Influence of different cutting instruments and rotational speeds on heat generation and cutting efficiency when sectioning different types of zirconia.

PURPOSE: The purpose of this study was to evaluate the temperature generated on the intaglio surface and efficiency when cutting different types of zirconia with different rotary instruments and rotational speeds. METHODS: A conventional diamond rotary instrument (Brasseler, grit size 107 µm) and special diamond rotary instrument marketed to cut zirconia (4 ZR, Brasseler, grit size 126 µm) were tested on 3Y-TZP and 4Y-TZP zirconia with a rotation speed of 100,000 rpm and 200,000 rpm. Zirconia specimens were cut under water cooling (110 mL/min) in a custom-made holder attached to a universal testing machine. The temperature was recorded with infrared sensors pointing at the intaglio surface of the zirconia specimens. RESULTS: A rotation speed of 200,000 rpm resulted in significantly shorter cutting times, but also in significantly higher temperatures at the intaglio surface of the zirconia specimens compared with a rotation speed of 100,000 rpm. Significantly shorter cutting times were observed for the conventional diamond rotary instrument than for the special rotary instrument marketed to cut zirconia. Using the special rotary instrument, significantly longer cutting times were recorded for 3Y-TZP than for 4Y-TZP. CONCLUSIONS: A conventional diamond rotary instrument was more efficient than a special rotary instrument. However, to avoid high temperatures when cutting zirconia clinically, a rotation speed of 100,000 rpm is recommended.

Influence of pretreating radicular dentin with different polyacrylic acids and isopropanol on the retention of posts.

STATEMENT OF PROBLEM: The optimal pretreatment of radicular dentin before cementing a post with glass ionomer cement is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the retention of prefabricated tapered titanium posts to endodontically treated teeth after applying different pretreatment protocols on the radicular dentin. MATERIAL AND METHODS: The coronal part of 32 single-rooted human teeth was removed 1-mm coronally to the cemento-enamel junction. All specimens received endodontic treatment, and the root canals were prepared with an instrument to a depth of 10 mm to receive a titanium post. The dentin walls of each specimen were roughened with a hand-held diamond cutting instrument. The specimens were randomly divided according to the surface treatments into 4 groups (n=8): KW: etched with 20% to 30% polyacrylic acid (PAA) (Ketac Conditioner) and rinsed with water; KWI: etched with 20% to 30% PAA, rinsed with water and 70% isopropanol; DW: etched with 30% to 50% PAA (Durelon Liquid) and rinsed with water; DWI: etched with 30% to 50% PAA, rinsed with water and 70% isopropanol. The prefabricated titanium posts were airborne-particle abraded and cemented with glass ionomer cement. The specimens were fixed in custom-made brass cylindrical holders with autopolymerizing acrylic resin with the holder parallel to the long axis of the post. All specimens were stored in water for 3 days at 37 °C. Retention was evaluated using a tensile test with a universal testing machine (Zwick Z010) at a crosshead speed of 2 mm/min. Data were statistically analyzed with a 1-way ANOVA, followed by the Tukey post hoc test for pairwise comparisons between groups (α=.05). RESULTS: Mean ±standard deviation retention values ranged from 201.8 ±55.5 N (KW) to 328.1 ±70.9 N (DWI). Groups DWI and KWI (316 ±58.3 N) showed statistically higher retention values than group KW (P<.05) but did not significantly differ from retention values obtained in group DW (P>.05). CONCLUSIONS: An additional final rinse with isopropanol after using PAA increased the retention of the post significantly for all groups. Although group DWI achieved the highest retention values, pretreatment of radicular dentin as in group KWI may also be considered.

Prosthetic restoration after atraumatic surgical extrusion: a report of two cases.

Preservation and restoration of teeth with little coronal tooth structure due to crown-root fractures or caries lesions, ensuring restoration margins do not encroach on the biologic width, constitute a challenge. Available treatment options include surgical crown lengthening and orthodontic or surgical extrusion. This report presents two patients in which teeth were restored by surgical extrusion with an atraumatic extraction system and prosthetic therapy.

Effect of alumina particle morphology used for air abrasion on loss of enamel and luting composite resin.

OBJECTIVE: To evaluate the volume loss after air abrasion with alumina particles with different morphology on bovine enamel and luting composite resin. METHODS: Air abrasion was performed on 12 unscathed bovine teeth and 72 luting composite resin discs with 85 µm round-shaped and 50 µm sharp-edged alumina particles applied for 20 s, 40 s and 60 s (n = 12). Air abrasion was standardized by uniform areas of 2 mm diameter, a pressure of 0.25 MPa and a distance of 3 mm. The volume loss was determined by using a laboratory scanner. RESULTS: Air abrasion with round-shaped alumina particles was mostly not measurable with the laboratory scanner, while sharp-edged alumina air abrasion resulted in significant loss of enamel. The median of volume loss by sharp-edged alumina particles ranged from 0.78 mm3 (20 s) to 2.52 mm3 (60 s). In contrast to round-shaped alumina the removal caused by sharp-edged alumina increased significantly with increasing application times (p ≤ 0.05). For air abrasion on luting composite resin the median of the removed volume ranged from 2.25 mm3 (20 s) to 6.18 mm3 (60 s), while round-shaped alumina showed a range from 0.45 mm3 (20 s) to 1.40mm3 (60 s). The round-shaped alumina produced a statistically significant lower volume loss than sharp-edged alumina for all three air abrasion times. SIGNIFICANCE: The 85 µm round-shaped alumina particles removed less composite resin than 50 µm sharp-edged alumina particles but barely any enamel, making it an option for removing composite resin residues from enamel.

Intra- and inter-rater reliability of the modified ENT assessment score (ENTAS 2) in granulomatosis with polyangiitis: a prospective randomised trial.

OBJECTIVES: Ears nose and throat (ENT) involvement is found on a substantial proportion of patients with granulomatosis with polyangiitis (GPA). Structured, reliable ENT assessment is essential in the management of GPA patients. It is the aim of this study to determine the repeatability (intra-rater reliability) and reproducibility (inter-rater reliability) of the ENT Assessment Score (ENTAS 2). METHODS: The ENTAS 2 built the fundament of the prospective randomized trial. Anamnestic, video endoscopic and diagnostic data of 47 patients were used. A single assessor reference was created. GPA/ENT activity and damage were evaluated by three physicians at two time points (T1/T2). GPA/ENT activity was evaluated in dichotomy (yes/no) and grading (none/mild/moderate/high) and GPA/ ENT damage in dichotomy. RESULTS: ENTAS 2 activity evaluations intra-rater reliability was 80.7% (κ=0.56) in dichotomy and 72.8% (κ=0.41) in grading. ENTAS 2 damage evaluations showed 87.8% (κ=0.74) intra-rater reliability. ENTAS 2 activity inter-rater reliability at T1 was 62.2% (κ=0.43) in dichotomy and 51.1% (κ=0.29) in grading, at T2 it was 68.2% (κ=0.48) in dichotomy and 55.32% (κ=0.33) in grading. Inter-rater reliability of ENTAS 2 damage evaluation was 84.4% (κ=0.79) at T1 and 72.5% (κ=0.64) at T2. CONCLUSIONS: ENTAS 2 intra-rater reliability was high in dichotomous and graded GPA/ENT activity and damage evaluations. Inter-rater reliability was high in dichotomous activity and damage evaluations, but low in graded activity evaluations. The data demonstrate that the ENTAS 2 is a reliable score-system considering GPA/ENT activity and damage evaluations.