What is Currently Known about Odontogenic Keratocysts?

PURPOSE: To present updated information on odontogenic keratocyst (OKC) classification, etiology, genetic and molecular alterations, epidemiology, clinical presentation, radiographic characteristics, histological and immune histochemical features, differential diagnosis, treatment, and controversies, as well as a literature review of case frequencies in different countries. MATERIALS AND METHODS: Studies were selected using the key words 'odontogenic keratocyst,' 'odontogenic cysts,' 'odontogenic keratocyst and clinical study'. Full-text papers were reviewed on the basis of the inclusion and exclusion criteria. The literature search aimed to find articles that would show the frequency of OKC, dentigerous cyst, radicular cyst, and other cysts. RESULTS: OKC presents local aggression and high recurrence; therefore, a better understanding of its clinical characteristics and the genetic and molecular factors involved in this peculiar and controversial lesion is required. It is always essential to discuss treatment alternatives. Although OKC is an entity with a high recurrence, aggressive treatment is not advisable in all cases because factors such as commitment to anatomical structures and possible complications should be considered. However, periodic radiographic controls are advised. CONCLUSION: To reduce the high number of present cases worldwide, it is important to improve knowledge on this pathology so that accurate diagnoses can be achieved and appropriate treatment can be provided. OKC presents local aggression and high recurrence; therefore, a better understanding is needed of the clinical characteristics and genetic and molecular factors involved in OKC. Furthermore, it is always essential to discuss treatment alternatives.

Genotoxicity Associated with Residual Monomers in Restorative Dentistry: A Systematic Review.

PURPOSE: Incomplete polymerisation processes produce several leachable substances. The aim of this work was to review, through existing research and published literature, the genotoxic effect of residual monomers of polymers used in restorative dentistry. MATERIALS AND METHODS: The selection of published studies was performed on six databases from January 2000 to June 2020. The keywords used were: 'genotoxicity' or 'DNA damage' and 'dental resin' or 'methacrylates' or 'residual monomers'. The selection was carried out according to the parameters and guidelines of the Preferred Reporting Items for Systematic Review and Metanalyses (PRISMA) and was based on patient, intervention, comparison, and outcome (PICO). The inclusion criteria were: in vitro and in vivo studies published in English that evaluated genotoxicity for residual monomers leached from polymers related to restorative dentistry. Case reports and review articles were excluded. RESULTS: Twenty-seven studies met the eligibility criteria. Two categories were constructed based on the experimental design, in vivo and in vitro reports. For the in vitro research, two main methods of assessing DNA damage were reported in selected studies: micronucleus (MN) counting and alkaline comet assay. For in vivo reports, the main method for assessing genotoxic damage was MN counting. CONCLUSION: From the electronic search, structured data extraction, and analysis by different independent reviewers, results from the present systematic review allow us to conclude that DNA damage is induced by monomers/co-monomers (triethylene glycol dimethacrylate, bisphenol-A-glycidyl methacrylate, urethane dimethacrylate, and 2-hydroxyethyl methacrylate) that are used in restorative dentistry. This systematic review highlights the need for more research on the use of monomers/co-monomers to properly assess clinical biocompatibility.

Métodos de Registro de Dimensión Vertical Oclusal en Pacientes Dentados: Revisión Sistemática

RESUMEN: La Dimensión Vertical Oclusal, es la distancia entre un punto anatómico fijo en el maxilar y otro sobre la parte móvil de la mandíbula cuando los órganos dentarios están en contacto oclusal. La obtención de este registro determina el espacio vertical necesario para la rehabilitación de los pacientes. En la actualidad existen distintos métodos para el registro de la Dimensión Vertical Oclusal, en este estudio se analizaron: Métodos fisiológicos y métodos mecánicos. El objetivo fue realizar una revisión sistemática, sobre los métodos de registro, para determinar la Dimensión Vertical Oclusal en pacientes dentados. Se recopiló información científica desde Mayo 2019 hasta Julio 2020 en diferentes bases de datos electrónicas, encontrando un tota l de 13948 artículos, después de eliminar artículos repetidos, por título, por resumen y por metodología PICO se seleccionaron un total de 24 artículos para su análisis y clasificación. Más de un autor menciona que no existe un método unirversalmente aceptado o exacto para determinar la Dimensión Vertical Oclusal. Se sugiere la combinación de varios métodos de registro de Dimensión Vertical Oclusal, se debe de considerar la manera más adecuada para lograr un registro más acertado.

