTS

The final sample consisted of 3,086 reports of adverse events from cetuximab therapy in head and neck cancer treatment, of which 2,746 reports were considered serious (89.0%) per the FAERS criteria. Mucosal inflammation was the most common adverse event. The strongest risk factor for a serious outcome was cetuximab therapy in countries outside the US (OR 105.2, P < 0.01). Polytherapy (OR 7.6, P < 0.01) was also a risk factor for serious outcome.

CONCLUSIONS

Health-care providers should be aware of potential complications following cetuximab administration, particularly when administered in countries outside the US and in conjunction with other medications.

Computer-Assisted Microvascular Free Flap Reconstruction and Implant Rehabilitation of the Maxilla-Treatment of a Rare Post-orthognathic Complication

Orthognathic surgery is generally a safe and predictable procedure. Major postoperative complications are rare and often non-life threatening. An example of a rare complication associated with the LeFort I osteotomy is avascular necrosis of the maxilla (ANM). While cases of ANM have been described in the literature, the majority involves only a portion or segment of the maxillary complex and is commonly treated with conservative measures such as strict oral hygiene, hyperbaric oxygen therapy and local debridement. Occasionally, larger segments of osteonecrosis may require extensive reconstruction such as bone grafting with local soft tissue flaps. Here, we present a patient that underwent a single-stage microvascular free tissue reconstruction with concomitant placement of dental implants and a patient-specific implant (PSI) for post-orthognathic ANM.

Complications in oncologic mandible reconstruction: A comparative study between the osteocutaneous radial forearm and fibula free flap

BACKGROUND

The osteocutaneous radial forearm free flap (OC-RFFF) has been proposed as a safe and reliable free flap for head and neck reconstruction with low donor site morbidity. The purpose of this study is to compare the late complications (>30 days) associated with using the OC-RFFF versus the free fibula flap (FFF) for mandibular reconstruction following oncologic segmental resection.

METHODS

We conducted a single-institution, retrospective study composed of patients who underwent oncologic microvascular composite mandibular reconstruction with either the OC-RFFF or FFF. The primary predictor variable was the type of free flap used. The outcome variable was late complication postoperatively (>30 days).

RESULTS

A total of 93 patients (28, OC-RFFF and 65, FFF) were analyzed. The majority of patients were male (62%) and with AJCC stage T4a disease (72%). Mean hospital length of stay was comparable between the two flap groups (p = .50). OC-RFFF was associated with more late complications (p = .03) compared to FFF. Nonunion occurred in 10.7% of OC-RFFF and 0% of FFF. Partial or complete flap failure was seen in 7.1% and 0% in the OC-RFFF and FFF, respectively. Two-year disease-free survival was comparable in both groups (p > .05).

CONCLUSIONS

The results of this study suggest that the rate of nonunion and odds of having a late complication were significantly greater in the OC-RFFF compared to the FFF following oncologic mandibular reconstruction. However, flap success, early complications (<30 days), and length of hospital stay were comparable between the two flaps.

Does Supplemental Regional Anesthesia Decrease Length of Stay and Opioid Use for Patients Undergoing Head and Neck Microvascular Reconstruction?

PURPOSE

The purpose of this study was to compare length of hospital stay and opioid usage among head and neck surgery (HNS) patients treated with and without regional anesthesia for microvascular free-flap donor sites.

METHODS

The authors performed a retrospective cohort study for HNS patients undergoing microvascular free-flap reconstruction. The control group received no regional anesthesia. The experimental group had a regional anesthesia nerve block performed immediately before surgery. The primary outcome variable was length of stay, and the secondary outcome variable was total morphine milliequivalents. The data were analyzed using Student t tests, analysis of variance, Mann-Whitney U test, Kruskal-Wallis test, χ² test, and multiple linear regression.

RESULTS

The study sample was composed of 148 patients with a mean age of 58.1 years. The mean length of stay for the control group was 6.74 ± 1.57 days, compared with the experimental group at 5.84 ± 1.01 days (P < .0001). The mean morphine milliequivalent was 256.5 ± 164.6 mg for the control group and 208.9 ± 164.8 mg for the experimental group (P = .56). Importantly, the demographics, pathology spectrum, flap selection, duration of procedure, and complication rate were similar in both groups.

