Occlusal Third Research Articles

Identification of the DSPP mutation in a new kindred and phenotype–genotype correlation

Hereditary dentin defects can be grouped into three types of dentinogenesis imperfecta (DGI) and two types of dentin dysplasia. Tooth enamel is considered normal in patients with hereditary dentin defects, but is easily worn down and fractured due to DSPP mutation-induced altered dentin properties. The purposes of this study were to identify genetic cause of a family with type II DGI and enamel defects. We identified a family with type II DGI and a unique form of hypoplastic enamel defect affecting occlusal third of the crown. Family members were recruited for the genetic analysis and DNA was obtained from peripheral whole blood. Mutational analysis revealed a T to A transversion in exon 3 of the DSPP (c.53T>A, p.V18D). Haplotype analysis showed that the same mutation arose separately in two different families having DGI with similar enamel defects, indicating that this phenotype is associated with this specific DSPP mutation. Clinical features suggest that enamel formation was affected in the affected individuals during early amelogenesis, in addition to the dentin defect. We observed that a DSPP gene mutation not only influences dentinogenesis but also affects early stage amelogenesis.

Effects of laser and acid etching and air abrasion on mineral content of dentin

The aim of this study was to evaluate the mineral content of dentin prepared using an Er,Cr:YSGG laser at four different power settings, acid etching, and air abrasion. The study teeth comprised 35 molars which were randomly divided into seven equal groups. The occlusal third of the crowns were cut with a slow-speed diamond saw. The groups were as follows: group A, control group; group B, dentin etched with 35% buffered phosphoric acid for 30 s; group C, dentin abraded at 60 psi with 50-µm aluminium oxide for 1 s; groups D-G, dentin irradiated with the Er,Cr:YSGG laser at 1.50 W (group D), 2.25 W (group E), 3.00 W (group F), and 3.50 W (group G). The levels of Mg, P, Ca, K and Na in each dentin slab were measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Data were analysed by one way analysis of variance and Tukey HSD tests. There were no significant differences between the groups in the levels of Ca, P and Na, and the Ca/P ratio (p>0.05); however, there were significant differences in the levels of K (p<0.001) and Mg (p=0.13). In addition, the levels of Mg in the air abrasion group were higher than in the other groups (p<0.01). Etching with the Er,Cr:YSGG laser system, air abrasion and acid etching did not affect the levels of Ca, P and Na, or the Ca/P ratio, in the dentin surface.

Idiopathic gingival enlargement and its management

Idiopathic gingival enlargement is a proliferative fibrous lesion of the gingival tissue that causes esthetic and functional problems. Both genetically and pharmacologically induced forms of gingival enlargement exist. This case report addresses the diagnosis and treatment of a case of idiopathic gingival enlargement in a 13-year-old female. The patient presented with generalized diffuse gingival enlargement involving the maxillary and mandibular arches extending on buccal and lingual/palatal surfaces and covering incisal / occlusal third of the tooth resulting in difficulty in speech and mastication since last three years. Patient also gave a history of surgical treatment being carried out four years back in upper anterior region suggesting of recurrence. Biopsy report confirmed the diagnosis of gingival hyperplasia. Gingivectomy was carried out in all four quadrants by using four different methods.

St Apollonias tooth - a relic in the cathedral treasury in Rab (Croatia)

To anatomically identify and describe the changes on the tooth of St Apollonia which is kept as a relic in Rab (Croatia). SOURCES AND METHODS: Reviewing relevant literature, macroscopic examination of the tooth in the reliquary, photographing and further examining the enlarged photos. The tooth in question is the first upper right premolar. Observed pathological change is type II enamel lesion, i.e. cervical or gingival caries. Other discovered characteristics are enamel fracture on the distoaproximal surface, shallow fracture on the occlusal third of the crown and two enamel formations, a cluster of smooth and shiny enamel surfaces. Attention is drawn to a relic that was previously virtually unknown. It is presented how important this relic is for Christian and ethnomedical tradition. Additionally, anatomical determination and the description of pathoanatomical changes are used to affirm the anthropological approach as one of the prerequisites in the attempt to scientifically evaluate the relic phenomenon.

Effect of acid etching duration on tensile bond strength of composite resin bonded to erbium:yttrium–aluminium–garnet laser-prepared dentine. Preliminary study

The purpose of this study was to compare the tensile bond strength of composite resin bonded to erbium:yttrium-aluminium-garnet (Er:YAG) laser-prepared dentine after different durations of acid etching. The occlusal third of 68 human third molars was removed in order to expose the dentine surface. The teeth were randomly divided into five groups: group B (control group), prepared with bur and total etch system with 15 s acid etching [37% orthophosphoric acid (H(3)PO(4))]; group L15, laser photo-ablated dentine (200 mJ) (laser irradiation conditions: pulse duration 100 micros, air-water spray, fluence 31.45 J/ cm(2), 10 Hz, non-contact hand pieces, beam spot size 0.9 mm, irradiation speed 3 mm/s, and total irradiation time 2 x 40 s); group L30, laser prepared, laser conditioned and 30 s acid etching; group L60, laser prepared, laser conditioned and 60 s acid etching; group L90, laser prepared, laser conditioned and 90 s acid etching. A plot of composite resin was bonded onto each exposed dentine and then tested for tensile bond strength. The values obtained were statistically analysed by analysis of variance (ANOVA) coupled with the Tukey-Kramer test at the 95% level. A 90 s acid etching before bonding showed the best bonding value (P < 0.05) when compared with all the other groups including the control group. There is no significance difference between other groups, nor within each group and the control group. There was a significant increase in tensile bond strength of the samples acid etched for 90 s.

