Use of Intraoral Welding to Increase the Predictability of Immediately Loaded Computer-Guided Implants

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1 591 Use of Intraoral Welding to Increase the Predictability of Immediately Loaded Computer-Guided Implants 1 Specialist in Maxillofacial Surgery, Private Practice, Udine, Italy. 2 Private Practice, Udine, Italy. 3 Private Practice, Bologna, Italy. Alberto Maria Albiero, MD 1 Renato Benato, MD, DMD 2 Andrea Benato, DDS 2 Marco Degidi, MD, DDS 3 Inaccuracy of computer-guided implant placement may lead to complications when combined with an immediately loaded prefabricated prosthesis. The aim of this case series was to describe the use of an intraoral welding technique to increase the predictability of immediately loaded implants supporting a fixed full-arch prosthesis after computer-guided flapless implant placement. A total of 60 Ankylos plus implants (Dentsply) with a width of 3.5 mm and a length of 8 to 14 mm were placed consecutively in 10 patients. The implants were functionally loaded using the intraoral welding technique on the day of surgery. The accuracy of guided implant placement was assessed by matching the planning cone beam computed tomography (CBCT) scans with postoperative CBCT scans. No mechanical or biologic complications were registered at the 1-year follow-up. The global coronal deviation of implant placement from the guide plan ranged from 0.25 to 2.84 mm (SD: 0.6 mm), with a mean of 1.28 mm. Average angle deviation was 3.42 degrees (range degrees; SD: 1.52 degrees). The global apical deviation ranged between 0.36 and 3.85 mm (SD: 0.71 mm), with a mean of 1.65 mm. Despite the inaccuracy registered, this guided-welded approach allowed successful achievement of a passive fit of the full-arch prosthesis on the inserted implants the same day of the surgery and provided a high implant and prosthetic survival rate at the 1-year follow-up. Int J Periodontics Restorative Dent 2017;37: doi: /prd.3027 Correspondence to: Dr Alberto Maria Albiero, Via Circonvallazione Ovest 1/1, Codroipo (UD) Italy. Fax: a.m.albiero@gmail.com 2017 by Quintessence Publishing Co Inc. Patient requests to shorten the treatment period and to avoid edentulous conditions led to the introduction of immediate loading protocols in implant dentistry. 1,2 In recent years, research has focused on the possibility of good survival rates with immediate loading of postextraction implants. 3,4 In the case of immediate loading, adequate stability of implants helps prevent the risk of micromovements and implant loss. The intraoral welded bar technique has been proven to be a successful option for stabilization of the implants in fullarch immediate restorations of the mandible and maxilla. 5 7 Computerassisted implantology (CAI) is well established for edentulous patients, and an inaccuracy of 1 to 2 mm has to be accepted. 8 As a possible consequence of the misfit between the placed implants and the prefabricated prosthesis, complications are frequently reported when computer-assisted flapless surgery is combined with an immediately loaded prefabricated prosthesis. 9,10 There are a few studies about computer-guided implants inserted and immediately loaded in healed and extraction sites In 2015, Albiero et al 15,16 published a new treatment approach to immediately load implants inserted with computerguided surgery using an intraoral welded full-arch prosthesis. Volume 37, Number 4, 2017

