Implant position is an important factor for functional and esthetic success. The pursuit of higher accuracy and reduced failure leads to the development of improved implant techniques. The widely used cone-beam computer tomography (CBCT) and computer-aided virtual design software can give surgeons a clear understanding of the bone shape, implant selection, and placement design.1 The surgeon's experience is also a determinant for ideal implantation, especially when implants are placed free-hand without any surgical template or navigation system.
Currently, there are 2 types of computer-guided systems: static and dynamic navigation.2 The digital template, also known as the static computer guide, is a stereolithographic implant surgical template manufactured by the professional software and computer-aided design (CAD)/computer-aided manufacture (CAM) technology, with the anatomical and histological data collected by CBCT and digital scanning. This template can provide not only angular or position accuracy but also safety protection for depth control with the physical stops of a drill in a special drill kit. The computer-generated guide has been reported to be more accurate than conventional surgical guides. Studies of different years show a tendency that the accuracy of angular deviations is increasing. Many published studies have evaluated the accuracy of a computer-aided surgical template for various systems in different jaw areas, but few compared computer-aided surgical templates with the free-hand method. For most clinical situations, free-hand implantation with CBCT aiding can receive a clinically desirable position without significant error impacting subsequent prosthetics and functions. Guided templates help in complex cases, such as alveolar bone defects, low and thin alveolar ridges, and multiple implant sites of complete edentulous jaws in patients who are eager to obtain a pair of prosthetic dentures for restoration of the chewing function.3 The complex anatomical structure of the posterior jaw area near the nerves or sinuses and the strict available bone structure of the anterior maxilla in long-term edentulous patients4 increase the surgical difficulty and require a more precise implantation. The CAD surgical template has been advocated during dental implantation to assist in the accuracy of implants. It is reported that with the assistance of a surgical guide, the esthetic and functional effects are desirable for edentulous cases. The application of computer-aided surgical systems reduces the experiment requirement for surgeons and prevents obvious deviation when drilling.5 In grade III and IV bone, the implants inserted with a surgical guide have a higher survival rate than the free-handed method. However, other opinions describe different aspects of the surgical guide. Cassetta et al6 indicated that the mucosa-supported surgical guide on smokers had lower accuracy than on nonsmokers in global coronal and global apical deviation. The shape of the mucosa, greater supporting surface of the maxilla, and fixation of the surgical guide influenced the stability and accuracy.7 This researcher also highlighted in another study that a reasonable mean accuracy with relatively high maximum deviations was observed between the postoperative position and the preoperative plan, warning that the clinician should be aware of the implant placement near vital structures.8 The circumferential supracrestal fiberotomy in flapless surgery may sacrifice more limited attached gingival tissue than does traditional open flap surgery.9 In addition, the high costs of surgical guide manufacture and the demand for accuracy in laboratory production limits the clinical applications when considering patients' desires.10
A variety of factors contributed to the success of implantation, although consensus cannot be reached on whether each factor leads to significant differences in results. Several studies indicated that experience was a decided factor for implantation success, whereas others showed no significance with the assistance of the guided system.5,11,12 Guide templates with different support styles were reported by different study organizations and groups to have unequal results of postoperation complications. Previous systematic reviews focused on different characteristics of the surgical procedure. It is reported that the accuracy of computer-aided implant surgery is influenced by different tissues, such as teeth, bone, or mucosa support.13,14 Several systematic reviews focused on the complications and survival rate of a static guide template system.15,16 Voulgarakis calculated the complications of free-hand flapless surgery and flapless-guided surgery, showing that survival rates ranged between 98.3% and 100% in free-hand flapless surgery and between 91% and 100% in flapless-guided surgery, whereas the mean marginal bone loss ranged between 0.09 and 1.40 mm in free-hand surgery and was 0.89 mm in guided surgery.17 However, these reviews did not provide a direct comparison between these 2 surgical methods.
