Reabsorción dentinaria interna coronaria: informe de un caso clínico / Coronary internal dentine resorption: report of a clinical case

Objetivo: La reabsorción dentinaria interna es un pro- ceso causado por la actividad odontoclástica asociada princi- palmente a la inflamación pulpar crónica y/o traumatismos, y se caracteriza por la pérdida progresiva de tejido dentinario y la posible invasión al cemento. El presente informe describe el diagnóstico y tratamiento de un molar inferior que presentó un cuadro sintomático de reabsorción dentinaria interna. Caso clínico: Un paciente de 38 años fue derivado a la consulta por presentar una zona de reabsorción interna en un segundo molar inferior. Durante el examen clínico y ra- diográfico se tomó una radiografía preoperatoria periapical con radiovisiógrafo en la que se observó la presencia de un área compatible con el diagnóstico de reabsorción dentinaria interna, el que fue posteriormente confirmado por medio de una tomografía computada de haz cónico. La imagen de la lesión se presentó como una zona radiolúcida deformante de bordes nítidos, localizada a nivel de la cámara pulpar. El tra- tamiento consistió en la extirpación de la pulpa coronaria y de la instrumentación, desinfección y obturación de los conduc- tos radiculares y la cavidad de acceso. En el control clínico y radiográfico realizado luego de 3 años se observó que el paciente estaba asintomático y las estructuras perirradiculares se encontraban dentro de los límites normales. La observación histológica del material removido de la cámara pulpar reveló la presencia de un tejido granulomatoso con numerosos vasos sanguíneos y escasos focos micro hemorrágicos. Hasta el momento, el tratamiento endodóntico es el pro- cedimiento indicado para el tratamiento de la reabsorción dentinaria interna. Se destaca la importancia de la tomografía computada de haz cónico para el diagnóstico y tratamiento temprano de las reabsorciones dentinarias internas a efectos de contar con un pronóstico favorable (AU)

Aim: Internal dentine resorption is aprocess caused by odontoclastic activity, mainly associated with chronic pulpal inflammation and/or trauma, and it'scharacterized by a pro- gressive loss of dentine tissue and the possible invasion of the cementum. This report describes the diagnosis and treatment of a lower molar that presented a symptomatic case of inter- nal dentine resorption. Clinical case: A 38-years old patient was referred to the office because of presenting an area of internal resorption in a lower second molar. During clinical and radiographic exam- ination, a periapical preoperative radiograph with radiovisio- graph was taken, in which the presence of an area compatible with the diagnosis of internal dentine resorption was observed, which was later confirmed by a cone-beam computed tomog- raphy.The image of the lesion was presented as a deforming radiolucent area with sharp edges, located at pulp chamber level. Treatment consisted of the removal of the coronary pulp and the instrumentation, disinfection and filling of the root ca- nals and the access cavity. In the clinical and radiographic control carried out 3 years after procedure, it was observed that the patient was asymptomatic and the periradicular struc- tures were within normal limits. The histological observation of the removed material from the pulp chamber revealed the presence of a granulomatous tissue with numerous blood ves- sels and scarce micro hemorrhagic focus. Until now, the endodontic treatment is the indicated pro- cedure to treat internal dentine resorption. It is necessary to highlight the importance of the cone-beam computerized to- mography for the early diagnosis and treatment of internal dentine resorptions in order to have a favorable outlook (AU)

Effect of ageing and endodontic treatment on the thermal stability of human dentin.

BACKGROUND: Human dentin is a highly calcified tissue of mesenchymal origin with a heterogeneous structure. Its morphology is constantly remodelled throughout the life span of the tooth, as well as under the influence of external stimuli. OBJECTIVE: The aim of the present study was to obtain information about the thermal changes in the crown and root dentin specimens of vital and devitalized teeth. METHODS: The investigated samples were divided into 6 groups, depending on the patients' age and dentin location (crown, root). An additional group of endodontically treated teeth was created. The methods of choice were were combined thermal analysis (DTA-TG(DTG)-MS and gas chromatography-mass spectrometry. RESULTS: After heating up to 1200 °C, endo- and exothermal effects were observed. The effects' dynamic was the same for all samples. The differences were in the samples' weight after the experiment, with root dentin showing the greatest mass loss percentage. CONCLUSIONS: The observed mass loss differences could be attributed to the presence of impurities in the dentin, as well as alterations in the collagen matrix. Ageing and endodontic treatment could catalyse the accumulation of such changes and affect the microstructure of the mineralized tissue.

