Evaluation and comparision of marginal fit of provisional restoration fabricated using light cure acrylic resin with other commercially available temporary crown resin materials.
Provisional Restoration plays a vital role in the long term success of fixed partial restorations. These interim restorations are used individually on single or multiple prepared teeth or they may provide coverage for abutment teeth as part of a splint or fixed partial denture prior to placement of permanent prosthesis [1,2]. The word provisional literally means established for time being. According to Glossary of Prosthodontic terms  "A provisional restoration is a transitional restoration that provides protection, stabilization and function before fabrication of the definitive prosthesis".
The success of provisional restoration depends upon good marginal adaptation as it promotes gingival health during the period between tooth preparation and placement of final restoration, and also helps in preventing pulpal damage from thermal, bacterial and chemical insults . A poorly adapted provisional restoration encourages plaque accumulation which can lead to periodontal conditions ranging from gingival inflammation to periodontal support breakdown, this being especially true in cases where finish line margins are placed equigingivally or subgingivally .
Many techniques such as the direct method, indirect method or relining and injection of coldcure acrylic resin to fabricate provisional restorations have been used for achieving good marginal adaptation of the provisional restoration [6,7]. Similarly a variety of materials such as methyl methacrylate and bis-acryl-composite resin have been commonly used to fabricate provisional restorations, however these materials have some inherent disadvantages. The disadvantages of methyl methacrylate include monomer is toxic to the pulp, high polymerizatioi shrinkage, causes discoloration and staining and causes porosity and surface roughness. The disadvantages of bis-acryl-composite resin include expensive, available in three component system, limited shade availability, does no polish to a high gloss finish, and detrimental effects on pulp [8,9].
A new material i.e. light cure acrylic resin is currently being used in the fabrication of fixed provisional restorations. These light cure acrylic resins have superior advantages over the other commercially available materials. The advantages include they available in single component system, ease of manipulation, minimal shrinkage, good marginal adaptation, easy to polish and finish and unlike acrylic, and bis acryl composites the light cure dose not require a pre-impression and avoids impression related problems like poor adaptation [8,9].
Many studies have been conducted to evaluate the effect of different techniques as well as the materials on the marginal adaptation of provisional restorations. Bargi and Simmons (1976)  advocated the relining of provisional restoration constructed with different technique after polymerization to increase the marginal adaptation. Crispin and coworkers (1980) [11 demonstrated a significant improvement in marginal adaptation with microscopic measurements that indirect fabrication of provisional restoration with methylmethacrylate and vinylethylmethacrylate resins Monday and Blais (1985)  reported in their study that prosthesis made by indirect method have improved marginal adaptations by approximately three to four time more than resulting from direct method.
In the recent times there has been an evolution of a new light cure resin provisional restoration material which claims to have better marginal adaptation and easy manipulation over other conventional self-cure resin materials. Hence this experimental study has been planned with the following objectives; to evaluate the effect of water absorption and thermocycling on marginal fit of new light cure resin provisional crown; to evaluate the effect of water absorption and thermocycling on the marginal accuracy of two commercially available provisional resin crowns; and To compare and evaluate the marginal fit and accuracy of new light cure provisional crown with two commercially available provisional crown.
Materials and Methods
Materials used in the study are as follows; DPI Selfcure tooth moulding powder (Polymethylmethacrylate, Lot no 742, Dental Products India Ltd.); PROTEMP II (BIS-GMA composite, three component paste, Lot No. 159959 3M ESPE--AG, Germany) and REVOTEK LC (visible light cure composite, Lot No. 0405101, GC Corporation Japan). Abbreviations used in the study are as follows, Cold Cure Acrylic Resin (CCAR), GC Light Cure Acrylic Resin (GC LCAR), Protemp II (P-II), Degree of Freedom (DF), Some of Squares (sS), Means of Squares (MSS), Standard Deviation (Std. Dev.), Significant (S) and Non-significant (NS).
Preparation of the tooth
A polyvinyl siloxane putty index (Aquasil, Dents ply Germany) relined with light body addition silicone impression material (Reprosil, Dentsply Germany) of an ivorine mandibular 1st molar was made in a plastic container which serve as a matrix for making provisional crowns for the materials to be tested. Six similar putty indexes were made and each was used for fabrication maximum of 10 samples only. The mandibular first molar was selected as it is one of the most of common tooth prepared to receive a full crown restoration and also the length of the margin is significantly greater as compared to other teeth due to which marginal discrepancy can be easily evaluated.
