The Saudi Journal for Dental Research最新文献

Statement of the problem

Poly methyl methacrylate (PMMA) acrylic resin, although being the most popular denture base material, is associated with poor mechanical properties. It has been documented that acrylic resin can be strengthened with an addition of structural component (filler) added in the acrylic matrix, to form a composite structure.

Objective

To evaluate and compare the transverse strength, impact strength, surface hardness and water sorption of 10% and 20% zirconia (ZrO₂) reinforced high impact acrylic resin with that of high impact acrylic resin (Trevalon HI, Dentsply India).

Materials and methods

There were 30 specimens in each of the four tests, amounting to a total of 120 specimens. Each of the tests had 10 specimens fabricated from high impact acrylic resin (control); 10 specimens fabricated from 10% zirconia (ZrO₂) and 10 specimens fabricated from 20% zirconia (ZrO₂) reinforced high impact acrylic resin. Specimens were subjected to the test of transverse strength in Universal Testing Machine, impact strength in Izod pendulum impact testing machine and surface hardness by Vickers Microhardness tester according to ISO Specification No. 1567. Water sorption was assessed according to ADA Specification No. 12. Data were analyzed by means of a one-way ANOVA and Bonferroni multiple comparison test.

Results

A significant increase in the transverse strength was observed in the reinforced specimens when compared to the control group. Impact strength and surface hardness were found having lesser values compared to the control group. Water sorption was found to increase on the addition of 10% and 20% zirconia (ZrO₂) but the value lied below 0.8 mg/cm² i.e. within the limit of ADA Specification No. 12.

Conclusion

Reinforcement of acrylic resin with zirconia powder affects its physical and mechanical properties significantly.

This in vitro study was undertaken to investigate the effects of an optional etching step with 35% phosphoric acid or double curing time on the shear bond strength (SBS) of one-step self-etch adhesives to dentin. A significant improvement in shear bond strength was demonstrated when dentin was acid-etched with 35% phosphoric acid prior to the application of one-step self-etch adhesives. The use of curing time double that was recommended by the manufacturers of the respective adhesives was capable of increasing the bond strength of the Single Bond Universal Adhesive but not that of the other two adhesives (Xeno® V⁺ and AdheSE®One F VivaPen), indicating that the bond strength is adhesive-dependent. Therefore, the use of phosphoric acid-etching on dentin is highly recommended, followed by one-step self-etch adhesives.

Kids under the age of 5 years generally spend most of their time with their parents. It has been found that young children’s oral health maintenance and outcomes are influenced by their parent’s knowledge and beliefs. This study was done to assess the parent’s knowledge about the oral health of their kids aged 1–5 years. The study bases it findings on the survey conducted at the Diagnosis Clinic of the King Khalid University, Abha through a 20-items questionnaire, which was distributed to 425 parents by the researchers. Responses of the parents were recorded on a Likert Scale and multiple choices questions written in Arabic language. The results show insufficient knowledge of Saudi parents about their kids oral health. It also shows that oral health care awareness programs are very important to secure a healthy oral condition among kids.

Aim: To evaluate pH, titratable acidity and in vitro enamel solubility potential of different commercially available soft drinks and fruit juices in Saudi Arabia.

Methods: Thirty two popular soft drinks and juices were tested for their enamel solubility potential. In addition, bottled drinking water was used as the control. Each drink was evaluated for its pH, titratable acidity which was measured by adding 0.1 N NaOH (sodium hydroxide) to a chosen end point. In addition, one enamel slice was immersed in each test beverage and percentage weight loss in the enamel slice was calculated after intervals of 6 and 24 h.

Results: The pH of all the test drinks ranged from 1.64 to 3.89. Mean pH of 2.84 in soft drinks was significantly lower than in the fruit juices. There was a significant difference between them for percentage weight loss after 6 and 24 h immersion with carbonated beverages causing greater enamel loss than the fruit juices. Colas and non-colas did not differ statistically for pH, titratable acidity and percentage weight loss of enamel slices.

Conclusions: The pH of all the test drinks was below the critical pH of 5.5 for enamel dissolution. Carbonated drinks were observed to have more enamel solubility potential than fruit juices while regular or diet variants and colas or non-colas had comparable solubility potential.

