Assessment of healing following low-level laser irradiation after gingivectomy operations using a novel soft tissue healing index: A randomized, double-blind, split-mouth clinical pilot study

Abstract

Background:

Lasers have become a part of modern dentistry since the past three decades. A wide-ranging assortment of lasers is being used in periodontology for both soft and hard tissue surgical procedures. Regardless of the frequent practice of using these well-known surgical lasers, there is another lesser familiar class of lasers called the low-level lasers. The main doctrine behind using low-level laser therapy (LLLT) is centered on the biostimulation, or the biomodulation effect, which relies on the dexterity of low-intensity laser energy when irradiated at a specific wavelength, is able to modify cellular activities (increase in cell metabolism and fibroblast and keratinocyte proliferation).

Aim:

The aim of the present study was to investigate the adjunctive use of LLLT on gingival healing after gingivectomy procedures.

Materials and Methods:

Ten systemically healthy patients requiring gingivectomy or gingivoplasty procedures bilaterally in either the maxillary or mandibular teeth were included in the study. After surgical intervention, a diode laser (810 nm) was randomly activated to one side of the operated area while other side did not receive any treatment and served as the control. The healing index given by Landry et al. was used to evaluate the soft tissue healing immediately postsurgery and at the 3^rd day, 1 week, and 2 weeks postoperatively. After the follow-up period, results were analyzed using appropriate statistical tests.

Results:

There was no statistically significant difference observed in the surface epithelialization between both groups on the 3^rd and 7^th-postoperative days, but highly significant differences were observed on the 14^th day.

Conclusion:

Within the confines of this pilot study, the outcomes have indicated that gingival wound healing may be improved using LLLT after gingivectomy and gingivoplasty operations.

INTRODUCTION

Laser dentistry has been at its zenith regarding research and clinical practice since the past decade. The first prototype of the laser was first developed by Maiman in 1960. The semiconductor diode lasers, also called as the GaAlAs or the “soft” lasers are compact and inexpensive compared to hard tissue lasers which have varied uses in the fields of medicine and dentistry.[1] These lasers fall under the infrared and red spectrum of light and range from 600 nm to 900 nm. Diode lasers have multiple applications, and in periodontology, it is used for laser bacterial reduction, laser-assisted periodontal therapy, mucogingival surgeries, etc., All diode lasers have an added property referred to as low-level laser therapy (LLLT) or “biostimulation” when used in low power.[2] This property of diodes is widely used for postoperative analgesia, for temporomandibular joint (TMJ) disturbances, to improve wound healing, etc. The mechanisms by which LLLT acts are complex but essentially rely on the fact that low levels of laser energy results in the stimulation of normal functions of cells. This result is accomplished by altering the mitochondrial respiratory chain or by acting on the calcium channels of the cell membrane.[3,4,5] This consequently stimulates cell proliferation and metabolism.[6,7]

In vitro and in vivo studies demonstrate the ability of this therapy in stimulating human fibroblasts, immune cells, and epithelial cells along with superior angiogenesis, growth factor release, and postoperative pain management which eventually leads to improved wound healing.[8,9,10] Various applications of LLLT have been tried and tested successfully in cases of TMJ pain, paresthesia, and periodontal ligament pain during orthodontic tooth movement, dentinal hypersensitivity and in periodontal wound healing after various mucogingival and gingivectomy procedures.[11,12]

Nonetheless, the results obtained after in vivo application of low-level lasers remains unclear even to this day. Due to an insufficient number of controlled clinical trials, not much is known about the ideal type of laser to be used, mode of delivery, optimum power output, best energy settings, and the manner of using these lasers in association with periodontal surgery.

Therefore, the aim of this randomized controlled clinical pilot study was to investigate the adjunctive use of LLLT on gingival healing after gingivectomy procedures.

MATERIALS AND METHODS

This pilot study was designed as a split-mouth, double-blinded study where both the examiner and the patients were blinded.

Study population

This study had a double-blinded, placebo-controlled, and split-mouth design. The study population comprised systemically healthy nonsmoking patients with existing gingival enlargement, who had been referred to the postgraduate clinic of the Department of Periodontics between June 1, 2015, and October 15, 2015. Ten patients who fulfilled the study's inclusion criteria were selected. Inclusion criteria were patients aged 18–50 years, systemically healthy patient with no history of pregnancy/lactation, patients without any history of periodontal surgery in the past 1 year, and diagnosed as inflammatory type gingival enlargement. Exclusion criteria include patients who were not likely to maintain appointment schedule, previous periodontal surgery within 1 year on study tooth, pregnant/lactating mothers, and smokers. Gingivectomy or gingivoplasty operations had been planned in each of these patients based on his/her customized treatment plan. Since this is designed as a pilot study, a small sample size is selected. Each individual signed a detailed informed consent form, and ethical approval was granted by the Institutional Review Board for ethical issues (436/SSCDS/IRB-E/OS/2014).

