Abutment screw loosening in angulation-correcting implants: An in vitro study.

STATEMENT OF PROBLEM: Techniques that allow angulation correction for screw-retained implant-supported restorations are now available. However, whether angulation correction built into the head of the implant affects abutment screw loosening is unclear. PURPOSE: The purpose of this in vitro study was to assess abutment screw loosening in angulation-correcting implants and straight implants subjected to simulated nonaxial occlusal loading. MATERIAL AND METHODS: Seven external connection 12-degree angulation-correcting implants and 7 straight implants were embedded in an acrylic resin housing, and titanium abutments were secured with titanium screws tightened to 32 Ncm. Each specimen was secured in a tooth wear machine and subjected to 1 000 000 cycles of 50-N nonaxial load to simulate 1 year of clinical service. The mean abutment screw removal torque values were calculated, and the association between number of cycles and the abutment screw removal torque was analyzed using a linear mixed-effects model and statistical software (α=.05) RESULTS: The mean abutment screw torque loss was 59.8% for the angulation-correcting implant group and 68.7% for the straight implant group. A statistically significantly greater mean abutment screw removal torque was recorded in the angulation-correcting implant group compared with the straight implant group after 1 000 000 cycles (P=.019). CONCLUSIONS: A significant loss of abutment screw torque was found in both implant groups with increased cycles of occlusal loading. The angulation-correcting implants resisted screw loosening significantly more than the straight implants because of the reduced angle of abutment screw loading.

Dental Implant Length and Diameter: A Proposed Classification Scheme.

PURPOSE: To propose a length-and-diameter-based classification scheme for dental implants to standardize terminology in the dental literature and communication between interested parties. MATERIALS AND METHODS: This study was mainly based on searching two major resources: published scientific research papers and 14 of the most popular dental implant manufacturers. Indexed databases were searched from January 2004 up to and including February 2016 using the keywords "dental implant length" and "dental implant diameter." Retrieved titles and abstracts were screened, and related full-text articles were reviewed. Full-text articles that clearly stated the terms and measurements of implants used were included and considered for proposing this classification scheme. RESULTS: The initial search for implant diameter and length yielded 1007 and 936 articles, respectively. A total of 85 studies (41 about diameter, 44 about length) were selected and reviewed. The remaining studies (966 about diameter, 892 about length) that did not abide by the eligibility criteria were excluded. The terms "long," "short," "standard," "wide," and "narrow" were the most commonly used terms in the literature. A classification scheme for implants by diameter and length was proposed. CONCLUSIONS: Indexed publications contain a variety of terms used by authors to describe diameter and length of dental implants without conformity and standardization. The classification scheme proposed in this article could serve as a reference for interested parties.

Biomechanical evaluation of one-piece and two-piece small-diameter dental implants: In-vitro experimental and three-dimensional finite element analyses.

BACKGROUND/PURPOSE: Small-diameter dental implants are associated with a higher risk of implant failure. This study used both three-dimensional finite-element (FE) simulations and in-vitro experimental tests to analyze the stresses and strains in both the implant and the surrounding bone when using one-piece (NobelDirect) and two-piece (NobelReplace) small-diameter implants, with the aim of understanding the underlying biomechanical mechanisms. METHODS: Six experimental artificial jawbone models and two FE models were prepared for one-piece and two-piece 3.5-mm diameter implants. Rosette strain gauges were used for in-vitro tests, with peak values of the principal bone strain recorded with a data acquisition system. Implant stability as quantified by Periotest values (PTV) were also recorded for both types of implants. Experimental data were analyzed statistically using Wilcoxon's rank-sum test. In FE simulations, the peak value and distribution of von-Mises stresses in the implant and bone were selected for evaluation. RESULTS: In in-vitro tests, the peak bone strain was 42% lower for two-piece implants than for one-piece implants. The PTV was slightly lower for one-piece implants (PTV = -6) than for two-piece implants (PTV = -5). In FE simulations, the stresses in the bone and implant were about 23% higher and 12% lower, respectively, for one-piece implants than those for two-piece implants. CONCLUSION: Due to the higher peri-implant bone stresses and strains, one-piece implants (NobelDirect) might be not suitable for use as small-diameter implants.

Immediate rehabilitation of the posterior maxilla with extensive sinus pneumatization with one axial and one trans-sinus tilted implant: a 3-year clinical report and a classification.

