Knochenschädigung im Rahmen der Implantatinsertion : eine biomechanische und histologische Pilotstudie

Aim: Achieving primary implant stability during implant placement is an important factor in attaining osseointegration, which determines the long-term clinical success of dental implants. Primary stability is largely dependent on the quality of the alveolar bone as well as the implant design with its specific drilling protocol. Due to the creation of a drill hole as well as cortical bone compression during implant placement, traumatization of the bone appears unavoidable. To reduce the extent of marginal bone resorption, implant manufacturers as well as implantologists try to minimize the traumatic bone damage during the implantation procedure. The aim of this in vitro study was to measure the forces acting on the alveolar bone during the insertion of two different implant systems, to evaluate the extent of bone damage by means of a subsequent histological analysis and to establish possible correlations. Material and Methods: Implants of two bone-level systems (Astra; Straumann; n = 5) were inserted into fresh bovine bone. The insertion torque was recorded with the surgical contra-angle handpiece. Strain gauges were used to monitor the resulting bone strain on the buccal wall. Subsequently, primary stability of the implant was determined by means of Osstell measurement. Histological analysis determined bone to implant contact and bone density as well as signs of bone damage such as microcracks, macrocracks and the extent of bone deformation. In addition to comparing the implant systems (Welch t-Tests), all measurement parameters were tested for possible correlations (Pearson product moment correlation coefficient), with the level of significance set at α = 0.05. Results: Straumann implants produced slightly increased readings for insertion torque (p = 0.772), strain development (p = 0.893) and primary implant stability (p = 0.642). Histologic assessment revealed significantly increased bone to implant contact in the Straumann group compared to the Astra group (cortical p = 0.014; trabecular p = 0.016), with only slight differences in bone density (cortical p = 0.466; trabecular p = 0.360). A significantly increased number of microcracks in the cortical bone was observed in the Astra group (p = 0.020). A correlation of insertion torque with bone to implant contact in cortical bone (p = 0.029) was found in the Straumann group. In trabecular bone, the number of macrocracks correlated with bone to implant contact (p = 0.029). Astra implants showed a correlation of insertion torque with bone to implant contact in the trabecular region (p = 0.007). There was also a correlation between implant stability and the number of macrocracks in the trabecular bone (p = 0.016), furthermore between the number of macrocracks in the cortical region and the bone to implant contact (p = 0.019). Conclusion: The present study demonstrated that bone damage of varying degrees is inevitable during implant placement. Clinically, they mainly manifest in the peri-implant cortical bone. When developing a new implant macrodesign, attempts should be made to achieve implant stability by compression in the trabecular bone so as to relieve the peri-implant cortical area.Ziel: Das Erreichen von Primärstabilität bei der Implantation ist ein wichtiger Faktor zur Erzielung von Osseointegration, was den langfristigen klinischen Erfolg dentaler Implantate bedingt. Die Primärstabilität hängt maßgeblich von der Qualität des Alveolarknochens sowie der Implantatform mit seinem spezifischen Bohrprotokoll ab. Durch das Anlegen eines Bohrstollens sowie durch die kortikale Knochenkompression bei der Implantatinsertion erscheint eine Traumatisierung des Knochens unvermeidbar. Um das Ausmaß einer marginalen Knochenresorption zu verringern, versuchen Implantathersteller sowie Implantologen die traumatische Knochenschädigung während des Implantationsvorganges zu minimieren. Ziel dieser in vitro Studie war es, die während der Insertion zweier verschiedener Implantatsysteme am Alveolarknochen einwirkenden Kräfte messtechnisch zu erfassen, anhand einer anschließenden histologischen Analyse das Ausmaß der Knochenschädigung zu evaluieren und mögliche Zusammenhänge zu erkennen. Material und Methoden: Die Implantate zweier Bone-Level Systeme (Astra; Straumann; n = 5) wurden in frische Rinderknochen inseriert. Das Eindrehmoment wurde mit dem chirurgischen Winkelstück festgehalten. Mit Hilfe von Dehnungsmessstreifen zeichnete man die dabei an der bukkalen Wand entstehende Knochendehnung auf. Anschließend erfolgte die Bestimmung der Primärstabilität des Implantates mittels Osstell-Messung. In der histologischen Analyse ermittelte man den Knochen-Implantat-Kontakt und die Knochendichte sowie Anzeichen von Knochenschäden wie Mikrorisse, Makrorisse und das Ausmaß der Knochendeformation. Neben dem Vergleich der Implantatsysteme (Welch t-Test) wurden alle Messparameter auf mögliche Korrelationen untersucht (Pearson Produkt-Moment-Korrelationskoeffizient), wobei das Signifikanzniveau auf α = 0.05 festgelegt wurde. Ergebnisse: Straumann-Implantate wiesen leicht erhöhte Messwerte für das Eindrehmoment (p = 0.772), die Knochendehnung (p = 0.893) und die Primärstabilität (p = 0.642) auf. Die histologische Beurteilung erbrachte einen signifikant größeren Knochen-Implantat-Kontakt der Straumann Gruppe im Vergleich zur Astra Gruppe (kortikal p = 0.014; trabekulär p = 0.016), wobei sich die Knochendichte nur gering unterschied (kortikal p = 0.466; trabekulär p = 0.360). Eine signifikant erhöhte Zahl an Mikrorissen im kortikalen Knochen fand sich bei den Astra-Implantaten (p = 0.020). Eine Korrelation des Eindrehmomentes mit dem Knochen-Implantat-Kontakt im kortikalen Knochen (p = 0.029) ergab sich in der Straumann Gruppe. Im trabekulären Knochen korrelierte die Anzahl der Makrorisse mit dem Knochen-Implantat-Kontakt (p = 0.029). Bei Astra-Implantaten fand sich eine Korrelation des Eindrehmomentes mit dem Knochen-Implantat-Kontakt im trabekulären Bereich (p = 0.007). Auch zwischen der Implantatstabilität und der Anzahl der Makrorisse im trabekulären Knochen bestand eine Korrelation (p = 0.016), weiterhin zwischen der Anzahl der Makrorisse im kortikalen Bereich und dem Knochen-Implantat-Kontakt (p = 0.019). Schlussfolgerung: In der vorliegenden Untersuchung konnte gezeigt werden, dass bei der Implantatinsertion Knochenschäden unterschiedlichen Ausmaßes unvermeidlich sind. Klinisch treten sie vornehmlich im peri-implantären kortikalen Knochen in Erscheinung. Bei der Entwicklung eines neuen Implantat-Makrodesigns sollte man daher versuchen, Implantatstabilität durch Kompression im trabekulären Knochen zu erzielen, um den kortikalen Bereich zu entlasten

