|Year : 2016 | Volume
| Issue : 1 | Page : 8-12
Effect of modified cementation technique on marginal fit and apical spread of excess cement for implant restorations: An in vitro study
Brijesh Patel, Vilas Patel, TR Ramesh, Aishwarya Soundharya
Department of Prosthodontics and Crown and Bridge, Narsinhbhai Patel Dental College and Hospital, Visnagar, Gujarat, India
|Date of Web Publication||12-Apr-2016|
Department of Prosthodontics and Crown and Bridge, Narsinhbhai Patel Dental College and Hospital, Visnagar, Gujarat
Source of Support: None, Conflict of Interest: None
Aim: To investigate and compare the vertical marginal discrepancy and spread of excess cement after cementation with modified cementation technique and conventional technique. Materials and Methods: Ten implant analogs with prefabricated standard abutments of similar dimensions were mounted individually in self-cure acrylic blocks subcrestally. Forty ideal metal coping specimens were prepared by conventional lost wax technique. Measurement of the marginal discrepancy at the implant-crown interface was done using a stereomicroscope before cementation. Abutment replicas (ARs) were prepared for twenty specimens using cast copings and pattern resin. All forty copings were cemented according to the following cementation techniques and cement types, with ten specimens in each group. (1) Group 1: Half filling (HF) cementation technique using provisional cement. (2) Group 2: HF cementation technique using permanent cement. (3) Group 3: AR technique using provisional cement. (4) Group 4: AR technique using permanent cement. Specimens were subjected to measurement of marginal discrepancy and spread of excess cement using stereomicroscope after cementation procedure. Data were analyzed using paired t-test and unpaired t-test. Results: AR technique showed significantly less marginal discrepancy (P = 0.000) and apical spread of excess cement (P = 0.002) than conventional HF technique. Provisional cement showed significantly more marginal discrepancy (HF-P = 0.000 and AR-P = 0.001) and less apical spread of excess cement (HF-P = 0.023 and AR-P = 0.002) and among both technique. Statistical Analysis: Unpaired t-test. Conclusion: An alternative technique of using AR is effective technique to prevent peri-implant diseases.
Keywords: Implant-crown cementation, marginal discrepancy, peri-implantitis, residual excess cement
|How to cite this article:|
Patel B, Patel V, Ramesh T R, Soundharya A. Effect of modified cementation technique on marginal fit and apical spread of excess cement for implant restorations: An in vitro study. J Dent Res Rev 2016;3:8-12
|How to cite this URL:|
Patel B, Patel V, Ramesh T R, Soundharya A. Effect of modified cementation technique on marginal fit and apical spread of excess cement for implant restorations: An in vitro study. J Dent Res Rev [serial online] 2016 [cited 2020 Apr 2];3:8-12. Available from: http://www.jdrr.org/text.asp?2016/3/1/8/180106
| Introduction|| |
There are constant efforts from implantologists to reduce crestal bone loss with respect to implant placement, implant selection, abutment contour, margin, and cementation procedure. While there are a variety of causes for crestal bone loss around dental implants, one iatrogenic cause is retained dental cement.  Wilson reported that excess dental cement was associated with signs of peri-implant disease in the majority (81%) of the cases. 
Hence, cementation procedure of implant restoration is the weak link when it comes to management of excess cement around the implant abutment junction. Presence of excess cement is difficult to remove in total in routine clinical practice. This excess may end up in plaque accumulation and acting as nidus for colonization of microorganisms resulting in peri-implantitis and crestal bone loss. ,,,
In natural dentition, gingival sulcus area is self-cleansing due to firm gingival attachment and presence of fluid. Whereas junction between tissue around the implant, neither firmly attached nor self-cleansing. As a result the flow of cement is not restricted and easily migrates apically; hence, it becomes empirical to remove all the cement. 
Often clinicians do not pay attention when it comes to details of accurate cementation protocols. A recent survey showed that clinician has used cements in excess than required cement, which could results in excess cement in the peri-implant area. This excess cement is very difficult to locate and remove completely. 
