Degree of conversion of resin cement with varying methacrylate compositions used to cement fiber dowels: A Raman spectroscopy study.

STATEMENT OF PROBLEM: Studies on the degree of conversion of dental cement in relation to the number of methacrylate components are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the degree of conversion of single- and multicomponent methacrylate-containing dental cements around opaque and translucent fiber dowels at varying depths. MATERIAL AND METHODS: Teeth were prepared for standard endodontic therapy, and a dowel space was created. Opaque and translucent fiber dowels consisting of Aestheti-Plus (AP) and FiberKleer were cemented with 4 methacrylate (MA)-containing cements, including RelyX U100 (R), which contains TEGDMA; Duolink (D), which contains TEGDMA and BisGMA; and Variolink N LC (V) and Breeze (B), which contain TEGDMA, BisGMA, and UDMA. Light-emitting diode polymerization was performed for 60 seconds. The specimens were immediately cut into halves and measured within the first hour at depths of 1, 3, and 5 mm using Raman spectroscopy, and the degree of conversion (DC) of resin cement was calculated. Data were analyzed using 3-way ANOVA and the Tukey multiple comparison test (α=.05). RESULTS: The measured dowel regions were not significantly different at various depths (P=.10). The dowel and cement types significantly influenced the degree of conversion of the cement (P<.05). The V and B cements exhibited a higher DC than D and R cements. With AP dowels, the DC of cement D was lower than that of the V, B, and R cements. CONCLUSIONS: Within the limitations of this in vitro study, the degrees of conversion of the tested resin cements were not affected by the tested dowel depths. Higher DC was found in cement with more than 2 types of flexible MA. Opaque dowels produced a lower DC than translucent dowels.

Influence of tooth preparation burs on the roughness and bond strength of adhesives to human dentin surfaces.

PURPOSE: To characterize the surface roughness of human dentin prepared with different rotary instruments and its influence on the micro-tensile bond strength (microTBS) of self-etch adhesives. METHODS: Dentin surfaces were created from mid-coronal sound dentin in extracted, human third molars. The teeth were ground with high-speed diamond, tungsten carbide finishing, and cross-cut carbide rotary instruments. Morphological changes obtained were investigated with a surface texture analyzer. Two additional specimens from each group were treated and prepared for scanning electron microscopy. Resin composite (Z 100) was bonded to the surfaces using Optibond FL (control), Adper Prompt L-Pop (strong), Clearfil SE Bond (mild), or Clearfil S3 Bond (ultra-mild). Rectangular micro-specimens were prepared using the slow-speed diamond saw and tested in tensile to determine the microTBS. The data were analyzed with one-way analysis of variance and Tukey's HSD test (alpha= 0.05). RESULTS: Surface preparation resulted in significant differences for surface topography and micro-tensile bond strength (P< 0.001). The cross-cut carbide burs had significantly higher mean roughness readings (SD) for all parameters: Ra [8.6 (1.9) microm], Rq [10.9 (2.2) microm], and Ry [41.1 (2.1) microm], except for the mean Rz [12.1 (3.1) microm] value, which was recorded for diamonds. The other roughness parameters for the diamond rotary instruments were intermediate. Dentin surfaces completed with tungsten carbide finishing burs produced a smoother surface Ra [1.2 (0.5) microm)] Rq ([1.6 (0.6) microm], Ry [6.4 (2.6) microm)] and Rz [1.9 (0.6) microm)]. The etch-and-rinse adhesive (OptiBond FL) yielded high micro-tensile values (58.1-68.3 MPa), irrespective of the rotary instruments used. The micro-tensile bond strength values were comparable for self-etch adhesives (Adper Prompt L-Pop, Clearfil SE Bond, Clearfil S3 Bond) irrespective of the burs used. The microTBS values were significantly higher with tungsten carbide finishing burs and smooth dentin surfaces.

Relationship of margin design for fiber-reinforced composite crowns to compressive fracture resistance.

