Wide Restorative Emergence Angle Increases Marginal Bone Loss and Impairs Integrity of the Junctional Epithelium of the Implant Supracrestal Complex: A Preclinical Study.

AIM: To assess the influence of the emergence angle on marginal bone loss (MBL) and supracrestal soft tissue around dental implants. MATERIALS AND METHODS: In six mongrel dogs, the mandibular premolars and molars were extracted. After 3 months of healing, four dental implants were placed in each hemimandible. The implants were randomly allocated to receive one of four customized healing abutments, each with a different value of the restorative emergence angle: 20°, 40°, 60° or 80°. Intra-oral radiographs were taken after placing the healing abutments and at 6, 9, 16 and 24 weeks of follow-up. Then, micro-CT and undecalcified histology and synchrotron were performed. MBL over time was analysed with generalized estimating equations (GEEs) and adjusted for baseline soft-tissue thickness. RESULTS: From implant placement to 24 weeks, GEE modelling showed that the MBL at mesial and distal sites consistently increased over time, indicating MBL in all groups (p < 0.001). The model indicated that MBL varied significantly across the different restorative angles (angle effect, p < 0.001), with 80° showing the greatest bone loss. Micro-CT, histology and synchrotron confirmed the corresponding trends and showed that wide restorative angles (60° and 80°) impaired the integrity of the junctional epithelium of the supracrestal tissue. CONCLUSIONS: A wide restorative angle increases MBL and impairs the integrity of the junctional epithelium of the implant supracrestal complex.

Clinical outcomes of implant- versus abutment-level connection in screw-retained fixed dental prostheses: A 5-year randomized controlled trial.

AIM: The aim of the study was to evaluate the 5 years clinical outcomes associated with implant-level connection (IL) versus abutment-level connection (AL) for implants with an internal conical connection (ICC) supporting a screw-retained fixed partial denture. MATERIALS AND METHODS: Fifty patients with 119 implants were randomly allocated to either the AL or IL group. Radiographic (Marginal bone loss) and clinical outcomes (Bleeding on Probing, probing pocket depth, plaque accumulation, incidence of peri-implantitis and peri-implant mucositis as well as prosthetic complications) were collected and compared at 1, 2, 3, and 5 years. A linear mixed model was used to evaluate the differences between groups. RESULTS: Five years after treatment, the MBL change was not significantly different between the groups at any point. The MBL was 0.23 ± 0.64 mm (AL) and 0.23 ± 0.29 mm (IL). The bleeding on Probing was 44% (AL) and 45% (IL) (p = .89). The mean probing depth was 2.91 ± 1.01 mm (AL) and 3.51 ± 0.67 mm (IL). This difference between the groups was statistically significant but clinical insignificant. Presence of plaque was slightly higher (p = .06) in the IL group (34.4%) compared with the AL group (26.3%). The overall technical, biological, and prosthetic complication rates were similar between groups. None of the implants developed peri-implantitis during the entire follow-up period. CONCLUSION: The results of this clinical trial indicated that all clinical and radiographical parameters were clinically comparable between the study groups.

Mechanical stability of posterior implant-supported monolithic zirconia cantilever on titanium-base abutments. An in vitro study.

