[Effect of thickness of zirconia core on marginal adaptation of all-ceramic restorations]

Marginal adaptation is important for long-term success of full-coverage restorations. Thickness of core is one of the important factors influencing the marginal integrity. Thus, the aim of this study was to evaluate the effect of different thicknesses of zirconia core on marginal adaptation of all-ceramic restorations. In this single blind in vitro study, a standard brass die 7 mm in length and 5 mm in diameter was prepared with a classic chamfer finish line with 0.8 mm depth and 10 degrees of wall taper. Copings were made using the CAD / CAM system. We had three groups of 10 samples each. Group 1 with a zirconia thickness of 3.0 mm, group 2 with a thickness of 0.5 mm and group 3 with a thickness of 0.7 mm. Copings were then placed on the die and randomly numbered. The vertical gap in the margin was measured at 10 points using scanning electron microscopy [SEM]. Data were collected. The mean and standard deviation values were calculated and ANOVA was used for the comparison of the three groups. Tukey's test was also applied. The gap in 0.3, 0.5 and 0.7 mm thicknesses of zirconia before porcelain firing was 89.21 +/- 28.90, 79.55 +/- 39.32 and 40.813 +/- 10.3 micro, respectively. The difference in marginal gap between the three groups was statistically significant [P=0.001]. Tukey's test failed to find a significant difference in marginal gap between 0.3 and 0.5 mm thicknesses [P=0.006]. But, the difference between 0.3 and 0.7 mm [P=0.001] and also 0.5 and 0.7 mm [P=0.001] was statistically significant. Based on the results, by increasing the thickness of the zirconia core marginal gap decreases in all ceramic restorations

Comparison of dimensional accuracy between open-tray and closed-tray implant impression technique in 15° angled implants

Statement of Problem: Various impression techniques have different effects on the accuracy of final cast dimensions. Meanwhile; there are some controversies about the best technique

Purpose: This study was performed to compare two kinds of implant impression methods [open tray and closed tray] on 15 degree angled implants

Materials and Method: In this experimental study, a steel model with 8 cm in diameter and 3 cm in height were produced with 3 holes devised inside to stabilize 3 implants

The central implant was straight and the other two implants were 15° angled. The two angled implants had 5 cm distance from each other and 3.5 cm from the central implant

Dental stone, high strength [type IV] was used for the main casts. Impression trays were filled with poly ether, and then the two impression techniques [open tray and closed tray] were compared. To evaluate positions of the implants, each cast was analyzed by CMM device in 3 dimensions [x,y,z]. Differences in the measurements obtained from final casts and laboratory model were analyzed using t-Test

Results: The obtained results indicated that closed tray impression technique was significantly different in dimensional accuracy when compared with open tray method. Dimensional changes were 129 +/= 37? and 143.5 +/= 43.67? in closed tray and open tray, while coefficient of variation in closed- tray and open tray were reported to be 27.2% and 30.4%, respectively

Conclusion: Closed impression technique had less dimensional changes in comparison with open tray method, so this study suggests that closed tray impression technique is more accurate

Evaluation of the effect of different glass fiber post lengths on fracture resistance of endodontically treated central incisors

Use of glass fiber posts is of widespread acceptance in restoring root canal treated teeth, but studies concerning the most proper length of the post to provide the utmost fracture resistance are inadequate. The aim of this study was to evaluate the effect of glass fiber post length on fracture resistance of root canal treated central incisors. This experimental study was carried out on 40 maxillary central incisors in 4 groups of 10 each. RDT posts and cement was used in this experimental study with the lengths of 6, 8, 10, and 12 mm in the study groups. The samples were debrided and decoronated at the CEJ levels and endodontically treated using step-back technique. RDT drills were used for post space preparation. Then, the root canal walls were etched and the posts cemented in place. The composite cores were then prepared at the height of 5 mm and samples mounted 2mm down to their CEJ levels within acrylic blocks. An impression material [Impregum, 3M, ESPE] with a thickness of 0.2mm was used to simulate PDL around the samples. The samples were subjected to compressive forces at a 135-degree angle to their long axes using a Universal Testing Machine. Data pertaining to the fracture of the samples were analyzed using ANOVA and Tukey statistical tests. The maximum resistance to fracture was recorded in 8-and 10-mm-long posts and the minimum was observed in the lengths of 6 and 12 mm. Statistical tests showed a significant difference between 8- and 10-mm-long posts with those having lengths of 6 and 12 mm in terms of fracture resistance. There was no significant difference between 8- and 10-mm-long posts as well as 6- and 12-mm-long ones. It can be concluded that the length of post is influential in the fracture resistance of the root so that the maximal resistance can be obtained in 8 to 10 mm of length and such lengths can be recommended for non-metal posts

