The International Journal of Prosthodontics, 05/2012

Purpose: The objective of this systematic review was to evaluate the clinical fracture incidence of tooth-supported all-ceramic crowns according to restored tooth type. Materials and Methods: An electronic search of clinical trials published in English and Chinese was performed using four databases (Medline/PubMed, EMBASE, Cochrane Library, and the Chinese Biomedical Literature Database) from 1990 to 2011 and complemented by an additional manual search. The annual core and veneer fracture rates of various tooth types were estimated and compared using Poisson regression. Moreover, the 5-year cumulative incidence was calculated. Results: Of 5,600 titles and abstracts retrieved, 37 publications were included, with a follow-up period that ranged from 36 to 97 months. Based on the calculated results, all-ceramic crowns demonstrated an acceptable overall 5-year fracture rate of 4.4% irrespective of the materials used. Molar crowns (8.1%) showed a significantly higher 5-year fracture rate than premolar crowns (3.0%), and the difference between anterior (3.0%) and posterior crowns (5.4%) also achieved significance. Fractures were classified as either core or veneer fractures. Core fracture rates were calculated as having a 5-year incidence of 2.5%, and a significantly higher core fracture rate was found in the posterior region (3.9%). The overall 5-year incidence of veneer fracture was 3.0%, and no clear difference was found between restored tooth types, with incidences of 2.0%, 2.5%, 1.0%, and 3.0% for incisor, canine, premolar, and molar crowns, respectively. Conclusions: Within the limitations of this study, current dental ceramic materials demonstrated acceptable 5-year core and veneer fracture incidences when used for tooth-supported single crowns in both anterior and posterior segments. A higher fracture tendency for posterior crowns was the trend for all-ceramic crowns, while molar crowns showed a significantly higher fracture rate than premolar crowns. Moreover, it is recommended that randomized controlled trials with large sample sizes be undertaken to obtain more definitive results.

Purpose: The aim of this study was to compare the survival rates and biologic and technical complications of three-unit metal-ceramic posterior fixed dental prostheses (FDPs) with those obtained with zirconia frameworks. Materials and Methods: Thirty-seven patients in need of 40 three-unit posterior FDPs were included in this study. The FDPs were randomly assigned to 20 zirconia and 20 metal-ceramic restorations. Abutment preparation guidelines consisted of a 1-mm-wide circumferential chamfer, axial reduction of 1 mm, and occlusal reduction of 1.5 to 2 mm. At baseline and 1, 2, 3, and 4 years after cementation, success of both types of restorations was evaluated. The restorations were assessed using the California Dental Association's assessment system. Periodontal parameters were assessed by determining the Plaque Index (PI), Gingival Index (GI), Marginal Index (MI), and pocket depth of the abutment and control teeth. Statistical analysis was performed by applying Wilcoxon rank sum and Wilcoxon signed-rank tests. Results: Patients were examined after a mean observation period of 50 ± 2.4 months. The survival rates for metal-ceramic and zirconia restorations were 100% and 95%, respectively. One biologic complication in a zirconia FDP was observed at the 3-year follow-up. No fractures of the zirconia or metal frameworks were observed. Restorations from both groups were assessed as satisfactory. Minor chipping of the veneering ceramic was observed in 2 zirconia FDPs after 4 years. No significant differences were observed between abutment and contralateral teeth for either type of restoration or within the groups with regard to PI, GI, and pocket depth. Conclusion: Zirconia-based FDPs demonstrated a similar survival rate to metal-ceramic FDPs after medium-term clinical use.

A healthy Caucasian male lost all of his teeth because of aggressive cervical, apical, and lateral root resorption over a period of 11 years. Microscopically, there was no sign of reparative cementum apposition, but cell-rich fibrous connective tissue filling the deep resorptions was seen. The resorbed teeth were surrounded by fibro-osseous tissue of osteolytic appearance, as noted during radiologic examination. Radiography showed the osteolytic processes to regress dramatically with the removal or loss of teeth. No underlying systemic or local factor was identified. In spite of endodontic and surgical treatment, none of the resorptions went into remission.

