Adhesive removable partial denture attachments made from zirconia ceramic: A finite element analysis and in vitro study.

STATEMENT OF PROBLEM: Whether adhesive zirconia ceramic removable partial denture attachments are feasible with current technology is unclear. PURPOSE: The purpose of this finite element analysis and in vitro study was to evaluate the effect of the lever arm, tooth preparation, and aging on the loading of the tooth-zirconia attachment interface. MATERIAL AND METHODS: Three different finite element analysis (FEA) models allowing for the loading of an adhesive attachment either directly or through a removable partial denture were used. Two models represented a human tooth with 2 different types of attachments, while the third model also included a removable partial denture. For the evaluation of bond strength, a combination of shear and hydrostatic stress was used. In addition, composite resin teeth were fabricated, and zirconia bars were bonded to them with varying tooth preparations and lever arm lengths. In 1 group the influence of aging was analyzed. Fracture load was determined by using a universal testing machine. Statistical analysis was based on the Shapiro-Wilk normality test, ANOVA, and Games-Howell test (α=.05). RESULTS: The maximum stress of 65 MPa occurring in the bonding area was reduced to 37 MPa by adding a retainer to the attachment. Loading of the denture resulted in a maximum stress of 9 MPa. Mean fracture loads ranged from 33.6 N to 209.1 N. Preparing a flat bonding surface showed a nonsignificant increase (P=.197), whereas aging led to a nonsignificant decrease in fracture load (P=.075). A lever arm extended by 2 mm significantly reduced fracture load (P=.002). The addition of an occlusal-distal (OD) cavity led to a nonsignificant increase (P=.186), which became significant when a mesial-occlusal-distal (MOD) preparation was applied (P=.001). CONCLUSIONS: Adhesive zirconia attachments should use a MOD cavity and have a cross section of at least 2.5×2.5 mm. The attachment should not extend more than 3 mm.

Wedge Shaped vs Round Implants: Bone Strain During the Insertion Process.

A novel implant system resembling the shape of a wedge and employing piezosurgery for implant bed preparation has been introduced with the aim of solving the problem of horizontal bone deficiency. This in vitro study compared emerging bone strain during insertion of a conventionally round implant vs the wedge implant. Adhering to the manufacturers' protocols, implant surgery was performed in polyurethane foam blocks equipped with strain gauges attached to the buccal and occlusal surfaces. Five implants per group were placed while strain development during insertion was recorded. Primary implant stability was determined using resonance frequency analysis. Statistical analysis was based on Welch's 2-sample tests (α = 0.05). In general, greater strain development was found on the buccal aspect of bone compared to the occlusal aspect with an overall range between -724 µm/m and 9132 µm/m. A stepwise increase in strain development was seen in the wedge implants while, in the round implants, a continuous increase in strain development was recorded. Absolute strain development on the buccal aspect of bone was significantly greater in wedge implants (P = .0137) while, on the occlusal aspect, significantly lower strain development was seen for wedge implants (P = .0012). Primary stability of wedge implants was significantly lower compared to round implants (P = .0005). Wedge implants differ from round implants with respect to the insertion process characterized by a stepwise increase in bone deformation. High strain development in buccal bone may constitute a risk factor for bone resorption and should be avoided by reducing the degree of underpreparation of the implant site.

Students at Saarland University dental school-A survey on their background and curriculum perception.

INTRODUCTION: With the aim of optimising dental education without overburdening students, new legislation restructuring the undergraduate dental curriculum in German is under way. The goal of this study was to survey the current situation of dental students at one specific university with respect to their socio-economic background, admission to dental school, curriculum perception and work-life balance. MATERIALS AND METHODS: An online questionnaire was presented to all undergraduate students enrolled at Saarland University who had at least completed the first preclinical practical course in dentistry. RESULTS: A response rate of 85% was reached with two-thirds of the student body being females. The profession of 40% of students' parents either was physicians or dentist. Students reported a slight reduction in time spent for leisure activities during their studies, however, with sports activities hardly being affected. With respect to a proper work-life balance, almost 50% of respondents considered their clinical workload as being too high. Students did not express a clear opinion regarding curriculum structure, whilst the content mostly satisfied their expectations (59%). The majority (71%) of students considered their preclinical training as being demanding whilst less than 3% fully agreed that preclinical training provided an optimal background for patient treatment. The learning modules in the first clinical semester were considered as being adequate by 56% of students. Examinations during courses were seen as properly reflecting the students' knowledge by 79% of students. DISCUSSION: The status quo of German dental students is characterised by a high workload affecting the students' work-life balance and by a transition between preclinical and clinical education which only about half the student body perceives as being adequate. Patient-based examinations obviously are not considered as being problematic.

