Gianpaolo Sannino

Minimally invasive treatment of the atrophic posterior maxilla: A proof-of-concept prospective study with a follow-up of between 36 and 54 months

STATEMENT OF PROBLEM In the posterior maxilla, tooth loss is usually associated with alveolar bone resorption and sinus pneumatization, limiting the placement of implants without grafting procedures. PURPOSE The purpose of this study was to evaluate a minimally invasive treatment of the atrophic posterior maxilla, with axial and tilted implants and immediate loading. The research hypothesis was that the combination of a guided, minimally invasive approach and the biomimetic features of computer-aided design and computer-aided manufacturing (CAD/CAM) abutments would be an effective alternative to maxillary sinus floor augmentation procedures with reduced bone resorption around implants. MATERIAL AND METHODS Twenty-seven consecutive participants (female=12, male=15) (mean age 54.18 years) with severe atrophy of the posterior maxilla were treated by using guided surgery with immediately loaded axial (39) and tilted (42) implants supporting CAD/CAM zirconia (39) and titanium (42) abutments (81 total) and partial fixed prostheses. Each participant underwent a computed tomography scan, after which 2 or 3 implants were positioned with a flapless or miniflap approach. The drilling protocol was adapted to the bone density of each implant site to obtain an insertion torque ranging between 40 and 50 Ncm. CAD/CAM customized abutments composed of zirconia or titanium were fixed to the implants with prosthetic screws tightened with a torque of 35 Ncm. An acrylic resin interim restoration reinforced with metal was placed immediately. Five to 6 months after initial loading, a zirconia framework was manufactured, and a definitive prosthesis was placed. Clinical and radiological controls were performed at baseline and after 1 and 3 years to assess implant and prosthesis survival and success rate and compare marginal bone remodeling of axial and tilted implants. Inferential statistics for radiological data were acquired by using the Mann-Whitney U-test. All statistical comparisons were conducted at the .05 significance level. RESULTS The mean follow-up period was 43.3 months (ranging from 36 months to 54 months). The cumulative implant survival rate was 96.3% at 3 years. All prosthetic restorations were stable and in good function, resulting in a cumulative prosthetic survival rate of 100%. Three restorations had chipping of the veneer material; thereafter, the cumulative prosthetic success rate was 91.9%. CONCLUSIONS Treatment of the posterior partially edentulous atrophic maxilla with guided surgery and immediate loading of tilted and straight implants supporting short-span partial fixed dental prostheses is effective.

Erratum to “Comparative Evaluation of Osseointegrated Dental Implants Based on Platform-Switching Concept: Influence of Diameter, Length, Thread Shape, and In-Bone Positioning Depth on Stress-Based Performance”

This study aimed to investigate the influence of implant design (in terms of diameter, length, and thread shape), in-bone positioning depth, and bone posthealing crestal morphology on load transfer mechanisms of osseointegrated dental implants based on platform-switching concept. In order to perform an effective multiparametric comparative analysis, 11 implants different in dimensions and in thread features were analyzed by a linearly elastic 3-dimensional finite element approach, under a static load. Implant models were integrated with the detailed model of a maxillary premolar bone segment. Different implant in-bone positioning levels were modeled, considering also different posthealing crestal bone morphologies. Bone overloading risk was quantified by introducing proper local stress measures, highlighting that implant diameter is a more effective design parameter than the implant length, as well as that thread shape and thread details can significantly affect stresses at peri-implant bone, especially for short implants. Numerical simulations revealed that the optimal in-bone positioning depth results from the balance of 2 counteracting effects: cratering phenomena and bone apposition induced by platform-switching configuration. Proposed results contribute to identify the mutual influence of a number of factors affecting the bone-implant loading transfer mechanisms, furnishing useful insights and indications for choosing and/or designing threaded osseointegrated implants.

Mechanical evaluation of an implant-abutment self-locking taper connection: finite element analysis and experimental tests.

PURPOSE To evaluate the mechanical properties and behavior of a self-locking taper connection with three different techniques: three-dimensional finite element analysis (FEA), ultimate failure loading, and cyclic loading analysis. MATERIALS AND METHODS The implant-abutment complex was embedded vertically in the center of an acrylic resin support block (Youngs modulus > 3 GPa). All materials used in this study were assumed to be homogenous and isotropic, but while the resin was assumed to be linearly elastic, the titanium was assumed to have a multilinear behavior to better represent the implant system in its plastic phase and to compare as closely as possible the numeric simulation with the experimental tests. An 800-N 30-degree off-axis load was applied to the occlusal surface of the abutment. In addition to the FEA, static and dynamic tests were carried out. RESULTS The greatest von Mises stresses were concentrated in the coronal portion of the abutments tapered connection, while at the implant neck they were lower and less extensive than the abutment ones. Experimental results confirmed the FEA findings, in which the structural limit of the system was reached, with permanent deformation of the abutment that exceeded a predefined limit, rather than fracture. CONCLUSION Within the limitations of the reported analyses, these static and dynamic tests appear to supply congruent results, thus allowing evaluation of the mechanical behavior of a self-locking tapered-connection implant system. High resistance to an off-axis load was exhibited, exceeding that usually offered by screw-retained implant systems, thus indicating good stability of the implant-abutment connection.

