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Introduction: Fixed prosthodontics is considered one of the most vital dental treatments that patients receive. Sometimes, however, complication is encountered along with limited information regarding the quality and precision of preparation. Which that led to the conception of this study in order to highlight the shortcomings and obstacles in an attempt to avoid them. This study aims to evaluate the quality of preparation by students of the faculty of dentistry in Damascus University and Al-Baath University by assessing the finish lines. Materials and methods: The specimen of this study consists of 244 prepared abutments divided into two groups: the first group consists of 122 clinically prepared abutments conducted by fifth year students in Damascus University. The second group consists of 122 clinically prepared abutments conducted by fifth year students in Al-Baath University. The specimen also consists of gypsum casts containing replicas of the clinically prepared teeth in addition to the primary casts. All casts - primary casts and post preparation casts - were collected and 3D scans were conducted to each abutment - before and after preparation - and a 3D image was acquired. Statistical analysis was conducted using SPSS v.26 (IBM, USA) with a P-Value of 0.05. Results: The preparation with a simple finishing line at Al-Baath University was 103% greater than it with a statistically significant difference at 56% at Damascus University, by 38%, and the percentage of preparation with a semi-shoulder finish line at Al-Baath University was 5% and at Damascus University was 3% without there being a statistically significant difference Between the two universities, the percentage of preparation with a shoulder finish line in Al-Baath University 14% was lower by a statistically significant difference than in Damascus University 63% by 40% (P < 0.001). Conclusion: The percentage of preparation with a simple finishing line at Al-Baath University was 103% greater than it with a statistically significant difference at 56% at Damascus University, by 38%, and the percentage of preparation with a semi-shoulder finish line at Al-Baath University was 5% and at Damascus University was 3%.
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OBJECTIVE: To determine the efficiency of debonding porcelain laminate veneers (PLV) by using several laser parameters and two different application modes of Er:YAG laser [contact (CM) and non-contact (NCM)], by verification of the consumed PLV debonding time and the changes in dental pulp temperature. MATERIALS AND METHODS: Forty extracted non-carious human maxillary premolars were prepared for receiving PLV. Sixteen of them were divided into two groups, each of them comprised eight samples based on the application mode; group A with NCM, and group B with CM. Veneers of both groups were debonded by the same laser parameters (360 mJ, 15 Hz) during loading of a 15 N force on specially fabricated veneer cervical margins. The primary results showed that the NCM was more efficient, thus, additional groups (C, D, and E) of the same mode and number of samples were tested with different laser parameters of energy and frequency; group C (400 mJ, 10 Hz), group D (270 mJ, 15 Hz), group E (300 mJ, 10 Hz). The failure mode was determined and classified for the debonded samples of all groups. RESULTS: All veneers were debonded and samples of the NCM group had considerably lower debonding time (12.6 seconds) than the CM samples (96.3 seconds), however, higher changes of temperature in NCM (4.2°C) than in CM were observed (2.9°C). The failure mode of samples was either type 1 or 3. CONCLUSION: Er:YAG laser is an effective tool in debonding PLVs. The NCM application mode was more efficient in reducing debonding time than CM application mode but with a higher change in pulp temperature. CLINICAL SIGNIFICANCE: Investigating the efficacy of Er:YAG laser as a non-invasive particle technique for debonding of failed or malpositioned of porcelain laminated veneers.
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Lasers de Estado Sólido , Descolagem Dentária , Porcelana Dentária , HumanosRESUMO
BACKGROUND: Resin-bonded fixed partial dentures appeared to prevent the excessive preparation of dental tissue. Investigation of surface treatments to improve the bond of resin cements to metals may contribute to the longevity of these restorations. Due to the potential lack of ideal preparation form, the type of alloy and its surface pretreatment may have clinically relevant correlations with the retentive strength of castings to minimally retentive preparations. AIM: The aim of this search is to study the bonding resin cement strength to different types of the metal alloy due to the surface treatment. PURPOSE: Evaluate the effects of two different surface treatments on shear bond strength (SBS) between a palladium-silver alloy (Pb-Ag) and commercially pure titanium (CP Ti) cast alloy with resin luting cements. MATERIALS AND METHODS: A total of 120 cylinders having 5 mm in diameter and 4 mm in height were divided into two different main groups of metal type: 60 cylinders cast from CP Ti Grade I (Tritan - Reintitan - Germany-Dentaurum) as a base metal and 60 cylinders cast from Pb-Ag (Status-Yamakin, Japan) as a noble metal. 30 cylinders from each type were embedded in acrylic resin, and the rest were left without embedded in acrylic resin. All of the cylinders were smoothed with silicon carbide papers and sandblasting with 50-µm aluminum oxide. Specimens of each metal type were divided into two subgroups, which received one of the following luting techniques: (1) Multilink (Ivoclar Vivadent), (2) Multilink (Ivoclar Vivadent) plus metal zirconia primer (MZP). Every two cylinders from the same metal type and surface treatment were bonded to each other. All specimens were stored in distilled water at 37°C for 24 h and then thermal cycled (500 cycles, 5-55°C). After thermal cycling, the specimens were stored in 37°C distilled water for an additional 24 h before being tested in shear strength. Data (MPa) were analyzed using T-s tests to study the significance of various - means among groups and perform a comparison between each two groups of them. RESULTS: The T-s tests indicated significant effect of combination of the sandblasting technique (aluminum oxide particles 50 µm) with the application of primer MZP before using resin cement (P < 0.05) independent of the metal type used. The metal type did not significantly affect SBS for any of the compared surface pretreatments. CONCLUSION: Metal primer application significantly enhanced SBS to base and a noble metal. No significant differences in shear strength were found between alloys.
