Journal of Dental Medicine

Background and Aim: Microleakage has been always a major concern in restorative dentistry. The curing contraction of composites still presents a problem with controlling microleakage and postoperative sensitivity. The aim of this study was to investigate the effect of flowable and dual-cure resin composite liners on gingival microleakage of packable resin composite restorations.

Materials and Methods: Sixty Class II cavities with cervical margins 1 mm below the CEJ were prepared in 30 extracted human molars. The teeth were randomly divided into five groups of 12 each. In control group, each tooth was restored incrementally with Tetric Ceram composite without applying any liner. In the second and forth groups, flowable materials- Tetric Flow and dual-cure composite resin cement Relay X ARC were placed respectively as a 1-mm thick gingival increment and cured before the resin composite restoration, whereas, in the third and fifth groups liners were cured with the first increment of packable composite.The restored teeth were stored for one week in distilled water at 37⁰C, and thermocycled between 5⁰C and 55⁰C, sealed with nail varnish except the tooth - composite interface in cervical restoration margins and immersed in 2% basic fuchsin for 24 hours. Dye penetration was evaluated using a stereomicroscope with 28x magnification. The data were analyzed by Kruskal-Wallis and Mann-Whitney U-tests with p<0.05 as the level of significance.

Results: The results of this study indicated that there were significant statistical differences between control - cured flowable liner, control-flowable liner without separately curing, control-cured dual cure composite resin cement groups.However there were no significant differences between dual-cure composite resin cement without separately curing-control,cured flowable liner-cured dual cure composite resin cement, flowable liner without separately curing-dual cure composite resin cement without separately curing groups.

Conclusion: The results of this study indicated that none of techniques could thoroughly eliminate microleakage in gingival floor, however the effect of flowable or a dual-cure liner on reducing the gingival microleakage was found to be statistically significant in tested restorative material.

Background and Aim: The role of applying rotary instruments in reducing preparation time and proper root canal preparation have been approved in permanent teeth. The aim of this study was to compare the rotary instruments (Hero642) and K-files in root canal preparation of primary molars. Time and canal transportation were compared.

Materials and Methods: In this experimental, invitro study, 30 human extracted primary molars with 8 mm length were selected and divided into two equal groups. After preparing access cavity, group 1was prepared by K-files and group 2 by Hero642 systems. Before canal preparation, with # 15 K-file and after canal preparation, with master apical file, canal curvature was evaluated by Weine technique using Radiovisiography. Apical transportation was calculated. Time taken for preparation was recorded by chronometer. The results were analyzed with T-test and Mann-Whitney. P<0.05 was considered as the level of significance.

Results: The average canal transportation angle was 3.42 for Hero642 group and 7.33 for K-file group (p<0.04). The mean instrumentation time was 4.28 for Hero642 group and 8.76 minutes for K-file group (p<0.001). There was a significant difference between two groups.

Conclusion: Based on the findings of this study, it is suggested to apply Hero642 rotary instrument for primary molar canal preparation due to less preparation time and less canal transposition.

Background and Aim: Black staining after taking iron drops on the primary teeth is always concern of parents. There is not an exact explanation for the mechanism of iron black staining. The purpose of this study was to compare tooth discolorations, atomic absorption and structural changes of primary teeth enamel caused by two kinds of iron drops[ Kharazmi(Iran) and Fer-in-sol(USA)].

Materials and Methods: In this ex-vivo study, 93 sound primary teeth in normal color range were divided into five groups. Two groups of samples were immersed into the Artificial Caries Challenge(ACC) for two weeks before getting exposured to iron drops: Group 1 Control(NS): sound enamel teeth which were kept in Normal Saline environment(NS)(13teeth). Group 2 (NS-KH): NS, kharazmi iron drop (20 teeth). Group 3 (ACC-KH): ACC, Kharazmi iron drop (20teeth). Group 4 (NS-F-in-S): NS, Fer-in-Sol iron drop (20teeth). Group 5 (ACC-F-in-S): ACC, Fer-in-Sol iron drop. Visual tooth discolorations were determined by a specialist in operative dentistry who was not aware of experimental groups. The iron concentration was measured by ICP system (Vista-pro, Australia) and the structural changes were studied by SEM (Philips, Netherland). The data of discoloration were studied with Kruskal-Wallis test and multiple comparison using Bonferroni type test, and with the data of atomic absorption were studied with oneway ANOVA test and Tukey HSD test.