Intensity and duration of in-vitro antibacterial activity of different adhesives used in orthodontics

This work investigated the antibacterial activity of 14 bonding agents to predict their ability to inhibit white-spot development during orthodontic treatment. Standardized, sterilized disks of each material were continuously rinsed (for up to 180 d) in a flow of sterile saline. At predetermined time points, the residual ability of each material to inhibit bacterial growth (determined by measuring the size of inhibition halos around disks placed onto appropriate culture media seeded with Streptococcus gordonii DSM6777, Streptococcus sanguinis DSM20567, Streptococcus mutans DSM20523, or Lactobacillus acidophilus DSM20079) and biofilm formation (determined by measuring the numbers of bacteria adherent to disks following incubation in appropriate broths) was tested in triplicate and compared with the baseline activities of freshly prepared materials. Overall antibacterial and anti-biofilm activities, adjusted for exposure time and strain of bacteria, were assessed. The decrease of antibacterial activity was faster (30-60 d) and complete for fluoride-enriched materials, but slower (90 d) and partial for antimicrobial-containing materials (benzalkonium chloride, zinc oxide, chlorexidine, or MDPB). Materials enriched with benzalkonium chloride, chlorexidine, or MDPB showed the highest antibacterial activities. Anti-biofilm assays yielded similar results. These data could be helpful for clinicians in the choice of the best performing bonding agent also in light of duration of the clinical application.

Straight Versus Angulated Abutments on Tilted Implants in Immediate Fixed Rehabilitation of the Edentulous Mandible: A 3-Year Retrospective Comparative Study.

PURPOSE The aim of this study was to evaluate and compare the use of straight versus angulated abutments on tilted implants in the All-on-Four immediate function protocol. MATERIALS AND METHODS A total of 85 patients (36 men and 49 women; mean age 56.5 years) with edentulous mandibles were treated according to the All-on-Four concept using computer-guided implant placement. All patients received immediate interim prostheses screwed onto distal tilted implants by means of angulated (control group, n = 42) or straight abutments (test group, n = 43) and were followed for at least 3 years. Outcome considerations comprised implant and prosthetic survival and success rates, marginal bone level changes, patient satisfaction, and required clinical time. Student t test at a significance level of P < .05 was used to correlate the influence of the prosthetic protocol on marginal bone levels around the implants. RESULTS Overall implant survival rate was 98.21% for the control group and 98.83% for the test group. None of the 85 fixed prostheses were lost during the observation period (prosthetic survival rate of 100%). Statistically significant differences (P = .0068) in marginal bone loss were found between control and test groups. All patients were functionally and esthetically satisfied with their restorations. Required clinical time averaged 50 minutes for the control group and 30 minutes for the test group. CONCLUSION The described simplified and shortened surgical-prosthodontic protocol that avoids use of angulated abutments may be considered a reliable alternative to the traditional All-on-Four protocol.

In Vitro Evaluation of Ferrule Effect and Depth of Post Insertion on Fracture Resistance of Fiber Posts

Purpose. The analysis of the complex model of fiber post and ferrule is given and studied in this paper. A novel approach and a solution to the evaluation of stress of post and core system within the ferrule effect are proposed. Methods. Sixty freshly extracted premolars were selected for the study. The following experimental groups were therefore defined (n = 10): (1) 5 mm, (2) 7 mm, (3) 9 mm, (4) ferrule-5 mm, (5) ferrule-7 mm, and (6) ferrule-9 mm. Preshaping drills (C) were used to prepare the root canals at 5, 7, and 9 mm in depth. In specimens of groups 3–6 a circumferential collar of tooth structure of 2 mm in height. Fluorocore 2 core build-up material (I) was used for fiber post luting. With the same material, a buildup of 2 mm in height was created. A controlled compressive load (crosshead speed: 0.75 mm/min) was applied by means of a stainless steel stylus (Ø 1 mm) at the coronal end of the post extruding out of the root. Results. In all the tests the level of significance was set at P < 0.05 . Significantly higher fracture strengths were measured in the presence of a ferrule effect. In groups 1, 2, and 3 (ferrule group), the mean fracture values were, respectively, 163,8 N, 270,9 N, and 254,7 N. These data are higher and statistically significantly different when compared with the three groups 4, 5, and 6 (no-ferrule group), in which the values obtained were, respectively, 40,5 N, 41,7 N, and 44,9 N. Conclusion. The ferrule effect in the endodontically treated teeth positively affects the fracture strength of the fiber post. Conversely, post depth insertion did not affect the resistance to fracture.

A Retrospective 2-Year Clinical Study of Immediate Prosthetic Rehabilitation of Edentulous Jaws with Four Implants and Prefabricated Bars.

