Biomechanical influence of narrow-diameter implants placed at the crestal and subcrestal level in the maxillary anterior region. A 3D finite element analysis.

PURPOSE: To evaluate the tendency of movement, stress distribution, and microstrain of single-unit crowns in simulated cortical and trabecular bone, implants, and prosthetic components of narrow-diameter implants with different lengths placed at the crestal and subcrestal levels in the maxillary anterior region using 3D finite element analysis (FEA). MATERIALS AND METHODS: Six 3D models were simulated using Invesalius 3.0, Rhinoceros 4.0, and SolidWorks software. Each model simulated the right anterior maxillary region including a Morse taper implant of Ø2.9 mm with different lengths (7, 10, and 13 mm) placed at the crestal and subcrestal level and supporting a cement-retained monolithic single crown in the area of tooth 12. The FEA was performed using ANSYS 19.2. The simulated applied force was 178 N at 0°, 30°, and 60°. The results were analyzed using maps of displacement, von Mises (vM) stress, maximum principal stress, and microstrain. RESULTS: Models with implants at the subcrestal level showed greater displacement. vM stress increased in the implant and prosthetic components when implants were placed at the subcrestal level compared with the crestal level; the length of the implants had a low influence on the stress distribution. Higher stress and strain concentrations were observed in the cortical bone of the subcrestal placement, independent of implant length. Non-axial loading influenced the increased stress and strain in all the evaluated structures. CONCLUSIONS: Narrow-diameter implants positioned at the crestal level showed a more favorable biomechanical behavior for simulated cortical bone, implants, and prosthetic components. Implant length had a smaller influence on stress or strain distribution than the other variables.

Biomechanical effects of different materials for an occlusal device on implant-supported rehabilitation in a tooth clenching situation. A 3D finite element analysis.

PURPOSE: The purpose of this 3D finite element analysis was to evaluate the biomechanical effects of different materials used to fabricate occlusal devices to achieve stress distribution in simulated abutment screws, dental implants, and peri-implant bone tissue in individuals who clench their teeth. MATERIALS AND METHODS: Eight 3D models simulated a posterior maxillary bone block with three external hexagon implants (Ø4.0 × 7.0 mm) supporting a 3-unit screw-retained metal-ceramic prosthesis with different crown connection (splinting), and the use of an occlusal device (OD). The OD was modeled to be 2-mm thick. ANSYS 19.2 software was used to generate the finite-element models in the pre-and post-processing phases. Simulated abutment screws and dental implants were evaluated by von Mises stress maps, and simulated bone was evaluated by maximum principal stress and microstrain maps by using a finite element software program. RESULTS: The highest stress values in the dental implants and screws were observed in single crowns without OD (M1). Furthermore, the highest stress values and bone tissue strain were found in single crowns without OD (M1). The simulated material for the OD did not cause many discrepancies in terms of the stress magnitude in the simulated dental implant and abutment screw for both single and splinted crowns; however, more rigid materials exhibited lower stress values. CONCLUSION: The use of OD was effective in reducing stress in the simulated implants and abutment screws and stress and strain in the simulated bone tissue. The material used to simulate the OD influenced the biomechanical behavior of implant-supported fixed prostheses, whereas splints with rigid materials such as PEEK and PMMA exhibited better biomechanical behavior.

Biomechanical Evaluation of Different Implant-Abutment Connections, Retention Systems, and Restorative Materials in the Implant-Supported Single Crowns Using 3D Finite Element Analysis.

