Objective

The purpose of this report is to present the clinical outcomes and patients’ satisfaction of full-mouth rehabilitation using computer-aided flapless implant placement and immediate loading of a prefabricated prosthesis.ű

Materials and Methods

The study included 30 consecutive fully edentulous patients who received 312 implants. Mandible and maxilla were treated in the same surgical session with computer-guided flapless approach using the NobelGuide protocol. Prefabricated screw-retained fixed prostheses were inserted at the end of surgery. Clinical and radiographic evaluations were assessed at 6, 12, and 36 months. At baseline and 6 months after surgery, patients answered Oral Health Impact Profile in Edentulous Adults questionnaire to assess satisfaction.

Results

The implant survival rate was 97.9%, whereas the average marginal bone loss was 1.9 (6)1.3 mm after 3 years. At 6 months, patients showed significantly greater satisfaction with their fixed rehabilitation when compared with conventional dentures. The treatment of the edentulous patient using implants introduced by Brånemark et al1,2 in a 2-staged approach was demonstrated to be a predictable treatment and represented the “standard of care” for the treatment of the edentulous patient. Despite the highly successful outcomes3,4 for the implant-supported dentures, some patients may have been discouraged from selecting dental implant therapy as a result of the lag time between implant placement and delivery of the final prosthesis.5 Over the last decade, newer immediate provisionalization/loading protocols have been demonstrated to reduce the treatment time resulting in high implant success rates.6–13 The use of panoramic radiographs may affect the correct planning for implant therapy by leading the surgeon to an incorrect estimation of the bone level.14 Recent improvements in diagnostic and treatment plan software have substantially and positively enhanced the treatment of edentulous patients.(15–21) Using a computed tomography (CT) scan-based planning system, the surgeon is able to select the optimal location for implant placement even in the presence of minimum volume, avoiding the needs for bone augmentation procedures in many cases. Precise osteotomy control is performed using surgical guides, allowing transfer of planned implant positions to the mouth in a flapless way so as to reduce pain and swelling. Current management of the edentulous population should include continued development of oral implant technology to use techniques that can provide function, aesthetics, and comfort with a minimally invasive surgical approach.(22) Assessments of rehabilitation treatments must consider patients’ opinions as a variable of treatment success.(23) Patients often express dissatisfaction with their lower arch dentures,24 and complaints include reduced retention stability of conventional dentures and difficulties with mastication and verbal communication, all because of bone resorption of the alveolar process with time.(25) A patient’s perception of his or her own oral health is very important. Oral health, as related to quality of life (oral health-related quality of life [OHRQoL]), characterizes an individual’s perception of buccal health and can be used as an indicator of the advantages of prosthetic rehabilitation strategies.(26,27) The Oral Health Impact Profile (OHIP) questionnaire is one of the most technically sophisticated instruments for assessment of OHRQoL.(28) The aim of this study is to report the clinical outcomes of full-mouth rehabilitation using computer-aided flapless implant placement and immediate loading of a prefabricated prosthesis with a 3-year follow-up and to evaluate satisfaction of edentulous individuals treated with NobelGuide protocol.

