Vertical marginal fit of zirconia copings fabricated with one direct and three indirect digital scanning techniques.

STATEMENT OF PROBLEM: Direct digitization of the impression by using an intraoral scanner is a newly introduced technique, but studies comparing the method with other digitization techniques are lacking. PURPOSE: The purpose of this in vitro study was to compare the marginal accuracy of zirconia copings fabricated with 4 different scanning methods. MATERIAL AND METHODS: Scans (n=10) of a brass master die were made with a direct method (ISD) in which the die was directly digitized by using an intraoral scanner (IOS) and 3 indirect scanning methods, a conventional impression with polyvinyl siloxane material digitized with either the same IOS (ISI) or with a laboratory extraoral scanner (ESI), or a cast from the impression was scanned by using a laboratory extraoral scanner (ESC). Forty zirconia copings were milled from presintered zirconia blanks and sintered. The vertical marginal gap was measured at 12 points on the master die by using a digital microscope. One-way ANOVA was used to compare the mean differences among the 4 groups, and post hoc analysis was used for pairwise comparison of the groups (α=.05). RESULTS: The mean ±standard deviation of the vertical marginal gap was 73 ±7 µm in the ISD group, 109 ±36 µm in the ISI group, 42 ±4 µm in the ESI group, and 97 ±5 µm in the ESC group. The lowest marginal gap was seen in the ESI group, which was significantly different from the 3 other groups (P≤.001). The copings in the ISD group had a significantly lower marginal gap than those in the ISI (P=.04) and ESC (P<.001) groups. However, the ISI and ESC groups were not significantly different (P=.69). CONCLUSIONS: Marginal adaptation of all zirconia copings fabricated with these 4 scanning techniques was within a clinically acceptable range. However, ESI was the best method of digitization and yielded copings with minimum vertical marginal gap.

Evaluation of the marginal fit of metal copings fabricated by using 3 different CAD-CAM techniques: Milling, stereolithography, and 3D wax printer.

STATEMENT OF PROBLEM: Digital systems have been developed as substitutes for the traditional fabrication of wax patterns and definitive restorations, but the accuracy of these systems is unclear. PURPOSE: The purpose of this in vitro study was to evaluate and compare the marginal fit of metal copings fabricated from milling, stereolithography (SLA), and 3D wax printer (PolyJet) patterns. MATERIAL AND METHODS: A standard machined brass die model was designed and prepared. To fabricate metal copings of standardized shape and dimensions, the die was scanned and nickel-chromium (Ni-Cr) copings were designed by using a dental designer software program. By using the same CAD data to fabricate 30 patterns through milling, SLA, and PolyJet techniques, 10 resin patterns were milled by using a 5-axis milling machine, 10 resin patterns were produced by using a NextDent 5100 3D Printer, and 10 wax patterns were printed by using a Solidscape 3D printer. The patterns were invested and cast in Ni-Cr alloy. Each coping was evaluated by using a digital microscope on 16 points around the finish line on the metal die at ×230 magnification. The mean marginal discrepancy was calculated. The mean differences among the groups were compared by using 1-way ANOVA, and post hoc analysis was used for pairwise comparison of the groups (α=.05). RESULTS: The mean value of marginal discrepancy was 93.1 ±25 µm in the milling, 71.1 ±25 µm in the SLA, and 41.3 ±6 µm in the PolyJet group. No statistically significant difference was found between the milling and SLA groups (P=.158), while the PolyJet group showed significantly lower mean marginal discrepancy than the 2 other groups (P<.05). CONCLUSIONS: The PolyJet method produces metal copings with better marginal fit than the SLA or milling techniques. However, the marginal fit was clinically acceptable in metal copings made with all the 3 methods.

Dimensional stability of two solder index materials.

OBJECTIVES: This study aimed to compare the dimensional accuracy of two indexing materials, an acrylic resin (GC pattern resin) and a castable composite (Bredent). The effect of time lapse until investment was also investigated. MATERIALS AND METHODS: Two standardized brass dies 15 mm apart were prepared and then 20 identical coping-bar assemblies were designed and fabricated by a rapid prototyping device. Each bar was sectioned at the center, and indices were fabricated from an acrylic resin or castable composite (n = 10 per group). The distances between the reference points were measured with a digital microscope at ×80 magnifications at 15 min, 60 min, and 24 h after indexing. Data were statically analyzed using repeated-measure ANOVA (α = 0.05). RESULTS: The distance between the reference points without the coping being joined was considered as the baseline measurement (control group). The mean distance was 19.30 ± 0.04 mm between the reference points where the copings were not joined. When indexed with acrylic resin, the mean ± standard deviation (SD) dimensions were 19.27 ± 0.087 mm (15 min), 19.25 ± 0.09 mm (60 min), and 18.98 ± 0.1 mm (24 h). The mean ± SD dimensions for composite were 19.29 ± 0.087 mm (15 min), 19.28 ± 0.08 mm (60 min), and 19.26 ± 0.08 mm (24 h). All tested groups showed significant differences compared to the control group except when it was indexed with composite and where the distances were measured after 15 and 60 min (P > 0.05). CONCLUSIONS: The most accurate indexed-assemblies belonged to castable composite at 15 and 60 min.

