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An in vitro investigation comparing methods of minimizing excess luting agent for cement-retained implant-supported fixed partial dentures
RESEARCH AND EDUCATION
An in vitro investigation comparing methods of minimizing excess luting agent for cement-retained implant-supported fixed partial dentures Sarah A. Bukhari, BDS, MS,a Abdulaziz AlHelal, BDS, MS,b Mathew T. Kattadiyil, BDS, MDS, MS,c Chandur P. K. Wadhwani, BDS, MSD,d Abdulrahman Taleb, BDS,e and Salem Dehom, MPHf Cement-retained implantABSTRACT supported prostheses are Statement of problem. The use of cement-retained implant-supported prostheses is a widely accepted as a good well-established treatment option. Techniques have been proposed to reduce the amount of 1 ,2 treatment option because of residual excess cement (REC) around cement-retained single-implant restorations. However, their passive fit, excellent esstudies evaluating the effectiveness of such techniques related to cement-retained implantthetics, and adaptability to supported fixed partial dentures (CRISFPDs) are lacking. situations where the implant Purpose. The purpose of this in vitro study was to evaluate the effectiveness of various cement placement is less than ideal.3-5 application techniques for CRISFPDs. However, residual excess Material and methods. Two implant analogs were placed in the lateral incisor sites in a maxillary, cement (REC) and the diffi3D printed cast with 4 missing incisors. Twenty standardized, removable, printed soft-tissue replicas, culty associated with its 40 milled titanium custom abutments, and 20 milled zirconia CRISFPDs were fabricated. Two detection and removal have cement application techniques, the brush on technique (BOT), and the polyvinyl siloxane index been major limiting factors for (PI) technique were compared. Two cementation techniques, without bib (control) (n=10) and with a polytetrafluoroethylene (PTFE) bib (test) (n=10), were used. A premeasured amount of this type of prosthesis.6-8 interim cement was used to cement the CRISFPDs. The CRISFPDs were retrieved after REC has been linked with cementation, and standardized photographs of 4 quadrants of each abutment-CRISFPD assembly peri-implant disease, bone were made by using a software program that is used to calculate the ratio between the area 9-16 resorption, and implant loss. covered with REC and the total specimen area. The extension of the REC on both the abutment Some of the factors that inand soft-tissue replica was measured at sites before and after cleaning the REC. A generalized fluence the amount of REC linear mixed-model procedure was used for statistical analysis (a=.05). include the location of the Results. For cement application, the polyvinyl siloxane (PVS) index technique had significantly less abutment margin7 and the REC than the brush on technique (P<.05). The use of a PTFE bib led to significantly less REC than 17 cementation technique. when no bib was used (P<.05). Linkevicius et al7 studied the Conclusions. The use of the PVS index technique along with a PTFE bib was effective in reducing amount of REC after cemenREC for CRISFPDs. (J Prosthet Dent 2019;-:---) tation and the subsequent cleaning of implant-supported restorations at various amount of REC after attempted cement removal depths and configurations of the abutment margin. The increased for the more subgingival restorations.
a
Assistant Professor, Division of General Dentistry, Loma Linda University School of Dentistry, Loma Linda, Calif. Assistant Professor, Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia. Professor and Director, Advanced Specialty Education Program in Prosthodontics, Loma Linda University School of Dentistry, Loma Linda, Calif. d Adjunct Assistant Professor, Advanced Specialty Education Program in Prosthodontics School of Dentistry, Loma Linda University, Loma Linda, Calif. e Graduate student, Advanced Specialty Education Program in Prosthodontics, University of Southern California, Los Angeles, Calif. f Assistant Professor, Loma Linda University School of Nursing, Loma Linda, Calif. b c
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Clinical Implications Clinicians should consider a cementation protocol such as the PVS index technique along with a PTFE bib for CRISFPDS to reduce the amount and extent of excess cement.
Wadhwani et al18 reported on 3 cement application techniques when luting implant-supported crowns. They stated that most of the participants surveyed (54.7%) used the brush on technique, where the cement was painted on the intaglio surface of the crown. Chee et al17 reported that the least amount of excess cement was observed when a putty index was formed to the configuration of the internal form of the crown to be cemented and used as a precementation extrusion device. The study reported that higher amounts of residual cement were noted with the brush on technique.17 Different techniques have been described that protect the soft tissue from excess cement, including the use of polytetrafluoroethylene (PTFE) tape19 or rubber dam,20 a
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putty index, and vent holes.21-23 However, the authors are unaware of studies evaluating the effectiveness of the PTFE bib and cementation techniques in reducing REC around CRISFPDs. The purpose of this study was to evaluate the effectiveness of the PTFE implant bib technique24 in reducing REC during CRISFPD cementation by using 2 different cement application techniques. The null hypotheses were that no difference would be found in the amount of REC on the abutment or the soft-tissue replica between the control (no bib) and the test groups (with PTFE bib) for CRISFPDs and that no difference would be found in the amount of REC with 2 different cement application techniques for CRISFPDs. MATERIAL AND METHODS A dentate maxillary cast was scanned (Fig. 1A), and the 4 anterior teeth were digitally removed (Fig. 1B). Using a computer-aided design (CAD) software program (Dental System; 3Shape), a virtual 4-unit CRISFPD was designed with ovate pontics replacing the maxillary central incisors. The CRISFPD abutments for maxillary lateral incisors were designed for Nobel Replace narrow platform (3.5 mm)
Figure 1. A, Maxillary cast. B, Scanned maxillary cast before and after trimming teeth and virtually designing soft tissue. C, Printed maxillary cast with implant analogs. D, Printed maxillary cast and soft-tissue replica.
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Figure 2. A, Occlusal and frontal view of scanned maxillary cast showing virtual design of abutments. B, Frontal view of printed maxillary cast showing titanium abutments in area of maxillary lateral incisors. C, Frontal view of printed maxillary cast showing milled zirconia CRISFPD. D, Virtual design of CRISFPD showing reference line for probe measurements of REC and indentation for CRISFPD retrieval. E, Lingual view of zirconia CRISFPD showing reference line for probe measurements of REC and indentations for CRISFPD retrieval. CRISFPD, cement-retained implant-supported fixed partial denture.
internal connection implants (Nobel Replace Select Tapered; Nobel Biocare). The 20 identical, 1-piece softtissue replica designs that included identical right and left sides followed the contour of the abutments. Analogs were designed virtually to be placed 2 mm from the representative buccal bone margin, 2 mm apical to the midfacial gingival margin, and 1.5 mm from the adjacent canines.25,26 From the digital scan, a master cast was fabricated by using a 3D printer with standard white resin (Form 2;
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Formlabs) (Fig. 1C). The soft-tissue replicas around the CRISFPDs were printed by using Formlabs flexible gray resin (Form 2; Formlabs) (Fig. 1D). From the master model, custom abutments were virtually designed (Fig. 2A) and fabricated in titanium (Ti) by using a computer-aided manufacturing (CAM) process (Fig. 2B). The custom abutments had a 1-mm subgingival finish line at the facial and interproximal areas, transitioning to an equigingival finish line on the lingual surfaces. The
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(Temp-Bond) 1 Maxillary cast 20 CRISFPDs 40 Custom abutments
Brush on technique 10 Soft tissue replicas 10 CRISFPDs 20 abutments
Control No Bib 10 abutments
Test PTFE Bib 10 abutments
PVS index technique 10 Soft tissue replicas 10 CRISFPDs 20 abutments
Control No Bib 10 abutments
Test PTFE Bib 10 abutments
Figure 3. Schematic diagram of study material and methods. CRISFPD, cement-retained implant-supported fixed partial denture; PTFB, polytetrafluoroethylene.