Comparison of stress distribution in two type of metal and non metal posts by photo elastic method

Intrapulpal posts are used as retention for reconstructing of missed crown. Today fiber posts eliminated most of disadvantages of metal posts. The purpose of this study is a comparison of stress distribution in these types of posts [casting and Quartz fiber post] on root canals of teeth with photo elastic method. In this experimental study Quartz fiber and casting posts with length of 15mm and diameter of 0.9mm were used. Four epoxy resin models [10x20x40mm] were made that two of them include casting posts and two other include Quartz fiber posts. Then, cores were prepared for each model. Vertical force of 100N and oblique force with 30' and 150 N were applied on cores and isochromatic fringe patterns around post were recorded in the field of Polariscope. In the vertical loads the minimum cervical stress was observed in casting post that was 1.22 [in Quartz fiber post it was 2.65] But in apical region maximum stress was recorded in casting post that was 1.63 [in Quartz fiber post it was 1.38]. In the oblique load, casting post showd 1.39 stress in cervical that was the minimum [in Quartz fiber post it was 2.35] and in the apical region, casting post showed the maximum stress that was 1.68 [in Quarts fiber post it was 1] display more critical stress pattern [1.63]. In the vertical and oblique loads casting posts shows the maximum stress in the apical region that makes the worse fracture in tooth that couldn't be prepared but in Quartz fiber post maximum stress was in cervical region so it is more repairable

All- ceramic crown preparation and the remained wall thickness of the pulp chamber

Statement of Problem: A minimally invasive method of preparation is essential to prevent tooth structure weakening and pulp irritation; especially for mandibular anterior single-tooth all-ceramic crowns. According to many investigations, one of the most important reasons of pulp injury caused by tooth preparation for different restorative procedures is reduced "remained wall thickness" [RWT]. In order to protect the pulp from irritation, it is necessary to maintain a 0.5 mm of RWT

Purpose: The purpose of the present study was to evaluate the effect of all-ceramic crown preparation on pulp chamber RWT of mandibular incisors

Materials and Method: Mesiodistal and buccolingual initial images of 24 extracted mandibular incisors were provided. The pulp chamber initial wall thicknesses of buccal, lingual and proximal surfaces of cervical, 1and 2 mm above the cervical areas and also the incisal surfaces of incisal sections were measured using digital radiography and Photoshop software. After all-ceramic crown preparation, images were provided at the same initial positions. The initial and remained pulp chamber wall thicknesses were statistically evaluated and analyzed by ANOVA, paired t-test and a post hoc Tukey test

Results: Repeated measures ANOVA showed that the mean of pre- or post preparation wall thicknesses were not significantly different for each surface at the three horizontal levels [p> 0.05]. However, there were significant differences between the surfaces for each section. Comparison of pre- and post-preparation wall thicknesses revealed significant differences [p< 0.05]. Proximal surfaces of cervical sections had the least RWT [0.42 +/- 0.12]

Conclusion: According to the results of the present study, the least amount of initial and remained wall thicknesses of pulp chamber were related to the proximal surfaces, particularly in cervical areas. Therefore a reduction of preparation to 0.7 mm is suggested to prevent future pulp injury for mandibular incisors of 35 to 40-year- old patients and younger who require all-ceramic crown preparations

[ effect of chamfer and shoulder marginal designs on the fracture resistance of all ceramic restorations, inceram]

Statement of Problem: One of the major problems of the all ceramic restorations is their probable fracture against the occlusal force. However, there is not enough information about fracture resistance of all the ceramic crowns in different finishing lines

Purpose: The aim of present in-vitro study was to compare the effect of two marginal designs [shoulder and chamfer] on the fracture resistance of all ceramic restorations, Inceram

Methods and Material: On an extracted caries-free first maxillary premolar a 50-degree chamfer margin [0.7 mm] was prepared. Ten impressions were taken using a polyvinylsiloxane. The impressions were poured with epoxy resin to fabricate the dies. The same tooth was retrieved and the 50-degree chamfer was converted into a 90-degree shoulder margin [1mm]. Ten impressions were prepared and 10 more epoxy resin dies were fabricated. The impressions of each epoxy resin die were taken using polyvinylsiloxane impression material and poured with die stone. Alumina cores with a thicknes of 0.5mm were fabricated on the stone dies in a dental laboratory. The alumina cores were then cemented with panavia on the epoxy resin dies and underwent a fracture test with a universal testing machine. The samples were then investigated regarding the origin of the failure. The statistical analysis was done using T-test