In Vitro Handling Characteristics of a Particulate Bone Substitute for Ridge Preservation Procedures.

While particulate bone substitute materials are applied in a variety of augmentation procedures, standardized defects are being used for preclinical testing. This in vitro study evaluated the density and homogeneity of a particulate bone substitute in ridge preservation procedures. Premolars and molars were extracted in ten semimandibles of minipig cadavers. Light body impression material was used for determining the volume of the extraction sites followed by augmentation with particulate material, thereby weighing the graft material needed. Microradiographs and histologic sections were obtained for evaluating the homogeneity and density of the augmentation material. Statistical analyses were based on Shapiro-Wilk tests, Spearman's rho and one sample Wilcoxon test followed by Bonferroni-Holm correction for multiple testing (α = 0.05). Based on 103 single alveoli evaluated, the mean volume determined was 0.120 cm3 requiring a mean amount of graft material of 0.155 g. With only three exceptions, all parameters (volume, mass of augmentation material, density and homogeneity) correlated significantly (p < 0.020). The apical parts of the alveoli showed reduced density as compared to the middle parts (p < 0.001) and the homogeneity of the augmentation material was also lower as compared to the middle (p < 0.001) and cervical parts (p

Rationale for a novel attachment system for implant-supported overdentures.

PURPOSE: To quantify the effect of support stiffness on the retention forces of telescopic crowns and to evaluate a prototype attachment system incorporating a nickel-titanium element. MATERIALS AND METHODS: In the first part of the study, telescopic crowns were fabricated employing standard laboratory procedures. For six combinations of telescopic crowns, the separation force was determined while varying the stiffness of their supporting implants. In the second study part, an in vitro mandibular model with three interforaminal implants was equipped with strain gauges and extensometers. Two prostheses either employing cylindrical telescopic crowns or prototype attachments were fabricated and statically loaded on the model using either the midline or the left canine or both canine implants for support while strain in the peri-implant area and prosthesis displacement were recorded. Statistical analysis of both study parts was based on pairwise comparisons with the level of significance set at α = .05. RESULTS: With one exception (P = .161), for each assembly of two telescopic crowns, the separating force was always dependent on the stiffness of the supporting implants. With 3 exceptions out of a total of 14 comparisons for peri-implant strain and prosthesis displacement, the use of the prototype attachments always led to significantly lower mean values compared to the use of cylindrical telescopes (P < .00). CONCLUSION: The individual retention force of telescopic crowns on implants should be set at a lower level compared to telescopic crowns on natural abutments. Incorporating a nickel-titanium element into attachment systems for implant-supported removable prostheses reduces peri-implant strain and may facilitate the use of telescopic crowns.

Pilot study on the applicability of boron-doped diamond electrodes for tooth whitening.

OBJECTIVES: While various approaches are available for tooth whitening, the basic concept employs the use of peroxides in the form of gels, which are applied to tooth surfaces. Previous studies have shown that reactive oxygen species acting as potent disinfectants can be produced using boron-doped diamond (BDD) electrodes for the electrolysis of water. With these electrodes being applicable, for example, for endodontic treatment, it was the goal of this pilot study to use such electrodes for tooth whitening. MATERIAL AND METHODS: Two groups (n = 10) of intact clinical crowns were obtained by horizontally cutting off roots of extracted human teeth. The crowns were either bleached by applying a commercially available agent based on 40% hydrogen peroxide or were immersed in saline undergoing electrolysis with BDD electrodes. Whitening of specimens was judged on standardized photographs by examiners with three different levels of experience. Statistical analysis was based on Gwet's AC2 coefficient with quadratic weights, Shapiro-Wilk tests, and two-way analysis of variance of aligned rank transformed data (level of significance set at α = .05). RESULTS: Levels of reliability ranging from fair to substantial were recorded for single persons while the level of reliability ranged between fair and moderate for groups of raters. The level of experience had no significant effect on the ratings (p = .2500). The bleaching method had a significant effect on ratings (p = .0005) with BDD electrodes showing less effect. CONCLUSIONS: Bleaching by applying BDD electrodes was possible, but was not as effective as the use of commercially available in-office whitening gel. A potential explanation may be seen in different concentrations of reactive oxygen species.

