Reliability and failure modes of internal conical dental implant connections

Retrieval of a fractured implant abutment using a modified cover screw removal instrument: A clinical report

Implant abutment fractures are an uncommon mechanical complication, and the removal of the abutment fragment and replacement with a new prosthesis is the best solution. However, successful retrieval of the fractured abutment fragment from the implant is challenging, and effective rescue kits are lacking. This clinical report describes the retrieval of a fractured implant abutment in a conical connection implant using a modified manufacturer-specific instrument.

Influence of toothbrushing methods on tightening torque with healing abutments of different lengths: An in vitro study

STATEMENT OF PROBLEM

Early tightening torque at the implant-healing abutment interface is a recognized concern in implant treatment. However, little is known regarding the effects of toothbrushing methods on the interface established between the implant and healing abutments of different heights.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of different toothbrushing methods on tightening torque for healing abutments of different heights.

MATERIAL AND METHODS

A total of 60 implants (Bilimplant; Proimtech) were embedded in epoxy resin blocks. The following 6 test groups were established: healing abutments with manual toothbrush group (Oral B Pro Expert All in one; Oral B) and 4 mm height (MTB-4, (which served as the control); 6 mm height (MTB-6, which served as the control); sonic toothbrush group (Philips Sonicare 3100 Series; Philips Oral Healthcare) and 4 mm height (S-4); 6 mm height (S-6); oscillating/rotating toothbrush group (Oral B Smart 6 6000N; Oral B) and 4 mm height (OR-4) and 6 mm height (OR-6). Each specimen was tightened to 15 Ncm and brushed. The digital torque meter (Cap Torque Tester Series TT01; Mark10) was used to calculate the reverse torque values.

RESULTS

The highest torque loss value in the average torque losses in the test groups was 1.3 (OR-6); the lowest was 0.3 (S-4). While a significant difference was found between groups S-4 and S-6 (P=.018), no statistically significant difference was found among the other groups (P>.05).

CONCLUSIONS

Torque loss was greater in the healing abutment with a height of 6 mm and with the oscillatory and rotational brushing method.

Clinical Performance of 170 Frictional Morse Taper Implants: 2 Years Follow-Up

This study evaluated the clinical survival rates of 170 Morse taper implants through clinical and mechanical parameters in different therapeutic approaches such as single crowns, fixed partial prostheses, and fixed full-arch prostheses. Patients referred to the Center on Education and Research on Dental Implants from May 2017 to July 2018 with the indication for dental implant therapy, aged >18 years, without periodontal disease, recent evidence of inflammatory activity or other oral disorders, current pregnancy, uncontrolled diabetes mellitus or heavy smoking habit were included in this study. After 12 weeks of healing since the implants were placed in the mandible and after 16 weeks following implants placed in the maxilla, patients returned to the Center for prosthetic rehabilitation. After implant therapy, all patients underwent periodical, clinical, and prosthetic examinations every 6 months. Prosthetic restorations involved 109 fixed reconstructions in function. Few prosthetic complications were reported (6.55%). Twenty implants were rehabilitated with cemented prostheses; from those, 1 crown suffered a loss in retention/decementation. Of the 148 implants rehabilitated with screwed-retained prostheses, 6.76% suffered prosthetic screw loosening. The cumulative implant survival rate was 98.2%. When peri-implant tissue health was evaluated, the keratinized mucosa band appeared related to peri-implant tissue stability. Thus, Morse taper implants represented a successful procedure for implant rehabilitation, with a high cumulative implant survival rate, low prevalence of biological and prosthetic complications, and good stability of peri-implant tissues over the assessed period.

SEM Analysis and Micro-CT Evaluation of Four Dental Implants after Three Different Mechanical Requests-In Vitro Study

STATEMENT OF PROBLEM

Implant-supported rehabilitations are an increasingly frequent practice to replace lost teeth. Before clinical application, all implant components should demonstrate suitable durability in laboratory studies, through fatigue tests.

OBJECTIVE

The purpose of this in vitro study was to evaluate the integrity and wear of implant components using SEM, and to assess the axial displacement of the implant-abutment assembly by Micro-CT, in different implant connections, after three distinct mechanical requests.

