Effect of a buried knot in the healing process of dental extraction sites: a prospective study in cats

Abstract

Objectives

This study aimed to evaluate the effect of the buried-knot suture technique on gingival wound healing in cats undergoing dental extractions. We hypothesised that a simple buried-knot interrupted suture would provide a healing advantage at the extraction sites.

Methods

A prospective, randomised, split-mouth design was used, involving 40 cats sequentially included in the study. Each side of the mouth was sutured using simple interrupted sutures, with and without a buried knot. Healing was assessed at 2, 4 and 6 weeks postoperatively through visual inspection of the maxillary sites. Indicators of wound healing, such as swelling, bleeding on inspection, redness of the wound margins, dehiscence, ulceration, exudate, halitosis, pain on palpation, presence of necrotic tissue, flap instability, suture loosening and entrapment of food debris or foreign bodies were recorded.

Results

Although both sutures showed similar mechanical behaviour as assessed through flap stability, dehiscence, suture loosening and the presence of necrotic tissue, the buried-knot technique was significantly associated with reduced inflammatory signs, including less swelling, bleeding on inspection, redness of wound margins, ulceration, exudate, halitosis and pain.

Conclusions and relevance

The findings suggest that simple interrupted sutures with a buried knot provide a healing advantage in gingival wound closure after dental extractions in cats.

Introduction

The primary objective of suturing is to achieve proper wound margin apposition and promote optimal healing by creating a favourable environment for tissue repair. Suturing helps minimise infection risks while preserving comfort and functionality. Open extractions are the most common procedure in feline veterinary dentistry, often requiring flaps and alveoloplasty. In such procedures, the most common suture pattern used is a simple interrupted pattern using absorbable monofilament 5/0 placed approximately 3 mm apart, with an even distance between the wound margins. ¹

Knotless sutures can potentially reduce complications and dehiscence. ² Continuous knotless barbed sutures offer time-saving advantages, particularly in clinical settings involving feline patients with chronic gingivostomatitis. ³ However, because of the limited availability of barbed sutures in most veterinary clinics, simple interrupted buried-knot sutures present a viable alternative. This technique can potentially enhance healing by reducing inflammation and minimising the loss of tensile strength due to knot exposure in the oral cavity. Similar buried-knot suture techniques have been reported in human cosmetic surgery literature, where they are associated with improved cosmetic results.^{4 –6}

The rationale behind using buried knots for gingival closure is that exposed knots can provoke trauma and an inflammatory response, leading to plaque accumulation. This, in turn, may trigger licking behaviour in cats, which could contribute to wound dehiscence.

We hypothesised that simple interrupted sutures with buried knots would be associated with reduced inflammation, less plaque and debris accumulation, and fewer wound-healing complications compared with traditional sutures.

Materials and methods

Study design and groups

Clinical cases from two veterinary clinics that underwent anaesthesia and subsequent dental extractions for orodental disease were sequentially included in this study. Only cats classified as American Society of Anesthesiologists risk groups I and II that required bilateral extractions (either partial mouth extraction [PMX] or full mouth extraction [FMX]) were included. The exclusion criteria included positivity for retroviral disease (feline leukaemia virus and feline immunodeficiency virus) and chronic gingivostomatitis with long-term treatment involving antibiotics or corticosteroids. Indications for extraction included periodontal disease and tooth resorption, especially for PMX (where all premolar and molar teeth were extracted). FMX was performed especially in chronic gingivostomatitis cases.

Two authors, one board-certified dentist (JG) and one European Veterinary Dental College training resident (EK), performed the procedures and scoring.

The study employed a randomised, prospective, split-mouth model. The gingiva of one side of the oral cavity (maxillary and mandibular) was sutured using the buried-knot technique (group B) and the other side was sutured with a standard simple interrupted technique (group S). Randomisation was determined by flipping a coin.

Procedures

Sedation was achieved using recommended doses of dexmedetomidine (2–4 µg/kg; Le Vet Beheer), midazolam (0.2–0.3 mg/kg; Sandoz) and methadone (0.15–0.2 mg/kg; Eurovet), all administered intramuscularly. Subsequently, a 22–24 G intravenous catheter was placed in the cephalic vein. Preoxygenation was then performed using a mask to deliver medical oxygen for 5 mins. Anaesthesia was induced slowly with alphaxalone (2–4 mg/kg IV; Zoetis) or propofol (4–6 mg/kg IV; Baxter). Topical lidocaine hydrochloride monohydrate (Intubeaze 20 mg/ml; Dechra) was applied before intubation. General anaesthesia was maintained using a mixture of isoflurane and oxygen. Finally, each patient received intravenous fluid therapy (OptiLyte; Fresenius).