PURPOSE: Investigate survival and technical complications of two-unit posterior implant-supported cantilever made of monolithic zirconia on titanium-base abutments (Zr-TiB) vs. porcelain-fused-to-metal on castable gold abutments (PFM-GA) using two different implant connections, internal butt-joint (IBJ) and internal conical (IC). MATERIALS AND METHODS: Forty-eight implants (4.3 mm diameter) were divided into four groups (n = 12) to support 2-unit mandibular premolar cantilevers with two different materials (Zr-TiB vs. PFM-GA) and two connection types (IBJ vs. IC). Tested groups were as follows: (1) IBJ/Zr-TiB; (2) IBJ/PFM-GA; (3) IC/Zr-TiB; and (4) IC/PFM-GA. Specimens were thermomechanical aged (1,200,000 cycles, 98 N, 5-55°C) with occlusal axial load on the pontic. Catastrophic and non-catastrophic events were registered, and removal torque values measured before and after aging. Specimens surviving aging were subjected to loading until failure. Survival, total complication rates, torque loss (%), and bending moments were calculated. RESULTS: From 48 specimens, 38 survived aging. Survival rates significantly varied from 16.7% (IC/PFM-GA) to 100% (IBJ/Zr-TiB; IBJ/PFM-GA; IC/Zr-TiB) (p < .01). Internal conical connection revealed significantly higher torque loss (IC/ZrTiB - 67%) compared to internal butt-joint (IBJ/Zr-TiB - 44%; IBJ/PFM-GA - 46%) (p < .01). Bending moments were higher in internal butt-joint connections than in internal conical (p < .05). CONCLUSION AND CLINICAL IMPLICATIONS: Two-unit posterior implant-supported cantilever FDPs replacing mandibular premolars composed of monolithic zirconia on titanium-base abutments demonstrated higher mechanical stability compared to porcelain-fused-to-metal on castable gold abutments in this in vitro study. The internal conical connection combined with porcelain-fused-to-metal on gold abutments revealed a high number of failures; therefore, their clinical use may be considered cautiously for this indication.

Performance of a new implant system and drilling protocol-A minipig intraoral dental implant model study.

AIM: A new implant system encompassing implants with a tri-oval cross-sectional design and a simplified site preparation protocol at low speed and no irrigation has been developed. The objective of this study was to assess the safety and efficacy of the new implant system using the minipig intraoral dental implant model. METHODS: Eight Yucatan minipigs were included. Twelve weeks after extractions, four implants per animal were randomly placed and allowed to heal transmucosal for 13 weeks: two Ø3.5 × 10 mm implants with a back-tapered collar and circular cross-section (control) and two Ø3.5 × 11 mm implants with tri-oval collar and cross-section (test). MicroCT and histological analysis was performed. RESULTS: Thirty-two implants were placed; one implant for the control group was lost. Histologically, BIC was higher in the test compared with the control group (74.1% vs. 60.9%, p < .001). At the platform level, inflammation was statistically significantly higher albeit mild in the test compared with the control group. No other significant differences were observed between groups. MicroCT analysis showed that bone-to-implant-contact (BIC) and trabecular thickness were statistically significantly higher for the test than the control group. Test group had significantly higher first BIC distance than controls on lingual sites. CONCLUSIONS: The present study results support the safety and efficacy of the new dental implant system and simplified site preparation protocol; human studies should be carried out to confirm these findings.

In vitro assessment of cementation of CAD/CAM fabricated prostheses over titanium bases. A systematic review.

OBJECTIVES: The objective of this study is to investigate the outcomes of clinically relevant laboratory studies regarding the cementation of implant-supported restorations over ti-bases. MATERIALS AND METHODS: The present study has been conducted according to PRISMA statement. An electronic search was performed, including publications up to March 2024, to identify studies investigating the parameters affecting the cementation between ti-bases and CAD/CAM prostheses. An assessment of the internal validity was performed, using a custom-made risk of bias tool (QUIN). RESULTS: From the included studies, 40.1% were reported on luting systems, 25% on ti-base surface treatment, 25% on restoration surface, 21.8% on restoration material, and 18.7% on ti-base height. The majority of the included studies were associated with a medium risk of bias. In the absence of micro-retentive features, air-abrasion of ti-bases with a minimum height of 3.5 mm can be beneficial for restoration's retention. The bonding performance can vary not only between different bonding systems but also for different applications within the same system, based on a restoration's material and surface treatment as well as on ti-base height and surface treatment. CONCLUSIONS: The height of the ti-base seems to be the prevailing factor as it constitutes the prerequisite for other modifications of the bonding surfaces to have an advantageous effect. Since the parameters that can affect bonding performance between ti-base and restoration can interact with each other, it is important for the clinician to focus on verified bonding protocols.

