Factors influencing the non-surgical eruption of palatally impacted canines

BACKGROUND

Many palatally impacted canines in children do not require surgical exposure prior to the start of orthodontic treatment. They erupt in mid-alveolar positions providing excess space is made for them in the arch. The time required for an impacted tooth to emerge under these conditions is highly variable.

AIM

To determine the factors influencing the time required for a palatally impacted canine to spontaneously disimpact following orthodontic treatment to create excess space in the arch.

METHOD

Thirty palatally impacted canines, which emerged following orthodontic treatment to open excess space in the arch, were used. The impacted teeth were present in 28 children. No canines were surgically exposed. The positions of the impacted canines before treatment, the mesiodistal widths and rotations of the adjacent and contralateral lateral incisors, age and gender of the subjects, subjects' dental ages, presence of either incisor or premolar hypodontia, number of subjects with bilaterally impacted canines, and number of siblings with impacted canines were recorded. Canines that erupted in less than nine months of treatment were compared with canines that required more than nine months of treatment. The canines were grouped by severity of impaction (sectors II - IV) and compared.

RESULTS

There were significantly more severe (sector IV) impactions in the long duration group compared with the short duration group. Significantly more cases of incisor-premolar hypodontia were found in the short duration group. Canines impacted in sector IV emerged after 21 months of treatment and canines in sectors II and III emerged after eight months of treatment. Lateral incisors adjacent to the impacted teeth were rotated mesiolabially to a greater extent in the sector IV group compared with lateral incisors in the sector II group. Differences in rotation of the adjacent and contralateral lateral incisors were significantly less in the sector II group compared with the lateral incisors in the sector III and IV groups.

CONCLUSIONS

The sector of impaction was the best guide to the duration of treatment prior to emergence.

Raman spectroscopic study of noncarious cervical lesions

The surface of noncarious cervical lesions (NCCLs) consists of sclerosed dentin. This type of dentin may affect the ability of adhesive restorative materials to bond well to its surface, but little information exists on the chemical nature of this dentin surface and how it may be affected during acidic treatment. The inorganic part of normal dentin and dentin from NCCLs before and after acid conditioning with phosphoric acid or polyacrylic acid was investigated. Ten premolars with NCCLs and four human third molars (control) were used. Replicas of NCCLs were examined using scanning electron microscopy (SEM). Surfaces and longitudinal sections of four NCCLs and control dentin discs were analyzed using Raman spectroscopy. The discs and NCCLs were sectioned, and treated with 35% phosphoric acid or 20% polyacrylic acid/3% aluminum chloride, and Raman spectra obtained. The area under phosphate nu1 of the dentin spectrum was computed to obtain a ratio with the area under the second-order spectrum of a silicon phonon comparative standard. Mean phosphate nu1 and silicon phonon ratios from normal dentin and NCCLs were compared using a linear model with repeated measurements and Tukey's pairwise tests. Mean ratios from different locations of the NCCLs were compared using one-way analysis of variance (ANOVA) and Tukey's pairwise tests. SEM micrographs of NCCL surfaces showed variation from relatively smooth with no dentinal tubule openings to surfaces with occluded tubules. The mean phosphate nu1 and silicon phonon ratios for NCCLs were higher than those of normal dentin in all treatment groups (P < 0.05). Ratios from the untreated specimens were higher than those of the polyacrylic acid-treated specimens, and those for the phosphoric acid-treated group were the lowest (P < 0.05). The ratios obtained for the surfaces of NCCLs were higher than those halfway towards the pulp, and those adjacent to the pulp were the lowest (P < 0.05).

Cervical microleakage in composite restorations of primary teeth--in vitro study

OBJECTIVE

The purpose of this study is to evaluate in vitro the cervical microleakage of two bonding systems (Group 1: Scotchbond Multi-Purpose-3M; Group 2: Clearfil Mega Bond-Kuraray) in occluso-proximal composite restorations of primary molars.

METHODS

Two occluso-proximal standard cavities preparations (vertical slots) were made in each one of the 11 primary molars. The cavities were filled using adhesive systems (one for each cavity) and hybrid composite (Filtek Z250-3M) by incremental technique. The first increment was inserted horizontally at the cervical wall and light-cured with 100 mW/cm2 intensity for 60 s (VIP-Bisco). Other two increments were inserted diagonally on the buccal and lingual portion and each one light-cured with 200 mW/cm2 intensity for 60s. The restorations were finished and polished, and then partially sealed and embedded in 0.5% methylene blue solution for 24 h. The specimens were sectioned mesio-distally and the dye penetration was evaluated (score from 0 to 3) under a stereomicroscope.

RESULTS

The statistical analysis (Qui square and Mann-Whitney non-parametric test) revealed no statistical difference (p=0.193) between the two adhesive systems tested.

CONCLUSIONS

Both bonding systems provided small early cervical microleakage in occluso-proximal restorations of primary molars.

Can the severity of root resorption be accurately judged by means of radiographs? A case report with histology

INTRODUCTION

Root resorption of lateral incisors caused by the pressure of erupting canines is a well-known but relatively rare problem in orthodontics and general dentistry. It is usually diagnosed on radiographs. The purpose of this article is to discuss some difficulties associated with evaluating root resorption from radiographs alone. A case report is presented as an example.

METHODS

Radiographs showed that an 11-year-old girl had marked root resorption of the maxillary lateral incisors, caused by the impacted permanent canines. The incisors were to be extracted. Several months before the extractions, a canine had been surgically exposed to remove pressure from the incisor root. The lateral incisors were analyzed histologically, and the histologic findings were compared with those of the patient's mandibular first premolars, which had been extracted.

RESULTS

The resorption of the lateral incisors was more severe than expected from the radiographs. The resorption extended far into the pulp. Most, although not all, root resorption areas showed histologic evidence of repair, but the amount of repair was far from functional repair levels. The mandibular first premolars had no signs of resorption, thus excluding systemic causes.

CONCLUSIONS

The severity of root resorption of lateral incisors cannot be accurately judged from radiographs alone.

Clinical performance of a self-etching adhesive at 18 months

PURPOSE

To test the null hypothesis that beveling and/or etching enamel would not affect the 18-month clinical performance of the self-etching adhesive Clearfil SE Bond (CSEB) in noncarious cervical lesions (NCCL).

METHODS

With Institutional Review Board approval, 34 patients were enrolled in this study. A total of 120 NCCL was selected and assigned to four groups: (1) CSEB was applied without any cavity preparation; (2) CSEB was applied after beveling enamel; (3) CSEB was applied after etching enamel for 15 seconds with 35% phosphoric acid; (4) CSEB was applied after beveling and etching enamel. A microfilled composite resin was used for all restorations.

RESULTS

At 6 months after initial placement, 120 restorations (a 100% recall rate) were evaluated. At 18 months, 87 restorations (a 72.5% recall rate) were available for evaluation. A survival rate of 100% was measured for all groups at both 6 and 18 months. Sensitivity to air decreased significantly only for Group 3 (no bevel+acid etch) from baseline to 18 months without statistical changes from 6 months to 18 months. None of the other parameters resulted in significant differences for any of the four groups. However, when data were pooled, both the overall marginal discoloration and the overall marginal adaptation were significantly worse at 18 months than at baseline, while sensitivity to air decreased significantly from baseline to 18 months. The 18-month survival rate of the self-etching adhesive Clearfil SE Bond was not improved by enamel bevel or by enamel etching. Both overall marginal adaptation and overall marginal discoloration were worse at 18 months than at baseline. .