Use of a dentin bonding agent for the fixation of strain gauges on bone.

Capturing deformation of bone using strain gauges is still a common approach in biomechanics. So far, the bone surfaces had to be sanded and cleaned using various solvents prior to attaching the sensors using cyanoacrylate. This work proposes a novel approach employing common bonding procedures to enamel and dentin as used in restorative dentistry. Bovine ribs were obtained and osteotomies were created following clinical protocols for dental implant insertion. A unidirectional strain gauge was attached to the outer surface of the bone specimens using the steps of acid etching with phosphoric acid, application of a three-bottle dentin adhesive and light curing. Emerging strains were then captured during implant insertion as well as during static loading of the implants in a universal testing machine. The method described here allowed for the reliable fixation of strain gauges on unaltered bone surfaces. Both, compressive and tensile strains emerging in the surrounding of the dental implants could be captured.

Insertion torque/time integral as a measure of primary implant stability.

The goal of this in vitro study was to determine the insertion torque/time integral for three implant systems. Bone level implants (n = 10; BLT - Straumann Bone Level Tapered 4.1 mm × 12 mm, V3 - MIS V3 3.9 mm × 11.5 mm, ASTRA - Dentsply-Sirona ASTRA TX 4.0 mm × 13 mm) were placed in polyurethane foam material consisting of a trabecular and a cortical layer applying protocols for medium quality bone. Besides measuring maximum insertion torque and primary implant stability using resonance frequency analysis (RFA), torque time curves recorded during insertion were used for calculating insertion torque/time integrals. Statistical analysis was based on ANOVA, Tukey's honest differences test and Pearson product moment correlation (α = 0.05). Significantly greater mean maximum insertion torque (59.9 ± 4.94 Ncm) and mean maximum insertion torque/time integral (961.64 ± 54.07 Ncm∗s) were recorded for BLT implants (p < 0.01). V3 showed significantly higher mean maximum insertion torque as compared to ASTRA (p < 0.01), but significantly lower insertion torque/time integral (p < 0.01). Primary implant stability did not differ significantly among groups. Only a single weak (r = 0.61) but significant correlation could be established between maximum insertion torque and insertion torque/time integral (p < 0.01) when all data from all three implant groups were pooled. Implant design (length, thread pitch) seems to affect insertion torque/time integral more than maximum insertion torque.

Insertion and Loading Characteristics of Three Different Bone-Level Implants.

PURPOSE: While primary stability still constitutes an important factor for implant success, high levels of insertion torque resulting from bone compression are controversial and may constitute a co-factor in peri-implant bone loss. MATERIALS AND METHODS: Adhering to the manufacturers' protocols for medium-quality bone, implant surgery was performed in polyurethane foam blocks equipped with strain gauges attached to the buccal aspect. Following insertion and attachment of provisional abutments, oblique loading was performed. The following parameters were recorded for three different implant types (Straumann Bone Level Tapered [BLT], MIS V3 [V3], Dentsply Sirona ASTRA TX [ASTRA]): maximum insertion and removal torque, maximum strain during insertion and loading, and implant stability before and after loading (resonance frequency analysis [RFA]). Statistical analysis was based on analysis of variance (ANOVA), Tukey honest significant difference test, and Pearson's product moment correlation (α = .05). RESULTS: Maximum insertion torque (59.9 ± 4.94 Ncm) was recorded for BLT followed by V3 and ASTRA (P < .01 for all comparisons). Maximum removal torque (43.7 ± 9.69 Ncm) was also recorded for BLT, but the pairwise comparisons reached significance only for BLT vs ASTRA (P < .01) and V3 vs BLT (P = .03). Implant stability differed among groups only after loading, where the pairwise comparison between BLT and ASTRA reached significance (P = .02). Maximum strain during insertion was caused by BLT reaching 19,482.62

Mechanical stress during implant surgery and its effects on marginal bone: a literature review.