custom abutments were designed and fabricated to be 0.2 mm smaller than the soft-tissue replicas. This resulted in a space between the custom abutment and the soft-tissue replica, simulating the gingival sulcus around a dental implant. CAD-CAM (Vericore ZR HT A1 Disc w/ collar; Whip Mix Corp) was used to fabricate zirconia (Zir) CRISFDPs (Fig. 2C). Fiducial marks 1-mm coronal to the margin (Fig. 2D, 2E) of the restoration provided a reference for measuring the subgingival extension of the REC. An indentation was added virtually on the lingual surface of both retainers to aid in the retrieval of the CRISFPDs (Fig. 2D, 2E). Each group consisted of 10 CRISFPDs and 20 Ti custom abutments (Fig. 3). The Zir CRISFPDs were cemented by using zinc oxide-eugenol cement (Temp-Bond; Kerr Corp), following the manufacturer’s instructions. Two different cement application techniques were used to apply the luting agent to the intaglio surface of the CRISFPD retainers: BOT and PI. For BOT, a predetermined volume of the mixed cement was used to coat the entire intaglio surface of the retainers with a microbrush (Micro Disposable Applicator; PLASDENT Corp) (Fig. 4A). For the PI technique, a polyvinyl siloxane (PVS) analog of the custom abutment was fabricated and used to control cement volume (Fig. 4B).22 Each CRISFPD was seated by a single operator (S.B.) by using finger pressure to mimic the cementation protocol.8 The interim cement was allowed to set for 4 minutes before the CRISFPD was removed to determine the amount and extent of the REC. The CRISFPD was replaced on the abutments, and the screws were handtightened. The implant bib was removed with cotton pliers. The REC was removed by 1 operator (A.A.) by using a stainless-steel explorer (#2H Double End Explorer; Hu-Friedy), followed by dental floss (ESSENTIAL Floss; Oral-B) and superfloss (Super Floss; Oral-B).8 THE JOURNAL OF PROSTHETIC DENTISTRY
Figure 4. A, Zirconia CRISFPD showing BOT. B, Frontal view showing titanium abutment and PVS replica. C, Occlusal view of maxillary cast showing bib application around abutment in area of maxillary left lateral incisor. BOT, brush on technique; CRISFPD, cement-retained implantsupported fixed partial denture; PVS, polyvinyl siloxane.
To compare REC with the use of a PTFE bib for cementation with no bib, the implant in the maxillary right lateral incisor region, where no bib was used, served as the control. The maxillary left lateral incisor region was used as the test, where a 2- to 3-cm-long PTFE tape with a thickness of 100 mm (UL yellow gas line tape; Seal Tape Inc) was used. With a rubber dam punch, a hole was created in the center of the PTFE tape, the implant Bukhari et al
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Figure 5. A, Maxillary cast showing drilled holed for prosthesis retrieval. B, Retrieved abutment-CRISFPD assembly mounted on device. C, Total surface area of abutment-CRISFPD assembly marked.
abutment was inserted into the hole, and the tape was moved gingivally and close to the margin without entrapment at the abutment-implant interface. The abutment was fixed onto the implant analog by handtightening (Fig. 4C). After cementation, a hole was made through the screw site indentations on the lingual surface, and then the abutments were unscrewed (Fig. 5A) and examined (Fig. 5B). A digital single-lens reflex camera (Nikon D610; Nikon) was used to obtain the photographs. The specimens were mounted on a device in a standardized Bukhari et al
manner to maintain a 16-mm distance between the camera and the restoration.7 All 4 sides (mesial, distal, facial, and lingual) of each abutment-CRISFPD assembly were photographed. The images were then imported and analyzed by using a photo-editing software program (Adobe Photoshop CC; Adobe Systems Ltd). Each surface area of the prosthesis was marked with the “drawing tool” to outline the boundaries of each side. The area covered with REC on each of the 4 sides (mesial, distal, facial, and lingual) was calculated by using the “pen tool” and “make path” options. The total THE JOURNAL OF PROSTHETIC DENTISTRY
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Figure 5. (continued) D, Area covered with REC marked. E, Probe measurement from reference line on CRISFPD. CRISFPD, cement-retained implantsupported fixed partial denture; REC, residual excess cement.
surface area for each side was marked, and the number of pixels representing the surface area was recorded from the histogram (Fig. 5C). The same method was
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applied to the area covered with REC (Fig. 5D). The ratio of the combined total surface area to the REC covered area was then calculated for every abutment-CRISFPD
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Table 1. Scoring criteria for subgingival extension of REC
Table 2. Surface area covered by REC on abutments Before Cleaning
After Cleaning
Pc
Means (95% CI)a,b
Means (95% CI)a,b
Group Effect Interaction
0
No excess cement
1
Excess cement extended >0-0.5 mm subgingivally
2
Excess cement extended >0.5-<2 mm subgingivally
Cement Application Technique
3
Excess cement extended 2 mm or more subgingivally
BOT_no Bib
45.94 (25.61, 82.43) 14.38 (9.56, 21.61) <.001
BOT_Bib
52.58 (29.31, 94.35) 6.86 (4.56, 10.31)
PVS Index_no Bib 14.44 (8.05, 25.89) PVS Index_Bib
Table 3. Surface area covered by REC on soft-tissue replica Cement Application Technique BOT_No Bib
Before Cleaning
After Cleaning
Means (95% CI)a,b
Means (95% CI)a,b
P
2.09 (1.14, 3.84)
1.80 (1.22, 2.65)
PVS Index_No Bib
6.44 (3.28, 12.64)
1.83 (1.09, 3.09)
PVS Index_Bib
1.36 (0.92, 2.02)
1.28 (0.93, 1.75)
1.6 (1.07, 2.41)
Estimated means. bLog transformed variable was used in the analysis. cBonferroni adjustment.
Group Effect Interaction <.001
a
Estimated means. bLog transformed variable was used in the analysis. cBonferroni adjustment.
