An In Vitro Evaluation of Periotest Implant Stability Measurements Taken on Implant Retained Crowns and Healing Abutments.

OBJECTIVE: To assess the reliability of implant stability measurements recorded with the Periotest device and to investigate the differences in values when these measurements were taken on implant retained crowns and healing abutments. MATERIALS AND METHODS: Fifty-six implants in eight synthetic bone blocks were used to carry out implant stability measurements using the Periotest device by two different operators. Each block constituted an example of bone of density D1, D2, D3, or D4, and two blocks of each density were used. The healing abutments placed were of a height to allow approximately 6 mm of the implant-abutment complex to be supracrestal and temporary crowns were made to match the dimensions of an average central incisor. Descriptive statistics were used to describe the perio test values (PTVs) at each of the different heights on the implant abutments and implant crowns. Means for each site were calculated and distribution of data assessed using the Kruskal Wallis test. The interclass correlation coefficient (ICC) was used to determine the relationship between the PTVs recorded on the implant abutments and implant crowns. RESULTS: The mean PTV (±standard devidation) recorded across all sites was 5.57 ± 11.643 on the implant abutments, and 12.27 ± 11.735 on the temporary crowns. Excellent/good inter-operator ICCs were recorded for the mid-abutment site in all bone blocks D1-D4 (ICC = 0.814, p < 0.001, ICC = 0.922, p < 0.001, ICC = 0.938, p < 0.001, ICC = 776, p < 0.001). For mid crown sites, ICC between operators was excellent/good only for recordings in D2 bone (ICC = 0.897, p < 0.001). CONCLUSIONS: Periotest device seems to be able to reliably measure implant stability across all types of bones when the implant stability is assessed at approximately 3 mm coronal to the implant platform for abutments and 4.5 mm for implant supported single crowns.

Coronas cementadas comparado con coronas atornilladas para pacientes con restauraciones fijas implantosoportadas / Cement-retained versus screw-retained crowns in patients with implant rehabilitation

RESUMEN: Introducción: Los implantes dentales se han transformado en una opción de tratamiento de suma relevancia para pacientes parcial o totalmente desdentados. El éxito del tratamiento puede verse afectado por la elección del tipo de retención de estos (cementada o atornillada). A pesar que ambas presentan ventajas, aún no existe consenso sobre el mejor tipo de retención para restauraciones fijas implantosoportadas. Métodos: Realizamos una búsqueda en Epistemonikos, la mayor base de datos de revisiones sistemáticas en salud, la cual es mantenida mediante el cribado de múltiples fuentes de información, incluyendo MEDLINE, EMBASE, Cochrane, entre otras. Extrajimos los datos desde las revisiones identificadas, analizamos los datos de los estudios primarios, realizamos un metanálisis y preparamos una tabla de resumen de los resultados utilizando el método GRADE. Resultados y conclusiones: Identificamos 14 revisiones sistemáticas que en conjunto incluyeron 43 estudios primarios, de los cuales cinco corresponden a ensayos aleatorizados. De estos, solamente dos ensayos responden a la pregunta de interés de manera directa. Concluimos que las coronas atornilladas podrían aumentar levemente el riesgo de pérdida de implante a largo plazo, podrían resultar en nula o poca diferencia en el riesgo de pérdida de implante a mediano plazo, reabsorción ósea y periimplantitis, pero la certeza de evidencia ha sido evaluada como baja. Por otro lado, no es posible establecer con claridad si las coronas cementadas disminuyen el riesgo de complicaciones estéticas y protésicas, ya que la certeza de la evidencia existente ha sido evaluada como muy baja.