The typhodont mandibular 1st molar was embedded in a stone block and prepared for a full crown restoration with a 1mm shoulder finish line and a uniform height of 6 mm of all the axial surfaces.
Preparation of the master die
A polyvinyl siloxane putty index (Aquasil soft putty/ regular set of both base and catalyst, dentsply Germany) relined with light body (Reprosil, hydrophilic vinyl polysiloxane, Dents ply Germany) of the prepared tooth was made in a plastic container. This index was used to fabricate a wax pattern of the prepared tooth along with the base using inlay wax. The wax pattern was retrieved from the putty index by cutting it with a bard parker blade. After thorough application of de-bubbliser (Auro fluid) the pattern was invested in phosphate bonded investment and cast using wirobond alloy. After divesting the master die was carefully air abraded with 50 micrometer aluminum oxide and finished.
Preparation of Samples
A putty index of the master die was prepared and die stone (kalrock die stone class IV, kalabhai karson pvt. ltd. India.) mixed with water, as per the manufacturers instructions was poured in to the index. Jump pins were modified to serve as hooks by bending them for easy removal of the die stone models. After the die stone was completely set, the dies were separated from the putty index. A new index of the master die was prepared for every 10 die stone models to maintain the accuracy of the prepared dies.
A total of 60 stone dies were prepared. They were divided in to 3 groups i.e. 20 dies for each material to be tested. The 3 provisional restorative materials involved in this study are D P I self-cure tooth moulding powder (dental products of India ltd. India.), PROTEMP II (Bis-GMA 3M ESPE AG, Germany) and REVOTEK LC (GC Corporation, Japan). The stone dies were thoroughly lubricated with petroleum jelly and the index made before the tooth preparation was used as a matrix to fabricate the provisional restorations was made from each material and 20 samples were made of each material.
The provisional crowns were cemented using Freegenol  (Eugenol free temporary luting cement, GC corporation, Japan.) according to manufacturer's instructions. Die hardener was applied to the remaining apart of the stone dies to prevent distortion of the die stone during water immersion and thermocycling.
Measuring of marginal discrepancy
The axial surfaces of all the provisional crowns were divided in to 3 equal parts so that the marginal discrepancy at 3 different points on each surface could be evaluated. A traveling microscope was used to assess the marginal discrepancy of each sample before subjecting them to water immersion and thermocycling.
10 samples of each group were stored under water at room temperature for 4 days to evaluate marginal discrepancy due to water absorption. The other 10 samples from each group were subjected to thermocycling for 2500 cycles between 5[degrees]C and 55[degrees]C with a dwell time of 5 seconds in each water bath . The difference in marginal discrepancy at the 3 points on each surface before and after water absorption and thermocycling were evaluated using a traveling microscope.
Data obtained in the present study is subjected to statistical analysis using one way ANOVA and inter group comparison is done using Student t test.
Mean marginal discrepancy of three provisional restorative crowns (pm) fabricated by using three different provisional restorative materials Group CCAR, Group PII, Group GC LCAR before and after thermocycling are 27.5 [+ or -] 18.5, 27 [+ or -] 16.8 and 7.25 [+ or -] 2.9 respectively. Statistical analysis using analysis of variance (ANOVA) test between three groups before and after thermocycling are tabulated in table 1. Statistical comparison (Students 't' test) for marginal discrepancy between three groups before and after thermocycling are tabulated in table 2.
Mean marginal discrepancy of three provisional restorative crowns (pm) fabricated by using three different provisional restorative materials Group CCAR, Group PII, Group GC LCAR before and after water immersion are 13.25 [+ or -] 7.4, 9.0 [+ or -] 5.2 and 4.75 [+ or -] 2.2 respectively. Statistical analysis using analysis of variance (ANOVA) test between three Groups before and after water immersion are tabulated in table 3. Statistical comparison (Students 't' test) for marginal discrepancy between three Groups before and after water immersion are tabulated in table 4.