Oral and dental examinations included full-mouth periodontal probing, dental charting and full-mouth dental radiography, according to the American Veterinary Dental College guidelines for cats. Each cat received regional nerve blocks in all four quadrants using 4% articaine with epinephrine at a concentration of 1/100,000 (Ubistesin Forte 4%; 3M ESPE), 5–7 mg/kg adjusted to a maximum volume of 0.8 ml for four blocks.

Extractions were performed after the initial supragingival scaling, with no predetermined order between the right and left jaws. An envelope flap was adapted based on the extent of the extraction needed after a sulcular incision. The alveolar bone was partially removed, and the teeth were sectioned before luxating and elevating the teeth roots. Postoperative radiographs were taken after extraction to confirm the absence of root remnants. Alveoloplasty was performed to remove any sharp bone edges. Before suturing, flap edges were trimmed to eliminate the most inflamed parts. Suturing was carried out with an absorbable glyconate monofilament 5/0, using a half-circle, round-body, tapered-point needle (17 mm). The same knot-tying technique was applied in all cases, involving a surgeon’s knot combined with four simple knots. Sutures were placed 3 mm apart and 2 mm from the wound margin. In the case of the buried knot, the needle was introduced from the interior to the exterior side of the wound and then inserted from the exterior side on the other wound edge. This sequence leads to inversion of the knot (Figure 1).

Figure 1.

Series of pictures illustrating the buried-knot technique step-by-step in an artificial skin model. (a) First, the needle is introduced from the interior to the exterior side of the wound and then (b) it is inserted from the exterior side on the other wound edge. (c–e) The ends of the suture meet inside the wound and (d) are tightened (e) without tension. (f) The suture material is cut short. (g) Subsequent sutures are placed using the same technique. (h) The final result of placing four buried-knot sutures

Postoperative care

During the postoperative period, each cat received one injection of cefovecin subcutaneously (8 mg/kg, Convenia; Zoetis). Pain management included initial intramuscular administration of buprenorphine (0.01–0.03 mg/kg, Bupaq; Orion Pharma), followed by transmucosal administration of the same dose every 8 h for 3 days.

In addition, meloxicam (Melovem 5 mg/ml SC; Dopharma) was administered at an initial dose of 0.1 mg/kg, followed by oral suspension at 0.05 mg/kg PO daily for 6 days (Meloxidyl 0.5 mg/ml; Ceva).

All cats were discharged on the same day, with a clinical evaluation performed 8 h after recovery from anaesthesia.

Owners were advised to feed their cats soft foods for the next 2 weeks and clinical examinations were scheduled at 2, 4 and 6 weeks postoperatively.

Postoperative assessment

All cats were followed up at 2, 4 and 6 weeks from the procedure date, with a thorough clinical assessment and visual inspection of awake patients performed by the two investigators (EK and JG).

Variables

Healing variables were assessed at 2 and 4 weeks for both mandibular and maxillary wounds, including swelling (presence of external signs of gingival oedema), bleeding (spontaneous bleeding or bleeding on palpation), redness (signs of hyperaemic gingiva), wound dehiscence, ulceration, exudate, pain on palpation (avoids palpation or responds aggressively), presence of necrotic tissue, flap instability (absence of adhesion of the wound edges to the underlying tissues), suture loosening and food debris on the suture material. Photographic documentation was collected for the maxillary wounds only because of inconsistent image capture of the mandibular wounds.

All categorical variables were recorded as 0 (absent) or 1 (present). Statistical analysis was conducted using STATISTICA 10.0 (StatSoft) and Microsoft Excel (MS Office 2013; Microsoft Corporation). Qualitative data were analysed using the χ² test, V² test, Fisher’s exact test or χ² test with Yates correction. Quantitative data were assessed for conformity with a normal distribution using the Shapiro–Wilk test and compared using the Student’s t-test if normality was confirmed. Statistical significance was set at P <0.05 with a 95% confidence interval.

Ethical statement

All procedures performed during the study followed standard veterinary care procedures and complied with Polish Regulations (Art.1 ust.2 pkt1 Dz. U.2015 poz. 266). All owners were informed of the study and provided signed written consent.

Results

In total, 40 cats were included in the study, with a mean age of 6.4 years and a mean body weight of 4.41 kg. The cohort comprised 22 males and 18 females. The majority were domestic shorthair cats (80.0%), with other breeds comprising British Shorthair (7.5%), Persian (2.5%), Sphinx (2.5%), Tonkinese (2.5%), Norwegian Forest Cat (2.5%) and Siberian (2.5%).

