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Authors: Dr. Manpreet Kaur, Dr. Neelansh Sikri, Dr. Rahul Nagrath

INTRODUCTION:

Ridge atrophy poses a clinical challenge towards the fabrication of a successful prosthesis. Extreme resorption of the maxillary and mandibular denture bearing areas results in sunken appearance of cheeks, unstable and non-retentive dentures with associated pain and discomfort. Residual ridge resorption is a complex biophysical process and a common occurrence following extraction of teeth. Ridge atrophy is most dramatic during the first year after tooth loss followed by a slower but more progressive rate of resorption thereafter. Loss of alveolar bone from an edentulous ridge is more pronounced in the mandible than the maxilla, particularly in the early (3 months) post-extraction period. The mean reduction in anterior maxillary vertical radiographic bone height during the first year after extraction has varied between 2 and 4 mm compared with 4 to 6 mm in the mandible. The various factors influencing ridge resorption are:
 
Fig. 1a, b Lateral and Frontal Profiles of the patient showing sunken cheeks and obtuse naso- labial angle and depressed lips.
Fig. 1a, b Lateral and Frontal Profiles of the patient showing sunken cheeks and obtuse naso- labial angle and depressed lips.
 
Fig 2a,b Resorbed Maxillary and Mandibular ridges
Fig 2a,b Resorbed Maxillary and Mandibular ridges
 
Fig. 3 The tray is stabilised by adapting the modelling compound on the stubs.
Fig. 3 The tray is stabilised by adapting the modelling compound on the stubs.
 
Fig. 4 The functional impression made with greenstick and modelling compound
Fig. 4 The functional impression made with greenstick and modelling compound


1. Anatomic factors:
  • Amount of bone: Are the ridges high or low, broad or narrow, rounded or spiny, or are they covered by thick or thin mucoperiosteum and if there are recent extractions.
  • Quality of Bone: Whether wide and poorly calcified bone or a narrow and highly calcified bone. Denser the bone, slower will be the rate of resorption.
 
Fig. 5a, b Final Impression made using greenstick and modelling compound
Fig. 5a, b Final Impression made using greenstick and modelling compound
 
Fig. 4 The functional impression made with greenstick and modelling compound
Fig.6 After articulation, the denture base was fabricated with spurs and acrylic stubs


2. Metabolic factors:

Bone metabolism is dependent on cell metabolism (especially osteoblasts and osteoclasts)The four main levels of bone activity are (1) equilibrium, (2) growth, (3) atrophy, resulting from decreased osteoblastic activity, as in osteoporosis and in disuse atrophy, and (4) resorption, caused by increased osteoclastic activity, as in hyperparathyroidism and in pressure resorption. Therefore factors that influence ridge resorption are:
 
 
Fig. 7 a, b The Denture base is evaluated intra orally and compound is adapted to record the neutral zone
Fig. 7 a, b The Denture base is evaluated intra orally and compound is adapted to record the neutral zone
 
Fig.8Plaster index is made around the neutral zone and teeth arrangement is done
Fig.8Plaster index is made around the neutral zone and teeth arrangement is done
 
  • PTH imbalance
  • Post-menopausal osteoporosis
  • Continuous synthesis of local prostaglandins
  • Hypervitaminosis A and D
  • Hypovitaminosis C
3. Functional factors
  • Frequency, duration, direction and strength of forces acting on bone
  • Disuse atrophy and fracture
 
Fig.8Plaster index is made around the neutral zone and teeth arrangement is done
Fig.9 a.b Lateral and Frontal Profile revealing corrected facial appearance
 
Fig.10 Intra oral view of the stable dentures in occlusion
Fig.10 Intra oral view of the stable dentures in occlusion
 
Fig. 11 Mandibular custom tray checked intra-orally
Fig. 11 Mandibular custom tray checked intra-orally


4. Prosthetic factors

Include the myriad of techniques, materials, concepts, principles, and practices which are incorporated into the prostheses.
  • Type and fit of prosthesis
  • Duration of prosthodontic treatment
  • Hours of prosthesis wearing per day
  • Occlusal disharmony
  • Lack of prosthodontic treatment (disuse atrophy)

The stresses causing instability come from many directions and are created during most of the functions of the mouth. The qualities necessary to create and maintain stability are dependent upon the following factors.
  1. Retention,
  2. Tongue Position,
  3. The Lateral Throat form,
  4. The Border Seal,
  5. The Occlusal Plane,
  6. The Arch Arrangement, and
  7. Instruction and Education of the Patient.

The following case reports describe various techniques for management of the hyperplastic and resorbed ridges for achieving the best retention, stability and support during fabrication of complete dentures without pre-prosthetic management.