ABSTRACT: Occlusal Vertical Dimension is the distance between an anatomical point in the maxilla and another on the mobile part of the mandible when the teeth are in occlusal contact. Obtaining this record determines the vertical space necessary for the rehabilitation of patients. Nowadays there are different methods for the record of the Occlusal Vertical Dimension, in this study the following were analyzed: physiological methods and mechanical methods. The objective was to do a systematic review of the registration methods to determine the Occlusal Vertical Dimension in dentate patients. Scientific information was collected from May 2019 to July 2020 in different electronic databases, finding a total of 13,948 articles, after eliminating repeated articles, by title, by abstract and by PICO methodology, a total of 24 articles were selected for analysis and classification. More than one author mentions that there is no universally accepted or exact method for determining Occlusal Vertical Dimension. A combination of several methods of Occlusal Vertical Dimension registration is suggested; it should be considered the most appropriate way to achieve a more accurate registration.

Biomechanical Effect of Ferrule on Incisors Restored with a Fiberglass Post and Lithium-Disilicate Ceramic Crown after Thermal Cycling and Fatigue Loading.

PURPOSE: To evaluate the biomechanics of endodontically treated incisors restored with a fiberglass post and a CAD/CAM lithium-disilicate ceramic crown with/without a ferrule after thermal and mechanical aging. MATERIALS AND METHODS: Twenty bovine incisors were divided into two groups (n = 10): 1. Fe, with a ferrule of 2 mm, and 2. NFe, without a ferrule. After endodontic treatment, the teeth were restored using a fiberglass post (Exacto 3, Angelus) and composite core (Tetric Ceram, Ivoclar Vivadent). They then received a CAD/CAM lithium-disilicate ceramic crown (IPS e.max CAD) luted using a self-adhesive composite (RelyX Unicem 2, 3M Oral Care). All specimens were subjected to 20,000 thermocycles and 2,400,000 simulated chewing cycles. Ceramic crown and root dentin strains (µS) were measured using strain gauges (n = 10) during 100-N loading before and after the thermal and mechanical aging, and upon fracture loading. The specimens were subsequently loaded to fracture (N). The stress distribution was analyzed using 3D individualized finite-element models created by micro-CT of experimental samples (n = 3). Strain data were analyzed using two-way ANOVA and Tukey's HSD test. Fracture resistance was analyzed using Student's t-test and fracture mode was analyzed using the chi-squared test (α = 0.05). RESULTS: After aging, NFe exhibited significantly higher root dentin deformation (buccal: 1248.0 ± 282.8; lingual: 516.2 ± 195.0; p < 0.001) than Fe (buccal, 554.0 ± 233.8; lingual: 311.8 ± 159.0; p < 0.001). The deformation measured on ceramic crowns was not influenced by ferrule presence or aging process. Significantly higher fracture resistance (N) was observed for the Fe (1099.6 ± 214.8) than the NFe group (675.3 ± 113.8) (p < 0.001). The NFe group revealed a lower fracture resistance:root strain ratio than did the Fe group. The stress levels on root dentin and fiberglass were lower for the Fe group. CONCLUSION: The NFe group showed increased root dentin strain after the aging process. The Fe group revealed higher fracture resistance, lower stress concentration on root dentin and fewer catastrophic fractures.

Influence of crosshead speed on failure load and failure mode of restored maxillary premolars.

We analyzed the effect of the crosshead speed of an applied load on failure load and failure mode of restored human premolars. Fifty intact, noncarious human premolars were selected. Class II mesio-occlusodistal preparations were made with a water-cooled high-speed preparation machine, and the teeth were restored with composite resin. The specimens were divided into five groups (n = 10 each) and tested individually in a mechanical testing machine, in which a 6.0-mm-diameter steel cylinder was mounted to vary the crosshead speed: v0.5: 0.5 mm/min; v1: 1.0 mm/min; v2.5: 2.5 mm/min; v5: 5.0 mm/min; and v10: 10.0 mm/min. The cylinder contacted the facial and lingual ridges beyond the margins of the restorations. Peak load to fracture was measured for each specimen (N). The means were calculated and analyzed with one-way analysis of variance followed by Tukey's test (a = 0.05). The mean load at failure values were (N) as follows: v0.5, 769.4 ± 174.8; v1, 645.2 ± 115.7; v5, 614.3 ± 126.0; v2.5, 609.2 ± 208.1; and v10, 432.5 ± 136.9. The fracture modes were recorded on the basis of the degree of the tooth structural and restorative damage: (I) fracture of the restoration involving a small portion of the tooth; (II) fractures involving the coronal portion of the tooth with cohesive failure of the composite resin; (III) oblique tooth and restoration fracture with periodontal involvement; and (IV) vertical root and coronal fracture. Varying crosshead speeds of 0.5-5.0 mm/min did not influence the failure load of restored maxillary premolars; however, increasing the crosshead speed to 10 mm/min decreased the failure load values and the degree of tooth structural damage.

