Comparison of internal fit of metal-ceramic crowns in CAD/CAM and lost-wax techniques in all fabrication stages through replica weighting, triple scanning, and scanning electron microscope

OBJECTIVES

Restoration fit is one of the prerequisites of clinical durability. It is controversial as to whether computer-assisted design/computer-aided milling (CAD/CAM) or lost-wax fabrication methods result in more fit metal-ceramic crowns. This in-vitro study was conducted to examine the internal fit of porcelain fused to metal crowns fabricated using CAD/CAM and lost-wax techniques during fabrication stages (framework, porcelain, cementation) through digital triple scanning, replica weighting, and observation with electron microscopy.

MATERIAL AND METHODS

Twenty uniform resin dies of prepared first maxillary molars were randomly divided into two groups according to the fabrication technique: lost wax and CAD/CAM. The internal fit was measured in all steps of completing the crowns (framework, porcelain, and cementation) using different methods, including triple scanning, replica weighting, and scanning electron microscopy. The data were statistically analyzed using t test, Pearson, and repeated measures analysis of variance (α = .05).

RESULTS

Triple scanning revealed no difference in the internal fit of CAD/CAM and lost-wax groups in all the fabrication steps (p > .05). The replica weighting method showed no difference between groups in the framework step (p > .05), while the internal fit was significantly better in the CAD/CAM group after porcelain application (p < .05). After cementation, electron microscopy measurements showed no difference between CAD/CAM and lost wax groups (p > .05). The Pearson correlation test showed no significant correlation between electron microscopy, replica weighing, and triple scanning methods (p > .05).

CONCLUSION

According to scanning electron microscopy as the superior evaluation method, the internal fit of cobalt-chrome PFM crown of both CAD/CAM and lost wax groups was within the acceptable clinical range and there was no significant difference between them. Triple scanning revealed no difference in the internal fit of framework and porcelain steps but a better fit after cementation. According to replica weighting, the internal fit in the porcelain step was higher than the framework.

Comparison of the marginal discrepancy of PFM crowns in the CAD/CAM and lost-wax fabrication techniques by triple scanning

BACKGROUND

Computer-aided design/computer-aided manufacturing (CAD/CAM) systems are widely used for the fabrication of porcelain-fused-to-metal (PFM) crowns.

OBJECTIVES

This study was conducted to compare PFM crowns through triple scanning in terms of marginal discrepancy between the CAD/CAM and lost-wax fabrication techniques.

MATERIAL AND METHODS

Twenty uniform resin dies of a prepared maxillary first molar were randomly divided into 2 groups: conventional lost-wax; and milling. Marginal discrepancy was evaluated at the framework and porcelain steps through triple scanning and direct visualization under a stereomicroscope. Then, the crowns were cemented to the related die and the marginal gap was measured with triple scanning, direct visualization under a stereomicroscope and scanning electron microscopy (SEM). The data was analyzed using the independent t test and the one-way analysis of variance (ANOVA). The significance level was set at 0.05.

RESULTS

Differences in the mean marginal gap were measured by the various evaluation methods. Triple scanning and stereomicroscopy identified increasing discrepancy during the fabrication process. According to the results of the independent t test, stereomicroscopy showed no difference after cementation between the CAD/CAM and lost-wax groups (p > 0.05), triple scanning showed higher fitness in the CAD/CAM group (p < 0.05), and SEM showed better adaptation in the lost-wax group (p < 0.05); however, there was a positive correlation between the findings of stereomicroscopy and SEM (p < 0.05).

CONCLUSIONS

The cobalt-chromium crowns had clinically acceptable marginal fitness from both the CAD/CAM and lost-wax techniques; however, the lost-wax group showed lower marginal discrepancy after cementation according to SEM.

Anatomical variations in sinus imaging in sinusitis: a case control study

OBJECTIVE

To compare anatomical variations in sinusitis patients and control subjects.

SUBJECTS AND METHODS

We reviewed and compared the computed tomography (CT) scans of 87 sinusitis patients after adequate medical treatment and scans of 103 healthy subjects. All images were scored for sinusitis severity using the Lund-Mackay scoring system. Anatomical variations such as septal deviation, concha bullosa, presence of the Haller's cell, paradoxical middle turbinate, prominent agger nasi cell, and Onodi cell were also recorded.

RESULTS

Of the 190 evaluated CT images, 55.2% of the cases and 47.6% of the controls had septal deviation (p > 0.05). The prevalence of concha bullosa was 68% in patients and 61% in controls (p > 0.05).

CONCLUSION

There were no significant differences in the evaluated anatomical variations between cases and controls in this study. Mucosal inflammation may play a more essential role than anatomical variation in the development of sinusitis.

Hypertension in Iranian urban population, epidemiology, awareness, treatment and control

BACKGROUND

To assess the epidemiological characteristics of hypertensive patients in urban population of Yazd, A central city in Iran.

METHODS

This cross sectional study was conducted from 2005-2006 and carried out on population aging 20-74 years. It is a part of the phase I of Yazd healthy heart program that it is a community interventional study for prevention of cardiovascular disease. Data obtained from questionnaires were analyzed by SPSS version 13. P value less than 0.05 were considered significant level.

RESULTS

This study comprised of 2000 participants that 847 (42.5%) were diagnosed as being hypertensive. After age adjustment, prevalence of hypertension was 25.6% (23.3% for women and 27.5% for men (P< 0.001). Age, Total cholesterol, LDL-cholesterol, triglyceride, fasting blood glucose, impaired glucose tolerance test, body mass index and waist were significantly higher in the hypertensive groups. 53.7% of hypertensive cases were aware of own condition, 45% were treated, and 33.9% of treated were controlled (30.7% and 35.4% in men and women respectively). In other word, 24% of all hypertensives (aware or unaware about own blood pressure condition) were treated and only 8% of them were controlled. Men significantly had less awareness (P< 0.001), lower tendency to take medication (P< 0.001), and less were controlled (P= 0.046).

CONCLUSION

We understand high prevalence, low awareness, treatment, and control of hypertension and higher prevalence of other traditional metabolic risk factors in these cases. It seems that urgent preventional studies should be conducted in this population.