Recurrence rate of odontogenic myxoma after different treatments: a systematic review.

Our aim was to establish the recurrence rate of odontogenic myxoma after different treatments. Our search covered papers from 1972-2017 from different sources. The papers were evaluated and critically appraised by two independent investigators. The recurrence rate and 95% CI were calculated in relation to each specific treatment, and the chi squared test was calculated to find out if there was any significant difference in the recurrence rate between conservative treatment and resection. The overall recurrence rate was 5 of 39 patients (13%) during a mean follow up period of 10 years. With conservative treatment the recurrence rate was 4/22 (19%) (mean follow up 11 years) and after resection it was 1/17 (6%) (mean follow up nine years). Maxillary lesions were more likely to recur than mandibular ones. Quality of life variables such as disfigurement and neural deficit were more common after resection than with conservative treatment. The frequency of recurrence was relatively low over 10 years' follow up, irrespective of whether resection or a more conservative approach was used, despite being slightly lower (as might be expected) after resection. Conservative treatment should be considered first to avoid resection-associated morbidity and the effect on the quality of life. Maxillary lesions have more room to spread before they are clinically evident, making them difficult to treat optimally and contributing to the recurrence rate.

Productive performance, egg quality, hematological parameters and serum chemistry of laying hens fed diets supplemented with certain fat-soluble vitamins, individually or combined, during summer season.

This present study aimed to determine the efficacy of supplementing layer diets with vitamin A (0, 8,000 and 16,000 IU/kg diet) and vitamin E (0, 250 and 500 mg/kg diet) either individually or in combination on egg production and quality, and blood hematology and chemistry of birds reared under summer conditions. A total of 135 Bovans Brown laying hens were distributed to 9 treatment groups with 5 replicates of 3 hens/pen in a 3 × 3 factorial design. A significant improvement in feed conversion ratio (FCR) was observed as supplementary vitamin A or E increased (P ≤ 0.01). Hens fed diets supplemented with 16,000 IU vitamin A plus 500 mg vitamin E/kg diet had the best FCR among all groups. Egg quality traits were not significantly affected by the interaction of vitamin A and vitamin E levels. There was a significant increase in monocytes (P ≤ 0.01) and a decrease in basophils counts (P ≤ 0.05) in response to vitamin E. Significant decreases were observed in packed cell volume (PCV), thyroxine (T4), alanine transferase (ALT), albumin, total cholesterol and total lipids ( (P ≤ 0.05 or P ≤ 0.01) P ≤ 0.01) , and increases were observed in serum concentrations of globulin (P ≤ 0.05) and calcium (P ≤ 0.01) due to vitamin A. The combination of 0 IU vitamin A and 500 mg vitamin E/kg diet had the highest values of PCV (40.09%) and hemoglobin (Hb) (10.33 mg/100 mL) among all groups. Vitamin E raised serum values of total protein, total cholesterol and total lipids (P ≤ 0.05 or P ≤ 0.01). Feed intake, FCR, PCV, Hb, lymphocytes, monocytes, eosinophils, T4, ALT and total protein were significantly affected by the interaction of vitamins A and E (P ≤ 0.05 or P ≤ 0.01). The interaction of vitamins A and E was only significant with respect to serum total protein (P ≤ 0.05). It can be concluded that layer diets supplemented with vitamins A and E had good results in alleviating the harmful impacts of high ambient temperature. The combination of 16,000 IU vitamin A and 500 mg vitamin E per kilogram diet is preferable for obtaining better production of laying hens reared under hot summer conditions.

Impacts of selenium and vitamin E supplementation on mRNA of heat shock proteins, selenoproteins and antioxidants in broilers exposed to high temperature.

