A comparative study of radiofrequency and diode laser assisted crown lengthening procedure with clinical and patient centered outcomes

Abstract

Background

Excessive gingival display can be treated with crown lengthening by scalpel, lasers, or electrosurgical equipment. This study aimed to evaluate the effects of crown lengthening, performed with diode laser or radiofrequency in terms of patient comfort and clinical outcomes.

Methods

19 patients with type 1A altered passive eruption in the maxillary anterior treated with diode laser (n = 11) or radiofrequency (n = 8) were included. A total of 114 teeth were analyzed. Patient-centered outcomes (post-operative bleeding, pain level, esthetic satisfaction) and clinical outcomes (swelling, gingival color, gingival margin stability) were evaluated at baseline and post-operative seven days, six weeks, and six months.

Results

No significant differences were observed in terms of post-operative bleeding, pain, swelling, and gingival color at different time intervals between groups. In both groups, gingival margin change was significant from baseline to six weeks (p < 0.05); while it was non-significant between six weeks and six months, confirming the gingival margin stability (p > 0.05). In terms of esthetics, 17 patients were fully satisfied, with a higher proportion in the laser group.

Conclusions

A clinician can safely use both laser and radiofrequency in the treatment of excessive gingival display as both yield favorable clinical and patient-centered outcomes.

Background

Gingival components play a significant role in determining the overall appearance of a smile, and changes in texture, color, shape, and position of the gingival margin can impact how appealing a smile appears. Dentists often consider these factors along with other elements including the alignment of the teeth, symmetry, and overall oral health when evaluating smile aesthetics.

Excessive gingival display (EGD) or “gummy smile” is the main issue of the periodontium associated with an attractive smile [1]. EGD describes the condition in which 3–4 mm or more gingiva is apparent and has been recognized as a “mucogingival deformity affecting the tissues surrounding the teeth” by the American Academy of Periodontology [2, 3]. EGD may develop due to skeletal (vertical overdevelopment of maxilla), muscular (short or hypertonic upper lip) or dentogingival abnormalities (altered passive eruption), or a combination of them. Altered passive eruption (APE), occurs when the gingival margin is positioned more coronally due to the inadequate completion of the passive eruption phase of tooth development, resulting in a shorter clinical crown. A recent study reported that approximately 12.1 to 35.8% of diagnosed EGD cases are associated with APE [4]. Accordingly, APE is defined as the most common etiologic factor of EGD [2, 5].

Altered passive eruption was classified morphologically into two groups and two subgroups by Coslet et al. [6] Type 1A: The bone crest is located apically to the cementoenamel junction (CEJ), and there is an adequate amount of keratinized gingiva. Type 1B: The bone crest is located at the same level as the CEJ, and there is an adequate amount of keratinized gingiva. Type 2A: The bone crest is located apically to the CEJ, but there is an inadequate amount of keratinized gingiva. Type 2B: The bone crest is located at the same level as the CEJ, and there is an inadequate amount of keratinized gingiva. APE can be ideally treated by crown lengthening to increase the length of the clinical crown and reduce the EGD [7]. Crown lengthening can be performed by gingivectomy alone or gingivectomy combined with osteotomy. The choice of technique is determined based on the type of APE. For instance, in cases classified as APE type 1A, gingivectomy alone is sufficient. However, for type 1B, a combination of osteotomy and gingivectomy is necessary. Conversely, in type 2B cases, gingivectomy is contraindicated due to the critical width of the keratinized gingiva, and instead, the procedure should be made using a sulcular incision [5].