Currently, whether it is more beneficial for dental implantation to use a surgical template than the traditional free-hand method is controversial. This question has not been answered because there are not sufficient data regarding the number of participants in single clinical studies, in vitro studies, or case reports. There were several studies that calculated the accuracy of dental implantation by surgical guide, but few compared the differences between guided and free-hand methods. The aim of this systematic review was to further evaluate how the accuracy and survival rate of dental implantation are affected by the use of these 2 surgical methods.
Materials and Methods
This systematic review was performed according to the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Initially, this systematic review was designed to include randomized control trials and retrospective or prospective cohort studies. However, because it was difficult to perform accuracy comparison between 2 groups of patients, many research methods were designed without a control group and only compared the preoperative/postoperative data. Lacking sufficient available clinical studies, it was decided that the review would also include laboratory reports, which were based on the models impressed by clinical patients, although the laboratory reports were considerably lower on the hierarchy of evidence compared with clinical results.
A systematic research was performed in PubMed-MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials. Published time started from January 2007 to December 2017. Old articles were not included because there may be limitations in the technique of CAM. The criteria of included or excluded original studies followed the principle of PICOS.
Types of Participants
Edentulous patients who received dental implantation without age, area, or sex limitation and patients who received a bone transplant for craniomaxillofacial defect or prosthetic implantation after tumor surgeries were included.
Types of Interventions and Types of Comparisons
Dental implantation using a surgical template or free-hand method, which means without a surgical guide but dependent on CBCT performance and the experience of the dentist.
Types of Outcome Measures
The primary outcomes were the accuracy and survival rate. The secondary outcomes were inflammation, marginal bone loss, and pain level. The accuracy and pain level measurements were often conducted after implantation. The survival rate and other complications were evaluated after at least a 1-year follow-up.
Types of Studies
Clinical randomized control trials, and prospective or retrospective cohort studies were included.
The following MeSH terms and their combinations were searched in [title/abstract]: computer guided surgery, surgical plate, surgical guide, template, CAD/CAM, dental implant, oral implant, implantation, randomized study, randomized clinical trial, and comparative study. Details are showed in Table 1.
The article search was conducted through the related articles function of digital databases. The newest or most complete article was chosen if there were multiple publications describing the same case groups from one research group or organization. Artificial retrieval was also used for references of recent reviews or other publications to expand the search range that the database results did not include.
Included and Excluded Criteria
Studies should meet the following inclusion criteria to be included in this article: (1) randomized control trials, retrospective comparative studies (cohort or case-control studies); (2) at least one quantitative outcome of the 2 methods with regard to accuracy or complications was mentioned in the following analysis in the next section of this article; and (3) at least a 1-year follow-up after loading for complication results.
Studies were excluded if they failed to fulfill the inclusion criteria. Excluded studies included the following: (1) editorials, clinical case report, letters to the editor, comments, and review articles; (2) animal experimental research; (3) older or smaller data of multiple reports from the same institution or authors in different publications describing a same population; (4) full porcelain implant, tibia implants, microimplants for orthodontics, implants for prosthetic function after tumor operation, and maxillofacial defect; and (5) research reports that were not written in English.
Quality Assessment and Data Extraction
Two of the authors extracted, summarized, and assessed the data of the included studies independently according to the quality assessment criteria. The identical was compared with the included studies and their quality assessment result. A discussion would be conducted if a disagreement occurs. Authority opinion was solicited if there was still disagreement after discussion.
Data were extracted following the predesigned data extraction tabulation. The extracted data and characteristics included title, first author, years of publication, type of study, duration of follow-up, numbers of participants, drop outs, age deviation, operation method, numbers and specifications of implant, types of guide template system, insertion torque, healing period and loading time, antibiotic or mouth rinse, and insert place (jaws and surgical area). The primary results to be extracted were mean and SD of angle deviation, deviation at the entry point, and deviation at the apex. The complications to be extracted included pain, implant failure, postoperative infection, and marginal bone loss.