Effect of flexural load cycling on microleakage of extended root caries restorations

This study evaluated the microleakage of resin-modified glass ionomer, flowable compomer and flowable resin composite restorations on a Class V cavity of simulated advanced root caries under a flexural load cycling condition. Thirty-six non-carious human maxillary premolars were mounted in cylindrical acrylic resin molds. The cavities were prepared in the proximal root surface, from the middle of the buccal surface to the middle of the lingual surface, approximately 1 mm below the cemento-enamel junction, 2 mm axial width and 1.2 mm in depth. The teeth were randomly assigned to one of three groups with 12 teeth in each group: Group 1: Cavity conditioner and Fuji II LC (GC America), Group 2: Prime & Bond NT and Dyract Flow (Caulk-Dentsply), Group 3: Excite and Tetric flow (Ivoclar/Vivadent). Specimens were settled laterally on a fatigue-testing machine that was adjusted to deliver a force of 60N. The specimens were load cycled at 1 Hz for 5000 cycles, placed in a staining solution and sectioned to evaluate microleakage penetration. Results indicate that the coronal and gingival margins showed significant microleakage differences among the three restorations (p<0.05). At the coronal margin, there was no significant difference between Groups 2 and 3. At the gingival margin, there was no significant difference between Groups 1 and 2. It was concluded that the marginal sealing ability of a flowable resin composite under a flexural cycling load was better than in other selected materials and that flowable resin composite with dentin adhesive was a desirable alternative for root caries restorations extended to the proximal surface.

In vivo correlation of noncarious cervical lesions and occlusal wear

STATEMENT OF PROBLEM

The etiology of noncarious cervical lesions is not well understood. An understanding of the etiology helps the clinician determine appropriate treatment and management strategies. Purpose This study evaluated the relationship between noncarious cervical lesions and occlusal (or incisal) wear.

MATERIAL AND METHODS

Casts (n = 299) made from dental students were articulated in a semi-adjustable articulator and evaluated. Data included the presence and contour of noncarious cervical lesions (NCLs) and the presence, location, and severity of any occlusal/incisal wear facets. Also included were Angle's classification, occlusal guidance patterns, midline, presence of tori, tooth restoration, reverse articulation (crossbite), open occlusal relationship, and posterior excursive contacts where present. Following a calibration procedure, 2 evaluators made independent observations on the casts. The first evaluator recorded for each tooth in each subject: presence and severity of NCLs, presence and extent of occlusal/proximal restorations, and presence of reverse articulation and open occlusal relationship. Following the first evaluation red rope wax was placed at the cervical margins of each tooth for the purpose of blinding the second evaluator from NCL observations. The second evaluator recorded severity and location of occlusal/incisal wear, presence or absence of posterior excursive contacts, Angle's classification, occlusal guidance pattern, any midline discrepancy, and presence or absence of tori. The Spearman correlation coefficient and chi 2 tests were used to analyze the data (alpha=.05).

RESULTS

There was no relationship between noncarious cervical lesions and occlusal/incisal wear. There was also no correlation between NCLs and other parameters examined.

CONCLUSIONS

Under the conditions of this study, noncarious cervical lesions are not related to occlusal wear.

Microleakage of compomer restorations in primary teeth after preparation with bur or air abrasion

This study compared the degree of marginal leakage of a compomer in Class V cavities of human primary molars prepared by a conventional dental bur and air abrasion with or without acid etching. Fifty-six non-carious extracted primary molars were randomly divided into four groups (n=14) to be prepared by four techniques: Group-1: Bur followed by acid etching: Class V cavity preparations were placed on the buccal surfaces of each tooth using a high-speed handpiece. The preparations were 1.5-mm deep, 3-mm long and 2-mm wide, with the occlusal margin in enamel and the cervical margin extending 0.5 mm below the cementoenamel junction. The preparations were acid etched with 37% phosphoric acid starting at the enamel margins for 30 seconds and rinsed with water for 20 seconds. The preparations were then restored with Compoglass F. 2-Group 2: Bur: The preparations and the treatment procedures were the same as in Group 1, with the exception of 37% phosphoric acid application. Group 3: Air abrasion followed by acid etching: Class V cavity preparations were placed on the buccal surfaces of each tooth using a handpiece of an air-abrasive system (PrepStart, Danville Engineering). The system was supplied with dry compressed air at 80 psi. In all tests, the air-abrasion system was operated with an 80 degrees-angle handpiece tip and 50-mm aluminum oxide particles. A tip with a 0.38-mm inner diameter was used at a 2-mm distance. The treatment procedures were the same as in Groups 1 and 2. Group 4: Air abrasion: The preparations and treatment procedures were the same as in Group 3, with the exception of 37% phosphoric acid. After finishing the restorations, the teeth were stored in distilled water at 37 degrees C for 24 hours. The samples were thermocycled for 500 cycles between 5 degrees C and 55 degrees C with a dwell time of 30 seconds. The samples were then immersed in 0.5 percent basic fuchsin dye for 24 hours at 37 degrees C. The surface-adhered dye was then rinsed in tap water and the teeth were embedded in a chemically-activated acrylic resin and bisected longitudinally in a mesiodistal direction with a low speed diamond disk. Each section was examined under a stereomicroscope (Nikon, Tokyo, Japan) at 20x magnification. The data were analyzed statistically by Kruskal-Wallis analysis of variance to determine any statistical significant differences in microleakage scores among the groups at a p-value of 0.05. Also, the enamel versus cementum-dentin microleakage scores of each group were compared using z-test at the 0.05 significance level. There was no statistically significant difference among the groups (p>0.05), but a statistical difference between enamel and cementum-dentin surfaces was evaluated (p<0.05).

Cuspal movement and microleakage in premolar teeth restored with posterior filling materials of varying reported volumetric shrinkage values

OBJECTIVES

To investigate the effect of polymerisation shrinkage stress of various aesthetic posterior filling materials on cuspal movement and cervical gingival microleakage of mesio-occlusal-distal (MOD) restorations placed in increments in extracted maxillary premolar teeth.

METHODS

Forty sound extracted upper premolar teeth were subjected to standardised preparation of a large MOD cavity. One curing regimen was used and each posterior filling material was placed in eight increments with the appropriate bonding system. A twin channel deflection-measuring gauge allowed a measurement of individual cusp deflections at each stage of polymerisation. Restored teeth were thermocycled before immersion in 0.2% basic fuchsin dye for 24h. After sagittal sectioning of the restored teeth in a mesio-distal plane, the sectioned restorations were examined to assess cervical gingival microleakage.

RESULTS

In general, cuspal deflection measurements were dependent upon the constituent monomers and the associated shrinkage on curing, with significantly increased cuspal movement (P<0.05) being recorded for Z100 (20.03+/-2.92 microm) compared with Filtek Z250 (12.34+/-2.18 microm), P60 (13.41+/-4.43 microm) and Admira (11.2+/-2.58 microm). No significant differences were identified between the posterior filling materials when the cervical gingival microleakage scores were examined.