Results: The discoloration in the teeth immersed into the ACC (ACC-KH, ACC-F-in-S) was more severe than the sound enamel surface (NS-KH, NS-F-IN-S) (p<0.001) and Kharazmi iron drop caused more discoloration in the teeth immersed into the ACC (p=0.018). The teeth immersed into the ACC, absorbed more iron than the sound enamel surface (p<0.001) and also the teeth immersed into the ACC absorbed more Kharazmi iron drop (p<0.001). In the Scanning Electron Microscopy study, at low magnification in the sound teeth the perikymata was arranged regular. At low magnification in the teeth immersed into the ACC, many fractures were observed. The fractures in group 3(ACC-KH) were more and deeper.

Conclusion: Being immersed into the ACC, caused more iron absorption, severe discoloration and structural changes in the enamel of primary teeth. Such changes were more distinct in the teeth exposed to Kharazmi iron drop than the teeth exposed to Fer-in-Sol iron drop.

Background and Aim: The aim of this investigation was to evaluate the osteopromotion property of homogenous demineralized dentin matrix (HDDM) on experimental surgical bone defects in parietal bone of rabbits using the guided bone regeneration (G.B.R.) technique incorporating Paroguide collagen membrane.

Materials and Methods: Surgical bone defects were created in 6 Newzland white rabbits (2 defects in each rabbit). The defects were protected by Paroguide membrane alone (control group) or filled with HDDM and protected by Paroguide membrane (experimental group). The HDDM had been obtained from the central incisors of rabbits. The rabbits were sacrificed after 15, 30, 45, 60, 75 and 90 days and the defects examined histologically. Data were analyzed using pair-t test. The level of significance was set at p=0.03.

Results: Histologically, the volume of newly formed bone matrix was significantly greater in the experimental group. No inflammatory reaction was seen in either experimental or control groups.

Conclusion: Bone regeneration was accelerated in the bone defects filled with HDDM in comparison to the control group.

Background and Aims: Soft tissue management with providing the esthetic for restoration of a single implant in the anterior maxilla is of great importance. Tissue training helps to develop a proper emergence profile and natural tooth appearance. The aim of this article was to report a nonsurgical management of undesirable contours of soft tissue around maxillary anterior implants to achieve an optimum appearance.

Materials and Methods: A 23-year-old female with congenital missing of maxillary lateral incisors, after completion of a fixed orthodontic treatment and gain enough space, received 2 dental implants. After second phase surgery and healing period, construction of the restorations was not possible through conventional method because of severe soft tissue collapse. In this case, soft tissue contours were corrected using a provisional restoration and then final restoration was made and delivered.

Conclusion: Tissue training with a provisional restoration helps to re-establish normal gingival tissue contours and interdental papillae around the restoration of maxillary anterior implants.

Background and Aims: Despite the significant improvement in dentistry, pain after endodontic therapy is still of concern for patients. Non-steroidal anti-inflammatory drugs are the most commonly prescribed oral analgesics used for dental pain relief after root canal treatment. The purpose of this study was to compare the effectiveness of Ibuprofen versus slow-released Diclofenac Sodium in controlling pain following root canal treatment.

