Dr. Tarana Raghani, Dr. Praveen Badwaik, Dr. Shruti Gill, Dr. Vishrut Bhatnagar, Dr.Prashant Patil, Dr.Sailee Bhogwekar
Post-graduate Student
Professor,
Asso. Professor,
Asst. Professor,
Department of Prosthodontics, Crown & Bridge.,
T.P.C.T’s Terna Dental College, Navi Mumbai
ABSTRACT
Background: Provisional cementation in cases like full mouth rehabilitation and implants needs longterm retention as well as repeated and clean retrieval of the prosthesis. Selecting an appropriate provisional luting agent is important.
Aim: The aim of this study is to comparatively evaluate the retention of the metal copings cemented with three different provisional luting agents
Materials and Methods: 15 Freshly extracted human first premolars were prepared to receive cast metal copings. Copings were evaluated for adequate fit on the teeth using a Stereomicroscope. The fifteen copings were cemented on fifteen prepared extracted teeth in three groups (five in each group). Group I castings were luted with zinc oxide eugenol free carboxylic acid based provisional luting cement (Prime Dental Templute), Group II castings luted with zinc oxide polymethyl siloxane based provisional luting cement (ColteneTempoSIL® 2), and Group III castings luted with zinc oxide polyvinyl siloxane based provisional luting cement (Prime Dental Temp-Sil). The Tensile strength was evaluated using a Universal Testing Machine by applying a tensile load which was increased till the coping was debonded. After first round of testing, the three groups were cemented with other two cements for the second and third rounds of testing, which were performed in the same manner.
Results: The mean tensile strengths of zinc oxide eugenol free carboxylic acid based provisional luting cement (Prime Dental Templute) is 2.985 Mpa, zinc oxide polymethyl siloxane based provisional luting cement (ColteneTempoSIL® 2) is 1.943 Mpa and zinc oxide polyvinyl siloxane based provisional luting cement (Prime Dental Temp-Sil) is 2.069 Mpa.
Conclusions: The Tensile strength of zinc oxide eugenol free carboxylic acid based provisional luting cement (Prime Dental Templute) is the highest, followed by zinc oxide polyvinyl siloxane based provisional luting cement (Prime Dental Temp-Sil)aand zinc oxide polymethyl siloxane based provisional luting cement (ColteneTempoSIL® 2).
Citations: Raghani T, Badwaik P, Gill S, Bhatnagar V, Patil P, Bhogwekar S. A comparative evaluation of the retention of metal copings cemented with different provisional luting agents – an in vitro study. J Prosthodont Dent Mater 2021;2(2) 46-54.
INTRODUCTION
In Fixed Prosthodontics, the provisional prosthesis and/or provisional cementation of definitive prosthesis govern the success of permanent cementation of definitive prosthesis. Retention is one essential parameter that may affect the success of long-term provisional cementation. The provisional cementation should intend to retain the teeth in a stable position, as well as ensure clean and easy retrieval. The addition silicone based luting agent show easy and clean retrieval, less marginal microleakage and improved bond strength,1 which are desired properties for long term provisional cementation. However, their retentive strength needs to be evaluated. Thus, this study was planned to comparatively evaluate the retentive strengths of eugenol free and addition silicone based provisional luting agents.
METHOD
I) Preparation of Samples
1. Mounting of teeth
This study was conducted on Fifteen human maxillary first premolars. Teeth were placed in 0.2% Thymol solution (PubChem, US) in a closed container, for disinfection for seven days.The teeth were mounted in an acrylic fixture by submerging the root portion into the acrylic (Autopolymerising acrylic resin - Acralyn “R” Asian Acrylates, India) such that the CEJ of the anatomic crown was 1 mm above the acrylic. The teeth mounted in the acrylic fixture was placed in artificial saliva.
2. Preparation of teeth
The tooth preparation was carried out with a diamond bur attached to Airotor handpiece on a surveyor (Figure 1). The occlusal surface was made flat. The axial height of 4 mm and 20- degree convergence angle (each axial wall with 100 taper bur)2, was achieved with chamfer margin of 1mm. This was done for all the fifteen extracted teeth. After preparation, the teeth were again stored in artificial saliva.
3. Fabrication of the metal copings
Custom trays were fabricated for all fifteen samples and impressions were made using medium body impression material(Aquasil Ultra MonophaseDentsply Sirona HQ, North Carolina, USA) and poured in die stone(Kalabhai Ultra Rock Class 4- Kalabhai Karson Pvt Ltd, India). The dip in wax method was used to fabricate the wax pattern by dipping the tooth in molten wax and then taking it out to allow the wax to set. Patterns were invested using Phosphate bonded investment material (Bego sol- Bego,Germany) and casted with Nickel-Chromium alloy (Ruby Max White Ruby dental products Japan). After the initial fitting procedure was carried out, they were evaluated for adequate fit on the teeth using a stereomicroscope (Figure 2).