Torque differences according to tooth morphology and bracket placement: a finite element study.

INTRODUCTION: Torque of the maxillary incisors is essential in esthetics and proper occlusion, while torque expression is influenced by many factors. The aim of this finite element study was to assess the relative effect of tooth morphology, bracket prescription, and bracket positioning on tooth displacement and developed stresses/strains after torque application. METHODS: A three-dimensional upper right central incisor with its periodontal ligament (PDL) and alveolus was modelled. The tooth varied in the crown-root angle (CRA) between 156°, 170°, and 184°. An 0.018-inch slot discovery® (Dentaurum, Ispringen, Germany) bracket with a rectangular 0.018 × 0.025-inch ß-titanium wire was modelled. Bracket torque prescription varied between 0°, 12°, and 22°, with bracket placement at the centre of the middle, gingival or incisal third of the crown. A total of 27 models were generated and a buccal root torque of 30° was applied. Afterwards, crown and apex displacement, strains in the PDL, and stresses in the bracket were calculated and analysed statistically. RESULTS: The palatal crown displacement was significantly affected by bracket positioning (up to 94 per cent), while the buccal apex displacement was significantly affected by bracket prescription (up to 42 per cent) and bracket positioning (up to 23 per cent). Strains in the PDL were affected mainly by CRA (up to 54 per cent), followed by bracket positioning (up to 45 per cent). Finally, bracket prescription considerably affected the stresses in the bracket (up to 144 per cent). LIMITATIONS: These in silico results need to be validated in vivo before they can be clinically extrapolated. CONCLUSION: Tooth anatomy and the characteristics of the orthodontic appliance should be considered during torque application.

Biomechanical Behavior of Extensively Restored Premolars: Cusp Deformation, Marginal Integrity, and Fracture Resistance.

PURPOSE: To study the biomechanical behavior of extensively restored premolars by determining the effect of the composite type, presence of cusp weakening, and compressive loading on the cusp deformation (CD), marginal integrity (MI), and fracture resistance (FR) of directly restored premolars. MATERIALS AND METHODS: Forty premolars received Class II mesio-occlusal-distal (MOD) cavities and were divided into 4 groups (n = 10) in accordance with the two study variables: composite type (conventional: Filtek Z250 XT [Z250], 3M ESPE; low shrinkage: Venus Diamond [VD], Heraeus-Kulzer) and the presence of cusp weakening (with/without). Cusp deformation upon restoration was assessed using strain gauges during the restorative procedure and thereafter when the restorations were subjected to an occlusal load of 100 N. The samples were subjected to thermal and mechanical cycling. Epoxy resin replicas of the proximal tooth/restoration interfaces were made to analyze the marginal integrity (MI) using scanning electron microscopy. To determine the fracture resistance (FR), the teeth were loaded at a crosshead speed of 0.5 mm/min until fracture. RESULTS: The conventional composite Z250 had higher CD, lower MI, and lower FR than the low-shrinkage composite VD. Cusp weakening had no influence on CD, but MI and FR decreased. CONCLUSION: The low-shrinkage composite VD performed better in restoring extensively destroyed premolars than did Z250.

Case report of an internal granuloma investigated by light and scanning electron microscopy.