OBJECTIVE: High levels of primary implant stability have been advocated particularly for immediate loading protocols. Current implant systems and drill protocols are intended not to cause excessive stress on bone during implant insertion as resorptive processes might compromise esthetics and function. The goal of this narrative review was to summarize current data on the effect of mechanical stress on alveolar bone. METHOD AND MATERIALS: PubMed was searched (final search conducted on 30 September 2019) applying the user query "(dental implant insertion) AND (mechanical stress) AND (bone)." The papers identified were grouped according to the research methodology applied (in vitro studies and finite element analysis, animal studies, and clinical trials). RESULTS: In total, 176 articles were identified, of which 58 were included. A clear tendency towards increased stress in bone resulting from the use of undersized osteotomies was shown. Depending on the degree of undersizing, the inner parts of implant threads create healing chambers in which bone formation seems to progress very well, while areas of direct contact between implant body and alveolar bone experience resorption during healing. More resorption seems to occur when implants have been placed with higher insertion torque, although these implants maintain greater total bone-to-implant contact during initial healing. Clinically, mobile implants seem to have a compromised prognosis and high insertion torques seem not to guarantee successful osseointegration. Marginal bone level changes obviously have a tendency of being greater in implants inserted with high levels of torque. CONCLUSION: Clinicians should be cautious during implant surgery not to overstress bone. Future implant systems should focus on optimized drill protocols and apply macrodesigns that also derive stability from trabecular bone as well, instead of merely compressing the cortical layer.

A Pilot Animal Study Aimed at Assessing the Mechanical Quality of Regenerated Alveolar Bone.

PURPOSE: Bone regeneration procedures are often evaluated based on biologic aspects only. As regenerated bone also has to ensure primary implant stability, the goal of this study was to determine the mechanical quality of regenerated bone. MATERIALS AND METHODS: Six adult minipigs were allocated for this experiment with four mandibular study sites each established following tooth removal. Two different types of bovine bone mineral as well as autogenous bone were used for augmenting three-walled defects, while native bone served as the control. Implants were placed after 12, 18, and 24 weeks of healing, and bone quality was determined using intraoperative compressive testing (BoneProbe), insertion torque measurements, and resonance frequency analysis. The mandibles were then harvested for determining bone mineral density (BMD) and bone-to-implant contact (BIC). Statistical analysis was based on two-way analysis of variance of aligned rank transformed data and Spearman's rank correlation tests (α = .05). RESULTS: The effects of the factors healing time and material on the parameters tested were too small to be significant (P ranging from .34 to .98). Weak correlations were observed for implant insertion torque with BoneProbe measurements in the cortical (0.481; P = .032) and in the trabecular area (0.639; P = .002). BoneProbe measurements in the trabecular part and in the cortical part also correlated with each other (0.477; P = .035). CONCLUSION: While differences may exist between bone regenerated using different biomaterials with respect to biologic behavior, differences in the mechanical properties determining primary implant stability seem to be minor. Implant insertion torque measurements appear to be a reliable tool for determining bone quality if only one specific implant type is considered.

Evaluation of Insertion Energy as Novel Parameter for Dental Implant Stability.

Insertion energy has been advocated as a novel measure for primary implant stability, but the effect of implant length, diameter, or surgical protocol remains unclear. Twenty implants from one specific bone level implant system were placed in layered polyurethane foam measuring maximum insertion torque, torque-time curves, and primary stability using resonance frequency analysis (RFA). Insertion energy was calculated as area under torque-time curve applying the trapezoidal formula. Statistical analysis was based on analysis of variance, Tukey honest differences tests and Pearson's product moment correlation tests (α = 0.05). Implant stability (p = 0.01) and insertion energy (p < 0.01) differed significantly among groups, while maximum insertion torque did not (p = 0.17). Short implants showed a significant decrease in implant stability (p = 0.01), while reducing implant diameter did not cause any significant effect. Applying the drilling protocol for dense bone resulted in significantly increased insertion energy (p = 0.02) but a significant decrease in implant stability (p = 0.04). Insertion energy was not found to be a more reliable parameter for evaluating primary implant stability when compared to maximum insertion torque and resonance frequency analysis.

Pilot Study on the Use of a Laser-Structured Double Diamond Electrode (DDE) for Biofilm Removal from Dental Implant Surfaces.