ABSTRACT: Introduction: Dental implants have become a highly relevant treatment option for partially or totally edentulous patients. Implant retention systems (cemented or screwed) can influence the treatment success. Although both have advantages, there is still no consensus on the best type of retention for implant-supported fixed restorations. Methods: We searched in Epistemonikos, the largest database of systematic reviews in health, which is maintained by screening multiple information sources, including MEDLINE, EMBASE, Cochrane, among others. We extracted data from the systematic reviews, reanalyzed data of primary studies, conducted a meta-analysis and generated a summary of findings table using the GRADE approach. Results and conclusions: We identified 14 systematic reviews including 43 primary studies overall, of which five were randomized trials. Of these, only two trials answer the question of interest. We concluded that screw-retained crowns may increase long-term implant loss, may make little or no difference in the risk of medium-term implant loss, bone resorption, and peri-implantitis, but the certainty of the evidence has been assessed as low. On the other hand, it is not possible to clearly establish whether cemented crowns reduce the risk of cosmetic and prosthetic complications, since the certainty of the evidence has been assessed as very low.

Does intraoperative bone density testing correlate with parameters of primary implant stability? A pilot study in minipigs.

Objectives: Bone density, surgical protocol, and implant design are the major determinants of primary stability. The goal of this animal trial was to investigate potential correlations of intraoperative bone density testing with clinical and histologic parameters of primary implant stability. Material and methods: Following extractions of all mandibular premolars and subsequent healing, four implants each were placed in a total of four minipigs. Bone density was determined by applying intraoperative compressive tests using a device named BoneProbe whereas measurements of implant insertion torque and resonance frequency analysis were used for evaluating implant stability. Bone mineral density (BMD) and bone to implant contact were quantified after harvesting mandibular block sections. Spearman rank correlation tests were performed for evaluating correlations (α = .05). Results: Due to variation in clinical measurements, only weak correlations could be identified. A positive correlation was found between the parameters bone to implant contact and BMD (Spearman's rho .53; p = .05) whereas an inverse correlation was observed between BMD and implant stability (Spearman's rho -.61; p = .03). Both BoneProbe measurements in the cortical and trabecular area positively correlated with implant insertion torque (Spearman's rho 0.60; p = .02). A slightly stronger correlation was observed between the average of both BoneProbe measurements and implant insertion torque (Spearman's rho.66; p = .01). Conclusions: While establishing exact relationships among parameters of implant stability and the measurement techniques applied would require greater sample size, intraoperative compressive testing of bone might, despite the weak correlations seen here, be a useful tool for predicting primary implant stability.

Clinical and Radiographic Evaluation of Bar, Telescopic, and Locator Attachments for Implant-Stabilized Overdentures in Patients with Mandibular Atrophied Ridges: A Randomized Controlled Clinical Trial.

PURPOSE: The aim of this study was to evaluate the clinical and radiographic peri-implant tissues of bar, Locator, and resilient telescopic attachments for two-implant stabilized overdentures in subjects with mandibular atrophied ridges. MATERIALS AND METHODS: Ninety edentulous individuals with mandibular ridge atrophy were randomly assigned into three equal groups and received two implants in the canine areas. Mandibular overdentures were constructed and attached to implants with Dolder bar attachments (BOD), resilient telescopes (TOD), and Locators (LOD). Plaque scores, gingival scores, pocket depths, implant stability, width of keratinized mucosa, vertical bone loss, and horizontal bone loss were evaluated at the time of prosthesis delivery and 6 months and 12 months after delivery. RESULTS: With the exception of pocket depth and implant stability, all parameters showed a significant increase from prosthesis delivery to 6 months. BOD recorded the highest plaque scores, gingival scores, and pocket depths followed by LOD, and TOD recorded the lowest values. No significant difference in implant stability and keratinized mucosa was observed between groups. TOD and BOD recorded the highest vertical and horizontal bone losses, respectively. LOD recorded the lowest vertical and horizontal bone losses. There was no difference in implant survival rate between groups. CONCLUSION: Bar, resilient telescopic, and Locator attachments can be used successfully for two-implant stabilized overdentures in subjects with mandibular atrophied ridges after a 1-year follow-up period. Telescopic attachments were associated with improved clinical peri-implant soft tissues compared with other attachments. However, Locator attachments may be advantageous in terms of peri-implant bone preservation.