To overcome this problem, there is a need to adapt a cementation protocol which results in minimal or no excess cement. Solution to avoid this problem is to limit the amount of cement that is placed in the crown. A technique has been developed using a crown, spacer, and light body elastomer impression material to make an abutment replica (AR) that can be used to coat the inside of the crown with close to the 50 μ needed. Such replica is used just before cementation to remove excess cement.  AR in this study was made using pattern resin which offers advantage of accuracy due to rigid in nature.
In this study, the effect of such modified cementation protocol on marginal fit and apical spread of excess cement is evaluated.
| Materials and Methods|| |
Ten implant (MIS Implant) analogs of similar dimensions with standard abutment were embedded individually in self-cure acrylic (DPI, India) blocks leaving 4 mm from the abutment-implant junction. The access holes of abutments were sealed with Gutta-percha stick and flush with the occlusal surface of each abutment. Forty ideal metal copings were prepared by conventional lost wax technique. The internal surfaces of the copings were airborne-particle abraded with aluminum oxide for 15 s at 0.5 MPa and steam cleaned elastic orthodontic separator was placed at the cervical margin of abutment and low viscosity condensation silicone impression material (Oranwash - L, Zhermack) was injected around abutment to simulate peri-implant soft tissue. Once light body elastomer impression material was set separator was removed which created a sulcus around abutment to simulate natural condition [Figure 1].
|Figure 1: Specimen showing implant analog with abutment embedded in acrylic block with simulated peri-implant area using elastic orthodontic ring and light body elastomer|
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The prepared copings were tried and tested on the implant abutments for any gross errors and subsequently placed under pressure using stationary clamps. Vertical laser engraved marking passing from coping to analog was done on all four surfaces of copings. Distance between most distal points of mark was measured under stereomicroscope for vertical marginal discrepancy at selected four points of each crown.
Measurement of the marginal discrepancy at the implant coping interface was done under 50x magnification using a stereomicroscope Model SZX7, Olympus Corporation, Tokyo, Japan) before cementation.
To prepare AR, the small piece of Teflon tape was cut and placed into the internal surface of the coping. Coping with Teflon tape on the abutment was seated which adapted. Teflon tape to the internal surface of crown and would act as 50 μ spacer for cement then coping was carefully removed from abutment without disturbing the adaptation of tape. Then, ARs were fabricated by injecting pattern resin inside the copings for twenty specimens, which were belonged to AR group. Remaining twenty specimens were cemented using conventional half filling (HF) technique.
Further specimens were divided according to types of cements, two type of cements including Eugenol-free temporary cement (Freegenol - GC Europe, leuven) and more retentive glass ionomer cement (GIC) (GC Fuji I, GC Co., Tokyo, Japan) were used in this study.
- Group 1: HF cementation technique using provisional cement
- Group 2: HF cementation technique using permanent cement
- Group 3: ARs technique using provisional cement
- Group 4: ARs using permanent cement.
Cement and cementation
Two types of luting agents including Eugenol free temporary cement (GC Freegenol - GC EUROPE) and more retentive glass ionomer (GC Fuji I, GC Co., Tokyo, Japan) were used in this study.
The cement was mixed following the manufacturer's instructions. Cement will applied on the internal surface of the crown with a brush.
The manufacturer's specifications for proper mixing times and ratios were carefully followed.
- Group 1 (HF): Half filling of the crown: For this group, cement was applied on the apical half of the axial walls of the crown
- Group 2 (AR): Abutment replica technique [Figure 2].
For this group, copings half filled with cement seated on the corresponding AR fabricated with pattern resin to thinly coat the internal surfaces of the crown just before seating the restoration on the abutment within initial setting time of cement.
The excess cement around the crown margin was then carefully removed using a stainless steel explorer.
Cement was applied to each crown, and after seating, the crowns were put under constant load (80 N) for 10 min with laboratory clamps. After cementation specimens were preserved for 24 h at room temperature.
