The use of an artificial intelligence-driven novel tool for the evaluation of dental implants primary stability and immediate loading feasibility: an in vitro pilot study

PURPOSE

The primary aim of this study is to evaluate the correspondence between an Artificial Intelligence driven new tool prediction and the clinician's evaluation in the immediate loading suitability of curves recorded during implant insertion in an in vitro test. The secondary aim is to analyse peak insertion torque (pIT) and variable torque work (VTW) values of the implants used for the in vitro study.

MATERIAL AND METHODS

The study was performed on artificial bone blocks of solid rigid polyurethane without cortical layer with four different densities. Five types of implants with different macrogeometries were used. A total of 140 implants (7 implants of each type in the four polyurethane blocks) were inserted. Immediately after implant placement the insertion curves were classified by the operator as suitable or non-suitable for immediate loading. In a second moment the same curves were analyzed by the new AIT that classified them as belonging to YES or NO class. For each implant pIT and VTW were also recorded.

RESULTS

The correspondence between surgeon and AIT evaluation was 99,3% with only one false-negative reported by the algorithm analysis. The sensitivity resulted 98.95%, the specificity 100%, positive predictive value 100% and negative predictive value 97.8%. Mean pIT of the whole sample was 34.19 + 19.43 Ncm while mean VTW was 2266.89 + 1993.73 Ncm. Statistically significant differences were found between implant systems in the whole sample and when divided by polyurethane block density.

CONCLUSIONS

AIT showed a high level of accuracy in the prediction of immediate loading suitability of insertion curves examined. All the implants used in the in vitro test were able to reach good levels of primary stability, excluding when inserted in the less dense polyurethane block. Clinical studies conducted in larger samples and with more surgeons involved are necessary to confirm these results.

Primary Stability Evaluation of a Novel Tapered Implant Inserted in Low-Density Bone Sites: An In Vitro Study

Purpose: To evaluate primary stability of a new dental implant design in low-density bone sites, compare it with another implant design previously studied in the same bone density, and explore possible correlations between primary stability parameters. Materials and Methods: The study was carried out on fresh humid bovine bone classified as type III. The test group consisted of 30 DS Prime Taper implants (PT), and the control group consisted of 30 Astra Tech EV implants (EV). All the implants were inserted according to the protocol provided by the manufacturer. After placement, variable torque work (VTW), peak insertion torque (pIT), and resonance frequency analysis (RFA) were recorded. Results: Mann-Whitney test showed that the mean VTW and pIT were significantly higher in the test group PT compared to the control group EV; furthermore, statistical analysis showed that the mean RFA was slightly higher in the control group EV but without reaching statistical significance. Pearson correlation analysis showed a very strong positive correlation between pIT and VTW values in both groups; furthermore, it showed a positive correlation between pIT and RFA values and between VTW and RFA values again in both groups. Conclusion: The results showed that the novel tapered implants were able to reach good primary stability in low-density bone sites and that this was superior to parallel-walled implants when measured with VTW and pIT. Moreover, a statistically significant correlation was found between the three methods used to measure implant primary stability.

The Conometric Concept: Definitive Rehabilitation of a Single Posterior Implant Using a Friction Retention Abutment. A 1-year Follow-up Report

PURPOSE

To provide a 1-year assessment of friction-retention abutments (Acuris, Dentsply Sirona) used to retain a single lithium disilicate (LS2) monolithic restoration.

MATERIALS AND METHODS

A total of 522 implants were placed to treat single-tooth premolar and molar edentulous sites in the mandible or maxilla. Three types of implants were used. The tested abutments were connected 3 months after implant placement. A single pressed LS2 monolithic restoration was cemented to a dedicated titanium cap and engaged to the abutment without the use of screws or cement. Any complications affecting the restoration or the opposing dentition, soft tissue dimensional changes, the distance between the implant platform and the bone peak, and pocket probing depths were recorded at the time of restoration placement (T0), after 6 months of function (T1), and after 1 year of function (T2). Esthetic, functional, and biologic parameters were recorded at T0 and T2.

RESULTS

A total of 507 patients (284 women and 223 men) received a restoration (T0), and 504 of them reached the T2 1-year follow-up. One restoration fractured after 10 months in function. No statistically significant difference was assessed in the soft tissue measurements or in the measurements of the distance between the supporting implant platform and the bone peak. None of the restorations detached during the observation period.

CONCLUSION

The friction retention abutment is a viable option to retain an implant-supported monolithic LS2 glass-ceramic restoration in cases of premolar or molar single-tooth edentulism.

Fixed Partial Restorations Made of a New Zirconia-Reinforced Lithium Silicate Material: A 2-Year Short-Term Report

PURPOSE

To evaluate the 2-year performance of definitive implant- or tooth-supported three-unit fixed dental prostheses made of zirconia-reinforced lithium silicate placed to restore premolars and molars in clinical cases of partial edentulism.

MATERIALS AND METHODS

All patients received a three-unit fixed restoration made of monolithic, hot-pressed, zirconia-reinforced lithium silicate glass-ceramic. The restoration was cemented to two natural teeth or attached to two 3.5- or 4.5-mm-diameter square threaded, grit-blasted, acid-etched integrated implants with a Morse taper connection. Peri-implant pocket depth and bone and soft tissue remodeling were recorded for 2 years at each follow-up visit. Esthetic, functional, and biologic United States Public Health Services (USPHS) parameters modified by the World Dental Federation study design were assessed yearly until the final follow-up appointment. At the time of placement of the definitive restorations and at the 2-year follow-up visit, the opposing dentitions were identified by type of restoration and supporting structures.

