Mohamed I. Abu-Hassan

Evaluation of load at fracture of Procera AllCeram copings using different luting cements.

Purpose: The current study investigated the effect of different luting agents on the fracture resistance of Procera AllCeram copings. Methods: Six master dies were duplicated from the prepared maxillary first premolar tooth using nonprecious metal alloy (Wiron 99). Thirty copings (Procera AllCeram) of 0.6-mm thickness were manufactured. Three types of luting media were used: zinc phosphate cement (Elite), glass ionomer cement (Fuji I), and dual-cured composite resin cement (Panavia F). Ten copings were cemented with each type. Two master dies were used for each group, and each of them was used to lute five copings. All groups were cemented according to manufacturers instructions and received a static load of 5 kg during cementation. After 24 hours of distilled water storage at 37°C, the copings were vertically compressed using a universal testing machine at a crosshead speed of 1 mm/min. Results: ANOVA revealed significant differences in the load at fracture among the three groups (p < 0.001). The fracture strength results showed that the mean fracture strength of zinc phosphate cement (Elite), glass ionomer cement (Fuji I), and resin luting cement (Panavia F) were 1091.9 N, 784.8 N, and 1953.5 N, respectively. Conclusion: Different luting agents have an influence on the fracture resistance of Procera AllCeram copings.PURPOSE The current study investigated the effect of different luting agents on the fracture resistance of Procera AllCeram copings. METHODS Six master dies were duplicated from the prepared maxillary first premolar tooth using nonprecious metal alloy (Wiron 99). Thirty copings (Procera AllCeram) of 0.6-mm thickness were manufactured. Three types of luting media were used: zinc phosphate cement (Elite), glass ionomer cement (Fuji I), and dual-cured composite resin cement (Panavia F). Ten copings were cemented with each type. Two master dies were used for each group, and each of them was used to lute five copings. All groups were cemented according to manufacturers instructions and received a static load of 5 kg during cementation. After 24 hours of distilled water storage at 37 degrees C, the copings were vertically compressed using a universal testing machine at a crosshead speed of 1 mm/min. RESULTS ANOVA revealed significant differences in the load at fracture among the three groups (p < 0.001). The fracture strength results showed that the mean fracture strength of zinc phosphate cement (Elite), glass ionomer cement (Fuji I), and resin luting cement (Panavia F) were 1091.9 N, 784.8 N, and 1953.5 N, respectively. CONCLUSION Different luting agents have an influence on the fracture resistance of Procera AllCeram copings.

Three dimensional quantification of mandibular bone remodeling using standard tessellation language registration based superimposition

OBJECTIVE The aim of this study was to evaluate a new method to quantify longitudinal mandibular bone remodeling three-dimensionally by superimposition of cone beam computed tomography images. MATERIALS AND METHODS This method is used to quantify the treatment effects of implant-retained overdentures in 20 patients aged 52-79 at recruitment after 1 and 2 years post treatment. Three dimensional models of pre- and post-treatment were reconstructed for each patient and superimposed using Standard Tessellation Language registration method and segmentation. RESULTS Color maps of the differences generated by superimposition allow detailed examination and quantification of the progressive dimensional changes of bone in a three-dimensional manner and enable the visualization of the apical displacement and thinning of the cortical layer of bone underneath the denture base. Most of the remodeling changes took place during the first year with a mean decrease in volume of 3.7% (SD = 4.4%; range = +3.7% to -15.9%, median = -3.7%). This remodeling pattern continued during the second year, but at a reduced rate of 2.5% per year (SD = 4.2%; range = +2.1% to -11.3%, median = -3.9%). CONCLUSION Standard Tessellation Language registration based superimposition of cone beam computed tomography images may be considered an objective and reproducible method to three-dimensionally quantify mandibular bone remodeling.

Investigation of mucosa-induced residual ridge resorption under implant-retained overdentures and complete dentures in the mandible.