No proper treatment option for peri-implantitis exists yet. Based on previous studies showing the in vitro effectiveness of electrochemical disinfection using boron-doped diamond electrodes, novel double diamond electrodes (DDE) were tested here. Using a ceramic carrier and a laser structuring process, a clinically applicable electrode array was manufactured. Roughened metal discs (n = 24) made from Ti-Zr alloy were exposed to the oral cavities of six volunteers for 24 h in order to generate biofilm. Then, biofilm removal was carried out either using plastic curettes and chlorhexidine digluconate or electrochemical disinfection. In addition, dental implants were contaminated with ex vivo multispecies biofilm and disinfected using DDE treatment. Bacterial growth and the formation of biofilm polymer were determined as outcome measures. Chemo-mechanical treatment could not eliminate bacteria from roughened surfaces, while in most cases, a massive reduction of bacteria and biofilm polymer was observed following DDE treatment. Electrochemical disinfection was charge- and time-dependent and could also not reach complete disinfection in all instances. Implant threads had no negative effect on DDE treatment. Bacteria exhibit varying resistance to electrochemical disinfection with Bacillus subtilis, Neisseria sp., Rothiamucilaginosa, Staphylococcus haemolyticus, and Streptococcus mitis surviving 5 min of DDE application at 6 V. Electrochemical disinfection is promising but requires further optimization with respect to charge quantity and application time in order to achieve disinfection without harming host tissue.

Reliability of clinical techniques for evaluating alveolar bone quality and primary implant stability.

OBJECTIVE: A novel device for intraoperative compressive testing of alveolar bone during implant surgery has been introduced. It was the goal of this study to compare the performance of this device with traditional methods used for determining alveolar bone quality and primary implant stability. METHOD AND MATERIALS: Implant surgery in human cadaver bone was performed by two implantologists differing in experience. Bone quality was rated radiographically, based on tactile sensation during drilling and using intraoperative compressive tests. Implant stability was evaluated using insertion torque measurements and resonance frequency analysis. Statistical analysis was based on two way ANOVA followed by Tukey multiple comparisons and Pearson's product moment correlation. The level of significance was set at α = .05. RESULTS: Human cadaver bone was ranked according to implant insertion torque. Radiographic assessment, tactile sensation during drilling, and implant stability measurements did not allow differentiating bone types in all instances. Cortical BoneProbe measurements showed a significant trend towards higher measurement values in greater bone quality types (P < .01); in trabecular bone this trend was also present but was not statistically significant. Significant correlations existed between BoneProbe measurements and most other parameters evaluated. CONCLUSION: Despite the limited number of measurements performed, intraoperative compressive testing of bone may be an option for objectively classifying alveolar bone quality.

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.

Electrochemical Disinfection of Experimentally Infected Teeth by Boron-Doped Diamond Electrode Treatment.

Disinfection and prevention of re-infection are the decisive treatment steps in endodontic therapy. In this study, boron-doped diamond (BDD) electrodes have been fabricated and used for disinfecting the root canals of extracted human teeth, which had been covered with bacterial biofilms formed by Bacillus subtilis and Staphylococcus epidermidis. The growth of B. subtilis could be successfully impaired, achieving a complete disinfection after 8.5 min treatment time with the success of disinfection depending on the insertion depth of the electrode in the root canal. S. epidermidis could completely be removed after 3.5 min treatment time. A clinically applicable electrode array led to complete disinfection after treatment times of 10 min for S. epidermidis and 25 min for B. subtilis. BDD electrode application allowed for the improved disinfection of root canals and dentin tubules based on a continuous production of reactive oxygen species and their enhanced penetration of dentin tubules most likely due the formation of a continuous stream of small gas bubbles. The treatment times that are required here will be shortened in clinical application, as mechanical shaping of the canal system would precede the disinfection process.

Effect of bone quality, implant design, and surgical technique on primary implant stability.

