Are healing abutments being reused in periodontics residency programs in the United States? A survey-based study.

PURPOSE: Recent studies indicate that reusing healing abutments (HAs) may pose a risk of biomaterial cross contamination among patients. The intent is to investigate whether postgraduate periodontics residency programs in the United States are reusing dental implant HAs and determine if there is a standardization in the decontamination and sterilization protocol of used HAs. METHODS: An electronic survey consisting of-seven multiple choice and/or short answer questions pertaining to the re-use of HAs among postdoctoral periodontics programs was sent to program directors of 57 accredited dental schools in the United States via an online survey system (Qualtrics). Three follow-up remainder emails were sent to programs that did not respond after over a 6-month period. Data were analyzed using descriptive statistics. RESULTS: Of the 57 postdoctoral periodontics program directors contacted, only 14 responded with three programs (3/14, 21%) reported reusing HAs. Approximately, 46% stated their residents place dental implants in two stages, while ∼54% stated they used a one-stage protocol indicating varied time exposure of HA to the oral cavity. Even in a two-stage protocol, the extended time HA remained in situ varied from 4 weeks to 6 months. Each program reusing HAs employed a distinct decontamination approach highlighting a notable lack of standardization in practices. CONCLUSION: The findings from our study suggest that a minority of residency programs in the United States are reusing HAs. However, the limited number of responses leaves uncertainty regarding whether our findings underestimate the prevalence of this practice and accurately reflect the reality. Among those re-using HAs, there seems to be a lack of standardization in their decontamination, potentially leading to cross-contamination of residual biomaterial among patients.

Multi-objective optimization of custom implant abutment design for enhanced bone remodeling in single-crown implants using 3D finite element analysis.

The optimal configuration of a customized implant abutment is crucial for bone remodeling and is influenced by various design parameters. This study introduces an optimization process for designing two-piece zirconia dental implant abutments. The aim is to enhance bone remodeling, increase bone density in the peri-implant region, and reduce the risk of late implant failure. A 12-month bone remodeling algorithm subroutine in finite element analysis to optimize three parameters: implant placement depth, abutment taper degree, and gingival height of the titanium base abutment. The response surface analysis shows that implant placement depth and gingival height significantly impact bone density and uniformity. The taper degree has a smaller effect on bone remodeling. The optimization identified optimal values of 1.5 mm for depth, 35° for taper, and 0.5 mm for gingival height. The optimum model significantly increased cortical bone density from 1.2 to 1.937 g/cm3 in 2 months, while the original model reached 1.91 g/cm3 in 11 months. The standard deviation of density showed more uniform bone apposition, with the optimum model showing values 2 to 6 times lower than the original over 12 months. The cancellous bone showed a similar trend. In conclusion, the depth and taper have a significant effect on bone remodeling. This optimized model significantly improves bone density uniformity.

Three-Dimensional Bowing Measurement of Distal Femur at Actual Size and Clinical Implications of Total Knee Arthroplasty.

Background and Objectives: To assess femoral shaft bowing (FSB) in coronal and sagittal planes and introduce the clinical implications of total knee arthroplasty (TKA) by analyzing a three-dimensional (3D) model with virtual implantation of the femoral component. Materials and Methods: Sixty-eight patients (average age: 69.1 years) underwent 3D model reconstruction of medullary canals using computed tomography (CT) data imported into Mimics® software (version 21.0). A mechanical axis (MA) line was drawn from the midportion of the femoral head to the center of the intercondylar notch. Proximal/distal straight centerlines (length, 60 mm; diameter, 1 mm) were placed in the medullary canal's center. Acute angles between these centerlines were measured to assess lateral and anterior bowing. The acute angle between the distal centerline and MA line was measured for distal coronal and sagittal alignment in both anteroposterior (AP) and lateral views. The diameter of curve (DOC) along the posterior border of the medulla was measured. Results: The mean lateral bowing in the AP view was 3.71°, and the mean anterior bowing in the lateral view was 11.82°. The average DOC of the medullary canal was 1501.68 mm. The average distal coronal alignment of all femurs was 6.40°, while the distal sagittal alignment was 2.66°. Overall, 22 femurs had coronal bowing, 42 had sagittal bowing, and 15 had both. Conclusions: In Asian populations, FSB can occur in coronal, sagittal, or both planes. Increased anterolateral FSB may lead to cortical abutment in the sagittal plane, despite limited space in the coronal plane. During TKA, distal coronal alignment guides the distal femoral valgus cut angle, whereas distal sagittal alignment aids in predicting femoral component positioning to avoid anterior notching. However, osteotomies along the anterior cortical bone intended to prevent notching may result in outliers due to differences between the distal sagittal alignment and the distal anterior cortical axis.

