Adhesion and cohesion.

The phenomena of adhesion and cohesion are reviewed and discussed with particular reference to dentistry. This review considers the forces involved in cohesion and adhesion together with the mechanisms of adhesion and the underlying molecular processes involved in bonding of dissimilar materials. The forces involved in surface tension, surface wetting, chemical adhesion, dispersive adhesion, diffusive adhesion, and mechanical adhesion are reviewed in detail and examples relevant to adhesive dentistry and bonding are given. Substrate surface chemistry and its influence on adhesion, together with the properties of adhesive materials, are evaluated. The underlying mechanisms involved in adhesion failure are covered. The relevance of the adhesion zone and its importance with regard to adhesive dentistry and bonding to enamel and dentin is discussed.

What every dentist should know about zinc.

Zinc plays an important role in human physiology, from its involvement in the proper function of the immune system to its role in cellular growth, cell proliferation, and cell apoptosis as well as its essential role in the activity of numerous zinc-binding proteins. However, zinc also plays a key pathophysiological role in major neurological disorders and diabetes. Zinc deficiency is a worldwide problem, whereas excessive intake of zinc is relatively rare. Many patients are exposed to zinc on a regular basis through dentistry as a result of its use in certain restorative materials, mouthwashes, toothpastes and, notably, denture adhesives. Of particular importance to dental professionals are various case reports concerning the neurologic effects of excess zinc intake by patients who routinely use large quantities of zinc-containing denture adhesives. This review presents relevant information concerning the use of zinc in dentistry.

Strength analysis of 6 resorbable implant systems: does heating affect the stress-strain curve?

PURPOSE: The objective was to directly compare the strength of 6 different resorbable implant plating systems using an in vitro model before and after heating. MATERIALS AND METHODS: Red oak wood was cut and fixated using various resorbable plates and screws. Vertical load was applied and the specimens fractured, while a test machine gathered data. This was repeated after heating of the specimens. RESULTS: Several parameters were analyzed, and force versus displacement curves were plotted for each specimen. CONCLUSIONS: There were no statistically significant differences for total maximum loads between heat-treated and non heat-treated specimens. There were differences in strengths amongst the various systems.

The leakage resistance of endodontic fiber obturators.

Fiber obturators have been introduced into endodontics but few reports exist regarding their efficacy compared to standard obturation materials. This study evaluated the leakage resistance of fiber obturators compared with other obturation materials. All specimens showed a progressive increase in leakage with time. The data indicate that fiber obturation and a new cone/sealer system provide the best canal obturation as evidenced by the leakage behavior.

Leakage resistance of the InnoEndo fiber obturation system.

To ensure long-term function, endodontic restorations require proper sealing of the root canal system. Recent studies have recognized that microleakage in endodontically treated teeth has negative consequences (ie, apical migration of bacteria) on their prognosis, often resulting in failure. Findings in the dental literature suggest that the innovative technology, consisting of fiber-based obturation and adhesive obturation materials, can minimize this leakage. As demonstrated in this article, the ability to achieve an adequate marginal seal represents a significant advance in endodontic therapy.

Screw-retained prosthesis for Straumann implant sites with limited interocclusal clearance.

This article reports a technique that addresses the problem of the restricted interocclusal distance when screw-retained prostheses are selected.

Microleakage within endodontically treated teeth using a simplified root canal preparation technique: an in vitro study.

This study evaluated the effects of two canal preparation methods on leakage in endodontically treated teeth, comparing the relative leakage rates for conventionally prepared teeth and those instrumented and obturated with the Ultradent Endo-Eze system. Two groups (n=11) of freshly extracted human premolars (and some canines) with closed apices and single roots were used. The roots in the first group were instrumented with conventional stainless steel hand files and obturated with gutta-percha and Sealapex. The experimental group were instrumented and obturated using the Ultradent Endo-Eze system. Radiographic examination showed no difference in the level or quality of root canal fill for teeth prepared conventionally and those prepared using the Endo-Eze system. Leakage followed a linear trend for both groups of teeth but the rate of leakage increase was approximately twice as high (that is, 80% greater) for the conventional group than for the Endo-Eze teeth. This difference was not statistically significant due to the wide variability in the conventional group data. It was noted that canal preparation time for the Endo-Eze teeth was approximately 50% shorter than that required for conventional root canal therapy.

Success or failure of dental implants? A literature review with treatment considerations.

This study reviews the literature concerning the success or failure of dental implants and provides the general dentist with information to decide whether to recommend dental implant therapy to a patient. The authors conducted an extensive literature search for articles relating to dental implant failure. Metaanalyses and multi-center studies were predominant in the selection. Predictors of dental implant success or failure were gleaned from various articles and presented in the form of text and tables. The main predictors for implant success are the quantity and quality of bone, the patient's age, the dentist's experience, location of implant placement, length of the implant, axial loading, and oral hygiene maintenance. Primary predictors of implant failure are poor bone quality, chronic periodontitis, systemic diseases, smoking, unresolved caries or infection, advanced age, implant location, short implants, acentric loading, an inadequate number of implants, parafunctional habits and absence/loss of implant integration with hard and soft tissues. Inappropriate prosthesis design also may contribute to implant failure.