RESULTS

A total of 100 patients were consecutively enrolled in the period between June 2016 and July 2017, and 50 patients each received an implant-supported restoration (Group A) or a tooth-supported restoration (Group B). One (2%) of the 50 implant-supported prostheses fractured after 21 months of function. None of the other prostheses failed or became loose or detached. No significant differences involving probing levels or bone and soft tissue remodeling were found between the follow-up times. No cases of inflammation or infection of the mucosal cuff around the neck of the implants were recorded. The most common issue occurred immediately after placement of the prosthesis, when 3 patients (6%) from Group A and 4 patients (8%) from Group B asked for a modification of tooth shade.

CONCLUSION

Implant-supported or tooth-supported three-unit fixed dental prostheses made of zirconia-reinforced lithium silicate can be used to successfully restore cases of posterior partial edentulism. The 2-year results of this report will be studied more in depth in ongoing long-term research.

Computer-Aided Crown Design Using Digital Scanning Technology for Immediate Postextraction Single-Implant Restorations Supported by Conical Indexed Abutments

Conical retention with antirotational features (Acuris abutment) has been recently proposed for restorations of healed single implants. The conometric abutments use the retentive force of the coping-abutment system to retain the prosthetic crown without the use of cement or screws. This retentive force must be overcome to obtain detachment of the relined provisional crown in immediate restorations. The present article describes the use of digital scanning technology to virtually plan computer-guided implant placement and restoration with conical indexed abutments in postextraction sites. Importing the scan data of both matrix and patrix abutments that are seated on the definitive cast into the computer-aided design software provides a workflow to preoperatively mill a crown that perfectly fits the abutment into the postextraction site. This technique simplifies the provisional crown relining onto the conometric indexed abutment and reduces the intraoperative time.

A 30-Year (1988-2018) Retrospective Microscopical Evaluation of Dental Implants Retrieved for Different Causes: A Narrative Review

For decades, the histologic evidence about osseointegration and the bone-implant interface has been discussed in the literature. In this review, the effectiveness of dental implants retrieved for different causes was evaluated. A literature search was performed in databases for papers about implants retrieved from humans published by the Implant Retrieval Center of the University of Chieti-Pescara, Italy. Sixty-eight articles were selected into categories based on topics. The data indicated high level of bone-to-implant contact, lamellar bone close to the surface, roughness related to an increased bone response, organized and remodeled bone after loading, and peri-implant interfaces subjected to a continuous dynamic function.

A Narrative Review of the Histological and Histomorphometrical Evaluation of the Peri-Implant Bone in Loaded and Unloaded Dental Implants. A 30-Year Experience (1988-2018)

Background: The aim of the present review was to assess the histological and histomorphometrical data from the paper published by our Laboratory on peri-implant bone in dental implants in different loading conditions. Methods: The papers published in different implant loading conditions, in dental implants retrieved from humans, and in the Hard Tissues Research Center of the University of Chieti-Pescara, Italy, were screened on MEDLINE/PubMed, Embase, Scopus, and other electronic databases until 31 December 2018. Only articles that reported the histological and histomorphometrical values of the Bone-Implant Contact (BIC) were selected. Results: The system selection provided a total of 155 papers. The manuscripts included for the narrative review were 57. These papers provided histological and histomorphometrical data. Conclusions: The bone remodeling around dental implants was found to be a dynamic process; loading changed the microstructure of the peri-implant bone; and implants were found to provide a successful function, over several decades, with different range of degrees of BIC in vivo (varying from a little more than 30% to a little more than 90%). Loaded implants presented a 10%-12% higher BIC values when compared to submerged, unloaded implants, and rougher surfaces had, on average, about a 10% higher BIC than machined surfaces.

Guided-welded approach planning using digital scanning technology for combined screw- and conometric-retained implant-supported maxillary prosthesis

AIM

The goal of this case series was to evaluate the clinical outcome at the 2-year follow-up of immediately loaded combined screw- and conometric-retained implant-supported full-arch restorations virtually planned using digital scanning technology.

MATERIALS AND METHODS

This series included 12 patients presenting hopeless teeth in the maxilla treated with computer-guided flapless implant placement. A total of 72 implants were inserted. All implants were immediately loaded with a complete-arch restoration supported by an intraorally welded framework. Digital scanning technology was used to virtually plan a combined screw and conometric retention of the frameworks. Clinical parameters were assessed at 1 week and at 1, 3, 6, 12, and 24 months follow-up.

RESULTS

The survival rate after 2 years was 98.6%, as one implant failed during the osseointegration period. No major prosthetic complications were observed such as issues with mobility, unscrewed abutments, disconnected conometric copings, and prosthetic fracture. Only one patient registered the chipping of a prosthesis.

CONCLUSION

Based on the results of the present study, the use of combined screw and conometric retention for fixed immediate restorations properly planned using digital scanning technology seems to be a viable treatment alternative to screw or conometric retention alone for immediately loaded rehabilitations.

Microchemical and Micromorphologic ESEM-EDX Analysis of Bone Mineralization at the Thread Interface in Human Dental Implants Retrieved for Mechanical Complications After 2 Months to 17 Years

The aim of this study was to analyze the degree of mineralization around nine clinically stable titanium dental implants retrieved after 2 months to 17 years for mechanical complications from five patients. The micromorphology and microchemistry of the interface bone at the coronal and apical sides of the threads were analyzed by environmental scanning electron microscope and energy-dispersive X-ray spectroscopy (EDX) on histologic samples. Mineralization was investigated by atomic calcium-to-nitrogen (Ca/N), phosphorous-to-nitrogen (P/N), and calcium-to-phosphorous (Ca/P) ratio evaluation (statistical analysis by two-way analysis of variance with Student-Newman-Keuls; P < .05). EDX showed higher Ca/N, P/N, and Ca/P values for the bone at the coronal side compared to the apical side of the threads in the long-term (≥ 14 years) samples. The two most significant findings were that (1) the interface bone located at the coronal side of the implant threads was generally more mineralized than the interface bone located at the apical side, and (2) the mineralization of the peri-implant bone at the interface increased over time. A higher degree of mineralization was found at 2 months in an immediately loaded implant when compared to the 2-month submerged unloaded control, likely related to the different remodeling events (coronal vs apical side of the implant threads) due to the direction of the loading forces.

