Comparison of different digital shade selection methodologies in terms of accuracy

PURPOSE

This study aims to evaluate the accuracy of different shade selection techniques and determine the matching success of crown restorations fabricated using digital shade selection techniques.

MATERIALS AND METHODS

Teeth numbers 11 and 21 were prepared on a typodont model. For the #11 tooth, six different crowns were fabricated with randomly selected colors and set as the target crowns. The following four test groups were established: Group C, where the visual shade selection was performed using the Vita 3D Master Shade Guide and the group served as the control; Group Ph, where the shade selection was performed under the guidance of dental photography; Group S, where the shade selection was performed by measuring the target tooth color using a spectrophotometer; and Group I, where the shade selection was performed by scanning the test specimens and target crowns using an intraoral scanner. Based on the test groups, 24 crowns were fabricated using different shade selection techniques. The ΔE values were calculated according to the CIEDE2000 (2:1:1) formula. The collected data were analyzed by means of a one-way analysis of variance.

RESULTS

For the four test groups (Groups C, Ph, S, and I), the following mean ΔE values were obtained: 2.74, 3.62, 2.13, and 3.5, respectively. No significant differences were found among the test groups.

CONCLUSION

Although there was no statistically significant difference among the shade selection techniques, Group S had relatively lower ΔE values. Moreover, according to the test results, the spectrophotometer shade selection technique may provide more successful clinical results.

Sarcoidosis of the vagina treated with methotrexate

We describe the first case of mediolateral episiotomic sarcoidosis of the deep vaginal tissue, without involvement of the pulmonary parenchyma or pulmonary symptoms. A 68-year-old female was admitted with a vaginal mass that had developed about 1 month prior. On bimanual examination, we found a painful solid mass approximately 4 cm in diameter on the episiotomy line of the deep vaginal tissue. The patient underwent pelvic magnetic resonance imaging on suspicion of a malignancy, and a vaginal true-cut biopsy was performed. The biopsy specimen exhibited non-caseating, granulomatous inflammation and many multinucleated giant cells, strongly suggesting sarcoidosis. We had excluded other granulomatous diseases; a final diagnosis was made of stage-1 sarcoidosis in the deep vaginal mass. A 3-month course of methotrexate (2.5 mg/week) was commenced to treat a flare-up of rheumatoid arthritis. The vaginal mass resolved. To the best of our knowledge, this is the first case of sarcoidosis in a deep vaginal mass without pulmonary parenchymal or other solid-organ involvement.

Minor actinide burning in a CANDU thorium reactor

Nuclear waste actinides can be used as a booster fissile fuel material in form of mixed fuel with thorium in a CANDU reactor in order to assure the initial criticality at startup. Two different fuel compositions have been found useful to provide sufficient reactor criticality over a long operation period: 1) 95% thoria (ThO2)+5% minor actinides MAO2 and 2) 90% ThO2+5% MAO2+5% UO2. The latter allows a higher degree of nuclear safeguarding through denaturing the new 233U fuel with 238U. The temporal variation of the criticality k∞ and the burn-up values of the reactor have been calculated by full power operation for a period of 10 years. The criticality starts by k∞>1.3 for both fuel compositions. A sharp decrease of the criticality has been observed in the first year as a consequence of rapid plutonium burnout in the actinide fuel. The criticality becomes quasi constant after the 2nd year and remains close to k∞ = ∼1.06 for ∼10 years. After the 2nd year, the CANDU reactor begins to operate practically as a thorium burner. Very high burn up could be achieved with the same fuel material (up to 200000 MW.D/MT), provided that the fuel rod claddings would be replaced periodically (after every 50000 or 100000 MW.D/MT). The reactor criticality can be maintained until a great fraction of the thorium fuel is burnt up. This would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically.

Prevalence of femoroacetabular impingement in asymptomatic contralateral hips in patients with unilateral idiopathic osteoarthritis

Radiographic findings of femoroace tabular impingement in the contralateral asymptomatic hip of patients who had undergone total hip arthroplasty because of primary osteoarthritis (n = 44) were compared with controls (n = 40). The centre-edge angle and caput-collum-diaphyseal angle were measured and the presence of crossover sign and a prominent ischial spine noted on anteroposterior radiographs of the pelvis. The α-angle and offset ratio were measured on cross-table lateral radiographs of the hip. The centre-edge angle and offset ratio were significantly lower and the α-angle significantly higher in the study group compared with controls. While the number of cases with an abnormal centre-edge angle was similar in both groups, the numbers with an α-angle > 50° and the number with an offset ratio ≤ 15 were significantly higher in the study group. It was concluded that morphological anomalies associated with femoroacetabular impingement are seen more frequently in the asymptomatic contralateral hip of patients who have undergone hip replacement for primary osteoarthritis than in controls.