MATERIALS AND METHODS

Four KLOCKNER implants (external connection SK2 and KL; and internal connection VEGA and ESSENTIAL) were submitted to three different mechanical requests: single tightening, multiple tightening, and multiple tightening and cyclic loading (500 N × 100 cycles). A total of 16 samples were evaluated by SEM, by the X-ray Bragg-Brentano method to obtain residual stresses, and scratch tests were realized for each surface and Micro-CT (4 control samples; 4 single tightening; 4 multiple tightening; 4 multiple tightening and cyclic loading). All dental implants were fabricated with commercially pure titanium (grade 3 titanium). Surface topography and axial displacement of abutment into the implant, from each group, were evaluated by SEM and Micro-CT.

RESULTS

In the manufacturing state, implants and abutments revealed minor structural changes and minimal damage from the machining process. The application of the tightening torque and loading was decisive in the appearance and increase in contact marks on the faces of the hexagon of the abutment and the implant. Vega has the maximum compressive residual stress and, as a consequence, higher scratch force. The abutment-implant distances in SK2 and KL samples did not show statistically significant differences, for any of the mechanical demands analyzed. In contrast, statistically significant differences were observed in abutment-implant distance in the internal connection implants Vega and Essential.

CONCLUSIONS

The application of mechanical compression loads caused deformation and contact marks in all models tested. Only internal connection implants revealed an axial displacement of the abutment into the implant, but at a general level, a clear intrusion of the abutment into the implant could only be confirmed in the Essential model, which obtained its maximal axial displacement with cyclic loading.

Biomechanical efficiency of different implant-abutment connection: a systematic review of studies using photoelastic stress analysis

PURPOSE

The present review aimed to comparatively evaluate the biomechanical efficiency of different implant-abutment connections studied by photoelastic stress analysis.

MATERIALS AND METHODS

A comprehensive online literature search was conducted on Medline (Pubmed), Web of Science, and Google Scholar from 2000(Jan) to 2023(Jan). Keywords used initially to carry out the search included implant-abutment connection & photoelastic stress analysis, and stress distribution in different implant-abutment connections. 34 photoelastic stress analysis studies were screened and 30 studies were excluded after the screening of the title, abstract and full article. Finally, 4 studies were included for complete review.

RESULT

The result of this systematic review showed that the internal connection was more efficient then the external connection as there was less marginal bone loss and favorable distribution of stress in internal connection.

CONCLUSION

Crestal bone loss is more in external connection when compared to internal connection. In Internal connection, there is more intimate contact between the abutment's outer surface and implant which renders a more stable interface, which favoring uniform stress distribution and protects the retention screw.

Abutment mechanical complications of a Morse taper connection implant system: A 1- to 9-year retrospective study

BACKGROUND

The fracture of a Morse tapered abutment connection in an osseointegrated implant is one of the most serious mechanical complications, and it is extremely hard to deal with this complication in clinical practice.

PURPOSE

The aim of this study was to explore the cumulative mechanical complications focus on abutment of a platform switching Morse taper connection implant system after loading, and to perform a retrospective, approximately 1- to 9-year follow-up study to identify the predisposing factors.

MATERIALS AND METHODS

A total of 495 patients with 945 fitted implants were enrolled in this study with a follow-up from January 2012 to January 2020. The data of mechanical complications of the abutment, including abutment fracture (AF) and abutment screw loosening (ASL), and possible causative factors were extracted and evaluated statistically.

RESULTS

A total of 25 out of 945 (2.65%) cumulative abutment mechanical complications occurred. AF was the most common complication (n = 13, 1.38%), followed by ASL (n = 12, 1.27%). For AF, gender, type of prosthesis, abutment design, and implant diameter were identified as the causative factors. AF was mostly observed in the single crown of males in molar areas, while ASL was more likely to occur on an angled abutment than on a non-angled abutment. Moreover, the abutment with the positioning index (/X) had a higher incidence of fracture than the abutment without the positioning index (C/).

CONCLUSIONS

This study shows that the Morse taper connection is a safe abutment connection. AF occurs more frequently within single crowns in molar area of males, especially with the positioning index (/X), while ASL is more likely to occur in an angled abutment.