Influence of crosshead speed on failure load and failure mode of restored maxillary premolars

We analyzed the effect of the crosshead speed of an applied load on failure load and failure mode of restored human premolars. Fifty intact, noncarious human premolars were selected. Class II mesio-occlusodistal preparations were made with a water-cooled high-speed preparation machine, and the teeth were restored with composite resin. The specimens were divided into five groups (n = 10 each) and tested individually in a mechanical testing machine, in which a 6.0-mm-diameter steel cylinder was mounted to vary the crosshead speed: v0.5: 0.5 mm/min; v1: 1.0 mm/min; v2.5: 2.5 mm/min; v5: 5.0 mm/min; and v10: 10.0 mm/min. The cylinder contacted the facial and lingual ridges beyond the margins of the restorations. Peak load to fracture was measured for each specimen (N). The means were calculated and analyzed with one-way analysis of variance followed by Tukey's test (a = 0.05). The mean load at failure values were (N) as follows: v0.5, 769.4 ± 174.8; v1, 645.2 ± 115.7; v5, 614.3 ± 126.0; v2.5, 609.2 ± 208.1; and v10, 432.5 ± 136.9. The fracture modes were recorded on the basis of the degree of the tooth structural and restorative damage: (I) fracture of the restoration involving a small portion of the tooth; (II) fractures involving the coronal portion of the tooth with cohesive failure of the composite resin; (III) oblique tooth and restoration fracture with periodontal involvement; and (IV) vertical root and coronal fracture. Varying crosshead speeds of 0.5–5.0 mm/min did not influence the failure load of restored maxillary premolars; however, increasing the crosshead speed to 10 mm/min decreased the failure load values and the degree of tooth structural damage.

Effect of surface treatment of fiberglass posts on bond strength to root dentin.

This study evaluated the influence of the surface treatments of fiberglass posts on bond strength to root dentin using push-out test. Forty bovine incisor roots were endodontically treated. The surface of the fiberglass posts (Exacto #2, Angelus) were treated using 4 different protocols (n=10): Control - 70% ethanol for 1 min; 37% phosphoric acid for 1 min; 10% hydrofluoric acid for 1 min; and 24% hydrogen peroxide for 1 min. After a silane coupling agent was applied for 1 min and all posts were cemented using self-adhesive resin cement (RelyX Unicem, 3M-ESPE). The roots were sectioned and two 1-mm-thick slices were obtained from each third: cervical, middle and apical. The specimens were subjected to the push-out test with a crosshead speed of 0.5 mm/min. Data were analyzed by repeated measures ANOVA followed by Tukey's HSD tests (=0.05). The surface treatment (p<0.001) and root third region (p=0.007) factors were significant. The retention to root canal was affected by surface treatment type. The post surface treatment with 24% hydrogen peroxide for 1 min yielded significantly higher bond strength when the fiberglass posts were cemented with RelyX Unicem.

Effect of Surface Treatment of Fiberglass Posts on Bond Strength to Root Dentin

This study evaluated the influence of the surface treatments of fiberglass posts on bond strength to root dentin using push-out test. Forty bovine incisor roots were endodontically treated. The surface of the fiberglass posts (Exacto #2, Angelus) were treated using 4 different protocols (n=10): Control - 70% ethanol for 1 min; 37% phosphoric acid for 1 min; 10% hydrofluoric acid for 1 min; and 24% hydrogen peroxide for 1 min. After a silane coupling agent was applied for 1 min and all posts were cemented using self-adhesive resin cement (RelyX Unicem, 3M-ESPE). The roots were sectioned and two 1-mm-thick slices were obtained from each third: cervical, middle and apical. The specimens were subjected to the push-out test with a crosshead speed of 0.5 mm/min. Data were analyzed by repeated measures ANOVA followed by Tukey's HSD tests (=0.05). The surface treatment (p<0.001) and root third region (p=0.007) factors were significant. The retention to root canal was affected by surface treatment type. The post surface treatment with 24% hydrogen peroxide for 1 min yielded significantly higher bond strength when the fiberglass posts were cemented with RelyX Unicem.