2 592 6 per arch) with an insertion torque 25 Ncm; and good oral hygiene. Patients were excluded from the study if they met any of the following criteria: active infection in the sites intended for implant placement; systemic disease that could compromise osseointegration; history of local irradiation; smoking > 20 cigarettes per day; severe bruxism; fitted with a pacemaker; and need for bone grafting and/or sinus lift in the planned implant area. Fig 1 Preoperative clinical condition. Planning Procedure The aim of this study is to describe the results of a guided-welded approach developed to reduce the risk of prosthetic misfit and the consequent likelihood of developing the prosthetic complications reported in the past when computer-assisted flapless surgery was combined with immediate loading restoration, thereby enhancing the predictability of the restoration. To this end, a series of 10 consecutive patients are reported with a followup at 1 year. Materials and Methods This case series presents data collected from 10 consecutive patients (4 women, 6 men; aged 43 to 79 years; mean age 52.4 years), who presented a compromised dentition in the maxilla or in the mandible. They were treated with a guided-welded approach 15,16 in which implants inserted using computer-assisted surgery were immediately loaded with a fixed full-arch prosthesis supported by an intraoral welded titanium framework. The surgical interventions were performed by the same operator (A.M.A.), an expert in computer-assisted implantology (CAI), who performed the virtual surgical planning using an implant-planning software (Simplant, Dentsply). A total of 60 Ankylos plus implants (Dentsply) (42 in maxillae and 18 in mandibles) with a diameter of 3.5 mm and lengths ranging from 8 to 14 mm were inserted in 6 healed and 54 extraction sites. The patients gave their informed consent for the treatment and to use their data for research purposes. The patients were consecutively enrolled and treated after fulfilling the following inclusion criteria: patients with hopeless residual dentition (confirmed by clinical and radiologic examination) requiring a full-arch implant-supported rehabilitation in the maxilla or in the mandible; healthy condition; aged at least 18 years; 4 or more implants (out of Impressions were made of the maxilla and mandible, and laboratory casts were made and mounted on a semiadjustable articulator. The teeth to be extracted were removed from the cast to the gingival level. The shade and structure of the prosthetic teeth were selected, and appropriate commercial denture teeth were chosen and premounted on laboratory casts in their ideal position, disregarding the teeth to be extracted. The teeth were joined with acrylic resin. This final acrylic cross-arch restoration was then hollowed to create a space to house the future titanium framework. 17 Since the patients had to retain their teeth until surgery (Fig 1), a two-piece radiographic guide was fabricated starting from the new teeth set-up (Figs 2 and 3) as suggested by Cantoni and Polizzi 18 and relined in the patient s mouth. Cone beam computed tomography (CBCT) scans (KaVo 3D exam, Imaging Sciences International) at 120 kv and 0.02 mas, 0.4-mm slice thickness, and The International Journal of Periodontics & Restorative Dentistry

3 593 Fig 2 (left) Base portion of the radiographic guide. Fig 3 (right) The two parts of the radiographic guide assembled. Fig 4 (left) Virtual prosthetic-driven planning. Fig 5 (right) Previsualization of the titanium bar (yellow) inside the future prosthetic plan (green). voxel size 0.4 mm were obtained through a dual scan protocol (guidelines for Simplant). A minimum of eight small gutta-percha markers were inserted in the radiographic guide. These markers served as radiopaque fiducials to allow visualization of the scan prosthesis in the software. The first scan was taken of the patient wearing the base portion of the radiographic guide. The second scan was taken of the two parts (base and teeth setup portions) of the radiographic guide assembled. Both sets of DICOM images were imported in Simplant software, and six implants were planned in each jaw. Implants and abutments were planned according to the prosthetic-driven position (radio graphic guide is a perfect copy of the future prosthetic restoration) and considering the final position of the titanium bar designed using the nerve-drawing tool of the software (Figs 4 and 5). A conometric retention on the two implants in the incisor region and screw retention in the other four implants was planned to provide fixed retention between the implants and the prosthetic framework. The planning was transferred to the manufacturer (Simplant) for fabrication of a stereolithographic (mucosa-supported) drill guide. Implant positions were transferred from the surgical guide to the master model using special components and implant replicas. With the abutments seated on implant replicas, a 2-mm-diameter titanium bar (WeldOne, Dentsply) was preshaped following the curvature of the implant positions and remaining inside the prosthetic design similar to virtual planning (Fig 6). Fig 6 The titanium bar preshaped on the model. Surgical Protocol All patients underwent the same surgical protocol. Antimicrobial prophylaxis was achieved with 2 g amoxicillin 1 hour before surgery. After local anesthesia (mepivacaine 2% with adrenaline 1:100,000) hopeless teeth were carefully extracted. The mucosa-supported surgical guide was fixed with osteosynthesis Volume 37, Number 4, 2017

4 594 Fig 7 The bar welded with abutments and copings in the mouth of the patient. Fig 8 Superimposition of Figs 6 and 7. The red arrow shows the intraoral modeling of the bar needed because of the angular deviation between the planned and the placed implant. After corrections, perfect contact was achieved between the titanium bar and the welding copings to ensure a correct passive fit after the welding procedure. Fig 9 Extraoral view of the bar welded with copings and reinforced. Fig 10 Maxillary metal-reinforced final restoration after relining, trimming, and polishing, ready to be delivered. screws (2 14-mm fixation screws, Dentsply) in the correct position and flapless CAI was performed with the ExpertEase system (Dentsply). Drilling and implant placement were performed with depth control (physical stops). The surgical template was then removed from the oral cavity. During the implant placement procedure, the insertion torque was registered by a surgical unit. After a socket preservation procedure of implant sites with Bio-Oss Collagen (Geistlich), the titanium abutments and welding copings (WeldOne, Dentsply) specific for intraoral welding were connected to the implants. The titanium bar preshaped on the model was tested in position, and necessary corrections were performed to achieve perfect contact between the titanium bar and all the copings to ensure passive fit after the welding procedure. Titanium copings were then welded with the titanium bar in the oral cavity as described by Degidi et al 5 using the WeldOne welding unit (Dentsply) (Figs 7 and 8). The prosthetic frameworks, created by welding the titanium bar to the implant abutments, were removed and reinforced (Fig 9), and opaque was applied. The restoration was trimmed, polished (Fig 10), and engaged with the two anterior abutments using a conical coupling while the other copings were screwed on the day of surgery (Fig 11). Occlusal surfaces were flattened to reduce horizontal relations as suggested by Crespi et al. 19 Antimicrobial therapy was continued with 1 g of amoxicillin twice daily for 5 days. Postsurgical analgesic treatment was performed using 80 mg of ketoprofen twice daily for 3 days. The patients were recalled for follow-up and oral hygiene checks after 1 week and 1, 3, 6, and 12 months (Figs 12 to 14). On average, the prostheses were removed and relined after 6 months. To be considered successful, implants were required to meet all the following criteria: clinical stability, patient-reported functionality without discomfort, and absence of infection. 13 The International Journal of Periodontics & Restorative Dentistry

