Laser Surgical Approach of Upper Labial Frenulum: A Systematic Review

An abnormal and hypertrophied upper labial frenulum (ULF) can cause diastemas, gingival recession, eruption abnormalities, and the onset of carious and periodontal problems in the upper central incisors, as well as aesthetic and functional disorders of the upper lip. The goal of this investigation is to review the evidence on the surgical techniques that are currently available for treating ULF in order to identify the best approach. PubMed, Scopus, Cochrane Library, and Embase were searched for papers that matched our topic from 13 November 2012 up to 22 November 2022 using the following Boolean keywords: “frenulum” and “surgery*”. A total of eight articles were selected for the purpose of the review. ULF can be surgically treated using either traditional scalpel surgery or laser surgery. The latter is the better option due to its intra- and post-operative benefits for both the patients and the clinicians, in terms of faster healing, fewer side effects and discomfort, and greater patient compliance. However, a higher learning curve is required for this technique, especially to calibrate the appropriate power of the laser. To date, it is not possible to identify which type of laser achieves the best clinical results for the treatment of ULF.


Introduction
The medial upper labial frenulum (ULF) is a thin band or fold of mucus tissue extending from the middle of the maxillary gingiva to the center of the upper lip. Its insertion height is variable. It develops from the tecto-labial bands connecting the upper lip to the tecto-labial papilla, which will originate the incisive papilla in the third to fourth month of intrauterine life [1].
The position of the frenulum remains stable from birth until the eruption of the maxillary central incisors. Atrophy and translocation of the insertion in the apical direction extending from the middle of the maxillary gingiva to the center of the upper lip. Its insertion height is variable. It develops from the tecto-labial bands connecting the upper lip to the tecto-labial papilla, which will originate the incisive papilla in the third to fourth month of intrauterine life [1].
The position of the frenulum remains stable from birth until the eruption of the maxillary central incisors. Atrophy and translocation of the insertion in the apical direction are correlated with the development of the permanent teeth and the growth of the alveolar process. During primary dentition, although the frenulum insertion remains stationary, fresh bone deposits heighten the alveolar ridge. The permanent central upper incisors usually erupt with a diastema. The thrust of lateral incisors and canines (11-12 years) tends to minimize the diastema and bring the incisors closer together [1,2].
The frenulum is mostly made of collagen, although it also has elastic and lax reticular fibers. The lining is distinguished by stratified compound pavimentous epithelium.
It is unknown if there is muscle tissue in the frenulum, however, it is now believed that muscle tissue is not an essential component of the frenulum [3]. Due to the lack of muscle fibers and developmental behavior, the frenulum does not appear to affect tooth emergence, gingival morphology, or the mobility of mucosal structures. At this time, an interincisal diastema is not thought to be determined by the persistence of frenulum insertion at the level of the papilla [1,4].
Different classifications for ULF have been proposed by authors, based on the place of implantation and site of insertion. Placek in 1974 classified the different forms of frenulum according to the place of implantation, distinguishing a) mucosal attachment frenulum when the frenulum is inserted into mucosa; b) gingival attachment frenulum, when it is inserted into adherent gingiva; c) papillary-attached frenulum, when it inserts into the palatine papilla; and d) penetrating papillary attachment frenulum, when the frenulum fibers pass through the interincisive papilla and insert into palatine adherent gingival [5,6].
In 1977, Popovich et al. classified the frenulum according to the site of insertion. In this case, the frenulum is divided into two primary morphotypes, thick and thin, which can be distinguished into in: high (alveolar mucosa), medium (adherent gingiva), and low (marginal gingiva) [7].
Likewise, Rui et al. proposed a classification of frenulum considering site insertion: a) Type I: alveolar mucosa; b) Type II: gingival insertion; c) Type III: interdental papilla; and d) Type IV: transpapillar [8].
Generally, the type of insertion, the width of the frenulum, the mechanical action on the gingival margin, and the difficulty in performing dental care procedures have all been regarded as criteria to identify a normal frenulum from a defective one without ever arriving at a uniformity of evaluation.
A characteristic of an abnormal frenulum, known as "pull syndrome," is the ischemization of the palatine papilla and mesial gingival borders of the upper central incisors after traction of the top lip ( Figure 1).  Others experience the taut, fibrous, papillary, or transpapillary insertion interincisional frenulum more frequently, which has a broad triangular upper insertion known as the tectolabial frenulum. This kind of frenulum is regarded as a genuine dysontogenic manifestation of fetal frenulum persistence after birth [5]. The surgical approaches that are currently in use are: (a) frenectomy or excision, which involves complete removal of the frenulum; (b) frenulotomy, which involves partial removal of the frenulum ( Figure 2); (c) apical repositioning of the frenulum [9][10][11].
Others experience the taut, fibrous, papillary, or transpapillary insert interincisional frenulum more frequently, which has a broad triangular upper insert known as the tecto-labial frenulum. This kind of frenulum is regarded as a genu dysontogenic manifestation of fetal frenulum persistence after birth [5]. The surg approaches that are currently in use are: (a) frenectomy or excision, which invol complete removal of the frenulum; (b) frenulotomy, which involves partial removal of frenulum ( Figure 2); (c) apical repositioning of the frenulum [9][10][11]. The types of surgical techniques that are currently available are conventional scal surgery and laser surgery.

