Development of Noncarious Cervical Notch Lesions in Vitro

Abstract: Purpose : The initiation and progression of noncarious cervical notch lesions (NCCL) continues to perplex clinicians worldwide and poses a considerable restorative challenge. The purpose of this brief communication is to report what is believed to be the first in vitro production of notch-shaped lesions in the cervical third of premolar teeth.
Materials and Methods : The lesions, were produced by axial loading of selected permanent premolar teeth in a 10% aqueous solution of sulfuric acid over a period of 5 days, followed by immersion in water for 7 days.
Results : Results revealed macroscopic and microscopic features similar to those observed in noncarious cervical lesions in vivo. The lesions were incidental findings while the authors were studying stress corrosion of enamel at low pH. Although much remains to be investigated regarding the etiology and pathogenesis of NCCL, axial loading and a corrosive environment may be implicated in these processes. The artificial lesions arose in clinically sound teeth, suggesting that there is no simple clinical examination to identify teeth at risk from NCCL.     

Biomechanics of Cantilever Fixed Partial Dentures in Shortened Dental Arch Therapy

PURPOSE: The purpose of the present study was to investigate, by means of 3-dimensional finite element analysis, aspects of the biomechanics of cantilever fixed partial dentures replacing the maxillary canine in shortened dental arch therapy. The null hypothesis was that no differences would be identified by finite element analysis in the mechanical behavior of the 2 designs of cantilever fixed partial denture under different scenarios of occlusal loading. MATERIALS AND METHODS: Single- and double-abutted cantilever fixed partial dentures were modeled and analyzed using the finite element packages PATRAN and ABAQUS. Displacement and maximum principal stresses (magnitude and location) within the fixed partial dentures, supporting structures, and the periodontal ligament/bone and abutment/retainer interfaces were examined under 20 different scenarios of axial and lateral occlusal loading. RESULTS: The results indicate that more displacement occurred in the 2 rather than the 3-unit cantilever fixed partial denture, with the greatest displacement having occurred under lateral loading. The maximum principal stresses observed in the periodontal ligament/bone interfaces were greatest buccocervically, with the highest value being observed in the 2-unit fixed partial denture under lateral loading. The highest maximum principal stresses observed in the retainer/abutment interfaces were located cervically in relation to the distal margin of the retainer of the 2-unit fixed partial denture under axial loading. CONCLUSIONS: It was concluded that in adopting a cantilever fixed partial denture approach for the replacement of a missing maxillary canine in shortened dental arch therapy, there may be merits, in terms of mechanical behavior, in selecting a double-rather than a single-abutment design. Furthermore, prostheses' displacement and functional stresses may be minimized by reducing lateral loading and avoiding pontic only loading.     

Porosity in composite resins—an Achilles' heel?

An investigation of the porosity present in a wide range of composite resin dental restorative materials has shown mean levels of 2·0–3·3 per cent by volume in the cured restoration when using the two-paste systems. Most single-paste light-activated materials showed a mean porosity of less than 0·8 per cent by volume. The relationships between porosity and some clinical and physical properties of the resultant restoration are discussed.     

A comparison of midazolam and diazepam for intravenous sedation in dentistry

In a randomised cross-over trial, midazolam, a new water soluble benzodiazepine was compared with the conventional diazepam preparation (Valium) in 34 patients aged 16-45 years who were undergoing outpatient conservation dentistry. Midazolam hydrochloride (0.17 mg/kg) was virtually free of venous complications and showed advantages over diazepam (0.32 mg/kg) in providing a faster onset of action, higher incidence of amnesia and more rapid recovery. Midazolam produced a higher incidence of respiratory side effects hiccough (17.6% compared with 2.9%), brief apnoea following induction (11.8% compared with 5.8%), and airway obstruction during maintenance (8.8% compared with 0%). These may be related to the greater potency of midazolam as suggested by the smaller total dose required. Cardiovascular changes and operating conditions were similar.     

Perceptions of denture aesthetics: A two-centre study of denture wearers and denture providers

A study into perceptions of complete dentures was carried out in two dental schools, one in Australia and the other in England. Two-hundred participants were asked to assess photographs of five sets of dentures for age, gender and personality. Results were subjected to a multi-rater kappa statistic. Although no centre was determined to be better than the other, it was highly significant that Australian teachers were confident enough to state that they were unable to determine age or gender from the information supplied.     

Errors in mounting maxillary casts using face-bow records as a result of an anatomical variation

The relationship of the teeth to the intercondylar axis and horizontal plane is transferred to the articulator by means of a face-bow record. In most semi-adjustable articulators, the horizontal plane to which the maxillary cast is orientated is the Frankfort plane or its near equivalent, the orbital-axis plane. For this purpose the infraorbital notch is used as the anterior reference point Clinical observations of Cantonese patients suggest that in some individuals the Frankfort plane may not be horizontal, with the result that the orientation of the casts in the articulator is incorrect with respect to the horizontal plane, and a preliminary study has been undertaken to investigate this range of variation.

Lateral cephalometric radiographs were taken of 33 Cantonese male adult subjects in natural head posture. The cephalometric landmarks of the Frankfort plane were recorded relative to the true vertical axis and, by the use of a digitizer, fed into a computer for analysis. The results show that there is considerable individual variation in the orientation of the Frankfort plane. Variations ranging between +11° and -2° in relation to the horizontal were recorded. Large anatomical variations may make errors difficult to avoid when the manufacturers' recommended anterior reference point for a particular face-bow is the infraorbital notch. Clearly this is a source of potential error which should be recognized when treating this ethnic group.     