Closed marginal adaptation of a provisional resin crown to the finish line of a prepared tooth protects the pulp from the thermal, bacterial and chemical inserts. In order to overcome from these insults materials for provisional restorations with improved physical properties are available and they are important because of the emphasis on the marginal accuracy of provisional restorations.
To establish the dimensions of initial marginal gap and changes after thermocycling was evaluated in the study, subjecting a provisional restoration to the thermocycling was felt necessary to simulate the oral conditions were provisional restorations are subjected to thermal changes [13,14,15]. The thermocycling regime which was followed in the study was 2500 cycles between 5[degrees]C and 55[degrees]C with a dual time of 5 seconds in each water bath because it is predicted on 2-5 seconds maximum intraoral exposure of tooth to the thermal extremes [4,16,17]. After this, tooth accommodates to intraoral temperatures (37[degrees]C). The effect of continuous / intermittent contact of provisional restorative crowns by intraoral fluids (saliva, fluid intakes) was evaluated by immersing the provisional restorative crowns in 37[degrees]C room temperature water bath for four days. It was also evaluated the effect of water compensating marginal leakage by expansion of provisional restorative crowns .
The samples in group CCAR, P-II and GCLC were cemented and observed the marginal discrepancy using travelling microscope before and after thermocycling and water immersion. Values were tabulated and converted into micrometers. The data were further subjected to statistical analysis and it showed that the maximum marginal discrepancy was found with cold cure acrylic resin and minimum with of GC light cure acrylic resin when the samples were subjected to thermocycling. The mean standard deviation was less for GCLC (7.25 [+ or -] 2.9) compared to CCAR (27.5 [+ or -] 18.4) and P-II (27 [+ or -] 16.7). It was observed that difference was significant between the three gropus F-value 6.3233 at P-value 0.0056 respectively when subjected to analysis of variance (ANOVA) test before and after thermocycling.
By statistical comparison (student's t-test), t-values, p-values between the groups CCAR and GCLC, t-value = 3.4986, p-value 0.0026 to be significant. Between groups CCAR and P-II, t-value = 1.4942, p-value 0.1524 to be not significant and between groups of GCLC and P-II, t-value = -2.3962, P-value 0.0276 to be significant. The marginal discrepancy between groups CCAR and GCLC, GCLC and P-II shows significant difference and no significant difference was found between CCAR and PII (figure 1). This is because difference in coefficient of thermal expansion between the material which mainly depends on chemical composition of material. It was found that the cold cure acrylic resin showed significant marginal discrepancy in direct technique used compared to the other provisional restorative materials . Similarly we were also found the same results with the coldcure acrylic resins used in indirect technique.
On the basis of statistical analysis it can inferred that effect of thermocycling on marginal integrity of cold cure acrylic resin was more compare to P-II and GCLC. The effect of thermocycling on marginal discrepancy of CCAR and PII found to be statistically insignificant. GCLC provided the best marginal integrity when subjected to thermocycling.
The maximum marginal discrepancy was found with cold cure acrylic resin and minimum with of GC light cure acrylic resin when the samples were immersed in water. It was found that the group GCLC (4.75 [+ or -] 2.1890) was having less mean marginal discrepancy when compared to CCAR (13.25 [+ or -] 7.3645) and P-II (9.0 [+ or -] 5.1640) after water immersion. From the analysis of variance (ANOVA) test there was a significant difference between the groups with F-value 6.3292 and P-value 0.0056 after water immersion.
The statistical comparison of values of marginal discrepancy (student's t-test) between groups CCAR and GCLC, GCLC and P-II to be significant between groups of CCAR and P-II marginal discrepancy values were statistically insignificant. Between the groups CCAR and GCLC, CCAR and P-II, GCLC and P-II the t-values was 3.4198, P-value 0.0031 and t-value 0.0633, P-value 0.9502, t-value -3.6635, p-value 0.0018 respectively. The presented data showed maximum marginal discrepancy with group CCAR and minimum with group GCLC (figure 2). On the basis of statistical anlaysis GCLC showed better marginal fit compare to cold cure acrylic resin (CCAR) and protemp-II (P-II) after water immersion.
