[Effect of Aging on the Mechanical Properties of CAD/CAM-Milled and 3D-Printed Acrylic Resins for Denture Bases].

PURPOSE: The purpose of this study was to investigate the mechanical properties of acrylic resins at different aging times for denture bases manufactured using the conventional method, microwave processing, milling, and 3D printing. MATERIALS AND METHODS: A total of 160 rectangular samples (64 Å~ 10 Å~ 3.3 ± 0.03 mm) were prepared, divided among the four main resin groups, and subdivided into four analysis times (T0, T1, T2, and T3), resulting in 10 samples per subgroup. The samples were stored in distilled water at 37° ± 2°C for 24 hours (T0), then subjected to thermocycling at temperatures of 5° ± 1°C and 55° ± 1°C in different numbers of cycles: 5,000 (T1); 10,000 (T2); and 20,000 (T3). The mechanical properties evaluated were surface microhardness, flexural strength, and modulus of elasticity. Statistical differences between resin groups and aging time were evaluated using two-way analysis of variance (P < .05). RESULTS: The 3D-printed resin showed the significantly lowest values of microhardness, flexural strength, and modulus of elasticity compared to other resins (P < .001). CONCLUSIONS: The CAD/CAM-milled denture resin showed mechanical properties similar to those of traditional resins (conventional and microwave-processed). The 3D-printing resin did not show adequate mechanical properties for long-term clinical use. Despite this, new studies are developing better properties of this resin for long-term use.

Prevalence of proximal contact loss between implant-supported prostheses and adjacent natural teeth: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Proximal contact loss between implant-supported prostheses and adjacent natural teeth is a complication that has been reported in clinical practice. However, the prevalence of the condition is unclear. PURPOSE: The purpose of this systematic review and meta-analysis was to assess the proportion of reported proximal contact loss between implant-supported prostheses and adjacent natural teeth. MATERIAL AND METHODS: This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology criteria and was registered on the international prospective register of systematic reviews (PROSPERO) platform (CRD42021225138). The electronic search was conducted by using the PubMed/MEDLINE, Embase, and Cochrane Library databases to September 2020. The formulated population, intervention, comparison, outcome (PICO) question was "Is there a correlation of the proximal contact loss between implant-supported prostheses and the adjacent natural tooth?" A single-arm meta-analysis of proportion was performed to evaluate the cumulative prevalence of survival and complication rates. RESULTS: This review included 10 studies, half of which presented proximal contact loss rates higher than 50%. In the general analysis, the open proximal contact showed a cumulative proportion of 41% (confidence interval: 30% to 53%; heterogeneity: I2=98%; t2=0.578; P<.01). From the subanalysis, the mesial contact (47%; confidence interval: 32% to 62%; heterogeneity: I2= 96%; t2=0.657; P<.01) and the mandibular arch (41%; confidence interval: 30% to 52%; heterogeneity: I2=92%; t2=0.302; P<.01) were found to have higher prevalence. CONCLUSIONS: The prevalence of proximal contact loss was high, occurring more frequently with the mesial contact and in the mandibular arch. Significant differences were not found in relation to sex or between the posterior and anterior regions.

Effect of Splinting of Tilted External Hexagon Implants on 3-Unit Implant-Supported Prostheses in the Posterior Maxilla: A 3D Finite Element Analysis.

PURPOSE: To assess the effects of tilted external hexagon implants and splinted restorations in terms of stress distribution on the bone tissue, implants, and prosthetic screws, using three-dimensional finite element analysis. MATERIALS AND METHODS: Six models were used to simulate a posterior maxilla bone block (type IV) from the first premolar to the first molar. Each model included three 4.1-mm-diameter external hexagon implants with varying inclinations (0°, 17°, and 30°) and crown designs (splinted and nonsplinted restorations). The forces applied were as follows: 400 N axially (50 N for each slope of the cusp) and 200 N obliquely (45° only on the buccal slope of the cusp). Stress distribution on the implants and prosthetic screw was evaluated using Von Mises stress, while the maximum principal stress was used to evaluate the stress distribution in the bone tissue. RESULTS: The oblique load increased the stress on all the structures in all the models. Increased inclination of the implants resulted in higher stress concentration in the bone tissue, implants, and prosthetic screws. However, splinted restorations contributed to reduction of the stress for the oblique loading, mainly in the bone tissue and prosthetic screw of the first molar, as the stress was shared between the first and second premolar restorations. CONCLUSIONS: Tilted implants increased proportionally the stress on bone tissue and prosthetic screws of models. Additionally, splinting restorations reduced the stress concentration area in the simulated bone tissue, implants, and prosthetic screws in the first molar, as the stress was shared with the adjacent implants.

