An in vitro investigation into the effects of retained coronal dentine on the strength of a tooth restored with a cemented post and partial core restoration.

AIM: This study aimed to examine the fracture resistance of teeth restored with cast post and partial cores supported by different heights of coronal tooth structure. METHODOLOGY: Four specimen groups were prepared. Group A was the control and consisted of 10 single-rooted teeth restored with post and cores cemented in dowel channels with no retained coronal dentine.The test groups, B, C and D differed in the amount of retained buccal coronal dentine having 3, 4 and 5 mm, respectively. All groups were tested to failure using an Instron Universal Testing Machine, Model 1195. The mode of failure for representative specimens for each group was recorded photographically. RESULTS: Specimens in group B where the remaining dentine core was 3 mm in height fractured at a higher force than specimens in the control group (P = 0.0239). There were no statistically significant differences in the forces required to fracture teeth with retained buccal coronal dentine cores of 4 and 5 mm when compared to the control. There was no statistically significant difference between forces required to fracture groups B and C or groups B and D. CONCLUSION: In this in vitro study, 3 mm of retained coronal buccal dentine improved fracture resistance of teeth restored with partial post and cores when compared to teeth without retained coronal dentine.

An in vitro study into the effect of the ferrule preparation on the fracture resistance of crowned teeth incorporating prefabricated post and composite core restorations.

AIM: This in vitro study investigated the effect of a ferrule preparation on the fracture resistance of crowned central incisors incorporating a prefabricated post (Parapost) cemented with Panavia-Ex and with a composite core. METHODOLOGY: The test group consisted of 10 post crowned natural central incisor teeth with a 2-mm wide ferrule preparation, whilst the control group of 10 teeth had no ferrule. The specimens were mounted on a Lloyd universal testing machine and a compressive load was applied at an angle of 135 degrees to the palatal surface of the crown until failure occurred. RESULTS: In both groups, failure occurred at higher loads compared with previous studies. The mean failure load was 1218 N for the unferruled group and 1407 N for the ferruled group. Statistical analysis showed no significant difference between the groups. CONCLUSIONS: Under the conditions of this study, when composite cement and core materials are utilized with a Parapost prefabricated system in vitro the additional use of a ferrule preparation has no benefit in terms of resistance to fracture.

An in vitro study of coronal microleakage in root-canal-treated teeth restored by the post and core technique.

The aims of this study were to compare coronal microleakage around cast and prefabricated post and cores and to examine the coronal seal achieved by temporary post crowns. Thirty extracted, single-rooted, human teeth were prepared chemomechanically, root filled with gutta-percha and sealer and prepared for a standard post. Three groups, each of 10 teeth, were restored with either: (i) cast post and cores cemented with zinc phosphate cement; (ii) prefabricated posts and composite cores cemented with a composite luting cement; or (iii) temporary post crowns cemented with a temporary zinc oxide-eugenol cement. The teeth were thermocycled and placed in Indian ink for 1 week, then demineralized and rendered transparent. Linear coronal dye penetration around the posts was measured and recorded. Results indicated that while cast post and cores and prefabricated posts and composite cores produced a good seal, leakage was significantly greater with temporary post crowns (P < 0.05). It is concluded that to prevent re-infection of the root canal system, it may be preferable to restore the tooth immediately with a prefabricated post and composite system rather than place a temporary post crown and subsequently a cast post and core.

An in vitro investigation of cast post and partial core design.

OBJECTIVES: Following endodontic therapy, the provision of a cast post and core restoration may be indicated. Many authors advocate retaining sound coronal dentine where possible, improving the resistance to fracture of the endodontically treated tooth. However, there is little conclusive experimental evidence to support this recommendation. This laboratory study was designed to investigate the effect of retained sound coronal dentine on the strength of a tooth restored with a cemented post and partial core restoration under direct loading. METHODS: Specimens with retained coronal dentine buccally, lingually, or buccally and lingually were restored with cast post and partial cores and tested to failure using an Instron Universal Testing Machine, Model 1195. Control post and full core restorations were also tested. The mode of failure for all specimens was recorded photographically. RESULTS: Teeth with retained buccal coronal dentine and post and partial cores were significantly less resistant to failure than controls with post and full cores (P < 0.01), failure occurring through crack initiation and propagation at the junction of the cast partial core and dentine core. There was no statistically significant difference in the strength of teeth with retained lingual coronal dentine or buccal and lingual dentine when compared to the control. CONCLUSIONS: In conclusion, this in vitro model demonstrates that retained coronal dentine will not strengthen a tooth restored with a cast post and partial core. The clinical benefit of retaining buccal coronal dentine is brought into question when set against the increased technical effort and difficulty of producing the restoration in the dental technical laboratory and the possible overriding benefit of ferruling the crown margin onto a sound root structure.