The study was carried out to investigate the effect of dietary selenium (Se) and vitamin E (VE) supplementation on mRNA level of heat shock proteins, selenoproteins, and antioxidant enzyme activities in the breast meat of broilers under summer heat stress conditions. A total of 200 male broilers (Ross 308) of 1 day age were randomly separated into 4 groups in a complete randomized design and were given a basal diet (Control, 0.08 mg Se/kg diet) or basal diet supplemented with VE (250 mg/kg VE), sodium selenite (0.2 mg/kg Se), or Se + VE (0.2 mg/kg Se + 250 mg/kg VE) to investigate the expression of key antioxidant and heat shock protein (HSP) genes under high temperature stress. Dietary Se, VE and Se + VE significantly enhanced the activities and mRNA levels of catalase as well as superoxide dismutase (SOD) but decreased the mRNA levels of HSP70 and HSP90. Se alone or combined with VE increased the concentration of selenoprotein P and selenoproteins mRNA level and decreased the expression of HSP60. In addition, Se and Se + VE significantly enhanced the glutathione peroxidase (GPx) activity and the expression of GPx1 and GPx4 in breast muscle tissues. It is noteworthy that all the treatments significantly decreased malondialdehyde (MDA) level in the breast meat. Overall results showed that Se in combination with VE has maximal effects to mitigate heat stress. Based on given results it can be recommended that Se + VE are a suitable dietary supplement for broilers to ameliorate the negative effects of summer heat stress conditions.

Intrauterine growth retardation promotes fetal intestinal autophagy in rats via the mechanistic target of rapamycin pathway.

Intrauterine growth retardation (IUGR) impairs fetal intestinal development, and is associated with high perinatal morbidity and mortality. However, the mechanism underlying this intestinal injury is largely unknown. We aimed to investigate this mechanism through analysis of intestinal autophagy and related signaling pathways in a rat model of IUGR. Normal weight (NW) and IUGR fetuses were obtained from primiparous rats via ad libitum food intake and 50% food restriction, respectively. Maternal serum parameters, fetal body weight, organ weights, and fetal blood glucose were determined. Intestinal apoptosis, autophagy, and the mechanistic target of rapamycin (mTOR) signaling pathway were analyzed. The results indicated that maternal 50% food restriction reduced maternal serum glucose, bilirubin, and total cholesterol and produced IUGR fetuses, which had decreased body weight; blood glucose; and weights of the small intestine, stomach, spleen, pancreas, and kidney. Decreased Bcl-2 and increased Casp9 mRNA expression was observed in IUGR fetal intestines. Analysis of intestinal autophagy showed that the mRNA expression of WIPI1, MAP1LC3B, Atg5, and Atg14 was also increased, while the protein levels of p62 were decreased in IUGR fetuses. Compared to NW fetuses, IUGR fetuses showed decreased mTOR protein levels and enhanced mRNA expression of ULK1 and Beclin1 in the small intestine. In summary, the results indicated that maternal 50% food restriction on gestational days 10-21 reduced maternal serum glucose, bilirubin, and total cholesterol contents, and produced IUGR fetuses that had low blood glucose and reduced small intestine weight. Intestinal injury of IUGR fetuses caused by maternal food restriction might be due to enhanced apoptosis and autophagy via the mTOR signaling pathway.

Cone Beam Computed Tomographic imaging in orthodontics.

Over the last 15 years, cone beam computed tomographic (CBCT) imaging has emerged as an important supplemental radiographic technique for orthodontic diagnosis and treatment planning, especially in situations which require an understanding of the complex anatomic relationships and surrounding structures of the maxillofacial skeleton. CBCT imaging provides unique features and advantages to enhance orthodontic practice over conventional extraoral radiographic imaging. While it is the responsibility of each practitioner to make a decision, in tandem with the patient/family, consensus-derived, evidence-based clinical guidelines are available to assist the clinician in the decision-making process. Specific recommendations provide selection guidance based on variables such as phase of treatment, clinically-assessed treatment difficulty, the presence of dental and/or skeletal modifying conditions, and pathology. CBCT imaging in orthodontics should always be considered wisely as children have conservatively, on average, a three to five times greater radiation risk compared with adults for the same exposure. The purpose of this paper is to provide an understanding of the operation of CBCT equipment as it relates to image quality and dose, highlight the benefits of the technique in orthodontic practice, and provide guidance on appropriate clinical use with respect to radiation dose and relative risk, particularly for the paediatric patient.