Probability of survival and stress distribution of narrow diameter implants with different implant-abutment taper angles

This study evaluated the probability of survival, failure mode, and stress distribution of narrow diameter implants (NDIs) with internal implant-abutment conical connection comprised of different taper angles and thread designs. Sixty-three NDIs (Ø 3.5 × 8.5 mm) were divided according to the taper angle (TA), internal diameter (ID), and trapezoidal thread design (TD) (n = 21/group), as follows: (a) 11.5°U (11.5° TA; ID: 2.5 mm; TD: dual threaded); (b) 11.5°S (11.5° TA; ID: 2.5 mm; TD: single threaded); (c) 16°S (16° TA; ID: 2.72 mm; TD: single threaded). They were subjected to step-stress accelerated life testing. The reliability and use-level probability Weibull curves were calculated at 50, 100, and 150 N for a mission of 100,000 cycles and the failure mode was analyzed using a scanning electron microscope. For finite element analysis the von-Mises stress (σ_vM ) was calculated for the abutment and implant. All groups showed high reliability (above 84%) and failures occurred predominantly in the abutment. In the FEA, 11.5°U showed higher σ_vM for the implant. All NDIs showed high reliability at clinically challenging loads. The system with greater taper angle showed lower σ_Vm in the implant, and dual threaded implants showed a higher stress concentration in the implant and cortical bone.

Dynamic and static load performance of dental biomaterial systems with conical implant-abutment connections

BACKGROUND

The stability of the implant-abutment interface is an important factor that influences load distribution on the marginal bone.

OBJECTIVE

In this study, three dental implants with the same connection were subjected to different dynamic loading cycles. The fracture strengths and the horizontal compatibility of implants were assessed.

METHODS

Eighty four implant specimens were embedded in a polyacetal cylinder as simulated bone loss of 3 mm from the implant platform. Three of the implants were used to determine the endurance limit. The other specimens were subdivided into four subgroups (n = 6): three for dynamic + static loading, and one for static loading (control group). The tests were performed by applying a compression load. The dynamic loading experiments included three different cycles with endurance upper limit loads at a frequency of 10 Hz.

RESULTS

The differences between the fracture strength values of the implant brands were found to be statistically significant. However, there were no meaningful differences between the fracture strength values of implants of the same brand. The specimens of the DTI implant system had the lowest strength (647.9 ± 41.5 N) and the SEM analysis indicated that the Implantium implant system had the shortest horizontal gaps.

CONCLUSIONS

There was a negative correlation between the fracture strengths and size of the microgaps. The importance of these in vitro results needs to be validated by clinical trials because the loads in the mouth can be applied from various angles.

Prosthetic Complications Affecting Single-Tooth Morse-Taper Connection Implants

PURPOSE

To evaluate the long-term cumulative implant survival rate (CISR%) and cumulative implant-crown success rate (CICSR%) of single-tooth Morse-taper connection implants, with particular attention to documenting the incidence of prosthetic complications.

METHODS

The customized records of all patients who had been treated with single-tooth Morse-taper connection implants in 2 dental centers during the period between January 2002 and December 2012 were revisited. These records included patient-related (gender, age at surgery, smoking, bruxism), implant-related (date of insertion, site/location, and length/diameter of the implant, previous/concomitant bone regeneration), and restoration-related (date of delivery of the provisional and final crown) information. In addition, these records contained information about any implant failure and biologic and/or prosthetic complication that occurred during the follow-up period as well as the radiographic documentation. The follow-up period comprised between 5 and 15 years. The main outcomes were CISR% and CICSR%, with the latter being defined as the condition in which no complication had affected the surviving implant-supported crown during the entire follow-up. Life-table analysis was used for the analysis of CISR% and CICSR%. Peri-implant marginal bone resorption (PIMBR) at 5, 10, and 15 years was a secondary outcome of this study.

RESULTS

In total, 578 patients who had received 612 implants were included in this study. The overall CISR% at 15 years was 94.8% (94.2% maxilla, 95.3% mandible). Among the surviving crowns, the overall CICSR% at 15 years was 94.5% (93.1% and 94.9% for anterior and posterior crowns, respectively), and the incidence of prosthetic complications was low (1.5%). The PIMBL amounted to 0.38 ± 0.29 mm, 0.49 ± 0.35 mm, and 0.94 ± 0.58 mm at the 5-, 10-, and 15-year follow-ups, respectively.

