Assessment of convergence angle of full-coverage porcelain fused to metal crowns in clinical practice.

BACKGROUND: Full-coverage porcelain fused to metal crowns is commonly recommended for restoration of extensively damaged teeth. Ability of the dentist to adequately prepare teeth is fundamental to success and longevity of these restorations. AIMS: This study was designed to compare recommended convergence angle and taper values of tooth preparation with clinically practiced values and to assess the factors such as tooth position, operator experience, vitality, and restorative status on convergence angle of prepared teeth. SETTING AND DESIGN: It was a descriptive, cross-sectional study design and held at The Aga Khan University Hospital, Dental Section, for a period of 1 year. MATERIALS AND METHODS: A minimum of 197 crown preparation models of molar and premolar teeth prepared by residents and specialists were collected in order to achieve the objectives of the study on the basis of convenient sampling technique. STATISTICAL ANALYSIS: One sample t-test used to compare the mean practiced convergence angle values with its recommended values. Independent sample t-test and one-way ANOVA was used to see difference in the convergence angle values of the teeth prepared by different operators, tooth type, vitality status, and restorative status of teeth. RESULTS: Mean reported convergence angle and axial wall taper values were 23.7° ± 8.9° and 11.3° ± 7.8°, respectively, which is significantly greater (P<0.001) than the recommended values. Convergence angle values were greater for molars as compared to premolars. CONCLUSION: There was a considerable disparity between the convergent angles values recorded in this study and the recommended guidelines and are affected by tooth type, vitality, and restorative status of tooth.

Comparison of convergence angle of prepared teeth for full veneer metal ceramic crowns.

OBJECTIVE: To compare clinically practiced convergence angle values of tooth preparation with recommended values, and also the effect of tooth position and operator experience on convergence angle. STUDY DESIGN: Analytical study. PLACE AND DURATION OF STUDY: The study was carried out at the Dental clinic, The Aga Khan University Hospital, Karachi, from January to June 2007. METHODOLOGY: A minimum of 75 crown preparation dies including 25 dies in each group of teeth (anterior, premolars and molars) were collected retrospectively which were prepared by residents and specialists of operative dentistry. AutoCAD 2007 software was used for measurement of convergence angle. One sample t-test was applied to compare the mean practiced convergence angle values with its recommended values. Two way ANOVA was applied to measure difference in convergence angle values with respect to operator experience and tooth type with the level of significance being α=0.050. RESULTS: Mean reported convergence angle value was 22.72°, which was significantly greater (p < 0.001) than the recommended values. Statistically significant difference in convergence angle was found between anterior vs. molar teeth and between premolars vs. molar teeth (p=0.0001 and p=0.002, respectively). CONCLUSION: There was a considerable disparity between the convergent angles values recorded in this study and the recommended guidelines. Measured convergence angle values were greater for posterior teeth as compared to the anterior teeth.

Immediate loading of single-tooth restorations: one-year prospective results.

Immediate loading of splinted implant restorations is a growing trend, but limited clinical documentation hampers evidence-based treatment planning for single-tooth applications. This study prospectively evaluated the clinical efficacy of placing implant-supported, single-tooth restorations into immediate, full-occlusal loading. Sixty consecutive patients (intent-to-treat group) with 1 missing tooth between 2 intact teeth were treated with a total of 69 implants. At placement, final impressions were made and implants were provisionalized with nonoccluding prostheses. Definitive prostheses were delivered 2 weeks later. A claim of noninferiority was made with a 95% confidence interval (Mann-Whitney U test) if the success rates between the experimental group and a 97% historical control was > 7%. Standardized radiographs taken at placement and bimonthly intervals were analyzed for crestal bone changes at a type I (alpha) error level of .05; significance levels were not adjusted for multiplicity (Fisher exact tests and Student t tests). Sixteen patients (18 implants) were withdrawn for protocol deviations. The resulting treated-per-protocol group consisted of 44 subjects with 51 implants. Cumulative implant success rates were 98.55% (n = 68/69) for the intent-to-treat group and 98.04% (n = 50/51) for the treated-per-protocol group. There were no significant adverse events or statistically significant differences between the experimental and historical control groups. At 12 months mean crestal bone loss was 1.05 mm, and ranged from 0.38 to 1.5 mm (77%) and 1.6 to 2.69 mm (23%). Immediate full-occlusal loading of single-tooth restorations was safely performed in selected subjects when good primary implant stability and an appropriate occlusal load were achieved.

Lateral bone condensing and expansion for placement of endosseous dental implants: a new technique.

Placement of endosseous dental implants can be a problem due to bone resorption if the patient has been missing teeth for a considerable period of time. In the literature, bone-grafting techniques have shown variable results. Additionally, bone grafting requires a longer treatment time and a need for a second surgery, and it adds significant cost to the treatment. These factors often discourage patients from having dental-implant treatment. Another technique for placement of dental implants in narrow bone ridges is repositioning and remodeling of alveolar bone by condensing and expansion with the help of bone osteotomes. This article presents 2 cases, 1 in the maxilla and 1 in the mandible, for placement of endosseous dental implants with the use of a new bone-expansion osteotome kit that utilizes a screw-type configuration for bone condensing and expansion.

Use of mini implants for replacement and immediate loading of 2 single-tooth restorations: a clinical case report.

Numerous long-term studies have shown that treatment with dental implants can provide edentulous patients with a more stable alternative to complete dentures and partially edentulous patients with a more conservative form of tooth replacement than conventional fixed partial dentures. Until recently, commercially available dental implants have been limited to diameters ranging from 3.0 mm to 7.0 mm. Although this range of diameters has been able to address most clinical needs, partially edentulous patients who could not accommodate a 3.0-mm-diameter implant without damaging adjacent dental structures were excluded from implant therapy. This article reports on the surgical treatment and immediate restoration of a patient who received mini implants that were 2.4 mm in diameter.