PURPOSE This study aimed to investigate and compare the residual ridge resorption (RRR) induced by an implant-retained overdenture (IRO) and associative biomechanics and by a conventional complete denture (CD) without implants. MATERIALS AND METHODS Cone beam computed tomography was used to quantify RRR in a three-dimensional (3D) manner before and after 1 year of treatment with either IROs or CDs. Twenty patients were treated with IROs, and nine patients were treated with CDs in the mandible. Their maximum bite forces were recorded. The same sets of high-resolution scan images were used to create patient-specific 3D finite element analysis models. The hydrostatic stresses, contact surface deformation, and strain energy absorption in soft tissue mucosa were correlated with the changes in RRR for patients with and without implants. RESULTS With the IROs, contact surface deformation on the mucosa was two times greater than with CDs (0.32 ± 0.23 mm vs 0.16 ± 0.06 mm) and was in agreement with the amount of RRR measured, which was also two times higher for the IRO than the CD (-3.8% ± 4.5% vs -1.9% ± 0.4%). Taking into account the differences in bite forces with and without implants, which again were twice as high with IROs, the hydrostatic stress within the mucosa was found to correlate well to the RRR map measured over the 1-year interval of treatment. CONCLUSION IROs resulted in at least twice the RRR as CDs. This could be caused by the higher hydrostatic stress and less effective energy absorption capabilities of the mucosa underneath the IRO. While implants associated with the IRO provide stronger bite force, they could potentially concentrate hydrostatic stress and cause greater RRR compared to a conventional CD.

Biaxial flexural strength of Turkom-Cera core compared to two other all-ceramic systems

Advances in all-ceramic systems have established predictable means of providing metal-free aesthetic and biocompatible materials. These materials must have sufficient strength to be a practical treatment alternative for the fabrication of crowns and fixed partial dentures. Objectives The aim of this study was to compare the biaxial flexural strength of three core ceramic materials. Material and methods Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm thickness - in accordance with ISO-6872, 1995) were made from the following ceramic materials: Turkom-Cera Fused Alumina [(Turkom-Ceramic (M) Sdn Bhd, Puchong, Selangor, Malaysia)], In-Ceram (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany) and Vitadur-N (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany), which were sintered according to the manufacturers recommendations. The specimens were subjected to biaxial flexural strength test in a universal testing machine at a crosshead speed of 0.5 mm/min. The definitive fracture load was recorded for each specimen and the biaxial flexural strength was calculated from an equation in accordance with ISO-6872. Results The mean biaxial flexural strength values were: Turkom-Cera: 506.8±87.01 MPa, In-Ceram: 347.4±28.83 MPa and Vitadur-N: 128.7±12.72 MPa. The results were analyzed by the Levenes test and Dunnetts T3 post-hoc test (SPSS software V11.5.0 for Windows, SPSS, Chicago, IL, USA ) at a preset significance level of 5% because of unequal group variances (P<0.001). There was statistically significant difference between the three core ceramics (P<0.05). Turkom-Cera showed the highest biaxial flexural strength, followed by In-Ceram and Vitadur-N. Conclusions Turkom-Cera core had significantly higher flexural strength than In-Ceram and Vitadur-N ceramic core materials.

General dental practitioners' views on early childhood caries and timing of the first dental visit in Selangor, Malaysia

This survey evaluated the knowledge, attitudes, and practices of general dental practitioners (GDPs) in Selangor regarding early childhood caries (ECC) prevention and the recommended timing of a child’s first dental visit. A questionnaire was mailed to 521 licensed GDPs. Descriptive statistics were used, and bivariate and logistic regression analyses were performed. The response rate was 52.6%. Although 89.8% mentioned counseling parents and caregivers, only 44.2% were familiar with anticipatory guidance. Whereas 98.2% agreed that early examinations are important to prevent ECC, only 51.8% were aware of the recommendation for a first visit by 12 months of age. GDPs who recommended early dental visits were significantly more likely to be recent graduates, more familiar with professional guidelines, and less likely to be deterred by a child’s crying or behavior. In conclusion, GDPs in Selangor are aware about the importance of early dental visits in ECC prevention. However, a considerable number of them are still not aware of the recommendation that children must first visit the dentist by 12 months of age. Furthermore, some of their current practices in ECC management and prevention do not match professional recommendations.