The Conometric Concept: A 5-Year Follow-up of Fixed Partial Monolithic Zirconia Restorations Supported by Cone-in-Cone Abutments

The use of the cone-in-cone connection to support definitive restorations was previously evaluated in cases involving full-acrylic resin or hybrid acrylic-resin composite prostheses. The aim of this study was to evaluate the performance of definitive fixed partial prostheses made with monolithic zirconia and supported by cone-in-cone abutments and integrated implants. Implants were placed into healed sites and fresh extraction sockets. The prostheses were placed in the posterior regions of partially edentulous patients after healing periods of 3 months. A total of 76 patients received fixed monolithic zirconia restorations splinted with cone-in-cone connections to two implants that were followed up yearly for 5 years. At each follow-up visit, peri-implant bone levels and pocket depths were recorded. Esthetic, functional, and biologic United States Public Health Services parameters modified by the World Dental Federation study design were assessed at the last follow-up appointments. The opposing dentition was categorized by type of restoration and supporting structure at the time of placement of the definitive zirconia partial restoration and at the 5-year follow-up. The treatment achieved an 88.2% success rate and a 97.4% survival rate at the 5-year follow-up. None of the prostheses became loose or detached. One fixed prosthesis (0.76%) fractured 41 months after placement. No significant difference involving peri-implant bone and probing levels between the experimental times was found. The results of this research indicated that abutment-prosthesis cone-in-cone connections were successful within the 5-year study period.

The Conometric Concept: A Two-Year Follow-Up of Fixed Partial CEREC Restorations Supported By Cone-In-Cone Abutments

PURPOSE

To evaluate the performance of definitive, implant-supported, lithium disilicate fixed dental prostheses (LS₂ FDPs) manufactured with a computer-assisted design/computer-assisted manufacturing (CAD/CAM) system. All patients received two-unit restorations placed in posterior regions, supported by osseointegrated implants with cone-in-cone connection abutments.

MATERIALS AND METHODS

Two implants (Ankylos) were placed into healed sites or fresh extraction sockets in the maxillary/mandibular posterior regions of partially edentulous patients. Definitive digital impressions were made 3 months after surgery. Twenty-four patients received fixed  monolithic LS₂ restorations manufactured with the CEREC system. All restorations were connected to the implants using cone-in-cone connection abutments. Peri-implant pocket depths were recorded for 2 years at each follow-up visit. Esthetic, functional, and biologic United States Public Health Services (USPHS) parameters modified by the FDI World Dental Federation study design were assessed yearly until the last follow-up appointment. The opposing dentitions were identified by type of restoration and supporting structures at the time of placement of the definitive restorations and at the 2-year follow-up visits.

RESULTS

One patient (4.16%) moved to an unknown location during the study. A total of 23 FDPs (95.8%) supported by 46 implants reached the 2-year follow-up. None of the prostheses failed, or became loose or detached. No significant difference involving probing levels between the experimental times were found.

CONCLUSIONS

The results of this research indicated that the abutment-prostheses connection using a cone-in-cone approach was successful within the 2-year period of this study. None of the studied monolithic LS₂ glass-ceramic prostheses milled using the CEREC CAD/CAM system fractured or became detached.

Molecular, Cellular and Pharmaceutical Aspects of Bone Grafting Materials and Membranes During Maxillary Sinus-lift Procedures. Part 1: A General Overview

Sinus augmentation procedure has been demonstrated to be a highly predictable treatment in posterior maxilla atrophy. All the surgical interventions in the maxillary region require deep knowledge of anatomy and possible anatomical variations. In this article, pre-operative and post- operative assessments of sinus cavity as well as novel approaches to deepen our knowledge of the behavior of bone substitute materials are described. The awareness of the patient's morphologic conditions enables exact planning of invasive surgery and aids to avoid complications. Pre- operative radiologic evaluation of the region before sinus lift is advisable both for a planning of the sinus augmentation and for selection and alignment of the optimum placement of implants. On the orthopantomography it is possible to measure the vertical dimension of graft, but not the volume and 3D changes. Cone-beam computed tomography (CBCT) has become the "gold standard" to plan a comprehensive implant treatment and to achieve a post-operative assessment. A computer-aided design/computer-aided manufacturing (CAD/CAM) technique is proposed to produce custom-made block grafts for sinus lift procedure, and a customized cutting guide to accurately place the lateral wall and ease membrane elevation. This procedure allows to reduce intervention time, to precisely adapt the scaffold, to reduce risk of complications and to improve operation quality. Recently, a novel approach has been used to deepen our knowledge of the behavior of BSBs: by means of synchrotron micro-tomography (SCT). It is a 3-D analyzing method, suitable to examine the dynamic and spatial arrangement of regenerative phenomena in complex anatomical structures such as bone, where tissues with several morphologies (alveolar process, unmineralized extracellular matrix, regenerated vessels, etc.) compete to achieve the final goal of bone regeneration.