PURPOSE The purpose of this retrospective investigation was to evaluate the use of a prefabricated bar system for immediately loaded implants placed and restored according to the All-on-Four concept with up to 24-month follow-up. MATERIALS AND METHODS A total of 51 patients (31 males and 20 females; mean age 63.4 years) presented with edentulous or partially edentulous jaws with severe atrophy of the posterior regions. All patients were treated with full-arch fixed prostheses (28 maxillary, 34 mandibular) each supported by four implants (two vertical, two distally tilted). The implants were immediately loaded with screw-retained full-arch restorations. Each prosthesis was supported by a prefabricated metal bar combined with high-density acrylic resin. Follow-up visits were scheduled at 6, 12, and 24 months after initial prosthetic loading. Intraoral radiographs were obtained immediately after surgery and at each follow-up visit by using a custom radiograph holder and parallel technique. Marginal bone levels were assessed using digital image analysis. Implant and prosthetic survival and success rates were evaluated. Patient satisfaction was further assessed using a 100-mm visual analog scale (VAS). Data were compared by means of the Mantel-Haenszel test. RESULTS No drop-outs occurred. The overall implant survival rates were 100% and 98.38% for the vertical and tilted implants respectively. Two of the 62 definitive fixed prostheses were lost during the observation period due to implant failure. Since restoration replacement due to implant failure was not judged a prosthodontic failure according to the survival criteria provided in this study, the overall prosthetic survival rate was 100%. No statistically significant differences in marginal bone levels between vertical and tilted implants were detected at 24-month follow-up evaluation in either jaw. All participants were functionally and esthetically satisfied with their definitive restorations after 2 years functioning, as confirmed by the average VAS scores (masticatory function: 99.7; phonetic function: 99.5, esthetics: 99.2). CONCLUSIONS The preliminary 24-month results indicate that immediate loading of vertical and tilted implants using the evaluated prefabricated bar system may be a viable solution for edentulous jaw rehabilitation; however, more long-term prospective clinical trials are needed to affirm the effectiveness of this surgical-prosthetic protocol.

Influence of the implant drill design and sequence on temperature changes during site preparation

PURPOSE The purpose of this study was to compare bone temperature changes during implant drilling with two drill designs employed in three different drilling sequences. MATERIALS AND METHODS Two implant drill designs and three drilling sequences were evaluated in vitro using artificial bone cylinders. The evaluated drills were different only in the cutting-surface length (control, 16 mm; test, 4 mm). Three drilling sequences (control A, test B1, and test B2) were evaluated with and without irrigation. Temperatures were measured with thermocouple technology. The temperature changes generated by the final drill of each sequence were recorded as the experimental results and were subjected to the Student t test. RESULTS There were statistically significant differences in temperature changes when comparing the control group A with the test groups B1 (P = .001) and B2 (P = .01) during drilling without coolant. The mean temperature changes were 12.4°C, 6.5°C, and 13.7°C for groups A, B1, and B2, respectively. The Student t test showed statistically significant differences between temperature changes of the control group A and the test groups B1 (P < .01) and B2 (P < .05) during drilling with coolant. The mean temperature changes were 0.9°C, 0.7°C, and 1.9°C for groups A, B1, and B2, respectively. CONCLUSION Reduction in length of the cutting surface of the drill may limit frictional heat. Drills with the same length of cutting surface may induce lower bone temperature changes, when considering a preliminary drilling step with a pilot drill.

Fractal analysis of elastographic images for automatic detection of diffuse diseases of salivary glands: preliminary results.

The geometry of some medical images of tissues, obtained by elastography and ultrasonography, is characterized in terms of complexity parameters such as the fractal dimension (FD). It is well known that in any image there are very subtle details that are not easily detectable by the human eye. However, in many cases like medical imaging diagnosis, these details are very important since they might contain some hidden information about the possible existence of certain pathological lesions like tissue degeneration, inflammation, or tumors. Therefore, an automatic method of analysis could be an expedient tool for physicians to give a faultless diagnosis. The fractal analysis is of great importance in relation to a quantitative evaluation of “real-time” elastography, a procedure considered to be operator dependent in the current clinical practice. Mathematical analysis reveals significant discrepancies among normal and pathological image patterns. The main objective of our work is to demonstrate the clinical utility of this procedure on an ultrasound image corresponding to a submandibular diffuse pathology.

Dental and Biological Aspects for the Design of an Integrated Wireless Warning System for Implant Supported Prostheses: A Possible Approach

The paper proposes a system for an early warning on the prosthesis performance, in particular in terms of micro- displacements of the implant-prostheses connection, enabling actions to prevent fatal damages to the structure. The system includes a sensor for micro-displacement to be inserted in the prosthesis volume, with embedded wireless communications capabilities. Key elements of the system are the system enabling the wireless transmission of the recorded data and the molecular and biochemical approaches to unravel possible metabolic alterations. For these two elements, the paper presents and discusses several solutions.