Lacrimo-auriculo-dento-digital syndrome: a literature review and case reports.

Lacrimo-auriculo-dento-digital syndrome, which has an autosomal-dominant pattern of inheritance, typically affects the lacrimal apparatus, ears, teeth, and hands. More recent case reports have uncovered involvement of the kidneys and the respiratory and skeletal systems. Salivary gland malformation may also be a feature of the syndrome, leading to dry mouth. The characteristics of the syndrome vary among individuals, but dental anomalies seem to be prevalent. Microdontia and hypodontia occur, possibly with gray enamel, wear, and caries. This case report introduces a new three-generation family of six individuals affected with lacrimo-auriculo-dento-digital syndrome and concentrates on the dental presentation and management of two of the members.

The use of radiographic techniques in the diagnosis and management of periodontal diseases.

Radiographs continue to play an important role in the diagnosis and management of periodontal disease although opinions as to the most appropriate form of assessment vary. It is important to recognize the limitations of each technique in terms of resolution, repeatability and accuracy so that radiographs can be correctly interpreted to the benefit of the patient. The value of intra-oral and panoramic radiography is reviewed, with particular reference to articles published over the past five years, followed by a consideration of developing computer-aided techniques which may, in time, prove of value to the dental practitioner in the diagnosis and management of periodontal disease.

An update on conventional fixed bridgework. Part 4: Clinical techniques.

The first three articles of this series have emphasized the importance of careful treatment planning in conventional fixed bridgework. In this, the fourth article, attention to detail continues to be the theme. The clinical procedures for fixed bridgework (tooth preparation, temporization, impression taking and occlusal registration) will be discussed.

An update on conventional fixed bridges:. 3. Planning ahead.

The first two articles in this series dealt with patient assessment and selection for bridgework and the available options in conventional bridgework design. Having decided to provide a conventional bridge for a patient, the practitioner must plan ahead so that the clinical execution of the bridge proceeds smoothly and successfully. Time taken to plan ahead carefully will always benefit both patient and operator.

An update on conventional fixed bridges: 2. Designing fixed bridgework.

Most patients who have lost teeth prefer a fixed prosthesis to a removable prosthesis. In this, the second article in the series, we consider the principles of design that are applicable to conventional fixed bridgework and which will enable the clinician to select the prosthesis most appropriate for a partially dentate patient.

A survey of the dissatisfied denture patient.

A small but important group of complete denture wearers find great difficulty in adjusting to, and wearing, dentures. In the past, efforts have been made to identify a factor or group of factors which typify these patients so that the clinician, having recognised the factors, might modify the management approach accordingly. Most research has concentrated on one form of investigation. In this study a wide range of tests was applied to complete denture wearers attending for treatment at Cardiff or Leeds Dental School, including an exhaustive interview and questionnaire, clinical examination and a personality assessment. In the majority of cases technical errors in denture construction accounted for the presenting complaint. It was not possible to identify a factor or group of factors common to those patients who had suffered chronic denture problems.

The effect of variations in fibre length on the impact strength of poly(methyl methacrylate) resin reinforced with ultra-high-modulus polyethylene fibre.

A previous study demonstrated that the impact strength of poly(methyl methacrylate) resin can be improved by including randomly distributed 6-mm lengths of ultra-high-modulus polyethylene (UHMPE) fibre. In this study the effect of varying the fibre length on impact strength, fibre distribution and manipulative properties of the resin were investigated. A scanning electron microscopic examination of fibres at the fracture surface was also carried out. It was found that a 1% by weight loading of 3-mm, 6-mm and 12-mm fibre significantly improved impact strength when compared to control resin, the 3-mm and 6-mm groups performing significantly better than the 12-mm group. The 3-mm and 6-mm fibres afforded the optimum manipulative properties in the mixing and processing of the resin. Scanning electron microscopy revealed evidence of fibre pull-out.

Reinforcement of poly(methyl methacrylate) with ultra-high-modulus polyethylene fibre.

A previous study demonstrated that the impact strength of poly(methyl methacrylate) resin can be improved by including randomly distributed 6 mm lengths of untreated ultra-high-modulus polyethylene (UHMPE) fibre. In this study transverse bend and hardness testing of specimens containing 1 or 2 per cent by weight of untreated or plasma-etched UHMPE fibre were carried out, as well as impact testing of specimens containing 0.5, 1, 2 and 3 per cent by weight of plasma-etched UHMPE fibre. Young's modulus and transverse strength were unaffected by the inclusion of fibre, whereas hardness was unaffected at the 1 per cent level but reduced at the 2 per cent level. Impact strength of specimens containing 1 or 2 per cent by weight of plasma-etched UHMPE fibre was not significantly different to that recorded in the previous study of untreated fibre specimens.