Surgical protocol and low-level laser therapy application

In all patients, presurgical preparation consisted of one stage full-mouth scaling and root planning using hand and ultrasonic instruments and oral hygiene instructions.[13] After 4 weeks, the physiologic gingival contours were reexamined for the need of gingivectomy/gingivoplasty.

On reevaluation, ten patients (eight female and two male) who had bulbous or overcontoured gingiva in either of the jaws with a minimum of six teeth affected were enrolled in the study.

A simple external bevel gingivectomy procedure was carried out in these patients with the help of a Kirkland and Orban's knives and #15 Bard-Parker blade. Excised tissue was removed using curettes, and superficial gingivoplasty was performed to reestablish suitable esthetic contours. Once, hemostasis was achieved one half of the surgical site which was assigned to the test group by coin toss. The test site was irradiated with a diode laser (810 nm Picasso diode laser, AMD lasers, Indianapolis, USA) at a power setting of 0.1 W applied in a continuous wave, noncontact mode for 5 min [Figure 1]. Sham laser application was imitated for the control sites.

Figure 1.

Application of low-level laser therapy in noncontact defocused mode on test side

In all the patients, periodontal dressing (Coe-Pak) was placed. The dressing was replaced at the 3^rd and 7^th-postoperative visits when laser was reapplied on the test sites [Figures 2 and 3] while the control sites again underwent laser imitation. On the 14^th day, the dressing was removed, and final application of laser was performed [Figure 4]. To cope with postoperative pain, the patients were prescribed ibuprofen and were instructed to take as needed but not more than thrice per day.

Figure 2.

Third-day postoperative view after application of low-level laser therapy and two-tone dye

Figure 3.

Seventh-day postoperative view after application of low-level laser therapy and two-tone dye

Figure 4.

Fourteenth-day postoperative view after application of low-level laser therapy and two-tone dye

At each appointment, the wound healing was assessed postlaser application using a healing index Landry et al., [Table 1] which grades the wound on a scale of 1–5, where 1 indicates very poor healing and five indicates excellent healing.[14] All gingivectomy procedures and laser stimulations were performed by one examiner (S.L.), whereas healing index scores were given by a different examiner (L. M.).

Table 1.

Healing index by Landry et al.

Surface area determination

After application of LLLT on each postoperative visit, the surgical sites were stained by a plaque-disclosing agent (2-Tone disclosing tablets, Young, USA) to identify the regions of gingiva in which the epithelialization was incomplete or lacked complete keratinization [Figures 2 and 4].

The surface area was determined by digitizing the clinical photographs of the surgical sites and by superimposing a 1 mm × 1 mm digital grid onto the digitized images to standardize all the clinical photographs. These digital images were obtained immediately after the gingivectomy procedure and on all the following visits after applying the laser.

The darkly stained bluish areas were deliberated as sites still going through the process of wound healing and showing incomplete surface epithelialization. Surface areas of stained sites in both the test and control groups were compared at the 3^rd, 7^th, and 14^th-postoperative day and were further evaluated using appropriate statistical tests.

Statistical analysis

The Mann–Whitney U-test was used to evaluate the differences between the test and control groups at each time point. Statistical significance was set at P ≤ 0.05, with <0.001 considered highly significant and >0.05 considered as not statistically significant. The Statistical Package for the Social Sciences version 20.0 for Windows (SPSS Inc., Chicago, IL, USA) was used for statistical tests.

RESULTS

Ten systemically healthy controls diagnosed with inflammatory type gingival enlargement with the age of 30–50 years (mean ± standard deviation: 34.5 ± 5.9 years) comprised the study population in the present study. All the ten enrolled patients completed the study without any dropouts in any of the postsurgical visits. Healing took place uneventfully with no patients reporting any adverse postoperative complications. The results for the surface area keratinization are summarized in Table 2 and Graph 1 and the healing index scores in Table 3 and Graph 2.

Table 2.

Intergroup comparison of darkly stained areas in % on the 3^rd, 7^th, and 14^th days

Graph 1.

Intergroup comparison of darkly stained areas in percentage (%) on the 3^rd, 7^th, and 14^th day. Graph 1 illustrates intergroup comparison of darkly stained areas in percentage (%) on the 3^rd, 7^th, and 14^th day showing that the test group resulted in better healing by having lower percentage of darkly stained areas. Darkly stained areas indicate epithelialization was incomplete or lacked complete keratinization

Table 3.

Intergroup comparison of healing index scores on the 3^rd, 7^th, and 14^th days

Graph 2.