Molecular, Cellular and Pharmaceutical Aspects of Bone Grafting Materials and Membranes During Maxillary Sinus-lift Procedures. Part 2: Detailed Characteristics of the Materials

Various grafts or combination of bone substitute materials have been used in sinus lift procedures. Currently, ongoing developments in several disciplines, from molecular biology and chemistry to computer science and engineering, have contributed to the understanding of biological processes leading to bone healing after the use of bone substitute materials (BSBs) and therefore of the behavior of BSBs. The understanding of the properties of each graft enables individual treatment concepts and therefore allows shift from a simple replacement material to the modern concept of an individually created composite biomaterial. Indeed, the choice of the best BSB still remains crucial for success in maxillary sinus augmentation procedures. The present article provides an overview of most of the materials currently available for sinus lift, with a specific focus on their histological, molecular, cellular and pharmaceutical aspects.

Retention Strength of Conical Welding Caps for Fixed Implant-Supported Prostheses

PURPOSE

This study evaluated the retention strength of welding caps for Ankylos standard abutments using a pull-out test.

MATERIALS AND METHODS

Each sample consisted of an implant abutment and its welding cap. The tests were performed with a Zwick Roell testing machine with a 1-kN load cell.

RESULTS

The retention strength of the welding caps increased with higher abutment diameters and higher head heights and was comparable or superior to the values reported in the literature for the temporary cements used in implant dentistry.

CONCLUSION

Welding caps provide a reliable connection between an abutment and a fixed prosthesis without the use of cement.

The Conometric Concept: Coupling Connection for Immediately Loaded Titanium-Reinforced Provisional Fixed Partial Dentures-A Case Series

The aim of this prospective study was to demonstrate the feasibility of the conic coupling connection as a novel approach for the retention of immediately loaded, titanium-reinforced, temporary fixed partial restorations. The patients received a fixed, immediate partial restoration, attached using the conic coupling connection to two implants placed in a fresh extraction socket. Changes in marginal peri-implant bone level or probing depth measurements, biologic or technical complications, and any other adverse event were recorded at yearly follow-ups up to 3 years after implantation. A total of 78 implants placed in 39 patients reached the 3-year follow-up. A trend of bone overgrowth over the implant platform (mean: 0.2 mm) and a complete fill of the vertical gap between the implant platform level and the first point of contact of the bone with the implant surface was seen after the 6-month follow-up. No disconnection of any prosthesis was noted during 3 years of full occlusal function. The results of this study suggest that titanium-reinforced, temporary partial restorations with conic coupling retention supported by immediate implants provide a successful, cost-effective treatment modality.

Fatigue limits of titanium-bar joints made with the laser and the electric resistance welding techniques: microstructural characterization and hardness properties

Fatigue behavior of the titanium bars is of utmost importance for the safe and reliable operation of dental implants and prosthetic constructions based on these implants. To date, however, only few data are available on the fatigue strength of dental prostheses made with electric resistance welding and laser welding techniques. This in-vitro study highlighted that although the joints made with the laser welding approach are credited of a superior tensile strength, joints made with electric resistance welding exhibited double the minimum fatigue strength with respect to the joints made with laser welding (120 vs 60 N).

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

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 0.38-7.82 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.

Influence of Stepped Osteotomy on Primary Stability of Implants Inserted in Low-Density Bone Sites: An In Vitro Study

PURPOSE

The aims of this study were to evaluate the ability of a stepped osteotomy to improve dental implant primary stability in low-density bone sites and to investigate possible correlations between primary stability parameters.

MATERIALS AND METHODS

The study was performed on fresh humid bovine bone classified as type III. The test group consisted of 30 Astra Tech EV implants inserted following the protocol provided by the manufacturer. The first control group consisted of 30 Astra Tech EV implants inserted in sites without the underpreparation of the apical portion. The second control group consisted of 30 Astra Tech TX implants inserted following the protocol provided by the manufacturer. Implant insertion was performed at the predetermined 30 rpm. The insertion torque data were recorded and exported as a curve; using a trapezoidal integration technique, the area underlying the curve was calculated: this area represents the variable torque work (VTW). Peak insertion torque (pIT) and resonance frequency analysis (RFA) were also recorded.

RESULTS

A Mann-Whitney test showed that the mean VTW was significantly higher in the test group compared with the first control and second control groups; furthermore, statistical analysis showed that pIT also was significantly higher in the test group compared with the first and second control groups. Analyzing RFA values, only the difference between the test group and second control group showed statistical significance. Pearson correlation analysis showed a very strong positive correlation between pIT and VTW values in all groups; furthermore, it showed a positive correlation between pIT and RFA values and between VTW and RFA values only in the test group.

CONCLUSION

Within the limitations of an in vitro study, the results show that stepped osteotomy can be a viable method to improve implant primary stability in low-density bone sites, and that, when a traditional osteotomy method is performed, RFA presents no correlation with pIT and VTW.

The Conometric Concept: Definitive Fixed Lithium Disilicate Restorations Supported by Conical Abutments

PURPOSE

The use of the conical coupling connection to support definitive restorations was evaluated in cases involving full acrylic resin or hybrid acrylic resin-composite prostheses. The aim of this study was to evaluate the performance of definitive fixed partial prostheses made with lithium disilicate and supported by coupling connection abutments and healed implants.

MATERIALS AND METHODS

The prostheses were placed in the posterior regions of partially edentulous patients; 65 patients received fixed lithium disilicate restorations splinted with conical coupling connections to two implants. Implants were placed into healed sites and fresh extraction sockets. The prostheses were placed after healing periods of 3 months: restorations were followed yearly for 3 years. At each follow-up visit, peri-implant bone levels and pocket depths were recorded. Esthetic, functional, and biologic United States Public Health Services (USPHS) parameters modified by the FDI World Dental Federation study design were assessed at the last follow-up appointments.