Twist Expression in Pleomorphic Adenoma, Adenoid Cystic Carcinoma and Mucoepidermoid Carcinoma of Salivary Glands.

OBJECTIVE: Twist is an important transcription factor that induces epithelial-mesenchymal transition and therefore plays an important role in tumor progression. There are a few studies on Twist expression in salivary gland carcinomas. The aim of this study was to evaluate and compare the expression of Twist in the most common benign and malignant salivary gland tumors and to determine whether its expression was correlated with any tumor characteristics. MATERIAL AND METHOD: In this retrospective cross-sectional study, 45 cases including 11 cases of normal salivary gland, 12 pleomorphic adenomas, 12 adenoid cystic carcinomas and 10 mucoepidermoid carcinomas were enrolled. The mean and intensity of Twist expression were evaluated immunohistochemically and were compared using statistical analysis. RESULTS: The expression of Twist was higher in malignant salivary gland tumors in comparison with normal glands and benign tumors (p= 0.03). It was also higher in pleomorphic adenomas in comparison with normal tissue. Adenoid cystic carcinomas and mucoepidermoid carcinomas showed no significant difference in Twist expression (p= 0.50). There was no correlation with the size, stage or grade of tumor. CONCLUSION: The findings showed that Twist might play a role in the formation of salivary gland neoplasm and also may affect malignant transformation and tumoral invasion. The exact mechanism of this marker and the possibility of using it as a therapeutic target require further investigation.

Occupational Exposure of Shiraz Dental Students to Patients' Blood and Body Fluid.

STATEMENT OF THE PROBLEM: Exposure to patients' blood and body fluids would prone the dental students to the risk of blood borne infections. Several studies have shown a high prevalence of these exposures in dental settings particularly in developing countries. However, few studies have evaluated the epidemiology of these exposures in dental students in Iran. PURPOSE: To assess the epidemiology of occupational exposures among dental students and consequently designing the appropriate interventions in order to prevent these exposures. MATERIALS AND METHOD: In this cross-sectional study performed during March to June 2011, all 191 Shiraz clinical dental students were asked to complete a self-administered questionnaire. This questionnaire included demographic information and experience of sharp injuries and mucocutaneous contaminations. Chi square and t-test were employed to evaluate the risk factors of exposure. RESULTS: 80%of the participants were exposed to the patients' blood or body fluids during their clinical course. No association was found between the exposure and demographic factors. Injection needle and recapping were the most common causes of these injuries. The most common sites that were injured and caused mucocutaneous contamination were finger and face, respectively. The most frequent activity causing contamination was using high-speed rotary instruments. Only 6.4% of the exposures had been reported to the related authorities and the remains were underreported. CONCLUSION: Blood and body fluid exposure in dental setting is common and a lot of them are not reported. To reduce the hazards of these exposures, infection control authorities should design interventions especially for mentioned high-risk conditions. They should change dental students' behavior especially regarding not recapping injection needles and using eyewear. Dental schools seem to need a management center and a standard protocol for following up the exposures.

The effect of various veneering techniques on the marginal fit of zirconia copings.

PURPOSE: This study aimed to evaluate the fit of zirconia ceramics before and after veneering, using 3 different veneering processes (layering, press-over, and CAD-on techniques). MATERIALS AND METHODS: Thirty standardized zirconia CAD/CAM frameworks were constructed and divided into three groups of 10 each. The first group was veneered using the traditional layering technique. Press-over and CAD-on techniques were used to veneer second and third groups. The marginal gap of specimens was measured before and after veneering process at 18 sites on the master die using a digital microscope. Paired t-test was used to evaluate mean marginal gap changes. One-way ANOVA and post hoc tests were also employed for comparison among 3 groups (α=.05). RESULTS: Marginal gap of 3 groups was increased after porcelain veneering. The mean marginal gap values after veneering in the layering group (63.06 µm) was higher than press-over (50.64 µm) and CAD-on (51.50 µm) veneered groups (P<.001). CONCLUSION: Three veneering methods altered the marginal fit of zirconia copings. Conventional layering technique increased the marginal gap of zirconia framework more than pressing and CAD-on techniques. All ceramic crowns made through three different veneering methods revealed clinically acceptable marginal fit.