CONCLUSIONS

It would appear that a reduction in the manufacturers' reported volumetric polymerisation shrinkage for Z100 (4.0%) to below 3% for Filtek Z250, P60 and Admira, resulted in a significant reduction in the associated cuspal strain on the MOD cavity. The diluent triethyleneglycol dimethacrylate (TEGDMA) increases the polymerisation shrinkage of Z100 resin-based composite due to an increased concentration of carbon-to-carbon double bonds (CC). The replacement of TEGDMA with urethane dimethacrylate (UDMA) and Bis-EMA in Filtek Z250 and P60, decreases the polymerisation shrinkage stress by increasing the cross-linking of polymer networks. However, no group was identified as producing less gingival microleakage at the cervical dentine cavosurface margin when the cavities were sectioned and examined, regardless of the reported variations in cuspal strain and the associated volumetric polymerisation shrinkage values.

Longevity of a resin-modified glass ionomer cement and a polyacid-modified resin composite restoring non-carious cervical lesions in a general dental practice

BACKGROUND

Long-term prospective survival studies of resin-modified glass ionomer cements (RMGICs) and polyacid-modified resin composites (compomers) placed in non-carious cervical lesions (NCCLs) are lacking from general dental practice. Short-term studies have shown an unsatisfactory clinical performance for several materials.

METHODS

One practitioner placed 87 compomer (Compoglass, Vivadent-Ivoclar) and 73 encapsulated RMGIC (Fuji II LC, GC Int.) restorations in NCCLs for 61 adults. Compoglass was placed using SCA primer, and Fuji II LC using GC Dentin Conditioner. No cavity preparation was undertaken. The Kaplan-Meier method was used for estimating the cumulative survivals for those restorations that were replaced, with the probability level set at alpha = 0.05 for statistical significance.

RESULTS

Restorations were judged unsatisfactory (by the practitioner and the subjects) because of surface and marginal loss of material (68.8 per cent), dislodgement (18.8 per cent) and discoloration (12.4 per cent), these modes being similar for both materials (P = 0.35). Unsatisfactory restorations were replaced in 121 (75.6 per cent) instances. After periods of up to five years, cumulative survival estimates were 14.9 (5.8 Standard Error) per cent for Compoglass and zero per cent for Fuji II LC (P = 0.74). Median survivals were 30 months for Compoglass and 42 months for Fuji II LC.

CONCLUSION

Both materials had high long-term unsatisfactory performances when placed in non-prepared NCCLs in a general dental practice.

Effect of dentinal fluid composition on dentin demineralization in vitro

Dentin demineralization is reduced by perfusion with water. We hypothesized that a simulated dentinal fluid (SDF) that contains albumin, in addition to electrolytes, would be more effective in reducing dentin demineralization than water alone, and this effect would increase with increasing flow rate of SDF. Perfusion rate in tooth segments that carried buccal cervical dentin windows was measured in a fluid transport set-up. These windows were then demineralized under perfusion with water, or SDF at 1.47 kPa for 31 days. We analyzed integrated mineral loss and lesion depth with the use of transverse microradiography (TMR), which revealed that 38% more mineral dissolved from dentin lesions perfused with water than from those perfused with SDF. The former were also 18% deeper. Flow rate of dentinal fluid showed no correlation with demineralization. We concluded that composition of dentinal fluid is an important determinant of the rate of lesion formation and progression in dentin.

The Papilla Presence Index (PPI): A New System to Assess Interproximal Papillary Levels

The present article describes a classification system used to assess the interdental papillary height on natural teeth; the index can also be used in cases of lack of contact points and presence of diastemata. This system is particularly useful to define the loss of the interdental papilla because of periodontal disease and papilla reconstruction after periodontal treatment, particularly if tooth repositioning is involved. The index, based on esthetic evaluations, measures interproximal soft tissue height in relation to the CEJ, adjacent teeth, and the point corresponding to the ideal contact point. The four index scores are useful for an easy clinical assessment with respect to patient esthetics.

Prediction and causes of open gingival embrasure spaces between the mandibular central incisors following orthodontic treatment

BACKGROUND

An open gingival embrasure space (OGES) between the mandibular incisors, also known as a "black triangle" (BT), can be an undesirable outcome of adult orthodontic treatment.

OBJECTIVES

The purpose of this study was to determine the parameters that contributed most to the occurrence of an OGES between the mandibular central incisors, the area with the highest incidence of BT in the lower arch following orthodontic treatment.

METHODS

A stepwise regression model was used to identify the variables (age, crowding, treatment duration, alveolar bone height, and six variables describing crown morphology) related independently to OGES score. Intra-oral photographs taken before and after orthodontic treatment, study models and intra-oral radiographs of 60 patients were used. Embrasures between the mandibular central incisors were measured and classified into three types: papilla filling, pinpoint, and BT.

RESULTS

Age at the first consultation, length of active treatment and maximum crown width were larger in the BT group than in the normal group. In contrast, incisal edge - centre of the contact point, upper contact point - lower contact point, mesial CEJ - distal CEJ, and mesial CEJ - distal CEJ / maximum crown width were smaller in the BT group than in the normal group. Variation in OGES score was explained by the independent contributions of age at the first consultation, duration of active treatment, maximum crown width, and mesial CEJ - distal CEJ width. The multiple regression coefficient was 0.98, and the regression coefficient square was 96 per cent.

CONCLUSION

We conclude that age at the first consultation, duration of active treatment, and crown morphology are involved in OGES manifestation. We suggest also that BT occurrence may be predictable prior to treatment.

Undermining of enamel as a mechanism of abfraction lesion formation: a finite element study

Many workers have suggested that abfraction lesion formation is caused by the physical overloading of enamel. However, an alternative mechanism, involving undermining of the cervical enamel along the amelodentinal junction (ADJ), may be a more realistic explanation. The aim of this study was to examine what effect undermining of the buccal cervical enamel would have on the stress distribution in upper teeth. Two-dimensional plain strain finite element meshes of an upper incisor, canine and first premolar and the supporting periodontal ligament and alveolar bone were developed. Each tooth was loaded with an oblique 100 N load, and the nodal maximum principal stresses (MPS) along a buccal horizontal sampling plane 1.1 mm above the amelo-cemental junction was measured. A discontinuity between the cervical enamel and dentine elements was then introduced (0.1 mm wide) using gap elements. The vertical extent of this defect varied from 0.1 to 0.5 mm. The value of the MPS varied from 1.8 to 209 Mpa, and the lowest values were found for the intact teeth (range 0.6-30.3 MPa). The discontinuity caused a dramatic increase in the numerical values of the MPS, and in many instances these exceeded the known failure stress for enamel.