The effect of one-time abutment placement on clinical and radiographic outcomes: A 5-year randomized clinical trial.

OBJECTIVE: The aim of this study was to evaluate the long-term (5 years) clinical efficacy of the one-abutment one-time protocol (test) versus the standard of care by placing the definitive abutment on the day of the prosthetic delivery (control). MATERIALS AND METHODS: In this study, 39 subjects with 60 implants were randomly allocated to either the test or the control group. Changes in the radiographic interproximal bone levels (DIB), modified sulcus bleeding index, probing depth, modified plaque index, papilla fill (Jemt score), incidence of peri-implantitis and peri-implant mucositis as well as patient-reported outcomes measures (PROMs) were collected and compared at 1, 3 and 5 years. RESULTS: At 5 years, the control group showed a greater, although not statistically significant, change in mean DIB values (0.97 mm vs. 0.53 mm). Regarding the other clinical parameters evaluated, no statistically significant differences were observed between groups at any time point. At 5 years, 51% of the implants presented peri-implant mucositis (25.5% in the control and 23.5% in the test), and only one implant in the test group developed peri-implantitis. CONCLUSIONS: The connection and disconnection of healing abutments during the healing period was not associated with higher long-term bone loss. Clinical outcomes and PROMs were similar between groups.

Influence of sterilization on the retention forces of lithium disilicate and polymer-infiltrated ceramic-network crowns bonded to titanium base abutments: An in-vitro study.

OBJECTIVES: The aim of this study was to evaluate the effect of sterilization on the retention forces of lithium disilicate (LD) and polymer-infiltrated ceramic network (PICN) crowns bonded to titanium base (Ti-base) abutments. MATERIALS AND METHODS: Forty LD and 40 PICN crowns were milled and then bonded to 80 Ti-bases with two resin composite cements: Multilink Hybrid Abutment (mh) and Panavia V5 (pv) for a total of 8 groups (n = 10). Half of the specimens (test) underwent an autoclaving protocol (pressure 1.1 bar, 121°C, 20.5 min) and the other half not (control). Restorations were screw-retained to implants, and retention forces (N) were measured with a pull-off testing machine. The surfaces of the Ti-bases and the crowns were inspected for the analysis of the integrity of the marginal bonding interface and failure mode. Student's t-test, chi-square test, and univariate linear regression model were performed to analyze the data (α = 0.05). RESULTS: The mean pull-off retention forces ranged from 487.7 ± 73.4 N to 742.2 ± 150.3 N. Sterilized groups showed statistically significant overall higher maximum retention forces (p < .05), except for one combination (LD + mh). Sterilization led to an increased presence of marginal gaps and deformities compared to no-sterilization (p < .001), while no statistically significant relationship was found between failure mode and sterilization (p > .05). CONCLUSIONS: Sterilization may have a beneficial effect on the retention forces of LD and PICN crowns bonded to titanium base abutments, although it may negatively influence the integrity of the marginal bonding interface.

Clinical, radiographic and patient-reported outcomes of zirconia and titanium implants in the posterior zone after 1 year of loading-A randomized controlled trial.

OBJECTIVE: To assess the clinical, radiographic and patient-reported outcomes (PROMs) of posterior zirconia and titanium implants at 1 year of implant loading. MATERIALS AND METHODS: Forty-two patients with two adjacent missing teeth were enrolled in a randomized controlled trial with a within-subject controlled design. Each patient received one zirconia (Zr) and one titanium (Ti) implant, with the mesial and distal positions randomized. The implant restoration consisted of multiple layered zirconia, with the buccal aspect veneered. In group Zr, the restoration was intraorally cemented onto the one-piece Zr implant, whereas in group Ti, the restoration was extraorally cemented onto the titanium base abutment and intraorally screw-retained onto the Ti implant. Examinations were performed following restoration delivery at baseline (BL) and at 1 year. Measurements included clinical parameters, radiographic outcomes (MBL) and PROMs. RESULTS: Bleeding on probing showed an increase from BL to 1 year (34 ± 30% for Zr; 25 ± 21% for Ti). MBL remained stable with minimal changes from BL to 1 year, measuring 0.1 ± 0.4 mm (mean ± SD) for Zr and -0.1 ± 0.7 mm for Ti. Veneering fractures were the most frequent technical complication and amounted to 17.5% in group Zr and 5% in group Ti (p = .100). Patients preferred Zr implants for their soft tissue color, with a significant difference in perception between patients and clinicians (p < .017). CONCLUSION: The study showed that both Zr and Ti implants had similar clinical outcomes, despite a high prevalence of mucositis and a few technical complications. Both implant types demonstrated stable marginal bone levels and similar patient-reported outcome measures.