Crown lengthening can be achieved by using a scalpel, electrosurgery, and lasers [2]. Lasers, particularly diode lasers, have advantages such as patient comfort, safety, hemostasis, bactericidal effects, less post-operative pain, and minimal pulp damage. Due to these advantages, it is used more widely than conventional surgery in crown lengthening [2, 8] Radiofrequency (RF) is one of the electrosurgery methods, in which soft tissue is removed by the conversion of electrical current to radio waves. Radio waves pass through cells and produce heat. Increasing the temperature to varying degrees has different biological effects on tissues resulting in incision, excision, or coagulation. RF has advantages such as minimal bleeding, less chairside time, and increased patient comfort [9]. Although there is a considerable number of studies about the use of diode lasers in soft tissues [10–13], the effect of RF remains to be explored. Recently, Elemek et al. [14], in a rat model performed scalpel, diode laser, and RF to evaluate wound healing and found comparable results emphasizing the need for further in-vivo studies. To our knowledge, there is no clinical study comparing the effect of diode laser and RF in soft tissue wound healing.

The aim of this study was to evaluate two treatment approaches for crown lengthening: diode laser and radiofrequency, in patients with altered passive eruption type 1A in terms of patient comfort, satisfaction, and clinical stability.

Methods

A total of 28 patients applied to Department of Periodontology in Bahçeşehir University School of Dental Medicine and private practice between June 2018 and March 2024, with a chief complaint of EGD when smiling, were screened. University of North Carolina (UNC)-15 periodontal probe was used to classify patients in terms of APE Coslet et al. [6].

Patients who were systemically healthy had no clinical attachment loss, provided good oral hygiene, and had APE type 1A in the maxillary anterior region that were treated with diode laser or RF, were included in the study. Exclusion criteria were the presence of systemic disease, pregnancy or breastfeeding, the use of medications that would affect periodontal wound healing, periodontally compromised patients, and those who had undergone periodontal surgery in the maxillary anterior region in the last 6 months. Consequently, nine patients were excluded as they did not match the criteria because of different APE diagnoses, treatment by conventional surgical therapy and not having good-quality photographs. Therefore, the study group consisted of 19 patients (16 female, 3 male) aged between 20 and 37 years. A total of 114 teeth (n = 66 laser group, n = 48 RF group) were analyzed. Üsküdar University Ethics Committee for Non-Interventional Studies approved the study protocol (approval number: 2024-33).

Clinical procedures were performed by a single periodontist (E.E.). Initial periodontal treatment was performed, and oral hygiene instructions were given to all patients before the procedure. The diode laser group was treated using an 810 nm wavelength diode laser at an output power of 1.2 W in contact mode, positioning the 400 μm fiber optic tip at a 45-degree angle to the long axis of the tooth (CheeseTM, GIGAA Laser, Wuhan, China) [10, 13, 15]. Saline-soaked sponges were used to provide cooling and remove the debris. The crown lengthening procedures in RF group were achieved by a monopolar radiofrequency device (Surtron 50D; LEDSpA, Aprilia, Italy) at 15 W in a fully rectified waveform. A round-shaped electrode was used with sweeping motions to bevel the tissue [16]. No antibiotics and analgesics were prescribed, only 0.12% chlorhexidine containing mouthwash was recommended twice a day during a 7-day period post-operatively. No sutures were needed for any of the treatment methods, as crown lengthening was achieved with gingivectomy alone.

Patient-centered outcomes

To assess the perception of patients; the presence of bleeding, pain, and overall satisfaction was evaluated. Patients were asked to report if they experienced any post-operative bleeding (yes/no) the day after the procedure. Pain level was also assessed one and seven days after the surgery, using a visual analog scale (VAS) on a 10-cm scale (0 indicating “no pain” while 10 indicating “excruciating pain”) [2, 17].

Finally, the patient’s esthetic satisfaction was assessed using a three-point rating scale (fully satisfied, satisfied, unsatisfied) [2] .

Clinical measurements

Clinical features of periodontal wound healing were observed one week and six weeks after the procedure. At week one, soft tissue swelling (0 = No swelling, 1 = Moderate swelling, 2 = Pronounced swelling), and at weeks one and six, gingival color (0 = No redness, 1 = Moderate redness, 2 = Pronounced redness) was evaluated visually as described in the study by Borham et al. [7]

Intraoral photographs were taken standardized by every patient before and after the procedure, including follow-ups.