A Multivariate Logistic Regression Analysis of Risk Factors for Peri-implant Bone Loss.

OBJECTIVE: To evaluate multiple risk factors of peri-implant bone loss. MATERIALS AND METHODS: A case-control study was conducted on patients who had received dental implants treatment from January 2018 to December 2021. Implants with bone loss were included in the case group, and implants with no bone loss were included in the control group. Risk factors including history of periodontitis, abutment connection type, implant surface, diameter, location, three-dimensional position, opposing dentition, adjacent teeth, prosthetic type, retention type and custom abutment were evaluated. A multivariate logistic regression model was used to evaluate these risk factors, providing corresponding odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: A total of 776 implants in 479 patients were included in the analysis. The number of implants in the case group and the control group were 84 and 692, respectively. Cement-retained prostheses (OR=2.439, 95%CI=1.241-4.795) and nonplatform switch design (OR=2.055, 95%CI=1.167-3.619) were identified as weak risk factors. Horizontal deviation (OR=4.177, 95%CI=2.265-7.703) was a moderate risk factor. Vertical deviation (OR=10.107, 95%CI=5.280-19.347) and implants located in the mandibular molar region (OR=10.427, 95%CI=1.176-92.461) were considered high risk factors. CONCLUSION: Implants in the molar region, cement retained, non-platform switch design, and poor three-dimensional implant positioning are identified as significant risk factors for peri-implant bone loss.

Retrospective, Multi-center, Cohort Study Evaluating Clinical, Technical, Biological, and Esthetic Outcomes of Implant Supported Zirconia Single Crowns Cemented on Titanium-base Abutments: 7-year Mean Follow-up.

PURPOSE: To retrospectively evaluate the long-term clinical, technical, biological, and esthetic outcomes of implant supported single zirconia crowns (ISCs) intraorally cemented to Ti-base hybrid-abutments up to 16 years after placement. MATERIALS AND METHODS: A total of 63 ISCs (Xive S, Camlog Screw Line, Replace Select TC NP, Branemark MK II, and 3i Osseotite) were evaluated in 36 patients at two different centers. Original Ti-bases were selected and zirconia meso structures and zirconia crowns were designed using CAD/CAM software and then milled from partially stabilized zirconia blocks. After the meso structures were cemented extraorally onto the Ti-bases, the ceramic crowns were intraorally luted to the hybrid abutments. The Ti-base ISC restorations were followed up for up to 16 years, and their clinical, biological, and esthetic outcomes were recorded at distinct time points (T1; T2) at three-year intervals. RESULTS: 36 patients (18 men, 18 women) received 32 ISCs in the anterior region and 31 in the posterior region of the maxilla and mandible. The mean follow-up of the Ti-base ISCs was 6.93 ± 2.60 years. The mean follow-up of the implants amounted to 8.11 ± 3.26 years. No implants were lost during follow-up, resulting in a cumulative implant survival rate of 100%. Abutment screw loosening was observed in two ISCs after one year in service. The overall cumulative restorative survival rate of the Ti-base restorations reached thus 96.83%. At T2 follow-up 24% of the ISCs exhibited an increase in PD despite maintaining clinically healthy peri-implant tissue. An 11% increase in BOP and a 3.17% decrease in PI were recorded. Despite spectrophotometrically measured ΔE values indicating visible discoloration of some restorations and their peri-implant soft tissue, a low incidence of esthetic complications was observed with an average PES/WES score of ≥ 12. No correlation was found between PES (R = -0.25; p = 0.27) and WES (R = -0.18; p = 0.43) scores and digital shade determination. CONCLUSIONS: The results of the present retrospective, multicenter, cohort study indicate satisfactory clinical outcomes for intraorally cemented single zirconia crowns (ISCs) supported by Ti-base hybrid abutments. An overall esthetic superiority of Ti-base ISCs could not be confirmed.

Longitudinal Observation of Micromotion upon Loading of Implant-Abutment Connection.