Materials and Methods: In this randomized clinical trial, mandibular molars with irreversible pulpitis in 90 patients were selected. The patients were divided into three groups (Ibuprofen, slow-released Diclofenac Sodium and placebo). After examination patients filled in the consent form. Then they received one of the mentioned drugs. After inferior alveolar nerve block, access cavity was prepared and the root canals were prepared using passive step back method. The canals were dried and temporary filling material was placed. Then the pain evaluation form (visual analog scale) was explained and delivered to the patients. Data were analyzed using Repeated Measurement ANOVA, Kruskal-wallis and Man-Whitney U tests.

Results: The mean pain intensity in slow-released Diclofenac Sodium group was 0.87 0.95, 1.17 1.10 for Ibuprofen group, and 2.14  1.70 for placebo group. The differences between groups were statistically significant (P<0.001). The effect of Ibuprofen in controlling post endodontic pain in the first 2 hours was more than slow-released Diclofenac Sodium (P=0.01), but in 10, 18, and 36 hours after treatment, slow-released Diclofenac Sodium was more effective than Ibuprofen (P<0.001).

Conclusion: Premedication with single dose of slow-released Diclofenac Sodium can control post endodontic pain for a longer period of time compared with Ibuprofen.

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 The goal of each root canal therapy is cleaning and obturating the entire root canal system. A thorough knowledge of root and root canal morphology and a good anticipation of their possible morphologic variations are essential and will help to reduce endodontic failure caused by incomplete root canal preparation and obturation. In this study, one case of maxillary molar with two palatal roots has been reported in a a 40-year-old woman is reported..

Background and Aims: Intrabony periodontal defects are one of the important problems in periodontal diseases. Treatment of intrabony periodontal defects with synthetic materials such as Cerasorb has been shown to enhance periodontal regeneration. The aim of this study was to compare the effect of Cerasorb with autogenous bone graft (A.B.G) as a gold standard in treatment of two to three wall periodontal defects.
Materials and Methods: In this interventional or randomized clinical trial study, 24 two to three wall intrabony defects were selected in a double blind manner. Defects were randomly (with tossing a coin) divided into two groups (test and control). Defects in test group were treated with flap surgery and Cerasorb. In control group, defects were treated with flap surgery and autogenous bone graft. At baseline and 3-month, 6-month and one-year follow up evaluations clinical and radiographic assessments were performed. Data were statistically analyzed using the paired t test, Wilcoxon and Mann-whiteny. The level of significance was set at P<0.05.
Result: At the 3-month, 6-month and one-year visits, the parameters of probing pocket depth (PPD), probing attachment level (PAL), bone level (distance between CEJ and alveolar crest), and bone density were not significantly difference in test and control groups (P>0.05). However, in each group there was significant difference in 4 parameters before and after surgery (P<0.05).
Conclusion: Treatment with Cerasorb compared to A.B.G produced the same results of improvement in two to three-wall intrabony defects. So the use of Cerasorb can be suggested for treatment of intrabony periodontal defects.

Background and Aims: Nowadays reconstruction of alveolar defects has become one of dentists' problems especially in areas which are going to get dental implants. Inorganic bovine bone mineral (Bio-Oss) is one of the most popular graft materials that acts as a structure for migration of osteoblasts. If migration, proliferation, and differentiation of osteoblasts can be promoted by a material, it would be possible to reconstruct more amount of bone in a shorter period of time. Milk contains vital proteins that regulate bone growth. One of these important proteins is lactoferrin. The aim of this study was to examine the effect of added bovine lactoferrin to Bio-Oss on osteogenesis.
Materials and Methods: Two doses of 50 and 500 µg/ml of lactoferrin were prepared. Ten New Zealand white rabbits were selected for this study. Four 6-mm symmetrical detects were created in each rabbit's calvarium. Two of these sites were filled with Bio-Oss that was wetted with two doses of lactoferrin. Third detect was filled with Bio-Oss alone and the forth one was left empty as control group. After 4 weeks histologic and histomorphometric analysis was performed.
Result: There was no sign of obvious inflammation in any of four groups. Also there was no difference among four groups in terms of vitality, type of new bone, and foreign body reaction. However, amount of bone formation in control group was significantly lower compared with the other 3 groups. Although lactoferrin containing groups showed little increase in bone formation especially in higher concentration, there was not statistically significant difference among the three test groups. Amount of remaining biomaterial also was lower in lactoferrin containing groups compared with the Bio-Oss group but the differences were not significant.
Conclusion: Although there was no significant difference among the test groups, it seems that the added lactoferrin increases bone formation. Considering the limitations of this study, more studies are needed in different concentrations of lactoferrin and different healing periods. Furthermore, because of possible washout of the lactoferrin from the defects, it would be helpful to find and evaluate a proper carrier agent for lactoferrin to see its real effects.