The effect of porcelain firing and type of finish line on the marginal fit of zirconia copings.

STATEMENT OF THE PROBLEM: Although all-ceramic restorations are broadly used, there is a lack of information concerning how their fit is affected by fabrication procedure and marginal configuration. PURPOSE: The purpose of this study was to evaluate the marginal fit of zirconia CAD/CAM ceramic crowns before and after porcelain firing. The influence of finish line configuration on the marginal fit was also evaluated. MATERIALS AND METHOD: Twenty standardized zirconia CAD/CAM copings were fabricated for chamfer and shoulder finish line designs (n=10). The marginal fit of specimens was measured on 18 points, marked on the master metal die by using a digital microscope. After the crowns were finalized by porcelain veneering, the measurements of marginal fit were performed again. The means and standard deviations were calculated and data were analyzed using student's t-test and paired t-test (α=0.05). RESULTS: There were significant differences between marginal fit of chamfer and shoulder finish line groups before and after porcelain firing (p= 0.014 and p= 0.000, respectively). The marginal gap of copings with shoulder finish line was significantly smaller than those with chamfer configuration (p= 0.000), but there were no significant differences between the two marginal designs, after porcelain firing (p= 0.341). CONCLUSION: Porcelain veneering was found to have a statistically significant influence on the marginal fit of zirconia CAD/CAM crowns. Both margin configurations showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy.

Twist expression in dentigerous cyst, odontogenic keratocyst, and ameloblastoma.

Epithelial-mesenchymal transition (EMT) is a process which is associated with a loss of intercellular adhesion, acquired mesenchymal shape, and increased motility by epithelial cells. Twist is one of the key regulators of EMT.In view of the distinct clinical behavior of odontogenic lesions, the objective of the present study was to investigate the immunohistochemical expression of Twist in these lesions. In this study, 70 formalin-fixed, paraffin-embedded tissue blocks of odontogenic lesion consisting of 16 unicystic ameloblastomas (UA), 17 solid ameloblastomas (SA), 18 odontogenic keratocysts (OKC), and 19 dentigerous cysts (DC) were reviewed using immunohistochemistry for Twist staining. In this study, Twist immunostaining was evident in all groups of the specimens except the dentigerous cyst group. Twist expression was seen in 58.8 % (10/17) of SA, 50 % (8/16) of UA, and 44.4 % (8/18) of OKCs. 23.5 % of SA, 18.8 % of UA, and 16.7 % of OKCs showed Twist expression in more than 50 % of cells. Statistical analysis showed that Twist expression levels were significantly higher in ameloblastomas (SA and UA) and OKCs than dentigerous cysts (P = 0.002). There were no significant differences between Twist expression in SAs, UAs, and OKCs (P > 0.05). The results of this study propose that the high expression rate of Twist plays a role in the pathogenesis of ameloblastomas and OKCs and might be one of the reasons for the aggressive behavior of ameloblastomas and high recurrence of OKCs and could reinforce the classification of OKC as an odontogenic tumor.

Metastasis-associated protein 1 expression in oral squamous cell carcinomas: correlation with metastasis and angiogenesis.

OBJECTIVE: Metastasis-associated protein 1 (MTA1) has been associated with poor prognosis in several carcinomas. Recent investigation has found that in different tumors, MTA1 protein significantly correlates with tumor angiogenesis, suggesting that MTA1 may be a possible angiogenesis-promoting molecule in malignant tumors. Thus, the current study was performed to determine the role of MTA1 protein in the biological behavior of oral squamous cell carcinoma and its relation with tumor angiogenesis. MATERIAL AND METHOD: In this study, 44 oral squamous cell carcinomas and 15 normal epitheliums were reviewed by IHC staining for MTA1 and CD105. RESULTS: Frequency of MTA1 expression in SCCs was recorded as 97.7%, which was significantly higher than that of the control group (33.3%). Mean percentage of MTA1 expression in oral squamous cell carcinomas was 76.88 ± 25.33% which was significantly higher than that of the control group (22.81 ± 10.83). Our data showed a correlation between MTA1 expression with lymph node metastasis, tumor size and, stage. Evaluation of the correlation between MTA1 protein expression and micro vessel density showed that high micro vessel density was detected more frequently in tumors with MTA1 protein overexpression than in those without overexpression. CONCLUSION: In the present study, high expression of the MTA1 protein was seen in oral squamous cell carcinoma, and was closely associated with tumor progression and increased tumor angiogenesis. The findings may indicate that MTA1 protein has clinical potentials as a useful indicator of progressive phenotype, a promising prognostic predictor to identify patients with poor prognosis and may be a potential novel therapeutic target of anti-angiogenesis for patients with oral squamous cell carcinoma.