Gingival margin stability was assessed using the Image J program (Wayne Rasband, National Institute of Health, USA) [18, 19]. The resolution of photographs was arranged equally, and the clinical crown length of the operated teeth was measured from the incisal edge to the most coronal part of the gingival margin at baseline, six weeks and six months. The change in percentage was taken into consideration.

All assessments were performed by a single periodontist (E.R.T). To reduce bias, measurements were conducted using anonymized intraoral photographs, and the examiner was blinded to the treatment group. To ensure measurement reproducibility on Image J program, a calibration procedure was performed in 7 randomly selected cases by the same examiner at a 7-day interval. Intra-class correlation coefficient (ICC) was found to be 0.91, indicating excellent reliability.

Statistical analysis

Data were analyzed using IBM SPSS v23. Normality was assessed using the Kolmogorov-Smirnov and Shapiro-Wilk tests. For comparing two-category independent variables, the Independent Samples t-test was used for normally distributed data, while the Mann-Whitney U test was used for non-normally distributed data. The Wilcoxon Test was used to compare two category-dependent variables for non-normally distributed data. For comparing three or more dependent variables, Repeated Measures ANOVA was used for normally distributed data, with multiple comparisons examined using the Bonferroni test. For non-normally distributed data, the Friedman Test was used, and multiple comparisons were examined using the Dunn Test. For both statistical methods, 95% confidence intervals (CI) for the mean differences between the laser and RF groups were reported. Fisher’s Exact Test was used to examine the association between categorical variables. In addition to p-values, absolute risk differences (RDs) and their corresponding 95% CI were calculated to provide a more interpretable estimate of group differences. Quantitative data were presented as Mean ± Standard Deviation or Median (minimum-maximum), while categorical variables were presented as frequency and percentage. The significance level was set at p < 0.05.

Results

A total of 19 patients (16 female and 3 male), aged 20 to 37 years (Mean age: 30.37 ± 4.63), were included in this study. Each patient randomly received laser or RF treatments. (11 laser, 8 RF). Out of 19 patients, only 3 were smokers and they were all in the laser group. The demographic data of patients are presented in Table 1.

Table 1.

Demographic data

	Laser	RF†	Total	p
Gender (n)
Male	1	2	3	0.546a
Female	10	6	16
Smoking (n)
No	8	8	16	0.228a
Yes	3	0	3
Age
Mean ± SD	29.55 ± 4.01	31.5 ± 5.45	30.37 ± 4.63	0.262b

^aFisher Exact Test; ^b Mann Whitney U test

^†Radiofrequency

Data about swelling, pain, post-operative bleeding, VAS, esthetic satisfaction, and gingival margin stability measured at different time points are given in detail in Table 2. In intergroup analysis, no significant differences were found in swelling at day seven (95% CI: −0.76 to 0.40; p = 0.545) and in gingival color at day seven and 6 weeks (95% CI:-1.09 to 0.045; p = 0.075 and 95% CI: -0.29 to 0.39; p = 0.744). In intragroup analysis, gingival color demonstrated significant improvements at the sixth week as compared to the first week (p < 0.05) (Figs. 1a-b and 2a-b).

Table 2.

Evaluation of swelling score, gingival color, VAS score, post-operative bleeding, gingival margin levels and esthetic satisfaction in laser and radiofrequency groups