Implant rehabilitation of the posterior maxilla can entail difficulties due to reduced bone quantity and poor bone quality, especially after long-term edentulism. In some patients, multiple surgeries are necessary, which may lead to higher patient morbidity and longer treatment times before a prosthetic rehabilitation can be achieved. This article presents an immediate fixed prosthesis in a posterior atrophic maxilla supported by 1 anterior axial implant and 1 posterior tilted fixture placed with an intrasinus insertion. Additionally, a classification scheme for immediate treatment for the posterior maxilla based on the available residual bone is provided.

Complete arch site classification for all-on-4 immediate function.

Complete arch immediate function of dental implants requires a treatment protocol that takes advantage of residual areas of cortical bone for the apical fixation of implants. A site and jaw bone classification is proposed that has been in use since 2006 for all stages of atrophy for both jaws. The use of the classification is strictly for immediate function based on specific cortical bone sites in the facial skeleton to assist practitioners in diagnosis, treatment planning, and interdisciplinary communication, as well as to reduce human error in patient management. A recent series of 100 consecutive arches that were treated according to this classification is presented.

Dental devices; reclassification of blade-form endosseous dental implant. Final order.

The Food and Drug Administration (FDA) is issuing a final order to reclassify the blade-form endosseous dental implant, a preamendments class III device, into class II (special controls). On its own initiative, based on new information, FDA is revising the classification of blade-form endosseous dental implants.

TADs: an evolutionary road to success.

UNLABELLED: This is a literature search about the clinical use of temporary anchorage devices (TADs) as a means of providing effective orthodontic anchorage. It takes the reader through a journey from the initial description of the technique to the enormous popularity TADs are currently experiencing in clinical practice. This paper aims to present good quality clinical information to allow the clinician and the patient to make an informed decision. CLINICAL RELEVANCE: The purpose of this literature review is to provide readers with an overview of the current available literature on this subject and encourage general dental practitioners to adopt a more evidence-based approach to this aspect of orthodontic care.

A robust deep learning model for the classification of dental implant brands.

OBJECTIVE: In cases where the brands of implants are not known, treatment options can be significantly limited in potential complications arising from implant procedures. This research aims to explore the application of deep learning techniques for the classification of dental implant systems using panoramic radiographs. The primary objective is to assess the superiority of the proposed model in achieving accurate and efficient dental implant classification. MATERIAL AND METHODS: A comprehensive analysis was conducted using a diverse set of 25 convolutional neural network (CNN) models, including popular architectures such as VGG16, ResNet-50, EfficientNet, and ConvNeXt. The dataset of 1258 panoramic radiographs from patients who underwent implant treatment at faculty of dentistry was utilized for training and evaluation. Six different dental implant systems were employed as prototypes for the classification task. The precision, recall, F1 score, and support scores for each class have included in the classification accuracy report to ensure accurate and reliable results from the model. RESULTS: The experimental results demonstrate that the proposed model consistently outperformed the other evaluated CNN architectures in terms of accuracy, precision, recall, and F1-score. With an impressive accuracy of 95.74 % and high precision and recall rates, the ConvNeXt model showcased its superiority in accurately classifying dental implant systems. Notably, the model's performance was achieved with a relatively smaller number of parameters, indicating its efficiency and speed during inference. CONCLUSION: The findings highlight the effectiveness of deep learning techniques, particularly the proposed model, in accurately classifying dental implant systems from panoramic radiographs.

Miniscrew implants as temporary anchorage devices in orthodontics: a comprehensive review.

In recent times, the use of miniscrew implants to obtain absolute anchorage has gained momentum in clinical orthodontics as rigid anchorage modality. Miniscrew implants offers many advantages when used as temporary anchorage devices like, easy placement and removal, immediate loading, can be used in a variety of locations, provide absolute anchorage, economic and requires less patient cooperation. This makes them as a necessary treatment option in cases with critical anchorage that would have otherwise resulted in anchorage loss if treated with conventional means of anchorage. The aim of this comprehensive review is to highlight the gradual evolution, clinical use, advantages and disadvantages of the miniscrew implants when used to obtain a temporary but absolute skeletal anchorage for orthodontic applications.

Regular and platform switching: bone stress analysis varying implant type.

