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STATEMENT OF PROBLEM: A digital workflow in fixed prosthodontics may use a 3D printer to obtain a cast for porcelain application. Standards exist that define the accuracy of traditional casts, but the accuracy requirements of 3D-printed casts have not been defined. PURPOSE: The purpose of this retrospective study was to investigate how the accuracy of 3D-printed casts affected prosthesis fit and whether they correctly reproduced interproximal contacts. MATERIAL AND METHODS: Copings with different die spacings were used to test different 3D-printed casts of the same dental arch. The accuracy of the 3D casts was assessed by imaging and comparing the resulting standard tessellation language (STL) files with the original through a matching software program. Accuracy scores were then correlated with a score measuring how well the copings fit the casts. The first data set was obtained from a patient receiving restoration of the 4 maxillary incisors. The teeth were prepared, the dental arch was imaged intraorally, and 10 resin casts were printed with four 3D printers. Two sets of 4 zirconia test copings were prepared, and 3 clinicians assessed their fit on each cast. A further set of casts was created from a second patient requiring prosthetic restoration for 5 adjacent teeth to assess whether undersizing affected the best fit of the copings on their dies. RESULTS: The clinical scores and accuracy scores did not correlate. The results suggested that printed dies showing a certain degree of undersizing might provide a better fit than those showing better correspondence to the actual anatomic structure. The oversized dies were the worst. Only 7 of 17 casts being assessed were deemed suitable for veneering of the copings. The undersized casts tested clinically better than casts printed by using the same printer under standard settings. CONCLUSIONS: This retrospective study indicated that 3D-printed casts that do not allow copings to fit appropriately usually show mean excess oversizing. Axially undersizing the printed dies on casts might allow a better fit of copings to be veneered.

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PURPOSE: Implant site preparation may be adjusted to achieve the maximum possible primary stability. The aim of this investigation was to study the relation among bone-to-implant contact at insertion, bone density, and implant primary stability intra-operatively measured by a torque-measuring implant motor, when implant sites were undersized or tapped. MATERIALS AND METHODS: Undersized (n=14), standard (n=13), and tapped (n=13) implant sites were prepared on 9 segments of bovine ribs. After measuring bone density using the implant motor, 40 implants were placed, and their primary stability assessed by measuring the integral of the torque-depth insertion curve. Bovine ribs were then processed histologically, the bone-to-implant contact measured and statistically correlated to bone density and the integral. RESULTS: Bone-to-implant contact and the integral of the torque-depth curve were significantly greater for undersized sites than tapped sites. Moreover, a correlation between bone to implant contact, the integral and bone density was found under all preparation conditions. The slope of the bone-to-implant/density and integral/density lines was significantly greater for undersized sites, while those corresponding to standard prepared and tapped sites did not differ significantly. CONCLUSION: The integral of the torque-depth curve provided reliable information about bone-to-implant contact and primary implant stability even in tapped or undersized sites. The linear relations found among the parameters suggests a connection between extent and modality of undersizing and the corresponding increase of the integral and, consequently, of primary stability. These results might help the physician determine the extent of undersizing needed to achieve the proper implant primary stability, according to the planned loading protocol.

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BACKGROUND: Recently, a torque-measuring micromotor has been shown to provide a reliable, quantitative intraoperative evaluation of bone density and implant primary stability. This may be particularly useful for determining bone quality of residual bone and consequently the most appropriate site preparation in the posterior maxilla, where bone often is of low density and quality. PURPOSE: This work aimed to assess the medium-term success of implants placed during 1-stage sinus augmentations using an undersized drilling protocol. In case of low bone density, the relationship between residual bone height (RBH) and primary stability was also investigated. MATERIALS AND METHODS: Clinical records of patients who underwent sinus augmentation and concomitant implant placement following a 12.5% undersized drilling protocol were retrospectively analyzed. In all patients, bone density measured intraoperatively was ≤ 0.45 g/cm3 . A minimum of 60 months of follow-up was required for inclusion. RESULTS: Records of 106 patients who received 253 implants were reviewed. No significant difference in the implant success rate was found for patients who had less than 4 mm of RBH and those who had more. CONCLUSIONS: Underpreparation of the implant-placement sites enabled achievement of successful implant-supported rehabilitation of the posterior maxilla even when both RBH and bone density were low.