A systematic review of orthodontic retention systems: The verdict.

INTRODUCTION: Retention during both the active and passive phases of treatment has given rise to numerous publications concerning its efficacy, the range of systems available and its variability over time. There are currently many different retention protocols regularly used by orthodontists; however, their efficacy and duration are still subject to debate. There is as yet no consensus as to which retention protocol is the most effective or for how long the retention device needs to be worn. The aim of this research was to perform a systematic review of the scientific literature in order to evaluate the efficacy of the different retention systems and clinical protocols among those most widely used, so as to make recommendations beneficial to both patient and practitioner. MATERIALS AND METHODS: A search of the literature was performed in the following databases: PubMed (MEDLINE), ScienceDirect and Cochrane Library. The search was limited to publications in English and French during the period 2006-2016. RESULTS: Out of 1952 references initially identified, 17 articles corresponded to our inclusion criteria. The results show that: fixed retention is more effective than removable retainers for the maintenance of incisor alignment during the first six months of retention; there is no significant difference in efficacy between the different fixed retention systems; there is no significant difference in efficacy between the vacuum-formed systems and the Hawley retainer; part-time use of removable retainers (between 8-10h/day) is sufficient; the most widely used retention protocol combines a vacuum-formed splint or Hawley retainer in the upper arch with mandibular fixed retention. CONCLUSION: Despite the large number of studies devoted to orthodontic retention only a few articles corresponded to the methodological criteria of bio statistical analysis. Also, on account of the variations in experimental protocols, the levels of proof relating to the efficacy of different systems are very weak. Research into this topic should first seek to normalize methods of analysis and then perform randomized controlled long-term trials to shed light on this problem.

Clinical follow-up evaluation of Dalbo®-Rotex® retention elements in the private practice

The aim of this retrospective study was to investigate the clinical outcome of Dalbo®-Rotex® retention elements in a private practice. The majority of the retention elements was fixed with self-adhesive composite cement, and in almost 40% the exposed root surface was additionally covered with composite. The success rate of 96.3% after 24 months in a total of 50 included patients (response rate 48.5%) demonstrated that a simple and cost-effective fixation of removable dentures using prefabricated, chair-side inserted retention elements is feasible. Maintenance care comprised single or repeated replacement and activation of the female part in 12.3% and 39.4% of the cases, respectively. Fractures were rare, occurring in 3.4% of the cases and more likely in patients with parafunctional habits. Frequent oral hygiene correlated with probing depths up to 3 mm at the maxi- mum, while the risk of greater probing depths associated with less frequent oral hygiene increased by a factor of 2.4. Patients' assessment of the parameters handling and wearing comfort, chewing ability and prosthesis retention was predominantly positive. Based on the findings of the study, covering of exposed dentin areas with composite resin and regular recall comprising professional cleaning, fluoride application and oral hygiene instruction are recommended.

Effect of Repeated Screw Joint Closing and Opening Cycles and Cyclic Loading on Abutment Screw Removal Torque and Screw Thread Morphology: Scanning Electron Microscopy Evaluation.

PURPOSE: To evaluate the effect of repeated screw joint closing and opening cycles and cyclic loading on abutment screw removal torque and screw thread morphology using scanning electron microscopy (SEM). MATERIALS AND METHODS: Three groups (n = 10 in each group) of implant-abutment-abutment screw assemblies were created. There were also 10 extra abutment screws as new screws in group 3. The abutment screws were tightened to 12 Ncm with an electronic torque meter; then they were removed and removal torque values were recorded. This sequence was repeated 5 times for group 1 and 15 times for groups 2 and 3. The same screws in groups 1 and 2 and the new screws in group 3 were then tightened to 12 Ncm; this was also followed by screw tightening to 30 Ncm and retightening to 30 Ncm 15 minutes later. Removal torque measurements were performed after screws were subjected to cyclic loading (0.5 × 106 cycles; 1 Hz; 75 N). Moreover, the surface topography of one screw from each group before and after cyclic loading was evaluated with SEM and compared with an unused screw. RESULTS: All groups exhibited reduced removal torque values in comparison to insertion torque in each cycle. However, there was a steady trend of torque loss in each group. A comparison of the last cycle of the groups before loading showed significantly greater torque loss value in the 15th cycle of groups 2 and 3 compared with the fifth cycle of group 1 (P < .05). Nonetheless, torque loss values after loading were not shown to be significantly different from each other. CONCLUSION: Using a new screw could not significantly increase the value of removal torque. It was concluded that restricting the amount of screw tightening is more important than replacing the screw with a new one when an abutment is definitively placed.