Intergroup comparison of healing index scores on the 3^rd, 7^th, and 14^th day. Graph 2, with healing index scores on the Y-axis and day of evaluation on the X-axis, illustrates better healing with test group compared to the control group

On the evaluation of surface keratinization, it was observed that the stained areas of both groups on the baseline (immediate postsurgery) and on the 3^rd and 7^th postoperative days showed no statistically significant differences. However, on the 14^th postoperative day, laser-activated sites showed significantly less surface area that was darkly stained when compared to the controls (P = 0.001), demonstrating better surface epithelialization. Intergroup comparison of the healing index scores indicates results similar to that of the surface keratinization, wherein there was no statistically significant difference in healing scores at day 0, 3^rd postoperative, and 7^th postoperative visit. On the 14^th postoperative day, a significant difference in healing was observed among the two groups (P = 0.004).

DISCUSSION

The prevailing concept of the use of laser biostimulation as an adjuvant to conventional periodontal procedures is that LLLT influences the patient's postoperative pain perception along with enhancing the outcome of the treatment and has been the area of curiosity to both researchers and clinicians alike. However, there seems to be paucity in the available literature in the form of randomized clinical trials assessing the effectiveness of LLLT in periodontal procedures.

In the present study, the outcomes discovered indicated that laser biostimulation helps stimulate wound healing and improves the amount of surface keratinization after gingivectomy and gingivoplasty. Healing postsurgery is the interplay of various cells of the gingiva such as fibroblasts, keratinocytes, and the immune cells. Fibroblasts begin laying a new connective tissue beneath the epithelial seal which forms due to the migration of cells over the wound surface.[15] Throughout the process of healing, a series of events occur which are mediated by cytokines and growth factors that are released by immune cells. Literature suggests that LLLT -application increases the motility of epithelial cells and proliferation of fibroblasts which ultimately leads to enhanced wound healing.[8] It has been shown by Tuby et al. in an animal study on rats that macrophages and fibroblasts show enhanced expression of fibroblast growth factors after low-level laser application.[16] Laser biostimulation is known to heighten the revascularization process. It is known that higher rates of revascularization lead to successful healing.[17] An in vitro study showed that gingival fibroblast proliferation was higher when irradiated with low-level laser.[18]

In spite of the above-mentioned studies, there are hardly any clinical trials available to compare the results obtained in the present study. In 2006, Amorim et al. have stated that wound healing following gingivectomy was significantly promoted by the application of LLLT (at 685 nm), but contrasting results were seen in a study by Damante et al. in 2004 where a 670 nm diode laser biostimulation failed to improve healing of the gingiva when subjective criteria such as color, contour, and texture were taken into account.[11,12] In a recent study by Ozcelik et al. in which a 588 nm diode laser was used, showed superior wound healing in sites where LLLT was applied for 7 consecutive days.[19] The authors showed that the test sites had significantly better epithelialization when compared to control sites on the 3^rd, 7^th, and 15^th-postoperative days. In the present study, the results clearly show a significant difference in the levels of surface keratinization between both groups on the 14^th-postoperative day (P = 0.001), while no significant difference was observed on the 3^rd and 7^th-postoperative days. This difference may be attributed to the difference in the wavelength and settings of the laser used.

Moreover, the majority of variance seen may be due to the difference in the study design, i.e., laser application was not done on the consecutive days.

The novelty of this study when compared with those of the ones described earlier is the incorporation of a healing index that was given by Landry et al.[14] This index has been used earlier in the evaluation of various soft tissue procedures in the fields of periodontology and oral and maxillofacial surgery. Scoring criteria of this index are based on five criteria redness, presence or absence of granulation tissue, bleeding, suppuration, and epithelialization. The score ranges from 1 to 5, with 1 being very poor and 5 being excellent healing. Jankovic et al. used this index to assess the healing of gingival recessions treated with coronally advanced flaps and connective tissue grafts in combination with platelet-rich plasma (PRP) gel.[20] This healing index was also used to measure soft tissue healing after PRP placement in extraction sockets and after periodontal, implant surgery.[21,22]

Like any other work of research, this pilot study also has some limitations. To begin with, being a pilot study, small sample size was recruited, this may affect the consistency of the results, and hence, larger clinical trials are required to assess the true beneficial nature of LLLT. Available literature was not sufficient in this regard, especially for the population in question, and so, a pilot was attempted which can provide valid estimates for sample size calculation for further studies. Second, this study was designed as a purely clinical study with no histological evaluation. Therefore, to assess the effect of LLLT on gingival healing at a cellular level, further histological studies with larger sample sizes are required. Furthermore, the application of customized setting which has not been described earlier in literature is also a notable and influencing factor in predicting the outcome of the study.

CONCLUSION

Within the confines of this pilot study, the outcomes have indicated that gingival wound healing may be improved using LLLT after gingivectomy and gingivoplasty operations. Greater insight into the action of LLLT and its effects on the various cellular structures will largely increase our knowledge and help us in further sophisticating this treatment modality.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.