Result: The mean value of the fracture resistance for the chamfer samples was 610.18+/-58.79 N and that of the shoulder samples was 502.72+/-105.83 N. The student's T-test revealed a statistically significant difference between the groups [p <0.05]

Conclusion: The results of this study indicate a relationship between the marginal design and fracture resistance. A chamfer margin could improve the biomechanical performance of the posterior single crown alumina restorations. This might be due to the strong unity in the chamfer margin

[Comparison of glaze or polish on dental porcelain's surface roughness]

Surface roughness of dental restorations can reduce the biological properties and wear the opposite. The goal of this investigation was comparing these process effects on the surface roughness of porcelain. In this experimental study, 20 Noritake porcelain disks of 1 cm diameter and 2-2.5 mm thickness with non-percious metal base were fabricated. All samples were finished with medium grit silicone disk and then randomly divided into four groups [n=5]. In the first group, the samples were self glazed. In the second group, the samples were polished [EVE Polisher Kit]. In the third group, after self glazing with a coarse grit stone, the self glaze layer was omitted, then reglazed. The fourth group was similar to the third group, but in the end stage a polishing kit was used. Samples were evaluated with Profilometer and then with SEM. As a result of normal distribution of the data, One-Way analysis of variance [ANOVA] was used for statistical analysis. The mean roughness for the glazed group was 1.06 +/- 0.0547; the polished group, 0.92 +/- 0.1304; the reglazed group, 1.22 +/- 1304; and the polished after glaze group 1.14 +/- 0.1342. The polished and polished after glaze groups had a round shape in 100%, but the glazed and reglazed groups had a sharp shape in 60%. The polished surface is less rough compared to the glazed surface and in the polish after glaze group, the surface of the porcelain is less rough compared to the reglaze group

[ evaluation of the effect of two preparation design: shoulder and heavy chamfer in IPS e.max press restorations - in vitro]

Marginal integrity in all ceramic restorations is one of the important elements of the success rate. According to the importance of design preparation in the marginal integrity, in this in-vitro study, decided to compare the marginal integrity between 2 different types of the marginal preparation: shoulder and classic chamfer in IPS e.max press restoration. This experimental research has been done in vitro with the single blind technique. One standard die with 7mm height, 5mm diameter was prepared by the milling machine. the preparation design consists half shoulder 90 degree and in the other half classic chamfer, with 1mm depth in both of them and 10 degree tapering and then crowns were made of IPS e.max press and after cementation, were ground at the buccolingually direction. Then they were coated by gold and observed under SEM. The data assessed by T-Test. A difference between 2 types of marginal preparation was significant [p<0.05]. Marginal gap in shoulder preparation was 15.45 +/- 0.79 and in classic chamfer site was 13.78 +/- 0.52. The marginal fitness in the classic chamfer preparation was better than shoulder preparation in all ceramic restorations

[Comparison of the effect of four non-metal posts on fracture resistance of endodontically treated teeth restored with composite]

Statement of problem: The fracture resistance of the root canal is mainly associated to the kind of the post used for treatment, and studies indicate that there are still different opinions about the fracture resistance of root canals when Non-Metal posts are used

Purpose: The purpose of this study was to compare the fracture resistance of four adhesive non-metal posts with different MOEs against compressive load in endodontically treated teeth

Materials and Method: In this In-vitro experimental study, a total of 40 recently extracted mandibular premolars were selected, sectioned adjacent to the CEJ, and endodontically treated. The specimens were randomly assigned to four groups [n=10]. Post spaces were prepared and the fiber D.T. Light posts, D.T. Composi post, D.T. white posts and Cosmopost were cemented. Composite resin [Lumiglass] cores were built up. After simulating the PDL, the specimens were embedded in acrylic resin, and then secured in a Universal Testing Machine. A compressive load was applied at a 45[degree sign] angle to the long axis of the tooth until fracture, at a crosshead speed of 1mm/min. The data were analyzed, using one-way ANOVA and Tukey's test [ p <0.05]