PURPOSE: This study aimed to evaluate stress distribution on peri-implant bone simulating the influence of platform switching in external and internal hexagon implants using three-dimensional finite element analysis. MATERIALS AND METHODS: Four mathematical models of a central incisor supported by an implant were created: External Regular model (ER) with 5.0 mm × 11.5 mm external hexagon implant and 5.0 mm abutment (0% abutment shifting), Internal Regular model (IR) with 4.5 mm × 11.5 mm internal hexagon implant and 4.5 mm abutment (0% abutment shifting), External Switching model (ES) with 5.0 mm × 11.5 mm external hexagon implant and 4.1 mm abutment (18% abutment shifting), and Internal Switching model (IS) with 4.5 mm × 11.5 mm internal hexagon implant and 3.8 mm abutment (15% abutment shifting). The models were created by SolidWorks software. The numerical analysis was performed using ANSYS Workbench. Oblique forces (100 N) were applied to the palatal surface of the central incisor. The maximum (σ(max)) and minimum (σ(min)) principal stress, equivalent von Mises stress (σ(vM)), and maximum principal elastic strain (ε(max)) values were evaluated for the cortical and trabecular bone. RESULTS: For cortical bone, the highest stress values (σ(max) and σ(vm) ) (MPa) were observed in IR (87.4 and 82.3), followed by IS (83.3 and 72.4), ER (82 and 65.1), and ES (56.7 and 51.6). For ε(max), IR showed the highest stress (5.46e-003), followed by IS (5.23e-003), ER (5.22e-003), and ES (3.67e-003). For the trabecular bone, the highest stress values (σ(max)) (MPa) were observed in ER (12.5), followed by IS (12), ES (11.9), and IR (4.95). For σ(vM), the highest stress values (MPa) were observed in IS (9.65), followed by ER (9.3), ES (8.61), and IR (5.62). For ε(max) , ER showed the highest stress (5.5e-003), followed by ES (5.43e-003), IS (3.75e-003), and IR (3.15e-003). CONCLUSION: The influence of platform switching was more evident for cortical bone than for trabecular bone, mainly for the external hexagon implants. In addition, the external hexagon implants showed less stress concentration in the regular and switching platforms in comparison to the internal hexagon implants.

New approach for immediate prosthetic rehabilitation of the edentulous mandible with three implants: a retrospective study.

BACKGROUND: Immediate/early prosthetic rehabilitation of the edentulous mandible with four or more implants for support of a fixed bridge is a well-documented procedure. Only a few studies have reported on the outcome of using three implants for this purpose. AIM: To retrospectively analyze the clinical outcome when using three implants for support of an immediately loaded fixed bridge in the totally edentulous mandible. MATERIALS AND METHODS: In total, 132 patients (67 females and 65 males, mean age 62.6 years, range 35-85 years) treated with 396 implants (Brånemark System) over an 11-year period in one clinic were retrospectively analyzed with regard to implant survival. Implants with both machined and oxidized surface had been used. Eighty percent of the implants were 13 mm in length or longer. The permanent bridge with acrylic teeth was delivered to the patient the same day. The patients were re-called annually for clinical examinations. RESULTS: All patients had been followed for at least 1 year, with the longest follow-up of 10 years and a mean follow-up of 5 years. Thirteen implant failures in 10 patients were experienced, all occurring during the first 12 months of loading. The overall survival rate was 96.7% for implants and 92.4% for original bridges. More machined than oxidized implants failed, 7% vs. 1.2%. Fourteen additional implants were placed at the time of removal of the failed implants when also the fixed bridge was adjusted on the same day. Thus, all patients received and maintained a fixed bridge, except for a few hours in the 10 failure cases when the bridges were adjusted. CONCLUSIONS: This retrospective survival analysis shows that three implants can be used to support a fixed bridge for immediate loading in the edentulous mandible. The study indicated that oxidized implants were more successful than machined ones.

Principal component analysis: a novel analysis to evaluate the characteristics of osseointegration of different implant surfaces.