OBJECTIVE: Adaptation of the surgical protocol and implant selection depending on bone quality has been advocated. It was the goal of this in-vitro study to quantify the effect of implant geometry and implant site preparation on micromotion at the implant-bone interface. METHOD AND MATERIALS: A parametric study was conducted with implants differing in shape, length, and diameter placed in polyurethane foam material differing in density and structure following various methods of implant site preparation. Measurement parameters included bone quality in the cervical and apical area, insertion torque, implant stability, and implant displacement under load application. Statistical analysis was based on ANOVA and Pearson's product moment correlation with the level of significance set at α = .05. RESULTS: Compressive testing of bone allowed different bone densities (P = .000) to be distinguished. Minor changes in bone density caused by implant site preparation with osteotomes could not be detected (P > .05). Undersized drilling (P = .001), the presence of a cortical layer (P = .000), and the use of osteotomes (P = .000) led to a significant increase in implant insertion torque. Thread cutting reduced insertion torque (P = .000) whereas the use of short (P = 1.000) and wide diameter (P = .235) implants had no effect. Implant stability measurements did not always allow for differentiation of implants varying in shape and placed with different protocols. Increasing bone density led to a general reduction in maximum implant displacement under loading. Significant correlations between all parameters were found, with the exception of residual implant displacement, which only correlated with compressive bone testing in the cortical (P = .0341) and trabecular (P = .0359) areas. CONCLUSION: Compressive testing of bone seems to allow the prediction of implant performance.

Fracture of Reduced-Diameter Zirconia Dental Implants Following Repeated Insertion.

PURPOSE: Achievement of high insertion torque values indicating good primary stability is a goal during dental implant placement. The objective of this study was to evaluate whether or not two-piece implants made from zirconia ceramic may be damaged as a result of torque application. MATERIALS AND METHODS: A total of 10 two-piece zirconia implants were repeatedly inserted into polyurethane foam material with increasing density and decreasing osteotomy size. The insertion torque applied was measured, and implants were checked for fractures by applying the fluorescent penetrant method. Weibull probability of failure was calculated based on the recorded insertion torque values. RESULTS: Catastrophic failures could be seen in five of the implants from two different batches at insertion torques ranging from 46.0 to 70.5 Ncm, while the remaining implants (all belonging to one batch) survived. Weibull probability of failure seems to be low at the manufacturer-recommended maximum insertion torque of 35 Ncm. Chipping fractures at the thread tips as well as tool marks were the only otherwise observed irregularities. CONCLUSION: While high insertion torques may be desirable for immediate loading protocols, zirconia implants may fracture when manufacturer-recommended insertion torques are exceeded. Evaluating bone quality prior to implant insertion may be useful.

Correlation Between Micromotion and Gap Formation at the Implant-Abutment Interface.

PURPOSE: This study aimed to correlate micromotion and gap measurements at the implant-abutment interface. MATERIALS AND METHODS: A total of 10 implant-abutment assemblies were subjected to micromotion measurements under cyclic loading and subsequently quartered and inspected under a light microscope to measure vertical and horizontal gaps between implant and abutment. Statistical analysis was based on Pearson product-moment correlations (α = .05). RESULTS: Micromotion varied from 8.03 µm to 100.32 µm, while horizontal gaps ranged from 8.72 µm to 59.93 µm and vertical gaps ranged from 3.93 µm to 30.82 µm. No significant correlations were found (P > .05). CONCLUSION: Simplistic gap measurements at the implant-abutment interface are inadequate for predicting micromotion.

Comparison of simplistic biofilm models for evaluating irrigating solutions.

OBJECTIVE: Many innovations have recently been implemented in the field of endodontics, often based on a variety of in-vitro/ex-vivo test setups. It was the goal of this research to compare different biofilm models for evaluating the effectiveness of rinsing solutions. METHOD AND MATERIALS: Three different models have been applied in this study, including petri dishes with nutrient medium, arrays of human dentin disks, and split bovine root segments. The susceptibility of biofilms formed by Enterococcus faecalis to commonly used endodontic irrigants was tested. RESULTS: While citric acid 3% did not show an inhibitory effect on solid medium, mean maximum inhibition areolae of 9.8 ±â€¯1.6 mm were found for sodium hypochlorite 3%. Fluorescein solution was shown to penetrate dentin tubules to a depth of 0.5 to 1 mm, indicating that the dentin tubules are not freely accessible, but clotted by E faecalis biofilms. Rinsing root canals with a combination of citric acid, hydrogen peroxide, chlorhexidine, and sodium hypochlorite removed bacterial biofilms from the dentin tubules only to a depth of 0.5 mm, while bacteria in deeper regions were not affected. CONCLUSION: Standard irrigating solutions inhibit bacterial growth; however, due to the morphology of the tooth, the effect of irrigating media is restricted to the root canal and the adjacent volume of dentin tubules. Results from standardizable diffusion tests seem not to be predictive for clinical performance of irrigating solutions.