Dental implant treatment requires a surgical procedure to place the implant, and very often it involves additional surgical procedures such as tooth extraction and bone augmentation. Each procedure creates a wound. For optimal healing, surgical flaps - and often other surgical wounds - must be properly closed with sutures. Satisfactory closure of surgical wounds and flaps promotes healing and reduces complications such as wound breakdown, dehiscence, and infection. This module will present the appropriate materials and proper techniques for suturing that contribute to a successful outcome, as well as the improper techniques that can lead to potential complications.

After completing this ITI Academy Module, you should be able to: describe the different instruments and materials for suturing; describe the principles and basic techniques for suturing; and explain the association between improper suturing and complications.

The purpose of sutures is to provide mechanical support to the wound until healing has progressed to the point that the soft tissue can withstand functional forces without breaking down. The sutures should support the wound edges in close approximation in order to promote wound healing by primary intention. It is therefore important that the flap is situated passively in the correct position before sutures are placed. Sutures should not be placed so that they pull the flap into position under tension, as there is a risk that the wound will then break down.

The instruments needed for suturing are a needle holder, forceps with or without teeth, and suture scissors. The needle holder is used to grab onto and maneuver the suture needle. The forceps are used to hold the tissue gently and to grab the needle, and the suture scissors are used to cut the stitch from the rest of the suture material.

To maneuver the needle holder, the correct grasp is important. When grasping a standard needle holder, the thumb and ring finger are placed in the holes. The Castroviejo needle holder should be held with a pen grasp, as shown. This instrument is useful for holding the small, delicate needles often used in surgical implant procedures. The needle should be held in the jaws of the needle holder at its midpoint, or one-third from the thread end of the needle, with the tip pointing upward. Try not to grab the tip of the needle as it will become blunt, making it difficult to pass the tip through the mucosa.

There are many different types of suture available, offering different qualities in terms of handling, knot security, and strength for different purposes. General classification of sutures includes resorbable or nonresorbable sutures and monofilament or multifilament sutures. Multifilament sutures may be braided or twisted. Sutures may also be natural or synthetic. Natural materials such as gut and silk have limited use in routine wound care but are still used in the oral environment. Gut sutures are mostly composed of collagen and are obtained from animal sources. Synthetic materials tend to cause less tissue reaction than natural materials, which helps to minimize the resultant inflammatory reaction around the suture.

Resorbable sutures are indicated for wounds that heal quickly and need minimal temporary support. Their purpose is to alleviate tension on wound edges. Resorbable suture materials lose their suture integrity before complete resorption. Depending on the duration of suture integrity, resorbable materials are categorized as short term or long term. Gut can last 4 to 5 days in terms of suture integrity. Gut sutures that are treated with chromic acid salts can last up to 3 weeks. Polyglactin and polyglycolic acid are frequently used for mucosal closure and maintain suture integrity for 7 to 14 days, although complete resorption takes several months. Polyglycolide-trimethylene carbonate and polydioxanone are considered long-term resorbable sutures, lasting several weeks and likewise requiring several months for complete resorption.

Nonresorbable sutures such as nylon, polybutester, polypropylene, polytetrafluoroethylene, and polyester offer longer-lasting mechanical support when compared to resorbable sutures. However, these sutures have varying tensile strengths and may be subject to some degree of degradation. Silk has the lowest tensile strength, and nylon has the highest. Polyester also has a high degree of tensile strength. Some nonresorbable suture types exhibit additional properties such as elasticity and memory. They are explained on the next slide.

Nonresorbable sutures have properties that affect their handling. A property of both nylon and polypropylene sutures is memory, which is the ability of a suture material to return to its previous shape after deformation. The higher the filament memory, the more likely the 'unraveling' or loosening of knots after tying. Both nylon and polypropylene require extra throws to secure knots in place, owing to the memory of these monofilaments. A property of polybutester is elasticity, which allows the suture material to accommodate swelling during the healing process. Therefore postoperative swelling is less likely to result in increased tension. As the swelling subsides, the elasticity allows the suture tension originally applied by the surgeon to be maintained.

Monofilament sutures have less 'drag' or pull as they pass through the tissues. Infection is less likely with monofilaments as compared to braided multifilaments, which can potentially carry and transmit bacteria. However, these sutures are susceptible to instrumentation damage. The natural gut suture is considered a monofilament. Among the various synthetic resorbable materials, poliglecaprone, polyglycolide-trimethylene carbonate, and polydioxanone are monofilaments. The synthetic nonresorbable sutures polypropylene, polybutester, polytetrafluoroethylene, and nylon are monofilaments. For closure of flaps raised in connection with implant treatment, monofilament nonresorbable sutures are recommended due to their lower levels of tissue reactivity.

