Interdisciplinary treatment for an adolescent with fusion of the left maxillary lateral and central incisors: A clinical report.

The interdisciplinary treatment provided for a 12-year-old boy with fusion of his left central and lateral incisors and concomitant distal space loss is described. His treatment was initiated with orthodontic therapy followed by endodontic treatment of the fused tooth. A conservative zirconia and porcelain cantilevered bonded fixed dental prosthesis was then completed to replace his left lateral incisor.

Clinical and cone beam computed tomography outcomes of maxillary anterior implant restorations after immediate implant placement with interim restorations: A 1- to 14-year retrospective analysis.

STATEMENT OF PROBLEM: Achieving and maintaining optimal tissue health and esthetics when immediately placing maxillary anterior implants with interim restorations has been challenging and the clinical outcomes heterogenous. PURPOSE: The purpose of this retrospective study was to evaluate the clinical outcomes of immediate placement of maxillary anterior implants with interim restorations and compare the tomographic and clinical results before and after implant placement in participants followed for 1 to 14 years. MATERIAL AND METHODS: Twenty participants receiving 25 postextraction single implants in the anterior maxilla were studied. Clinical parameters included pink esthetic score (PES) and white esthetic score (WES), peri-implant phenotype, implant probing, plaque index, and cone beam computed tomography (CBCT) to compare initial and at least 1 year after crown placement (postoperative). For qualitative variables, a descriptive analysis was carried out. The PES and WES results were analyzed by using nonparametric statistics, the median (ME) and the interquartile range (IQR) were used as summary measures, and the Wilcoxon sum of signs test was used to compare the total scores between the intervention area and the contralateral tooth. To compare pre- and postoperative data points, the paired t test was used (α=.05). RESULTS: Mean ±standard deviation (SD) time of follow-up was 7.6 ±4.2 years. Twenty participants with a mean ±SD age of 62.4 ±11.0 years old received 25 implants. Mean ±SD initial torque value at implant placement was 38.6 ±9.63 Ncm. Bone height at the top of the alveolar ridge (BH) and bone width at the middle of the alveolar ridge (BW2) showed a statistically significant decrease between the initial and subsequent CBCT measurements (both P<.001). Likewise, the bone width at the alveolar crest (BW1) showed a statistically significant decrease between the initial and post-CBCT measurements (P=.006). Facial bone integrity (FBI) revealed a statistically significant increase between the initial and postoperative time periods (P<.001). The PES index showed a median of 9.0 IQR (8-10), statistically lower than the contralateral tooth (P=.032). No significant differences were found for the WES index or for FBI, regardless of the peri-implant phenotype. CONCLUSIONS: Immediate implant placement in the maxillary anterior sextant was found to be a predictable procedure with good esthetic results when the protocol described was used. Labial bone loss is inevitable after tooth extraction but can be compensated for by filling the space with a xenograft material. Long-term gingival tissue integrity was maintained, regardless of phenotype, in periodontally healthy participants.

Evaluation of two implant-supported fixed partial denture abutment designs: Influence on screw surface characteristics.

PURPOSE: To compare screw surface characteristics between hemi-engaging and non-engaging implant-supported fixed partial denture (FPD) designs after cyclic loading. MATERIALS AND METHODS: Twenty-four implants measuring 4.3 × 10 mm were mounted on acrylic resin blocks. Specimens were divided into two groups. An experimental group included twelve 3-unit FPD with a hemi-engaging design; a control group included twelve 3-unit FPDs with the conventional design of two non-engaging abutments. Both groups were subjected to two types of cycling loading (CL), first axial loading, and then lateral loading at 30°. Load was applied to the units one million times (1.0 × 106 cycles) for each loading axis. Data on screw surface roughness in three locations and screw thread depth were collected before (BL) and after (AL) each loading type. Screw surface roughness was measured in µm using a mechanical digital surface profilometer and optical profiler. To evaluate screw thread depth in µm, an upright optical microscope Axio-imager 2 was used. To confirm readings made from the optical microscope, four random samples were selected from each group for scanning electron microscopy (SEM) analysis. The effect of cyclic loading was evaluated by averaging values across the two screws within each specimen, then calculating difference scores (DL) between BL and AL (DL = AL - BL). Additional difference scores were computed between the non-engaging screws in each experimental group specimen, and one randomly selected non-engaging screw in each control specimen. This difference was referred to as the non-engaging DL. Statistical significance was assessed using Mann-Whitney U tests (α = 0.05). RESULTS: Comparisons of DL and non-engaging DL by loading type revealed one significant difference regarding surface roughness at the screw thread. Significantly greater mean changes were observed after axial loading compared to lateral loading regarding both DL (axial M = -0.36 ± 0.08; lateral M = -0.21 ± 0.09; U = 20; p = 0.003) and non-engaging DL (axial M = -0.40 ± 0.22; lateral M = -0.21 ± 0.11; U = 29; p = 0.013). No significant differences in screw surface roughness in other sites or thread depth were found between the experimental and control abutment designs in DL or in non-engaging DL. No significant differences were found for DL (axial U = 13, p = 0.423; lateral U = 9, p = 0.150;) or non-engaging DL (axial U = 13, p = 0.423; lateral U = 18, p = 1.00). CONCLUSIONS: Results suggest that overall, changes in screw surface physical characteristics did not differ between hemi-engaging and non-engaging designs after evaluating screw surface roughness and thread depth before and after axial and lateral cyclic loading.