Fracture resistance of human root dentin exposed to intracanal calcium hydroxide.

The purpose of the present study was to determine if exposure to intracanal calcium hydroxide [Ca(OH2)] alters the fracture resistance of human root dentin. One hundred and two freshly extracted single rooted human teeth divided into three groups of 34 teeth each. Coronal access and endodontic instrumentation using round burs, stainless steel files, and Profile GT rotary files were completed for each tooth. The prepared root canal system of each tooth was filled with saline solution (group 1), USP Ca(OH)2 (group 2), or Metapaste (group 3). The apicies and access openings were sealed with composite resin and the teeth were immersed in saline. After 30 days, the roots of 17 teeth from each group were sectioned horizontally into 1-mm thick disks and each disk was loaded to fracture at 2.5 mm/min with a SATEC universal-testing machine. After 180 days the same procedure was performed on the remaining 17 teeth in each of the 3 groups. The peak load at fracture was measured for each dentin disk. Data were analyzed using one-way ANOVA and a post hoc Student-Newman-Keuls test. After 30 days exposure to the test solution, there was no difference in the peak load at fracture for the three groups of teeth. However, after 180 days, the roots of the teeth exposed to USP Ca(OH)2 showed a significant decrease in peak load at fracture when compared to the 30-day groups and the 180-day groups exposed to saline or Metapaste.

Camouflaging changes in the appearance of a patient with ectodermal dysplasia.

This clinical report describes an innovative method to ease the transition of a patient from old implant-retained prostheses to enhanced prostheses that altered the vertical dimension, esthetics, smile, and overall facial appearance. This procedure was accomplished by a customized labial bow, such as the one commonly used for a removable Hawley-type retainer, adjusted to follow the contour of teeth waxed into a denture. This option was adopted because it is reversible, nondamaging to the denture teeth, yet still camouflages the appearance of the maxillary denture and changes in facial contour during the early transition stage from the old to the new prostheses.

Strength analysis of titanium and resorbable internal fixation in a mandibulotomy model.

PURPOSE: Mandibulotomy is used to access various tumors of the tongue base, posterior oral cavity, pharynx, parapharyngeal space, and cranial base. Internal fixation using titanium plates and screws is the most common method of stabilization. These have the potential for interference with radiotherapy delivery. This in vitro study compares the strength of titanium and resorbable internal fixation in a mandibulotomy model by analyzing the force required for plate and screw breakage. MATERIALS AND METHODS: Red oak wood board was used to simulate the mandible. Titanium and resorbable plates and screws in various configurations were used to stabilize pieces of the wood. They were arranged in 6 different groups. The specimens were individually tested with a vertical load, while the test machine recorded the force-versus-displacement behavior automatically. RESULTS: Plate type and configuration affected the applied load required to induce displacement of the simulated mandibulotomy. Heating and cooling the resorbable plates prior to strength testing also affected the load-versus-displacement curve. CONCLUSIONS: Overall, the titanium system we studied exhibited greater resistance to deformation from a vertical load than did the resorbable plate groups.

Effects of sports drinks and other beverages on dental enamel.

A high percentage of people consume soft drinks that contain sugar or artificial sweeteners, flavorings, and various additives. The popularity of sports (energy) drinks is growing and this pilot study compares enamel dissolution in these and a variety of other beverages. Enamel blocks (approximately 7.0 x 5.0 x 2.5 mm) were sectioned from sound extracted human premolars and molars and measured, weighed, and immersed in the selected beverages for a total of 14 days. The pH of all beverages was measured. The enamel sections were weighed at regular intervals throughout the immersion period with the solutions being changed daily; all studies were performed in duplicate. The data were subjected to one-way ANOVA with post hoc Scheffe testing. Enamel dissolution occurred in all of the tested beverages, with far greater attack occurring in flavored and energy (sports) drinks than previously noted for water and cola drinks. No correlation was found between enamel dissolution and beverage pH. Non-cola drinks, commercial lemonades, and energy/sports drinks showed the most aggressive dissolution effect on dental enamel. Reduced residence times of beverages in the mouth by salivary clearance or rinsing would appear to be beneficial.

The shortened dental arch: a review of the literature.

The functional demands of patients are highly variable and individual, requiring dental treatment to be tailored to the individual's needs and adaptive capability. The World Health Organization indicates that a functional, esthetic, natural dentition has at least 20 teeth, while the literature indicates that dental arches comprising the anterior and premolar regions meet the requirements of a functional dentition. The English-language peer-reviewed literature pertaining to the short dental arch (SDA) was identified through the Medline search engine covering the period between 1966 and the present and critically reviewed. This treatment option for the partially dentate patient may provide oral functionality, improved oral hygiene, comfort, and, possibly, reduced costs.