Randomized control trials were assessed according to the Cochrane risk of bias tool to evaluate the methodological quality. The factors were as follows: adequate sequence generation, allocation concealment, blinding, incomplete outcome data addressed, free of selective reporting, and free of other bias. The methodological quality assessment of unrandomized control trials (retrospective studies) was conducted following the modified Newcastle-Ottawa scale, of which the factors included 3 aspects, including patient selection, comparability of the study groups, and assessment of outcome.
The meta-analysis in this article was conducted by using the software Review Manager 5.2 (Cochrane collaboration, Oxford, United Kingdom). A chi-square test was first applied for the statistical heterogeneity test (P < 0.10). If heterogeneity existed, a random-effects model was applied for analysis. Otherwise, the fixed effects model was applied. The odds ratio (OR) was calculated for the dichotomous variables, whereas the mean difference and SD was used for the continuous data. Sensitivity analysis was not used in this article for the limitation of numbers of total studies.
Three hundred fifty-nine studies were searched according to the MeSH items mentioned above in the digital database from 2007 to Jan 2018. Three studies were added by artificial search from references. Seventy-five repeated articles were excluded from the 362 articles. After scanning the titles and abstracts, 31 articles were full-text scanned. Only 6 studies were included into the analysis at last, including 2 clinical randomized control trials, 2 retrospective studies, 1 in vivo-in vitro study, and 1 in vitro study based on the laboratory jaw models.5,18–22 The full search strategy and the identified, included or excluded results are shown as a flow diagram in Figure 1. The characteristics of each study are summarized in Tables 2 and 3. Quality assessments were displayed as Table 4 for randomized control trials under the guidance of the Cochrane Collaboration's tool for assessing risk of bias and Table 5 for retrospective studies according to the Newcastle-Ottawa scale. The quality of evidence was generally low because most of the included studies were retrospective with unclear details in the protocol, and only 2 were randomized controlled trials (RCTs) that adapted true randomization. Publication bias of these studies also existed.
Four articles in the 5 clinical studies compared the survival rate between surgical guided and free-hand operation on dental implantation, including 2 randomized control trials and 2 retrospective cohort studies. Both studies had described in detail the criteria and characteristics of a case to be defined successful. A total number of 899 implants (553 guide templates and 346 free-hand implants) were included. Two studies designed multiple groups of guide templates compared with the free-hand control group. Data from these studies were merged by statistical methods after discussion and consultation. The result is shown in Figure 2. These 4 articles showed that there was no significant difference in the survival rate between these 2 implantation methods (OR = 1.71, 95% confidence interval [CI] 0.65–4.51, Z = 1.08, P = 0.28, Fig. 2). Heterogeneity among studies was not indicated (Q = 2.52, P = 0.47, I2 = 0%, Fig. 2). No significant publication bias was inspected according to the Begg funnel plot and Begg test (Fig. 3).
Comparison of the Variable “Accuracy”
Three articles in the total 6 studies compared the accuracy between these 2 kinds of implantation methods: 1 clinical randomized control trial, 1 in vivo-in vitro study, and 1 in vitro study based on the laboratory models. Sixty-two human and 20 jaw models were analyzed, including 470 implants and 3 types of implant guide templates. The randomized control trial of Vercruyssen et al compared 5 types of guide templates of different support designs and companies (Materialise Universal ((R))/mucosa, Materialise Universal ((R))/bone, facilitate/mucosa, facilitate/bone, or a pilot-drill template) with free-hand surgery by mental navigation with the assistant of CBCT. Nickenig manufactured resin models for free-hand operation based on the shape of the edentulous jaw in patients who had experienced guided dental implantation, and a comparison was conducted on the measured data. Park compared the experienced surgeons and nonexperienced surgeons with 2 kinds of implant insert methods.
