Journal of Islamic Dental Association of IRAN
Volume:19 Issue: 3, 2007

One of the difficult aspects of designing complete denture prosthesis is the selection of appropriately sized maxillary anterior teeth. The aim of this investigation was to determine if there is any relationship between the intercanthal dimension and mesiodistal width of combined four maxillary anterior teeth. The maxillary anterior teeth were examined in 300 adult subjects. The distance between the median palpebral fissures was measured as the intercanthal distance. The mean width of the two central incisors, the combined widths of the central incisors, the combined width of the four incisors and the combined width of six anterior teeth were determined intra-orally at the widest dimension. T-test and Pearson correlation were used for statistical analysis. The men width of 4 maxillary incisor teeth was 30.8±1.91 mm and the mean width of 6 anterior maxillary teeth was 46.47±2.54 mm. Although the Pearson correlation was relatively small, a significant relationship was detected between the intercanthal and four maxillary teeth dimensions in all subjects (P=0.0001). It was found that biometric ratio of 0.266 and 1.447 could be used to estimate the central incisor width and the combined widths of the six anterior teeth, respectively The intercanthal distance can be used as preliminary criteria to determine the width of maxillary anterior teeth for edentulous patients.

It has been reported that some patients with multiple sclerosis may develop trigeminal neuralgia (TN) that may cause the loss of patient’s intact teeth when incorrectly diagnosed by dentists. This study was conducted with the aim of assessing the frequency of trigeminal neuralgia in MS patients who were referred to the Iranian MS Association during 2004-2005. This descriptive cross-sectional study was conducted on 179 MS patients whose diagnosis was confirmed by MRI protocol. Patients were selected randomly among those who participated in educational courses at the Iranian MS Association. The data was collected by questionnaire, interview and clinical examinations. The collected information was analyzed by student-t and fisher’s exact tests. The study showed that 7.8% of MS patients to have definitive signs of TN while detection of such involvement was not so clear in 2.8% of cases. About 76.5% of all patients were females and the rest (23.5%) were males. About 36.8% of TN patients showed some manifestations in the maxilla, 31.6% in the eye region, and 21.1% in the mandible. About 10.5% of the manifestations have occurred in the right side, 47.4% in the left and 42.1% in both sides. Seven patients (36.8%) demonstrated with trigger zones. Only about 10.6% of studied MS patients demonstrated trigeminal neuralgia. The ratio of TN development in patients with history of Baclofen usage was less than nonusers.

It has been shown that bonding agents reduce the sealant micro-leakage especially after salivary contamination. This study attempts to evaluate the effect of a bonding agent (Single-Bond) and salivary contamination on a sealant micro-leakage (Embrace). In this study a wet-bonding sealant (Embrace) was used in 64 sound human premolars after being etched with 35% phosphoric acid. The sealant micro-leakage was investigated under four different conditions: 1) Saliva + Bonding, 2) with bonding alone, 3) with saliva and 4) sealant alone. After thermocycling process, the teeth were covered with wax & nail polish except for 1-1.5 mm around the sealant. The samples were rinsed after immersed in 0.5% basic - fushin solution for 24 hours. Two buccolingual sections were prepared from central and proximal areas of the crowns. The micro-leakage was assessed according to the degree of dye penetration around the sealants. Dye penetration occurred in 5 cases of group 3 which was more than other groups. In the first group, 8 cases had a score more than 1, one less than the other groups. The Kruskal-Wallis test did not show any significant statistical differences between the groups. The use of a bonding agent, prior to application of a Wet-bonding fissure sealant, does not have a significant effect on the micro-leakage of Embrace Sealant in isolated or saliva contaminated conditions.

This study was designed to evaluate the stress distributions of different post materials in radicular dentine for providing a useful clinical guideline. In this experimental study, 5 three - dimensional models of maxillary central incisors were simulated by using ANSYS software and Finite Element Method. The models included: 1) Stainless Steel post 2) Titanium post 3) Carbon fiber post 4) Glass fiber post, and 5) Quartz fiber post. A composite core and PFM crown was constructed for all samples. Each model contained gingival, cortical and spongy bone, PDL and gutta-percha as well. All specimens were subjected to a compressive load at 45-degree angle to its long axis with a constant intensity of 100N. In all models there were two stress concentration sites: 1- a point between middle third and cervical third of the root and 2 - the cervical edge of the root. The amount of stresses between middle and the cervical third of fiber reinforced posts were nearly 1 MPa greater than those of the metallic ones. Compared to other materials, the metallic posts caused less stress in the radicular dentin and therefore are recommended for clinical use. Among fiber reinforced posts, Quartz fiber post showed the lowest stress peak.