Biomechanical effect of an occlusal device for patients with an implant-supported fixed dental prosthesis under parafunctional loading: A 3D finite element analysis.

STATEMENT OF PROBLEM: Whether providing an occlusal device for a patient with bruxism and an implant-supported fixed dental prosthesis leads to improved biomechanics is unclear. PURPOSE: The purpose of this 3D finite element analysis (FEA) study was to evaluate the biomechanical behavior of 3-unit implant-supported prostheses under parafunctional forces with and without an occlusal device. MATERIALS AND METHODS: Eight 3D models consisting of a posterior (type IV) maxillary bone block with 3 external hexagon implants (Ø4.0×7.0 mm) and 3-unit implant-supported prostheses with different crown connections (splinted or unsplinted) and an occlusal device under functional and parafunctional loading were simulated. The abutment screws were evaluated by von Mises stress maps, and the bone tissue by maximum principal stress and microstrain maps by using a finite element software program. RESULTS: An occlusal device improved the biomechanical behavior of the prostheses by reducing stress in the abutment screws and stress and strain in the bone tissue. However, the use of an occlusal device was not sufficiently effective to negate the biomechanical benefit of splinting. CONCLUSIONS: The use of splinted crowns in the posterior maxillary region with an occlusal device was the most effective method of reducing stress in the abutment screws and stress and strain in the bone tissue when parafunction was modeled.

Influence of Complete Denture Use on Respiratory Capacity: A Systematic Review.

AIM AND OBJECTIVE: This study aimed to determine whether the use of complete dentures has an influence on the respiratory capacity, assessed by the spirometry examination. MATERIALS AND METHODS: A systematic review was conducted following the Preferred Reporting Items for Systematic Review and Meta-Analysis and registered in the International Prospective Register of Systematic Reviews (CRD42021255224). The PICO question (population/exposure/comparison/outcome) was "Does the use of complete dentures influence the respiratory capacity of a toothless subject?" A search strategy was adapted for the PubMed/MEDLINE, The Cochrane Library, OpenGrey, Lilacs, Scopus, and Embase databases. Inclusion criteria were prospective and retrospective studies. The new castle ottawa (NOS) scale and the Methodological Index for Non-randomized studies were selected to assess the quality of the included studies. RESULTS: Four studies were selected, totalizing the evaluation of 242 participants, aged ranging from 40 to 73 years old. Two studies concluded that the use of complete dentures can negatively affect the respiratory capacity. One study stated that it did not interfere regardless of its use during spirometric measurements, and the other reported that dental prosthesis was required in cases of evaluation of the extrathoracic airways. CONCLUSION: The use of complete dentures did not represent relevant changes from the reference values for pulmonary function in the spirometry test. Considering the results of this review, it is not yet possible to establish a clinical protocol for the use of complete dentures during the test. CLINICAL SIGNIFICANCE: Oral rehabilitation with conventional complete dentures is widely used for the treatment of edentulism, especially in elderly patients. In addition, with aging, many complex changes in immunity and respiratory function contribute to the increase in the development of lung diseases. Therefore, it is important to establish a guidance regarding the use or not of the removable dental prostheses in the respiratory capacity test through spirometry examination.