There is no doubt that the main reason for an internal grauloma is a traumatic event. The trauma may be physical or chemical as in the case of caries or coronal pulpectomy. In most of the cases it is diagnosed by hazard or, when in case of fracture or mobility, extraction is the only therapy to be performed. If diagnosed in time root canal treatment may be adequate.In the presented case no single specific event could be determined being the cause of this large internal granuloma extending from the coronal third of the root canal to the whole crown just leaving an eggshell of enamel that fractured and mimicked mobility of the whole tooth to the patient finally causing him to attend the clinic. As the patient presented severe aggressive periodontitis and mobility of all teeth it first was assumed that periodontitis was the ethiological reason in this case. Due to secondary trauma the front teeth were labially positioned thus probably being exposed to traumatic insults more frequently. Clinically the upper right medial incisor appeared discoloured darkly not showing the typical pink spot. Without any force the coronal part of the right medial incisor could be removed manually and the root was extracted using a periostal extractor. As it was not suitable to leave the patient with a missing tooth in the front the wound was sutured and as a temporary solution the tooth was reconstructed with composite intraorally and fixed to the neighbour teeth adhesively. The histopathology of the internal granuloma and the crown was investigated.

Influence of apical root resection on the biomechanical response of a single-rooted tooth-part 2: apical root resection combined with periodontal bone loss.

INTRODUCTION: In a clinical situation, an apically resected tooth is often accompanied by a varying degree of periodontal bone loss. The purpose of this study was to assess the influence of apical root resection combined with periodontal bone loss on the biomechanical response of a single-rooted tooth. METHODS: A basic intact model and a basic apically resected model of the upper central incisor were selected for the numerical analysis. From each basic model, 6 models were developed assuming different amounts of periodontal bone loss (0, 0.5, 1, 1.5, 2, and 3 mm). Maximum von Mises stress (σ max), maximum tooth displacement (ΔR max), and effective crown-to-root ratio (α) were calculated for each condition. RESULTS: There were only marginal differences (a 2.1% difference in σ max and a 16.9% difference in ΔR max) between the biomechanical responses of the intact model and the apically resected model when the tooth was supported by a normal periodontium. However, when destruction of the periodontium was assumed, the intact model and the apically resected model responded differently. The difference increased as the periodontal bone loss progressed, resulting in a 68.7% difference in σ max and a 56.3% difference in ΔR max when the periodontal bone loss increased to 3 mm (α = 0.48). CONCLUSIONS: Although the biomechanical response of an apically resected tooth was relatively stable when the tooth was supported by a normal periodontium, the apically resected tooth showed a more deteriorated response compared with the intact tooth as the periodontal bone loss progressed.

Fracture resistance and cuspal deflection of incompletely excavated teeth.

OBJECTIVES: Incomplete excavation reduces the risk of pulpal complications, but doubts remain regarding the mechanical properties of incompletely excavated teeth. Remaining carious dentine is suspected to not sufficiently support the restoration and to reduce bond strengths between the tooth and the restoration, with effects possibly varying depending on the depth of the remaining caries lesion. This study investigated fracture resistance (FR) and cuspal deflection (CD) of premolars after leaving or removing demineralized dentine in vitro. METHODS: In 48 premolars, shallow and deep artificial lesions (depths [mean ± SD] of 64 ± 18 µm and 771 ± 176 µm) were created on pulpo-axial walls of standardised mesial-distal-occlusal cavities. Demineralized dentine was either removed or left before adhesively restoring the tooth (n=12/group). Restored teeth were submitted to thermo-mechanical cycling. CD was subsequently measured at loads of 200 N and 400 N, and teeth submitted to occlusal-perpendicular loading until fracturing occurred. RESULTS: FR was not significantly different between teeth with or without remaining demineralized dentine regardless of the lesion depth (p>0.30, t-test). Irrespective of the removal technique, teeth with deep lesions showed significantly decreased FR (p ≤ 0.001). In contrast, CD was significantly increased in teeth with remaining demineralized dentine compared with completely excavated teeth (p ≤ 0.05; Mann-Whitney test). CONCLUSIONS: Remaining demineralized dentine did not significantly decrease the fracture resistance of premolars in vitro. Effects of increased cuspal deflection on restoration margins should be assessed. This study showed no indication that incomplete excavation increases the risk of non-pulpal complications. CLINICAL SIGNIFICANCE: Incomplete caries removal seems suitable to treat especially deep lesions. Leaving demineralized dentine does not seem to affect the fracture resistance of incompletely excavated teeth regardless of the lesion depth.

Comparison of the fracture resistance of reattached incisor tooth fragments using 4 different materials.