Next day, light body elastomer material was removed to inspect the area of interest. Each crown-abutment assembly was observed via a stereomicroscope set at ×25, which was attached to a PC that ran an image program capable of linear measurements (SImage). To evaluate marginal discrepancy, the distance between most distal point of the mark was measured under stereomicroscope at previously selected four points of each crown. Previous value is deducted from this new value to calculate marginal discrepancy due to cement [Figure 3].
Apical spread of excess cement
Inspection of apical spread of excess residual cement was done at the abutment-crown interface under ×25 magnifications using a stereomicroscope after cementation. Distance from crown margin to maximum apically spread cement was measured from all four surface, and mean was calculated to determine apical spread of excess cement [Figure 4].
After every test cycle was completed, each abutment was placed in a cement-removal solution for 15 min in an ultrasonic bath. They were then dried and observed under the microscope to ensure complete cement removal. After no cement was visible, both the abutment and crown were steam-cleaned, placed in an ultrasonic bath of distilled water 5 min, and dried. Abutment pair was recemented with other luting agents and technique under the above-described conditions to give a total of ten samples for each group. A similar procedure was used in a previous study as an effective way to conserve supplies with no loss of scientific validity.
| Results|| |
Collected data were tabulated and analyzed using SPSS 17 software (SPSS Inc., Chicago, IL, USA).
Results of [Table 1] represents mean marginal discrepancy and mean apical spread of residual excess cement. Results of unpaired t-test [Table 2] indicate that AR technique also showed significantly less marginal discrepancy [Graph 1] compared to HF technique (P = 0.002) and significantly less apical spread of excess cement [Graph 2] than HF technique (P = 0.000).
|Table 1: Mean apical spread of excess cement and mean marginal discrepancy of all four group|
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Results of [Table 3] and [Table 4] represent a comparison of provisional cements and permanent cements among both groups. This indicates that permanent cement has significantly less marginal discrepancy than provisional cement, whereas comparing apical spread of excess cement and permanent cement showed significantly less apical spread of excess cement.
|Table 3: Comparison of provisional and permanent cementation using half filling technique using unpaired test|
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|Table 4: Comparison of provisional and permanent cementation using abutment replica technique using unpaired test|
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| Discussion|| |
Residual cement around crown abutment junction is associated with peri-implant diseases. To prevent this problem, a modified technique is advocated by authors in which AR made up of silicone elastomer impression material is used to remove excess cement just before cementation. In this study, pattern resin AR was fabricated to avoid inaccuracy due to flexibility of silicone.
Results of this study showed that AR technique showed less marginal discrepancy and less apical spread of excess compared to apical HF technique for implant retained crowns. While using AR technique, uniform layer of luting cement was distributed over the interior surface of crown and excess cement removed along with AR that minimum spread of residual cement was found. Due to excess amount of cement hydraulic pressure generated which leads to the marginal discrepancy which can be avoided using AR technique.
Spread of residual cement was more in permanent cement compared to provisional cement which can be attributed to their flow properties. While comparing type of cement, provisional cement produced more marginal discrepancy compared to permanent cement which can be due to difference in film thickness of GIC (22-24 μ) and Freegenol (40 μ). 
Choice of cement for implant retained restoration should be based on retrievability of prosthesis and ease of excess cement removal. Spread of residual cement was more in permanent cement compared to provisional cement which can be attributed to their flow properties. Many clinicians prefer to use provisional cement of implant cement prosthesis; however, these cements provide less retention and are soluble, and these cements wash out in the oral cavity leaving a gap at the margin of the restoration and thereby risking peri-implant health.
The importance of postoperative appointments for implant patients following cementation of the restoration cannot be overemphasized. Ideally, the first postoperative visit should be scheduled no later than 1 week after cementation of the restoration to detect early changes or reactions of the peri-implant tissues.
Dentists should be made aware of the differences between implants and teeth. Because their peri-implant biology is not the same, the appropriate cementation techniques and suitable cement selections are different. Alternative cementation technique of using AR can be useful to prevent postcementation peri-implant disease.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]