Demineralization inhibition of direct tooth-colored restorative materials

This study compared the demineralization inhibition properties of fluoride releasing tooth-colored restorative materials. Materials evaluated included a giomer (Reactmer, Shofu [RM]), a conventional glass ionomer (Fuji II, GC [FJ]), a resin modified glass ionomer (Fuji II LC, GC [FL]) and a compomer (Dyract AP, Dentsply [DY]). A non-fluoride releasing composite (Spectrum TPH, Dentsply [SP]) was used for comparison. Class V preparations on buccal and palatal/lingual were made at the CEJ of 75 freshly extracted molars. The teeth were randomly divided into five groups of 15 and restored with the various materials. The occlusal half of each restoration was in enamel, while the gingival half was in dentin. The restored teeth were stored in distilled water at 37 degrees C for two weeks and subjected to artificial caries challenge (18 hours demineralization [pH 5.0] followed by six hours of remineralization [pH 7.0]) for three days. Sections of 130 +/- 20 microm were examined with a polarized light microscope, and outer lesion depth [OLD] and wall area [WA] lesion/inhibition measurements were made using image analysis software. All data were subjected to statistical analyses at 0.05 significance level. For the various materials, OLD ranged from 54.55 to 65.86 microm and 124.68 to 145.97 microm in enamel and dentin, respectively. WA ranged from -2356.13 to 1398.20 microm2 and -3011.73 to 5095.80 microm2 (positive values indicate wall inhibition, negative values indicate wall lesion) in enamel and dentin, respectively. Results of ANOVA/Scheffe's post-hoc test (p<0.05) were as follows: Enamel OLD--no significant difference between materials; Dentin OLD--SP > FJ, FL & RM; Enamel WA inhibition--FJ, FL & RM > DY & SP and Dentin WA inhibition--FJ > FL > RM > DY > SP. The demineralization inhibition effect of giomers, conventional and resin-modified glass ionomer cements appear to be more evident at the margins of restorations.

Partial ceramic crowns: influence of preparation design and luting material on internal adaptation

The influence of three different cavity preparations on the marginal integrity of partial ceramic crowns (PCC) luted with four different luting systems was investigated in this in vitro study. PCC preparations were performed in 144 extracted human molars using one of the following preparation designs (n=48/preparation): A--Coverage of functional cusps/butt joint preparation; B--horizontal reduction of functional cusps and C--complete reduction of functional cusps/butt joint preparation. Non-functional cusps were not covered; mesial and distal proximal boxes were extended 1 mm below the cemento-enamel-junction. PCC were fabricated from Vita Mark II ceramic (Vita) with a Cerec 3 Unit (Sirona) and adhesively luted to the cavities using the following luting systems: (VL) Variolink II/Excite (Vivadent), (PA) Panavia F/ED Primer (Kuraray), (DY) Dyract/Prime & Bond NT (DeTrey/Dentsply) and (FU) Fuji Plus/GC Cavity Conditioner (GC). Samples were simultaneously exposed to thermocycling and mechanical loading (TC: 5000x8-55 degrees C, 30 seconds/cycle; ML: 500000x72.5N, 1.6Hz). Marginal adaptation was assessed by evaluating dye penetration on multiple sections by relating the actual penetration distance to the maximal length of the corresponding cavity wall (100%). Ceramic- and tooth-luting material interfaces were evaluated separately. The data were statistically analyzed with the Mann Whitney U-test and Wilcoxon Rank Sumtest. In general, no significant differences could be found between preparations A, B and C. The combination of preparation C and luting material PA showed a tendency for the lowest dye penetration values, especially within dentin (30%). Significant differences could be determined between luting materials: Composite luting materials PA (0%) and VL (1%) revealed less dye penetration than the compomer DY (6%) and resin-modified glass ionomer cement (RMGIC) FU (26%); use of RMGIC caused fractures of the restorations. The dentin/luting material interface showed the highest penetration values, ranging from 17% to 100%. In conclusion, with adhesively bonded partial ceramic crowns, the choice of luting material proved to be more relevant than preparation design under the limitations of this study. Margins below the cemento-enamel junction reveal significant loss of adhesion in spite of subsequent application of adhesive luting techniques. RMGIC cannot be recommended as a luting material for feldspathic PCC.

Attrition, abrasion, corrosion and abfraction revisited

OVERVIEW

The authors propose updated and revised nomenclature, definitions and classification for tooth surface lesions. Their objective is standardization, clarity and clinical utility for the dental practitioner. The article presents a schema of the pathodynamic mechanisms in the formation of tooth surface lesions--three basic physical and chemical mechanisms, their interactions and their dental manifestations.

CONCLUSIONS AND CLINICAL IMPLICATIONS

The use of precise definitions will assist the practitioner in determining the etiology of various tooth surface lesions. Understanding the pathodynamic mechanisms and their many possible interactions, as set forth in the schema, will enable the practitioner to make an accurate differential diagnosis and to provide effective prevention and treatment. It also will assist dentists in communicating more effectively with their colleagues as well as with their patients. In addition, the schema helps identify areas in which future research is indicated.

Chlorhexidine with an Anti Discoloration System. A comparative study

Correct oral hygiene is believed to be the basis of primary and secondary prevention. Sometimes, using a toothbrush or other mechanical instruments for oral hygiene may be difficult and it may become necessary to use an antiseptic. Chlorhexidine is an essential component in many available preparations on sale, because of its marked antiseptic qualities. One of the most frequent side-effects is the appearance of stains on the teeth and mucous membranes, which particularly disturbs the patient. A new mouthwash containing chlorhexidine has recently become available, besides maintaining its antiseptic qualities, also avoids the side-effect of staining.

OBJECTIVES

The aim of this study was to check the capacity of the new mouthwash, which contains chlorhexidine and Anti Discoloration System (ADS), not only to prevent plaque formation like the other mouthwashes containing chlorhexidine but also to avoid staining that is one of the most frequent side-effects.

STUDY DESIGN

The comparative study was carried out on a sample of 15 patients treated with two mouthwashes both containing 0.2% chlorhexidine, but different in that the first does not contain ADS, which is instead present in the second, a new product. The results obtained show that in the 15 patients treated, there is no statistically significant difference in the ability of the mouthwash to prevent bacterial plaque, however evidence of the stain was much less with the new mouthwash.

Wedged cervical lesions produced by toothbrushing

PURPOSE

To compare the morphology of experimentally induced cervical toothbrush abrasion lesions to teeth demonstrating non-carious cervical lesions in vivo.

METHODS

Eighteen premolars extracted for orthodontic reasons were each subjected to 80 hours (1.4 million strokes) of horizontal brushing in a custom fabricated toothbrushing machine. Toothpaste slurry was applied continuously and specimens were subjected to 300 gms of toothbrushing force. Denture base resin was used to simulate gingival recession of 1 mm and a sulcus width of 0.1 mm. Cervical abrasions were analyzed by optical and scanning electron microscopy and classified as either V-shape/wedged vs. U-shape/rounded lesions. When lesions exhibited both shapes, they were classified as mixed. Shapes of experimentally induced lesions then were compared to naturally occurring ones found on extracted premolars. RESULTSts: Experimentally induced toothbrush abrasion duplicated the classical clinical shapes. Half (9/18) of the experimentally induced toothbrush abrasions exhibited wedged lesions, 28% (5/18) showed a mixed wedged/rounded lesion, and 22% (4/18) showed rounded lesions. Serial photography showed progression of the morphology of the lesions. Toothbrush abrasion apparently begins apical to the cemento-enamel junction, progresses to dentin, and then undermines enamel with loss of the original cemento-enamel junction. Wedged lesions may appear with the apex oriented coronal or apical, or may be symmetrical.