CONCLUSION

Morse-taper connection implants represent a reliable treatment procedure for the restoration of single-tooth gaps in the long term, with high CISR% (94.8%) at 15 years, a very low incidence of complications, and a high CICSR% (94.5%).

Advantages of Autologous Platelet-Rich Fibrin Membrane on Gingival Crevicular Fluid Growth Factor Levels and Periodontal Healing: A Randomized Split-Mouth Clinical Study

BACKGROUND

This study evaluates contributions of platelet-rich fibrin (PRF) combined with conventional flap surgery on growth factor levels in gingival crevicular fluid (GCF) and periodontal healing.

METHODS

Twenty-six patients (52 sites) with chronic periodontitis were treated either with autologous PRF with open flap debridement (OFD+PRF) or OFD alone. Growth factor levels in GCF at baseline and 2, 4, and 6 weeks after surgery were analyzed, and clinical parameters such as probing depth (PD), relative clinical attachment level (rCAL), and gingival margin level (GML) at baseline and 9 months after surgery were measured.

RESULTS

Mean PD reduction and rCAL gain were significantly greater in OFD+PRF sites than in OFD sites. Mean GML change was -0.38 + 0.10 mm in OFD sites and 0.11 + 0.08 mm in the test group; difference between the two groups was statistically significant (P <0.05). Both groups demonstrated increased expression levels of fibroblast growth factor-2, transforming growth factor-β1, and platelet-derived growth factor-BB at 2 weeks compared with baseline, followed by reductions at 4 and 6 weeks. The OFD+PRF group showed significantly higher growth factor levels compared with the OFD group at 2 and 4 weeks.

CONCLUSION

PRF membrane combined with OFD provides significantly higher GCF concentrations of angiogenic biomarkers for ≈2 to 4 weeks and better periodontal healing in terms of conventional flap sites.

Influence of the connection design and titanium grades of the implant complex on resistance under static loading

PURPOSE

The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections.

MATERIALS AND METHODS

Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student's t-test with the level of significance at P=.05.

RESULTS

The group IT4_S had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups IT4_N and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation.

CONCLUSION

A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

Early loading of splinted implants in the posterior mandible: a prospective multicentre case series

AIM

To evaluate the 12-months clinical and radiological outcomes with the OsseoSpeed(™) TX implant using an early loading protocol in patients with missing teeth in the posterior mandible.

MATERIAL AND METHODS

Forty-five subjects, with Kennedy class I or II edentulism in the mandible, were enrolled at three centres in China. Two or three implants were placed in one edentulous region using a one-stage procedure. Patients received a screw-retained splinted fixed permanent restoration in one edentulous region 6-8 weeks after surgery. Follow-up took place at 6 and 12 months after loading. Marginal bone level alteration, implant survival and clinical findings were assessed using descriptive statistics. The data were analysed on a patient level, implying that the mean overall implants by patient was used as the statistical unit. The data from the three centres were pooled in the statistical analyses.

RESULTS

A total of 107 implants were inserted in 45 patients. Twelve months after loading, the implant survival rate was 100%, with a mean (± std) marginal bone gain of 0.08 ± 0.411 mm and healthy soft tissue status.

CONCLUSIONS

Early loading of splinted OsseoSpeed(™) TX implants was an effective and safe treatment for partial edentulism of the posterior mandible. CLINICAL TRIAL REGISTRATION NUMBER ON CLINICALTRIALS.GOV: NCT01346683.

Long-term cumulative survival and mechanical complications of single-tooth Ankylos Implants: focus on the abutment neck fractures

PURPOSE

To evaluate the cumulative survival rate (CSR) and mechanical complications of single-tooth Ankylos® implants.

MATERIALS AND METHODS

This was a retrospective clinical study that analyzed 450 single Ankylos® implants installed in 275 patients between December 2005 and December 2012. The main outcomes were survival results CSR and implant failure) and mechanical complications (screw loosening, fracture, and cumulative fracture rate [CFR]). The main outcomes were analyzed according to age, sex, implant length or diameter, bone graft, arch, and position.