Este estudo avaliou a influência de tratamentos de superfície de pinos de fibra de vidro na resistência de união à dentina radicular por meio do teste de push-out. Quarenta raízes de incisivos bovinos foram submetidas a tratamento endodôntico. A superfície dos pinos de fibra de vidro (Exacto #2, Angelus) foram tratadas com 4 protocolos diferentes (n=10): Controle - 70 % de etanol durante 1 min; 37 % de ácido fosfórico durante 1 min, 10% de ácido fluorídrico durante 1 min e 24 % de peróxido de hidrogênio durante 1 min. Depois foi aplicado agente de união silano por 1 min e todos os pinos foram cimentados com cimento resinoso auto-adesivo (RelyX Unicem, 3M- ESPE). As raízes foram seccionadas e foram obtidas duas fatias de 1 mm de espessura em cada terço: cervical, médio e apical. Os espécimes foram submetidos ao teste de push-out com uma velocidade de 0.5 mm/min. Os dados foram analisados pelo teste ANOVA com medidas repetidas, seguido pelo teste de Tukey HSD (=0,05). Os fatores tratamento de superfície (p<0,001) e região do terço radicular (p=0,007) foram significantes; no entanto, a interação entre os dois fatores não foi significante (p=0,827). A retenção ao canal radicular foi afetada pelo tipo de tratamento de superfície. O tratamento de superfície com 24% de peróxido de hidrogênio por 1 min rendeu significativamente maior resistência de união quando os pinos de fibra de vidro foram cimentados com RelyX Unicem.

The effect of fiber post presence and restorative technique on the biomechanical behavior of endodontically treated maxillary incisors: an in vitro study.

STATEMENT OF PROBLEM: Unresolved controversy exists concerning the best technique for restoring endodontically treated teeth. Prefabricated posts have been recommended with some debate as a method of restoring pulpless teeth before placement of the final restoration. PURPOSE: The purpose of this in vitro study was to evaluate the effect on the strain, fracture resistance, and fracture mode of endodontically treated human incisors of 4 types of restorations with or without glass fiber posts after thermal cycling. MATERIAL AND METHODS: Ninety human maxillary central incisors were selected and divided into 1 control group and 8 treatment groups (n=10). The teeth were endodontically treated and received 2 large Class III preparations simulating coronal destruction. The teeth were then restored with or without glass fiber posts and by using 4 restorative techniques: direct composite resin, direct composite veneer, feldspathic ceramic veneer, or a feldspathic ceramic crown. After artificial aging by thermal cycling, the incisors were loaded at a 135-degree angle, and the strain was measured by using strain gauges placed on the facial and proximal root surfaces. Specimens were subsequently loaded to the point of fracture. Strain and fracture resistance results were analyzed by a 1-way and 2-way ANOVA, followed by the Tukey HSD and Dunnett tests (α=.05). RESULTS: One-way analyses showed that the control group and the direct composite resin restoration with and without post groups presented significantly higher fracture resistance values (P<.001). Two-way analyses showed no significant differences for the post system. Proximal strain values were higher in the control and composite resin groups and lower in the feldspathic ceramic groups. CONCLUSIONS: The presence of glass fiber posts did not increase the fracture resistance of endodontically treated incisors. Conservative composite resin restorations showed higher fracture resistance values.

Longitudinal clinical evaluation of post systems: a literature review.

In this survey, retrospective and prospective clinical studies dealing with cast-post-and core and fiber posts were reviewed regarding the rate of survival of restorations and the most prevalent failures. Electronic searches of the literature were performed in MEDLINE by crossing the key words: "Fiber post and clinical study", "Fiber post and clinical evaluation", "Cast post-and-core and clinical study", and "Root post and retrospective survival study". The cut-off dates were December 1990 through the end of December 2010. Review of literature showed that several interrelated biological, mechanical, and aesthetic factors are involved in the survival rate of restorative procedures in endodontically treated teeth, and post selection should fulfill and optimize these factors. Data based on long-term clinical studies are essential for the general practitioner when making clinical decisions. An adequate selection of teeth and post system must be made, and a minimal amount of existing tooth substance should be removed. A ferrule must be present for safe indication of the fiber posts. Fiber glass posts have demonstrated good survival in clinical studies, with similar performance to cast-post-and cores. Metallic posts have good clinical survival, but the associated failures are mostly irreversible, unlike what happens with the glass fiber posts.