While technological advances have made implants a good treatment option with a good long-term prognosis, peri-implantitis, which results in alveolar bone resorption around implants, has been observed in some cases. Micromotion at the implant abutment connection can cause peri-implantitis. However, the temporal progression of micromotion upon loading remains unclear. Therefore, we aimed to longitudinally measure micromotion upon loading application on an implant. Implants with Morse-tapered connections were prepared. Custom titanium abutments were fabricated and tightened onto implant bodies at 35 N. A 100 N vertical load was applied for 200,000 cycles. Micromotion was measured when the load was applied, as was the total implant length and removal torque before and after loading. The micromotion was measured from the position data of the jig of the testing machine during loading. The average removal torque was 30.67 N after 10 min of tightening and 27.95 N after loading, indicating a decrease due to loading. The implant length reduced by 3.6 µm under the load. The average micromotion was 0.018 mm at 2 cycles, 0.016 mm at 100,000 cycles, and 0.0157 mm at 200,000 cycles, indicating implant length reduction under the load but not reaching 0. The micromotion between the implant and abutment under a cyclic load decreased over time but did not completely cease. These results highlight the relationship between micromotion and loading, underscoring the importance of careful monitoring and management to mitigate potential complications, such as peri-implantitis, and ensure optimal performance and durability of the implant.

Effect of implant‒abutment connections on abutment screw loosening: An in vitro study.

Background: The widespread use of dental implants as a predictable treatment choice has drawn attention to their complications as a major challenge despite their high clinical success rates. In this context, loosening of the abutment screw in posterior single crowns is the most common problem; the use of adequate preload and proper anti-rotational features at implant‒abutment interface appear to be two main solutions to such a problem. The present study evaluated the effect of implant‒abutment connections in four different implant systems before and after cyclic loading. Methods: Intra-Lock, Dentis, Xive, and Dio implant systems were used in this study. Each system underwent one million cycles of dynamic forces eight times with a magnitude of 110 N. For each specimen after tightening the screw with a torque of 32 Ncm, the detorque values were measured and recorded by a digital torquemeter after and before cyclic loading. Data were analyzed by Kolmogorov-Smirnov, Levene's, one-way ANOVA, and post hoc Tukey tests. Results: Initial detorque values between the study groups showed significant differences (P<0.0001). Pairwise comparisons showed significantly lower primary detorque values in the Dentis system compared to the three other systems (P<0.0001). After cyclic loading, significant differences were observed between the study groups (P<0.0001). Pairwise comparisons of the groups showed significant differences between all the systems after loading. Conclusion: The type of implant‒abutment connection is an essential factor influencing the amount of abutment screw loosening.

Comparative in vitro evaluation of microgap in titanium stock versus cobalt-chrome custom abutments on a conical connection implant: Effect of crown cementation and ceramic veneering.

OBJECTIVE: To compare the implant-abutment connection microgap between computer-aided design and computer-aided manufacturing (CAD/CAM) milled or laser-sintered cobalt-chrome custom abutments with or without ceramic veneering and titanium stock abutments with or without crown cementation. MATERIAL AND METHODS: Six groups of six abutments each were prepared: (1) CAD/CAM cobalt-chrome custom abutments: milled, milled with ceramic veneering, laser-sintered, and laser-sintered with ceramic veneering (four groups: MIL, MIL-C, SIN, and SIN-C, respectively) and (2) titanium stock abutments with or without zirconia crown cementation (two groups: STK and STK-Z, respectively). Abutments were screwed to the implants by applying 30 Ncm torque. All 36 samples were sectioned along their long axes. The implant-abutment connection microgap was measured using scanning electron microscopy on the right and left sides of the connection at the upper, middle, and lower levels. Data were analyzed using the Kruskal-Wallis test (p < .05). RESULTS: Mean values (µm) of the microgap were 0.54 ± 0.44 (STK), 0.55 ± 0.48 (STK-Z), 1.53 ± 1.30 (MIL), 2.30 ± 2.2 (MIL-C), 1.53 ± 1.37 (SIN), and 1.87 ± 1.8 (SIN-C). Although significant differences were observed between the STK and STK-Z groups and the other groups (p < .05), none were observed between the milled and laser-sintered groups before or after ceramic veneering. The largest microgap was observed at the upper level in all groups. CONCLUSIONS: Titanium stock abutments provided a closer fit than cobalt-chrome custom abutments. Neither crown cementation nor ceramic veneering resulted in significant changes in the implant-abutment connection microgap.

Comparative Analysis of Internal Tapered Implant-Abutment Connections: Evaluating the Morse Effect.