This is an in silico study aimed to evaluate the biomechanical influence of different implant-abutment interfaces (external hexagon and Morse taper implants), retention systems (cement and screw retained), and restorative crowns (metal-ceramic and monolithic) using 3-dimensional finite element analysis (3D-FEA). Eight 3D models were simulated for the maxillary first molar area using InVesalius, Rhinoceros, and SolidWorks and processed using Femap and NEi Nastran software. Axial and oblique forces of 200 and 100 N, respectively, were applied on the occlusal surface of the prostheses. Microstrain and von Mises stress maps were used to evaluate the deformation (cortical bone tissue) and stress (implants/fixation screws/crowns), respectively, for each model. For both loadings, Morse taper implants had lower microstrain values than the external hexagon implants. The retention system did not affect microstrain on the cortical bone tissue under both loadings. However, the cemented prosthesis displayed higher stress with the fixation screw than the external hexagon implants. No difference was observed between the metal-ceramic and zirconia monolithic crowns in terms of microstrain and stress distribution on the cortical bone, implants, or components. Morse taper implants can be considered as a good alternative for dental implant rehabilitation because they demonstrated better biomechanical behavior for the bone and fixation screw as compared to external hexagon implants. Cement-retained prosthesis increased the stress on the fixation screw of the external hexagon implants, thereby increasing the risk of screw loosening/fracture in the posterior maxillary area. The use of metal-ceramic or monolithic crowns did not affect the biomechanical behavior of the evaluated structures.

Oral prosthetic microbiology: aspects related to the oral microbiome, surface properties, and strategies for controlling biofilms.

The oral cavity is an environment that allows for the development of complex ecosystems; the placement of prosthetic devices as a consequence of partial or total tooth loss may alter the diversity of microbial communities. Biofilms on the surface of materials used in dental prostheses can promote important changes in the mechanic and aesthetic properties of the material itself and may cause local and systemic diseases for the prosthetic wearer. This review presents the main features of the oral microbiome associated with complete or partial dentures and dental implants. The main diseases associated with microbial colonization of prosthetic surfaces, factors that may affect biofilm formation on prosthetic materials, as well as novel alternative therapies aiming to reduce biofilm formation and/or to eradicate biofilms formed on these materials are also explored.

Is the Fixed Mandibular 3-Implant Retained Prosthesis Safe and Predicable for Full-Arch Mandibular Prostheses? A Systematic Review.

PURPOSE: To evaluate implant and prosthetic survival rates of full-arch rehabilitations retained by three implants in patients with edentulous mandibles. MATERIALS AND METHODS: This systematic review was developed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The focused question was: Are fixed mandibular 3-implant retained prostheses safe and predicable for full-arch mandibular prostheses? The Medline/PubMed and Cochrane Library databases were used to conduct the systematic search for clinical trials on fixed mandibular 3-implant retained prostheses published between 1999 and 2020. Only English-language studies that presented information on implant and prosthetic survival were included. RESULTS: A total of 302 studies were identified, of which 13 addressed the inclusion criteria. Additionally, 574 participants were included in these studies. As reported, 73 (4.57%) of 1596 implants failed, with a survival rate of 95.43%. In addition, the mean survival rate of the presented prostheses was 89.66%. The mean marginal bone loss was 1.09 mm. CONCLUSION: Within the limitations of the present review, implant and prosthetic survival rates of fixed mandibular 3-implant retained prostheses were similar to those of full-arch mandibular prostheses retained by four or more implants. Further research exploring the topic is necessary.

Ceramic versus metal-ceramic implant-supported prostheses: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: There is insufficient evidence to recommend the restorative material for implant-supported prostheses. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate studies that compared ceramic and metal-ceramic restorations for implant-supported prostheses (within the same study to avoid indirect comparison) in terms of the mechanical and biological complication rates, prosthesis survival rate, and marginal bone loss. MATERIAL AND METHODS: Two independent reviewers performed a comprehensive search in databases (PubMed/MEDLINE, Web of Science, and Cochrane Library) for articles indexed until March 31, 2018. The search was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and methods were registered in the International Prospective Register of Systematic Reviews (PROSPERO). The focused question was "Do ceramic restorations have mechanical/biological complication rates, prosthesis survival rates, and marginal bone loss similar to those of metal-ceramic restorations?" RESULTS: The search identified 949 references. The interinvestigator agreement using kappa values was 0.87 for PubMed/MEDLINE, 0.93 for Scopus, and 1.0 for the Cochrane Library. After analysis, 12 studies were selected for qualitative and quantitative analysis. The mechanical complication rate did not differ between ceramic and metal-ceramic restorations (P=.89), independent of the type of prostheses (single crown: P=.63; fixed partial denture: P=.65). The biological complication rate was also not significantly different between ceramic and metal-ceramic restorations (P=.21). The prosthesis survival rate showed no significant differences between the 2 types of restorations (P=.56). Marginal bone loss was also similar for both types of restorations (P=.12). CONCLUSIONS: This systematic review indicated that ceramic and metal-ceramic implant-supported prostheses have similar mechanical and biological complication rates, prosthesis survival rates, and marginal bone loss. Thus, both treatments are appropriate options for long-term rehabilitation treatment.