Marginal changes at bone-level implants supporting dental prostheses with or without intermediate standardised abutments after 36 months: Randomised controlled clinical trial.

OBJECTIVE: The objective of this study is to evaluate the changes at marginal bone level at implants restored with screw-retained prosthesis connected directly to the implants or with an intermediate abutment, after 3-year follow-up. MATERIAL AND METHODS: Thirty-six partially edentulous patients received 72 implants. Each patient received 2 implants and a 2-4-unit screw-retained implant-prosthesis. The test group implants received a screw-retained prosthesis connected directly to the implant shoulder, the control group prosthesis were connected through a 3-mm standardised intermediate abutment. Clinical and radiological data were recorded at baseline and at 6-, 12-, and 36-month follow-up. RESULTS: At 36 months, the mean marginal bone loss was 0.13 ± 0.18 mm for the control group and 0.20 ± 0.24 for the test group, with no significant differences between groups (p > .05). Clinical variables (Probing Pocket Depth, Bleeding on Probing and Plaque Index) at 36 months also showed no significant difference between groups. Minor complications frequency was 6.7% in the control group and 5.3% in test group. None of the groups suffered from mayor complications. Patient Reported Outcomes (PROs) showed a General Satisfaction mean score in the control group of 9.40 (SD 0.82) and 9.37 (SD 1.06) in the test group with no significant differences between groups. CONCLUSIONS: Bone-level implants restored with screw-retained partial prostheses with or without intermediate abutments showed similar radiographic and clinical outcomes after 3 years.

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.

Cone beam computed tomography assessment of maxillary anterior teeth cervix dimensions in healthy adults for optimal anatomic healing abutments.

OBJECTIVES: The abutments produced with circular symmetry failed to accurately replicate the natural teeth's cervical shapes. The purpose of this study was to measure cervical cross-sections of maxillary anterior teeth using cone beam computed tomography (CBCT) images to design anatomic healing abutments. MATERIALS AND METHODS: CBCT data of 61 patients were analyzed using Ez3D Plus software. Measurements were taken at the cemento-enamel junction (CEJ) and 1 mm coronal to CEJ for maxillary central incisors, lateral incisors, and canines. Various parameters, including area, perimeter, and eight line segments in the distal (a), disto-palatal (b), palatal (c), mesio-palatal (d), mesial (e), mesio-labial (f), labial (g), and disto-labial (h) directions, were used to describe dental neck contours. The ratios (f/b and h/d) were analyzed, and differences based on sex and dental arch morphology were explored. RESULTS: Significant differences were found in area and perimeter between males and females, but not in f/b and h/d ratios. Differences in the f/b ratio were observed among dental arch morphologies for maxillary central incisors, lateral incisors, and canines. CONCLUSIONS: CBCT measurements of cervical cross-sections provide more accurate data for designing anatomic healing abutments. The fabrication of anatomical healing abutments needs to consider the influence of gender on cervical size and to explore the potential effect of arch shape on cervical morphology. CLINICAL SIGNIFICANCE: The novel method provides detailed measurements for the description of dental cervical contours for patients with bilateral homonymous teeth missing. The measurements of this study could be utilized to design more accurate anatomic healing abutments to create desired morphology of peri-implant soft tissue.

Evaluation of Vertical Misfit and Torque Loss of Different Abutments for Tri-Channel Type Internal Connection Dental Implants After Mechanical Cycling.

