| Abstract|| |
Aims: This study evaluated the effect of ultrasonic scaling on surface roughness of four different tooth-colored class V restorations.
Materials and Methods: Out of 100 human extracted teeth, 20 were randomly selected for each group, marked with the outline of class V cavity. Class V cavities were prepared on facial surface of teeth of all groups except control group. These cavities were then restored with GC 2, GC 9, GC 2 LC, and Filtek Z 250 XT. All the specimens were stored in artificial saliva at 37 o C for 1 month. Initial surface roughness values (Ra in μm) of restorations were evaluated with the surface roughness tester. Ultrasonic instrumentation was then carried out for 60 s on the restoration surface and final roughness values were evaluated. Data were analyzed with Paired t-test, One-way ANOVA, Tukey's test.
Results: Mean Pre-instrumentation surface roughness was highest with GC 2, whereas it was least in case of Filtek Z 250 XT. Mean post-instrumentation surface roughness was highest with GC 2, whereas it is least in case of Filtek Z 250 XT.
Conclusion: GC 2 LC showed highest and Filtek Z 250 XT showed least susceptibility to ultrasonic scaling.
Keywords: Class V restorations, Filtek Z250 XT, GC 2, GC 2LC, GC 9, GIC, nanohybrid composite, Resin modified GIC, surface roughness, ultrasonic scaling
|How to cite this article:|
Shenoi PR, Badole GP, Khode RT, Morey ES, Singare PG. Evaluation of effect of ultrasonic scaling on surface roughness of four different tooth-colored class V restorations: An in-vitro study. J Conserv Dent 2014;17:471-5
|How to cite this URL:|
Shenoi PR, Badole GP, Khode RT, Morey ES, Singare PG. Evaluation of effect of ultrasonic scaling on surface roughness of four different tooth-colored class V restorations: An in-vitro study. J Conserv Dent [serial online] 2014 [cited 2020 Jul 14];17:471-5. Available from: http://www.jcd.org.in/text.asp?2014/17/5/471/139845
| Introduction|| |
Class V lesions are the defects that occurs on the gingival third of facial and lingual surface of all teeth.  Due to esthetic concerns; these types of defects are preferentially restored with tooth-colored restorations such as glass ionomers and composites. Ultrasonic scaling is routine periodontal procedure recommended by periodontist after every 6 months.  It is common clinical finding that plaque and calculus deposits occur heavily in the gingival third of teeth causing irritation to the gingiva. Due to these deposits the dentist or dental hygienist may fail to differentiate between tooth and tooth-colored restorations and thus may run the ultrasonic insert over the surface of these tooth-colored restorations.
The tips of the ultrasonic inserts are found to vibrate between 18,000 and 45,000 cycles per second. , These are excellent for removing plaque, calculus, and bacterial endotoxins  but at the same time, they may cause undue damage to the surface integrity of tooth structure and the restorations placed over it. ,, Many studies (Bjornson et al., Teughels et al.) have stated that there is definite correlation between tooth roughness and increased bacterial colonization. , So, the increased surface roughness of tooth and class V restorations that are in close proximity to gingiva may lead to more plaque accumulation, staining, gingival irritation, increased patient discomfort, and recurrent caries. , Further Bollen et al. have suggested that the surface roughness beyond 0.2 μm results in increased plaque deposition, whereas Jones et al. have mentioned that tooth surface roughness of even 0.5 μm can cause remarkable patient discomfort.
A search of literature revealed that very few studies have compared the effect of ultrasonic scaling on different tooth-colored class V restorations and there is no conclusive evidence of which restorative material can best withstand the ultrasonic instrumentation. Thus, the aim of this study was to evaluate the effect of ultrasonic scaling on surface roughness of four different tooth-colored class V restorations.
| MATERIALS AND METHODs|| |
Hundred human freshly extracted teeth excluding mandibular incisors were used in this study. Out of these, 20 teeth were randomly selected and included in a control group (Group I). These were marked with area of 2 × 4 mm to simulate outline of class V cavity; however, no cavity preparation was done on them. Class V cavities of 4 mm width, 2 mm length, and 1.5 mm depth were prepared on facial surface of remaining 80 teeth with FG1 and FG 271 carbide bur (SS white, Fleet street, London). Each pair of these burs was discarded after preparation of eight class V cavities. These 80 class V cavities were randomly and equally divided into 4 groups (n = 20) according to type they were restored with:
Group II: GC 2 (Tokyo, Japan),
Group III: GC 9 (Tokyo, Japan),
Group IV: GC 2 LC (Tokyo, Japan),
Group V: Filtek Z 250 XT (3M ESPE, St. Paul, MN, USA).
Restorative materials in each group were manipulated according to manufacturer's instructions and placed into the prepared cavity. A transparent matrix band was placed over it, and pressure was applied to extrude excess material. The restorations in Group 2 and Group 3 were allowed to set against Mylar strip. Restorations in Group 4 and Group 5 were cured against a Mylar strip with light curing unit (Blue phase, Ivoclar Vivadent, Astria) for 40 seconds. After initial set of each material, excess was carefully removed. Restorations in Group II, III, and IV were covered with petroleum jelly and allowed to set in 100% humidity. All specimens were then stored in artificial saliva prepared by Oshiro's method  at 37 o C for 1 month.