Results: The teeth restored with D.T. white fiber posts exhibited significantly higher resistance to fracture. Those restored with the other 3 groups were statistically similar [ p >0.05]. Fractures observed in the fiber groups would allow further restorations of the tooth, whereas unrestorable, catastrophic fractures were observed in the Zirconia [Composi] group

Conclusion: Since Zirconia post should be used catiously due to the unfavorable and unrestorable fractures created, fiber posts are indicated, in endodontically treated teeth

influence of porcelain firing cycle on marginal fitness of electroformed metal-ceramic crowns

Metal ceramic restorations are widely used in crowns. The marginal fitness of these artificial crowns is prone to alteration during the firing cycle of porcelain. Gold electro formed metal-ceramic restorations have been introduced as alternatives to conventional metal-ceramic restorations. However little is known about the relationship between procelain firing procedures and marginal adaptation of this type of crown. The aim of the present study was to evaluate the influence of firing procedures on the marginal adaptation of electroformed metal-ceramic crown restoration. One steel die was prepared for maxillary molar crowns with deep chamfer finishing line design. Ten standardized gold electroformed copings were fabricated. Marginal discrepancy was measured at four sites along the circumferential margin of each coping [Midbuccal - Midpalatal - Midmesial - Middistal] using SEM [Mag: X400] prior to and after porcelain firing procedure. Data among the 2 different groups [before porcelain firing] were statistically analyzed using the paired t-test [a=0.05] analysis. The marginal discrepancy of the postflring procedures [21.45 +/- 2.27micro m] were significantly greater than those of the prefiring procedures [18.23 +/- 1.96 micro m] [p<0.002]. The porcelain-firing procedures influenced the marginal distortion of electroformed metal-ceramic crown restorations, but the marginal discrepancies for all copings and examined design are clinically acceptable [less than 100 miro m]

[Evaluation of the accuracy of three common methods in determining hinge axis points]

Determining the true hinge axis point in order to transfer the orientation relation to articulator is of great importance in reducing occlusal errors. Because of the high cost and time consuming nature of kinematic method in determining hinge axis point, different arbitrary methods have been introduced which rendered controversial results throughout literature. The aim of this study was to evaluate some arbitrary methods for determining hinge axis point and to introduce a precise arbitrary method which has the least distance from kinematic point. This cross-sectional study was performed sequentially on 40 subjects without any TM-disorders with an age range of 21-37. At first true hinge axis point was determined by DENAR hinge axis locator and marked bilateraly on the skin. Then 3 arbitrary points [Beyron, Gysi, Tetruck and Laundeen] was also determined by a flexible ruler and marked on the skin. The distance between the arbitrary points and kinematic point was measured and the data were charted and subjected to Repeated ANOVA and Paired sample test. According to the results of the study, Beyron method was significantly more accurate than the other two methods. 88.88% of Beyron points were within 3 mm distance from kinematic point, but the other points didn't show any significant difference with each other. It is concluded that Beyron method has a high accuracy as an arbitrary method and because of its proximity to the true point, application of this method is recommended

[Marginal fitness comparison between three systems: IPS empress 2, IPS e.max press, and In-Ceram]

Marginal gap determines the success rate in all ceramic crown restorations. However, there is insufficient information about marginal fitness of different ceramic systems. The aim of this study was to compare the marginal gap in three different kinds of ceramic restorations namely "In-Ceram", "IPS-e.max Press" and "IPS Empress2". This in-vitro experimental investigation was conducted using a single blind technique. A total of 10 upper incisor teeth were prepared with size reduction 7mm in height, and 5mm diagonally. With a 1mm shoulder finishing line and tapered about 3 degrees. Then 10 ceramic crowns were built on top of each preparation. After cementation they were grinded at buccolingual direction. Finally, marginal gap analysis was conducted using Stereotactic electronic microscope [SEM]. The marginal gap in IPS e.max pres was 29.22 [ +/- 8/59] microm. In-Ceram showed 49.94 [ +/- 9/32] microm and IPS Empress 2 group demonstrated 40.88 [ +/- 5/84] microm. The gap in IPS e.max Press was less than the gap in In-Ceram and IPS Empress 2 in full ceramic restorations

[Die dimension variation in three impression taking methods]