Dissolution of dental enamel in soft drinks.

A high percentage of the population consumes a variety of soft drinks on a daily basis. Many of these soft drinks contain sugar and various additives and have a low pH. This study compares enamel dissolution from both regular and diet beverages.

Mandibulotomy fixation: a laboratory analysis.

PURPOSE: Mandibulotomy is an access osteotomy technique associated with significant complications. Critical evaluation of available fixation systems is required to aid in the selection of the most stable fixation method. This study was designed to provide data on the stability of traditionally used plating configurations and a low-profile 2.0-mm locking plate (mandibular locking plate, Synthes MLP; Synthes Maxillofacial, Paoli, PA). MATERIALS AND METHODS: An in vitro red oak model was used to evaluate the stability provided by the study fixation devices. Five groups were studied as follows: group 1, two 4-hole 2.0-mm nonlocking miniplates; group 2, two 4-hole 2.0-mm mandibular locking plates; group 3, one 6-hole 2.0-mm mandibular locking plate; group 4, one 6-hole 2.4-mm nonlocking rigid plate; and group 5, control (uncut red oak blocks). Each specimen was tested with vertical loads applied over the osteotomy site. The force-versus-displacement behavior was recorded for each specimen and analyzed statistically. RESULTS: Plate type and configuration affected the resistance to vertical peak load (kilogram/force [kgf]) and the fixation stiffness (kgf/mm). The greatest peak load (58.92 kgf) and stiffness (7.07 kgf/mm) was found with group 2 specimens. The differences in system stiffness were statistically significant (P <.05), as were the peak loads for groups 1, 2, and 3. The control group (nonosteotomized red oak) had markedly higher values of peak load and stiffness (484 kg and 83 kg/mm, respectively). Group 2 specimens exhibited increased resistance to flexion. CONCLUSIONS: Two 2.0-mm locking plates provided the greatest resistance to vertical load.

Using chemomechanically assisted diamond bur cutting for improved efficiency.

BACKGROUND: Surface active agents added to handpiece coolants enhance bur cutting rates, or CRs, through chemomechanical effects, or CMEs. The authors evaluate the effect of CMEs on long-term cutting by diamond burs. METHODS: The authors tested medium-grit diamonds in a high-speed handpiece under a 147.5-gram load at 350,000 revolutions per minute, with 22 milliliters per minute coolant flow consisting of distilled water or a 1:10 mouthwash/water mixture. Repeated 6-millimeter-long edge cuts were made through machinable glass ceramic bars until the CR (determined as the time to transect the bars) had decreased by more than 75 percent. The authors used six burs for each coolant and analyzed the data via one-way analysis of variance with post hoc Scheffé tests. RESULTS: CRs with water irrigation continuously decreased with the number of cuts and declined by 87 percent over eight cuts. The authors found faster CRs with CMEs; after 12 cuts, the CR was still close to 40 percent of the initial CR, compared with only 13 percent of the initial CR for water irrigation after eight cuts. These differences between CME-enhanced CRs and those found with water irrigation were statistically significant. CONCLUSIONS: Diluted alcohol- and glycerol-based mouthwash/water mixtures significantly enhanced the CRs of diamond burs and prolonged their service life by more than 50 percent compared with water irrigation alone. CLINICAL IMPLICATIONS: Dentists can increase bur CRs and extend bur cutting life by as much as 200 percent through the addition of diluted alcohol and glycerol mouthwash to the handpiece coolant.

The effect of handpiece spray patterns on cutting efficiency.

BACKGROUND: High-speed handpieces' spray ports direct coolant at the cutting interface. The authors evaluated the effect of the number of ports and their positions on cutting rates, or CRs. METHODS: The authors performed cutting studies on a machinable ceramic block using an established testing regimen. One-port, three-port and four-port handpieces from one manufacturer were operated at maximum torque and rotation speed under a water flow of 25 milliliters per minute. The authors made 6-millimeter long edge and groove cuts in 13-mm cross-section blocks using six medium-grit diamond burs for each handpiece. Each bur cut a total of 78 mm. The authors determined CR as the time to transect the block and analyzed the data by two-way analysis of variance with post hoc Scheffé tests. RESULTS: CRs varied by the type of cut and the number of spray ports. No differences were found in CRs for the three handpieces during edge cutting. The one-port handpiece cut significantly slower (P < .001) than did the three- and four-port handpieces during groove cutting. CONCLUSION: The data indicate that the number of handpiece spray ports, and their positioning relative to the bur affect water supply to the cutting interface and, consequently, the CR under these study conditions. CLINICAL IMPLICATIONS: Optimal cutting efficiency requires good coolant access, especially within restricted areas. A multiple-port handpiece may be advantageous when preparing the interproximal region for a crown or a proximal box, owing to the better water spray pattern. Dentists should consider the influence of the number of spray ports when selecting handpieces for cutting procedures.