Use of Resin-Based Provisional Material to Create the Posterior Palatal Seal in Complete Denture Definitive Impressions.

The purpose of this article was to present an alternative procedure using resin-based provisional material to create the posterior palatal seal (PPS). This method offers more practicality in clinical routine and increased control for addition of material to create the PPS when compared to traditional techniques such as the use of impression wax.

Comparison of the Use of Titanium-Zirconium Alloy and Titanium Alloy in Dental Implants: A Systematic Review and Meta-Analysis.

The aim of this study was to compare the values of bone-implant contact (BIC) and removal torque (RTQ) reported in different animal studies for titanium-zirconium (TiZr) and titanium (Ti) dental implants. This review has been registered at PROSPERO under number CRD42016047745. We undertook an electronic search for data published up until November 2017 using the PubMed/Medline, Embase, and The Cochrane Library databases. Eligibility criteria included in vivo studies, comparisons between Ti and TiZr implants in the same study, and studies published in English that evaluated BIC and RTQ. After inclusion criteria, 8 studies were assessed for eligibility. Of the 8 studies, 7 analyzed BIC outcome and 3 analyzed RTQ outcome. Among such studies, 6 studies were considered for meta-analysis of quantitative for BIC and 2 studies for RTQ. There was no significant difference for BIC analysis ( P = .89; random ration [RR]: -0.21; 95% confidence interval [CI]: -3.14 to 2.72). The heterogeneity of the primary outcome studies was considered low (7.19; P = .21; I 2 : 30%). However, the RTQ analysis showed different results favoring the TiZr dental implants ( P = .001; RR: 23.62; 95%CI: 9.15 to 38.10). Low heterogeneity was observed for RTQ (χ2: 1.25; P = .26; I 2 : 20%). Within the limitations of this study, there was no difference between TiZr and Ti alloys implants in terms of BIC. However, TiZr implants had higher RTQ than Ti alloys.

Surface Characterization of a Glass Fiber Post after Nonthermal Plasma Treatment with Hexamethyldisiloxane.

PURPOSE: To characterize the surface of glass fiber posts (GFP) after different surface treatments and evaluate which method incorporates higher amounts of silicon (Si) particles, as well as to evaluate the bond strength at the post/ composite-cement interface with four different surface treatments of glass fiber posts luted with composite cement. MATERIALS AND METHODS: Twelve glass fiber posts were obtained from the manufacturer. The posts were randomly distributed into four groups (n = 3): Co (control), no surface treatment; S, 70% alcohol and silane (60 s); HF + S, 10% hydrofluoric acid gel (60 s) and silane (60 s); NTP, nonthermal plasma of hexamethyldisiloxane (HMDSO) associated with argon (30 min). The surface of each GFP was characterized through scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Forty GFPs were randomly divided into 4 groups according the surface treatments (n = 10) and cemented with one composite cement (Rely X U200) into artificial canine teeth. The specimens were placed in a universal testing machine and subjected to tensile testing until failure occurred. Statistical analysis of the atomic percentage and bond strength was performed using ANOVA, followed by the post-hoc Tukey test (p = 0.05). RESULTS: EDS graphics showed that the NTP group had a higher Si atomic percentage (at%) than the other groups (p < 0.001). The HF + S group had a higher Si at% than did the Co and S groups. SEM images illustrated that the surfaces of the GFPs were variously modified after different treatments. The NTP group incorporated higher Si levels on the GFP surface and yielded the highest bond strengths (p < 0.005) compared to the other tested groups. CONCLUSION: Treatment with HMDSO + Ar plasma (NTP) incorporated higher Si levels on the surface of the GFPs without inducing critical defects. NTP treatment promoted better bond strength results when compared to the other tested group when GFPs were cemented with composite cement.