4. Provisional Cementation of Metal copings
The 15 samples were divided into a group of three, with five samples in each group. Group I samples were luted withzinc oxide eugenol free carboxylic acid based provisional luting cement (Prime Dental Templute)(Figure 3a) Group II samples were luted with zinc oxide polymethyl siloxane based provisional luting cement (ColteneTempoSIL® 2)(Figure 3b) Group III samples were luted with zinc oxide polyvinyl siloxane based provisional luting cement (Prime Dental Temp-Sil) (Figure 3c) All fifteen samples with luted crowns (Figure 4) were stored at 37°C at 100% relative humidity in a humidifier for 48 hours before testing.
II) Testing of Samples
Three rounds of testing were performed on 15 samples divided in three groups: five in each group to eliminate probability of biasdue to variance in preparations of extracted teeth and fabrication of metal copings.
1. First round of testing
The fifteen ready samples were removed from the humidifier. One by one, they were placed in the base clamp fastened on the universal testing machine. A hook was placed in the opposing clamp. Each sample was aligned such that the hook passed through the metal loop attached to the occlusal surface of the metal coping. (Figure 5) A tensile load was applied and was increased till the coping was debonded. All fifteen samples were subjected to the above testing. After the testing of the 15 samples, the residual cement was scrapped with the help of hand instrument (excavator) followed by ultrasonic cleaning and sandblasting, and the prepared teeth were scaled with an ultrasonic scaling unit again. A latch type polishing brush mounted in a contra-angle hand piece attached to a micromotor was dipped in a dappen dish filled with Medicept Protec dental prophylactic polishing paste and was used for polishing all surfaces of the teeth for 30 seconds each to remove the residual cement from the prepared tooth. The debris was rinsed with water from a three-way syringe.
2. Second round of testing
Group I samples were luted with zinc oxide polymethylsiloxane based provisional luting cement (ColteneTempoSIL® 2). Group II samples were luted with zinc oxide polyvinyl siloxane based provisional luting cement (Prime Dental Temp-Sil). Group III samples were luted with zinc oxide eugenol free carboxylic acid based provisional luting cement (Prime Dental Templute). All the fifteen samples were subjected to the second round of testing in the same manner. After the second round of testing, all the copings and the prepared teeth were cleaned in the same manner.
3. Third round of testing
Group I samples were luted with zinc oxide polyvinyl siloxane based provisional luting cement (Prime Dental Temp-Sil). Group II samples were luted withzinc oxide eugenol free carboxylic acid based provisional luting cement (Prime Dental Templute). Group III samples were luted withzinc oxide polymethyl siloxane based provisional luting cement (ColteneTempoSIL® 2). All the fifteen samples were subjected to the third round of testing in the same manner.
Fig. 1 Tooth Preparation
Fig. 2 Evaluation of initial fitting using stereo microscope
Fig. 3a. Luting with Prime Dental Templute
Fig. 3b. Luting with ColteneTempoSIL 2
Fig. 3c. Luting with Prime Dental TempSil
RESULTS
The tensile strength of each sample was calculated from the load applied on a Universal Testing Machine with crosshead speed of 0.5 mm per second. The values were taken up to three decimal digits and tabulated (Tables 1, 2 and 3).The mean tensile strength of each group was calculated (Graph 1).The mean tensile strengths of group 1 - zinc oxide eugenol free carboxylic acid based provisional luting cement (Prime Dental Templute)is 2.985 Mpa, group 2 - zinc oxide polymethylsiloxane based provisional luting cement (ColteneTempoSIL® 2) is 1.943 Mpa and group 3 - zinc oxide polyvinyl siloxane based provisional luting cement (Prime Dental Temp-Sil) is 2.069 Mpa.
The distribution in the boxplot (Graph 2) indicates that for group 1, the mean and the median are approximately coinciding. There are no outliers present. For Group 2, the median is shifted slightly above the mean. There are no outliers present.For Group 3, the median is skewed towards the first quartile. However, it lies within the IQR (Interquartile range). There are no outliers present. The skewness ratio in table 4 is used as a test of normality.
One-way ANOVA test is applied. The F-stat value (41.1592) and the P-value (<0.00001) denotes that the data is statistically significant (Table 5).
To identify which pair of groups differs statistically significant from each other in terms of Mean Tensile Strength, Scheffe’s multiple comparisons test was applied (Table 6).The first comparison, between groups 1 and 2 shows mean difference of 1.042 with p value (<0.001). This reveals the difference between the tensile strengths of group 1and group 2is statistically significant. The second comparison, between groups 1 and 3 shows mean difference of 0.914 with p value (<0.001). This reveals the difference between the tensile strengths of group 1 and group 3 is statistically significant. The third comparison between groups 2 and 3 shows mean difference of 0.128 and p value (0.5673) indicates that the difference between the tensile strengths of group 2 and group 3 is statistically insignificant.