RESULTS

Two prostheses (3.07%) fractured: one was related to framework design error; one was caused by a car accident. Three patients reported small chips: these restorations were immediately polished. No significant difference involving peri-implant bone and probing levels between the experimental times were found. None of the prostheses became loose.

CONCLUSIONS

The results of this research indicated that abutment-prostheses coupling connections were successful within the timeframe of this study.

Strain gauge analysis of implant-supported, screw-retained metal frameworks: Comparison between different manufacturing technologies

Over the past decades, the technological development in the medical field, coupled with the ongoing scientific research, has led to the development and improvement of dental prostheses supported by screw-retained metal frameworks. A key point in the manufacture of the framework is the achievement of a passive fit, intended as the capability of an implant-supported reconstruction to transmit minimum strain to implant components as well as to the surrounding bone, when subject to any load. The fitting of four different kinds of screw-retained metal frameworks was tested in this article. They differ both in materials and manufacturing process: two frameworks are made by casting, one framework is made by computer-aided design and computer-aided manufacturing and one framework is made by electric resistance spot welding (WeldONE, DENTSPLY Implants Manufacturing GmbH, Mannheim, Germany). The passivity of the frameworks was evaluated on the entire system, composed of a resin master cast, the implant analogues embedded in the cast and the frameworks. Strains were recorded by means of an electrical strain gauge connected to a control unit for strain gauge measurements. The experimental tests were carried out in the laboratories of the Department of INdustrial engineering at the University of Bologna. The results of the test campaigns, which compared three samples for each technological process, showed that no significant differences exist between the four framework types. In particular, the frameworks made by the resistance welding approach led to a mechanical response that is well comparable to that of the other tested frameworks.

Marginal bone loss around implants with platform-switched Morse-cone connection: a radiographic cross-sectional study

OBJECTIVES

The aims of the present cross-sectional study are to evaluate the bone remodeling around Morse-cone implants placed subcrestally 1 year after loading and the prevalence of bone loss >0.5 mm after at least 3 years of loading.

MATERIAL AND METHODS

Subjects who underwent a radiographic check in 2013 with implants that had been in function for at least 3 years were considered for inclusion. The study population comprised of 145 subjects with a total of 523 implants. At the moment of insertion, all the implants were placed subcrestally from 1 to 3 mm as clinically measured. Radiographs taken at baseline, that is 1 year after loading (T0), and at the follow-up visit in 2013 (T1) were examined. The distance between the rim of the implant and the marginal bone level at mesial and distal aspects of each implant was determined and the mean bone loss calculated.

RESULTS

In the total sample, the mean bone loss occurred between baseline and 2013 examination was 0.42 ± 0.77 mm; at T1 424 implants presented the marginal bone level at the implant rim (78) or above it (346). On the other hand, 99 implants presented the rim above the bone crest. Fifty-one implants that at T1 presented the rim above the bone crest, and that between T0 and T1 had lost at least 0.5 mm, were considered losers: 10 implants lost up to 0.5 mm, 11 lost from 0.6 to 1 mm, 16 lost from 1.1 to 2 mm, and 14 lost more than 2 mm of bone. On a subject basis, 34 subjects (group A) with a total of 200 implant sites presented loser implants, while 111 subjects (group B) with 323 implants displayed non-loser implants.

CONCLUSIONS

Within the limits of a cross-sectional study, the results show that Morse-cone implants placed subcrestally in the vast majority of cases (89.9%) are able to maintain the bone crest at level of the rim or above it 1 year after loading. The incidence of loser sites (bone loss >0.5 mm) after at least 3 years of follow-up is 9.7% at implant level and 23.5% at patient level.

Microstructural characterization and hardness properties of electric resistance welding titanium joints for dental applications

The electric resistance welding procedure is used to join a titanium bar with specific implant abutments in order to produce a framework directly in the oral cavity of the patient. This investigation studied the effects of the welding process on microstructure and hardness properties of commercially pure (CP2 and CP4) Ti components. Different welding powers and cooling procedures were applied to bars and abutments, normally used to produce the framework, in order to simulate the clinical intraoral welding procedure. The analyses highlighted that the joining process did not induce appreciable changes in the geometry of the abutments. However, because of unavoidable microstructural modifications in the welded zones, the hardness decreased to values lower than those of the unwelded CP2 and CP4 Ti grades, irrespective of the welding environments and parameters.

Adult stem cells properties in terms of commitment, aging and biological safety of grit-blasted and Acid-etched ti dental implants surfaces

Titanium (Ti) is one of the most widely used biomaterials for manufacturing dental implants. The implant surface properties strongly influence osseointegration. The aim of the present study was to in vitro investigate the characteristics of Ti dental implants in terms of mutagenicity, hemocompatibility, biocompatibility, osteoinductivity and biological safety. The Ames test was used to test the mutagenicity of the Ti dental implants, and the hemolysis assay for evaluating their hemocompatibility. Human adipose - derived stem cells (ADSCs) were then seeded onto these implants in order to evaluate their cytotoxicity. Gene expression analyzing with real-time PCR was carried out to investigate the osteoinductivity of the biomaterials. Finally, the genetic stability of the cells cultured onto dental implants was determined by karyotyping. Our results demonstrated that Ti dental implants are not mutagenic, do not cause hemolysis, and are biocompatible. The MTT assay revealed that ADSCs, seeded on Ti dental implants, proliferate up to 30 days in culture. Moreover, ADSCs loaded on Ti dental implants show a substantial expression of some osteoblast specific markers, such as COL1A1, OPN, ALPL, and RUNX2, as well as chromosomal stability after 30 days of culture in a medium without osteogenic factors. In conclusion, the grit-blasted and acid-etched treatment seems to favor the adhesion and proliferation of ADSCs and improve the osteoinductivity of Ti dental implant surfaces.