The purpose of the present study was to evaluate the Morse effect of different internal tapered implant-abutment connections (ITCs) using a pullout test. Implants with different ITCs were selected: Short (Bicon, USA), G1; Novo Colosso (Medens, Brazil), G2; Epkut (SIN, Brazil), G3; Strong SW (SIN, Brazil), G4; Flash (Conexão, Brazil), G5 and Bone Level (Straumann, Switzerland), G6. The respective CAD files were loaded into the analysis software to measure each ITC's taper angle and implant-abutment contact area. Six implants from each group were embedded in acrylic resin blocks, and the respective universal abutments were fixed using a mallet (G1) or by applying 20 Ncm of torque (G2 to G6). After ten minutes, each abutment's retention screw was removed, and the force necessary for abutment rupture was recorded using a universal testing machine at a crosshead speed of 0.5 mm/min. The groups were compared using a one-way ANOVA and Tukey's test. Spearman's correlation was used to check the correlation of the taper angle and contacting area with the pullout strength. G1, a no-screw abutment with a 3° taper, and G2, a 10°tapered abutment tightened by 20 Ncm, presented the highest pullout strength (p<.05). The increased taper angle of G4, compared to G3, reduced the Morse effect despite their similar implant-abutment contacting areas (p<0.05). The G5 and G6 abutments loosened after screw removal and did not exhibit pullout resistance. The closer the tapered angle (r=-.958) and the higher the implant-abutment contact area (r=.880), the higher the pullout strength (p<.001). Within the limits of this study, the Morse effect is different among tapered implant-abutment connections. The closer the tapered angle and the higher the interface area, the higher the Morse effect between the abutment and the implant.

Clinical efficacy of a two-piece abutment conforming to the concept of one abutment one time in the posterior region: A clinical pilot study.

OBJECTIVES: To assess the impact of a two-piece abutment workflow on enhancing the stability of the alveolar bone and gingiva surrounding the dental implant, and to determine the level of patient satisfaction. MATERIALS AND METHODS: A total of 48 patients with dentition defect in the posterior region were included and divided into two groups: the two-piece abutment workflow (TAW) and the sealing screw with submerged healing workflow (SHW). Marginal bone level (MBL), soft tissue indicators, oral hygiene indicators, and patient satisfaction were assessed and recorded partially at 0, 3, 6, and 12 months after surgery. The primary outcome was the change of MBL in different time periods. A generalized linear mixed model (GLMM) was used to take into account the correlated nature of the data, and adjust for potential confounding factors within inter-group differences. RESULTS: The survival rate of implants and prosthesis reached 100% at 12-month follow-up, with an average decrease of 0.25 mm (SD 0.23 mm) of MBL in the TAW group and 0.48 mm (SD 0.45 mm) in the SHW group. The change of MBL in the TAW group (0.15 ± 0.31 mm) was significantly lower than the SHW group (0.41 ± 0.41 mm) through the analysis of GLMM within 6 months, while no significance was found in 12 months. Moreover, less gingival pain and oppression during prosthesis loading, and less time consumption overall duration were showed in the TAW group through Visual Analogue Scale (VAS, p < 0.05). CONCLUSIONS: Within a 6-month period, the two-piece abutment workflow showed superior efficacy in preserving the integrity of the marginal bone level. Furthermore, it streamlined treatment procedures and mitigated discomfort, hence increasing patient satisfaction.

Ulnocarpal Abutment Syndrome With Triquetrum Degeneration.

We present the case of a 47-year-old patient with a congenital positive ulnar variance and elucidate its effects on nearby structures in relation to ulnocarpal abutment syndrome (UAS). While magnetic resonance imaging (MRI) helped to identify soft tissue changes in the wrist, the use of an arthrogram, in this case, allowed for a more comprehensive and detailed analysis of the ligaments and soft tissues. Image findings included a complex degenerative tear of the disc of the triangular fibrocartilage (TFCC), a degenerated triquetrum, and partial tears of the scapholunate and lunotriquetral ligaments. Mild dorsal angulation of the lunate was noted, representing dorsal intercalated segmental instability (DISI), suggesting scapholunate ligament injury. Palmar classification was utilized to classify the extent of the TFCC injury as Type IIE. This case shines a light on the presentation of UAS in a patient that was not the usual demographic affected by this pathology, as well as their UAS affecting the triquetrum rather than the more commonly associated lunate.

Longevity of different abutments placed on narrow diameter implants: Assessment of structural damage and loosening.