Immediate Dental Implant Placement After Removal of Complex Odontoma.

The aim of the authors was to report a clinical case about immediate implant placement after the removal of complex odontoma. A 35-year-old female patient presented to private service complaining about absence of lower right first premolar. The computed tomographic showed radiopaque attenuation, surrounded by a narrow radiolucency in the area of dental absence, suggesting a mineralized lesion. The surgical removal of lesion was performed by intraoral access with general anesthesia and the implant of 3.75 × 10 mm (Neodent) was placed with the aid of a surgical guide, following the drill sequence established by the manufacturer. No complications were observed after 1 year with the prosthetic rehabilitation.

Removable Partial Denture After Gunshot Injury: Five Year Follow-Up.

The aim of this study was to report a patient of rehabilitation with removable partial denture retained by implants in-patient who suffered injury after firearm shooting. A 19-year-old man presented to the hospital of the Val Paraíso city after being hit by a bullet in the right on the face, affecting the teeth 12 to 16. The surgery to remove the shards of teeth, and bullet was performed. Surgical team opted for installation of implants without bone grafts; however, due to extensive loss of alveolar bone, only 3 tilted implants (2 Ø3.75 × 8.5 mm and 1 Ø3.75 × 10 mm) were installed. After recovery, the patient was referred to the Araçatuba Dental School-UNESP for the rehabilitation on the affected region. The difficulty of rehabilitation with conventional fixed prostheses was verified during the prosthetic phase. This way, it was opted for rehabilitation with removable partial dentures associated with dental implant. Two attachment system ERA (ERA, Sterngold) were positioned in the bar to make the removable partial denture. After 5 years of follow-up, the authors can conclude that the use of removable partial denture retained by implants is effective for functional and aesthetic rehabilitation, favoring socialization and self-esteem of the patient.

Evaluation of the effect of an offset implant configuration in the posterior maxilla with external hexagon implant platform: A 3-dimensional finite element analysis.

STATEMENT OF PROBLEM: Slight offset of the central implant in 3-unit implant-supported prostheses has been reported to improve biomechanical behavior. However, studies that assessed the effects of an offset implant configuration in the posterior maxilla are scarce. PURPOSE: The purpose of this 3-dimensional (3D) finite element analysis was to assess the effects of splinting in 3-unit implant-supported prostheses with varying implant positions (straight-line or offset configuration) in terms of the stress/strain distribution on bone tissue and the stress distribution on abutment screws. MATERIAL AND METHODS: Three 3D models were used to simulate a posterior maxilla bone block (type IV): straight-line implants supporting single crowns (model M1), straight-line implants supporting 3-unit splinted fixed dental prosthesis (model M2), and an offset implant configuration supporting 3-unit splinted fixed dental prosthesis (model M3). The applied forces were 400 N axially and 200 N obliquely. The type of implant platform simulated was an external hexagon. von Mises stress on the abutment screws was measured, and the maximum principal stress and microstrain values were used to perform cortical bone tissue analysis. Analysis of variance (ANOVA) and the Tukey honest significant differences post hoc test were used to determine the significance of the results and interactions among the main variables (α=.05). RESULTS: In all models, oblique load increased the stress on abutment screws and bone tissue and the microstrain on bone tissue. Model M3 decreased the stress concentration on the abutment screws and bone tissue. With regard to microstrain distribution, model M3 had the smallest values, and M1 and M2 had similar values. CONCLUSIONS: Splinting associated with an offset implant configuration was effective for decreasing the stress on abutment screws and bone tissue and the microstrain on bone tissue.

Assessment of treatment outcomes for facial prostheses in patients with craniofacial defects: A pilot retrospective study.

