Titanium allergy: could it affect dental implant integration?

Purpose: Degradation products of metallic biomaterials including titanium may result in metal hypersensitivity reaction. Hypersensitivity to biomaterials is often described in terms of vague pain, skin rashes, fatigue and malaise and in some cases implant loss. Recently, titanium hypersensitivity has been suggested as one of the factors responsible for implant failure. Although titanium hypersensitivity is a growing concern, epidemiological data on incidence of titanium‐related allergic reactions are still lacking. Materials and methods: A computer search of electronic databases primarily MEDLINE and PUBMED was performed with the following key words: ‘titanium hypersensitivity’, ‘titanium allergy’, ‘titanium release’ without any language restriction. Manual searches of the bibliographies of all the retrieved articles were also performed. In addition, a complementary hand search was also conducted to identify recent articles and case reports. Results: Most of the literature comprised case reports and prospective in vivo/in vitro trials. One hundred and twenty‐seven publications were selected for full text reading. The bulk of the literature originated from the orthopaedic discipline, reporting wear debris following knee/hip arthroplasties. The rest comprised osteosynthesis (plates/screws), oral implant/dental materials, dermatology/cardiac‐pacemaker, pathology/cancer, biomaterials and general reports. Conclusion: This review of the literature indicates that titanium can induce hypersensitivity in susceptible patients and could play a critical role in implant failure. Furthermore, this review supports the need for long‐term clinical and radiographic follow‐up of all implant patients who are sensitive to metals. At present, we know little about titanium hypersensitivity, but it cannot be excluded as a reason for implant failure. To cite this article:
Siddiqi A, Payne AGT, De Silva RK, Duncan WJ. Titanium allergy: could it affect dental implant integration?
Clin. Oral Impl. Res. 22 , 2011; 673–680
doi: 10.1111/j.1600‐0501.2010.02081.x     

A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

Objectives

Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw.

Material and methods

Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment.

Results

There was a significant difference between the means of Group 1 (38.62±6.43 Ncm) and Group 2 (48.47±5.04 Ncm), with p=0.001.

Conclusion

This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws.     

Characterization of dental nociceptive neurons

Selective blockade of nociceptive neurons can be achieved by the delivery of permanently charged sodium channel blockers through the pores of nociceptive ion channels. To assess the feasibility of this application in the dental area, we investigated the electrophysiological and neurochemical characteristics of nociceptive dental primary afferent (DPA) neurons. DPA neurons were identified within trigeminal ganglia labeling with a retrograde fluorescent dye applied to the upper molars of adult rats. Electrophysiological studies revealed that the majority of dental primary afferent neurons showed characteristics of nociceptive neurons, such as sensitivity to capsaicin and the presence of a hump in action potential. Immunohistochemical analysis revealed a large proportion of DPA neurons to be IB(4)-positive and to express TRPV1 and P2X(3). Single-cell RT-PCR revealed mRNA expression of various nociceptive channels, including the temperature-sensitive TRPV1, TRPA1, TRPM8 channels, the extracellular ATP receptor channels P2X(2) and P2X(3), as well as the nociceptor-specific sodium channel, Na(V)1.8. In conclusion, DPA neurons have the electrophysiological characteristics of nociceptors and express several nociceptor-specific ion channels. Analysis of these data may assist in the search for a new route of entry for the delivery of membrane-impermeant local anesthetics.     

Ganglion cyst of the temporomandibular joint

Ganglion cysts of the temporomandibular joint are rare and arise from myxoid degeneration of die collagenous tissue of the capsule of the joint as a result of trauma.     

Temperature change and hardness with different resin composites and photo-activation methods

This study verifies whether there is any temperature change during photoactivation of two resin composites (Filtek Z250 and Filtek Flow) with three different light curing methods (conventional halogen light curing unit, light emitting diodes curing unit and xenon plasma arc curing unit) and the relationship of temperature change with resin composite hardness. A type-K thermocouple registered the temperature rise peak in an elastomer mold during photoactivation. After photoactivation, the specimens were submitted to Knoop hardness test performed by an indenter (HMV-2000) under a load of 50g for 15 seconds. Both the temperature change data and results of the Knoop hardness test were submitted to ANOVA and Tukey's test at the 5% significance level. No statistical differences in temperature rise were recorded for the different composites following processing by light curing unit (p>0.05). The conventional halogen source produced statistically higher temperatures (p<0.05) than the other units. The plasma arc source promoted statistically lower (p<0.05) Knoop hardness values and temperature changes than the other light curing units.     