Each cat had dental extractions performed in all four quadrants; therefore, each group (S and B) included 40 ipsilateral maxillary and mandibular gingival wounds.

In total, 33 (82.5%) cats underwent PMX (involving maxillary and mandibular cheek dentition), while seven (17.5%) cats underwent FMX.

Table 1 summarises the healing variables at 2 and 4 weeks. Additional information about the study groups is available in Table S1 in the supplementary material. Examples of postoperative photographic documentation and differences between the split-mouth model are presented in Figure 2. No significant differences were observed between the groups in terms of dehiscence, necrotic tissue, flap instability or suture loosening. At 2 and 4 weeks, group B showed significantly less swelling (P = 0.0025 and P = 0.0072), bleeding (P <0.0001 and P = 0.0019), redness (P = 0.0027 and P = 0.0024), ulceration (P = 0.0017 and P = 0.0176), pain on palpation (P <0.001 and P = 0.0017) and food debris (P <0.0001 at both time points). In six cats in group B, knot exposure was observed at 4 weeks, which did not contribute to redness, bleeding and swelling. Group S also had a significantly higher presence of exudates at the first assessment (P = 0.0338), but no difference was noted at the second time point (P = 1.000). No dehiscence or flap instability was observed 4 weeks postoperatively. No complications were observed at the 6-week postoperative assessment in both groups.

Table 1.

Complication variables compared between the standard simple interrupted technique and the buried-knot technique 2 and 4 weeks after the procedure (N = 80)

Complication	After 2 weeks			After 4 weeks
	Simple	Buried knot	P value	Simple	Buried knot	P value
Swelling	21	8	0.0025*	9	1	0.0072 †
Bleeding	20	3	<0.0001*	11	1	0.0019 †
Redness	35	23	0.0027*	29	16	0.0024*
Dehiscence	0	2	0.4739 ‡	0	0	NC
Ulceration	13	2	0.0017 †	7	0	0.0176 ‡
Exudate	6	0	0.0338 ‡	0	1	1.0000 ‡
Pain on palpation	24	6	<0.0001 *	13	2	0.0017 †
Necrotic tissue	0	0	NC	0	0	NC
Flap instability	3	2	1.0000 ‡	0	0	NC
Suture loosening	4	4	0.7094 ‡	1	0	1.0000 ‡
Food debris	30	3	<0.0001 *	22	2	<0.0001*
Total	40	40		40	40

^*χ² test

^†V² test

^‡χ² test with Yates correction

NC = not calculated

Figure 2.

Photographic documentation of the studied variables in a patient that randomly received the buried-knot technique (group B) on the left side and the standard simple interrupted technique (group S) on the right side. It should be noted that no flap was performed for closure of the canine tooth alveolus since at the time of surgical extraction the tooth was absent, and the alveolus was granulated

Discussion

Seal closure of the surgical access after dental extraction in cats is essential to maintain oral comfort and functionality. This study indicates that gingival flap closure using a simple interrupted suture with buried knots provides potential healing advantages since the sutured sites using buried knots had significantly less swelling, bleeding, redness, ulceration, pain on palpation and food debris entrapment when compared with the standard technique. The healing process can be assessed over time by monitoring the occurrence of complications. The healing variables selected by the authors were based on clinical indices previously reported in human patient literature for extraction sites^7,8 and later systematically reviewed, with healing time identified as a key parameter. ⁹

The presence of an exposed knot can contribute to suboptimal tissue healing by trapping debris and bacteria, traumatising surrounding tissue, thereby perpetuating inflammation. Bacterial plaque accumulation on sutures is a subject of interest and research in many available reports in human medicine.^{10 –12} Bacteria adhere with various affinities to different suture materials.^{12 –16} Bacterial accumulation is more impactful in multifilament sutures^14,15 and less impactful in monofilaments^15,17 and sutures impregnated with antiseptics. ¹⁶ Most of the studies were developed in human patients and include non-absorbable materials like nylon or silk, which are removable. In a comparative study, the least microbial accumulation was observed in monofilament resorptive sutures, specifically poliglecaprone 25. ¹² For oral surgery in veterinary practice, monofilament sutures with rapid absorption are recommended. ³ Absorbable sutures are preferred in veterinary patients, as they eliminate the need for a second anaesthetic procedure for suture removal. Although this study did not evaluate bacterial colonies in detail, a significant clinical accumulation of plaque and debris was noted in group S, likely indicating biofilm formation around the knot. Therefore, the absence of the knot can potentially address this problem, at least until the suture material is completely resorbed.