STATEMENT OF PROBLEM: The longevity of silicone facial prostheses is short, and published data concerning this type of rehabilitation are limited. PURPOSE: The purpose of this retrospective study was to identify predictive variables for prosthetic failure and to highlight the results that can be expected after treatment with silicone facial prostheses. MATERIAL AND METHODS: After institutional approval, patient records from a single Brazilian institution for the time period 2004 to 2015 were assessed. A standardized form was used to collect patient data. Frailty survival modeling (simple random effects survival model) was used to test whether age, sex, type of prosthesis, source of defect, number of implants, and type of retention have a direct impact on the prosthetic failure rate (α=.05). RESULTS: Auricular prostheses were the most frequently fabricated prostheses. Eighty-four prostheses were fabricated during the follow-up period. The overall survival rate for facial prostheses was 34.5%. Color alteration was the most common reason for new prostheses (27.38%). The implant success rate was 98.18%. The number of implants approached statistical significance (P=.06) with a reduced risk of failure when the patient had 2 implants compared with patients with zero implants and patients with more than 2 implants. CONCLUSIONS: Patients should be recalled frequently so that retouches can be performed, avoiding the repeated fabrication of new prostheses. Well-designed studies are necessary to identify more relevant complications and factors that lead to prosthetic failure.

A systematic comparison of bar-clips versus magnets.

STATEMENT OF PROBLEM: Currently, which type of suprastructure is preferred when fabricating implant-retained craniofacial prostheses is unknown. PURPOSE: The purpose of this systematic review was to identify the best retention system (bar-clips versus magnets) for implant-retained craniofacial prostheses. MATERIAL AND METHODS: This systematic review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A systematic search of Medline/PubMed and Web of Science databases for clinical trials was conducted on implant-retained craniofacial prostheses published between 2005 and 2015. English-language studies that directly compared different types of retention systems or presented information on implant survival, periimplant soft tissue reactions, and prosthetic complications were included. Nonclinical studies were excluded to eliminate bias. RESULTS: A total to 173 studies were identified, of which 10 satisfied the inclusion criteria. In total, 492 participants were included in these studies. Four selected studies displayed detailed information with regard to the number of implant failures according to the retention system. As reported, 29 (18.2%) of 159 implants with magnets failed, whereas 25 (31.6%) of 79 implants with bars failed. Overall auricular superstructures showed the highest survival (99.08%). In addition, 55.4% of all participants in the selected studies showed grade 0 of periimplant soft tissue reactions. CONCLUSIONS: A systematic search for clinical studies resulted in few studies with a short-term follow-up and small number of participants. The limited data collected indicated that magnets show fewer complications than bar superstructures; however, no hard conclusions could be drawn. Further research, preferably in the form of clinical trials, is needed to validate these findings.

Rehabilitation With Mandibular Implant-Retained Complete Overdenture Using the Association of Two Retention Systems.

This article reports a case of oral rehabilitation with two-implant-retained mandibular overdenture using bar/clip and ball attachment bilaterally on the distal side. A patient aged 69 years, fully edentulous, presented herself to private practice complaining about the instability of mandibular denture. Several possibilities of rehabilitation with advantages and disadvantages were explained to the patient, based in the clinical and radiograph examinations, and patient desire, in which she opted by conventional maxillary complete denture and two-implant-retained mandibular overdenture. Two external hexagon implants of 3.75 × 10 mm were placed in anterior area of mandible. The fabrication of the metal framework with bar/clip and ball attachment bilaterally on the distal side was planned based on prior arrangement of the artificial teeth. Internal adaptation and occlusal adjustments were performed in the day of insertion of finalized denture and instructions about maintenance and sanitation. The patient showed satisfaction with the final result of her treatment, and no complications were observed during this period. The association of bar/clip with ball system may be viable as option of retention for mandibular implant-retained complete overdenture; however, further randomized controlled trials are necessary to obtain detailed knowledge about the topic.