The aim of this study was to evaluate the mechanical behavior of UCLA and Mini-conical abutments for implants with Tri-channel connections regarding torque loss and vertical misfit. Twenty 3-element metal-ceramic fixed partial dentures (FPD) supported by 2 implants were manufactured and divided into 2 groups (n = 10): UCLA (group 1) and Mini-conical Abutments (group 2). The evaluation of torque loss was carried out before and after mechanical cycling, while the vertical fit was evaluated throughout the different stages of manufacturing the prostheses, as well pre- and postcycling (300,000 cycles, 30 N). Statistical analyses of torque loss and vertical misfit were performed using the linear mixed effects model. Both groups showed torque loss after mechanical cycling (P < .05); however, there was no significant percentage differences between them (P = .795). Before cycling, the groups showed a significant difference in terms of vertical misfit values (P < .05); however, this difference was no long observed after cycling (P = .894). Both groups showed torque loss after the cycling test, with no significant difference (P > .05). There was no significant difference in vertical misfit after mechanical cycling; however, in group 1 (UCLA) there was accommodation of the implant-UCLA abutment interface, while group 2 (Mini-conical abutment) did not show changes in the interface with the implant after the test. Both groups behaved similarly regarding the torque loss of the prosthesis retention screws pre- and postmechanical cycling, with greater loss after the test.

Effect of polishing process on torque loss ratio and microgap of selective laser melting abutment: an in vitro study.

BACKGROUND: The purpose of this in vitro study was to investigate the effect of polishing post-treatment process on the torque loss ratio and microgap of Selective Laser Melting (SLM) abutments before and after mechanical cycling test through improving the surface roughness of the implant-abutment interface. MATERIALS AND METHODS: Forty SLM abutments were fabricated, with 20 underwent minor back-cutting, designated as polishing, in the implant-abutment interface. The abutments were divided into three groups: SLM abutments (group A), original abutments (group B), and polished SLM abutments (group C), each containing 20 abutments. Surface roughness was evaluated using a laser microscope. Implant-abutment specimens were subjected to mechanical cycling test, and disassembly torque values were measured before and after. Scanning electron microscope (SEM) was used to measure microgap after longitudinal sectioning of specimens. Correlation between surface roughness, torque loss ratio, and microgap were evaluated. LSD's test and Tamhane's T2 comparison were used to analyze the data (α = 0.05). RESULTS: The Sz value of polished SLM abutments (6.86 ± 0.64 µm) demonstrated a significant reduction compared to SLM abutments (26.52 ± 7.12 µm). The torque loss ratio of polished SLM abutments (24.16%) was significantly lower than SLM abutments (58.26%), while no statistically significant difference that original abutments (18.23%). The implant-abutment microgap of polished SLM abutments (2.38 ± 1.39 µm) was significantly lower than SLM abutments (8.69 ± 5.30 µm), and this difference was not statistically significant with original abutments (1.87 ± 0.81 µm). A significant positive correlation was identified between Sz values and the ratio of torque loss after cycling test (r = 0.903, P < 0.01), as well as Sz values and the microgap for all specimens in SLM abutments and polished SLM abutments (r = 0.800, P < 0.01). CONCLUSION: The findings of this study indicated that the polishing step of minor back-cutting can lead to a notable improvement in the roughness of SLM abutments interface, which subsequently optimized the implant-abutment fit. It can be seen that the application of minor back-cutting method has advanced the clinical use of SLM abutments.

Static and dynamic stress analysis of different crown materials on a titanium base abutment in an implant-supported single crown: a 3D finite element analysis.