Eight-Year Results of Site Retention of Anorganic Bovine Bone and Anorganic Bovine Matrix

The long-term fate of some biomaterials is still unknown, and the reports present in the literature are not conclusive as to whether these biomaterials are resorbed over time or not. Different reports can be found with regard to the resorption behavior of anorganic bovine bone (ABB). The aim of the present study was to provide a comparative histological and histomorphometrical evaluation, in the same patient, of 2 specimens retrieved from a sinus augmented with ABB and with anorganic bovine matrix added to a cell-binding peptide (PepGen P-15), respectively, after a healing period of 6 months and after 8 years of implant loading, to evaluate the resorption of both biomaterials. A unilateral sinus augmentation procedure with ABB (50%) and with PepGen P-15 (50%) was performed in a 54-year-old male patient. Two titanium dental implants with a sandblasted and acid-etched surface were inserted after 6 months. During this procedure, 2 tissue cores were retrieved from the sinus with a trephine, before implant insertion. After an additional 6 months, a fixed prosthetic restoration was fabricated. One of these implants, after a loading period of 8 years, fractured in the coronal portion and was removed. Both specimens, one retrieved after a 6-month healing period and the other after an 8-year loading period, were treated to obtain thin ground sections. In the 6-month specimen, the histomorphometry showed that the percentage of newly formed bone was 27.2% ± 3.6%, marrow spaces 35.6% ± 2.3%, residual ABB particles 25.1% ± 1.2%, and residual PepGen P-15 particles 12.1% ± 2.2%. In the 8-year specimen, the histomorphometry showed that the percentage of newly formed bone was 51.4% ± 4.8%, marrow spaces 40% ± 7.1%, residual ABB particles 6.2% ± 0.7%, and residual PepGen P-15 particles 2.4% ± 0.5%. Both biomaterials underwent significant resorption over the course of this study.

Osteocyte density in the peri-implant bone of implants retrieved after different time periods (4 weeks to 27 years)

Bone tissue is characterized by a constant turnover in response to mechanical stimuli, and osteocytes play an essential role in bone mechanical adaptation. However, little to no information has been published regarding osteocyte density as a function of implantation time in vivo. The aim of this retrospective histological study was to evaluate the osteocyte density of the peri-implant bone in implants retrieved because of different reasons in a time period from 4 weeks to 27 years. A total of 18 samples were included in the present study. Specimens were divided into 3 groups depending on the loading history of the implants: loading between 4 weeks and 7 months (group 1); loading between 1 and 5 years (group 2); loading between 14 and 27 years (group 3). All the samples were histologically evaluated and osteocyte density was obtained using the ratio of the number of osteocytes to the bone-area (mm(2) ). The osteocyte density values significantly increased in the Group 2 (1-5 years) compared with Group 1 (4 weeks-7 months), and significantly decreased in the Group 3 (14-27 years) compared to Group 2. No significant differences were detected between Group 1 and Group 3. The decrease in osteocyte density observed in samples that were in vivo for long periods of time under loading is possibly because of the fact that once the bone structure is well aligned and biomechanically competent, a lower number of osteocytes are necessary to keep the tissue homeostasis under loading.

Blood vessels are concentrated within the implant surface concavities: a histologic study in rabbit tibia

Angiogenesis plays a key role in bone formation and maintenance. Bone formation has been reported to initiate in the concavities rather than the convexities in a hydroxyapatite substratum and the implant threads of dental implants. The aim of the present study was to evaluate the number of the blood vessels inside the concavities and around the convexities of the threads of implants in a rabbit tibia model. A total of 32 thread-shaped implants blasted with apatitic calcium phosphate (TCP/HA blend) (Resorbable Blast Texturing, RBT) (Maestro, BioHorizons(®), Birmingham, AL, USA) were inserted in 8 rabbits. Each rabbit received 4 implants, 2 in the right and 2 in left tibia. Implants were retrieved after 1, 2, 4, and 8 weeks and treated to obtain thin ground sections. Statistically significant differences were found in the number of vessels that had formed in the concavities rather than the convexities of the implants after 1 (p = 0.000), and 2 weeks (p = 0.000), whilst no significant differences after 4 (p = 0.546) and 8 weeks (p = 0.275) were detected. The present results supported the hypothesis that blood vessel formation was stimulated by the presence of the concavities, which may provide a suitable environment in which mechanical forces, concentrations and gradients of chemotactic molecules and blood clot retention may all drive vascular and bone cell migration.

Fibrin clot extension on zirconia surface for dental implants: a quantitative in vitro study

PURPOSE

The surface chemical and physical properties of materials used for implants have a major influence on blood clot organization. This study aims to evaluate the blood clot extension (bce) on zirconia and titanium. bce was measured in association to surface roughness (Ra) and static contact angle (θ).

MATERIALS AND METHODS

Forty disk-shaped samples of sandblasted yttria tetragonal zirconia polycrystal (sb-YTZP), machined titanium (m-Ti), and sandblasted, high-temperature, acid-etched titanium (p-Ti) were used in the present study. About 0.2 mL of human blood, immediately dropped onto the specimen's surface and left in contact for 5 minutes at room temperature, was used to measure the bce. Specimens were observed under confocal scanning laser and scanning electron microscopes.

