Ultra-morphology of root surface subsequent to periodontal instrumentation: A scanning electron microscope study.

BACKGROUND: The aim of this study was to compare root surface characteristic following root planing with various hand and power driven instruments.
MATERIALS AND METHODS: A total of 20 single rooted teeth were used in this study, of which two specimens were used as control (no instrumentation done) and remaining 18 specimens were equally divided into three groups. Specimens from each group were then subjected to root planing by one of the following instruments: (1) a Gracey curette (2) Ultrasonic tip and (3) a Rotary bur. In each case, the time required for scaling and root planing was measured. After treatment, the specimens were observed under scanning electron microscope and surface roughness was measured by using Roughness and loss of tooth substance index (RLTSI).
RESULTS: The mean RLTSI scores for Gracey curette, ultrasonic and rotary instrument group were 2.5, 2.0 and 0.667 respectively. The mean scores of time spent for scaling and root planing by Gracey curette, ultrasonic and rotary instrument group in seconds were 42.50, 35.83 and 54.50.
CONCLUSION: All the three instruments namely Gracey curette, Ultrasonic tip and Rotary bur were effective in mechanical debridement of root surface. The results favoured the use of rotary instruments for root planing to achieve smooth clean root surface; however, the use of rotary instrument was more time consuming which might limit its use in clinical practice.

INTRODUCTION

A primary goal in the treatment of periodontitis is the removal of bacterial deposits and the arrest of disease progression. Mechanical removal of these deposits from the root surface is required for establishing and maintaining periodontal health. Large number of studies has reported beneficial results from mechanical therapy in term of both clinical and microbiological aspects.[1-3] Since long, the hand instruments were the first choice of clinicians. It was believed that these instruments produced a smooth root surface; however, considerable manual dexterity is required for their effective operation. Moreover, hand instruments are more time consuming and are unable to reach deeper root surface where pockets are more than 4 mm deep.[45] Ultrasonic tips were originally designed for gross scaling and removal of supragingival calculus and stains. More recently, these power driven instruments have been modified to have smaller diameter tips and longer working lengths, thereby providing better access to deep probing sites and more efficient subgingival instrumentation. Ultrasonic instruments are simple to use; however, it is often difficult to achieve a smooth and calculus free root surface.[67]

To overcome these challenges associated with use of ultrasonic and hand scalers, rotary instruments for scaling and root planing have been developed. These are found to be more effective in root furrows, furcation areas and root surfaces in areas of deep and narrow infra bony pockets.[8] It has been now well documented that all the hand and power driven instruments cause some gouging and removal of tooth substance. This could have an important clinical implication keeping in view the problems of hypersensitivity and roughness of the root surfaces. Hence, the present study aimed to evaluate root surface characteristics following treatment with hand and power driven instruments.

MATERIALS AND METHODS

The teeth selected for study were extracted from patients who reported to the outpatient department of oral and maxillofacial surgery of Dayanand Anglo Vedic (DAV) Dental College and Hospital, Yamuna Nagar, Haryana (India). Teeth that had undergone a root canal and/or treatment associated with any periapical lesion, caries, or had history of scaling and root planing in previous 6 months were excluded from the study.

Collection and storage of teeth

20 single rooted human teeth, extracted due to severe chronic periodontitis and having hopeless prognosis with bone loss >70% and grade III mobility, were used in this study. The teeth were then washed with distilled water and treated with 2% sodium hypochlorite solution and then stored in normal saline until further study.

Preparation of teeth

Two specimens were used as control and remaining 18 specimens were equally divided in the following three groups.

Group I Specimens treated with hand instruments

Group II Specimens treated with ultrasonic instrument

Group III Specimens treated with rotary instrument

Control

The specimens of control group were thoroughly cleaned and washed using toothbrush only.

Hand instruments

1-2 and 3-4 Gracey Curettes (Hu-Friedy, USA) were used for instrumentation. Strokes were given on the proximal surfaces along the long axis of the root.

Ultrasonic instrument

Instrumentation was performed with Piezo-electric ultrasonic scaling unit (EMS SA, Germany). A sub-gingival slim perio (PS) ultrasonic tip was used according to the manufacturer's instruction under profuse rinsing with water spray and at a medium power setting. Lateral side of the ultrasonic tip was used with feather light touch. Unidirectional strokes were given on the proximal surfaces along the long axis of the teeth under study.