Background and Aims: Marginal adaptation is important for the long-term success of full-coverage restorations. Preparation design is one of the important factors influencing the marginal integrity. Therefore, the purpose of this study was to compare the effect of radial shoulder and chamfer finish line designs on the marginal adaptation of all-ceramic Cercon restorations.
Materials and Methods: This in vitro study was done using single blind experimental technique. One stainless steel die with 7 mm height and 5 mm diameter was prepared by milling machine. The preparation design consisted of half radial shoulder with 1mm depth and half chamfer with 0.8mm depth. All walls had a convergence angle of 10º. Ten stone dies and ten ZrO2 copings of Cercon (Cercon Smart Ceramics, DeguDent, Hanau, Germany) were made and after cementation were ground at buccolingual direction. Then marginal gap of each sample was measured by scanning electron microscopy. Data were then analyzed using t-test.
Result: The mean marginal gap for radial shoulder was 98.4µ and for chamfer was 39.7µ. The difference was statistically significant (P=0.002).
Conclusion: The marginal gap of chamfer preparation is less than that of radial shoulder.

Background and Aims: This ex vivo study was done to evaluate the effect of different adhesive systems on microleakage of class V composite restorations.
Materials and Methods: Thirty extracted human third molar teeth were selected and class V cavities were prepared (3×3×1.5 mm) on buccal and lingual surfaces. Then, teeth were divided into 3 groups. Adhesives used in this study were Excite (Ivoclar/Vivadent), AdheSE(Ivoclar/Vivadent) and AdheSE-one Ivoclar (Vivadent/Vivadent). After application of adhesives, cavities were restored with a resine composite (InTen-S A1/ Ivoclar), in 3 increments and cured with QTH light curing unit (700 mW/cm). After 24 hours storage of teeth in 370C water, teeth were thermocycled (500 cycles in 5-550C) and stored in 1% basic fushin for 24 hours. After that, the specimens were rinsed with running water and mounted in a self-cured acryl. Finally, the specimens were sectioned and maximum depth of dye penetration for each restoration was measured using stereomicroscopy. The results were statistically analyzed with Mann-Whitney U test.
Results: In comparison between enamel and dentin margins in each group, microleakage in enamel margins were less than that of dentin margins. This difference was statistically significant in Excite and AdheSE-one groups (P=0.001, P=0.043). AdheSE showed the least microleakage in dentin margins however, there was no significant difference between 3 bonding agents (P=0.14). In enamel margins, there were significant differences between 3 bonding agents (P=0.001). Excite showed the lowest microleakage and AdheSE-one had the highest microleakage.
Conclusion: The least enamel microleakage was associated with the total-etch and least dentin microleakage was observed in the two-step self-etch adhesive system.

Background and Aims: Teaching of clinical skills is one of the most important aspects in training medical students. The aim of this study was to compare the effectiveness of videotaped and live demonstrations for applying fissure sealant on permanent molar teeth at Zahedan University of Medical Sciences (2010-2011).

Materials and Methods: Thirty 8th-semester dental students were randomly assigned in two groups (n = 15). In group 1, fissure sealant placement was taught using live demonstration while, in group 2, education was performed by videotaped demonstration. Then, each student applied fissure sealant on the patient's permanent molar tooth. The procedure of fissure sealant placement was assessed and scored by a pedodontist. The students were subsequently asked to rate how helpful the videotape or live demonstration had been. The data were analyzed using T-test and Chi-square test.