Time interval
		Baseline	1 Day	1 Week	6 Weeks	6 Months	p-value
Swelling score (Mean ± SD)	Laser RF† p-value 95% CI^			0.82 ± 0.4 1 ± 0.76 0.545a -0.76-0.40
Gingival Color (Mean ± SD)	Laser RF p-value 95% CI			0.73 ± 0.47 1.25 ± 0.71 0.075a -1.09-0.05	0.18 ± 0.4 0.13 ± 0.35 0.744a -0.29-0.39		0.014b 0.014b
VAS (Mean ± SD)	Laser RF p-value 95% CI		0.73 ± 1.01 1.25 ± 2.31 0.920a -2.23-1.19	0 ± 0 0 ± 0 1.000a 0–0			0.046b 0.157b
Post-operative bleeding (yes)(n)	Laser RF p-value RD¥ (95% CI)		0 2 0.164c -0.25 (95%-0.55-0.05)
Change in gingival margin levels from baseline (%) (Mean ± SD)	Laser				-12.85 ± 12.01*	-15.8 ± 11.69*	< 0.001d
	RF				-14.54 ± 11.06*	-17.09 ± 12.16*	< 0.001e
	p-value				0.435a	0.477a
	95% CI				-8.76-12.14	-9.61-12.19
						Change between 6w‡-6 m§	0.089d
	Laser					-2.94 ± 7.41	0.080e
	RF					-2.41 ± 7.15
	p-value					0.143a
	95% CI					-7.14-6.08
Esthetic satisfaction (fully satisfied) (n) (%)	Laser RF p-value RD (95% CI)					11 (100) 6 (75) 0.164c + 0.25 (95%CI − 0.05–0.55)

^a Mann Whitney U test ^b Wilcoxon test ^cFisher Exact Test ^dFriedman Test ^e Repeated measures ANOVA

*Statistically significant compared to baseline

^† Radiofrequency

^{^} 95% Confidence Interval

^¥ Risk difference

^‡ 6 weeks

^§ 6 months

Fig. 1.

Diode laser assisted crown lengthening. 1a: Baseline. 1b: 6 weeks after treatment with diode laser. 1c: 6-months follow-up

Fig. 2.

Radiofrequency assisted crown lengthening. 2a: Baseline. 2b: 6 weeks after treatment with Radiofrequency. 2c: 6-months follow-up

There was no significant difference in VAS score between groups on day one and seven, while it was measured slightly more but not statistically significant in the RF group on day one (95% CI: -2.23 to 1.19; p = 0.920). At the end of the first week, the VAS score decreased to zero for both groups, but statistical significance as compared to the first day was only found in the laser group (p < 0.05).

Subjective evaluations were also made by the presence of post-operative bleeding and esthetic satisfaction level reported by patients. Only two patients reported bleeding the day after the treatment, and they were all in the RF group. In total, 89.5% of patients were fully satisfied whereas only two patients in the RF group were satisfied. No significant differences were found in terms of post-operative bleeding [RD − 0.25 (95% CI: −0.55 to 0.05); p = 0.164] and esthetic satisfaction [RD + 0.25 (95% CI: −0.05 to 0.55; p = 0.164)] between groups.

Gingival margin stability was evaluated by the change in gingival margin level from baseline to sixth weeks and sixth months. Intragroup analysis revealed significant differences between baseline and sixth weeks, as well as from baseline to sixth months, in both laser and RF groups (p < 0.05). However, there was no significant change in gingival margin levels between the sixth weeks and sixth months in the two groups, confirming stable gingival margins (p > 0.05) (Figs. 1c and 2c).

Discussion

Patients apply to the clinic with a chief complaint of gummy smiles mostly due to APE. Different treatment approaches and instruments such as scalpel, diode laser, and RF are preferred for the treatment. In our previous study, we evaluated the effect of those three different techniques in an animal model and observed no difference in terms of wound healing [14]. To our knowledge, no studies have compared the effect of RF to other treatment modalities in terms of clinical stability and patient-centered outcomes in patients with APE type 1A. In this study, increased patient comfort was obtained after the crown lengthening procedure performed by either diode laser or RF. Moreover, clinical marginal levels achieved after 6 weeks were kept stable during a 6-month period which also improved patients’ esthetic satisfaction.