Rapid Bioassay-Guided Isolation of Antibacterial Clerodane Type Diterpenoid from Dodonaea viscosa (L.) Jaeq.

Plant extracts are complex matrices and, although crude extracts are widely in use, purified compounds are pivotal in drug discovery. This study describes the application of automated preparative-HPLC combined with a rapid off-line bacterial bioassay, using reduction of a tetrazolium salt as an indicator of bacterial metabolism. This approach enabled the identification of fractions from Dodonaea viscosa that were active against Staphylococcus aureus and Escherichia coli, which, ultimately, resulted in the identification of a clerodane type diterpenoid, 6ß-hydroxy-15,16-epoxy-5ß, 8ß, 9ß, 10α-cleroda-3, 13(16), 14-trien-18-oic acid, showing bacteriostatic activity (minimum inhibitory concentration (MIC) = 64-128 µg/mL) against test bacteria. To the best of our knowledge, this is the first report on antibacterial activity of this metabolite from D. viscosa.

Accuracy of CBCT images in the assessment of buccal marginal alveolar peri-implant defects: effect of field of view.

OBJECTIVES: To investigate the reliability and accuracy of cone beam CT (CBCT) images obtained at different fields of view in detecting and quantifying simulated buccal marginal alveolar peri-implant defects. METHODS: Simulated buccal defects were prepared in 69 implants inserted into cadaver mandibles. CBCT images at three different fields of view were acquired: 40 × 40, 60 × 60 and 100 × 100 mm. The presence or absence of defects was assessed on three sets of images using a five-point scale by three observers. Observers also measured the depth, width and volume of defects on CBCT images, which were compared with physical measurements. The kappa value was calculated to assess intra- and interobserver agreement. Six-way repeated analysis of variance was used to evaluate treatment effects on the diagnosis. Pairwise comparisons of median true-positive and true-negative rates were calculated by the χ² test. Pearson's correlation coefficient was used to determine the relationship between measurements. Significance level was set as p < 0.05. RESULTS: All observers had excellent intra-observer agreement. Defect status (p < 0.001) and defect size (p < 0.001) factors were statistically significant. Pairwise interactions were found between defect status and defect size (p = 0.001). No differences between median true-positive or true-negative values were found between CBCT field of views (p > 0.05). Significant correlations were found between physical and CBCT measurements (p < 0.001). CONCLUSIONS: All CBCT images performed similarly for the detection of simulated buccal marginal alveolar peri-implant defects. Depth, width and volume measurements of the defects from various CBCT images correlated highly with physical measurements.

Comparative diagnostic yield of cone beam CT reconstruction using various software programs on the detection of vertical root fractures.

OBJECTIVES: To evaluate the effect on diagnostic yield in the detection of experimentally induced vertical root fractures on cone beam CT images using four dental software program. METHODS: 190 single-rooted extracted human teeth were divided into three groups according to the pulp canal status: unrestored (UR), filled with gutta-percha (GP) and restored with a metallic custom post (Post). One-half of the sample of each group was artificially fractured and the segments repositioned. All teeth were scanned on a cone beam CT device at 0.2 mm nominal voxel resolution (i-CAT Platinum; Imaging Sciences International, Hatfield, PA). The data were exported as digital imaging and communications in medicine files and imported into Dolphin Imaging & Management Solutions, v. 11.5 (Patterson Dental Supply Inc., St Paul, MN), InVivoDental, v. 5.0 (Anatomage Inc., San Jose, CA) and Kodak Dental Imaging Software 3D module, v. 2.1.11 (Carestream Health Inc., Rochester, NY) software. Cross-sectional images in the acquisition (using Xoran CAT™, v. 3.0.34 software; Xoran Technologies, Ann Arbor, MI) and additional software were presented to three calibrated oral radiologists who rated the presence or absence of root fracture on a five-point scale. Receiver operating characteristic analysis was performed, and treatment comparisons compared by analysis of variance and pairwise comparisons were performed using Tukey's test at an a priori value of α < 0.05%. RESULTS: All dental software performed equally at detecting fractures. Fractures were significantly more difficult to detect when posts were present. CONCLUSIONS: The diagnosis of root fracture is software-independent. The presence of an intracanal metallic post significantly decreases the detection of artificially created root fractures.

