The clinical effect of the digital guide in the early implant restoration of second molars

1. Introduction

Second molar loss is common, and its restoration methods mainly include removable partial denture repair, single-end fixed repair, fixed-removable repair, and implant repair [1]. In the absence of contraindications to implants, implant repair is the preferred method to treat mandibular second molar loss [2]. Using an implant guide can ensure accurate positioning during the implant operation, which is the foundation of functional and aesthetic restoration [3]. Implant guides mainly include the traditional film pressing implantation guide and the digitized computer-aided design/computer-assisted manufacturing (CAD/CAM) guide. The traditional method has some errors because the matching accuracy between the model and the tooth may not be good enough. Moreover, in the process of implantation surgery, if the retention of the guide plate is unstable, it would be difficult for the surgeon to get implant location accurately and avoid other problems. The digital guide captured images with a digital scanning probe and digital image of jaw, followed by computer-aided design/computer-aided manufacturing. The occlusal contact and other aspects of measurement data accuracy are obviously higher than with the traditional film pressing implantation guide, so the application of digital guide plate is becoming more frequent [4, 5, 6].

At present, most studies focus on the aesthetic repair of missing anterior teeth [7, 8]. However, the posterior teeth, as occlusal functional teeth, are also important. Early implant repair treatment can shorten the healing period for implants and resolve the situation of missing posterior teeth, so the chewing function is regained as soon as possible [9, 10, 11]. However, it is difficult to obtain better initial stability and guarantee the effect of later repair because of the thin bone wall encountered during early repair. Therefore, it is necessary to find a more appropriate implant aid in such cases, but there are few studies on this. This study aimed to find a more appropriate method of implant guidance for the early repair of posterior molar loss and to provide a more comprehensive theoretical basis for clinicians to compare the effect of a dental support implant guide obtained by the traditional film pressing method and the CAD/CAM production method in the early implant restoration of second molars.

2. Materials and methods

3. Results

Accuracy is of great significance for a long-term and stable implant repair effect. Inaccurate implantation will create great difficulties in the implant repair for upper teeth, such as difficulty in emplacement caused by non-parallel implants when multiple implants are implanted, in implant arrangement, and aesthetic impact of the exposed implant or abutment metal [13, 14]. The implant guide plate can accurately transfer the repair-oriented implant design during surgery, and at the same time, it can also take into account jaw anatomical conditions, which can ensure more accurate implant implantation [15]. It can not only improve the accuracy of surgery but also improve the reliability predicting the repair effect [16]. At present, according to the different production methods, fabrication of planting guide plates includes the traditional pressing mold method and CAD/CAM method [17]. The traditional implant guide is mainly made of resin, which has the advantages of lower cost and easier production compared with the CAD/CAM guide [18]. Existing studies have pointed out that in complex cases, using traditional guide plates made of resin has great limitations [19, 20]. Although they can better guarantee the implant superstructure, the 3D anatomical structure information on bone tissues in the implant area is not taken into account, and their implantation accuracy is lower than that of digital implantation guide plates [21, 22]. The application of a digital implant guide plate allows full consideration of the internal anatomy of the jaw and avoids damage to important anatomical structures, such as the inferior alveolar neural tube and maxillary sinus [23].

In recent years, some studies have reported that at 4–8 weeks after tooth extraction, a large amount of the alveolar crest has not been absorbed [24, 25]. In order to prevent excessive absorption of alveolar bone and obtain a good aesthetic effect later on, early implantation is encouraged [26]. During this period after implantation, the healing of the extraction wound can occur simultaneously with the osseous bonding of the implant, which can effectively prevent the absorption of alveolar bone and the loss of keratinized gingiva, and it is of great significance in obtaining a good aesthetic effect later [27]. However, because of the thin bone wall of the extraction socket, it is difficult to control the angle of the drilling needle after positioning in early implantation cases. Using an implant guide plate can help surgeons perform the implantation operation more accurately.