Conventional Surgery
The surgical techniques are: (a) classical frenectomy/V-shaped Archer/diamo shaped incision; (b) Z-plasty incision; (c) extension of the vestibular groove; and frenectomy according to Miller's technique.
The conventional cold-blade method has all the side effects of classical surgery, su as tissue bleeding with the need for suturing and possible bacterial overinfection of surgical site [12,13].
Classical frenectomy/V-shaped Archer/diamond-shaped incision: devised by Arc (1961) and Kruger (1964). The cold blade procedure is the traditional technique a involves a V-shaped incision along the edges of the frenulum, removal of the coro insertion of the frenulum with subsequent apical repositioning. The periosteal fibres then cut horizontally and vertically, and the wound is closed with sutures. This techniq involves more side effects because it produces the development of scar tissue w possible periodontal repercussions until the disappearance of the interincisive pap ( Figure 3).  The types of surgical techniques that are currently available are conventional scalpel surgery and laser surgery. The conventional cold-blade method has all the side effects of classical surgery, such as tissue bleeding with the need for suturing and possible bacterial overinfection of the surgical site [12,13].
Classical frenectomy/V-shaped Archer/diamond-shaped incision: devised by Archer (1961) and Kruger (1964). The cold blade procedure is the traditional technique and involves a V-shaped incision along the edges of the frenulum, removal of the coronal insertion of the frenulum with subsequent apical repositioning. The periosteal fibres are then cut horizontally and vertically, and the wound is closed with sutures. This technique involves more side effects because it produces the development of scar tissue with possible periodontal repercussions until the disappearance of the interincisive papilla ( Figure 3). complete removal of the frenulum; (b) frenulotomy, which involves partial remov frenulum ( Figure 2); (c) apical repositioning of the frenulum [9][10][11]. The types of surgical techniques that are currently available are conventiona surgery and laser surgery.