Peri-implantitis after 40 years: Evidence, mechanisms, and implications: A mapping review.

STATEMENT OF PROBLEM: The high prevalence of peri-implantitis (PI) continues to plague patients and the disease is resistant to present treatment regimens. An analysis of the available research is lacking. PURPOSE: Given the abundance and diversity of research on the topic of PI, the purpose of this mapping review was to synthesize the literature on the prevention of PI, the histopathology of the disease, the state of present therapeutics, and any emerging treatments. MATERIAL AND METHODS: An extensive literature search was undertaken by using the electronic databases of PubMed, Web of Science, and Science Direct. The keyword strings were peri-implantitis, dental implant, risk assessment, histopathology, prosthesis design, and treatment. The filters applied were time interval from 2000 to 2002; language, English. RESULTS: A total of 3635 articles were taken from PubMed, 3686 articles from Web of Science, and 2450 articles from Science Direct. After applying the inclusion and exclusion criteria to the titles and abstracts of selected investigations, 214 studies were retrieved. CONCLUSIONS: The evidence reflects a concerning incidence of PI, without a predictable treatment protocol. An in-depth patient risk assessment considering risk modification, emphasis on surgical and restorative expertise, and strict recall and maintenance is essential to minimize PI.

Preload evaluation of 2 implant-supported fixed partial denture abutment designs.

STATEMENT OF PROBLEM: A hemi-engaging abutment design has been suggested to improve the stability of the implant-to-abutment interface compared with that of a fully nonengaging design to restore implant-supported fixed partial denture. However, controversy persists regarding the benefit of using a hemi-engaging abutment design and prompts the need for specific mechanical testing on the effect of these designs on screw preload under simulated clinical conditions. PURPOSE: The purpose of this in vitro study was to determine whether significant differences in preload values of the screw before and after cyclic loading exist between hemi-engaging and nonengaging abutment fixed partial denture designs. MATERIAL AND METHODS: Twenty-four conical connection implants measuring 4.3×10 mm (Nobel Biocare Replace Conical Connection; Nobel Biocare) were mounted in acrylic resin blocks. Specimens were divided into 2 groups. An experimental group included 12 three-unit fixed partial dentures with a hemi-engaging design; a control group included 12 three-unit fixed partial dentures with the conventional design of 2 nonengaging abutments. A digital screw torque meter was used to measure screw torque values per the manufacturer's recommendation of 35 Ncm. Reverse torque value was measured before cyclic loading and referred to as initial preload. After cyclic loading, reverse torque value was measured and referred to as final preload. The effect of cyclic loading was evaluated by averaging the reverse torque value across the 2 screws in each specimen and then calculating the changes between the initial preload and final preload. The difference between initial and final preload was referred to as reverse torque difference. An additional reverse torque difference, referred to as reverse torque difference-nonengaging, was calculated for the nonengaging screws in each experimental specimen and for 1 randomly selected screw of the 2 in each control specimen. Preload efficiency before and after cyclic loading was also calculated. All groups went through cyclic loading using a universal testing machine. The specimens went through axial loading first, and then the reverse torque value was measured. Twenty-four new abutment screws were then used, and the specimens then went through lateral loading at 30 degrees. Load was applied to the units (1.0×106 cycles) for each loading axis. The statistical significance of differences between the axial and lateral reverse torque difference and between the 2 groups of reverse torque difference and reverse torque difference-nonengaging were assessed using Mann-Whitney U tests (α=.05). RESULTS: A comparison of reverse torque difference between loading types revealed no significant difference (P=.773). Therefore, data for the 2 loading types were combined before comparing the reverse torque difference and reverse torque difference-nonengaging values between the 2 groups based on abutment design (12 hemi-engaging designs in the experimental group and 12 fully nonengaging designs in the control group). The experimental group mean reverse torque difference was -0.65 ±1.95 Ncm (range -4.0 to 2.4 Ncm), and the control group mean reverse torque difference was -2.5 ±5.44 Ncm (range -15.3 to 5.3 Ncm). No significant difference was found (P=.340). Furthermore, no significant difference was found between the reverse torque difference for the nonengaging screw in each of the 12 implants with a hemi-engaging design versus 1 randomly selected nonengaging screw in each of the 12 implants with a fully nonengaging design (P=.355). CONCLUSIONS: No significant difference was found in screw preload between a hemi-engaging and a full nonengaging 3-unit fixed partial denture supported by conical connection implant configurations before and after cyclic loading.