Table-1: Tensile Strength for Group I zinc oxide eugenol free carboxylic acid based provisional luting cement (Prime Dental Templute)
Graph-1: Mean Tensile strength comparison of the retention of metal copings (MPa)
Graph-2: Box Plots for Tensile Strengths (MPa)
DISCUSSION
Biologically acceptable fixed prosthodontic treatment demands that the prepared teeth are to be protected and stabilized by a provisional cementation of the provisional or definitive restoration till the final cementation of the definitive restoration. Long term provisional cementation is more susceptible to cement washout and thereby resulting in documentation of the prosthesis. So provisional luting agents should have good mechanical and retentive properties for the success of a long-term provisional cementation. Most of the studies done to evaluate the retentive values of provisional cements are done with evaluating retention of provisional crowns made up of self-curing acrylic resin, heat cured acrylic resin, Bis-GMA or CADCAM made provisional crowns.
The present in vitro study was designed to comparatively evaluate the retention of Nickel chromium metal copings cemented with eugenol free provisional luting agent and addition silicone based provisional luting agents to mimic the clinical scenarios in which tooth supported definitive prosthesis or implant cement retained prosthesis are cemented with provisional luting agents3. The study performed by Mariana Riberio de et al4 showed that, zinc oxide eugenol containing provisional luting agents were more retentive results than eugenol free provisional luting agents. However, the study by Olin et al3 found different results. They showed that eugenol free provisional luting agents (Nogenol and Freegenol) presented higher retentive values than zinc oxide eugenol containing provisional luting agents (Temp Bond).
In the present study, all three provisional luting agents used are eugenol free cements, one is carboxylic acid based and the other two are addition silicone based provisional luting agents. From the results of the present study, which was performed on Nickel-chromium metal copings cemented with provisional luting agents, we observe that the eugenol free provisional luting agent shows significantly higher retentive value than additional silicone based provisional luting agents.
This observation is in accordance with the study by Nathaniel et al5 which evaluated the retention of Rexillium III (aluminum, beryllium, chromium, cobalt, molybdenum, nickel, titanium) castings cemented with provisional cements, and showed that the eugenol free provisional luting agent (Temp Bond NE) shows higher retentive values than addition silicone based provisional luting agent (TempoSIL). Both the studies were performed on extracted teeth and the tensile strength was tested using universal testing machine. The sample size was 10 for the study by Nathaniel et al and the sample size is 15 for the present study. In both the studies, same tooth/crown pairs were used with each luting agent i.e. the specimens were recemented in the same manner using each provisional luting cement until all the cements were tested. Although the studies show variation in the casting alloys, the conclusions are in correspondence.
Rego M et al6 has ascertained the mean tensile strength values of four commercially different eugenol free provisional luting agents; Nogenol, Freegenol, TempBond NE and Provicol as 20.1, 31.0, 33.8 and 36.3 in Newtons respectively. The present study shows the mean tensile strength of eugenol free provisional luting agent as 35.75 Newtons. Although their study was conducted on provisional crowns made with self-curing acrylic resin and the present study is done on Nickel-chromium metal copings and the results are comparable. This indicates the commercially available brands present different physical properties, which might be due to the different compositions of the evaluated provisional luting agents, as proposed by Olin PS et al3.
Pan Y H et al7 conducted a pilot study on castings cemented to Steri-Oss abutment/ analog assemblies with provisional cements and found out that cement failure load for a eugenol free provisional luting agent (TempBond NE) is at 40.8 Newtons, which is comparable to the present study’s result of break load for eugenol free provisional luting agent (Templute) as 35.75 Newtons. Even though there is difference in the samples (Steri Oss abutment/ analog assemblies of brass cylinders and prepared extracted teeth) and the commercial brands of eugenol free provisional luting agents (Temp Bond NE and Templute), the results are comparable.
To further compare retentive strengths of eugenol free luting agent with zinc phosphate cement on natural teeth, we compare the present study with an in vitro study by Sreeramulu B et al8. Both the studies are conducted on Nickel Chromium copings cemented on prepared extracted teeth and tensile strengths were tested in the similar manner using the similar apparatus. Sreeramulu B et al showed retentive strength value of zinc phosphate cement as 4.23 Mpa. The present study shows retentive strength value of eugenol free provisional luting agent as 2.98 Mpa. Hence, it can be concluded that zinc phosphate cement shows significantly higher retention than eugenol free provisional luting agent.
CLINICAL SIGNIFICANCE
From the results of the present study, it can be suggested that when long term provisional cementation is required, Eugenol free provisional luting agent should be preferred over addition silicone based provisional luting agents. When there is a need for repeated provisional cementation and easy and clean retrievability is required, polymethylsiloxane and polyvinylsiloxane based provisional luting agents can be used.
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