Responsible use of cone beam computed tomography: minimising medico-legal risks.

This communication highlights some of the ethical and possible legal responsibilities which pertain to the taking, reading, reporting, and communication of findings from cone-beam computed tomography (CBCT) scans. The importance of knowledge of head and neck anatomy and pathology to reduce the likelihood of incorrect interpretation is emphasised. Failure to detect critical findings in any diagnostic image can potentially result in medico-legal consequences. CBCT is no exception to this rule. Dental schools are advised to include CBCT imaging as a diagnostic tool in their under- and postgraduate curricula thereby equipping graduates to use 3D imaging in general and CBCT in particular. Existing dental practitioners are advised to seek continuing education on 3D imaging as part of their required lifelong learning.

Maxillofacial cone beam computed tomography: essence, elements and steps to interpretation.

Maxillofacial cone beam computed tomography (CBCT) is one of the most significant advances in dental imaging since rotational panoramic radiography. While the acquisition of CBCT data is technically simple, numerous parameters should be considered so that CBCT imaging is performed appropriately and 'task specific'. This involves an understanding of not only exposure (e.g. geometric and software parameters to minimize patient dose, while sustaining diagnostic image quality) but also image formatting options to maximize image display. CBCT images contain far more detailed information of the maxillofacial region than do panoramic or other 2-D images and necessitate a thorough knowledge of the 3-D anatomy of the region and considerations of variability in the range of the anatomically normal. These principles, procedures and protocols, together with the interpretation of CBCT images form the basis of best practices in maxillofacial CBCT imaging. This communication aims to provide: (1) an overview of the fundamental principles of operation of maxillofacial CBCT technology; (2) an understanding of 'task specific' equipment, image selection and image display modes; and (3) a systematic methodology for sequencing interpretation of CBCT images.

Ex vivo detection of mesiobuccal canals in maxillary molars using CBCT at four different isotropic voxel dimensions.

AIM: To study observers' ability to detect mesiobuccal (MB) canals in maxillary molars using iCAT cone-beam computed tomography (CBCT) at different voxel dimensions and to assess the impact of clinical experience on accuracy of detection. METHODOLOGY: Using 12 experimental models with two molars each, CBCT scans were acquired at four different voxel dimensions. From the cross-section view of these scans, 96 videos were generated. Five endodontic postgraduate students and two endodontic staff watched the videos and counted the MB canals in each root. Horizontal sections of the roots were evaluated under magnification to determine the true canal numbers. The detection of MB canals within the four resolutions was compared by odds ratio, and the weighted χ(2) test compared detection accuracy to raters' clinical experience. Rater agreement was measured by kappa statistics. RESULTS: Overall, 92% of the maxillary molars had two MB canals upon analysis of horizontal cross-sections. The CBCT detection increased from 60.1% at 0.4 mm voxel size to 93.3% at 0.125 mm voxel size. Significant differences (P < 0.01) were observed between the different resolutions except for the 0.2 and the 0.125 voxel scans. Second-year trainees were significantly (CI = 0.2929-0.712) more accurate than first-year trainees and endodontic staff at MB canal detection (87.9% against 77.1% and 76.8%). Intra-rater reliability increased with higher-resolution scans (41.1% to 96.4%). CONCLUSIONS: The reliability of detection of maxillary molar MB2 canals in CBCT scans increased as the resolution improved. Accuracy of MB2 canal detection among observer groups could not be correlated with the observers' level of clinical experience.

Developing the function of 'Magnitude-of-Effect' (MoE) for artificial neural networks to demonstrate the causal effect of exposure variables on outcome variable.