Dimensional stability of die plays very important role in fixed prosthodontic treatments. Different impression taking techniques may be the main source of die dimensional changes. However, in this regards, contradictory results have been reported in the literature. This study was designed to assess the dimensional accuracy of master casts prepared by means of three impression techniques using Speedex silicone impression material. This quasi-experimental study was carried out using laboratory stainless steel master models that contained three complete crown abutment preparations. The one-step, two-step with and without relief methods were the three putty-wash impression techniques used in this investigation. Fifteen impressions were taken for each technique and velmix casting material was used to prepare stone models. Profile Projector and micrometer were used to measure the final die's height, diameter and different dimensions in order to compare them with laboratory model. ANOVA and paired samples t-test were used for data analyses. The two step technique with spacer was the most accurate method with zero LC distance [distance between left and middle abutment]. However, in the other two techniques, the mean difference was 0.22 [ +/- 0.01], [P<0.05]. Regarding the distances between abutments, there was no significant difference when comparing one-stage and two-stage technique without spacer. Although, the height of abutment was more accurate in two-stage technique without spacer than one-stage. The two-step technique with spacer was the most accurate technique when using Speedex impression material

[In vitro evaluation of different diameters of quartz fiber posts on root fracture resistance]

The fiber diameter of fiber post used in reconstruction of endodontically treated teeth is one of the controversial factors in root fracture resistance. The aim of this study was to evaluate the effect of three different diameters of quartz fiber posts on root fracture resistance. This in vitro study was conducted on 30 mandibular premolars that were sectioned from CEJ. They were endodontically treated and randomly assigned to 3 groups A, B, C [n=10]. Post spaces were prepared and D.T. Light-Post[TM] with three different diameters [0.8, 1, 1.2 mm] was cemented respectively in each group with dual cure resin bonding and resin cement Panavia F 2.0. Composite resin cores were built up using a preformed polyester matrix. Specimens were embedded in acrylic resin blocks with a layer of elastic polyether Impergum around roots as PDL. A compressive load at a crosshead speed of 1mm/min was applied axially to the central fossa of each specimen using a Universal Testing Machine, until root fracture occurred. Data was analyzed using one-way analysis of variance [ANOVA]. Mean fracture load was 1010 [ +/- 250.95] N for group A with 0.8 mm post diameter and 934.4 [ +/- 295.18] N for group B with 1 mm post diameter and 1001 [ +/- 301.42] N for group C with 1.2 mm post diameter. We could not detect any statistically significant difference in root fracture resistance among the three groups. According to the findings of this study, with larger fiber posts the root fracture resistance is higher and they can provide more stability for core material, although, group differences in fracture resistance were not statistically significant

[Comparison of fracture strength between two systems: IPS empress 2 and IPS E. max press]

Statement of problem: One of the major problems of all-ceramic restorations is their probable fracture against lateral forces. However there is not enough information about fracture strength of various all-ceramic restorations

Propose: The aim of this experimental research was to compare the fracture strength and the most probable fracture points in all-ceramic restorations

Materials and methods: In this laboratory-based experimental study, 10 symmetric crowns from each IPS Empress2 and IPS e. max press system were constructed on a laboratory model for maxillary central incisor with 2mm occlusal reduction and deep chamfer finishing line. The core thickness was between 0.7-0.8 mm and porcelain was placed over the core using the layering technique. Each of the crowns was cemented onto the dye using Dual cure Variolink II cement and were imposed to compressive forces in Universal testing machine [V=1mm/min] at 30 degrees angle in palatal surface until the fracture occurred. Then the samples were inspected for fracture points by observation. The statistical evaluations were done with Independent Sample T-test [alpha=0.05]

Result: The average force leading to fracture was 385 N [SD=79/96] for IPS Empress 2 and 380 N [SD=106/28] for IPS e. max press. The most common fracture points in two groups were the incisal edge and buccal surface. There was no meaningful statistical difference in fracture force between the two systems [P>0.05]

Conclusion: The findings of this research indicated that there is no meaningful statistical difference between these two systems in their fracture strength. therefor they are both suitable for constructing anterior all-ceramic restorations

Effect of ferrule on fracture resistance in endodontically treated teeth that were restored with bonded posts and cores

A dowel in an endodontically treated tooth could transfer occlusal forces intraradicularly which may increase the vertical root fracture susceptibility. Ferrule is one of the methods by which tooth structure can be reinforced. Thirty freshly extracted central incisors were endodontically treated. The teeth were randomly divided into two groups. Those in the control group were treated using prefabricated post and composite core [with no ferrule], and the teeth in test group were treated with similar prefabricated posts and cores while having two mm ferrule height. All teeth were restored with full metal crowns. The specimens were mounted on a universal testing machine and a compressive load was applied to the long axis of the teeth until fracture occurred. There was a significant difference between the ferrule and non-ferrule groups [P < 0.000]. The mean for ferrule group was 584N, while this value was 194N in non-ferrule group. The ferrule effect increases the fracture resistance of endodontically treated teeth that are restored with bonded post and cores