OBJECTIVE: To apply a new statistical method (principle component analysis; PCA) to evaluate osseointegration. MATERIALS AND METHODS: Two different commercially available implants were selected for the study. Twenty implants, 10 of each type, were placed in the rabbit tibiae (n = 10). The fluorochromes (FLCs) alizarin complexone and calcein green were administered after 20 days and 4 days before sacrifice for labeling. On the day of implantation and retrieval (6 weeks), implant stability was measured with a resonance frequency analyzer (RFA). The retrieved samples were ground sectioned for histomorphometric and FLC quantification. The collected data were analyzed by a PCA software program (Qlucore Omics Explorer, Lund, Sweden) to explore and determine the correlation between different study variables and to analyze the differences between different implants. RESULTS: The RFA presented no significant differences at either time point. The bone-to-implant contact was significantly higher for the TiUnite (NobelBiocare, Gothenburg, Sweden); however, the bone area and FLC quantification showed higher values for the Osseotite (3i Implant Innovation, FL). Consistent with these results, the PCA indicated a strong correlation between TiUnite and high bone-to-implant contact values and between Osseotite and high bone area and FLC values. No correlation between RFA and the biological responses were found. CONCLUSION: The application of the PCA analysis may help interpret and correlate results obtained from numerous evaluations.

A meta-analysis indicating extra-short implants (≤ 6 mm) as an alternative to longer implants (≥ 8 mm) with bone augmentation.

Extra-short implants, of which clinical outcomes remain controversial, are becoming a potential option rather than long implants with bone augmentation in atrophic partially or totally edentulous jaws. The aim of this study was to compare the clinical outcomes and complications between extra-short implants (≤ 6 mm) and longer implants (≥ 8 mm), with and without bone augmentation procedures. Electronic (via PubMed, Web of Science, EMBASE, Cochrane Library) and manual searches were performed for articles published prior to November 2020. Only randomized controlled trials (RCTs) comparing extra-short implants and longer implants in the same study reporting survival rate with an observation period at least 1 year were selected. Data extraction and methodological quality (AMSTAR-2) was assessed by 2 authors independently. A quantitative meta-analysis was performed to compare the survival rate, marginal bone loss (MBL), biological and prosthesis complication rate. Risk of bias was assessed with the Cochrane risk of bias tool 2 and the quality of evidence was determined with the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. 21 RCTs were included, among which two were prior registered and 14 adhered to the CONSORT statement. No significant difference was found in the survival rate between extra-short and longer implant at 1- and 3-years follow-up (RR: 1.002, CI 0.981 to 1.024, P = 0.856 at 1 year; RR: 0.996, CI 0.968 to 1.025, P = 0.772 at 3 years, moderate quality), while longer implants had significantly higher survival rate than extra-short implants (RR: 0.970, CI 0.944 to 0.997, P < 0.05) at 5 years. Interestingly, no significant difference was observed when bone augmentations were performed at 5 years (RR: 0.977, CI 0.945 to 1.010, P = 0.171 for reconstructed bone; RR: 0.955, CI 0.912 to 0.999, P < 0.05 for native bone). Both the MBL (from implant placement) (WMD: - 0.22, CI - 0.277 to - 0.164, P < 0.01, low quality) and biological complications rate (RR: 0.321, CI 0.243 to 0.422, P < 0.01, moderate quality) preferred extra-short implants. However, there was no significant difference in terms of MBL (from prosthesis restoration) (WMD: 0.016, CI - 0.036 to 0.068, P = 0.555, moderate quality) or prosthesis complications rate (RR: 1.308, CI 0.893 to 1.915, P = 0.168, moderate quality). The placement of extra-short implants could be an acceptable alternative to longer implants in atrophic posterior arch. Further high-quality RCTs with a long follow-up period are required to corroborate the present outcomes.Registration number The review protocol was registered with PROSPERO (CRD42020155342).

A 3-year prospective radiographic evaluation of marginal bone level around different implant systems.

The aim of this study was to evaluate the change of marginal bone level radiographically around three different implant systems after 3 years in function. Fifty-four patients were included and randomly assigned to three treatment groups of rough-surface implants (TiUnite, n = 37), hybrid of smooth and rough-surface implants (Restore, n = 38) and rough surface with microthread implants (Hexplant, n = 45). Clinical and radiographic examinations were conducted at the time of implant loading (baseline), 1 and 3 years after loading. A three-level mixed-effect analysis of covariance (ancova) was used to test the significance of the mean marginal bone change of the three implant groups. A total 120 of 135 implants completed the study. None of the implants failed to integrate. Significant differences were noted in the marginal bone loss recorded for the three groups (P < 0.0001). At 3 years, the rough surface with microthread implants had a mean crestal bone loss of 0.59 +/- 0.30 mm; the rough-surface implants, 0.95 +/- 0.27 mm; and the hybrid surface implants, 1.05 +/- 0.34 mm. Within the limitations of this study, rough-surface implants with microthread at the coronal part might have a long-term positive effect in maintaining the marginal bone level against functional loading in comparison with implants without these two features.