Statistical analysis and logistic regression (LR) in particular are among the most popular tools being used by safety professionals and practitioners to assess the association between exposures and possible occupational disorders or diseases and predict the outcome. Recently, artificial neural network (ANN) models are gradually finding their way into safety field. It has been shown that they are capable of predicting outcomes more accurately than LR, but they are incapable of demonstrating the direct correlation between exposure variables and a possible outcome variable. The objective of this study was to develop a mathematical function that can use the result of ANN models to produce a measure for evaluating the direct association between exposure and possible outcome variables. This function was referred to as the function of Magnitude-of-Effect (MoE). Safety experts and practitioners can use the MoE function to interpret how strongly an exposure variable can affect the outcome variable, similar to an odds ratio, which can be calculated by using estimated parameters in LR models. The significance of such achievement is that it can eliminate one of the ANN model's shortcoming and make them more applicable in the occupational safety and health engineering field.

Guidelines for the safe use of dental and maxillofacial CBCT: a review with recommendations for South Africa.

The aim of this manuscript is to provide the South African dental profession with guidelines and recommendations on the safe and responsible clinical use of cone beam computed tomography (CBCT) equipment. Dental practitioners who prescribe and refer patients for CBCT examinations as well as those who operate CBCT systems and interpret the images, share responsibility for the use of CBCT systems. Applicable information pertaining to the current status of the use of CBCT was reviewed, and the Directorate of Radiation Control of the Department of Health, South Africa, was invited to participate in the development of evidence-based guidelines on the safe use of cone beam computed tomography in dentistry. These guidelines establish a basis for discussions that are likely to lead to legislation.

Application of artificial neural network models in occupational safety and health utilizing ordinal variables.

Safety professionals and practitioners are always searching for methods to accurately assess the association between exposures and possible occupational disorders or diseases and predict the outcome of any variable. Statistical analysis and logistic regression (LR) in particular are among the most popular tools being used today. Artificial neural network (ANN) models are another method of predicting outcomes, which are gradually finding their way into the safety field. Limited studies have shown that they are capable of predicting outcomes more accurately than LR, but they have been tested either on continuous or on dichotomous variables or combinations of them. The objective of this research was to demonstrate that ANN models can perform better than LR models with data sets comprised of all ordinal variables, which has not been done so far. The data set used in this research was collected from construction workers using the Work Compatibility questionnaire. The data set contained only ordinal variables both as input (exposure) and as output (outcome) variables. LR models and ANN models were constructed using the same data set and the performance of all models was compared by using the log-likelihood ratio. The result of this study showed that ANN models performed significantly better than LR models with a data set of all ordinal variables as well as other types of variables such as dichotomous and continuous.

Time and motion study: a comparison of two photostimulable phosphor imaging systems used in dentistry.

OBJECTIVES: To compare two photostimulable phosphor (PSP) dental radiographic systems in terms of time efficiency in making full mouth intraoral X-ray surveys (FMS). METHODS: PSP systems compared were (1) DenOptix) (Kavo/Gendex, Des Plaines, IL) and (2) ScanX) (Air Techniques, Hicksville, NY). Twenty one FMS of a DXTRR) Manikin (Dentsply, Des Plaines, IL) were made with each of the systems. Time for each procedural step was determined using a stopwatch. Steps studied were: (1) plate erasure; (2) packaging; (3) positioning/exposure; (4) unpacking, loading processor, scanning; and (5) image transfer to virtual FMS mount. The first six test runs for each system were excluded to eliminate the learning curve period influencing results. An independent groups t-test was employed for statistical analysis. The a priori was set at P< or =0.05. RESULTS: The total time involved in producing a FMS was not proven to be statistically significant comparing DenOptix) and ScanX). The mean procedure time for DenOptix) was 31.2 min; for ScanX) it was 27.1 min. While the processing time with ScanX) (mean time: 3.9 min) was shorter than for DenOptix) (mean time =7.8 min), the opposite was true for the image transfer to FMS format with the time much shorter with DenOptix) using VixWin) software (mean time =2.0 min) compared with ScanX) using Vipersoft) (mean time =3.9 min). The differences between the systems for these two steps did prove to be statistically significant (P< or =0.05). CONCLUSIONS: Although the mean time to make a FMS was slightly shorter on average with ScanX) than DenOptix), this difference was not proven to be statistically significant (P>0.05) in terms of time efficiency in producing a FMS.