[ positional evaluation of connector zone between the maxillary anterior teeth at Tehran Islamic Azad University, school of dentistry in 2005-6]

Background: the places in which the anterior teeth appear to touch have been referred to as the Connector Zone [Space].There is the distinction between a connector zone and contact point. Connector zone is one the interposing factor if smile design which may vary with moving away from midline in anterior teeth, so the variation of this space should be very well noticed in order to reconstruct a good smile. Because of absence of this kind of a research in Iran and also presence of some incomplete article related to this topic, we decided to assess [ analyze ] the position of connector zone in anterior teeth of both female and male scholars and referred patients with different ages at Tehran Islamic Azad University, school of dentistry in 1384

Materials and Methods: this was a descriptive study in which 320 female and male samples divided in to four 10-year old groups[20-30 year-old,30-40 year-old,40-50 year-old, above50 year- old]. All of the interfering variables were omitted. Different stages of this study were clinical examination, completion of informative form, providing two photographs from frontal and lateral view of anterior teeth using digital camera and analyzing images in P.C. Connector zone rate between maxillary central incisors, between maxillary central and lateral incisors, and also between maxillary lateral incisors canine were finally measured considering 100 percent of the maxillary central incisors length and this results ere obtained which presented in tables and charts

Results: this study showed that the rate of C.Z. among maxillary anterior teeth decrease with moving away from midline. It has been also defined that sexuality is not an influencing factor in this issue. Rate of C.Z between maxillary central and lateral incisors and also between maxillary lateral incisors canine will increase with aging while it will not change noticeably between maxillary central incisors with aging

Conclusions: these results may empower dentists a criterion which will help them to reconstruct a proper smile line regarding their patient age

[Comparison between two desensitizer materials: potassium nitrate and gluma desensitizer in reducing tooth sensitivity]

Dentin hypersensitivity is characterized by a short and sharp pain that arises when thermal, evaporative, mechanical or osmotic stimuli are applied to exposed dentin. Most of vital teeth after preparation for fixed crowns encounter dentin hypersensitivity. There are some available categories of materials such as Gluma desensitizer and potassium nitrate designed for treating this problem which needs more clinical evaluation to confirm their efficiency. This study was performed to compare the effect of Gluma desensitizer and potassium nitrate on reduction of hypersensitivity of prepared teeth for full crowns. This research was performed on 75 vital teeth in 25 patients who needed a fixed prosthesis treatment. After completing routine examinations, the hypersensitivity of teeth was determined with the air sensitivity test. The measurement was done by a VAS scale before preparation, after preparation, before using desensitizers, after using desensitizers and before cementation. Each tooth was randomly assigned in one of the three groups [potassium nitrate, gluma and control]. It was shown that both desensitizers decreased dentinal hypersensitivity in vital teeth prepared for fix prosthesis; but potassium nitrate was more effective after application and before cementation. Meanwhile in 88% of the cases which gluma was used on, a vascular pain [with pulse] was seen. Considering the results, both desensitizers were effective in decreasing dentinal hypersensitivity in vital teeth prepared for fix prosthesis; but potassium nitrate showed better results. Therefore, this substance can be used in a therapeutic protocol

[Evaluation of relationship between smile line and age]

Smile line is one of the most important element of the smile esthetics. In an attractive smile, the maxillary anterior curve is parallel to the lower lip. With the changes in face, lips and teeth muscles. Which are caused by aging, this element [smile line] a1so changes. Aging causes smile line to move from its parallel position and in complete smile. Formulate deferent shapes relative to the lower lip curve. Therefore, thorough and accurate information about smile elements and anatomy seems to be essential for attractive smile restoration in various ages. A descriptive research on this issue has been done on 300 men and women between 20 to 70 years of age. Each subject was analyzed and evaluated by carful visual judgment. After the completion of information and evaluation of the result finding based on the clinical observation on students und clients at .Azad University - School of Dentistry have shown that with the passing of age, the smile line gradually changes from parallel from to straight and then reverse form. Other elements of smile such as tooth lower lip position also changes their forms through aging, and different forms such as slightly covered and touching decline while not touching increases. In the position of lip line the high, form declines whereas the low form increases