RESULTS

The 8-year CSR was 96.9%. Thirteen (2.9%) implants failed because of early osseointegration failure in 3, marginal bone loss in 6, and abutment fracture in 4. Screw loosening occurred in 10 implants (2.2%), and 10 abutment fractures occurred. All abutment fractures were located in the neck, and concurrent screw fractures were observed. The CSR and rate of screw loosening did not differ significantly according to factors. The CFR was higher in middle-aged patients (5.3% vs 0.0% in younger and older patients); for teeth in a molar position (5.8% vs 0.0% for premolar or 1.1% for anterior position); and for larger-diameter implants (4.5% for 4.5 mm and 6.7% for 5.5 mm diameter vs 0.5% for 3.5 mm diameter) (all P<.05).

CONCLUSION

The Ankylos® implant is suitable for single-tooth restoration in Koreans. However, relatively frequent abutment fractures (2.2%) were observed and some fractures resulted in implant failures. Middle-aged patients, the molar position, and a large implant diameter were associated with a high incidence of abutment fracture.

Reliability and failure modes of narrow implant systems

OBJECTIVES

Narrow implants are indicated in areas of limited bone width or when grafting is nonviable. However, the reduction of implant diameter may compromise their performance. This study evaluated the reliability of several narrow implant systems under fatigue, after restored with single-unit crowns.

MATERIALS AND METHODS

Narrow implant systems were divided (n = 18 each), as follows: Astra (ASC); BioHorizons (BSC); Straumann Roxolid (SNC), Intra-Lock (IMC), and Intra-Lock one-piece abutment (ILO). Maxillary central incisor crowns were cemented and subjected to step-stress accelerated life testing in water. Use level probability Weibull curves and reliability for a mission of 100,000 cycles at 130- and 180-N loads (90 % two-sided confidence intervals) were calculated. Scanning electron microscopy was used for fractography.

RESULTS

Reliability for 100,000 cycles at 130 N was ∼99 % in group ASC, ∼99 % in BSC, ∼96 % in SNC, ∼99 % in IMC, and ∼100 % in ILO. At 180 N, reliability of ∼34 % resulted for the ASC group, ∼91 % for BSC, ∼53 % for SNC, ∼70 % for IMC, and ∼99 % for ILO. Abutment screw fracture was the main failure mode for all groups.

CONCLUSIONS

Reliability was not different between systems for 100,000 cycles at the 130-N load. A significant decrease was observed at the 180-N load for ASC, SNC, and IMC, whereas it was maintained for BSC and ILO.

CLINICAL RELEVANCE

The investigated narrow implants presented mechanical performance under fatigue that suggests their safe use as single crowns in the anterior region.

Implant-abutment connection designs for anterior crowns: reliability and failure modes

OBJECTIVES

To investigate the effect of implant-abutment connection types on reliability and failure modes of anterior single-unit crowns.

METHODS

Fifty-four implants were divided in 3 groups (n = 18 each): external hexagon (EH), internal hexagon (IH), and Morse taper (MT) connection. Abutments were screwed to the implants, and maxillary central incisor metal crowns were cemented and subjected to step-stress accelerated life testing.

RESULTS

The beta values derived from use-level probability Weibull calculations for groups IH (2.52), EH (1.67), and MT (0.88) indicated that fatigue influenced the failure only of IH and EH groups. The reliability for a mission of 100,000 cycles at 175 N was 0.99 (0.98-1.00), 0.84 (0.62-0.94) and 0.97 (0.87-0.99) for the EH, IH, and MT, respectively. The characteristic strength was not significantly different between EH (290 N) and IH (251 N) but significantly higher for MT (357 N). For IH and EH groups, failure involved screw fracture, and the MT implants primary failure mode was abutment fracture.

CONCLUSIONS

Reliability was higher for the EH and MT relative to IH groups, whereas the characteristic strength was significantly higher for implants with MT connection.

Is the internal connection more efficient than external connection in mechanical, biological, and esthetical point of views? A systematic review

PURPOSE

This systematic review aimed to evaluate if the internal connection is more efficient than the external connection and its associated influencing factors.