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OBJECTIVE: The aim of this retrospective study was to evaluate medium-term marginal peri-implant bone loss following placement of root-form implants featuring a micro-threaded rough-surfaced neck and a platform-switched implant-abutment connection. METHOD AND MATERIALS: Records were identified of patients treated with such implants over a 3-year period at three Italian dental centers. Patient radiographs were digitized and subjected to computerized analysis of peri-implant bone resorption. RESULTS: Records of 112 patients who received 257 implants were analyzed. Although implant diameters and lengths varied, all had a 0.3-mm platform-switching width and a 2.5-mm high micro-threaded neck. All patients healed uneventfully, and no peri-implant infection, implant mobility, or radiolucency around the implant were detected at any follow-up control. At the 72-month control (average 71 ±â€¯5 months) all implants were successful according to Albrektsson and Zarb's criteria. At implant level, average peri-implant bone resorption was 0.18 ±â€¯0.12 mm at 6 months, 0.22 ±â€¯0.15 mm at 12 months, 0.23 ±â€¯0.16 mm at 24 months, 0.25 ±â€¯0.17 mm at 36 months, 0.26 ±â€¯0.15 mm at 48 months, and stable at subsequent controls, regardless of the implant diameter and length. At patient level, a similar trend was observed, with crestal bone loss stabilizing from 48 months onward. CONCLUSION: The surface, geometry, and platform-switching features of the implant under investigation allowed effective bone preservation on a medium-term basis.

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The aim of this work was to test the effectiveness of using enzymatically deantigenated equine bone block as a scaffold for guided bone regeneration (GBR) during a horizontal augmentation of the lower jaw. A partially edentulous atrophic mandible was augmented using an equine-derived block with an expanded polytetrafluoroethylene membrane. After 8.5 months, two bone core samples were collected at the augmentation site, and implants were placed. A definitive prosthesis delivered 6 months after implant placement provided excellent functional and aesthetic rehabilitation throughout the follow-up period. Histological and histomorphometrical analysis of the biopsies showed newly formed bone to be present and the residual biomaterial was still undergoing remodeling. Comparison of cone beam computed tomography scans taken before augmentation and 26 months later showed maintenance of ridge width and possible corticalization of the vestibular augmented ridge side. The equine-derived bone block placed in accordance with GBR principles provided a successful clinical, radiographic, and histological outcome.

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AIM: The present work describes a horizontal ridge augmentation in which a titanium mesh was preshaped by adapting it to a stereolithographic model of the patient's jaw that was fabricated from CT scans. BACKGROUND: Guided bone regeneration (GBR) involves covering the augmentation site with a long-lasting barrier to protect it from the invasion of surrounding soft tissues. Among barriers, titanium meshes may provide a successful outcome, but the intraoperatory time needed to shape them is a disadvantage. CASE DESCRIPTION: The 54-year-old patient, missing the right mandibular second bicuspid, first molar, and second molar, had her atrophic ridge augmented with a 30:70 mixture of autogenous bone and equine, enzyme-deantigenic collagen-preserved bone substitute. Two conical implants were inserted concomitantly in the second bicuspid and first molar positions, and the site was protected with the preshaped mesh. Four months later, the titanium mesh was retrieved, a bone sample was collected, and histological and histomorphometric analyses were performed. Provisional and definitive prostheses were then delivered, and follow-up controls were performed for up to 24 months. CONCLUSION: Preshaping the mesh on a model of the patient's mandible shortened the surgical time and enabled faster mesh placement. Two years after surgery, the implants were perfectly functional, and the bone width was stable over time as shown by radiographic controls. Histological analysis of the bone sample showed the heterologous biomaterial to be biocompatible and undergoing advanced remodeling and replacement with newly formed bone. CLINICAL SIGNIFICANCE: Preshaping a titanium mesh over a stereolithographic model of the patient's jaw allowed for a significant reduction of the intraoperative time and may be therefore, advisable in routine practice.

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