Assessing the impact of dairy waste lagoons on groundwater quality using a spatial analysis of vadose zone and groundwater information in a coastal phreatic aquifer

Dairy waste lagoons are considered to be point sources of groundwater contamination by chloride (Cl(-)), different nitrogen-species and pathogens/microorganisms. The objective of this work is to introduce a methodology to assess the past and future impacts of such lagoons on regional groundwater quality. The method is based on a spatial statistical analysis of Cl(-) and total nitrogen (TN) concentration distributions in the saturated and the vadose (unsaturated) zones. The method provides quantitative data on the relation between the locations of dairy lagoons and the spatial variability in Cl(-) and TN concentrations in groundwater. The method was applied to the Beer-Tuvia region, Israel, where intensive dairy farming has been practiced for over 50 years above the local phreatic aquifer. Mass balance calculations accounted for the various groundwater recharge and abstraction sources and sinks in the entire region. The mass balances showed that despite the small surface area covered by the dairy lagoons in this region (0.8%), leachates from lagoons have contributed 6.0% and 12.6% of the total mass of Cl(-) and TN (mainly as NO3(-)-N) added to the aquifer. The chemical composition of the aquifer and vadose zone water suggested that irrigated agricultural activity in the region is the main contributor of Cl(-) and TN to the groundwater. A low spatial correlation between the Cl(-) and NO3(-)-N concentrations in the groundwater and the on-land location of the dairy farms strengthened this assumption, despite the dairy waste lagoon being a point source for groundwater contamination by Cl(-) and NO3(-)-N. Mass balance calculations, for the vadose zone of the entire region, indicated that drying of the lagoons would decrease the regional groundwater salinization process (11% of the total Cl(-) load is stored under lagoons). A more considerable reduction in the groundwater contamination by NO3(-)-N is expected (25% of the NO3(-)-N load is stored under lagoons). Results demonstrate that analyzing vadose zone and groundwater data by spatial statistical analysis methods can significantly contribute to the understanding of the relations between groundwater contaminating sources, and to assessing appropriate remediation steps.

Infiltration mechanism controls nitrification and denitrification processes under dairy waste lagoon

Earthen waste lagoons are commonly used to store liquid wastes from concentrated animal feeding operations. The fate of ammonium (NH) and nitrate (NO) was studied in the vadose zone below earthen-clay dairy farm waste lagoons using three independent vadose zone monitoring systems. The vadose zone was monitored from 0.5 to 30 m below land surface through direct sampling of the sediment porewater and continuous measurement of the sediment profile's water content variations. Four years of monitoring revealed that wastewater infiltration from the lagoon is controlled by two mechanisms: slow (mm d), constant infiltration from the lagoon bed; and rapid (m h) infiltration of wastewater and rainwater via preferential flow in desiccation cracks formed in the unsaturated clay sediment surrounding the lagoon banks. The preferential flow mechanism is active mainly during wastewater-level fluctuations and intensive rain events. The vadose zone below the waste sources remained unsaturated throughout the monitoring period, and all infiltrating NH was oxidized in the upper 0.5 m. The NH oxidation (nitrification) was coupled with NO reduction (denitrification) and depended on the sediment water content, which was controlled by the infiltration mechanism. Coupled nitrification-denitrification (CND) resulted in 90 to 100% reduction in the total nitrogen mass in the vadose zone, with higher removal under high water content (∼0.55 m m). Mass balance of nitrogen and isotopic composition of NO indicated that CND, rather than cation exchange capacity, is the key factor regulating nitrogen's fate in the vadose zone underlying earthen waste lagoons.

Aesthetic enhancement of anterior dental implants with the use of tapered osteotomes and soft tissue manipulation

An adequate bone base is usually a prerequisite for functionally and aesthetically optimal reconstruction of the soft tissue architecture around a dental implant. In patients with sufficient bone height but insufficient bone width as a result of tooth loss, a jaw enlargement technique with osteotomes combined with soft tissue manipulation may be utilized to facilitate proper implant placement while concomitantly optimizing the aesthetics of the final implant prosthesis. The learning objective of this article is to familiarize the reader with the principles of ridge expansion with tapered osteotomes combined with periodontal plastic soft tissue surgery to aid in proper implant placement and enhance the aesthetic result of the final prosthesis.