In order to improve the retention and stability of the mandibular removable prosthesis with distal extension, it is usually required to make a secondary impression (the altered cast impression). This study was designed to clinically evaluate the conventional method of altered cast technique with modified altered cast technique. This prospective experimental study was conducted with 15 patients. They were treated with two methods of conventional and modified altered cast techniques. Following an oral examination, a questionnaire was used to collect clinical information on the occurrence of ulceration on the ridge, denture border areas, buccal shelf and retromolar pad areas, as well as the sufficiency of denture base extension. Patients were followed up 24 hours and one week after using the partial dentures. In conventional altered cast impression technique, it is required to dissect the casts and form the impression boxing in order to make sure that the master cast is properly registering the distal extension ridge anatomical features. Separation of the edentulous portion from the master cast is eliminated in the modified altered cast impression technique. This makes it more efficient, convenient for patient and less time consuming procedure. The X2 and fisher’s exact tests were used to detect significant levels. The percent of ulceration on the ridge, denture border areas, and buccal shelf as well as the retromolar pad areas were lower in modified altered cast impression technique compared with the conventional altered cast impression method. The percentage of the denture base extension in the modified altered cast impression technique was better than the conventional altered cast impression method. The extension of denture base in distolingual areas of modified altered cast impression technique was the same as the conventional altered cast technique. The difference between the two procedures was not statistically significant. The modified alerted cast technique can result in saving time, increasing the patient’s satisfaction and comfort, which makes it the recommendable procedure for making removable partial dentures with distal extensions.

Resin cements are usually used for bonding ceramic inlays. The aim of this study was to evaluate the micro-leakage in class V ceramic inlays cemented with two different resin cements. A total of 30 class V cavities were prepared in buccal surfaces of human extracted molars with occlusal margins in enamel and gingival margins in dentin (cementum). Ceramic inlays were prepared for all cavities and were cemented either with Variolink / Excite DSC or Panavia F/ED primer. These teeth were thermocycled and covered with sticky wax except for 1 mm around cavities and were immersed into 2% Methylen blue for 48 hours. The teeth were sectioned longitudinally and dye penetration was evaluated using stereomicroscope. Data was analyzed using nonparametric tests. There were no significant difference between the two types of cements in dentin or enamel margins (P>0.05). Compared with enamel margins, Panavia F showed less micro-leakage in dentin margins (P<0.05). The resin cements under evaluation in this study can not completely prevent micro-leakage. It seems that both cements have almost the same effects regarding micro-leakage reduction.

Several studies have shown a reduction in enamel bond strength when the bonding procedure is carried out immediately after vital bleaching with peroxides. The purpose of this study was to compare the effects of antioxidant agents (sodium ascorbate, sodium sulfite) and delayed bonding on shear bond strength of composite resin to enamel after bleaching with two different concentrations of carbamide peroxide. In this in-vitro study, 100 human premolars were collected and randomly divided into 10 groups. The investigation was conducted in two parts according to bleaching agent and elapsed time after bonding. In part I, bleaching was with 35% carbamide peroxide (Opalescense Quick) for 30 minutes was performed. In part II, bleaching was performed with 15% carbamide peroxide (Opalescense Regular) for 6 days and 6 hours for each case. The teeth in both parts were divided in 5 groups: 1: No Bleaching-Bonding (control) 2: Bleaching-Bonding 3: Bleaching-Sodium ascorbate-Bonding 4: Bleaching-Sodium sulfite-Bonding 5: Bleaching- Saliva immersed (for 3 weeks)-Bonding After bonding and thermocycling (1000 cycles between 5-55◦C) and 7 days of storage, shear bond strength was measured in all specimens. Groups differences were analyzed by using Kolmogrove Smirnov, one way NOVA and Sheffe tests. Statistical analysis indicated that treatment with antioxidant agents after bleaching with carbamide peroxide can cause such a compromised bonding comparable to the control group (p>0.05). Antioxidant treatment can severely decrease the bonding strength.

Rater’s reliability is an important issue in index calculation. The purpose of this study was to evaluate the intra-examiner agreement in identification of orthodontic treatment needs using modified IOTN. In this analytical cross-section study, six senior dental students identified IOTN on 42 dental casts by means of a standard DHC ruler with a two-week time lag. The kappa and association models were used to analyze the data. The kappa statistics showed intra-rater agreements between 0.54 and 0.77 (±0.65), which can be considered as “good”. About 33% of the students had problems in distinguishing the first and second levels of the index, while there were fewer problems in distinguishing between the second and third levels. The category identification with most problems was the distinction between the first and second levels (0.48), and the one with the least problem was that of the second and third levels (0.99). The distinction of the first and second levels in modified IOTN is hard for the examiners. Therefore, this issue should be considered in calibration training programs when using this index in screening, survey or epidemiological evaluations.