Conventional Surgery
The surgical techniques are: (a) classical frenectomy/V-shaped Archer/di shaped incision; (b) Z-plasty incision; (c) extension of the vestibular groove; frenectomy according to Miller's technique.
The conventional cold-blade method has all the side effects of classical surge as tissue bleeding with the need for suturing and possible bacterial overinfectio surgical site [12,13].
Classical frenectomy/V-shaped Archer/diamond-shaped incision: devised by (1961) and Kruger (1964). The cold blade procedure is the traditional techniq involves a V-shaped incision along the edges of the frenulum, removal of the insertion of the frenulum with subsequent apical repositioning. The periosteal fi then cut horizontally and vertically, and the wound is closed with sutures. This te involves more side effects because it produces the development of scar tiss possible periodontal repercussions until the disappearance of the interincisive ( Figure 3).  papilla, where they connect with a horizontal cut; the frenulum is raised and the periosteum is exposed; (C) the margins are sutured along the midline, not involving the adherent gingiva; and periodontal wrap and healing by second intention. Z-plasty incision: uses a Z-shaped incision to create two triangular flaps of equal size that are then transposed and sutured. The stitches are removed 5-7 days after surgery. It has minor scar outcomes and is indicated in cases of the deep fornix, with wide, hypertrophic frenules and low insertion. It determines the partial removal of frenulum tissue that is associated with the deepening of the fornix. It may cause recurrence ( Figure 4).
Extension of the vestibular groove: mucosa is incised and repositioned more apically, with suturing to the periosteum and healing by second intention. It has a high relief rate.
Frenectomy according to Miller's technique: the free gingival pedicle is placed laterally in order to reduce scar tissue formation. Although this incurs a more complex procedure for the operator, it has an aesthetic advantage and it is particularly indicated in cases of a gingival smile.
Electrosurgery: recommended in patients with coagulation problems. It also provides effective hemostasis in patients with poor compliance [14].
exposed; (C) the margins are sutured along the midline, not involving the adherent gingiva; and periodontal wrap and healing by second intention. Z-plasty incision: uses a Z-shaped incision to create two triangular flaps of equal size that are then transposed and sutured. The stitches are removed 5-7 days after surgery. It has minor scar outcomes and is indicated in cases of the deep fornix, with wide, hypertrophic frenules and low insertion. It determines the partial removal of frenulum tissue that is associated with the deepening of the fornix. It may cause recurrence ( Figure  4). Extension of the vestibular groove: mucosa is incised and repositioned more apically, with suturing to the periosteum and healing by second intention. It has a high relief rate.
Frenectomy according to Miller's technique: the free gingival pedicle is placed laterally in order to reduce scar tissue formation. Although this incurs a more complex procedure for the operator, it has an aesthetic advantage and it is particularly indicated in cases of a gingival smile.
Electrosurgery: recommended in patients with coagulation problems. It also provides effective hemostasis in patients with poor compliance [14].

Laser Surgery
Nowadays, different types of lasers are commonly used in everyday practice. Each one produces a different wavelength of light, which is defined by the active medium (solid, liquid, or gas) [15].