Rotary instruments

Rotary instruments were used with contra-angle hand piece of micro-motor for root instrumentation. These rotary carbide burs [Desmoclean (Hager, Germany)] were used at 8000 revolutions per minute (RPM) with light pressure and water spraying. These burs have non-cutting, elliptical, hexagonal, narrow and long heads (1:1) = 29 mm. Unidirectional strokes were given on the proximal surface along the long axis of the teeth. In our study, degree of sharpness, application force and clinician skills were maintained during the preparation of specimens. Degree of sharpness was maintained as curettes were sharpened after every 10 strokes to maintain a standard optimum sharpness.[9] The normal force was established based on the mean force generated on a gram scale by 6 trained periodontists with periodontal instruments. The standard force of 500 g or 5 N was chosen for the study because it would allow sufficient root surface removal that would be easily detectable by digital calliper and this force could be easily controlled, reproduced and verified in bench top analysis.[10] The application of this force was verified prior to instrumentation using a digital gram scale to ensure similar force with each instrument.[11] The proximal surfaces were chosen for the study as they have a higher surface area as compared to the buccal/labial or lingual/palatal surfaces, and thus help for better evaluation of the root surface characteristics.[1213] So as to maintain the skills as constant, a single clinician prepared all the specimens. After instrumentation, 7-8 mm of the treated root surface was cut by a carbide disc from the cementoenamel junction and the apical root pieces were discarded.

Measurement of time required for scaling and root planing

The length of time required for scaling and root planing with each instrument was measured by using a stopwatch from the start, until the root surface appeared smooth again upon visual inspection and examination with an explorer.

Preparation of root specimens for scanning electron microscope study

Following the mechanical treatment, all specimens were dehydrated in graded series of ethanol (50, 70, 80, 90, 95% and absolute alcohol using 100% acetone as the final step). The specimens were kept for half an hour in all grade series of ethanol and for 1 hour in 100% ethanol. The specimens were dried for half an hour. They were then mounted on the aluminum stub with an adhesive tape in such a way that root specimens were placed in the center of stubs. The specimens were then sputter coated with gold with the help of a sputter coating machine. The gold coating was done to ensure a proper conducting surface to the non-conducting specimens.

Determination of root surface roughness

The scanning electron microscope (SEM) photomicrographs at ×500 were scored blindly and independently by two investigators using roughness and loss of tooth substance index [Table 1]. To eliminate bias, the study was designed so that the person who evaluated roughness was unaware of the procedure used.

Table 1

Roughness and loss of tooth substance index scored by two examiners for three experimental groups (by Gracey curette, ultrasonic tips and rotary instrument groups) in the study

Roughness and loss of tooth substance index

Smooth and even root surface without marks from instrumentation and with no loss of tooth substance

Slightly roughened and corrugated local areas confined to cementum

Definitely corrugated local areas where cementum may be completely removed, although most of the overall cementum is still present

Considerable loss of tooth substance with instrumentation marks into the dentin. The cementum is completely removed in large areas. Or, it has a considerable number of lesions from the instrumentation.

RESULTS

Measurement of surface roughness

The mean roughness scores for Gracey curette, ultrasonic and rotary instrument group were 2.5, 2.0 and 0.667 respectively. This suggested that rotary instruments produced the smoothest surface followed by ultrasonic tips and hand curette. Results were significant when rotary instrument group was compared to Gracey curettes and ultrasonic group. However, non-significant differences were found while comparing Gracey curettes and ultrasonic groups [Table 2].

Table 2

Comparison of root roughness in all the three experimental groups (by Gracey curette, ultrasonic tips and rotary instrument groups) in the study

Measurement of time spent for scaling and root planing of test surface

The time required for treatment using a rotary instrument was significantly longer than that required by the Gracey curette and ultrasonic instrument tips. The mean scores for Gracey curette, ultrasonic and rotary instrument groups were 42.50, 35.83 and 54.50 second [Table 3]. Comparison of time spent by rotary instrument group with other two groups was significant. However, there were no significant differences between the ultrasonic and Gracey curette groups [Table 4].

Table 3

Measurement of time (in seconds) for instrumentation in three experimental groups (by Gracey curette, ultrasonic tips and rotary instrument groups) in the study

Table 4

Comparison of time in second for instrumentation in all the three experimental groups (by Gracey curette, ultrasonic tips and rotary instrument groups) in the study

DISCUSSION

In earlier studies, root surface roughness and tooth substance loss was evaluated by measuring the size of instrument marks,[14] by calculating weight of removed tooth surface,[15] by inspecting the surface under light microscope[16] and measuring the surface roughness by profilometer. The results of such studies have been variable and inconclusive; however, the use of scanning electron microscope can eliminate various difficulties encountered with other techniques of examining root surfaces and help us to have more definite results. Some studies reported significant differences in the tooth topography with respect to type and/or sharpness of the instrument, number of strokes used and whether the tooth was moist, and under copious lavage or dentifrice use. Sharp hand curette clearly planed away considerably more accretions and dental tissue than its dull counterparts. Hand instruments often produced a haphazard, irregular pattern particularly when vertical and horizontal strokes were combined. Distinct pattern was not noted with dull instruments. Therefore, increasing the number of strokes with dull curette might serve adequate to remove surface accretions with minimum of structural alteration of the tissues.[17]