In vitro interfacial relationship between human dentin and one-bottle dental adhesives.

OBJECTIVES: One-bottle dentin adhesives combine primer and adhesive resin into a single solution. This study was conducted to determine the bond strengths to dentin of four one-bottle bonding systems and to evaluate their SEM interfacial morphology. The hypothesis to be tested was that the water-based bonding system would produce lower bond strengths and less complete penetration into dentin than other bonding systems that are dissolved in organic solvents. METHODS: Forty extracted molars were ground to expose middle dentin and were randomly assigned to four groups (n = 10): Group 1--Experimental Single Bond (3M Dental Products Division); Group 2--Prime&Bond 2.1, pre-launch version (Dentsply DeTrey); Group 3--Syntac Single-Component (Vivadent); Group 4--Tenure Quik with Fluoride (Den-Mat Co.) The surfaces were treated according to manufacturers' instructions. After 24 h in water, the specimens were thermocycled, and the bond strengths were measured in shear. The data were analyzed with ANOVA and Duncan's test at a confidence level of 95%. Further, the adhesives were also applied to 600 microns thick dentin disks. After preparing polished cross sections, the bonded interfaces were demineralized, deproteinized, and observed under a FE-SEM. The morphological appearance of the resin-dentin interface surfaces was compared by screening the entire resin-dentin interface for each specimen. RESULTS: Two morphological characteristics were evaluated: 1) the depth of resin penetration into the tubules and 2) the thickness and density of the resin-dentin interdiffusion zone. Single Bond showed statistically higher mean shear bond strengths (p < 0.001) compared to the other three materials. Specimens prepared with Syntac Single-Component and Prime&Bond 2.1 were ranked in the intermediary Duncan's grouping. Specimens bonded with Tenure Quik with Fluoride exhibited the lowest mean shear bond strength. All materials penetrated and hybridized dentin. Single Bond formed a thick layer of adhesive resin on the top of the interdiffusion area without debonding, whereas some areas of debonding were observed on the top of the hybrid layers for Prime&Bond 2.1 and Syntac Single-Component. For the water-based adhesive Syntac Single-Component, the interdiffusion zone displayed a thick filigree pattern, containing scattered open spaces between the resin-enveloped collagen fibers. Tenure Quik with Fluoride did not thoroughly infiltrate the demineralized dentin zone, resulting in wide gaps in all specimens. Prime&Bond 2.1 formed the shortest resin tags, whereas Syntac Single-Component formed the longest resin tags. SIGNIFICANCE: Bonding to dentin remains unpredictable using one-bottle bonding systems. The chemistry of each individual material may be more important than the type of solvent.     

Freestanding and multiunit immediate loading of the expandable implant: an up-to-40-month prospective survival study

STATEMENT OF PROBLEM: The subject of immediate loading of dental implants has received substantial attention, although it appears to conflict with the basic principles of dental implant therapies developed and established over the past 20 years. Clinicians would welcome the use of a reliable, immediate-loading implant system. PURPOSE: The purpose of this study was to evaluate the effectiveness of an expandable implant design for immediate and delayed loading and for freestanding and multiunit situations. MATERIAL AND METHODS: Two hundred eighty-six immediate-load Sargon implants were placed in 75 patients during a 40-month period. Of the 273 implants that survived, 81 were placed into fresh extraction sockets and immediately loaded, 162 were placed into healed sites and immediately loaded, and 30 were delay loaded. Some implants that had failed to remain stable after immediate loading became stable and osseointegrated after the load was removed and their expansion mechanisms were reactivated. RESULTS: The overall survival rate during the 40-month period was 96.0% in the maxilla and 94.8% in the mandible. Implants placed in fresh extraction sockets showed a 98.9% survival rate. Healed sites showed a 93.9% survival rate. Immediate loading of 52 fresh extraction socket implants in the maxilla showed a 100% survival rate during the evaluation period. CONCLUSION: Within the limitations of this study, it was shown that the feature of mechanical expandability may provide operators some control over implant stability during the vulnerable period after immediate loading of single, freestanding implants.