Knot exposure can cause local trauma and contribute to inflammation, especially with monofilament sutures, as was the case here. Monofilament threads are less flexible and have shape memory, making stitches less secure when using the same number of throws as with multifilament materials. To improve knot security, more throws are required, which increases the overall volume. ¹⁸ However, larger knot volumes mean a greater density of foreign material in contact with tissue, which can also lead to inflammation. Burying the knot can reduce this trauma, but it also introduces more material into the tissues, potentially perpetuating inflammation. While using multifilament sutures may decrease trauma caused by the knot, these sutures have other drawbacks, such as a higher risk of bacterial accumulation.

Healing was completed in all cases after 6 weeks, with no complications recorded at this time point. However, in two cats with chronic stomatitis, the buried knot flaps showed signs of dehiscence at 2 weeks. The limited number of chronic gingivostomatitis cases requiring FMX (n = 7) prevented any statistically significant results between the groups. However, given the likely similarity in biomechanical behaviour between the sutures, the authors speculate that persistent inflammation from the underlying condition could potentially contribute to an early disturbance of the knot’s biomechanical properties, leading to a reduction in suture strength earlier than expected. Future studies with a larger sample size, including more cases of chronic gingivostomatitis, are required to explore these issues further.

On some occasions, buried-knot exposure was observed at 4 weeks with limited inflammation. Exposure did not contribute to additional redness, bleeding or swelling. This occurrence could be related to the rate of absorption and the rate of loss of tensile strength of the suture material, features that are not interchangeable. In the case of knot exposure, the loss of tensile strength in the oral environment leads to the loss of the knot. On the other hand, in the case of a buried knot, the rate of absorption plays an important role in late suture complications, such as sinus tracts and granulomas. Given the specific environment of the oral cavity and the absorption and tensile strength features of the suture material, this can be an expected event but with minor or negligible impact. Exposure of the knot after loss of tensile strength leads to a quick shed of the exposed material, secondary to the washing effects of saliva or the abrasive effects of the tongue and/or teeth during mastication.

The split-mouth randomised design of the study provided the advantage of having an internal control and reducing selection bias. Such designs, including crossover studies, enhance efficiency, reduce variability and allow for a more direct comparison of treatments among patients. ¹⁹ Tests based on the split-mouth method are considered reliable since the host’s response to the material used for the surgical procedure is the same.

The same suture material, size, needle type and manufacturer were used to avoid additional variations related to manufacturer-associated performance of the surgical material.

Postoperative care included 6 days of pain management, and no further pain management was needed even in the presence of most of the complications observed. This suggests that most of the complications observed did not cause significant pain or discomfort that required additional analgesic care.

The postoperative use of the antibiotic cefovecin is debatable, as antibiotic therapy may not be necessary in every case. However, antibiotics were prescribed for all animals to minimise bias from opportunistic infections or individual susceptibility to infection. Prolonged anaesthesia and surgical times are known to increase the risk of surgical site infections.^20,21 Cefovecin was chosen to ensure owner compliance, which could otherwise lead to variability in healing.

The limitations of the study are intrinsically related to the study design. A blinded evaluation was not feasible, as the evaluators could easily identify the suture type used. To mitigate this, an independent group of evaluators who were not involved in the publication of results could be employed or systematic photographic documentation of the healing sites could be provided. Combining this approach with the evaluation of a wide range of healing variables would help reduce subjectivity. In addition, the homogeneity of cases and controls could also be improved beyond the internal control provided by the split-mouth design by accounting for sex and age differences when assessing the healing process. Extraction indications were consistent across cases, but extraction indications could be matched. Chronic gingivitis, periodontitis and stomatitis, often associated with various types and stages of tooth resorption, were the primary indications for PMX or FMX. These conditions represent complex, chronic inflammatory diseases that can lead to more healing complications than extractions performed for advanced periodontal disease. To minimise variability, cases involving chronic gingivostomatitis treated with long-term antibiotics or corticosteroids were excluded, as were cats with retroviral infections or other systemic issues. As a result of the client-owned nature of the animals in this study, it was not possible to determine the precise healing time. Consequently, assessments were performed every 2 weeks based on the expected and described average healing time. ²²

The time spent performing both types of sutures was not evaluated or compared in this study. However, because of the simplicity of the buried-knot technique, the authors believe that this adaptation is unlikely to significantly impact the procedure’s duration, as the learning curve is very quick.

Conclusions

The simple interrupted suture with a buried-knot technique offers healing advantages, including reduced redness, less entrapment of food debris, decreased pain on palpation, reduced halitosis, and less swelling and bleeding compared with the simple interrupted pattern. Although both techniques yield similar successful outcomes, the buried knot seems to offer fewer complications and easier recovery.