Chewing side preference and laterality in patients treated with unilateral posterior implant-supported fixed partial prostheses.

BACKGROUND: It is not clear to what extent chewing is improved by unilateral oral rehabilitation with implant-supported fixed partial prostheses (ISFPPs). OBJECTIVES: This study aimed to investigate whether patients treated with unilateral ISFPPs in the maxilla use their prostheses during mastication to the same extent as they used their contralateral natural teeth. A further aim was to investigate whether there is a correlation between preferred chewing side and laterality. METHODS: Chewing side preference was assessed in 15 participants treated with unilateral ISFPPs in the maxilla. The first, second, third, fifth and tenth chewing cycles were assessed, and the test was repeated 10 times. All participants also answered a questionnaire about their chewing side preference. RESULTS: Most of the participants presented bilateral chewing, but two (13%) chewed only on the ISFPP. There was no statistically significant association between the objectively assessed chewing side and dental status (natural teeth or ISFPPs) during any of the recorded chewing cycles (p > .1). There were statistically significant correlations between both the subjectively reported usually preferred chewing side and the subjective chewing side preference during the test and the objectively assessed chewing side for the first three chewing cycles (p < .01). No correlation was found between handedness and the objectively assessed chewing side. CONCLUSION: In the present study, most participants chewed bilaterally, and chewing was performed both on the ISFPP and on the natural teeth. No correlation was found between the preferred chewing side, objectively or subjectively determined and laterality.

Effect of airborne-particle abrasion and polishing on novel translucent zirconias: Surface morphology, phase transformation and insights into bonding.

PURPOSE: The purpose this study was to investigate the effect of Kern´s air-borne particle abrasion protocol (KAPA) and polishing on two translucent zirconias (4Y, 5Y-zirconias) compared to a traditional zirconia (3Y-zirconia). METHODS: Two different surface treatments were analysed by X-ray diffraction (XRD) and interferometry 1) KAPA (0.1 MPa, 50 µm alumina, 10-12 mm distance, 15 sec and 30 sec and cleaning in ultrasound using isopropyl alcohol 99%) and 2) Clinical-delivery polishing paste (Zircon Brite, Dental Ventures, USA). Shear-bond strength tests (SBS's) were performed with a highly polished and virtually flat surface in combination with a 10-MDP based cement and a surface modified by KAPA in combination with zinc phosphate cement. The SBS was expressed in terms of MPa. RESULTS: The mean values for monoclinic content were 13 wt%, 7 wt% and 2 wt% for 3Y-, 4Y- and 5Y-zirconias respectively, no differences were found between 15 and 30 seconds. Polishing did not result in phase transformation to monoclinic phase in any of the zirconias. The rhombohedral phase was identified in all types of zirconias regardless of surface treatment. Shear-bond strength tests showed 5 MPa for polished/10-MDP based cement and 3 MPa for KAPA/ Zinc phosphate. Statistically significant differences were found between the two different surface treatments but not between the types of zirconias. CONCLUSIONS: KAPA for 15 sec seems to be equal to 30 sec regarding morphology and phase transformation. Sole micro-retention appears not to be fully responsible for the bonding phenomena of 10-MDP and zirconia that underwent KAPA.

Cobalt-chromium alloys fabricated with four different techniques: Ion release, toxicity of released elements and surface roughness.

OBJECTIVE: To investigate the metal ion release, surface roughness and cytoxicity for Co-Cr alloys produced by different manufacturing techniques before and after heat treatment. In addition, to evaluate if the combination of materials affects the ion release. METHODS: Five Co-Cr alloys were included, based on four manufacturing techniques. Commercially pure titanium, CpTi grade 4 and a titanium alloy were included for comparison. The ion release tests involved both Inductive Coupled Plasma Optical Emission Spectrometry and Inductive Coupled Plasma Mass Spectrometry analyses. The surface analysis was conducted with optical interferometry. Cells were indirectly exposed to the materials and cell viability was evaluated with the MTT (3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide) method. RESULTS: All alloys showed a decrease of the total ion release when CpTi grade 4 was present. The total ion release decreased over time for all specimens and the highest ion release was observed from the cast and milled Co-Cr alloy in acidic conditions. The cast and laser-melted Co-Cr alloy and the titanium alloy became rougher after heat treatment. All materials were within the limits of cell viability according to standards. SIGNIFICANCE: The ion release from Co-Cr alloys is influenced by the combination of materials, pH and time. Surface roughness is influenced by heat treatment. Furthermore, both ion release and surface roughness are influenced by the manufacturing technique and the alloy type. The clinical implication needs to be further investigated.