Specimens in each group were rinsed in running tap water for 30 seconds and further cleaned in an ultrasonic cleaner for 6 minutes. They were air dried, and initial surface roughness was evaluated in terms of Ra value (μm) using Surface Roughness Tester (Mitutoyo, Japan, SJ 210) with stylus moving at the speed 0.5 mm/s.
Later, ultrasonic scaling was performed on all specimens with SATELLAC (Satellac, Cedex, France) ultrasonic scaler having N1 insert/tip under copious water flow for 60 seconds at level 2 power setting. The scaling tip was angled approximately to 15 o to the restoration surface. The direction of scaling was approximately perpendicular to the long axis of the tooth in the horizontal plane, moving the scaler insert slowly from gingival to coronal third of the restoration. All instrumentations were performed by one experienced periodontist who was not aware of the type of restorative material and their groups. The specimens were rinsed in running tap water for 30 seconds and cleaned in an ultrasonic bath for 6 minutes. All specimens were air dried, and post-ultrasonic instrumentation roughness was then evaluated as mentioned previously. Data were analyzed with paired t-test, one-way ANOVA, Tukey's test.
| Results|| |
Initial surface roughness values (Ra) from highest to lowest were in the order of GC2, GC9, control group, GC2 LC, and Filtek Z 250 XT, whereas post-instrumentation surface roughness were in the order of GC2, GC9, GC2LC, control group, and Filtek Z 250 XT. There was statistically significant difference between roughness values before and after ultrasonic instrumentation [Table 1], [Figure 1].
|Table 1: Mean surface roughness (Ra in μm) observed before and after ultrasonic instrumentation|
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|Figure 1: Bar chart showing the mean initial and final surface roughness (μm) for the control and four study groups and their comparison with critical thresholds|
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The difference (δ) between the mean pre-instrumentation and post-instrumentation roughness, which gives actual effect of ultrasonic scaling on the surface roughness of control and test group, was highest in case of GC 2 LC followed by GC 9, control group, GC 2, and least in of Filtek Z 250 XT [Figure 2]. Though initial surface roughness values of all the groups were significantly different, there was no correlation found between initial surface roughness and change in mean surface roughness (δ). The value of F(4, 95) was 25.38 with a P-value <0.0001 indicating that change in the mean roughness (δ) across groups is unequal. Paired comparison with Tukey's test showed statistically significant difference between deltas of all group pairs except for pairs between control and GC2, GC2 and Filtek Z 250 XT, GC9 and GC2 LC [Table 2].
|Figure 2: Bar chart showing the mean change in the roughness (δ) for control and four study groups|
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| Discussion|| |
Class V caries usually develops due to many reasons like unclean tooth surface, caries inducing diet, gingival recession, a reduced salivary flow caused by certain medical conditions (e.g., Sjogren's syndrome), medication or head and neck radiation therapy.  The other cervical lesions that need to be restored are abrasion, abfraction, and erosion.  To restore such defects, materials used should have qualities and properties such as strength, longevity, ease of use, past success, esthetics, being able to bond to tooth structure, good finishing and polishing ability.  Glass ionomer cements are typically used to restore cervical lesions because of its true adhesion, anticariogenic property and high flexural strength.  However, recently it has been found that nanohybrid composites also posses better flexural properties and low surface roughness. ,
Glass ionomers have the initial setting time ranging from 4-7 minutes, but entire setting reaction continues for several weeks (ion-exchange mechanism). In this study, prior to ultrasonic instrumentation, we have stored the entire specimen in artificial saliva for 1 month to simulate oral conditions that may have effect on surface characteristics of restorations.
Ultrasonics, which basically works on acoustic streaming, acoustic turbulence, and cavitation phenomenon are widely used in routine dental practice for diagnostic, therapeutic as well as for cleaning of the instruments before sterilization.  Its main uses are scaling and root planning of the teeth.  In Endodontics, they are used for access refinement, finding calcified canals, and removal of attached pulp stones, removal of intracanal obstructions (separated instruments, root canal posts, silver points, and fractured metallic posts), to enhance the action of the irrigating solution, condensation of gutta percha, placement of mineral trioxide aggregate (MTA), and root canal preparation. In surgical endodontics; it is used for root-end cavity preparation, placement and refinement of root-end obturation. 
Ultrasonic scaling is essential part of periodontal therapy that includes elimination of plaque, calculus, and bacterial endotoxins from the tooth and exposed root surfaces. Ultrasonic scaling is routine oral prophylaxis advocated by periodontist by every 6 months  ; however, various tooth-colored class V restorations have considerable life. Plaque and calculus are deposited heavily in cervical regions of the teeth; thus, class V restorations are also exposed to the periodontal prophylaxis.  These cleaning procedures may lead to a number of unintended side effects most commonly increase in the surface roughness of dental hard tissues and restorative materials.  This kind of surface irregularities increases the available surface area 2 to 3 times, which provides the niche to attach and grow to the microorganisms leading to quicker plaque accumulation and more difficult plaque removal. , Eid et al. have mentioned that bacterial adhesion is directly proportional to surface roughness of the restorations.  Ikeda et al., also stated that surface roughness has a positive influence on S. mutans biofilm adherence. 