Clinical effect of the high insertion torque on dental implants: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: A consensus on the clinical performance in dental implants placed with different insertion torques is lacking. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate the effect of high insertion torque compared with regular or low torques during dental implant placement in terms of implant survival rate and marginal bone loss. MATERIAL AND METHODS: Two independent reviewers searched electronic databases for studies published until April 2019. The population, intervention, comparison, outcome (PICO) question was "Do patients who receive implants with a high torque (equal or higher than 50 Ncm) show similar implant survival rates and marginal bone loss as compared with those who receive implants with a regular or low torque (less than 50 Ncm)?". The meta-analysis was based on the Mantel-Haenszel (MH) and the inverse variance (IV) methods (α=.05). RESULTS: The search yielded 6 articles, which included 389 patients (mean age: 55.28 years) who had received 651 dental implants (437 with high torque and 214 with low or regular torque). Most studies evaluated delayed loading, except 1 study that evaluated immediate implant loading (n=50 for each group). Low or regular insertion torque had a high failure rate (4.2%) compared with high insertion torque (1.1%), chiefly because of immediate loading. However, the meta-analysis indicated no significant difference between high- and regular- or low-torque implant placement in implant survival rate (P=.52, risk ratio [RR]: 0.51, 95% confidence interval [CI]: 0.06-4.06) and marginal bone loss (P=.30, mean difference [MD]: 0.15, 95% CI: -0.14 to 0.44). CONCLUSIONS: A high insertion torque during implant placement does not affect implant survival rate or marginal bone loss. However, further research is recommended to reassess this clinical performance.

Sleep Disorders in Patients with Temporomandibular Disorders (TMD) in an Adult Population-Based Cross-Sectional Survey in Southern Brazil.

PURPOSE: To verify the prevalence of sleep disorders in temporomandibular disorders (TMD) subjects in a Brazilian population-based, cross-sectional survey (N = 1,643). MATERIALS AND METHODS: Patients were assessed with the Research Diagnostic Criteria for TMD (RDC/TMD) Axes I and II and the Sleep Assessment Questionnaire. Student t test and Pearson chi-square test were used for continuous and categorical data analyses, respectively. RESULTS: TMD subjects had significantly worse sleep disorders than controls (Graded Chronic Pain Severity categories I through IV vs 0, respectively) in RDC/TMD Axis II variables. Sleep disorders were also worse in the Axis I TMD groups (myofascial pain and arthralgia/osteoarthritis/osteoarthrosis), with the exception of disc displacements. CONCLUSION: TMD subjects had worse sleep disorders, mainly in Axis I TMD groups, with higher pain/disability levels.

Evaluation of the accuracy and stress distribution of 3-unit implant supported prostheses obtained by different manufacturing methods.

The purpose of this in vitro study was to measure the vertical, positive-horizontal, and negative-horizontal misfit (VM, PHM, and NHM, respectively) of the zirconia three-element prosthetic framework, fabricated using different methods, and compare them with conventional fabrication methods (lost-wax casting). Furthermore, this study aimed to evaluate the influence of the misfit values on the biomechanical behavior of the 3-unit fixed prosthetic frameworks using three-dimensional finite element analysis (3D-FEA). Forty frameworks (n = 10) were fabricated as follow: G1, Cerec Bluecam; G2, iTero; G3, 3Series; and G4, conventional method. The samples were randomized to measure marginal misfit using a high-precision three-dimensional (3D)-optical microscope. The results were submitted to analysis of variance (ANOVA), with the significance level set at 5%. The mean VM values of each group were used in creating the models by 3D-FEA with the misfit found in optical microscopy. The programs used were the InVesalius, Rhinoceros, SolidWorks, FEMAP and NEiNastran. The von Mises map was plotted for each model. The G4 showed the lowest mean VM value (16.73 µm), followed by G3 (20.71 µm), G2 (21.01 µm), and G1 (41.77 µm) (p < 0.001). G2 was more accurate than G1 (p < 0.05) and similar to G3 (p = 0.319). For PHM, G4 was the most accurate and did not present overextended values. With regard to NHM, the computer-aided design and computer-aided manufacturing (CAD-CAM) systems were more accurate (-61.91 µm) than G4 (-95.36 µm) (p = 0.014). In biomechanical analysis, stress concentration caused by oblique loading is greater than caused by axial loading. In axial loading, G4 was the most favorable while G1 was the least favorable, biomechanically, in oblique loading, similar stress patterns were observed in all the models. The prosthetic screw was the most overloaded structure, but the material did not influence the stress distribution. The misfit prostheses showed a greater degree of stress than the controls (without misfit). The manufacturing method influenced the marginal misfit of the frameworks, with the conventional method being the most accurate and the Cerec Bluecam System (closed system) the least accurate. Biomechanically, fitting prostheses were more favorable than misfit prostheses.