 
Fig. 12Mandibular ridge is marked with indelible pencil
Fig. 12Mandibular ridge is marked with indelible pencil
 
Fig. 13 The mark is transferred to the tray
Fig. 11 Mandibular custom tray checked intra-orally
 
Fig.14 The relief is cut on the knife ridge to record tissues without displacement
Fig.14 The relief is cut on the knife ridge to record tissues without displacement


CASE 1: NEUTRAL ZONE TECHNIQUE:

Clinical evaluation revealed resorbed maxillary ridge with sunken cheeks (Fig. 1a, b), flat mandibular ridge (Fig 2a,b) and adequate inter-arch space.
After a thorough evaluation of the patient’s history, radiographs and existing clinical conditions, various treatment options were discussed. The patient did not give any relevant medical history that could have possibly contributed to ridge resorption. Treatment options included pre-prosthetic surgeries followed by conventional complete denture prosthesis, implant supported prosthesis, conventional complete denture prosthesis. However, the patient was not interested in any surgical intervention and thus opted for conventional complete denture.

Primary impressions were made and poured in dental plaster. Custom tray was fabricated on the cast obtained and for mandibular custom tray, double spacer was adapted onto the cast and custom tray is made by making two stub handles on the 1st molar region. The tray was adjusted intra-orally and modelling compound was adapted on the stub handles by asking the patient to close the mouth. (Fig. 3)

Then a closed mouth mandibular impression is recorded by mixing 3 parts of modelling compound and 7 parts of greenstick compound and adapting to the intaglio surface of the tray. The patient was asked to carry out different functional movements like sucking, swallowing, smiling, licking the lips, whistling, pronouncing vowels and counting. (Fig.4) Excess compound was trimmed away and the material was re-softened and placed back into the mouth asking the patient to repeat the functional movements. (Fig. 5a, b)

After this, the registration of maxillo-mandibular relations is done, the casts were mounted on an articulator. A new mandibular denture base was fabricated with spurs in the anterior region made using orthodontic wire and two acrylic pillars in the molar region.

Then the modelling compound and greenstick compound is kneaded and placed on the new denture base and the patient is asked to perform the functional movements and the mouth is closed in same maxilla mandibular relation as recorded earlier and the vertical of the patient is verified on the articulator (Fig. 7 a, b). Plaster index of the impression was made and the mandibular teeth were arranged in the neutral zone following the index (Fig. 8).

Try in is done and the laboratory procedures are carried out for fabrication of the denture, then the denture is adjusted in the patient’s mouth so that the denture is stable in the mouth even during function.

 
Fig.15 Border moulding is performed on the tray
Fig.15 Border moulding is performed on the tray
 
Fig. 16 Final Impression made with medium body
Fig. 16 Final Impression made with medium body
 
Fig. 17 Intraoral view of the dentures
Fig. 17 Intraoral view of the dentures


CASE 2: DIFFERENTIAL PRESSURE TECHNIQUE:

Clinical evaluation revealed resorbed maxillary ridge and knife edge mandibular ridge and adequate inter-arch space. The patient was not monetarily sound thus opted for conventional complete denture. Primary impressions were made and poured in dental plaster. Custom tray was fabricated on the cast obtained and for mandibular custom tray, double spacer was adapted onto the cast and custom tray is made without and handle. (Fig.11) The tray was adjusted intra-orally and the knife edge area is marked with an indelible pencil on the mandibular ridge (Fig.12) and the marks are transferred on the custom tray after removing the spacer wax from the intaglio surface.(Fig.13)

The marked area was cut and a window was created in the tray and border moulding was done.(Fig.14, 15) The medium body was injected on the intaglio surface of the tray and the tissues were recorded at rest without displacement of the tissues.(Fig.16) After this, the registration of maxillo-mandibular relations is done, the casts were mounted on an articulator and teeth arrangement is performed. Try in is done and the laboratory procedures are carried out to fabricate the denture, then the denture is adjusted in the patient’s mouth so that the denture is stable in the mouth even during function. (Fig. 17)
 
Fig.18 a, b Intra-oral view of maxillary and mandibular ridges
Fig.18 a, b Intra-oral view of maxillary and mandibular ridges
 
Fig.19 Placement of 2 Adin Implants at the lower canine regions
Fig.19 Placement of 2 Adin Implants at the lower canine regions


CASE 3: IMPLANT OVERDENTURE

A 64 year old male patient reported for replacement of missing teeth in both the upper and lower jaws. Clinical and radiographic evaluation revealed completely edentulous upper and lower jaws with significant bone loss and deficiency in height and width. (Fig. 18 a,b)

Advantages and disadvantages of different treatment options were discussed and patient was convinced for an implant supported overdenture. In stage one surgery two (Adin) implants were placed based on the bone thickness and anatomical considerations. (Fig. 19)

Stage two (three months after the initial implant placement) consisted of exposing the implants after the removal of the cover screws followed by the placement of prefabricated healing caps to allow formation of soft tissue cuff. Record bases and occlusal rims were fabricated on the master casts. Vertical and horizontal jaw relations were recorded. Trial arrangement was checked for esthetic appearance, phonetics, vertical occlusal dimension and centric relation. Denture was fabricated in a conventional manner to be worn during the course of osseointegration.