The impact of recycling and repeated recycling on shear bond strength of stainless steel orthodontic brackets

Abstract Purpose To compare Shear Bond Strength (SBS) of new, recycled and repeated recycled stainless steel orthodontic brackets with and without bracket base primer. Materials and methods 120 extracted human premolar teeth and 120 premolar stainless steel orthodontic brackets were divided into six groups for 20 teeth each. Orthodontic brackets of four groups were sandblasted with 50 μm aluminum oxide powder and half of them were recycled for second time. Light cure orthodontic adhesive primer was applied for half of total brackets. Light cure composite was applied for all brackets and polymerization was carried out. Groups 1–6 were subjected to a shear force within half hour to simulate as done clinically with a universal testing machine (Shimadzu Trapezium X) until the bracket debond. Results The results of this study demonstrated that the mean SBS of all groups were more than that recommended by Reynolds in 1975, there was no significant difference between new and recycled brackets. Only one group (repeated recycled without bond) has significantly lower SBS. Conclusion It can be concluded that: sandblasted recycled orthodontic brackets can be used as an alternative to new brackets which might provide cost reduction and in case of using repeated recycled brackets, better to apply bonding agent on bracket base for more bond strength.

Parent's Perception on the Importance of Their Children's First Dental Visit ( a Cross - Sectional Pilot Study in Malaysia )

Introduction: Understanding parental perceptions about early childhood oral health is important in order to develop effective preventive measures since parents’ health behaviours and practices usually have a direct influence on their children’s dental health. The aim of this pilot study was to evaluate parental views about the primary teeth, first dental visit, and use of behaviour modification at the time of a first clinical visit. Materials and Methods: This was a cross-sectional study conducted among parents who brought their children to the Paediatric Dental Clinic at Universiti Teknologi MARA, Malaysia. Parents completed a close-ended interviewer-administrated questionnaire (n=110). The questionnaire had eleven items addressing knowledge and attitudes towards the importance of primary teeth, effects of early extractions, and the main reason to visit the dentist for the first time. It also assessed views on appropriate treatment for decayed primary teeth, methods used to prepare children for their dental visit, and the timing of first dental visit. Data were analyzed using descriptive, frequency and Chi-Square analysis. Results: Overall, 82.3% of parents recognized the importance of primary teeth. However, only (12.5%) were aware that the first dental examination should be by age 12 months. Regarding treating primary teeth with decay, 47.9% thought that these teeth should be restored, whereas 37.5% believed extractions were appropriate. Two-third of parents (67.7%) had agreed to promote behaviour modification during the first visit if their children had no pain. Conclusion: Many parents realised the importance of primary teeth, however, lacked the sufficient knowledge on how to appropriately deal with these teeth with caries and the recommended time for first dental visit. Hence the parents must receive appropriate anticipatory guidance and also need to appreciate the benefits of early dental visit to the oral health and well-being of children.

Effects of recycling and bonding agent application on bond strength of stainless steel orthodontic brackets.

Objectives: 1) to assess different methods of recycling orthodontic brackets, 2) to evaluate Shear Bond Strength (SBS) of (a) new, (b) recycled and (c) repeated recycled stainless steel brackets (i) with and (ii) without bracket base primer. Study Design: A total of 180 extracted human premolar teeth and 180 premolar stainless steel brackets were used. One hundred teeth and 100 brackets were divided into five groups of 20-teeth each. Four methods of recycling orthodontic brackets were used in each of the first four groups while the last one (group V) was used as the control. Groups (I-V) were subjected to shear force within half an hour until the brackets debond. SBS was measured and the method showing the highest SBS was selected. A New group (VI) was recycled twice with the selected method. Six subgroups (1-6) were established; the primer was applied for three sub-groups, and the composite was applied for all brackets. Brackets were subjected to the same shear force, and SBS was measured for all sub-groups. Results: There was a significant difference between the mean SBS of the sandblasting method and the means of SBS of each of the other three methods. There was however, no significant difference between the mean SBS of the new bracket and the mean SBS of recycled bracket using sandblasting. The mean SBS of all sub-groups were more than that recommended by Reynolds (17) in 1975. Brackets with primer showed slightly higher SBS compared to those of brackets without bonding agent. Conclusion: To decrease cost, sandblasted recycled orthodontic brackets can be used as an alternative to new brackets. It is recommended to apply a bonding agent on the bracket base to provide greater bond strength. Key words:Recycled bracket, shear bond strength, sandblasting, stainless steel orthodontic bracket.