Occlusal Changes Following Posterior Tooth Loss in Adults. Part 2. Clinical Parameters Associated with Movement of Teeth Adjacent to the Site of Posterior Tooth Loss

PURPOSE: Much anecdotal evidence is available on tooth positional changes following loss of an adjacent tooth, but only a few studies are available. In Part 1 of this series, supraeruption was assessed and Generalized Linear Models were made to determine the clinical parameters associated with the supraeruptive process. The models demonstrated that clinical parameters were not only associated with the extent of supraeruption, but also with the type of eruption present. This investigation of tooth positional changes adjacent to sites of posterior tooth loss attempts to provide increased understanding of the magnitude, direction, and associated features that may be helpful in decision making and treatment planning in the clinical setting. MATERIALS AND METHODS: One hundred patients with an unopposed posterior tooth, with 100 age, sex, and bone level matched controls, were drawn from patients undergoing routine restorative care at Leeds Dental Institute. Study models were scanned, and the extent of eruption, type of eruption of the unopposed tooth, the overbite, overjet, buccal occlusion, and degree of crowding in the dentition, tipping, rotation, and buccal movement of the teeth associated with the edentulous site were recorded. Generalized Linear Models were developed to examine associations between each tooth movement and patient or dental factors. RESULTS: A statistical significance in the degree of tipping of teeth both mesial and distal to the extraction site was detected between the subject and control groups. There was also a significant difference in rotation of the tooth mesial to the site. Four Generalized Linear Models were produced of the types of non-vertical movements found in teeth associated with sites of tooth loss. CONCLUSIONS: Teeth adjacent to the site of tooth loss may undergo non-vertical movements. Teeth mesial to the extraction site had a tendency to tip distally. The degree of tipping was increased in upper teeth and in subjects with a cusp-to-cusp buccal occlusion. Rotation of teeth mesial to the extraction site was more prevalent in the lower arch. Tipping of the tooth distal to the extraction site could be extreme and was found to be more prevalent in subjects with a reduced (Code 1) overbite and in the lower arch. Rotation of teeth distal to the extraction site was greater in the upper arch and was also associated with a reduced (Code 1) overbite. It also had an association with rotation of the tooth mesial to the extraction site. Models of non-vertical movement are likely to be of limited value due to overdispersion, indicating a high degree of variability within the model.     

Serum cysteine proteases and their inhibitors in rheumatoid arthritis: relation to disease activity and radiographic progression

This study aims to investigate the serum levels of cysteine proteases cathepsins B and H and their inhibitors stefin A, stefin B, and cystatin C, as well as traditional inflammatory markers such as C-reactive protein in patients with rheumatoid arthritis and to correlate these markers with scores of disease activity and radiographic progression. Seventy-two patients with rheumatoid arthritis were included from two previously described cohorts of patients with chronic polyarthritis. At inclusion, disease activity was assessed by a 28-joint count, patient global assessment, and serum C-reactive protein. Erosive status of hands and wrists was expressed by the Larsen score and recorded at inclusion and after 1 year. Serum levels of cathepsin B, cathepsin H, stefin A, stefin B, and cystatin C were determined by enzyme-linked immunosorbent assay. Neither cathepsin B nor cathepsin H serum levels were associated with disease activity, presence or progression of erosive disease. Number of swollen joints correlated with serum levels of stefin A and B and correlated negatively with cystatin C serum levels. Erosive disease was associated with high serum levels of C-reactive protein and stefin A and low serum levels of cystatin C. Progression of radiographic destruction was associated with high serum levels of C-reactive protein, stefin A and B, whereas serum levels of cystatin C were not associated with radiographic progression. The findings in this study support further investigation in the regulation of the activity of cathepsins and their inhibitors in erosive rheumatoid arthritis.     

Denture soft lining materials: clinical indications

The success or failure of a soft lining in a denture is dependent not only upon the physical properties of the material employed, but also on an understanding of the intended function of this group of products, and the physiological and biological properties of the resilient oral tissues upon which the denture rests. This paper identifies the clinical factors that must be reviewed in order to assess the need for and likely success of a denture soft lining material.     

Removal of Porcelain Veneers Aided by a Fluorescing Luting Cement

Purpose: Porcelain veneers are a safe and effective treatment modality for selected teeth that have poor esthetics. However, removal of porcelain veneers that have failed may be time‐consuming and involve considerable removal of sound tooth structure adjacent to the veneer. The aim of this study was to evaluate a novel method of porcelain laminate veneer removal by incorporating a fluorescent dye into the luting cement that allows the practitioner to visualize the cement on the tooth and remove the veneer without causing residual damage to the adjacent tooth substance. Materials and Methods: Porcelain veneers were luted on extracted teeth with a luting cement modified with a fluorescing agent. Faculty teaching staff and final year dental undergraduates were asked to remove the veneers with the aid of a curing light to render the luting cement visible by fluorescing. They were then asked to compare the removal of comparable veneers without this visual aid and to complete a standard questionnaire. The depth of cure of the conventional and modified cements was measured using a penetrometer. Results: Results of the questionnaire indicated that the operators found removing the veneer cemented with the modified (fluorescing) cement considerably easier than removing the veneer cemented with the conventional cement. Microscopy indicated that more damage was caused to the underlying tooth during removal of conventionally cemented veneers. The incorporation of the dye into the cement reduced the depth of cure from 4.238 mm (SD = 0.025) to 3.761 mm (SD = 0.096). CLINICAL SIGNIFICANCE The fluorescent cement was considered to be superior to conventional cements in its ease of visibility, and as a consequence, veneers cemented with the fluorescing cement are easier to remove. The fluorescing dye significantly reduced the depth of cure, but this may not be clinically significant, because of the small thickness of cement employed when luting adhesive restorations. The use of such fluorescing materials may not be restricted to a luting cement for veneers but may also be incorporated into bases and lining materials so they can be visualized on removal of tooth‐colored restorations, to prevent further tooth destruction.