In Vitro Analysis of the Removability of Fractured Prosthetic Screws within Endosseous Implants Using Conventional and Mechanical Techniques.

STATEMENT OF PROBLEM: The extraction of fractured abutment screws can be a difficult challenge to overcome. PURPOSE: To compare the removal capacity, dental implant connection damage, and time required to remove the fractured abutment screws between three drilling techniques and a conventional method. MATERIALS AND METHODS: A total of 180 prefabricated screw-retained abutments were intentionally fractured in internal connection dental implants after being subjected to a cyclic load and a static compression load. Afterwards, three operators randomly removed the fractured abutment screws with the following drilling techniques and a conventional method: A: a conventional technique using an exploration probe and ultrasonic appliance (n = 45), Rhein83® (n = 45); B: Sanhigia® (n = 45); C: Phibo® (n = 45). Two-way ANOVA models were estimated to evaluate the mean time according to the method and operator used. RESULTS: The probability of removal of the screws with mobility was twelve times higher than that of the screws without mobility (OR = 12.4; p < 0.001). The success rate according to the operators did not show statistically significant differences (p = 0.371). The location of the fractured screw did not affect removal success (p = 0.530). The internal thread of the implant was affected after the removal process in 9.8% of the cases. The mean extraction time was 3.17 ± 2.52 min. The Rhein83® method showed a success rate of 84.4%, followed by the Phibo® and conventional methods (71.1%) and the Sanhigia® method (46.7%). CONCLUSIONS: The Rhein83® drilling technique increases the removal probability of fractured abutment screws. The initial mobility of the fragment is also a significant factor in the removal success.

Resistance to loosening of intentionally shortened screws used to solve the unsuccessful removal of fractured prosthetic screws.

STATEMENT OF PROBLEM: Fractured prosthetic implant screws cannot be removed in all patients, ultimately leading to the removal of the implant. Whether an intentionally shortened prosthetic implant screw (SPIS) can provide adequate retention is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the resistance to loosening of SPISs engaging the remaining coronal internal threads as a possible solution to maintaining both implant and restoration. MATERIAL AND METHODS: Fifty grade V titanium SPISs were used to tighten 50 titanium transepithelial abutments on implants to 30 Ncm. The specimens were distributed into 5 groups (n=10) according to the conditions under which the screws were secured to manufacturer-recommended preload: dry (D), moistened in saliva (AS), moistened in chlorhexidine (CLHX), wrapped in polytetrafluoroethylene tape (PTFE), and resin cemented (RE). All groups were subjected to a cyclic loading test (240 000 cycles). The reverse torque value (RTV) of the SPIS was registered twice: 24 hours after initial tightening (T1); and after retightening and the cyclic loading test (T2). The resultant RTV was compared with the 30-Ncm tightening torque to assess torque loosening. The Kruskal-Wallis and Mann-Whitney tests were used for the comparisons between groups and the Wilcoxon test for the intragroup comparisons (α=.05 with Bonferroni correction). RESULTS: At T1, all groups found lower mean±standard deviation RTVs than the reference tightening torque (30 Ncm) (D 24.82±2.34 Ncm, AS 25.56±2.89 Ncm, PTFE 26.02±2.26 Ncm, CLHX 26.26±1.82 Ncm), except the resin-cemented group, which increased its RTV (RE 44.01±19.94 Ncm). At T2, all the groups found lower RTVs than the reference tightening torque, and the torque values at T1 (D 19.81±6.59 Ncm, CLHX 18.98±6.36 Ncm, AS 21.28±7.32 Ncm), with the exception of PTFE (24.07±3.41 Ncm) and RE (41.47±21.68 Ncm), where RTV was similar to that recorded at T1. At T1, significant differences were found among the groups (P=.024). At T2, after cyclic loading, the RE group found the highest RTV, reporting significant differences with the D and CHLX groups (P<.05) and statistically similar to the AS group (P=.068). CONCLUSIONS: PTFE-wrapped screws found similar RTVs after the fatigue test than dry, moistened with saliva, and moistened with chlorhexidine screws. Resin-cemented shortened prosthetic implant screws were found to be the most resistant to loosening after cyclic loading.

Microtensile Bond Strength of CAD-CAM Restorative Dental Material Blocks to Resin Cement: An In Vitro Study.

