Alveolar ridge preservation technology in oral implants

We often encounter soft tissue and bone tissue defects during implantation. Soft tissue defects will affect the aesthetic effect of treatment, and bone tissue defects often affect the success rate of implantation. Although there are various methods to solve such problems, more and more experts believe that it is the best way to prevent such problems as much as possible. In this article, Professor Chen Ning communicated with readers on the issue of alveolar ridge preservation technology, hoping to use this technology to reduce or prevent soft tissue and bone tissue defects, improve implant success rate and aesthetic effect, and simplify implant treatment procedures.​​

Healing of extraction wounds Histological changes in extraction wounds Healing dentists are very concerned about the changes in the morphology of extraction wounds after they have healed. The histological changes of the tooth extraction wound start with bleeding and blood clot formation (30 minutes to several hours) in the tooth extraction wound, and the blood clot organizes and forms granulation tissue 3 to 7 days after tooth extraction; Connective tissue filled the extraction wound and formed immature woven bone; 30 days after tooth extraction, new fibrous bone tissue filled the alveolar bone and began to undergo bone remodeling; 30 to 45 days after tooth extraction, massive osteogenesis began; 60 days after tooth extraction Around 180 days, the mineralized bone bridge formed on the surface of the extraction wound and gradually corticalized; about 180 days after the extraction, the normal bone structure was formed in the extraction socket.​​

Changes of the alveolar ridge after tooth extraction A large number of animal experiments and clinical studies have shown that the shape of the alveolar ridge has changed significantly after tooth extraction with the healing of the extraction wound.

The main manifestations are that the height and width of the alveolar ridge have decreased, the bone density has decreased, and the gingival soft tissue has also changed. Lang (Lang, N.P.) and other clinical studies showed that the width of the alveolar ridge that healed naturally after 6 months of tooth extraction decreased on average by 3.8mm, and the average height decreased by 1.24mm; the study by Michael (Michael S. Block) et al. showed that tooth extraction 6 months Naturally healed alveolar ridges had an average reduction of 4.4 mm in width and 1.2 mm in height. Many studies have found that when the tooth is extracted, the buccal and lingual bone walls of the alveolar ridge have changed, but the buccal alveolar ridge bone resorption is more obvious.

Some researchers analyzed the changes of the alveolar bone with and without teeth. The results showed that the area and height of the alveolar ridge decreased by 32% and 24%, respectively, when the teeth were lost 3 months later. Table 1 shows the changes of bone tissue after tooth extraction.​​

Results of alveolar ridge changes Pilot studies and clinical observations show that 50% of the original height and width of the alveolar ridge will be lost within one year of tooth extraction, and 2/3 of the lost part will occur within the first 3 months of tooth extraction The absorption of the height and width of the alveolar ridge is significantly more than that of the lingual side; and the absorption of the width of the alveolar ridge is more than that of the height of the alveolar ridge; the alveolar ridge lost by absorption is difficult to regenerate by itself. At the same time, the soft tissue of the alveolar ridge will also undergo certain changes after tooth extraction, mainly the recession of the gingival soft tissue and the reduction or even disappearance of the keratinized gingiva.​​

Definition of alveolar ridge preservation The internationally accepted alveolar ridge preservation (Ridge Preservation or Alveolar Preservation) refers to the use of biomaterials to fill and cover only the alveolar socket during tooth extraction, and the use of biological materials for tooth extraction. Partial treatment, such as GBR and other methods, is called alveolar ridge augmentation (Ridge Augmentation), which is different from alveolar ridge preservation. In addition, many experts believe that the concepts of extraction site preservation (ESP) and alveolar ridge preservation are more consistent, so when the extraction site is followed by implant treatment, it can also be called implant site preservation (Implant Site Preservation, ISP). ).​​

The narrow sense of alveolar ridge preservation only refers to filling with biological materials only in the extraction socket during tooth extraction; the broad sense of alveolar ridge preservation includes the narrow sense of alveolar ridge preservation and the implantation of implants during the healing process of the extraction wound, namely Immediate planting and early planting are included.​​

Because according to research, immediate implantation and early implantation also have the effect of reducing or preventing alveolar ridge atrophy. Therefore, the treatment method of tooth extraction wound after tooth extraction can be shown in Figure 2.​​

Indications, contraindications and significance The indications of alveolar ridge preservation recommendations have no authoritative and unified definite conclusion on the indications of alveolar ridge preservation. The recommended indications for preservation are as follows, for your reference:

1. Immediate or early planters are not suitable for some reasons, such as lack of initial stability, patient pregnancy, patient age, etc.;