Evaluation of cement-retained versus screw-retained implant-supported restorations for marginal bone loss: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: No consensus has been reached on which retention system, cement- or screw-retained, is best to avoid bone loss around the implant of a fixed implant-supported restoration. PURPOSE: The purpose of this systematic review and meta-analysis was to compare cement- and screw-retained retention systems in fixed implant-supported restorations in terms of marginal bone loss, implant survival, and prosthetic complications. MATERIAL AND METHODS: A comprehensive search of studies published from January 1995 to March 2015 and listed in the PubMed/MEDLINE, Embase, Scopus and the Cochrane Library databases was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The meta-analysis was based on the Mantel-Haenszel and inverse variance methods. Marginal bone loss was the continuous outcome measure evaluated by mean difference (MD), and implant survival and prosthetic complications were the dichotomous outcome measures evaluated by risk ratio (RR), both with corresponding 95% confidence intervals (CI). RESULTS: The 20 studies selected for review evaluated 2139 participants, whose mean age was 47.14 years and who had received 8989 dental implants. The mean follow-up was 65.4 months (range: 12-180 months). Results of the MD for marginal bone loss showed statistically significant differences in favor of the cement-retained prosthesis (P =.04; MD: -0.19; CI: -0.37 to -0.01). The implant survival rate was higher for the cement-retained prosthesis (P =.01; RR: 0.49; CI: 0.28 to 0.85), and the prosthetic complication rate was higher for the screw-retained prosthesis (P =.04; RR: 0.52; CI: 0.28 to 0.98). Additional analysis of the mean plaque index did not show differences between retention systems (P=.58; MD: 0.13; CI: -0.32 to 0.57). CONCLUSIONS: The current meta-analysis indicated that cement-retained, fixed implant-supported restorations showed less marginal bone loss than screw-retained, fixed implant-supported restorations during the follow-up period, which ranged from 12 to 180 months. However, the small difference between the mean values may not show clinical significance. The rates of prosthetic complication and implant survival also compared favorably with cement-retained prostheses.

Photoelastic analysis of conventional and locking system for treatment of mandibular angle fractures with a single plate.

BACKGROUND: This photoelastic analysis evaluated stress distribution in different osteosynthesis systems, conventional and locking, used for treatment of mandibular angle fractures with a single plate. MATERIAL AND METHODS: Angle fractures were simulated in mandibles made of photoelastic resin. Following Champy's method, plate osteosynthesis was performed. The samples were divided into five groups: Group 1, non-fractured mandible; Group 2, two screws were installed in each segment using a conventional system; Group 3, two screws were installed in each segment using a locking system; Group 4, three screws were installed in the proximal segment and four screws in the distal segment using a conventional plate; Group 5, three screws were installed in the proximal segment and four screws in the distal segment using a locking plate. In an universal testing machine coupled to a polariscope, a load was applied to the first molar 10 times. The 50 images were randomly numbered and analyzed qualitatively and quantitatively by two raters. RESULTS: The locking system promoted better stress distribution along the osteosynthesis. The locking system reduced stress magnitude in the distal segment, with a significant between-group difference (P≤ 0.001). CONCLUSIONS: The locking plate/screw system can distribute stress more evenly throughout the osteosynthesis, especially when long seven-hole plates are used. Key words:Internal fracture fixation, osteosynthesis, mandibular fracture, bone plates.

Reciprocating kinematics leads to lower incidences of postoperative pain than rotary kinematics after endodontic treatment: A systematic review and meta-analysis of randomized controlled trial.

BACKGROUND: Extrusion of infected debris into the periapical tissue has been cited as the major cause of postoperative pain, regardless of instrumentation technique. AIM: Comprehensively review two different kinematics of instrumentation (reciprocating and rotary) and association to the postoperative pain after endodontic treatment. METHODS: Two investigators performed a systematic review with meta-analysis. MEDLINE/PubMed, Cochrane Library, and Scopus supplied relevant data from studies published until February 2018 to answer the PICO question. Primary outcome was overall postoperative pain, and the secondary outcomes were nature of the pain (mild, moderate, and severe) at 12, 24, and 48 h. RESULTS: Ten randomized clinical trials fulfilled eligibility criteria, and five of them were submitted in the meta-analysis. Primary outcome indicated that reciprocating system results in less postoperative pain compared to rotary system (P < 0.05). As a secondary outcome, there was no statistical difference for mild, moderate, and severe pain after 12 and 24 h using reciprocating or rotary systems (P > 0.05). However, the reciprocation system showed less severe pain after 48 h (P < 0.05). CONCLUSION: Rotary motion had a negative impact on postoperative pain after endodontic treatment. Furthermore, after 48 h, more patients presented severe pain under rotary motion. More randomized clinical studies would be helpful.