assembly to determine the percentage of the surface covered with REC.7 For the soft-tissue replica, the REC was evaluated in a similar manner. A periodontal probe (#15 UNC; Hu-Friedy Qulix) was used to measure the subgingival extension of the REC. The engraved line on the CRISFPD retainers was used as a reference point (Fig. 5E). The 4 sides of the abutment and the soft-tissue replica were evaluated, and scoring criteria (Table 1) were used to assess the extent of the REC. A statistical software program (SAS, v9.4; SAS Institute Inc) was used for data analysis. To determine whether different techniques resulted in differences in REC, the generalized linear mixed-model procedure was used to analyze the effect of the method type, time (before and after cleaning), and method type × time interaction on the abutment and gingiva (soft-tissue replica) scores. ANOVA tests using the Bonferroni adjustment for multiple comparisons were used. As the normality assumption was not met using the original scores, log-transformed variables were used for both outcomes. A constant value of 1 was added to all specimens to adjust for the zero values. RESULTS For the brush on technique (BOT) before cleaning, the amount of REC on the abutment immediately after cementation (Table 2) was found to be significantly lower (P<.05) with no bib (Fig. 6A, 6B), whereas in the softtissue replica (Table 3), significantly less REC (P<.05) was found when the PTFE bib was used (Fig. 6C, 6D) For the PVS index (PI) technique before cleaning, the REC evaluated immediately after cementation was found to be significantly lower (P<.05) with bib for both the abutment and soft-tissue replicas (Tables 2 and 3). In both cement application techniques, lower REC (P<.05) was found with PI whether a bib was used or not (Fig. 6A, 6B). Bukhari et al
2.74 (1.82, 4.11)
a
c
39.61 (33.58, 46.71) 11.27 (9.41, 13.48) <.001
BOT_Bib
2.89 (1.61, 5.18)
<.001
Table 4. Number of surfaces involved with each technique at both evaluation intervals for abutment Evaluation Before cleaning
After cleaning
Number of Surfaces Involved
BOT (%)
PVS Index (%)
No Bib
Bib
No Bib
Bib
0
0.0
0.0
0.0
40.0
1
0.0
0.0
40.0
40.0
2
0.0
10.0
40.0
0.0
3
20.0
10.0
20.0
20.0
4
80.0
80.0
0.0
0.0
0
0.0
0.0
20.0
50.0 40.0
1
0.0
20.0
50.0
2
30.0
60.0
30.0
0.0
3
20.0
0.0
0.0
10.0
4
50.0
20.0
0.0
0.0
For the BOT after cleaning, the REC evaluated on the abutment (Table 2) and soft-tissue replica (Table 3) was found to be significantly lower with bib (P<.05). With the PI technique after cleaning, no significant difference in REC was found between the 2 groups (with and without bib) for both the abutment and soft-tissue replicas (P>.05). Significantly lower REC (P<.05) was observed on the abutment after cleaning with the PI technique than with BOT in both groups. The use of the bib revealed no significant difference regarding REC between the 2 cement application techniques (PI and BOT) on softtissue replicas after cleaning (Fig. 6C, 6D). Probe measurements for the subgingival extension of REC on the abutment after cleaning showed that the use of the bib reduced subgingival extension and surface involvement for both cement application techniques (Table 4) (Fig. 7A, 7B). REC was not detected on softtissue replicas after cleaning in most of the specimens, with less surface involvement for both cement application techniques (Table 5) (Fig. 7C, 7D). Comparing the 2 cement application techniques, PI had less subgingival extension of REC and less surface involvement. DISCUSSION In this present study, the null hypothesis was rejected as the use of a bib around the implant significantly reduced the amount and the subgingival extension of REC. Cementation techniques can influence the amount and extent of REC, and this has an impact on the prognosis of THE JOURNAL OF PROSTHETIC DENTISTRY
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Photoshop 1 - All Surfaces
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Abutment - All Surfaces
PVS index with Bib
45.0
Post
Brush ON without Bib
40.0
Estimated Means
Pre
Method
-
PVS index without Bib
Brush ON with Bib
Brush ON without Bib
35.0
Brush ON with Bib
30.0
PVS index without Bib
25.0
PVS index with Bib
20.0 15.0 10.0 5.0 0.0
0
10
20
30
40
50
60
Estimated Means
BOT_Yes_BIB
PVS_Yes_BIB
PVS_No_BIB
PVS_Yes_BIB
Before Cleaning
Post
Time
A
BOT_Yes_BIB
BOT_No_BIB
Pre
BOT_No_BIB
PVS_No_BIB
PVS_Yes_BIB
After Cleaning
BOT_Yes_BIB
BOT_No_BIB
PVS_No_BIB
PVS_Yes_BIB
Before Cleaning
Time Significant contrasts are shaded gold. The sequential bonferroni adjusted significance level is .05.
BOT_Yes_BIB
C
BOT_No_BIB
PVS_No_BIB
After Cleaning
Time
B
Significant contrasts are shaded gold. The sequential bonferroni adjusted significance level is .05.
D
Figure 6. A, Abutment analysis. B, Statistical differences among groups for abutment. C, Soft-tissue replica analysis. D, Statistical differences among groups for abutment.
the implant. The factors associated with cement-induced peri-implant disease have not been fully elucidated but likely include bacterial colonization,12 corrosion from fluoride in the cement,13 allergic response,14 and direct cement intrusion into the tissues.15,16 Also, smokers are more likely to have complications with REC than nonsmokers.27 While single implants can typically be restored with a screw-retained restoration, an ISFPD on multiple implants may necessitate a cemented restoration to overcome implant divergence.3-5 Cementing a CRISFPD as compared with a single restoration is more challenging, as the removal of excess cement is more difficult because of the reduced access and multiple abutments. The goal of the present study was to evaluate the amount and extent of REC with different cementation techniques for CRISFPDs. With the use of the 2 retainers for the CRISFPD, the study simulated a split mouth type of design, with 1 retainer serving as control and the other as the test group for each specimen. In this present study, the recommendation of Linkevicius et al7 of a shallow finish line level was followed, and the margin of custom abutment was kept 1 mm subgingival on the facial and proximal margins. More extensive and more subgingival extensions of REC could have been found if the margins of the custom abutments
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had been placed deeper. Furthermore, upon removal of the abutment-CRISFPD assembly for evaluation before cleaning, some of the excess cement was lost because of its brittle nature. This could have resulted in an underestimation of the amount and extension of the REC. However, despite these limitations, a significant difference indicates that clinically, the presence of REC, even in shallow subgingival margins, is likely to compromise the health of the peri-implant soft tissues. REC was detected whenever the margin was located subgingivally, consistent with the study by Linkevicius et al.7 The lingual surface was the least involved, with the shallowest subgingival extension of REC. The use of the bib influenced the location of the REC. Most REC remained on the abutment surfaces rather than the softtissue replicas. This could explain the presence of more REC on the abutment before cleaning with BOT when the bib was used. Even though careful bib placement takes time to ensure proper seating of the prosthesis, the bib probably prevented the cement from contacting the soft tissue, making removal easier, and thereby decreasing soft-tissue trauma and preventing crevicular fluid contact from affecting the setting reaction of the cement. For both techniques, the lingual surfaces on the abutments revealed the least subgingival extension of Bukhari et al
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Abutment
Soft Tissue Replica
80%
10%
m m
5
.5 >0
.5 >0
.5 >0
>0
Before Cleaning
_> 2
>0
_0 .
≤2
m m
5 >0
_> 2
_0 .
0
≤2
m m
5
_> 2
_0 .
.5
>0
0
0%
≤2
20%
5
30%
_> 2
40%
_0 .
50%
>0
60%
≤2
70%
m m
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
-
Before Cleaning
After Cleaning
After Cleaning
BOT_No Bib
BOT_Bib
BOT_No Bib 30%
BOT_Bib 77.50%
PVS_No Bib
PVS_Bib
PVS_No Bib 52.50%
PVS_Bib 95%
A
Abutment
B
Soft Tissue Replica 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
1
2
3
4
0
1
2
3
0
4
1
2
3
4
0
1
2
3
4
Number of Surfaces Involved
Number of Surfaces Involved
Number of Surfaces Involved
Number of Surfaces Involved
Before Cleaning
After Cleaning
Before Cleaning
After Cleaning
BOT No_Bib %
BOT Bib %
BOT No_Bib %
BOT Bib %
PVS Index PVS Index_No Bib %
PVS Index Bib %
PVS Index PVS Index_No Bib %
PVS Index Bib %
C
D
Figure 7. A, Subgingival extension of REC on abutment. B, Subgingival extension of REC on soft-tissue replica. C, Number of surfaces involved for each abutment. D, Number of surfaces involved for soft-tissue replica. REC, residual excess cement.