AIM: To evaluate and compare the fracture resistance of reattached teeth using four different materials. MATERIALS AND METHODS: 150 extracted human permanent maxillary incisors were randomly divided into five groups of 30 teeth each of one control and four experimental groups. Teeth in experimental groups were sectioned 2.5 mm from incisal edge and reattached using four different materials. The reattached teeth were subjected to evaluate fracture resistance. RESULTS: The mean fracture resistance of reattached teeth using resin modified glass ionomer cement, compomer, composite resin and dual curing resin cement was 8.10 ± 2.34, 11.15 ± 3.36, 17.11 ± 3.99 and 14.13 ± 3.71 kg respectively. Results showed highly significant difference between the groups ( P < 0.001). CONCLUSION: Fracture resistance of reattached teeth in the different groups varied from 24-51% of that for an intact tooth. Reattachment with composite resin provides highest fracture resistance ( P < 0.05). Reattachment with resin-modified glass ionomer cement was the weakest ( P < 0.05).

In vitro study comparing fracture strength recovery of teeth restored with three esthetic bonding materials using different techniques.

Reattachment of the fractured fragment of a traumatized tooth (whenever available and usable) has become the treatment of choice in cases of uncomplicated crown fractures. Despite the presence of various bonding materials and techniques, laboratory data evaluating the biomechanical aspects of such procedures is largely lacking in the literature. The objective of this in vitro study was to evaluate the fracture strength recovery of incisors, following fragment restoration with three different techniques. A total of 90 extracted human maxillary central incisors were subjected to crown fractured under standard conditions. This was carried out by applying a compressive force from the buccal aspect of the clinical crown using a universal strength testing machine. The fractured teeth were equality distributed in three groups, defined on the basis of the technique used for reattachment: i) overcontour, ii) internal dentinal groove and iii) direct buildup. Each group was further subdivided into three subgroups on the basis of the intermediate restorative material used for reattachment, namely: i) hybrid composite (Filtek Z100 Universal Restorative, ii) nanocomposite (Filtek Z350) and iii) Ormocer (Voco Admira). Following reattachment, the crowns were re-fractured under standard conditions. The force required for fracture was recorded and was expressed as a percentage of the fracture strength of the intact tooth. The data was expressed as a percentage of the fracture strength of the intact tooth. The data was analyzed using two-way ANOVA and Bonferroni tests for pair-wise comparison. The results showed no statistically significant differences in fractures strength between the three groups (P > 0.05). However, comparison of the subgroups revealed statistically significant higher strength recovery percentages for the hybrid and the nanocomposite compared with the Ormocer material (P < 0.05). It was concluded that material properties have a significant influence on the success of reattachment procedures.

Reattachment of anterior fractured teeth: effect of materials and techniques on impact strength.

BACKGROUND/AIM: The reattachment of dental fragments, as a conservative treatment, should be the first choice to restore fractured teeth. Therefore, the aim of this study was to evaluate the effect of different materials and reattachment techniques on impact strength of bovine incisors. MATERIAL AND METHODS: Standardized fragments were obtained when 80 crowns were sectioned 12 mm from the incisal edge. Teeth were mounted in PVC rings, embedded in acrylic resin and polyether to simulate bone support and periodontal ligament. Specimens were distributed in nine groups (n = 10), according to the reattachment technique (Direct bonding or Circumferential chamfer); the adhesive system (Single Bond or Clearfil SE Bond); and the intermediated material (Filtek Z350 Flow or Rely X CRA). Sound teeth composed the control group. Circumferential chamfer was prepared after the bonding of the fragment by means of a spherical point and filled with the composite Filtek Z250. The impact strength was evaluated in a universal testing machine Instron. A compressive load was applied at a crosshead speed of 500 mm min(-1) on the buccal surface, 2 mm from the incisal edge. Data were submitted to anova and Ryan-Einot-Gabriel-Welsch Multiple Range test (5%). RESULTS: Mean value of impact strength for control group was 64.8 Kgf. The fragment reattachment using Circumferential chamfer was significantly superior to Direct Bonding. The use of Single Bond significantly increased the impact strength when compared to the use of Clearfil SE. There was no significant difference among Rely X and Filtek X350 Flow. CONCLUSION: No technique or material, when individually considered, was capable of achieving the mechanical strength of the sound teeth; however, the association of reattachment technique Circumferential chamfer with bonding system Single Bond could approximate the immediate impact strength of the restored teeth to that observed in the sound teeth.