At present, researchers mainly focus on the aesthetic repair of anterior teeth in the early implant repair [28]. So far, there are no other studies of any differences in implant effect when the two types of guides are applied to the second molar area similar to the experimental design and verification carried out in this study. As Table 3 shows, the exit positions of reserved screw holes in the upper part of the experimental group were all in alignment with the corresponding functional cusp, while in the control group, there were four cases with a relatively large deviation, with statistical differences between the two groups. This is also related to unstable fixation when using the traditional implant guide plate. The implant drill is susceptible to producing deviation and reversing to the alveolar bone on the side with less resistance, which easily leads to the implant position deviation, thus affecting the stability of the implant and the later repair effect. In this study, the preoperative design of the digital implant guide plate was accurately transferred during the intraoperative stage, with only a small deviation in the 3D direction. When the upper prosthesis was implanted, the design of the prosthesis was basically the same as that of the tooth, and the occlusal relationship between the maxilla and mandible was stable. Therefore, when using the traditional guide plate, the final screw hole position of the prosthesis in some cases was biased to the buccal lingual or buccal palatal side of the maxillary functional cusp, which was not conducive to the recovery of occlusal function in later stages and may have adverse effects on the subsequent recovery of occlusal function.

Tables 4 and 5 compare the post-insertion deviation and deviation direction of the prosthesis in the two groups, and the results show that the digital guide plate had little influence on the deviation direction and deviation. When the traditional guide was applied to the second molars in patients with early repair, the retention of the traditional guide plate was not stable because of the limited degree of mouth opening. Thus, the coronal deviation of the control group was not affected by the position. However, the coronal direction deviation of the upper implant crown in the digital guide group was lower than that in the control group, because the application of the digital guide allowed the surgeon to fully consider the internal anatomy of the jaw, and the implantation was highly accurate, thus having little influence on the upper implant deviation. In the control group, deviations were inclined to the mesial side, because the bone density was low during the early repair of the second molars and the traditional guide plate had poor control over the direction of the drill needle root, which was greatly affected by mouth opening and bone density. After positioning the drill, it was difficult to control the direction and depth of the expansion step by step. However, the digital guide plate can help in accurately locating the implant site, but the control of degree of the direction is limited, and it is greatly affected by bone mineral density. Therefore, the deviation direction of the experimental group in Table 5 is presented as buccal deviation with low buccal lateral deflection, and whether the deviation occurred on the left or right side had no obvious influence on the results. These results indicate that in early implantation cases, the digital guide plate has a significantly better outcome than the traditional guide plate for later crown restoration, especially for controlling crown deviation.

As can be seen in Table 6, the disease improvement rate in both groups was 100%. After implant repair treatment, the masticatory function of both groups was improved, and the tooth occlusion was basically normal. This is because using an implant guide can help ensure accurate positioning, including the position angle and depth of implantation, thereby achieving better clinical effects in the later repair of the upper part of an implant. Table 7 compares the clinical effects in the two groups of patients 1 week after the prosthesis was implanted. There was no statistical difference between the two groups in terms of the marginal adaptation, anatomic form, marginal discoloration, surface roughness, postoperative sensitivity, and secondary caries. Currently, many studies have recommended the use of an implant guide plate to assist implant implantation in the anterior tooth area. The results of this study proved that both traditional and digital guide plates can achieve good clinical effects for patients in early restoration of second molars. Therefore, patients with early repair in the posterior dental area can achieve better results with the assistance of an implant guide.

At present, digital processing technology is becoming increasingly mature and is being widely used in the field of dental implantation. The precision of the implant location and depth after using an implant guide is one of the research hotspots in dental implants. The digital implant guide reduces the risks in implantation surgery and improves its success rate. However, at present, most researchers focus on the application of a digital guide plate for the anterior teeth. The results of this study showed that the digital guide plate plays an important role in cases of dental implant support in the early repair of the posterior teeth. The research team of this project also focused on the clinical restoration effect in patients with early implantation of the second molars, explored the role of the digital guide plate, and described a more appropriate guide plate method in the early implantation of posterior teeth. Thus, it is recommended to use a digital guide plate in such cases.

Complex conditions such as bone grafting or maxillary sinus lift were not included in this study. We intend to do further research to provide a greater theoretical basis for clinical application.

5. Conclusion

In the cases of dental implant support in the early repair of the posterior teeth, the digital implant guide can effectively reduce the deviation of the screw hole and the upper prosthesis in the restoration.