Three studies reported angular deviation and showed that implantation with a surgical guide had significantly less deviation than free-hand in Figure 4 (mean difference = −5.45 degrees, 95% CI −0.66 to −4.24 degrees, Z = 8.83, P < 0.05). Heterogeneity among studies was not indicated (Q = 0.74, P = 0.69, I2 = 0%).
Deviation at the Apex
Three studies reported lateral deviation on the apical level. Figure 5 indicated that implantation with a surgical guide had significantly better accuracy than free-hand. Vercruyssen reported that a mucosa- or bone-support guide demonstrated less deviation than free-hand, whereas the pilot-drill surgical template had a larger 3.40 mm deviation than 2.91 of mental navigation (mean difference = −0.83 mm, 95% CI −1.12 to −0.54 mm, Z = 5.62, P < 0.01). Heterogeneity among studies was not observed (Q = 1.41, P = 0.49, I2 = 0%).
Deviation at Coronal
Three studies reported lateral deviation on the coronal level. The studies indicated that implantation with surgical guide was significantly more accurate than free-hand. The heterogeneity test showed significant heterogeneity distribution (Q = 11.53, P < 0.1, I2 = 82.7%). The random-effect model was used but could not change the heterogeneity. Because the number of included studies was less than 10, it is difficult to conduct a meta-regression or sensitivity analysis. Vercruyssen et al reported that both the mucosa-support and bone-support guide were significantly more accurate than free-hand (mean = 2.77 mm, SD = 1.54 mm) and the surgical template (mean = 2.97 mm, SD = 1.41 mm). The in vitro study of Park showed that the template group (mean = 0.6 mm, SD = 0.39 mm) was significantly more accurate than the free-hand group (mean = 2.4 mm, SD = 0.91 mm). Nickenig also demonstrated this result that the accuracy was better in models from patients with implants inserted with a template (mean = 0.9 mm, SD = 1.22 mm) than in models from the patients without a template (mean = 2.4 mm, SD = 0.91 mm).
Pain and Swelling
Two articles described differences between the guide template and the free-hand method with regard to pain score, as well as the swelling observed in postoperative visits, including one randomized control trial and one retrospective study. Arisan reported that the pain scores in the bone-supported groups and free-hand groups were significantly higher than in the flapless group, although no statistically significant differences appeared between groups in the postoperative examinations. In Pozzi's study, the prospective pain of immediately loaded implants in the conventional free-hand groups (0.92 ± 0.74) was significantly higher than in the computer-guided group (0.32 ± 0.56, P = 0.002), whereas the postoperative swelling was 1.00 ± 0.85 in the conventional group and 0.48 ± 0.65 in the computer-guided group, showing that the conventional group was significantly more visible than computer-guided groups (P = 0.024). A meta-analysis could not be conducted in this study because only 2 studies were included.
Marginal Bone Loss
Only one study of Pozzi compared the periimplant marginal bone level changes up to 1 year after loading. The result showed that there was no statistically significant difference between the conventional free-hand group (0.80 ± 0.29 mm) and the computer-guided group (0.71 ± 0.25 mm) for marginal bone loss (mean difference = −0.09 mm, 95% CI −0.24 to 0.06; P = 0.236). There was no meta-analysis conducted because of the research limitation.
This systematic review aimed to analyze the differences in outcomes between the dental implantation methods of free-hand placing or template guide. The 3D navigation system, which uses a stereo vision computer triangulation setup to guide implant placement, was not included in this study.23 Because there are limitations regarding the number of included articles and article quality, the credibility of the conclusions in this study should be cautiously accepted. Although a randomized control trial was regarded as the gold standard, published reports of RCTs were limited and had high bias aspects. Because most of the included articles were retrospective studies, a significant heterogeneity might exist. In addition, different implant systems with various sizes and guide designs or prosthetic designs, different implant sizes and loading strategy, and different patient and experienced surgeon selection might reduce the scores during quality assessment.