The fixture macro-design is one of the most important factors influencing the implant’s primary stability and micro-motion. The aim of this study was to evaluate the peri-implant stress distribution and micro-motion in 2 types of immediately loaded implants in order to determine the best design by using finite element analysis. In this experimental study the accurate pictures of the two fixtures (ILS and Xive) were taken by a digital camera. By using computer simulation technique, a three dimensional finite element model was inserted in a simulated mandibular bone. The displacement and Von Misses stress was recorded after loading. It was found that, the primary stability of ILS was greater (152 mm) than Xive (284mm). Likewise, ILS exhibited favorable behavior in stress distribution. Moreover, the maximum stress concentration in Xive peri-bone (≈30MPa) was lesser than Nisastan (≈37MPa). The ILS macro-design provides better primary stability and stress distribution, with less stress around the Xive.

There are controversies about the effect of eugenol containing cements on composite-dentin bond strength. This study was designed to evaluate the effect of eugenol containing temporary cements on shear bond strength of composite bonds to deep dentin when using Single Bond. In this in-vitro study, ninety extracted human third molars were sectioned horizontally at deep dentin and randomly divided in six groups after embedded into self cure acrylic material. Samples in five groups were covered with: Cavisol, Temband, and Zoliran with three different powder/liquid ratios of 10/2 gr., 10/3 gr., and 10/2 gr. respectively. The samples in group six were used as control and therefore they received no treatment. After elapse of one week, the temporary cements were removed mechanically from all samples in the first five groups. Only the samples in group five were cleaned by ethanol. All groups were pretreated with single bond and then composite cylinders were added. Debonding and shear bond strength was tested by using DARTEC universal testing machine. These data were analyzed using One-Way ANOVA and Duncan tests. The median shear bond strength were calculated for all six groups as follows: The values were 17.96 (0.73), 15.06 (0.78), 16.14 (0.75), 13.76 (0.66), 16.79 (0.34), 18.12 (36) Mega Paschal respectively. Significant group differences were found for all groups (P<0.001) except for first and sixth (P >0.05) as well as third and fifth groups. Temporary cements containing eugenol significantly reduced the shear bond strength of composite to deep dentin when using Single Bond.

There are insufficient data on the shear bond strength of Porcelain Veneers to enamel by using flowable composite as a luting Cement. This study was conducted in order to compare the shear bond strength of two different systems by using bovine enamel. Thirty freshly extracted anterior mandibular intact bovine teeth were randomly divided into two groups. Feldespatic Porcelain discs were attached to the enamel by Panavia F2 resin Cement and Filtek Flow flowable composite according to the manufacture’s instruction. The bonded specimens were immersed in 37oC water for 30 days and then thermocycled at 5oC and 55oC for 500 cycles. Samples were subjected to shear bond strength test. The modes of failure were determined under stereo microscope. Group differences were statistically analyzed by using the student-t test. The mean bonding strength in Panavia F2 group was 24.26(±8.2) mega paschal (Mpa), and 17.25 (± 8.1) Mpa, in Filtek Flow group. The statistical analysis showed significant difference between the two groups (P<0.005). Mode of failure in the first group was mainly cohesive and adhesive in the second one. This study revealed that the shear bond strength of dual cure Panavia F2 resin cement is considerably higher than that of light cure Filtek Flow flowable composite.

The smear layer is a thin layer of microcrystalline and organic debris which forms due to instrumentation of canal walls. Today, it is known that the smear layer contains bacteria as well as the nutrients necessary for bacteria. However, it is at the same time a barrier against penetration of irrigants and filling materials into dentinal tubules. Thus it is a factor that can cause micro-leakage and treatment failure. Smear layer removal will increase the adaptation between filling material and canal walls, and therefore it improves the overall sealing quality. Obtaining the cleanest canal possible before obturation is one of the goals of Endodontic treatment. The purpose of this in vitro study was to evaluate the smear layer removal ability of the 10% phosphoric acid and RCprep-5.25% NaOCL in the middle third of the root canals. Twenty freshly extracted human mature anterior teeth with single root canals were used in this study. Then the teeth were divided into three groups. Root canal instrumentation was conducted after decrownation of teeth at the CEJ level. Normal saline was used as irrigants during instrumentation in group 1. After final preparation, the canals were irrigated by 10 ml 10% phosphoric acid for 5-min. In group 2, the irrigants used during instrumentation by files coated with RCprep was 2 ml 5.25% NaOCL. At the end, both groups were irrigated with 5 ml normal saline. In 2 control specimens (teeth), normal saline was the only irrigants used during instrumentation. The roots were first split longitudinally, and then one section was randomly selected for further analysis under the electron microscope. The photomicrographs were evaluated by two different investigators (in group 1) and three different investigators (in group 2). Statistical analysis was performed to detect group differences and student-t test was used to determine the significance level. Canal walls were covered with smear layer in control group. The results showed that canals irrigated with 10% phosphoric acid had less smear layer throughout the canal walls compared with the group prepared with RCprep that contained 5.25% NaOCL. This difference was statistically significant in method used in group one (P<0.05) only. Based on the findings of this study, 10% phosphoric acid is superior to RCprep - 5.25% NaOCL in terms of removing smear layer from root canal walls.