The International journal of oral & maxillofacial implants最新文献

Purpose: The purpose of this study was to examine and compare the strain distribution around long and short implant mandibular overdentures retained either by ball or self-aligning stud (Positioner) attachments.

Material and methods: Two completely edentulous mandibular models made of epoxy resin were used with implants placed equidistantly in the canine region. In the first model, two long implants were inserted, while two short implants were inserted in the second model. Two attachment mechanisms were examined for each model. A total of twentyfour identical mandibular overdentures were constructed and divided into two groups for each model (n = 12). Each model had two subgroups: ball attachments (n = 6) and Positioner attachments (n = 6). Two linear strain gauges were bonded to the epoxy at their corresponding prepared sites around each implant, where the microstrain was measured under bilateral and unilateral vertical loads of 100N. One-way ANOVA with post-hoc pairwise comparison and an independent t-test were used to analyze the microstrain value data (α =.05).

Results: When comparing ball and Positioner attachments, the Positioner showed significantly higher microstrain than the ball attachment (P <0.001) for both bilateral and unilateral loading. When long and short implants were compared, no statistically significant difference was found in bilateral loading (P = 0.22) or unilateral loading (P = 0.19; P = 0.16) on both loading and nonloading sides.

Conclusions: A higher strain distribution around implants was induced by the Positioner attachment compared to the ball attachment, regardless of the implant length. Increasing the implant length was not advantageous. Thus, the use of short implants for retaining mandibular overdentures can be a viable alternative treatment option.

Purpose: To investigate the effect of basis images' number (BI) and metal artifact reduction (MAR) on artifact's expression and trabecular bone architecture assessment in a medullary bone area close to a zirconium implant placed in different mandibular regions on CBCT.

Materials and methods: CBCT volumes were acquired using the Picasso Trio unit with a zirconium implant placed individually in either the anterior or posterior mandibular region, both with and without MAR, under two scanning modes: normal (450 BI) and high (720 BI). To measure the standard deviation (SD) of gray values, a region of interest was placed mesial to the zirconium implant fixture area for artifact's assessment. For trabecular bone architecture analysis, a volume of interest was established in the same area. The fractal dimension (FD), connectivity density (Conn. Dn.), trabecular thickness (Tb. Th.), and trabecular spacing were calculated.

Results: The zirconium implant fixture increased the SD of gray values, especially in the posterior region without MAR, while activating MAR reduced these values regardless of the scanning mode (P < .05). The number of BI generally had no impact on SD (P > .05), except in the posterior region without MAR, where the normal scanning mode showed higher SD (P < .05). Implant presence reduced FD and Conn. Dens. in the posterior region, although this effect was less pronounced with MAR enabled (P < .05). In the control group, overall, high scanning mode reduced FD and Conn. Dens (P < .05), with minimal effect on Tb. Th. and Tb. Sp (P > .05).

Conclusions: The zirconium implant fixture increased artifact expression, particularly in the posterior mandibular region without MAR, which also resulted in decreased FD and Conn. Dens. While increasing the number of basis images had little effect on the parameters, MAR minimized artifact expression and the reductions in FD and Conn. Dens.

Values:

Objective: To report the implant survival rates, clinical, and radiographic outcomes following a duration of over five years in the function of 2 immediately placed implants supported by a short-span fixed partial denture (FPD) in the anterior mandible.

Materials and methods: 100 individuals with immediately placed 2 implants (n=200) to support a 4-unit FPD in the lateral incisor's region of the mandible for long-term functional life with different loading protocols were chosen for this research. The participants were divided into 3 groups according to loading protocol after implant placement. Plaque index (PI), bleeding on probing (BOP), probing depth (PD), radiographic crestal bone level (CBL) and implant survival rate were evaluated.

Results: Three implants failed out of 200. Seven years was the average years that the implants were in function, and the overall survival rate was 98.5%. The mean PI was 24.86 in group I, 24.45 in group ΙΙ, and 24.77 in group ΙΙΙ. Group Λ had a mean BOP of 29.48, group ΙΙ had a mean BOP of 29.03, and group ΙΙΙ had a mean BOP of 29.12. For group Ι, the mean PD was 2.03; for group ΙΙ, it was 2.09; and for group ΙΙΙ, it was 2.11. For group Ι, the mean radiographic CBL was 1.69; for group ΙΙ, it was 1.56; and for group ΙΙΙ, it was 1.57. There was no significant difference among the 3 groups regarding PI, BOP, PD, CBL, and implant survival.