5 595 Fig 11 Postoperative clinical examination. Fig 12 Clinical view at 3-month follow-up. Fig 13 Clinical view at 1-year follow-up. Fig 14 Orthopantomography at 1-year follow-up. Accuracy Analysis All subjects underwent a postoperative CBCT scan using the same parameters as for the preoperative scan. The postoperative positions were matched to the preoperative planning using Mimics software (Materialise). This process was based on surface registration via minimization of distances between pre- and postoperative jaw bone models (Fig 15). An iterative closest point algorithm was used to match the jaws. The established coordinate transformation operations were applied to the threedimensional (3D) representations of the planned and placed implants to allow for relative comparisons between the pre- and postoperative implant positions (Fig 16). Three deviation parameters (global coronal, global apical, and angular) were evaluated as described by Cassetta et al 20 and Van Assche et al, 8 and one deviation parameter (depth) was evaluated as described by Van Assche et al 8 and by Vercruyssen et al 21 (Fig 17). Global deviation is defined as the 3D distance between the coronal (or apical) center of the corresponding planned and placed implants. Angular deviation is calculated as the 3D angle between the longitudinal axes of the planned and placed implants. Depth deviation is the distance between the coronal center of the longitudinal axis of the planned implant and a parallel plane through the coronal center of the placed implant. Statistical Analysis Descriptive statistics were reported as mean ± SD according to the normal distribution of the quantitative variables, as verified by Shapiro- Wilk test of normality. Distance from the ideal test value of 0 for each measure was calculated by t test. Volume 37, Number 4, 2017

6 596 Fig 15 Overlapping of preoperative (red) and postoperative (yellow) 3D representations of maxillary CBCT images using Mimics software. Fig 16 Superimposition of pre- and postoperative implant images. Fig 17 Parameters used to analyze the accuracy of the implant placement. A = global coronal deviation; B = global apical deviation; Y = depth deviation; α = angular deviation Length (mm) Table 1 Global Coronal, Global Apical, Angular, and Depth Deviations (mm) Global coronal Global apical Angular Depth Mean Median Standard deviation Min Max Fig 18 Implant length distribution. Results Surgical and Prosthetic Procedure The total number of implants inserted with computer-guided mucosa-supported stereolithographic guides was 60 (6 in healed and 54 in extraction sites). Implant length distribution is summarized in Fig 18. The mean insertion torque value was 42.6 ± 17.5 Ncm. The preoperatively determined choice of implant length and width was respected during the surgical procedure. There were no complications such as fracture of the surgical template during the surgical procedure. No other complications, such as hemorrhages, sinus pathology, nerve palsy, or severe postoperative pain, were noted after the surgical procedure. All implants osseointegrated (100%) and appeared to be clinically stable at the 1-year follow-up. No infection, mobility, pain or discomfort, or prosthetic complications (screw loosening or prosthetic fractures) were recorded. Accuracy Analysis Distance from the ideal test value of 0 was statistically significant for all the considered variables. Table 1 illustrates the mean values, ranges, and SDs of the sample. Discussion It is widely accepted that CAI presents a certain grade of inaccuracy, 22 and complications are frequently reported when computer-assisted The International Journal of Periodontics & Restorative Dentistry