General Health Quality of Life in Patients with Temporomandibular Disorders in a Population-Based Cross-Sectional Study in Southern Brazil.

PURPOSE: To assess the impact of temporomandibular disorders (TMD) on general health quality of life in a Brazilian population-based cross-sectional survey. MATERIALS AND METHODS: A total of 1,643 patients were assessed using the World Health Organization Quality of Life Bref (WHOQOL-Bref) and the Research Diagnostic Criteria for Temporomandibular Disorders Axes I and II (RDC/TMD). Cross-tabulation of the data was carried out to compare TMD subjects to controls in all domains of the WHOQOL-Bref and the RDC/TMD. RESULTS: TMD subjects had significantly worse quality of life than controls in Axes I and II of the RDC/TMD and in all WHOQOL-Bref domains except for disc displacement. Osteoarthrosis was significantly different only in the WHOQOL-Bref physical domain. CONCLUSION: TMD subjects had worse general health quality of life, particularly in Axis I groups with higher pain/disability levels (muscle disorders/arthralgia/arthritis).

Current Methods of Bruxism Diagnosis: A Short Communication.

PURPOSE: To assess the current diagnostic methods for sleep bruxism (SB). MATERIALS AND METHODS: This review of the literature evaluates all available instrumental and noninstrumental methods of bruxism/SB diagnosis. RESULTS: SB diagnosis can be performed using self-reports and clinical examination, but these methods have little agreement with polysomnography. Two portable electromyography/electrocardiography appliances have been validated against polysomnography (BiteStrip and Bruxoff), but they are indicated only for primary SB. Polysomnography is considered the gold standard and is indicated for secondary SB; however, it is expensive and time-consuming. CONCLUSION: No perfect method of SB diagnosis exists, and future research should concentrate on improving SB self-reports.

Depression and Somatization in Patients with Temporomandibular Disorders in a Population-Based Cross-Sectional Study in Southern Brazil.

PURPOSE: To assess the prevalence of depression and somatization in patients with temporomandibular disorders (TMD) in a Brazilian population-based cross-sectional survey. MATERIALS AND METHODS: A total of 1,643 subjects were assessed for TMD using the Research Diagnostic Criteria for Temporomandibular Disorders Axes I and II and were assessed for depression and somatization using the Graded Chronic Pain Scale. The data were cross-tabulated for comparison between TMD subjects and controls. RESULTS: TMD subjects had significantly worse depression and somatization levels than controls in the RDC/TMD Axis II. The levels were also worse in most Axis I TMD groups (muscle disorders and arthralgia/osteoarthritis/osteoarthrosis). CONCLUSION: TMD subjects had worse depression and somatization, particularly in diagnostic groups with higher pain/disability levels.

Influence of Bariatric Surgery on Salivary Flow: a Systematic Review and Meta-Analysis.

Bariatric surgery is the most effective treatment for morbid obesity, but it can cause numerous adverse effects. This systematic review and meta-analysis aimed to evaluate whether bariatric surgery changes patient salivary flow. We searched for articles in the Web of Science, Pubmed/MEDLINE, and Scopus databases using the search terms "oral health AND bariatric surgery OR gastrectomy OR obesity surgery." We recovered 845 articles. After the removal of duplicates and exclusions, eight studies remained. Of them, five showed no significant difference in salivary flow values, two showed an increase in flow rate, and one showed a reduction in flow rate (p < 0.05). The results of the included studies showed no significant alteration in salivary flow rate for up to 24 months after bariatric surgery.

Should the restoration of adjacent implants be splinted or nonsplinted? A systematic review and meta-analysis.