BACKGROUND: This Finite Element Analysis was conducted to analyze the biomechanical behaviors of titanium base abutments and several crown materials with respect to fatigue lifetime and stress distribution in implants and prosthetic components. METHODS: Five distinct designs of implant-supported single crowns were modeled, including a polyetheretherketone (PEEK), polymer-infiltrated ceramic network, monolithic lithium disilicate, and precrystallized and crystallized zirconia-reinforced lithium silicates supported by a titanium base abutment. For the static load, a 100 N oblique load was applied to the buccal incline of the palatal cusp of the maxillary right first premolar. The dynamic load was applied in the same way as in static loading with a frequency of 1 Hz. The principal stresses in the peripheral bone as well as the von Mises stresses and fatigue strength of the implants, abutments, prosthetic screws, and crowns were assessed. RESULTS: All of the models had comparable von Mises stress values from the implants and abutments, as well as comparable maximum and minimum principal stress values from the cortical and trabecular bones. The PEEK crown showed the lowest stress (46.89 MPa) in the cervical region. The prosthetic screws and implants exhibited the highest von Mises stress among the models. The lithium disilicate crown model had approximately 9.5 times more cycles to fatique values for implants and 1.7 times more cycles to fatique values for abutments than for the lowest ones. CONCLUSIONS: With the promise of at least ten years of clinical success and favorable stress distributions in implants and prosthetic components, clinicians can suggest using an implant-supported lithium disilicate crown with a titanium base abutment.

A finite element analysis study on different angle correction designs for inclined implants in All-On-Four protocol.

BACKGROUND: The aim of this study is to investigate, through finite element analysis (FEA), the biomechanical behavior of the built-in angle corrected dental implant versus implant with angled multiunit abutment used in All-On-Four treatment protocol. METHODS: Two (3D) finite element models of a simplified edentulous mandible were constructed with two different posterior implant designs based on the All-On-Four protocol. Four implants were placed in each model, the two anterior implants were positioned vertically at the lateral incisor/canine sites. Depending on the implant fixture design in posterior area, there are two models created; Model I; the mandible was rehabilitated with four co-axis (4 mm in diameter × 15 mm in length) implants with distally built-in angle corrected implants (24-degree angle correction) .While Model II, the mandible was rehabilitated with four conventional (4 mm in diameter × 14 mm in length) implants with a distally inclined posterior implants (25 degree) and angled multiunit abutments. CAD software (Solidworks© 2017; Dassault Systems Solidworks Corp) was used to model the desired geometry. Axial and inclined Loads were applied on the two models. A Finite element analysis study was done using an efficient software ANSYS© with specified materials. The resultant equivalent Von-Misses stresses (VMS), maximum principal stresses and deformation analysis were calculated for each part (implants and prosthetic components). RESULTS: When applying axial and non-axial forces, model II (angled multiunit model) showed higher deformation on the level of Ti mesh about 13.286 µm and higher VMS 246.68 MPa than model I (angle corrected implant). Model I exhibited higher maximum stresses 107.83 MPa than Model II 94.988 MPa but the difference was not statistically significant. CONCLUSION: Within the limitation of the FEA study, although angle correcting implant design is showing higher values in maximum principle stresses compared with angled multiunit abutments, model deformation and resultant VMS increased with angled multiunit abutments. The angle correcting designs at implant level have more promising results in terms of deformation and VMS distribution than angle correction at abutment level.

Biomechanical behaviour of tilted abutment after fixed partial denture restoration of CAD/CAM materials.

BACKGROUND: Failure to restore missing teeth in time can easily lead to the mesial tilting of the distal abutment teeth. However, a fixed partial denture (FPD) can improve stress conduction and distribution and prevent periodontal injuries. In these more complex cases, it is necessary to consider various factors comprehensively to improve conventional treatment planning and achieve better results. METHODS: We selected a patient with a missing first molar and a mesial inclination of the second molar, leaving inadequate space or bone mass for implant denture restoration, necessitating an FPD for restoration. Three-dimensional finite element analysis (3D-FEA) combined with photoelastic analysis were used to explore how the inclination angle (0 ‒ 30°) and different dental restoration materials (zirconia, lithium disilicate, polymer-infiltrated ceramic network, and resin composite) affect the biomechanical behaviour of FPD‒abutments‒periodontal tissue complex. RESULTS: The stress was easily concentrated in the FPD connectors, enamel shoulder collar, periapical area, and root bifurcation. The stress on FPD and the periodontal ligament (PDL) of the second premolar increased with an increase in the elastic modulus of FPD, with an opposite trend in the abutments, the alveolar bone, and the PDL of the second molar. The stress on the FPD and alveolar bone increased with increased inclination angle of the distal abutment. The stress on two abutments and their PDL were positively correlated with the inclination angle in two stages; however, when the inclination angle > 12°, the second premolar and its PDL showed a negative correlation. CONCLUSIONS: FPDs can be used for restoration within 24° of distal abutment inclination, but protecting the abutments (< 12° especially) and the periodontal tissue (> 12° especially) must be taken seriously. For this purpose, an FPD material with higher strength is recommended.