Caveolin-1 expression in odontogenic cysts and ameloblastomas.

OBJECTIVE: The aim of this study is to evaluate the caveolin-1 expression in a group of odontogenic cysts and tumors. MATERIAL AND METHOD: In this cross-sectional study, the expression of caveolin-1 was evaluated immunohistochemically in 75 samples including 18 cases of dentigerous cyst, 18 odontogenic keratocysts, 3 orthokeratinized odontogenic cysts, 2 calcifying odontogenic cysts and 34 ameloblastomas (solid and unicystic). RESULTS: Positive immunohistochemical reaction was found in 100% of odontogenic cysts and this was significantly more than both unicystic (65%) and solid (55%) ameloblastomas. CONCLUSION: The present study showed the expression of caveolin-1 in all odontogenic cysts and more than ameloblastomas. The results suggested that absence of caveolin-1 might enhance aggressiveness of odontogenic lesions and could be a useful marker for distinguishing ameloblastomas from other odontogenic lesions.

MCM3 as a novel diagnostic marker in benign and malignant salivary gland tumors.

BACKGROUND: Proliferation markers widely have been used to diagnose and determine the behaviour and prognosis of benign and malignant tumours. Minichromosome maintenance 3 (MCM3) is a novel proliferation marker. The aim of this study was to evaluate and compare MCM3 with Ki-67 in diagnosis of salivary gland tumours. MATERIALS AND METHODS: In this retrospective study, immunohistochemical expression of MCM3 and Ki-67 was evaluated in 15 pleomorphic adenomas (PA), 17 mucoepidermoid carcinomas (MEC) and 18 adenoid cystic carcinomas (ADCC) . Labeling indices (LIs) for the two markers were calculated and compared. RESULTS: MCM3 and Ki-67 LIs were significantly higher in MEC and ADCC compared to PA. The LI of MCM3 was significantly higher than that of Ki-67 in MEC and PA. There was no significant difference between the two markers in ADCC. A cut-off point of 8% with 74.3% sensitivity and 93.3% specificity for MCM3 was obtained to discern between benign and malignant tumors. CONCLUSIONS: These results suggest that MCM3 might be a useful proliferation marker for differential diagnosis and recognition of clinical behavior of salivary gland tumors.

Expression of Ki67 and CD105 as proliferation and angiogenesis markers in salivary gland tumors.

OBJECTIVE: To investigate the association between CD105 and tumor cell proliferation in salivary gland tumors. METHODS: In this study, 59 samples of salivary tumors from Khalili Hospital archive, including 20 cases of pleomorphic adenoma (PA), 20 cases of mucoepidermoid carcinoma (MEC) and 19 cases of adenoid cystic carcinoma, as well as 10 cases of normal salivary gland tissue, were reviewed by immunohistochemistry (IHC) for CD105 and Ki67 staining. RESULTS: CD105 positive vessels were absent in normal salivary gland tissue in the vicinity of tumors (51.6% of all tumors were positive). There was a statistically significant difference in frequency of CD105 staining between PA and malignant tumors and between four groups of different lesions (p<0.000) being highest in MEC. Intratumoral microvessel density was also elevated in malignant neoplasms (2.61 ± 3.1) as compared to PA (0.46 ± 0.6). Normal salivary glands did not express Ki67. There was a statistically significant difference in frequency and percentage of Ki67 immunoreactivity in malignant neoplasms (86.5% and 10.7 ± 10.8 respectively) compared to PA (50% and 0.78 ± 0.2) and among the four groups values were highest in MEC (p<0.000). CONCLUSION: n this study, it was observed a higher rate of angiogenesis and cellular proliferation was noted in malignant tumors compared to benign tumors, but no correlation was observed between these two markers.

HER2/neu expression in head and neck squamous cell carcinoma patients is not significantly elevated.

