Cherilyn G. Sheets

Tooth intrusion in implant-assisted prostheses

STATEMENT OF PROBLEM Numerous reports and surveys have been published on natural tooth abutment intrusion with implant-connected fixed partial dentures. The consensus of these publications was that the cause of intrusion was multifactorial, with causative factors such as disuse atrophy, debris impaction, impaired rebound memory, and mechanical binding. It was also believed that the process was irreversible. PURPOSE In this article, the limitations with these theories are discussed, and two patient reports of tooth intrusion reversal are reviewed. A review of the current literature is discussed, as well as the current theory of tooth movement in response to dynamic mechanical stimulus, a brief discussion of current experimental procedures and results, and the current recommendations for reversal of intrusion.

Natural tooth intrusion and reversal in implant-assisted prosthesis: Evidence of and a hypothesis for the occurrence

Based on clinical observation, a hypothesis of the mechanism of intrusion of natural teeth in an implant-assisted prosthesis is suggested. Engineering principles are presented that establish an energy absorption model as it relates to the implant-assisted prosthesis. In addition, in the course of patient treatment it has been discovered that the intrusion of natural teeth can be reversed. Patient histories that demonstrate intrusion reversal are reviewed. The possible mechanisms for the intrusion/reversal phenomenon are presented and preventative recommendations are given.

Advantages and limitations in the use of porcelain veneer restorations

Porcelain veneer restorations including preparations, impression materials, cast materials, refractory casts, handling of porcelain, the try-in, and the final luting are discussed. Techniques are described to increase marginal accuracy, establish predictable natural polychromatic color within the porcelain, establish good contours and surface textures, and shorten final placement time. Tooth preparation is routinely recommended, as is the combination of epoxy dies, refractory casts, and anatomic buildup techniques. Emphasis is placed on a close working relationship and communication among the dentist, dental technician, and patient.

Tissue engineering in dentistry

Advances in tissue engineering provide an increased level of understanding of the mechanical and chemical stimuli that regulate tissue responses. Oral tissue engineering can be applied to recreate missing osseous or dental structures or correct orofacial deformities, changing the patients smile, midfacial height, and the soft tissue drape. Biomechanical principles can also be applied to tissue engineering to enhance the bone/tooth or bone/implant functionality and long-term stability. Advancements are also being achieved in the area of biomimetics that will allow the creation of new biologic replacements for missing oral structures. The opportunity for bioengineering to charter the course of tooth regeneration is an exciting prospect and will improve the quality of life for patients for decades to come.

Analysis of percussion response of dental implants: An in vitro study

The Periometer® quantitative percussion system was used to interrogate the interfacial stability of implants in vitro for comparison with X-ray computer tomography (CT) data. Selected implants were placed as per standard practice in bone stimulant polyurethane blocks. The dimensions of the surgical sites surrounding the implants were analyzed using X-ray computer tomography (CT) to determine the quality of support at the implant-bone interface. In particular, the misfit between the size of the surgical site and the corresponding implant was determined for each sample. The resulting average surgical site error from the CT scans was found to exhibit good agreement with the presence of irregularities found in the percussion data.

An in vitro comparison of quantitative percussion diagnostics with a standard technique for determining the presence of cracks in natural teeth.

STATEMENT OF PROBLEM The detection of cracks and fractures in natural teeth is a diagnostic challenge. Cracks are often not visible clinically nor detectable in radiographs. PURPOSE The purpose of this study was to evaluate the diagnostic parity of quantitative percussion diagnostics, transillumination, clinical microscopy, and dye penetration. MATERIAL AND METHODS Three independent examiners provided blind testing for the study. Examiner 1 transilluminated 30 extracted teeth and 23 three-dimensional copy replica control teeth and documented any visible cracks. Each tooth was then mounted in acrylic resin with a periodontal ligament substitute. Examiner 2 examined each specimen aided by the clinical microscope and transillumination and documented visible tooth cracks and fractures. Examiners 1 and 3 then independently tested all specimens with a device developed for quantitative percussion diagnostics. All visible cracks/fractures were removed with a water-cooled fine diamond rotary instrument. Crack visibility was enhanced by the use of a clinical microscope, dye penetrant, and accessory transillumination. This disassembly process was video documented/photographed for each specimen. One more quantitative percussion diagnostics testing was administered when the disassembly was complete. RESULTS Quantitative percussion diagnostics crack detection agreed with the gold standard microscope and transillumination method in 52 of 53 comparisons (98% agreement). Moreover, the method achieved 96% specificity and 100% sensitivity for detecting cracks and fractures in natural teeth. When all tooth cracks were removed, quantitative percussion diagnostics indicated no further structural instability. CONCLUSIONS Quantitative percussion diagnostics can nondestructively detect cracks and fractures in natural teeth with accuracy similar to that of the clinical microscope, transillumination, and dye penetrant. In addition, the method was able to reveal the presence of many cracks that were not detected by conventional transillumination.