Laser Surgery
Nowadays, different types of lasers are commonly used in everyday practice. Each one produces a different wavelength of light, which is defined by the active medium (solid, liquid, or gas) [15].
Lasers that are actually used in oral surgery are: Potassium titanyl phosphate laser, or KTP (532 nm); diode laser (810-930 nm); neodymium-doped yttrium aluminum garnet laser, or Nd:YAG (1064 nm); erbium family lasers (2780-2940 nm), which includes the erbiumdoped yttrium aluminum garnet laser, or Er:YAG; the erbium chromium yttrium scandium gallium-garnet laser, or Er,Cr:YSGG; and a carbon dioxide laser, or CO 2 (10,600 nm) [15,16]  The fundamental distinction among them is the capacity to operate strictly on soft or hard tissues or both [17,18]. When just soft tissue surgery is required, the choice of the clinician must fall upon KTP, Diode, Nd:YAG or CO2 lasers [19,20]. Instead, the erbium family lasers (Er;Cr:YSGG or Er:YAG lasers) may be required when both soft and hard tissue surgery is necessary [20][21][22] (Figure 6). The fundamental distinction among them is the capacity to operate strictly on soft or hard tissues or both [17,18]. When just soft tissue surgery is required, the choice of the clinician must fall upon KTP, Diode, Nd:YAG or CO 2 lasers [19,20]. Instead, the erbium family lasers (Er;Cr:YSGG or Er:YAG lasers) may be required when both soft and hard tissue surgery is necessary [20][21][22] (Figure 6).
Several authors have highlighted the benefits of lasers over other types of traditional dental techniques, namely increased coagulation and hemostasis, which results in a dry surgical area for greater vision and a significantly diminished requirement for suturing (the erbium family lasers are an exception to this rule as they offer only a little haemostasis); decrease in bacteremia (tissue temperature changes brought on by laser surgery are efficient at reducing bacteria); accelerated healing process (laser beam can promote healing via photo-biomodulation); and reduced post-surgical pain [17,20,[23][24][25]. The fundamental distinction among them is the capacity to operate strictly on soft or hard tissues or both [17,18]. When just soft tissue surgery is required, the choice of the clinician must fall upon KTP, Diode, Nd:YAG or CO2 lasers [19,20]. Instead, the erbium family lasers (Er;Cr:YSGG or Er:YAG lasers) may be required when both soft and hard tissue surgery is necessary [20][21][22] (Figure 6). Several authors have highlighted the benefits of lasers over other types of traditional dental techniques, namely increased coagulation and hemostasis, which results in a dry surgical area for greater vision and a significantly diminished requirement for suturing (the erbium family lasers are an exception to this rule as they offer only a little haemostasis); decrease in bacteremia (tissue temperature changes brought on by laser surgery are efficient at reducing bacteria); accelerated healing process (laser beam can promote healing via photo-biomodulation); and reduced post-surgical pain [17,20,[23][24][25]. Furthermore, the diode laser has become highly popular in dental practice given its small size, low cost and easy application for minor soft tissue surgery, for its properties of straightforward tissue incision, and its coagulation and post-surgery benefits [26,27] (Figure 7). Furthermore, the diode laser has become highly popular in dental practice given its small size, low cost and easy application for minor soft tissue surgery, for its properties of straightforward tissue incision, and its coagulation and post-surgery benefits [26,27] (Figure 7). Regardless of the surgical technique that is used, labial frenulums are anatomical structures with high biological memory, so surgery should include not only the removal of the frenulum, but also that of its deep periosteal insertions up to the muco-gingival line, in order to prevent a recurrence. Fibrotomy of the circular and transseptal fibers should be prolonged up to the level of the palatal bone in cases of Type IV maxillary labial frenulum with palatine insertion [9,28,29].
There are already numerous articles in the literature dealing with the lingual frenulum and its resolution, instead, although ULF is the most frequent type of frenulum and has the greatest impact on orthodontic treatments, there is little evidence about its surgical treatment. Herein, the purpose of this study is to review the surgical techniques that are currently available for the treatment of ULF, analyzing the advantages and disadvantages of each approach.

Protocol and Registration
The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used in this systematic review [30]. The review protocol was registered at PROSPERO under the unique number 381024.

Data Sources and Search Strategy
The qualifying criteria were developed using the PICOS (population, intervention, comparison, outcomes, and study design) framework. Pubmed, Cochrane, Scopus, and Embase databases were searched from 13 November 2012 up to 13 November 2022, using the keywords "frenulum" and "surgery". The authors checked the titles and complete texts of any papers that might be relevant. Table 1 summarizes the search approach in detail (Table 1).   Regardless of the surgical technique that is used, labial frenulums are anatomical structures with high biological memory, so surgery should include not only the removal of the frenulum, but also that of its deep periosteal insertions up to the muco-gingival line, in order to prevent a recurrence. Fibrotomy of the circular and transseptal fibers should be prolonged up to the level of the palatal bone in cases of Type IV maxillary labial frenulum with palatine insertion [9,28,29].
There are already numerous articles in the literature dealing with the lingual frenulum and its resolution, instead, although ULF is the most frequent type of frenulum and has the greatest impact on orthodontic treatments, there is little evidence about its surgical treatment. Herein, the purpose of this study is to review the surgical techniques that are currently available for the treatment of ULF, analyzing the advantages and disadvantages of each approach.

Protocol and Registration
The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used in this systematic review [30]. The review protocol was registered at PROSPERO under the unique number 381024.

Data Sources and Search Strategy
The qualifying criteria were developed using the PICOS (population, intervention, comparison, outcomes, and study design) framework. Pubmed, Cochrane, Scopus, and Embase databases were searched from 13 November 2012 up to 13 November 2022, using the keywords "frenulum" and "surgery". The authors checked the titles and complete texts of any papers that might be relevant. Table 1 summarizes the search approach in detail (Table 1).

Inclusion and Exclusion Criteria
Articles that met the following criteria were included: (1) studies only on humans; (2) open access studies; (3) randomized trials, retrospective and observational studies; and (4) studies dealing with surgical approach of ULF and comparing the different techniques.
The exclusion criteria were: reviews, letters to the editors; animal models or dry skulls studies; and craniofacial syndromes, or cleft lip and palate.