BACKGROUND: HER2/neu, a member of EGFR family, is over expressed in some tumors .The purpose of this study was to determine the salivary level and tissue expression of HER2/neu in patients with head and neck squamous cell carcinoma (HNSCC) and any correlation with clinicopathologic parameters. METHODS: An enzyme- linked immunosorbent assay (ELISA) was used to evaluate the salivary level and immunohistochemistry (IHC) to assess tissue expression of HER2/neu in 28 patients with HNSCC and 25 healthy controls. RESULTS: The salivary levels of HER2/neu in HNSCC patients was not significantly higher than in the healthy controls (p>0.005). There was no apparent correlation in salivary HER2/neu level with clinicopathological features such as age, sex, grade, tumor size and nodal status. All HNSCC specimens were positive (membranous or/and cytoplasmic) for HER2/ neu, except one sample. Only one HNSCC specimen was stained in cytoplasm purely. All control specimens were membranous and cytoplasmic positive for HER2/neu. There was a significant difference between cytoplasmic staining in case and control groups (p-value<0.05). CONCLUSION: In our cases, no overexpression of HER2/neu was observed. Thus, our findings suggested that the use of Her-2 as a salivary marker of HNSCC cannot be recommended.

Evaluation of Tissue Expression and Salivary Levels of HER2/neu in Patients with Head and Neck Squamous cell Carcinoma.

INTRODUCTION: HER2/neu, a member of the epidermal growth factor receptor family, has been shown to be over-expressed in some tumors. The purpose of this study was to determine the salivary levels and tissue expression of HER2/neu in patients with head and neck squamous cell carcinoma (HNSCC) and their correlation with clinicopathologic parameters. MATERIALS AND METHODS: Enzyme-linked immunosorbent assays (ELISA) were used to evaluate the salivary levels of HER2/neu and immunohistochemistry was used to measure tissue expression of HER2/neu in 28 patients with HNSCC and 25 healthy control subjects. RESULTS: The salivary levels of HER2/neu in patients with HNSCC were not significantly higher compared to healthy control subjects. There was no apparent correlation between salivary HER2/neu levels and clinicopathological features such as age, sex, tumor grade, tumor size and nodal status. All HNSCC specimens were positive (membranous or/and cytoplasmic) for HER2/neu, except one sample. Only one HNSCC specimen showed staining purely in the tumor-cell cytoplasm. All control specimens were also positive for both membranous and cytoplasmic HER2/neu but there was a significant difference between the level of cytoplasmic staining in the HNSCC specimens and in the control specimens (P<0.05). CONCLUSION: In our study, no overexpression of HER2/neu was observed. Thus, identification of HER2/neu levels plays no role in differentiating between normal and squamous cell carcinoma tissues or detecting the carcinogenesis process. Our findings suggest that the use of HER2/neu as a salivary marker of HNSCC is not recommended, because no significant preoperative elevation and no association with clinicopathological features were found.

Oral mucocutaneous diseases: clinicopathologic analysis and malignant transformation.

Oral mucocutaneous diseases (MCDs) are a heterogeneous group of disorders that could involve oral mucous membrane frequently. The purpose of this study was analysis of clinicopathologic features and relative frequency of MCDs with emphasize on malignant transformation of oral lichen planus (OLP). In this retrospective study, clinical data regarding to site of involvement, patient's age and sex, and accompanied symptoms were noted, and pathologic slides of OLP were reviewed for the detection of dysplastic changes. Among 309 patients, OLP and pemphigus vulgaris were the first and second most common MCDs. Buccal mucosa was the most frequent affected site. Female predominance (70.23%) and mean age of 45.3 years were seen. Approximately 12.4% of OLPs showed dysplastic and neoplastic changes. In conclusion, MCD with oral manifestation is most probably to be OLP and pemphigus vulgaris rather than other rare disorders. Malignant transformation may occur in all forms of OLP, and hence, regular, exact follow-up of the patient is necessary for enhancing quality of life.

Histological evaluation of the effect of three medicaments; trichloracetic acid, formocresol and mineral trioxide aggregate on pulpotomised teeth of dogs.

The aim of this study was to use clinical, radiographic and histological examinations to compare the dental pulp response in 162 premolar roots of eight dogs when trichloracetic acid (TCA), formocresol, mineral trioxide aggregate (MTA) and zinc oxide eugenol were used as pulpotomy agents. The teeth were divided into four groups. Following pulpotomy, the teeth were restored with amalgam. The animals were sacrificed at 48 h, 2, 4 and 8 weeks (two dogs at each interval). Histological evaluation indicated no cases with necrosis. After 8 weeks follow up, dentine bridge formation was evident in 20%, 50% and 91.7% of formocresol, TCA and MTA cases respectively. The first signs of bridge formation were seen for MTA at 2 weeks and for TCA at 4 weeks. MTA was superior to formocresol and TCA in treating pulps in dogs. However, bridge formation was seen in 50% of TCA cases after 8 weeks which is a desirable finding in pulpotomy procedures.