Objectives: The aim of this pilot study was to assess the effect of orthodontic treatment and gender on plaque index.

Materials and methods: In this prospective cohort study, the O’Leary plaque index of 25 orthodontic patients was clinically examined before the beginning of treatment (as control) and after the leveling stage (as treatment group). The role of treatment and gender was assessed using two-way repeated-measure ANOVA, paired and independent-sample t-tests, and Pearson correlation coefficient (α = 0.05, β ⩽ 0.1).

Results: ANOVA showed a significant increase in plaque index after treatment (P = 0.000), but without any difference between the genders (P = 0.997) or any interaction between the variables gender and treatment (P = 0.796). There were significant post-treatment increases in plaque index in males (paired t-test’s P = 0.018) and females (P = 0.000). The plaque indices were not different between males and females, either before leveling (independent-sample t-test’s P = 0.785) or after it (P = 0.880). There were no correlations between patients’ gender and either of pre- or post-treatment PI levels (both r statistics < 0.06, both P values > 0.83). However, the correlation between pre- and post-treatment plaque indices was significant (r = 0.623, P = 0.001).

Conclusion: Initial stage of active fixed orthodontic treatment can cause considerable dental plaque accumulation, similarly in men and women.

Objectives

The study assessed the changes in surface roughness and microhardness of three esthetic restorative materials after bleaching with 10%, 20% and 35% carbamide peroxide (CP).

Methods

Standardized cylindrical specimens (n = 210) of 3 esthetic materials (nano composite resin (NC), resin modified glass ionomer (GI), feldspathic porcelain (FP) were fabricated (n = 70). They were divided into 3 groups (n = 20) and a control group (n = 10). Each group was bleached with different concentrations of CP. The specimens of group 1 and 2 (10% CP and 20% CP) were immersed in the bleaching gels for 6 h daily, while group 3 (35% CP) was immersed for 30 min weekly. The control group was stored in artificial saliva. After 21 days, the morphological changes of the specimens were investigated with surface texture analyzer, while the hardness was assessed by performing superficial microhardness analysis. The data were analyzed with one-way ANOVA, and Scheffe test at α = 0.05.

Results

No significant differences in roughness average (Ra) were recorded among the control group and 10% CP bleached groups of all tested restorative materials (NC (p = 0.1495), GI (p = 0.0761), FP (p = 0.2848)). However, there were significant differences in Ra among the control group, 20% CP, and 35% CP (p < 0.05). There were no significant differences in the microhardness of feldspathic porcelain (10% (p = 0.0786), 20% (p = 0.1041), and 35% (p = 0.2066). While nano composite resin and resin modified glass ionomer specimens were significantly affected by concentration of 20% and 35% CP (p < 0.05).

Conclusion

The effect of bleaching depends on the concentration of CP. The higher surface roughness was produced by 35% CP. Bleaching with different concentrations did not reduce the microhardness of the feldspathic porcelain. However, microhardness of nano composite resin and resin modified glass ionomer specimens was affected by 20% CP and 35% CP.

Abstract

Objective: The objective of this study was to assess the stress level among Yemeni dentists and to evaluate their stress manifestations and stress management.

Materials and methods: Nearly 368 dentists were given a self-administered questionnaire and 119 returned the filled questionnaire form. A questionnaire was composed of four sections including, demographic information, professional practice characteristics, work stress factors and response of dentist to stress as well as methods to deal with stress. 56 females and 63 males were incorporated, 83.2% of them were general dental practitioners. The descriptive data were analyzed and Chi-square, t-test and F tests were used for statistical significance (P < 0.05).

Results: The response rate was 32.3%. Of the whole, 71.4% of them were aged less than 30 years, 73.1% have experience less than 5 years. Among stressors, those related to dental procedure have highest mean scores (SD) of stress 2.93 (1.46). The most prevalent factors that contribute to stress were uncooperative patients (72.3%), amount of work (too much, too little) (60.5%) and constant drive for technical perfection (54.6%). Stress was reflected in dentists by many signs among them are musculoskeletal fatigue in 63% and nervousness in 57.1%. Praying and reading the Quran was reported by over two thirds (70.6%) of the participants to manage stress.