Bone Damage during Dental Implant Insertion: A Pilot Study Combining Strain Gauge and Histologic Analysis

Besides alveolar bone quality, the drilling protocol applied in conjunction with the design of an implant are the major determinants of primary implant stability. Surgical trauma and bone compression resulting from implant insertion may constitute one cause for marginal bone resorption. Inserting two current bone-level implant designs (Astra; Straumann; n = 5) in bovine ribs, primary stability, strain development on the buccal bone plate and histologic signs of bone damage were recorded. Besides comparing the implant designs (Welch t-tests), all measurement parameters were checked for potential correlations (Pearson product moment correlation coefficients) with the level of significance set at α = 0.05. Considerable numbers of crack formation and plastic deformation of bone were observed after implant insertion. Straumann implants showed slightly greater values for insertion torque (p = 0.772), strain development (p = 0.893) and implant stability (p = 0.642). Significantly greater bone to implant contact (cortical p = 0.014; trabecular p = 0.016) was observed in Straumann implants, while Astra implants caused a significantly greater number of microcracks in cortical bone (p = 0.020). In Straumann implants, insertion torque correlated with bone to implant contact in the cortical area (p = 0.029) and the number of macrocracks in trabecular bone correlated with bone to implant contact (p = 0.029). In Astra implants, insertion torque and bone to implant contact in the trabecular area correlated (p = 0.007) as well as the number of macrocracks in trabecular bone and implant stability (p = 0.016). Additionally, in the area of cortical bone, the number of macrocracks correlated with bone to implant contact (p = 0.019). Implant placement results in bone damage of varying magnitude, which is governed by the drill protocol, implant macrodesign and bone quality

Biomechanical Performance of a Novel Implant Design in Simulated Extraction Sites and Sinuslift Procedures

With increasing experience and in an attempt to shorten overall treatment times, implant placement in combination with tooth extractions and sinus lift procedures has become popular. In both cases, primary stability has to be achieved by either engaging apical and oral regions of trabecular bone or by engaging residual host bone beneath the sinus cavity. Extraction sites were formed by pressing a root analog into homogeneous low density polyurethane foam which was used as bone surrogate while a 3 mm thick sheet of medium density foam was used for mimicking a sinus lift situation. Two types (n = 10) of bone level implants with a conventional tapered design and a cervical back taper (NobelActive; control) and a novel design characterized by a shift in core diameter and thread geometry (AlfaGate; test) were placed in these models following conventional osteotomy preparation. Insertion torque was measured using a surgical motor and primary stability was determined by resonance frequency analysis. Statistical analysis was based on Welch two sample t tests with the level of significance set at α = 0.05. In sinuslifting, NobelActive implants required significantly higher insertion torques as compared to AlfaGate (p = 0.000) but did not achieve greater implant stability (p = 0.076). In extraction sites, AlfaGate implants showed both, significantly higher insertion torques (p = 0.004) and significantly greater implant stability (p = 0.000). The novel implant design allowed for greater primary stability when being placed in simulated extraction sockets and sinuslift situations. While in extraction sockets the position of condensing threads in combination with an increase in core diameter is beneficial, the deep cervical threads of the novel implant lead to superior performance in sinuslift situations