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Materials and Methods

At 4 different study centers, 30 consecutive fully edentulous patients (18 women and 12 men) in both arches were enrolled in the trial and provided written informed consent to participate in the study. At the first visit, medical history and clinical evaluation were recorded. There was no limitation on the basis of medically compromising conditions such as anticoagulants, betablocking agents, hypertension, and hypothyroidism. The exclusion criteria were radiotherapy in the maxillary region, bisphosphonate therapy, remaining teeth that could interfere with implant placement, inability of mouth opening sufficiently to accommodate the surgical tooling (at least 50 mm), and lack of available bone. For the edentulous maxilla, the anatomical inclusion criteria was a residual ridge crest of a minimum of 4 mm wide, buccolingually, and 10 mm high from canine to canine; for the mandible, the anatomical inclusion criteria was an alveolar width of 4 mm and a height of at least 8 mm (Fig. 1). For radiographic guide, the patient’s prosthesis was used, when adequate, or a new one was fabricated before CT examination. At least 6 gutta-percha (Gutta-percha Points ISO Sizes,Colored; Dentsply DeTrey GmbH, Konstanz, Germany) markers (1.5 mm deep) were included in the scan prosthesis in different axial planes to serve as radiopaque references. A silicone (Zhermack Spa) interocclusal index was also made as a radiographic index to allow reproducible placement of the scan template intraorally by having the patient gently occlude against it. The patient was then referred to the radiologist for a high-resolution spiral CT (Somatom Volume Zoom; Siemens, Erlanger, Germany) scan. A double scanning procedure was followed. The first CT scan, with the subject wearing the radiographic scan template and interocclusal index, was used to visualize the bony architecture and anatomy of the potential implant sites. A second CT of the scan template alone was performed using NobelGuide protocol to visualize the nonradiopaque radiographic guide. The 2 resulting sets of Digital Imaging and Communication in Medicine (DICOM) files were then fused by making the radiopaque gutta-percha markers coincide. The 2 resulting sets of DICOM files were fused on the basis of the presence of radiopaque gutta-percha markers. Surface representations of the bone and the prosthesis were computed from these CT data sets by means of segmentation and loaded into a 3-dimensional (3D) image-based treatment planning software (Procera software; NobelBiocare AB, Göteborg, Sweden).The Procera software was used to virtually plan the ideal position according to the anatomical condition of each patient (Figs. 2 and 3), and the planning data were sent to Sweden, where surgical templates with hollow metallic cylinders for guiding implant placement were prepared (Fig. 4). The laboratory procedure consisted of fabricating a working cast from the surgical template, mounting the cast onto an articulator, and then fabricating a metal-acrylic fixed complete prosthesis from molar to molar. Therefore, a new silicone surgical index was prepared to allow the correct position of upper and lower surgical templates in the mouth before surgery. Both maxilla and mandible were treated during the same surgical session under conscious sedation and local anesthesia with articaine chlorohydrate with 4% epinephrine (Alfacaina 40 mg; Dentsply Italia, Rome, Italy). All patient were subjected to intravenous sedation (fractioned administration of 0.5–1 mg midazolam and 0.5 mg atropine). All patients were prescribed 2 g amoxicillin (Zimox; Pfizer Italia Srl, Rome, Italy) 1 hour before surgery and rinsed with chlorhexidine gluconate (0.2% for 1 minute) before the intervention. The 2 surgical templates (mandible and maxilla) were seated into the mouth of each patient using the silicone index and stabilized with at least 3 transalveolar pins (anchor pins; NobelBiocare AB) (Figs. 5 and 6). The acrylic resin surgical guide contained metal cylinders holding removable sleeves of different diameters, to fit the drill diameters used to prepare the implant sites. Drills with increasing diameters were used to prepare the implant site as suggested by the manufacturer. When limited bone resistance was noted by tactile assessment during drilling, undersized drilling of the alveolus was performed before implant insertion to ensure primary stability trabecular bone compaction. On the contrary, in the case of extremely dense bone, oversized drilling in length and/or screw tapping of the 2 of the 3 implant sites was performed. Bicorticalization was used for the maxillary implants to improve the primary stability. All implants were inserted with a minimum torque of 35 N/cm and a maximum of 50 N/cm, which indicates whether the implants were placed level with the crest or countersunk. Once all implants were inserted, the surgical templates were removed, and the prefabricated metal and acrylic resin complete-fixed dentures were connected to the implants by means of the expanding abutments. When tilted implants were used, 30-degree Multi-Unit Abutment (NobelBiocare AB) was placed using a custom jig manufactured in laboratory before surgery. A panoramic radiograph or serial intraoral radiographs were immediately made to evaluate the proper adaptation of all abutments to the implant platform (Fig. 7). Once this was successfully confirmed, the abutments were tightened to 35 N/cm. The upper and lower prostheses were placed immediately in function, and occlusal adjustments were performed (Fig. 8). The following postoperative protocol was followed: Anti-inflammatory drugs with ibuprofen (600 mg twice a day; Brufen; Abbott spa, Campoverde di Aprilia, Italy) was prescribed for 4 days postoperatively, and if necessary amoxicillin + clavulanic acid (1 g twice a day for 6 days; Zimox) were prescribed. Patients were also instructed to maintain oral hygiene and to use a chlorhexidine rinse (Curasept 0.2%; Curaden Healthcare Srl, Milan, Italy) twice a day for 15 days and placed on a soft diet during the first 2 months after surgery to limit occlusal loading.