Purpose: Implant geometry has a major impact on insertion torque values and primary stability, and bone engagement during implant insertion differs according to implant morphology. Primary stability of straight-walled and tapered implants was compared using insertion torque monitoring. Materials and Methods: A total of 57 implants (36 straight-walled OSSEOTITE and 21 tapered OSSEOTITE NT) were inserted in 20 patients. Implant torque values and insertion times were recorded, and the data were processed and interpolated to determine torque as a function of time. Results: Tapered implants required less insertion time and a higher insertion torque than straight-walled implants; this provided better primary stability, although the success rate was 86% for tapered and 100% for straight-walled implants. Conclusions: Tapered implants showed better primary stability than straight-walled implants but had a lower success rate. The authors suggest that in low-density bone, in which only a thin dense cortical layer can contribute to primary stability, a higher insertion torque can lead to the destruction of peri-implant bone, compromising osseointegration.

Purpose: The aim of this study was to determine the influence of occlusal support length (OSL) of free-end removable partial dentures (RPDs) on masticatory function. Materials and Methods: Twenty-three subjects (mean age: 55.2 ± 8.4 years) who were edentulous in the maxilla and classified as Kennedy Class I in the mandible were selected. Subjects received new maxillary complete dentures and mandibular RPDs. Five OSL conditions were determined by RPD artificial tooth wear: full occlusal support (L1, control), OSL to first molar (L2), OSL to second premolar (L3), OSL to first premolar (L4), and absence of occlusal support (L5). Masticatory performance and efficiency were evaluated using the sieve method. Chewing rate was defined as the number of masticatory cycles per minute. Bolus selection opportunities and bolus breakage function were evaluated using the one-chew method. Qualitative and quantitative measurements of masticatory cycle patterns were recorded kinesiographically. Data were analyzed using repeated-measures analysis of variance and Friedman and Fisher exact tests (α = .05). Results: Masticatory performance and efficiency decreased (P .05) from L1 (5.46 ± 0.64 mm and 51.21% ± 19.44%, respectively) to L5 (6.24 ± 0.44 mm and 24.50% ± 15.98%, respectively). Chewing rate was higher for L4 than L1 (P .05). Bolus selection chances and bolus breakage function decreased as OSL was reduced (P .05); however, there were no differences in masticatory cycle pattern among the OSL conditions (P > .05). Conclusion: Reduction of OSL altered masticatory function, thereby decreasing masticatory performance and efficiency resulting from a lower capacity to select and break down food.

The aim of this retrospective study was to evaluate the clinical performance of cobalt-chromium (Co-Cr) single crowns. Ninety restorations were placed in 55 patients, and follow-up examinations were performed annually for 5 years. Six patients (8 crowns) were regarded as dropouts. During the follow-up period, 15 (17%) crowns/abutment teeth experienced some type of complication; 8 (9%) of these were regarded as failures. The cumulative survival rate was estimated at 90.3% over 5 years, though only 3 (3%) crowns had complications that could be related to the crown material. The results suggest that Co-Cr single crowns are a promising alternative to other alloys used in fixed prosthodontics.

Purpose: Patient variables and expectations may influence patients' evaluations of treatment outcomes, which are essential to the success of therapy. The main objective of this study was to compare patients' expectations before and satisfaction after receiving implant-supported fixed partial dentures (FPDs) and single crowns. A secondary objective was to evaluate other variables that may affect patient satisfaction. Materials and Methods: The sample comprised 52 volunteers (mean age: 51.2 ± 10.6 years) who had received implant-supported FPDs (n = 25) and single crowns (n = 27). A visual analog scale (VAS) was used to assess their expectations before and satisfaction after therapy with regard to mastication, esthetics, comfort, and phonetics. Patients also completed a questionnaire concerning other variables involved in the treatment and their evaluation of their clinician's conduct. Results: Patient expectations before treatment were higher than satisfaction after treatment, but this difference was significant only for esthetics in patients who had received implant-supported FPDs. Negative correlations were found between satisfaction and age and between number of absent teeth and number of postdelivery adjustments, but only for implant-supported FPDs. A positive relationship was found for the majority of questions concerning patients' evaluations of clinician conduct and VAS scores. Conclusion: Patients' evaluation of clinician conduct appears to be an important factor that influences their expectations before and satisfaction after receiving implant-supported FPDs and single crowns.