Following a periodontal surgical procedure, patients may experience some degree of swelling, pain, and bleeding [20]. Gingival color and swelling are clinical parameters that provide insight into early wound healing. Kazakova et al. [15] assessed healing following gingivectomy using a diode laser and reported that gingival color remained red between the first and third days and normalized in 80% of cases by the end of the first week and was completely restored at 14 days. Additionally, gingival edema was present only on the first day and resolved entirely by the third day. No further edema was observed in weeks one and two. Sherman et al. [21] observed slight redness which persisted in the surgical field one week after the treatment of gingival pigmentation by RF. The normal color was restored shortly after 10 days. Our results showed beneficial outcomes regarding gingival color and swelling for both groups. No significant difference was present in terms of swelling between groups at the end of the first week. This can be explained by the similar lateral thermal effect created by both instruments as shown histologically in our previous study [14].The normal appearance of gingiva, which is characterized by revascularization, was maintained in both groups at the end of six weeks, which was also statistically significant as compared to the first week. Similar to other studies, early wound healing observed clinically was obtained with no complication in both diode laser and RF groups.

Post-operative bleeding is one of the most seen complications after manipulation of the oral soft tissue. Abdelhafez et al. [2] observed no significant difference in postoperative bleeding between diode laser and scalpel techniques in crown lengthening; however, since the study design includes osteotomy, their results are not comparable with our study. Dween et al. [22]performed a diode laser for esthetic crown lengthening and observed post-operative bleeding in three patients out of 16 on day one. Additionally, Hasar et al. [23] evaluated healing after incisions made using a scalpel, electrosurgery, and RF on rats and they noted that post-operative bleeding was absent in electrosurgery and could be stopped with light pressure in RF procedures. In the present study, post-operative bleeding was assessed through self-reporting the day after the procedure and only two patients, all in the RF group, reported bleeding; however, the difference among groups was not statistically significant. One of the advantages of diode laser and RF are their anti-hemostatic properties. They contract blood vessels which provide controlled and predictable bleeding during and after the procedure. Our results are consistent with other studies showing the benefit of diode laser and RF in terms of post-operative bleeding.

In a study [22] where a diode laser assisted gingivectomy was performed for crown lengthening, post-operative pain was reported to be decreased from the third day. Additionally, Koppolu et al. [11] evaluated VAS after the use of laser and scalpel in gingivectomy for esthetic crown lengthening procedures and found results in favor of the laser group on day one, however, there was no difference on day seven. Farista et al. [10] performed gingivectomy combined with osteotomy for crown lengthening and compared diode laser and scalpel in terms of VAS score. They recorded VAS on days three, seven, and ten and found that lasers yielded significantly better results on days three and seven, but this difference was no longer significant by day 10. A similar study [2] compared scalpel and laser with a split-mouth design and found no significant difference in VAS scores on days one, three, and seven. Notably, there is no clinical study in the literature evaluating pain scores associated with RF in crown lengthening. Hasar et al. [23] in their rat study compared soft tissue wound healing after making an incision by RF, electrocautery, and scalpel. They identified “increased weight loss” as an indicator of post-operative pain and reported greater weight loss in the RF and electrosurgery groups compared to the scalpel group during the first seven days, suggesting higher post-operative pain levels. On the contrary, in our previous study on rats [14] comparing scalpel, diode laser, and RF in terms of palatal wound healing, there was no significant difference in terms of weight. These contradictory results may be explained due to different sample sizes and measurement times between studies. In the present study, VAS assessments were conducted on the first day and first week. On the first day, VAS was slightly higher in the RF group, without significance. By the end of day seven in both groups the VAS score dropped to zero. Since there is minimal lateral thermal damage, the healing after both diode laser and RF is considered to be fast and usually uneventful. Taken together, these advantages may contribute to lower VAS scores.