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All 30 patients were recalled after 1 day, 10 days, 4 and 6 months, and subsequently, annually. Panoramic radiographs were made at annual recalls. The presence of eventual radiolucencies, indicative of a fibrous encapsulation and failure of the implants, was noted. Periapical radiographs were made at implant insertion and again at 6 and 12 months with a long-cone parallel technique using a conventional radiograph holder (Rinn centrator bite; Dentsply Rinn, Elgin, IL) individualized for each site with an acrylic resin template. Bone level measurements were performed by an independent radiologist at the Division of Neuro-Radiology, University of Florence CTO, Italy; the reference point for the reading was the implant platform (the horizontal interface between the implant shoulder and the abutment), and marginal bone remodeling was defined as the difference in marginal bone level relative to the bone level at the time of surgery. The mean and SD of the marginal bone level were calculated. The patient records were retrospectively analyzed using descriptive statistics. The marginal bone remodeling, the number of implants placed, the number of implants lost, their diameters, and survival time were recorded. Implant survival rate analysis at 3 years follow-up with Mantel-Cox test of log ranks and a paired t test for assessing differences in marginal bone levels at 12 and 36 months were performed.

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Questionnaire
Patient satisfaction was assessed using the OHIP in Edentulous Adults (OHIP-EDENT) questionnaire. The OHIP was developed in Australia by Slade and Spencer29 in 1994, and the tool comprises 49 questions distributed into 7 subscales. However, the questionnaire is considered too farreaching by some, and a number of studies have explored the possibility of downsizing it, without impairing its scope of application. Among the short versions that have been developed, the authors selected for this study the OHIP-EDENT,29–31 which deemed the most appropriate for edentulous patients. The tool detects the impact of oral health on the quality of life of patients with total prostheses, before and after they have received them.31,32 The OHIP-EDENT is a 14-question survey, grouped as 7 subscales or domains: functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability, and handicap. It is specific to edentulous patients and presents questions addressing masticatory capacity, pleasure in eating, level of comfort and assuredness while wearingthe prosthesis, and relationship problems, among others. The questionnaire (Table 1) was applied by 1 examiner only. To make it easier for the patient, a choice of only 3 answers was given: (0)¼ never; (1)¼ sometimes; (2) ¼ almost always, unlike the English version of the questionnaire, which gives a choice of 5 answers. The lowest scores represent a satisfactory perception of an individual’s oral conditions, and therefore higher satisfaction and better quality of life. At baseline, before surgery, subjects were asked to rate their satisfaction with various aspects of their dentures and their functional difficulties. Six months after the surgery, subjects completed further OHIP-14 questionnaires to assess the impact of their prostheses on their OHRQoL. Baseline and 6 months data were collected, and mean and SD were calculated as summary statistics for all variables. Within-group changes were tested using Fisher exact test: P values lower than 0.05 were considered statistically significant. All statistic analyses were performed using IBM SPSS software version 18.0 (IBM, Corp., Armonk, NY).