Purpose: This study evaluated the recall attendance and maintenance for a patient population after prosthodontic treatment in undergraduate student courses. Materials and Methods: Four hundred ninety-three patients who received fixed restorations (FRs; crowns or fixed partial dentures) or removable partial dentures (RPDs; conical crown-retained or precision attachment-retained dental prostheses) were included in a recall program. The number of patients attending regularly scheduled follow-up visits every 6 months was recorded. On the basis of the complexity of the performed treatment, all follow-up interventions were assigned to the categories minimal, moderate, or extensive. Results: After 60 months, a cumulative follow-up attendance rate between 63% (RPD) and 74% (FR) was evident and not gender related. Altogether, 399 patients (193 FR, 206 RPD) regularly attended the follow-up visits. Between 61.9% (RPD) and 93.8% (FR) of these patients did not need any extensive treatment; however, only 19.2% (RPD) to 85.6% (FR) did not need any moderate or extensive treatment between follow-up visits. Conclusions: Patients treated with FRs showed a higher recall attendance than patients treated with RPDs. Further, patients with RPDs needed more extensive and moderate treatments than patients with FRs. This difference should be taken into consideration during prosthetic planning and patient consultation.

Purpose: The aims of this study were to evaluate the effect of a mandibular advancement device on oropharyngeal dimension in patients with obstructive sleep apnea (OSA) and reveal the predominate site of changes produced by mandibular advancement using computed tomography (CT). Materials and Methods: CT scans of 20 patients diagnosed with OSA were taken with and without the appliance. Three-dimensional changes in pharyngeal shape measured on cross-sectional CT images during two respiratory cycles after oral appliance insertion were estimated at five vertical levels using three variables: (1) lateral dimension, (2) anteroposterior dimension, and (3) cross-sectional area. Various parameters related to severity of OSA such as snoring volume, frequency, duration, and episodes; breathing pauses; oxygen saturation; Epworth Sleepiness Scale (ESS) score; and Apnea Hypopnea Index (AHI) score underwent comparative evaluation subjectively and objectively. Data were analyzed using the Student t test for parametric analysis. Results: A significant increase in the lateral and anteroposterior dimension of the pharyngeal lumen was observed at all five levels, but the mean change was greatest at the retroglossal level and smallest at the hypopharyngral level in both the lateral and anteroposterior dimensions. The cross-sectional area at all levels appeared to increase significantly, and apnea indices improved significantly. A significant decrease in snoring volume, snoring frequency, breathing pauses, snoring duration, snoring episodes, ESS score, and AHI score and a significant increase in oxygen saturation were found after treatment with the mandibular advancement device. Conclusion: Within the limitations of this study, CT was shown to be useful in evaluating treatment efficacy in subjects with OSA.

The aim of this report is to describe an alternative technique to record the neutral zone. An acrylic resin base with posterior occlusal rims was applied using a thermoplastic denture adhesive. After being worn for 2 days, the base was transferred into an acrylic resin complete denture. Most patients reported an improvement in denture stability and a reduction of pressure sores. This procedure seems to be helpful to improve denture function, especially in the mandible, in patients who cannot be treated with implants. However, because of its complexity, this neutral zone technique cannot be recommended for routine clinical use.

The purpose of this study was to observe the aging effects of post surface treatment with nonthermal plasma using air or helium mixed with 2% oxygen as the working gas. Two groups of fiber posts were treated with one of the nonthermal plasmas. Both groups were further divided into four subgroups, each receiving an air exposure time of 0, 1, 12, or 24 hours before being bonded with composite resin cement. The microtensile bond strength of each subgroup was measured. The results showed that the improvement in bond strength disappeared when fiber posts were exposed to air for 1 hour or longer after being treated with plasma.

The aim of this preliminary laboratory study was to evaluate the effects of 5- and 25-degree implant angulations in simulated clinical casts on an impression's accuracy when using different impression materials and tray selections. A convenience sample of each implant angulation group was selected for both open and closed trays in combination with one polyether and two polyvinyl siloxane impression materials. The influence of material and technique appeared to be significant for both 5- and 25-degree angulations (P .05), and increased angulation tended to decrease impression accuracy. The open-tray technique was more accurate with highly nonaxially oriented implants for the small sample size investigated.