2. The patient’s alveolar ridge has a good appearance, and there is no obvious serious defect in the bone wall of the extraction socket and gingival soft tissue;

3. In the future, bone augmentation surgery such as maxillary sinus lift and Onlay bone graft may be required in the implant area;

4. Alveolar ridge preservation has a good cost-effectiveness for patients. Contraindications to alveolar ridge preservation advice

Suggested contraindications include:

1. Conventional contraindications for oral and maxillofacial surgery, such as patients with severe blood diseases, diabetes, oral and maxillofacial infections, etc.;

2. The patient has severe bone tissue defects or soft tissue defects in the tooth extraction wound, such as the disappearance of the labial bone plate of the alveolar socket, or the presence of only alveolar bone tissue with less apex due to horizontal bone resorption in advanced periodontal disease;

3. There is a serious infection in the extraction wound;

4. The alveolar ridge preservation area is treated with radiotherapy;

5. The patient is being treated with bisphosphonates. For example, patients with osteoporosis often take bisphosphonates, and the osteonecrosis caused by bisphosphonates is often related to trauma (such as implant surgery, etc.).​​

The purpose of alveolar ridge preservation We expect the purpose of alveolar ridge preservation to reduce the absorption or change of alveolar ridge bone tissue and soft tissue, maintain the shape of alveolar ridge soft and hard tissue, facilitate subsequent implantation, and simplify bone and soft tissue surgery (For example, the alveolar ridge preservation technology may avoid the patient’s future lifting of the maxillary sinus), shorten the patient’s tooth loss time, simplify the implant placement operation, and benefit the improvement of implant function and aesthetic effect.​​

The basic steps of alveolar ridge preservation The basic steps of alveolar site preservation generally include:

①Minimally invasive or non-invasive tooth extraction, avoid traditional methods such as tooth lift and periosteal separator, because such trauma will damage the alveolar socket, especially the labial bone plate, and easily cause alveolar bone resorption, so minimally invasive tooth extraction should be used as much as possible. preserve the integrity of the socket;

② Clean up the tooth extraction wound. There are often some inflammatory tissue or granulation tissue in the tooth extraction wound, which should be cleaned up;

③ Fill in biological materials, such as autologous bone, artificial bone, artificial bone meal, bone growth factor, etc.;

④ biofilm covering, such as absorbent or non-absorbable membrane;

⑤ Suture the wound or use autologous connective tissue flap to cover the wound;

⑥Use a temporary crown for repair.​​

The effect of alveolar ridge preservation Research on the effect of alveolar ridge preservation The study by Kushel et al. showed that there was a significant difference in the loss of alveolar ridge width and height with or without alveolar ridge preservation. The resorption of alveolar ridge width and height was significantly reduced in patients who underwent alveolar ridge site preservation after tooth extraction.

The biological materials used in alveolar ridge preservation technology include autologous granular bone, allogeneic demineralized bone, xenogeneic biological bone and bone biological materials. Comparison of the shape of alveolar ridge without alveolar ridge preservation and with alveolar ridge preservation. The results of alveolar ridge preservation clinical and animal experiments have shown that although alveolar ridge preservation cannot completely prevent the change of alveolar ridge, it can reduce the alveolar ridge. Absorption of crest width and height.​​

Bone augmentation surgery is rarely required for implant placement after ridge preservation. There is currently no evidence that alveolar ridge preservation can promote the formation of new bone in tooth extraction. It is not yet possible to prove which bone graft material is better, nor which biological barrier membrane is better.​​

Whether alveolar ridge preservation must be covered with a barrier membrane and whether autologous mucosal transplantation must be used is also inconclusive. The labial flap may facilitate resorption of the labial plate. Factors affecting the successful preservation of the extraction site Infection such as root abscess, severe bone defect, bone graft material or barrier membrane affecting wound healing, local anatomical factors (labial bone wall, gingival biotype) and other factors may affect tooth extraction Site preservation. The time of tooth extraction wound healing and implant healing is shown in Table 2.​​

Changes after implant healing The thickness of the buccal bone wall is very important. The thinner the buccal bone wall, the more obvious the loss of vertical height; in terms of the thickness of the alveolar ridge and the biological properties of the gum, the bone without bone tissue defect The gaps (2mm) of the wall and a small amount of defects and the thick gingival biotype can be repaired by themselves; the thickness reduction of the alveolar ridge with bone defect and the thin gingival biotype of the labial bone plate is more obvious.​​

Immediate implantation combined with guided bone regeneration technology only reduces the height and width of the alveolar ridge by 15% to 30% 2 months after implant placement.

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