Survey of United States dental schools on cementation protocols for implant crown restorations.

STATEMENT OF PROBLEM: With conflicting results in the literature and various manufacturer recommendations, it is not known what cementation protocols are currently being used for implant restorations in US dental schools. PURPOSE: The purpose of this survey was to determine what dental cementation protocols are taught and recommended by 62 US dental schools and postgraduate programs. MATERIAL AND METHODS: From February to September 2008, 96 questionnaires consisting of 8 questions were sent to the chairperson or director of restorative departments, advanced prosthodontics programs, and implant programs. The questionnaire asked recipients which implant manufacturers provided the products used at their dental schools. Additionally, recipients were queried as to the choice of material and techniques for abutment and restoration preparations prior to definitive cementation. Data were analyzed with descriptive statistics. RESULTS: A total of 68 (71%) surveys were returned, and 52 (84%) of the 62 predoctoral and postgraduate programs were represented. After deleting duplicate responses, 31 surveys were returned from restorative department chairpersons, 29 from advanced prosthodontic program directors, and 2 from implant program directors. Frequency of responses to each question was tabulated, and results are presented in 3 sections. For all 3 types of programs, Nobel Biocare was reported to be the most widely used implant system, followed by Biomet 3i, Straumann, Astra Tech, and Zimmer Dental systems. The most commonly used technique prior to definitive cementation is to airborne-particle abrade the intaglio surface of the restoration. Resin-modified glass ionomer is the most frequently used luting agent for cementing implant restorations. The 5 most commonly used materials to fill screw access openings are cotton pellets, composite resin, rubber-based material, gutta-percha, and light-polymerized provisional composite resin. Most predoctoral and postgraduate programs teach students to fill the screw access opening completely to the occlusal surface. CONCLUSIONS: There are a wide range of implant cementation protocols and materials used; however, some common trends were identified among predoctoral and postgraduate programs.

Potential of self-drilling orthodontic microimplants under immediate loading.

INTRODUCTION: The aim of this study was to investigate clinically and histologically the efficiency of self-drilling microimplants as orthodontic anchorage with immediate, continuous, and constant loadings. METHODS: Titanium-alloy microimplants with diameters of 1.2 to 1.3mm were manually placed into the buccal sides of both jaws, including the interradicular areas, in 3 dogs. Implants were placed without predrilling in thin cortical bone areas; in thick cortical bone areas, a 2-mm deep pilot hole was drilled. Thirty-six microimplants, subjected to approximately 200g of immediate horizontal loading, served as the study group. The remaining 8 received no loading and were the controls over the 9-week observation period. The distances of reciprocally loaded microimplants and crevicular pockets were measured at the beginning and end of loading. Serially undecalcified and decalcified sections of the microimplants and surrounding tissues were studied with light and fluorescent microscopes. After 9 weeks of observation, 22 fixtures were easily removed with a screwdriver. Two were broken, and 1 was movable. RESULTS: Histologic analysis showed good osseointegration in all stable samples, and new bone formation and bone apposition to the surface of the threads in loaded and unloaded samples. Histomorphometric evaluation showed high bone-to-implant contact values in the loaded samples, but no significant statistical differences from the unloaded ones. CONCLUSIONS: Titanium alloy microimplants with small diameters (1.2-1.3mm) are strong enough for self-drilling and immediate loading in thin cortical bone areas, but, to reduce the chance of breakage, a drilling of a pilot hole is suggested in thick cortical bone areas.

Treatment planning implant dentistry with a 2-mm twist drill.

Drilling with a 2-mm twist drill is the first time a clinician can assess variations in bone density for the length of bone where an implant will be placed. Evaluation of bone density is critically important with respect to making decisions regarding depth and width of an osteotomy, undersizing the drilling sequence, submerging vs not submerging an implant, supracrestal vs subcrestal implant placement, selecting a tapered vs nontapered implant, countersinking, platform switching, immediate loading, healing time, etc. This article addresses how information acquired with a 2-mm twist drill can affect treatment planning. In particular, this article underscores that the clinician must be prepared to alter drilling protocols based on tactile feedback from a 2-mm twist drill.