Multifilament braided materials are woven together to provide better knots and wound tension, but they are also considered to cause more tissue reaction and present a greater risk for infection due to the presence of grooves or fissures through which bacteria may enter the wound. Natural silk is a multifilament suture. Synthetic nylon sutures are available in multifilament form as well as monofilament form. Other synthetic braided multifilament sutures are polyglactin, polyglycolic acid, and polyester.

Needles for suturing can have round bodies or triangular-shaped bodies. The latter are called 'cutting needles'. The triangular body of a cutting needle has two sharpened edges that oppose one another. Cutting needles are designed for use on tough dermal tissue that is difficult to penetrate, such as dense, thick, and irregular connective tissue. Cutting needles cause less injury to tough tissue types because less force is required to penetrate the tissue as compared to round-bodied needles. On the other hand, cutting needles can cause more damage in softer tissues like fascia. They can easily tear through these tissues, cause scarring, and indirectly increase the risk of infection. Variations include conventional cutting needles and reverse cutting needles. Conventional cutting needles have a three-bladed, triangular-shaped tip that is sharpened on the inner curvature for better penetration and a flattened outer curvature that is more easily grasped by a needle holder. Reverse cutting needles have a sharpened edge on the outer curvature and are used to suture tough yet delicate tissue such as oral mucosa. The cutting edge helps the needle pass through the fairly tough mucoperiosteal flap tissue.

The needles are curved to allow a predictable turnout after penetrating the tissue. Maneuvering a curved or circular shape requires less space than maneuvering a straight needle. The shape of a needle is described as a fraction of a circle. The most common needle shapes used in oral surgery are the three-eights and half-circle reverse cutting needles. A five-eights needle may be used in the palate.

Surgical sutures are available in a number of sizes. The most commonly used classification system is the USP or United States Pharmacopeia. This system uses the number of zeros to differentiate among sutures. For any given suture material, for example nylon, the larger the number of zeros, the smaller or weaker the suture. Therefore, a 6-0 nylon suture is smaller than a 3-0 nylon suture.

It is important to note that in the USP system suture size is based on a combination of the thread diameter, tensile strength, and handling characteristics such as knot security. For this reason, sutures from different materials with the same USP size (for example, 4-0) can be of slightly different dimensions. Using the chart, note the difference in diameter between a 4-0 gut and a 4-0 synthetic suture. In general, synthetic materials have greater tensile strength and therefore smaller diameters than the corresponding natural equivalents such as gut. In oral surgery a 4-0 synthetic suture is often used. In implant treatment 5-0 or 6-0 synthetic sutures are recommended, especially in the esthetic zone.

In the European or metric classification system the decimal system is used, with sizes based on the diameter of the suture thread. The metric size corresponds to the suture diameter in one-tenths of a millimeter. For example, in this system a #1.5 suture is 0.15 millimeters in diameter.

Instruments and Materials for Suturing, Key Learning Points: The purpose of sutures is to support the wound edges in close approximation. Resorbable sutures are appropriate for quickly healing wounds. Nonresorbable sutures cause less tissue reaction than resorbable sutures. Braided multifilament sutures may carry and transmit bacteria into the wound. Monofilament nonresorbable sutures are recommended for closure of implant flaps. Sutures with 3/8 and 1/2 reverse cutting needles can penetrate tough mucoperiosteal tissue and are maneuverable in constricted spaces such as the oral cavity. Sutures are classified according to diameter, material, and handling using the USP system or according to diameter using the metric system.

The most atraumatic suturing technique is performed in two steps. The needle is passed through each side of the incision separately, first through one side and then through the other. This is opposed to stitching through both sides of the wound at the same time. If a flap has been raised, the needle is passed through the mobile elevated tissue first, and secondly through the immobile tissue. The sutures should be placed approximately every 5 millimeters; however, because placement of a suture is technically an injury to the soft tissue, the smallest number of sutures possible to achieve adequate wound support should be used.