The provisional restorative materials used in this study showed some marginal discrepancy before and after thermalcycling and water immersion But GC Light cure acrylic resin had a better fit when compared to Cold Cure acrylic resin and Protemp - II provisional restorative materials before and after thermocycling. This is because difference in coefficient of thermal expansion, between the material which mainly depends on chemical composition of material. The GC light cure acrylic resin had better marginal fit when compared to protemp - II and cold cure acrylic resin provisional restorative materials before and after water immersion.
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Subbarayudu Gudapati (1), Jagadish H.G. (2), Rama Krishna Alla (3), Suresh Sajjan (1), K. Ramya (4), D. Naveen (5)
(1) Department of Prosthodontics & Implontology, (3) Department of Dental Materials, Department of Oral Medicine & Radiology, Vishnu Dental College, Bhimavaram 534 202, Andhra Pradesh
(2) Department of Prosthodontics, School of Dental Sciences, Sharada University, Greater Noida 201306, Uttar Pradesh Department of Prosthodontics & Implontology, Aditya Dental College Beed, Beed 431122, Maharashtra
Corresponding author: Dr. Subbarayudu Gudapati. e-mail: firstname.lastname@example.org
Received 1 November 2013; Accepted 31 May 2014; Available online 1 June 2014
Table 1: Statistical analysis using analysis of variance (ANOVA) test between Group CCAR, Group GCLC and Group P-II before and after thermocycling Source of variation DF SS MSS Between materials 2 361.2500 180.6250 Within materials 27 771.2500 28.5648 Total 29 1132.5000 209.1898 Source of variation F-value P-value Significance Between materials 6.3233 0.0056 S Within materials Total S--Significant at 1% level of confidence Table 2: Statistical comparison (Students 't' test) for marginal discrepancy between Group CCAR, Group GCLC and Group P-II (n=10) before and after thermocycling Materials Mean Std. Dev. t-value CCAR 13.2500 7.3645 GCLC 4.7500 2.1890 3.4986 CCAR 13.2500 7.3645 P-II 9.0000 5.1640 1.4942 GCLC 4.7500 2.1890 P-II 9.0000 5.1640 -2.3962 Materials P-value Significance CCAR GCLC 0.0026 S CCAR P-II 0.1524 NS GCLC P-II 0.0276 S S - Significant at 1% level of confidence Table 3: Statistical analysis using analysis of variance (ANOVA) test between Group CCAR, Group GCLC and Group P-II before and after water immersion Source of variation DF SS MSS Between materials 2 2667.9167 1333.9583 Within materials 27 5690.6250 210.7639 Total 29 8358.5417 1544.7222 Source of variation F-value P-value Significance Between materials 6.3292 0.0056 S Within materials Total S - Significant at 1% level of confidence Table 4: Statistical comparison (Students 't' test) for marginal discrepancy between Group CCAR, Group GCLC and Group P-II (n=10) before and after water immersion Materials Mean Std. Dev. t-value CCAR 27.5000 184842 3.4198 GCLC 7.2500 2.9930 CCAR 27.5000 18.4842 0.0633 P-II 27.0000 16.7829 GCLC 7.2500 2.9930 -3.6635 P-II 27.0000 16.7829 Materials P-value Significance CCAR 0.0031 S GCLC CCAR 0.9502 NS P-II GCLC 0.0018 S P-II S--Significant at 1% level of confidence Figure 1: Mean and standard deviation of marginal discrepancy (im) between three provisional restorative crowns, using three different materials after thermocycling (Mean and Std. Dev.) Groups CCAR 13.25 7.3645 P-II 9 5.164 GCLCAR 4.75 2.189 Note: Table made from bar graph. Figure 2: Mean and standard deviation of marginal discrepancy (im) between three provisional restorative crowns, using three different materials after water immersion (Mean and Std. Dev.) Groups CCAR 27.5 18.4842 P-II 27 16.7829 GCLCAR 7.25 2.993 Note: Table made from bar graph.
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|Title Annotation:||Original Article|
|Author:||Gudapati, Subbarayudu; H.G., Jagadish; Alla, Rama Krishna; Sajjan, Suresh; Ramya, K.; Naveen, D.|
|Publication:||Trends in Biomaterials and Artificial Organs|
|Date:||Apr 1, 2014|
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