REC. REC extended more than 1 mm subgingivally more often when the bib was not used with either of the cement application techniques. In a few specimens, REC was found in areas not previously involved or deeper than before cleaning. This could be attributed to the brittle nature of the cement. Some particles might have flaked off during the removal and replacement of the abutment for evaluation. Also, some of the excess cement particles could have been pushed subgingivally during cleaning. The results of this study are consistent with those of Chee et al,17 where PVS dies were used to control the amount of cement before cementation. While the PVS die technique resulted in the least amount of cement extrusion in the study by Chee et al,17 the combination of the PVS die and the use of the bib used in the present study resulted in the lowest amount and least extension of REC. Bukhari et al
Table 5. Number of surfaces involved with each technique at both evaluation intervals for soft-tissue replica Evaluation Before cleaning
After cleaning
Number of Surfaces Involved 0
BOT (%)
PVS Index (%)
No Bib
Bib
No Bib
Bib
0.0
60.0
20.0
80.0
1
0.0
10.0
10.0
20.0
2
50.0
20.0
30.0
0.0
3
20.0
0.0
40.0
0.0
4
30.0
10.0
0.0
0.0
0
0.0
50.0
60.0
80.0
1
20.0
10.0
0.0
10.0
2
70.0
20.0
30.0
10.0
3
10.0
20.0
10.0
0.0
4
0.0
0.0
0.0
0.0
The need for a bib or barrier to prevent complications during implant crown cementation has been documented. Whether excess cement is more damaging when THE JOURNAL OF PROSTHETIC DENTISTRY
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it remains on the restoration or in contact with the soft tissues is currently unclear. Linkevicius et al7 reported that cement residue is found at both these sites. Ramer et al15 and Burbano et al16 have both reported finding embedded cement particles around failed removed dental implants in human biopsy. Limitations of this study include that the soft-tissue replica model had no crevicular fluid or the resiliency of natural peri-implant soft tissues. This made the removal of the excess cement more difficult and could have influenced the outcome. Also, in the present study, only 1 type of cement and 2 cement application techniques were tested. Future studies should include different cement types, abutment margin depths, cement application techniques, and assessment protocols. Different methods of removing excess cement evaluating the motion and direction of instrumentation are recommended. CONCLUSIONS Based on the findings of this in vitro study, the following conclusions were drawn: 1. The use of an implant PTFE bib during the cementation of the CRISFPD can reduce the amount and the extent of REC on the abutments and peri-implant soft tissues. 2. When an implant PTFE bib was used, the cement application technique was less critical, whereas when no bib was used, the PI technique had significantly less REC than BOT. 3. The use of an implant bib along with the PI cement application technique was most effective in reducing subgingival REC around abutments. REFERENCES 1. Hebel KS, Gajjar RC. Cement-retained versus screw-retained implant restorations. Achieving optimal occlusion and esthetics in implant dentistry. J Prosthet Dent 1997;77:28-35. 2. Taylor TD, Agar JR. Twenty years of progress in implant prosthodontics. J Prosthet Dent 2002;88:89-98. 3. Chee WW, Torbati A, Albouy JP. Retrievable cemented implant restorations. J Prosthodont 1998;7:120-5. 4. Chee WW, Jivraj S. Screw versus cemented implant supported restorations. Br Dent J 2006;21:501-7. 5. Chee W, Felton DA, Johnson PF, Sullivan DY. Cemented versus screwretained implant prostheses: which is better? Int J Oral Maxillofac Implants 1999;14:137-41. 6. Wadhwani C, Hess T, Faber T, Piñeyro A, Chen CSK. A descriptive study of the radiographic density of implant restorative cements. J Prosthet Dent 2010;103:295-302. 7. Linkevicius T, Vindasiute E, Puisys A, Peciuliene V. The influence of margin location on the amount of undetected cement excess after delivery of cement retained implant restorations. Clin Oral Implants Res 2011;22:1379-84. 8. Agar JR, Cameron SM, Hughbanks JC, Parker MH. Cement removal from restorations luted to titanium abutments with simulated subgingival margins. J Prosthet Dent 1997;78:43-7.
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9. Weber HP, Kim DM, Ng MW, Hwang JW, Fiorellini JP. Peri-implant softtissue health surrounding cement- and screw-retained implant restorations: a multi-center, 3-year prospective study. Clin Oral Implants Res 2006;17: 375-9. 10. Pauletto N, Lahiffe BJ, Walton JN. Complications associated with excess cement around crowns on osseointegrated implants: a clinical report. Int J Oral Maxillofac Implants 1999;14:865-8. 11. Gapski R, Neueboren N, Pomeranz AZ, Reissner MW. Endosseous implant failure influenced by crown cementation: a clinical case report. Int J Oral Maxillofac Implants 2008;23:943-6. 12. Wilson TG Jr. The positive relationship between excess cement and periimplant disease: a prospective clinical endoscopic study. J Periodontol 2009;80:1388-92. 13. Wadhwani C, Chung KH. In-office technique to selectively etch titanium abutments to achieve bonding for interim implant prostheses. J Prosthet Dent 2016;115:271-3. 14. Wadhwani CP. Peri-implant disease and cemented implant restorations: a multifactorial etiology. Compend Contin Educ Dent 2013;34:32-7. 15. Ramer N, Wadhwani C, Kim A, Hershman D. Histologic findings within peri-implant soft tissue in failed implants secondary to excess cement: report of two cases and review of literature. N Y State Dent J 2014;80:43-6. 16. Burbano M, Wilson TG Jr, Valderrama P, Blansett J, Wadhwani CP, Choudhary PK, et al. Characterization of cement particles found in periimplantitis affected human biopsy specimens. Int J Oral Maxillofac Implants 2015;30:1168-73. 17. Chee WW, Duncan J, Afshar M, Moshaverinia A. Evaluation of the amount of excess cement around the margins of cement-retained dental implant restorations: the effect of the cement application method. J Prosthet Dent 2013;109:216-21. 18. Wadhwani C, Hess T, Piñeyro A, Opler R, Chung KH. Cement application techniques in luting implant-supported crowns: a quantitative and qualitative survey. Int J Oral Maxillofac Implants 2012;27:859-64. 19. Hess TA. A technique to eliminate subgingival cement adhesion to implant abutments by using polytetrafluoroethylene tape. J Prosthet Dent 2014;112: 365-8. 20. Seo CW, Seo JM. A technique for minimizing subgingival residual cement by using rubber dam for cement-retained implant crowns. J Prosthet Dent 2017;117:327-8. 21. Dumbrigue HB, Abanomi AA, Cheng LL. Techniques to minimize excess luting agent in cement-retained implant restorations. J Prosthet Dent 2002;87:112-4. 22. Wadhwani C, Piñeyro A. Technique for controlling the cement for an implant crown. J Prosthet Dent 2009;102:57-8. 23. Patel D, Invest JC, Tredwin CJ, Setchell DJ, Moles DR. An analysis of the effect of a vent hole on excess cement expressed at the crownabutment margin for cement-retained implant crowns. J Prosthodont 2009;18:54-9. 24. Wadhwani C. Cementation in dental implantology. 1st ed. Berlin: Springer; 2015. p. 148-9. 25. Buser D, Martin W, Belser UC. Optimizing esthetics for implant restorations in the anterior maxilla: anatomic and surgical considerations. Int J Oral Maxillofac Implants 2004;19:43-61. 26. Morton D, Chen ST, Martin WC, Levine R, Buser D. Consensus statements and recommended clinical procedures regarding optimizing esthetic outcomes in implant dentistry. Int J Oral Maxillofac Implants 2013;19:216-20. 27. Linkevicius T, Puisys A, Vindasiute E, Linkeviciene L, Apse P. Does residual cement around implant-supported restorations cause peri-implant disease? A retrospective case analysis. Clin Oral Implants Res 2013;24: 1179-84.