CONCLUSIONS

This study demonstrates that for HNS patients undergoing microvascular reconstruction, regional nerve block at the donor site is associated with significantly shorter hospital stays. Although there was a trend toward decreased opioid usage in the regional anesthesia group, these results did not reach statistical significance. Consideration should be given to incorporate regional anesthesia techniques into early recovery after surgery protocols for centers performing high-volume head and neck microvascular reconstruction.

Titanium Alloy Cutting Guides in Craniomaxillofacial Surgery-A Minimally Invasive Alternative to Synthetic Polymer Guides

PURPOSE

Historically, synthetic polymers, such as polyamide, have been the predominate material used for patient-specific cutting guides in 3-dimensionally guided craniomaxillofacial surgery. The physical properties of polyamide result in guides that are bulky and difficult to place within the confines of the facial soft tissue envelope, requiring larger incisions with resultant morbidity. Despite their utility, we found the need for wider exposure simply for guide placement was unacceptable. The purpose of the present study was to evaluate our experience with the newly marketed titanium alloy cutting guides.

MATERIALS AND METHODS

We conducted a retrospective cohort study of patients who had undergone either segmental mandibulectomy or maxillectomy using patient-specific titanium alloy cutting guides from May to December 2019. The primary outcome variable was the need for an extended-access cervical incision or a transfacial incision for either maxillectomy or segmental mandibulectomy in patients with benign disorders. The secondary outcome variables included the need for a transfacial incision in patients with malignant pathology requiring either maxillectomy or composite oromandibular resection and the final histopathologic bone margin status.

RESULTS

Of the 21 included patients, 11 had undergone maxillectomy (1 of 2) or segmental mandibulectomy (9 of 9) for benign disorders, with 91% (10 of 11) having undergone titanium alloy guide placement and resection entirely transorally without the need for an extended cervical or a transfacial incision. For 10 of the 11 patients undergoing immediate reconstruction with vascularized bone flaps, transcervical access was limited to small 1.5- to 2.5-cm incisions for target vessel access and microvascular anastomosis. None of the 10 patients with a malignant disorder requiring either maxillectomy or composite oromandibular resection required a transfacial incision. The bone margins, as determined by histopathologic analysis, were negative for 100% of the patients.

CONCLUSIONS

Patient-specific titanium alloy cutting guides represent a viable alternative to traditional synthetic polymer guides. Their superior properties permit easier intraoral placement, decreasing the need for cutaneous incisions and excessive periosteal stripping.

Fluorescently Labeled Cetuximab-IRDye800 for Guided Surgical Excision of Ameloblastoma: A Proof of Principle Study

PURPOSE

Fluorescently labeled epidermal growth factor receptor (EGFR) antibodies have successfully identified microscopic tumors in multiple in vivo models of human cancers with limited toxicity. The present study sought to demonstrate the ability of fluorescently labeled anti-EGFR, cetuximab-IRDye800, to localize to ameloblastoma (AB) tumor cells in vitro and in vivo.

MATERIAL AND METHODS

EGFR expression in AB cells was confirmed by quantitative real-time polymerase chain reaction and immunohistochemistry. Primary AB cells were labeled in vitro with cetuximab-IRDye800 or nonspecific IgG-IRDye800. An in vivo patient-derived xenograft (PDX) model of AB was developed. The tumor tissue from 3 patients was implanted subcutaneously into immunocompromised mice. The mice received an intravenous injection of cetuximab-IRDye800 or IgG-IRDye800 and underwent imaging to detect infrared fluorescence using a Pearl imaging system (LI-COR Biosciences, Lincoln, NE). After resection of the overlying skin, the tumor/background ratios (TBRs) were calculated and statistically analyzed using a paired t test.

RESULTS

EGFR expression was seen in all AB samples. Tumor-specific labeling was achieved, as evidenced by a positive fluorescence signal from cetuximab-IRDye800 binding to AB cells, with little staining seen in the negative controls treated with IgG-IRDye800. In the animal PDX model, imaging revealed that the TBRs produced by cetuximab were significantly greater than those produced by IgG on days 7 to 14 for AB-20 tumors. After skin flap removal to simulate a preresection state, the TBRs increased with cetuximab and were significantly greater than the TBRs with the IgG control for PDX tumors derived from the 3 patients with AB. The excised tissues were embedded in paraffin and examined to confirm the presence of tumor.