Cobalt-chromium alloys in fixed prosthodontics in Sweden.

Aim: The aim of this study was to compile the usage of Co-Cr alloys in fixed prosthodontics (FP) among dental laboratories in Sweden. Methods: From March to October 2015, questionnaires were sent to 542 registered dental laboratories in Sweden. The questionnaires were divided in two parts, one for fixed dental-supported prosthodontics (FDP) and one for fixed implant-supported prosthodontics (FIP). Reminders were sent three times. Results: In total of 542 dental laboratories, 55% answered the questionnaires. Most dental laboratories use Co-Cr in FP, 134 (74%) in FDP and 89(66%) in FIP. The laboratories used Co-Cr alloys of various compositions in the prostheses, 35 for FDP and 30 for FIP. The most commonly used Co-Cr alloys for tooth-supported FDPs were (a) Wirobond® 280, (b) Cara SLM and (c) Wirobond® C. For implant-supported frameworks the frequently used alloys were: (a) Cara SLM, (b) Cara Milled and (c) Wirobond® 280. Except for the difference in composition of these alloys, they were also manufactured with various techniques. In tooth-supported prostheses the dominating technique was the cast technique while newer techniques as laser-sintering and milling were more commonly reported for implant-supported constructions. A fourth technique; the 'pre-state' milling was reported in FDP. Conclusion: More than 30 different Co-Cr alloys were reported as being used in FP. Thus, there is a need for studies exploring the mechanical and physical behavior and the biological response to the most commonly used Co-Cr alloys.

Incidence of First Implant Failure: A Retroprospective Study of 27 Years of Implant Operations at One Specialist Clinic.

BACKGROUND: Even though there are many studies available reporting on implant failures, there are few studies that follow implant failures over time in large populations. PURPOSE: The purpose of this article is to present an overview of the annual incidence of reported implant failures for patients and operations over a 28-year period. MATERIALS AND METHODS: A total of 8,528 patients were consecutively provided with 39,077 implants in 10,719 implant operations during a 27-year period (1986-2012) at one specialist clinic. All patients with reported failures of implants during a 28-year routine follow-up period (1986-2013) were included, and data from the patients' files were retrieved and reported. RESULTS: Altogether, 857 patients (882 jaws/operations) were identified with one or more failures (10.0% of patients/8.5% of operations). Mean annual incidence of first failure showed obvious variations between years, even between seemingly clinically similar situations. However, incidence of first implant failure was higher for upper than lower jaws (p < .05), within 1 year of surgery (69%) than after 1 year (p < .05), and for implants with a turned surface compared with implants with a moderately rough surface (p < .05). CONCLUSIONS: With regard to annual failure incidence in relation to total number of operations over time, obvious variations in failure rate can be observed between seemingly similar clinical situations, as well as significant differences in incidence of first implant failure between the first year after surgery and later time points, between upper and lower jaws using implants with turned surfaces, and between operations to install implants with turned surfaces and those to install implants with moderately rough surfaces.

Evaluation of bone healing on sandblasted and Acid etched implants coated with nanocrystalline hydroxyapatite: an in vivo study in rabbit femur.

This study aimed at investigating if a coating of hydroxyapatite nanocrystals would enhance bone healing over time in trabecular bone. Sandblasted and acid etched titanium implants with and without a submicron thick coat of hydroxyapatite nanocrystals (nano-HA) were implanted in rabbit femur with healing times of 2, 4, and 9 weeks. Removal torque analyses and histological evaluations were performed. The torque analysis did not show any significant differences between the implants at any healing time. The control implant showed a tendency of more newly formed bone after 4 weeks of healing and significantly higher bone area values after 9 weeks of healing. According to the results from this present study, both control and nano-HA surfaces were biocompatible and osteoconductive. A submicron thick coating of hydroxyapatite nanocrystals deposited onto blasted and acid etched screw shaped titanium implants did not enhance bone healing, as compared to blasted and etched control implants when placed in trabecular bone.

Importance of Ca(2+) modifications for osseointegration of smooth and moderately rough anodized titanium implants - a removal torque and histological evaluation in rabbit.