Corresponding author: Dr Sarah A. Bukhari Loma Linda University, School of Dentistry 11092 Anderson Street Loma Linda, CA 92350 Email: [email protected] Acknowledgments Some materials for this study were donated by Nobel Biocare. Copyright © 2019 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2019.11.016
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An in vitro investigation comparing methods of minimizing excess luting agent for cement-retained implant-supported fixed partial dentures Sarah A. Bukhari, BDS, MS,a Abdulaziz AlHelal, BDS, MS,b Mathew T. Kattadiyil, BDS, MDS, MS,c Chandur P. K. Wadhwani, BDS, MSD,d Abdulrahman Taleb, BDS,e and Salem Dehom, MPHf Cement-retained implantABSTRACT supported prostheses are Statement of problem. The use of cement-retained implant-supported prostheses is a widely accepted as a good well-established treatment option. Techniques have been proposed to reduce the amount of 1 ,2 treatment option because of residual excess cement (REC) around cement-retained single-implant restorations. However, their passive fit, excellent esstudies evaluating the effectiveness of such techniques related to cement-retained implantthetics, and adaptability to supported fixed partial dentures (CRISFPDs) are lacking. situations where the implant Purpose. The purpose of this in vitro study was to evaluate the effectiveness of various cement placement is less than ideal.3-5 application techniques for CRISFPDs. However, residual excess Material and methods. Two implant analogs were placed in the lateral incisor sites in a maxillary, cement (REC) and the diffi3D printed cast with 4 missing incisors. Twenty standardized, removable, printed soft-tissue replicas, culty associated with its 40 milled titanium custom abutments, and 20 milled zirconia CRISFPDs were fabricated. Two detection and removal have cement application techniques, the brush on technique (BOT), and the polyvinyl siloxane index been major limiting factors for (PI) technique were compared. Two cementation techniques, without bib (control) (n=10) and with a polytetrafluoroethylene (PTFE) bib (test) (n=10), were used. A premeasured amount of this type of prosthesis.6-8 interim cement was used to cement the CRISFPDs. The CRISFPDs were retrieved after REC has been linked with cementation, and standardized photographs of 4 quadrants of each abutment-CRISFPD assembly peri-implant disease, bone were made by using a software program that is used to calculate the ratio between the area 9-16 resorption, and implant loss. covered with REC and the total specimen area. The extension of the REC on both the abutment Some of the factors that inand soft-tissue replica was measured at sites before and after cleaning the REC. A generalized fluence the amount of REC linear mixed-model procedure was used for statistical analysis (a=.05). include the location of the Results. For cement application, the polyvinyl siloxane (PVS) index technique had significantly less abutment margin7 and the REC than the brush on technique (P<.05). The use of a PTFE bib led to significantly less REC than 17 cementation technique. when no bib was used (P<.05). Linkevicius et al7 studied the Conclusions. The use of the PVS index technique along with a PTFE bib was effective in reducing amount of REC after cemenREC for CRISFPDs. (J Prosthet Dent 2019;-:---) tation and the subsequent cleaning of implant-supported restorations at various amount of REC after attempted cement removal depths and configurations of the abutment margin. The increased for the more subgingival restorations.
a
Assistant Professor, Division of General Dentistry, Loma Linda University School of Dentistry, Loma Linda, Calif. Assistant Professor, Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia. Professor and Director, Advanced Specialty Education Program in Prosthodontics, Loma Linda University School of Dentistry, Loma Linda, Calif. d Adjunct Assistant Professor, Advanced Specialty Education Program in Prosthodontics School of Dentistry, Loma Linda University, Loma Linda, Calif. e Graduate student, Advanced Specialty Education Program in Prosthodontics, University of Southern California, Los Angeles, Calif. f Assistant Professor, Loma Linda University School of Nursing, Loma Linda, Calif. b c
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Clinical Implications Clinicians should consider a cementation protocol such as the PVS index technique along with a PTFE bib for CRISFPDS to reduce the amount and extent of excess cement.
Wadhwani et al18 reported on 3 cement application techniques when luting implant-supported crowns. They stated that most of the participants surveyed (54.7%) used the brush on technique, where the cement was painted on the intaglio surface of the crown. Chee et al17 reported that the least amount of excess cement was observed when a putty index was formed to the configuration of the internal form of the crown to be cemented and used as a precementation extrusion device. The study reported that higher amounts of residual cement were noted with the brush on technique.17 Different techniques have been described that protect the soft tissue from excess cement, including the use of polytetrafluoroethylene (PTFE) tape19 or rubber dam,20 a
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putty index, and vent holes.21-23 However, the authors are unaware of studies evaluating the effectiveness of the PTFE bib and cementation techniques in reducing REC around CRISFPDs. The purpose of this study was to evaluate the effectiveness of the PTFE implant bib technique24 in reducing REC during CRISFPD cementation by using 2 different cement application techniques. The null hypotheses were that no difference would be found in the amount of REC on the abutment or the soft-tissue replica between the control (no bib) and the test groups (with PTFE bib) for CRISFPDs and that no difference would be found in the amount of REC with 2 different cement application techniques for CRISFPDs. MATERIAL AND METHODS A dentate maxillary cast was scanned (Fig. 1A), and the 4 anterior teeth were digitally removed (Fig. 1B). Using a computer-aided design (CAD) software program (Dental System; 3Shape), a virtual 4-unit CRISFPD was designed with ovate pontics replacing the maxillary central incisors. The CRISFPD abutments for maxillary lateral incisors were designed for Nobel Replace narrow platform (3.5 mm)
Figure 1. A, Maxillary cast. B, Scanned maxillary cast before and after trimming teeth and virtually designing soft tissue. C, Printed maxillary cast with implant analogs. D, Printed maxillary cast and soft-tissue replica.
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Figure 2. A, Occlusal and frontal view of scanned maxillary cast showing virtual design of abutments. B, Frontal view of printed maxillary cast showing titanium abutments in area of maxillary lateral incisors. C, Frontal view of printed maxillary cast showing milled zirconia CRISFPD. D, Virtual design of CRISFPD showing reference line for probe measurements of REC and indentation for CRISFPD retrieval. E, Lingual view of zirconia CRISFPD showing reference line for probe measurements of REC and indentations for CRISFPD retrieval. CRISFPD, cement-retained implant-supported fixed partial denture.
internal connection implants (Nobel Replace Select Tapered; Nobel Biocare). The 20 identical, 1-piece softtissue replica designs that included identical right and left sides followed the contour of the abutments. Analogs were designed virtually to be placed 2 mm from the representative buccal bone margin, 2 mm apical to the midfacial gingival margin, and 1.5 mm from the adjacent canines.25,26 From the digital scan, a master cast was fabricated by using a 3D printer with standard white resin (Form 2;
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Formlabs) (Fig. 1C). The soft-tissue replicas around the CRISFPDs were printed by using Formlabs flexible gray resin (Form 2; Formlabs) (Fig. 1D). From the master model, custom abutments were virtually designed (Fig. 2A) and fabricated in titanium (Ti) by using a computer-aided manufacturing (CAM) process (Fig. 2B). The custom abutments had a 1-mm subgingival finish line at the facial and interproximal areas, transitioning to an equigingival finish line on the lingual surfaces. The
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(Temp-Bond) 1 Maxillary cast 20 CRISFPDs 40 Custom abutments
Brush on technique 10 Soft tissue replicas 10 CRISFPDs 20 abutments
Control No Bib 10 abutments
Test PTFE Bib 10 abutments
PVS index technique 10 Soft tissue replicas 10 CRISFPDs 20 abutments
Control No Bib 10 abutments
Test PTFE Bib 10 abutments
Figure 3. Schematic diagram of study material and methods. CRISFPD, cement-retained implant-supported fixed partial denture; PTFB, polytetrafluoroethylene.