Results: The mean students' scores for videotaped and live demonstration were 16.5 and 16.53, respectively. There was no significant difference between the teaching methods according to students' scores (P>0.05). 33% of students rated videotaped demonstration as "good" for its helpfulness and 66% as "very good". However, live demonstration was rated as "good" and "very good" by 66% and 33% of students, respectively. There was no significant difference between two groups (P>0.05).

Conclusion: Both teaching methods were equally effective. Therefore, videotaped demonstration can be used in combination with live demonstration or as an alternative for it.

Background and Aims: Reliable bonding between tooth substrate and zirconia-based ceramic restorations is always of great importance. The laser might be useful for treatment of ceramic surfaces. The aim of the present study was to investigate the effect of laser irradiation on the shear bond strength of zirconia ceramic surface to dentin.

Materials and Methods: In this experimental in vitro study, 40 Cercon zirconia ceramic blocks were fabricated. The surface treatment was performed using sandblasting with 50-micrometer Al2O3, CO₂ laser, or Nd:YAG laser in each test groups. After that, the specimens were cemented to human dentin with resin cement. The shear bond strength of ceramics to dentin was determined and failure mode of each specimen was analyzed by stereo-microscope and SEM investigations. The data were statistically analyzed by one-way analysis of variance and Tukey multiple comparisons. The surface morphology of one specimen from each group was investigated under SEM.

Results: The mean shear bond strength of zirconia ceramic to dentin was 7.79±3.03, 9.85±4.69, 14.92±4.48 MPa for CO₂ irradiated, Nd:YAG irradiated, and sandblasted specimens, respectively. Significant differences were noted between CO₂ (P=0.001) and Nd:YAG laser (P=0.017) irradiated specimens with sandblasted specimens. No significant differences were observed between two laser methods (P=0.47). The mode of bond failure was predominantly adhesive in test groups (CO₂ irradiated specimens: 75%, Nd:YAG irradiated: 66.7%, and sandblasting: 41.7%).

Conclusion: Under the limitations of the present study, surface treatment of zirconia ceramics using CO₂ and Nd:YAG lasers was not able to produce adequate bond strength with dentin surfaces in comparison to sandblasting technique. Therefore, the use of lasers with the mentioned parameters may not be recommended for the surface treatment of Cercon ceramics.

Background and Aims: When composite resin polymerizes, shrinkage stresses tend to produce gaps at the tooth/ restoration interfaces. Surface sealants may reduce or avoid problems related to the marginal interface. The aim of this study was to evaluate the effect of two different surface sealants (Fortify and Optiguard) on the microleakage of class V resin composite restorations.

Materials and Methods: Twenty three sound noncarious molars were collected. Totally, 45 Class V cavities with the occlusal margins in enamel and cervical margins in cementum were prepared in both buccal and lingual surfaces. The specimens were randomly assigned in three groups (15 cavities in each group) and then restored with a resin composite. After the finishing and polishing procedures, the restorations in each group were covered with a specific surface sealant, except for the control samples, which were not sealed. After placing restorations, the specimens were thermocycled and then immersed in a 50% silver nitrate solution (tracer agent) for four hours, sectioned longitudinally and analyzed for leakage using a stereomicroscope in a blind manner. The marginal microleakage was evaluated at the occlusal and cervical interfaces and compared among the three groups using the Kruskall-Wallis and the Mann-Whitney U tests.

Results: Microleakage was found in all groups at both occlusal and cervical margins. Significantly greater leakage was observed at the cervical margins compared to the enamel margins of the material groups (P=0.005). There was no statistically significant difference among the groups at occlusal margins (P=0.66). In the cervical region, Fortify showed improved results and statistically presented the lowest degree of microleakage (P=0.003).