Premolar cuspal flexure as a function of restorative material and occlusal contact location.

OBJECTIVE: To measure cuspal flexure of intact and restored maxillary premolars with different restorative materials and occlusal contacts. METHOD AND MATERIALS: Micro?computed tomography data were used to generate finite-element models with a mesio-occlusaldistal (MOD) cavity preparation and the corresponding restoration. The tooth parts were imported in finite-element software to create 3D volumetric models. Occlusal loading either in enamel, at restoration margin, or in restorative material was simulated by linear contact analysis. Cuspal widening was measured for the different contact locations and restorative conditions (unaltered tooth, MOD porcelain, and composite-inlay restorations). RESULTS: For a given material property, contacts in restoration generated the least amount of cuspal deformation, followed by the enamel contacts and contacts at restoration margin. Models of the intact tooth and ceramic inlay behaved similarly (cuspal widening at 100 N ranging from 1.8 to 3.0 microm and 1.6 to 2.6 microm, respectively). Cuspal flexure was increased in the MOD composite resin restorations (3.4 to 5.7 microm at 100 N of axial force). The least amount of deformation was generated in the ceramic inlay with contacts in only restoration (1.6 microm at 100 N) and the largest in the composite inlay with contacts at restoration margins (5.7 microm at 100 N). For the composite restoration, antagonist contacts at restoration margins were less favorable compared to located on either enamel or the restoration itself. CONCLUSION: A relatively small cuspal deformation was observed in all models. There is an increased cusp-stabilizing effect of ceramic inlays compared to composite ones.

Cuspal deflection, strain and microleakage of endodontically treated premolar teeth restored with direct resin composites.

OBJECTIVES: To measure cuspal deflection and tooth strain, plus marginal leakage and gap formation caused by polymerization shrinkage during direct resin composite restoration of root-filled premolars. METHODS: Thirty-two first and second maxillary premolars were divided into four groups (n=8). Group 1 had standardised mesio-occlusal-distal (MOD) cavities and served as the control group. Group 2 had endodontic access and root canal treatment through the occlusal floor of the MOD cavity, leaving the axial dentine intact. Group 3 had endodontic access and root canal treatment with the mesial and distal axial dentine removed. Group 4 had endodontic access and root canal treatment with axial dentine removed and a glass ionomer base (GIC). All groups were restored incrementally using a low shrink resin composite. Cuspal deflection was measured using direct current differential transformers (DCDTs), and buccal and palatal strain was measured using strain gauges. Teeth were immersed in 2% methylene blue for 24h, sectioned and scored for leakage and gap formation under light and scanning electron microscopy. RESULTS: Total cuspal deflection was 4.9+/-1.3 microm for the MOD cavity (group 1), 7.8+/-3.3 microm for endodontic access with intact axial dentine (group 2), 12.2+/-2.6 microm for endodontic access without axial dentine (group 3), and 11.1+/-3.8 microm for endodontic access with a GIC base (group 4). Maximum buccal strain was 134+/-56, 139+/-61, 251+/-125, and 183+/-63 mustrain for groups 1-4 respectively, while the maximum palatal strain was 256+/-215, 184+/-149, 561+/-123, 264+/-87 mustrain respectively. All groups showed marginal leakage; however placement of GIC base significantly improved the seal (p=0.007). CONCLUSION: Cusp deflection and strain increased significantly when axial dentine was removed as part of the endodontic access. Placement of a glass ionomer base significantly reduced tooth strain and marginal leakage. Therefore, a conservative endodontic access and placement of a glass ionomer base are recommended if endodontically treated teeth undergo direct restoration with resin composite.

Fracture resistance of endodontically treated teeth: three walls versus four walls of remaining coronal tooth structure.