Comparison of misfit and roughness of CAD-CAM ZrO, selective laser sintered CoCr and preformed Ti implant abutment crowns.

BACKGROUND: Marginal misfit and surface roughness of customized implant abutments is critical for restorative success. However, little is known about the comparison of misfit and surface roughness of CAD-CAM Zirconium oxide (ZrO), selective laser melting (SLM) Cobalt Chrome (CoCr) and preformed abutments. The aim of the study is to investigate the relation of misfit and micro-roughness of selective laser melting (SLM), preformed and CAD-CAM implant abutments. METHODS: Thirty internal connection, endosseous dental implants (Ø 4.0 mm x 10 mm, Dentium) were mounted in Polymethyl methacrylate vertically. Ten preformed Titanium alloy (Ti) abutments with 1 mm soft tissue height and Ø 4.5 mm were included as controls. Ten each of Y-TZP and SLM-CoCr, abutment/crowns were fabricated using CAD-CAM milling (CAD-CAM-ZrO) and SLM techniques. Surface micro-roughness (Ra) of the fabricated implant abutment/crown was evaluated with a 3D optical non-contact microscope. All implant restorations were torqued to implants (30 Ncm) using a Tohnichi BTGE digital torque gauge and were analyzed with Bruker micro-CT (Skyscan 1173) to detect micro-gaps at pre-selected points at implant abutment interface. The Ra and misfit data were compared using ANOVA, Tukey-Kramer, Kruskal-Wallis test and Pearson correlation (p < 0.05). RESULTS: Mean Ra among SLM CoCr abutments [0.88 (0.09) µm] were lower than CAD-CAM-ZrO and higher than preformed Ti abutments. Horizontal misfit among SLM-CoCr [45.43 (9.41) µm] and preformed Ti [36.87 (13.23) µm] abutments was not statistically different (p > 0.05). Misfit was significantly higher in Y-TZP samples compared to SLM-CoCr (p = 0.031) and preformed Ti abutments (p = 0.01). Preformed Ti abutments showed significantly lower misfit compared to SLM-CoCr abutments (p = 0.01). A positive linear correlation was observed between the surface roughness (Ra) and vertical misfit (r = 0.61, p < 0.05). CONCLUSION: SLM CoCr abutments showed rough surface compared to preformed Ti abutments, while horizontal misfit was comparable among SLM-CoCr and preformed abutments. Misfit was significantly greater in Y-TZP abutments, compared to SLM and preformed abutments. SLM abutment fabrication technique needs further improvement to provide better fit and surface topography.

Assessing peri-implant bacterial community structure: the effect of microbiome sample collection method.