Conclusions: Within the limitations of this retrospective study, immediate loading protocol of immediately placed dental implants in the mandibular lateral incisor's region is a reliable dental rehabilitation choice and represents a valid alternative to the traditional delayed loading rehabilitation.

Clinical significance: Immediate implant placement and immediate loading protocol can be advantageous for both patients and physicians. It can save costs and treatment times, and it might be a good alternative for patients who have high aesthetic standards for their anterior mandible.

Purpose: This study compared three-dimensional (3D) accuracy of conventional and digital workflows in the fabrication of implant FAFDP frameworks for an edentulous mandible.

Materials and methods: A heat-polymerized polymethyl-methacrylate master model simulated an edentulous mandible to be restored with a fixed prosthesis supported by five implants (A-E). A conventional open-tray, splinted-coping polyether impression was poured with Type IV dental stone to produce a stone model, which was scanned with a dental laboratory scanner to produce a virtual model. Full-contour (ZFC, n=5) and cutback (ZCB, n=5) zirconia frameworks were fabricated with CAD/CAM. The stone model was used as a working model to fabricate conventional noble metal frameworks (CNB, n=5). Each test framework was attached to five implants with 35Ncm torque application. Test models were fabricated with Type IV dental stone and allowed to set completely before removing the test frameworks. Centroid positions and central axes of the implants in master and test models were measured with a coordinate measuring machine and compared. The local coordinate system comprised of implant A centroid as origin; implants A, C, E as XY-plane; implants A, E as X-axis. Four linear distortion parameters (dx, dy, dz, dR), two angular distortion parameters (dθx, dθy), and 3D distance distortion values (ΔR, %ΔR) were assessed.

Results: Magnitude of mean dx, dy, dz, and dR ranged from 39.9±26.4μm (CNB-B) to 263.3±94.6μm (CNB-E), from 56.9±5.4μm (ZFC-B) to 124.5±37.6μm (ZCB-C), from -8.3±27.6μm (ZFCD) to -24.6±17.3μm (ZCB-D), and from 80.6±29.4μm (CNB-B) to 263.3±94.6μm (CNB-E) respectively. Magnitude of mean dθx and dθy ranged from 0.025±0.486 degree (ZFC-C) to 1.490±0.383 degree (CNB-C), and from -0.050±0.171 degree (ZCB-B) to 1.263±0.501 degree (ZFC-C) respectively. One-way ANOVA found differences among groups for dx, dy, dz, dθx, and dθy at some implants, but there was no clear pattern on the poorest group. For global linear distortion, CNB-D fared the worst. CNB exhibited the worst accuracy in ΔR and %ΔR for all reference distances except A-E.

Conclusions: There were no differences between ZFC and ZCB for all parameters. CNB fared poorest for ΔR and %ΔR for three of four reference distances, and for dR for one of four implant positions.

Purpose: Regenerative hard or soft tissue augmentation procedures (ReP) are crucial in dental implant therapy. This study evaluates the frequency, timing, and financial implication of these procedures before and after implant placement, alongside the influence of systemic conditions on the need for additional interventions.

Materials and methods: This cohort included patients who received implants with or without ReP at the University of Michigan Graduate School of Dentistry from 2011-2023. Data on demographics and systemic health conditions were collected and analyzed using univariable and multivariable logistic regression.

Results: 4,803 patients (10,247 implants) were included-48.9% of the patients and 21.7% of the implants received at least one ReP. Ancillary ReP was needed for 14.7% of the implants. The most common of these was alveolar ridge augmentation (ARA) simultaneous with implant placement (42.1%) and alveolar ridge preservation (ARP) (26.4). Diabetics showed significantly higher odds of repeating procedures pre-implant (OR=5.47; p=0.016) and required more frequent hard tissue augmentations post-implant (OR=3.58; p=0.006). Cost analysis revealed that ReP constituted 12.9% of the total implant procedure cost. Notably, the mandibular anterior area was the most likely to undergo ReP (OR=2.08; p=0.001).

Conclusions: One of every two patients received a ReP. Almost half of these patients received ARA (simultaneous or staged), and 1/4 received ARP. Diabetic patients exhibited significantly higher odds of requiring hard tissue augmentation pre-IP and post-IP. Trends showed a shift towards soft tissue augmentation over hard tissue procedures for managing peri-implant deficiencies.

Purpose: To evaluate multiple risk factors for peri-implant bone loss via a statistical analysis with a multivariate logistic regression model to provide recommendations for clinical treatment.