Clinical evaluation of four Class 5 restorative materials: 3-year recall

PURPOSE

To place four restorative materials, including two resin-based composites (Pertac III and Synergy), an improved resin-modified glass-ionomer (Fuji II LC Improved), and a compomer (Dyract AP), in Class 5 non-carious cervical lesions and to evaluate and compare those restorations for marginal discoloration, anatomic form, surface texture, secondary caries, retention, and marginal adaptation at baseline and annually for 3 years.

METHODS

The tested materials were used to restore moderate-size Class 5 non-carious cervical lesions. All materials were used following the manufacturers' directions for etching, bonding, curing, and finishing. Thirty restorations of each material were placed. After rubber-dam isolation, a bevel was placed on the occlusal margin of all preparations except the Fuji II LC Improved, and all preparations were cleaned with pumice. Each restorative material was placed and cured in increments except Fuji II LC Improved. All restorations were evaluated at baseline, 6 months, 1, 2, and 3-year recalls using a modified USPHS scale.

RESULTS

Analysis with Chi Square and Logit Analysis revealed that, at 3 years, Pertac III and Fuji II LC Improved were significantly rougher than all other materials. Pertac III had significantly poorer marginal adaptation than all other materials. All other comparisons were not significant. At 3-year recall, most restorations were satisfactory.

Resin bonding to cervical sclerotic dentin: a review

Several reports have indicated that resin bond strengths to noncarious sclerotic cervical dentine are lower than bonds made to normal dentine. This is thought to be due to tubule occlusion by mineral salts, preventing resin tag formation. The purpose of this review was to critically examine what is known about the structure of this type of dentine. Recent transmission electron microscopy revealed that in addition to occlusion of the tubules by mineral crystals, many parts of wedge-shaped cervical lesions contain a hypermineralised surface that resists the etching action of both self-etching primers and phosphoric acid. This layer prevents hybridisation of the underlying sclerotic dentine. In addition, bacteria are often detected on top of the hypermineralised layer. Sometimes the bacteria were embedded in a partially mineralised matrix. Acidic conditioners and resins penetrate variable distances into these multilayered structures. Examination of both sides of the failed bonds revealed a wide variation in fracture patterns that involved all of these structures. Microtensile bond strengths to the occlusal, gingival and deepest portions of these wedge-shaped lesions were significantly lower than similar areas artificially prepared in normal teeth. When resin bonds to sclerotic dentine are extended to include peripheral sound dentine, their bond strengths are probably high enough to permit retention of class V restorations by adhesion, without additional retention.

Observations on experimental marginal periodontitis in rats

OBJECTIVE

The purpose of this study was to assess periodontal destruction following experimentally induced marginal periodontitis in rats by ligatures over a 60-day observation period. The extent to which the physiological movement of teeth influenced the effect of the ligatures was also examined. In addition, two methods for measuring bone loss in the defleshed jaw were compared.

METHODS

Thirty-five male Sprague-Dawley rats (SD) were divided into five groups. Marginal periodontitis was induced by ligatures on the second maxillary molars. Rats were killed after 15, 30, and 60 days. Rats in the control group were killed on day 1 and day 60. Bone loss was determined with two different methods on the buccal and palatinal surfaces of the defleshed jaw. In the first method, the distance of the cementoenamel junction (CEJ) from the alveolar bone crest (ABC) was measured at different sites; in the second method, the area of the exposed root surface of the molars was measured.

RESULTS

Comparison of the control groups from day 1 and day 60 using both measuring methods showed significant differences in bone loss. In the area where the ligature was located, test rats exhibited significantly greater bone loss than control rats. Comparison of control rats from day 1 with test rats from day 15 showed that the increase in bone loss between the groups within the area of the ligature was significantly greater than outside it. The age-dependent bone loss increases over the entire observation period of 60 days. The ligature-induced bone loss increased most from day 1 to day 15; on days 30 and 60, slighter increases in bone loss were observed.

CONCLUSIONS

The application of this model can only be recommended for short (</=15 days) observation periods. The distance method should be preferred to the area method.

Effects of occlusal load on cervical lesions

Toothbrush abrasion has been considered to cause cervical lesions. However, some investigators have proposed that occlusal loading factors direct tensile stresses at the cervical area, resulting in wedge-shaped abfraction defects. The purpose of this study is to investigate the role of axial and non-axial load on the development of cervical lesions. Matched paired premolars, extracted for orthodontic purposes, were used in a custom-fabricated toothbrushing apparatus. A periodontal sulcus width of 0b1 mm with 1 mm gingival recession was simulated with denture base resin. In phase 1, eight matched premolar pairs were subjected to 80 h (1b4 million strokes) of brushing and 300 g of toothbrush force. Toothpaste slurry was applied continuously through the toothbrush. One specimen in each pair was subjected to 250 h and 45 kg of continuous axial load, while the other unloaded tooth served as a negative control. In phase 2, 10 matched premolar pairs were subjected to the same conditions; however, the experimental teeth were subjected to 250 h and 45 kg of intermittent non-axial load, directed at a 45 degrees angle to the buccal cusp. Rubber impressions were made of the cervical lesions, then trimmed, weighed, and compared to determine the amount of tooth material lost. When teeth were loaded axially, there was significantly less tooth material loss (P < 0b02); however, when teeth were loaded non-axially, there was no significant difference (P =0b80) when compared with controls. Optical and scanning electron microscopy did not reveal any significant differences in the morphology between pairs. Our data suggest that the application of occlusal load may not necessarily play a significant role in the progression of cervical tooth wear commonly referred to as abfraction.

Accuracy of probing attachment levels using a CEJ Probe versus traditional probes

BACKGROUND

Current interest in the assessment of probing attachment level measurements has been stimulated by recent introduction of novel periodontal probes as well as by the reclassification of periodontal diseases. Clinical attachment level (CAL) is currently the "gold standard" for diagnosing and monitoring periodontal diseases.

AIM

To evaluate the performance of the newly introduced cementoenamel junction (CEJ) Probe in detecting CAL using the CEJ as a fixed reference point, and to compare the CEJ Probe with the Florida Disk Probe and a standard Manual Probe (North Carolina Probe).

MATERIALS AND METHODS

Three examiners probed 12 periodontal patients to determine intra- and inter-consistency of both the probes and the examiners, over a 4-week time interval. Subjects ranged in age from 22 to 74 years. The experimental design was structured to balance the intra- and inter-examiner consistency at the same site during the two visits.

RESULTS

Using the PROC MIXED of SAS, a strong interaction (p<0.001) between the examiner and probes was found. The consistency of probing (repeatability of measurements) depended upon the type of periodontal probe used as well as the skill (experience) of the examiner. Overall, the CEJ Probe displayed a more consistent performance. The CEJ Probe demonstrated greater intra-examiner consistency than the Disk Probe for two examiners (p<0.01). The CEJ Probe also showed increased inter-examiner consistency (p<0.01).

CONCLUSIONS

The CEJ Probe has the potential to offer the dental team an efficient, accurate mechanism to chart and monitor attachment level measurements over time. Additional studies, using large numbers of examiners, are needed to assess more clearly the performance of each individual probe.