INTRODUCTION: Today's dentistry frequently employs bonded partial restorations, which are usually fabricated in ceramic materials. In the last decade, hybrid materials have emerged that attempt to combine the properties of composites and ceramics. OBJECTIVES: To evaluate in vitro, by means of a microtensile test, the bond strength between CAD-CAM restorative materials and the cement recommended by their manufacturer. MATERIAL AND METHOD: From blocks of CAD-CAM restorative material bonded to composite blocks (Filtek 500®), beams with a bonding area of approximately 1 mm2 were made and divided into four groups: EMAX (IPS e.max CAD® lithium disilicate), VE (VITA Enamic® polymer-infiltrated ceramic matrix), LUA (Lava Ultimate® nano-ceramic resin with sandblasting protocol) and LUS (Lava Ultimate® nano-ceramic resin with silica coating protocol). In each group, perimeter (external) or central (internal) beams were differentiated according to the position in the block. The samples were tested on the LMT 100® microtensile machine. Using optical microscopy, the fractures were categorized as adhesive or cohesive (of the restorative material or composite), and the data were analysed with parametric tests (ANOVA). RESULTS: The LUS group had the highest results (42 ± 20 MPa), followed by the LUA group (38 ± 18 MPa). EMAX had a mean of 34 ± 16 MPa, and VE was the lowest in this study (30 ± 17 MPa). In all groups, the central beams performed better than the perimeter beams. Both EMAX and VE had the most adhesive fractures, while LUA and LUS had a predominance of cohesive fractures. CONCLUSIONS: Lava Ultimate® nanoceramic resin with the silica coating protocol obtains the best bond strength values.

Factores de riesgos en la génesis de la caries dental en edad temprana y efectos de la lactancia materna / Risk factors for early childhood dental caries and effects of breastfeeding

RESUMEN Introducción: Varios son los factores descritos en la literatura como determinantes en la génesis de la caries dental en edad temprana. Sin embargo, el papel de la lactancia materna como factor protector sigue siendo un tema controvertido. Objetivo: Determinar los factores de riesgos implicados en la génesis de la caries dental en edad temprana y los efectos de la lactancia materna. Métodos: Estudio caso-control con un total de 80 pacientes entre 3 y 8 años de edad, 35 con caries dental y 45 controles sanos, procedentes de la provincia de Valencia, España, seleccionados bajo un modelo no probabilístico. Se analizaron variables relacionadas con lactancia materna y variables vinculadas a características sociodemográficas y hábitos de alimentación e higiene. Para el análisis de las variables cuantitativas se utilizó la media aritmética y la desviación estándar como medidas de centralidad. Las variables cualitativas se describieron por sus frecuencias absolutas y relativas. Para el estudio de factores asociados al desarrollo de la caries dental se utilizó la prueba de chi cuadrado y la estimación de riesgo (odds ratio). Resultados: No se encontró relación estadísticamente significativa con las variables relacionadas con la lactancia materna. Pudo establecerse relación entre la aparición de caries dental y nivel de estudios materno (OR= 4,17) y paterno (OR= 4,87), consumo de azúcares diario (OR= 4), madre fumadora (OR=4,23) y edad gestacional (mayor incidencia en los pretérmino). Conclusiones: La lactancia materna es un factor protector para la producción de caries dental en el niño, aunque el estudio no pudo establecer dicha relación. Los factores más importantes relacionados con la aparición de caries en la muestra de estudio fueron: edad gestacional, nivel educativo de los padres, madre fumadora y consumo de azúcares diario(AU)

ABSTRACT Introduction: Several factors are described in the literature as determinant in the genesis of early childhood dental caries. However, the role of breastfeeding as a protective factor continues to be a controversial subject. Objective: Determine the risk factors involved in the genesis of early childhood dental caries and the effects of breastfeeding. Methods: A case-control study was conducted of a total 80 patients aged 3-8 years, 35 with dental caries and 45 healthy controls, from the province of Valencia, Spain, selected by nonprobability sampling. The variables analyzed had to do with breastfeeding, sociodemographic characteristics, and eating and hygiene habits. Analysis of quantitative variables was based on arithmetic mean and standard deviation as measures of centrality. Qualitative variables were described in terms of their absolute and relative frequencies. Factors associated to dental caries development were examined with chi-square and odds ratio testing. Results: No statistically significant relationship was found between the variables analyzed and breastfeeding. A relationship could be established between the emergence of dental caries and the educational level of the mother (OR= 4.17) and the father (OR= 4.87), daily sugar intake (OR= 4), smoking mother (OR= 4.23) and gestational age (a greater incidence in preterm deliveries). Conclusions: Breastfeeding is a protective factor against childhood dental caries, though the study could not establish that relationship. The most important factors related to the emergence of dental caries in the study sample were gestational age, educational level of parents, smoking mother and daily sugar intake(AU)

In vitro comparison of the efficacy of two fractured implant-prosthesis screw extraction methods: Conventional versus mechanical.