CONCLUSIONS

Fluorescently labeled anti-EGFR demonstrated specificity for AB cells and PDX tumors. The present study is the first report of tumor-specific, antibody-based imaging of odontogenic tumors, of which AB is one of the most clinically aggressive. We expect this technology will ultimately assist surgeons treating AB by helping to accurately assess the tumor margins during surgery, leading to improved long-term local tumor control and less surgical morbidity.

Surgical margins in oral cavity squamous cell carcinoma: Current practices and future directions

OBJECTIVE

To discuss the current available techniques for intraoperative margin assessment in the surgical treatment of oral squamous cell carcinoma (OSCC) through a review of the available literature.

METHODS

A systematic review was undertaken of the available English literature between 2008 through 2018 regarding surgical margins in OCSS. A total of 893 relevant articles were returned; 144 met criteria for review; and 64 articles were included.

RESULTS

In this review, we discuss the data surrounding the use of frozen section in OCSS. Additionally, alternative techniques for margin assessment are discussed, including Mohs, molecular analysis, nonfluorescent dyes, fluorescent dyes, autofluorescent imaging, narrow-band imaging, optical coherence tomography, confocal microscopy, high-resolution microendoscopy, and spectroscopy. For each technique, particular emphasis is placed on the local recurrence, disease-free survival, and overall survival rates when available.

CONCLUSION

This review provides support for the practice of specimen-driven margin assessment when using frozen section analysis to improve the utility of the results. Finally, several alternatives for intraoperative margin assessment currently under investigation, including pathologic, wide-field imaging and narrow-field imaging techniques, are presented. We aim to fuel further investigation into methods for margin assessment that will improve survival for patients with OSCC through a critical analysis of the available techniques.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:128-138, 2020.

Fluorescence Imaging for Cancer Screening and Surveillance

The advent of fluorescence imaging (FI) for cancer cell detection in the field of oncology is promising for both cancer screening and surgical resection. Particularly, FI in cancer screening and surveillance is actively being evaluated in many new clinical trials with over 30 listed on Clinical Trials.gov . While surgical resection forms the foundation of many oncologic treatments, early detection is the cornerstone for improving outcomes and reducing cancer-related morbidity and mortality. The applications of FI are twofold as it can be applied to high-risk patients in addition to those undergoing active surveillance. This technology has the promise of highlighting lesions not readily detected by conventional imaging or physical examination, allowing disease detection at an earlier stage of development. Additionally, there is a persistent need for innovative, cost-effective imaging modalities to ameliorate healthcare disparities and the global burden of cancer worldwide. In this review, we outline the current utility of FI for screening and detection in a range of cancer types.

Effects of an Unlabeled Loading Dose on Tumor-Specific Uptake of a Fluorescently Labeled Antibody for Optical Surgical Navigation

PURPOSE

Intraoperative optical imaging to guide surgeons during oncologic resections offers a unique and promising solution to the ambiguity of cancer margins to tactile and visual assessment that results in devastatingly high rates of positive margins. Sequestering of labeled antibodies by normal tissues with high expression of the antibody target, or "antigen sinks", diminishes the efficacy of these probes to provide contrast between the tumor and background tissues by decreasing the amount of circulating probe available for uptake by the tumor and by increasing the fluorescence of non-tumor tissues. We hypothesized that administering a dose of unlabeled antibody prior to infusion of the near-infrared (NIR) fluorescently labeled antibody would improve tumor-specific uptake and contrast of the fluorescently labeled probe by occupying extra-tumoral binding sites, thereby increasing the amount of labeled probe available for uptake by the tumor.

PROCEDURES

In this study, we explore this concept by testing two different "pre-load" doses of unlabeled cetuximab (the standard 10-mg test dose, and a larger, experimental 100-mg test dose) in six patients receiving cetuximab conjugated to the fluorescent dye IRDye800CW (cetuximab-IRDye800CW) in a clinical trial, and compared the amount of fluorescent antibody in tumor and background tissues, as well as the tumor-specific contrast of each.