STATEMENT OF PROBLEM: The decision to splint or to restore independently generally occurs during the planning stage, when the advantages and disadvantages of each clinical situation are considered based on the proposed treatment. However, clinical evidence to help clinicians make this decision is lacking. PURPOSE: The purpose of this systematic review and meta-analysis was to assess the marginal bone loss, implant survival rate, and prosthetic complications of splinted and nonsplinted implant restorations. MATERIAL AND METHODS: This study was designed according to the Cochrane criteria for elaborating a systematic review and meta-analysis and adopted the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Also, this review was registered at the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42017080162). An electronic search in the PubMed/MEDLINE, Cochrane Library, and Scopus databases was conducted up to November 2017. A specific clinical question was structured according to the population, intervention, comparison, outcome (PICO) approach. The addressed focused question was "Should the restoration of adjacent implants be splinted or nonsplinted?" The meta-analysis was based on the Mantel-Haenszel and inverse variance methods to assess the marginal bone loss, implant survival, and prosthetic complications of splinted and nonsplinted implant restorations. RESULTS: Nineteen studies were selected for qualitative and quantitative analyses. A total of 4215 implants were placed in 2185 patients (splinted, 2768; nonsplinted, 1447); the mean follow-up was 87.8 months (range=12-264 months). Quantitative analysis found no significant differences between splinted and nonsplinted restorations for marginal bone loss. The assessed studies reported that 75 implants failed (3.4%), of which 24 were splinted (99.1% of survival rate) and 51 were nonsplinted (96.5% of survival rate). Quantitative analysis of all studies showed statistically significant higher survival rates for splinted restorations than for nonsplinted restorations. Ceramic chipping, screw loosening, abutment screw breakage, and soft tissue inflammation were reported in the selected studies. The quantitative analysis found no statistically significant difference in the prosthetic complications of splinted and nonsplinted restorations. CONCLUSIONS: Within the limitations of this systematic review and meta-analysis, it was concluded that there was no difference in the marginal bone loss and prosthetic complications of splinted and nonsplinted implant restorations; this is especially true for restorations in the posterior region. However, splinted restorations were associated with decreased implant failure.

Efficacy of Dental Bleaching with Whitening Dentifrices: A Systematic Review.

A systematic review was performed to evaluate whether whitening toothpastes promote tooth whitening when compared to the use of conventional (nonbleaching) dentifrices. This review was registered at PROSPERO (CRD42017065132) and is based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Electronic systematic searches of PubMed/MEDLINE, Scopus, and the Cochrane Library were conducted for published articles. Only randomized clinical trials in adults that compared the use of so-called whitening dentifrices to the use of nonwhitening dentifrices were selected. The outcome was tooth color change. Twenty-two articles from 703 data sources met the eligibility criteria. After title and abstract screening, 16 studies remained, after which a further five studies were excluded. In total, nine studies were qualitatively analyzed. Significant differences in tooth color change were found between the groups using whitening dentifrices and those using nonwhitening dentifrices. Within the limitations of this study, the evidence from this systematic review suggests that bleaching dentifrices have potential in tooth whitening. However, although many whitening dentifrices have been introduced into the dental market for bleaching treatments, it is important to analyze tooth surface and color changes when performing home bleaching.

Biomechanical analysis of different implant-abutments interfaces in different bone types: An in silico analysis.

The purpose of this study was to analyze the stress distribution of bone tissue around implants with different implant-abutment interfaces: platform switching (PSW); external hexagon (EH) and Morse taper (MT) with different diameters (regular: Ø 4 mm and wide: Ø 5 mm), bone types (I-IV) and subjected to axial and oblique load conditions using three-dimensional finite element analysis (3D-FEA). Sixteen 3D models of various configurations were simulated using InVesalius, Rhinoceros 3D 4.0, and SolidWorks 2011 software, and processed using Femap 11.2 and NeiNastran 11.0 programs. Axial and oblique forces of 200 N and 100 N, respectively, applied at the occlusal surface of prostheses. Maximum principal stress values were obtained from the peri-implant cortical bone of each model. Statistical analyses were performed using ANOVA and Tukey's test for maximum principal stress values. Oblique loading showed higher tensile stress than axial loading (P < 0.001). Wide-diameter implants showed lower stress concentration rather than regular-diameter implants, regardless of both connection and bone type (P < 0.001). Under axial loading, wide-diameter EH implants with regular platforms showed more favorable stress distribution than PSW implants for axial loading (P < 0.001); however, under oblique loading, PSW implants exhibited lower stress concentrations (P < 0.001). Regular-diameter MT implants showed lower stress than EH implants (P < 0.001). Bone type IV showed higher stress in the cortical region than bone types I and II (P < 0.001), but no significant difference when compared with bone type III (P > 0.05). The conclusion drawn from this in silico is that MT implants should be considered for use in situations that preclude the placement of wide-diameter implants, particularly where bone types III and IV are concerned.