Biomechanical Rationale for a Novel Implant Design Reducing Stress on Buccal Bone

Modern implant designs should allow for adequate primary stability but limit mechanical stress on buccal bone in order to prevent initial marginal bone loss. A dental implant characterized by a shift in core diameter and thread geometry was evaluated. Polyurethane foam was used as bone surrogate material and implant placement was performed measuring insertion torque and strain development on buccal bone using strain gauges as well as primary stability by using damping capacity assessments. An existing tapered bone-level implant was used as a control while the novel experimental implant described above (n = 10) was used in the test group. Statistical analysis was based on t-tests (α = 0.05). Both the maximum insertion torque (p = 0.0016) and maximum strain development in buccal bone (p = 0.1069) were greater in control implants as compared to the novel implant design. Moreover, in the control group, these were reached at a significantly later timepoint of the insertion process, i.e., when the implant was almost fully seated (maximum insertion torque p = 0.0001, maximum strain development p < 0.00001). The final insertion torque (p < 0.00001) and final strain development (p = 0.0137) were significantly lower in the novel implant design while the primary stability of both implant types did not differ significantly (p = 0.219). The novel implant design allowed for a greater undersizing of osteotomies while not mechanically overstressing buccal bone. Comparable primary stability was obtained from trabecular bone instead of compressing cortical bone as occurs in conventional, existing tapered implant designs

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

Bone Damage during Dental Implant Insertion: A Pilot Study Combining Strain Gauge and Histologic Analysis

Besides alveolar bone quality, the drilling protocol applied in conjunction with the design of an implant are the major determinants of primary implant stability. Surgical trauma and bone compression resulting from implant insertion may constitute one cause for marginal bone resorption. Inserting two current bone-level implant designs (Astra; Straumann; n = 5) in bovine ribs, primary stability, strain development on the buccal bone plate and histologic signs of bone damage were recorded. Besides comparing the implant designs (Welch t-tests), all measurement parameters were checked for potential correlations (Pearson product moment correlation coefficients) with the level of significance set at &alpha; = 0.05. Considerable numbers of crack formation and plastic deformation of bone were observed after implant insertion. Straumann implants showed slightly greater values for insertion torque (p = 0.772), strain development (p = 0.893) and implant stability (p = 0.642). Significantly greater bone to implant contact (cortical p = 0.014; trabecular p = 0.016) was observed in Straumann implants, while Astra implants caused a significantly greater number of microcracks in cortical bone (p = 0.020). In Straumann implants, insertion torque correlated with bone to implant contact in the cortical area (p = 0.029) and the number of macrocracks in trabecular bone correlated with bone to implant contact (p = 0.029). In Astra implants, insertion torque and bone to implant contact in the trabecular area correlated (p = 0.007) as well as the number of macrocracks in trabecular bone and implant stability (p = 0.016). Additionally, in the area of cortical bone, the number of macrocracks correlated with bone to implant contact (p = 0.019). Implant placement results in bone damage of varying magnitude, which is governed by the drill protocol, implant macrodesign and bone quality

Biomechanical Rationale for a Novel Implant Design Reducing Stress on Buccal Bone

Modern implant designs should allow for adequate primary stability but limit mechanical stress on buccal bone in order to prevent initial marginal bone loss. A dental implant characterized by a shift in core diameter and thread geometry was evaluated. Polyurethane foam was used as bone surrogate material and implant placement was performed measuring insertion torque and strain development on buccal bone using strain gauges as well as primary stability by using damping capacity assessments. An existing tapered bone-level implant was used as a control while the novel experimental implant described above (n = 10) was used in the test group. Statistical analysis was based on t-tests (&alpha; = 0.05). Both the maximum insertion torque (p = 0.0016) and maximum strain development in buccal bone (p = 0.1069) were greater in control implants as compared to the novel implant design. Moreover, in the control group, these were reached at a significantly later timepoint of the insertion process, i.e., when the implant was almost fully seated (maximum insertion torque p = 0.0001, maximum strain development p &lt; 0.00001). The final insertion torque (p &lt; 0.00001) and final strain development (p = 0.0137) were significantly lower in the novel implant design while the primary stability of both implant types did not differ significantly (p = 0.219). The novel implant design allowed for a greater undersizing of osteotomies while not mechanically overstressing buccal bone. Comparable primary stability was obtained from trabecular bone instead of compressing cortical bone as occurs in conventional, existing tapered implant designs

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 </= 0.040). The packing of augmentation material is critical when non-standardized defects are treated