A histomorphometric evaluation of factors influencing the healing of bony defects surrounding implants.

PURPOSE: The authors' aim was to perform a histomorphometric study of the healing of bone defects created adjacent to titanium and hydroxyapatite (HA) -coated implants and covered with either a resorbable or a nonresorbable membrane in combination with different filler materials and to evaluate to what degree coating, membrane, and/or filler influenced the healing of the defects. MATERIALS AND METHODS: Posterior teeth were extracted from the mandibles of 10 baboons, and 12 implants were placed in each animal in the edentulous areas. The implants were either titanium or HA-coated, the membranes were either Vicryl, Gore-Tex, or Resolut, and the filler was either demineralized freeze-dried bone (DFDB), autogenous bone, or Biocoral. The implants were observed for either 3, 6, 9, 12, or 18 months. The volume of newly generated tissue and the relative contribution of bone, marrow, and filler were evaluated, as was relative extension of resorption, formation, and quiescent surface. RESULTS: The results indicated that autogenous bone is still the gold standard, but both the DFDB and Biocoral compared favorably to it. Both filler materials were being gradually replaced by bone; this process was not yet finished at 18 months postsurgery. DISCUSSION: Since even the sterilization of DFDB cannot exclude the possibility of a disease transmission, it is important to find an appropriate substitute. Both filler and membranes contributed to the re-establishment of the original volume; better results were achieved with the Vicryl and Gore-Tex membranes than with the Resolut. Biocoral can be considered an effective material. CONCLUSION: A bony defect is not necessarily a contraindication for the placement of an implant. (More than 50 references.)

Evaluation of impression accuracy for osseointegrated implant supported superstructures.

STATEMENT OF PROBLEM: An often-debated issue still exists concerning implant impression techniques, whether to splint impression copings. Different configurations are available for these copings for a variety of manufacturers' implant systems. PURPOSE: This study evaluated and compared 4 impression techniques in terms of their dimensional accuracy to reproduce implant positions on working casts. MATERIAL AND METHODS: A master model was designed to simulate a clinical situation. Impressions were made using 4 techniques: (1) tapered impression copings not splinted; (2) squared impression copings not splinted; (3) squared impression copings splinted with autopolymerizing acrylic resin; and (4) squared impression copings with a lateral extension on one side not splinted. Reference points machined onto the master model and onto special healing abutments were compared after abutments were transferred to casts using the 4 techniques. Measurements were made using a Reflex microscope, capable of recording in the x-, y-, and z-dimensions. RESULTS: The dimensional accuracy was high and, although statistically significant (P =.022; power > 80%), a maximum distortion difference of only 0.31% was registered. CONCLUSION: The dimensional accuracy of all the techniques was exceptional and the observed differences can be regarded as clinically negligible.

[The effect of bonded and nonbonded posts on the fracture resistance of dentin]. / Die effek van gebonde en ongebonde stiwwe op die fraktuurweerstand van dentien.

This in vitro study determined the effect of bonded and non-bonded cast, serrated, tin plated, parallel gold posts on the fracture resistance of surrounding dentine walls. Specimens were divided into two groups. One group's posts were luted with zinc phosphate cement and the other group's posts were tin-plated and adhesively bonded with an adhesive resin cement. Three different dentine wall thicknesses, namely 0.5 mm, 0.75 mm and 1.0 mm were prepared, subdividing the specimens of each main group into three subgroups. Specimens were subjected to a 50 degrees oblique force. The force required to fracture the dentinal walls was registered. There was no statistically significant differences in the fracture resistance of dentine with the two different cements or of the different dentine wall thicknesses.

Restoring function and esthetics in a patient with amelogenesis imperfecta.

Amelogenesis imperfecta is a rare dental disease and presents a major challenge to the dentist. With the tremendous advances in the field of esthetic dentistry, especially in bonding to dentin, it is today possible to restore function and esthetics to an acceptable level. The need for full crown preparation has been decreased to an absolute minimum. A case of amelogenesis imperfecta, complicated by a malocclusion, is presented. A combination of periodontal treatment and resin-bonded porcelain onlays and nobel alloys resulted in a highly successful outcome. The virtual absence of enamel was overcome with the aid of dentin bonding.

[Bond strength of composite resin bonded to deciduous and permanent dentin]. / Bindsterkte van hars aan primêre en permanente dentien.