RESULTS

The patients receiving the larger preload (100 mg) of unlabeled cetuximab demonstrated significantly higher concentrations (9.5 vs. 0.1 μg) and a longer half-life (30.3 vs. 20.6 days) of the labeled cetuximab in plasma, as well as significantly greater tumor fluorescence (32.3 vs. 9.3 relative fluorescence units) and tumor to background ratios (TBRs) (5.5 vs. 1.7).

CONCLUSIONS

Administering a preload of unlabeled antibody prior to infusion of the fluorescently labeled drug may be a simple and effective way to improve the performance of antibody-based probes to guide surgical resection of solid malignancies.

The National Student Research Group of the AADR—An Introduction

The 2005–06 officers of the National Student Research Group (NSRG) of the American Association for Dental Research (AADR) have summarized their activities in developing the NSRG into an effective organization aimed at fostering future dental researchers. The officers have focused their efforts on establishing opportunities for the pre-doctoral dental student members of the AADR to participate in and formally present their research during dental school. In addition to the many research awards and fellowships already sponsored by the NSRG and the AADR, the NSRG has established new travel awards for students to present at specialty groups’ annual meetings. Other recent initiatives have included a contact list of all dental schools, along with local student research group (SRG) leadership contacts, advice during the creation of a new teaching fellowship opportunity, fundraising efforts to support student research and the NSRG infrastructure, and successfully pursuing a student voting position on the AADR Board. A brief addendum detailing recent activities and future initiatives is also included. The article describes membership requirements, selection of officers, and contacts for additional information. We hope that this Discovery! will serve to increase the awareness of students, researchers, and administrators regarding the role of the NSRG.

Characterizing the Utility and Limitations of Repurposing an Open-Field Optical Imaging Device for Fluorescence-Guided Surgery in Head and Neck Cancer Patients

The purpose of this study was to assess the potential of U.S. Food and Drug Administration-cleared devices designed for indocyanine green-based perfusion imaging to identify cancer-specific bioconjugates with overlapping excitation and emission wavelengths. Recent clinical trials have demonstrated potential for fluorescence-guided surgery, but the time and cost of the approval process may impede clinical translation. To expedite this translation, we explored the feasibility of repurposing existing optical imaging devices for fluorescence-guided surgery.

METHODS

Consenting patients (n = 15) scheduled for curative resection were enrolled in a clinical trial evaluating the safety and specificity of cetuximab-IRDye800 (NCT01987375). Open-field fluorescence imaging was performed preoperatively and during the surgical resection. Fluorescence intensity was quantified using integrated instrument software, and the tumor-to-background ratio characterized fluorescence contrast.

RESULTS

In the preoperative clinic, the open-field device demonstrated potential to guide preoperative mapping of tumor borders, optimize the day of surgery, and identify occult lesions. Intraoperatively, the device demonstrated robust potential to guide surgical resections, as all peak tumor-to-background ratios were greater than 2 (range, 2.2-14.1). Postresection wound bed fluorescence was significantly less than preresection tumor fluorescence (P < 0.001). The repurposed device also successfully identified positive margins.

CONCLUSION

The open-field imaging device was successfully repurposed to distinguish cancer from normal tissue in the preoperative clinic and throughout surgical resection. This study illuminated the potential for existing open-field optical imaging devices with overlapping excitation and emission spectra to be used for fluorescence-guided surgery.

A ratiometric threshold for determining presence of cancer during fluorescence-guided surgery

BACKGROUND AND OBJECTIVE

Fluorescence-guided imaging to assist in identification of malignant margins has the potential to dramatically improve oncologic surgery. However, a standardized method for quantitative assessment of disease-specific fluorescence has not been investigated. Introduced here is a ratiometric threshold derived from mean fluorescent tissue intensity that can be used to semi-quantitatively delineate tumor from normal tissue.