Antibiotic use for irreversible pulpitis.

BACKGROUND: Irreversible pulpitis, which is characterised by acute and intense pain, is one of the most frequent reasons that patients attend for emergency dental care. Apart from removal of the tooth the customary way of relieving the pain of irreversible pulpitis is by drilling into the tooth, removing the inflamed pulp (nerve) and cleaning the root canal. However, a significant minority of dentists continue to prescribe antibiotics to stop the pain of irreversible pulpitis. OBJECTIVES: The objective of this review was to provide reliable evidence regarding the effectiveness of prescribing systemic antibiotics for irreversible pulpitis by comparing clinical outcomes expressed as pain relief. SEARCH STRATEGY: We searched the following databases: Cochrane Oral Health Group Trials Register and Pain, Palliative Care and Supportive (PaPaS) Care Group Trials Register to 6th September 2004; the Cochrane Central Register of Controlled Trials (CENTRAL) The Cochrane Library Issue 3 2004; MEDLINE (1966 to 6th September 2004); EMBASE (1980 to week 36 2004). SELECTION CRITERIA: This review includes one randomised controlled trial which compared pain relief with systemic antibiotics and analgesics, against placebo and analgesics in the acute preoperative phase of irreversible pulpitis. DATA COLLECTION AND ANALYSIS: Only one trial is included in this review, therefore pooling of data from studies was not possible and a descriptive summary is presented. MAIN RESULTS: One trial involving 40 participants was included in this review. There was a close parallel distribution of the pain ratings in both the intervention and placebo groups over the 7 day study period. The between-group differences in sum pain intensity differences (SPID) for the penicillin group were (6.0+/-10.5), and for placebo (6.0+/-9.5) P = 0.776. The sum pain percussion intensity differences (SPPID) for the penicillin group were (3.5+/-7.5) and placebo (2.0+/-7.0) P = 0.290, with differences as assessed by the Mann-Whitney-Wilcoxon test considered to be statistically significant at P < 0.05. There was no significant difference in the mean total number of ibuprofen tablets (P = 0.839) and Tylenol tablets (P = 0.325), in either group over the study period. The administration of penicillin over placebo did not appear to significantly reduce the quantity of analgesic medication taken (P > 0.05) for irreversible pulpitis. AUTHORS' CONCLUSIONS: This review which was based on one methodologically sound but low powered small sample trial provided some evidence that there is no significant difference in pain relief for patients with untreated irreversible pulpitis who did or did not receive antibiotics in addition to analgesics.

Impact of ambient lighting intensity and duration on the signal-to-noise ratio of images from photostimulable phosphor plates processed using DenOptix and ScanX systems.

OBJECTIVES: To evaluate the impact on photostimulable phosphor (PSP) image signal-to-noise ratio (SNR) of pre-scanning ambient lighting exposures. METHOD: PSP imaging plates (IPs) were exposed to different radiation exposures to achieve flat field images. The exposed IPs were subjected variously to visible light of different intensities (300, 150 or 20 lux) for durations ranging from < 10 s to 120 s. They were processed using laser scanners from two systems for further comparison (DenOptix versus ScanX). Histogram analysis was performed in each case and mean pixel value and its standard deviation were used as surrogates to assess SNR. Statistical methods applied included analysis of variance with Tukey honestly significant difference test for pair wise comparisons. The a priori alpha was set at P < or = 0.05. RESULTS: SNR decreased with increased duration and intensity of pre-scanning light exposure. Lower X-ray exposures resulted in decreased signal resulting in reduced SNR, and increased the need to reduce ambient lighting. No statistically significant differences were found comparing ScanX and DenOptix digital imaging systems in terms of SNR. CONCLUSION: Reduced ambient lighting is preferred for handling IPs prior to processing in the laser scanner.