Capacidad retentiva de una nueva crema adhesiva para prótesis dentales: estudio pilot / Retentive capacity of a new adhesive cream for dental prostheses: Pilot study

Introducción: un adhesivo para prótesis dentales debe mostrar, como principales propiedades, una fuerza adhesiva y una viscosidad perdurables en el tiempo. Objetivo: Determinar la capacidad de fijación de prótesis de un nuevo adhesivo protésico durante 8 días en condiciones normales de uso. Se evaluaron sus propiedades organolépticas y la percepción de eficacia por los participantes. Métodos: Estudio clínico exploratorio, longitudinal y observacional en 20 pacientes con prótesis dental completa removible. El producto se aplicó 1 vez/día, durante 8 días, en la arcada superior. Se establecieron 5 visitas del estudio, con determinaciones de la resistencia a la tracción en el momento basal (T0), a los 30 minutos (T30'), a las 12 horas (T12) y a las 24 horas (T24). Resultados: La fuerza media empleada para desplazar la prótesis dental fue de 188,13±113,52 cN; 418,50 ±93,60 cN; 470,50±76,03 cN y 428,0±140,73 cN para los puntos temporales T0, T30', T12 y T24, respectivamente; todas las diferencias fue-ron significativas vs. basal (p≤0,0001). El total de pacientes mostró una percepción satisfactoria sobre la eficacia y las características organolépticas del producto. No se registraron efectos adversos. Conclusiones: El adhesivo dental estudiado, aplicado durante 8 días en condiciones normales de uso, se asoció a un incremento significativo en la resistencia a la tracción durante 24 horas, aumento que fue máximo a las 12 horas. El adhesivo dental presentó muy buena aceptabilidad y tolerancia (AU)

Introduction: The ideal denture adhesive should show, as main properties, a durable adhesive strength and viscosity. Objective: To determine the denture retention capacity of a dental adhesive for 8 days under normal conditions of use. Its organoleptic properties and perception of efficacy were evaluated by the participants. Methods: Exploratory, longitudinal and observational clinical study in 20 patients with complete removable dental prostheses. The product was applied once a day for 8 days in the upper arch. Five study visits were established, with determinations of tensile strength at baseline (T0), at 30 minutes, at 12 and at 24 hours. Results: The mean force used to displace the dental prosthesis was 188.13±113.52 cN; 418.50±93.60 cN; 470.50±76.03 cN and 428.0±140.73 cN for the time points T0, T30', T12 and T24, respectively; all differences were significant vs. baseline (p≤0,0001). The total of patients showed a satisfactory impression on the efficiency and organoleptic characteristics of the product. No adverse effects were reported. Conclusions: The dental adhesive studied, applied during 8 days under normal conditions of use, was associated with a signigicant 24-hour increase in tensile strength, effect which was maximum at 12 hours. The cream presented very good acceptability and tolerance (AU)

Release of Irretrievable Abutment Healing Caps Using Cooling: Proof of Concept and Clinical Recommendations.