The purpose of this in vitro investigation was to determine the shear bond strength (SBS) of composite resin bonded to deciduous (D) and permanent (P) dentine using the Scotchbond Multi-Purpose system (SMP, 3M). Twenty extracted, sound permanent human molar teeth (Group A) and twenty carious primary molars (Group B) were used in this study. All samples were ground wet on a polishing machine (220 grit) in order to expose superficial buccal dentine surfaces. Dentine surfaces were treated with the Scotchbond Multi-Purpose system according to manufacturers instructions. Z100 composite stubs were bonded to the treated dentine surfaces using a silicone rubber split mould. Bonds were stressed to failure in an Instron using a shear load. Data were calculated and analysed statistically (Student-t test). The mean SBS in MPa were 17.12 +/- 3.71 to deciduous and 23.60 +/- 2.47 to permanent dentine. SMP demonstrated a statistical higher (p < 0.01) shear bond strength to permanent than to deciduous dentine.

A comparison of two systems for bonding type II gold alloy to dentine: an in vitro study.

This in vitro investigation compares the shear bond strength of two systems that can be used to bond gold alloys to dentine. In the first group, sandblasted gold alloy surfaces were tin-plated and bonded to dentine using C&B-Metabond, an adhesive resin cement. In the second group sandblasted gold alloy surfaces were silicoated (Kulzer) and bonded to dentine using Denthesive II, Adhesive Bond II and Twinlook cement. Forty eight hours after bonding the bonds were stressed to failure in the sheer mode in an Instron testing machine. All data were statistically analysed (Student-t-test). The results in MPa were: Tin-plated gold to dentine 18.23; silicoated gold to dentine: 10.35. C&B-Metabond demonstrated a statistically significantly higher bond strength (p < 0.01). It can be concluded that tin-plating in conjunction with C&B-Metabond produces a stronger bond than silicoating in conjunction with Denthesive II and Twinlook cement when used to bond gold alloys to dentine.

Surface hardness of light-cured composite resin cured directly or through a transparent matrix using three different light guides.

The purpose of this study was to compare the Vickers Hardness (HV) of composite resin which was light-cured by 3 different light guides, either through or without a transparent polyester matrix band. The 3 light guides, standard Demetron (SG), Turbo Tip (TT) and a standard Demetron, with obvious accidental damage (DL) were tested with both Model 100 and Cure Rite radiometers. HV tests were done on all samples both immediately and one hour after light-curing. Results were analysed using the Anova and Student t-test. The light intensity readings in mW/cm2 were SG 600 and TT 850 with both radiometers and DL tested 350 and 380. Composite resin surfaces undergo significant surface hardening in the first hour after light-curing. A 350-380 mW/cm2 intensity gives significantly lower HV than 600 + mW/cm2 but 800 mW/cm2 does not produce significantly greater HV than 600 mW/cm2. Curing through a transparent polyester matrix gives marginally greater HV than curing directly. The output of light guides is a significant factor in the surface hardness of cured composite resin.

The effect of airborne particle abrasion on the dentin smear layer and dentin: an in vitro investigation.

This study investigated the effect of airborne particle abrasion on the exposed dentin surfaces of 40 extracted teeth. A Siroflow abrasion unit was used to treat four groups of ten specimens that were subjected to 5, 10, 20, and 40 seconds of abrasion respectively. Statistical analysis (Spearman Rank Order) showed a significant difference between all groups (P < .05) but not within groups (P > .05). Scanning electron micrographs showed smear layer removal as an immediate effect of air polishing. Application times of longer than 5 seconds showed obstruction of dentinal tubule openings, possibly a result of abrasive powder residue. It was concluded that airborne particle abrasion removes the smear layer, and the amount of dentin removed corresponded to the time of application.

Bruxism threshold: an explanation for successful treatment of the multifactorial aetiology of bruxism.

Many authors claim successful treatment of bruxism by various treatment modalities. This paper presents a review of the nature of bruxism, the multifactorial aetiology of bruxism and a discussion of successful treatment of bruxism by various treatment modalities. The aim of this paper is to provide an explanation for successful treatment of bruxism on the basis of decreasing or eliminating any one or more of the aetiological stimuli to a combined level below the bruxism threshold.

Aesthetic alternative to conventional posterior restorations.

In South Africa silver amalgam is still widely used as a filling material. Concern about the safety of the patient and dental personnel does exist, however, due to the possibilities of mercury poisoning. Demands for aesthetic dentistry are increasing in response to wider media coverage. More and more patients are asking their dentists to replace acceptable and faulty amalgam restorations with aesthetic alternatives. Such alternatives to conventional posterior restorations are discussed and their respective merits are considered.