Effect of beam energy and filtration on the signal-to-noise ratio of the Dexis intraoral X-ray detector.

OBJECTIVE: To evaluate the signal-to-noise ratio (SNR) of the Dexis charge-coupled device (CCD) intraoral X-ray detector, with special reference to the influence of beam energy and filtration. MATERIAL AND METHODS: Digital radiographic images were made of a nine-step dental aluminium step wedge using a Dexis intraoral detector. The X-ray generator was a GE 1000 operating at 10 mA with 2.7 mm aluminium filtration. The peak tube voltage settings applied were 50 kVp, 60 kVp, 70 kVp, 80 kVp and 90 kVp. Various exposure times were used at each beam energy and the exposures (in micro C kg(-1)) were determined in each case using a 3 cl beryllium-windowed ionization chamber. SNR was defined using the surrogate measure of mean pixel value (surrogate for signal) divided by the standard deviation of the pixel value (surrogate for noise). SNRs were measured at separate regions of interest (ROIs) at the centre and at both sides of the detector for each aluminium step as well as without the step. RESULTS: For beam energies of 50 kVp and 60 kVp, the estimated SNR improved both with increased exposure and with increased filtration (thickness of the aluminium step), and image saturation did not occur within the exposure time range permitted by the Dexis software. At 70 kVp and above, the SNR was optimized in the middle of the exposure range: 4 micro C kg(-1) with 290:1 at the ninth step (13.5 mm Al) for 70 kVp; 3.5 micro C kg(-1) with 240:1 at the ninth step (13.5 mm Al) for 80 kVp; 3.5 micro C kg(-1) with 160:1 at the ninth step (13.5 mm Al) for 90 kVp. Saturation did occur at these beam energies within the exposure time range permitted by the Dexis software. CONCLUSION: For the Dexis intraoral radiographic imaging system, estimated SNR improved both with higher filtration and with lower kVp. The Dexis detector was capable of generating acceptable images of the step wedge at a wide range of kVp settings.

Array geometry for assessment of mandibular implant position using tuned aperture computed tomography (TACT).

OBJECTIVE: To evaluate observer faciolingual depth and vertical depth reading errors when using various X-ray beam array geometries to make basis images for tomosynthetic reconstruction using tuned aperture computed tomography (TACT). MATERIALS AND METHODS: Tissue-equivalent models were constructed to replicate the position of dental implants in relation to simulated mandibular canals. X-ray beam geometries used to acquire the basis images for TACT(TM) integration included horizontal linear, vertical linear, and symmetric and asymmetric conical arrays. Twenty-one dentists trained in the use of TACT acted independently as observers. Tasks included: (1) determination of the relative position of the implant in relation to the simulated canal; and (2) measurement of the vertical depth and faciolingual (lateral) depth dimensions between these two structures. As the study did not involve repeated measures (only one measure was obtained from each observer on each of the two dependent variables), data for faciolingual depth and vertical depth reading errors were analysed using a one-way analysis of variance (ANOVA) with Tukey's honestly significant different (HSD) procedure. RESULTS: Errors in determining the relative position of the implant to the simulated canal were most frequent when the linear horizontal projection geometry was employed for producing basis images (57% error for model #2 where the implant was lingually placed). The mean measurement errors for TACT images constructed using the various different projection arrays depended both on the structural relationship of anatomic features and the employed beam array geometry. CONCLUSION: Conical beam arrays are preferred over linear beam arrays for constructing basis images used with TACT for the purpose of correlating the position of a mandibular dental implant in relation to the mandibular canal. They more consistently allowed the observers to establish a measurement of the faciolingual relationship of the implant to the canal. For vertical depth measurement of the relationship of a mandibular dental implant to the mandibular canal, TACT does not appear to have any advantage over individual simple transmission radiographic images.