PURPOSE: The purpose of this study was to evaluate the fracture resistance of endodontically treated teeth between those with four walls and those with three walls of remaining coronal tooth structure and the effect of the site of the missing coronal wall. MATERIALS AND METHODS: Thirty-two endodontically treated second mandibular premolars were decoronated, leaving 3 mm above the cementoenamel junction (CEJ). A 0.5-mm-wide chamfer was prepared 1 mm above the CEJ. The teeth were randomly divided into four groups. Group 1 had four walls of coronal tooth structure, whereas groups 2, 3, and 4 had only three walls, missing the buccal, lingual, and mesial wall, respectively. The cast dowel and cores and crowns (Ni-Cr alloy) were cemented with zinc phosphate cement. A compressive load was applied 45 degrees to the long axis, 2 mm below the buccal cusp, with an Instron machine until failure at a crosshead speed of 5 mm/min. Failure load (kg) and mode of failure were recorded. Data were analyzed with one-way ANOVA and Scheffé tests (p < 0.05). RESULTS: Group 1 had the highest fracture resistance (1190.3 +/- 110.5 kg), significantly different from the other groups (p < 0.05) (group 2: 578.5 +/- 197.4 kg; group 3: 786.6 +/- 132.8 kg; group 4: 785.4 +/- 289.9 kg). There were no significant differences among the test groups. The mode of failure in group 1 was a horizontal root fracture, whereas that of the other groups was either vertical or oblique fracture. CONCLUSIONS: Teeth with four walls of remaining coronal dentine had significantly higher fracture resistance than teeth with only three walls. The site of the missing coronal wall did not affect the fracture resistance of endodontically treated teeth.

Mechanical interactions of cuspal-coverage designs and cement thickness in a cusp-replacing ceramic premolar restoration: a finite element study.

The aim of this study was to investigate the biomechanical interactions between cuspal preparation designs and cement thickness in a cusp-replacing ceramic premolar restoration. The cavity was designed in a typical MODP (mesial-occlusal-distal- palatal) restoration failure shape when the palatal cusp has been lost. Twelve 3D finite element (FE) models with four cavity preparations (without coverage and with buccal cuspal coverage in 1.0, 1.5 and 2.0 mm reducing in cuspal height) and three cement thicknesses (50, 100 and 150 microm) were constructed to perform the simulations. The results indicated that enamel and cement stresses in designs with no buccal cusp replacement or a 1.0 mm thick buccal cusp replacement were higher than the designs with 1.5 and 2.0 mm thick replacement. No apparent differences were found in the dentin, enamel, and cement stresses based on cement thicknesses of 50, 100, or 150 microm. This study concluded that when cusp replacement is indicated, reduction of the buccal cusp by 1.5 mm at least could reduce stress.

Factors affecting buccal bone changes of maxillary posterior teeth after rapid maxillary expansion.

INTRODUCTION: The purpose of this study was to use cone-beam computed tomography (CBCT) images to determine the factors that might affect buccal bone changes of maxillary posterior teeth after rapid maxillary expansion (RME). METHODS: Thirty consecutive patients (17 boys, 13 girls; mean age, 13.8 +/- 1.7 years) who required RME as part of their orthodontic treatment and had the pre-RME (T1) and post-RME (T2) CBCT images available were included in the study. The T1 and T2 measurements of interdental distance, interdental angle (IA), buccal bone thickness (BBT), and buccal marginal bone levels (BMBL) of the first premolar (P1), the second premolar (P2), and the first molar (M1) were compared with the Friedman and the Wilcoxon signed rank tests. To determine which variables were associated with the changes in IA, BBT, and BMBL, the Spearman rank correlation analysis was performed (alpha = .05). RESULTS AND CONCLUSIONS: The results suggest that buccal crown tipping, and reduction of BBT and BMBL of the maxillary posterior teeth are the expected immediate effects of RME. There were no significant differences in dental expansion among P1, P2, and M1 (P >.05). P2 had clinically more buccal crown tipping (P = .116) but statistically less reduction in BBT and BMBL (P <.0001 and P = .001) than P1 and M1. Buccal bone changes and dental tipping on P2 were not affected by any other variables. Factors that showed significant correlation to buccal bone changes and dental tipping on P1 and M1 were age, appliance expansion, initial buccal bone thickness, and differential expansion (P <.05), but rate of expansion and retention time had no significant association (P >.05).