Effects of masticatory loading on bone remodeling around teeth versus implants: Insights from a preclinical model.

OBJECTIVES: Teeth connect to bone via a periodontal ligament, whereas implants connect to bone directly. Consequently, masticatory loads are distributed differently to periodontal versus peri-implant bone. Our objective was to determine how masticatory loading of an implant versus a tooth affected peri-implant versus periodontal bone remodeling. Our hypothesis was that strains produced by functional loading of an implant would be elevated compared with the strains around teeth, and that this would stimulate a greater degree of bone turnover around implants versus in periodontal bone. MATERIALS AND METHODS: Sixty skeletally mature mice were divided into two groups. In the implant group, maxillary first molars (mxM1) were extracted, and after socket healing, titanium alloy implants were positioned subocclusally. After osseointegration, implants were exposed, resin crowns were placed, and masticatory loading was initiated. In the control group, the dentition was left intact. Responses of peri-implant and periodontal bone were measured using micro-CT, histology, bone remodeling assays, and quantitative histomorphometry while bone strains were estimated using finite element (FE) analyses. CONCLUSIONS: When a submerged osseointegrated implant is exposed to masticatory forces, peri-implant strains are elevated, and peri-implant bone undergoes significant remodeling that culminates in new bone accrual. The accumulation of new bone functions to reduce both peri-implant strains and bone remodeling activities, equivalent to those observed around the intact dentition.

A custom screw-retained implant-supported prosthesis for a patient with amelogenesis imperfecta: An 8-year clinical follow-up.

This clinical report with an 8-year follow-up describes the multidisciplinary management of a patient diagnosed with amelogenesis imperfecta. The rehabilitation included horizontal-guided bone regeneration, implant placement, use of a fixed interim prosthesis to preview the correction of occlusal disharmonies, and placement of a custom screw-retained definitive implant-supported restoration with a design that was retrievable and minimized maintenance problems.

Are teeth superior to implants? A mapping review.

STATEMENT OF PROBLEM: There is a long-held assumption that teeth are superior to implants because the periodontal ligament (PDL) confers a preeminent defense against biologic and mechanical challenges. However, adequate analysis of the literature is lacking. As a result, differential treatment planning of tooth- and implant-supported restorations has been compromised. PURPOSE: Given an abundance and diversity of research, the purpose of this mapping review was to identify basic scientific gaps in the knowledge of how teeth and implants respond to biologic and mechanical loads. The findings will offer enhanced evidence-based clinical decision-making when considering replacement of periodontally compromised teeth and the design of implant prostheses. MATERIAL AND METHODS: The online databases PubMed, Science Direct, and Web of Science were searched. Published work from 1965 to 2020 was collected and independently analyzed by both authors for inclusion in this review. RESULTS: A total of 108 articles met the inclusion criteria of clinical, in vivo, and in vitro studies in the English language on the periradicular and peri-implant bone response to biologic and mechanical loads. The qualitative analysis found that the PDL's enhanced vascularity, stem cell ability, and resident cells that respond to inflammation allow for a more robust defense against biologic threats compared with implants. While the suspensory PDL acts to mediate moderate loads to the bone, higher compressive stress and strain within the PDL itself can initiate a biologic sequence of osteoclastic activity that can affect changes in the adjacent bone. Conversely, the peri-implant bone is more resistant to similar loads and the threshold for overload is higher because of the absence of a stress or strain sensitivity inherent in the PDL. CONCLUSIONS: Based on this mapping review, teeth are superior to implants in their ability to resist biologic challenges, but implants are superior to teeth in managing higher compressive loads without prompting bone resorption.

Effects of Occlusal Scheme on All-on-Four Abutments, Screws, and Prostheses: A Three-Dimensional Finite Element Study.