custom abutments were designed and fabricated to be 0.2 mm smaller than the soft-tissue replicas. This resulted in a space between the custom abutment and the soft-tissue replica, simulating the gingival sulcus around a dental implant. CAD-CAM (Vericore ZR HT A1 Disc w/ collar; Whip Mix Corp) was used to fabricate zirconia (Zir) CRISFDPs (Fig. 2C). Fiducial marks 1-mm coronal to the margin (Fig. 2D, 2E) of the restoration provided a reference for measuring the subgingival extension of the REC. An indentation was added virtually on the lingual surface of both retainers to aid in the retrieval of the CRISFPDs (Fig. 2D, 2E). Each group consisted of 10 CRISFPDs and 20 Ti custom abutments (Fig. 3). The Zir CRISFPDs were cemented by using zinc oxide-eugenol cement (Temp-Bond; Kerr Corp), following the manufacturer’s instructions. Two different cement application techniques were used to apply the luting agent to the intaglio surface of the CRISFPD retainers: BOT and PI. For BOT, a predetermined volume of the mixed cement was used to coat the entire intaglio surface of the retainers with a microbrush (Micro Disposable Applicator; PLASDENT Corp) (Fig. 4A). For the PI technique, a polyvinyl siloxane (PVS) analog of the custom abutment was fabricated and used to control cement volume (Fig. 4B).22 Each CRISFPD was seated by a single operator (S.B.) by using finger pressure to mimic the cementation protocol.8 The interim cement was allowed to set for 4 minutes before the CRISFPD was removed to determine the amount and extent of the REC. The CRISFPD was replaced on the abutments, and the screws were handtightened. The implant bib was removed with cotton pliers. The REC was removed by 1 operator (A.A.) by using a stainless-steel explorer (#2H Double End Explorer; Hu-Friedy), followed by dental floss (ESSENTIAL Floss; Oral-B) and superfloss (Super Floss; Oral-B).8 THE JOURNAL OF PROSTHETIC DENTISTRY
Figure 4. A, Zirconia CRISFPD showing BOT. B, Frontal view showing titanium abutment and PVS replica. C, Occlusal view of maxillary cast showing bib application around abutment in area of maxillary left lateral incisor. BOT, brush on technique; CRISFPD, cement-retained implantsupported fixed partial denture; PVS, polyvinyl siloxane.
To compare REC with the use of a PTFE bib for cementation with no bib, the implant in the maxillary right lateral incisor region, where no bib was used, served as the control. The maxillary left lateral incisor region was used as the test, where a 2- to 3-cm-long PTFE tape with a thickness of 100 mm (UL yellow gas line tape; Seal Tape Inc) was used. With a rubber dam punch, a hole was created in the center of the PTFE tape, the implant Bukhari et al
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Figure 5. A, Maxillary cast showing drilled holed for prosthesis retrieval. B, Retrieved abutment-CRISFPD assembly mounted on device. C, Total surface area of abutment-CRISFPD assembly marked.
abutment was inserted into the hole, and the tape was moved gingivally and close to the margin without entrapment at the abutment-implant interface. The abutment was fixed onto the implant analog by handtightening (Fig. 4C). After cementation, a hole was made through the screw site indentations on the lingual surface, and then the abutments were unscrewed (Fig. 5A) and examined (Fig. 5B). A digital single-lens reflex camera (Nikon D610; Nikon) was used to obtain the photographs. The specimens were mounted on a device in a standardized Bukhari et al
manner to maintain a 16-mm distance between the camera and the restoration.7 All 4 sides (mesial, distal, facial, and lingual) of each abutment-CRISFPD assembly were photographed. The images were then imported and analyzed by using a photo-editing software program (Adobe Photoshop CC; Adobe Systems Ltd). Each surface area of the prosthesis was marked with the “drawing tool” to outline the boundaries of each side. The area covered with REC on each of the 4 sides (mesial, distal, facial, and lingual) was calculated by using the “pen tool” and “make path” options. The total THE JOURNAL OF PROSTHETIC DENTISTRY
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Figure 5. (continued) D, Area covered with REC marked. E, Probe measurement from reference line on CRISFPD. CRISFPD, cement-retained implantsupported fixed partial denture; REC, residual excess cement.
surface area for each side was marked, and the number of pixels representing the surface area was recorded from the histogram (Fig. 5C). The same method was
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applied to the area covered with REC (Fig. 5D). The ratio of the combined total surface area to the REC covered area was then calculated for every abutment-CRISFPD
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Table 1. Scoring criteria for subgingival extension of REC
Table 2. Surface area covered by REC on abutments Before Cleaning
After Cleaning
Pc
Means (95% CI)a,b
Means (95% CI)a,b
Group Effect Interaction
0
No excess cement
1
Excess cement extended >0-0.5 mm subgingivally
2
Excess cement extended >0.5-<2 mm subgingivally
Cement Application Technique
3
Excess cement extended 2 mm or more subgingivally
BOT_no Bib
45.94 (25.61, 82.43) 14.38 (9.56, 21.61) <.001
BOT_Bib
52.58 (29.31, 94.35) 6.86 (4.56, 10.31)
PVS Index_no Bib 14.44 (8.05, 25.89) PVS Index_Bib
Table 3. Surface area covered by REC on soft-tissue replica Cement Application Technique BOT_No Bib
Before Cleaning
After Cleaning
Means (95% CI)a,b
Means (95% CI)a,b
P
2.09 (1.14, 3.84)
1.80 (1.22, 2.65)
PVS Index_No Bib
6.44 (3.28, 12.64)
1.83 (1.09, 3.09)
PVS Index_Bib
1.36 (0.92, 2.02)
1.28 (0.93, 1.75)
1.6 (1.07, 2.41)
Estimated means. bLog transformed variable was used in the analysis. cBonferroni adjustment.
Group Effect Interaction <.001
a
Estimated means. bLog transformed variable was used in the analysis. cBonferroni adjustment.