There is no significant difference in implant survival between these 2 methods according to our study because the 95% CI of the OR covered 1. However, it is worth mentioning that these 4 studies had a different study design, which might influence the conclusions reached during analysis because different surgical and prosthetic designs might have influenced the final result. Pozzi et al24 suggested in a review that survival rates of guided surgery were as good as conventional free-hand protocols, but the available scientific evidence was limited. A previous systematic review published in 2009 provided statistics regarding computer-guided template-based surgery without comparison and showed that computer-guided template-based implant placement had higher implant survival rates ranging from 91% to 100% after 12 to 60 months of observation in 6 clinical studies with 537 implants, while surgical and prosthetics complication were also indicated.15 Another systematic review compared the accuracy of implant placement of guided surgery in clinical, cadaver, and in vitro studies, indicating that implant accuracy was higher in in vitro studies than in clinical and cadaver studies, especially in angular deviation and horizontal apical deviation.16 In 2015, a meta-analysis by Moraschini et al25 concluded a survival rate of 97.2% and a mean marginal bone loss of 1.45 mm during 1 to 4 years of follow-up with guided surgery for the treatment of fully edentulous patients with follow-up for over 1 year.
The accuracy of the implant template, which was defined as the deviation in location and angular between the planning position and placement, is influenced by a variety of factors. Each stage in manufacture or application has a possibility of deviation. For photography as the basic data used for design and manufacture, the histological and anatomical image plays an important role. Image acquisition and scanning technology decreased the deviation by resolution improvement and calibration. Slight movement by the patient and other metal prosthetic structures could lead to a deviation. During the implant surgery, deviation could be caused by many factors, such as limited access and degree of mouth opening, poorer visual control, possible movement of the patient, and the presence of blood and saliva, which would not appear as important influenced factors in in vitro studies.26 Soft-tissue thickness and open mouth limited the guide design, and bone density or type also influences the drill accuracy and final position deviation.27 Therefore, it would have been better to find more related studies to perform subgroup comparisons with different study types to decrease the heterogeneity. The deviation values were selected according to the clinical studies and previous reviews. Jung et al26 compared horizontal coronal and horizontal apical deviation. Schneider et al15 added angular deviation, and Van Assche et al28 compared vertical deviation. The final consideration of deviation was horizontal apical and coronal deviation, as well as angular deviation. Vertical deviation was not in discussion, as few of the clinical studies had commonly recorded data in this direction.
The design of the surgical template is an important factor that influences accuracy both in the aspect of application steps and tissue support. In the study by Vercruyssen, different guide designs had different deviations. The deviation of the surgical template for a pilot drill was nearer the free-hand group than the other 2 types of templates and even higher in angular and in apical deviation. Arisan also compared a partial guide and total guide and concluded that the partial guide had higher deviations in apical, coronal, and angular error than the totally guided group. An observation of a controlled study among 38 identical implants inserted into 5 human cadaver jaws showed that the differences were not statistically significant, which means the accuracy of half-guided implant surgery is comparable with full-guided implant surgery.29 The supporting type was not included in our subgroup discussion because of the lack of articles, but which kinds of guide support can lead to a more accurate outcome is still controversial. In a critical review focused on cases of single missing teeth, tooth-supported template resulted in greater accuracy of implant positioning than that of mucosa-supported or bone-supported templates.24 A previous meta-analysis concluded that tooth support was more accurate than mucosa support, whereas bone support was less accurate in entry error, apical error, and angular error.13 This finding might be due to the thickness and movement of soft tissue when scanned by a digital scanner, and 3D-image error combined the soft-tissue surface with underlying anatomical structures by a digital scanner and CBCT for guide manufacture. However, a recent systematic review compared 3 studies on the factor of the flap approach, which included 190 implants from 2 prospective studies and 1 retrospective study, indicating that the flapless approach was significantly more accurate than the open flap approach.30 This finding suggested that a totally guided system using fixation screws with a flapless protocol demonstrated the greatest accuracy. A clinical study showed that tooth-supported surgical guides were more accurate than mucosa-supported guides.31 The study also showed that both partially and totally guided templates can simplify surgery and aid in optimal implant placement, but there were no significant differences in any parameter between partially guided and totally guided templates. The reproducibility and stability of the template position during implantation was also crucial for precision. Arisan's group reported that fixation screws were occasionally found to be loose and required tightening during surgery in the mucosa-support group. In our study, the conclusion was weakly recommended because the included studies were few and included different experimental methods. Implant accuracy was reported to be higher in in vitro studies than in clinical and cadaver studies, especially in angular deviation and horizontal apical deviation.