PURPOSE: To study the relation between irretrievable abutment healing caps (AHCs), temperature, and the torque required to remove the AHCs from implants. MATERIALS AND METHODS: Twenty implants, 13 mm long and 4.2 mm in diameter, were inserted into four acrylic boxes and covered with acrylic resin. An AHC was screwed into each implant, using a 30 N/cm torque. The acrylic blocks were placed in a 37°C water bath, and subsequently, a block was removed from the bath, the AHCs were cooled, and the torque needed to release each AHC from the implant was measured using a torque wrench. The cooling methods applied were contact with an ice cube for 10 or 25 seconds or spraying of endodontic refrigerant spray for 3 seconds. The control abutments were similarly tested, but without prior cooling. RESULTS: The application of ice cubes for 10 seconds reduced the mean releasing torque from 29.60 ± 1.22 N/cm to 28.55 ± 1.96 N/cm (P = .01). Cooling the AHCs with ice cubes for 25 seconds reduced the mean required releasing torque from 29.6 N/cm to 27.85 ± 1.22 N/cm (P < .001). Cooling the same abutments using endodontic refrigerant spray for 3 seconds reduced the mean releasing torque to 27.74 ± 2.13 N/cm (P < .001). CONCLUSION: Within the limitations of this study, it is possible to conclude that cooling the AHC reduces the torque required for its release from the implant. This finding may also be relevant to the removal of prosthetic abutments with irretrievable screws.

Misfit of Three Different Implant-Abutment Connections Before and After Cyclic Load Application: An In Vitro Study.

PURPOSE: This study aimed to evaluate the misfit of three different implant-abutment connections before and after cycling load. MATERIALS AND METHODS: One hundred twenty dental implants and correspondent prefabricated titanium abutments were used. Three different implant-abutment connections were evaluated: Morse taper (MT group), external hexagon (EH group), and internal hexagon (IH group). Forty implants and 40 abutments were used per group. The parameters for the mechanical evaluation were set as: 360,000 cycles, load of 150 N, and frequency of 4 Hz. Samples were sectioned in their longitudinal and transversal axes, and the misfit of the implant-abutment connection was evaluated by scanning electron microscopy analysis. One-way analyses of variance, Tukey post hoc analyses (α = .05), and t test (P < .05) were used to determine differences between groups. RESULTS: At the longitudinal direction, all the groups showed the presence of microgaps before cycling load; after cycling load, microgaps were reduced in all groups (P > .05). Transversally, only the MT group showed full fitting after cycling load compared with the other groups (EH and IH) (P < .0001). CONCLUSION: The application of cycling load produces an accommodation of the implant-abutment connection in internal, external, and Morse taper connections. In the longitudinal direction, the accommodation decreases and/or eliminates the gap observed initially (before load). In the horizontal direction, Morse cone implant-abutment connections experience a complete accommodation with the elimination of the gap.

An In Vitro Evaluation of the Loosening of Different Interchangeable Abutments in Internal-Connection-Type Implants.

PURPOSE: The aim of this study was to compare the loosening of interchangeable one-piece abutments connected to internal-connection-type implants after cyclic loading. MATERIALS AND METHODS: Four implant abutment groups (n = 7 in each group) with Straumann tissue-level implants were assessed: Straumann solid abutment (group S), Southern Implants solid abutment (group SI), Implant Direct straight abutment (group ID), and Blue Sky Bio regular platform abutment (group BSB). The implant was firmly held in a special jig to ensure fixation. Abutment screws were tightened to manufacturers' recommended torque with a digital torque gauge. The hemispherical loading members were fabricated for the load cell of a universal testing machine to evenly distribute the force on the specimens and to fulfill the ISO 14801:2007 standard. A cyclic loading of 25 N at 30 degrees to the implant's long axis was applied for a duty of a half million cycles. Tightening torques were measured prior to the loading. Removal torques were measured after cyclic loading. The data were analyzed with one-way analysis of variance (ANOVA), and the significance level was set at P < .05. RESULTS: The mean removal torques after cyclic loading were 34.0 ± 1.1 Ncm (group S), 25.0 ± 1.5 Ncm (group SI), 23.9 ± 2.1 Ncm (group ID), and 27.9 ± 1.3 Ncm (group BSB). Removal torques of each group were statistically different in the order of group S > group BSB > groups SI and ID (P < .05). The mean reduction rates were -2.9% ± 3.2% (group S), -21.9% ± 4.8% (group SI), -20.2% ± 7.2% (group ID), and -6.9% ± 4.3% (group BSB) after a half million cycles, respectively. Reduction rates of groups S and BSB were statistically lower than those of groups SI and ID (P < .01). The standard deviation of group S was lower than group BSB. CONCLUSION: The removal torque of the original Straumann abutment was significantly higher than those of the copy abutments. The reduction rate of the groups S and BSB abutments was lower than those of the other copy abutments.