PURPOSE: Fiber-reinforced composite restorations provide excellent esthetics; however, little is known regarding the influence of margin design on marginal fit and fracture resistance for this type of crown. This study evaluated the effect of variations in tooth-preparation design on the marginal fit and compressive fracture resistance of fiber-reinforced composite crowns. MATERIALS AND METHODS: Three metal dies with a total convergence of 5° and different margin designs (0.5-mm light chamfer, 1.0-mm deep chamfer, and 1.0-mm shoulder) were prepared. Sixty standardized crowns (FibreKor) were made on duplicated base metal alloy dies (n = 20 for each margin design). Marginal fit was stereoscopically evaluated by measuring the distances between each of the four pairs of indentations on the crowns and on the dies. The specimens were then subjected to a compressive fracture-loading test using a universal testing machine. The data were analyzed with one-way analysis of variance (ANOVA) followed by Ryan-Einot-Gabriel-Welsch multiple-range test (α = 0.05). RESULTS: Analysis of marginal fit and fracture resistance disclosed a statistically significant difference for tooth-preparation design (p < 0.001). The marginal adaptation of preparations with the 0.5-mm light chamfer (66.2 µm) and 1.0-mm deep chamfer (69.7 µm) was significantly better than preparations with a shoulder finish line (92.8 µm) (p < 0.001). The fracture strength of the preparations with the 0.5-mm light chamfer (15.8 MPa) and 1.0-mm deep chamfer (15.1 MPa) was significantly greater than those of the preparations with the 1.0-mm shoulder (13.7 MPa) (p < 0.001). CONCLUSIONS: Marginal fit of fiber-reinforced crowns was adversely affected by tooth-preparation design. The marginal gaps were greater for the shoulder margin specimens than in the light or deep chamfer margin specimens; however, the fracture strength of the chamfer margin specimens was greater than that of the shoulder margin specimens.

Effect of dentin sealers on postoperative sensitivity of complete cast crowns cemented with glass ionomer cement.

PURPOSE: The purpose of this study was to clinically evaluate the effects of pretreatments with copal/ether varnish and dentin bonding system on postoperative sensitivity of complete cast crowns cemented with glass ionomer cement. MATERIALS AND METHODS: Three posterior teeth with no pain symptoms were selected from each of 17 patients, totaling 51 teeth, for which a crown was indicated. Rexillium III complete cast crowns were prepared using conventional laboratory techniques. For each patient, the first tooth, which served as the control, received only glass ionomer cement (Ketac-Cem). Copal/ether varnish (Bosworth Copaliner) was applied to the second tooth preparation prior to cementation. Dentin bonding agent (OptiBond Solo Plus) was used on the third tooth before cementation. Sensitivity to different stimuli (cold, heat) was assessed at 7 days, 1 month, and 6 months following restorative procedures by questionnaire. RESULTS: There were no statistically significant differences between the three groups regarding applied stimulus and day of the study (p > 0.05). No statistically significant differences were found between the postoperative sensitivity responses from 7 days to 1 month, and from 1 month to 6 months (p > 0.05). CONCLUSIONS: Postoperative sensitivity resulting from glass ionomer cement with complete cast crowns cannot be completely eliminated with the prior use of a cavity varnish or bonding agent.

Resin composite polyethylene fiber reinforcement: effect on fracture resistance of weakened marginal ridges.

PURPOSE: To investigate the in vitro effect of polyethylene woven fiber reinforcement of resin composite on the fracture resistance of weakened marginal ridges in molar teeth. METHODS: 50 sound extracted human mandibular molars were used. Specimens were divided into five groups (n = 10). Group 1: served as a control for comparison; Group 2: Class I cavity preparation with resin composite (Prodigy); Group 3: Class I cavity preparation with polyethylene ribbon fiber (Ribbond) and resin composite. Group 4: Class II cavity preparation with resin composite restoration; Group 5: Class II cavity preparation with polyethylene woven fiber and resin composite. Specimens were stored in 100% humidity at 37 degrees C for 7 days. Compressive loading of the teeth was performed with a universal testing machine at a cross-head speed of 0.5 mm/minute until failure. The data were analyzed with 1-way ANOVA followed by the Ryan-Einot-Gabriel-Welsch Multiple Range Test (alpha = 0.05). RESULTS: Reinforcement with polyethylene fiber resulted in significant differences for fracture resistance (P < 0.001). Mean fracture resistance (SD) was [1737.4 (84.8) N] for control group. Among the experimental groups, the highest mean fracture resistance (SD) [1543.8 (71.1) N] was associated with Class I cavity preparation with polyethylene fiber and resin composite. The lowest mean fracture resistance (SD) [869.2 (91.7) N] was recorded for Class II cavity preparation with conventional resin composite.

Quality assessment of dental health services provided at the Faculty of Dentistry, King Abdulaziz University.

OBJECTIVES: The objectives of this research were to assess the quality of dental services delivered in King Abdulaziz University and highlight the necessary recommendations that would improve it. METHODS: The methods used were live photographs illustrating the structure of dental services of the faculty presented in the clinic buildings, waiting places, equipments, instruments and supplies, as well as the comfort and privacy. Review of official records of the faculty for the number, qualifications and training of the dental staff and auxiliary personnel, as well as the process of care (starting from patient registration until completion of treatment). Records also demonstrated the access and utilization of services delivered in the various departments, the quality of these services and of infection control measures and procedures. RESULTS: The results revealed the high quality of services delivered through evaluating the structure and process of care in the university dental clinics. CONCLUSIONS: Dental services of King Abdulaziz University conform to high quality standards, with implementation of some changes for improvement and development.