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RESULTS
In 30 consecutive patients, followed up to a 3-year period, a total of 312 implants were placed. The implant lengths varied between 8.5 and 18 mm and implant diameters were 3.3 mm (n ¼ 18), 3.75 mm (n ¼ 130), or 4 mm (n ¼ 164). The types of implants used were Nobel Speedy Groovy (192) and Brånemark Standard MKIII (130) (NobelBiocare AB). A total of 135 implants were inserted in the mandible and 177 in the maxilla. The overall implant survival rate at 3 years was 97.9% (96.6% for the maxilla and 99.2% for
the mandible) (Fig. 9). No statistical significant difference was recorded between survival of maxillary and mandibular implants (P ¼ 0.12). Three maxillary implants were lost in the first 3 months of healing, 2 after 6 months, and 1 after 12 months of loading. The only 1 implant lost in the mandible failed after 2 years because of periimplantitis, but it was not necessary to be substituted. All the maxillary implants lost were reinserted and were not included in the statistical analysis in this study. The time necessary for implant placement and delivery of 2 prostheses varied from 1.5 to 2.5 hours. No provisional prosthesis failed to fit, and all could be placed the same day. The patient’s postoperative discomfort such as swelling and pain was almost negligible. After 4 to 6 months of osseointegration healing patients had the choice of replacing the fixed provisional prosthesis with a definitive metal-acrylic or metal-ceramic complete bridge. Only 3 patients opted to replace the maxillary prosthesis with metal-ceramic fixed denture for aesthetic reason, whereas 6 patients received a definitive titaniumacrylic fixed denture (Figs. 8 and 10). After 3 years of follow-up, the definitive and the provisional prostheses were all still in function. Nine patient experienced fracture of the acrylic resin, 6 mandibular and 3 maxillaryprostheses. Six of these patients were heavy bruxers, and another explanation for prosthesis fracture could be the fact that patient did not follow instructions regarding the soft food diet or the absence of the perfect passive fit of the prosthesis at the end of surgery. This problem was solved by repairing the prosthesis, adjusting the occlusion, manufacturing an occlusal night guard, and giving patient further instruction regarding overloading of the prosthesis. Thus, no further mechanical complications occurred. The mean bone loss was –1.2 mm (SD: 0.7) and –1.9 mm (SD: 1.3) after 1 year and 3 years, respectively (Figs. 11 and 12). The distributions can be found in Figures 13 and 14.

Statistical Analysis
When the OHIP-EDENT-14 questionnaires filled at baseline and at 6 months follow-up were compared, a statistically significant difference was found for questions PA1, PA2, PD1, PS2, SO1, and SO2 and a tendency to significance was found for questions PS1, HA1, and HA2.