RESULTS

The bce (mean × 10(7)  ± standard deviation [SD] × 10(6)  μm(2) ) was 2.97 ± 6.68 for m-Ti, 5.64 ± 6.83 for p-Ti, and 3.61 ± 7.67 for sb-YTZP. p-Ti samples showed a significantly higher bce. Ra (mean ± SD [μm]) was 0.56 ± 0.7 for m-Ti, 3.78 ± 0.8 for p-Ti, and 2.68 ± 0.6 for sb-YTZP. The difference was not significant between sb-YTZP and p-Ti. θ (mean ± SD) was 55.6 ± 5.6 for m-Ti, 48.7 ± 2.8 for sb-YTZP, and 38.0 ± 2.2 for p-Ti. The difference was not significant between m-Ti and sb-YTZP.

CONCLUSIONS

The sb-YTZP demonstrated a significantly lesser amount of bce compared with p-Ti specimens, notwithstanding that any significant difference was present between Ra and θ.

Immediate rehabilitation of the edentulous mandible using Ankylos SynCone telescopic copings and intraoral welding: a pilot study

The aim of this prospective study was to assess the suitability of immediate rehabilitation of the edentulous mandible using SynCone copings and the intraoral welding technique. Patients with an edentulous mandible were fitted with a removable restoration supported by an intraorally welded titanium bar. Copings were connected to their respective SynCone 5-degree abutments and then welded to a titanium bar using an intraoral welding unit. This framework was used to support the definitive restoration, which was delivered on the day of implant placement. Restoration success and survival, implant success, and biologic or technical complications were assessed immediately after surgery and at 6 and 12 months. Twenty-two patients were consecutively treated with 88 immediately loaded implants. No acrylic resin fractures or radiographically detectable alterations of the welded frameworks were present in the 22 restorations delivered. One implant (1.1%) failed 1 month after surgery; all remaining implants (98.9%) were clinically stable at the 12-month follow-up. Within its limitations, this pilot study demonstrated that it is possible to successfully rehabilitate the edentulous mandible on the day of surgery with a definitive restoration supported by an intraorally welded titanium framework and SynCone 5-degree abutments.

Immediate loading of zygomatic implants using the intraoral welding technique: a 12-month case series

The aim of this prospective study was to evaluate the concept of intraoral welding as a suitable technique for fabricating a fixed restoration for the edentulous maxilla the day of surgery using standard and zygomatic implants. Ten consecutive patients (four men, six women; mean age, 62.3 ± 11.6 years) were involved in this study, each of whom had an edentulous atrophic maxilla and received two standard and two zygomatic implants. All implants were loaded immediately with a fixed prosthesis supported by an intraorally welded titanium framework. Definitive abutments were connected to the implants, and a titanium bar was welded to them using an intraoral welding unit. This framework was used to support the definitive prosthesis, which was fitted the day of implant placement. Patients were checked for swelling, pain, and framework stability at 1, 3, 6, and 12 months. A total of 20 immediately loaded standard and 20 zygomatic implants were used. The cases included in this study achieved a 100% prosthetic success rate at the 12-month follow-up. No fracture or radiographically detectable alteration of the welded frameworks was noticed. It is possible to successfully rehabilitate the edentulous atrophic maxilla with a permanently fixed prosthesis supported by an intraorally welded titanium framework attached to standard and zygomatic implants the day of surgery.

Histologic and histomorphometric evaluation of an implant retrieved 8 years after insertion in a sinus augmented with anorganic bovine bone and anorganic bovine matrix associated with a cell-binding peptide: a case report

Few histologic and histomorphometric reports are present in the literature regarding the peri-implant bone response around implants inserted in sinuses grafted with different biomaterials. Anorganic bovine bone (ABB) and anorganic bovine matrix with the addition of an active cell-binding peptide (PepGen P-15) are xenogenic materials that have been reported to present biocompatibility and osteoconductivity. A monolateral sinus augmentation procedure with ABB (50%) and PepGen P-15 (50%) was performed in a 54-year-old man. Two titanium implants with a sandblasted and acid-etched surface were inserted after 6 months. After an additional 6 months, a fixed prosthetic restoration was fabricated. One implant fractured in the coronal portion after an 8-year loading period and was removed using a 5-mm trephine bur. Few particles of both grafting materials were present in the peri-implant bone. No graft material particles were found in contact with the implant surface, and bone was always interposed between the graft materials and surface. No inflammatory cell infiltrate, multinucleated giant cells, or foreign body reaction cells were found. The tissues around the implant were composed of 51.4% ± 4.8% bone, 6.2% ± 0.7% ABB particles, 2.4% ± 0.5% PepGen P-15, and 40.0% ± 7.1% marrow spaces. The bone-implant contact percentage was 78.4% ± 4.1%. A sinus augmentation procedure using ABB and PepGen P-15 produced bone formation with subsequent implant osseointegration, which was still present after 8 years of implant loading.

Effect of titanium surface topographies on human bone marrow stem cells differentiation in vitro

Coating characteristics of dental implants such as composition and topography regulate cell response during implant healing. The aim of this study was to assess how surface topography can affect osteogenic differentiation of mesenchymal stem cells (MSCs) by analyzing the expression levels of bone-related genes and MSCs marker. Thirty disk-shaped, commercially pure Grade 2 titanium samples (10 × 2 mm) with 3 different surface topographies (DENTSPLY-Friadent GmbH, Mannheim, Germany) were used in the present study: 10 Ti machined disks (control), 10 Ti sandblasted and acid-etched disks (DPS(®)) and 10 sandblasted and acid-etched disks at high temperature (Plus(®)). Samples were processed for real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. By comparing machined and Plus(®) disks, quantitative real-time RT-PCR showed a significant reduction of the bone-related genes osteocalcin (BGLAP) and osteoblast transcriptional factor (RUNX2). The comparison between DPS(®) and Plus(®) disks showed a slight induction of all the genes examined (RUNX2, ALPL, COL1A1, COL3A1, ENG, FOSL1, SPP1, and SP7); only the expression of BGLAP remained stable. The present study, demonstrated that implant surface topography affects osteoblast gene expression. Indeed, Plus(®) surface produces an effect on MSCs in the late differentiation stages.