Data Collection
The study data were selected by analyzing the study design, sample size, control group, age of intervention, type of surgery, follow-up, and outcome ( Table 2).  An incision with scalpel number 15 and suture with nylon thread 5.0 7 days More time-effective and less intra-and post-operative bleeding in laser surgery Post-operative drug intake, discomfort, and edema in scalpel surgery Diode laser infrared wavelength 808 nm infrared 808 nm, power of 2 W, the energy of 120 J, pulsed mode pulsed mode and 20 pps repetition frequency

Study Selection and Included Study Characteristics
The electronic database search identified a total of 334 studies. After duplicate removal, 274 studies underwent title and abstract screening. In total, 274 papers were not selected after the abstract screening, and 56 articles were chosen for the eligibility assessment. Subsequently, 48 papers were eliminated after the full-text evaluation: 42 off-topic, 5 wrong setting, and 1 with no outcome of interest. Finally, 8 articles were selected for the systematic review. The selection process is summarized in Figure 8.

Discussion
The presence of an abnormal and hypertrophied interdental ULF could cau diastemas, gingival recession, eruption abnormalities, and the onset of carious an periodontal problems of the upper central incisors, as well as aesthetic and function disorders of the upper lip [8,33]. The surgical approach to solving the problem involv the use of a conventional scalpel [31,36,37], electrosurgery, or the use of different types high-intensity laser devices [8,[31][32][33][34][35][36][37]. Although electrosurgery is a well-known surgic technique for ULF [14], in this review only studies about traditional surgery and las surgery have passed the screening phase. The surgical techniques that are used hav always been studied and compared, and although no study emphasizes which techniqu is the most effective, the literature is unanimous that conventional surgery unle combined with a Z-plasty is contraindicated in the presence of a short lip and fornix, a the scarring outcome would worsen the initial clinical situation [32,38].
In the case of conventional scalpel surgery, suturing is always necessary; the electr scalpel has great hemostatic capabilities, but it causes cicatricial outcomes and ofte postoperative pain; the laser irradiation, on the other hand, under the correct paramete does not penetrate deeply into the tissues, but draws precise, non-bleeding surgic margins, consequently improving the visibility of the surgical site and the comfort an compliance of the patient [8,39].
Studies comparing traditional surgical techniques vs. diode laser surgery highlig the superiority of the laser surgery technique in terms of hemostasis, surgical time, pai