Longitudinal clinical evaluation of post systems: a literature review

In this survey, retrospective and prospective clinical studies dealing with cast-post-and core and fiber posts were reviewed regarding the rate of survival of restorations and the most prevalent failures. Electronic searches of the literature were performed in MEDLINE by crossing the key words: "Fiber post and clinical study", "Fiber post and clinical evaluation", "Cast post-and-core and clinical study", and "Root post and retrospective survival study". The cut-off dates were December 1990 through the end of December 2010. Review of literature showed that several interrelated biological, mechanical, and aesthetic factors are involved in the survival rate of restorative procedures in endodontically treated teeth, and post selection should fulfill and optimize these factors. Data based on long-term clinical studies are essential for the general practitioner when making clinical decisions. An adequate selection of teeth and post system must be made, and a minimal amount of existing tooth substance should be removed. A ferrule must be present for safe indication of the fiber posts. Fiber glass posts have demonstrated good survival in clinical studies, with similar performance to cast-post-and cores. Metallic posts have good clinical survival, but the associated failures are mostly irreversible, unlike what happens with the glass fiber posts.

O objetivo foi realizar revisão de estudos clínicos retrospectivos e prospectivos de pinos e núcleos metálicos e pinos de fibra em relação à taxa de sobrevivência e tipo de falhas prevalentes. A revisão de literatura foi realizada utilizando a base de dados MEDLINE com os seguintes termos para pesquisa: “Pino de fibra e estudo clínico”, “Pino de fibra e avaliação clínica”, “Pinos e núcleos metálicos e estudo clínico”, “Pinos intra-radiculares e estudo clínicos retrospectivos”. O período avaliado foi de Dezembro de 1990 até o final de Dezembro de 2010. Vários fatores biológicos, mecânicos e estéticos estão envolvidos na taxa de sobrevivência do procedimento restaurador de dentes tratados endodonticamente. A seleção do pino deve satisfazer e otimizar esses fatores. Dados com base em estudos clínicos de longo prazo são essenciais para o clínico geral na tomada de decisões. Adequada indicação na seleção do sistema de pino devem ser feitas. Adicionalmente, desgaste mínimo da estrutura dentária existente deve ser priorizado. A presença de férula deve estar presente para garantir e melhorar a previsibilidade de pinos de fibra. Pinos de fibra de vidro têm demonstrado boa sobrevivência em estudos clínicos, com desempenho semelhante aos pinos metálicos e núcleos moldados e fundidos. Retentores metálicos apresentam boa sobrevivência clínica, no entanto as falhas envolvidas são em sua maioria irreversíveis, ao contrário do que acontece com os pinos de fibra de vidro.

Surface treatment of glass fiber and carbon fiber posts: SEM characterization.

Morphology, etching patterns, surface modification, and characterization of 2 different fiber posts: Gfp, Glass fiber post; and Cfp, carbon fiber were investigated by SEM analysis, after different surface treatments. Thirty fiber posts, being 15 Gfp and 15 Cfp were divided into a 5 surface treatments (n = 3): C-alcohol 70% (control); HF 4%-immersion in 4% hydrofluoric acid for 1min; H(3) PO(4) 37%-immersion in 37% phosphoric acid for 30s; H(2) O(2) 10%-immersion in 10% hydrogen peroxide for 20 min; H(2) O(2) 24%-immersion in 24% hydrogen peroxide for 10 min. Morphology, etching patterns, surface modification and surface characterization were acessed by SEM analysis. SEM evaluation revealed that the post surface morphology was modified following all treatment when compared with a control group, for both type of reinforced posts. HF seems to penetrate around the fibers of Gfp and promoted surface alterations. The Cfp surface seems to be inert to treatment with HF 4%. Dissolution of epoxy resin and exposure of the superficial fiber was observed in both post groups, regardless the type of reinforcing fiber, H(2) O(2) in both concentrations. Relative smooth surface area was produced by H(3) PO(4) 37% treatment, but with similar features to untreated group. Surface treatment of fiber post is a determinant factor on micromechanical entanglement to resin composite core. Post treatment with hydrogen peroxide resulted strength of carbon and glass/epoxy resin fiber posts to resin composite core.