METHODS

A specific question was formulated according to the Population, Intervention, Control, and Outcome (PICO): Is internal connection more efficient than external connection in mechanical, biological, and esthetical point of views? An electronic search of the MEDLINE and the Web of Knowledge databases was performed for relevant studies published in English up to November 2013 by two independent reviewers. The keywords used in the search included a combination of "dental implant" and "internal connection" or "Morse connection" or "external connection." Selected studies were randomized clinical trials, prospective or retrospective studies, and in vitro studies with a clear aim of investigating the internal and/or external implant connection use.

RESULTS

From an initial screening yield of 674 articles, 64 potentially relevant articles were selected after an evaluation of their titles and abstracts. Full texts of these articles were obtained with 29 articles fulfilling the inclusion criteria. Morse taper connection has the best sealing ability. Concerning crestal bone loss, internal connections presented better results than external connections. The limitation of the present study was the absence of randomized clinical trials that investigated if the internal connection was more efficient than the external connection.

CONCLUSIONS

The external and internal connections have different mechanical, biological, and esthetical characteristics. Besides all systems that show proper success rates and effectiveness, crestal bone level maintenance is more important around internal connections than external connections. The Morse taper connection seems to be more efficient concerning biological aspects, allowing lower bacterial leakage and bone loss in single implants, including aesthetic regions. Additionally, this connection type can be successfully indicated for fixed partial prostheses and overdenture planning, since it exhibits high mechanical stability.

Effects of different abutment material and surgical insertion torque on the marginal adaptation of an internal conical interface: an in vitro study

PURPOSE

To evaluate the marginal adaptation at implant-abutment connection of an implant featuring a conical (45° taper) internal hexagonal abutment with a connection depth of 2.5mm, comparing the performance of two identical abutments of different material (titanium grade-4 and Co-Cr-alloy).

METHODS

Twenty implants (3.75 mm×15 mm) were connected to non-matching abutments (5.5 mm×10 mm) of two different materials (titanium grade-4: n=10; Co-Cr-alloy: n=10). The specimens were separately embedded in epoxylite resin, inside copper cylinders, and submerged without covering the most coronal portion (5 mm) of the fixture. Five specimens per group were stressed simulating a surgical 100 Ncm insertion torque, while the others had no torque simulation. All specimens were subjected to a non-axial static load (100 N) in a universal testing machine, under an angle of 30° with respect to the implant axis. Once 100 N load was reached, low shrinkage self-curing resin was injected inside the cylinders, and load was maintained until complete resin polymerization. Specimens were cut and analyzed with optical and scanning-electron-microscope (SEM) to evaluate the marginal adaptation at the implant-abutment connection. Statistical analysis was performed using one-way ANOVA (p=0.02).

RESULTS

None of the 20 samples failed. The implant-abutment connection was able to guarantee a good optical seal; SEM analysis confirmed the absence of microgaps.

CONCLUSIONS

Within the limits of this study (small sample size, limited time) the marginal adaptation of the implant-abutment connection was not affected by the abutment material nor by the application of surgical insertion torque.

Fixed restorations supported by Morse-taper connection implants: a retrospective clinical study with 10-20 years of follow-up

OBJECTIVES

Rehabilitation with implant-supported fixed prostheses is a predictable modality to restore lost function and esthetics; however, fixed restorations are subject to biological and prosthetic complications, which may represent a problem in the long-term. The aim of this study was to evaluate the long-term survival and complication rates of fixed restorations supported by Morse-taper connection implants.

MATERIALS AND METHODS

Between January 1992 and December 2002, 49 patients (age range 22-70 years), were included in this study. The restorations involved 58 fixed reconstructions (15 single crowns [SCS], 29 partial prostheses, 14 full-arches), supported by 178 Morse-taper connection implants with a follow-up ranging from 10 to 20 years. Outcomes such as implant survival, marginal bone loss, frequency of biological and prosthetic complications as well as "complication-free" survival of restorations were investigated.

RESULTS

The 20-year overall cumulative implant survival was 97.2%. A few biological (3.4%) and prosthetic (10.3%) complications were reported. The "complication-free" survival rate of restorations was 85.5%. No statistically significant differences were observed among patients' gender, age, smoking or parafunctional habits, prosthesis site and type.

CONCLUSIONS

Satisfactory "complication-free" survival rates can be achieved after 20 years for fixed restorations supported by Morse-taper connection implants, with minimal marginal bone loss and complications.