Peri-implant collagen fibers around human cone Morse connection implants under polarized light: a report of three cases

Most of the histologic studies found in the literature on the peri-implant soft tissues have been done in animals and usually have been confined to mandibular implants fitted with healing or standard abutments. Few studies have investigated human peri-implant soft tissues. Moreover, the structure and dimensions of the peri-implant soft tissues in immediately loaded implants have not been investigated in depth. Human histologic data are valuable to validate animal models. This histologic and histomorphometric study evaluated the peri-implant soft tissues around three immediately loaded implants in humans. The implants were retrieved using a trephine and treated to obtain thin, ground sections. The sulcular epithelium was composed of approximately four to five layers of parakeratinized epithelial cells and had a length of approximately 1.2 to 1.3 mm. The junctional epithelium was composed of approximately three to four layers of epithelial cells and had a length of approximately 1.0 to 1.5 mm. Connective tissue attachment had a width of between 400 and 800 μm. Peri-implant collagen fibers, in the form of bundles (1- to 5-μm thick), began at the crestal bone and were oriented perpendicular to the abutment surface until 200 μm from the surface, where they became parallel running in several directions. Collagen fibers appeared to form a three-dimensional network around the abutment. No acute or chronic inflammatory cell infiltrate was present. Collagen fibers oriented in a perpendicular manner and in direct contact with the abutment surface were not observed in any of the specimens. This differentiated network of fibers may have clinical relevance as a mechanical protection of the underlying bone. These human histologic data are extremely valuable to validate and confirm those obtained from studies performed on animal models. Moreover, immediate loading of the implants did not compromise soft tissue integration.

Bone regeneration with algae-derived hydroxyapatite: a pilot histologic and histomorphometric study in rabbit tibia defects

PURPOSE

Algipore is a biologic hydroxyapatite derived from calcifying maritime algae. The present study evaluated this material histologically and histomorphometrically after implantation in rabbit tibia defects for 4 weeks.

MATERIALS AND METHODS

Six New Zealand rabbits were used in this study. In each rabbit tibia, two 7-mm defects were prepared. Control defects were left empty, and test defects were filled with Algipore. Twenty-four specimens (12 test and 12 control) were retrieved and processed for histology.

RESULTS

In control sites, newly formed trabecular bone with large marrow spaces was plentiful in the most peripheral areas of the defects but sparse elsewhere. In contrast, in test sites, a large quantity of newly formed bone around the biomaterial particles was detected in the central medullary portion of the defect. In addition, in several areas, the biomaterial particles were bridged by newly formed bone. The percentage of contact between newly formed bone and biomaterial particles was 71.2% ± 9.8%. Inside the central portion of the biomaterial particles, it was possible to see newly formed bone (about 35.3% ± 4.8% in each particle). In test sites, newly formed bone represented 31.1% ± 1.9% of the material, with residual biomaterial particles occupying 33.4% ± 2.8% and marrow spaces another 34.7% ± 4.3%. In the control sites, the values were 30.2% ± 2.2% for newly formed bone and 68.7% ± 4.1% for marrow spaces. A statistically significant difference was found in the percentage of marrow space between the two groups, but no significant difference was observed in the percentage of newly formed bone.

CONCLUSIONS

The present rabbit study confirmed the high osteoconductivity and resorbability of this biomaterial.

Sinus augmentation with phycogene hydroxyapatite: histological and histomorphometrical results after 6 months in humans. A case series

BACKGROUND

Phycogene hydroxyapatite is a biological hydroxyapatite derived from calcifying maritime algae, and is prepared by hydrothermal conversion by pyrolitical segmentation of the calcium carbonate of native algae into fluorhydroxyapatite. The aim of the present study was a histological and histomorphometrical evaluation, in humans, of specimens retrieved from sinuses augmented with phycogene hydroxyapatite, after a healing period of 6 months.

CASE SERIES

Ten healthy patients with noncontributory past medical history (four women and six men, all nonsmokers, mean age 59 years, range 54-65 years) were included in this study. All patients were candidates for augmentation in the posterior maxilla in order to receive fixed restorations. The maxillary sinuses were filled with phycogene hydroxyapatite (Algipore®, Dentsply Friadent, Mannheim, Germany). Twenty-three implants (XiVE®, Dentsply Friadent, Mannheim, Germany) were placed in the augmented sinuses after a healing period of about 6 months. The bone cores were retrieved and were processed for histology. Most particles of phycogene hydroxyapatite were surrounded by a mineralized tissue, and the biomaterial particles had served as an osteoconductive scaffold. Most particles were bridged by newly formed bone characterized by the presence of large osteocytic lacunae, also around the phycogene hydroxyapatite particles, which appeared to be partially resorbed and substituted by new bone. No inflammatory cells or foreign body reaction cells were present around the biomaterial. No gaps were present at the bone-particle interface, and the bone was always in close contact with the particles. Histomorphometry showed that the percentage of newly formed bone was 35.2 ± 3.6%, marrow spaces 35.6 ± 2.3%, and residual grafted material 37.1 ± 3.8%.

DISCUSSION

In conclusion, the present results support the literature findings that phycogene hydroxyapatite can be used, successfully, for sinus augmentation procedures.