Materials and methods: This case-control study was conducted on patients who had received dental implant treatment from January 2018 to December 2021. Patients who had implants with bone loss were included in the case group, and patients who had implants with no bone loss were included in the control group. The following risk factors were evaluated: history of periodontitis, abutment connection type, implant surface type, implant diameter, implant location, implant 3D position, opposing dentition, adjacent teeth, prosthetic type, retention type, and the use of custom abutments. A multivariate logistic regression model was used to evaluate these risk factors, providing corresponding odds ratios (ORs) and 95% 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 non-platform-switched designs (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 demonstrated to be 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.

Conclusions: Implants in the molar region, cement-retained prostheses, non-platform-switched designs, and poor 3D implant positioning were identified as significant risk factors for peri-implant bone loss.

Purpose: To compare the prosthetic outcomes of screw-retained monolithic zirconia (Zr) single crowns supported by either narrow-diameter (3.3 mm) or standard-diameter (4.1 mm) tissue-level titanium-zirconia (TiZr) implants in posterior sites.

Materials and methods: A total of 18 participants, each with a missing molar or premolar tooth requiring an implantsupported single crown, were randomly assigned to either the test or control group. All participants received screwretained monolithic Zr single crowns supported by single tissue-level TiZr implants. Test group participants received narrow-diameter implants (3.3 mm), whereas control group participants received standard-diameter implants (4.1 mm). A modified version of the United States Public Health Service (USPHS) criteria was used to assess the prosthetic outcome across 12 parameters after 1 year of function. Data were analyzed descriptively, and statistical analysis was performed using a statistical software (SPSS, Version 28.0; IBM) with the level of significance set at P < .05.

Results: Of the 18 single crowns delivered, 16 were available for review at the 1-year follow-up, including 7 in the test group and 9 in the control group. Patient characteristics and crown site distribution were similar, with no significant differences observed between the two groups (chi-square test; P < .05). There were no crown failures, meaning a crown survival rate of 100% was achieved after 1 year. The prosthetic outcome based on USPHS criteria was comparable between the two groups with no significant differences observed (chi-square test; P < .05). There were 19 prosthetic events in total (10 in the test group and 9 in the control group), with no significant differences between the groups (chi-square test; P < .05). Loss of proximal contact was the dominant event, with a total of eight events (three in the test group and five in the control group). Patient satisfaction after 1 year was high in both treatment groups, with no significant differences detected.

Conclusions: Screw-retained monolithic Zr single crowns supported by either narrow- or standard-diameter tissue-level TiZr implants in posterior sites have comparable prosthetic outcomes after 1 year. Long-term results from well-designed trials are still needed to validate the findings of the present study.

Purpose: To assess whether (and to what extent) average torque readings evaluating the bone density of polyurethane foam blocks and bovine ribs are correlated with that of gray values (GVs) measured via CBCT scans, both at the site of reading and at adjacent sites where bone is expected to engage the implant threads.

Materials and methods: Average torque readings were collected on blocks and ribs via CBCT scans that were then analyzed to measure the GVs of purposedly designed regions of interest (ROIs). The ROIs were shaped as concentric hollow cylinders centered on the sites of average torque measurements. The relation between average torque and GVs was investigated through correlation analyses.

Results: The correlation between average torque and GVs from blocks was strong (r = 0.94, r2 = 0.89, P < .001), which was independent of the ROI size. On the bovine ribs, the correlation was weak but significant (r = 0.23, P = .029); however, it become stronger when denser bone (average torque ≥ 7 Ncm) was tested (r = 0.41, P = .008). This result was independent from the distance of the site where the average torque had been read. Loss of average torque-GV interchangeability observed on bovine ribs was likely caused by intrinsic bone characteristics, such as an abundance of bone marrow and nonmineralized tissue, possibly having a confounding effect on GV measurements, especially at lower bone densities.

Conclusions: Within the limitations of the study, average torque values were found to estimate physical bone density just as well as GVs from CBCT scans. In low-density bone, the assessment of mineral bone density was also found to possibly be more informative than GVs. Results of this study suggest that the micromotor may be presently regarded as a complementary tool to CBCT assessment of bone density and quality in the clinical setting.

Principal component analysis (PCA) is a statistical tool that condenses the information contained in a large group of independent variables to a more manageable number of variables. This is useful when performing an analysis on data sets with a large number of variables. PCA restructures the original independent variables into new variables called principal components that maximize the information present in the data. The principal components then act as a substitute for the independent variables in an analysis. The purpose of this article is to present PCA in an understandable way for researchers without advanced statistical and mathematical backgrounds. To solidify the comprehension of the process and provide a template for researchers, we present an extended step-by-step example of PCA in use on a fictitious peri-implantitis data set.