Prosthetic considerations with periodontal root resective therapy, Part 2. Hemisections

When a root and the overlying anatomic crown are removed as a unit, this procedure is referred to as a hemisection. Hemisection of a maxillary or mandibular molar is often a means of retaining teeth needed for restorative abutments or occlusal support. This treatment can yield predictable results using proper diagnostic, endodontic, surgical, and prosthetic techniques.

Prosthetic considerations with periodontal root resective therapy, Part 1: Root amputations

Root resective periodontal therapy is a procedure used to retain teeth needed for restorative abutments or occlusal support. Contraindications of root resective therapy include fused roots and inadequate bony support around remaining roots. When these situations exist, extraction is necessary. But in the appropriate cases, a patient with a periodontal condition resulting in alveolar bone loss in the furcation region is amenable to treatment with a predictable result using a combination of resective periodontal surgical therapy and subsequent timely prosthetic rehabilitation.

Aesthetic enhancement of pontic sites for fixed partial dentures

The ridge expansion technique using tapered osteotomes can be used anywhere in the maxilla when a change in external ridge morphology would be advantageous for both aesthetics and/or proper dental implant placement. Usually subsequent to tooth loss, the maxilla is generally somewhat undercut in form. This ridge expansion technique can be used to reduce the undercut by bulging out the base of the facial/buccal plate. This would recreate the illusion of root prominences (Figure 12) or permit implant fixtures to be inserted in a more upright position. The tapered osteotomes can therefore predictably be used to expand the buccal bone to simulate the presence of a root prominence for optimal aesthetics for placement of a fixed partial denture prosthesis (Figure 13).

Using cross-sectional tomography to perform exploratory radiography in lieu of exploratory surgery

Preoperative treatment planning for dental implants is crucial to their integration and especially prosthetic rehabilitation. Exploratory radiography is an essential component of treatment planning. Radiographic examination using cross-sectional tomography as an adjunct to panoramic radiographs can significantly decrease the incidence of exploratory surgery that could result in unplanned bone augmentation procedures due to insufficiency in alveolar bone height, width, quantity, quality, and will not allow proper aesthetic prosthetic rehabilitation subsequent to improper implant placement.

Salvaging of adjacent fixed partial dentures using an overcasting technique

Occasionally, clinicians are faced with a situation in which a solitary tooth between two bridges requires extraction. When this type of situation occurs, we must ponder the dilemma of how to replace the missing tooth. Options include placing an implant where the tooth was extracted or remaking one large multiunit bridge. Implants are not always possible or practical, and remaking a multiunit bridge that involves the abutments of the two existing bridges can be challenging and becomes much more expensive to the patients. The overcasting technique is a treatment modality that offers a solution in these particular situations.

Connective tissue grafting for improved implant esthetics: clinical technique

The subepithelial connective tissue graft can be used to enhance the esthetic appearance and gingival contour of the peri-implant tissues. A technique is described and illustrated to create a soft-tissue root prominence and mask the grayish color that may be present as a result of a thin facial alveolar bony plate and/or thin labial attached gingival tissue over dental implants.

The microbiota of the peri-implant region in health and disease

The subgingival microflora associated with dental implants has been shown to be similar to that associated with natural teeth. Like the natural tooth, a dental implant may be susceptible to a plaque-induced gingivitis which may progress to peri-implantitis. A similarity exists between the microbial flora around failing implants and organisms classically associated with periodontal disease. The same anaerobic gram-negative organisms are found in periodontitis and peri-implantitis. The periodontium must be in a healthy state before the placement of dental implants and constantly monitored while implants are in function for early detection of potential periodontal and/or prosthodontic problems. The relationship between the microbial flora around dental implants and peri-implantitis is discussed and recommendations are presented to improve the efficacy of dental implants.