Shear Bond Strength of Four Resin Cements Used to Lute Ceramic Core Material to Human Dentin

This study evaluated the effect of four resin cements on the shear bond strength of a ceramic core material to dentin. One hundred twenty molar teeth were embedded in a self-curing acrylic resin. The occlusal third of the crowns were sectioned under water cooling. All specimens were randomly divided into four groups of 30 teeth each according to the resin cement used. One hundred twenty cylindrical-shaped, 2.7-mm wide, 3-mm high ceramic core materials were heat-pressed. The core cylinders were then luted with one of the four resin systems to dentin (Super-Bond C&B, Chemiace II, Variolink II, and Panavia F). Half of the specimens (n = 15) were tested after 24 hours; the other half (n = 15) were stored in distilled water at 37 degrees C for 1 day and then thermocycled 1000 times between 5 degrees C and 55 degrees C prior to testing. Shear bond strength of each specimen was measured using a universal testing machine at a crosshead speed of 1 mm/min. The bond strength values were calculated in MPa, and the results were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey HSD tests. The shear bond strength varied significantly depending on the resin cement used (p < 0.05). The differences in the bond strengths after thermocycling were not remarkable as compared with the corresponding prethermal cycling groups (p > 0.05). Significant interactions were present between resin cement and thermocycling (p < 0.05). After 24 hours, the specimens luted with Variolink II (5.3 +/- 2.2 MPa) showed the highest shear bond strength, whereas the specimens luted with Chemiace II (1.6 +/- 0.4 MPa) showed the lowest. After thermocycling, the bond strength values of specimens luted with Chemiace II (1.1 +/- 0.1 MPa) and Super-Bond C&B (1.7 +/- 0.4 MPa) decreased; however, this was not statistically significant (p > 0.05). The increase in the shear bond strength values in the Panavia F (4.5 +/- 0.7 MPa) and Variolink II (5.5 +/- 2.1 MPa) groups after thermocycling was also not statistically significant (p > 0.05). Variolink II and Panavia F systems showed higher shear bond strength values than Chemiace II and Super-Bond C&B. They can be recommended for luting ceramic cores to dentin surfaces.

Swine teeth as potential substitutes for in vitro studies in tooth adhesion: A SEM observation

Animal teeth are routinely used in studies that test dental materials; however, no studies have yet proposed the use of swine teeth in laboratory tests. The purpose of this study was to compare the effects of acid etching on the dentine and enamel of human and swine teeth, aiming at the use of swine teeth as substitutes for human teeth in adhesion tests. Four human molars and four swine molars free of caries were used. For the study of enamel, two human and two swine teeth were longitudinally sectioned with a dental handpiece and a carborundum disk. For evaluation of dentine, the remaining teeth had the occlusal third of their crowns removed using a low speed diamond saw. All specimens underwent acid etching with 37% phosphoric acid for 30s. The etched surfaces were then washed with air/water spray for 10s. The specimens were then prepared for analysis in a Sterioscan 440 scanning electron microscope. It was observed a similar morphology in human and swine teeth, despite swine enamel was thinner than human enamel. Acid etching of swine enamel promoted a demineralization similar to that observed in human enamel in which the three types of Silverstone's patterns were observed. Acid etching of dentine exposed the opening of dentinal tubules in both swine and human teeth. Peritubular dentine was removed by phosphoric acid, while collagen fibrils appeared discernible in intertubular dentine. Thus, this study showed that enamel and dentine from swine and human teeth share many structural similarities after acid etching.

The effects of sprue design on the roughness and porosity of titanium castings

Purpose. This study measured the effects of the sprue number and position on the roughness and porosity of cast titanium crowns. Material and methods. Twenty-four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30-degree bevel finish line. Twelve wax patterns were sprued with one 8-gauge wax sprue and the remaining 12 were double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting, according to the manufacturer's instructions, with commercially pure titanium (> 99.5%) ingots. The castings were carefully cleaned and the surface roughness was measured with a profilometer. The specimens were then embedded and sectioned. Internal porosities were quantified with photographs by computerized image analysis. Data were analyzed with an ANOVA and the Student's t test with a confidence level of 95%. Results. The roughness value of the occlusal third of the crowns for the single sprue group (Ra = 3.0 ± 0.9 μm) was significantly higher than other measurements ( p < 0.05). There were statistically significant differences in values of porosity areas between the single sprue group (1.5 ± 0.7 mm 2 ) and the double sprue group (0.2 ± 0.2 mm 2 ) ( p < 0.01). The double sprue design resulted in a relatively smoother casting surface and less internal porosity than the single sprue design. Conclusions. Improvements in the degree of roughness and porosity of titanium crown castings were the result of the double sprue design. (J Prosthet Dent 1997;78:400-4.)