BACKGROUND: Incorporation of Ca(2+) into the titania of anodized titanium surfaces has been found to enhance osseointegration. It provides a stable surface when the ions are incorporated into the oxide layer during the anodizing process. The Ca(2+) may suggestively be prominent sites for mineral induction, attract proteins, and catalyze intracellular cascades. PURPOSE: The aim of the present study was to evaluate the osseointegration of smooth (S(a) < 0.5 µm) and moderately rough (S(a) 1.0-2.0 µm) commercially pure titanium implants, with and without Ca(2+) , in order to reflect on the importance of surface chemistry in relation to topography. MATERIALS AND METHODS: Anodized implants with (OxCa) or without Ca(2+) (Ox), blasted implants (Bl), and blasted anodized implants, with (BlOxCa) or without Ca(2+) (BlOx), were inserted in rabbit femur and tibia. The implant surfaces were characterized using interferometry, scanning electron microscopy, and X-ray photoelectron spectroscopy prior to implant installation. Removal torque (RTQ) measurements were executed on all implants after a healing period of 12 weeks. The implants were, thereafter, removed en bloc with surrounding tissues and prepared for histological evaluations. RESULTS: RTQ measurements of tibial implants revealed significantly higher values for BlOxCa implants (90.7 ± 23.3 Ncm) compared to OxCa (64.6 ± 18.2 Ncm) and BlOx implants (69.7 ± 17.5 Ncm) (p = 0.029). Ca(2+) modification of smooth implants placed in the femur did not reveal any differences. CONCLUSION: Ca(2+) modification of smooth implants resulted in similar interfacial shear strength as moderately rough implants and Ca(2+) modification of moderately rough implants demonstrated the significantly strongest interfacial shear strength when placed in rabbit tibia. This possibly demonstrated surface chemistry compensating for lesser roughness.

Early interactions between leukocytes and three different potentially bioactive titanium surface modifications.

The aim of the present study was to compare the early interactions between leukocytes and three different surface modifications, suggested as bioactive. Blasted titanium discs were modified by alkali and heat treatment, sodium fluoride treatment, or hydroxyapatite coating. A number of these discs were also immersed in simulated body fluid (SBF) for a week, a treatment which yielded high levels of calcium and phosphate on each surface type. The specimens were exposed for human venous blood for 32 minutes and the respiratory burst response was measured in terms of reactive oxygen species with a luminometer, and coverage of viable cells with a fluorescence microscope after staining steps. The topography, morphology, and chemistry of the surfaces were evaluated with optical interferometry and scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX). A high respiratory burst response was found for HA coated titanium in comparison with the other surface groups (p < 0.0005). The SBF immersion resulted in an increased respiratory burst response (p < 0.0005) and removed statistically significant differences between the surface groups. Thus, the results in the present study indicate that different titanium surface modifications influence the early inflammatory response differently, and that calcium phosphate compounds increase the inflammatory response.

Bone reaction to nano hydroxyapatite modified titanium implants placed in a gap-healing model.

Nanohydroxyapatite materials show similar chemistry to the bone apatite and depending on the underlying topography and the method of preparation, the nanohydroxyapatite may simulate the specific arrangement of the crystals in bone. Hydroxyapatite (HA) and other CaP materials have been indicated in cases in which the optimal surgical fit is not achievable during surgery, and the HA surface properties may enhance bone filling of the defect area. In this study, very smooth electropolished titanium implants were used as substrata for nano-HA surface modification and as control. One of each implant (control and nano HA) was placed in the rabbit tibia in a surgical site 0.7 mm wider than the implant diameter, resulting in a gap of 0.35 mm on each implant side. Implant stability was ensured by a fixating plate fastened with two side screws. Topographical evaluation performed with an optical interferometer revealed the absence of microstructures on both implants and higher resolution evaluation with AFM showed similar nanoroughness parameters. Surface pores detected on the AFM measurements had similar diameter, depth, and surface porosity (%). Histological evaluation demonstrated similar bone formation for the nano HA and electropolished implants after 4 weeks of healing. These results do not support that nano-HA chemistry and nanotopography will enhance bone formation when placed in a gap-healing model. The very smooth surface may have prevented optimal activity of the material and future studies may evaluate the synergic effects of the surface chemistry, micro, and nanotopography, establishing the optimal parameters for each of them.

Formation of calcium phosphates on titanium implants with four different bioactive surface preparations. An in vitro study.

The aim of the present study was to compare the nucleating and growing behaviour on four types of bioactive surfaces by using the simulated body fluid (SBF) model. Titanium discs were blasted and then prepared by alkali and heat treatment, anodic oxidation, fluoridation, or hydroxyapatite coating. The discs were immersed in SBF for 1, 2, 4 and 6 weeks. Calcium phosphates were found on all specimens, as analysed with scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX). After 1 and 2 weeks of SBF immersion more titanium was accessible with SEM/EDX on the blasted surfaces than the four bioactive surface types, indicating a difference in coverage by calcium phosphates. The Ca/P mean ratio of the surfaces was approximately 1.5 after 1 week, in contrast to the fluoridated specimens which displayed a Ca/P mean ratio of approximately 2. Powder X-ray diffraction (P-XRD) analyses showed the presence of hydroxyapatite on all types of surfaces after 4 and 6 weeks of immersion. The samples immersed for 6 weeks showed a higher degree of crystallinity than the samples immersed for 4 weeks. In conclusion, differences appeared at the early SBF immersion times of 1 and 2 weeks between controls and bioactive surface types, as well as between different bioactive surface types.