The knots should be placed at the point of needle insertion. Placing the knot over the wound edges may induce infection, as the knot attracts bacteria that may infect the wound edges. Sutures placed too tightly may compromise blood flow and result in local tissue necrosis, which can worsen scarring and potentially hamper the esthetic result. The wound edges need only to touch to begin proper primary healing. This means that the wound edges should be approximated, not strangulated, by the sutures. Sutures that are placed and tied tightly on the day of surgery will be even tighter on the following day due to wound edema. The wound edges will swell, and the tension at the site of the sutures will increase. This is another reason for not over-tightening the sutures.

The simple interrupted suture, or everting interrupted suture, is the most commonly used suture in the oral environment. Each stitch is tied separately. The needle is inserted into the underlying tissue at a 90-degree angle to the tissue surface within 3 to 4 millimeters of the wound edge. Insertion at a 90-degree angle helps to ensure that the wound edges will evert (or turn slightly outward) and the underlying tissues will come into contact.

If the point of insertion is not at 90 degrees to the tissue surface, there is a risk that the underlying tissue will not be well approximated, thereby creating a space in the wound. This space will be occupied by a hematoma that may become infected, resulting in healing by secondary intention instead of by primary intention. Also, if the needle enters soft tissue at an acute angle there is a risk of tearing the mucosa with either the needle or the suture.

Once the sutures are passed through the mobile flap and the immobile flap, the suture is tied with a surgeon's knot. This is a type of square knot. The suture is pulled through tissue until a short tail remains. This tail should be approximately 1 to 2 centimeters long. The needle holder is held horizontally by the dominant hand and positioned between the two ends of the suture. The other hand is used to wrap the long end of the suture around the needle holder twice, making two loops of a suture around the needle holder. Next, the needle holder is opened to grasp the short end of the suture near its end. The knot is then tightened by pulling mainly on the longer end of the suture while the shorter end is kept in tension with the needle holder grip. This is the end of the first step or 'throw' of a surgeon's knot. The two wraps have created a double overhand knot at the first needle insertion point. The friction in the double overhand knot keeps the wound edges in place until the second part of the knot is tied.

To make the second throw of the surgeon's knot, the needle holder is released from the short end of the suture and again positioned horizontally between the two suture ends. The long end of the suture is wrapped once around the needle holder. Next, the needle holder is opened to grasp the short end of the suture near its end. The knot is then tightened against the previous knot by again pulling mainly on the longer end of the suture while the shorter end is kept in tension. This completes the surgeon's knot. Note that additional throws may be required depending on the suture material being used.

The tensile strength and handling characteristics of the suture material determine the number of throws for a knot. Silk sutures should be knotted with three or more throws. Resorbable, braided sutures such as polyglactin, polyglycolic acid, and polyester should be knotted with four or more throws, whereas resorbable or nonresorbable monofilament sutures should be knotted with six or more throws. This is due to the 'memory' of these materials. In the clinical example shown, the arrow points to a knot throw that has become loose.

A mattress suture is a double stitch that is made either parallel or perpendicular to the wound edge. The primary advantage of this technique is the strength of closure. A mattress stitch penetrates each side of the wound twice and is inserted deep into the tissue, incorporating a larger amount of tissue than a simple interrupted suture. The horizontal mattress suture is parallel to the wound edges, while the vertical mattress suture is perpendicular. The vertical mattress suture in particular can aid in everting the wound edges. Mattress sutures provide stronger resistance to muscle pull, ensure proper wound edge alignment (either everted or inverted), and tightly adapt tissue flaps to underlying structures such as implants or bone grafts.

Mattress sutures may be used in conjunction with simple interrupted sutures to support the flap closure. In the clinical image, the arrows indicate one of the vertical mattress sutures used to supplement the interrupted sutures.

This clinical example shows simple interrupted sutures. It demonstrates a situation in which vertical mattress sutures could have been used with better results. The flap was not raised sufficiently, and the periosteal releasing incisions were insufficient as well. Therefore the flap was not tension-free before the placement of simple interrupted sutures. This resulted in a soft tissue dehiscence at the time of suturing. The sutures were also excessively tightened, hampering the blood supply, as evidenced by the blanching of the tissues. Moreover, the wound edges were not sufficiently everted. The papillae on the adjacent teeth were compressed, as shown in the 1-week follow-up image. At 2 weeks, the cover screw of the implant became unintentionally exposed. Rather than simple interrupted sutures, vertical mattress sutures might have aided in everting the wound edges without excessive tightening. The flaps should have been approximated, not strangulated. In this example the cover screw was replaced by a healing abutment, and the rest of the healing was uneventful.