STATEMENT OF PROBLEM: Implant-supported prostheses may be subject to esthetic, biological, or mechanical complications. Protocols for dealing with these mechanical problems are sparse. PURPOSE: The purpose of this in vitro study was to compare the efficacy of a mechanical system for extracting fractured implant-prosthesis screws with the conventional method. MATERIAL AND METHODS: A total of 60 screws were divided into 2 groups according to their morphology (flat screws with a smooth shaft and threaded apical area and screws with a completely threaded body) and subjected to fatiguing and static load testing until fracture. The specimens were assigned to 3 operators with varying levels of clinical experience (high, medium, low) in extracting fractured screws by using the conventional method (explorer and ultrasound device) and a mechanical method (extractor kit). The extraction event (whether the screw fragment was extracted or not within 10 minutes) was recorded, and the time taken to perform the extraction was measured for each method in relation to screw type, operator experience, and damage to the threads. The influence of screw morphology, extraction method, operator experience, and fracture type on the time needed to extract a screw fragment was assessed with the Mann-Whitney and Kruskal-Wallis tests. Thread damage was compared by using the Fisher's exact test and the Kruskal-Wallis test (α=.05). RESULTS: The mechanical method was more effective for screw extraction than the conventional method (P=.032). Screw morphology also had a significant influence on extraction, whereby the screw design with apical thread took less time to extract (P=.022). Coronal fractures had a higher probability of extraction than apical fractures (P=.05). CONCLUSIONS: Mechanical extraction is more effective for extracting fractured implant-prosthetic screws, showing a higher probability of extraction than the conventional method. Prosthetic fixing screws with a smooth shaft and threaded apical area are the easiest to extract.

Accuracy combining different brands of implants and abutments

Objective: To evaluate the vertical misfit between different brands of dental implants and prosthetic abutments, with or without mechanical torque, and to study their possible combination. Study design: Five different brands of implant were used in the study: Biofit (Castemaggiore, Italy), Bioner S.A.(Barcelona, Spain), 3i Biomet (Palm Beach, U.S.A.), BTI (Alava, Spain) and Nobel Biocare (Göteborg, Sweden), with standard 4.1 mm heads and external hexagons, and their respective machined prosthetic abutments. The implant-toabutmentfit/misfit was evaluated at four points (vestibular, lingual/palatine, mesial and distal) between implants and abutments of the same brand and different brands, with or without mechanical torque, using SEM micrographs at5000X. Image analysis was performed using NIS-Elements software (Nikon Instruments Europe B.V.).Results: Before applying torque, vertical misfit (microgaps) of the different combinations tested varied between1.6 and 5.4 microns and after applying torque, between 0.9 and 5.9 microns, an overall average of 3.46±2.96microns. For manual assembly without the use of mechanical torque, the best results were obtained with the combination of the 3i implant and the BTI abutment. The Nobel implant and Nobel abutment, 3i-3i and BTI-BTI and the combination of 3i implant with BTI or Nobel abutment provided the best vertical fit when mechanical torque was applied. Conclusions: The vertical fits obtained were within the limits considered clinically acceptable. The application of mechanical torque improved outcomes. There is compatibility between implants and abutments of different brand and so their combination is a clinical possibility (AU)

Accuracy combining different brands of implants and abutments.

OBJECTIVE: To evaluate the vertical misfit between different brands of dental implants and prosthetic abutments, with or without mechanical torque, and to study their possible combination. STUDY DESIGN: Five different brands of implant were used in the study: Biofit (Castemaggiore, Italy), Bioner S.A. (Barcelona, Spain), 3i Biomet (Palm Beach, U.S.A.), BTI (Alava, Spain) and Nobel Biocare (Göteborg, Sweden), with standard 4.1 mm heads and external hexagons, and their respective machined prosthetic abutments. The implant-to-abutment fit/misfit was evaluated at four points (vestibular, lingual/palatine, mesial and distal) between implants and abutments of the same brand and different brands, with or without mechanical torque, using SEM micrographs at 5000X. Image analysis was performed using NIS-Elements software (Nikon Instruments Europe B.V.). RESULTS: Before applying torque, vertical misfit (microgaps) of the different combinations tested varied between 1.6 and 5.4 microns and after applying torque, between 0.9 and 5.9 microns, an overall average of 3.46 ± 2.96 microns. For manual assembly without the use of mechanical torque, the best results were obtained with the combination of the 3i implant and the BTI abutment. The Nobel implant and Nobel abutment, 3i-3i and BTI-BTI and the combination of 3i implant with BTI or Nobel abutment provided the best vertical fit when mechanical torque was applied. CONCLUSIONS: The vertical fits obtained were within the limits considered clinically acceptable. The application of mechanical torque improved outcomes. There is compatibility between implants and abutments of different brand and so their combination is a clinical possibility.