Effects of cross-sectional area on resin-enamel tensile bond strength

Objective. It was hypothesized that there is an inverse relationship between resin-enamel bond strength and bonded cross-sectional area, and that there are regional differences in resin-enamel bond strength. Methods. The facial and lingual surfaces of extracted human third molars were ground down 0.3 mm using 240 grit abrasive paper and were then bonded with either Clearfil Liner Bond 2 or Scotchbond Multi-Purpose Plus adhesive systems using the manufacturer's instructions. The bonded surfaces then received a resin composite build-up. After 24 h of storage in water, the bonded teeth were vertically serially sectioned into 1.0 mm thick slabs using a diamond saw, and the bonded surface area at the resin-enamel interface was varied from 0.5 to 3.0 mmz using a diamond saw under microscopic observation. The trimmed region was varied from the occlusal third of the facial or lingual enamel to the middle third, to the cervical third. The trimmed specimens were then glued to a Bencor Multi-T device, placed in an Instron testing machine and stressed to failure at 1 mm/min. A three-factor ANOVA was used to compare bond strengths (buccal vs. lingual, occlusal vs. middle vs. cervical-third, vs. materials). Regression analysis was used to examine the relationship between bond strength and bonded cross-sectional area for each material on occlusal enamel. Results. For both bonding systems, there was a highly significant (p < 0.001) inverse exponential relationship between tensile bond strength (y axis) and bonded cross-sectional area (x axis) with y intercepts of 51 and 59 MPa for Clearfil Liner Bond 2 and Multi-Purpose Plus, respectively. Using both materials, the highest bond strengths were measured in the occlusal third, which were significantly higher (p < 0.05) than those made to cervical enamel. Significance. Like resin-dentin bonds, resin-enamel bonds exhibit an inverse relationship with cross-sectional area. This relationship becomes more apparent at bonded surface areas below 2 mm 2 and is probably due to reductions in the number of interfacial stress-raisers as samples are made smaller.

Tooth preparation guide for embrasure clasp designs

T he need to prepare rest seats in two adjoining posterior teeth arises when a removable partial denture survey and design indicates selection of an embrasure clasp. The design of the clasp dictates that the body of the clasp extend through the buccal embrasures of the approximating teeth. Sufficient space must be provided in the occlusal third of the prepared teeth to facilitate passage of the clasp arm. Preparation for the embrasure clasp is generally described as 1.5 to 2 mm wide and 1 to 1.5 mm deep

A New Reinforced Intracoronal Composite Resin Splint: Clinical Results After 1 Year

An intracoronal technique for semipermanent splinting of mobile or migrating teeth is described and clinically evaluated. Circumferential grooves of 1 to 1.5 mm depth were cut into the enamel in the occlusal third of the teeth to be splinted. The teeth were splinted by placing a polyester ligature in two or more figure-8 loops along the grooves, and sealing the grooves and interproximal contact areas with an acid-etch composite resin system. A total of 51 splints involving 183 teeth and 132 interproximal contact areas were placed in 34 patients. One year after insertion, 46 splints were found intact. Five splints presented with one fractured interdental element, each. Average mobility of the splinted teeth was 51% below the preoperative level. Splinting improved the masticatory comfort. The esthetic results were satisfactory.

Treatment of Class I malocclusion in the mixed dentition

This study provides an in vivo evaluation of the inflammatory response, levels of cell proliferation and apoptosis, and the presence of necrosis after dental bleaching with two concentrations of hydrogen peroxide (H2O2).Wistar rats were divided into Control (placebo gel), BLUE (20% H2O2, 1 × 50 min), and MAXX (35% H2O2, 3 × 15 min) groups. At 2 and 30 days, the rats were killed (n = 10). The jaws were processed for histology analysis and PCNA and Caspase-3-cleaved immunohistochemistry, and data were submitted to the Mann-Whitney or ANOVA test (P < 0.05).At 2 days, the MAXX group showed necrosis and the BLUE group revealed moderate inflammation on the occlusal third of the crown (P < 0.05). At 30 days, tertiary dentin had formed and there was an absence of inflammation. The level of cell proliferation was higher in the middle third of the BLUE group (P < 0.05), and cervical of MAXX at 2 days (P < 0.05), decreasing at 30 days. The apoptosis was present at 2 days, particularly in the cervical third of the crown in the bleached groups (P < 0.05), with a decrease only at 30 days in the BLUE group (P < 0.05).The concentration of H2O2 influences effects on the pulp tissue, where a higher concentration of H2O2 can cause necrosis in the pulp and a prolonged effect within the apoptotic process; lower concentrations of H2O2 provide moderate inflammation, cell proliferation and apoptosis with a reduction of these processes over time.