Quantitative percussion diagnostics and bone density analysis of the implant-bone interface in a pre- and postmortem human subject.

PURPOSE It has been hypothesized that a correlation exists between the density of surrounding cortical bone and the stability of an implant under percussion loading that can be used to quantify the implants osseointegration. The purpose of the present research was to explore whether quantitative percussion testing of dental implants gives reasonable indications of the level of osseointegration that are consistent with bone configuration and its influence on osseointegration quality. MATERIALS AND METHODS Data from percussion testing of a live human subject, obtained using the Periometer, were compared with corresponding bone density estimates from high-resolution computed tomography images and postmortem percussion probe data. RESULTS The results confirm the hypothesis that the nature of an implants response to percussion is determined by its cortical bone support. CONCLUSIONS The findings suggest that the cortical bone supporting the crestal and apical regions of the implant is primarily responsible for structural stability.

A comparison of the marginal adaptation of cathode-arc vapor-deposited titanium and cast base metal copings

STATEMENT OF PROBLEM A new fabrication process where a titanium coping, with a gold colored titanium nitride outer layer, can be reliably fused to porcelain; however, the marginal adaptation characteristics are undetermined. PURPOSE The purpose of the study was to compare the clinically acceptable marginal adaptation (CAMA - defined as a marginal gap mean of ≤ 60 μm) rates of cathode-arc vapor-deposited titanium and cast base metal copings to determine whether the titanium copings would produce a higher CAMA rate than the cast base metal copings. MATERIAL AND METHODS Thirty-seven cathode-arc vapor-deposited titanium copings and 40 cast base metal copings were evaluated using an optical microscope. Fifty vertical marginal gap measurements were made of each coping, and the mean of these measurements was used to form the gap score. A 1-tailed t test was used to compare the CAMA rates, and the Satterthwaite t-score was used to analyze the consistency of the coping adaptation (α =.05). RESULTS CAMA was achieved by 24 of the 37 (64.86%) titanium copings compared to 19 of the 40 (47.50%) base metal copings. A 1-tailed t test produced a Z-score of 1.533 (1-tailed P=.063), which allowed acceptance of the study hypothesis with only a modest risk of a Type I error. CONCLUSIONS Cathode-arc vapor-deposited titanium copings exhibited a higher rate of CAMA compared to base metal copings.

A multidie technique for the fabrication of porcelain laminate veneers

Porcelain veneers are a challenge for the dentist and dental technician when they are an integral part of complex restorative treatment plans. A multidie technique is described that allows construction of laminate veneers on removable refractory dies in a stone master cast. This system provides flexibility and accuracy with less chair time when used in combination with epoxy resin dies. Multiple restorative techniques can be used simultaneously with one master cast, and emphasis is directed to harmonious working relationships between the dentist, dental technician, and patient.

In Vivo Evaluation of Quantitative Percussion Diagnostics for Determining Implant Stability

PURPOSE To test in a rat model whether quantitative percussion diagnostics provide reliable, reproducible indications of osseointegration. MATERIALS AND METHODS Titanium implants were placed in femurs of 36 Sprague-Dawley rats. Each animal was assigned to one of six groups defined by one of three time points (2, 4, or 8 weeks postplacement) and one of two treatments (matrix metalloproteinase [MMP] inhibitor GM6001 or control). Percussion testing was conducted three times per subject at implant placement and before sacrifice at one of the time points. For each time point, there was an experimental group that received daily intraperitoneal injections of GM6001, and a control group that received no MMP inhibitor. The percussion data consisted of loss coefficient (LC) values that characterize energy dissipation. Statistical analysis was performed on the LC values for the two animal groups using the paired Student t test to assess differences as a function of time, and the independent t test to compare mean LC for the study groups at sacrifice (α = .05). Histologic evaluation using the osteogenic CD40 protein marker was also performed. RESULTS A nearly significant difference in mean LC at the 2-week time point was observed between the two treatments with the GM6001 group having the higher value (P = .053). There was a greater difference between the mean LC values for the 4-week GM6001 and control groups (P = .001). The histologic evidence for subjects in these two groups confirmed reduction of osteogenesis at the implant interface after administration of the MMP inhibitor. CONCLUSIONS Lower control LC values relative to the GM6001 therapeutic group were observed, consistent with the effect MMP inhibition has on matrix remodeling at the implant bone interface. This finding in conjunction with histologic observations confirms that osseointegration can be monitored using percussion diagnostics.