DISCUSSION
In this trial, 30 patients with resorbed fully edentulous maxillae and mandibles were treated. All implants were placed without flap elevation and all prostheses, fabricated before surgery, could be immediately applied and loaded with low rate of complications. This study reports medium-term observations in which the stability of the marginal bone level and high cumulative implant survival rate over such a period are reassuring and confirm the results already reported in literature.15–20 The key to success with immediate loading in the mandible and maxilla is the immediate and rigid connection of the implants by using an acrylic resin and metal-fixed complete denture immediately placed at the end of the surgery. Some authors reported the occurrence of surgical and technical complications with this protocol such as extensive adjustments of occlusion, misfit of abutment bridge, disconnection of the bridge, and fixture losses resulted in the removal of the superstructure in some cases, who returned to removable dentures.33,34 None of our patients returned to removable dentures, and all the fixed prostheses were fixed in a fewminutes at the end of the surgery. In the opinion of the authors of this study, the explanation for severe misfittings was derived from an incorrect planning such as implants virtually positioned with high degree of divergent axis or more often from an incorrect handling of the surgical tools such as high torque of insertion of the implants and displacement or fracture of the surgical template, which may cause a deviated implant position from the virtual planning. The results reported here confirm that, if the NobelGuide protocol is strictly followed and the surgery is carefully performed, avoiding displacement of the surgical template is possible to fit the prefabricated prosthesis in a predicable way. The key point is the accurate stent positioning at the beginning of surgery; so, it is recommended to administrate the majority of local anesthesia buccally to minimize the risk of template displacement inducted by palatal soft tissue deformation, the use of more than 3 transalveolar pins (Anchor Pins) to improve the stabilization of the surgical stent, and partial pretapping of the implant sites, even in soft bone, reducing the insertion torque although the underpreparation of the implant site is still performed. In a study conducted on cadavers, preoperative cone-beam CT images were subsequently matched with postoperative ones to calculate the deviation between planned and installed implants.35 This study showed an average angular deviation of 2 degrees (SD, 0.8 degrees; range, 0.7–4.0 degrees) when compared with the planning, whereas the mean linear deviation was 1.1 mm (SD, 0.7 mm; range, 0.3–2.3 mm) at the hex and 2.0 mm (SD, 0.7 mm; range, 0.7–2.4 mm) at the tip, confirming the accuracy of this protocol.35 In this study, satisfaction was determined using the OHIP-EDENT questionnaire, which has been validated in the literature, to detect the impact of OHRQoL of patients with total prostheses (overdentures and fixed types).29The majority of previous studies that have reported the influence of prosthetic treatment on the quality of life of patients have used nonvalidated instruments to assess patient satisfaction.31 Several studies have shown that patients treated with implant-supported lower overdentures are more satisfied than those who wear conventional overdentures.36,37 A similar tendency has been observed for patients treated with fixed prostheses, where the majority was generally satisfied with this type of rehabilitation. Therefore, the current results are similar to those already reported, indicating that patients treated with implantsupported total fixed prostheses are content with the result, especially because previously they had worn total conventional prostheses, which were ineffective in terms of retention, stability, and support. However, to the authors’ knowledge, this is the first time that the patient satisfaction is evaluated with the
OHIP questionnaire in full-mouth rehabilitation with prefabricated fixed prostheses and computer-assisted surgery. In this study, patients treated with the NobelGuide protocol showed significantly greater satisfaction than the conventional denture demonstrating a positive effect on patient OHRQoL. However, the absence of a control group limits the importance that can be placed on this observation. Although some disadvantages of this procedure have to be taken into consideration, such as cost, software acquisition, and planning time, there are evident gains including improved surgical planning avoiding in most of cases bone augmentation procedures, reduced
surgery time, postoperative pain, and swelling reduced to the minimum. The entire clinical procedure is not a simple procedure and should be recommended to clinicians with advanced clinical and surgical experience, especially in complex cases. In the authors opinion, however, this represents the future standard of care to treat fully edentulous patients. Disadvantages of this advanced computer technology are increased costs, for software purchase and doctor training and for the stereolithographically produced surgical templates. Time investment for the planning process also means an increase in cost. However, once the doctor is familiar with the software, 3D analysis of computer tomograms and virtual implant placement are fast. A compensation of costs results from reduced chairside time when doing surgery and a reduction of follow-up visits of the patients. Reduced patient morbidity is further an important aspect that cannot be calculated directly in money but is beneficial for the patients.

CONCLUSIONS
Computer-guided implant systems give provide an elevate amount of diagnostic, anatomic, and prosthetic data for the clinicians. The use of these protocols allows the placement of implants with flapless surgery and the immediate delivering of prosthesis. Immediate loading of implants placed in edentulous mouth is a reliable and predictable technique for full-mouth rehabilitation. Following the standard protocol assures a low occurrence ofcomplications and improves the patient’s compliance. Data from this study show that survival rates for implants placed with the NobelGuide protocol are high and comparable with other implant procedures. Moreover, the flapless surgery and the immediate loading increase the patients’ compliance. The OHIP-14 proved to be well accepted from the patients and suitable for describing the satisfaction for dental therapies in edentulous patients. Patient’s grade of satisfaction with this rehabilitation is very high, as attested by the OHRQoL, because it grants a better stability and support, together with lower postoperative discomfort. Therefore, implants’ placement with flapless surgery, following the NobelGuide protocol and their immediate loading, provides a fast and an efficient rehabilitation for edentulous patients. Additional studies involving the OHIP-14 can be planned to compare the NobelGuide protocol with other computer-guided implant protocols not only on the basis of clinical results but on the patient’s satisfaction as well.

DISCLOSURES
The authors claim to have no financial interest, either directly or indirectly, in the products or information listed in the article.

References

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