OBJECTIVES: To evaluate structural damage and loosening of abutments placed on narrow diameter implants after cyclic fatigue. METHODS: Sixty Morse taper narrow diameter implants (Neodent, Brazil) received two types of abutments (1PA- one-piece abutment or 2PA- two-piece abutment), which were randomly divided into 3 fatigue experiments (n = 10). The implants were placed into a customized supporting holder and a software-assisted digital torque wrench secured the manufacturer recommended torque for each abutment. Cone beam computed tomography (CBCT) scans were acquired, before and after fatigue, and post-processed (software e-Vol DX) to assess damage and abutment displacement. The boundary fatigue method was adapted to use 2 × 106 cycles, 2 Hz of frequency and constant peak load of 80 N (first experiment) that varied according to the failure rate of previous specimens (second and third experiments). Failure was evaluated using CBCT scans and removal torque values. Data were used to estimate long-term torque degradation, probability of failure and Weibull modulus (software ALTA PRO9). RESULTS: All 2PA specimens became loosen independently of the applied fatigue load, and structural bending was observed in 14 abutments. Eight 1PA got loosen during the fatigue experiment. The Weibull analysis showed a lower modulus (m = 1.0; 0.7, 1.4) for 1PA than for 2PA (m = 2.6; 2, 3.4) resulting in longer predicted lifetimes and slower torque degradation for 1PA than for 2PA specimens. SIGNIFICANCE: 1PA showed greater long-term survival probability than 2PA. Predicting the lifetime and mechanical behavior of implant-abutment systems are useful information to clinicians during the decision-making process of oral rehabilitations.

Application of Polyether Ketone in Oral Implantology and Prosthodontics.

Polyetheretherketone (PEEK) is a polymer that has a comprehensive range of possible uses in dental treatment. The goal of this study was to compile research findings on the substance of dental claims and highlight the upcoming predictions of PEEK in clinical dentistry. PEEK is a novel polymeric material that is yet in its preliminary stage of evolution. Biomolecules are elastic materials with remarkable mechanical strength, barrier properties, and heat resistance compared to other matrix materials. The efficacy of PEEK in clinical dentistry has been acknowledged. Polyetherketone (PEKK) and PEEK are the most commonly mentioned members of the polyaryletherketone (PAEK) family. PEEK has also found significant use in dentistry, notably in prosthodontics and implant dentistry. It also offers exceptional mechanical qualities, including high strength and toughness, making it ideal for dental implants and prostheses. It can endure the stresses of chewing and grinding, resulting in long-lasting restorations. PEEK's tooth-colored look and ability to simulate natural tooth translucency make it suitable for use in dental prostheses such as crowns and bridges. This makes it a more esthetically acceptable alternative to standard metal-based repairs.

Effects of denture use on occlusal force on abutment teeth in molar distal-extension edentulism.

PURPOSE: The present clinical study aimed to investigate the load exerted on abutment teeth in patients with distal extension edentulism, with and without a removable partial denture (RPD). METHODS: A total of 55 volunteers with distal extension edentulism who were fitted with an RPD participated in the present study. Occlusal force was measured by having the patients bite down on an occlusal force measuring sheet, and the occlusal forces on both the abutment teeth and the entire dentition with and without the RPD were compared using the Wilcoxon signed-rank test (P < 0.05). The occlusal forces on the abutment and non-abutment teeth were also compared. RESULTS: The median total occlusal force with the RPD in place was significantly greater than that without the RPD, while the median occlusal force on the abutment teeth without the RPD in place was significantly greater than that on the abutment teeth with the RPD. The occlusal forces on the abutment teeth were significantly greater than those on the non-abutment teeth. CONCLUSIONS: Within the limitations of the present study, we found that the occlusal forces were greater on the abutment than the non-abutment teeth, and that RPDs may reduce the occlusal forces on abutment teeth.

"A conservative technique for fractured implant abutment screw retrieval on an internal connection implant: proof of concept (PoC)".

INTRODUCTION: Broken screw removal from the implant connection is a common but challenging process. Several proposed methods and technical solutions may result in unsuccessful removal; thus, a novel, more conservative, risk-free method is proposed as a first attempt. DESCRIPTION OF THE CASE: The proposal is to use a silicon restoration holder to be twisted counterclockwise on the dried surface of the broken fragment inside the implant connection. This method, within the limitations of a minimal case series, yielded 100% results; however, despite previous attempts with less con- servative techniques, this approach showed no efficacy. CONCLUSION: This article aims to promote the use of silicon restoration holders as a minimally invasive first attempt at broken screw retrieval treatment before considering other options.