Conclusion: The used sealant materials presented different rates of effectiveness and Fortify decreased marginal microleakage significantly.

Dentistry has been a field dominated by a constant improvement of synthetic biomaterials. Tissue engineering of tooth is coming to change the panel of the dental materials such as restorative materials and implants. Certainly, it is the largest transition in history of dental materials science in terms of accepting this new and exciting technology. The objective of this article is to present various implications of tissue engineering in different fields of dentistry. To achieve this goal, a review of the literature was carried out by using Medline database to search topics including "dental stem cells", "teeth tissue engineering", "regenerative dentistry", "oral surgery", "periodontal regeneration" and "regenerative endodontics". These searches were limited to articles published after the year 2000. On the basis of our literature review, we have found that although there are significant challenges in oral tissues engineering, engineered tissues will find many applications in dentistry within the next few years.

Background and Aims: The purpose of this study was to design a new device assisting dental students to measure the tapering of the prepared teeth for fixed crown prosthesis in which the desired tapering for better clinical prognosis could be obtained.

Materials and Methods: The designed device in this study had two arms that were placed on two opposite walls of the prepared teeth. To evaluate the validity and reliability of this device, 3 dies with different degrees (13, 29 and 45°) were used and 20 teeth were prepared by dental students with undefined tapering degrees. The measurements of tapering were performed by six last year-dental students in two different time periods. Comparison of errors in measurements on standard dies between observers and between time intervals were analyzed by (Wilcoxon) Paired t-test with a significance level of α=0.05.

Results: For the three dies used in this study, we compared the differences for each measurement taken by observers with the standard taper of the dies. Maximum difference of measurements with true standard die tapering was 1 degree. A number of 6 measurements were under the true standard tapers and 2 measurements were above it. Interclass Correlation Coefficients (ICC) of the first and second measurements on prepared teeth were 97.4 and 97.5, respectively.  There were no significant differences between different observers or two measurements of the same observer in different time intervals (P>0.05).

Conclusion: The results indicated that this device can be valid and reliable for measuring the angle of convergence of the prepared teeth and can be used as an educational device in dental schools as a replacement for previous tapering measurement methods.

Background and Aims: Using the conservative adhesive resin restoration (CAR) in uncooperative children lead to numerous problems because of being time consuming. The purpose of this study was to compare the microleakage of conservative adhesive resin restoration under separate curing and co-curing.

Materials and Methods: In this experimental study, 120 intact premolar teeth were collected and 120 vertical grooves were prepared on them. Then the teeth were divided into four groups: group 1, separated curing of bonding agent, flowable composite and sealant group 2, co-curing of all materials for 60 seconds group 3,
co-curing of all materials for 40 seconds and group 4, co-curing of all materials for 20 seconds. Then the specimens were thermocycled and immersed in basic fuchsin solution. The teeth were sectioned horizontally and dye penetration was evaluated with stereomicroscope. Date were analyzed using one-way ANOVA and Scheffe test.

Results: Mean value of dye penetration in groups 1, 2, 3, and 4 was 1.53±0.6, 2.06±0.6, 2.5±0.7 and 3.53±0.6, respectively. There was a statistically significant difference between group 1 and the other groups (P=0.0001).

Conclusion: Considering the problems caused by microleakage in conservative resin adhesive restorations, co-curing method should not be used. In the case of using co-curing method, 60 second curing time is suggested for sufficient polymerization.