In this study, no additional finishing and polishing procedure were carried out to avoid intergroup variation. Bjorson et al. mentioned that the smoothest surface of a composite resin is produced when restoration is cured against a Mylar strip. , Pre- and post-instrumentation roughness were calculated in terms of Ra values (μm). Ra can be defined as the arithmetic mean of the departure of the profile from a mean line derived from the top and bottom of the undulations on the trace. 
Ultrasonic instrumentation has significantly altered the surface roughness of all the specimens [Figure 1]. This may be due to the preferential removal weak matrix phase; thus leaving the harder unreacted glass or filler particles protruding out from the surface. , Eid et al. also mentioned that differences in the roughness of different composites is due to differences in their size and content of filler particles.  Jyothi et al. also mentioned that the difference in the surface finish of Giomer and resin-modified glass ionomer cement (RMGIC) was due to the microstructure and mean particle size of the restoration.  That means higher the powder particle size of test group higher will be the post-ultrasonic roughness.
If the particle size of test groups are compared, it was in the order of GC9 (10 μm) > GC 2 LC (4.8 μm) > GC2 (4.4 μm) > Filtek Z 250 XT (sub 100 nm-0.2 μm). ,, According to this, GC9 should have highest delta value followed by GC2 LC, but in our study, GC2 LC showed highest delta value followed by GC 9 and rest of the sequence was similar as above [Figure 2]. This can be explained by the study of Berzin et al. who mentioned that RMGIC (GC2 LC) set by acid base and polymerization reaction and reactant of both these reactions compete and inhibit each other resulting into the formation of different structured material that may be more susceptible to ultrasonic scaling.  Hickel et al. also have mentioned that RMGI showed no increase in wear resistance as compared to conventional GICs.  Filtek Z 250 XT showed least pre- and post-ultrasonic instrumentation roughness, which is attributable to its smaller and wide distribution of particle sizes, higher filler loading (82% by weight) with resultant high strength and wear resistance when compared to other test groups. ,
The other reason might be the form of the restorative materials in which they are supplied. Composite is a single component material, whereas in case of Glass ionomers, powder has to be mixed with liquid, therefore risking the more air bubble incorporation and increased porosity. , These porosities may get enhanced after ultrasonic instrumentation leading to greater surface roughness.
When the critical threshold roughness for plaque (0.2 μm) is considered  , initial surface roughness of control and all the test groups except GC2 and GC9 were well below it. Post-ultrasonic instrumentation roughnesses of all groups except Filtek Z 250 XT were well above it [Figure 1]. When the critical threshold roughness for patient discomfort (0.5 μm) is considered  , initial surface roughness of all except GC9 were below this level suggesting that additional finishing and polishing is must for GC9. Post-ultrasonic instrumentation roughnesses of all except Filtek Z 250 XT were well above this critical level [Figure 1]. Thus, Filtek Z 250 XT has been found to withstand the vibrations of ultrasonic instrumentation better than other test groups and will cause no problem regarding plaque accumulation and patient discomfort [Figure 1] and [Figure 2].
However, the results of this in-vitro study may vary in in-vivo conditions as they are frequently subjected to various deleterious actions inside oral cavity like abrasion (brushing), attrition and erosion (citrus drinks, fruit, soft drinks, alcoholic and non-alcoholic beverages), exogenous substances including acids, bases, salts, alcohol, oxygen, etc. contacting the restoration surfaces during oral food and fluid intake and oral hygiene , and also to the cyclic flexural forces in the cervical region during occlusal loading.  However, Roselino et al. and Zuryati et al. concluded that abrasiveness of dentifrice and home bleaching procedure did not change the surface roughness of the composites. In contrast, Uppal et al. have concluded that oral hygiene maintenance procedure has significantly increased the roughness of the restorations.  Results after ultrasonic scaling are also subjected to vary depending on operator, power setting, tip to surface angle, sharpness of the working edge, instrumentation time after placement of the restoration, which may require further long-term studies for different time periods.
| Conclusion|| |
Within the limitations of this study, ultrasonic instrumentation has caused significant changes in the surface roughness of both control and test specimen. Type II GIC had highest, whereas nanohybrid composites had lowest pre- and post-instrumentation roughness values. Resin-modified GIC was found most susceptible to ultrasonic instrumentation, but the post-instrumentation roughness values were still close to that of control group. Nanohybrid composites are found to withstand the US instrumentation better than other tested materials, but still we would like to pass a message that carry out the routine ultrasonic scaling with caution, and subsequently polish the roughened restorations after scaling.
| Acknowledgment|| |
Our sincere thanks to Mr. Dhananjay Raje; MDS Bioanalytics Pvt. Ltd., Nagpur, India for their kind cooperation while conducting this study.
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Rajiv T Khode
Department of Conservative Dentistry and Endodontics, Vidya Shikshan Prasarak Mandal's Dental College and Research Center, Nagpur-440 019, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]
[Table 1], [Table 2]