7 597 flapless surgery is combined with an immediately loaded prefabricated prosthesis. 9,10,23 27 Final implant positions are frequently different from planned positions, even if only slightly. This provides a misfit between the installed implants and the prefabricated prosthesis, 9 and absence of passive fit may lead to complications such as marginal bone loss, implant loss, screw loosening, or prosthetic fractures. 9,10,23,27 Albiero et al 16 proposed a guidedwelded approach in which the use of an intraoral welding technique allowed immediate loading and provisionalization of implants with a correct passive fit despite the inaccuracy registered. In the present study, the overall mean global coronal deviation was 1.28 ± 0.6 and the overall mean global apical deviation was 1.65 ± These data are consistent with data regarding mucosa-supported CAI reported by Vercruyssen et al 28 (mean global coronal deviation 1.23 ± 0.6; mean global apical deviation 1.57 ± 0.71) and slightly lower than those reported by Cassetta et al 29 (mean global coronal deviation 1.68 ± 0.6; mean global apical deviation 2.19 ± 0.83). Accurate passive fit of the prosthesis has been suggested as a clinical prerequisite for the longterm success of implant treatment. 30 Prosthetic framework stability is crucial to prevent the risk of micromovement and ensure successful rehabilitation. 17 CAI is far from accurate when using computerdesigned stereolithographic surgical guides. Deviations at the implant shoulder hamper the correct fit of a prefabricated construction and require adaptation of fit. The proposed guided-welded approach allowed assembly and welding of the prosthetic framework directly in the patient s mouth, creating a precise and passive structure with no discrepancies between the abutments and implants. Many authors 9,10,23,24,26,27,31 have reported surgical and prosthetic complications when combining computer-guided flapless surgery with an immediately loaded prefabricated prosthesis and an implant survival rate ranging from 83% (Komiyama et al 24 ) to 100% (van Steenberghe et al 31 ). The present case series showed an implant survival rate of 100% with no surgical or prosthetic complications at the 1-year follow-up, suggesting that the present guided-welded approach might be considered a predictable procedure to reduce the occurrence of adverse complications. Advantages were also related to the possibility of titanium bar preshaping on the model cast thanks to implant positions transferring from the surgical guide to the master model, resulting in less time needed for intraoperative titanium bar shaping. Conclusions The present article suggests that the use of the intraoral welding technique to immediately load computer-guided implants could be a successful treatment approach, allowing the creation of an immediate and passive definitive restoration that could limit complications reported in the past when combining computer-assisted surgery with an immediately loaded prefabricated restoration. Acknowledgments The authors reported no conflicts of interest related to this study. The authors woud like to thank Dr Luca Quartuccio, MD, PhD, University of Udine, Italy, for his statistical support in data analyses, and Mr Pierfrancesco Piccinini, software technician, for his technical support. References 1. Ledermann P. Bar-prosthetic management of the edentulous mandible by means of plasma-coated implantation with titanium screws [in German]. Dtsch Zahnarztl Z 1979;34: Schnitman PA, Wohrle PS, Rubenstein JE. Immediate fixed interim prostheses supported by two-stage threaded implants: Methodology and results. J Oral Implantol 1990;16: Grunder U. Immediate functional loading of immediate implants in edentulous arches: Two-year results. Int J Periodontics Restorative Dent 2001;21: Cooper LF, Rahman A, Moriarty J, Chaffee N, Sacco D. Immediate mandibular rehabilitation with endosseous implants: Simultaneous extraction, implant placement, and loading. Int J Oral Maxillofac Implants 2002;17: Degidi M, Nardi D, Piattelli A. Immediate rehabilitation of the edentulous mandible with a definitive prosthesis supported by an intraorally welded titanium bar. Int J Oral Maxillofac Implants 2009; 24: Degidi M, Nardi D, Piattelli A. Immediate loading of the edentulous maxilla with a definitive restoration supported by an intraorally welded titanium bar and tilted implants. Int J Oral Maxillofac Implants 2010;25: Volume 37, Number 4, 2017

8 Degidi M, Nardi D, Piattelli A. A six-year follow-up of full-arch immediate restorations fabricated with an intraoral welding technique. Implant Dent 2013;22: Van Assche N, Vercruyssen M, Coucke W, Teughels W, Jacobs R, Quirynen M. Accuracy of computer-aided implant placement. Clin Oral Implants Res 2012; 23(suppl):s112 s D haese J, Van De Velde T, Komiyama A, Hultin M, De Bruyn H. Accuracy and complications using computer-designed stereolithographic surgical guides for oral rehabilitation by means of dental Implants: A review of the literature. Clin Implant Dent Relat Res 2012;14: Moraschini V, Velloso G, Luz D, Barboza EP. Implant survival rates, marginal bone level changes, and complications in full-mouth rehabilitation with flapless computer-guided surgery: A systematic review and meta-analysis. Int J Oral Maxillofac Surg 2015;44: Polizzi G, Cantoni T. 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