An ideal occlusal scheme plays an important role in a good prognosis of All-on-Four applications, as it does for other implant therapies, because of the potential impact of occlusal loads on implant prosthetic components. The aim of the present 3D finite element analysis (FEA) study was to investigate the stresses on abutments, screws, and prostheses that are generated by occlusal loads via different occlusal schemes in the All-on-Four concept. 3D models of the maxilla, mandible, implants, implant substructures, and prostheses were designed according to the All-on-Four concept. Forces were applied from the occlusal contact points formed in maximum intercuspation and eccentric movements in canine guidance occlusion (CGO), group function occlusion (GFO), and lingualized occlusion (LO). The von Mises stress values for abutment and screws and deformation values for prostheses were obtained, and results were evaluated comparatively. It was observed that the stresses on screws and abutments were more evenly distributed in GFO. Maximum deformation values for prosthesis were observed in the CFO model for lateral movement both in the maxilla and mandible. Within the limits of the present study, GFO may be suggested to reduce stresses on screws, abutments, and prostheses in the All-on-Four concept.

Mechano-adaptive Responses of Alveolar Bone to Implant Hyper-loading in a pre-clinical in vivo model.

OBJECTIVES: Oral implants transmit biting forces to peri-implant bone. In turn, those forces subject peri-implant bone to mechanical stresses and strains. Here, our objective was to understand how peri-implant bone responded to conditions of normal versus hyper-loading in a mouse model. MATERIAL AND METHODS: Sixty-six mice were randomly assigned to 2 groups; both groups underwent bilateral maxillary first molar extraction followed by complete healing. Titanium alloy implants were placed in healed sites and positioned below the occlusal plane. After osseointegration, a composite crown was affixed to the implant so masticatory loading would ensue. In controls, the remaining dentition was left intact but in the hyper-loaded (test) group, the remaining molars were extracted. 3D finite element analysis (FEA) calculated peri-implant strains resulting from normal and hyper-loading. Peri-implant tissues were analyzed at multiple time points using micro-computed tomography (µCT) imaging, histology, enzymatic assays of bone remodeling, and vital dye labeling to evaluate bone accrual. RESULTS: Compared to controls, hyper-loaded implants experienced a 3.6-fold increase in occlusal force, producing higher peri-implant strains. Bone formation and resorption were both significantly elevated around hyper-loaded implants, eventually culminating in a significant increase in peri-implant bone volume/total volume (BV/TV). In our mouse model, masticatory hyper-loading of an osseointegrated implant was associated with increased peri-implant strain, increased peri-implant bone remodeling, and a net gain in bone deposition. CONCLUSION: Hyper-loading results in bone strain with catabolic and anabolic bone responses, leading to a net gain in bone deposition.

Has zirconia made a material difference in implant prosthodontics? A review.

OBJECTIVE: The main goal of this review is to provide an in-depth description of published work on the application of zirconia for dental implansts and restorations on titanium implants, with an emphasis on clinical studies from the past dozen years with at least 1-year follow-up. METHODS: Online databases (Pubmed, Science Direct, Web of Science) were consulted on this topic. Published work from 2007 to 2019 was collected, analyzed and pertinent articles were selected for inclusion on this review. RESULTS: No clear superiority has been documented in biocompatibility, osteoconductivity, physical properties or allergenicity with zirconia implants compared to titanium, notwithstanding an esthetic benefit. While short-term studies have been promising, larger multicentered, longitudinal and randomized clinical trials with success data are required to validate zirconia as a viable alternative to the titanium implant and its design. Zirconia abutments with a titanium base have revealed a high survival rate and show no difference to metal. Bi-layered zirconia ceramic restorations are a valid treatment alternative to metal ceramic implant restorations for single crowns with similar biological complications and enhanced esthetics. Monolithic zirconia restorations hold promise to address the chipping incidence of the bi-layered ceramic restoration, but longer-term studies are necessary, and work needs to be done to improve their esthetics. The gingival feldspathic porcelain veneered monolithic zirconia complete arch prosthesis versus a resin metal prosthesis, in medium-term studies, offers a high survival rate and low mechanical complication rate, reduced laboratory costs, superior durability and wear characteristics, enhanced fit due to digital fabrication, availability of a digital file for duplication in the future, acrylic try-for adjustment and approval, and reduced plaque and biofilm accumulation. SIGNIFICANCE: Zirconia is a versatile material for implant prosthodontic application. Longer-term multi-centered studies are needed to assess success criteria and patient-related outcomes measurements. Monolithic zirconia offers enhanced mechanical properties for implant restorations, but development is needed to optimize esthetics.