Influence of Two Types of Connections in Driver-Retention Screw Assembly.

Rehabilitation with implant-supported prostheses has reached high success rates. However, mechanical failures are still reported, mainly in retention screws of abutments in single implant-supported crowns; which is designed to be the weakest structure and the first component to fail under overloading. In this sense, the aim of this in vitro study was to evaluate the influence of different joint designs (square or hexagonal) on resistance to deformation of driver-retention screw assembly of 3 commercial brands (Neodent, Singular, and Sin). A total of 42 retention screws from 3 commercial brands were used. The samples were divided into 2 joint groups, square (SQU) and hexagonal (HEX), and separated by commercial brands. Several components (implants and abutments) with standard platform (4.1 mm in diameter) were used. The resistance to deformation of the driver-retention screw assembly was measured using an accurate digital torque wrench for all commercial brands (Neodent [NEO], Singular [SGL], and Sin [SIN]) and joint designs (square or hexagonal). It was found no statistically significant difference (P <0.05) among the brands evaluated. On the other hand, square screws showed higher resistance to torsion than hexagonal screws; regardless the commercial brand.

Intended and Achieved Torque of Implant Abutment's Screw using Manual Wrenches in Simulated Clinical Setting.

OBJECTIVE: To measure the difference between the intended torque and the achieved torque by the operator using the spring-style mechanical torque-limiting device (MTLD). MATERIALS AND METHODS: Inexperienced and experienced clinicians used one spring-type MTLD to torque two abutment screws of each anterior and posterior implants, which were attached to two digital torque meters through a jaw model. The jaw model was part of a preclinical bench manikin attached to a dental chair. The intended torque value was 35 N cm (recommended by manufacturer) and the technique of torquing was observed for all the participants (instantaneous and repeated). The mean torque value was calculated for each subject for the anterior and posterior implants independently; t-test was used to compare between the intended and achieved torque values and to compare between the experienced and inexperienced clinicians (p ≤ 0.05). RESULTS: Thirty-seven clinicians participated, with an overall mean torque value of 34.30 N cm. The mean torque value of the achieved torque (34.30 ± 4.13 N cm) was statistically significantly less than the intended torque (p = 0.041). The male clinicians produced more statistically significantly accurate torque value (34.54 ± 3.78 N cm) than the female clinicians (p = 0.034), and the experienced clinicians produced more accurate torque values (34.9 ± 5.13 N cm) than the inexperienced clinicians (p = 0.048). CONCLUSION: Within the limitation of this study, the use of MTLDs did not always produce consistent torque values and the technique by which the operators use the MTLD might affect the torque value.

Successful Restoration of Severely Mutilated Primary Incisors Using a Novel Method to Retain Zirconia Crowns - Two Year Results.