A comparison of impact strength of fragment-bonded anterior teeth using three different restorative materials: an in vitro study.

BACKGROUND AND OBJECTIVE: The purpose of this investigation was to estimate the impact strength of fractured anterior teeth reattached using three different restorative materials and compare their impact strengths to those of control. MATERIALS AND METHODS: Sixty human maxillary permanent central incisors were selected and divided into control and experimental groups. The teeth in the experimental groups were fractured and then bonded using Composite resin, Compomer and resin-modified GIC. Intact teeth served as control. All the specimens were then tested in an impact testing machine. RESULTS: The results revealed statistically significant differences between Compomer and resin-modified GIC groups, control and experimental groups. No statistically significant differences were observed between Composite resin and Compomer groups. CONCLUSION: Thus the fractured fragments bonded with Composite resin and Compomer provided better adhesion than resin-modified GIC.

Cuspal flexure of teeth with composite restorations subjected to occlusal loading.

PURPOSE: To measure in vitro the cuspal deflection produced by polymerization shrinkage and occlusal loading in mesio-occlusal (MO) and mesio-occlusal-distal (MOD) bonded composite restorations. MATERIALS AND METHODS: Twenty first premolars were studied, attaching a small crystal ball to each cusp vertex as a reference point for intercuspal distance measurements. MO cavities were made in ten premolars and MOD cavities in the other ten. Cavities were then restored with Syntac Single adhesive and Tetric Ceram composite in two increments. A precision micrometer was used to measure intercuspal distances in unaltered teeth (baseline distance), unaltered teeth under 150 N load, restored teeth at 5 min after restoration completion, and restored teeth under 150 N load. RESULTS: In the two study groups, both polymerization shrinkage and application of 150 N load produced a statistically significant change in intercuspal distance compared with baseline measurement. The cuspal deflection produced by 150 N load was statistically similar between unaltered and restored teeth, although polymerization shrinkage acted as a preload in the latter case (starting point was not baseline condition). The cuspal deflection produced by polymerization shrinkage and occlusal load was significantly greater in MOD than in MO restorations. CONCLUSION: The cuspal deflection produced by composite polymerization shrinkage and occlusal loading is significantly greater in MOD vs MO composite restorations.

¿Son los adhesivos dentinarios una opción válida para el tratamiento de la sensibilidad cervical dentinaria? / Are dentin bonding systems a valid option for the treatment of Cervical Dentin Sensitivity (C. D. S.)?

El objetivo de este trabajo es evaluar la capacidad in vitro de sellar túbulos dentinarios y reducir la permeabilidad dentinaria que tienen catorce productos propuestos para el tratamiento de la sensibilidad cervical dentinaria (SCD) y evaluar el efecto que la humedad y el cepillado tienen sobre ellos. Material y método: 140 discos de dentina (obtenidos de 3º molares humanos recién extraídos) se dividen en catorce grupos de 10 discos que se montan en un sistema de perfusión basado en la máquina de Pashley que mantiene una presión positiva sobre las discos. Cada disco se graba con ácido ortofosfórico al 35% y su permeabilidad se mide en una hora, este valor se considera el de referencia (100%). Un disco queda como control y se aplica tratamiento a los otros 9, midiéndose su permeabilidad en una hora. Después se deja un disco como control, a los 8 restantes se les realiza un lavado y cepillado, viéndose su permeabilidad en una hora. Resultados: Todos los productos afectaron a la perfusión dentinaria en mayor o menor grado. El cepillado de las muestras con el producto aplicado afectó a la permeabilidad, que en todas las preparaciones aumentó en mayor o menor grado. El mejor producto fue el Seal & Protect, seguido del Amm-i-dent + Xeno III, el Clearfil SE Bond y el Amm-i-dent + Scotchbond1. Conclusiones: Todos los productos presentan mala resistencia al lavado y cepillado, lo que justifica el limitado éxito clínico de los agentes desensibilizantes. El que los cuatro mejores productos o combinaciones en cuanto a reducción de permeabilidad pertenezcan al grupo de los adhesivos dentinarios indica que estos pueden ser una alternativa válida para ser investigada y perfeccionada como tratamiento de la SCD