Posterior partially edentulous jaws, planning a rehabilitation with dental implants.

AIM: To discuss important characteristics of the use of dental implants in posterior quadrants and the rehabilitation planning. METHODS: An electronic search of English articles was conducted on MEDLINE (PubMed) from 1990 up to the period of March 2014. The key terms were dental implants and posterior jaws, dental implants/treatment planning and posterior maxilla, and dental implants/treatment planning and posterior mandible. No exclusion criteria were used for the initial search. Clinical trials, randomized and non randomized studies, classical and comparative studies, multicenter studies, in vitro and in vivo studies, case reports, longitudinal studies and reviews of the literature were included in this review. RESULTS: One hundred and fifty-two articles met the inclusion criteria of treatment planning of dental implants in posterior jaw and were read in their entirety. The selected articles were categorized with respect to their context on space for restoration, anatomic considerations (bone quantity and density), radiographic techniques, implant selection (number, position, diameter and surface), tilted and pterygoid implants, short implants, occlusal considerations, and success rates of implants placed in the posterior region. The results derived from the review process were described under several different topic headings to give readers a clear overview of the literature. In general, it was observed that the use of dental implants in posterior region requires a careful treatment plan. It is important that the practitioner has knowledge about the theme to evaluate the treatment parameters. CONCLUSION: The use of implants to restore the posterior arch presents many challenges and requires a detailed treatment planning.

Phantom eye syndrome: a review of the literature.

The purpose of this literature review was to describe the main features of phantom eye syndrome in relation to their possible causes, symptoms, treatments, and influence of eye amputation on quality of life of anophthalmic patients. For this, a bibliographical research was performed in Pubmed database using the following terms: "eye amputation," "eye trauma," "phantom eye syndrome," "phantom pain," and "quality of life," associated or not. Thirteen studies were selected, besides some relevant references contained in the selected manuscripts and other studies hallowed in the literature. Thus, 56 articles were included in this review. The phantom eye syndrome is defined as any sensation reported by the patient with anophthalmia, originated anophthalmic cavity. In phantom eye syndrome, at least one of these three symptoms has to be present: phantom vision, phantom pain, and phantom sensations. This syndrome has a direct influence on the quality of life of the patients, and psychological support is recommended before and after the amputation of the eyeball as well as aid in the treatment of the syndrome. Therefore, it is suggested that, for more effective treatment of phantom eye syndrome, drug therapy should be associated with psychological approach.

Prevalence of removable partial dentures users treated at the Aracatuba Dental School-UNESP.

OBJECTIVES: The aim of this study was to evaluate the frequency of removable partial dentures (RPD) at the Aracatuba Dental School. METHODS: The study was conducted by analysing 412 clinical history of patients attended at the RPD clinics in the period from 2000 to 2007. RESULTS: 412 charts were analysed: 148 (35.9%) men and 264 (64.1%) women. The mean age was 53.8 years (men) and 52.4 years (women). A total of 556 dentures were made; of these, 233 (41.90%) were maxillary and 323 (58.09%) were mandibular dentures. The most frequent Kennedy classification found was Class III (maxilla) and Class I (mandible). In the maxilla, 55% (126) of the major connectors were of the anterior-posterior palatal bar, while in the mandible, 64% (202) were the lingual bar. As regards the claps, 401 were circumferential and 318 were bar claps. CONCLUSION: The mean age of the patients was 52.9 years with higher prevalence of female patients; the most frequent Kennedy's classification was Class I in mandible and Class III in maxilla; the most common major connector was anterior-posterior palatal bar for maxilla and lingual bar for mandible; the circumferential clasps were the most common retainer used in both jaws.