It is widely known that smoking is a risk factor for implant survival and periimplant bone loss of dental implants. Smokers are reported to have higher failure rate than nonsmokers. Furthermore, it is also discovered that smoking influences accuracy. Significant differences were observed in global coronal and apical deviation when comparing the accuracy of implant placement of the smokers with that of the nonsmokers using mucosal-supported stereolithographic surgical guides. The researchers explained that inaccuracy because of less stability of the surgical guide or the scanning prosthesis, as the mucosal biotype was significantly thicker in smokers than in nonsmokers.32 A clinical study investigated the influence of smoking on the accuracy of mucosa-supported stereolithographic surgical guide in complete edentulous upper jaws. This study reported that mucosa thickness of smokers was 4.53 mm on average, whereas the mean value of nonsmoking patients was 3.42 mm. Owing to the inaccuracy in global coronal and global apical deviation, smokers were suggested to strictly obey the minimum safety distance of 3 mm from limiting anatomical structures.6
The direct difference in complications was not a focus of discussion because few of the included studies had recorded this problem. Thus, the conclusion for this study was limited. Early complications include bleeding, pain, and swelling. Late complications were represented by periimplant marginal bone level loss and periimplant inflammations, which may lead to prosthesis failure or implant failure. A bone-support template or free-hand operation was reported to have a higher pain score, possibly due to the larger and wider flaps, which were elevated to better visualize where to place the implants during the surgery. The conclusion was in line with the findings of another randomized clinical study that compared flap or flapless techniques based on patient-based outcome measures.33 However, another randomized clinical trial observed that there is no significant difference.34 A Cochrane systematic review reported that flapless surgery is associated with low postoperative pain and significantly less analgesic consumption.34 Less soft-tissue trauma was made to ensure that swelling was not as significant as in open flap surgery.
To the best of our knowledge, there were no other published meta-analyses that directly compared the accuracy and failure rate using computer-guided surgery with conventional free-hand treatment. Although various search strategies and databases were used to obtain an exhaustive result, this systematic review and meta-analysis has possible additional limitations that might be overlooked in articles due to not only language limitations but also use of different terminologies.
Based on the available literature that included randomized control trials without high-quality, cohort studies, and in vitro study, there is limited weak evidence suggesting that a computer-guided surgical template demonstrated a higher accuracy effect than the conventional free-hand method in each direction and had a lower degree of swelling and pain than the latter. There was no statistically significant difference in the survival rate between these 2 implantation methods. The difference in marginal bone changes between these 2 methods has not been thoroughly elucidated to date and requires more research data. Higher quantity, long-term follow-up, and wider case selectiveness in studies, especially randomized control trials, are needed for more comprehensive and reliable conclusions.
The authors claim to have no financial interest, either directly or indirectly, in the products or information listed in the article.
Roles/Contributions by Authors
S. Chen: Study design, article search, data extraction, quality assessment, statistical analysis, and manuscript draft. Q. Ou: Article search, data extraction, and quality assessment. Y. Wang: Study design and manuscript draft. X. Lin: Study design. All authors read and approved the final manuscript.
Suya Chen and Qianmin Ou contributes equally to this study.
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