A comparison of the effect of differentocclusal forms in mandibular implantoverdenturesMohamed Moataz et.al .University of Pittsburgh Medical Center, PittsburghJournal of Prosthetic Dentistry1 998;79:422-9
STATEMENT OF PROBLEMPosterior tooth form selection for implant overdenturesis made according to personal preference andexperience using the concepts of conventionalcomplete denture Prosthodontics.
PURPOSE.(1) Compared the masticatory efficiency of threeocclusal forms, 0 degrees, 30 degrees, and lingualcontact (lingualized occlusion), in subjects withmandibular implant overdentures,(2) Determined their effects on the implant supportingtissues.
MATERIAL AND METHODSINCLUSION CRITERIA1. Eight edentulous subjects, four men and four women,ages 52 to 78 years.2. Skeletal class I jaw relationships.3. Four root form endosseous-type implants (Nobel Biocare, Göteborg, Sweden) in the mandibular symphysis area that had been restored with Hader bar retained implant overdentures and that had been in function for at least 1 year before the study.
For each patient, a mandibular implant overdenture and amaxillary conventional complete denture were constructedboth with interchangeable posterior occlusal segments.(A posterior occlusal form was randomly selected foreach patient)
A, Maxillary and mandibular anterior teeth were set according to esthetics and phonetics and were not changed throughout study. B, Cross-section of maxillary and mandibular bases before attachingdifferent posterior tooth forms. C, Zero degree posterior teeth attached to denture bases. D, Lingualized posterior occlusion. Maxillary lingual cusps of posterior teethtouch central fossa of mandibular teeth. E, Use of 30 degree posterior segments
Patients used each occlusal form for 6 months during whichtime three test sessions were performed at 2- monthintervals.IN EACH TEST SESSION, PATIENTS’ MASTICATORYEFFICIENCY WAS EVALUATED AND PERI-IMPLANTMUCOSA AND BONE ASSESSED CLINICALLY ANDRADIOGRAPHICALLY.Masticatory efficiency was evaluated through five measuresrecorded while patients were chewing standardized pieces(1 cm cubes) of test foods in normal manner.
The test foods used were bread, hard cheese, beef sausage,raw carrots, and apples.Patients were seated in an upright position and wereinstructed to chew at a normal rate and swallow.Four trials (four cubes) were made for each test food.
While chewing the food specimens, five measurementswere recorded: a) The number of chewing strokes up to the first swallow. b) The number of chewing strokes until the mouth wasfree of food.c) The number of swallows until the mouth was free offood.d) The time (in seconds) elapsed until the firstswallow.e) The time (in seconds) until the mouth was free of food.(two persons who remained the same ,One recorded the number ofchewing strokes and swallows, and the other recorded the time.)
Patients’ chewing preferences were assessed with astandardized questionnaire administered to patientsonce every 6 months at the end of use for each posteriorocclusal form. (The questionnaire evaluated the patients’ opinion concerning comfort during rest and chewing, stability, speech, ease of cleaning, and appearance (esthetics) of their dentures.)
CLINICAL EVALUATION OF THE PERI-IMPLANT TISSUES1. Plaque Index.2. Gingival Index.3. Mobility .4. Probing Depth.5. Measurement Of The Epithelial Attachment Level.6. Changes in bone level around the necks of implantswas assessed with standardized periapical radiographswith a superimposed grid.7. Bone density along the length of the implantswas alsodeterminedanddetect minor bone changes. forms were (The second to third randomly selected occlusalsimilarly tested every 2 months for 6 months.)
STATISTICAL ANALYSES1. The mean chewing efficiency and clinical andradiographic differences between the occlusal formswere evaluated by a repeated measures analysis ofvariance (MANOVA). 2. Repeated measures analysis of variance (ANOVA) was used to analyze self-report questionnaire data. All analyses were computed with the SYSTAT (Version 7) p value of < 0.05 was considered to be statistically significant
PATIENTS SUBJECTIVE OCCLUSAL FORM RATING 57.14% of patients preferred the 30 degree occlusal form 42.86% preferred the lingualized occlusal form. None of the patients selected the 0 degree occlusal form
DISCUSSIONThe primary results of this study showed that 30 degreeand lingualized occlusal forms provide better chewingefficiency than 0 degree occlusal form in implantoverdentures.The use of implants to stabilize and retain mandibulardentures therefore improved denture retention andstability closer to natural dentition than the removabledenture condition.
The values of the chewing efficiency measures also variedsignificantly with the type of food used. Patients thereforechewed and swallowed differently depending on thehardness and texture of the food. Validation of methods for the analysis of masticatory function. J Dent Res 1990;69:334. Chewing efficiency and state of dentition. A methodologic study. Acta Odontol Scand 1978;36:33-41. The influence of food type on experimental design in studies of chewing efficiency. J Dent Res 1991;70:277.
Radiographic assessment of the bone surrounding theimplants did not show any significant difference in heightor density associated with the different occlusal formsused. Lingualized and 30 degree occlusal forms had significantly less gingival index scores compared with the 0 degree occlusal form.
CONCLUSIONS1. The choice of posterior occlusal forms in implantoverdentures should not be based on conventionalcomplete denture occlusion.2. The number of chewing strokes up to the first swallowand until the mouth was free of food provided betterdiscrimination between the different occlusal forms thanthe chewing time and number of swallows.4. The use of 30 degree and lingualized occlusal formsprovided better chewing efficiency than 0 degree occlusalform.NONE OF THE OCCLUSAL FORMS TESTED SHOWED ANY CLINICALOR RADIOGRAPHIC DETRIMENTAL CHANGES IN IMPLANTSUPPORTING TISSUES