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Biomedical subjects

P K Shivapuja

Publications and source records attributed to P K Shivapuja.

6 recordsLinked to original sources
PubMed1997

The effect of premolar extractions on the soft-tissue profile in adult African American females.

The present study was designed to evaluate the effect of four first premolar extractions on the soft tissue profile in African American patients. Pretreatment and posttreatment cephalograms of 28 adult female patients were assessed. The data were subjected to ANOVA, and correlation coefficients were performed between the significantly different dental and soft tissue variables. Variables that showed correlation at r value of greater than 0.6 were subjected to a stepwise multiple regression. The results of the study indicate that retraction of the lower lip correlates with retraction of both maxillary and mandibular anterior teeth. A ratio of 1.2:1 [corrected] was obtained between mandibular incisor retraction and retraction of the lower lip. The relationship between the upper lip and retraction of maxillary incisors was not significant. A ratio of 1.75:1 [corrected] was attained between maxillary incisor retraction and upper lip change. The upper lip correlated most strongly with lower lip retraction. Mandibular incisor angulation was the only hard-tissue variable that could be used as a predictor in a regression model to explain lip response to orthodontic therapy. Changes in the maxillary complex were more difficult to predict because of the complex nature of the soft-tissue integument and the details of muscle tension and soft-tissue tone that were lost by conversion of a three-dimensional structure into a roentgenographic cephalogram. A significant profile change did occur following the extraction of four first premolars and subsequent orthodontic therapy.

Adolescent↗
PubMed1995

Pulpal response in electrothermal debonding.

An alternative method to conventional bracket removal that minimizes the potential for ceramic bracket failure as well as trauma to the enamel surface is electrothermal debonding (ETD). However, the potential for pulpal damage using ETD on ceramic brackets still needs assessment. The purpose of this research is to investigate and assess any pulpal damage caused by ETD. Ten patients requiring four premolar extractions each were randomly selected (5 boys and 5 girls). Ceramic brackets were bonded to experimental and control teeth. A total of 30 teeth were used to provide histologic material of the human pulp. Fifteen teeth were extracted 24 hours after ETD, seven were extracted 28 to 32 days after ETD, and eight were the control teeth and debonded by a conventional method, with pliers. The pulp was normal in most cases in the control group. There was significant hyperemia seen 24 hours after debonding in teeth debonded by ETD. Teeth extracted 30 days afer ETD showed varied responses, ranging from complete recovery in some cases to persistence of inflammation and pulpal fibrosis. Teeth subjected to the conventional debonding were normal histologically. The teeth in our research were healthy teeth with a rich blood supply and were from a younger age group. Patients with compromised teeth that have large restorations or a questionable pulpal status could behave more adversely to this significant amount of heat applied. In compromised cases and on older patients, performing pulp vitality tests before ETD may inform the operator about the status of the pulp and thereby prevent the potential for pulpal damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

A comparative study of conventional ligation and self-ligation bracket systems.

The increased use of self-ligating bracket systems frequently raises the question of how they compare with conventional ligation systems. An in vitro and clinical investigation was undertaken to evaluate and compare these distinctly different groups, by using five different brackets. The Activa ("A" Company, Johnson & Johnson, San Diego, Calif.), Edgelok (Ormco, Glendora, Calif.), and SPEED (Strite Industries Ltd., Cambridge, Ontario) self-ligating bracket systems displayed a significantly lower level of frictional resistance, dramatically less chairtime for arch wire removal and insertion, and promoted improved infection control, when compared with polyurethane elastomeric and stainless steel tie wire ligation for ceramic and metal twin brackets.

Ceramics↗
PubMed1994

Skeletodental changes in the adolescent accruing from use of the lip bumper.

Cast and cephalometric analyses were performed to measure the effects of treatment with a lip bumper. The lip bumper was fabricated from an 0.045 inch wire with shrink tubing and no acrylic shields. Nine of the 32 patients were evaluated two years after the comprehensive phase of treatment. Patients were in the mixed dentition stage of development (mean age of 9.9 yrs). A single orthodontist designed all the appliances and treated all the cases. There was significant expansion between the canines, first premolars, second premolars and molars, with the greatest expansion occurring between the first premolars. Cephalometric analysis revealed that the molars underwent angular uprighting but did not move bodily. Incisor irregularity decreased 60% during this phase of treatment. The retention cases revealed that the arch depth decreased, perhaps due to loss of leeway space, but arch widths all were broader, especially in the anterior segment, than at the end of the lip bumper phase. Incisor irregularity also remained trivial (x = 0.3 mm), suggesting appreciable stability.

Adolescent↗
PubMed1993

The evaluation of dual cement resins in orthodontic bonding.

Dual-cement resins are composite resins that are both light activated and chemically cured. They can be cured completely with a visible light source or by the catalyst and base reaction of the material. With the control of setting time, dual cements appear to offer clinicians advantages in orthodontic bonding. The purposes of the present research are to compare various dual cements in regard to orthodontic bonding and to evaluate them in relation to currently used chemically cured and light-cured composite resins for bonding stainless steel mesh-backed orthodontic brackets. Seven currently available orthodontic bonding systems (three light cured and four chemically cured) and three dual cements were evaluated. Each of the 10 groups contained 15 noncarious mandibular incisors. Mandibular incisor brackets were bonded to the teeth in accordance with the manufacturer's recommendation. After bonding, the teeth were stored for 5 days in water at 37 degrees C. An Instron machine (Instron Corp., Canton, Mass.) was used to test samples. All samples were compared with Concise orthodontic bonding composite (3M, St. Paul, Minn.). The results of this investigation show that it is possible to bond solid, mesh-backed metal orthodontic brackets to teeth with a dual cement. The shear bond strengths of the dual cements, as tested in the laboratory, should be adequate to withstand normal orthodontic forces. Increased control of the setting time of the dual cements will allow the clinician more time to correctly position brackets and to remove excess resin before curing. In addition, the clinician can be assured of complete polymerization with the chemical properties of the dual cement resins.

Analysis of Variance↗