The relationship of mandibular morphology with residual ridge resorption associated with implant-retained overdentures

PURPOSE The objective of this clinical study was to determine the relationship of mandibular morphology with residual ridge resorption (RRR) of implant-retained overdenture (IRO) patients. MATERIALS AND METHODS RRR was quantified as change in bone volume over 1- and 2-year periods using cone beam computed tomography and a medical imaging program. Features of the mandibular morphology, namely the gonial angle, ramus length, ramus width, corpus length, and corpus height, were measured on three-dimensional models and correlated to the RRR. A total of 25 participants were treated with mandibular IROs opposing maxillary complete dentures. By the 2-year follow-up, radiographic data for 18 patients were complete for analysis. Of these 18 participants, half fall into the low gonial angle category and the other half into the high angle. RESULTS The extent of RRR was highly variable among participants and ranged from -2 to +2 mm in depth over the 2-year period. The mean decrease in bone volume after the first year was 3.8 ± 4.5%. This rate decreased to 3.2 ± 4.1% after the second year. RRR occurs either by translation of the entire thickness of cortical layer apically or by thinning of the outer cortical layer. RRR was significantly correlated to gonial angle (r = .471; P = .048) and predominantly occurred in the molar region in low-angle participants and more anteriorly in high-angle participants. There was no association between RRR and ramus length (r = -.341; P = .166), ramus width (r = -.183; P =.468), corpus length (r = .057; P = .821), and corpus height (r = .097; P = .702). CONCLUSION Within the limitations of this study, it may be concluded that gonial angle is significantly related to RRR associated with IROs.

Strength of a New All-Ceramic Restorative Material “Turkom-Cera” Compared to Two Other Alumina-Based All-Ceramic Systems

Early types of metal-free ceramics did not enjoy success in dentistry, especially in the posterior region (Shimada et al., 2002). The high crystalline content ceramic systems have been developed in an attempt to improve the strength of metal-free restorations as well as deliver more esthetic results than conventional metal-fused-to-ceramic restorations (Ozcan et al., 2001; Valandro et al., 2006). Glass infiltrated alumina ceramic (eg. In-Ceram Alumina, Vita Zahnfabrik, Bad Sackingen, Germany), densely sintered aluminum oxide ceramic (eg, Procera AllCeram, Nobel Biocare AB, Gothenburg, Sweden) and zirconium oxide ceramic (eg, Lava 3M ESPE, St. Paul, MN, USA) are popular oxide-based high-strength ceramic materials that offer favorable esthetic characteristics, mechanical properties and biocompatibility (Blatz et al., 2004; Della Bona et al., 2007). It is obvious from the different studies in relation to the occlusal fracture resistance of allceramic systems that the values reported are highly variable. This is because the testing of the occlusal fracture resistance of crowns is not a standard procedure like a bending test for a geometrically well-defined bar. As reported by some researchers (Webber et al., 2003; ALMakramani et al., 2008a; Di Iorio et al., 2008), the results of the fracture load of all-ceramic crowns may be influenced by different factors. These include the microstructure of the ceramic material, preparation design, shape and thickness of the restoration, size and distribution of surface flaws, the magnitude, direction and location of the applied load, luting methods, the elastic modulus of the restoration components and storage conditions before loading to fracture. Regarding the effect of finish line on the occlusal fracture resistance of all-ceramic crowns, it was shown that preparation with a 1.2 mm shoulder finish line and sharp axiogingival line