assembly to determine the percentage of the surface covered with REC.7 For the soft-tissue replica, the REC was evaluated in a similar manner. A periodontal probe (#15 UNC; Hu-Friedy Qulix) was used to measure the subgingival extension of the REC. The engraved line on the CRISFPD retainers was used as a reference point (Fig. 5E). The 4 sides of the abutment and the soft-tissue replica were evaluated, and scoring criteria (Table 1) were used to assess the extent of the REC. A statistical software program (SAS, v9.4; SAS Institute Inc) was used for data analysis. To determine whether different techniques resulted in differences in REC, the generalized linear mixed-model procedure was used to analyze the effect of the method type, time (before and after cleaning), and method type × time interaction on the abutment and gingiva (soft-tissue replica) scores. ANOVA tests using the Bonferroni adjustment for multiple comparisons were used. As the normality assumption was not met using the original scores, log-transformed variables were used for both outcomes. A constant value of 1 was added to all specimens to adjust for the zero values. RESULTS For the brush on technique (BOT) before cleaning, the amount of REC on the abutment immediately after cementation (Table 2) was found to be significantly lower (P<.05) with no bib (Fig. 6A, 6B), whereas in the softtissue replica (Table 3), significantly less REC (P<.05) was found when the PTFE bib was used (Fig. 6C, 6D) For the PVS index (PI) technique before cleaning, the REC evaluated immediately after cementation was found to be significantly lower (P<.05) with bib for both the abutment and soft-tissue replicas (Tables 2 and 3). In both cement application techniques, lower REC (P<.05) was found with PI whether a bib was used or not (Fig. 6A, 6B). Bukhari et al
2.74 (1.82, 4.11)
a
c
39.61 (33.58, 46.71) 11.27 (9.41, 13.48) <.001
BOT_Bib
2.89 (1.61, 5.18)
<.001
Table 4. Number of surfaces involved with each technique at both evaluation intervals for abutment Evaluation Before cleaning
After cleaning
Number of Surfaces Involved
BOT (%)
PVS Index (%)
No Bib
Bib
No Bib
Bib
0
0.0
0.0
0.0
40.0
1
0.0
0.0
40.0
40.0
2
0.0
10.0
40.0
0.0
3
20.0
10.0
20.0
20.0
4
80.0
80.0
0.0
0.0
0
0.0
0.0
20.0
50.0 40.0
1
0.0
20.0
50.0
2
30.0
60.0
30.0
0.0
3
20.0
0.0
0.0
10.0
4
50.0
20.0
0.0
0.0
For the BOT after cleaning, the REC evaluated on the abutment (Table 2) and soft-tissue replica (Table 3) was found to be significantly lower with bib (P<.05). With the PI technique after cleaning, no significant difference in REC was found between the 2 groups (with and without bib) for both the abutment and soft-tissue replicas (P>.05). Significantly lower REC (P<.05) was observed on the abutment after cleaning with the PI technique than with BOT in both groups. The use of the bib revealed no significant difference regarding REC between the 2 cement application techniques (PI and BOT) on softtissue replicas after cleaning (Fig. 6C, 6D). Probe measurements for the subgingival extension of REC on the abutment after cleaning showed that the use of the bib reduced subgingival extension and surface involvement for both cement application techniques (Table 4) (Fig. 7A, 7B). REC was not detected on softtissue replicas after cleaning in most of the specimens, with less surface involvement for both cement application techniques (Table 5) (Fig. 7C, 7D). Comparing the 2 cement application techniques, PI had less subgingival extension of REC and less surface involvement. DISCUSSION In this present study, the null hypothesis was rejected as the use of a bib around the implant significantly reduced the amount and the subgingival extension of REC. Cementation techniques can influence the amount and extent of REC, and this has an impact on the prognosis of THE JOURNAL OF PROSTHETIC DENTISTRY
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Photoshop 1 - All Surfaces
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Abutment - All Surfaces
PVS index with Bib
45.0
Post
Brush ON without Bib
40.0
Estimated Means
Pre
Method
-
PVS index without Bib
Brush ON with Bib
Brush ON without Bib
35.0
Brush ON with Bib
30.0
PVS index without Bib
25.0
PVS index with Bib
20.0 15.0 10.0 5.0 0.0
0
10
20
30
40
50
60
Estimated Means
BOT_Yes_BIB
PVS_Yes_BIB
PVS_No_BIB
PVS_Yes_BIB
Before Cleaning
Post
Time
A
BOT_Yes_BIB
BOT_No_BIB
Pre
BOT_No_BIB
PVS_No_BIB
PVS_Yes_BIB
After Cleaning
BOT_Yes_BIB
BOT_No_BIB
PVS_No_BIB
PVS_Yes_BIB
Before Cleaning
Time Significant contrasts are shaded gold. The sequential bonferroni adjusted significance level is .05.
BOT_Yes_BIB
C
BOT_No_BIB
PVS_No_BIB
After Cleaning
Time
B
Significant contrasts are shaded gold. The sequential bonferroni adjusted significance level is .05.
D
Figure 6. A, Abutment analysis. B, Statistical differences among groups for abutment. C, Soft-tissue replica analysis. D, Statistical differences among groups for abutment.
the implant. The factors associated with cement-induced peri-implant disease have not been fully elucidated but likely include bacterial colonization,12 corrosion from fluoride in the cement,13 allergic response,14 and direct cement intrusion into the tissues.15,16 Also, smokers are more likely to have complications with REC than nonsmokers.27 While single implants can typically be restored with a screw-retained restoration, an ISFPD on multiple implants may necessitate a cemented restoration to overcome implant divergence.3-5 Cementing a CRISFPD as compared with a single restoration is more challenging, as the removal of excess cement is more difficult because of the reduced access and multiple abutments. The goal of the present study was to evaluate the amount and extent of REC with different cementation techniques for CRISFPDs. With the use of the 2 retainers for the CRISFPD, the study simulated a split mouth type of design, with 1 retainer serving as control and the other as the test group for each specimen. In this present study, the recommendation of Linkevicius et al7 of a shallow finish line level was followed, and the margin of custom abutment was kept 1 mm subgingival on the facial and proximal margins. More extensive and more subgingival extensions of REC could have been found if the margins of the custom abutments
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had been placed deeper. Furthermore, upon removal of the abutment-CRISFPD assembly for evaluation before cleaning, some of the excess cement was lost because of its brittle nature. This could have resulted in an underestimation of the amount and extension of the REC. However, despite these limitations, a significant difference indicates that clinically, the presence of REC, even in shallow subgingival margins, is likely to compromise the health of the peri-implant soft tissues. REC was detected whenever the margin was located subgingivally, consistent with the study by Linkevicius et al.7 The lingual surface was the least involved, with the shallowest subgingival extension of REC. The use of the bib influenced the location of the REC. Most REC remained on the abutment surfaces rather than the softtissue replicas. This could explain the presence of more REC on the abutment before cleaning with BOT when the bib was used. Even though careful bib placement takes time to ensure proper seating of the prosthesis, the bib probably prevented the cement from contacting the soft tissue, making removal easier, and thereby decreasing soft-tissue trauma and preventing crevicular fluid contact from affecting the setting reaction of the cement. For both techniques, the lingual surfaces on the abutments revealed the least subgingival extension of Bukhari et al
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Abutment
Soft Tissue Replica
80%
10%
m m
5
.5 >0
.5 >0
.5 >0
>0
Before Cleaning
_> 2
>0
_0 .
≤2
m m
5 >0
_> 2
_0 .
0
≤2
m m
5
_> 2
_0 .
.5
>0
0
0%
≤2
20%
5
30%
_> 2
40%
_0 .
50%
>0
60%
≤2
70%
m m
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
-
Before Cleaning
After Cleaning
After Cleaning
BOT_No Bib
BOT_Bib
BOT_No Bib 30%
BOT_Bib 77.50%
PVS_No Bib
PVS_Bib
PVS_No Bib 52.50%
PVS_Bib 95%
A
Abutment
B
Soft Tissue Replica 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
1
2
3
4
0
1
2
3
0
4
1
2
3
4
0
1
2
3
4
Number of Surfaces Involved
Number of Surfaces Involved
Number of Surfaces Involved
Number of Surfaces Involved
Before Cleaning
After Cleaning
Before Cleaning
After Cleaning
BOT No_Bib %
BOT Bib %
BOT No_Bib %
BOT Bib %
PVS Index PVS Index_No Bib %
PVS Index Bib %
PVS Index PVS Index_No Bib %
PVS Index Bib %
C
D
Figure 7. A, Subgingival extension of REC on abutment. B, Subgingival extension of REC on soft-tissue replica. C, Number of surfaces involved for each abutment. D, Number of surfaces involved for soft-tissue replica. REC, residual excess cement.