Does Implant Placement Below the Ridge Reduce Crestal Bone Loss? A Split-Mouth Randomized Controlled Clinical Trial.

Reducing crestal bone loss (CBL) around implants allows for soft tissue stability and long-term success. The aim of the present study was to evaluate the extent of CBL in implants placed with the implant shoulder at the equi-crestal level and 2 mm below the alveolar ridge at 2, 12, 36, and 60 months. A split-mouth randomized controlled clinical trial was conducted by selecting subjects with Kennedy Class IV partial edentulism of the lower jaw. Two implants were inserted, of equal length and diameter, one equi-crestal and the other sub-crestal, in the site corresponding to the lateral incisor. Intraoral periapical radiographs with Rinn centering devices were performed at the time of implant insertion (T0), at 2 (T1), 12 (T2), 36 (T3), and 60 months (T4). Descriptive statistics and the T-test were used, setting the significance to P⩽ 0.05. Twenty-five subjects were recruited, with a mean age of 65 years (SD 9.88, range 42-82). No subject dropped out. A total of 50 implants were inserted, 25 at crestal and 25 sub-crest level. At the 60-month follow-up, no implant or prosthetic failure was recorded. An average loss of -0.81 mm was recorded in the crestal implant group (n.25; SD: 0.40; max-min: -1.6 - -0.1) while in the implants positioned below the crest the average CBL was -0.87mm (n.25; SD: 0.41; max-min: -2 - -0.2); however, the higher CBL in the sub-crestal implant group was not statistically significant (P=0.65). Comparing the mean CBL values of the two groups at the various follow-ups, a greater crestal bone resorption was recorded in sub-crest implants between T0 and T1 (-0.25 vs -0.1) and between T1 and T2 (-0.39 vs -0.23), while in subsequent follow-ups a greater, statistically significant (P=0.01), crestal bone loss was recorded in ridge implants between T3 and T4 (-0.05 vs -0.18). Over time, therefore, the extent of CBL seems to be reduced in implants placed below the crest, with bone retention above the implant shoulder. Ultimately, although the position of the implant shoulder relative to the crestal ridge doesn't affect the CBL, sub-crestal placement is recommended in order to reduce the risk of exposure of the rough surface of the implant.

Fracture Resistance of a Bone-Level Two-Piece Zirconia Oral Implant System-The Influence of Artificial Loading and Hydrothermal Aging.

Preclinical and clinical research on two-piece zirconia implants are warranted. Therefore, we evaluated the in vitro fracture resistance of such a zirconia oral implant system. The present study comprised 32 two-piece zirconia implants and abutments attached to the implants using a titanium (n = 16) or a zirconia abutment screw (n = 16). Both groups were subdivided (n = 8): group T-0 comprised implants with a titanium abutment screw and no artificial loading; group T-HL was the titanium screw group exposed to hydro-thermomechanical loading in a chewing simulator; group Z-0 was the zirconia abutment screw group with no artificial loading; and group Z-HL comprised the zirconia screw group with hydro-thermomechanical loading. Groups T-HL and Z-HL were loaded with 98 N and aged in 85 °C hot water for 107 chewing cycles. All samples were loaded to fracture. Kruskal-Wallis tests were executed to assess the loading/bending moment group differences. The significance level was established at a probability of 0.05. During the artificial loading, there was a single occurrence of an implant fracture. The mean fracture resistances measured in a universal testing machine were 749 N for group T-0, 828 N for group Z-0, 652 N for group T-HL, and 826 N for group Z-HL. The corresponding bending moments were as follows: group T-0, 411 Ncm; group Z-0, 452 Ncm; group T-HL, 356 Ncm; and group Z-HL, 456 Ncm. There were no statistically significant differences found between the experimental groups. Therefore, the conclusion was that loading and aging did not diminish the fracture resistance of the evaluated implant system.

A Case of Anterior Single Tooth Implant with Fractured Zirconia Abutment due to Trauma.