AIM: This manuscript describes a simple reliable technique for restoring severely mutilated primary anterior teeth. A rigid glass ionomer post is created over which zirconia crowns can be fitted to achieve a long-term stable esthetic restoration for primary anterior teeth. STUDY DESIGN: Children aged 2-5 years with two up to six extensively decayed upper primary incisors were included. Fuji IX was condensed into an intracanal space created to a depth of 3mm, to provide a core which also extended 3mm supragingivally. Crown preparations were completed upon these cores. Zirconia crowns (Nusmile, Houston Texas USA) were fitted and cemented over the prepared cores. All patients were recalled at regular intervals. RESULTS: Twenty-three healthy children with 86 restorations participated in the study. The overall survival of the restorations was 95.3% after 12 months and 80.2% after 24 months. According to Kaplan-Meier survival analysis, the median survival time was not reached while the estimated mean survival time was 22.9 months. CONCLUSIONS: This newly described clinical technique is simple and reliable to use for restoration of extensively decayed primary incisors. Use of zirconia crowns retained using this technique offers superior esthetic, durable restorations with remarkable gingival response up to 24 months.

Effect of Double Screw on Abutment Screw Loosening in Single-Implant Prostheses.

PURPOSE: This study was conducted to assess the effect of using a double screw on the prevention of abutment screw loosening. MATERIALS AND METHODS: Internal connected abutment with a single screw (IS), internal connected abutment with a double screw (ID), external connected abutment with a single screw (ES), and external connected abutment with a double screw (ED) groups were prepared (n = 10 in each group). After 50,000 loading cycles, postload removal torque loss (RTL) percentage was measured. RESULTS: Postload RTL of ID and ED were smaller than those of IS and ES (P = .000 and P = .039, respectively). CONCLUSION: This study showed that a double screw was more effective in prevention of screw loosening.

Vertical Misfit of Single-Implant Abutments Made from Different Materials Under Cyclic Loading.

PURPOSE: Little information is available in the literature regarding the accuracy of marginal fit of abutments made from different materials. The aim of this study was to compare the level of vertical misfit in abutments made from different materials before and after cyclic loading. MATERIALS AND METHODS: Thirty external hexagon implants, 3.75-mm diameter and 13-mm length, were embedded in epoxy resin and divided into three groups according to abutment type (n = 10): (1) machined titanium (Ti) abutments; (2) premachined gold-alloy (Au) abutments; and (3) machined zirconia (Zr) abutments. The abutments were attached to their respective implants by titanium alloy screws at the manufacturer's recommended torque. A cyclic loading (0.5 × 10(6) cycles; 15 Hz) between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants. Implant-abutment vertical misfits (µm) were measured at four predetermined points before and after loading with a stereomicroscope at 60× magnification. The group means were compared using a three-way repeated-measure analysis of variance (ANOVA) and Tukey test (α = .05). RESULTS: The results from the ANOVA identified significant effects of the abutment type (P < .001). However, there were no significant effects of cyclic loading (P = .978) or measured surfaces (P = .955). When the abutment groups were compared regardless of cyclic loading and measured surfaces, the Au group showed the highest value of vertical misfit (14.93 ± 0.78), followed by the Ti group (8.53 ± 0.44) and the Zr group (5.64 ± 0.73), with statistically significant differences among them (P < .05). CONCLUSION: The abutment groups showed statistically significant differences in vertical misfit. Zr abutments showed the highest accuracy in terms of marginal fit, and Au abutments showed the lowest. Cyclic loading did not significantly change the level of vertical misfit. All experimental groups presented acceptable values of marginal misfit.

Extraoral Cementation Technique to Minimize Cement-Associated Peri-implant Marginal Bone Loss: Can a Thin Layer of Zinc Oxide Cement Provide Sufficient Retention?

This report describes the use of laboratory-fabricated crown intaglio replicas for extraorally prepared cementation of fixed restorations to implants. This technique minimizes excess cement and may therefore reduce the risk of cement-related marginal peri-implant bone loss. It is unclear whether the remaining thin layer of luting agent provides sufficient retention if low-adhesive zinc oxide (ZnO) cement is used. In 85 consecutive patients, 113 single crowns were cemented to implants using extraoral cementation technique (ECT) and ZnO cement. All patients were followed for 6 months and investigated for decementation. Seven events of decementation (incidence: 6.19%) were found in 7 patients (8.24%). ECT may represent a viable cementation technique for implant-supported single crowns, even using low-adhesion cements.