REC. REC extended more than 1 mm subgingivally more often when the bib was not used with either of the cement application techniques. In a few specimens, REC was found in areas not previously involved or deeper than before cleaning. This could be attributed to the brittle nature of the cement. Some particles might have flaked off during the removal and replacement of the abutment for evaluation. Also, some of the excess cement particles could have been pushed subgingivally during cleaning. The results of this study are consistent with those of Chee et al,17 where PVS dies were used to control the amount of cement before cementation. While the PVS die technique resulted in the least amount of cement extrusion in the study by Chee et al,17 the combination of the PVS die and the use of the bib used in the present study resulted in the lowest amount and least extension of REC. Bukhari et al
Table 5. Number of surfaces involved with each technique at both evaluation intervals for soft-tissue replica Evaluation Before cleaning
After cleaning
Number of Surfaces Involved 0
BOT (%)
PVS Index (%)
No Bib
Bib
No Bib
Bib
0.0
60.0
20.0
80.0
1
0.0
10.0
10.0
20.0
2
50.0
20.0
30.0
0.0
3
20.0
0.0
40.0
0.0
4
30.0
10.0
0.0
0.0
0
0.0
50.0
60.0
80.0
1
20.0
10.0
0.0
10.0
2
70.0
20.0
30.0
10.0
3
10.0
20.0
10.0
0.0
4
0.0
0.0
0.0
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The need for a bib or barrier to prevent complications during implant crown cementation has been documented. Whether excess cement is more damaging when THE JOURNAL OF PROSTHETIC DENTISTRY
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it remains on the restoration or in contact with the soft tissues is currently unclear. Linkevicius et al7 reported that cement residue is found at both these sites. Ramer et al15 and Burbano et al16 have both reported finding embedded cement particles around failed removed dental implants in human biopsy. Limitations of this study include that the soft-tissue replica model had no crevicular fluid or the resiliency of natural peri-implant soft tissues. This made the removal of the excess cement more difficult and could have influenced the outcome. Also, in the present study, only 1 type of cement and 2 cement application techniques were tested. Future studies should include different cement types, abutment margin depths, cement application techniques, and assessment protocols. Different methods of removing excess cement evaluating the motion and direction of instrumentation are recommended. CONCLUSIONS Based on the findings of this in vitro study, the following conclusions were drawn: 1. The use of an implant PTFE bib during the cementation of the CRISFPD can reduce the amount and the extent of REC on the abutments and peri-implant soft tissues. 2. When an implant PTFE bib was used, the cement application technique was less critical, whereas when no bib was used, the PI technique had significantly less REC than BOT. 3. The use of an implant bib along with the PI cement application technique was most effective in reducing subgingival REC around abutments. REFERENCES 1. Hebel KS, Gajjar RC. Cement-retained versus screw-retained implant restorations. Achieving optimal occlusion and esthetics in implant dentistry. J Prosthet Dent 1997;77:28-35. 2. Taylor TD, Agar JR. Twenty years of progress in implant prosthodontics. J Prosthet Dent 2002;88:89-98. 3. Chee WW, Torbati A, Albouy JP. Retrievable cemented implant restorations. J Prosthodont 1998;7:120-5. 4. Chee WW, Jivraj S. Screw versus cemented implant supported restorations. Br Dent J 2006;21:501-7. 5. Chee W, Felton DA, Johnson PF, Sullivan DY. Cemented versus screwretained implant prostheses: which is better? Int J Oral Maxillofac Implants 1999;14:137-41. 6. Wadhwani C, Hess T, Faber T, Piñeyro A, Chen CSK. A descriptive study of the radiographic density of implant restorative cements. J Prosthet Dent 2010;103:295-302. 7. Linkevicius T, Vindasiute E, Puisys A, Peciuliene V. The influence of margin location on the amount of undetected cement excess after delivery of cement retained implant restorations. Clin Oral Implants Res 2011;22:1379-84. 8. Agar JR, Cameron SM, Hughbanks JC, Parker MH. Cement removal from restorations luted to titanium abutments with simulated subgingival margins. J Prosthet Dent 1997;78:43-7.
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9. Weber HP, Kim DM, Ng MW, Hwang JW, Fiorellini JP. Peri-implant softtissue health surrounding cement- and screw-retained implant restorations: a multi-center, 3-year prospective study. Clin Oral Implants Res 2006;17: 375-9. 10. Pauletto N, Lahiffe BJ, Walton JN. Complications associated with excess cement around crowns on osseointegrated implants: a clinical report. Int J Oral Maxillofac Implants 1999;14:865-8. 11. Gapski R, Neueboren N, Pomeranz AZ, Reissner MW. Endosseous implant failure influenced by crown cementation: a clinical case report. Int J Oral Maxillofac Implants 2008;23:943-6. 12. Wilson TG Jr. The positive relationship between excess cement and periimplant disease: a prospective clinical endoscopic study. J Periodontol 2009;80:1388-92. 13. Wadhwani C, Chung KH. In-office technique to selectively etch titanium abutments to achieve bonding for interim implant prostheses. J Prosthet Dent 2016;115:271-3. 14. Wadhwani CP. Peri-implant disease and cemented implant restorations: a multifactorial etiology. Compend Contin Educ Dent 2013;34:32-7. 15. Ramer N, Wadhwani C, Kim A, Hershman D. Histologic findings within peri-implant soft tissue in failed implants secondary to excess cement: report of two cases and review of literature. N Y State Dent J 2014;80:43-6. 16. Burbano M, Wilson TG Jr, Valderrama P, Blansett J, Wadhwani CP, Choudhary PK, et al. Characterization of cement particles found in periimplantitis affected human biopsy specimens. Int J Oral Maxillofac Implants 2015;30:1168-73. 17. Chee WW, Duncan J, Afshar M, Moshaverinia A. Evaluation of the amount of excess cement around the margins of cement-retained dental implant restorations: the effect of the cement application method. J Prosthet Dent 2013;109:216-21. 18. Wadhwani C, Hess T, Piñeyro A, Opler R, Chung KH. Cement application techniques in luting implant-supported crowns: a quantitative and qualitative survey. Int J Oral Maxillofac Implants 2012;27:859-64. 19. Hess TA. A technique to eliminate subgingival cement adhesion to implant abutments by using polytetrafluoroethylene tape. J Prosthet Dent 2014;112: 365-8. 20. Seo CW, Seo JM. A technique for minimizing subgingival residual cement by using rubber dam for cement-retained implant crowns. J Prosthet Dent 2017;117:327-8. 21. Dumbrigue HB, Abanomi AA, Cheng LL. Techniques to minimize excess luting agent in cement-retained implant restorations. J Prosthet Dent 2002;87:112-4. 22. Wadhwani C, Piñeyro A. Technique for controlling the cement for an implant crown. J Prosthet Dent 2009;102:57-8. 23. Patel D, Invest JC, Tredwin CJ, Setchell DJ, Moles DR. An analysis of the effect of a vent hole on excess cement expressed at the crownabutment margin for cement-retained implant crowns. J Prosthodont 2009;18:54-9. 24. Wadhwani C. Cementation in dental implantology. 1st ed. Berlin: Springer; 2015. p. 148-9. 25. Buser D, Martin W, Belser UC. Optimizing esthetics for implant restorations in the anterior maxilla: anatomic and surgical considerations. Int J Oral Maxillofac Implants 2004;19:43-61. 26. Morton D, Chen ST, Martin WC, Levine R, Buser D. Consensus statements and recommended clinical procedures regarding optimizing esthetic outcomes in implant dentistry. Int J Oral Maxillofac Implants 2013;19:216-20. 27. Linkevicius T, Puisys A, Vindasiute E, Linkeviciene L, Apse P. Does residual cement around implant-supported restorations cause peri-implant disease? A retrospective case analysis. Clin Oral Implants Res 2013;24: 1179-84.
Corresponding author: Dr Sarah A. Bukhari Loma Linda University, School of Dentistry 11092 Anderson Street Loma Linda, CA 92350 Email: [email protected] Acknowledgments Some materials for this study were donated by Nobel Biocare. Copyright © 2019 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2019.11.016
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