After 3months of healing, the area around the metal housing was marked and relieved to create space in the denture, then the spacer was applied around the attachments and autopolymerizing resin was added to incorporate the ball attachments directly into the denture base.(Fig. 21, 22,23) Home care instructions were discussed with the patient during the placement visit and patient was recalled after 1 week for a follow up. After 1 week follow up the patient expressed his satisfaction with the new denture in terms of its stability and retention.
 
Fig 20 Conventional Complete denture
Fig 20 Conventional Complete denture
 
Fig 21 Ball attachments on the implant
Fig 21 Ball attachments on the implant
 
Fig.22 Metal Housings to be picked up and transfer in the denture
Fig.22 Metal Housings to be picked up and transfer in the denture


DISCUSSION

Neutral zone mandibular impression was recorded in order to determine the space within which the denture could be seated without being subjected to excessive displacing forces from the surrounding musculature and thus aid in denture base stability. Neutral zone is defined as “the potential space between the lips and cheeks on one side and the tongue on the other; that area or position where the forces between the tongue and cheeks or lips are equal”.

Maxillary neutral zone impression was not recorded as the effect of tongue size and position do not appear to have as profound an impact on the stability of a maxillary denture as compared to the mandibular denture. Besides, the position of the mandibular teeth arranged in the neutral zone was used as a guide to position the maxillary teeth in the neutral zone Previously surgical treatment of ridge atrophy was concentrated on the replacement of bone where it was lost, or efforts to further use the existing residual ridge through procedures aimed at lowering the floor of the mouth or deepening the vestibules. Surgical complications may include infection, paresthesias, broad unretentive residual ridges, and rapid loss of the graft to resorption. Because of the nature of the surgery, patients also experienced a lengthy recovery period of at least 6 months during which they were unable to wear their dentures.

The introduction of dental implants to the surgeon’s armamentarium has dramatically reduced the need to consider preprosthetic soft and hard tissue surgical procedures. Overdentures are designed to distribute the masticatory load between the edentulous ridge and the abutments. The overdenture transfers occlusal forces to the alveolar bone through the periodontal ligament of the retained tooth roots. Proprioceptive feedback, from the periodontal ligament to the muscles of mastication, may act to prevent occlusal overload and thereby prevent bone resorption because of excessive forces. The short term and long-term preservation of alveolar bone has been documented not only adjacent to the overdenture abutments but also adjacent to the edentulous ridges.
 
 
Fig 23 metal housing with nylon caps picked in the lower denture
Fig 23 metal housing with nylon caps picked in the lower denture
CONCLUSION:

Bone resorption of residual ridges is common. The rate of resorption varies among different individuals and within the same individual at different times. Factors related to the rate of resorption are divided into anatomic, metabolic, functional, and prosthetic factors. The pathological changes must be carefully examined and resolved, prior to the beginning of the new prosthetic rehabilitation.Also carefully evaluate the border seal area for the mandibular denture which extends downward to the floor of the mouth and posteriorly into the lateral throat form. These areas undergo extensive movement during many of the functions of the oral cavity.

It is important for the dentist to know what tongue positions are necessary to maintain a seal during the major functions of the mouth. It is also essential to know the relationship between normal tongue position and the floor of the mouth and lateral throat forms.It, therefore, becomes possible for the dentist to instruct the patient so that these positions will remain constant during the making of a mandibular impression and when retention is tested.

Retracted tongue positions are not compatible withstability. Therefore, recognition of normal and retracted tongue positions and means of improving retracted positions are important adjuncts to successful denture service. A thorough history, a keen eye in clinical examinations and sound knowledge about the possible treatment alternatives will help the prosthodontist to provide his patients with satisfactory complete denture prosthesis

REFERENCES:
 
  1. Douglas Allen Atwood. Some clinical factors related to rate of resorption of residual ridges. J Prosthet Dent 2001 86;2: 119-125.
  2. Christopher Whitmyer, Salvatore J. Esposito, and Scott Alperin. Longitudinal treatment of a severely atrophic mandible: A clinical report. J Prosthet Dent 2003 90;2: 116-120.
  3. Corwin R. Wright. Evaluation of the factors necessary to develop stability in mandibular dentures. J Prosthet Dent 2004 92;6: 509-518.
  4. Chris C. L. Wyatt. The effect of prosthodontic treatment on alveolar bone loss: A review of theliterature. J Prosthet Dent 1998 80;3: 362- 366.
  5. Joseph E. Makzoume. Morphologic comparison of two neutral zone impression techniques: A pilot study. J Prosthet Dent 2004 92;6: 563-567.
  6. Krishna Prasad D., Divya Mehra & Anupama Prasad D. Prosthodontic management of compromised ridges and situations. NUJHS 2014 4; 1: 141-148.

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