Deep Neural Networks for Dental Implant System Classification.

In this study, we used panoramic X-ray images to classify and clarify the accuracy of different dental implant brands via deep convolutional neural networks (CNNs) with transfer-learning strategies. For objective labeling, 8859 implant images of 11 implant systems were used from digital panoramic radiographs obtained from patients who underwent dental implant treatment at Kagawa Prefectural Central Hospital, Japan, between 2005 and 2019. Five deep CNN models (specifically, a basic CNN with three convolutional layers, VGG16 and VGG19 transfer-learning models, and finely tuned VGG16 and VGG19) were evaluated for implant classification. Among the five models, the finely tuned VGG16 model exhibited the highest implant classification performance. The finely tuned VGG19 was second best, followed by the normal transfer-learning VGG16. We confirmed that the finely tuned VGG16 and VGG19 CNNs could accurately classify dental implant systems from 11 types of panoramic X-ray images.

Comparative Analysis of Peri-Implant Bone Loss in Extra-Short, Short, and Conventional Implants. A 3-Year Retrospective Study.

OBJECTIVE: To evaluate the influence of implant length on marginal bone loss, comparing implants of 4 mm, 6 mm, and >8 mm, supporting two splinted crowns after 36-month functional loading. MATERIALS AND METHODS: this retrospective clinical trial evaluated the peri-implant behavior of splinted crowns (two per case) on pairs of implants of the same length placed in the posterior maxilla (molar area). Implants were divided into three groups according to length (Group 1: extra-short 4 mm; Group 2: short 6 mm; Group 3: conventional length >8 mm). Marginal bone loss was analyzed using standardized periapical radiographs at the time of loading and 36 months later. RESULTS: 24 patients (19 women and 5 men) were divided into three groups, eight rehabilitations per group, in the position of the maxillary first and second molars. The 48 Straumann® Standard Plus (Regular Neck (RN)/Wide Neck (WN)) implants were examined after 36 months of functional loading. Statistical analysis found no significant differences in bone loss between the three groups (p = 0.421). No implant suffered biological complications or implant loss. Long implants were associated with less radiographic bone loss. CONCLUSIONS: extra-short (4 mm); short (6 mm); and conventional length (>8 mm) implants in the posterior maxilla present similar peri-implant bone loss and 100% survival rates in rehabilitation, by means of two splinted crowns after 36 months of functional loading. Implants placed in posterior positions present better bone loss results than implants placed in anterior positions, regardless of the interproximal area where bone loss is measured. Conventional length (>8 mm) implants show better behavior in terms of distal bone loss than short (6 mm) and extra-short (4 mm) implants.

Marginal bone loss around bone-level and tissue-level implants: A systematic review and meta-analysis.

PURPOSE: To review the scientific evidence regarding the marginal bone loss around the tissue-level and bone-level implants. METHODS: MEDLINE-PubMed and EMBASE databases were searched for the relevant English articles (up to February 2019) assessing the marginal bone loss (MBL) as the primary outcome. To be selected, studies were supposed to directly mention "tissue-level" and "bone-level" implants or implants with and without a smooth neck. Relevant data were extracted and meta-analysis was performed to evaluate the effect of implant neck design. RESULTS: A total of 19 studies (10 clinical, and 9 RCT studies) were included for qualitative analysis. There was a vast heterogeneity between studies in terms of implant designs and study protocol. Out of 19 articles included, 11 studies reached to a statistically significant difference in MBL between the groups; however, the differences were not found to be clinically relevant. Bone-level implants with platform-switched abutments in most of the cases showed better marginal bone stability compared to tissue-level implants or bone-level implants with matching abutments. Seven RCTs with 12 months follow-up data were selected for meta-analysis (I2=93%; heterogeneous), and the results showed less MBL around bone-level implants compared to tissue-level group (WMD=-0.21mm; 95% CI -0.42, 0.00; P=0.06). CONCLUSION: The available data regarding comparison of MBL around bone-level and tissue-level implants are heterogeneous. Bone-level implants with platform switching may better preserve crestal bone.