Survival and complication rates of fixed restorations supported by locking-taper implants: a prospective study with 1 to 10 years of follow-up

PURPOSE

The aim of this 10-year follow-up study was to evaluate the implant survival and complication rates of fixed restorations supported by locking-taper implants.

MATERIALS AND METHODS

Over a 10-year period (January 2002 to December 2011) all patients referred to a single private practice for treatment with fixed restorations (single crowns, SCs; fixed partial prostheses, FPPs; fixed full arches, FFAs) supported by dental implants were considered for inclusion in the study. At each annual follow-up session, clinical, radiographic, and prosthetic parameters were assessed. The surviving implant-supported restorations were defined as "complication free" in the absence of any biological or prosthetic (mechanical or technical) complication. The cumulative implant survival and the "complication-free" survival of fixed implant-supported restorations were identified using the Kaplan-Meier method. The Log-rank test was used to identify correlations between the study variables.

RESULTS

In total, 1494 locking-taper implants (727 maxilla, 767 mandible) were placed in 642 patients (356 males, 286 females). Nineteen implants (12 maxilla, 7 mandible) failed. Implant failures were attributed to lack of osseointegration (14 implants), peri-implantitis (4 implants), and mechanical overloading (1 implant). An overall 10-year cumulative implant survival rate of 98.7% (98.3% maxilla, 99.1% mandible) was found. The implant survival rates did not significantly differ with respect to implant location, position, bone type, implant length and diameter, and type of restorations. Among the surviving implant-supported restorations (478 SC, 242 FPP, 19 FFA), a few biological (11/739: 1.4%) and prosthetic (27/739: 3.6%) complications were reported. The incidence of mechanical complications was low (3/739: 0.4%), with three loosened abutments in three SCs (3/478: 0.6%), and no abutment fractures; technical complications were more frequent (24/739: 3.2%), with an incidence of decementation of 2.0% (SC 2.0%, FPP 1.6%, FFA 5.2%) and ceramic/veneer chipping/fracture of 1.2% (SC 0.0%, FPP 2.8%, FFA 10.5%). A 10-year cumulative "complication-free" survival of restorations of 88.6% (SC 91.7%, FPP 83.1%, FFA 73.8%) was reported. The complication rates differ significantly with respect to the type of restoration (p < 0.05).

CONCLUSIONS

Fixed restorations on locking-taper implants seem to be a successful procedure for the rehabilitation of partially and completely edentulous arches.

Zirconia-Based Screw-Retained Prostheses Supported by Implants: A Retrospective Study on Technical Complications and Failures

BACKGROUND

Little information is yet available on zirconia-based prostheses supported by implants.

PURPOSE

To evaluate technical problems and failures of implant-supported zirconia-based prostheses with exclusive screw-retention.

MATERIAL AND METHODS

Consecutive patients received screw-retained zirconia-based prostheses supported by implants and were followed over a time period of 5 years. The implant placement and prosthetic rehabilitation were performed in one clinical setting, and all patients participated in the maintenance program. The treatment comprised single crowns (SCs) and fixed dental prostheses (FDPs) of three to 12 units. Screw-retention of the CAD/CAM-fabricated SCs and FDPs was performed with direct connection at the implant level. The primary outcome was the complete failure of zirconia-based prostheses; outcome measures were fracture of the framework or extensive chipping resulting in the need for refabrication. A life table analysis was performed, the cumulative survival rate (CSR) calculated, and a Kaplan-Meier curve drawn.

RESULTS

Two hundred and ninety-four implants supported 156 zirconia-based prostheses in 95 patients (52 men, 43 women, average age 59.1 ± 11.7 years). Sixty-five SCs and 91 FDPs were identified, comprising a total of 441 units. Fractures of the zirconia framework and extensive chipping resulted in refabrication of nine prostheses. Nearly all the prostheses (94.2%) remained in situ during the observation period. The 5-year CSR was 90.5%, and 41 prostheses (14 SCs, 27 FDPs) comprising 113 units survived for an observation time of more than 5 years. Six SCs exhibited screw loosening, and polishing of minor chipping was required for five prostheses.

CONCLUSIONS

This study shows that zirconia-based implant-supported fixed prostheses exhibit satisfactory treatment outcomes and that screw-retention directly at the implant level is feasible.