For general oral surgery, sutures in the oral mucosa are usually removed after 5 to 7 days. Sutures after implant surgery are removed after 7 to 10 days, and sutures after bone augmentation procedures are removed after 10 to 14 days. One thread of the suture should be cut at the tissue surface, so that the part of the thread that is not exposed to the oral cavity can be drawn through the tissue. If the sutures are contaminated with plaque, the area should be cleaned before suture removal. However, the contaminated part of the thread should never be drawn through the tissue.

Basic Suturing Techniques, Key Learning Points: The needle should enter the tissue at a 90-degree angle to evert the wound edges and bring the underlying tissues into close approximation. Suturing should be done in two steps by passing the needle through the elevated flap first. Knots should not be placed over the wound edges. Knots must have at least two throws; some suture materials require additional throws to prevent loosening. Mattress sutures are a strong method of closure that can supplement interrupted sutures. The objective is to approximate the tissues without excessive tension or compression. Sutures should be removed in a manner that prevents the exposed thread from passing through the tissues.

The purpose of suturing is to approximate the tissue so that healing occurs by primary intention. Improper suturing technique contributes to impaired healing and an increased risk of complications such as hematoma formation or wound infection. Inappropriate technique can also result in scar formation or persisting stitch marks. Wound dehiscence is another possible outcome of poor suturing. A wound dehiscence is defined as incomplete wound healing because of insufficient blood supply, excessive postsurgical edema, or compromised healing. If severe, dehiscence can lead to failure of implant treatment. Many factors besides suturing - such as age, smoking, and medical status - influence wound healing and thereby also influence the formation of wound dehiscences.

Failure to achieve hemostasis before suturing can result in the formation of a hematoma. A growing hematoma will promptly cause the wound to open, resulting in slow healing by secondary intention. Before suturing, hemostasis should be confirmed and existing hematomas removed.

Suturing a wound under too much tension will inevitably lead to complications. After surgery, wound edema is inevitable. The wound edges swell, and the tension at the site of the sutures increases. This is why the flap must be replaced without tension before suturing and the sutures not tied too tightly. On the other hand, the knots must not be tied too loosely either, as this will cause the surgical wound to open up and the edges of the flaps to move away from each other. The knots must be placed in proper positions in relation to the suture technique as well as the wound being treated in order to remain secure. The knots should be square surgeon's knots and should be positioned away from wound edges. Knots placed over the wound edges attract bacteria that may lead to infection. Inserting the suture needle too close to the wound edge may result in jeopardized healing and dehiscence due to the inflammatory changes, swelling, decreased blood supply, and reduced collagen structure present at the wound edge.

Sutures are applied to close a wound in order to keep bacteria out and to allow union of the tissues. If the sutures are removed before the underlying tissues have sufficiently joined together, the wound will reopen. On the other hand, sutures left too long may result in formation of scar tissue around the sutures. In addition to scarring of the wound closure, if the sutures remain past the ideal removal time the stitch marks - sometimes called "railroad tracks" - may persist. Selection of an inappropriate suture material can also lead to complications. Choosing a thin monofilament suture in an area under tension may result in rupture of the sutures and development of a wound dehiscence. Cutting needles cause less injury to tough types of tissue because they penetrate the tissue with minimal force, but they may still damage the delicate oral mucosa by tearing through the tissue and thus causing scarring. A reverse cutting needle is recommended for suturing of extremely tough yet delicate tissue such as oral mucosa.

Improper Suturing Related to Complications, Key Learning Points: Many complications caused by improper suturing technique are related to excessive wound tension leading to dehiscence. Selection, placement, and tying of sutures are also key factors in avoiding complications. Hematomas caused by insufficient hemostasis can force the wound edges apart.

Suturing Materials and Techniques, Module Summary: Properly placed sutures support wound edges in close approximation to promote healing by primary intention; sutures should not pull the wound edges into position under tension. Suture materials vary in tensile strength, tissue reactivity, knot security, and other properties. Monofilament nonresorbable sutures with a 3/8 or 1/2 reverse cutting needle are recommended for implant procedures. The needle should enter the tissue at a 90-degree angle to minimize tissue damage and facilitate healing by primary intention. Mattress sutures are an effective method of everting wound edges for close approximation of healing tissues. Many complications related to suturing can be avoided by approximating - rather than strangulating - the tissues.