Conclusions: Dentistry is a stressful profession in Yemen. Lack of experience, low income, uncooperative patients, and dental procedure-related factors were the main significant factors that caused stress. Political instability in the country and the lack of laws governing the dental profession in addition to conservative nature of the community may be considered as sources of stress.

The aim of this study is to report a case of large aggressive central giant cell granuloma (CGCG) of the mandible treated with corticosteroids and surgery. A 22-year-old male presented with painless progressive swelling in the chin region. Biopsy confirmed the diagnosis of CGCG. Management of the lesion was carried out in 3 phases. Phase-1 comprised of intra-lesional corticosteroids, phase-2 comprised of surgical management and phase-3 consisted of post-surgical intra-lesional corticosteroid. In this extensive case, although intra-lesional corticosteroid was given pre-operatively, there was no evidence of a reduction in size of the lesion both clinically and radio-graphically. This case suggests that injection of a low dose of corticosteroids pre-operatively may not be effective in such large aggressive CGCGs. Nevertheless, combined medical and surgical management is always advantageous for extensive aggressive lesions in order to reduce the size and thus minimize the need for mutilating bone resections and loss of teeth that ultimately result in functional and esthetic defects.

Objectives: The aim of the present study was to assess the self-reported oral health attitudes and behaviors of dental students from four Asian countries based on their gender and level of dental education.

Subjects and methods: A structured, pre-tested, self-administered 12-item questionnaire survey was conducted among undergraduate dental students at all study levels. The sample was drawn from the Kerala University of Health Sciences; India, King Saud University, Al-Kharj University and University of Dammam; Saudi Arabia, Ajman University of Science and Technology and University of Sharjah; United Arab Emirates and University of Aden; Yemen. The questionnaire included demographic details and questions on the students’ oral health attitudes and behaviors.

Results: A total of 1553 dental students (955 females, 598 males) consisting of 655 pre-clinical and 898 clinical students participated in the study. Majority of respondents (74%) reported cleaning their tongue daily and 61.8% reported that regular dental check-up should be carried out every 6 months. However, 61.9% reported that they do not use a dental floss and 72.6% reported visiting their dentist only when having dental problems.

Conclusions: Within the limitations of this study, noticeable differences in the oral health attitudes and behaviors of the surveyed female- and clinical-dental students compared to male- and pre-clinical-dental students respectively could not be elicited. Teaching student dentists the necessary skills in attaining good oral hygiene is as imperative as imparting knowledge on various aspects of oral health.

Objective: Resin based composite (RBC) restoration, existing at tooth bonding sites can compromise the bond between the framework and the tooth. Therefore, the aim of the study was to evaluate the effect of in vitro ageing of RBC on its micro-tensile bond strength with resin luting cement (RLC).

Materials and methods: Forty standardised RBC blocks (4 × 6 × 8 mm) were fabricated. Twenty blocks were divided into four groups (N = 5 per group). Group 1 (control) received no ageing; in group 2, specimens were exposed to 500 cycles of thermocycling (TC) at 5–55 °C; in group 3, specimens were exposed to 5000 cycles of TC and in group 4 specimens were placed in Sodium hydroxide (0.1 N, NaOH) for one week. Following treatment, RBC blocks were paired with identical untreated RBC blocks and bonded, using RLC (Panavia F 2.0) under constant load. RLC was cured for 160 s at the intensity of 650 mWcm⁻². Bonded blocks were sectioned using a diamond saw at 500 rpm and 250 ground force. A total of 160 specimen sticks were subjected to micro-tensile bond strength testing (Bisco Inc., Virginia, USA) at a crosshead speed of 0.5 mm/min. Fractographic analysis was performed using a stereomicroscope (63×). Means of micro-tensile bond strength (μ-tbs) were analysed with ANOVA and Tukey-Kramer multiple comparisons test (P = 0.05).

Results: μ-tbs was significantly higher for group 1 (54.20 ± 7.34 MPa) as compared to group 2 (44.17 ± 8.61 MPa) and group 3 (20.32 ± 7.91 MPa). Specimens in group 4 debonded prior to μ-tbs testing. 77.5% specimens in group1 and 100% specimens in groups 2 and 3 showed adhesive failures at the RBC and RLC bonding interface.

Conclusion: RLC showed significantly lower micro tensile bond strengths when bonded to aged RBC as compared to when RLC was bonded to non-aged RBC.