METHODS

Open-field and a closed-field imaging devices were used to quantify fluorescence in punch biopsy tissues sampled from primary tumors collected during a phase 1 trial evaluating the safety of cetuximab-IRDye800 in patients (n = 11) undergoing surgical intervention for head and neck cancer. Fluorescence ratios were calculated using mean fluorescence intensity (MFI) from punch biopsy normalized by MFI of patient-matched tissues. Ratios were compared to pathological assessment and a ratiometric threshold was established to predict presence of cancer.

RESULTS

During open-field imaging using an intraoperative device, the threshold for muscle normalized tumor fluorescence was found to be 2.7, which produced a sensitivity of 90.5% and specificity of 78.6% for delineating disease tissue. The skin-normalized threshold generated greater sensitivity (92.9%) and specificity (81.0%).

CONCLUSION

Successful implementation of a semi-quantitative threshold can provide a scientific methodology for delineating disease from normal tissue during fluorescence-guided resection of cancer.

Safety and Tumor Specificity of Cetuximab-IRDye800 for Surgical Navigation in Head and Neck Cancer

PURPOSE

Positive margins dominate clinical outcomes after surgical resections in most solid cancer types, including head and neck squamous cell carcinoma. Unfortunately, surgeons remove cancer in the same manner they have for a century with complete dependence on subjective tissue changes to identify cancer in the operating room. To effect change, we hypothesize that EGFR can be targeted for safe and specific real-time localization of cancer.

EXPERIMENTAL DESIGN

A dose escalation study of cetuximab conjugated to IRDye800 was performed in patients (n = 12) undergoing surgical resection of squamous cell carcinoma arising in the head and neck. Safety and pharmacokinetic data were obtained out to 30 days after infusion. Multi-instrument fluorescence imaging was performed in the operating room and in surgical pathology.

RESULTS

There were no grade 2 or higher adverse events attributable to cetuximab-IRDye800. Fluorescence imaging with an intraoperative, wide-field device successfully differentiated tumor from normal tissue during resection with an average tumor-to-background ratio of 5.2 in the highest dose range. Optical imaging identified opportunity for more precise identification of tumor during the surgical procedure and during the pathologic analysis of tissues ex vivo. Fluorescence levels positively correlated with EGFR levels.

CONCLUSIONS

We demonstrate for the first time that commercially available antibodies can be fluorescently labeled and safely administered to humans to identify cancer with sub-millimeter resolution, which has the potential to improve outcomes in clinical oncology.

Tetracycline at Subcytotoxic Levels Inhibits Matrix Metalloproteinase-2 and -9 But Does Not Remove the Smear Layer

BACKGROUND

The antibacterial and anticollagenolytic properties of tetracycline (TCN) are valuable in periodontal therapy, and TCN treatment can remove the smear layer following root instrumentation. However, recent reports pointing to cytotoxic effects of several acids prompted this study to define TCN concentrations that are anticollagenolytic and remove the smear layer, but have low cytotoxicity.

METHODS

Human gingival (hGF) and periodontal ligament (hPDL) cells were treated short- (3 minutes) or long-term (24 hours) with TCN to determine concentrations yielding 50% (TD(50)) and 90% (TD(10)) cell survival. Activity assays measured TCN concentrations with half-maximal inhibition (IC(50)) of matrix metalloproteinase- 2 and -9 (MMP-2 and -9). Finally, we analyzed the effects of TCN with high (75 mg/ml) or low (1 mg/ml) cytotoxicity on the smear layer by scanning electron microscopy (SEM).

RESULTS

The TD(50) for TCN after short-term treatment was 4 mg/ml for both hGF and hPDL. Ninety percent of the cells survived 0.2 mg/ml. With long-term treatment, the TD(50) for hGF and hPDL was 70 and 30 microg/ml, respectively, and the TD(10) was 20 and 5 microg/ml. HGF and hPDL recovered from the 3-minute treatment with 1 mg/ml, but not from concentrations exceeding 3 and 9 mg/ml, respectively. The IC(50) was 25 microg/ml for both MMP-2 and MMP-9. Whereas 75 mg/ml TCN removed the smear layer, 1 mg/ml TCN had no effects.

CONCLUSIONS

Tetracycline has significant cytotoxicity on periodontal cells. Since non-cytotoxic concentrations of TCN inhibited MMP-2 and -9 but had no effects on the smear layer, TCN is not recommended for root surface treatment.