Background and Aims: Although composite resin restorations have many advantages, they can lead to several clinical problems. The primary reason for these problems is microleakage. The aim of this study was to compare the rebonding effect on microleakage of class V composite restorations using two low viscosity resins.
Materials and Methods: In this in vitro study, 60 class V composite restorations were performed in buccal and lingual surfaces of human extracted premolars with the occlusal margin in enamel and the gingival margin in dentin/cementum. The teeth were randomly divided into 3 groups: (I) restorations with no rebonding, (II) restoration margins rebonded with an enamel adhesive (Margin Bond), (III) restoration margins rebonded with a specific unfilled resin. The specimens were then thermocycled and immersed in 0.5% fuchsin dye solution. The samples were sectioned longitudinally and observed under a stereomicroscope for assessment of microleakage. The data were analyzed by Kruskal-Wallis, Wilcoxon and Mann-Whitney tests. P<0.05 was considered as the level of significance.
Results: Statistical analysis showed a significant difference in the microleakage of gingival margins (P<0.0001), but not in enamel margins (P=0.148). Microleakage at the gingival margins of group (III) was significantly less than that of group (II). Group (I) showed the highest amount of microleakage.
Conclusion: Rebonding by a low viscosity resin reduces microleakage at the gingival margins of class V composite restorations, but has no significant effect on the occlusal margins.

Background and Aims: Approximately 5% of cancers involve structures of oral cavity. Partial resection of maxilla (maxillectomy) may be performed in these cases. Maxillectomy often results in significant functional disabilities such as inability in mastication, deglutition and speech with adverse impact on psychological status and social life of patients. Obturator prosthesis is a prosthodontic treatment to separate nasal and oral cavities and restore the critical above mentioned functions. The assessment of speech is considered to examine speech function restored by the treatment. The purpose of this study was to evaluate the speech in patients with resected maxilla who have been treated by obturator prosthesis from a pool of related patients in the Prosthodotnics department of dental faculty, Tehran University of Medical Sciences. The evaluation was performed with computer software using sentence intelligibility (SI) test.

Materials and Methods: This cross sectional study was conducted on 10 subjects (23-66 years) referred to the Prosthodontics department of the faculty and received an obturator. After primary examination of the prosthesis, the patients completed SI test in an acoustic room under guidance of a speech therapist. The performed tests were analyzed by the speech therapist. In addition, the SI with and without the prosthesis was evaluate by lay audience. The statistical analyses were performed using Wilcoxon-signed rank test and Weighted Kappa.

Results: Significant differences were found between SI tests with and without the obturators (P<0.001). Two of 10 patients showed problems in speech function using obturator.

Conclusion: Within the limitations of the present study, obturators had significant effect on improvement of the speech outcomes of examined patients. Improvement of the quality of life could be predicted.

Background and Aims: The marginal integrity of fixed restorations always is a major matter of concern for dental clinicians. Any cause of distortion, including veneering processes, in the marginal integrity is supposed to be detrimental for long-term success of fixed dental prostheses. The aim of this in vitro study was to compare the marginal adaptation of two different full ceramic restoration systems (Zirkouzahu&Cercon) and possible changes in marginal integrity following the multiple veneering process.

Materials and Methods: Twelve all-ceramic crowns in the form of coping were fabricated on a pre-made standard metal die with finish line of shoulder preparation from two commercial systems: Cercon® and Zirkonzahn®. The specimens were not cemented. The Crown/Die discrepancy were measured by means of a precise stereo microscope (accuracy±0.1 μm), at various points (n=12) selected along circumferential margin of the restorations. Same procedure was accomplished after applying the veneering porcelain. The mean gap dimensions were calculated and data were analyzed by multivariate (b) test.

Results: Mean marginal gap dimensions before and after veneering porcelain firing cycles, for Cercon® were (59.67±13.46 µm) and (63.75±14.16 µm) and for Zirkonzahn® were (65.81±24.37 µm) and (64.74±21.94 µm), respectively. Hotelling trace Multivariate(b) test method showed that the rate of mismatching marginal integrity in two groups (Cercon® and Zirkonzahn®) had no significant difference before and after porcelain firing (P>0.05).

Conclusion: Within the limitation of this study, the marginal integrity of both systems were seems to be within the clinically acceptable standard dimension, i.e. 120μm.The marginal gap of both all-ceramic systems were not affected by veneering porcelain firing cycles.