BACKGROUND: Oral microbiota comprises polymicrobial communities shaped by mutualistic coevolution with the host, contributing to homeostasis and regulating immune function. Nevertheless, dysbiosis of oral bacterial communities is associated with a number of clinical symptoms that ranges from infections to oral cancer. Peri-implant diseases are biofilm-associated inflammatory conditions affecting the soft and hard tissues around dental implants. Characterization and identification of the biofilm community are essential for the understanding of the pathophysiology of such diseases. For that sampling methods should be representative of the biofilm communities Therefore, there is a need to know the effect of different sampling strategies on the biofilm characterization by next generation sequencing. METHODS: With the aim of selecting an appropriate microbiome sampling procedure for periimplant biofilms, next generation sequencing was used for characterizing the bacterial communities obtained by three different sampling strategies two months after transepithelial abutment placement: adjacent periodontal crevicular fluid (ToCF), crevicular fluid from transepithelial abutment (TACF) and transepithelial abutment (TA). RESULTS: Significant differences in multiple alpha diversity indices were detected at both the OTU and the genus level between different sampling procedures. Differentially abundant taxa were detected between sample collection strategies, including peri-implant health and disease related taxa. At the community level significant differences were also detected between TACF and TA and also between TA and ToCF. Moreover, differential network properties and association patterns were identified. CONCLUSIONS: The selection of sample collection strategy can significantly affect the community composition and structure. TRIAL REGISTRATION: This research is part of a randomized clinical trial that was designed to assess the effect of transepithelial abutment surface on the biofilm formation. The trial was registered at Trial Registration ClinicalTrials.gov under the number NCT03554876.

Removal of broken abutment screws using ultrasonic tip - a heat development in-vitro study.

BACKGROUND: Dental implants can cause complications, including the loosening of the abutment screw or fracture. However, there is no standardized technique for removing broken abutment screws. This necessitates further research. OBJECTIVE: This study aimed to measure heat generation during screw removal to better understand its implications for dental implant procedures. MATERIAL AND METHODS: The experimental setup involved using synthetic bone blocks and titanium implants. An ultrasonically operated instrument tip was utilized for screw removal. Infrared thermometry was employed for accurate temperature measurement, considering factors such as emissivity and distance. Statistical analysis using linear regression and ANOVA was conducted. RESULTS: The findings revealed an initial rapid temperature increase during the removal process, followed by a gradual decrease. The regression model demonstrated a strong correlation between time and temperature, indicating the heat generation pattern. CONCLUSION: Heat generation during screw removal poses risks such as tissue damage and integration issues. Clinicians should minimize heat risks through an intermittent approach. The lack of a standardized technique requires further research and caution. Understanding the generated heat optimizes implant procedures.

Post sterilization of intraoral scan body and the effect it has on the axes and distances between three adjacent implants: in-vitro study.

BACKGROUND: The purpose of this pilot in-vitro study was to assess the effect of sterilization on the intra-implant axis, inter-implant axis, intra-implant distance and inter-implant distance of three implants in a straight line by using laboratory scanner (LBS) versus intra-oral scanner (IOS) with intra-oral scan bodies (ISB). METHODS: A printed 3D model with three internal hex analogs in the positions 15#,16#,17# was used. Zirkonzhan (ZZ) intra-oral scan body (ISB), two-piece titanium was used. The ZZ ISBs were scanned by 7 Series dental wings (LBS) and 30 times by Primescan (IOS) pre sterilization and 30 times post sterilization. For each scan (pre and post) stereolithography (STL) file was created and a comparison between all the scans pre sterilization and post sterilization were superimposed on the laboratory scan by using a 3D analyzing software. A Kolmogorov-Smirnov test performed followed by Wilcoxon Signed Ranks tests. (p < 0.05) Results: Post sterilization of the ZZ ISB, the mean errors were significantly increased for the inter-implant distances (p < 0.0005), intra-implant distances 1,2,3 (p < 0.0005), intra-implant axis 1,3 (p < 0.0005) and inter-implant axes 13,23 (p < 0.05). In contrast, the mean errors for intra-implant axis 2 (p < 0.0005) and inter-implant axis 12 (p < 0.0005) were significantly reduced. CONCLUSIONS: ZZ ISB showed changes in all four parameters after sterilization. The middle ISB had the largest changes in mean error regarding all four parameters. Sterilization process may affect the three-dimensional (3D) structure of the ZZ ISB after three cycles. There is a lack in the literature in this field and there is a need for further studies to explore the effect of sterilization (multiple cycles) on different ISBs and for creating an approved guidelines regarding the amount of sterilization for each ISB in the industry.