In the present study, microscopic examination of the control specimens affected with periodontal disease showed areas of small foreign particles [Figure 1]. These particles were nodular and irregular in texture. These small foreign bodies were deposits of calculus. Other areas on root surface appeared amorphous and were suggestive of aggregates of microorganisms or plaque. Specimens treated with Gracey curette were comparatively smoother as compared to the control specimens [Figure 2]. However, deep scratches and gouging were present, representing the pathway of instrumentation and considerable loss of tooth substance during the root planing. Wilkinson suggested that even a delicate hand instrument creates irregularities and scratches on root surface, which would possibly be attributed to the microscopic roughness of the instrument's cutting edge.[18] The mean value of score as calculated by roughness and loss of tooth substance index was 2.5. This high mean value suggested that more of the tooth substance was removed by curette, resulting in a roughened root surface.

Figure 1

Morphology of root surface of control specimen, scanning electron microscope photograph, ×500

Figure 2

Morphology of root surface planed with Gracey curette, scanning electron microscope photograph, ×500

Ultrasonic instruments have been used as valuable adjuncts to conventional hand instruments for many years. Newly designed thin ultrasonic tips have allowed better access to sub-gingival areas previously accessible only with hand instruments.[19] Earlier studies using older tips’ designs generally showed that ultrasonic instruments left a “stippled” root surface and had a greater potential for producing root surface damage than curettes.[2021] More recent studies, especially those using the newer, thinner tips show that ultrasonic instruments can produce root surfaces as smooth as or smoother than what is produced by the curettes.[2223] Current evidence suggests that ultrasonic tips used on medium power may do less damage to the root surface than the hand or sonic scalers.[24] Some studies suggested that the rotary instruments at high speed (2,00,000 revolutions per minute) and ultrasonic instruments caused more damaged to root surface when compared with hand curettes.[14] Lie and Mayer in 1977 found that diamond points with a constant speed of 3000 revolutions per minute produced the roughest surfaces when compared to hand curettes and ultrasonic instruments.[25]

The specimens treated with ultrasonic instrument provided an interesting topography [Figure 3]. The instrument created an irregular surface, consisting of depression and elevations. The mean score as calculated by RLTSI was 2.0. The specimens treated with rotary instruments were flat and smooth, with no signs of gouging and scratching [Figure 4]. The mean score for RLTSI was 0.667, which represented a smooth, flat and clear root surface. The specimens treated with rotary instruments produced the smoothest surface, which might be because the burs had a non-cutting, and elliptical or hexagonal in shape heads. The effectiveness of ultrasonic instrumentation as a function of time was proved by the present study. The mean time required for Gracey Curette instrumentation, ultrasonic instrumentation and rotary instrument group was 42.50 seconds, 35.83 seconds and 54.50 seconds, respectively. The result showed that far more time was required by the rotary instruments than the ultrasonic and hand instruments. However, the comparison of the curette and ultrasonic group was not significant (P>0.01). We would also acknowledge that a large sample size would have yield more statistically significant results as compared to smaller data; however, in the literature, there are a number of pubmed indexed studies in which the sample size is either less or comparable to our study.[26]

Figure 3

Morphology of root surface planed with ultrasonic instrument, scanning electron microscope photograph, ×500

Figure 4

Morphology of root surface planed with rotary bur, scanning electron microscope photograph, ×500

CONCLUSION

In the present study, it was proved that all the three, namely curette, ultrasonic and rotary instruments were effective in mechanical debridement of the tooth root surface. The root surface treated with rotary instruments appeared flat and glossy to naked eye and the SEM pictures revealed the smoothest surface. The roughness produced by Gracey curette was found to be high, followed by ultrasonic tip and the rotary bur. The time spent for scaling and root planing with rotary bur was significantly long than the time needed for Gracey curette and ultrasonic tip instrumentation. The results favoured the use of rotary instruments for root planing to achieve a smooth clean root surface. However, the use of rotary bur was more time consuming which might limit its use in clinical practice. In the literature, there are number of in vitro studies that evaluated gracey curettes, sonic and ultrasonic scalers, diamond burs on the root surface characteristics; however, our study compared non cutting hexagonal carbide bur with the ultrasonic tip and Gracey curette by maintaining constant angulation, force and clinical skills. However, the therapeutic efficacy of these carbide burs can be better evaluated after long term clinical studies with some better clinical parameters on a large sample size.

Further researches in this area may include a quantitative study of tooth substance loss with various periodontal instruments and effects of root surface characteristics on fibroblast attachment after mechanical debridement. Such studies will be very helpful in opening new vistas of research for understanding the treatment modalities for optimal regeneration of supporting tissue onto the tooth surface affected by periodontitis.