In recent years, a wide variety of materials have been used in dental implant treatment. In selecting the superstructures and abutments to be used it is important to consider their potential effect on the stability and durability of the planned implant. Excessive force applied to an implant during maintenance commonly results in complications, such as fracture of the superstructure or abutment, and loosening or fracture of the screws. This report describes a case of implant treatment for a 23-year-old man with esthetic disturbance due to trauma to the maxillary anterior teeth. The left maxillary central incisor could not be conserved due to this trauma, which had been caused by a traffic accident. After extraction, the tooth was restored with an anterior bridge. The crown of the left maxillary lateral incisor was fractured at the crown margin and, at the patient's request, implant treatment was selected as the restorative treatment for the missing tooth. A thorough preoperative examination was performed using placement simulation software. One titanium screw-type implant was placed in the maxillary left central incisor under local anesthesia. An all-ceramic crown with a zirconia frame was placed as a screw-fixed direct superstructure. At one year postoperatively, however, the superstructure and abutment became detached due to trauma. The fractured zirconia abutment was removed and replaced with a remanufactured abutment and superstructure. The patient has reported no subsequent dental complaint over the last 11 years. In this case, a surface analysis of the fractured zirconia abutment was performed. The scanned images revealed a difference in the fracture surfaces between the tensile and compressive sides, and electron probe microanalysis demonstrated the presence of titanium on the fracture surface. It was inferred that the hard zirconia abutment had scraped the titanium from the internal surface of the implant.

Fracture resistance of cement-retained lithium disilicate implant-supported crowns: Effect of material used for two-piece abutments.

PURPOSE: This study compared the fracture strength of single lithium disilicate implant-supported crowns fabricated on two-piece abutments with various materials: ceramic-reinforced PEEK, zirconia, and lithium disilicate. MATERIALS AND METHODS: Thirty-six implants were embedded in acrylic cylinders. A two-piece abutment and a crown were designed following a pre-operation scan for a maxillary left central incisor. The designed crown was used to fabricate 36 lithium disilicate crowns. The designed abutment was used to manufacture 36 abutments from 3 materials, 12 each: (A) zirconia; (B) lithium disilicate; and (C) ceramic-reinforced PEEK. Abutments were surface treated and bonded on the titanium base abutments with resin cement. Then, lithium disilicate crowns were bonded on the assigned abutments. Specimens were then subjected to dynamic loading for 1,200,000 cycles. The fracture strength (N) of the assembly was assessed using a universal testing machine. One-way ANOVA followed by multiple comparison tests was used to evaluate the effect of abutment material on the fracture strength of single implant-supported restorations at a significance of .05. RESULTS: The average fracture strength for the groups with zirconia, PEEK, and lithium disilicate two-piece abutments were 1362N ± 218N, 1235N ± 115N, and 1472N ± 171N, respectively. There was a significant (p < 0.05) difference in fracture strength among the groups. The lithium disilicate group had significantly higher fracture strength (p = 0.0058) than the group with PEEK; however, there was no significant (p > 0.05) difference between the other groups. CONCLUSIONS: Two-piece abutments restored with lithium disilicate crowns investigated in the study have the potential to withstand the average physiological occlusal forces in the anterior region.

Prospective observational cohort study of the change of the marginal bone crest in relation to the prosthetic abutment height and the peri-implant vertical mucosal thickness at implants positioned subcrestally.

AIM: To evaluate the influence on peri-implant crestal bone loss exerted by the vertical mucosal thickness and the abutment height over 12 months after placement of the restoration on subcrestal implants with change of platform, using a restoration abutment platform smaller than the implant platform. MATERIALS AND METHODS: A total of 99 implants were rehabilitated in the maxillary and mandibular posterior regions. A total of 22 implants were rehabilitated in the maxilla and 77 implants in the mandible, using digitally designed customized abutments with Atlantis weborder software, from the commercial house Dentsply Sirona (Dentsply Sirona S.A., Barcelona, Spain), version 4.6.5, adapting the height to the vertical thickness of the mucosa. Clinical and radiographic monitoring begins during the surgical procedure of placement of the implant and ends 12 months afterwards. Crestal bone loss was evaluated through the Carestream® CS8100 3D radiographic equipment. RESULTS: In all cases, the greatest loss of marginal bone occurred between the day of surgery (Tx) and placement of the rehabilitation (To). The average bone loss between both times was greater when the abutment height and vertical mucosal thickness did not exceed 3 mm. Subsequently, bone loss slowed and stabilized at 12 months. CONCLUSIONS: The minimum abutment height and the vertical mucosal thickness are factors to take into account when minimizing peri-implant marginal bone loss, the abutment height having the greatest importance according to the clinical data obtained.