Periodontal Repair in Surgically Created Intrabony Defects in Dogs: Influence of the Number of Bone Walls on Healing Response

BACKGROUND

The objective of this study was to histologically evaluate periodontal healing following flap surgery in intrabony periodontal defects to determine the influence of the number of bone walls on periodontal regeneration.

METHODS

One-, 2-, and 3-wall intrabony periodontal defects were surgically produced at the proximal aspect of mandibular premolars in either right or left jaw quadrants in six beagle dogs. Mucoperiosteal flaps were positioned and sutured to their presurgery position following defect preparation. The animals were euthanized at 8 weeks post-surgery, and block sections of the defect sites were collected for histologic and histometric analysis.

RESULTS

Bone and cementum regeneration was positively correlated to the number of bone walls limiting the intrabony periodontal defects. The junctional epithelium averaged (+/- SD) 1.5 +/- 0.2, 1.2 +/- 0.3, and 0.9 +/- 0.2 mm for the 1-, 2-, and 3-wall defects, respectively, with the 3-wall defects being significantly different from the 1-wall defects (P <0.05). Cementum regeneration averaged 1.2 +/- 0.6, 2.0 +/- 0.6, and 2.8 +/- 0.5 mm for the 1-, 2-, and 3-wall defects, respectively; all groups were significantly different from each other (P <0.05). Bone regeneration averaged 1.5 +/- 0.5, 1.7 +/- 0.6, and 2.3 +/- 0.5 mm for the 1-, 2-, and 3-wall defects, respectively, with the 3-wall defects being significantly different from the 1-wall defects (P <0.05).

CONCLUSIONS

The results suggest that the number of bone walls is a critical factor determining treatment outcomes in intrabony periodontal defects. One- and 3-wall intrabony defects appear to be reproducible models to evaluate candidate technologies for periodontal regeneration.

Accelerated alveolar bone loss in male HLA-B27 transgenic rats: adult onset

OBJECTIVE AND BACKGROUND

HLA-B27 transgenic (TG) rats exhibit severe colitis, arthritis and other inflammatory lesions. Previous studies in female TG rats indicate that they develop severe alveolar bone loss (ABL). Lack of data on male TG rats has left open the question of possible hormonal/sex dependence for the observed ABL. The purpose of the present study was to assess the natural history of ABL in male HLA-B27 rats, compared to age- and sex-matched wild-type Fischer 344 (WT) rats.

MATERIALS AND METHODS

Fourteen WT and 11 TG male rats, aged 7-8 weeks, were used. Sacrifice times occurred at 10, 22 and 35 weeks. Animal heads were defleshed and treated to remove organic material, and skulls were stained to locate the cemento-enamel junction. ABL was measured as exposed molar root surface area (mm2) on the right maxilla and right mandible. Blinded measurements were performed using a computer-assisted image analysis system.

RESULTS

ABL for the entire TG group was significantly different from the WT group (p < 0.05). There was no significant difference in ABL between WT and TG rats at 10 weeks of age. At 22 and 35 weeks of age TG rats experienced 23% and 37% greater ABL than WT rats, respectively; these differences were statistically significant (p < 0.015). For both TG and WT animals, ABL was significantly different between the three age groups.

CONCLUSIONS

These results, consistent with previous findings in female TG rats, suggest that the accelerated ABL found in TG rats is an adult-onset, age-dependent, and sex-independent process.

Perioesthetic approach to the diagnosis and treatment of carious and noncarious cervical lesions: Part I

Several factors can contribute to the development of noncarious cervical lesions. Therefore, these lesions can be described and classified according to their primary etiology. Traditionally, most dentists have treated noncarious cervical lesions only with restorative methods, for example, composite resin restorations. However, in many cases, a periodontal or a combined restorative/periodontal approach provides a better esthetic and functional result. In part I of this two-part report, we provide a review of noncarious cervical lesions and a series of clinical case reports showing surgical techniques used and the importance of the periodontal aspect of lesion management.

Effect of different application and polymerization techniques on the microleakage of proximal resin composite restorations in vitro

This in vitro study investigated cervical microleakage of proximal resin composite restorations placed with three application and polymerization techniques. Uniform mesio-occlusal-distal (MOD) preparations featuring cervical margins above (mesial) and below (distal) the CEJ suitable for restoration with resin composite were copy milled into 33 recently extracted permanent molars. The teeth were divided randomly into three groups of 11 teeth and restored using a conventional incremental technique (Group A) and two novel curing devices (Groups B and C). After 24 hours, a dye penetration test was used to assess microleakage. Conventional placement in preparations with cervical margins in enamel had significantly lower interfacial leakage scores than those recorded for placement in preparations with margins in cementum regardless of the technique used to place the restorative material. Use of the two novel curing devices conferred no advantage in reducing microleakage irrespective of where preparation margins were placed.

Effect of variable moderate chronic stress on ligature-induced periodontal disease in Wistar rats

The aim of this investigation was to study the impact of stress on ligature-induced periodontal disease in rats by means of a variable moderate chronic stress model. Thirty male Wistar rats were randomly assigned to six groups. Control groups received only ligatures around the second maxillary molars, while experimental groups were exposed to stress in additional. Stress was imposed by means of flashing light, isolation, rat blood smelling, new environment exposure, immobilization in cold temperature and immobilization at room temperature. Stress was applied randomly, thereby diminishing adaptation of the animals to the model. The animals were killed after 29, 43, and 57 days. The distance between the cementum-enamel junction and the alveolar bone (CEJ-AB) was measured. Alveolar bone loss was statistically different between stressed and control animals, whereas differences were not observed between experimental periods. The mean CEJ-AB distance in animals exposed to stress was 154.50 microm smaller than the corresponding distance in the controls. It might be concluded that variable moderate chronic stress decreased alveolar bone loss in a ligature-induced periodontal disease model.

Clinical evaluation of an ‘all-in-one’ bonding system to non-carious cervical lesions—results at one year

BACKGROUND

The recent trend in using dentine adhesives is to simplify the number of steps required for bonding. The simplest are now the so-called 'all-in-one' products which combine the etching, priming and bonding steps into a single application. However, few clinical trials have been reported using this type of material. The current study reports the one-year results of a clinical trial with One-Up Bond F and Palfique Estilite resin composite.

METHODS

Fifty-one non-undercut non-carious cervical lesions were restored with One-Up Bond F and Palfique Estilite in 15 patients (mean age 57.5 years). Restorations were evaluated at six months and one year for presence or absence and for marginal staining using standardized colour photographs for comparison.

RESULTS

At one year, 42 restorations could be evaluated and all were intact. Slight marginal staining was observed around three restorations but was considered to be of no clinical significance.

CONCLUSIONS

One-Up Bond F with Palfique Estelite shows good promise for the restoration of non-carious cervical lesions.

The prevalence of dentine hypersensitivity in a hospital clinic population in Hong Kong

OBJECTIVES

Dentine hypersensitivity is a common clinical finding with a wide variation in prevalence values. The aim of this study was to establish the prevalence of dentine hypersensitivity and to examine some associated aetiological factors in a cross-sectional study of patients visiting the Periodontology and Oral Hygiene Clinic at Prince Phillip Dental Hospital, Hong Kong over a three-week period.