Discussion
The presence of an abnormal and hypertrophied interdental ULF could cause diastemas, gingival recession, eruption abnormalities, and the onset of carious and periodontal problems of the upper central incisors, as well as aesthetic and functional disorders of the upper lip [8,33]. The surgical approach to solving the problem involves the use of a conventional scalpel [31,36,37], electrosurgery, or the use of different types of high-intensity laser devices [8,[31][32][33][34][35][36][37]. Although electrosurgery is a well-known surgical technique for ULF [14], in this review only studies about traditional surgery and laser surgery have passed the screening phase. The surgical techniques that are used have always been studied and compared, and although no study emphasizes which technique is the most effective, the literature is unanimous that conventional surgery unless combined with a Z-plasty is contraindicated in the presence of a short lip and fornix, as the scarring outcome would worsen the initial clinical situation [32,38].
In the case of conventional scalpel surgery, suturing is always necessary; the electric scalpel has great hemostatic capabilities, but it causes cicatricial outcomes and often postoperative pain; the laser irradiation, on the other hand, under the correct parameters does not penetrate deeply into the tissues, but draws precise, non-bleeding surgical margins, consequently improving the visibility of the surgical site and the comfort and compliance of the patient [8,39].
Studies comparing traditional surgical techniques vs. diode laser surgery highlight the superiority of the laser surgery technique in terms of hemostasis, surgical time, pain, edema, post-surgical inflammation, and wound healing time [35][36][37].
In a clinical retrospective study, Komori et al. analyzed the use of CO 2 laser with a wavelength of 10.6 µm on six pediatric patients, of which two presented Type II frenulum and four presented Type III frenulum according to Rui's classification. Suturing was necessary for only one patient out of the six that were treated, as the high-frequency laser irradiation demonstrates excellent hemostatic activity, as well as precise resection and vaporization of the soft tissues of the oral cavity. None of the patients complained of postoperative problems such as pain, difficulty in chewing, hemorrhage, and recurrence with fiber reattachment. The surgical time is short and the technique is simpler than traditional surgery [8,[40][41][42][43].
Ling et al. compared the conventional surgical approach with a frenectomy procedure that uses two successive pulses of the Er:YAG and Nd:YAG lasers. The authors demonstrate that the laser surgery technique is more comfortable and less painful for the patient both intra-operatively and post-operatively, and chair time is reduced as there is no need to suture and then remove the suture, so there is an increase in patient cooperation. The patient does not even need to take antibiotic therapy due to the laser irradiation's ability to sterilize and hemostasis the area. On the other hand, the conventional surgical technique may result in longer healing times if the patient does not observe strict oral hygiene leading to plaque accumulation on the sutures, but it has the advantage of having a shorter learning curve for the operator and being less expensive [31,44].
In a prospective study of 50 patients, Pie-Sanchez et al. compared the efficiency of two types of laser devices: CO 2 and Er,Cr:YSGG concluding that the CO 2 laser allows the operator to perform surgery in a shorter time and with a bloodless surgical field, but the Er,Cr:YSGG laser gives faster wound healing [32,45,46].
The versatility of the laser surgery technique was illustrated in Rozo's case study. The 16-year-old patient received frenolectomy and anterior gingivoplasty in the same procedure, the first for functional reasons, and the second for artistic ones. Laser intervention may be utilized for two treatments at once, cutting down on visits and discomfort for patients [35].
Sfasciotti et. al. analyzed frenectomy treatment in pediatric patients that were at risk of developing gingival recessions aggravated by the presence of the frenulum. The study compared diode vs. CO 2 laser appliances and concluded that the former is a better performer in terms of pain management and wound healing speed, but the latter gives better bleeding control [33,47,[47][48][49].
In their work, Onur et al. analyzed pain perception and wound healing time in patients that were treated with Er,Cr: YSGG vs. diode laser surgery, with no statistically significant differences between the two groups with regards to safety and efficiency [3,34,50].
When employing lasers, caution must be taken to calibrate the appropriate power and to safeguard the operator's and patient's eyes using a particular equipment. Excessive power can cause damage to the bone surface [8,32]. Diode, Nd: YAG, and CO 2 lasers in particular overheat nearby tissues, and any fiber interaction with the periosteum must be avoided since this might result in localized, reversible tissue necrosis and pain for the patient [32,36].
The main limitation of this study is that although studies examined analyze the same clinical parameters, they use different classifications and compare one type of laser with the traditional surgical technique or only two types of laser appliances with each other. As a result, it is impossible to make an exact comparison between the traditional surgical technique and the different types of laser techniques.

Conclusions
Diastemas, gingival recession, eruption abnormalities, carious and periodontal lesions of the upper central incisors, as well as aesthetic and functional lip disorders, can all be caused by an abnormal median ULF.
This systematic review includes studies that examine the surgical techniques that are available for treatment, including traditional surgery and laser surgery.
Although traditional scalpel surgery has a shorter learning curve and lower costs, it has several drawbacks, including longer operating times, bleeding, decreased visibility of the surgical field, the need for tissue suturing, longer healing times, and the risk of plaque build-up on the sutures. In contrast, the laser surgery approach allows for treatment with significant reductions in intra-operative and post-operative discomfort for both the operator and the patient. It enables clean, bleed-free margins that improve surgical site visibility and do not require suturing. Based on the examination of the chosen articles, it appears that the laser surgery technique appears to be better in terms of haemostasis, surgical time, pain, edema, post-surgical inflammation, and healing time when compared with conventional surgery.
Despite this, it has not been possible to determine which type of laser source has the best clinical results. Consistent randomized controlled trials are necessary to compare the benefits and drawbacks of the various surgical laser devices currently available.