The aim of this study is to evaluate the “in vitro” capability of fourteen agents proposed for the treatment of cervical dentin sensibility (CDS) to seal dentine tubules, to reduce dentine permeability and to resist the effect of wetness and tooth brushing. Materials and Methods: 140 dentin discs were obtained from freshly extracted human third molars. Samples were divided into fourteen groups of 10 each and were mounted in a perfusion device based on the Pashley ´s system. Each disc was etched with 35% phosphoric acid. Permeability was measured after 1 hour, this value was considered the reference value (100%). One disc was used as a control and nine were treated with a bonding system. Permeability was measured again after 1 hour. One disc was used as a control and 8 were washed with water and subjected to simulated tooth brushing equivalent to three weeks of normal brushing. Subsequebtly, permeability was measured again. Results: All systems reduced dentinal perfusion when applied. Brushing of products produced an increase of permeability. The best results were obtained with Seal & Protect, follwed by Amm-i-dent + Xeno III, Clearfil SE Bond and Amm-i-dent+Scotchbond 1. Conclusions: All products have shown low resistance to washing and brushing. This can justify unsatisfactory clinical results in reducing dentinal sensibility. The best four products were all adhesives or a combination of these, it seems to indicate that adhesives are a good choice to be investigated and improved for the treatment of CDS

Effect of restorative procedures and occlusal loading on cuspal deflection.

This study examined the extent of cuspal flexure caused by progressively larger cavity preparations, including endodontic access, and progressive simulated occlusal loading with 50N, 100N and 150N. Ten intact extracted maxillary premolars were embedded in acrylic resin, and a small ball was attached to each cuspal tip as a reference point for intercuspal distance measurements. The teeth were subjected sequentially to the following procedures: conservative MO cavity preparation, extensive MO cavity preparation, endodontic access step and MOD cavity preparation. After each cavity preparation procedure, the specimens were subjected to increasing loads of 50, 100 and 150 N, and the intercuspal distance was recorded by means of a digital caliper. The extension of cavity preparation and the magnitude of occlusal load significantly influenced cuspal deflection. After 50 and 100 N loading, a similar cuspal deflection was exhibited by conservative and extensive MO preparations with or without the endodontic access step. With 150 N loading, the endodontic access step was related to a statistically larger cuspal deflection versus the deflection recorded for conservative and extensive MO preparations. The removal of both marginal ridges in MOD cavity preparation with endodontic access produced a dramatic increase in cuspal deflection for the three loads tested.

Compressive strength recovery by composite onlays in primary teeth. Substrate treatment and luting agent effects.

OBJECTIVES: To evaluate 1% NaOCl treatment and two resin luting agent effects on compressive strength recovery in composite onlays on primary teeth and to analyze the fractures type. METHODS: Forty sound primary molars crowns were prepared in the standard machine and randomly divided into four groups (n=10): G1 (1% NaOCl/ 30 min+EnForce); G2 (without 1% NaOCl EnForce); G3 (1% NaOCl/ 30 min+Rely X); G4 (without 1% NaOCl+Rely X). The onlays were made using Z250 composite on plaster models. Ten sound teeth were used as control group (CG). All groups were submitted to compression mechanic test in a universal test machine INSTRON at 1mm/min cross-head speed. After that, the data (kgf) were submitted to ANOVA test (alpha=0.05). Finally, the fracture types were classified in a crescent scale (1-5) related with severity degree and submitted to Fisher's Exact Test (p<0.05). Scanning electronic microscope analysis was done in order to illustrate the fractures sites. RESULTS: The values of compressive strength of experimental groups did not differ each others neither from control group (p>0.05). The results from fracture type showed that types 5 and 4 fractures (most severe) present the highest percentage to experimental groups. Conversely, the CG showed higher percentage of fracture types 2 and 3. CONCLUSIONS: This research found that the composite onlays recovered the compressive strength compared to sound teeth, regardless of the substrate treatment and cement agent used. Nevertheless, no group showed similar type of fractures to CG, which had more frequency of less severe fracture types.