METHODS

226 patients were examined over a three-week period using a triple syringe to administer a blast of cold air to confirm the diagnosis of dentine hypersensitivity. Additional factors such as smoking habits, initiating stimuli, gingival recession and cervical tooth surface loss were noted.

RESULTS

153 patients were diagnosed as having dentine hypersensitivity, giving a prevalence figure of 67.7%. The commonest teeth affected were the lower incisors and the commonest initiating factor was cold drinks.

CONCLUSIONS

The prevalence of dentine hypersensitivity in a hospital periodontology clinic population in Hong Kong was 67.7%.

Abfraction Lesions: Myth or Reality?

Loss of tooth substance in the cervical region is usually attributed to toothbrush abrasion, erosion, or a combination of both factors. Recently the role of occlusal loading has become increasingly prominent. It is suggested that high occlusal loads cause large cervical stress concentrations, resulting in a disruption of the bonds between the hydroxyapatite crystals and the eventual loss of cervical enamel. This process has been called noncarious cervical tooth loss or abfraction. This article reviews the available evidence to support the thesis that occlusal loading can contribute to the process of abfraction. It also reviews the potential interactions between occlusal loading and erosion that may contribute to abfraction lesion formation.

CLINICAL SIGNIFICANCE

It is important to recognize the potential role of occlusal loading in the loss of cervical tooth tissue so that management of the occlusion can be incorporated into a treatment plan for a patient with abfraction lesions.

Analysis of etiologic factors and periodontal conditions involved with 309 abfractions

OBJECTIVES

Non-carious cervical lesions (NCCL), also termed abfractions, have long been thought to be produced by excessive brushing. Nearly 20 years ago an occlusal etiology was proffered (Lee & Eagle 1984). Controversy still exists concerning these two concepts. The present work was carried out to verify the occurrence of signs of excessive brushing or occlusal disturbances associated with abfractions.

MATERIAL AND METHODS

All first consultants were screened for the presence of abfractions during one trimester. NCCL were found in 61 patients who consequently received a thorough examination searching for clinical evidence of excessive brushing or occlusal disturbances. The presence of plaque, calculus, periodontitis, or mobility was also noted. Simple frequency and percentage were used to describe the occurrence of different clinical signs in association with the presence of abfractions.

RESULTS

Abfractions often exist in mouths presenting plaque (40.1%), calculus (41.7%), or periodontitis (20.4%). Ulceration of the gingiva is a rare finding (1.6%). However, subgingival apical limits were frequent (32.5%). NCCL coexist almost systematically with occlusal wear facets (94.5%). Lack of canine disclusion (77.2%) was also closely associated with the presence of abfractions. Conversely, mobility was seldom found (1.9%).

CONCLUSIONS

Clinical signs of excessive brushing were lacking, whereas signs of occlusal disturbance were very consistent with the presence of abfractions.

Perioesthetic Approach to the Diagnosis and Treatment of Carious and Noncarious Cervical Lesions: Part II

Several classes of tooth-colored materials are available for restoring carious and noncarious cervical lesions. Included are the composite resins, which can be bonded into the cervical area to provide predictable form, function, and esthetics. Part I of this two-part report reviewed the etiology of noncarious cervical lesions and provided a series of clinical case reports showing the importance of the periodontal aspect of lesion management. In part II we present information about adhesive preparation design and esthetic restoration of the noncarious cervical lesion.

CLINICAL SIGNIFICANCE

When used with proper attention to preparation design and restoration placement and finishing, resin composites can be used to successfully restore form, function, and esthetics to defective cervical areas of teeth.

Effect of low-viscosity resin-based composite on the microleakage of cervical restorations

PURPOSE

To investigate the effect of a low-viscosity resin-based composite (LVC) liner on the microleakage of cervical resin-based composites bonded with new adhesive systems.

METHODS

180 wedge-shaped cervical cavities on bovine incisors were treated with AQ Bond (all-in-one), ABF (experimental two-step self-etching primer containing antibacterial monomer) or Clearfil SE Bond (two-step self-etching primer) systems according to the manufacturers' instructions. Half of the treated cavities in each adhesive system were lined with an LVC (Protect Liner F) and filled with a hybrid resin-based composite (Clearfil AP-X). Ten specimens from each group were immersed in 0.5% basic fuchsin solution immediately after finishing the restorations. The specimens to be subjected to thermocycling (5-60 degrees C, 15 seconds dwell time, 5,000 cycles) or to flexural load cycling (approximately 0.5 mm labio-lingual displacement at the incisal edge, 10,000 cycles, 1 Hz) prior to immersion in the dye solution were also prepared. The teeth were sectioned through the center of the restorations and the degrees of dye penetration were scored. The data were analyzed with the Mann-Whitney U-test or the Kruskal-Wallis test (P < 0.05).

RESULTS

The use of the LVC liner significantly improved marginal sealing of AQ Bond. However, the LVC liner could not prevent the deterioration in the marginal integrity caused by thermocycling or flexural load cycling. In the case of ABF, the use of the LVC liner showed a trend toward less microleakage. For Clearfil SE Bond, the LVC liner prevented the deterioration in the marginal seal caused by thermocycling.

Tooth surface floss loss: unusual interproximal and lingual cervical lesions as a result of bizarre dental flossing

There are many reported cases of cervical abrasion/erosion cavities in the literature with various theories offered in support of their pathogenesis. The vast majority of these cases involve the labial cervical regions of the affected teeth. This case report describes an unusual dental presentation of severe lingual cervical and interproximal lesions predominantly affecting the upper and lower anterior and premolar teeth. The differential diagnosis is presented, along with the likely cause of the lesions: in this case, a bizarre oral hygiene technique. The proposed treatment plan is outlined and the problems associated with restoring such cavities are highlighted.

Influence of the number of sections on reliability of in vitro microleakage evaluations

PURPOSE

To test how the number of sections affects the maximum depth of tracer penetration.

MATERIALS AND METHODS

This study was simultaneously performed in three different centers. C-shaped Class V cavities were made on 60 human third molars. The cavities were located across the cementum-enamel junction. One restorative system was used: Scotchbond Multi-Purpose and Z100. After restoration, the samples were thermally cycled 3000 times, between 5 and 55 degrees C with a dwell time immersion of 10 seconds. Silver nitrate was used by two centers and basic fuchsin was used by the third. The teeth were longitudinally sectioned with a diamond saw: 5 sections per tooth provided 10 surfaces for evaluation. The penetration of the tracer was recorded on a scale from 0 to 3. The deepest leakage per restoration was identified for comparison with lesser measured values elsewhere in the tooth. The Spearman test was applied to evaluate the relationship between the reference and data from one, two and three sections (i.e. two, four and six measurements). The Kruskal-Wallis test was applied to compare the three centers.

RESULTS

Whatever the study center, the Spearman correlation coefficient (r(s)) increased as a function of the number of sections (S) up to three: Center 1 (1S, 0.47; 2S, 0.68; 3S, 1.0), Center 2 (1S, 0.60; 2S, 0.99; 3S, 0.99), Center 3 (S1, 0.40; 2S, 0.73; 3S, 1.0). No statistically significant difference was found between the three study centers.