Gingival margin rebound is a common challenge following crown lengthening procedures [13].Pontoriero [24], in a 12-month follow-up study of surgical crown lengthening by gingivectomy combined with an osteotomy, observed a tendency for tissues to return to their original state by the 12th month, particularly in patients with thick biotypes. In a similar study design, Carneiro et al. [4] reported some rebound at the 12-month follow-up after surgical crown lengthening; however, it was not statistically significant and was attributed to normal tissue healing. Perez et al. [25] also described the coronal regrowth phenomenon as the body’s natural effort to reestablish the gingival complex during the healing and maturation phases. In our study, gingival margin levels were assessed at the baseline, sixth week, and sixth month. The significant changes observed between baseline and the sixth week in both groups indicate that both diode laser and RF were effective for crown lengthening. Moreover, no significant changes were noted between the sixth week and sixth-month follow-up, confirming the gingival margin remained stable in both groups. Our findings show the importance of selecting appropriate instruments for different types of patients with APE. Diode laser and RF can both be safely used in type 1A APE patients with stable gingival margin levels up to six months. Since Pontoriero and Carneiro [4, 24] observed their patients during a 12-month period, they cannot be directly compared with our results as they additionally performed osteotomy. Thus, more studies with a longer follow-up are needed to confirm our results.

In this study, esthetic satisfaction was notably high in both groups. As shown in previous studies [2, 11], regardless of the treatment method applied, most of the patients with a high smile line become satisfied in terms of esthetics right after the treatment. However, the question remains inconclusive how we can increase the patient’s quality of life, together with oral health improvement, particularly during the healing period. In this study, both diode laser and RF improved the patient’s comfort in terms of swelling, post-operative bleeding, and pain during the early healing phase. Along with stable clinical margins, these all may have contributed to higher satisfaction levels of patients.

Crown lengthening particularly for esthetic purposes has been performed by different approaches over decades [7, 10, 11, 26, 27]. Besides overwhelming studies about conventional scalpel technique, few studies have evaluated the effect of diode laser and RF both in terms of patient comfort and clinical marginal stability [2, 9, 12, 15]. In this context, our results showed a beneficial effect of two treatment modalities. However, a clinician should also take into consideration some other factors such as availability and cost of the instrument, clinical experience, and the chair time needed for the procedure.

The main limitation of our study was the short follow-up period of patients for the determination of clinical marginal stability. The absence of a scalpel group, due to the low number of patients, restricts comparisons with conventional crown lengthening methods. Although measurement of clinical parameters would add more value to the present study, as the periodontium was intact and phase-I periodontal therapy had already been completed, instead of emphasizing changes in periodontal parameters, we focused on highlighting patient-centered outcomes concerning different treatment modalities. Given the technique-sensitive nature of these interventions, the procedures in this study were performed by an experienced clinician to ensure reliable outcomes. However, this may limit the applicability of the instruments when used by less experienced practitioners, which should be considered when interpreting the results.

Conclusion

To our knowledge, our study is the first to compare diode laser and RF in crown lengthening in terms of both clinical and patient-centered outcomes. We found both treatments effective with clinically stable gingival margins up to six months. Additionally, patient comfort and esthetic satisfaction were high in both groups with no statistically significant difference. A clinician can safely perform a diode laser or RF for crown lengthening procedures in patients with type 1A APE. More studies with a larger sample size and longer follow-ups will give light to these findings.

Abbreviations

EGD

Excessive gingival display

APE

Altered passive eruption

CEJ

Cementoenamel Junction

RF

Radiofrequency

VAS

Visual Analog Scale

CI

Confidence Interval

RD

Risk Difference

Author contributions

E.E conceived the ideas and collected the data, E.R.T. searched the literature and analyzed the data, E.R.T. prepared the manuscript, E.E and Ö.Ö.Y. took role for manuscript editing.

Funding

This research is funded by Bahçeşehir University as a Research Projects Support number: BAP.2024.01.03 NAP-1.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with the principles of the Declaration of Helsinki. The study protocol was approved by the Üsküdar University Ethics Committee for Non-Interventional Studies (approval number: 2024-33). Informed consent was obtained from all participants.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Clinical trial registration

Not applicable.