Comparison of histomorphometrical data obtained with two different image analysis methods.

A common way to determine tissue acceptance of biomaterials is to perform histomorphometrical analysis on histologically stained sections from retrieved samples with surrounding tissue, using various methods. The "time and money consuming" methods and techniques used are often "in house standards". We address light microscopic investigations of bone tissue reactions on un-decalcified cut and ground sections of threaded implants. In order to screen sections and generate results faster, the aim of this pilot project was to compare results generated with the in-house standard visual image analysis tool (i.e., quantifications and judgements done by the naked eye) with a custom made automatic image analysis program. The histomorphometrical bone area measurements revealed no significant differences between the methods but the results of the bony contacts varied significantly. The raw results were in relative agreement, i.e., the values from the two methods were proportional to each other: low bony contact values in the visual method corresponded to low values with the automatic method. With similar resolution images and further improvements of the automatic method this difference should become insignificant. A great advantage using the new automatic image analysis method is that it is time saving--analysis time can be significantly reduced.

FGF-4 and titanium implants: a pilot study in rabbit bone.

AIM: To evaluate the effect of a local single injection of amino-terminally truncated recombinant human fibroblast growth factor-4 (rhFGF-4s) on titanium implant incorporation in a rabbit bone. MATERIAL AND METHODS: Thirty-six threaded titanium implants were inserted into the femur and tibia of six rabbits. Three weeks prior to implant insertion 10 microg of FGF-4 in an altelocollagen carrier or the carrier alone was injected into the intended implant sites. Biomechanical evaluation by (i) resonance frequency analysis and (ii) peak removal torque measurements was performed after 6 weeks. The implants with surrounding tissue were processed to undecalcified ground sections followed by light-microscopic quantifications of the bone in threaded area and the apical parts of the implants. RESULTS: A general trend, however not statistically significant, with higher mean values obtained in the above-mentioned tests was found. The FGF-4-treated implants revealed a significantly increased bone area in the apical part of the implants compared to the corresponding control implants. CONCLUSION: A local single injection of rhFGF-4 may stimulate bone formation around titanium implants in bone. However, further research is required to confirm these results, understand the mechanisms of FGF, and establish optimal dose and delivery methods.

Dog model for study of supracrestal bone apposition around partially inserted implants.

A dog model for study of supracrestal bone growth around partially inserted implants is described. The mandibular premolar teeth (P1, P2, P3 and P4) were extracted on both sides of the mandible in four dogs. At a surgical exposure 12 weeks later, two 10 mm titanium implants were partially inserted on each side, 15 mm apart, in the areas of the P1 and the P3 so that five threads protruded from the bone crest. A titanium mesh was fastened to the coronal aspect of the two fixtures and covered with an ePTFE membrane. Thus, a space for potential bone formation was created between the two implants. The surgical flaps were coronally positioned and secured with vertical mattress sutures. After 12 weeks of healing, biopsy specimens were retrieved and examined histologically. In three of the four dogs under study, the partially inserted implants had integrated and the intended large wound spaces had been created around the noninserted parts of the implants. However, bone was not formed around the protruding implants. Accordingly, this experimental model may prove useful for future studies on the use of various procedures that hypothetically may enhance bone formation.

Recent outcomes and perspectives of the application of bone morphogenetic proteins in implant dentistry.

BACKGROUND: Since the discovery of bone morphogenetic proteins (BMPs), the number of related studies has increased substantially, and more recent outcomes have cast encouraging perspectives on their use in reconstructive surgery. PURPOSE: The aim of the present review was to summarize the present knowledge about the use of BMPs in conjunction with dental implants based on the literature. MATERIALS AND METHODS: Scientific articles dealing with the use of growth factors and bone healing with or without dental implants were searched for on MEDLINE and critically scrutinized. RESULTS: Thirty-nine scientific reports formed the base for the present review. Whereas the osteoinductive capability of BMPs is well documented, studies on their effects in implant dentistry are still incipient. Preclinical and clinical studies did not show outstandingly good outcomes of the application of BMPs compared with conventional treatments or controls. CONCLUSIONS: The number of studies in the field of dental implantology in which BMPs have been used is still too small for establishing clinical protocols of their use in order to improve a recipient bone bed prior to implant placement or to enhance the integration process of an implant.