Effect of the cavity configuration factor on the marginal microleakage of esthetic restorative materials

PURPOSE

To evaluate the effect of the cavity configuration factor (CF) on the marginal microleakage of cervical restorations with four aesthetic restorative materials.

MATERIALS AND METHODS

Conventional cavities, 2.9 mm in diameter and 1.5 mm deep, with CF=2.7 and "saucer"-shaped ones with CF=2 were created in 60 extracted premolars. The following groups were established: G1: Z100/Single Bond, G2: Freedom/Stae, G3: Vitremer/Primer and G4: Durafill/Durafill Bond, following each manufacturer's directions. Thermocycling of the specimens was performed in an aqueous solution of 2% buffered methylene blue, with the temperature varying between 5 to 55 degrees C, for a total of cycles of 60 minutes per day, for 7 days. The specimens were then sectioned and evaluated by two observers using photographs acquired from a stereomicroscope. The values were subjected to Kruskal-Wallis analysis and the Dunn and Wilcoxon test.

RESULTS

The averages of the microleakage scores observed in the conventional and "saucer"-shaped cavities were respectively: G1: 0.66/0.46; G2: 0.92/0.69; G3: 1.8/1.86; G4: 3.54/2.3.

On dental erosion and associated factors

The aim of this thesis was to explore aspects of dental erosion by investigating its prevalence among young Saudi men and young children, develop a system for its assessment and to evaluate various tentative background factors that may be associated with its occurrence. Saudi military inductees (n = 95) were subjected to questionnaire and clinical examination, including recordings of severity of dental erosion and a number of other oral health parameters. The system applied for grading the severity of dental erosion showed an intraexaminer agreement of 78%. Around one-fourth of the maxillary anterior tooth surfaces exhibited pronounced dental erosion and the average soft drink consumption was 247 liters/year. High level of soft drink consumption and long retention time of the drink in the mouth before swallowing, intensified oral hygiene, mouth breathing and low gingival bleeding index were found to have significant correlations with the presence of dental erosion. Furthermore, less plaque on maxillary palatal tooth surfaces, increased numbers of buccal cervical defects, first permanent molar "cuppings", missing teeth, and lower salivary urea content had significant correlations with the severity of dental erosion. High intake of acidic drinks and fruits, upper respiratory tract problems and frequent taking of medication were common findings in young Saudi children (n = 16) with severe dental erosion. The clinical diagnosis of erosion in deciduous teeth was confirmed by SEM. Enamel from various healthy teeth were subjected to microhardness measurements before and after in vitro exposure to citric acid. Deciduous enamel was found to be softer and relatively more prone to erosion than permanent enamel but the potential for erosion was about the same regardless of the origin of the teeth. Six methods of drinking a sugar-free cola-type drink were assessed in two groups of healthy volunteers. Intraoral pH was measured at specific locations and at predetermined time points using the microtouch method (n = 12), and continuously by using telemetric measurement (n = 6). Of the six methods tested, those in which the drink was in contact with the tooth surface for a prolonged period of time were found to strongly affect intraoral pH. It may be concluded from this thesis that dental erosion is common among young Saudi men and that erosion is associated with many etiological, aggravating and modifying factors. Consumption of soft drinks, amount of palatal plaque on maxillary anterior teeth and salivary urea concentration are some factors related to erosion. The presence of dental erosion in children is likely to be associated with a number of general health and dietary factors but is also aggravated by the relatively more rapid progression of erosion in the deciduous teeth. Drinking method seems to be an important factor in the risk of developing dental erosion.

Brief communication: Study of noncarious cervical tooth lesions in samples of prehistoric, historic, and modern populations from the South of France

Noncarious tooth lesions (NCTL) are frequent findings in contemporary dental practices. Unlike other dental and periodontal diseases, NCTL have not been studied in an anthropological context. The purpose of the present study was to compare the prevalence of NCTL in three archaeological samples from the Copper Age and Middle Ages and in subjects examined in three dental practices. Both archaeological samples and dental-practice subjects were from southern France. In the archaeological sample group, no NCTL were detected in 3,927 teeth from 259 individuals. In the dental-practice group, prevalence rates were in agreement with current epidemiological data. Our data also suggest that prevalence of NCTL increases with age and is higher in females. Premolars were the most affected tooth type. Occurrence of NCTL has long been attributed to toothbrushing and to erosion by intrinsic and extrinsic acids. More recently, occlusal stress associated with tooth flexure has been implicated. The reasons underlying the total absence of NCTL in archaeological samples are discussed. The most likely explanations involve differences in lifestyle, diet, and dental condition.

Influence of curing methods and materials on the marginal seal of class V composite restorations in vitro

The study tests the hypothesis that soft-start irradiation improves, whereas, high intensity irradiation compromises the margin quality and marginal seal of Class V resin based composite [RBC] restorations. Box-shaped Class V cavities were prepared in extracted, human third molars with cervical margins located apical to the CEJ. Cavities were restored using a multi-step bonding agent (Optibond FL, Kerr), a thin layer of flowable resin composite and two increments of fine hybrid resin composite (Filtek Flow/Filtek Z250, 3M ESPE; Revolution f2/Herculite XRV, Kerr). Light irradiation was performed using either the standard (40 seconds) or the soft-start mode (40 seconds with exponential increase) of a quartz tungsten halogen or an LED curing light (Elipar Trilight, Elipar Freelight, 3M ESPE); for high intensity irradiation, a Plasma Are curing unit was used with three irradiations of three seconds (Apollo 95E, DMDS). After 30 days of water storage and thermal cycling (n = 2500, 5-55 degrees C), margin quality was assessed in the SEM using the replica technique and marginal seal was evaluated using dye penetration (AgNO3 50%). Few differences were observed between the light curing protocols. However, less leakage was observed in the case of the lower shrinking RBC Filtek Z250.

An in vitro comparison of metal and transparent matrices used for bonded class II resin composite restorations

This study compared excess formation of direct bonded Class II restorations using different matrix systems-metal or transparent. Sixty freshly extracted, non-carious, posterior human teeth were used. In all of the teeth, standardized MOD-cavities were prepared with the gingivoproximal margins located 1.0-1.5 mm cervical to the cemento-enamel junction. The prepared teeth were randomly assigned to six groups. Half were restored using metal matrices and wooden wedges; the other half were restored using transparent matrices and reflective wedges. Three different material systems were used to fill the cavities: 1) a hybrid composite (Tetric) plus an adhesive bonding agent (Syntac Classic), 2) a flowable composite (Tetric Flow) plus Syntac Classic and 3) a compomer (Dyract AP) together with an adhesive bonding agent designed for compomers (Prime & Bond NT). After the specimens were preserved in saline solution, scanning electron microscopy (SEM) assessed the amount of overhang formation at the restoration margins. The data collected indicated the use of transparent matrices resulted in significantly higher amounts of excess material at the restoration margins compared with metal matrices. Moreover, there was no significant difference between the materials when the same matrix was used. All of the dental restorations examined displayed material overhang. Based on these findings, the authors concluded that the type of matrix exerts a major impact on overhang formation, with metal matrices resulting in significantly less excess material buildup.